JOURNAL OF THE ROYAL SOCIETY OF WESTERN AUSTRALIA. VOLUME XXXII. BIOLOGICAL CONTROL IN WESTERN AUSTRALIA. PRESIDENTIAL ADDRESS, 1946. By C. F. H. Jenkins, YLA. Delivered 9th July, 1946. CONTENTS. Introduction ... COLLEMBOLA Sminthuri(la) ... Hemiptera Pentatomidic Jassidse Aphklula* Coccidw COLEOPTERA Bnichida? Biptera Trypetidic Muscida? Calliphorida.* ... Lepidoptera Plutellida.' Pyralida? Gelechida* Pierida* Vertebratp:s ... 1 3 4 5 5 7 11 12 13 14 14 15 15 16 16 TNTRODrCTION. No method of combating pests has appealed so generally to the ])opular fancy as that usually known as biological control. This is readily understand- able' for it involves the use of one creature to subject another and reduces to a minimum all manual lalionr. Despite their general appeal, the ]>rinciples 15775/2/48—750 2 C. F. H. Jenkins. of biological control are by no means generally understood, and the very popu- larity of the nietliod sometimes leads to tlie appearance of the most extravagant claims or unreasonable criticisms. Many of the most outstanding successes with biological control have been achieved under insular conditions. Tlie Hawaiian Islands are probably the best examples followed by Fiji and New Zealand. Where pests have become widely established on a continental land mass, the chances of successfully introducing parasites are seriously limited. The new environment })resents such a complex of factors to be contended with, biotic, climatic and physiographic, that no single i>arasite or j^redator is likely to be of more than local signilicance. Tliis does not mean that successes have not been achieved on large land masses siicli as America and Australia, Init in these instances, the introductions have been made into areas winch may be re- garded as distinct ecological entities. South W'ostein Australia is generally recognised as an ecological island and possessing a warm etpiable climate and a certain degree of physiographic isolation, it conforms with the main require- ments necessary for the successful establishmoTit of jiarasites. The first definite experiment along the lines of biological control is rejDorted to ha\6 been made in 1873 (Imms. 1037) when Planchon and liiley introduced an American in'edatory mite (Tjjroglyphus jjlnjlloxct'm Kiley) into France to try and combat the growing menace of I^hyllox'pra vlfiJoJm in French vineyards. Parasite introduction received its first real stimulus from the subjugation of the Cottony-cushion scale {Iceriia piirchasi) following the mission of A. Koebelo to Australia and tlie transference to the United States of the lady- bird Rodolia cardinuUs. The appouitment in 1001 of George Compere (Fssig. 1931) to collect para- sites and make investigations into prolilems of biological control on behalf of the W esteni Australian Clovormnent, marks the commencement of a peiiod of very active local interest in this lirancli of insect control and one which has been keenly maintained u]i to the present day. In 1004 it was arranged for Compere to collect jointly for the Californian and W est Australian Governments and his services were retained until 1010 when he returned to California. Prior to tbmpere’s ap]K>intme.nt, however, several attempts had been made to acclimatise useful msocts. As early as 1805 (Anon 1805) it was suggested that local parasites and predators be exchanged for insects to control woolly aphis, cabbage aphis and coccids and tlie first local introduction was the ladv- hivd L^s conform'^ by Claude Fuller in 1896 (Anon 1901). Compere spent much of his time travelling and collecting, his specimens being forwarded to Nevmmn at the W est Australian Department of Agriculture for breeding and distri- bution. Suiprising as it may seem the early exponents of biological control did not receive general commendation and in some instances were the subject of ill-concmvod abuse. The late W^ VV. Froggatt { 1 909) rather bitterly attacked some ot Compere s work and strongly refuted many of the claims made on behalf of biological control. The ensuing pages comprise an account of tlie various attempts at para- site and predator introduction into \^'estern Australia. The information lias been gleaned from all possible sources including many unpublished manuscripts. Where possible the information given in these early Biological Control in Western Australia. 3 records lias been checked by reference to subsequent literature and specimens in various collections. In many cases, however, the original meagre statements cannot in any way be amplified. Unsatisfactory as such information may be from many iioints of view, it is felt that the following details may serve a useful purpose in the planning of futiue biological control programmes. A knowledge of what insects have already been tried and their subsequent fate must be of iiaramount importance in considering new projects and it is with this consideration in mind that the following data are jnesented. LITERATURE. Anon 1895 “ Beneficial Insects,” Joiirn. Bur. Agric. If. Aiisl., Vol. 2, p. 499. Anon 1901 Journ. Dept. Agric. IP. Aust., Vol. 3, p. 143. Essig, E. 0. 1931 A history of Entomology,” Macmillan (X.Y.), p. 375. Eroggatt, W. AV. 1909 “ Report on Parasitic and Injurious Itisects,” N.S.AA^. Dept. Agric. p. 56, et seq. Lea, A. 1895 “ Exchanging Useful Insects,” Journ. Bur. Agric. IP. Aust. \"ol. 2, p. 564. Imm.s, A. D. 1937 “ Recent Advances in Entomology,” J. and A. Churchill Ltd., Lon- don, j). 370. Imms, A. D. 1937A, ibid. p. 395. Xewman, L. J. 1909 “ Beneficial Parasites,” Journ. Dept. Agric. TP. Aust., Vol XVIII., p. 380. Olliff, S. A. 1895, “ A Xew AA^estern Australian Lady-bird,” Journ. Bur. Agric. IP. Aust., Vol. 2, p. 313. Order. COLLEMBOLA. E. SMINTHURIDAE. Sminthurus viridis Linn. (Clover Springtail or Lucerne Flea). The Clover Springtail is believed to have reached Western Australia in 19 ID (Newman 1910) per medium of baled fodder imported into the State from South Australia. Since that date it has spread rapidly through the South-West, its distribution being boimded roughly by the 15 isohyet, although the princi- pal damage is done within the 19 in. rainfall line where the subterranean clover pastures are established. On accoimt of the large areas involved, artificial control measures never offered a practical solution to the problem, so cultural and biological methods seemed the most worthy of investigation. The biological aspect of Lucerne Flea control came into evidence in 1931 when the Bdellid Alite [Biscirus ktpida- rius (Kramer)] was discovered at Waroona (Newman and AVomserley 1932). Since then, colonies have been distributed to all parts of South Western Australia where the flea is troublesome, as well as to South Australia, Victoria, New South Wales, Tasmania, and New Zealand. The mite established itself most readily in the higher rainfall areas and for some time it appeared doubtful as to whether it would gain a footing in the com- paratively dry Avon Valley districts (Newman 1934). In recent years, how- ever, it has increased greatly in these regions, with apparently beneficial results. 4 C. F. H. Jenkins. An account of tlie biology of the mite is given by Jenkins (1935) shoM^- ing that the creature passes over tlie summer in the egg stage. Discussing the population density of Sniinlliurus and Biscit'Ufij on a small area intensively studied over a period of 2 years, Norris { 1 938) states “ The impression was gained in the held that BrnBiihurus diminished in numbers at the end of the season long before the meteorological conditions were siifheiently adverse to account for the fall whilst Haloiydetis, though oven more susceptible to conditions of drouglit and high temperatuies was still present in large mmibers. It seems possible that the Bdellid was at least partly responsible for this early decline.” LFTKRATUKE. Anon, 1930 Journ. Cimn. ^ci. Ind. Res., (Anst.) iU, p. 189. Currie, G. 1931, Ihid. vii, p. 9. Davidson, J. 1934 Conn. Sri. Ind. Res. (Auat.) Bull, p. 79. Holdaway, F. G. 1927, Coun. Sci. Ind. Res. Ansi. Pmnphlet 4. Jenkins, C. F. H. 193“) Journ. I)epl.. Agric. IT. di/sh 2nd ser. Vol. XII., p. 342. Madagcn, D. S. 1932. Bull Eni. Res. Vol. XXIH.. p. 182. Newman L. J. 1910, Ann. Repf. Dept. Agric. IT. p. 46. Newman, L. J. 1927. Journ. Dept. Agric. If. 2nd ser. Vol. IV., p. 78. 449. Newman, L. J. 1934. Ibid. Vol. XI., p. 100. Newman, L. J. and Womersley, H. 1932, Ibid. 2nd ser. Vol. IX., p, 289. Norris, K. R. 1938, Conn. Sci. Ind. Res. Aust. Pamphlet 84. Womersley, H. 1933, Journ. Coun. Sci. Ind. Res. (Aust.) Vol. 6, No. 2, p. 83. Order. HEMIPTERA. F. PENTATOMIDAE. Nezara viridula (Linn.) (Green Tomato Bug.) This introduced bug was first reported within the State at Bunbury in 1920. Since then, it grndually spread tliroughout the loAver South West to become ,a serious A*egetable ]iest. Artificial control measures have never proved very satisfactor>- owing to tlio robust nature of the insect, and several experiments with parasite introductions have been made. The tirst attem]>t at biological control was made in 1932 Avhen Newman obtained from tlie Kkuhla Agricultural Experimental Station, two consign- ments ot a tachiiiid fly {Trickopoda pemiipcs E.). In both instances no living material survi\ed tJie journey. In 1933 from 14r. Rriesner of Egypt, NcAvman obtained a few rafts of bug eggs parasitised by the Scelionid Microphinurns hasalis Woll. and from the 30 wasps wliich emerged, a nucleus colony was formed (Newman 1934). Dui’iug 1934 about I.O(K) wasps were distributed and parasitised material was regained in the held. The wasp carrietl over the winter as an adult in the laboratory and suivi\ed successfully in the field as parasitised material was obtained from several localities in the spring of 1935. Ill 1935, 30.000 and in 1936, 20,000 parasites were distributed and the in- sect is now Av itlely established. A marked decrease in the importance of the pest has been noted since the establisliment of the Egyptian parasite. Mkrophanurus has been reared from the eggs of Oechalia consocialis and the Pittos])oruni hug (A^rines geminata) in Western Australia. Biological Control in Western Australia. 5 literature. Newman, L. J. 1934, Journ. Dept. Agric. W. Aust. Ser. 2., Vol. XI., p. Ill, Newman, L. J., Ibid. Vol. XI, p. 573. Newman, L. J., Ibid. Vol. XI, p. 434. F. JASSIDAE. Typhlocyba froggatti Baker (Apple leafhopper). The apple leafhopper is a native of Europe which has now become estab- lished in many apple grOAving coimtries of the world. It was first recorded in Australia in 1918 but did not reach AVestem Aust- ralia until 1938 when it wa« reported at Bridgetowm. Artificial control measures employing nicotine suljihate and D.D.T. have* proved very satisfactory^ but an attempt to establish a wasp parasite was con- sidered justified. Anagrits armatus A.shm. was successfully introduced from New Zealand by Hr. J. Evans of the Tasmanian Department of Agriculture and parasitised overwintering egg.s Avere obtained from this soru-ce in 1943^ The wasps were liberated at Bridgetown in Octobei’, 1943, but so far there is no evidence of their having become established. Arrangements are in hand for further introductons to be carried out. LITERATURE. Jenkins, C. F. H. 1943, Journ. Dept. Agric. W. Aust. ser. 2, A^ol. XX., p. 194. F. APHIDIDAE. Brevicoryne brassicae Linn. (Cabbage Aphis), Several attempts have been made to control cabbage aphis biologically and, although complete success has not been attained, the pest has been greatly reduced. The chief controlling factor is recorded as being a hymenopterous parasite obtained from Ceylon, tAventy' four having been originally introduced by George Com])ere in 1907 (Robinson 1908). Taa’o Coccinellids and two hymen- opterous parasites (one possibly being Direretus rapee Curt.) Avere also introduced by Compere from Eastern Australia in 1902 (Comjiero 1902 and Anon 1906). Ormis chahjbens Bd. became established, but O. lajartei Alls, did not survive. Lea (1897) referred to the Cabbage Aphis as the “ Avorst enemy tliat the cab- bage has.” Newman (1934) says the position is greatly improved by the introduction of parasites from the Orient.” So far it has not been possible to check the identity of the hymenoptera involved. LITERATURE. Compere, G. 1902, Introduction of Parasites,” Journ. Dept. Agric. W. Aust. Vol. VI., p. 238. Despeissis, A. 1906, “Acting Director’s Report,” Ibid. Vol. XIA^, p. 327. Lea, A. AI. 1895, Journ. Bxir. Agric. W. Aust. Vol. 2, p. 551. Newman, L. J. 1907, “ Rejjort of Assist. Entomologist,” Journ, Dept. Agric. W. Ausf. Vol. XV., p. 918. 6 C. F. H. Jenkins. Newman, L. J. 1934, Ibid. 2nd ser. Vol. XI., p. 203. Robinson, J. 1909, Journ. Dept. Agric. O'. Aiist. Vol. XVII., p. 683. Smith, J. H. 1945, Journ. Queensland Dept. Agric. Vol. 62, p. 341. Eriosoma lanigera. Hausm. (\^ ooliy Aphis). When this apliis reached Western Australia is not definitely known, but as early as 1895 (Lea 1895) it was recorded as “ widely distributed through- out Western Australia and one of the most serious pests which tlie apple grower has to contend with.” The suppression of the aphis by the wasp Aphelimis mali Hans, is one (^f the most outstanding local achievments in biological con- trol. The parasite was introduced into the state in 1923 from New Zealand with tlio co-operation of Dr. TiH_yanl of the Cawthron Institute. The first experiments were carried out in an orchard at Guildford and subsequently the insect was disti’ibutoil to orchardists throughout the South West. Before the introduction of Ajdadinus several routine spn'uy treatments failed to control the Woolly Aphis in the principal apple growing districts whereas now, arti- ficial treatments for the pest are soldotn necessary. Lady-birdvS (Lcis conjormis) also ]ila.ys a part in the control of this pest and the first colony ^yas introduced into the State from Tasmania as early as. 1896 by Claude Fuller (Breen 1906 ane no authentic grounds for this assumption. For many years, Olive or Black Scale was one of the most serious pests of local orchards (Newunan 1909), but successful parasite introductions have greatly reduced the toll taken by this insect. 8 C. F. H. Jenkins. Se^•eral specievS of parasites have been experimented with over the past 50 years but the three which have proved most successful are Scutellista cijanea Mot. MciapJiycus loundsburyi How. and Tomoc('ni californica How. The results of tlie recent trials with Mrtaphyciis helvolus Comp, must not be taken as conclusive as only a small colony was procured from the C.S.I.R. and satisfactory host material was not available in sufficient quantity to bleed a second generation. Table II indicates the various attempts at insect introduction which have been made in past years : — TABLE II. Parasite or Predator. Introduced Prom. Date of Intro- duction. Number Intro- duced. Number Liber- ated. Where Liberated. Intro- duced By. Subse- quent History. Red scutellista China 1905 3 ? ? Compere Failed Do. do Timor 1905 3 Metropolitan Area do. do. Scutellista cyatiea Brazil 1904 60 ? ? do. do. Motsch Do. do. California .... 1904 19 19 Metropolitan Area do. do. Established Do. do. Capetown .... 1902 30 30 T. Hooper Failed Do. do. do. 1903 85 85 do. do. do. Do, do. do 1902 ? 11 Perth and Coolup Compere 9 Do. do. ('alifornia .... 1903 ? 90 Various do. Established Metaphycus loundsburyi How. Capetown .... 1902 9 ? Metropolitan Area T. Hooper do. Microterys sp. do 1902 ? ? do. do. Failed Do.' do. 1902 ? 20 do. Compere do. Tomocera californica How. N.S.W 1902 9 45 9 do. Established Quaylea ivhittieri (Girault) = Hymen.' cyrtiis crau'i Ashm. do 1902 ? 11 Metropolitan! Area. do. Failed (Essig., 1931 a) *Myiocnema comperei Ashm. Queensland... 1902 9 938 51 colonie.s, various do. Established Aristolochia sp Hong Kong.... 1903 ? 12 Metropolitan Area do. Failed IViizobius ventralis Ericks Eastern Aus- tralia 1902 ? 9 do. do. Established Metaphyeus Mvolus Comp. Canberra (C.S.I.R.) 1943 No lib- erations made ? Jenkins Unnamed Eastern Aus- tralia 1903 9 60 Compere 9 Do South Africa 1903 ? 85 do. 9 Do. Brazil 1904 9 60 • do. 9 Do California .... 1904 9 19 .... do. 9 Do Canton 1903 ? 10 Metropolitan Area Compere 9 Do Hong Kong ... 1903 9 12 do. do. 9 Do Capetown .... 1903 9 83 Various do. ? Do do 1903 9 17 Metropolitan do. 9 ♦Now considered to be a possible secondary parasite (Essig., 1931 b). LITERATURE. Anon, 1903, In Seorch of Parasites,” Journ. Dept. Agric. It. Aust. VoL VII., p. 51. Anon, 1906, “ Saving California's Fruit Crops,” ibid. Vol. XIII., p. 333. Compere, G. 1902, ” Introduction of Parasites,” ibid. Vol. VI., p. 238. Compere, G. 1904, “ Black Scale Parasites,” ibid. Vol. X., p. 94. Despeissis, A. and Compere, G. 1903, Dept. Agric. IT. Aust., Bull 4, p. 91. Despeissis, 1904, “ Black Scale and Fruit Fly Parasites,” Journ. Dept. Agric. W. Aust. Vol. X., p. 172. Essig. E. O. 1931A, “ A History of Entomology,” (N.Y. MacMillan), p. 359. Essig, E, O. 1931B, ibid, p. 330. Harper, 1906, " Introduction of Parasites,” Journ. Dept. Agric. W. Aust. Vol. XIV., p. 178. Biological Control in Western Australia. 9 Lea, A. 1895, “ Scale Insects,” Journ. Bur. Ayric. W. AtisL Vol. 2, p. 564. Newman, L. J. 1907, “ Report of Assist, Entomologist,” Journ. Dept. Aqric. ?!'. Aust. Vol, XV., p. 914. Newman, L. J. 1909, “ Beneficial Parasites,” ibid, Vol. XVIII., p. 381. Aonidiella aurantii (Mask.) (Red Scale) Red Scale was first reported on citrus in Western Australia from the Metropolitan Area by Lea in 1895. Since that date, it has gradually spread to most of the citrus growing districts of the State. Various attempts to control this scale biologically have been made and a number of Coccinellids as well as wasp parasites have been introfluced. The most successful introduction is the liyrnenopteron Apliytis chrysomphali Mercet. imported by Compere from C^hina in 1905. The most recent introductions have been made with the co-operation of the Entomological Division of the C.S.I.R., the wasp having been originally obtained from China by the Imperial Parasite Service, Canada. Comperislla hifasciata How. has long been known as a parasite of the Vellow Scale [A. ciirina (Coc{.)] but it is only in recent years that a race has been detected capable of developing in A. aurantii. In Table III details of the v'arious attempted introductions are set out ; — TABLE in. Parasite or Predator. Introduced Prom. Bate of Intro- duction. Number Intro- duced. Number Liber- ated. M'here Liberated. Intro- duced. By. Subse- quent History Cocdnellid China 1905 9 14 Metropolitan Area Compere Established Bo. Jerusalem .... 1904 9 160 do. do. Failed? Bo. Japan 1907 ? 9 do. do. Failed Bo. Ceylon 1907 ? 9 Comperiella bifasciata Japan 1909 9 9 ? do. Failed How. Bo. do. Canlierra (C.S.l.K.) 1943-44 400 1000 Harvey, Saw- yers Valley, Gosnells, Metropolitan Area Jenkins 9 literature. Compere, G. 1906, “ Red Scale Parasites,” Journ. Dept. Agric. IF. Aust. Vol. XIV., P- 5. Compere, H. 1936. Bull. Ent. Res. Vol. 27,, p. 494. Despeissi.s, A. 1906, Acting Directors Report,” Journ. Dept. Agric. W. Aust. Vol.,, XIV., p. 326. Lea, A. 1985, Journ. Bur. Agric. W. Aust. Vol. 2. p. .564. Newman, L. J. 1907, '‘Report of Assist. Entomologist,” Journ. Dept. Agric. If. Au^' . Vol. XV., p. 918. Newman, L. J. 1909, “ Beneficial Parasites,” Ibid. Vol. XVIII., p. 381. Jenkins, C. E. H. 1945, “ The Citrus Red Scale,” Ibid. Vol. XXII, (2nd Sen) p. 10. 10 C. F. H. Jenkins. Aonidiella perniciosus (Comst.) (San Jose Scale) Tlie above pest was first recorded in Western Australia in 1897 (Despeissis 1897 and Fuller 1897). Its presence was so much dreaded that very stringent ■control measures were at once adopted and infested trees were grubbed and burned. Attempts at ])arasite establishment have been made, two introductions from Pennsylvania being reported (Newman 1915). Unfortunately no living material reached tins State and the species concenied is not mentioned. Two -attempts to introduce hymenoptera from California in 1907 also failed. An unnamed ladybird forwarded by C^ompere from Spain was liberated (Anon. 1903), but with no better results than the otlier attenij^ts listed. LITERATUliE. Anon, 1903, “ In Search of Parasites,” Journ. Dept. Agric. IK. Aust. Vol. VII., p. 432. Despeissis, A. 1897, Journ, Bur. Agric. IK. Aust. Vol. IV., p. 1290. Fuller, C. 1897, Ibid. Vol. p. 1293. Newman, L. J. 1909, “ Beneficial Parasites,” Journ. Dept. Agric. W. Aust. A^ol. XA’III., p. 380. NeAvman, L. J. 1915, Ann. Kept. Dept. Agric. AAK Anst. 1914-15, (unpublished). Aspidiotus sp. Compere in 1902 introduced a coccinellid Chiloconis circumdatus Shon. from Hong Kong. Releases were made in the metropolitan area but without success. In 1903 a batch of 350 coccinellids imported from Seville were also libei'ated in tlie Perth area, but were not known to become established. Coccus hesperidum L. (Soft Brown Scale). Ihis scale first appeared in local literature in 1894 (Anon. 1894) although the actual date of its introduction into AVestem Australia is not known. Althougli not a major pest, it has a wide host range and causes orehardists some inconvenience. Attempts to control this scale biologically have not been successful, but the introductions attempted are itemised in Table IV. TABLE IV. Parasite or Predator. Scutellista sp. Bo. CoccopJtaqus lycimnia Walk. Unnamed parasites (? hymenoptera) Do. do. Do. Ser., Vol. X., p. 228. Pseudococcus Spp. (Mealy Bugs) In 1902, Compere introduced colonies of CryjAolaemus montrouzieri Muls. from New South Wales and Queensland and some 1,300 were liberated in the Metropolitan Area. The ladybird is now firmly established and is an important factor in Mealy Bug control. IJTKRATURE. ' Compere, G. 1902, “ Introdiucton of Parasites,” Journ. De 2 )t, Agric. IF. Aust. Vol. VI., p. 238. Bespeissis, A. 1906, “ Acting Director’s Report,” Ibid. Vol. XIV., p. 327. Xewman, L. J. 1909, “ Beneficial Parasites,” Ibid. Vol. XVIIL, p. 381. Xewman, L. J. 1934, “ Entomological Problems,” Ibid 2nd Ser. Vol. II., p. 203. Order. COLEOPTERA F. BRUCHIDAE. Bruchus pisorum Linn. (Pea Weevil). The pea weevil was first recorded in Western Australia in 1931 (Newman 1932). It is widely. distributed in the major pea-growing districts of the South- 12 C. F. H. Jenkins. West and is a sei'ioiis menace to the industry. The first attempted biological control was made in 1939 when, through the co-operation of the C.S.I.R., the wasp Triaspis thomcicus Curt, was introduced from France. Approximately 1,000 parasites were reared and liberated at the following localities : Burges Siding, Seabrook, Wooroloo aiid Muresk. Field recoveries were made from peas Jiarv'csted the same season at Wooroloo but altliough peas were planted on that site for two successive seasons no further recoveries were made either there or elsewhere. In 1942 parasitised bean wee\dl eggs (B. ohteetus) Avere obtained from the U.S.D.A. Bur. Rut. and Plant Quarantine, and further attempts were made to rear Triaspis. These were imsuccessful, however, and further introductions were prevented by war conditions. LITERATURE. Newman, L. J. 1932, Jowm. Dept. Agric. If. Aust. 2nd. Ser. Vol. IX., p. 297. Order. DIPTERA. F. TRYPETIDAE. Ceratitis capitata Wied. (Mediterranean Fruit Fly.) The first record of Fruit fly in Western Australia came from Claremont in 1895. The following year it was found in Perth and by 1897 it had spread to Guildford. The.se appear to bo the first records for the Commonwealth, as N.S.W. did not report the fly until 1898. This insect is the most serious fruit pest established in Western Australia and strenuous efforts have been marie to bring about its subjection by the introduction of parasites. Unfortunately, however, all attempts at biological control liave met with absolute failure. The parasites from Avhich the heM> results were expected were : — Syniomosphyrum indiciim Silv. and Diacka^sma tryoni Com. These wasps and also Teirastichus giffardianus Silv. were rcaj'ed in large numbers in cages- and liberated in the field, but not in a single case was parasitised material obtained as a result of these liberations. Table V summarises the attempts so far made to control fruit fly by biological means : — TABLE V. Parasite or Predator. Hate of Introduced Intro- From. duction. Number Intro- duced. Number Liber- ated. Where Liberated. Intro- duced, By. Subse- quent History. Staphylinid (Huafii- Brazil erocera brasiliensis) (Essiji., 1931) Hymenoptera do. Syntomosphuram in- India dicum silv. Hymenoptera do. Diachasma tryoni Com. Queensla Teirastichus yiffardi- Fiii .... anus Silv. 1904 9 ? Metro])olitan Area Compere Failed 1904 ') 9 do. do. do. 1908 9 250,000 Guildford do. do. 1908 9 9 Metro])o}itan do. do. Area. 1909 9 5,000 Guildford do. do. 1936 50 para- 20,000 Metropolitan Newman do. sitised Area and pupae Darling Range Biological Control in Western Avstralia. 13 As seen from the table, the last parasite tested was Teirastichu-s giffardianus, obtained from Fiji through the courtesy of H. W. t^immonds. Parasitised pupae were safely imported and a number of generations were reared in captivity, thin slices of orange being used to rear the liost maggots. Tlie laboratory colony was kept going until August, 1937, but the overwintering wasps, although apparently well developed, failed to emerge from the pupae and all breeding stock was lost. literature. Baker, C. 190S, “ Fruit Fly Parasites,” Jmirn, Dept. .Agrie. If. Aust. Vol. XVl., p. 27. Compere, G. 1903, “ In Search of Para.site3,’^ ibid. Vol. VIIL, p. 518. Compere, G. 1904, “ The Introduction of the Fruit Fly Parasite,” ibid. Vol. X., p. 68. Compere, G. 1905, “Fruit Fly Parasite,” ibid. Vol. XII, p. 6. Beapeissis, A. ” Acting Directors Report,” ibid. Vol. XIV\, p. 328. Essig, E. (). 1931, “ A Historj' of Entomology,” (X.Y. MacMillan), p. 376. Hooper, T. 1904, " Black Scale and Fruit Fly Paradtei,” Journ. Dept. Agric. (('. Aust. Vol. X., p. 172. Newman, L. d. 1908, “ The Fruit Fly Parasite,” Vol. XVII, p. 561. Newman, L. J. 1909, “ Beneficial Parasites,” ibid. Vol. XVIII, p. 382. Newman, L. •!. 1910, Dept. Agric. 11 . Aust. Bull. p. 38. Newman, L. J. 1916, ibid. Bull., p. 48. Newman, L. J. 1924, ibid. Bull, p. 122. F. MUSCIDAE. Musca domestica Linn. (House Fly) The only record of any attempt at the biological control of houseflies appears in the Annual Report of the Department of Agriculture and Industries of Western Australia for 1911. (Newman 1911.) Sarcopbagid parasites said to control houseflies and blowdlies were introduced from Hawaii, wliere they had been received from Japan. No details are available as to the technique adopted in handling these flies but the insect failed to become established. LITERATURE. Newman, L. J. 1911, Ann. Kept. Dept. Agric. and Ind. 11 . Aust., p. 29. Siphona exigua (de Meij.) (Buffalo fly) The Buffalo fly is believed to have reached Australia about 1825 wlien the first buffaloes were introduced on to Melville Ishinfl. In 1838 they were taken to the mainland and with them, the fly. The possibilities of biological control were discussed hy Handschin (1932) and a summary of the life histor\' of jBpalangla spp. was given. Tlie parasite thought to be most ])romising was .S', sienelaica Graham from Java. A siiecial strain of this species was teste furflier supplies for distribution. In May, further sendings (approximately 3,000 pupae) were received from Brock’s Creek and further releases of flies were made. In June 14 C. F. H. Jenkins. more releases were made and in July, Twa «p.‘:u.«.w;-S:' • •• S ^-}n,r R- a/ A ir (S t ; ^ B^cM0ns Do/n 7 .- 7 . . .'s* V . . .VAv.‘ .• * \ h\. l:v.- : •• : . ; / • • • • ‘ • V • V : ••• ’\'j{ • . , . . , • • • • . I • • H • • • \ c \ • • • * . . • /ZJ» i • \ • ' \ *. 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'• • • a a • , a ' a • • . .• • a a ^ ‘ 4 . * • • a • • • a a \ a a HOMeSTEAD *• * a #, a* I- • • XARHAH^ //S' 26* 'Ettis/ Riwp -a-* .d5 unbitan I^CURIOOS » \V TUMBLACCtot ' tv'*'. •.•••'••••*.• v\V!-’ • •; ; /'Nj.'/- •.:', irtCj •,a "a* •*! ••# aa ajU .• a**a a a , * i - ifl ^ . •• ■ *. a -•'•■• A/< a a • • -a • : ' Kx!*- - • ^ D* a a . a ■ \0^ ip 6LU 0 <.? f7 HanoLnos*^ fSlAf-Oi OiRALOTOM Iny/Q 9 * • • V ^rv • * • • • • f • • • a ■ • V • , a a • a a • ,*1 • . ^v* , iV • • * * • vN/ ••••• %••• »\ jfl'' • a a a ^ir .» . 4 rr Catmofxf' < P'v^’- ■ •'•• ' i; r MEANARRA >4 HILL Locality Map US' HCoI«Y 194! J03D A . “ .r. sto Hi, IWL (*/. ' CVA-^O^iA ■'!^ ?, 3v^'0QV\ iW : j m :.^\C>C\2. *, >vv ■. / Cretaceous Stratigraphy of Loaver Murchison River Area, 19 Western Australia. L— CRETACEOUS STRATIGRAPHY OF LOWER jMURCHISON river area, western AUSTRALIA By E. DE C. Clarke and C. Teichert (Department of Geolog>% University of Western Australia) Read : 12th June, 1945. CONTENTS. I. Introduction Page 1. Previous Work 19 2. Present Investigations ... ... ... ... ... ... 21 3. Geographical Notes 22 IT. General Geology 23 III. Cretaceous Stratigraphy (Murchison House Series) 1. General * 24 2. Tumblagooda Sandstone ... ... ... ... ... ... 26 3. Butte Sandstone ... ... ... ... ... ... ... 32 4. Thirindine Shale ... ... ... ... ... ... ... 35 5. Alinga Beds 36 6. Toolonga Chalk 37 7. Second Gully Shale ... ... ... ... ... ... ... 39 8. Age and Correlation ... ... ... ... ... ... ... 41 IV. Geological History’ of the Area 42 V. Extension of Cretaceous North of Murchison River ... ... 44 \T. Bibliography 45 1. INTRODUCTION. The latest available geological map of Western Australia, published in 1933 by the Geological Survey of AVestern Australia, shows an area ■of Cretaceous rocks extending northward from the mouth of the Murchi- son River almost as far as Shark P>ay, that is between 27°40' and 26°30' S. lat. As practically nothing was known about the succession, thickness, lithology, and fossils of the rocks in this area it had long been our desire to investigate the geology of the lower Alurchison River where good out- ■erops in these little knowui strata were reported to exist. After a preliminary visit to parts of the area by the junior author in 1943, our ■wish was finally realized in August, 1944. 1. Previous AYobk. As early as 1007 the occurrence of sedimentary strata along the lower part of the Arurehison River was noted by Alaitland who described 14157 / 2 / 48—750 20 E. DE C. Clarke and C. Teichert. how, about 20 miles east of the sea coast the river enters a narrow gorge, flanked by vertical walls of sandstone and grit. ^‘The junction between these sandstones and the older gneissic rocks (to the east), as j caix be seen by a seotion on the north bank of the river, is a fault dipping to the west. Tliis sedimentary formation occupies the wliole of the Murchison Valley as far as (Jantheainne May.’’ This fault had been discovered by ^Maitland on an (‘arlier occaHi(m. In 1808, he stated that in tlie vicinity of Hardabut Pool, on the Murchison Kiver, sandstones and grits are exposed a few yards from gneissic and schistose rocks and that the junction between the two series is a fault dipping west. However, Maitland did not then realize the extent of the sedimentary area to the west of this fault. Xeither in 1808 nor in 1907 does Maitland give any indication otfl the ])ossil)le age of the sandstone series, hut in 1019 he refen’ed to it briefly in connection with a description of the Jurassic rocks of Westera Australia. Jutson, in 1904, quoled Maitland's observations and was puzzled by the appearance of a deep gorge in this country. The reason for tliis, he- said, is not apparent. The Hrst indication of lln? presence of fossiliferons rocks in the area was in November, 1929, when Mr. L. Glauert of the Perth Museum received some fossils, collected on ^Vrurchison House Station. These he found to- be identical with species from the Gingin chalk. Nothing was jnihlished about this occurrence, except a brief notic(‘ in the local press. In 1992, tlu' country ju'ar tlu' month of lln^ ^rnrehison Kiver was visited separately liy K. S. Simpson and F. G. Forman. Dr. Simpson, who had been attracted liy a report of jibospiiatie rocks, spent a few days at ^lurcliison House, live niil<*s from (he mouih of the river, and in lb;!!- publislied a note on apatite, bai’ite, and glanconili' from these- beds. In this connection he stated that the :\rurchisnn River flows for about fifty miles througli ji deep gorge before reaching Ganthcaunic Bay. **rhe walls on the south side ot this gorgi- are about 800 feet high and consist essentially of reddish sandstone ( -fiirassic ? ) . The north side is^ somewhat higlu'r, the sandstone being overlaid by glauconitic' sands and shales, end finally capped by clialk, both of pro^'ed G retacenus age.''"' I This latter ])iece ot information was be-^ed on an examinadion by ^Fr. L. (ilanert of sonic fossils colb'cted liy Dr. Simpson, but no fossils were mentioned by nann^ in Simpson's paper. ^Ir. Forman crossed the ^lurchison on camels, travelling from the south I towards Shark Bay, luit the full rc'port of his lilp has never lieen tniblished. Reference was first made lo it in a paper by Hobson in 193(i who says that Foi'inan found (. relaceous sedinnmts overlying a sandstone series, the whole sef|Uence dipping 1® or 2° west. Forman himself briefly refemnl to hi.s- obsenations in a. report in lf)3^, when he ]>roposed a tentative correlatioit of tlu* lower sandstoiu's Avitli the Permian TCennedy 'Sandstones which had then become known from RaggatPs investigations (193(1) in the Carnarvon Natural Region. He recognised the Cretaceous nge of the beds overlying- this sandstone series and noted the ocenrreuce. in tin* vicinity of Mt. Curious,, of lossiliferons clialk containing TTifjonosf tnns^ Cithtrlft, Ostroa,^ and other fossils. Crktackuus iSTiiAXiCiRAPiiY OF LowFil ^luiiCHiaojs UiVFR Aufa, W'estehn Austraeia. 21 ill aub.sequeiil years the junior author frequently crosi^ed this same aixa by aeroiilane; the senior auiiiur liiul already seen it frtiin the air in 1927. i’rom these observations it was clear tliat the h)wer sandstones which could be seen outcroiiiiing all along the boltoni and the sides of the Aliu’chison Ki^er \‘alley were overhiiu by a series of whitish rocks which formed an escarj.ment a few miles noiih of the river and more or less |>aralled to it. These white dill's extended inland at least as far as the l(*leg‘raph linCj more than 10 mih's iqir^tream from the coast, and since Sinqjson's discovery of dialk in th(‘ vicinity ol' Alurdiison llous(‘ I!oine?^tead the conviction grew that llu'se dill's in their entirety were nioie tir less composed ttf the same kind of rock. In ^lardi lil-ld the IJriti.'h ITiosj.hate Commissioners de<*idcd to in\'esli- gate in somewhat greatcu’ detail the phosphate occiii-rences described by Siinjison and the junior author was fortunate enougli to be invited to ac- company the dovernment (Jeologi>t td' Westein Australia, Mr. F. (I. Forman, and th(‘ repi'esentati ve of tin* Hiltish ITiosphate Commissioners, Mi’. J. C. Dulfer, on an exiiloi'atory trip which took jdace in March of that year. The approach to the sedimentary area was made iVom the east, entering the <'Ountry from the Xorthamplon-Caiuarvon road, but very bad conditions were encountered and it was only with dil'Iicidty that tin* party readied the telegraph line at a small, now abandoned, (‘mergtuiey aerodronu', four miles north of Bettie, where* the lelegratih line crosses the river. It was soon found that the country was virtually impas>ahle I'or nuflor cars and since the (larty Avas not e(|uipiK‘d for any other form of transport its radius of acti\'ity Avas small and tin* results ol' tlie triji limited. However, the country along the telegraph liiu* AA'as (examined in some detail from the river Innl as far as the Avliite clilTs in lln* vicinity of the aerodrome, more than four miles from the river. Tin* lower samlstoncs wen* found to be strongly evoss- beddt'd and the cliff s(*clion was found to consist of glauconitic sands, glau- conitic shales and siliceous shales, ovei'lain liy chalk which contained a typical Tapper (h-etaceous (Siuionian) fauna, including Vintavrivnfi and Marsnpifesi. identical Avilh the AA*ell-knoAvn chalk fauna of Cingin, 280 miles to the south. Tn addition, several localities up to a distance of about 20 miles east of the telograpli line were examined, especially the vicinity of Weerinoogudda Dam, the upper ])art of Bungnbandy Ch-eek, and the country as far as Warranjabahlja Spring. 2. lOn-'.SKNT I XVFSTICATIONS. Tn August, 1944, Ave Avere enabled to visit the T.oAver ]^rurchison River .\rea and, hi tlu* sixteen days at our disposal, Ave tried to obtain a general jiiotiire of the geology of the main valley and its tributaries from the coast to a little Imyond tlie (leraldton-Farnarvon telegraph line. AVe also suw' sonudliing ol the coastliiu* irom the mouth of the ii\er to a lioint about ten miles farther north. This Avork was made possible by an invitation from Messrs, lluliert Evans and A. J. Sims of Evans. MaAvley and Sims Avho provided motor transport from Northampton to Murchison House homestead, a distance of seventy-two miles and, 'on the I’cinrn journey, from the Inmiestead to (Jeraldton, a distance of more than one hundred miles. Hu amval at the honn'-^tead a native jniide, ami riding ami ])ack liorses Averc placed at onr disposal I’m* tlie entln* dural ion of our stay. The first week Avas spent in camp at Buhu Avimlinill Avith Mr. Tom Pepper and his family 9 -> E. DE C. Clakke and C. Teicheht. wliose iiitcrofit and local kno^vledg^e greatly expedited our Avork. I't is our p]easaut duty to i-eeord liere oiir indebtedness to ^Messrs. Evans and Sims, to t\[r. E. Hlood, manager ot‘ t\rure]nson House Station, and to Afrs. Blood I'or their li()sj)italily, and to the others on tMurehison House Station who were always eager to help us in our work. Overlapping vertical aerial photograjdis, covering the entire area of our survey were made available to us by the Department of the Army. I ntortunately, we did not leai'ii oL‘ their existence until after our return from the field, they were, hoAVever, invaluable in the linal preparation of tliis report. d. Geouuaimjk.'Al _Notes. The IMurchison is one of the major rivers of Western Australia and is intermittent, as are all rivers in this State between 18° and 30° south latitude. It rarely Hoods more tlian once or twice in a year. It rises about ->*)0 miles inland ami after traversing tlie Pre-( ’ambrian shield for the lirst J/o niile^ oi ils course it enters an area ol sedimeiitai'y rocks near Bompas Hill (about 115° 20' east longitude). Here the river b<'nds shai'ply and piu'snes a general south-AvesI course. At Rocky I*ool about 45 miles soiitli-wcst from Bompas Hill it enters ih-e-t'ambriau rocks which persist ihi-oiigh Galena to IJardabui Pool, which is about 10 nules south- west ot Kocky Pool. Xear Hardabut I'ool the river turns sharplv north and h’avej'.ses a seile'^ ot sandstones which is an extension of the Tum- blagooda San^lslone described in ibis t>aper. Below Ilardabut Pool the river enters a gorge whic-h extends down- stnuim almost as far as Mi. Curious where it turns soulh-Avest and floAvs to the Indian Pceaii in a fairly Avide valley. On the north-Avost side of this parj of tiu* river Hie country rises to a plateau about tiOO feet aliove sea-level which breaks oft towards the river in a steep scarp about 200 feet high lormed ot I ]>per (h’etaceous shales, chalk, and sandstone (text figs. Id and 14). I he edge of tlu* -ccarp is broken by broad valleys (I Life 1). Tls (op is ])rotecle). The surface of this plateau is i^andy and wo did not not:c<‘ any outcrops of durierust such a.s are frequent on the higher plafean. There is. however, a latt'vifie layer Irelow the sandy surface: this is the lateri/ed top of the Tumbiagooda Sandstone which underlies the entire country south of the rhu*r mouth and west of the great bend oi the river. Good exposures shoAving the gradual transition from fhe sandstones lo (he laterite ean be seen in gravel pits close to the point Avhere the road from Murchison Homestead to Ajana reaches he general ])lateau level. The laterite is oVerlain bv several feet of sand which make very “Imavy going” for motor vebiides. The area which we investigated forms part of Ariirchison House ■ ation. It can hv reached liy motor over a verv sandy track from Ajana, the nearest railway station, 35 miles to the south/ Apart from 23 Cretaceous Stratigraphy of Lower Murchison River Area^, Western Australia. this track the country is impassable lor motor vehicles of the ordinary type. JL GENERAL ({EOLO(iY. The Cretaceous rocks fall readily into two divisions; a loiver of sandstonoj mostly reddish and cross-bedded, and an upper of softer, more easily eroded rocks, such as loosely cemented saiulstones, shales, and chalk. As already noted the Miireliison River enters a deep sandstone gorge at the point whei’e it leaves the Ere-Cambrian rocks north of Ajanu. Some glimpses of this gorge can be obtained from the road leading from Ajana to Murchison I louse Station, particularly in the vicinity of Pine Thicket rain-shed, about Id miles XAV. of Ajana and about the same distance S.E. of dleaiiarra Hill. The valley here is shallow and wide and the river o(^cuj>ies an over-dee[)ened gorge of which only the u[>per part is visible from the rain-fihed. This gorge apparently continues to a point south of Aft. Curious, hut farther west the valley widens and erosion has (-ut more dee[)ly into the lower sandstones all the way from Itottie Crossing to the sea shor'^. On the north-western side of the rivei', in this last ]>art of its course, the strata di]> to the X.W. Occasional dips of as much as o"’ have been measured, l)ut these are exceptional. X(t dips were imaisured on the south-eastern side of the river. South-east of the river in this part lh(‘ belt of ('Xj)osed sandstone is not moie than a mile wide, and in many places it is less, whereas north-west of tlu* river it is i-arely narrower than two miles, and, in many places is as much a.s four miles wide. This suggests a regional north- westerly dip. One of the most noticeable features of the sandstone l)elt on both sides of the river is the jointing. AVe noticed the presence of many parallel vertical joints but did not have time to study this fe.a.ture more closely. The iullueiice of jointing on the topogi'ai)hy becomes very clear on inspection of the aerial j)hotogra])hs. Text Fig. 1. Geological section the Murchison valley from Meanarra Hill to the vicinity of kSecond Gully (for location see Plato II.). The strike of the joints i.s between and 140®. Over wide areas differential erosion has taken place along them and cr)use(pienlly the out- cro]'>s are channelled by iuniiimerahlc paralh*] furrows. On the ])hot(jgraphs it can 1)0 seen that they are fi’om about 200 In 400 feel apart. Often they can be followed from decjily erod^ul into less (U'oded comitry, where the^^ may only ho indicated as sti-ips of .slightly denser vegelalion. On the gTound we observed the presence of numerous open joints with their walls ns much as four feet apart. Tu many places it seemed that they were due to tensional movements rather than to erosion. 24 1^]. Di5 C. (4 ^ARIvE and C. PRIORI tile air it can be s: eii tiiat the characleristii' X.\V.~S.Pb jointing' becomes less conspicuor.s a short bistancc' S.K. ol‘ Mt. Curioiis and still higher upstream is com})letely leplaced by a system ol' ])roininent Ph-A\ . joints which becomes more, and more marked towards the boundary of the sandstoiH' ar(‘a near liardabut Pool. The overlying' softer rocks are exposed along an escarpment about two to t'oui' mih^s north-west of the river. They undei'lie the [ilaiii to the north probably as far as Shark Pay. Along the eseai'pmentj gullying is active almost ev('rywher(‘, am; on the whole the esi'ai'pment is jirobably receding at a fairly ratiid rale. That this uiiiier sm’ies once extended across the river towards the south is shown l)y the occurnuice of these rucks at i\leaiiarra JLill Avhicli forms an erosion nmmant abont four miles south of the river (text hg. 5). The escarpment on tlu' north side appioaclu^s tlu' sea coast about five miles north of the mouth of the iMiu’chisou Kiver, where it turns in a direc- tion mor(‘ or less parallel with the coast. The ( istance between the toj) of the escardment and the shore is at lirst a mile or so, but diminishes graduall.y until, north of Nimgajay Spring, it is not more' than aliout 500 yards. Ex- posures idmig the coast arc exceedingly ];oor oAving to a covering of slipped durii-rust on tin* slo| es. There aio clialk ex])osiires in a few places, Imt the nature of the nvm’lying and underlying beds can rarely he ascertained. Text Fig. 2. V\q\v across lower part f)f Second Onlly from slope below Alingca lk)int. Tower shelf is Tiimblagonda Sandstoni' partly covered Avith loose sand, probably disintegregrated Butte Sandstone. In the distance is the scarp of the upper part of the .Aturchison House Scries (Alinga Beds to Second Gxdly Shale). (Traced from ])hotographs.) HI. (’KP]TACE()PS STHATIGKAPHY. (Murchison House Serii's.) 1. (Ikxkuau. 'I he name Murchison House Scrii’s is her(' projnised for the succession of sedimentary rocks which octuirs on botli sides of the IMurchison Uiver from the coast of the Indian Oc('an eastAvnrds to at least a foAV miU*s east of tile tel(‘gra|)h line i.i*. for a distance of aliout 18 miles. The eastern boundary of the ontcro)) area of this series has not yet lieen determinech Southwards the sediments disa[)pear a short distance from the river under a cover of loose sand, but outcrops exist along the coast at least as far as Bluit Point (text hg. (i) and very probably they contiiuu' still I’arther to the south. North of lln^ ri\'er the sediments likewise are covered hy sand, but, along tlie coast, outcrops Avere observ<'d to a point ten miles north of the mouth of the ri\erand th(w seem to extend consid(*ral)ly farther north. All good outcrops of the series and ai! sections studied liy us occur on Murcliison House Station. Cretaceous Stratigraphy of Lower Murchison River Area, 25 Western Australia. The iolloAviiig- subdiA'isions of the Mnrehison House series are here pro- posed : — Name. Lithology. Fossils. Thickness in feet. Second Gully Shale Light green glauconitic shales 92 -h Toolonga Chalk Mr)stly pure chalk, sometimes glauconitic ; in many places with a 6in. layer of phosphatic nodules at the base and Aisually rich in chert nodules in the Aipper part. Foraminifera, Cidaris^ Marsupites^ Uintacri- 71US, Oryphaeai Ino- cera?7ius, brachiopods 35-120 Alinga Beds Glauconitic shales, often sandy and with greensand i)ockets, grading into greensand Beleranites 10-75 Thirindine Shale Whitish to grey, siliceous shale, sometimes more massive and grading into siltstone Very ])Oor belemnite frag- ments, rare 0-63 Butte Sandstone Predominantly unbedded pure ejuartz sandstone, mostly loose- ly cemented or incoherent (“ running sand ”) ; upper- most part usually ferruginous and glauconitic Vertical and oblique burrows, fossil Avood (rare) 75-170 Tumblagooda Sandstone Predominantly ivddish and purple sandstones, as a rule strongly cross-bedded, but grading into well-bedded sand- stones above Vertical burrows and in- vertebrate trails on bedding planes 400+ Text Fig. 3. Selected (3ohimaar sections of the Murchison House Series above the Tiimblagooda Sandstone. The positions of these and other measured sections are indicated on Plate II. 26 E. DE C. Clarke and C. Teichert. Thickyiess . — Owing to tlu^ fact that the base of the Timiblagoocla Sand- stone is not exposed and also ])ecause of tlie lateral variations in thickness of most of the higher stages of the series^ it is somewhat difficult to give a reliable estimate of the total thickness of the IMiirchison House Series. Near the nortliern end of Second CJnlly 355 feet of sediments are exj^osed above the toji of the Tuuiblagooda sandstone. However, some members of the series, particularly the Toolonga Chalk ami the Alinga Beds, are thinner here than (‘ls(*where, so that the total thickness of the beds in other sections might well be somewhat greater. To this must he added the minimum thick- ness of the Tumblagooda sandstone (4IH) feet). It may then be concluded that the minimum thickm^ss of the IMurchison House Series in the area sur- veyeil by us is at least 75(1 feet. 2. TrjiULAGooDA Sandstone. Derivation of //uau'.— Tumblagooda Hill, on the coast two miles north of the month oi' the Mniadiison Jliver, about 290 feet high, where a typical section is exposed. Areal distribntion and ontvyopf ^. — The Tuinldagooda Sandstone crops out on lioth sides of tlie Arnrehison River (text fig. 4). On the south-east Text Fig. 4. River flat near Tutula windmill showing hillocks of Tumbla- gooda Sandstone. Cretaceous Stratigraphy of Lower Murchison River Area, 27 Western Australia. side the outcrops disappear at the edge of the sand j)lain at about 400 feet above sea level, in most places about a mile or so from the river bed. On the north-west side the belt of outcrops is wider, in places up to four miles wide, and towards the noiih the Tumldagooda Sandstone disappears under the Butte Sandstone and higher formations. The out- crops are generally good. The sandstone is strongly dissected by erosion and can be studied in numerous clift's along the river, along hill slopes,, and in the many tributaries. The Tumhlagooda Sandstone must have a wide distri])ution outside the area of our investigations. It seems to form the coastal elitfs as far south as one can see from Tumhlagooda Hill and other elevations north of the Miircliison River, that is for at least 12 miles as far as and beyond Bluff Point, but ])rol)ably much farther (text figs. 5, (3, and 7). Xo outcrops of the sandstone can be seen along the coast north of Tum- l)lagooda Hill, the lower parts of the coastal cliffs being liere entirely covered with younger formations (sand and ^‘coastal limestones”). In an easterly direction the Tnmblagooda Sandstone certainly continues beyond Mt. Curious — we mentioned under ^‘Previous Work’’ tlie deep gorge cut l)y the ■Murchison River, and the formation can be followed along Bungabandy Creek and still farther east. It was seen by the junior author in Ifilfi as fai’ east as Wai'ranjahaliba Spi’ing, 19 miles E.S.E. of iMt. Curious. Maitland reports that we.st of Ueraldiue at llardabut Pool, in the groat soutliern bond, the sandstone is faulted down against pre-Cambrian rocks, and, though tlie geology along the , Murchison River downstream from Hardabut Pool to the area wliieh Ave ha\'e mapped has Text Fig. 5. View from one of the low hills in Fig. 4 looking south across Murchison River to Meanarra Hill. 28 E. DE C. Clarke and C. Teichert. Text Fig. G. J^ooking south from sand hills west of Tumblagooda to Bluff Point vs'hioh is probably Tumblagooda Sandstone. Text Fig. 7. Looking south-east from the scarp just north of Thiriiidine over the Murehisoii valley to the saiidplain which is underlain by Timibla- gooda Sandstone. not lieeu studied, from tlie air it can be .seen that outcrops of sandstone 5ire continuous on botli sides of the river as far as Mt. Curious. Scope, rile base of the Tumblagooda Sandstone is not exposed tmy- wliere within the map area. Its upper limit though not as n rule well Cketaceous Stratigraphy of Lower Murchison River Area, Western Australia. 29 exposed, is clearly detined by a succession of well-bedded reddis.h and white sandstones and the contact with the overlying imbedded, incoherent lower part of the Unite Sandstone is sharp and well marked. L'itholog }}. — Seen from a distance outcrops of tli(‘ Tiunblagooda Sand- stone have the appearance of l)eing very Ibick-bedded, with bedding ])lancs ten or twenty or more feet apart, but closto- insj>eetion shows that nearly all ther,e thick beds are eery strongly and irregularly cross-bedded (text tig. 8). The bulk of the sandstone is reddish to ])urpiish in colour, but in many ]>laces, where it is very finely laminated, white layers alternate with red. (hi the whole the sandstone is medium-grained Text Fig. 8. Typical Tumblagooda , Sandstone near foot of east side of Tumblagooda showing cross-bedding and (aho\’e and to right of pick) worm burrows. Honeycomb structure in upper right cornei is due to weathering, not to worm burrows. with grains up to 1 or 2 mm. diameter. The components are predomin- antly quartz grains. Bands of pebbles of varying sizes, up to 1 or 2 cm. diameter are not uncommon, but larger pebbles of several centimetres in diameter are rare. Many of these large pebbles are surrounded by 30 E. DE C. Clarke and C. Teichert. bleached xonos as much as 10 ein. wide. Bleached spherical spots of any- thing lip to Li or d cm. diainetei' may also appear anywliere in the reddish sandstone. As regai'ds the cross-bedding, the inipi'ession was in general that the prevailing dip was in a westerly direction. We had not time to get sufficient data for a thorough statistical analysis, but about 50 measurements in the vicinity oi iMurchison House Homestead suggest that the source of the sedi- ments, at least in this locality was a p])roximately from the E.S.E. The di[) of th(‘ cross-bedding rarely exccaals about 20° Towards the top the cross-bedded sandstones change gradually into well bedded, more shaly sandstones (text lig. 9.) The transition is very gradual: At first a few horizontally bedded sandstone layers are intercalated between strongly cross-bedd(al strata; then the hoiizontally bedded layers become thick(‘r and more numerous and freqmmtly shaly, and cross-bedding becoines sul)(jrdinate ; also the red colour becomes less prominent, the horizontally Text Fig. 9. Well-bedded sandstones above Xats Flat (marked on Plate I.) forming the top part of the Tumblagooda Sandstone. Cretaceous Stratigraphy of Lower Murchison River Area, 31 Western Australia. bedded layers being- either whitish or brown. This transitu)n zone was only seen well in a few ])laceSj e.g‘, in the Pillarawa section and at Second Gulb/ Point, where it is aiiproxiiuately tio feet thick. In many ])laces detritus derived from the rather incoherent overlying Butte Sandstone conceals the higher part of the Tuinblagoodu Saruistone. At Tmnblagooda Hill itself the upper part of the sandstones is well exposed and here includes a 20-foot band of rather massive l)rov'nish. strongly cross-bedded sandstone which is intercalated in the well-bedded series, and makes the transition zone at least 60 feet thick in this ]dace. The sandstones exposed east of ^It. Curious, in the up])er reaches of Bungal)andy Creek and in the vicinity of Warranjababba Spring are fine- grained and thin bedded and cross-tx'dding is not much in evidence. It is at present impossible to say whether these are exjiosures of the normal facies of the top section of the Tumblagooda Sandstone, or Avhether a change in the character of tlie whole formation takes place in an eastwaial direction. Fossils . — The only fossils in this sandstone are invertelirate tracks and vertical burrows. The latter are iiarlicularly prominent and occur at many horizons throughout the entire secjiumce. Tliey were observed in more detail in the vicinity of “Stone Wall’’ at the foot of Toohmga Iknnt, in the out- crops below the cliffs between Tliirindine and Toolonga, in Second Gully, and in the Tumblagooda Tlill s(‘ction where several horizons with man}- bur- roAvs were seen. The burrows now form eyliuders wliicdi arc either filled Avith sandstone of a different colour from that of the surrounding rock, (for example they may consist of red sandstone penetrating laminated red and Avhite rock), or are merely made evident on cliff sides by rlifferential Aveathor- ing. They are always vertical and g(merally have a diameter of one half to one inch, although diameters up to two inches have hovn obstwved. They may be up to eight inches long, Init are mostly shorter. They are generally restricted to sandstone layei*s Avhich are tAA'o to four feet thick, and there is usually a considerable thickness, rarely less than 20 feet, bet\A'een suc- cessive burroAv horizons. \ The burrows are frequently rather crowded: in one horizon in the Tumblagooda Hill section 100 burrows were counted on a surface measuring 50 X 50 cm. On the bedding planes the place of a burrow is indicated by a little mound. Invertebrate tracks along bedding planes have been observed only in one locality, a low hill east of Tutula Avindmill where the inclined bedding planes of the cross-bedded sandstone are densely covered Avith meandei'ing trails which are six to eight mm. wide and stand out in low relief above the bed- ding plane; they are characterized by a sharp furrow in the middle and may have been made by gastropods. Thickness . — Since the base of this sandstone has not been discovered its true thickness cannot be stated. The plateau level on the south-east side of the river is about 400 feet above the sea and this may be taken as the approximate maximum exi)Osed thickness in the area of our investigations. This, hoAvever, must be taken as a minimum figure, for l)y extending the survey towards the south-east a somewhat greater thickness would probably be obtained. 32 E. DE C. Clarke and C. Teichert. 3. Butte Sandstone. Derivation of name . — Small prominent conical hill (butte) on south side of Second (hilly (text fig’. 10), where the greatest thickness (170 feet) of this sandstone was measured. Text Fig. 10. Second Gully seen from the north. In the centre is the butte with capping of Thirindine Shale, underlain by Butte Sandstone which extends nearly to tlie \alley floor. The scarp on the other side of the valley consists of Toolonga Chalk and Second Gully Shale. In the foi'eground is the hardened surface (duricrust) of the latter. Areal distribiiiion. and outcrops . — The Butte Sandstone forms the base of the scarp everywhere north of the Murchison River and can be traced all the way from the telegraph line to Mullewa Point, a mile or so from the coast. From the foot of the scar]> there extends a strongly dis- sected shelf of varying wddth which is covered with hiose sand, consisting, at least in jiart, of disintegrated Butte Sandstone (text fig 2). Although part of this loos(‘ sand may be derived from the to]> layers of the Tum- blagooda Sandstone, the whole of this shelf area has been included on our map in the upper part of the Gretaceous series which begins with the Butte Sandstone. The Butte Sandstone is not exposed along the coast, 'where it is probably buried under younger deposits of sand and “coastal limestone.” There is reason to suppose that it forms the base of Meanarra Hill, south of the Murchison Kiver, but no exposures have been seen. CnETACEOUS Stratigraphy of Lower Murchison River Area, 35 Western Australia. Scope . — The bnse of the Butte Sandstone is rarely well exposed, though, it is sharply detined by the sudden change from the lliin-bedded upper- most layers of the Tumblagooda Sandstone. The upper boundary with the Thirindine Shales is mostly sharp (text lig. 11), though occasionally a more gradual transition can be detected on closer inspection. The Text Tig. 11. Butte Sandstone and Thirindine Shale in scarp just west of emergency landing-ground. The boundary between the two forma- tions is marked by A. The top layer of the Butte Sandstone is here somewhat ferruginous and, therefore, harder. Butte Sandstone thus includes all the strata between the uppermost layer of the well-bedded upper part of the Tumblagooda Sandstone and the base of the grey, siliceous, and mostly whitish-weathering Thirindine Shales. Lithologically the Butte Sandstone is rather uniform throughout, 1 eing generally a whitish, imbedded, and incoherent deposit of quartz grains— in most places, inde(‘d, a ‘‘running sand.” The quartz grains have diameters of uj) to 3 mm. Tn the Toolonga section traces of cross-bedding can be seen, as well as occasional pebble bands with little pebbles not more than about 6 mm. across. Tn the Thirindine Point section the base of the Butte Sandstone is a deposit of three feet of massive, well cemented, mottled sandstone, with ferruginous patches and 34 E. DE C. Clarke and C. Teichert. large (iiiartz grains. In view o£ the fact lliat the base of the Butte Sandstone is in general nut well exposed, being buried under loose material slid down from above, it is not known whether this mottled sandstone zone has a very wide distribution. In the uppermost ID feet or so tlie loose quartz sand changes into glauconitic and ferruginous loosely cemented sandstone. South-west of Tooloiiga Point, at Thirindine, and in the gully north of \althoo windmill there is a somewhat gradual transition to the over- lying Ihiriudino Shales j the (pmrtz sand first becomes glauconitic, and the size of the quartz grains gradually diminishes until the deposit becomes a glauconitic clay; tlien the glauconite disapj)ears and the transi- tion to the overlying shales is complete. Farther south-west, at Second Gully Point, the I:oundary Avith the overlying shales is better marked, the top of the Butte Sandstone l)ping a broAva loose sand with ferruginous concretions. F'ossils. fossil Avond Avas found in a few places in the u[)permost two feet of the Butte Sandstone, notably to the south-west of Toolonga Point and at Thirindine Point. Some of the wood fragments are riddled Avith cylindi i<'*)l huiiOAA's, ju'ohahly made l)y a 7 crcdo-like mollusc. Their presence suggests that the Avood must have drift(‘d for some time hefoi’e it became ■embeddeil iu the saud. Very poor silicified l)e|{‘mnite fragments were found in the dills west of the emergency aerocli*ome four miles north of Bettie. Definitely recognizable tracks and burroAvs \vcrc only seen in one place in the hard (juartz sandstone layers near the top of the Butte Sandstone in tlie Pillnrawa st'ction. Vertical and oblique burrows, up to one inch Avide, jienelrate this sandstone bed to a depth of one to 10 inches. On the kedding plane the entrance to these hurroAA-s is surrounded by circular walls Avhidi are Iavo to three mm. high. In addition, the bedding plane is covered l)y a network of shallow, sometimes winding, but more often stiaight i iiri'OAA s, obviously the trails of some crawling iiiA’ertebrates. Most of these trails seem to bypass the openings of the vertical buiTows, but some issue trom them, so that it is reasonable to assume that both ImrroAvs and trails have been made by the same kind of animal, most probably a worm. ' ’ In the running sand of the Toolonga section long tube-like structures were observed AAdiic.h are about five mm. wide and up to 10 and 15 cm. long and are either vertical or inclined up to an angle of G0°. They aie foimed of sand grains Avhich are very loosely cemented and are occasionally brought out by Aveatheriug, the surrounding matrix being ' quite incoherent. Tt is believed that these structures are also due to the activities of some burrowing animals. TJiiclaiess.~The thickness of the Butte Sandstone varies rather consider- ably. In the PillavaAva section it is about 100 feet, farther east the sandstone is not sufiieiently well exposed for measurements of thickness to be taken. Farther west in the Toolonga Hills the thickness increases from M to lOo feet in a Avesterly direction. From there it increases probably rather regularly until it reaches 170 feet at the butte in Second Gully, the maximum thickness measured, and 152 feet at Second Gully Point. At Meanarra there must be about 50 feet of Butte Sandstone. Cretaceous Stratigraphy of Lower Murchison River Area, Western Australia. 35 L Thirindine Shale. Derivation of name . — Thirindine is the name of a prominent point in the scarps north-west of the Murchison Kiver, due north of Yalthoo Wind- mill. Areal distribution and outcrops ,— Thirindine Shale crops out all along the scarxis north-west of the INIurchisou River. It can he traced almost without interruption from Second Gully Point in the south-west to a i^oint about one and a half miles east of the telegraph line where the outcrops dis- api)ear under the vegetation cover and have not been traced farther east. In 1943, however, the junior author located an extensive outcrop area of these shales in the vicinity of ^Veerinoogudda Dam, about eight to nine miles farther X.X.R., whence it continues for a distance of about six miles to the south-east along the track to Warrfinjal)abba Siu'ing as far as a point about SIX miles north-east of Mt. Curious and about four miles north of Bungabaiuly Creek, near the eastern boundary of ^lurdiison House Station. Prom the air it can be seen that good outcrot>s of the shale extend X.E. and E.N.E. of Weerinoog^udda Dam for a distance of three to four miles. In the west, the Thirindine Shale is absent west of Second Gully Point and in the interior of Second Gully, l)ut south of the IMurehison River small patches were found on the north side of IMeanarra Hill. Scope . — The Thiiindine Shale is always easily recogonizable because it weathers with a whitish surface. Its lower boundary is mostly fairly well defined, although in certain ]»laces there is a transition zone, one or two feet thick, from the underlying Butte Sandstone. The upper boundai*^' against the glauconitic Alinga Beds is mostly quite sliaiq^. Lithologp . — The Thirindine Shale is a very tine-grained dcfiosit, usually of greyish colour. In | laces it consists of alternating softer and harder layers, the latter usually being whiter. However, the softer, greyish layers also harden 4)n exposure and form a whitish surface. This surface-harden- ing causes the Thirindine Shale to be less easily ei*od(>d than the softer sedi- ments above and below, so that it forms a characteristic teiTace in the jirofile of the slopes along which it crops out. In some x:)laces, the shale contains some glauconite. This is particularly marked in the scarp on the north-east side of Second Gully where its glau- conite content increases gradually upwards so that there is a transition to the overlying glauconitic Alinga Beds. Glauconite was also observed else- where in the Thirindine Shale, for example in the Toolonga Hill section, but it is usually subordinate. Fossils. — Remains. of fossils were found only in the lower part of the shale at Toolonga Hills, where hard bands contain cavities left by belemnite guards which have been dissolved by eirculating waters. In places where the shale is glauconitic a peculiar vermicular structure of the senliment was observed which is believed to be due to tlu' action of mnd-burrowiug organ- isms, probably worms. Thickness . — The thickness of the Thirindine Shale varies greatly. In the east, east of the telegraph line, it is 18 feet thick, and just west of the line, near the emergency landing ground, it c^ecreases to five-and-a-half feet, 36 E. DE C. Clarke and C. Teichert but farther west it iiica*eases again until it reaches a maximum of 60-63 feet at Tooloiiga Hills. At Thirindiiie it is still 52 feet thick, but from there westward the thickness decreases somewhat irregularly. In the Butte sec- tion in Second Gully it is still 35 feet, but at Second Gully Point it has- dwindled to three feet and at Alinga has disappeared. At Meanarra this- shale is about 15 feet thick. 5. Alinga Beds. Derivation of name. — Alinga, four-and-a-half miles N.W. of Murchison Homestead, is a prominent i.>oint in the chalk scarps, a little more than a mile north of Mullewa Point. Areal distribution and outcrojys.— The Alinga Beds could be follorved from Mullewa Point in the west to the eastern termination of our survey area, one-and-a-half miles east of the telegraph line. They form an easily recognizable zone of dark rock between the whitish Thirindine Shales below and the chalk above, but actual outcrops are poor, owing to the softness of the rock. Tliere is much slipping so that it is often difficult to get a correct picture of the lithology of the beds. Gully erosion and subsurface erosion are cutting strongly into this zone and removing large (|uantiti)‘s of it. About nine miles to the north-east of the area mapped the junior author found the Alinga Beds overlying the Thirindine Shales- at Weerinoogudda Dam where they form the top of the escarpment north of the dam. The Alinga Beds are also probably present at Meanarra Hill south of the Murchison hiver; no good outcrops have been seen but they most probably occur in a zone with no outcrops between the toj) of the Thirindine Shale and the base of the chalk. LithoJo(jif . — The Alinga Beds consist of dark green, always strongly glauconitic clays, shales, and sands. In general it seems that sandy components predominate to the noHh-east and that towards the south- west the beds become increasingly clayey and shaly. At Weerinoogudda Dam, nine miles north-east of our survey area and* 21 miles east of the coast, the Thirindine Shale is overlain by greensand Avhieh forms an escarpment immediately north of the dam. No higher strata are exposed in this \'icinity. Immediately west of the telegraph line, in the vicinity of the emergency latiding ground, the Alinga Beds are predominantly shaly, but farther west in the PillaraAva section they are sandy through- out the lower 15 fe(d, changing intn shales above which contain a number gypseous layers. Still farther west at Bracken’s Point the top of the Alinga Beds is formed by reddish Aveathering clay which changes down- ward into clayey greensand. In the Toolonga Hill section and to the west thereof the Alinga Beds change into almost pure glauconitic clay Avhich liere and there may contain beds or pockets of glauconitic sand such as are well exjioscd near the butte in Second Gully. At Alinga I oint (text fig. 12) the predominating sediment seems to be a very fino sandy clay or shale of very niiiform lithology. Fossds. The only fossils seen in these beds are belemnites, probably of the genus Dimdtohelus, which occur in great quantity at Alinga Point, but also at Thirindine Point and in the south-western part of the Toolonga Cretaceous Stratigraphy* of Lower ^Murchison River Area, 37 Western Australia. Text Fig. 12. Alinga Point. The darker greensands of the Alinga Beds forming the lower part of the slope are overlain by light-coloured Toolonga Chalk. Hills. The pri'sei-vation of these fossils is as a rule very poor, the guards Aveatherinsr (‘asily on exposure. Thicl'ii^ss . — The thickness is small in the east. East of the telegra])h line it is only 18 feet, increasing gradually to about 75 feet in the Pill- uraAva section. West of this there is again a decrease in thickness to 10 feet near the west end of Toolonga Hills followed by a rapid increase in the cliffs north of Yalthoo windmill to 00 feet. On the east side of Second dully the thickness has decreased to 25-30 feet and nenr Alingii it increases again to 55 feet. At M'eanarra there are about 22 feet of Alinga Beds. (). Toolonga Chalk. Derivation of name . — Toolonga Hills is the name of the highest ])art (about OOO feet above sea level) of the scarp 7iorth-west of the 5furchi- son River. This scarp of Avhite rocks is visiblf' from the plateau south of the river many miles away. Area] (llstrihnfion a^irl ontcrops . — The Toolonga Chalk is widely dis- tributed over the area. It forms the top of the coastal cliffs north of the ^rurcl'i ;nn River at least as far as several miles to the north of Nungajay S]n'ing% hut probably mueh farther. Outcrops along the coast are not good, because the slopes are everywhere covered with a crust of hard secondary travertine (“duricrust’’) and the chalk can only he 38 E. DE C. Clarke and C. Teichert. seen in a few places where this hard crust has been removed. North- west of the Murchison Kiver the chalk can be followed along the whole- length of the scarps from Mullewa Point in the west to a place about one-and-a-half miles east ot the telegraph line and the outcrops are generally very good (Plate 1). There is much slumping in the chalk, mainly owing to the slippery nature of the underlying Alinga Beds. The result is that in places the entire slope of the escarpment down almost to the top of the Tuinhlagooda Sandstone is covered Avith slumped chalk (text hg. 13). The eastern limit of the Tuolonga Chalk has not Text Pig. 13. Looldng south at the scarp of the upper part of the Murchison House Series from the site of section 3 near north end of Plate II., with Jannawa and PiUarawa Hills in the middle of the picture. yet been determined. xVs seen from the air a conspicuous belt of thick scrub Avhich chai'acteri/.es the lop of the chalk scarp, bends sharply to- the north-east east of the telegraph line; it is most likely that this marks the edge of the chalk outcrops. Parther east remnants of the chalk may occur in 2 )laces as, for example, in the durierust which coA^ers the Alinga Beds on top of the escarpment just north of Weerinoogudda Dam, about nine miles N.N.E. of the (‘astern end of the area of our surA'ey. South of the Murchison Kiver small outcrops of the Toolonga Chalk occur on the north side of ^Mcanarva Hill. Scope . — The Toolonga Chalk forms an exceedingly avoII defined zone. Its loAver boundary is rarely Avell exposed, but when seen (as in text fig. 12), seems to be sharp, though sometimes someAA’hat undulating. In the eastern half of the area mapped the chalk forms the top of the scarp north-Avest of the Murchison Kiver, ])ut in the Avest it is overlain by shales (Second dully Shales). The boundary is rarely exposed, but in general the transition from the chalk to the shales seems to he rather sudden. Lithology . — Lithologically the Toolonga Chalk is rather uniform throughout the entire area. It is a yelloAvish-Avhitc, massive, usually rather coherent rock Avhich, however, AA'eathers easily on the surface. At its base it contains in many places a layer of phosphatic nodules, usually not more than six inches thick. The nodules themselves are of irregular shape and are often geode-like, Avith chai’acteristieally cracked surfaces. The lower part of the chalk above the phosphate layer is as a rule very pure and Avhere fossils occur they are Aisually more numerous in this loAver part. In many places the upper part of the chalk is rich in chert Cretaceous Stratigraphy of Lowtbr Murchison River Area, 39 Western Australl^. nodules vliicli may reach large sizes, measuring sis inches and more across. Concentration of chert nodules in the upper half of the chalk was observed especially at Toolonga flills, hut farther west at Alinga Point the chalk is cherty throughout and chert nodules are numerous in the first few feet above the basal iihosphatic layer which is here well developed. Fossils, — On the whole the Toolonga chalk is rather fossiliferous although the distribution of fossils is very patchy and irregitlar. Fragments of Inoceramus shells are ubiquitous, but entire shells are quite rare. As a rule the lower half of the chalk is more fossiliferous than the uiq>er, but this does not hold everywhere because in some sections, such as west of the emergency landing ground, fossils are (juite ijlentiful in the upj)er half of the chalk. In addition to Inoceram-us the only common pelecypod is Gnjpliaea (^*Pycnodonta^’) ginginensis (Etheridge) which occurs in great quantities at Pillarawa and elsew'here. Other common fossils are the brachiopods Trigonosemus acanthodes Etheridge and Mogadiiia cretacea (Etheridge), and echinoid spines, probably belonging to Cidaris comptoni Glaueif, of which a few interambulacral plates were also found. Very important members of the chalk fauna are Mars}i piles and Uintacrimts whose detached plates are locally very numerous. Of the former genus there are two distinct types of calicular plates: one resembles the common Marsupites testiidmarius (Schloth.) of the Northern Hemisphere, both the smooth and the ribbed variety being present; the second ty])o of plate is considerably lai'gcr and indicates a calyx about twice the size of that of mature specimens of M. tesfudinarlus. These plates are always smooth. They might well repre- sent a new species of this interesting genus. Foraminifera are abundant but have not yet been studied. Following is a list of the non-foraminiferal fauna (preliminary deter- minations only) : Cidaris compt&ni Glauert, Marsupites testuddnarius ( Schlotheim) , Marsupites nov. sp., Uintacrinus sp., Serpula gregaria (Etheridge), Trigono- semus acanthodes (Etheridge), Magadina cretacea (Etheridge), Grijphaea ginginensis (Etheridge), Inoceramus sp., Ostrea sp., Sx)ondgliis sp., hclemnite fragments, Scilhdepas ginginensis (Etheridge) . Thickness. — The gi’eatest thickness of chalk, 320 feet, was measured just west of Jannawa, a small residual hill north of Pillarawa (text %. 13) ; of this thickness 20 feet is dnricrust and wc do not feel quite certain that part of this might not. consist of altered Second Gully Shale. However, even in that case the thickness of the chalk cannot be less than 100 feet. East of the telegraph line the thickness of the chalk is slightly more than 00 feet, but west of Pillarawa it decreases to little more than 35 feet at Toolonga Hills. Farther west it increases again to 55 and G5 feet at and near Thirin- dine. In Second Gully the thickness is again less (25-35 feet), hut at Alinga it has increased to 55-60 feet. At Meanara there are about 70 feet of chalk. 7. Second Gully Shale. Derivation of name. — Second Gully is the name of the valley of one of the northern tributaries of the Murchison River about three miles from 40 E. DE C. Clarke and C. Teichert. the sea coast and clue north of Tutula windmill. The shale is well exposed all along the sides of this valley. Areal distHbution and oatcrup.-^.^Thv S(‘eojid tlully Shale is of somewhat limited distribution. Jt is absent from the north-eastern halt of the area where it has been removed by ero.^iim. Owing to the general Avesterly dip of the entire sedimentary sei’ies it begins to appear above the chalk in the Toolouga Hills seedion. The oiitci’ops are here very poor', because the thin cover of shales is almost entirely indurated and penetrated by travertine. The appearance ot' the diiricrust is liere that of a travertine (or ^‘caliche*’) in which fragments of porcellanized green shales are embedded. West ot‘ Toolonga Hills the thickness of the shales increases, owing to the general north-Avesterly dip, and they are well exposed in Second Gully, in the valley between Second Gully and the coast, at Second (inlly Point, and at Alinga. They probably form the top of the coastal cJitTs north of the Murchison Kiver, but the durierust layer is here very thick and no outcrops of the shale were observed. South of the Murchison River the Second Gully Shale occurs at Meanarra Hill, where it forms tlu‘ top of the series, but is poorly exposed owing to heavy duri-, crust formation. Scojie . — Tile Second Gully Shale forms the highest beds of the Murchi- son House Series, in the mapi>ed area. Its contact with the Toolonga Chalk is never well exposed, owing [lartly to induration of the beds near the top of the scarps, partly to heavy slumping of the fine-grained rocks along the slopes (fig. 14). Text Fig. U. Chalk slips in the scarp west of Toolonga. Tlio chalk is in s!ta only near the top of the scarp. CkETACKOUS STliATlGliAPHA' OF LOWFR MUKCIIISON KiVER AeEA, 41 \Ve STE HN AuST 11 a lia . Litliohxjji . — As I'ar as (•<)ul(i !)(.* ast-artaiiual the lithology of this shale is very uiiilonn throughout the area of its oecurreuce. It is a very fine glaueonitic shale which seems to be devoid of any admixtures of other rock types. Fostyils , — Xo fossils were found in this shale st'ries. Thivimexfi . — The greai('st thicknesses of the Second Gully Shale were measured at Aliiiga (7o feet), along the east side of Second Gully near the Butte (92 feet) and north of Thirindine (80 feet). From here the thickness decreases eastward owing to the general rise of the strata in this direction. It was not observed anywhere east of Toolonga Hills. At ^leanarra Hill, south of the Murchison Kiver, about 45 feet of the Second (Jully Shale are pi*eserved. H. Auk axu Goruklatiox of the iMriuuiisox IlorsE Series. The only i)art of the Murchison House Series which can be accurately dated by means of fossils is the Toolonga CTialk. The occurrence of and riiitacrhius characterizes it dehnitely as an e(iuivalent of t]i(‘ Santonian stage of the Fi^Jcr Cretaceous. As to the remainder of the se(juence, more particularly the various sandstone and shale series below the chalk, no definite conclusion can bo drawn. From general considerations of the nature <4' these sediments it seems, however, unlikely that strata of an earlier age than Cretaceinis are present. Tlte whoh‘ sei|uence of rocks is conformable ami there are no major hreaks in the sedimentation ju'ocesscs. On the wlioh* there is a gradual change freiii i oarse-grained m-ar-shon* to tine-grained off-shore sediment«. The total (^x'i)osed thi<'kn(‘ss of beds below the chalk is less than 790 feet to which must be addcal an ludviiown thickness of I'ocks below tlie low^'St ex- posed beds of tile Tiimblagrjoda Sa!id>t(>ne. ]lowev(‘r, lliesf* lower sand- stones must have be(m dot)osit(Ml faii'ly rapidly and the time rcpres(‘nted by them cannot lie \(’ry long. From sucli general consichu’atioiis it might ))e concluded that sediment- ation in the area began ju-obably not before tlie lieginning of Ulipor Cretaceous time and ceilninly not eai’livr than some time in tin* Lower ('ndaceous. Contemporaneous deposits are widespread in M^estern Australia in a coastal belt betw('cn about 22*^ and S. hit,, seldom extending more than fifty miles inland from the shores of the Indian Ocean. The Tooloinra Chalk can (easily b(‘ (‘orrelaled with litliologically similar deposits at Gingin and at nandarragan, 00 and 100 miles north of Perth. (‘Iialk de[)osils occur in these placi's with a maximum Ihickiies.s of about 70 feiT, carrying a fauna idcntii'al with that of th(‘ Toolonga Chalk. However in both places ihc tliickncss of the ('I'ctaceous lagL is smaller and the whole sequence ap- imrently mucli less com])Iet('. Both at Daiidarragan and at Gingin the chalk is sandwiched between green>nnd^; a l.owcr Greensand which is 20 feet thick at Gingin and up to 70 feet at Dandarragan, and an Tapper Gr(‘ensand of which 140 feet are exi'osed at Gingin and less at Dandarragan (see Clarke, Teichert, and Pridcr, 1944, p. 274. and Teichert and Matheson. 1944, p. 168). The TAnv('r Greensand is most ])ro})ably contfmpioraiu'ous with the strongly glancoiiitic Alinga Beds of the iMurchison TTonse Sicries, but fartlier 42 E. DE C. ClAHKE and C. TeiCHE1{T. down ill the sec'tiou tlie })ni’:ill('lisni ct-ases. The gTeeuMand-elialk series at Gingin rests on sandstones Aviioso age has recently been determined as Jurassic (Walkom 1944). BeloAV the Lower Greensand at Dandarragau is a series of sandstones (jirobably several hundred feet) of unknown age, tentatively assigned 1o tJie Jurassic liy Forman (lOJo). In both sections there is an abrupt change in setlimentation from these lower sandstones to the greensands underlying the chalk. It would thus seem that these sandstones are no-t to be correlated witli the lower sandstone series (Tumblagooda Sand- stone and Butte Sandstone) of the Murchison House Series, but are- older, aud that no equivalents of the strata below the Alinga Beds are found in the south. Sandstone which is lithologically similar to the Tumblagooda Sandstone occurs in many places lietween Geraldton and Northampton, particularly in the \ icinity of Gakabella, on the railway line 20 miles north of Geraldton, but no survey of this sandstone area has been made. Another area of fairly Avell known Cretaceous stratigraphy, dis- covered by liaggfitt (193(1), is situated more than 300 miles north of tlie l\riirclii.son Fiver in the (Ardabia Range, south of Exmouth Gulf. Stratigraphical and ])a]aeontological information regarding this district is still fragmentary, but from published accounts (Raggatt 193G, Crespiu 1938) it seems evident lliat there is a considerable thickness (up to 800 feet and perliaj)s more) of chalk, ('ha1ky clays, and marls which underlie a greensand deposit witli ammonites of IMaestrichtian age (Spath 1940). It Avouid thus seem that much of the ehalky dei>osit is of Senonian age (Campaniau aud older) and, judging from foraminifcral evidence (Crespiu 1938), might also include Tiironiau e(iuivalents. From tlie Cardabia Range the t'retuceous extends southward as far as- the Gascoyne River where chalk and other rocks have been recognized in bores. Nothing is at present knoAvn about the possible continuation of this Cretaceous belt along the east side of Shark Bay, but in the vicinity of tin* southern end of Shark Bay there are numerous (Aitcrops of white shale which undoubtedly represent some part of the Cretaceous. That most of the sand plain between Shark Bay and the Murchison RLer may be underlain by (h*eta.(*eons sediments will he pointed out beloAv. It is thus possible that a more* or less continuous belt of Cretaceous sedi- ments extends from somewhere south of the Murchison River northward as far as' Exmonth (iulf. IV. GEOLOGICAL HISTORY OF THE AREA. At stnne time during the koAver or eaily Ui>per Cretaceous an area of some relief must have (*xisted east of the area under revieAv, the coast running someAvhere ea^t of E. long, A large river fioAving to the Avest or Avest-north-west entered the sea, approximately where the present lower course of llic IVlurchison is situated, and liuilt up a large delta Avhich was gradually pushed Avestward. The size of this delta Avas at least 1,099 square miles, though it may have been much liigger. Only some pai'ts of the western half of this delta liaA’e been investigated and from tin* uniformity and smallness of the sand gi-ain.s one may conclude that, when this part was being built, the river furnishing the sediment drained a Avide ])Iain suiTounded bv hillv countrv. During this time the Cretaceous Stratigraphy of Lower Murchison River Area, 43 AVestern Austjialia. sediuicntatioii avoji must have been subsiding, but so slowly that subsid- ence lagged behind sedimentation and the delta was gradually pushed out to sea. As denudation continued, relief was diminished and the supply of sediments decreased. Sinking of the sea-lloor continued, deltaic cross- bedding disappeared and Hue-grained bedded sandstones were deposited. Further deepening of the area of sedimentation led to I he deposition over the entire area of a uniform deposit of uuMlium-grained unbedded quartz ^aud, up to 170 feel thick, which must have* been laid down with great ra]>idity. Cross-bedding is practically absent from this deposit so pre- sumably it was formed in moderately deej) water at least below the zone of Avave action and surfa{*e currents. Continued deepening of the sea is indicated liy the apiiearanee of glauconite in the up]Jer l>art of the Hutte Sandstone whicli can hai’dly have formed at di^ptlis of less than about 2d fathoms. The deposition of the following Tlnvindine Sliale indicates further reduction of the relief of the adjoining laud or deepening of the sea and retreat of the coastline in an luisteily direction. There may have been a comhinatiou of both events. Throughout all this time, since the hegiuiting of the formation of the delta, conditions must have Ijeeu generally unfavourable for most types of life. ( ertain tyt)es of saml and ihud burrowers constituted ])ractica]!y the entii'e fauna, t )c<*asiouaily, especially during the closing stages of tile deposition of the Butte Sandstone, logs of wood drifted out to sea and AV(‘!'e buried in the sand. Souu* pinijiu (Snuiouiau) tinu'. This period Avas fol- loAved by a time of deposition of glauconitic shale which may indicate a slight rising of llu' sca-fioor and a Avestwnrd advanra* of the coastline. The ])ost-Cretaceous history of the area will not he discussed in this paper. t 44 E. DE C. Clahke and C. Teichert. Forman is Iho only geologist who has traversed the country between ' the ^lurehison Hivfu’ and Sliavk Bay west ol! the Carnarvon road and he r(*iiuirks bouni Station Avhcre Eorman ! (1.037) observed greensand in a dry soak. [ Another 33 to 40 miles farther north there are outcrops of Avhite ; to yellowisli shaly rocks witli brown chert bands which form low hills, j 40 t() -)0 leet high, along the road leading to Carnarvon and about seven [ to 10 miles east of ilamelin Fool. We traversed this area in 1041, but iiad no tinu' to stop for any detailed ('xamination. The rock seemed to = resemble the Thii'indiiie Shale, but lithologically very similar rocks are also known from the Lower (Cretaceous Winning Series of the Cardal)ia Range, 2.")() miles farther norlh. Thoi’e are many limestone outcrops in the country south of Hamelin Fool, but these are probaldy Recent travertines. The country has the character of a slightly undulating karst landscape, with weather'd lime- stone ridges about three-(|iiarters of a mile to a mile apart, and red soil } accumulating in the dejii’essions. Oil]' only knoAvledge of suhsurfa('e geology comes from a few scat- > tered snh-artesian liores of which only drillers' logs and no samples are UAuilahh'. Aloreover, tor most of tin* bores the heights of the l)ore sites I above sea level are not known. Of particnlar interest is a group of bores (Xos. 6, 7, 8 and lOt in the vicinity of (tee Oie ()utcam|), on Arui’chison House Station, about O mde-^ north of Xnugajay Siting, and about 15 miles X.AAC of Alt. (Tirious. Tyoical of these is Xo. 10. Driller’s Log. Stratigraphic Interjiretation. 0- 4 feet yellow sand ... 4-12 feet red sandy cla}^ Surface de])osits, 12 feet I 12- 40 feet Lfroen clav Second Gully Shale, 73 feet 85-286 feet chalk . Toolonga C'halk. 201 feet 280-334 feet dark shale Alinga Beds. 48 feet 334-341 feet, sand . 341—343 feet lilack sandstone Butte Sandstoue, 9 feet Cretaceous Stratigraphy of Lower IMurchison River Area, Western Australia, ^5 It is not possible fi’om the driller’s log- to differentiate clearly between the Second (.Tiilly Shale and the Toolonga Chalk and it may be that part or all ot the “yellow clay’’ between 40 and 8o feet shoii(ld rather be included in the Toolonga Chalk. It is of some interest that there is no indication of the occurrence of the Thirindine Shale in these bores. Gee Gie Outcamp is about lo miles west of Weerinoogudda Dam where con- siderable outcrops of Thirindine Shale are known to oeciu\ and the dis- appearance of the shale in a westerly direction is in complete agreement with eouditirnis found along the Murchison River where it peters out in Second Gully as described already in this paper. No further l)ore records are available until Cobourn and Boolagoorda Stations are reached, BO to 40 miles farther north, and it is plerhap^ inadvisable at this stage to attempt any detailed correlation of the driller’s logs in places so far removed from the type section of the Murchisoi^ House Series. It is, however, worth recording that all bores here, after penetrating a few hundred feet of soft strata, usually marked as ^^clay” or “shale," reach sandy layers. In bores on Coboinm Station the first sandy beds were struck at depths below the surface varying from 170 to 373 feet and on Boolagoorda Station at depths between 403 and 450 feet. These sandy beds are mostly described either as “sand” or ag “soft sandstone” and it would seem that they are most likely the northern continuation of the Butte Sandstone of tin* IMiirchison House Series. In the Shark Bay region the surfaee of these sandstones seems to dip towards the north-west, for in tin* eentre of Peron Peninsula n bore was put down to a depth of 1780 i'eet without renching nny sandy rocks at all. VT. BTBLTOORAPHT. Clarke. P. de C.. Prldor, P. T,, and Teiclievt, C., 1944. Plements of Geologv for Western Australian Students. Perth xii -j- HOT pp. Cre^pin, T.. 1938. Upper Cretaepous Poraininifera from the North-West Basin, Western Australia. Journ. Paleoyii.. Vol. 12, pp. 391-5. Forman, F. (k, 1935. The Geology and Petroleum Prospects of Part of O.P. 253TT, near Dandaragan. Ann. Vrogr. 7?r/y. Grol. Surr. IT. A. for 1.0S4, ru) 7-11. Forman, F. G., 1937. Artesian and Rnh-Artesian Water Possildlities, Woodleigh Station, Murcdiison District. Ihifl. for pp. 9-11. Hobson, R. A., 1936. Summary of Petroleum E.xploration in Western Australi;'? to January, 1935. Ihifl. for 1D3o^ pp. 22-34. Jutsou, J. T., 1934. The Physiography (Geomorphology) of Western Australia GeoL Snrv. IF. A., TIhII. No. 95, xvi -p 366 pp. Maitland, A. Gibb, 1898. The (huntry between Northampton and Peak Hill, Ann. Profp'. Rep. Geol. Rnrv. W.A. for 75.97, pp. 14-19. Maitland, A. Gibb, 1907. Possibility of the Oc^'iirrence of Artesian Water in the Northampton and Geraldine Districts. Geol. Snrv. W.A., Bull. No 26 pp. 7-9. Maitland, A. t!il)b, 1919. A Summary of the Geology of Western Australia. Minin f/ TTanflhoal\ Geol. Snrr. IJ\A., Mem. No. 1, ])p. 1-.j5. Raggatt, H. G., 1936. Geology of Nortli-West Basin, AVestern Australia, with partieular reference to the stratigraphy of the Permo-Oa rboniferous. Jonrn. Roy. Soc. N.S.W., Vol. 70, pp. 100-74. 46 E. DE C. Clarke and C. Teichert. Simpson, E, S., 1934. Contributions to the Minernlogy of Western Australia. Series VIII. Journ. Roy. Soc. W. Aust., Vol. XX (1933-4), pp. 47-61. Spath, L. F., 1940. On Upper Cretaceous (Maestriehtian) Ammonoidea from Wes- tern Australia. Journ. Boy. Soc. )V. Aio'it.f Vol. XXVI (1939-40), pp. 41-57. Teichert, C., and Watheson, R. S., 1944. Upper Cretaceous lehthyosaurian and Plesiosaurian Remains from Western Australia. Aust. Journ. Sc.^ Vol. VI, pp. 167-70. Walkom, A. B., 1944. Fossil Plants from Gingin, W.A. Journ-. Roy. Soc. IF. Aust., Vol. 30 (1943-1944), pp. 201-7. CllETACEOUS STHATIGRArHY OF LOWEli MURCHISON KiVER ArEA, Western Australia. I’l.ATE I. \'ertk:al aerial view of part of the eotintry north-west of ALiirchison River, showing the scarp at Toolonga Hills. In front of it is the fiat shelf covered with loose saiul, here interpreted as Butte Sandstoiie. The consj)icuously joint- ed ro(tk is 1’urnhlagooda Sandstone. At A is tlie part of the sear]) shown in fig. 14 (/iJ.A.A./’. 'photo.. Piihlinherl hi/ p«rniission). 47 i L GEOLOGICAL MAP OF THE Lawnswood Area K) chains ^ ^ ^ \' \ \ K Highly WeohKer«d \ \ \-:s \ \ \ \ \ \ \ \ L L L L <• * \ \ \ \ N \ V \ X\\\\' • * \ \ \ \ \ \ 17564 \ \ \ \ ' V ' - - • w ' V V S\ \ X X . \ \ \X\ \ \ X ,/5455 \ \ \ \ L \ \ \ L \ \ \ 18913 \ \ \ A \ \ \ \ . \ \ I60f6 \ ^ Xr4-' ^ \ \ ^ \ :^ \ \ \ \ \\\ \ \ \ \ \ \ ^ \ \ \ \ \ \ \ \ \ \ 5 ;: f \ LOCALITY PLAN SCALE LEGEND — L a ^ e r i h 9 F erru^inous Orit \~^ \ Roads □ R a / / w a ^ Q L o c a h i o n Li. I L~| Basic X e n o I i hh I • • ) Qu or^z/^e Oolerite I Y\ I S a n d Uniform Granite | X I Banded Quartzite Porph^ritic Granite HU ^ a r^fej O.r^ U PD e r G n ^ < I \ \ I Hornblende S c b i s f~ Sillimanife Mica Schish Form Lines - — »oo- ou s e s ' pp e r Cz n e f s S Lovver Gneiss X .- >3 Ori dg e S Tr/g Station Geological Boundaries' S trike ^ Dip - of Bedding h of Foliation Ih Direction 8; Pitch oF b — lineoti on S Cross Fold Axes Anticline, a a SVNCL/NE S S fr •i"' «, A T:^ :^'' \-i s \ 'fw « \ The Geology and Physiography of the Lawnswood Area. 49 2.— THE GEOLOGY AND PHYSIOGRAPHY OF THE LAWNSWOOD AREA By J. R. H. McWhae, B.Sc. (Hons.). I. Read : 12th March, 1940, CONTENTS. Introduction Page ... 49 11. Physiography ... 50 III. Geology A. Occurrence of the rocks ... 51 B. Structural interpretation of the Jimperding Series ... 54 IV. Petrology A. The Jimperding Series 55 1. Metasediments (a) Quartzites ... ... 55 (b) Mica schists ... 50 (c) Metajaspilites ... 58 2. Meta-igneous rocks (a) Hornblende schist and its variants ... 60 (b) Cordierite — aiithophyllite rook ... ... 01 3. Granitic gneiss and associated xenoliths (a) Upper granitic gneiss ... 02 (b) Xenoliths in the granitic gneiss ... 02 B. The younger igneous intrnsives 1. Younger granites ... ... 00 2. Quartz dolerites ... ... 70 V. Economic Geology A. Refractories ... 71 B. Charcoal iron ... ... 72 VI. History of the Area ... ... ... 72 VIL Acknoi\t:>edg>ient.s ... 73 VIII. List of References ... ... 73 1. JXTRODI’CTIOX. Lawiiswood is situated on the Claekliiie-Milidu- railway, three miles north 01 Claekliiie and approximately oO miles in au east-north-east direction from Perth (see locality jdan on Plate !.)■ The lanvnswood Area, which occupies about 10 square miles with the southern boundary less than one mile north of Clackline, is lar;tiely composed of early Pre-Cambrian rocks of the Jim- ])erding Series ((>, p. 107). This s<‘ri('.s is composed {)f pelilic and p.sammitic metasediments with intercalated layers of acid and basic igneous j'ocks all ot which have sutfered silHmanite zoiu' regimial melamorphism (20, p. 11; 23. p- 84; 9, p. 108). Tt extends from York (15 miles south oi' ( lackline) to at least as far north as the Irwin Ki\er District (23, p. 84). Forman (12, p. XXV) regards this series as eqiiivahmt in age to th(‘ Whitestom* and AIos. XXV), Late Proterozoic or Lower (kimbrian quartz dolerite dykes (24) and a superficial dejiosit of Tertiary laterite. This 14158/2/48—610 50 J. ii. \L McWiiAt^ iaU'i'iU*, imlik(^ most ol^ llic laU'ritc ol Ausli'aLia which is hoi'i/oulal (51, p. o2), is roi'iiu'd (til a siui'ace sloping at 4 to 8'^ away ivoiu the resistant melast (liiiientai'y vi(.g‘es. Two parties of senior stiuhiits of the rniversity ot Western Australia (•aj’i'i(Ml out Ihi' tield work, under the guidanee oE Dr. U. T. Prider, during tlu' first vacation, of 19.'!0 and 1945. Cliain and compass traverses tied to a rranu'work ol‘ I.ands and Survey I )epai‘tnient -"subdivisions were em])loyed in tin* mapping. II. PllVSIOfJltAiMLV. T!u' (Ireat Plateau of AYestein Australia (15, )>. 5) i.s generally mature, especially in the inland part ttf the plat('a.u. Theia- are, however, ocea- sional latrrite-ca[)p(al mesas and buttes, the .summitH of wliich mark the level of' a former juaieplain, atid raic‘ monadnocdvs rising above the general ])lateau levd {S, p. 11), whicli iH'come more numerous towards th{‘ (‘dgc of tlu' (derated peingdain pioducing an immature topography. In the Lawnswood Artai dii'lVn’ential erosion and weathering, botli in the pres('nt and juist cycle of ei'osion, have been responsible for the main topogra])hie iealures. As the (|uartzite& are resistant to both weathering and e]-osd>n tlu'v form two monadnocks elongated }>aral]el to tile regio}ial strike'. Tlu' broad, mature valley running through the centre of th(' area corresponds to llie less I'esistant granitic gneiss and possibly was formed by an ancient river whieh flowed in a south-east direction before it was (-aptni'ed by more vigorous west-tlowing streams (14, pp. 1 . Doh'rite dykes ane intermediate in resistance forming valleys in tiu' (|uart/.it('s and low i‘idge< in th(‘ gi’anitie gneiss (text fig. 1). Text Kig. 1 . Tlirc^e doleritc dykes in the upper granite gneiss, 20 chains soutli of (l.ackliiio. The doleritc dykes, hoirig more resistant to erosion tlian the gneiss, form ildgea. Note the iJuralleMstn of the dykes. The Geology and Physioghaphy of the Lawnswood Area. ol Dift'erential oi'OKion has been greatly aided by deep and long con- tinued weathering which took place towards the end. ol! the previous cycle of erosion. Granite and basic rocks alike were reduced to a whitish clay down to the base (»f the kaolinised zone, oil to 10b feet below the laterite which was fonning at that time. This extreme weathering is very unusual in Western Australia and is ]_>ossibly due to moderate to heavy rainfall during the time of laterite formation forming unusually acid ground waters which altered all the rocks, with the exception of (juartzite, into the residual clay deposit. In the [n'csent cycle of erttsiou, dihcvential erosion ol th»‘so deeply W(uithered rocks has produced a dissccli'd peneplain with latcndte-capped mesas and buttes, overlying soft kaidinisial rock, rising steeply above the unweathered rock to a height of 50 to 100 feet, n.'he laterite mesas and buttes invarialdy s!o]ie at 4° to 8° towards the centre of the valleV (>ee text tig. 12) and small streams conse'pnml on this slope, which Hoav into a larger stream in the eentre of the mature valley, have, in most l)laces stripped off the kaolinised r<)ck leaving the nnweathered rock exposed. \ ery immature hubsei[uent streams are dissecting narrow gorges in the soft hornblende and mica-schist bands in between the ({nartzite ridges. W. E. Scale of Feet 0 500 O lOOO 2000 =3 VERTICAL 1000 =3 HORIZONTAL. 3000 La ten te S Do!e rite G net ss Hornblende Schist Quortzi te Etc. Text Pig. 2. Cross section of tho Lawnswood Area along a line bearing 73° at 23 chains injrth of Lawnswood siding, showing the laterite capped mesas which slope down towaj-ds the central valley. The okt ju'O' file upon which the laterite was formed, is shown l>y broken fines. III. (JEOLOGV. a. OCCEHREXCK of the rogks. 1. Metasediments and Hornblende Schists. There are two broad hands of metasediments in the area both Avith the characteristic norlh-north-west strike. Tlie western band Avhich dips west at 25° to 35° in the northern ])arl, and west at 50° to 05° in the southern ]>art of tlie area, is corrclalcd with the upper metasedinieiit of the To'odyay Area, (23, p. 88) because it is on tli<‘ same line of strike (see text bg. 3) and petrologically tin' (piartzites are id(‘n1ical, both con- taining idioblastic palc-grcvn cln’onii'-niTiscovitc orienied parallel to the bedding and poikilobbistically included in ihe (juartz grains. The eastern meiasedinu'uts, which Inno been coniu'ctcd in tiu' Held to the lower quartzites’ of the Toodyay Ar(‘a (see text fig, 3), have dips varying from 40° to 50° to the east. \uYi^ 52 J. R. H. McWhae. AV \ N^RDI_ JfMPERDlN(^ “T^o. A \ NOONXmNO NODDY SCALE OP MILES Roi/'wa'j — - — Tri^ Stotio/^ A 10 ■Dip iS" Sfrike of Beddini^ or Foliation Major Structure Axis -H — #f- Section Line — — — BOBAKm M e I" a se d'me nts iJJncerto Aiawnswood Lowe er Cronii-e clackLine ! Scale (S' Le ^end as in Plan I I \ Sea Lews/^i Text Fig. 3. Geological sketch plan and sections to illustrate the structure of the country between Toodyay and Clackline. Data regarding the northern half of this area after Prider (23, p. 86). The Geology and Physiography of the Lawnswood Area. 53 A narrow strip of metasediments (mica schist and quartzite) out- crops ill the upper granite gneiss, at a distance varying from tive to 12 chains from the upper (piartzite. Owing to the very highly weathered nature of its component rocks it is not certain whether this band is continuous, whether it is a series of elongated lenticular xenoliths of the Jimperding Series, or whether it is an infold of the upper metasediments in the gneiss. Another narrow and discontinuous band, situated approxi- mately 40 chains east of Nunamullen lirook, dips 70° to the east in the south, ()0° to the west about a mile and a half north of l^awnswood, while in the vicinity of P.S. I'rig station there is an anomalous western sii'ike and a h)w dip to the south. As the sediments have been very highly metamorphosed causing com- l>lete re(-r\ ^tallisation, original features, such as graded bedding and ripple marks, have been almost completely obliterated. Prider (23, t>- 8")? mention-^ that, in the Toodyay Area there are some obscure current bed- ding structures but no certain interpretation of these was possible. Drag folding was not observed in this area, hut Prider (23, j). 87) has found drag fold-, in tlie lower quartzites of the Toodyay Area, approximately one mile south (if W.B, Trig station, which indicate overturning in that locality. Minor cross folds are indicated by the variable pitch of well developed h- liueations in the quartzites. 2. Granitic Gneiss. A diii-k, concordant, grajiilic gneiss body ota upies most of the central portion of the Area corrcsj'.oncing with a mature ^ alley about three, miles wide (see Blate 1). This is correlated with the Id'per Gneiss of the Toodyay Area. In llie north-east corner of the Area, a second concordant granitic gneiss oc:-urs, which corresjumds to the Lower Gneiss of Toodyay. Although ptygmatic folding is occasionally developed in the gneiss, as is well .-e(m in llie outcrops in the bed of Silencer's Brook at ('lackline, generally file j)laty paralleli'in of the gneiss conform^ closely in dip and strike with the as.soidatcd metasediments. Xo work was done on linear parallelism of the gneiss. 3. Intrusive Granite. Granitt' invades tlio Jimperding Series in tbe south-east corner of the Area and continues immediately south and west of Clackline. Probably the boundary of this Younger Gratiile and the Jiinjicrding Series turns north within a mile west of Clackline and thence runs north to the south-west corner of the Toodyay Area (see text iig. 3). The intrusive granite ap])cars massive in the field except near the con- tact with the metasediments south and west of Claekline, where the gneiss- like handing of the rock is due possibly to platy how structures developing near the contact with the country rocks There are two varieties of gi’anite, a ]iorphvritic and an eouigTaiiular. The porphyj'itic is eonfined to the south-east part of the Area, and passes in a distance of a chain or two into the etpiigrauiihu’ variety. 1 ho equigranular granite occiqiies the south-central portion of the Area and extends at least a mile Avest of Claekline. The por])liyritic granite passes into the granitic gneiss very abruptly, but the transition from cqnigranular granite into granitic gneiss is very gradual. 54 J. R. H. McWhae. 4. Quartz Doierite. Quartz doierite d^'kes, from half to two chains wide, are intrirsive into all the above rocks. They have a general norlh-north-Avest trend and are most numerous in the centre of the Area. In some places there ai’e closely spaced fractures resembling fracture cleavage in the dykes giving them a platy structure. Slight shearing of their edges indicates movement sub- sequent to intrusion. 5. Laterite. Laterite-capjied mesas and buttes are more common near the metasedi- mentary ridges and slo])e away from them at 4° to 8°. This sloping laterite is attributed to its formation on a gently inclined surface in the end stages of the jirevious cycle of erosion rather than to warping in late Kainozoic times, as in the case of an occurrence of dipping laterite in South Australia (31, pp. 32-33). n. STRUCTURAL INTERPRETATOON OF THE JIMPERDING SERIES. Text tig. 3 is a simi>lified diagram of the broader geological and structural features of the Toodyay and LaAvnsAvood Areas. The northern part of the map, the Iaa^o sections A-B and C-D and the interpretation of the structure are taken from Prider^s paper on the Toodyay Area (23, p. 87). hcreas fi'om the LawnsAVood Area to the southern part of the Tood- yay Area the strike is norlh-north-west, in the north of the Toodyay Area the strike is west and the dip is to the south at a fairly low angle. Again the quartzite near P.S. Trig has a Avesterly strike and a Ioav dip to the south. This unusual Avestei'ly strike, the drag fold evidence of iiiA’ersion of the lower metasediments and the discontinuous quartzite band running from near P.S. Trig to the intrusive granite at the south-east of the LaAvnsAvood Area, can be explained if Ave imagine the Toodyay and LaAA'iisAvood Areas to be in the main a major anticline pitching to the south-south-east, having a recumbent syncliue Avith an axial plane dijAping to the east on the eastern limb of this iniijor anticline. Tlie discontinuous quartzite band from near P.S. Trig is considered to be an infolded recumbent synclirie of the Upper Quartzites regardless of its petrological resemblance to the lower quartzites. Dr. Prider predicted the presence of thi.s infolded band of u]>per metasodiments at P.S. Trig, as a result of his structural interpretation of the Toodyay Area and he suggests that the discontinuous nature of this l)and is due to the presence of minor cross folds. The cross folds superimposed on the major north-AA^est trend- ing structure haA^e jAroduced a series of minor transverse synclines and anti- clines. Erosion has cut doAvn so far that only the transverse synclines remain as lenticular outcrops Avhile the transverse anticlines haA^e been removed. It is seen (Table 1.) that, Avhile the loAvest portion of the Toodyay se- quence is not represented in the Lawnswood Area, there is a considerably greater thickness of npjier metasediraents in the A\Tst of the area Avhicli probably correspond to the metasediments in the south-east of the Malkup Area (9, Table 1. p. 146). Probably of some importance in regard to the origin of the hornblende schists is the change of ^^llorizon 6” f]*om sillimanite schist in the Toodyay Area to hornblende schist in the Lawnswood Area. The Geology and Physiography oe the Lawnswood Area. 55 Table 1. comparison of STRATIGRAPHICAL SrcCESSION and thickness of the JIMPER pING SERIES IN THE LAWNSWOOD AND TOODYAY AREAS. Lawnswood Area. Toodyay Area. No. Horizon. Thickness Horizon. Thickness. Lower metasediments and hornblende Lower metasediments and hornblende schists. schists. 1 Quartzite unknown 2 >Not represented Hornblende schist 35ft. 3 J Quartzite 650ft. 4 Lower granitic gneiss unknown Lower granitic gneiss 5,400ft. 5 Quartzite 300ft. Quartzite 375ft. 6 Hornblende schist oOft. Sillimanite schist 100ft. 7 Quartzite 150ft. Quartzite 570ft. 8 Hornblende schist 70ft. Hornblende schist 40ft. 9 Quartzite 180ft. Quartzite 110ft. Upper metasedimenis. Upper metasediments. 10 Upper granitic gneiss approx. 2,000ft. Upper granitic gneiss 1,900ft. 11 Quartzite with some subordi- Quartzite 500ft.. nate quartzose mica schists 250-600ft. 12 Hornblende schist ISOft. Indication of hornblende schist 13 Quartzite 60-200ft. Not represented 14 Mica schist and quartzite 1, 850ft. Andalusite — muscovite schist 250ft.. 15 Quartzite and mica" 5 000ft. 4-? schist (Thickness may ^be due to in- Not represented 16 Metajaspilites and competent fold- banded iron-ore ing) IV. PETROLOGY. The rocks are divided into two groups : — A. The Jimperdiiig Series. B. The younger igneous intrusives. ^ A. THE .HMPERDING SERIES. 1. Metasediments. (a) Quartzites. These are coarse-grained almost pure <|uartz rocks with well defined! bedding on which corrugations or h~ lineations (19, p. 591) are developed. The Lawnswood quartzites are identical with those described by Prideir at Toodyay (23, pp. 88-94). (i) Tlie Upper Quartzites are characterised b^^ the presence of small (<0.1 mm.) pale green cln’ome-museovite idioblasts enclosed in the quartz grains and oriented parallel to the bedding. Felspar is not found in the main band of upper (piartzites in the west of the Lawnswood Area but is common in the infolded quartzite which is correlated with the upper quartzites on structural grounds. (ii) The Lower Quartzites are identical with those of the Toodyay Area and have been connected in the field. The chrome-muscovite grains 56 J. R. H. McWhae. are larger than those in the Upper Quartzite hcing 0.3 to 0.5 mm. in diameter and lie between the grains of the quartz mosaic, while there are iDoikiloblastie inclusions of rutile, magnetite, sillimanite (?), fels23ar, and zircon in the ipiartz grains. (iii) Tb(‘ Infcdded Quartzites lithologically reseinl.de the Lower Quartzites, b(‘ing a felspathic variety free froTii oriented, poikiloblastic inclusions of idiol)la.stie chrome-iuuseovite in the quartz grains. The felspar is slightly kaolinised microeline \\ilh frequent microperthite w^hieh generally oeeur.s in xenoblasts up to one mm. in diameter in the quartz mosaic and may form tive to six per cent, of the rock. The inclusions in the (lunrtz grains are zircon, red-brown biotite and a green pyroxene, forming two to three per cent, of one lax-k (22742)*. Ontjin of the quart — The s a})]iear to have been derived l]'om reiuaj’kably pure (piartz sands which have recrvstallized in the sillimanite zone r('sulliug‘ in the obliteration of the clastic structure (23, pp. 92 and 94). (b) Mica S chi. •it. The init'a schists occur in the western metasedimentary band and are light yellow-bi't)wn to grey brown, generally highly schistose, medium- gTained, micaceous rocks whi(4i are fre(]uently contorted. The characteristic features of tliese rocks are the constant jn'esence of bands and lenses of sil- linianite in very title aggregates of acicular crystals Avlnch are frequently alt(‘red to siwicite {26, p. 13) and the marked schistosity — the tjuartz grains having an index of (dongation of four to five. (i) The ^tiiseip ile-quartz-silliuuinite schist (22569) has the following miiun-als visible in hand specimen — gobhai plates of muscovite two to three nun. in length: colonrlcrs, strongly elongated ([uartz grains three to five mm. long; and bands up to two cm. wide ami more than 10 cm. long' containing an aggregate of line while acienUn- sillimanitf^ and .scricile. There arc rare inclusions of sericite ami minute silliniaiiite jirisms in the quartz and very corroded biotite is sometimes observed. The complete absence of uiidulose extinction in tlu' idongated quartz grains indicates that complete reerystal- lisatiou took place dui'ing metamorphism. The apju’oximate mineralogical composition is muscovite 40 per cent, quartz 30 per cent, sericite 30 per cent. Avith biotite, sillimanite and iron ores accessory. The serieite-sillimanite bands become most common in the south of the area in the vicinity of the Clackliue firi'-clay deposits, Avhich are highly kaolinised sillimanite-mica schists composed largely of white kaolin with up to 10 ptu' cent, of lenticular bands of very acicular sillimanite (26, ]i. 12). Quartz and kaolinised muscovite are visible in hand specimens. This sil- limanite f-lay lies close to the Younger Granite and seA'ernl ]3egmatite veins, genetically related to tills granite, occur in the west of the deposit. "Mr. IT. BoAvley ^‘picked up a loose crystal of kyanite a little to the north of the lirickpit” (26, p. 11), but no kyanite has been found in the present investigation. A lateritised form of the muscovite-quartz sillimanite schist (22568, 22569, 22570) occurs in a band in the upper granitic gneiss about 10 chains *N’iimbrrs refer jo llio catalogue of the collection of the Department of Gcolosrv of the University of W’.A. The Geology and Physiography of the Lawnswood Area. 57 east of the upper inetasediments. This is petrologically indentical with unlateritised specimens (22530) from the l)ase of the upper metasediments and is correlated with horizon 11 (Table 1.). (ii) The Biotite-cordierite-quartz-sericitc-sillimanite schist (19190) is frequently darker in colour and more gneissic than group (i). The biotite occurs in markedly elongated, strongly iileochroic ])lates — Y and Z = brown, X =: very light brown to colourless, absoriition X ■" Y — Z, c X ~ 0°, (-)2y very small. Pleochroio haloes around zircon grains are frequent. The quartz is very elongated and contains gas-lupiid inclusions and minute inclusions of sericile, rutile, rounded zircon and rare sillimanite. Cordierite was observed in an irregular intergrowth with quartz in one slide (19953) but equidimensional sericite aggregates are possibly pinite pseudo- moiqjhic after cordierite. The sericite aggregates are evidently derived some from bands of sillimanite and some from an equidimensional mineral — probably cordierite or even felspar (see text fig. 4). The sillimanite is Text Pig. 4. Biotite-corderite-quartz-aericite-sillimauite schist (19190), show- ing a band of sericite pseudomorphic after sillimanite (small prisms with high reUef) and equidimensional grains consisting of sericite after corderite (or felspar). Four rounded grains of rutile are seen in this Held. J. R. H. McWhae. 58 the variety tibrolite oceiirring in very tine ])rism 3 associated with elongated magnetite grains. It appears to be developing at the expense of biotite (23, p. 98). Muscovite, iron ores, zircon, sillimanite, and felspars, the latter occurring only in specimens from near the intrusive granite, are accessory minerals. The avei-age composition is cpiartz 40 per cent., biotite 15 per cent., eordierite and pinite 15 ])er cent., sericite 15 to 20 per cent., fibrolite is sometimes as high as 10 per cent. (iii) Garnet schist.^ — A highly weathered whitish to brownish schist witli numerous efiuidimcnsional, dark brown limonitic grains pseudomorphic after garnet (the original crystalline form being retained) has been noted only in th(» lire-clay (juai'ry at Clackline. The rock has a maculose tex- ture with about 40 per cent, of limonite pseudomorphs after garnet three to five mm. in diameter, the remainder of the rock being fine-grained quartz and mica. Origin of thr wivn sc-hh (^. — These mica schists are thought to be. the result of extreme regional nudamorphism of sandy argillaceous sediments or possibly glauconitic shales (20, p. 13). Silliinanile-(|uartz-cordicrito-hiotito schists were probably formed at this stage of high regional metamorphism, with a tendency of the biotite to change to fibrolite and magnetite. Proliably the original composition of the sediment deteianined whether the schist formed therefrom Avas high in sillimanite, mica, or garnet. The sillimanite clay (juarried at (Tackline is thought to be a highly kaolinised Auiriety of sillimanite-rich mica schist from the kaolinised zone below tlie laterite, i.e., the result of weathering, and not the result of hydrothei'iiial metasomatism at the time of the intrusion of the Younger Granite, as are the sillimanitic clay deposits at WilliamstoAvn, South Aus- tralia, (1, p. 10). Considerable retrograde metamorphism probably took place as a result of the intrusion of the Youngei' Granite. '‘Hot alkaline potash solutions ’’ (26, j). 13) metasomatised the sillimanite and cordierite producing sericite after sillimaniU; and pinite after cordierite and some of the biotite Avas altered to muscovite. { c ) Metajaspilites. (i) Banded . 325-328). Megascopically they are heavy, dark green, medium to coarse-grained, gTanular, coarsely banded rocks. The band- ing is considered to be a relict structure of the original bedding. In (19956) there are tliree ly])e.s of bands: (1) (Quartz-rich with subordinate pale green amphibole (gi'ain size of both t wo to three mm.) ; (2) a layer in which pale green amphibole predominates and wliicli has subordinate dark amphibole and garnet and rare magnetite; (3) a layer of red garnet (1 mm. diam.), dark amj)hiboIe ( two to three mm. diam.) and magnetite ( half to one mm. (diam.) with subordinate ])ale green amphibole. The rock has a coarse granoblastic striTctnre. The quartz forms a coai*se mosaic and has gas-liquid inclusions and sometimes slight undnlose extinc- tion. Xenohlastic inclusions of amphibole sometimes occur in the quartz. The Geology and Physiography of the Lavvnswood Area. 59 The amphiboles are of two varieties^ both with a high relief, containing lileochroie haloes around zircon grains and tending to be idioblastic in form (17, pp. 327 to 328). One vaidefy is a pale green amxdiibole with weak pleochroism, X = colourless, Y = b = pale yellow gi’een to brown, Z = l)ale green-blue; absorption X Y ■= Z; Z c = 13° ; (-) 2 v near 9(J°. Polysynthetic twinning is common on 100. The mineral is a grunerite with a composition near cummingtonite prol)abiy containing over 75 per cent FeSiO^ (17, p. 327). The other variety ih a dark amphibole with very strong pleochroism X = light green, Y = dark olive green, Z = intense blue-green. Absorption is strong and masks the intei'fereiice colours, Z slightly ^ Y" > X, Z /, c =22°, Y ^ b, ufitical character biaxial -ve with large 2V (about 80°), twinning not seen. The mineral is probably an actinolitic hornblende. The garnet xenoblasts have an irregular form and a poikiloblastic character, They contain numerous inclusions of a highly l)irefringent mineral forming up to 60 per cent, of their volume. This garnet is a pink, }irobably iron-rich variety, ^lagnetite forms very irregular ])atches. The crystalloldastic order is: amphiboles, garnet, quartz and magnetite. Average composition — quartz 40 per cent., grunerite 30 per cent., dark green amphibole 15 per cent., garnet 15 per cent., magnetite accessory. (ii) Banded quartz-iron ore rocks (19954) are bluish grey, strongly banded, fine to medium-grained, willi a granular texture, and are reddish brown where weathered. The bands are quartz, four cm. wide (grain-size about two mm.), quartz and iron ore, one cm. wide (grain-size 0.25 - 0.5 mm.), and narrow iron ore bands up to one mm. wide (grain-size 0.25 mm.). Bands of amphibole occur rarely. A granoblastic structure is seen in tlie (piai’tz and quartz-iron ore bands. The quartz has an irregular mosaic structure and is ]>T’a(4icany free from inclusions except next to the iron Z > Y, (-) 2Y large, -c a Z = 20°, P = 1.670. Its approximnte composition is hornblende 65 per cent., oligo- clase (Alg Aiiu) 25 i)e]’ cent., fpiartz five per cent., accessories (microcline, radio-active titanife and green diopside) five per cent. (ii) Qnartz-])l;)gioclase-pyroxene granulite (22732) is a variant of the idagioclase amphibolite. Tt is a granular type in Avhich green diopside is greatly developed wliile hornblende is rare or absent. The diopside is a bi’iglit green very feebly pleochroic variety, Z and X appearing to be gi’een and b — Y = yellow green, optically ])ositive, q /\ Z := 40° with simple twinning developed. The approximate composition of this is diopside 50 per cent., oligoclase 45 per cent., quartz four per cent., titanite one per cent. (iii) Quartz-zoisite-liornblendc schist (22583) — The hornblende schist layer intercalated in the Avestern metasediments differs from those described above in the prtHlominance of quartz and the absence of felspar. The presence of an aggregate of zoisite and sericite is probably the result of retrograde metamorphism (felspar ^ sericite + zoisite). Accessories are apatite, iron ores, ]mT])le zircon, and rutile. Titanite is absent. The approximate composition is (jiiartz 55 per cent., hornblende 30 per cent., zoisite and sericite 15 per cent. The Geology and Physiography of the Lawnswood Area. 61 Origin of the hornblende schists . — Types (i) and (ii) are thought to be the result of extreme regional luetamorphism of basic igneous flows or sills, as, according to Wiseman (db, p.394), hornblende Avith a refrac- tive index of ^ = 1.679 is indicative of an epidiorite formed in the sillimanite zone of metamorphism. Prider (23, ]>. 107) concluded, from the high refractive index of the hornblende, the occurrence of tlie rocks in beds intei'calated with the metasediments and their chemical compo- sition, that similar hornblende schists in the Toodyay Area arc highly metamorphosed basic igneous rocks. Previously when dealing Avith the correlation of the Toodyay and Lawnswood Areas it was painted out that Horizon 6 (see Table 1.) is a horn- blende schist in {lie LaAvnSAvood Area and a sillimanite schist in the Toodyay Area. The presence of hornblende schist in the same horizon as sillimanite schist suggests that this hornblende schist Avas a basic (dolcrite) sill that Avas injected in some places into a softer argillaceous stratum between tAAm arenaceous bands prior to regional folding. The quartz-rich hornblende schist (iii) is thought to be the result of extreme metamorphism of a basic sediment (greyAvacke) or basic tuff. (b) Cordierite-anthopligllite rock. About 50 chains west of Clackline an outcrop of a light greyish-green, medium to coarse-grained, uniform-textured cordierite-anthophyllite rock occurs. It has been described by Simpson (27, p. 115). It outcrops at the contact betAveen the Jimperding Series metasediments, AA’hich are ])eltic in this exiiosure, and a rock AA’hich is thought to be the Younger (Iranite al- though it is gncissic. The minerals are greyish-green cordierite, devoid of cleavage and up to three mm. in length, and grey prisms of antho])hyllite up to Iaa^o mm. in length. The microstructure is granoblastic gneiasic. Cordierite occurs in colourless xenoblasls frequently altered along irregular cracks to pinite, and the anthoithyllile is generally idioblastic. ReddiroAvu biotite, rutile, and chrnmile are accessory. The approximate composition is cordierite (and pinite) 55 per cent., anthophyllite 45 per cent. Simpson (27, {i. 116) suggests that this rock originated hy the ^'absorp- tion of some slate or similar aluminous rock” into a basic hypersthene-rich rock. Similar cordierite-anthophyllite rocks occur as xenoliths in the granitic gneiss of the Toodyay Area, and these have been shoAvn to be o'pnetically related to an ultrabasic sitinel-olivine-hypei"Sthene rock. Prider concluded that a "hypersthenite magma AA'hich had ])een contaminated by assimilation of aluminous material” had been altered to cordierite antho})hyl1ite rock “by the siinjde addition of silica (probably from the granite)’’ (21, p. 381). The presence of mica schist adjacent to the coi’dierite-anthophyllite rock in the Clackline occurrence suggests that a hypersthenite invaded a politic band of the metasediments and assimilated aluminous material, as- Simpson suggests. The cordierite was formed either during the highest stages of regifuial inetaninrphism or more ]>robably as a result of the contact metamorphism (Avith silica addition) by the A^ounger Granite. 62 J. K. H. McWhae. 3. Granitic Gneiss and associated xenoliths. The granitic gneiss is in two thick sills continuous with the Toodyay Area. The lower granitic gneiss outcrops in the north-east of the Lawns- Avood Area while the upper granitic gneiss covers its centre and has been -Studied in some detail. (a) Upper (jranitio gneiss. This gneiss is almost identical with the one described by Prider at Toodyay (23, p[». 107-111) except for the absence of augen structure. There appear to be two main types; — (i) Granitic Gneiss A (ehloritic) which is a medium- to coarse-grained, greyish gneiss, with widely spaced microcline jihenocrysts (two cm. diam.) and is characterised by the presence of chlorite and (-pidotej (ii) Granitic Gneiss B (biotitic)^ which occupies the edge of the sill near the metasediments, being characterised by a finer grain, a nuu-e strongly developed giieissie structure and the presence of biotite. (i) Granitic Gneiss A (ehloritic) {22479)— The type rock has a coarsely gneissic structure sometimes Avith slight cataclasis and the fol- lowing minerals: — slightly saussuritiscd oligoclase, clear microcline, quartz, ■chlorite, epidote {often in veinlets), and accessory apatite, magnetite, and zircon. The chlorite occurs in .Avell developed plates frequently Avith puri)l(‘ zircon inclusions surroiuuhul hy strong pleochroic luiloes. It is thought to 1)0 pseudomori)hic after biotite because ot* its form and the purple zircon inclusions which are common to both. Its optical properties are: — ])leochroism X = very pale yellow-green, V and Z = green, absorp- > tion Is S --- /, birefringence very low, anomalous blue colours frequent, ■elongation ])Ositive, optically negative, j3 = 1.025. These data indicate the variety as aphrosiderite Avhich has a composition similar to biotite. Approximate composition is oligoclase 35 per cent., quartz 30 per cent., microcline 25 pev cent., chlorite fiA^e per cent., epidote fi\’e per cent. (ii) Granitic Gneiss B (biotitic) (225/4) is characterised by biotite in very elongated [)lates rather than chlorite and epidote psendomorphie -after biotite as in (i). The biotite ])Iates arc crowded with sagenitic rutile inclusions and have .strong phmchroisin X = yellow, Y = dark brownish green, Z — very dark broAvn, absorption X <. ^ * Z. Miei'ocline pheno- crysts are absent but some larger grains (tAVo to three mm.) slightly kaolinised and with myrniokite frequently developed in associated oligoclase. probably represent early- formed microcline, AA'hile smaller (0.5 mm.) clear grains, strongly eross-hatehed and containing microperthite are prob- ably a later generation. The quartz generally occurs in rounded grains poikilohla.stieally enclosed in all the other minerals. The approximate comjoosition i.s microcline 35 per cent., quartz 35 per cent., oligoclase 15 per cent., biotite 15 per cent. (})) Xenoliths in the granitic gneiss. These are of amphibolites, except for one of sillimanite-mica schist and some of chlorite-epidote rock. Generally they are large, up to two or three chains in major diameter, and irregular, and are elongated parallel to the regional strike. The Geology and Physiography of the Lawnswood Area. 63 (i) The amphibolites are dark, grey-green medium- to coarse-grained, melanocratic rocks containing hornblende, plagioclase and diopside with accessory biotite, apatite, cpiartz, and sphene and are almost identical mineralogically with the hornblende schists ot the metasediments. There are. both granulose and schistose varieties. Granulose quartz-plagioclase amphil)olite3 (22524) are dark grey, uniform textured rocks with a medium to coarse grain and a granoblastic mierostructure. The minerals present are intensely pleochroic blue-green hornblende (c A ^ — 21°, 1.672), basic oligoclase (saussuritised and with normal gradational zoning occasionally developed), strongly pleochroic greenish-broAvn biotite, rpiartz, and accessory apatite, radio- active titanite, actinolite and diopside. The approximate conqmsition is hornblende 05 per cent., oligoclase 25 per cent., biotite live 2 )er cent., (iuartz three i)er cent., titanite two per cent. The schistose (luartz-diopside-plagioclase amphibolites (19188) differ from the above in their schistose structure and greenish-grey colour due to the presence of green diopside which sometimes forms more than 10 per cent, of the rock. Tin* liornlilende is similar to th.at in the granulose amphibolites (e A ^ ” 24°, ^ = 1.675) ; andesine (Ah^ AnJ is the plagioclase present; and the diopside is a green variety with very feeble pleochroism, (-j-) 2V large, e A — 41°. (ii) The quartz-plagioclase-epidote-clilorite rock (22487) is greenish- grey with a uniform texture and fine grain. Occasional veinlets of paie yellow-green epidote are seen in the rock. The minerals are a very dark green platy chlorite, average grain size 0.5 mm., veinlets and aggregates of pale yellow green epidote, equidimensional white grains of felspar 0.5 -1.0 mm. in diameter. There is a slight Ijanding caused by the parallelism of the ciilorite plates. A chemical analysis of 22487 (Table 2, T) shows that except for higher 8iO. and AlA), and the propoifional lowering of the other constituents the rock chemically resembles a hornblende .schist xenolith (Table 2, II) in the gneiss from Toodyay (23, p. 105). The rock Ls a rare type as shown by the quantitative classification (II, 4, 5), only one comparable rock, a gabbro, being listed in a.shington’s ^Themical Analyses of Igneous Rocks” (28, p. 419). The compo.sition except for the high SiO. is somewhat similar to that of quartz dolerite so that the rock might be the result of the granitization of a basic igneous rock. The rock (22487) has a granoblastic microstructuix with a tendency to be finely gneissic. The (]uartz is generally clear with an irregular form. Inclusions of chlorite are rare and an intergTOwth of quartz and untwinned plagioclase is sometimes obser^’ed. Chlorite is green, practically isotropic with occasional grey blue anomalous inlerPerence colours and weak pleo- chroism from green to light yelloAV gi'cen. It ap]>ears to be pseudomorpliie after an ampbihole as it occurs in forms similar to the typical amphibole basal section and occasional bands of epidote cross the chlorite at angles 64 J. R. H. McWhae. of about 60° which may be replacements along the .amphibole cleavages. Epidote forms irregular aggregates (average diameter 0.5 mm.) whic'h may in ]*art replace felspars. Some ei)idote was introduced at a later stage along cracks. The felspar is untwinned oligoclase which is difficult to distinguish from (juartz. Accessory minci'als are apalitCj titanite, iron ore, and zircon. The approximate mineralogical com[)osition is quartz 32 ])er cent., chlorite 30 per cent., epidote 25 per cent., plagioclase 10 per cent., and titanite and other accessories three per cent. Another specimen of this group (22488) is almost black in colour and contains SO per cent, chlorite. Table 2. Si02 AI2O3 Fe 203 FeO MsO CaO ICO NagO H2OJ- H20~ TiO, MnO P2O5 BaO ZrOg S Norms. Q Or Ab ... di hy mg ii ap ... py ! C.I.P.W. olasaifioation II, 4, I. 0/ /o 59-23 16-18 1-48 5-63 4-24 9-58 0-10 0- 65 1- 71 0-20 0-61 0-13 0-19 Nil Nil 003 99-96 25-86 0- 56 5-76 40-87 4-86 11-50 2-09 1 - 22 0-34 0-10 II. 0/ /o 50-20 15-00 3-83 8-93 6-04 10-65 0- 07 1- 90 1-62 0- 07 1- 06 0-16 0-12 99-65 6-18 0-56 16-24 31-97 16-41 19-18 5-57 2-13 0-34 I. Quiirtz-plao'ioelase-epidote-ehlorite roek (22487), xenolith in upper granitic gneiss, l,a\vns\vootl, W.A. {Anal. J. R. H. McWliae). II. Schistose plagioclase amphibolite (1241) xenolith in upper granitic gneiss, Toodyay, W.A, (23, p. 105). (m) Silliiiuuiite-iiiica .schist (19103) is a slightly contorted, lustrous, grey schist, composed largdy of platy mica, two to four mni. long, some of which is black biotitc. Xenoliths of this type are of rare occurrence. rile iiiaiii eoiislituciit is muscovite "which has 2V approximately 40°. It contains poikiloblastic inclusions of sericite and chloritised biotite. The Geology and Physiography of the Lawnswood Area. 65 Biotite is highly corroded and brownish in colour where associated with sericite and its pleochroisin is weak, X light brown, Y and Z = broAvn. Where associated with muscovite the biotite is invariably altered to green ehlorite. Sillinianite, variety tibrolite, occurs in bands of tine acicular aggregates and is largely alteiaul to sericite. Magnetite and sillinianite are accessory. Primary minerals appear to iiave been muscovite, biotite, and sillimanite; secondary minerals sericite, chlorite, and magnetite. The at)})roximate composition is muscovite 36 per cent., sericite 30 per cent., biotite 20 per cent, chlorite seven por cent., sillimanite five per cent., magnetite two per cent. (iv) Hybridised granitic gneiss. — Thei’e are several small occurrences of intermediate to basic rocks formed by the partial graniti^ation of the basic xenoliths. They vary from basic lioru])lende ])eg^^atites, Avith horn- blende, qiiartx. and felspar grains tAvo or three cm, in diameter, through coarsely Imnded dit>pside-plagioclas(' am])hihoHt(‘s Avith small scale ‘‘lit- par-lit’* injections of (iuart7. and microcdine from the granite, to strongly gneissic acihic horizons of the metas(‘diments and otlier metasediments such as mica scliists should also show the etfects of grani- tizaliou. As this is not llie (oise and as the granitic gneiss ('ontains different kinds of xenoliths it is considered to have been ititroduced ns a liighly viscous magma during the ])eriod of diasti’ophism. Plygmatic folding, protoclastie. structures, and the absence of preferred orientation in the quartz grains of these gneisses suggests that the magma Avas a viscous fluid, crowded Avith early formed jdienoci’ysts and xenoliths during the folding, the (juartz crystallising Avhen the tectonic activitv had ceased <23, p. 109). The Jiiagmn is considered to liave been inti'oduced at a considerable depth on tin* basis of the folloA\ing generalizalions of Bucher and Balk: ^ ‘large concordant acid intrusi\ms in folded sediments are’ Avide spread only in early ])re-Cambrian terranes” (1, ]). 281); and ‘hh'ep levels in the earth.... and slow consolidation of tlie mass during continuous movement are probably amongst tin* factors which seem to result in thick foliated shells’^ (2, p. 81). The more pronounced platy parallelism of the gneiss near its contact Avith the metasediments is probably due to movemeu: of the quasi-solid granitic magma against the relatively stationary metasediments. The typical granitic gneiss A has an abundance of hydrothermal minerals — epidote, chlorite, and “saussurito’’ — Avhich Avere probably formed durijig the end stages of consolidation. Pegmatite and c(uartz veins are frequent, some ])Ossibly derived from the Younger Granite. 66 J. R. H. McWhae. Granitic gneiss which lias no hydrothermal minerals and contains greenish brown biotite, is considered to be a less altered form of A formed in the border zone of the cooling magma by more rapid cooling and greater frictional forces. A cataclastie form of the gi'anitic gneiss, greenish in colour, with strained and cracked plagioclase grains, undulose extinction in the quartz, and with much introduced epidote, is freiinently found near epidote-filled veinlets genetically related to the muidi younger dolerite dykes. The great bulk of the xenoliths are amphibolites Avhich suggest, by their chemical and mineralogical composition (23, p. 105) that they are derived from the hornblende schists with little or no addition of material from the gneisses. The presmice of quartz in these basic rocks is probalily due to the conversion of pyroxenes to hornblende liberating silica (13, p. 311), The high refractive iiulices of the hornblende ( jS = 1.672 and /S —1.675) is in- dicative of recrystallisalion of a basic ig’iieous rock in the sillimanite zone (30, p. 107). According to Harker (13, p. 281), at the highest gi’ade of regional metamorphisin of basic igneous rocks, in bands “richer in lime, the place of honiblende is partly or wholly taken by colourless diopside” and the felspar is commonly a medium andesine. These features were noted in the petrological examination of the amphibolites. The hybridised granitic gneiss (iv) is considered to be the result of partial assimilation and granitization of these xenoliths by the granitic gneiss magma, and small scale lit-par-lit injection of acid material into the xenoliths from the magma. The basic epidote chlorite xenolith (ii) is considered to be a xenolith of basic igneous rock similar to the hornblende schists xenoliths in the gneiss at Toodyay except that it has been extensively ehloritized. The sillimanite-mica schist xenolith (iii) is a fragment from the mica schists of the met-asediments. n. THE YOUXGER IGXEOUS IXTRUSIVEb. 1. Younger Granites. Porphyritic granite occurs in tho south-east corner of the area and in a small intrusion into the granitic gneiss, about an acre in area, near the eastern metasediments. In the south-central portion of the area a uniform- grained gi*anite takes the place of the porphyritic type. About 30 chains- north of this a small dyke of gneissie granite outcrops. (a) Porphyritic granite arid xenoliths. A characteristic feature of this rock wherever seen in the field, is the presence of xenoliths up to four feet in diameter of finei’-grained slightly darker-coloured material (text fig. 5). The granite itself is a coarse-grained, porphyritic rock light grey in colour with frequent small, rounded gi’ey xenoliths up to four feet in diametei*. The “phenocrysts^^ are euhedral microclines averaging an inch in length which are dotted with random orientation throughout the granite and also in the xenoliths (text fig. 5). The groundmass is composed of The Geolohy and Physiography of the Lwvnswood Area. 6T Text Fig. .*). Porphyi'itie 'lounger Granite with adamellite xenolitlis. Note the " jihenoeryHts of mieroeline v hieh have developed both in the xeiiolitliH (compare rapakivi ovoids) and in the granite itself. Note also the absence of any j>refeiTed orientation of the mieroeline “ pheno- crysts of the granite. colourle^^s glassy puartz abou] live nun. in dianieltn*, pale green oligoclase^ three to five mm. in diatnetei-, , [>ink microi-iine averagt* (liameter live mm> and black biotite and hornblende average grain size four mm. Jhe mieroeline ‘‘ pheuoeryst.s” are (mhedral with many poikiloblastie inclusions of felspar, puartz, biotite, iuid hornblende. Smaller euhedral mieroeline grains, sometimes vt-ry slightly kaolinised, oeeui’ in the ground- mass. Mieroperthite is fre{iuently developed in the mieroeline, Oligoclase forms euhedi'al grains which are eitiier extiamiely sanssuritised, tlu^ “saus- surite” be:ng mu(di coar.sei- than in the granitic gneisses, ay clear ami slightly zane.l with well developed lami'llar twinning. The saussui'itised {)Hgoelase thought to be a relie from the granitic gneiss. Coarse myrmekite struc- tures are common. Quartz occurs in clear very irregular grains, free from inclusions, and appears to hav(‘ crvsiallised last in interstic<'s between oaidier formed oligoclase, liiotite, hoiaihlende, and mieroeline. The biotite is a .strongly pleochroic brown variety with suhhedi'al form, usually occurring in aggregates with the otluu' ferromagnesian ininerals surrounding the eolour- le.ss fe’snar and puartz grains. Tt has (-) 2V very small, pleoehroism .strong Y and Z — dark brown, X light hi’own, absorption Y = Z, h ^ X, c;^ c X = 0°. There are pleochroic haloes aroumf purple zircon inclusions and other inclusions of apatite and epidote. The hornblende is a strongly ])Ieochroic type X = yellow, Y — b = dark grey green, Z “ bluish green, absorption X <^Y<;Z,c^Z — 24°, optically uegatiA'e. Accessory minerals are titanite, magnetite, apatite and epidote. Order of crystallisation :—Afagnetife, titanite, apatite, hornblende, biotite, oligoclase, mieroeline, and quartz. The average composition is quartz 35 08 J. K. H. McWhae. per cent., microc-line 30 per cent., oligoclase 20 per cent., biotite 7 per cent., hornblende 5 per cent., titanite and magnetite 3 cent. ^ Tlio xenoliths in granite are grey, coarse-textured rocks containing the same minerals as the granite but with a much higher percentage of ferromagJiesians. Occ-asional microcline “ phenccrysts ’ ^ up to one inch ■ long occur in tiu- xt'uolitlns tig. 3). Some of the xenoliths are J slightly gneissic (text lig. (IB). - 1 The lock foi'ining lliese xenoliths apixmrs to be fairl3' constant in i character. It has a granitic micro-structure. The minerals luive the same ; optical properties as those in the granite, and are biotite with sagenitic j rutile webl)ing% (grain-size up to two mm.), greenish-blue hornbhmde, (grain-size two to four mm.), sau^.siu'itised oligoclaso with imdusions of magnetite ami chlorite, (grain-size four to six mm.), f^tuai'tz and niicro- cliiie are clear and vei-y irregular in form and occur in variable ijuantities i from two per cent, to 31.) pei' cent, (^)■ain-size two to live mm. except j for i-are microcline * * phenocrysts " crowded with inclusions of all the other minerals which liave an average size of 2cm. Laigi' (one mm.) j ouliedral titanite grains, probably the la'Milt of the alteration of original | ilmcnite, have inclusions of inagnetitt' (see text lig, tiA). A])atite, epidot*. ! and magnetite' are accessorie^s. Apatite', magnetite, titanite, hornblende, 1 biotite, and tin' microcline* •‘phenocrysts” are all euln'drah | Text Fig. 0. Adamellite xenoliths in tlie iiorpliyritic younger granite. A. Granohlastic textured, showhig association of titanite and magnetite (22317). -Alinerals are hornblende, biotite (b), [dagio- clase (slightly turbid), mierooliue (M), (|nartz (Q), titanite and mag- netite. B. Gneussie structnivd xenolifii showing tlie denelopment of titanite idioldasts (22.i81). Section from .sixunmen taken from the edge of a xenolith ntNU* the contact Ix'tweeu the granite and the xenolith. The Geology and Physiography of the Lawnswood Area. 69 Mierometric analysis of a more acid type of xeuolitli (22.517) shows the following composition : Oligocdase 31 per cent., (|uartz 28 per cent., microcline Iti.l per cent., hornblende 11.1 per cent., biotite 8.3 per cent., epidote 2,7 per cent., titanite 1.6 per cent., magnetite 1 per cent,, and apatite 0.2 per cent. These xenoliths are best described as adamellites and are similar in many respects to the xenoliths in the granite at Victor Harbour, South Australia described by Kleenian (Ida). (b) Unifunn-yraincd (jranite. This ditfers from the jmi'phyi’itie granite in being a iiuifurm, medium' grained type with no xenoliths and no * ‘ phenocrysts, ’ ’ but very frequent aplite and pegmatite veins. The minerals are the same as in the por- phyritic granite, Microcline forms clear irregular grains two to tire mm. in size, which poikiloblastically enclose relics of (piartz, oligoclase, and biotite. Micro]Hn‘thite is fretjuently deveUtped. tn one fresh looking specimen (22.597) tin' microcline was extremely kiudinised. Oligoclase (Ab, AnJ occurs in exti'emely sanssuritised grains (two to four mm.) considered to be relics I'roin the granite gneiss aiul also in clear grains. Quartz and green chlovitised biotite inclusions occur in the sanssuritised form. The quartz occurs iii two habits (i) small (0.1 to 0.3mm.) rounded inclusions in some of the microcline and oligoclase Avhich may be relies from the granite gneiKs, and (ii) larger, irregular, clear grains with an average size of tliree mm. Biotite is invariably associated Avith epidote and often Avith magnetite. It is a greenisb-'broAvn variety, X = light broAvn, Y and Z — dark green-brown to Iumjwu. This biotite may be developing from tiie epidote and magnet ite. jutle green auhodral, moderately pleochroic amphibole with an extiuclioii of about 20^, occurs closely associated with a micac(‘Ous mineral. The epidote, associated Avith biotite, is a strongly pleochroic ty})e, optically negative Avith a larg^ 2V. Pleoehroism is from yelloAv (Z) to colourless (V). Euhedral titanite, apatite, epidote, and magnetite are accessory minei'als. The approximate composition is mici’ocline 3.5 per cent., oligoclase 3>0 per cent., (juartz 2.5 per cent., biotite and amphibole eight per cent., titanite, epidote and apatite tAvo per cent. (e) Granite from (tyke (22518). This is a light grey, tine-grained, gneissic granite which occurs as a small dyke intrusive into the granitic gneiss. The micro-structiire is allotrioinori)hie granitic Avith slight gneissosity due to floAvage. The minerals are .sanssuritised oligoclase, grain-size 0.5 - 1.0 mm. ( 45 |)er cent.) ; clear microcline 0.5 mm. in diameter and rare pheno- crysts np to 5mm. in diameter (20 per cent.); quartz generally in very small rounded inclusions in the microcline and oligoclase poikiloblasts about 0.1 to 0.2 mm. in diameter and more rarely in larger irregular grains (20 per cent.) ; and greenish biotite associated Avith epidote (5 per cent). Apatite, zircon, and rutile are accessories. (d) Pegmatite!^ and aplites. Pegmatite and aplite veins are frequent in the granites especially the uniform granite. Pegmatite, a])lite, and quartz veins occur with less fre- •70 J. R. H. McWhae. quency in tin; granitic gneiss. Possibly some of these veins are genetically related to the Younger Granite. A small graphic granite outcrop occurs in the western band of metasediments in the southern part of the Area. This is a very coarse-grainedj white graidiic p(*gmatite (22575), composed of microcline { 80 ])er cent.) up to two inches in grain-size and quartz (20 per cent.), frtHpiently occurring at the etlge of mici'ocline crystals. Its genetic relationshij) is unknown. A very coarse-grained magnetite-microcline pegmatite (22522) occurs in the granitic gneiss and is thought to ha\o been derived from it in the end stages of crystallisatioji. iMhrocline (HO per cent.) grains arc one to two inches in size and frecpumtly have a graphic inte)'gir)wth of quartz witliln the grains. Irregular grapliic (juartz (8 per cent.), saussuritised plagioclase (0 per cent.) and magnetite (2 ])er cent.) make up the rest of the rock. The coarse pegmatites, aplograniles, and aplites intrusive into the younger granites are all com])Osed of quartz, saussuritised oligoclase, clear microcline (frequently microperthitic) and accessory epidote and green mica. The average conij)osition is microcline 40 ])er cent., oligot-last* ‘Jo per cent., quartz 25 ]‘)er (*ent. No rare ininerals have been found in any of the pegmatites. Origin of the lounger Grmiitcf ^. — All the younger granites have the same niinei'al assemblagt* which is almost identical witli the minerals of the granitic gneiss; there appear to be reli(‘ minerals (some oligoclase, horn- blende, and (|uartz) of the grajiitic gneiss in the Younger Granite, and the rounded xenolith.s in the porphyritic granite are very similar miuernlogically to the .veuoliths in the granitic gneiss, (the bluish green hoi-nbiende, one to two per cent, titanite and other minei-als being common to both). So the Younger Granites ai)]>('ar to be the restdt of the palingenesis of the g 7 *anitic gneiss and the xenoliths in the i)or])hyntic granite are relics of the xenoliths in the granitic gneiss. Th{‘ ^'idieuocrysts'' of microcline with inclusions of all the other minerals w. 7fi) and they have evidently grown from potash emanations from the granite. Granitization, rather than' crystal- lisation from a magma, is thought to hav(‘ f{)rmed these poikiloblasis. Tlu' reason for difference in texture between the iJorphyritic and tho uniform-grained granite is uot understood. The granite dyke and many of Ihe i)(‘ginatites are thought to be geuetically related to the Younger Granites. The retrograde nudamorjihism of siUimanite and eordierite of the nn'lasedimeiits to sericite and possibly the addition of silica in the forma- tion of the, cordierile-anthophvllite rock are thought to be the result of contact nietamorphism by the Younger Granite. 2. Quarts Dolerites. p -Tliese arc uniformly hard, dark , grt'v, nielaiiocratie rocks,' holn- crystafliiie, -witli fine to medium grain and a uniform texture. The Geology amd PiiYyiooiiAriiY oe tue Lawnswood Ahea. 71 Under the miei'oseope an texture^ uuil'oriu ni cluuueier^ is seen. The pyroxene is a pale [)urplish, n()n-pleo('hroic type, subiiedral in I'orni, in grains up to 1.5 nun. diameter partially changed to green uralite on the borders. It is optically positive with very weak dispersion, twin- ning, 12V appi'oxiniately 40°, jS — 1.050, exiinetion A ^ — 51° — indi- cating pigeonitie dioj^s'ide. The [)lagioeIasc i& in euhediad laths (0.5 to 1.0 ?nni. long) showing albite twimiiug and jnore rarely pericline twinning. This plagiocluse is perfectly iVesh labiadorite (Ab^^ with normal gradational zoning sometimes developed. llmenite occnirs in irregular opa.(inc areas up to one mm. in diamelm’, II ap])ears to have erj'stallised in the interstiees I'etween the earlier formed plagitndase and pyroxene grains. There is a pt'ripheral reaetion rim round the ilmenite of a brovcniah (diloritic malei’ial and chlorite stringcu'.s i)ass out into tlie plagioclase. (jluartz and ai)atite ai’e accessory minerals. Ai)proximate mineralogical composition is lal)radorite 50 ])er cent., })yroxene 40 per cent, ilmenite nine per c(ml., (juaifz one per cent. Tlu' rock is slightly uralitLsed quartz dolmate'. The hovdcu’s of the dykes are made up of line-grained uralitised dolerite allowing mon* advanced uralitisation tliau the central parts. ' In these Hiier-grained rocks the pyroxene is seen to he extensively uralitised to a greenish ami)hiboh> wliiidi is moderately pleochroic, X = light purplish colour, V green. Z ~ bluish green and the extinction is ai>proximately 10°. Aiilieed and described by Hobson (G.S.W.A. File 237/1910) who states that up to the end of 1907 they had produced 18,253 tons of iron ore for use as a iiux. These deposits are the result of latcritisation of iron-rich metajaspilites of the Jimperding Series. The area of iron-inch rocks is approximately 60 square chains accord- ing to Hobson’s ma^i; and the average iron content is 45.5 per cent. A plant is being erected at Wundowie, about 10 miles to the west-south-west of Clackline, to obtain jiig iron from similar ore, using charcoal as a fuel for smelting. IHob.son's Map and Rciport '•Proposed drilling in the vicinity of the Clackline iron- stone deposits” has since been published in the W.A. Mines Dept. Ann. Kept, for 1945, pp. 58-00.— Ed.] Vr. HISTORY OF THE AREA. 1. In early Pre-Cambrian time argillaceous, arenaceous and iron-rirdi sediments (jaspilites) were dei>osited along with contemporaneous tuffs and basic igneous lava flows or sills. 2. An orogenic period accompanied by the intrusion of a granitic magma followed. At this stage the, sediments suffered regional metamorphism under silli- manite zone conditions and considerable jilastic fiowage took place in the less competent argillaceous facies. There was no further orogeny or re- gional metamorphism after this period. 3. The granitic magma did not com])letely crystallize until after the folding had cea.sed (23, p. 109). It consolidated as granitic gneiss sills of huge size which indicates that the folding had taken place at considerable depth (4, p. 294, 2, p. 81). 4. A relatively short lime, geologically speaking, after the coinpletel consolidation of the granitic gneiss, palingenesis of the granitic gneiss and sediments of the Jimperding Series took i>lace. At the end of the orogenic period the base of the orogene Avonld be at a great depth and under great pressure due to the superincumbent loaped mesas and buttc'i j'e])resenting residuals of the old peneplain, above which project ridges of more resistant tjuartzites. Vn. A(4 aXOW!.EI)G5LEXT. T wish to ex[)ress my deepest thaidxs to Professor E. de G. (4arke for liis many luOpful sugg(‘stions and discussions during the preparation and revision of tins pa])er. I also wish to thank Dr. li. T. Prider for his very great help in the field, in llu' practical work, and for his advice in the ])reparalion of the text. Tin* mapping of the area d(‘sci'ibed was done* in the cenu'se of fic'ld instrmdion (dass(*s, by [)ai'lies of -<<‘ 1001 * geology sludenls of the 1 niversity ■of Westeiai Australia in IDoi) ami P)45. i\Iany of the thin sections used ill t!u‘ preparation of this })aper were cut by these students. The author tiesires to express his gratefulness for this assistance. l.IST OF hFFEHEXOKS. 1. A Ideniiaii. A. Ih, 1942. ‘ ‘ Silliinaiiite, Kyaiiite ami Olay Deposits near Willia ms- town, 8outIi Australia.’’ Trdiis, Hay. -S'oe. *S'. A/os-/., A'^ul. (ifi (1), p]>. 3-14. 2. Balk, Ji., 11)37, “ structural Heluiviour of Igneous Bocks.” Geol. Hoc. America, ^^cm. o. 3. P.astin, E. S., 199!), ^Chemical C'oinpositiou as a Criterion in Identifying -Metainorpliosed Rodinients. ” Jr»()'n. Gaol., Vol. 17, pp. 445-472. 4. Bucher. W. IF., 1933, “Tlie Deforinalion of the Earth’s Crust. An inductive approach to the prohlenis of Diastroidiisin. ” Prineetowu University Press, Priucctown. 5. Canavou, P.. and Edwards, A. B., l!)3s, ^'The Tron Ores of Vniupi Hound, Western Australia.” Proc. AkhI. Tns‘f. Min. & Met., XS. Xo. 100. 13. Clarke, E. dc C., 1930, “The J’rc-Camhrian Succession in Some Parts of Westei’ii Australia.” IGjA. Au-sl. A^s.ioc. AAv. He. for J03t>, ])p, 15.)-192. 7. Clarke, E. de 193S, “Middle and Western Australia.” Bd. 1 VII of lieg. Grle, W. F.. and Gloe, C. S., 1919, “The Getilogy and Physiography of the Malkup Area.” Journ. Hoy. Hoc. W. Aast., Vol. XXVI, pp. 139-171. 74 J. li. H. IMcVVhae. ] 0 . 11 . 12. IJ. 14. 15. 1*5 11 10 . 17. 18. 10 . 2U. 21 . 23. 24. 25. 20 . 27. 2S. 20 . :u). 31. 32. Ellis, II. A., 1030, “ Tlu- Ec'olo^y of tlic Vilii'iirn (Toldlic'Id South of the (Ireat Eastern Railway.^’ (ia)l. Surr. Wes/ Au.'tf. /Ivy//. 07. Eeriiior, L. L., 1000, Mvm. /Vro/. Sure. India, \'ol. XXXVII, ])|). 381-3. Eoniiaii, E. (J., 1037, “A Contrihution to our Knowledge of the Pre-Canil)riai Snceessiou in some parts of Western Australia. Journ. Hoy. Hoe. W. Aust., Vol. XXIII, pp. xvii-xxviii. liarker, A., 1032, “ Metamorplusni ” (Metlieim and Co. Ltd., Loudon). Jutson, J. T., 1012, “Geological and PIiysiogra])hieal AWtes on a Traverse over Portions of tho Darling Plateau.” (ieol. Saw. W. Aiist., Bidl 48 oo 138-173. Jutson, J. T., 1034, “The Physiography (Geoniorpliologv j of Western Aih- tralia.'^ (ir(d. Surv. IP. Ga.v/. lUdi. 05. . Kleenian, A. W., 1037, “The nature and origin of the so-called dioriH- inedusions in the granite of Granite Island.'’ Trans, liou. Hoc. S Au^t Vol. LXi, pj). 207-220. Matheson, H. S., 1038, “Report on the Clackline Eirebrick Clay Pits (South- AVest Division).'’ Geol. Snrv. West Aiist. Ann. Kept, for 1037, p. 13. Miles, K. R., 1041, “The Jasper Pars ami Related Roc-ks of Western Aus- tralia. (Cnpublishcd D.Sc. Thesis at the Cniversity of Western Australia.) Xevin, C. M., load, “Priuci])les of Stnidural Geology, Second Edition.” (John Wiley k Sons Inc., Xew York.) Phillips, E. (’., 1037, “A Eabric Study of some Moiue Schists and Associated Pocks.” QJ.G.S., Vol. XCIII, pp. 581 (!20. Prescott, J. A., 1031, “The Soils of Australia in Relation to Vegetation and Climate.” G.S.I.ll. An.siralia, Vndl. 52, j)p. 0-7(1. Prlder,R.T., I0IO,“Cordierite— Anthophyllite Rocks Associated with Sinnel- lIyper.sthonites from Toodyay, Western Australia.” Geol. Maa Vvd LXXA'II, pp. 3(14-382. Prider, R. T., 1011, “The Contact Del ween the Granitic Rocks :ind the Carduo Derjes at Armadale.” Journ. Soy. Soe. W. A us/., Vol. XXVII, pp. 27-55. ^ Prider, R. T., 1044, “The iVtrology of ihirt of the Toodvay District,” Journ. Roy. Soe. /E. .\iist., Vol. XXVI II., pp. 83-137. J lider, R. J 1048, “Igneous Aidivity, Metamoi pliism ami Orc-Eormatioii in Western Australia.” Journ. Roy. Soe. 113 Ansi., Vol. XXXI, pp. 43-84. Read, H. il., 1044, “Meditations on Giaiiite, ihirt Two.” Proc Geol Us Vol. LV, Pt. 2, p)). 45-03. ‘ " *' Simpson, K. S,, 1035, “ Contribiitioiis to the Mineralogy of AVestern ins- tralia, Series 1.” Journ. Roy. Soc. W. Aust., Vol. XXII, pp. us Simpson, E. S., 1037, “ (hmtributions to the Mineralogy of AVcstoni Australia Series XI.” Journ. Roy. Soe. /E. Aust,, Vol. XXIV, pp. 107-122. " Washington, H. S., 1017, “Chemical Analysis of Igneous Rocks.” US Geol Surv. Prof. Paper 00. AVhitehouse,P.W., 103(1.“ Studies in the Date Geological History of Queens- land. ’ / nn\ of Queensland Papvr.s {Gent.), Vol. 2 (N.S.), Xo"! 1, pp. 1-74 Wiseman, J. D. II., 1034, “Central and Sonta-West Highlands Ei)idioritcs V Study in Progressive Metamurphism. ” Q.J.G.S., Vol. XC, pp. 354-417.' Woolnongh, W. G., 1927, “ Tlie Chemical Ciiteria of Peiieplanation The Duricrust of Australia.” Journ. Proe. Roy. Soc. K.S.W., Xvl LXJ, pp. 1-53, Woolnongh, W. G., 1030, “The TntUience of Climate and Topographv in the Eormation and Distribution of Products of Weathcriug.” Geol. Maa Vol LX\11, pp. 123-132. ' CONTKIBUTIONES FLORAE AuSTRALIAE OcCIDENTALIS XII. 75 3 .- CONTKIBUTIONES FLORAE AUSTRALIAE OCCTOENTALIS XII. By Charles Austin Gardner. Roa,d llth June, 1040. IXTRODUCTION. Amongst t])o largo mimhc'r of iindc'scrllx'd spoeios solootod from the material \vorkod over during the f)ast year, t lirt'o of unusual iutorost have been selected for early publication. In September, !045. whilst engaged on a survey of plants for exarnmation for their economic possibilities as jiotential sources of drug materials, two interesting fisammo|)hytes growing in the sandy flat of the ^fortloek River <*am(‘ to notice. A .search for fruiting material was suhso(piently made in October. December and January, Init without success, only one i‘i]ie and partially damaged fruit being found unattached below one of the plants, but snfticient is noAV known to [)lace tlu!se plants in the family Clienopodiaeeae, although th<’y seem to be anomalous in this family. The solitary flowers, strictly unisexual and dioecious, the homomor- phic perianth, and the absence of bracteolt'S, together with tlie stamens isomerous witli and opposite' to tlie perianth-.segmeuts, and the three-partite styles, make tlieso plants (jiiite distinct from anything hitherto described, and show a centain affinity to th*' Caryophyilaceae, although the position of tJie stamt'ns and tlie nature of the styles is t'ntirely that of Cluaiopodiaceae. Remarkable too is tlie the difCewenice in the phyllotaxis of the two species, — in one closely spirally imbricate leaves ; in tli<* otlier opposite tt'aves or the leave.s in oppositf' Fascick's, with elongated inti‘rnodos and spinescent- branches. The former lias tlie habit, of some siieeies of PijcnopinjUuni (C'irryopbyllaceao) ; the latter is reminiscent of Bhauoflid (('heiiopodiacoae)- This gt'mis I have named Hoycert^ after my eompanion of these Iravtls. who first noticed R. pycnophijlloides liy reason of its briglit orange-red antiKTs protriuling from the sand-covered tufts of tlie plant. The second siiecies was discovered Avhile searching for fruits of the first. Until ri[>e fruits have been found, it would be unwise to assign this now and interesting gtmus to any ])articular s('etioii of the family. The second genus is of exceiitional inter(*st. from the [loint of view of plant- geograpliy, since it forms another link betw<‘eu the American and Australian (^outinf'nts. In March. 1944, Mr. F. D. Hamilton, the District Forester at Mundaring, a townsliii) less than thirty miles from Perth, brought me a branch of Davlesin perfinala from which protruded the flowers of a species of Piloslyles, of the Section KuplhsiyJes. TJie occurrence of this genus in South Western Australia is of more than passing interest ; not only is it the first record of anj^ of the 15500/2/48—750. 70 CiiAiiLEs Austin (Jardner. Kafllosiacoao in Australia, it is also a sj)eci(‘s hrioiiging to a Socfioji of a genus hitherto n^corded only fi*om America, and it is, ai)art from Trirhorllne. the only genus j-estrieted to fSoiitli America and South Western Australia. This relation- ship, usually exhibited by the Antarctic Element, is, as a rule, more strongly represented in X('w Zealand, Tasmania and Wctoria than in any other part of Australasia, and is excunjililit'd most strongly by Proteaceae, Cen(rolepLs\ Stylidiaceae and Ej)aci‘idaoeae. Tile distribution of the Rafflc'siaeeao is interesting. Of the four Tribes, tlie Rafllesieai!, a.Il large-flowered species, art? restricted to the Indo-Malayau region t a with 12 to 13 species toeing foiiml in Malaya, ^Vlalacca. Borneo and Sumatra ; Sitprtd, with one spt'cies eutlemic in the Eastern Himalayan region, a-nd /?/o2n///7/a.s* with two species from -lava, Sumatra, i^ornt'o and Malacca. .All of tliese are found on tlie roots and stems of tlu' \ itaeeae. I lie I ribe ^litrasfemouoat', Avith the single genus J//Pr/.s7e//u>a, com- prising thrt*(' specit'H, t'xlf'iids from Sonlhci'n -lapa-n tf) Siimati’a, atnl is parasitic oil tilt' roots of Eagaceae. ’’(’lu' Trilie Cyfint'ac includes t wo genera. Cijtinus and BdallopJiyion ; the formt'r, with six s])ocies, extends from the Alediterranean Region to South Africa and Aladagascar. and has various host plants, while the latter genus. Lidal}ophn(on, Avith four sjiecit's. is restricted to ^Mexico, and also lias various host plaufs. TIha '■j'rilie A]»alantheae comprises two genvra, Apodavfhes and PiJo.si pies. I he fot'iuer. willi two specii'S, is parasitic on the Elacourtiaceat' (Caspdvin) and is resi rifted to Tro[)ieaI AmtHea. Pilo-stples on the otlier hand, is the most AA'idely distributed genus oi the family. pdoshjles Harms, has fiftinsi spetht's extending from ( ahtoruia and lexas to I5razil and ('hile. '^fhe various sjiecios are parasitic on th(^ thriM' families of the Lt'guminosae, eacii specie's occurring on a single ge'iius. live oecurrhig on Calh'findni and Mlwosa (ATimosae.eac'), thn'o on Bdfdnnia ((Wsal|iiniae{'ae) and the n'lnaindt'r on Didea, Adesmitf, (jfdariitt, and J (t rose la {Papilionaeeae'). The new s|)eci(‘s described bi'loAV is t h(' first extra- Ami'riean specie's to hc' recorded, and is piirasitic on a genus of tht* Podalyrii'ae (Papiliouact'ae). Astraijaladehe. AA'ilh one s{)eei('s, is restricted to Peisia, A\'hf*re it eicctu's as a pai'asit-e on specie's Asb'ftfjfdas (T*apiIionaceae- dalege'ae'). and the ^ Berlinianche Avith two species is revstricted to tropica! Africa, where it. occurs as a [tarasite in the brandies of Berilnai and Brachip slepia ((’aesalpiniaceae-Amht'rstieao). BUostyles is pe-ihaps the smallest-floAATU'etl ge'uus of the Rafhesiaoeao. and all appear to he stem parasites with a restricted range of host-plants. The new spt'cies is rt'hitcd to tfio American jilants, just liow closely 1 do not knoAv, but the absi'iice of a distinct p('i*ianth-tube, the cla\v*ed Jicrianth-segmcnts. and the canai or tubi' of the column of tlie male floAA’er are points Avhich I luwe not been able to associate Avith any other species of this Section. The evidence suggests that Pihsfyles is an Auturlic Elc'ment AA'hich had its origin in the great soutlieni land. The main branch (§ Eapdosfijles) had two migration roiili's — out' iiortliAvards in the American i^ontiiK'nt, Avhere its distribution now I'xtends over the tropical and Avarm regions, and a second migiation loufe of whit'h iht' only cA'idence aa'o possess is this no\v' sjAocies in South Western Australia. Tlie § Be.rlinianche of tropical Africa, reiiresent a third migration route which may have terminati'd there, and this appears probable, for there are structural peculiarities in this Section Avhich indicate that the Persian species is not dt'rivi'd from them. The Persian species (§ Asfrngalanche) seems to be most closely related to the South American s})('ci('s. If this is triu', then it is ])rohable tliat is lias reached Persia by A\'ay Conthibutiones Flokae Austkaliae Occidentalts XU. 77 of the great traffic route which formerly extended from. Antarctica to Europe by way of Australia and Persia, witli India and the Mediterranea.n as inter- mediate points. If such is the cast', then PUosiijles should be looked for in Eastt'i’ii Australia. The fact that it has only no^v been tliscoveretl in South ^Vestern Australia, and so close to the Metropolis, indicates how little known the Australian flora is today, and further, the species M'hicli is only in evidence when in flower (and perhaps also in fruit) may easily be mistaken for some monstrosity, such as a gall-flower. Pilostyles Hamiltonii C. A, (Jardn. sp. nov. Alabastra 2 mm. diam., ov’oideo-glol)osa, solit.aria, e cortices irn'gulariter enunpentia, saepo numei'osa. Flores carnosi, exteriiis atro-purpurt'i, intus roseo-sanguinc'i. Bracteae phu’es. fere 1)-11. Ihseriatat?, iinbricatae, t'xteriores ovatae vel ovato-orbieulatae, obtusae, minore.s longitudine medio perianthii, interiort'S (fere 5) oblongae vel ovato-oblongae, obtusae. concavae, integrae vel eroso-laceratae. l^erianthii segmenta 4 -6, soluta, imbricata, ad basin attenuata vel constricta, oblonga vel oblongo-s[>athulata, Integra, obtusa, et sicut bracteae tenuiter striata.. Discus epigynus carnosus, sub-verticalis. Columna in floribus masculis cylimlrica, fere ecgialis iieriantliio vel rare longior, apice incrassata ('t alto couvexa vd capilata, tubulata et b?'(‘viter bilobata, margine finibrio-papillosa minutis papillis ; antiierae num(‘rosa(‘, submargine dense biseriataodia- cearum. (‘t ejus locum systematicum. fVuctu mature non vise, remanet ob- scurum. Plantae 'videntur esse striete unisexuales. et foliorum coi)ia est insueta. tleiius babet (piandam similutidinem cum Cftri/ophtjllareu' {Alb-ln- oideiS-Pt/cHophtjl/eis). sed stamina hypogyna stylus(|ue etc. sunt t'heno- i)odiacearum. Idantae occurrunt eumulatae in salini.s anaiis in alvt'o tluminis •' Mortloek “ projjc Meckering, in caules f<)liintis longo excedentibus, demum patentibus. Hab. in distr. Avon prope Meckering, in locis flepressis salinis (ita dictis Mortlock River ’’) fl. m. Oct. Gardner 7()59a. (Typus in Herbario Perthense). Haec species tarn dissimilis R. pycnophijUokleH in habitu et pliyllotaxis (sen foliornm formationem) crescit siinul cum specie dicta, sed in locis Icviter minus salinis. 80 Chables Austin Gardneb Plate I. Pilostyles Hamiltonii C. A. Gardn. Parasitic on stems of Daviesia 'pecthiata Lindl. i Conthibittiones Florae Australiae Occidentalis XIT. 81 82 C'haiiles Austin Gardner. l^lace TT. Roycea C, A. GanJn. A-K. R. pycnophylloides C. A. (hmhi. A, habit. B, branclilet. flowers. F, penanth-segment. G, anthers. H, $ flowei'. I K, section through ovary. L-S, R. spinescens C. A. (iardn. L, N, under-sinface of leaf. O, aide view of leaf. P, ^ flower. R, $ flower. S, ovary and style. C, leaf. U and F, , ovaries and styles, habit. M, branclilet. Q, pcrianth-segmento CONTRIBUTIONES FlOHAE AuSTRALIAE OCCIUENTALIS Xll. 83 1 Tertiary Deposits Near Norseman, Western Australia. 85 . 4.— TERTIARY DEPOSITS NEAR NORSEMAN, WESTERN AUSTRALIA E. DE C. Clarke, C. Teichert and J. K. H. McWhae (Department of Geology, University of Westei’ii Australia). (With an Appendix by Irene Crespin.) Head : 9tli April, 194i). (MINTENTS. I. Introduction Page 1. Locality ... ... ... ... ••. ••• Sa 2. Topograxjhy ... ... ... ... ^6 3. Previous work... ... ... ... ... ... ... ... 4. Present investigations ... ... ... ... ... ... 88 0. Acknowledgments ... ... ... ... 89 IT. Situation of outcrop arfas of the Tertiary sediments 89 III. Rock Types 1. Spongolito ... ... 89 2. I’nfossilileroiis dolomite ... ... ... ... ... ... 90 3. Eossiliferons limestoiu' and dolomite ... 90 IV. Description of outcrops 1. Canipbell’s “ oj>alized .soa-beaeh ” ... ... ... ... ... 00 2. Pr'ipess Royal ... ... ... .•• *.* ••• ••• ’d 3. The Peninsula 93 4. Lake Dimdas ... ... ... 97 .5. North shore of Jjake (Jowaii ... ... ... ... ... 97 V. Correlation and palaeogeography 98 \T. Appendix — N otes on the Bryozoa from limestones at Lake Cowan and NorsemaiL Western Australia ... 99 VH. References 1. iXTRODUCTION. 1. LOCALITY. Noi'seinan, one of the most southern gold-mining towns of Western Australia, is about 350 miles east of Perth and TOO miles north of the ‘Southern port Ksjieranee. It lies on an auriferous greenstone licit on the east shore of Lake Cowan and is eonneeted hy rail with Llsperance mid with (.'oolgardie on the Trans. Australian Tjine. (iold was di-'('ov('i'ed in the Norsimian district in T892 and is still being produeeil : the output in 1943 was a!)Ont 40,000 oz. 14159/2/4S~7.>0. E. DE C. Claeke, C. Teicheet and J. R. H. ]\[c\Vhae. 2. topogkaphy. Tho average annual rainfall of this part of the State is about inches and the average evaporation is well over 100 inches; consequentlr Lake Cowan, like the many lakes farther inland, is nearly always dry. 87 Tertiary Deposits Near Norseman, Western Australia. The iloors of the salt lakes of Western Australia are almost perfectly smooth and, after heavy rain, may for a short time be covered with water which is rarely as much as three feet deep. Lake Cowan, and Lake ibindas 5 miles farther east, occupy shallow depressions, about 900 feet above sea-level Avhich are elongated in a north- south direction approximately parallel to the strike of the Pre-Cambrian locks on which they lie. A bore sunk in 189b in the lake-bed Just Avest of N(n*s('man traversed 977 feet of lacustrine muds Lefore reaching Pre- Cambrian rocks (Campbell, 19(H), p. 15), so that the depth of part of the depression occupied by Lake Cowuui Avas once of the order of 400 feet. JMost of the auriferous greenstone belts of Western Australia are more liilly than the surrounding country, npparcnlly l)ecaase the green- stones are more resistant to tiie agents of ari to the gold bearing rocks was not recorded, lie suggested that the spongolite is probably “ncAver than Cretaceous'’ in age. lhat spongolite rocks have a wide distribution in the Norseman dis- trict was suggested by the discovery (Clarke, 1925, p. 12) of Ioav cliffs of sponge spicule rock on the north shore of T.ake Cowan, about 30 miles N.N.R. of Ih'incess Royal. Although no further field investigation of the fossiliferous rocks had been made, Cregory (191()) suggested, mainly from the identification of some Hryozoa, that the rocks in which Campbell had found marine shells were of Miocene age. Chapman and ('’respiu (1934) published determinations of a number of pelecypod and gastro])od species and of one l)rachiopod (MageUania insoliUi) from Campbell’s “opalized sea beach”, but they did not discuss the age of the beds, though it is clear from the context of their paper that they regarded them as Miocene. 4. REESENT INVESTIGATIONS. It is obvious that the occurrence of Tertiary rocks so far inland on the Pre-Cambrian shield throws light on the later geological history of this part of Australia but no further held study of the fossiliferous beds had been made since ra7npbell’s time, until in 1943, IMr. 11. AY. E. Talbot informed us of the discovery of a new fossil locality at the Peninsula, 15 miles north of* Norseinan, and gave some specimens of fossiliferous limestone to the Department of Oeology. In Alay, 1944, Ave Avere able to spend tAvo Aveoks in the Norseman district examining the fossilifeimus and other sedimentary deposits along the eastern side of Lake CoAvan betAveen Norseman and the east coast of the Peninsula, includinsr the Tertiary Deposits Near Norseman, Western Australia. 89 Princess Koyal deposits. AVe also visited an area near the northern end of Lake Dundas, where (Campbell had reported the occurrence of unfossili- ferous dolomites. 5. acknowledgments. The expenses of the excursion were defi'ayed by the Commonwealth Research Grant to the I'uiversity of AVestern Australia. Transport in the Norseman district was generously provided by Central Norseman Gold Alines. AA"e wish to express our gratitude to Air. AA", Lindesay Clark, director of the AA’^estern Alining Corporation, to Air. 11. AY. TL Talbot, geologist to the Corporation, and to Air. AA^. Dutton, supeihntendent of the Central Norseman Gold Alines for their courtesy and help, without which these observations could not have been made. AVe are also indebted to Dr. R. T. Prider for help in revising the text. II. SITUATION OF OUTCROP AREAS OF THE TERTIARA^ SEDIAIENTS. So far as known at present the T(*rtiary sediments occur in patches, isolated by erosion, along the east side of Lake Cowan and near the north end of Lake Dundas about five miles north-east of Norseman. The occur- rences which we examined may be grouped into the following live ^'outcrop areas” : — (1) CampbelUs '^opalized sea beach,” three miles north of Norse- man. (2) The spongolite deposits which underlie part of the old Princess Royal Townsite and extend west of it. To the north, between Princess Royal and Lake Cowan and on the shores of the lake itself are several disconnected patches of unfossiliferous dolomite which might be included in this outci*op area. (3) A number of limestone aud dolomite outcrops, mostly fossili- ferous, along the north side of the Peninsula, about 15 miles jiorth of Norseman. (4) Unfossiliferous dolomite outcrops on the north shore of Lake Dundas, live miles north-east of Norseman. (5) A spongolite occurrence at the north end of Lake CoAvan. This was visited by one of us (E. de C.C.) many years ago. It is to be expected that a close survey of the shores of Lake Cowan and Lake Dundas Avill reveal the presence of additional outcrops. III. ROCK TA^PES. There are three main roek types in these Tertiary deposits: — spongo- lite, unfossiliferous dolomite, and fu.ssiliferous limestone and dolomite. 1. The spongolite is jjorous, Avhite to orange-red in colour, and very light in Aveight. It is composed of the spicules of siliceous sponges of which many species Avere identified liy Hinde (I-9T0)» Associated with the typical spongolite are beds of blue clay and white shale only a feAV feet thick. The blue clay is a light bluish-grey rock Avith occasional Avhito 90 E. DE C. Clajrke, C. Teichert and J. R. H. McWhae. spots up to 15 iiiin. in diameter and irrefjularly scattered reddish-brown spots. ^Microscopic examination and heavy mineral determinations showed that it is largely composed of extremely tine particles of clay minerals Avith a. smaller amount of fine-grained, angular quartz, iron ores, and liypersthene; the hypersthene was no doubt derived from the adjoining norite dyke Avhich was mentioned in the introduction. The Avhite shale is exceedingly iine-grained, Avhite, and slightly friable and contains a minute amount of very fine-grained quartz, iron ores, and hypersthene. Sponge spicules occur in both rocks but are not uiimeroiis. 2. The tmfossiJifcrous dolom.ite (Campbell, lOOG, p. 21) is a hard, Avhite, tine-grained rock. Staining tests (Kodgers, 1040) show that it is an almost mono-minoralie dolomite containing occasional fragments of quartz up to one mm. in diameter and still rarer rounded bodies of ferruginous material up to three mm. in diameter Avhich may be concre- tions but are more ]u'obably pebbles. Neither fossils nor any sign of bedding can be seen in this rock Avhich is included in the Tertiary sci'ies because it overlies the Pre-Cambrian rocks and occurs near strata knoAvn from their fossils to be Tertiary in age. 3. There, are seAvral varieties of fossiliferous Iimesto?ic. Some are unaltered, others have been changed diagenetically to siliceous or to dolo- mitic rocks. They vary in character even in one outcroi"), and Avill therefore ho discussed in the next section. IV. DESCRIPTION OF OUTCROPS. 1. CAMPBELE’S •‘OPALIZKD SEA BEACH.” A very gently undulating area of about 100 acres covered with unfossilifcrous dolomite (Campbell, lOOO, fig. 11) occurs near the Norse- man end of the causeway over Lake CoAvan, about three-and-a-half miles north of Norseman on the south side of the great norite dyke. At the eastern end of this occurrence there are two small fossiliferous outcrops, about 40 yards apart Avhich underlie the unfossilifcrous dolomite. About 100 yards fartlier east is a knoll oA’er Avhicli are scattered many fragments of chrysoprase. The fossiliforous rocks are opalized and it is difficult to determine their original characteristics, Init there appear to have been three types; — (a) Fine laminated sandstone. (h) Very fiiu'-gi-ained mudstone Avith conchoidal fracture and few fossils. (c) Sandy limestone with ojialized fossils and rounded to angular sand grains. The sandy limestone is more fossiliferous than the other tAvo, but the fossils are A'ery much altered diagenetically and good specimens arc hard to obtain. iMiss Irene Crespin (see Appendix) has determined the folloAving P>i'yozoa from this locality : — 3£acropora chirl-ei (T. Woods), Amphihlestruin sp., Hitfrlisina r/emimta (Waters), Cellepora fossa (Ilaswell), Adeonellopsis elavata (StoL), lietepom aeiculifera iMcG., Crisia acropora Busk. Rome years ago Chapman and Crespin (1934, p. 12G) gave a list of fossils, other than Bryozoa and sponges, from “Norseman”. Since no other Tertiary Deposits Near Norseman, Western Australia. 91 fossil beds, with the excei^tion of the Princess Royal spongolite, were then known from the district, these fossils must have come from Camp- belPs discovery. The list is as follows; — Magellania insoliia (Tate), Lima hassi (T. Woods), V enericardia spinulosa (Tate), Venerlcardia cf, scahrosa (Tate), Corbula sp., Turritella trisiria (Tate), Semiacfaeon micro- ploctis Cossiu. Most of these species have also been recognized in our collections from this locality. We also found representatives of the following: — Glycimeris sp., Barhatia sp-, Corditu sp., Cardium arcaef orrnis (Chap- man and Crespin), Chlamys aldingensis (Tate). Our collection also includes some unidentified gastropods, one or two corals, Cidaris spines, and a columnal of Pentaerhms. 2. PRINCESS ROYAL. Spongolite beds occupy an area about one mile long and a quarter mile wide, in the vicinity of Princess Royal (Plate I). As mentioned above, the spongolite was first discovered in the deep lead under tlu^ main street Text fig. 3. Breakaway of spongolite, three-quarters of a mile north-west of Old Main Shaft, Princess Eoyal. 92 E. DE C. Clarke, C. Teichekt and J. H. H. McWhae. of Priiiccf-:^ Royal, but there are rather extensive outcrops in a gully whieli runs north just west of the townsite and in low breakaways north-west of the townsite. Text tig. 4. Contact of Prc-Caniljrian and Tertiary roi-k? in a small gully about eight feet deep, 40 c'liains Avest of Old yiain Khaft at Ibiiic'css Royal townsite. Weathered Pre- Cambrian rocks are exposed in the bottom of the gully, blue clay and white shale along the sides. The contact is marked l)y a black line. The sediments lie with marked unconformity on Pre-Chunbrian rockft Avdiich apfK'ar to 1)(‘ chielly amphihoIiU's with oc(‘asioiial iK)rp]iyry dykes and to belong to the Ivalgoorlie-Yilgam System. The surface of the Pre-Cam- briaii, at its contact with the spongolite series, is weathered and uneven and is overlain by two feet of blue clay: then come two to four feet of Avhite shale, followed by a bed of spongolite 20 to 25 feet thick which in some places is white and is composed very largely of sponge spicules: in others, where it is red, spicules are not nearly so abundant. These three beds are conformable. The sediments thicken as wo apiiroach L. Cowan because they occupy a north-south depression in the Pre-Cambrian rocks which deepens north- wai’ds. On the west, south, and east sides Pre-Cambrian rocks constitute Tertiary Deposits Near Norseman, Western Australia. 93 ±he higher ground so that their eonlaet with the sediments can he mapped, \vdier(?as the northern boundary is obscured by alluvium. The dumi-s along the deep lead contain spongolite, siliceous oolite, and an oolitic carbonate rock. The oolitic rocks are not found at the surface, and, all the shafts being inaccessible, it can only be assumed that they occur somewhere in the Tertiary series. About 200 yards north of the last s])ongolite outcrop is an exposure of dolomite north-west of which there are six or seven others all mapped by Campbell (Campbell ItlOO, fig. 3). They are all unfossiliferous. The relation of the spongolite to the dolomite has not been seen hut the base of the sxrongolite is about level with the top of the dolomite. The only palaeontological work on the spongolites was done by llinde (191(1). He cojisidered that the spicules wer(‘ idenlicai with or closely similar to, those of the following forms previously described: — Monaxonid. Latruncidia ; Desmucidon {llormteodictt/a) (jrandis LJidley and Dendy; Petrosia varddiUiH Kidley; II(dichondria infreqnens Carter; Sirongylophora dtwissitna Dendy ; Forcepia crossanchorata C'arter ; T ethga Lam., Myxdla hastata Kidley and Dendy. Tetrnctinellid. Stelhdta reticnhda Carter ; ErgJus Gray ; Craniella Schmidt; Cgdoninm. muUeri Fleming; (podia zetlandica Johnston. Lithistid. Ragadinia Zittel ; three species of Disoodermia Boeage ; CoraUistes Schmidt; TheoneUa sivinlioei Gray; Vetidina Schmidt; Dactglo- cidgcitfs Carter. / Ilexactinellid. Rosstdla aidarctica Carter. 3. PENINSULA. The shore of the Peninsula is broken into small bays, islands, sandspits, and promontories (Plate II). Outcroi)S which we call A, B, and C, of horizontal or very nearly horizontal fossiliferous limestone occur in three of the bays, the shores of which are generally steej^ banks, in i)laces under- cut, two to 15 feet high, formed by various agents of arid erosion and by very occasional coirasion by the lake water. In some of the bays there is a ‘daterite^' layer two to three feet above the bed of the lake but well below the present soil surface. Locality A is the west bank of the most southern of the bays. The out- crop at locality B in the third bay north of this extends across the floor of the lake to the north side where it disappears under a sand ridge lOO yards wide, on the otht*r side of which, in the next bay, is locality C a limestone bank 12 feet high and 130 yards long. Thin sections show that the Tertiary rocks at the Peninsula ure com- posed of fiiio-gi’ained matrix of dolomite unci ferruginous material in which there is a varying percentage of comy)lete or fragmentai-y fossils with angular, medium-grained fjuariz [tarlicles and more rounded ferruginous fragments and concretions, up to two mm. in diameter. Staining (Rodgers, 1940) shows that calcile occurs only in some of the casts, re])lacing the original shelly matter, but in most instances the replacing material is dolomitic, and, in some places it is secondary ferruginous matter. 94 E. DE C. Clabke, C. Teichebt and J. R. H. McWhae. Text fig. 5. Limestone cliff at Locality A, on the Peiiiitsula, Lake Cowan. Localit,, A h a miniature, almost vertical clitf of fossiliforous limestone extendijig- for a (juartor of a tnile. along the west side of the bay. It is 12 feet high and IIat-toi)])ed at the southern end, but only two or three feet high at the northern ejid. Liko the out('roi)S at the other localities at the Pen- insula if shows great lateral vanation in lithology and fossil content. The clitf for 2(10 yards from the southern end of the outcrop is composed of a haul, massive, light yellow-brown limestone, of which algal fragments and concretions constitute as much as 40 per cent., and echinoid spines and plates, and rare jielecypods five ]ier eent.; the matrix is partly doloinitic and partly ferruginous. For the next lOO yards farther north small peleeypods are veiy numerous, but Bryozoa and a feAv gastropods and brachiopods also occur. Ihe section here is 12 feet thick and shows distinct vertical valua- tion in colour and texture. Lensing bauds of shell grit compose the upper five leet, well-iireserved fossils being found only in the lower seven feet. For the next oO yai'ds tarther north the rock is a doloinitic limestone, being’ made up in great part of Bryozoa "with very subordinate numlicrs of brachiopods nnd echinoids. The expose, on the Peninsula, Lake Cowaiu variation of species in these disconnected outcrojJH although they are prob- ably all of the same bed. About 10 chains from the southern headland of the bay is a ver\' fossiliferous limestone composed almost entirely of gastro- pods. After deposition the shells were dissolved, leaving cavities which have since been lined Avith crystalline calcite so that the external features- 96 E. DE C. Clarke, C. Teichert and J. R. H. McWhae. of the shells have been lost. The other oaterops are less fossiliferous, con- taining but a few si)ecies of gastropods, peleeyiiods, Bryozoa^ and some echinoid s])ines. On the north shore of the bay the Hinestone is very massive and rather similar lithologically to the algal limestone of Locality A but algal concretions are rarer. The gastropods in this deposit seem to belong to such genera as Margntelhi, Xatica, Fhsu.h, Fullarid, itnd possibly others as well. Among the t^elet'Vpods Bdiinftia (lissiwilis (Tate), and Cardiam (O'caeformis Chap- man and Cres|)inj could be recognized. Some CuJtfris spines are also present. At. Loctditfi C limestotie is (*.\posed alniosi continuously for a distance of about 1-h) yards iii a clilf rising in jdaces to 20 feet abo\e the lake tloor. It shows the usual lateral variation in fauna ami some lensing of the beds. Text tig. 7. Locality C, on the Beiiinsnla, Lake Cowan. The beds are generally horizontal except at llie western end where for a few feet there is a dip to the south of 30° probably due to the action of groMuiig roots and of slumping consequent on undercutting. The lowest layer of the limestone is about eight feet thick and contains very numerous complete pectinid shells, the lower one or two feet being grey Tertiary Deposits Near Norseman, Western Australia. 97 with a light-coloured yellow-brown limestone above. A layer about five feet thick and made up almot^t entirely of fragments of Bryozoa overlies the pectinid bed. Dolomite two feet thick forms the toi) of tlie section and a superficial calcareous travertine rock, a product of arid weathering, over- lies the dolomite. The number of species in this deposit is small. The predominant })ectinids are Chlavuis murnujana (Tate) and Clilamys aldingensis (Tate). Other jxdecypods include ModiolarUi cf. arcacea (Tate). 4. lake duxdas. Boloynite. — At the extreme north end of Lake Dundas, about five miles north-east of Norseman, there are scattered outcro])s of unfossiliferous dolomite on the edge of the lake and farther inland. A considerable thickness of superficial gravel and finer alluvial material forms low head- lands and terraces along the west side of the lake and in them dolomite crops out. Several short gullies, a mile or two long, which drain the hills of Pre-Cambrian gre(mstone enter the lake near its nortlnwn end and have exposed other patches (tf dolomite but nowhere is its contact with the Pre-Cambrian visible. Most of the smaller patches are shown on Camp- bell's nui}), but the largest which is farthest north-east, on the lake shore near an old ti’ack to Israelite Bay, is outside its limits. It is a eonspieuous ■white hill over UK) yards long and rising steeply to about 4U feet above the lake, into wdiich it extends as a narrow headland for about 70 yards. The hill consists of dolomite which is a massive, erystalUne, almost mono- mineralic rock with oceasional angular (piart/. fragments and rounded limonitic ])ebhles as. in tin* rlolomites descriliial earlier in this paper. Weathering of this rock produces a rough, sculptured surface. Low out- crops extend sonth--west from the hill for 150 yards and the rock appears again in a promontory a})ont 250 yards south of the hill where it is overlain by gravel. Eiiealfipt Beds. — Campbell (1906, j). 22) re])ortcd the occurrence of .silicified speic forms suggests a close relationshi]) of the ‘Western Australian deposits with those in York Peninsula, South Australia. It is furtlier suggested that the Lake VoA\-an limestone can be correlated Avith the loAver jxirtion of 'the Balcombian stage as developed in Gippsland, Vic- toria. The genus Retepora is the common form in the limestone from Norse- man, Avhere the liryozoal assemblage is associated with the gasteropod Titr- ritella aldingae Tate, a form Avhich is common not only at Aldinga, South Australia, but also in the fossiliferous marls in the deep bores in Gippsland, AAdiich are referred to the Janjhikian Stage. But the species ranges up into the Balcombian Stage, and until some evidence based on the occurrence of zonal foraminifera. can be found in the Norseman beds the limestones are referred to the basal portion of the Balcombian. [“Lake Cowan limestx)no’’ is material collected from Outcrop A at the Peninsula, “Limestone from Norseman” is material from the occurrence discovered by Campbell near the causeway nortli of Norsemur. (E. de C. C. and C. T.)] VTI. ■REFERENCES. Campbell, W. B., 190(i; Tlie geology and uihiernl resources of the Norseman District, Dundas Goldfield. Geol. Hnr. Iflc.st. Auni., Bull, 21. Chapman, P., and Crespiu, T., 1934: The i)alaeontology of the Plantagenet Beds of Western Australia. Joarn. Boy, Soc. iVest Aust., Vol. XX, pp. 103-136. Clarke, E, do C., 1925: The geology of a portion of the East Coolgardie and Xorth-East Coolgardie Goldfields including the mining centres of Monger and St. Ives. Geol. Siirv. PVxf Ansi,, Bnll. 90. Clarke, E. de C., 1935: Re])ort of committee on the structural and land forms of Australia and Xcav Zealand. Aust. and N.Z. Ass. Adv. Sci., A ol. XXII, p. 467. Tertiary Deposits Near Norseman, Western Australia. 101 Gregory, J. W., Age of Norseman limestone, Western Australia. GeoL Mag., New Ser., Dee. VT., A^ol. Ill, pp. 320-321. Hincle, G. J., 1910: On the fossil sponge spicules in a rock from tlie deep lead (?) at Princess Koyal Township, Norseman District, Western Australia. Part of Geol. Surv. W(\st. A/(.s7., Bull. 30. Maitland, A. Gihl), 1907 : Kecciit advances in the knowledge of the geology of AVestern Australia, A.svs’. Advf. Sc., A"ol. XI, pp. 152-3. Podgers, J., 1940: Distinction l)etwecn calcite and dolomite on polished surfaces. Amer. Jourru Sri., \o\. 238, p]>. 788-98. Teichert, C,, 1944: Tlie genus A f aria in the Tertiary of Australia. Journ. Falcon, A^ol. 18, pp. 73-82. AA’'oodward, II. P., 1902; The Dundas Goldfield. Anyi. Frog. Mcp. GeoL Surv. of West Aust. for 1901, p. 15. 102 E. DE C. Clarke, C. Teichert and J. R. H. McWhae. Plate I. — Geological Map of Princess PoynL Tertiary Deposits Near Norseman, Western Australia. 103 LEGEND O Lake Floor pm Pre'Cambrian W7n Tertiary Limestone and Do/omae IHE3 Loose Sand and Hopae -rssffsr laCerUe Terraces Coast line of Lake Scarp conglomerate CEOLOC/CAL MAP Of POPT/ON Of EAST COAST OF PENINSULA, LAKE COWAN, \by Clarke, TeicherC and Me Whae SCAL£ _ ° chains Drown by Henry Coley 1946 Plate 1 r.*— Gcolojjical Map of part of Peninsula, Lake Cowan. GEOLOGICAL MAP ofthe RIDGE HILL AREA RdiUlVAl/ — Roads ^ — Scale, of Chains 0 S 10 20 LEGEND Geological boundaries Contours 250 '- Yellow sand ZHZ] Sandy &. pebbly soil over Ferru ginous Sandstone or Loyr Level Laterlte l-^-l Detritus from Ferruginous Series : (i) Sandstone fragments 1°. ; ? I &. iz) Haterworn boulders 1° o °1 High Level Laterite ffffH Low Level Laterlte tYY Ferruginous Sandstone 1: '■ I Epidiorite [5^3 Quartz veins Shear zones i ^ I Granitic Complex / The CJeology of the Darling Scarp at Ridge Hill. 105 5.— THE GEOLOGY OF THE DARLING SCARP AT RIDGE HILL By Rex T. Prider (Department of Geology, University of Western Australia). Read: 1 1th June, 194(5. CONTENTS. Page. I. Introduction 105 II. Physiography 106 III. Geology A. Field distribution and relationships of the rocks ... ... 108 B. The PreJ-arabrian rocks J. The granites ... ... ... ... ... ... 109 2. Sericite schists ... ... ... ... ... ... 110 3. Quartz veins ... ... ... ... ... ... 110 4. Basic dykes ... ... ... ... ... ... 110 C. The later rock.s 1 . The ferruginous sandstone series (i) Conglomerates ... ... ... ... ... HI (ii) Sandstones ... ... ... ... ... 112 2. Laterites (i) The high-level laterites ... ... ... 116 hi) The low-level laterites... ... ... ... H7 3. The yellow sands ... ... ... ... ... H8 IV. Summary and Conclusion.s ... ... ... ... ... ••• 127 V. Acknowledgments 128 VI. List of References (Jited 129 T. INTRODUCTION. The Darling tSearj) whi<‘li 1‘onns the western edge of the Darling Plateau has generally been j’egarded as a fault scarp ( Sainl-Sinith, 1912, p. 70; Jut- son, 1912, p. 149 and 1934, |l 8(5) but cdoser (‘xamination of some critical areas in recent years tlu’ows some doubt on this hy])othesis. Thus the slaty rocks at Armadale considered by Saint-Smith (1912, (). 71) to bo evidence of the Darling Fault have, on closer examination (Prider, 1941, p. 52), yielded evidence that the earth movements recorded in these rocUs are exactly the opposite of that required by the Darling ^‘F^auU”. A characteristic feature of the Darling Scarp in the vicinity of Perth is a laterite-covered shelf at an elevation of approximately 200 feet above sea-level (AAoolnough, 1920, p. 16) which Woolnough calls the RiJge Hill Shelf and which he considers is a step-faulted portion of the high- level laterite (Darling) 141G0/2/48 — 630 Rex T. PiiiDEii. loo jtlateau and tJins eoidiriiiatoi'y (‘vidcjieo of the Dai'liiig Raiill wliicdi lie Hup- poses is a stej) lault. l^hu'ther, in his arthde “Tiie p]iysiof»'raphic si;^’nilicaiu'e (>1 Jatei’ite in Western Australia'^ (1018, p. 800) he puts forvv'urd the g-eiieral eonelusion that ''c.iira, ordinary dijfrrrnrcs in laferite level in adjacent areas indicate block faal'tiny,'' citing- as evitlenee the iaterite-covered Ridge Hill Shell. These conclusions appear to he based on the supposition that the high- h^'cl laterite on the Darling Plateau which is exposed at an elevation of approximately 700 feet on Gooseberry Hill the east, of the Ridge Hill JShelf is the sani(‘ as the ^1(0*110 covering the Ridge Hill Shelf (at an elevation of apju*o.\imately ‘ibO feel). Xo dtfailed iinestigation of these laterites has pre- viously been made and i7i order to test Woolnough’s conclusions and to obtain turther infoi’ination about the vexed question of the origin of the low-level latei-ile and of' tlu' Darling Scarp a detailed survey of an area of a]))n'oximulelv tAVo S(|uare miles in the \icinity of Ridge Hill has beeji made by senior students of the De])artmcnt of Geology of the Univer’sity yl A\ csteru Ansti-alia working under tht^ author’s guidance. In the course ol this survey (mad(‘ iti ])art by plane table - telescopic alidade and in part by chain-compass-liarom(d(w methods) further study Avas made of the Pre- Camljriaii conijilox of the Darling RangCj a group of ])reviou,s]y unrecorded sedimentary I'ocks Avas dist-overed, the re]ationshi])s of the high- and low- level laterites were examiiu'd and an investigation into the origin of the ex- tensive sand areas fronting the Darling {Searj) was made. The present paper Sets out the r(‘sults ot‘ these iiiA'esligations. IT. PHYSIOGRAPPIY. The area examined is situated on the south side of the Helena valley adjacent to the Avestern boundary of the Darlington Area (Clarke and Wil- liams, 1920, iilate XXITI), It lies entirely on tlie Darling Scarp and ex- tends from tiic high-hn-el plateau, outliers of which occur iji the south- eastern coiaier of the area, almost to the Oat, low-lying country of the coastal ])Iain to the A\est. It therefore co\ers the area i'e|iresent.ed on Woolnough’s generalised section (1020, p. 20) from the Darling Plateau to the Swan Coastal Plain in the same \A'ay as tlu' area mapped at Armadale { Prider, 1941) covers a sojuewhat similar generalised section of tlie Scarp aiAproxi- mately lo miles lo the soutli of Ridge Hill AA’hich has been published bv Yb>olnough (1918, p. 391). The main eharacteristies of the Darling Scarp have been sufficiently described by ])revious authors (see for exnmjdo -Jutson, 1934, pp. 84-87) a?id re(inire no further consideration here, and attention Avill be conlined to the topogrni)hic featui'cs of the IDdge Hill area itself. The Draiiuifje Pattern . — The Scarp is dissected by: (a) the wsterly floAviiig streams, the Helena IHver and Parrants Creek, AA'hieh are conse- quent streams OAving their dcAmlopment to uplift of the Darling Plateau to the east: (b) minor streams iiowiug approximately parallel to the scarp AA'liieli have produced the dissected foothill zone mentioned by Wooluough (1929, ]). l'>). Such streams are Stathams Creek draining into the Helena to the X.X.E. and the tributary of lYirrants Creek draining to the S.S'.W. These appear to ho subsequent streams (Clarke, Prider and Teiehert, 1944, p. 78) Avliose direction has been determined by the X.N.E. strike of the sliear stnictiu’es in the granitic rocks and also by Hie presence of epi- The Geology of the Darling Scarp at Ridge Hill. 107 (liorite dykes. The divide between these two streams, at 15 chains south of Kidge Hill siding', is occupied by an epidiorite dyke. The role that the epidiorite dykes play in the development of these minor topographic features of the Darling Range is of interest. In most places in the Darling Scarp area the granitic rocks are nioi’e resistant to erosion than the basic dykes which are generally represented by shallow depressions (text tig. lA) or fattened areas on otherwise uniform slopes Text fig. 1. — Relative resif-lance to erosion of granitic rocTcs and basic dylccs in the Darling Ranges: A. Diagrammatic sketch plan of granite ridge at Armadale (not to scale) showing that dolerite dykes occupy the saddles in granite ridges. B. Diagrammatic sketch section (not to scale) of upper part of the Darling Soarp at Kidge Hill showing minor fiattened lieiiches wliicdi are under- lain by epidiorite dykes. C. Diagrammatic sketch section (not to sctile) of geological structure of ridges in the Toodyay District showing that altliougU ridges are coi'cd by dolerite dykes there is a shallow central depression. (dranitic rocks arc indicated by crosses, basic dykes by arrow heads and laterite by circles.) (text fig. IH). Similarly at Toodyay a most noticeable feature is that the main ridges in the granite gneiss areas have a central core of dolerite but the crest of such ridges has a shallow central depression over the dolerite dyke (text fig. 1C). It is evident, therefoi’e, that in the Darling 108 Rex T. Pridee. Range area the basic dykes are lesn resistant to erosion than the adjoining granite and not more resistant as indicated by Auronsseau and Budge (1921 p. do) and Clarke and Williams {1926, ]>. 167), but at the shme time they have contact metamorphosed the adjoining granite slightly thus rendering it more resistant to erosion than the unaffected granite at some distance from the basic dykes, thus accounting for the anomalous behaviour of the less resistant l)asic dykes forming the ridges. This observation of the relation of t( 4 )ography to the less resistant dykes is of some import- ance in geidogical mapping in the Uarling Range area — if shallow gullies or dei)ressions are examiued more closely it will generally be found that the 'underlying rock is edther basic dyke rock or else sheared granite. The Darling Plateau capped by the high-level laterite is exposed in several outliers of the plateau in the south-east corner of the area. These outliers are flat-topped and surrounded by breakaways (Clarke, Pridei* and Teiehert, 1944, ]>. (iO). The Ridge Hill Shelf forms almost the entire western part of Ihe map- ped area. To the north-west of Kidge Hill siding it is laterite-covercd at an elevation of 2o0 feet above sea level and from here it slopes down gently and uniformly to the west Avhere it passes eventually into the liat eoasal plain. It is immaturely dissected in the nortli-Avest part of the area by north-liowing tributaries of tlic Helena IHvei’ which flows almost parallel to the northern boundary of the mapped area and at some 10 to 20 chains to the noi’th of it. As noted above, AVoolnough considers this shelf to be the top of the downfaulted laterite-eapped Darling IMaleau but evidence Avill be put for- ward later in this paper vvhieh indicates rather that this shelf is actually an erosion feature such as a wave-cut bench and bears no relation to the Darling Plateau. Clarke and Williams (1920^ p. 167) have recognised high-level terraces in the Helena A'alley just to the east of the Ridge Hill area. These terraces fall into two series, one lying at about 4o0 feet, the other at about 2o0 feet above sea level. The 250 feet series mav be represented in the Ridge Hill area by the Hidge Hill Shelf and the 450 feet series by the tiattened spur south fr(un Stathams (piari'y, but otherwise these terraces cannot be detected in this area. The llattened st)urs both in the Darlington area (with the exee])tion of the terrace on which the village of Darlington stands) and above Stathams (juarry are cored with epidiorite dykes. As has been noted above the epidiorites are less resistant to erosion than the granitic rocks — is it possible therefore that those flattened spurs or terraces are due to the differential erosion of Aveakly resistant epidiorite, more resistant gTanite and most resistant contact altered granite as indi- cated in text hgure 1, rather than to two periods of still-stand during the uplift of the Darling Platea-U? III. GEOLOGY. A. FIELD DISTHIBUTION' AND RELATIONSHIPS OF THE ROCKS. The diagonal joining the north-east and south-west corners divides the area conveniently into two parts. To the east and south of this line the I’ocks are those of the Pre-Cambrian granitic complex with associated The Geology or the Darling Scarp at Ridge Hill. 109 t'pidioi'ite dykes which is ovei’lnin ui the extreme south-easi comer by [he hio'h-level laterite. To tlie north and west oi' this line tlie surt'ace is covered by younger sedimentary rocks — a thin series of ferruginous sand- stones and conglomerates — which, in the northern dissected jnii't of the area, can be seen lying uncouformably on the Pre-(hi.mbriau roc'ks. This I ferruginous sandstone series is in turn overlain by a thin crust of laterite and is boumh'd to the west, by sandplain country which sloi>es gently and luiiformly down to the coastal plain still fartlicr west. An attemjjt has tieen made in the course of tin* matii>ing to differentiate btd.ween actual I outcrop of the fei-ruginous sandstone series, the detritus (talus) derived ' from the weathei’ing of this series, the sandy and pehhly soils overlying I the ferruginous sandstones and low-level laterites, and the sandplain I country underlain by yellow sand. The areas occupied by these various ! formations are indicated on the accomipanying geological map (Plate 1). ! 13. THE PliK-CAMBlUAN ROCKS. These include granites, sheared granites (serieite scliist), epidiorite and quartz veins. ( 1 ) Tiu' (irauiies ar(' the basement rocks and form a complex of two main types— a coarse-graimul pnrphyritie tyi)e with a slightly gneissic slmcture, and a tiner even-grained lyi)e with no trace of handing. In addition end-phas(> ])egmatites (griiidiic mierocline pegmatites) are also to be found. It was found iiupos.sihle to map the tW(J different tyjies of granite setiai-ately hut tin* relations between the two can he clearly seen in the freshly exi)osed sui‘fac(‘s in Stathams (juai'ry. In the south-western corner of this (piai'ry large angular xeuolithic blocks of the coarse-grained ])n]’phyritic ami slightly gneissic granil{‘ occur in the massive liner-grained granite, lliiis inilicaling that the latter is the younger. The younger of these two granites exposed in Stathams quarry is very similar to the lounger Granite of Canning Dam which has l>een fully (h'^crihed in an earlier i)aper ( Pri(h‘r, 194"), p. 142) and no I'ui'ther peti’o- graphic details arc* retiuired here. Ther(' is, however, some dilference between the older granite of Statliams and the hybrid gneisses (Older Granite) of Canning Dam — the Older Granite fi-orn Canning Dam generally has a migmatitic structure and is free from mierocline whereas tlu> older granite ])hase at Stathams has 710 migmatitic structui'e and contains ab 7 jndant mici'odim*. It is similar in mineraiogical composition to the younger granite hut ditfeu's fi'om it in Ix'iiig much coarstw-grained and .'lightly gneissic. Plumocrystal microcli 7 ic in well-shaped crystals to one cm. or mo)-e diameter is an ahumhuit constituent and the periphcT’al zone o 7 i(' or two mm. wiile of such. ])iu‘no<'rysts consists g(merally of inicro- i•egmatit(^ 'Phe microclines contain iiicliisions of sei'icilised oligoclase and clotted hiotite Hakes which are the rno.st ahumhiiit coiistitiieiits of the liToundmass. The s’ig'ht gneissoid stiaictiire of these granites is due to the sub-parallel How orientatioii of the mim’ocliiie pluuiocrysts. In soine places this primary How structure is very well developed, e.g., at 17 chains .south-east froiii the centre of Stathaiiis (piaiuy it sti-ikes oo®. In view of the close similarity in minei alogical com])()sitio 7 i of the tine-grai7ied gi'anites and coarse-grained gneissoid granites of the xeno- liths it aiipears most i)rohahle that they both belong to the same magma vthe Younger Gi-anite magma) atid tliat tlu‘ xenoliths 7‘epresent an earlier 110 Rex T. Prider crystii liis(‘(l llow-bniultHl mist wliicli lias lieoii rractured ami tin* resultant blocks incorporated into the residual nia^'ina. There does not appear to he such a lonji' time ;;‘a[) between the two granites at Stathanis as there is at ('anninuf Dam (Prider, 1114o) and Armadale (Ih'ider, 1041) and both a])])ear to belong- to the sann- main period of granite intrusion (the Younger (Iranite) the pareiit magma heing of syntectic origin as outlined in the Canning Dam jiajuu* (Prider, 104‘), p. 14.'>). (‘4) 7'h(> Srricitf srlnsfs . — All the granites of this area show, on micro- scopie examination, the (bTects of eonsiderahle stress in the form of crushed ({iiart/. and quartz willi undnlose extinction. The stiess has been localised in ce.lain zones along which the granite has been cojiverted into sericite schist. 'l’h(‘se shear zones (see giMilogical mai)) are distributed, fairly uni- i'ormly Ihronghont the ar(*a ami all -trike* in a N.N.lh dirc'clion and dip- st('eji y to tlie east. Tin* best develo) I'd of these shear zones is exposed in the railway cutting near the 18-miIe |)eg. The eleavage surfaces of ihe schist from this well developed shear zone are traversed by innumerable minute (‘ona’gations which ai’c arrange'd hori/.onlally — unfortunately these* tiny drag sti’uctiires are not sutliciently well develo})ed to enable* any positive deter- minatieni of the* nature' of the earth movemie'nts responsible for the shearing. Since these* corrugations are* arranged horizontally the move-ments appear to ha\'c hce'Ji eleiminantly vertical. The*re is c(uisiel(*ral>l(‘ elivci'g(*ncc between the N.X.K. eliie'ction of those shear zones anel the* almost due north li'end of the* Darling Scarp whiedi in- dicat s that the'se* shears hear no relation to the sni)))osed Darling Fault. (4) Qnarl: — These have* h(*en noteel in se*\(-ral place's. They have a general Irenel ])arallel to the* shear zones and their dii'eedion lias evidently l)('en controlled by the* earlie*r iinpe)se‘d shear pattern. The* oce-urrence and jict 'ology of the (luactz veins and shear zones in the Darling Scarp have been sufficie*ntly dealt with in jirevious ])u})lications (Clarke ami William'^, ]). 174; Prider, 1941, p. 48; Davis, 1944, p. 456) and require mt further ennside-redion liere. (4) 77/c basic: dffkcs also have a general N.X.E. ti'end following the structure of the* gj'aniles. There apiiears to be erne age* eiuly represented and all Ihe speeimens t'xamineel preive to he epklioril(>s e-onsisting esseitlinliy of (ibnms uralite ( re*crys(allised around the* horeh'rs of the aggregates lei j)rismalic hlne-gret'u hornblende) and plagioclase witli smoky appearance. Relie'ts of ophitic ie'xtnrt* amt the presence of (*nel-phase micropeginatitc point to a close re'laliouship of these epielieirites with Ihe quartz dnierite's in other meu'e distant parts eif the Darling Range*. This matter has been dealt witli more fully in a pi’evious paper (Prider, 1948, pp. 4.4-S4). Tlie* ejiidiorites liave b<*en (|uai‘j'i(*d at Stathams for re>ad metal and concrete aggregates. In the exiiosures in the (]uarry basic ]iegmatile segrega- tions may eiccasionally he found anel the ocenrrene'e of stilhile ha-5 been re- cordeel by Simpson (1910, p. .'id and 1931, p. 36) from zeolite-calcite veins at the edges and also in the ce*ntre of tlte main dyke in Statham's (Jnarry. C. TITK T.ATKR ROCKS. The Later Rock< include the ferruginous sandstones and conglomerates, the high- and leiw-level laterites and the yellow sands the sanelplain forin. ing rn apron in front of the scarp. The Geology of the Darling Scarp at Ridge Hill. Ill (1) The ferraginoits sandstone -series t'orms a thin cover on tlie Ridge Hill Shelf where it lies unconformably on highly kaoliiiised granites. The unconformity is an undulating surface (see text hg. 2). The eastern contact of this series with the granite trends in a northeasterly direction and thus bears no relation to the supposed Darling Fault which trends due north. In the north-west part of the area small streams have cut down through this series to expose the underlying Pi'e-Cambrian rocks to the west of the ferruginous sandstone outcrops. Text fig. 2. — H.W.-X.E. section of South side of Helena Valley from the Helena \'alley to the Ridge Hill shelf showing unconformity between the ferrii- giiKJus 5-aiulstone scries (sandstone underlain by conglomerate and overlain by low level latei'ite) and the Pro-Cambrian (granite and epidiorite) . The series consists mainly of feiruginous sandstones underlain in ])laces by I)oulder conglomerates. Outcroj)s of tlie boulder conglomerates occur at (iO chains N. 10° P]. and (>7 chaijis N. 5° W. from Ridge Hill Siding. The slopes below the outcrop of ferruginous sandstom* in the northern part of the ar(‘a are strewn with well-rounded waterworn boulders which appear to have becii derived from this conglomerate. These bouldei's ha\e not been found in other parts of the area suggesting that the conglomerates are con- fined to that part of the ferruginous sandstones clost'sl to the ))i'(‘seni, Helena Ri\(*r. Since the known outcrops of conglomerate arc at lev'els below the sandstones and are confined to the small area lying to the south of the Helena River it a]^pears that they form a localised basal layer in the sandstones probably indicating an old stream channel or narroAV embayment in tlie coast. It is interesting to note that Fletcher and Hobsim (19;12) have described a similar occurrence of feiTuginous sandstone with rounde. 82). The tliet that the boulder beds are eonlined to a eoinpura- tivdy small arey stuoiis indicative of either a lliiviatile orig-in or as an aceumiilalion of beach l)onl{lers in a small bay. From the degree of rounding of tin* saml grains in the associated sandstones (to be described })resently) the possibility of Iluviatile origin seems remote. It appears most probable tiiat these i)oulders were derived by direct marine abrasion of the neai'by coast which was made uj) of these Fre-Cambrian rocks since the rock types noted amongst the boulders can Ijc matched with the rocks in the Hidge Hill area. (ii) Tin' sandstones form the bulk of the ext>osure of this series. They are I'eddish in colour, have no bedding, ai’e unfossiliferous and no i certain means exist of accni’ately determining their geological age. They contain occasu)nal water-worn cjuartz pebbles which arc well-rounded and ' in >omc instances highly j>(.»lished. The sand grains are almost entirely ] (juai-tz and two types can be distinguished: — (a) grains with a rough j irrcuular surl'ace whicli nevertheless shows signs of considerable a))rasion ; and {!)) smootli-hiirfaced rounde> of the insolul)le residue (79 per cent, of the sample) were j made, ^fhe results of these analyses are sol down in Table III and in j (Johuiin I) of the histograms of tigiires five and six. The results of a j chemical analysis of this specimen are recorded in Table I and the heavy minoi'al analyses are shown in Table V. ( The main features disclosed by these analyses are:^ — (a) The mechanical analysis (by lunid sieving with Tyler screens) indi- cates that the insoluble material is fairly well graded, 48 [)er cent, lying lx*- | tween Yj and Vi nun. ears to he either monlmorilkmite or a dehydraterl alumina-silica gel with ALO.. : SiO^— 1 : 2.8 (vSpiidial, 1922, p. 288) and in view of its tube- rose nature more pi-obalily the latte?'. *■ The ALO.. : Si(L ratio of approximately I : 3 is conlirmed by tlu' chemical analysis of the rock (Table 1, column 1) which shows that the rock contains alumina and combined silica in the mole- cular ratios 31 : 90. This material forms practically all of the minus 250 mesh fraction (11.2 per cent.) and ai)proximately half the 115-250 mesh fi'action (3.9 per cent.) but very little was present in the coai'ser grades and if this *Mr. A, J. Gaskin has recently (1947) made a thirmal examination of the clayey frac- tion of two soil samples from over the ferruginous sandstones and low'-level lateritVs and finds from the thermal data that they contain liimmite and kaolinite (much of which \- srmi-amorphous) with a possibility that gibbsite is also present. The Geology of the Darling Scarp at Ridge Hill. 113 material be disregarded it will he seen that the actual detrital material is well graded, 92 per cent, lying between Yg and % mm. diameter. (b) Heavy mineral analyses Avere made of the three finest grades, the material passing 250 mesh being separated by centrifuging. The light fractions consist entirely of (|uarix with the alumina-silica (allophanoid) mineral. The hea\'y fractions were further se])arated into magnetic ‘okI non-magnetie fractions, the magmdic fiaction (largely ilmenite) h\ each grade forming approximately 75 per cent, of the heavy fraction. The heavy minerals idiuitified are recorded in Tal)le V and of these zircon is the most abundant of the non-o}mc|nes and is wugh move than one cycle of erosion. The association of these two typ(*s of zircon may in- dicate derivation in the one cycle of erosion from a distributive province of the nature of the present Toodyay area (Prider, 1944) whicli is situated in a belt of igneous and metasedimentary Pre-Cambrian rocks lying some 2)0 to 40 miles inland from the Darling St-arp. (e) Visual projection roundness (Krumbein, 1941) and sphericity (Rittenhouse, 1943) values were determined for tlu^ light fractions of the 30-32, 32-00, 00-115, 115-250 Tyler mesh grades. The results (shown graphically in column 1) in tlgnres five and six) indicate that the average sphericity in all fractions is a])proximately the same (0.S3) and that the degi'ee of rounding decreases with ileereasing size but there is still appreciable rounding of some grains down to 0.124 nun. Oiaineter. During the roundness analysis and suliseipient examination of the surface texture of the grains it was e\'ident that tiuwe are two distinct types of (punlz sand grains i>resent — a well-rounded set and another the grains of which are much more angular although still showing considerable abrasion. The pro- portion of Avell-rounded to poorly-rounded grains increases with increasing grade thus : Grade ... •124- -246 •246- -495 ■495- -991 mm. mm. mm. % of well-rounded grains ... ... 5 50 90 The occurrence of a small in-oportion of Avell-ronnded grains in the Vs to Vi mm. grade seems indicative of the derivation of the detrital material from s(‘voral different sources. The high i)ro]iortion of Avell- rounded grains in tin* PS to 1 mm. grade indicates, however, very con- siderable abrasion during the last cycle of erosion and since this rounding is well marked doAvn to the giaiins of Vi mm. diameter it mii’^t be assumed {following TwenJiofeJ, 1945, p. (hi) that this final stage of abrasion must have taken plact' on a sea beach. The smaller well-rounded grains may he due to an admixture of some aeoliaii-transported sand with the beach sand, or may have l)Gen derived from some pre-existing sediment. Xo 114 Rex T. Prider. sucli sedimentary rocks ai'e known to the east of the Darling Scarp, although there are metasedimentary rocks Avhich could have yielded the well-rounded zircons ))ut these rocks (mica schists and quartzites) would not yield directly the small Avell-rounded quartz grains since the quartz in these rocks lias keen completely recrystallised and in the rock occurs as irregular interlocking grains (Prider, P)44, ]>. 1)2). (d) The surface (exture of the sand grains of the 10 to 32, 32 to 60, and 00 to llo Tyler mesh grades was examined with the binocular micro- scope in dry mounts on a dark ground for t!u‘ (piartz griains and on a white ground for th(‘ heavy minerals, with the following results: — The 00 to 11") mesh grade (Vs to mm.) consists of a]>proxiinateIy 0”) per cenl. of rough irregular-surfaced gi’aius with polished or fracture surface and live per cimt. of smooth-surfaced rounded grains with jiolished surfaces Avhicli are often pitted but not frosted. The 32 to 60 mesh grade I to V 2 nnn.) contains rough- and siuooUi-surfnced grains in a]>proxi- mately equal amounts. The smooth grains are well-rounded Avith polished (although somewhat pitterl) surfac(‘s — .some grain> show slight frosting and crescentic ]n*i'cussi(ui marks are not uncommon. The rough-surfaced grains mostly show slight rounding and are all jjolished or bounded l)y vitreous-lustred fracture .surfaces. In the 16 to 32 mesli grade (V 2 to 1 mm.) there is a high proportion (approximately 90 per cent.) of smooth- surfaced grains Avhich vary from dull to polished. Most of these grains have a matte appearance due to minute pitting but this is not a frosted surface but a|)pears rather to bo the result of a polish superimpAosed on earlier frosting. Crescentic percmssion marks are generally well developed. Twenhofei (194.'), p. 67) considers that frosting may bo developed on quartz grains exceeding one mm. diameter on marine beaches but not on grains smaller than one mm. whicli can only be frosted by Avind action. The aboA’e observations on the surface texture of the eri(}d of formation of the i)resent Ridge Hill shelf is later than that of the high-hwel laterite which was probably Miocene according to AVoolnough (1918). It rvas formed when the laterite-covered plateau area to the east had been elevated to aj>proximatcly 409 feet above sea level, i.e present elevation of high-level lalerite (700 feet) minus the elevation of the Ridge Hill Shelf (300 feet). If the ferruginous sandstone series be of Lower Cretaceous age then it represents an exhumed Lower Cretaceous shoreline with a wave-cut bench covered with marine sands; if of post- Miocene ag'e then it is a marine wave-eut b(mch with a thin veneer of beach deposits which have subsequently been cemented by iron-bearing solutions into a ferruginous sandstone, (2) The Ln/cr/tc.s.— Laterite occuj's at two distinct levels— the high-level laterite iu the south-eastern corner of the area at an elevation of 700 feet ^lbove sea-level and the low-level laterite on the Ridge Hill Slielf at eleva- tions of 220 feet— 280 feet above sca-lcvel. As has been pointed out in the introduction to this paper AVooluough regards these two laterites as being of the same age and origin, their differences in elevation being due to block- faulting. Simpson (1912, p. 400) considers that, broadly speaking, there are two cla.sses of laterite in M eslern Australia, fir.stly the primary (or high-level) laterites and secondly the secondary or low-level laterites occur* ring at lower levels and composed largely of mechanically transported frag- ments derived from the high-level laterite. I am not aware whether or no Simpson had in mind the lo^v-lcvel laterites fronting the Darling Scarp in his mention of secondary laterite but it seems from bis description that he would regard the low-level laterite of Ridge Hill as a secondary laterite (lateritite). Field map})ing has shown that in this area the high-level laterite Is developed over the Pre-Cambrian complex whereas the low-level laterite has developed over the ferruginous sandstones described in the previous ■section of this paper. ]Moreover the low-level laterite appears to be a 116 Rex T. Pkider. tnu* lat.erito dovoloiied in situ on llu‘ t'evrn^inous sandstones and not a | lateritite as su^'gested by Simi)son for the low-level lateiites g'enerally. j| (i) The high-level laterite varies in eharaetei- aecordin^^ to llie nature of Ihe underlyinu' Rre-(’ainbrian rocks. Jii one ])lace in tlie area when' it overli('s granitt' containing {juarlz veins it is crowded Avith larg(' <|uartz fragments. When develoi)ed over granitic rocks it genei'ally iias a ])iso!itie structure and is coni|»arative]y light-colourt*d but when over e])idiorite {as at the northern end of the high-level laterite outlier in the south-east coiner of tin' area) tlierc' is no pisolitic stnndure hut tlu' rock is somewhat cellular and appears to Ik' riclun* in iron, ih.ese iniii oxide i)atches being compact, tine-grained .and massive. .Ml the high-level laterites are under- lain by a higlily weatlu'red ( kaoIinis(*d ) /one which pass(‘s down into the nnweatliei'(‘d country rocks ns de.scrilied by Simpson (U)ll2). Analyses of tAvo high-lev(*l lateriti's aia' gi\en in Table I. cols. Ilf and I\'. Analysis !TJ is of a latf'i'itc developed over opidiovite from tlie Kidge Hill area. Analysis W piloted frtmi Si;ni>son p. 464) is from (fooseberry Hill which is sitnaU'd a|)]iroximately one mile south of the Kidge Hill area, ' but no details of the c.xaet loeality are available. Through the courtesy of the (lovertiment iliueralogist and Analyst 11. RoAvley) I have been able to e.xamine SinpisoiHs analysed syiecimen — it is a dense reddish- broAvn rock Avitli numerous iron-rich com-retions scattered uniformly throughout. The Kidge Hill sjiecimen ( Analysis HI) is a dense brownish coloured rock with occasional cavities pi'oducing a slightly cellular struc- ture but concretionary stimctures ar(' absent. (^Inunically the tAvo rocks dider in the loAver f'e/Al ratio of the (looseberry Hill rock. Tablt'] T. ANAl.YSES OF FERRUGINOUS SANDSTONE AND LATERITES FROM RIDGE HILL. :r. IT. HI. TV. SiO.,* m • 98 44-87 10-80 6-41 AU) 8-17 24-63 22-58 86-74 Fe.,0, 27-68 14-82 48-56 89-80 TiO., 0-99 1-25 8-24 1-98 Mii() 0-02 0-01 0-05 0-06 H.,Ot 4-40 14-61 15-82 14-98 Others ... 0-51 100-14 100-19 100-50 100-48 ^Combined SiO., ... 5-42 8-18 4-94 1-97 tLoss on ignition. r. Ferruginous sandstone (22798). three feet heloAv laterised surface rock in quarry 25 chains nortli of Kidge Hill Siding. AV.A. {Anal. H. T. f'ridei'.) 11. LoAA’-level latente (2185!)) overlying ferruginous sandstone, from quarry 25 chains north of Hidgt5 Hill siding, fV.A. {Anal. R. T. Priical s[)ecimen (21d59) which has been analysed average five mm. rocess the only fact{)r which may with some degrip of certainty be likely to remain constant is the (|uartz (free silica) content. In Table IT the analysis of the laterite (column 2) has been recalculated to quartz = 58.51, i.e. these figures would then represent the number of oTams of each constituent in a volume of the laterite which contains 58.5 ovams of quartz. Comparing these figures with those of the juiront fer- ruginous sandstone (column 1) the gains and losst^ in the vailous con- stituents per 100 grams of the original sandstone may l)e determined (column 4). 118 Kex T. Pbider. Table II. CHEMICAL CHANGES IN THE FORMATION OF THE LOW-LEVEL LATERITE. 1. 2. 3. 4. !Ferriiginoiis sandstone (Weight %) LoAv-level laterite (Weight %) 2. recalculated to quartz 58-51 Gains and losses during laterit- isation. (Gnis/lOO gms. of original rock) 58-ol 36-69 58-51 \Combinecl 5*42 8-18 13-05 r- 7-63 AhOs 3*17 24-63 39-27 -1- 36-10 27-63 14-82 23-63 ~ 4-00 TiOo 0-99 1-25 1-99 4- l-OU JVInO 0-02 0-01 0-02 • « . H^O 4-40 14-61 23-30 18-90 100-14 100-19 159-77 Gain 63-63 Loss ' 4-00 Net Gam ... ... ... 59 ■ 63gm.s. per. 100 gms. original rock. There lias been a slight loss in Pe.O.„ slight gain in titania and eoni- bined silica Imt vei'}' marked gains in alumina and Avater. The signiticant changes are those in the alumina and water content and these are in the molecular proportions alumina ; water =- 3dT : 1050 i.e., 1 : 3 so that the material added to the original rock during the lateritisation process is essentially aluminium hydroxide (Al(OH).d. The source of this aluminium hydroxide is unknown — the ferruginous sandstones are poor in alumina but the alumina may have come from the underlying gi’anitie rocks as there is only a thin veneer of sandstone, but on the other hand it may have been dei’ived from an overlying shale or mudstone which has noAV been entirely removed by erosion. The low-Ievol laterite is therefore a true laterite, and not a lateritite, ■due to the accumulation of alumina in the near-surface layer, formed in situ over the f(*rruginous sandstone. This laterite formation iDvobably took place shortly after the sand-covered marine bench (the Ridge Hill Shelf) was elevated a few feet above sea-level. This Avas later than the tormation of the high-level laterite. (;J) The I elloiv Sands . — The VelloAv Sands constitute tlie youngest formation and are exposed in the Avesternmost part of the mapped area Avhere they foi-m an even gentle slope doAvn to the level 'of the coastal plain to the Avest. The boundary betAveen the yelloAV sands and the earlier rocks is irregular (see Plate 1) thus precluding the possibility of a faulted contact or fault scai'p against AAdiich the sands have accumulated. There is an abi'upt change from the ferruginous sandstone and low-level laterite to the yelloAv sands and this has been Avell exposed by rainAvash in a di’ain on the south side of the railway line at seven chains soulh-Ave 5 ^t from the 14-mile peg. 0\*er the laterite this drain is tAvo feet deep but on -reaching the boundary Avith the incoherent yelloAv sand it deepens abruptly Thk Geology of the Darling Scarp at Ridge Hill. 119 lo about 12 foot. Downstream from this point the gulley continues as. a narrow Avashout four feet wide by 12 feet deep which is roofed by the roots of the adjacent jarrali trees (text tig*. 4). Text tig. 4. — Washout in yellow sand, seven eliai)is south-weat from the H-niile railway peg. The very recent develojnnent of this feature is evident from the uncovered roots of the nc^arhy Jarrnh trees. The yelloAV sand profile exposed consists of 12 to IS inches of light grey :sand Avith plant roots, the remaimler of the profile consisting entirely of yelloAv sand in whicli there is absolutely no sign of bedded structure, the whole ])rofile consisting of sand of uniform texture from top to bottom of the exposed section. Throughout the sand at intervals of several inches -are small nodules of more compact material averaging Va inch diameter Avhich project from the vertical sand face. These nodules which can be cut through Avith a knife consist of the sand Aveakly cemented Avith reddish iron oxide. On cutting a fresh surface Avith a hatchet they ai)j)ear only as red- dish iron-stained spots with a gradual transition lo the yelloAV saml. It is only Avhere they have been exijosed to the atmos))heve on the Avails that a ^liglitly hardened surface has been formed on them. At the bottom of the section exposed in tin' Avashed out drain the sand contains an abundance of these nodules, in some (>laccs aggregated to nodules several inches in diameter. These larger aggregates are weakly cemented and can be broken across with the liiigoi's. Tliey contain a higher proportion of fine-grained, light broAvnish to greyish clayey material. TIk'v appear to have been enriched in alumina AA’ilh respect lo the suirounding sand and if this material AAdiieh in places Avas slightl\- damp were desiccated it Avould he similar to non-con- cretioiiary laterite. It Avould appear then that Avith the development of these aluminous nodules at the base of the ex])osed ]u*ofile aud of the small iron-stained jjatclies throughout the mass of the sand incipient lateritisation is taking place Avithin this sand deposit. 120 Rex T. Prider. The yelloAV sand throug'hout the nia})ped area app(‘ars to be constant in character, wherevei* exposed in small pits the profile is similar, i.e. a thin surface layer of gr(‘y sand underlain by the structureless yelloAV sand. ]\rap- l)ing’ of Ibis formatidii was facilitated by the numerous small anthills of bright yellow sand brought uj) fi'om below th(‘ surface grey sand. The yellow sand possesses tht* ability to stand up in vertical walls such as the walls of a pit and in this respect and in its structurehss profile it vtu’.v closely resembles the yellow sand dt'posits of the Pei’lh .Alidropolitan Area. What is the origin of this sand ? It is (i) a residual sand derived from the low-level laterite and ferruginous sandstone, (ii) a dei)osit of the same- origin as the yellow sand of the Aletroimlitan Area or (iii) an aeolian de- posit against the Darling Scarp ? These various hy])otheses were lested by making mechanical analyses, heavy minei’al separations, shapt' analyses and an examination of the surface textui’es of the sand grains of the Ridge Hill yellow sand (two samples) and a yellow -sand from' tlie \icinity of the Department of Geology at Crawley (since t\u data exist I'Oiuau'ning the yellow sand of the Metro]>olitaii Ar<*a), on the lines described abov(* for the acid-insoluhle fraction of the Rid^ge Tlill ferruginous sandstone. The results of these determinations are set down in Tables HI, and V and the histograms of figures live and six. Ti’ask (lt)d2, p. 72) considers that if the eoenicient of sorting is less than 2.0 the sam]>le is well sorted— all the samples examined (see Table lAD therefore are Avell sorted. Aloreover in all cases the maximum sort- ing lies slightly on the fine side of the median as evidenced by the co- Tablu tit. MECriANirAL ANALYSIS OF YELLOW SANDS. (hand sieving with TvIcm* screens.) Grade. A 0/ /o by weight of grades indicated. Tyler screen mesh. V Size (mm.) A. B. C. D. 5- 9 > 1-981 XU XU 0-81 Nil 9- 10 •991-1-981 0-.58 1-44 3-88 0-04 10- 32 •495- -991 19-50 12-83 12-33 6-70 32- on ■240- -495 50- 01 35-42 40-40 18-03 60-115 •124- -240 22-22 20-90 23-11 30-41 115-250 •001- -124 3-47 1 1 • 85 7-12 3-02 < 250 < 001 3 ■ 50* 11 -.50* 0-29* 11-20* *Ry difference. A. Yellow sand (22804), Geology Department, Crawley. B. Yellow sand (21304), ft’om wall of gulley, 7 chains south-west from 14-mile peg. Ridge Hill. C. Yellow sand (22802), north-west corner Loc. 1298, IHdge Hill. D. Acid-insoluble residue from ferruginous sandstone (22798), Ridge Hill. The Geology of the Darling Scarp at Ridgp: Hill. ]2l Table IV. First, second {^Median) and third quartiles and coefficients of sorting (So) and skewness (Sk) of sands of Table HI. Sample. Q3 IM Q1 So Sk (mm.) (mm.) (mm.) A. ■469 ■341 •225 1-444 ■907 E. •417 ■243 ■ 130 I -791 ■918 0. ■450 •318 ■194 1-523 •863 E. -.384 •263 ■172 1-494 ■9.54 ^dieients of skewness (Table IV). If the secondary allophanoid of the feio’uginous .sainkstone be disregarded it will be seen that the grading of the detrital niat(‘rial of tlie feri'uginons sandstone is of still higher degree than tliat of the yellow sands. The mechanical analyses indicate that ^yRADE ^ ^ ^ ttrrr.) (T. cj ^ Q (T) le data eoiieerniug the variation in eoiu])osition of the nielro])olilan yelhiw sand. In their meeliauieal com- position all tile samples examined are very similar. The ferruginous sand- stones lunvev(‘r contain, as has been noted atiove, an allophanoid with tuberose form- this material is ab>eiit from the yellow sand. That this allophanoid jiei’sists in the soils formed over the fervuginoiis sandstones and low-level laterile is evidenced by its presence in the pebbly and sandy soil overlying the low-level laterite or ferruginous sandstone from a locality five eliains sonth-west from the 14-mile peg on the railway line i.e. two chains east of the easlern lioundai’v oi' the yellow sand. The presence of this allophanoid in the soils over llie ferruginous sandstones and low- level laterite and its absence in the yellow sand two chains farther west indicates that the y^dlow sands are not residual deposits from the ferru- ginous sandstone series. Tlie heavy mineral scpai'ations indicate that the yellow sands of Ridge Hill eontaiji a mueh higher propoi’tion of ‘dieavies’’ than the Crawley sand but in both the Ridge Hill and (^rawdey sands the “heavies^’ tend to The Geology of the Darling Scarp at Ridge Hill. J23 be (M)ueeiitriUt'(l in the ll.Vl’iO mesh *^raam])l(*s. Notes on the Heavy Minerals. — The magnetic fraction consists partly ot strongly magnetic nKtfjti/'tite and partly of weakly magnetic ilmvnile. The dominant constituents of the noii-maguetic fractions of all samples are o|»a(jU(* mineraiS of which le}icoji'f^ne is predominant. The leucoxene is cloudy and slowly solid)le in hot sulphuric acid, the resulting solution yielding posi- tive tests for titanium. Tile noii-opaiiue minerals are: — Zi. cou. This is the predominant non-opaiiue mineral in all samples ex- amined. There are two di.stiuct types: (a) perfectly rounded, col-.uvies.s and (h) eiihedral prisms whicli may occasionally show signs of slight abrasii.n. The euheale yellowish zoned varieties, 'fhe purple zircons are particularly characteristic of the Kidge Hill ferruginous sand- •stone but some occur iu the yellow sand ot the Coastal I Main. All .samples contain both well rounded and eiihedral types of zircon. Kifanite is also iircseiit in all tin* samples examined. (lenerally colour- less but a few grains of blue kyaniti* were noted in the residue from the ferrugiiKius sandstone. The kyauite occurs in stout prisms ami tablets with well rounded teiininations. Slau-roliie in pleochroic yellow-ln'own granules of somewhat irregular shai>e never shows the high degree of rounding of the zircon and kyanite. It appears in all the sands (*xamini‘d hut seems to be confined to the (-oarser grades. lintUe in deep reddish brown prisms, oftmi well rounded was noted in all sam[)les. Kpldftit; was the most abundant non-opaque mineral in the (‘rawlev yellow sand. In tin' other samples it was vmw i‘an* except in the finest grade ( 250) of the yellow sand I'rom the south i-nd of the Ridge Hill area (sample C.) where it is very abundant in tiny angulai' grains. The epidote in the Crawley sand is in stout pri'^ms showing very little sign of abrasion. The abundance of epiittcd, a few grains frosted, some with crescentic ])erciission marks. 50% rough witl) ])()lished or vitreous fracture surfaces 90% rounded, smooth, dull to polished with minute pitting and crescentic ])erciission marks. 10% rough with polished or vitre- ous fracture surfaces 126 Rex T. Prideh. Tlie examijKition of the surface textures Indicates that the fine sand grains of the ferruginous sandstone show no appi’eciable frosting. In tlu^ yellow sands on the other hand frosting is coininou down to grains Vi diameter. IVforeover all the yelloAr sands exhibit similar features so far as the surfaces of the grains ai'(' concerned, the proportion of rounded grains and the degree of frosting of such grains increasing with increasing’ grain size. ! ) The ycno\^■ colour of the sands is due to a very small amount of iron. When the yellow sand is lieated it changes to a brick red colour. Deter- minations of the iron content res]Jonsible for the yellow colouration of the Crawl(‘y and Kidga' flill sands Avere made by first removing the magnetic minerals (magnetite and ilmenite) and leaching the residue Avitli warm ItCl and determining the iron conteiit of the material leached oiit. The results Avere as follows: — Yellow sand, CraAvley (22801) : 0.80% Fe.O,. Yellow sand, Ridge Hill (218(H); 0.48% FeA- From the above considerations of mechanical composition, heaA’v minerals, shape ami surface texture of grains, the ferruginous sandstones, in view of the absence of frosted surfaces on the fine sand grains and tbe presence of tbe tuberose alloplianoid, together Avitb the different size distri- bution of the heavy minerals and the better grading than the yelloAA' sands, must be regarded as diftVring in mode and time of origin from the uncon- solidated sands. Theii* T)r(>venance however (as evidenced by the heavy mineral sfK'cies) was similar to that of th(‘ yelloAv sands. In all Avays excejit in their higher heavy mineral content the yellow sands of Ridge Hill are similar to the only examined sample of yelloAV sand from tlie IVretrojiolitan Area and each of these must, until further evidence to the contrary he lu'ougbt foi'ward, be regarded ns belonging to the same forma- tion. Tin* ju’esence of frosting* on grains less tlian one mni. diameter (grains down to ^ j mm. are frosted) is indicatiAu*’ of aeolian transporta- tion (Twenhofel, 1948, p. (i"). The yelloAv sands of the AFetropolitan Area have not previously lieeii examined in detail although Essou (192G, p. 14) suggests that th(*y are dune sands. It may rather ].k‘ tliat they are resi- duals from the disintegration of the Coastal Limestones. Pending further investigation il is im])ossilTle to say whether the yellow sands of Ridge Hill are sands blown from the sea bcuich and bankcal up vUgaiust the Darling Scarp oi* are residual deposits from the Coastal Limestones (in Avhich tlie sand grains may prove to haAX^ sul'fenMl aeolian transport). Th(‘ complete absema* of bedded and otlno* structures in these yellow sands seems to indicate the latter. The observation that the Ridge Hill sands have a much higher heavy mineral cont<*nl than the yellow sands of the l\Ietro])olit;ui Area also seems to indicate that tin* sands fronting the scarp are resiflual rather than sands blown from the west, in AA’hicli ease they would be expected to liave a lower heavy mineral index than the sands of the "Melropolitan Area. If the Ridge Hill sand be residual from the Coasal lamestone Series il means that the Coastal Limestone once covered the entire [>laiu in this I'egion or that there were belts of coastal limestone representing successive shore lines. The Geology of the Darling Scarp at Ridge Hill. 127 IV. SUMMARY AND CONdA SJONS. (a) Geological lii^torg , — The geology of the area has been described and the geological history may be summarised as follows: — (i) The oldest rocks exposed are granites, of wliicli there are two main phases: — a coarse-grained ])oi‘pliyritic and slightly gneissic granite and a. medium even-grained massive gi'anite. The gneissic type is the older of the two but Imth are considered to be comagmatic and to belong to the Younger Granite period (late Archaeozoic). (ii) The granites have been considerably sheared after their emplace- ment. These shears, because of their Pre-Cambrian age, cannot be related to the hypothetical Darling Fault. (iii) In Proterozoic tim(‘s igneous activity is re 2 )resentcd by the intru- sion of epidiorite dykes. (iv) There' is a complete blank in the succession until late Mesozoic times at least when it is j)ro])able that the ferruginous sandstones were deposited on a wave-cut platform and that the eastern boundary of the ferruginous sandstone series represents the shore-line in these times. tv) The next event recorded is the formatioji of the high-level laterite on a peneplaned surface, probably in Miocene limes. (vi) An uplift of the aiea of the order of 400 feet took place in late Miocene times and diiferentinl erosion of the soft rocks (Mesozoic and later) to the west and the hard rocks (Pre-Cambrian) t(j the east led to the forma- tion of a low lying coastal i>lain (the liidge Dill Shelf) or alteniativel^', if the ferruginous sandstones are not of iJesozoic age, tlie developnaait by marine erosion of a marine platform (the Ridge Hill Sliclf) covered with a thin veneer of beach deposits wliicli have later been cemented with fer- ruginous material to yi(‘ld the ferruginous sandstones and conglomerates. (vii) The area was then elevated slightly until the Ridge Hill Shelf stood slightly above sea-level and the low-levcl Uiterite developed in situ on this newly emerged terrain. (viii) The area has since been raised approximately 250 feet, after which much of the ferruginous sandstone series was removed ))y erosion, especially that }')ai’t whicli previously extended across tlie present Helena valley. (ix) Contem]mraneons]y with these upward inov(>meuts of the plateau to the east there was continual subsidence (downwai'ping) of the area lying to the west of the Scarp and dc])osition in this subsiding trough of the Tertiary deposits of the Swan Coastal Plain. (x) In comi)aralively recent times tlu' yellow sands have accumulated either as aeolian deposits blown against tin* erosion escar|)ment capped by the low-level laterite or l>y deiiosition of the Coastal Limestone formation against this escari)ment and the subsofiuent leaching of the calcareous cement yielding th(* structureless, unconsolidated yellow sands. As has been in- dicated on a ]n*evinus |)age these sands are not residual from the disintegra- tion of the ferruginous sandstones. (xi) Laterite formation aj^pears to be taking place within the yellow sands at the ])resent day. 128 Rex T . Pkideii The Hti’uclui'o ol‘ llu; IJai'ling Si'ai‘|) and Coastal Plain based on the assumption that the ferruginous sandstone series is of Lower Cretaceous age is shown diagrammatically in text fig. 7. Text fig. 7 . — Diagranunatic section (not to scale) of the Coastal Plain artesian basin on tlic assumption that the Kidge Hill ferruginous sandstones are of l.ower Cretaceous age (coinparal)le with the TUdlsbrook sandstones). (b) Tlir Darling Scarp . — Previous authors have considered that the ‘‘fault’’ hy])otliesis tor the origin of the Darling Scarp is supported by evidence of shear structures in the Pre-Cambrian rocks (Saint-Smitli, 1912, p. 7] ; Hlatchford, 1912, p. 59) and l)y the high and low- level laterites which were considered to be an indication of blocdc faulting (AYoolnough, 1920, p. Ki). The main conclusions drawn from the evidence set down in tliis paper ai'e: — (i) There are no striu-tnres in the Pre-Cambrian rocks which can be related to the supposed Darling Fault. The shear structures are considtu'ed to be of late Archaeozoic age sinee some of them liave been replaced by quartz vdns which are iidrudcd by late Pre-Cambrian epidiorites, and hence much older than the ]iostulated Darling Fault. ^Moreover they deviate very considerably from the dij'ectioii of the Darling Scarj). (ii) The high- and low-level laterites were formed at different periods and are no indication of block faulting and therefore yield no evidence in favour of the Darling Fault hy])othosis, (iii) It has l)eeu shown that lU) fault exists between the eastern and western edges of the area mapped and therefore if the Darling Fault exists it must be situated some distance to the west of the Ridge Hill .Area, where it is covered by the yellow smuls. If these conclusions are valid there no positive evidence for the existence of the Darling Fault. Aloreover all the observed characteristics of the scarp are explicable by dilterential erosion of the hard Pre- Cambrian rocks to the east and the softer later rocks to the Avest of the scarp. V. ACKXOWl.FDCAIEXTS. The held survey work in Ihe Ridge Hill Area Avas done by various parties of senior students of the University Geology Department Avorkiiig under my supervision and their assistance is gratefully acknowledged. 1 am indebted also lo Professor E. do C, Clarke for assistance during the revision of the text. The Geology of the Darling Scarp at Ridge Hill. 129 YI.— LIST OF WORKS TO WHICH REFERENCE IS MADE. Aiirousscau, M., and Budge, E. A., 1921, tenai'es of tlio Swan and Helena Rivers and their bearing on recent dlsplaecinent of the strand line.’’ Journ. Boy. 8oc. JV. Aigs-R, Vll^ pp. 24-13. Blatehford, T., 1912, “The possibilitv of obtaining artesian water in the vicinity of Moora.’' (ieol. Surv. IV. Aii.sl. BuU. 4S, pp. 56-02. Clarke, E. de C., Prider, R. T., and Teichort, C., 1944, “Elements of Geology *’ (I’niv. West. Aiist. Textbooks Board). Clarke, E. de C., and Williams, F. A., 1926, “The Geology and Physiogratiby cf parts of the Darling Range near Pcadh.’’ Journ Boy. Soc. W. Aio^t., Nil, pp. 161-178. Davis, C. E. S., 1942, “The Geology and Physiography of the Gosnclls Area.’’ Journ. Boy. Soc, flk Aui5. Prider, R. T., 1944, “The Petrology of part of the Toodyay District.” Journ. Boy. Hoc. W. AanU, XXVIII, pin 83-137. Prider, R. T., 194.5, “Granitic Rocks from Canning Dam.” Journ. Roy. Hoc. IV. Ausi., XXTX, pp. 137-149. Prider, R. T., 1948, “Igneous activity, metamorphism and ore-formation in Western Australia,” Journ. Boy. Soc. IP. Ayas-P, XXXT, ])p. 43-84. Saint-Smith, E. 1912, “A gc'ological reconnaissance of a portion of the South-West Division of Western Australia.” Gcol. Surv. IP. Ansi. BuU. 44. Ritteiihouse, G-, 1943, “Visual Projection Sphericity.” Journ. Sed. Ft troJ., 13, pp. 80-81. Simpson, E. S., 19Ht, “Report on Excursion to Zig Zag (Statliams) . ” Journ. Xai. Ifiul A- SOI. Soc. IP. Ayy-sP, HI, i)p. 36-38. Simpson, E. S., 1912, “Notes: on laterite in Western Australia," Gcol. May., dee, V, vol. TX, pp. 399-406. Simpson, E. S., 1931, “Contributions to tlie ATinmalogy of Western Australia, Series VI.” Jouryi. Boy. Soc. IP. Hy(.''P, X5TI, py. 137T49. Splichal, J., 1922, “Contribution to the Knowledge of Colloidal Clays.” Min. Ahsfr., 1, p. 288. Trask P. D., 1932, “(brigin and Environiiumt of Source Sediments of Petro- leum” (Gulf Publishing Co., Texas). Twenhofel, IV. H., 194-5, “The Rounding of Sand Grains.” Journ. Srd. Petrol., 15, pp. 59-71. Wentworth, C. K., 1922, “The Shapes of Beach Pebbles.” U .S. Gcol. Surv. Prof. Paper, lai-C’. Wooinough, W. G., 1918, “The Physiographic Significance of Laterite m West- ern Ausl’rnlia.” Gcol. Mag., dec'. VI, vol. V, pp. 3S5-393. Wooinough, W. G., 1926, “The Physiographic Elements of the Swan Coastal Plain.’'’ Journ. Boy. Soc. IP. Aunt., V, pp. 15-20. General Index. IX. GENERA]. INDEX. Generic and si)ecific names in heavy type arc new to science. Adamellite, at Clackline Adeonellopsis claraia Algal limestone Alinga Beds ... Alysiii manducator ... Amphiblestnu/i sp. ... Anagriis armatus Aonidiella aurantii ... A. pemicioftus Apatite AphelinU’S inali Aphycus thniff.rlakei ... Aphytis chrysomphali Apims (jeyidnata Aristolochia sp. Artesian hasin, C-oastal Plain, feeding aquifer of Page. 69 lOU 94, 96 2.^, .36-37, 41, 43, 44 14 99 9 10 20 6 11 9 4 8 Balcomhian Stage CMiocene) Barhaiia B. difisiwili^^ ... Barite ... Belemnites Biologi<-al control in Western Australia... BiMcirU’S laptdariu.H ... Bhitf Point Bompas Hill ... Boolagoorda Station Brachiopods ,.. ilraron gplechiae Brericotync hrassicae Hrurhns ohtarius B. pimnnn BubulruK ihit^ coromandus ... Bujo hufo BuUaria Bryo'zoa Burrows Butte Sandstone 14, 3r 98, 2-34, 42, 43, 95, 39. 1 - • 24 , 100 91 96 20 43 17 3 11 23 45 43 15 , 5 12 11 16 16 9() 99-100 . 31. 34 44, 45 “ Caliche'’ Calliphoridae ... (’ampanian Cumphell, W. 1)., on Tertiary deposits in Norseman District Cardahia Pange, Cretaceous rocks in Cardiia (■'ardiuiiL ('. arvaftforiiiis Cpif’arm depressa ('ellepora foMm Ceratitis capiiata 49 14 42 ...88. 97 42 ... 88, 91 88 91, 95, 96 99, 100 99 12 X. Oenehal IxDElx. Page. Chalcis vicloriae C. ruskini Cha])man, F. Chert nodules Chlainys aldtnffenjiij< ... C. iniorayana Cidaris C. comploul ... ClacUline, goolofrical structure of country between dackline and Toodvay Clarke, K. de C ‘ Coastal Idmestono Formation. ])robable extension to Darling Scarp ... Cobourn Station Cocci rifdla californica C. scniplGiiipundaia ... Coccopkafftf*! Ipra7iiL ... C. lyrimnui Coccna hespcridum ... ('om.pcriclUi bifaHrifila ('onglomerate, of ferruginous .sandstone series. Rhlgo Hill CoralUslm ... Cordierite-anthophyllite rock, (’^laekline ... (^owan. Lake, Tertiary deposits on Cranif'Uii Crespifj, Irene, on Tertiary fossils near Norseman ... ... 88, Cretaceous, possible oeourrenco of Lower Cretaceou.s at Ridge Hill Cretaceous stratigraphy of Lower ^turchison R. Area Crinoids Crisia acropora Cross-bedding... ... ... ... ... Cn/pfolap.mus ninntroiizicri ... Curious. Alt. ... ('ydoniinn- i/udlcrl 15 lb 88 ... 38-39 91, 95, 97 i ...95,97 29. 91, 9b i 19-47, S5-HK1 12b ... 44, 45 7 ■ 7 11 10 ■ 10 ■ 9 ... ni ' ... 93 : bl \ 85-103 ' 93 . 5, 98, 99-100 114 ... 19-47 43 100 ... 29-30 11 20 , >T 1 93 Daclyioralyriie-'^ Daiidarragan, (Tetaceous rocks at l)arli)ig Fault, hypothesis for origin of Darling Scarp, discussion Darling Si*ar]j, Ccology of, at Ridge Hill Delta deposits l)e.s)tta''idon (jmndin ... DiacJiufifna Iryoni Diacretus rapar J)hnitobdus Discodermia ... Dolomite Diindas, Lake, T(‘rtiary deposits near ... ■■ Duricnist " 93 ...41, 42 128 105-129 ... 42-43 93 12 3b r:- 93 88, 93, 97 ... 89, 97 j ...22, 37 'r /: Kjhdiorite, resistance to erosion as conipared witli granite ... /yrinaccfifi cin'opacKS Eriosowa laiilgcra EryJus Ktheridge. R.. Jun. Knca1y]it wood, fossil Fucla limestone lb b I 93 97 97 98 Ferruginous sandstone, occurrence at Ridge Hill Foraminifera ... Forcepia vro.'^mnchnvida Forman, F. G. Fusus ... 20, 111. 112 39 93 21, 42, 44 9b Gen k r al Ind ex XI Gardner, C. A. Garnet schist, Clackliiie Gee Gie Outcamp ... (Jeodia zeilandka Gingin, Cretaceous rocks at Glauconite Glauert, L. (jlyruneris Ouorimo-svhe.uia opf^rculella ... Granite, occTirrence at Clackline ... ,, of Darling Scar}) at Kidge Hill ,, Lawnswood Ai’ca, petrology of ^ oiingcT' Granite Granitic gneiss, occurrence in Lawnswood Area „ Lawnswood Area, }>etrology of Gregory J. W. (iryyhae.a f/ingmemis Page. 20, 34, ... 75-83 58 44 03 41 35, 41, 43 20 91 15 53 109 ... 00-70 53 ... 02-00 88 30 Halirhondria infreguens ... Hardabut Pool, ilurchisou IL, fault near naylzitt. itiellyii ... ... ••• ••• ••• ••• •••, Heavy minerals, of ferruginous sandstone and yellow saiids of Darling Coastal Plain ... ... ••• ••• ••• ••• ••• Jldlula undalifi Jlinrkslna geininata ... Hinde. G. J l/ippodamla roiivergens Hobson, K. A. Hornblende schist, Lawnswood Area f/nauurocera brasiliensi'i tJyhKiiiryrlus crawl ... HywdiLO.'ibosiniaa rapi 93 Scar}) and 123-5 15 99, 100 ... 88, 93, 98 ... ... 7 20 00-01 12 8 15 Icarya purchasi IdiH,onea sp. ... 1. incurra dnoceramus ... ... ... ••• ••• ••• Iron ore, “ charcoal iron ” deposits of Clackline 99 99. 100 20, 39, 43 7 -) Jaiijukian Stage (Miocene) Jenkins, C. F. H. ... .limperding Series, occurrence in Lawnswood Area Jointing Jurassic Jutson, J. T.... 100 ... 1-17 51 -.73, 54-55 ... 23-24 42 20 Kennedy sandstones 20 Laterite, high-level, occurrence at Ridge Hill ,, petrology and cbemical analyses „ low-level, occurrence at Kidge Hill ,, „ chemical analysis and petrology Laterite, see “ duricrust Laterite, occurrence on sloj)ing topped mesas, l^awnswood ... Lalruncuiia ... ... ••• ^ ••• Lawnswood, geology and physiograidiy of Leoanium persicae ... 115 110 115 11()-118 ... 51, 54 93 ... 49-74 11 XU. General Index. Lets coiiformis Lichenopora radiaia ... TAma bassi Lower Murchison IL Area, stratigraphy of Page. () 99 91 Macropora clarhel Macrosipkuni rosae Maestrichtian Magadliia cretacea ... Magellan ia insolHa ... Maitland, A. Gibb ... Marginella Marfiupites MarsupUax, uov. sp. M. leftindinarins McWhae, d.R.H Meanarra Hill Mecynoeda- prohosddv.a ^letajuspilite. of Lawnswood Area MetapkycuH helvolns 3/. loitnd^biiryl Mica schist, of Lawnswood Area ... Aficrnphanurufi bumiliji Aficrotery^ «p. Miocene fauna Miocene transgression in ^\^A. Modiolario cf. arcacea Mormoniella diripennis ^lurcbison, House Homestead and Station ,, River Series See. also Lower ^Iiuchison Muscu domeMka Myiocnema comperei Myxilla basiaia er A a 22, 34, 3 , 37, 90, 99, 100 () 42 39 ... 88. 91 19-20, 88 90 ... 21, 41 39 39 ... 8.7-103 8, 39, 40, 41 99 ... 58-60 8 8 ... .56-58 4 8 100 ... 98-99 97 14 ... 20 , 21 ... 20 , 22 ... 24-45 13 ... 8 , 11 93 Nasonia brevicornis ... Xatica Xezara riridnla Norseman. Tertiaiy deposits near Nnngajay Spring 14 96 4 ...8.5-103 ...24,37 ' Oakahella, sandstone at Oechalia consodalis ... Oolitic Rock ... Orcus hilunulatiis 0. dialybeus ... 0. laf artel Ostrea 42 4 93 7 5 .5 20, 39 Fecien Pelecypods Peninsula, Lake Cowan Pentacrinufi ... Peron Peninsula Peirosta variabilis Phosphate or phospliatic nodules Phylloxera vitifoliae ... 88 43 89, 93-97 91 45 93 ...21, 38 General Index. xiii. Pieris rapae ... Pilostyles P. Hamiltonii nov. sp. Plantagenet Beds Plutella tnm'Mlipennjs Porina gracilis Prider, K. T Princess Royal township Pseudocrcx'ciis spp. . . . Pteromalus pvparuw Pyejiodo7ita Page. 10 70 77 97, 98 14 99 105-129 88, 91-93, 98 11 10 39 Quartz dolerite, occurrence in Lawnswood Area „ ,, of Lawnswood Area, petrology of Quartzite, Lawnswood Area, petrology of Quayha whittierl 54 ... 70-71 ... 55-50 8 Rafflcsiaceae ... ... ... ... ... ... ... ... ... ... ... 70 Ragadmia ... ... ... ... ... ... ... ... ... ... ... 93 Raggatt, H. G. ... ... ... ... ... ... ... ... ■■■ ...20, 42 Refractories, sillimanite at Clackline ... ... ... ... ... ... ••• 71 Retepora sp. ... ... ... ... ... ... ... ... ... ... 99, 100 H, acicidifera ... ... ... ... ... ... ... ... ... ... 100 Rhizobius verdraiis ... ... ... ... ... ... ... ... ... •.• 8 Ridge Hill, Geology of Darling Scar]) at, by K. T. ibider 105-129 Rodolla cardinalls ... ... ... ... ... ... ... ... ••• ... 2 Rosp.lla anfan'fira ... ... ... ... ... ... ... ... ... ••. 93 Roycea unv. gen. ... ... ... ... ... ... ... ■■■ ■ '77 R. pyconophylloides nov. sj). 78 R, spinescens nov. .s]) 79 Sand, yellow, of Darling Scarj) ... Sand-plain Sandstone, ferruginous, of Darling Scarp „ ,, chemical analysis Saissetia oleae Santonian stage Sclllai.epas ginghmisls Schizellozoon permnnUum ... Sculellisla cyanea Satiellisfa sp.... Scymnodes Uvidigaster Second Gully Shale... Hemiactaeon microploms Senonian Sericite schist, of Darling Scarp ... Serptda gregaria Sillimanite schist, Claokline Simpson, E. S. Siphona e,rigua Rmintktjrus rirldls ... iS'orciT? vulgaris Spalanyla mtndaica ... Spiroporiua re.rtirlllata Spovdylus Spongolite Stellcta relic alula Stemoierys fulvoventralls Strongylophora durissima Stvrnus vulgaris 118-120 22 ! 111-112 110 7 41, 43 39 99 8 10 25, 38, 39-41, 44, 45 91 21, 42, 43 110 39 56, 71 20, 97 13 3 10 13 99, 100 39 88, 89-93, 98 93 14 93 16 XIV. General Index. Page. Synioiiwspliyruiii imJicutfi ... ... ... ... ... ... ... ... ... 12 Syrpliid flies ... ... ... ... ... ... ... ... ... ... ... 7 Talbot, H. W. B 88 Talpa europam 16 Tecticavea cf. schnapperensls 99, 100 Teichert. C. ... 19-47, 85-103 Teredo 34, 43 Tertiary deposits near Norseman 85-103 Tethya 93 TetraKiich ufi yiffard innus 12 TJieonella sir'm’hoel ... 93 Thirindine Shale 25, 35-36, 43, 44, 45 Toinorerti calif orn'n'th... 8 Toodyay. geologit^al structure of country betMeen Toodvav and Clackline ... 52 Tookmga Chalk 25, 37-39, 41, 44. 45 Toxoplera aarantU ... 6 Tracks and trails 31, 34 Travertine 40 Triaspis thoracktiH 12 Trkliohuja HorhiUatii<... 16 Trichopoda penuipes... 4 Trigo/io-semns 20 T. acanihodes 39 Tumblugooda Sandstone ... 22, 25, 26-31, 42 Turonian 42 TurriieUa 88 T. aldingae 100 T. tristria 91 Typhlocyha froyyatil ... 5 Tyroghyphus 2 )hyUoj.'erae 2 UiniacriniLs ... ... ... ... ... ... ... ... ... ... :ill, 41 Venericardia ... V. scahrosa V. spmvlo.sa ... Veravia line.ola Vehdina 95 91 91 7 93 Weeriiioogiulda Dam, rocks at ... ... ... ... ... ... 35. 36, 38, 45 Winning Series ... ... ... ... ... ... ... ... ... ... 44 Wood, fossil ... ... ... ... ... ... ... ... ... 34 Wcrin-burrows ... ... ... ... ... ... ... ... ... ...34, 35 Yellow Sand Voi'ination. of Darling Scarp and Swan Coastal Plain ... 118-126 York Peninsula (S.A.), Miocene beds of... ... ... ... ... ... ... 100 By Authority: William H, Wyatt, Govt. Printer, Perth.