JOURNAL OF THE ROYAL SOCIETY OF WESTERN AUSTRALIA VOLUME 53 PART 1 1970 REGISTERED AT THE G.P.O., PERTH FOR TRANSMISSION BY POST AS A PERIODICAL THE ROYAL SOCIETY OF WESTERN AUSTRALIA PATRON Her Majesty the Queen VICE-PATRON His Excellency Major-General Sir Douglas Kendrew, K.C.M.G., C.B., C.B.E., D.S.O., Governor of Western Australia COUNCIL 1969-1970 President Vice-Presidents Past President Joint Hon. Secretaries Hon. Treasurer Hon. Librarian Hon. Editor P. E. Playford, B.Sc., Ph.D. G. J. H. McCall, D.Sc., Ph.D., D.I.C., A.R.C.S., M.Aust.I.M.M. B. J. Grieve, M.Sc., Ph.D., D.I.C., F.L.S. A. B. Hatch, M.Sc., Dip. For. B. Ingram, B.Sc. (Hons.) P. G. Wilson, B.Sc. (Hons.) R. N. Hilton, M.A. Ariadna Neumann, B.A. A. S. George, B.A. S. J. Curry, M.A., Dip. Ag. Sci. R. W. George, B.Sc., Ph.D. W. A. Loneragan, B.Sc. (Hons.) J. H. Lord, B.Sc. D. Merrilees, B.Sc., Ph.D. R. T. Prider, B.Sc., Ph.D., M.Aust.I.M.M., F.G.S G. M. Storr, B.Sc., Ph.D. Journal of the Royal Society of Western Australia Vol. 53 Part 1 1. — Two xerophytic new species of Ptilotus (Amaranthaceae) from Western Australia By G. Beni, P.L.S.* Communicated by A. S. George Manuscript received and accepted 16 September. 1969 Abstract Two new species of Ptilotus, Pt. royceanus and Pt. mollis, from Western Australia are described and illustrated: the holotypes, housed at PERTH, are cited. Critical notes are made on some particular characters of the new taxa which are compared with previously described species, as well as with each other. Introduction By the courtesy of Mr. R. D. Royce (Govern- ment of Western Australia. Department of Agriculture) two new taxa of the genus Ptilo- tus came to my hands, one of which was re- cently gathered by Mr. A. S. George in the central Australian desert, the other preserved for more than 25 years as an indeterminate ("‘Trichinium, ? sp. nov.”. N. T. Burbidge) in the Western Australian Herbarium. Both species are very drought-resistant plants with an extremely dense pubescence covering stems branches and leaves as well as bracts and the ovary. 1. Ptilotus royceanus Beni, sp. nov. Descriptio .- — Fruticulus (rosei-)niveus ad 50 cm altus. ex fissuris rupis oriens et valde dif- fusus (Fig. 2). Caules lignosi virgati, primo stricti-erecti, postea arcuati, demum depen- dentes 0,5 cm et ultar diametro, multiramosi; rami ramulique numerosi erecte patuli vel curvati, subfastigiati, per totam longitudinem foliati (Fig. la), vetustiores apicem versus saepius pedunculum et rhacliidem spicarum formantes (Fig. lb) ; omnes tomento albidi- lanuginoso vestiti, pilis tortuosis, densissime in- tricatis; ramuli floriferi post deflorationem glabrescentes et apice tenus multo extenuati. Folia (Fig. la) integerrima opaca alterna, 1-2 cm distantia, basi petioliformi subsessilia (laminis vix in petiolum attenuatis), carnosa — laminis utrimque semper tomento crasso piloiTim ut in caulibus crisporum obsessis — , * Botanische Staatssammlung MUnchen, Germany. orbicularia (ad 1,2 cm diametro) vel rotundati- subovata vel late elliptica (ad 2 cm longa et 1 cm lata), apiculata, nervo medio subtus plus minusve prominente; superiora, quorum ex axillis ramuli floriferi vel flores singuli baud raro oriri solent, et summa in bracteas trans- euntia flavescenti-albida. infei'iora cineras- centia. Infloresceotiae (Fig. Ibi numerosae baud amplae longe spicatae, plerumque in paniculas complures laxas congestae. Spicae singulae elongati-cylindraceae, ad 15 cm et ultra longae et 1,0-1 ,3 cm diametro, pilmo pedunculati- erectae. ramos ramulosque terminantes, dein plus minusve curvatae vel fiexuosae, laxi- vel remotiflorae, usu solitariae, raro minoribus lateralibus breviter pedunculatis additis, axillae foliolarum summarum vel etiam florum sin- gulorum imorum enascentibus. Flores superiores spicae baud densius collect!, inferiores aequales dissiti 0, 3-1,0 cm fere remoti (Fig. lb), primo rosei dein pallescentes. Bractea et bracteolae scariosae integrae plus minusve carinatae, nervo mediano colorato in acumen breve (0,2 mm longum) excurrente, pilosae pilis subcrispis remote articulatis apicem attingentibus vel paulo superantibus. in- aequales: Bractea indumento abscondita rigidiuscuia (oblongi->ovata 2 - 2,3 mm longa et 1,2 - 1,6 mm lata, pellucida, (dilute) succinea, costa prominula distincte aurei-fusca. in toto dorso pilis densis ad 1.8 mm longis, mai'gines — apicem versus interdum paululo serrulatas — ubique semper valde praestantibus vestita, post lapsum perianthii superstes. Bracteolae mem- branaceae tepalis adpressae, late subovatae, circiter 3 mm longae et 1,8 mm latae, in lateri- bus glabris hyalinis lucidis nervum fiavi- fuscescentem versus pilis flexuosis dense obtectae. Perianthium (Fig. Ic) tepalis divergentibus subcampanulati-patens, basi ad pseudotubum (0,4 mm) connivente extus hirsuta vix in- duratum. Tepala impellucida rigida integerrima 1 b Figure 1 Ptilotus royceanus Beni, sp. nov. — a = sterile part of the plant; b = fertile end of a branchlet; c = expanded perianth, inner view: d = staminal cup spread open, inner view; e, f = pistil, two stages of devel- opment; g = pistil including the almost ripe nut. 2 libera, sublinearia acuta, in dimidio paene in- feriore distincte trinervia, in areola mediana nervis lateralibus circumscripta paulisper pur- purascentia. extus tota superflcie — apice nudo lucido, circiter 0,4 mm longo excepto — pilosa, pilis niveis subtilibus strictis oblique erectis, articulatis, ad 2 mm longis induta, intus lae- vigata, glabra. 2 exteriora 5-6 mm longa et usque 1 mm lata, marginibus apice tenus plus minusve abrupte involutis, hoc modo apicem brevem imperfectum— pubescentia eundem numquam attingente — formantibus: 3 interiora subaequilonga 0.5 - 0,7 mm lata, marginibus in- volutis in apicem acuminatum pilis dorsalibus vix superatum sensim Iranseuntia. Stamina 5, sterilia nulla (Fig. Id), in cupulam humilem f0,l - 0,15 mm) et planam glabram basi perianthii tantum insidentem connata: squamulis intrastamineis nullis. Pilamenta dilute fulva linearia. subulata, inferne sensim ad 0.2 mm dilatata, longitudine ab 1,2 ad 3.0 mm differentia: antherae in dorso affixae flavae ellipsoideae 0,35 mm longae et 0,15 mm latae. basi leniter bilobae. Ovarium (Fig. le-g) primo clavatum (circiter 0,8 mm longum), dein subglobosum (1,2 mm dia- metro), modice stipitatum (stipite ad 0,2 mm longo), basi excepta dense villosum, pilis 1 mm fere longis nodulosis, primo rectis, postea undulati-crispatis, fructum elongatum < circiter 2 mm) demum coronantibus; stylus centralis 1,5 mm longus, tenuis (0,06 mm diametro), glaberrimus, stigmata papilloso primo capi- tellato, dein inconspicuo. liolotypus speciei . — Bungabiddy Rockhole, Walter James Range, W.A. (128^ 44' E, 24° 40' S); A. S. George no. 8314, 5.X.1966. (“Much- branched perennial herb to 50 cm. growing in crevices on rock walls. FIs. pale pink.”) — PERTH. Isotypes: CANB, K, M, MEL, PERTH. Paratypes , — Glen Gumming, Rawlinson Range. W.A. (128° 23' E, 25° 00' S); A. S. George no. 8825, 21.VII.1967. (“Much-branched perennial herb, with pale pink fls. In crevices on vertical rock walls.”) — AD. B, CANB, M, NSW, PERTH. Habitat . — In addition to his notes on the labels Mr. A. S. George — Western Australian Herbarium, South Perth — communicated the following data to us in a letter of 10.11.1969; This Ptilotus “is known from two localities in the ranges of central Australia, just west of our State border. The species always (Xicurs on vertical rock walls in gorges, being replaced by the common P. obovatus where more soil has accumulated. A photograph of the plant in situ accompanies one of the collections.” (see Fig. 2.) Figure 2 . — Ptilotus royceanus Beni. — Photograph showing the habitat of George 8825 in the Rawlinson Range. — phot. A. S. George. 3 Material. — Our description is based on the holotype. a much-branched stem measui'ing 40 cm up to the top and bearing more than a dozen of inflorescences, on 6 isotypes (each a less copiously flourishing branch) and on 6 samples of George's no. 8825. These paratypes are characterized by larger and vsomewhat darker leaves, and by a stronger branching of the floriferous parts; the flexuous spikes are richer in flowers. The differences may be ex- plained by diverse local conditions and by the different times of collecting.* Discussion. — Apart from the dense and some- what villous pubescence the most striking features of the newly established species (“most attractive when seen growing from the rocky walls of its habitat”. A. S. George) are the usually orbicular leaves and the very elongated interrupted spikes, the number of their flowers varying exceedingly, i.e. from a few only to 30-50 a spike. Almost orbicular laminae may occur at times in Ptilotus obovatus (Gaud.) F.v.Muell. var. obovatus, besides the ordinary spathulate and obovate ones. More often we find those orbi- cular leaves in Ptilotus roei (F.v.Muell. ex Benth.) F.v.Muell., where they are. however, dis- tinctly pedunculate and only puberulent when young. In Ptilotus rotundifolius (F.v.Muell.) F.v.Muell. well-rounded thick leaves are met with in most of the specimens, and always coated with a dense tomentum of crispy hairs, in about the same way as in oiu* taxon; but the leaves may attain diameters of 6 cm. Furthermore, none of the three species ever bears inteiTupted spikes but always compact ones. More or less separated flowers are presented by Ptilotus dissitifiorus (F.v.Muell.* F.v.Muell. in its two varieties dissitifiorus and longifolius Beni: The 15-30 solitary flowers of the spike (up to 15 cm long) are inserted at intervals of 3-8 mm. Ptilotus distans (R.Br.) Poiret, too, is crowned by interrupted spikes of about the same kind, the distances of the inferior flowers measuring up to 2,3 cm. Finally, in Ptilotus forrestii F.v.Muell. we find the 15-30 flowers of the spike (6,5 cm) at a distance of about 1 mm from each other. None of the three cited species bears either orbicular leaves or a pubescence as described in the present plant: The yellow rough and more distinctly jointed hairs on stems and leaves in Ptilotus forrestii are crispy, too. but scarcely intricate. Ptilotus distans completely lacks pubescence, and in dissitiftorus the indumen- tum of dendroid hairs becomes deciduous in * Amon^ a collection of duplicates of Ptilotus. recently (2. II. 1970) sent to us by Mr J, R. Maconochle (Arid Zone Re.senrch Institute, Animal Industry and Agriculture Bi'anch. Northern Territory Administration, Alice Springs, N.T.) an undeter- mined specimen (Gorge, i mile E. Ewallnga Rock- hole. Petermann Ranges; J. R. Maconochie no. 780. 19. IX. 1969. — N.T. 25069) was included, which proved to be identical with our new species. It matches well some of Mr. George's samples, and its locality belongs to the same area where George's plants came from. J. R. Maconochle notes; "Perennial shrub to 12' high, leaves orbicular, soft and having woolly-textured surface, inflorescence an open spike each floret pink. Growing in crevices of rocks in gorge where hillside almost vertical." Older stages of the plant. Moreover, each of the three species has a dissimilar appearance in its general stature and differs markedly in the structure of its flowers. Thus Ptilotus royceanus is sharply separated from all forms previously described, un- doubtedly being a really distinctive species. Name. — The specific epithet of the new plant was given in honoui' of Mr. Robert D. Royce, having been active since 1933 in the Depart- ment of Agriculture of Western Australia; in 1960 he became Curator of the Herbarium suc- ceeding Mr. C. A. Gardner. Since 1945 he has made numerous collecting trips, exploring ex- cursions and surveys in Western Australia. Mr. Royce was kind enough to let me have access to the rich collections of Ptilotus in his herbarium and to send me the many hundreds of sheets over a period of time, thus enabling me to continue my studies. Furthermore, a considerable number of duplicates were gener- ously given by him to our Botanische Staatssammlung. 2. Ptilotus mollis Beni, sp. nov. Descriptio. — Planta perennis manifesto fruti- culosa indumento permolli ornata est. Rami floriferi suberecti foliosi, ramulis ex axillis orientibus abunde praediti. sordide flavidi, 20 cm et ultra longi, 5 mm et ultra diametro. lanuginosi-tomentosi, pilis albis tenuibus remote nodulosis circiter 2.5 mm longis. eximie crispatis et densissime intertextis, tegmentum continuum crassissimum (ad 1 mm) formantibus. petiolos eodem modo inducentibus. Folia alterna 0,5-1. 2 cm distantia, Integra, in- dumento crassa. argenteoli-nitida, primo subob- ovata dein spathulata (Fig. 3a* apiculata- laminis in specimine examinato ad 2,2 cm longis et 1,3 cm latis, gradatim in petiolum distinctum (ad 0.6 cm* contractis, utrimque pubescentia luxuriosa absconditis. pilis subrectis adpressis tenerrime sericeis visu laevibus (imperfecte articulatis) ad 3 mm longis, partem totam superiorem et dimidium fere apicale partis in- ferioris laminarum tegentibus. petiolo tenus in pilos crispos transeuntibus. Spicae inconspicuae axillares (Fig. 3a) — spica una demum terminante excepta — breviter pedunculatae (pedunculo 4 mm fere longo, interdum duobus foliis parvis onusto), hoc modo in racemum congestae; late obtuseque pyra- midales, in specimine exstante 0. 6-1.0 cm longae et 0. 7-1,0 cm latae, spica terminal! paulo maiore. Flores singuli (circiter 25) sub pelle pilorum albidorum bracteae bracteo- larumque et perianthii absconditi vix cerni pos- sunt. Bracteolae cum bractea scariosae costatae, nervo medio prominente flavo vel subfusco vix producto. apice plus minusve acutiusculo, pilis dossalibus ad 3 mm longis, basim versus (sub-) undulatis nodulosis semper superato. inaequales: Bi-acteolae membranaceae (Pig. 30 ventricosae (rotundati-)ovatae 2,5 - 2.8 mm longae, ad 2 mm latae, integerrimae, in lateribus glabris hyalinis nitidis, pubescentia in tertiam mediam restricta, tepalis arete adpressae. Bractea in- 4 Figure Z.—Ptilotus mollis Beni, sp. nov.— a = terminal piece of a floriferous branch; b bract, outer view; c " practeole, inner view; d outer perianth-segment and e rr inner perianth segment (both inner view); f z= stamina! cup; g = pistil. 5 ferior rigidior, oblongi-ovata vel ovati-lanceolata 2,2 - 3 mm longa et circiter 1 mm lata, in tergo omnino densissime villosula (Fig. 3b>. margine apicem versus interdum subserrulata. Penanthium rigidi-erectum, postea aliquan- tum aperiens, basi constricta parce induratum. Tepala libera in pseudotubum brevem (0,15 - 0,2 mm) conniventia. scariosi-flavescentia, basi plus minusve distincte trinervia et subcarinata, extus praeter apicem glabrum saepe praerupte angustatum (0,2 — 0.3 mm) pilis albis strictis ad 1,8 mm longis baud conspicue articulatis, apicem non attingentibus copiose vestita. baud (vix) limbata, intus laevigata, inaequalia: 2 extima lineari-eliiptica (Fig. 3di ad 3,5 mm longa et 1 rnm iata, apice baud raro visu bi- (tri-)furcato, 3 interiora sublanceolata (Fig. 3e) vix breviora. sed angustiora (0,6 mm> supra basim interdum nonnullis pilis marginalibus intvoflexis obsessa. apice plerumque peracuta. Stamina 5. omnia fertilia, cupulam tur- binatam membranaceam subglabram conspicuam (circiter 0,3 mm altam) liberam formantia (Fig. 3f): pseudostaminodiis interiectis nullis. Fila- menta ad 0,45 mm longa ligulata, superne subu- lata, interne gradatim et modice dilatata (0,1 mm). Antherae dorsifixae rufescentes. sublineares vel ellipticae 0,2 mm fere longae. Ovarium subglobosum, breviter stipitatum ad 0,8 mm. longum (stipite 0,15 mm fere longo incluso). echinatum, pilis breviter setaceis (0,1 - 0.2 mm) praeter stipitem omnino vesti- tum (Fig. 3g). Stylus centralis glaberrimus. eadem longitudine vel paulo longior et 0.1 mm diametro; stigma minutissimum. Holotypus speciei. — Gorge Ranger, Warra- long Station. W.A. (“Growing as an erect small undei*sbrub amongst loose boulders’’); N. T. Burbidge no. 780; May 1941. — PERTH. Material. — Tbe sheet containing only one branched top of a stem (21 cm high), it was natural to assume that further parts of the plant might be in the possession of the collector or of one of the institutes supplied by her with specimens. With regard to this Dr. Nancy T. Burbidge expressed herself in a letter of 9. V. 1969 as follows: "The Ptilotus specimen from Warralong (my 780), was obtained while I was working on a research grant at the University of Western Australia. Later, when I moved to South Australia, the plant collection was given to the State Herbarium from which Mr. Royce has forwarded material. So far as I know none of the collection is now held at the University. I did not retain any myself . . . It is possible that there was only enough of the specimen to make a single sheet. There is no reason why the sheet you have should not be made the holotype.’’ Habitat. — Ecological notes about the area in which the plant had been gathered were pub- lished by Dr. Burbidge in Journ. Roy. Soc. W. Austr. 29: 151-161 (1942-43. issued 1945), where Figure 2 of Plate II gives an idea of the terrain where Ptilotus mollis was (or possibly is still) growing. + The Gorge Range Is a chain of hills between the Shaw and the Coongan Rivers within the granitic De Gray — Coongan plain, with its semi-arid climate. Discussion. — Never before has such a con- spicuously dense indumentum of crisped hairs as that covering the branches and branchlets of the above taxon been found on any Ptilotus species. The soft woolly coat continues over the ped- uncle into the lamina, giving way. especially on the upper surface, to long straight fine hairs which give the leaf a peculiar silver-gray silky brightness reminiscent of the considerably narrower and by far more crowded leaves of Ptilotus helichrysoides F.v.Muell. This species is primarily different because of its cushion- forming growth, and the velvety pubescence consisting entirely of more or less straight hairs. With regard to the floral structure the two taxa only agree in the 5 equally long and fertile stamina as well as in the densely hairy ovary; but in any other detail, especially their proportions, they differ markedly from each other. As regards the thickness of the indumentum on branches and leaves, among the well-known species Ptilotus incanus (R.Br.) Poiret (in its var. iJicanus) does resemble our new plant at first sight; yet its pubescence consists of dend- roid hairs, and no closer relationship is to be considered, the inflorescences looking absolutely different. The same can be said about Ptilotus ohovatus (Gaud.,) F.v.Muell.. which (in its varieties obovatus and griseus Beni ) has at times a rather thick cover of dendroid and stellate hairs, respectively. In Ptilotus rotundi- folius F.v.Muell. the woolly indumentum of the stem is composed of fine crispy hairs, and the pubescence of the leaves may become rather thick; but the terminal spikes of this species will actually reach a length of 12 cm and a diameter of 4 cm, giving the plant quite a different habit. With regard to the kind of indumentum Ptilotus mollis bears a striking likeness to the above taxon, Ptilotus royceanus. There, too, stems and leaves are covered by a — though somewhat thinner — layer of crispy and intricate hairs; the bracts being completely concealed by their dorsal woolly fur, the ovary uncommonly pilose. In spite of those traits of resemblance a closer lelationship is not to be assumed either, as in Ptilotus mollis the flowers form a densely crowded spike, w'hilst in Ptilotus roy- ceanus they are inserted increasingly remote, up to a distance of 1 cm from one another. The genez’al facies of the new taxa can hardly be compared with each other. Ptilotus mollis being represented by a mere fragment. At least we are able to conclude from Dr. Burbidge’s notes that small bushes of the plant collected by her are growing upright between boulders in creeks, where Ficus platypoda. Ficus orbicularis, Terminalia circurnalata. Acacia trachycarpa, Corchorus parxnflorus var. ovatus and Ptilotus auriculifolius are also to be found, as well as an occasional Eucalypt. In contrast to this situation Ptilotus royceanus. a more or less hanging subshrub, seems to be dependent on vertical walls within some ranges of the central Australian desert (Fig. 2). Ptilotus mollis is quite unlike all other species hitherto knowm, thus representing a well dis- tinguishable taxon. 6 2. — Eurynome orientalis, a majid spider crab (Crustacea, Brachyura) new to Australia, and notes on E. granulosa By D. J. G. Griffin* Manuscript received and accepted 17 February, 1970 Abstract Eurynome orientalis Sakai is a new record for Australia and E. granulosa new for Western Australia. The morphology of each species is discussed in relation to the original descrip- tions. Introduction During examination of the Western Australian Museum's (W.A.M.t collections of majid spider crabs in August 1967 four specimens were found which belonged to the genus Eurynome, small crabs which typically bear rather unusually shaped, mushroom-like iboletate) tubercles on the dorsal surface of the carapace (see Griffin, 1964). These four specimens proved to belong to E. orientalis Sakai, a species previously known only from Japan, and E. granulosa Baker, a species oi'iginally described from South Austra- lia. The present paper contains notes on the two species. Terminology follows Griffin (1964). The specimens were collected by the Australian C.S.I.R.O. during cruises off Western Australia on H.M.A.S. “Diamantina.” Acknowledgements I am grateful to Dr. R. W. George of the Western Australian Museum for making the specimens available for study, and the C.S.I.R.O. Science and Industry Endowment Fund which provided travel funds for the visit to the Museum and Dr. J. C. Yaldwyn, Dominion Museum, Wellington, for reading a draft of the manuscript. Family MAJIDAE Samouelle, 1819 Genus Eurynome Leach, 1814 Eurynome orientalis Sakai (Fig. 1) Eurynome orientalis Sakai, 1961: 140-141, text- fig. Ic, d, pi. IV fig. 2; 1965: 79-80, pi. 37 fig. 5. Material examined: S.W. of Point Cloates, W.A., 23"39'S., llsnrE., beam trawl. 73 fms., 7/10/1963, H.M.A.S. “Diamantina'* Cruise 6/63, C.S.I.R.O.. Sta. 187, 1$ c.l. 6.7 mm (WAM 328- 67). N.W. of Carnarvon. W.A., 24°59'S., 112"27' E., beam trawl, 71 fms., 8/10/1963, H.M.A.S. “Diamantina” Cruise 6/63 C.S.I.R.O. Sta. 197. Ic5, c.l. 8.2 mm (WAM 58-67). Remarks: The rostral spines and supraorbital eaves bear a few spinules on the lateral surfaces but are not serrate as Sakai mentions. The edges and upper surface of the intercalated spine are minutely spinulate, a feature not mentioned by Sakai. The central cone of the cardiac plate (or expansion* mentioned by Sakai is low in the male of the present pair but * Australian Museum, Sydney, N.S.W. high in the female; the intestinal plate is in the form of a smooth circular lobe bordered by blunt tubercles dorsally and flanked laterally by oval plates. The remaining plates and spines on the carapace are as described by Sakai; the small expansions on the carapace are star- shaped. The following featui*es are not described by Sakai. The basal antennal article bears a few spinules on its surface and ends in two sharp spines. The anterolateral angle of the merus of the third maxilliped is spinulate. The carpus of the cheliped of the male bears, dorsally and laterally. 4 or 5 spines larger than the others: in the female the spines on the carpus are all about the same size. On the palm of the chela of the male about six spines on the dorsal and outer surfaces are markedly lai’ger than the others. The relatively smaller chelae of the female have only two or three larger spines. The spines on the dorsal surfaces of the ambu- latory legs are markedly larger than elsewhere. Figure 1 . — Eurynome orientalis Sakai. Male, c.l. 8.2 mm, N.W. of Carnarvon, W.A. (WAM 58-67); carapace, dorsal view. 7 The differences between the present speci- mens and the original description given by Sakai are small. In other features, including the shape of the first pleopod in the male, there is very close agreement. The present specimens therefore represent the addition of another Japanese species to the Australian fauna. Distribution: Sagami Bay, Japan, 75 metres. Western Australia between Carnarvon and North West Cape. 71-73 fms. Eurynome granulosa Baker Eurynome granulosa; Griffin. 1965: 30-34, figs. 1-5. Material examined: W. of Rottnest I., W.A. 32°00'S., 115“16'E., beam trawl, 175-78 fms., 12/10, 1963, H.M.A.S. “Diamantina’* Cruise 6 63, C.S.I.R.O. Sta. 225, 1 9 (ovig.), c.I. mm, 19, cl. 6.7 mm (WAM 327-67). Remarks: Comparison of these two specimens with the description of the holotype (Griffin, 1965) shows the following differences: The hepatic margin does not extend laterally further than the anteriorlateral edge of the branchial margin, the lateral surfaces of the rostral spines lack spinules, the tubercles on the branchial margins are blunt and not as distinct as in the holotype. The tubercles on the dorsal surface are not arranged in such distinct groups except that the group of tubercles forming a transverse row across the intestinal region is very obvious and consists of seven tubercles anteriorly and two close behind (in the holotype there are only five tubercles). The distal teeth on the fingers of the cheliped are present in the smaller specimen only. In all other features the two specimens from Western Austi*alia agree with the type material. Distribution: Off South Australian coast, 100- 104 fms.; South Western Australia 75-78 fms. References Griffin, D. J. G. 1 1964). —A review of the genus Eury- novie Leach (Decapoda, Majldae) and a new species from New Zealand. Crustaceana 6: 195-206. figs. 1-11. (1965). —A redescrlptlon of the Australian spider crab "EUTynome granulosa" Baker (Crustacea, Brachyura, Majidae). Rec. S. Aust. Mus. 15: 29-37. figs. 1-5. Sakai, T. (1961). — New species of Japanese crabs from the collection of His Majesty the Emperor of Japan. Crustaceana 3: 131-150, figs. 1-4, pis. Ill, IV. (1965). — The crabs of Sagami Bay collected by His Majesty the Emperor of Japan. Tokyo: Maruzen. Pp. xvi, 1-206. 1-26 (Eng- lish), 1-92, 27-32 (Japanese), 26 text figs.,. 100 pis., 1 map. 8 3. — The Merougil Creek Sub-Area By G. J. H. McCall*. J. C- Braybrooke** and D. D. Middletonv Manuscript received 18 March, Abstract The second of a series of accounts dealing with investigations of the Kalgoorlie system (early Precambrian, metamorphisni c.2700 m.y. age) to the west of Lake Lefroy. deals with the north-easternmost part of the area, called, for convenience, the Merougil Creek sub-area. The psammliic and rudltlc metasediments here exposed show particularly well-preserved gross primary sedimentational structures, though microscopic evidence of clastic texture is lacking, the microtextures being modifica- tions of original greywacke textures-semischist and schist textures. The lithologies are de- scribed, a stratigraphic sequence covering nearly 17.000 feet of sediments without igneous rock intercalations erected, and the depositional environment is deduced to be marine, off- shore and piedmontine. Metamorphism has produced assemblages corre-sponding to Green Schist Facies throughout the sub-area: meta- somatism is evident in this sub-urea. Igneous rocks Include those of the Ked Hill-Kambalda ophiolite belt, containing both metabasalts and serpentlnites. and the site of the recent major nickel ore discovery, made since this investiga- tion was completed: porphyries and udamellitic microgranites. Special attention is paid to the nature of the boulders In the Merougil Creek conglomerates: to their provenance: to their deformation; and to the porphyrold metasoma- tism that appears to affect these conglomerates. In this sub-area we see evidence of shearing and homogenisation of polymictic conglomerates to produce porcellanous rocks, in which the boulders show tendency to merge with the matrix, which they have come, by a process of homogenisation, to resemble. This process is believed to be the incipient stage in the more extreme porphyroid metasomatism recognised in similar rocks to the south, at Bayley’s Workings and at Widglemooltha. The conglomerates affected b}' the metasomatism are believed to consist mainly of igneous porphyry, metasedl- mentary. or granite boulders, The structure of the area is homoclinal to the west of the Kambalda Ophiolite Belt, which has been shown in mining operations to have a dome structure, reflected in pillow facings. The facing of the rocks of the homocline is con- sistently westwards. Introduction The Merougil Creek outcrops of metasedi- ments are bounded on either side by ridges of greenstone, comprising belts of ophiolitic rocks of basic to ultrabasic composition (Fig. 1>. To the east lies the Red Hill-Kambalda belt and to the west, the Yilmia belt.^ These residual * 34 Marita Rd.. Claremont, W.A. 6010. **c/- Snowy Mountains Authority. Cooma, N.S.W. 2630. tGeology Dept., University of Queensland. St. Lucia. Qld. 4067. JBraybrooke and Middleton (1964) mapped as far as a reported greenstone outcrop near the lower dam on Merougil Creek (Pig. 2 inset): Doepel and McCall have re-examined the creek section from Yilmia Dam (near Cave Rocks) to this point, and it is apparent that the Merougil Beds continue west- wards. probably to the fence line east of Yilmia Dam. where rocks of similar lithology still face west. No greenstone in place was recognised, and it seems possible that an outcrop of greenish weathered rock, believed to be the laterite capping 1969: accepted 17 March. 1970 ridges stand up above an area of low relief and poor exposure, corresponding to the outcrop of a thick sequence of metasediments. The actual exposure is negligible in this intervening strip, except in the creek itself, near to its outlet into Lake Lefroy, and along the shore of Lake Lefroy. Granite intrudes the greenstones of the Red Hill-Kambalda Ophiolite Belt to the east: and some of this granite is rimmed by quartz-albite porphyry, similar to the rocks that form dis- crete, irregular masses in the same belt. Most of the quartz-albite porphyries appear to be closely related to the granite bodies, and, at one point within the area mapped, there is an insensible giadation from porphyry into a microadamellite. Another suite of porphyries, of an intermediate character carrying horn- blende. seems also to be present in this belt, but not to be related to the granite intrusions. The Yilmia Ophiolite Belt is devoid of granites, but does contain some albite-quartz porphyry bodies of igneous aspect, apparently late intrusions into the basic and ultrabasic rocks forming the ophiolite belt. Like the porphyries of the Kam- balda locality, these appear to have suffered at least part of the effects of orogenic deformation and metamorphism. The Yilmia ophiolite belt is described by Doepel (1965) and in a brief introductory account (McCall and Doepel. 1969). The Red Hill-Kambalda Ophiolite Belt was only studied by Braybrooke and Middleton (1964) in a limited coastal area, and, while some of their results have been considered worth brief mention in the subsequent text, much more detailed information is now available, though unpublished, as a result of detailed surface and underground mapping by geologists of the West- ern Mining Corporation. The metasediments between the greenstone belts are dominantly psammitic. and include coarse, polymictic conglomerates. The meta- sandstones are of metagreywacke character, and so is the sandy matrix of the conglomerates. The greywackes have mostly been con- verted to semischists (Williams. Turner and Gilbert, p. 205: Turner. 1968. p. 31). Ihere are subordinate intercalations of pelites, of metasiltstone character — pelites of finer grain size do not seem to be represented, though they are present as minor intercalations within the Red Hill-Kambalda Ophiolite Belt, and in quite thick sequences to the west of the summit of Plantagenet beds, was taken for greenstone This account incorporates the results of the mapping by Doepel and McCall, and the Merougil Beds are thus considerably extended from the original thickness defined by Braybrooke and Middleton (op. cit.). A thickness of 16,000 feet given here includes this additional section: however, as noted in Part 1 of this series of accounts (McCall, in the press), it may be an overestimation. 9 Figure 1. — Sketch map showing the location of the area discussed in this account. 10 of Yilmia Hill. The psammitic and psephitic locks of the Merougil Beds (McCall, Braybrooke, Middleton and Muhling, 1967: McCall, in the press, part 1 of this series of accounts) have been found to extend, without any other rock type breaking the sequence, from the mouth of the Merougil Creek to a point just east of a north-south fence line, east of Yilmia Dam, where the last outcrop of them is cut by a small porphyry body. Except for this interrup- tion, they are neither cut by porphyry bodies nor do they show intercalations of basic or ultrabasic meta-igneous rocks. Near to the mouth of the creek a sequence of 5,700 feet of steeply disposed metasediments can be mapped in more or less continuous ex- posure. This sequence forms a homocline, showing consistent w^est facings, a regional strike of 310°. and a regional dip of 65® towards the south-west. A detailed subdivision can be made of this part of the Merougil Beds, but, to the west of the lower dam on Merougil Creek, the outcrop becomes sporadic and restricted to the creek bed in the upper part of the sequence: and what rocks are exposed in the creek bed are heavily kaolinised; it is thus impossible to make any detailed subdivision. Tlie very definite west facing just west of Yilmia Dam, the intermittent exposure of similar rocks throughout the creek section, and stratigraphic considerations of a regional nature, suggest that the Merougil Beds do continue right through this section without Interruption, though fine pelite intercalations might be obscured in the upper part of the sec- tion. They are believed to be overlain by the Cave Eocks Beds and Abattoir Line-Cave Pocks Ophiolite Belt, cut off on the west side from the Yilmia Ophiolite Belt by the Yilmia Dis- location. The Merougil Beds were at one time thought to be in virtual strike continuity with the Kur- rawang Conglomerates, and to be their sti'ati- graphic equivalents (Cleverly, unpublished paper, 1957: “The relation of the Younger Greenstones to the Kurrawang Series at Kun- dana”). The oblique, apparently cross-cutting Abattoir Line — Cave Rocks Ophiolite Belt, established by both aeromagnetic surveys and ground mapping by geologists of two mining companies, has alw^ays seemed to be incompat- ible with such interpretation, and this objection was strengthened by the recognition of the usual ophiolite belt assemblages — serpentinites, meta- gabbro sills, pillowed metabasalts etc. — within this belt, suggesting that it is a true ophiolite belt. The anomaly was resolved by McCall (in the press, part 1 of this series of accounts) by means of a revised stratigraphic interpretation (replacing that given in McCall et al (1967) ). an interpretation w'hich recognised that the Merou- gil Beds are stratigraphically a long way below the level of the Kurrawang Conglomerates. The Merougil homocline remains the east limb of the Kurawang Syncline extended southwards, but the syncline, though retaining its tight charac- ter, has been disrupted by the Yilmia Disloca- tion, and the corresponding beds on the west side of the structure have been displaced to the south. The northerly plunging structure be- comes open immediately to the south of the Merougil Sub-Area, on the east side of the Lefroy Peninsula, where the keel of the syn- cline has been brought up by the dislocation, on the upthrow side of the fault. The Merougil Beds are sub-divided as shown in Table 1, and their outcrop is shown in Fig. 2 (folding map). The sequence in the lower part of the succession in the area of good exposure is showm in Pig. 3. TABLE 1 Succession in the Merougil Creek Sub-Area. YILMIA DISLOCATION VI I. MIA DAM (Caves Hocks Beds) 11,000' j’dorly exposeil and katdinised niela-1 sandst(ii\i‘s, with .some pi*bble con- j glomeratcs. 1 LOWKR DAM 4,700' Metacongloinerates and metasand- stoTn'*^. OOO' l-'iue grained, .spotted nieta.sand- stones. j :ks(i' Sheared metiisandstones and ineta- conuloinerates. Slieared siliceous scliists. J (JAP IN l-IXPOSCKi: DISLOCATION 1 I- iH)rpliyi'y iiradin*; into niicro- | udaniellite j)orphyry.) I =”■ i Li -S X( llornblendic porphyry.) MetiiliasalTs, nictaj'abbros and ser- pentinites, etc. “ ~ Pi'lites, Hue clierty nudasediinents nictasandstones. J X Idipsp are sli Graphitic slates. The term “slate” is here used loosely: 52994* from the southern tip of the ridge, near the Red Hill Mine, Is typical. It forms a thin intercalation between meta- basalt and serpeuttnlte. It is a black, slatey rock, packed wdth pyrite cubes, partly replaced by limonite. In a very fine aggregate of recrystallised quartz and sericite, finely disseminated graphite and accessory tourmaline are also present. (b) Fine grained spotted metasandstone. 53001, from the southern tip of the ridge, near the Red Hill Mine, is typical: a flaggy, brown rock showing faint, dark spots on its surface, it is very similar to the “Fine grained spotted metasandstone” in the Merougil Beds, described below, displaying similar blotite rim- med spots. * Numbers quoted throughout this text refer to the collections of the Geology Department. University of Western Austraia. 11 COLUMN BED LITHOLOGY THICKNESS IN FEET META SANDSTONE CONGLOMERATE SEQUENCE V'^'s Poroconformlty — FINE GRAINED META SPOTTED SANDSTONE SEQUENCE Paroconrormity SHEARED META SANDSTONE CONGLOMERATE _ SEQUENCE _ Thick, pdymlctic conglomerate bonds grading upwards into a monotonous , cross- bedded sondstone sequence witho few thin pebbi/ bonds 4700 + Fne-grained sondstone with micro-cross-bedding soft-rock deformoTionol features and minor tectonic structures Sheared conglomeratic otxi sandy bonds, the shearing becoming more Intense towards the bose Schistose metosediments 600 380 60 ' Figure 3. — The stratigraphic c^kimn for the well exposed part of the Merougil Beds. 12 2. Metasediments of the Merougil Beds. (a) Basal Schistose rocks (60'). These are only exposed on “Morgan’s Island”. They are darker and more schistose than the rocks forming the remainder of the Merougil Beds. The low mag- nesia values revealed on analysis (Table 2) and the lack of modal felspar do not favour the metavolcanic origin suggested by Braybrooke and Middleton (1964) and it seems preferable to regard these as extremely sheared metasediments close to the dislocation. They have lost all trace of primary sedimentary texture. At the base of this unit a gap in exposure intervenes between these raetasediments and the porphyry of the peninsula called “Little Italy”, and the dislocation is believed to pass through this gap. A typical specimen. 53033, consists of small, black, parallel-aligned biotlte flakes set in a limonitic base. Mineralogically this rock resembles the matrix of the sheared metaconglomerate above it. but the texture is quite different. Small lenses of biotite and flakes of chlorite, together with accessory tourmaline, magnetite and limonite. are scattered through a granoblastlc groundmass. Biotite (20^;). pleochroic from light buff to orange brown or black, occurs as flakes, sinuous trains and poiklloblasts, showing alteration to a paler variety of the same mineral (pleochroic, colourless to yellow). Albite (4'^ ) forms sparse porphyroblasts and minute, parallel aligned, elongated grains, with good crystal form. The magnetite octahedra are commonly biotite rimmed, and there are ghost crystals, the out- lines of which are picked out by epldote grains. 53034 differs in that there are discrete lentlcles of quartz mosaic, and some calcite and sericite are present. The groundmass, in which a few incipient felspar porphyroblasts are evident, shows evidence of fine crushing and welding (merging of quartz grain outlines). The biotite in this specimen is very coarsely crystallised and associated with intergrown chlorite. 53035 displays a band. 4 mm thick. In which cord- ierite was surprisingly recognised (Pig. 7), in addition to albite (An.i). chlorite, magnetite, quartz, calcite and muscovite. The cordierlte shows sub-rounded outline, and is mostly clear, though some grains show small, parallel sericite (“gigantolite”) trains. A few Indis- tinct sector twins are. surprisingly, visible. The optical properties are: — biaxial | ; 2V — 71- ; — 1.547, corresponding to a composition of (Mg.j-iFei.ae) Al 4 Si:iOi 8 . The occurrence seems anomalous: contact metamor- phism is the most likely origin, but the igneous in- trusion responsible remains obscure. :b) Sheared metasandstone metaconglomerates (3S0). The lower metasandstone metaconglomerate sequence consists of an alternation of pebbly metaconglomerate and metasandstone bands, the conglomerates coarsening towards the west (upwards stratigraphically). The contacts with the schists below and spotted metasand- stone above are sharply defined. These rocks are characterised by more Intense shearing than the rocks stratigraphically above them, but less than the schists beneath them. A typical specimen. 53013, is sheared pebbly metacon- glomerate. in which rounded granules (AGI Dictionary of Geological Terms. 1962, p. 217. entry no. 1). pebbles and cobbles of contrasting lithology are evident. Rocks of acid porphyry appearance (but possibly either igneous or metasomatlc origin) predominate amongst the phenoclasts. which are set in a sandy matrix rich in secondary calcite. The calcite Is commonly aggre- gated in limonite stained patches. The sandy matrix consists of a quartz-sericite aggregate, including some small, elongated albite (Ane) grains. Albite and quartz porphyroblasts. In various stages of development, and some ghost porphyroblasts ( Invislhle under crossed nicols) are set in the matrix. Quartzite phenoclasts are also present, some showing fine coUoform patterns of dust lines suggesting chert. Accessories In the matrix are tourmaline, epidote and magnetite. The quartz grains show a merging of their outlines, a welding effect producing small patches of quartz por- phyroblasts. In 53014. a sheared pebbly metaconglomerate, the outlines of the pebbles are somewhat Indistinct in hand specimen, although some irregvilar metasedl- mentary and porphyroid pebbles are visible. The pebble outlines are extremely difficult to locate in thin sec- tion. 53020, another sheared pebbly metaconglomerate, differs in the degree of elongation and flatten- ing of the originally rounded phenoclasts. The mat- rix is granoblastic, consisting of quartz and sericite. The texture is locally so drawn out that It comes to resemble that of a micaceous schist, with bifurcation and anastomosing of the schistose matrix around pebbles and less sheared areas of the matrix. The pebbles in this metaconglomerate show neck like con- strictions (p. 30). Cataclasis increases in this stratigraphic unit down dip, that is towards the west. Shearing was manifestly selective, certain bands being highly sheared, others remaining undeformed. Shearing in the matrix is also inhomogeneously distributed. Both metamorphism and a form of metasomatism, tending towards the produc- tion of a homogeneous rock from a hetero- geneous parent, seem to have operated (p. 26). (c) Fine-grai7ied, spotted wcfa5andst07z.es (600', lensing out southwards K Sharp contacts bound these rocks above and below. They are characterised by micro-cross bedding, ripple-marks, soft rock deformations including ball and pillow structures: and all these give a consistent west facing. The only megascopic tectonic structures, besides joints, seen in the Merougil Beds ai*e fracture cleavage and small scale folding restricted to fine- grained layers in this unit. A typical speciment is 53996, a fine-grained metasand- stone: a dense, dark grey, micro-cross bedded rock, it Is traversed by thin veinlets of quartz and associated nematite. A fine-grained quartz-sericite groundmass encloses porphyroblasts (< .15 mm diameter) and scattered flakes of biotite (yellow -red brown), commonly associated with muscovite. The biotite Is altered to magnetite and prochlorlte. while calcite is also spar- ingly present as granoblastic grains and narrow vein- lets. Anhedral magnetite land hematite after it), epi- dote, tourmaline (var. schorl) and apatite are acces- sories present. There is much evidence of progressive re- crystallisation having occurred with increased shearing stress in these rocks, biotite progres- sively adopting a more perfectly parallel flake orientation, and other minerals tending to form an even, granoblastic aggregate which shows a concordant gi-ain elongation. The progres- sion is from the semi-schist texture to a true schist texture (Pigs. 8 and 9>. Spotting in rocks of this sequence ranges from quartz cored ag- gregates of biotite flakes to quartz cored single biotite flakes and single biotite flakes without a quartz core. Outlines are diamond shaped, hexagonal or rounded, and limonitic replace- ment is common. The origin of the spotting is discussed under metasomatism. Micro-cross bedding is evident in 53043, the biotite flakes within the foreset beds also form- ing an internal grading; flakes 0.1 mm long at the bottom grading upwards into progres- sively smaller dimensions, the upper part of the graded unit being quite free of biotite (Pig 40). The structure is unusual because else- where in the Kalgoorlie system biotite grades show an increase in size and content of biotite flakes in the reverse direction (Dunbar, 1966). (d) Metaconglomerate and metasandstone (4700'!. The upper limit of this subdivision is arbi- trarily drawn at the limit of good exposure near the lower dam on Merougil Creek. By far the thickest metaconglomeratic unit within the 13 Fracture Patterns in Pebbles Type I Without Displacement Displacement Without Displacement Figure 4. — Line diagram showing the two types of fracturing of the pebbles. 14 Undetormed Coriglomerate Onset ot Plastic Deformation Seeking" Begins Final Stage Figure 5. — Line diagram showing the mode of origin of dumbbell forms in deformed pebbles. Merougil Beds, this consists mainly of polymictic metaconglomerates composed of rounded pebbles, cobbles and boulders set in a metasandstone matrix, which commonly displays cross-bedding in coarse festoons. Metasandstone also forms intercalations in the metaconglomerate, and there is a gradual passage upwards, strati- graphically, into a monotonous sequence of metasandstone, relieved only by a few thin pebbly bands. A typical specimen of the metastandstone is 53004. a dark-grey, dense, medium-grained rock with a typical semicliist texUire (Fig. 10). Large, medium-sized and small-sized grains of quartz and felspar, mosaics of quartz, and blotlte flakes, are set In a finely grano- blastic matrix. In larger grains, grain boundaries tend to merge with the matrix. Many grains are fractured and healed by granoblasllc quartz. The quartz mosaics represent a stage in the homogenisation; various degrees of mergence of the large grains with the granoblastic groundmass can be seen (Figs. 13 to 16). Alblte is present as euhedral to anhedral grains showing albite and Carlsbad twinning. Larger grains show strain effects. Many grains are partly altered to sericite. Biotite flakes (buff; red-brown) occur as clots, small individual flakes and polkiloblastlc plates. They rim CROSS BEDDING AZIMUTHAL VARIATION 15 MEASUREMENTS INCLINATION VARIATION 0 6 12 18 24 30 36 42 40 ANGLES OF INCLINATION Figure 6. — Current-rose for the Merougil Creek sub-area. quartz and felspar crystals and are altered to magnetite and chlorite. Calcite of secondary origin is scattered throughout the rock. The groundmass is a fine grano- blastic aggregate of quartz and a little albite shot through with sericite flakes. In other similar rocks there are patterns of albite- quartz replacement intergrowth, commonly vermiform: also radiating net-works of secondary silica surround some grains (Pigs. 11 and 12). Zircon (rounded off euhedra), apatite and tourmaline (schorl) are acess- sories. These rocks show evidence of selective granula- tion of the quartz grains, dependent on the favour- ability of grain orientation to shearing stress (Fellow’s 1943, p. 1416). The qxiartz and albite show a cloudy dusting of dark particles at the centre and cleared rims (Fig. 10) (see Poldervaart and Gllkey, 1954 for a dis- cussion of the origin of this phenomenon). 53005. an albltic metasaudstone, is a dark grey, dense, medium grained rock containing more albite than 53004, as well as muscovite poiklloblasts, and chlorite-biotite intergrowths. There is a gradation from shapeless felspar grains showing some clear-cut faces, as well as some Indistinct boundaries to euhedral grains with only clear-cut boundaries (Pigs. 17 and 18). The biotite shows evidence of metamorphlc retrogressions to prochlorite. 53006 is typical of the metaconglomerate matrix, being a dense dark-grey, medium-grained metasandstone, with thin bands of biotlte-rlch material parallel to the bedding. It consists of recrystallised quartz grains (^ 3 mm) set in a fine grained quartz-sericite ground- mass. The matrix shows less shearing effects than the metasandstone layers, probably because of the pressure shadow effect of the pebbles. It is otherwise very similar to 53004. Secondary calcite and tourmaline may be present, the latter mineral as discrete needles and small “suns”. It is notable that the pebbles are very similar 15 r^'rexture^of a^metalntstoL^hiSftl^^^ Cordierite crystals in specimen 53035 (crossed nicols. X200) quartz and felspar grams are cemented by a fine, granoblastic quartzose matrix. The large grains hav^ had their clastic outline modified and the fine groundmass shows no trace of clastic texture. ^'r separated from their parent rock mass (b) transported to the site of deposition of the conglomerate (c) regionally metamorphosed (and meta- somatised in some cases). This is the simplest possible history, but stages in this cycle may have been repeated more than once. The igneous origin of some pebbles can- not be denied (evidence of relict zoning: granite pebbles). Some metasedimentary pebbles show isolated felspar porphyroblasts, indicating that some of the porphyroid pebbles may be of sedi- mentary origin, altered by metasomatism or metamorphism ivhile incorporated in the con- glomerate. However, the great variety in style and degree of large crystal development from one pebble to another, and between pebble and matrix, suggests that the origin of most large crystals is by crystallisation before incorpora- tion in the conglomerate, and that since then they have been modified and some new por- phyroblasts have been added to pebbles and mati'ix. Indeed, it is difficult to envisage a process whereby such heterogeneity of por- phyroblast development could develop in a con- glomerate, all parts of which, in the case of a restricted outcrop must have suffered an identi- cal metamorphic history after aggregation. Yet, if there is any truth in the concept of por- phyroid metasomatism (the mechanical and metasomatic transformation of rudites and psammites to porphyry-like, more homogeneous rocks within a low-grade metamorphic environ- ment) we must bear in mind the possibility that such a pattern of heterogeneity could develop in a conglomerate made up of porphy- roid rather than porphyry pebbles — i.e. of rock fragments derived from an earlier episode of porphyroid metasomatism, similar to that recog- nised in the Lake Lefroy area and discussed below on p. 25 and later in this series of accounts. Only in the very few cases of zoned crystals and in the case of granite inclusions have we really firm evidence of magmatic origin for the pebble material, but in spite of this, it is believed that the pebbles are mostly of mag- matic origin, though the texture of the felspars in these porphyroid pebbles indicates a complex metasomatic history: for example: — chess-board albite — replacement of original K-felspar by albite (Anderson, 1937, p. 62-3). quartz intergrowths and mica flakes as in- clusions — also likely to indicate replace- ment of an original K-felspar (libera- tion of excess SiO-. — Anderson, 1937, p. 28). zoning (palimpsest) — replacement of an earlier, more calcic, magmatic felspar by albite. biotite inclusion (sometimes marginal) — suggests expulsion of material from growing porphyroblasts (Goodspeed. 1937. p. 1136). Biotite is. however, two to four times as abundantly included in the felspars, as in the groundmass. and groundmass minerals are sel- dom observed as inclusions in the biotite. On the other hand, such large volumes of biotite, selectively included in phenocrysts of albite, are difficult to accept: indeed such textures are simply not typical of albite and quartz porphyry types of igneous rocks. Poldervaart and Gilkey (1954) have discussed the migration of iron down concentration gradients: — “Given a sufficiently high temperature level for diffusion, ions could migrate down concentration gradients: temperature probably also governs which particular Ions are predominant in a solution at any particular time. Iron apparently migrates at rather low temperatures. With an adequate tem- 20 25. Granitic pebble (53061 >, with subhedral albite (dusty grey) and interstitial micropegmatite (crossed nicols ]3C25 ) • Figures 26-29 —Metasedimentary pebbles In metaconglomerate.— 26. Biotite-rich metasediment (53065): biotite. dark- ouartz white- albite. grey (plane polarised light, crossed nicols X25). 27. Finer biotite metasedi- ment (53068) (crossed nicols X25). 2€. Quartzite (53072) (crossed nicols XIO). 29. Chert (53074) (crossed nicols XIO). Figures 30-31.— Comparison: dipyramidal quartz.— 30. Porphyroid pebble (Type IV) (53059): showing crudely dipyramidal quartz phenocrysts (?) with marginal embayments, set in a matrix of anhedral quartz and subhedral albite (crossed nicols XIO). 21 perature level, sufficient time and the presence of water, a fluid phase rich in iron will be de- veloped in rocks. In any plagioclase crystal, iron concentration along the internal phase boundaries and any other surfaces of greater separation (cleavage, twin composition planes) will be lower than in the surrounding pore fluid, hence iron will tend to migrate along these potential passages into the crystal and will go on doing so until some degree of equilibrium is maintained. Other ions will also tend to establish equilibrium by migration into and out of crystals. With a sub- sequent decrease in temperature, iron will be crystallised from the pore fluid, perhaps as magne- tite. At the same time magnetite will crystallise from iron present along internal phase boundaries since there is equilibrium. Similarly, hematite, spinel, ganiet. biotlte, rutile, hornblende, all these may form inside the crj'stal at the time when it is being crj'stallised from the pore fluid*.* This statement is quoted in full because it allowed for the possibility that the biotite within the plagioclase phenocrysts has originated in just this way. Sufficient heat could come from the nearby intrusive porphyry (p. 25) and thex'e is ample evidence of fluid movement dur- ing metamosphism. But the excessive concen- tration of biotite in the felspars is still not ex- plained, for the theory requires equilibrium be- tween matrix and phenocryst, and at the most, equal concentrations sho^ild be obtained. Rapid removal of pore fluid by migration out into the sedimentary matrix of the conglomerate after the attainment of equilibrium and while the component ions were still in solution could ex- plain this anomaly, but such a removal would have to be at a rate that inhibits continual readjustment of concentration to an even level, and so leaving the greater part of the biotite inside the phenocrysts and only depleting the groundmass of the pebble. This does seem a rather delicately controlled mechanism, but it is the best answer so far suggested, and though there can be no definite conclusion concerning the process which occurred during metamor- phism and metasomatism of the conglomerate, something on the lines given above does seem the most likely answer to the strange relation- ships observed. The conclusion that can be drawn is that the biotite inclusions are almost certainly late, metasomatic. and have no signi- ficance at all with regard to the ultimate origin of the porphyroid pebbles, which may in spite of their strange present appearance, be mag- matic (i.e, a porphyry) or metasomatic (i.e. a porphyroid derivative of a metasediment from an earlier depositional sequence, metasomatised during an earlier [ pre-Kalgoorlie System! meta- morphism) . Other possible criteria for porphyroblastic or phenocrystic origin of felspars appear ambi- guous. The most obvious are mineral ground- mass relationships. Groundmass relics have been considered by Misch (1949) and Good- speed < 1937b) to be indicative of porphyroblas- tic origin, and there certainly is some evidence here of such structures, and of porphyroblastic growth; however, most if not all of the relation- ships obsei'ved could be attributed to metasoma- tic outgrowth of original phenocrysts. Crystal shape is certainly no criterion (Davey, 1934). for rounding of outlines may be due to either magmatic resorption or porphyroblastic growth in a resistant medium. The quartz crystals cer- tainly show euhedral forms, with pyramid faces dominant (Pig. 27), which could be argued as indicative of the high-temperature /3-form commonly developed in intrusive quartz por- phyries (being first developed and later reverted to the low temperature form). However, the pyramid face may develop to a greater extent than the prism in metamorphic growth, as has been shown by Misch (1949, p. 388). Similarly, deep groundmass-filled embayments may be due to viagjriatic resorptio7i. though it is very diffi- cult to imagine a quartz-rich residual melt re- sorbing quartz phenocrysts which should be stable in it. and the narrow embayment form seen in these examples seems unlikely to de- velop during resorption which should operate on a wider front. So there is evidence favouring porphyroblastic origin for many of the quartz megacrusts, and to a lesser extent for the ablite megacrusts. The presence of diffuse margins to the quartz megacrusts near embayments supports this view (Misch, 1949 p. 389). Bradley. (1956. p. 177-9) attributes embayments to solution of strained parts of quartz crystals: where growth and resorption occur simul- taneously. the neck of the embayment tends to close. This concept is readily applicable to the Merougil rocks which have manifestly been highly stressed, but it also suggests that an origin in phenocrystic crystallisation in a mag- matic porphyry, and modification by later em- bayment, solution and recrystallisation, during the pei’iod of stress associated with the regional metamorphism of the conglomerate is quite tenable. The groundmass provides no clue, being re- crystallised so extensively that its original tex- ture is obliterated. From the evidence available the authors can only conclude that the criteria of magmatic or metasomatic origin for the porphyroid pebbles eludes them While a few can be firmly recog- nised as meta-igneous pebbles (e.g. Fig. 22), the majority are too modified by metamorphism and metasomatism within the conglomerate to be firmly identified as of one or the other origin. The porphyroid pebbles are not unlike similar rocks which are numbered among the more common vocK types of the Kalgoorlie system — the aJbite and quartz porphyries. No correla- tion can. however, be made with any known occurrence sharing some characteristic and unusual textural or mineralogical feature, and indeed local provenance remains unlikely. Con- sideration of the probable palaeogeography (p. 29) suggests that pebbles in this conglomerate deposited at the border of a geosynclinal furrow would have come from a raised land mass further to the west; and from nowhere near the Kalgoorlie systems' present outcrop. Studies by Glikson 'Thesis, 1968), of the Kurrawang conglimerate pebbles, suggest that the por- phyry material included as pebbles is, in part at least, exotic, not locally derived. It is prob- able that these similar porphyroid rock types were a common feature of early Precambrian metamorphic sequences, and that the pebbles are products of an earlier “pre-Kalgoorlie’' 22 metamorphic / intrusive / metasomatic event.’' That the “porphyroid” pebbles of the Merougil metaconglomerates and magmatic porphyry pebbles is the much simpler answer, and, largely intuitively, it is favoured. The granitic pebbles strangely, have not been greatly modified like the porphyroid pebbles. Modification is limited to albitisation of felspars (both K-felspar (?) and more calcic plagio- clase). These granites show no special charact- eristics indicative of a known area of proven- ance and. in fact, since they apparently stem from a granite intrusion or granitisation episode belonging to a *‘pre-K(ilgoOTlie” orogeny, their parent mass cannot be expected to be exposed at the present time (the Kalgoorlie metamorphic rocks being the oldest known in this part of Australia ) . These granites do represent one of the earliest known igneous events in Australian geology: with some of the porphyroid and the metasedimentary pebbles, all very similar to the host Kalgoorlie rocks, indicative of another, even earlier geological cycle, we are reminded of Hutton’s famous dictum: — “The result, therefore, of our present enquiry is that we find no vestige of a be- ginning. no prospect of an end." The metasedimentary pebbles may or may not be of rocks metamorphosed before incoxToi'a-tion in the conglomerate. The lack of any high grade assemblages means that, if they were metade- morphosed prior to incorporation, the meta- morphism was of similar low grade to that per- taining in this area (p. 25 1. For one can- not believe that this low grade of regional meta- morphism would not have left some residual traces of previous high grade index minerals. There is no evidence of polymetamorphism, yet it cannot be rxiled out. It is. however, easier to believe that these rocks have suffered but one metamorphism (i.e. while incorporated in the conglomerate). On the other hand they ai'e associated with granites and porphyroids which suggest provenance in a metamorphic terrain. These metasedimentary pebbles are much modified derivatives of a variety of rocks in which albite shoves a rather limited range of variation, in respect of which we must consider the fact that only certain resistant types are likely to survive to be incorporated in a con- glomerate of this type. The absence of pelitic pebbles and “greenstone" pebbles has com- monly been attributed to the fact that they did not survive, being chemically unstable, liable to attack and destruction by surface agencies. Thus, the total absence of “greenstone" pebbles does not remove the possibility of these con- glomerates being at least in part locally de- rived — certainly some of the metasedimentary pebbles appear very like the host rocks. Against local derivation of the greater part of the pebbles, one must, however, set the fact that this would surely require considerable uncon- formities in the Kalgoorlie system and these are not all evident in the Lake Lefroy area, though * Associated granite pebbles collected by Glikson have, in fact, now yielded Katarchaean ages (3000-3100 my.). Written' communication, A, Y. Glikson: Age determination by W. Compston. Australian National University. There are, however, considerable doubts about the validity of this age dating result. they could have been tectonically “ironed out" (see also discussion, p. 29). Also the granite pebbles, similarly chemically unstable, seem to have survived. The conclusion is reached that only a minor part of the meta-sedimentary pebbles is likely to be of local origin — derived from stratigraphically lower units of the Kal- goorlie system. The Kaolinised metasandstones — upper part of the Merougil Beds. Description of the West- ern exposures (based on the Thesis of J. J. G. Doepel (1965) and field notes of G. J. H. McCall). A few outcrops of kaolinised metasediments occur in the Merougil Creek, the last being near the north-south fenceline about half a mile east of Yilmia Dam. where graded bedding gives a west facing. The rock exposed there is a kaolin- ised meta-greyw'acke not unlike those of the Merougil Creek sub-area described by Bray- brooke and Middleton. Some of the kaolinised material of the intervening exposures is suf- ficiently well preserved to allow reasonably certain identification as meta-greywacke. The inference is drawn that the homocline con- tinues almost to Yilmia Dam. Chemica I Analyses . Chemical analyses by standard rapid methods (suitable for broad comparative purposes) of some of the Merougil metasediments are given in Table 2. TABLE 2 Chemical analyses — Merougil Beds; metasediments 5300t) 1 53021 53059 53066 ' 53034 SiO,. 60.7 73.4 70.7 54 . 5 62.0 13.1 12.0 12.2 12.0 12 9 re.o., f) . 0 6 . 7 4.9 10.9 6. 7 TiO-. 0.7 0.1 0.1 trace 0.9 CaC) 2.4 3.4 1.8 9 8 6.4 MsO (1.1 1 .2 5 6 0.4 Na.O 0.2 3.2 5 4 3 8 7.4 K,() 2.S 1.0 1.9 3.0 2.6 P.Or, 0.1 0 2 0.3 0.3 Total 100 0 100 9 98.2 99.9 99.6 I Mota- sandst. matrix of 11 n- deformed metecongl. 11 Matrix of sliearcd niptaconjil. III Porpliy- roid pebble. IV Biotite rich metasedt. pebble. v Basal schist. Anal. J.C.B. D.D.M. D.D.M. D.D.M. J.C.B. Meta-Igneous Rocks. The rocks of the Red Hill-Kambalda Ophio- lite Belt were not examined in detail. Specimens w'ere collected of actinolitlc rocks (metabasalts and metapicrites) and serpentinites from the ridge outcrop at its extreme southern tip, near the Red Hill Mine: and other specimens of actinolitic rocks wei’e collected from the sparse exposures in the low country of virtually no exposure which intervene between the outcrop of the Merougil Beds and Red Hill ridge. 23 Figure 31.— Quartz phenocrysts in a granodiorite porphyry, shown for comparison: taken from Misch 1949 p 388 In both cases prism faces are suppressed, and pyramid faces emphasised, to approach the characteristic form of rt-quartz. Figures 32, 33. — Meta-igneous rocks. — 32. Metabasalt, an actinolitic rock with blastophitic texture. The laths of actlnollte (grey) are ragged, and the individual grains of the quartz-felspar pools (white) are poorly defined though laths of felspar, considerably saussuritised are aparent (white) (53081). Plane polarised light, crossed nicols X25). 33. Serpentine-talc rock replaced by dolomite (light grey, rhombs: dark, thin bands are ma'^ne- tite, which also picks out olivine pseudomorphs in the serpentine talc aggregate (dark grey) (53083) (crossed nicols XIO). Figures 34. 35.— Igneous rocks.— 34. Quartz-alblte porphyry (53087): albite, dusty grey, twinned: quartz clear, subhedml phenocrysts: both set in a fine, allotriomorphic quartzose matrix carrying some felspar (crossed nicols XIO). 35. Porphyritic adamellite (53088): albite phenocrysts, dusty grey, subhedral: set in a fine allotrio- morphic matrix of quartz (clear white) and microcline (pale grey) crossed nicols XIO). Figure 36. Cross bedding in metasandstone of the metasandstone/metaconglomerate sequence. 24 Specimens from the low country include a medium- grained quartz-biotite-saussurite-actinolite rock (53079), deep-greenish grey and massive, lacking a directed texture. Actinolite (85% by volume). In the form of blade-llke interlocking prisms, patches of granoblastic quartz and saussuritised plagioclase are the main mineral constituents: some cpldote is associated with the felspare and blotite occurs as small flakes scattered throughout the rock. Relict igneous texture is not apparent, the texture being essentially crystalloblastlc. A fine-grained quartz blotlte-actinoUtc rock (53080) from the same area consists predominantly of actino- lite (95^ by volume): in the form of fibrous needles: biotite (colourless: red-brown) and pyrite make \ip the remainder of the rock. The lack of felspar In some of these rocks suggests that both basaltic and picritic volcanics were erupted. In the case of the actual Red Hill ridge, only lake shore exposures were examined, and the petrographic work carried out was mainly concerned with what was believed to be a pattern of progressive metasomat- ism of the actinolitic rocks (p. 26). 53081 and 53082 are representative of the metabasaltlc actinolitic rocks which have not suffered metasomatism (Fig. 32). The former Is a blastophltic quartz-saussurite-actinolite rock, whtch. in hand specimen, appears massive, dense, and of dark greenish-grey colour: there is no appar- ent structure or texture. It consists of actinolite (X: pale green: Y; light green: Z: blue-green) in the form of stumpy prisms and anhedra. Aggregates of saussurit- ised felspar are enclosed in the actinolite mat. Mag- netite is the only accessory. 53082 carries more bio- tite (5% by volume) and is appreciably carbonated. A dolomitised serpentine (53083) from the same area, appears in the field to form part of a pod-like body 10 feet thick. Large knots of dolomite are set in a fine matrix of grey-green, talcose serpentine, each present in nearly equal quantity (Fig. 33). Magnetite crystals have picked out the outlines of a pre-existing mineral, probably olivine: sub-parallel bands of mag- netite also traverse the rock which is sparingly punctu- ated by limonitised pyrite cubes. The rock Is presum- ably a derivative of an ultrabasic igneous rock, such as a peridotite. The metasomatic derivatives of the basic rocks are discussed below. The Acid Igneous Rocks. Extensive outcrops of quartz-albite porphyry and fine-grained granite occur in the Red Hill- Kambalda Ophiolite Belt. Other outcrops of porphyry occur on the lake shore at “Little Italy” and inland from there, within the low country of poor exposure. The evidence sug- gests that the intrusion of these rocks w'as not separated by a long interval from the peak of metamorphism, but, rather, they were emplaced in the weaning stages of metamorphism and orogenic deformation. The quartz-albite porphyry of “Little Italy" is separated from the lowest of the Merougil Beds by an exposure gap of 600 feet; it is strongly jointed, weathers to angular blocks, has a pale-buff colour in out- crop, and is extremely uniform in texture and composition. Phenocrysts of quartz show clearly, set in a very fine, porcellainous matrix. The few xenoliths of sedimentary rock set in it are apparently of local origin. 53075 is representative of this body: It is weakly foliated (being taken from a shear Z'^ne), but little evidence of directional texture Is seen In this section. Plagioclase lAn?) forms subhedral phenocrysts 2.5 mm) altered to serlcite, especially along twin com- position planes and cleavages: and showing albitc and Carlsbad twinning. Quartz pheiiocrj'sts (<- 3.0 mm), of sub-rounded form, show undulose extinction, and fracturing, together with some stretching and re- crystallisation in pressure shadows;. There is a very fine groundmass of quartz (< 0.02 mm), rare biotite ftakes, and accesory epidote, tourmaline, muscovite and flakes, and accessory epidote, tourmaline, muscovite -and apatite. Numerous quartz veins traverse this nor- phyry. The porphyry from the Red Hill-Kambalda ridge shows many signs of intrusive con- tacts. There is a gradational transition be- tween Quartz-albite porphyries and a fine grained adamellite; thei*e being no mappable contact between them. They do not appear to represent separate intrusions. Support for this interpretation is seen at the ‘'Ringneck Gran- ite"', a few' miles to the north along the same ridge; here fine-grained granite has a marginal zone of quartz albite porphyry (O'Beirne, 1968). 53087 (Fig. 34), from near the Red Hill Mine is a medium to fine-grained quartz-albite porphyry. Milk- white felspar phenocrysts and clear quartz pheno- crysts are set in a pale grey, porcellaneous ( “Chert-like”) matrix containing sparse, small cubes of pyrite. The plagioclase (An?) forms subhedral phenocrysts (< 3.0 mm> showing albite and Carlsbad twinning, some sericitisation. and sparse quartz inclusions. The quartz phenocrysts are anhodral to rounded-off sub- hednil in form, and show enibayments. The ground- mass Is very fine, consisting of lobate and sutured quartz grains, biotite (ragged flakes, -i:- 0.2 mni). epidote, pyrite and apatite. There is some albite on the ground- mass, and the presence of some K-felspar was sug- gested by staining. The adamellitlc rocks, into which the quartz-albite porphyry grades, are represented by 53088. a fine-grained, porphyrltlc biotite adamellite. Felspar forms small, subhedral phenocrysts. crammed into a fine interstitial base: it is albite (Annj). serici- tised and showing twinning, mainly on the albite laws. The fine matrix consists of quartz, plagioclase, micro- cline, biotite, epidote. apatite and pyrite (Fig. 35). Metamorphism There is considerable evidence of a complex history involving localised metasomatism super- imposed on a regional metamorphism of low grade. The mineral assemblages in the metasediments are: quartz * biotite i± albite. epidote. chlorite, muscovite, calcite and pyrite). This indicates assemblages consistently within the quartz-albite-epidote-biotite subfacies of the Green Schist Facies (only the cordierite, present in a single rock specimen, is anomalous, and this may be due to contact metamorphism). The porphyry boulders of the conglomerates and the porphyry intrusions (which appear to have suffered some metamorphism) show similar assemblages. The meta-igneous basic rocks have assem- blages: — quartz-bio tite-epidote-actinolite quartz-biotite-actinolite quartz-epidote-actinolite compatible with the same sub-facies. The presence of small quantities of chlorite and sericite is not anomalous (Turner and Ver- hoogen, 1960. p. 537), but there is some textural evidence that biotite has been converted to chlorite in a late retrogressive phase. Albite is the stable plagioclase. and other plagioclases are virtually absent, original more calcic plagio- glases having been converted to it: there are, how'ever, a very few relics of more calcic plagio- clase and of original K-felspar. Contact meta- morphism is of no significance in this area. Metasomatism There is evidence, in the form of numerous veins and replacement zones, of considerable metasomatism of the metasediments, and the micro-textures certainly support this. The 25 metasomatism is envisaged as a front, which moved out from the porphyry intrusives, them- selves, in some cases, marginal to a core of fine- grained granite. The evidence for what is es- sentially a contact metasomatism, but extend- ing over a very large contact zone, lies in the geographical distribution of the metasomatic rocks, and the apparent increase in intensity of the effects close to the intrusions. The sheared metasandstone /metaconglomer- ate closely abuts the porphyry of Little Italy and is clearly metasomatised ip. 21). As one moves towards the east (downwards in the suc- cession) the pebbles, sheared, but quite distinct at the western contact with the spotted sand- stone. tend to become indistinct, losing their identity by becoming flattened, attenuated and developing merging boundaries with the matrix. At the extreme eastern side of the exposure they become difficult to delineate, the mass becom- ing almost homogeneous. During the first reconnaissance of the area a piclure of severe metasomatism obscuring the original characteristics, and producing a rock indistinguishable from a porphyry, was sug- gested: and it was thought possible that the homogeneous porphyry of “Little Italy" with only a few “xenoliths” in the form of pebbles, could be the end-product of this process. Micro- scopic examination, however, suggests that this is not the case. Metasomatism and homo- genisation have undoubtedly occurred, but the metasomatism is not very severe: cataclasis and recrystallisation, always tending towards the smoothing out of irregularities in the rock fabric are the dominant processes in the homogenisa- tion — i.e. the mechanical adjustment outweighs chemical adjustment. The metasomatism is reflected by tourmaline and epidote occurring both as constituents of the numerous quartz veins and in narrow bands within the highly sheared rocks. The shearing must have facilitated movement of solutions by providing channels. The metasomatic develop- ment of albite, quartz and calcite seems also to have some correlation with degree of shear- ing, and consequent facility of movement of metasomatic agents. The development of spots of various sizes and structures in the spotted metasandstones (p. 13 > is further evidence of metasomatism. Goodspeed (1937a. p. 134) has ascribed the development of very similar spots within quartz porphyroblasts to the contact effects of a nearby granodiorite intrusion, and a similar origin is postulated here. The metaconglomerate above the spotted metasandstone shows some evidence of metaso- matism in a modification of the pebbles revealed in this section (p. 17 h but no megascopic evidence other than veining. The metasomatism seems to have involved introduction of soda and silica, and produced growth of new porphyroblasts. regrowth of quartz and albite phenocrysts in the pebbles, and conversion of original felspars to albite. The abundant biotite inclusions within the fel- spars )p. 17), are ascribed to this process. Porphyroblast development produced new large crystals within both pebbles, and to a lesser extent, the conglomerate matrix. Quartz-albite- epidote-tourmaline veins developed at the same time. The metasomatic process is regarded as the incipient stage in the more extreme meta- somatic process recognised further south by McCall, Muhling and O’Beirne (Muhling, 1965: O’Beirne. 1968: McCall and Muhling. and McCall and O’Eeirne, parts IV and V of this series of accounts lin preparation!). The nietasoviatisin of iiieta-igneous rocks of the Red Hill-Karnhalda Ophiolite Belts Near the contact between metamorphosed basic volcanics and porphyry at the Red Hill Mine, what has been supposed to be progressive metasomatism has been studied in its stages of development (Braybrooke and Middleton. 1964). Soda and silica introduction was believed to have produced quartz and albite porphyroblasts within the metamorphosed basic rocks. Since this metasomatism was studied by Braybrooke and Middleton. O’Beirne a968) has queried these authors’ conclusions. He is of the opinion that the pronounced zoning in the fel- spar of supposed metasomatic products indicates that these are igneous porphyries, and he sup- ports this contention with chemical analyses which do not favour progressive metasomatism to this end-stage product, but indicate that this rock is chemically similar to certain dacitic igneous rocks which occur at Kalgoorlie. His interpretation requires the supposed end-stage product to be a dacitic porphyry, cutting the rocks of the ophiolite belt. He accepts a limited amount of contact metasomatism related to this body. Structure The structure of the main sedimentary se- quence is homoclinal. steeply dipping to the west, and west facing. The regional structure, a synclinorium, is discussed in Part 1 of this series of accounts (McCall, in the press). The evidence for the dislocation supposed to separate the Merougil Beds from the Red Hill-Kambalda Ophiolites is in the increased defoi*mation recognised close to this line, and the apparent wedging out of the stratigraphy revealed by regional mapping to the north. This disloca- tion may well be the southerly extension of the Boulder Fault which separates the Mt Hunt Ophiolites from their supposed equivalent on the east side of the fault, the Kalgoorlie Ophio- iites (which are themselves in strike continuity with the Kambalda Ophiolites). An anticlinal dome has been recognised dur- ing mining operations at Kambalda. and pillow lavas in the melabasalts face antithetically east and west, off this dome. The minor tectonic structures within the Merougil sub-area are limited to a few small, gentle flexures in the Merougil Beds: some frac- ture cleavage in the finer members: and east- west joints, which are common and are frequently filled with vein quartz. An interesting feature is the set of these joints which traverse the conglomerates of the upper unit, cutting through boulders and matrix like a knife cut, and are vertically disposed (Fig. 43). 26 Figures 37-41— Primary sedimentational structures.— 37. Micro-crossbedding (the specimen is 9^ inches long): (53043 from the fine grained metasandstone). 38. Micro-crossbedding in a fine metasandstone (53003) show- ing associated grading of biotite flakes (the specimen is 4 inches long). Microfaulting of primary sedimenta- tioned origin is also evident. 39. Laminated, elongated, ball and pillow structure in fine-grained metasand- stone/metasiltstone (53045): the truncation is by penecontemporaneous erosion. The specimen is 10 inches long. 40. Laminated ball and pillow structure, producing a pseudo-concretionary character in the rock, a fine-grained metasandstone/metasiltstone (53046): the face shown measures 4x4 inches. 41. Contorted bed- ding in a fine-grained metasandstone band. Figure 42. — Bedded fine-grained metasandstone showing some fracture cleavage. 27 Deformation of the conglomerates. The sheared sandstone conglomerate shows abundant evidence of deformation by strong shearing stresses . Soft Rock Deformations, — These include load casts or pockets indicating only vertical move- ments: asymmetrical load casts indicating both vertical and lateral movement: and ball-and- pillow' structures which are a development of the latter. No particular environment is in- dicated by such stinctures: Potter and Pettijohn (1963, p. 147) suggest the requirement is simply any sand bed on a water-saturated hydroplastic layer, but Kelling and Walton (1957. p. 487), suggest that unequal loading, due to irregulari- ties in the upper surface of the underlying fine bed. is involved. The origin of the ball-and- pillow structures is debatable. Kay and Power (1963) invoke foundering of a sand layer into mud: Potter and Pettijohn (1963) following Kuenen (1958). suggest the requirement of seismic triggering. The ball-and-pillow structures, where trun- cated (Fig. 39), show a typical synclinal cut- off which gives a good facing indication: in this case always consistent with the cross- bedding. Complex pseudoconcretionary convolutions (Fig. 40) may be related to penecontempor- aneous turbulence causing rolling, and subse- quent flattening, during compaction. Contorted bedding is also present (Fig. 41) of the type that Sutton and Watson (I960, p. 116) consider to be due to quicksands, disturbed as the water is driven out. Graded bedding is not very com- mon. though in one case it has been recorded, where it is internal to cross-bedding. Microfaulting of primary origin and imbri- cation structure (Potter and Pettijohn, 1963, p. 26 > are other primary structures noted. Depositional emnronment The area appears to have been marginal to a geosyncline. Early Precambrian geocynclinal furrows were probably long and narrow (Petti- john, 1943, Wilson 1958). 28 The slates are pelitic metasediments; the presence of possibly primary pyrite and also graphite does not necessarily require anaerobic conditions for it is now commonly supposed that a reducing, anoxy genic atmosphere pertained at this early date (Rutten, 1962). Such ancient pyritic and graphitic rocks could well have been deposited in a marine geosynclinal basin. The pelitic rocks presumably reflect deepening of the environment. The jjietasandstones (Fig. 42), though largely modified in texture by metamorphism and metasomatism, show* enough of their original texture for one to be satisfied that they were originally poorly-rounded “dirty” arkoses (Petti- john, 1957, p. 332). Such sediments will have become predominant as the source land mass area suffered maturation of its relief, and its streams lost their transporting capacity. Thin pebble bands which appear abruptly in the sequence and disappear equally abruptly may reflect periods of increased precipitation rather than tectonic disturbance. The texture of the finer sandstones suggests periodic rather than continuous sedimentation, with finer material deposited after an initial period of coarse sedimentation. Thei’e is much evidence of lateral gradation, suggesting quiet water conditions allowing differential settle- ment. Tlie sedimentary structures within these beds suggest quiet conditions, with intermittent rougher periods. There is no direct evidence that these finer psammitic sediments are marine: but the over- all association rules out lacustrine deposition: and the great thickness of similar rocks seems to rule out fluviatile deposition. The deposition may have been estuarine, or paludal: or a com- bination of both. The metaconglomerates ■ ^ METASANDSTONE / METACONGLOMERATES FINE-GRAINED, SPOTTED METASANDSTONE SHEARED METASANDSTONE , CONGLOMERATE ^ ^ s BASAL SCHISTOSE METASEDIMENTS METASEDIMENTS: Kalgoorlie System ( metamorphic age c. 2700 m.y.) z + 44 + 44 + + •»• 4 4 4 4 + 4 V V V V V V V y V V V V V V V V V V JASPER BAR ALBITE - QUARTZ PORPHYRY grading to Micro - adamellite HORNBLENDIC PORPHYRY MICROGRANITE METABASIC and ULTRABASIC igneous -rocks of the Kambalda Ophiolite belt (metabasalt, metapicrite , serpentinite ) - undifferentiated inferred GEOLOGICAL BOUNDARIES against superficial cover METAMORPHOSED IGNEOUS ROCKS A] Sampling locations for pebble, cobble boulder PLUNGE OF SMALL SCALE FOLD Bj deformation studies DIP AND e-rDiu-ir l>®dding In metasediments o T RIKE foliation in metaigneous rocks DISLOCATION GEOLOGICAL SKETCH MAP OF MEROUGIL CREEK , LAKE LEFROY W.A. FENCE LINE 1000 0 SCALE IN FEET 5000 9000 CENTRE POINT OF AIR PHOTOS ( FLIGHTS FLOWN FOR WESTERN MINING CORP.) INSTRUCTIONS TO AUTHORS Contributions to this Journal should be sent to The Honorary Secretary, Royal Society of Western Australia, Western Australian Museum, Perth. Papers are received only from, or by communication through. Members of the Society. The Council decides whether any contribution will be accepted for publication. All papers accepted must be read either in full or in abstract or be tabled at an ordinary meeting before publication. Papers should be accompanied by a table of contents, on a separate sheet, showing clearly the status of all headings; this will not necessarily be published. Authors should maintain a proper balance between length and substance, and papers longer than 10,000 words would need to be of exceptional importance to be considered for publication. 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Journal of the Royal Society of Western Australia Volume 53 1970 Part 1 Contents 1. Two xerophytic new species of Ptilotus (Amaranthaceae) from Western Australia. By G. Beni. 2. Eurynome orientalis, a majid spider crab (Crustacea, Brachyura) new to Australia, and notes on E. granulosa. By D. J. G. Griffin. 3. The Merougil Creek Sub-Area. By G. J. H. McCall, J. C. Braybrooke, and D. D. Middleton. Editor: A. S. George Assistant Editor: W. A. Loneragan The Royal Society of Western Australia, Western Australian Museum, Perth 68182/2/70— 570— i ALEX. B. DAVIES, Government Printer, Perth, Western Australia