SURVEY un-.i , Pg h- nh FL0RIDx4 STATE GEOLOGICAL SURVEY E. H. SELLARDS, Ph. D., State Geologist FIFTH ANNUAL REPORT Published For THE STATE GEOLOGICAL SURVEY Tallahassee, 1913 / The Record Company ST. AUGCSTINE FLORIDA 52194 CONTENTS. page:. Administrative report . 7 Origin of the' Hard Rock Phosphates of Florida, by E. H. Sellards.. 23 Eist of Elevations in Florida, by E. H. Sellards . . 81 Artesian Water Supply of Eastern and Southern Florida, by E. H. Sellards and Herman Gunter . 103 Production of Phosphate in Florida during 1912, by E. H. Sellards... 291 Statistics on Public Roads in Florida, by E. H. Sellards . '295 Index . 299 Plate No. 1. 2. 3. 4. 5. 6. 7. 8. 9. PLATES. Phosphate boulder showing secondary deposition. Laminated phosphate boulder. Phosphate rock. Teeth of mastodon from the phosphate deposits. Teeth and foot bone of horse, and teeth of mastodon. Sharks’ teeth from the phosphate deposits. Sharks’ teeth from the phosphate deposits. Phosphate washer and prospect drill. Phosphate pit after the removal of the phosphate. Palmetto flatwoods, Amelia Island. Palmetto flatwoods, Ft. Myers. Scrub, east side of Lake Kingsley, Clay County. Sandy pineland, DeLeon Springs. Open flatwoods, three miles east of DeLeon Springs. Everglades west of Ft. Lauderdale. Small prairie, four miles west of Sebastian. Turnbull Hammock, one mile west of Daytona. Sand dune near Mayport. Ancient sand dune, two miles west of Daytona. Exposure at Saw Pit landing, St. Marys River. Exposure of hardpan at Black Bluff on Clark’s Creek eight miles from Fernandina. Artesian well used for power, Melbourne, in Brevard County. 10. Fig. 1. Fig. 2. 11. Fig. i. Fig. 2. Fig. 3. 12. Fig. 1. Fig. 2. Fig. 3. 13. Fig. 1. Fig. 2. Fig. 3. 14. Fig. 1. Fig. 2. FIGURES. Fig. 1. Artesian basin. Fig. 2. Artesian slope. Fig. 3. Artesian water from unconfined horizontal beds. Fig. 4. Artesian water from solution passages in limestone. Fig. 5. Method of measuring flow of artesian well. Fig. 6. Map showing area of artesian flow in Nassau and Duval Counties. Fig. 7. Map showing the area of artesian flow in St. Johns County. 4 CONTENTS. Fig. 8. Fig. 9. Fig. 10. Fig. 11. Fig. 13. Fig. 14. Fig. 15. Fig. 16. Fig. 17. Map showing the' areas of artesian flow in Clay and Putnam Counties. Map showing the area of artesian flow in Orange and Seminole Counties. Flowing artesian well. Map showing the area of artesian flow in Volusia County. Map showing the area of artesian flow in Pinellas and Hillsboro Counties. Map showing the area of artesian flow in Polk County. Map showing the area of artesian flow in Osceola County. Map showing the area of artesian flow in Manatee County. Map showing the area of artesian flow in DeSoto County. MAPS. Map showing the limestone region of Central Florida. Map showing the location of the hard rock and land pebble phosphates. LETTER OF TRANSMITTAL. To His Excellency, Hon. Park Trammell, Governor of Florida. Sir: — In accordance with the Survey law I submit herewith my Fifth Annual Report as State Geologist of Florida. This report contains the statement of expenditures by the Survey for the fiscal year ending June 30, 1912, to which I have added a list of the expenditures of the Survey for the succeeding half year ending December 31, 1912. The progress of the Survey inves¬ tigations during the year are shown by the scientific papers that will form a part of this report. These include a paper on the origin of the hard rock phosphates of Florida; a report on the artesian water supply of southern Florida, and a list of elevations in the State together with a second edition of the general topo¬ graphic map of the State previously published. I venture to add here a resume of the principal investigations of the Survey since its organization and to make certain recom¬ mendations which I believe to be for the good of the future use¬ fulness of the Survey. Permit me to express in this connection my appreciation of the interest you have shown in the work of the State Geological Survey. Very respectfully, E. H. SELLARDS, State Geologist. ADMINISTRATIVE REPORT. E. H. SELLARDS, STATE GEOLOGIST. PRINCIPAL RESULTS OF THE STATE GEOLOGICAL SURVEY INVESTIGATIONS. Aside from miscellaneous and routine work, the principal investigations that have been carried out by the State Geological Survey since its organization may be grouped under six heads as follows : I. Assemblage of the literature on the geology of Florida and a review of the important publications issued previous to the organization of the State Survey. This review of the literature together with the bibliography of publications relating to the geology of Florida was included in the First Annual Report. The publications obtained in this connection form a part of the Survey library. II. A Report on the Geology and Stratigraphy of Florida. This report included in the Second Annual Report was prepared in cooperation with the United States Geological Survey. It serves as a preliminary account of the geology of the State, and brings together all the information relating to the geology that was then available. III. A General Topographic and Geologic Map of Florida. With the general report on the geology of Florida referred to above there was included a topographic and geologic map of Flor¬ ida. The topography was shown on this map with as much detail as the information available regarding elevations would permit, the contour lines being placed at 50 foot intervals of elevation. A second edition of this map is included in the report now being issued. IV. A very important natural resource of Florida is the underground or artesian water supply. This subject was one of the first taken up by the Survey, and with the publication of the present report the preliminary investigation of the water supply is completed. The papers published on this subject are as follows : 8 FLORIDA STATE GEOLOGICAL SURVEY. The Underground Water Supply of Central Florida, Bulletin No. 1; The Artesian Water Supply of Eastern Florida, Third Annual Report; The Underground Water Supply of West-Cen¬ tral and West Florida, Fourth Annual Report; The Artesian Water Supply of Southern Florida, Fifth Annual Report. V. The Soils. A general report on the soils of the State formed a part of the Fourth Annual Report. This paper included an account of the origin and character of the soils of Florida, and was intended as a basis for subsequent detailed soil surveys. VI. The Mineral Resources. Information bearing on the mineral resources of the State has formed a part of each annual report issued. An account of the fuller’s earth deposits as complete as the information then at hand would permit was in¬ cluded in the Second Annual Report. Papers on the phosphate deposits formed a part of the Third and the present (Fifth) Annual Reports. The peat deposits of the State, which are exten¬ sive, were described in the Third Annual Report. The clay re¬ sources have received general treatment in the First and Second Annual Reports. RECOMMENDATIONS. MORE OFFICE SPACE NECESSARY. The State Survey is at present housed in two small rooms. Of these one is used as store room, photo room and exhibition room ; the other serves as library, office and work room. These small rooms including about 1,000 square feet of floor space are totally inadequate to the requirements of effective work. Fully 10,000 square feet of floor space is necessary to meet the immedi¬ ate requirements of the Survey. The library shelves are full, and it is now and for some time has been quite impossible to care for the publications that are being received. Many of these new publications represent the results of investigations by the neigh¬ boring State Surveys or by the National Survey, and are very necessary for comparative purposes to the Florida Survey. Other publications being received from various sources are for refer¬ ence purposes and are necessary to the determination of fossils or FIFTH ANNUAL REPORT. 9 mineral specimens, or of geological formations, or other matters in connection with the Survey work. The Survey at present is practically without a work room. There is no table or desk room available to store or to handle the maps, charts, and drawings that are constantly being used in the Survey work. It is impossible from lack of space to properly open up and study the collection of mineral and fossil specimens that have been obtained by the Survey. The store room space is too small to accommodate even the current issues of the Survey’s own publications which must be cared for temporarily awaiting their distribution. In connection with the work of the Survey there is a constant accumulation of notes, records, photographs, manuscripts, plates and cuts, as well as the general correspondence of the office which must be cared for. The present limited office space affords no room for storing, filing or properly caring for these records. I urgently recommend, if if meets with your approval, that the Legislature be asked to provide adequate rooms for the future work of the State Geological Survey. a. state; musfum. The desirability of an adequate museum in which to properly exhibit the resources of the State is apparent. The State Survey law makes it the duty of the State Geologist to collect, determine and label specimens illustrating the geological and mineral fea¬ tures of the State and large collections have been made since the Survey was organized. The small room used for exhibition purposes has long since been filled and a large amount of material suitable for exhibition remains unopened in boxes as collected. It .is important that the State provide for the proper preservation and exhibition of the Survey collections in a State Museum. DEMAND FOR CLAY TESTING LABORATORY. There is a very urgent demand on the part of the citizens of the State for a laboratory in which the various clays may be prop- erlv tested for brick making and other purposes. It is a well known fact that the utility of clays is determined not so much by 10 FLORIDA STATE GEOLOGICAL SURVEY. their chemical as by their physical properties. To properly test a clay it is therefore necessary to install the testing machinery. Effective clay testing machinery will require for installation more space than is now available in the Survey rooms. THE PREPARATION OE A DETAILED TOPOGRAPHIC MAP OE FLORIDA. While a general topographic map of Florida with contour lines at 50 foot intervals of elevation has been issued, as already stated, there is a constant demand for detailed topographic maps on a scale of about one inch to the mile and with contour lines at 10 foot intervals of elevation. Topographic maps are usually made in atlas sheets covering unit areas bounded by parallels and meridians. The unit adopted by the United States Geological Survey in topographic mapping designated as the quadrangle, includes when made on the scale of about one inch to the mile an area of 15' of latitude by 15' of longitude. A separate atlas sheet is issued for each unit area and when completed the maps so issued make up a complete map for the State as a whole. The maps thus made show the land area in relief by means of contour lines. In this way all hills, valleys, stream . channels, sinks, de¬ pressions and all changes in elevation are indicated. The actual elevation above sea, based on exact levels, are also shown by means of figures printed on the contour lines. Each contour passes through points which have the same altitude. One who follows the contour on the ground will go neither up hill nor down hill but on a level. By the use of contours the shapes of the plains, hills and valleys as well as their elevations are shown. The line of the sea coast itself is a contour line, the datum or zero of elevation being mean sea level. The contour line at, say, 20 feet above sea level is a line that would be the sea coast if the sea were to rise or the land to sink 20 feet. Such a line runs back up the valleys and forward around the points of hills and spurs. On a gentle slope this contour line is far from the present coast line, while on a steep slope it is near it. Thus a succession of these contour lines far apart on the map indicates a gentle slope; if close together a steep slope; and if the contours run together in one line, as if each were vertically under the one FIFTH ANNUAL REPORT. 11 above it, they indicate a cliff. The heights of many definite points, such as road corners, railroad crossings, railroad stations, sum¬ mits, water surfaces, triangulation stations and bench marks are also given on the map. The figures in each case are placed close to the point to which they apply, and express the elevation to the nearest foot. In addition to indicating relief and actual elevation above sea these maps show all other natural features such as lakes, ponds, rivers, streams, canals, swamps and all cultural features includ¬ ing public roads, railroads, towns, cities, county and State boundaries. The topographic maps thus prepared find many uses. They are above all essential to the proper planning of drainage opera¬ tions throughout all of the interior of the State. It is a well- known fact that we have in Florida, particularly in the flatwoods section, large areas of land that although not actually flooded yet would be much improved by the more rapid removal of the heavy summer rains. Other large and valuable tracts of land, but little used at present, by a proper system of drainage, can ultimately be made valuable and productive land. The topogra¬ phic maps such as are here contemplated are essential to the proper planning of drainage operations. The topographic maps are of very great assistance in the preparation of detailed soil maps. They afford first of all an exact base map of the area to be surveyed, thereby reducing the cost of the soil map about one-half. They also facilitate the study of the soils which bear well known relations to drainage and moisture conditions. In detailed geologic mapping and in the study of the mineral resources topographic maps are practically necessary for the detailed final reports. Topographic maps find many additional uses. They are of very great assistance in the laying out and developing a system of public roads, showing as they do the relief of the land includ¬ ing hills, depressions and valleys. In planning the location of railroads, canals, waterways or other public improvements thev are of great assistance. Finally they afford to the land owners 12 FLORIDA STATE GEOLOGICAL SURVEY. as well as to the citizens in general the manifold conveniences of a well-made and accurate map on a large scale. COOPERATION WITH THE UNITED STATES GEOLOGICAL SURVEY IN THE PREPARATION OE TOPOGRAPHIC MAPS. Many of the States cooperate with the National Geological Survey through their respective State Survey organizations in the preparation of topographic maps. The usual basis of such cooperation is an equal contribution of funds on the part of the State and National Survey. The plan of mapping followed is that already developed and established by the National Survey. The men employed in the mapping are the expert topographic mappers already in the employ of the National Survey. The following States are either now cooperating or have in the past cooperated with the National Geological Survey in this work: Alabama, California, Connecticut, Illinois, Iowa, Kentucky, Louis¬ iana, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio, Okla¬ homa, Oregon, Pennsylvania, Rhode Island, Tennessee, Texas, Virginia and West Virginia. It is probable that such cooperation can be secured in the preparation of the topographic maps of Florida, thus practically doubling for the State any appropriation made by tbe legislature for this purpose. The Director of the United States. Geological Survey has repeatedly expressed his willingness to cooperate with the State Geological Survey in the preparation of topographic maps, meeting any appropriation made by the State with an equal amount so far as funds permit. An appropriation made for the preparation of topographic maps may be so framed as to admit of cooperation with the United States Geological Survey ; or may be made if desired contingent upon such cooperation to be carried on in accordance with plans approved by the Governor. SOIL MAPS. Another very important line of investigation is the prepara¬ tion of detailed soil maps. While a general report on the soil's of the State has been issued by the Survey, there is a very great I FIFTH ANNUAL REPORT. 13 demand for specific information regarding local soils such as can be supplied only by detailed soil maps of the several counties. A limited amount of soil mapping has already been done by the United States Bureau of Soils. As in the case of topographic maps many of the States are cooperating with the National Bureaus in the preparation of soil maps, and it is probable that an appropriation made for this purpose would be doubled by the United States Bureau of Soils. I would urgently recommend an appropriation of $5,000 per annum for the preparation of topo¬ graphic and soil maps. Such an appropriation may be made contingent upon cooperation with the national bureaus and would thus result in the expenditure of $10,000 per annum in the State for this purpose. EXPOSITIONS. National Conservation Exposition at Knoxville. — A National Conservation Exposition will be held at Knoxville, Tennessee, during September, and October of the present year. This exposi¬ tion is intended especially to exhibit the natural resources of the Southern States and to encourage their development. The opportunity is favorable for making more widely known both the mineral and agricultural resources of Florida and it is to be hoped that provision will be made by which the State may make a good showing at this exposition. Panama Exposition at San Francisco. — A world exposition will be held at San Francisco in 1915 to commemorate the open¬ ing of the Panama Canal. Florida by reason of its extensive coast line and its nearness to the canal zone is specially interested in this exposition, and can not afford to lose the opportunity of making its favorable location with regard to the canal more widely known. It is none too soon to begin the compilation of data on the harbors of Florida, and the preparation of maps, charts and drawings showing their relation to the canal and to the population and business centers of the United States, as well as to the lines of transportation within the United States. The exhibitions of the mineral and agricultural resources made for 14 FLORIDA STATE GEOLOGICAL SURVEY. the exposition at Knoxville may be used subsequently for the Panama exposition. MEMBERS OE THE STATE SURVEY. The members of the State Survey during the past year have been, in addition to the State Geologist, Mr. Herman Gunter, and during, a part of the year Mr. Emil Gunter. Stenographic and clerical services were rendered at various times by Ada Moore and T. C. Alford. The chemical analyses necessary to the work of the State Survey are made by the State Chemist. PUBLICATIONS ISSUED DURING 1912. The Fourth Annual Report of the Geological Survey was issued during the year. This report contains in addition to statistics on phosphate rock and fuller’s earth, papers on the Soils and Other Surface Residual Materials of Florida, and on the Water Supply of West-Central and West Florida. distribution oe reports. • The reports issued by the State Geological Survey are dis¬ tributed upon request, and may be obtained without cost by addressing the State Geologist, Tallahassee, Florida. THE PURPOSE and DUTIES OE THE STATE GEOLOGICAL SURVEY. Among the specific objects for which the Survey exists, as stated in the enactment, is that of making known information regarding the minerals, water supply and other natural resources of the State, including the occurrence and location of minerals and other deposits of value, surface and subterranean water supply and power and mineral waters and the best and most economic methods of development, together with analysis of soils, minerals and mineral waters, with maps, charts, and drawings of the same. A distinctly educational function of the Survey is indicated by Section 4 of the law, which makes it the duty of the State Geologist to make collections of specimens, illustrating the geo¬ logical and mineral features of the State, duplicate sets of which i FIFTH ANNUAL REPORT. 15 shall be deposited with each of the State colleges. The publica¬ tion of annual reports is provided for as a means of disseminating the information obtained in the progress of the Survey. The Survey is thus intended to serve on the one hand an economic, and on the other an educational purpose. In its economic rela¬ tions a State Survey touches on very varied interests of the State's development. In its results it may be expected to contribute to an intelligent development of the State’s natural resources. Its educational’ value is of no less immediate concern to the State, both to the citizens within the State and to prospective citizens without. A knowledge of the soil and of the available water supply is very necessary to successful agriculture, and the Survey’s in¬ vestigations along these lines are of value to all land owners. A knowledge of the mineral deposits which may lie beneath the surface, is likewise necessary to a correct valuation of land. relation of the state survey to the OWNERSHIP of MINERAL LANDS. The relation of the State Geological Survey to the ownership of mineral lands is specifically defined. The Survey law provides that it shall be the duty of the State Geologist and his assistants, when they discover any mineral deposits or substances of value, to notify the owners of the land upon which such deposits occur before disclosing their location to any other person or persons. Failure to do so is punishable by fine and imprisonment. It is not intended by the law, however, that the State Geologist’s time shall be devoted to examinations and reports upon the value of private mineral lands. Reports of this character are properly the province of commercial geologists, who may be employed by the owners of land for that purpose. To accomplish the best results, the work of the Survey must be in accordance with definite plans by which the State’s resources are investigated in an orderly manner. Only such examinations of private lands can be made as are incidental to the regularly planned investigations of the Survey. 16 FLORIDA STAFF GEOLOGICAL SURVEY. SAMPLES SENT TO THE SURVEY FOR EXAMINATION. Samples of rocks, minerals and fossils will be at all times gladly received, and reported upon. Attention to inquiries and general correspondence are a part of the duties of the office, and afford a means through which the Survey may in many ways be useful to the citizens of the State. THE COLLECTION OF STATISTICAL INFORMATION. For many purposes the collection and publication of statistical information is helpful, both to the industries concerned and to the general public. Such statistical information is desired from all the mineral industries of the State. Such information will be recognized as strictly confidential, in so far as it relates to the private business of any individual or company, and will be used only in making up State and county totals. The cooperation of the various industries of the State is invited in order that the best possible showing of the State’s products may be made annually. EXHIBITION OF GEOLOGICAL MATERIAL. The space available for the exhibition of geological material is unfortunately as yet very limited. A part of one room is being used for this purpose. Three cases have been built, designed to serve the double purpose of storage and exhibition. The lower parts of the case contain drawers and are used for storage. In making the collections a definite plan has been followed to secure a representation of the rocks, minerals and fossils of each forma¬ tion in the State. The collection will be added to as rapidly as space is provided for taking care of the material. THE SURVEY LIBRARY. A well equipped reference library is essential to the investiga¬ tions of the Survey, and an effort has been and is being made to bring together those publications which are necessary to the immediate and future work of the department. The Survey library now contains more than 1,500 volumes. These include the reports of the several State Geological Surveys ; the reports of the National Geological Survey; the reports of the Canadian FIFTH ANNUAL REPORT. 17 and a few oth'er foreign Geological Surveys ; and many miscel¬ laneous volumes and papers on geology and related subjects. PUBLICATIONS ISSUED BY THE STATE GEOLOGICAL SURVEY. First Annual Report, 1908, 114 pp., 6 pis. This report contains: (1) a sketch of the geology of Florida; (2) a chapter on mineral industries, including phosphate, kaolin or ball clay, brick-making clays, fullers earth, peat, lime and cement and road-making materials; (3) a bibliography of publications on Florida geology, with a review of the more important papers published previous to the organ¬ ization of the present Geologocial Survey. Second Annual Report, 1909, 299 pp., 19 pis., 5 text figures, and one map. This report contains: (l) a preliminary report on the geology of Florida, with special reference to stratigraphy, including a topographic and geologic map of Florida, prepared in cooperation with the United States Geological Survey; (2) mineral industries; (3) the fuller’s earth deposits of Gadsden County, with notes on similar deposits found elsewhere in the State. Third Annual Report, 1910, 397 pp., 28 pis., 30 text figures. This report contains: (1) a preliminary paper on the Florida phos¬ phate deposits; (2) some Florida lakes and lake basins; (3) the artesian water supply of eastern Florida; (4) a preliminary report on the Florida peat deposits. Fourth Annual Report, 1912, 175 pp., 16 pis., 15 text figures, one map. This report contains: (1) The soils and other surface residual materials of Florida, their origin, character and the formation from which derived; (2) the water supply of west-central and west Florida; (3) the production of phosphate rock in Florida during 1910 and 1911. Bulletin No. 1. The Underground Water Supply of Central Florida, 1908, 103 pp., 6 pis., 6 text figures. This report contains: (1) Underground water; general discussion; (2) the underground water of central Florida, deep and shallow wells, spring and artesian prospects; (3) effects of underground solution, cavities, sinkholes, disappearing streams and solution basins; (4) drainage of lakes, ponds and swamp lands and disposal of sewage by bored wells; (5) water 18 FLORIDA STATE GEOLOGICAL SURVEY. analyses and tables giving general water resources, public water supplies, spring and well records. Bulletin No. 2. Roads and Road Materials of Florida, 1911, 31 pps., 4 pis. This bulletin contains: (1) An account of the road building materials of Florida; (2) a statistical table showing the amount of improved roads built by the counties of the State to the close of 1910. Fifth Annual Report, 1913. EXPENDITURES OF THE GEOLOGICAL SURVEY FOR THE YEAR ENDING JUNE 30, 1912, AND FOR THE HALF YEAR ENDING DECEMBER 31, 1912. The total appropriation for the State Geological Survey is $7,500.00 per annum. No part of this fund is handled direct by the State Geologist, as all Survey accounts are paid upon warrants issued by the Comptroller of the State as per itemized statements approved by the Governor. The original of all bills and the itemized statements of all expense accounts are on file in the office of the Comptroller. Duplicate copies of the same are on file in the office of the State Geologist. LIST OE WARRANTS ISSUED DURING THE YEAR ENDING JUNE 30, 1912. July, 1911. E. H. Sellards, State Geologist, expenses, July, 1911 . ....$ 30.00 Herman Gunter, Assistant, expenses, July, 1911 . . . 31.05 Ada Moore', stenographic services . . 25.30 The Record Company, printing . . . 7.50 John McDougall, postage . . . 62.75 Southern Express Company . . . . 3.02 August, 1911. E. H. Sellards, State Geologist, expenses, August, 1911. ..... 48.70 Herman Gunter, Assistant, expenses, August, 1911 . 18.50 American Peat Society, subscription . . . 5.00 John McDougall, postage . . . . 20.00 Carried forward $ 251.82 FIFTH ANNUAL REPORT. 19 Brought forward . $ 251.82 September, 1911. E. H. Sellards, State Geologist, salary for quarter ending September 30, 1911 . 625.00 Herman Gunter, Assistant, salary for quarter ending Septem¬ ber 30, 1911 . 300.00 Southern Express Company, express for July and August... 5.00 October, 1911. E. H. Sellards, State Geologist, expenses, October, 1911 . 23.70 H. & W. B. Drew Company, supplies . 4.62 P. Blankiston’s Son & Company, publications . 2.00 Verlag fur Fachliteratur, subscription . 5.76 John McDougall, postage . 20.00 November, 1911. E. H. Sellards, State Geologist, expenses, November, 1911.. 38.00 Herman Gunter, Assistant, expenses, November, 1911 . 12.60 Southern Express Company . 3.76 December, 1911. E. H. Sellards, State Geologist, salary for quarter ending December 31, 1911 . 625.00 E. H. Sellards, State Geologist, expenses, December, 1911... 41.10 Herman Gunter, Assistant, salary for quarter ending Decem¬ ber 31, 1911 . 300.00 Herman Gunter, Assistant, expenses, December, 1911 . 68.70 Emil Gunter, Assistant, salary ($62.50), expenses ($48.05), December, 1911 . 110.55 T. C. Alford, stenographic services . 6.00 H. & W. B. Drew Company, supplies . . . 2.34 F. H. King, publications . 2.50 American Journal of Science, subscription . 6.00 Engineering and Mining Journal, subscription . 5.00 January, 1912. E. H. Sellards, State Geologist, expenses, January, 1912.... 27.20 Herman Gunter, Assistant, expenses, January, 1912 . 103.82 Emil Gunter, Assistant, salary ($75.00), expenses ($91.92), January, 1912 . 166.92 T. C. Alford, stenographic services . . . 15.00 Francis J. Bulask, subscription . 5.00 Carried forward $ 2,777.39 20 FLORIDA STATE GEOLOGICAL SURVEY. Brought forward . $2,777.39 John McDougall, postage . 20.00 Southern Express Company . 2.72 February, 1912. E. H. Sellards, State Geologist, expenses, February, 1912.... 37.65 Herman Gunter, Assistant, expenses, February, 1912 . 108.20 Emil Gunter, Assistant, salary ($75.00), expenses ($81.25), February, 1912 . 156.25 T. C. Alford, stenographic services . 12.20 Wrigley Engraving Company, engravings . 39.78 H. & W. B. Drew Company, supplies . 4.70 Southern Express Company . 8.35 March, 1912. E. H. Sellards, State Geologist, salary for quarter ending March 31, 1912 . 625.00 Herman Gunter, Assistant, salary for quarter ending March 31, 1912 . 300.00 Herman Gunter, Assistant, expenses, March, 1912 . . 48.95 Emil Gunter, Assistant, salary ($17.30), expenses ($31.10), March, 1912 . 48.40 T. C. Alford, stenographic and clerical services . 36.00 Economic Geology Publishing Company, subscription . 3.00 April, 1912. E. H. Sellards, State Geologist, expenses, March and April, 1912 . 29.75 T. J. Appleyard, printing . 732.20 The Record Company, printing . 18.75 H. & W. B. Drew Company, supplies . 2.21 John McDougall, postage . 125.00 Southern Express Company . 15.70 May, 1912. E. H. Sellards, State Geologist, expenses, May, 1912 . 70.55 Herman Gunter, Assitant, expenses, May, 1912 . 78.60 Emil Gunter, services, April and May . 9.00 Alex. McDougall, postage . 25.00 June, 1912. E. H. Sellards, State Geologist, salary for quarter ending June 30, 1812 . 625.00 E. H. Sellards, State Geologist, expenses, June, 1912 . . 60.85 Carried forward .$ 6,021.20 FIFTH ANNUAL REPORT. 21 Brought forward . . . $ 6,021.20 Herman Gunter, Assistant, salary for quarter ending June 30, 1912 . 300.00 Herman Gunter, Assistant, expenses, June, 1912 . 23.05 D. R. Cox Furniture Company, supplies . 30.00 David S. Woodrow, Agent, subscription . 6.00 University of Chicago Press, subscription . 4.00 H. & W. B. Drew Company, supplies.. . 2.78 Total expenditures . $6,387.03 Overdrawn from preceding year . .10 $6,387.13 Balance available . 1,112.87 $7,500.00 LIST OF WARRANTS ISSUED DURING THE HALF YEAR ENDING DECEM¬ BER 31, 1912. July, 1912. T. J. Appleyard, State Printer . $ 100.00 Southern Express Company . 13.76 D. R. Cox Furniture Company, supplies . 4.13 August, 1912. Alex. McDougall, postage . 25.00 Southern Express Company . 3.03 September, 1912. E. H. Sellards, State Geologist, salary for quarter ending September 30, 1912 . 625.00 Herman Gunter, Assistant, salary for quarter ending Septem¬ ber 30, 1912 . 300.00 Southern Express Company . 1.60 October, 1912. E. H. Sellards, State Geologist, expenses, October, 1912 . 62.80 Herman Gunter, Assistant, expenses, October, 1912 . 42.71 Arthur H. Thomas Company, 4 supplies . 19.55 November, 1912. E. H. Sellards, State Geologist, expenses, November, 1912... 66.47 Herman Gunter, Assistant, expenses, November, 1912 . 29.10 Carried forward $ 1,293.15 22 FLORIDA STATE) GEOLOGICAL SURVEY. Brought forward . $ 1,293.15 H. R. Kaufman, repairing typewriter . 5.00 Alex. McDougall, postage . 25.00 Southern Express Company . . . . 3.13 December, 1912. E. H. Sellards, State Geologist, salary for quarter ending December 31, 1912 . 625.00 / E. H. Sellards, State Geologist, expenses, December, 1912... 72.85 Herman Gunter, Assistant, salary for quarter ending Decem¬ ber 31, 1912 . 300.00 H. & W. B. Drew Company, supplies. . 1.79 W. & L. E. Curley, supplies . . . 3.70 Keuffel & Esser Company, supplies . 39.90 Engineering and Mining Journal, subscription..... . 5.00 Southern Express Company . 8.02 Total . $2,382.54 ORIGIN OF THE HARD ROCK PHOSPHATE DEPOSITS OF FEORIDA. BY E. H. SELLARDS. CONTENTS. PAGE. Introduction . 27 Distribution of the hard rock phosphates . . 27 Distribution of the pebble phosphates . . ..; . 23 Matrix of the hard rock phosphate deposits. . . . . . 28 Gray sands . 28 Clay lenses . 28 Flint boulders . 29 Limestone inclusions . 29 Pebble conglomerate . 29 Vertebrate and invertebrate fossils . 29 Petrified wood . 29 The phosphate rock . . . j. . 29 Boulders . 29 Soft phosphate . 29 Fragmentary rock . 29 Plate rock . 29 Pebble rock . 29 Thickness of the phosphate bearing formation . 30 Amount of hard rock phosphate. . 31 Formation name . 31 Local details . 32 Suwannee county . 32 Columbia county . 32 Alachua county . 33 Marion county . 34 Citrus county . 35 Hernando county . 3(3 Problems to be accounted for . 37 Summary of explanation . 37 Acknowledgments . 38 Discovery of the Florida phosphate deposits . 40 Beginning of the Florida phosphate mining indusstry . 42 Investigations of the Florida phosphate deposits . 4:3 Review of theories previously proposed . 45 Albert R. Ledoux . 45 Francis Wyatt . 45 E. T. Cox . 46 N. H. Darton . 47 W. H. Dali . 47 Walter B. M. Davidson . 47 N. A. Pratt . 48 C. C. H. Millar . 48 George H. Eldridge . 48 L. C. Johnson . 50 Lucius P. Brown . 50 L. P. Jumeau . 50 26 CONTENTS. PAGE. Discussion of theories . 50 The fossils of the hard rock phosphate deposits . 56 Source of the phosphoric acid . 58 Agency by which the phosphate has accumulated . 59 Relation of the phosphate to the underground water level . 59 The formation of boulders . 60 Silica boulders . 60 Phosphate boulders . 61 Formed by the replacement process . 61 Formed by precipitation . 61 Secondary deposition of phosphate . 62 Origin of the plate rock . 62 Localization of the hard rock deposits . 63 Limitation of the hard rock phosphates . 63 Physiographic types in central Florida . 63 The gulf hammock belt . 64 The hard rock phosphate belt . . . 64 The middle Florida hammock belt . 64 The lake region . 65 E'conomic relation . 66 Bibliography . 66 PLATES. Plate No. 1. Phosphate boulder showing secondary deposition. 2. Laminated phosphate boulder. 3. Phosphate rock. x 4. Teeth of mastodon from the phosphate deposits. 5. Teeth and foot bone of horse, and teeth of mastodon. 6. Sharks’ teeth from the phosphate deposits. 7. Sharks’ teeth from the phosphate deposits. 8. Phosphate washer and prospect drill. 9. Phosphate pit after the removal of the phosphate. MAPS. Map showing the limestone region of Central Florida. Map showing the location of the hard rock and land pebble phosphates. ORIGIN OF THE HARD ROCK PHOSPHATES OF FLORIDA. E. H. SELLARDS. Two kinds of phosphate rock are now being mined in Florida,, the land pebble and the hard rock. The deposits which carry the hard rock phosphate are found over a considerable extent of country in the western part of central peninsular Florida. The area includes the southern part of Columbia and Suwannee Counties, the western part of Alachua and Marion Counties, the eastern part of Levy, Citrus and Hernando Counties, and the northern part of Pasco County. From north to south the hard rock area extends through a distance of about 100 miles. Its width from east to west is variable. The greatest width is found in Marion County, almost the whole of the western half of this, county being included in this belt. West of the Suwannee River a limited amount of hard rock phosphate has been fopnd in, Lafayette, Taylor and Jefferson Counties. The accompanying map shows approximately the extent of the phosphate-bearing deposits. The workable deposits are less extensive than* the area, here outlined, the mines now operated being confined to a com¬ paratively narrow belt reaching from Alachua to Hernando- Counties. Mining has been carried on continuously in this section for more than two decades. Seventy-four plants, under the owner¬ ship of twenty mining companies, operated here in 1909, while- forty plants, under the ownership of fourteen mining companies,, were operating at the close of 1912. Each phosphate plant opens, up in the process of mining one to several pits offering excep¬ tionally good exposures of the phosphate-bearing formation. The following paper is based on observations made in the many pits that have been opened up in this section during the past several years. The results that are presented in this paper have been gradually obtained, and have been published in part in the reports. 28 FLORIDA STATE GEOLOGICAL SURVEY. of the Florida Geological Survey during the past few years. The land pebble phosphates are found in southern Florida in Polk and Hillsboro Counties. This paper relates to the hard rock deposits only, the pebble deposits not being included in the dis¬ cussion, although their approximate location is indicated on the map. No attempt is made on this map to show the location of the low grade phosphates, which occur extensively in central Flor¬ ida. The matrix in which the hard rock phosphate is imbedded is extremely variable. The formation includes a mixture of materials from various sources and of the most diverse character, further complicated by pronounced chemical activity within the formation itself. The prevailing phase of the formation is feebly coherent, more or less phosphatic, light gray sands. Aside from these sands the principal materials of the formation are clays, phosphate rock, flint boulders, limestone inclusions, pebble conglomerate, erratic and occasional water-worn flint pebbles, vertebrate and invertebrate fossils, and occasional pieces of silicified tree trunks. Th$ gray sands may be observed in every pit that has been excavated in this section. Moreover, from drill and prospect holes it is known that these sands occur very 'generally over the intervening or barren area. The sands are of medium coarse texture, the grains being roughly angular. The amount of phos¬ phate associated with these sands is variable. Upon prolonged exposure, as seen in numerous abandoned pits, these sands oxidize at the surface, assuming a pink or purple color. When affected by slow decay and by water, carrying more or less iron in solution, thev become reddish or ochre yellow in color. Lithologically these sands resemble closely the gray phosphatic sands of the Alum Bluff formation as seen at the type locality at Alum Bluff, on the Apalachicola River. The clays in this formation occur locally as clay lenses im¬ bedded in the sand, or separating the sand from the phosphate rock, or overlying the phosphate rock. The clays are often of a light buff or blue color. When lying near the surface, however, they often oxidize to varying shades of red. The relative amount ORIGIN OR THE HARD ROCK PHOSPHATES. 29 of clay in the phosphate-bearing formation increases in a general way in passing to the south. The exposures in the southern part of the area show as a rule more clay than do similar exposures in the northern part of the area. The phosphate boulders seem to have a tendency to group around and to be associated with local clay lenses. Frequently the productive pit gives place laterally to barren gray sands. Flint boulders occur locally in this formation in some abun¬ dance, and occasionally phosphate pits that are otherwise work¬ able are abandoned on account of the number of flint boulders encountered. The flint boulders are usually oval or somewhat flattened in shape and are of varying size, some weighing several tons. The exterior is usually of a light color. Some of the boulders are hollow and occasionally the cavity is filled with water; other boulders are solid, compact and of a bluish color throughout. Limestone inclusions are frequent in this formation. The pebble conglomerate feature is not of frequent occurrence but may occasionally be observed in the northern part of the hard rock section. An exposure of flint pebbles may be seen in one of the pits of plant number 5 of the Cummer Lumber Company, about one mile southwest of Newberry, in Alachua County. The matrix at this exposure consists of more or less water-worn frag¬ ments of varying size together with round or oval water-worn, dark colored flint pebbles. This phase of the formation may be seen through a distance of ten or fifteen feet along the side of the pit. Water-worn pebbles weighing one or more pounds occur occasionally in the northern part of the field. The invertebrate fossils are found in the limestone inclusions. The vertebrate remains are mixed in with the other materials of the matrix. The fossil wood is of rare occurrence, but is occasionally found in this formation. Phosphate rock, although the constituent of special economic interest, nevertheless makes up a relatively small part of the formation. The phosphate in these deposits occurs as fragmentary rock, boulder rock, plate rock or pebble. The boulders are often of large size, in some instances weighing several tons, and not infrequently needing to be broken up by blasting before being 30 FLORIDA STATE) GEOLOGICAL SURVEY. removed from the pit. It is also necessary to operate a rock crusher in connection with all hard rock phosphate mines to reduce the larger pieces of rock to a size suitable for shipping. A certain portion of soft phosphate unavoidably lost in mining is also present. The relative amount of material that it is neces¬ sary to handle to obtain a definite amount of phosphate is always variable with each pit and with the different parts of any one pit. The workable deposits of phosphate lying within this formation occur very irregularly. While at one locality the phosphate may lie at the surface, elsewhere it may be so deep as not to be economically worked; while a deposit once located may cover more or less continuously a tract of land some acres in extent, elsewhere a deposit appearing equally promising on the surface, may in reality be found to be of very limited extent. As to loca¬ tion, depth from surface, extent into the ground, lateral extent, quantity and quality, the hard rock phosphate deposits conform to no rule. The desired information is to be obtained only by extensive and expensive prospecting and sampling. The phosphate rock may lie beneath the gray sands, or above the gray sands or may be entirely surrounded by them. In some instances the phosphate is interbedded with the sands. Such interbedding of sand and phosphate was observed by the writer in the Central Phosphate Company pit number 25, about three miles west of Clark. This phase of the relation of sand and phos¬ phate occurs not infrequently and is confined to no particular part of the phosphate field. It is frequently stated by the phosphate miners that there is a relation between the local clay lenses and the occurrence of phosphate. It is evident, however,, that there are many exceptions to this general statement. THICKNESS. The thickness of the phosphate bearing formation is as vari¬ able as its other characteristics. It rests upon the Vicksburg Limestone, the top surface of which owing to solution by under¬ ground water, has become extremely irregular. The limestone projects as peaks into the phosphate formation. In Citrus County the phosphate bearing formation is known to reach a thickness of ORIGIN OF THE HARD ROCK PHOSPHATES. 31 from 75 to 100 feet. When of this thickness it is worked to the permanent ground water level by the dry pit method of mining, and is then mined from 40 to 50 feet below this lev^l by the float¬ ing dredge. In the northern part of the area the formation is as a rule much thinner, and is worked almost entirely by dry pit mining. AMOUNT OF HARD ROCK PHOSPHATE. It is scarcely possible to give an estimate of the amount of hard rock phosphate in Florida that yet remains to be mined. This is due to the fact that the deposits are extremely local and irregular. While the whole extent of the phosphate bearing formation can be mapped with a fair degree of accuracy, the deposits of phosphate within the formation can be located and an estimate of the amount that is mineable made only after very exact prospecting. The cost of such prospecting is such that it is seldom undertaken on a , large scale except by the companies actually interested in producing the rock. It is true that some estimates as to the total tonnage available have been made, but these amount to little more than guess work. The amount actually mined during the twenty-two years since mining operations began in this field is approximately 9,313,071 tons. The output at present amounts to about one-half million tons per annum. FORMATION NAME. The term Dunnellon formation has been applied by the writer to the phosphate bearing formation.* These deposits are well developed in the vicinity of Dunnellon, in Marion County, and have been extensively mined in that section. It was here also that the deposits were first discovered and mined. The term Dunnellon is, therefore, appropriate. The formation is probably of Pliocene age as indicated by the fauna. ^Florida State Geological Survey, Third Annual Report, p. 32, 1910. 32 FLORIDA STATE GEOLOGICAL SURVEY. LOCAL DETAILS. SUWANNEE COUNTY. The southern and southeastern part of Suwannee County has pro¬ duced some phosphate, although no mines are operating in this county at present. A variable thickness of pale yellow sand occurs in the pits of this section. At the pits of plant No. 10 of Dutton Phosphate Company, two miles north of Hildreth, from two to twelve feet of this incoherent sand rests directly upon the phosphate bearing matrix. In one of the pits of this plant the phosphate matrix grades at the bottom into a yellow phosphatic clay overlying the limestone to a depth of 4 or 5 feet. In one of the pits at this plant are observed, as frequently seen elsewhere in the hard rock section, many large round elongate siliceous boulders inter- bedded in the phosphate matrix. The underlying formation here is the Vicksburg Limestone, which occurs as peaks and as “hog backs” of lime projecting into or even through the phosphate matrix. COLUMBIA COUNTY. The southern part of Columbia County, adjacent to Suwannee County, has produced considerable phosphate, although only one mine in this county was in operation at the close of 1912. At plant No. 2 of the Dutton Phosphate Company, now abandoned, about one-half mile west of Ichatucknee Springs, the following section was obtained : Pale incoherent sand . 10 to 20 feet Phosphate-bearing matrix . 20 to 25 feet Buff yellow phosphatic clays . . • 5 to 6 feet Dark sandy phosphatic clays (exposed) . 4 feet The incoherent sands in this pit, as at Dutton No. 10, rest directly upon the phosphate stratum, the top of which is exceedingly irregular. Clay lenses 6 to 12 inches thick are of frequent occurrence, especially near the top. The underlying limestone is reached in places. The buff yellow phosphatic clay observed in Dutton No. 10 is seen here also and is under¬ laid by 4 feet of dark, sandy' phosphatic clay. The following section was made in one of the pits of the Schilman & Bene phosphate plant, about two miles northwest of Ft. White : Pale yellow incoherent sand . 3 to 5 feet Fed clayey sands . . 5 to 10 feet Phosphate matrix . 15 to 25 feet Limestone at the bottom of the pit. ORIGIN OR THR HARD ROCK PHOSPHATE'S. 33 This section differs from the preceding chiefly in the presence of the red clayey sands, which are sufficiently coherent to form a vertical wall in the pit. This clayey sand stratum when present is referred to by the miners as “hardpan.” In the pit of the Fort White Hard Rock Company, one-mile south¬ east of Ft. White, the foundation rock, as is usual in this section, is the Vicksburg Limestone. The top of this limestone is exceedingly irregular, projecting as rounded peaks. Shells, sea urchins, and other fossils are partly eroded away, the limestone having a comparatively smooth surface. The phosphate rock consists chiefly of angular fragmental pieces, plates, pebbles and boulders imbedded in a sandy clayey matrix. This matrix fills up the irregularities in the underlying limestone. In several instances the phosphate matrix was seen to fill up cavities and solution channels in the limestone. Slickensides occur, due to the settling of the phosphate matrix as the underlying limestone dissolved away. Limestone inclusions and siliceous boulders occur in the phosphate stratum. The following section is seen in an abandoned pit of this plant: Pale yellow incoherent sand . 1 to 15 feet Phosphate matrix . 1 to 20 feet Limestone top surface exceedingly irregular. The phosphate producing area of southern Columbia and Suwannee Counties lies adjacent to and in the angle between the Suwannee and Santa Fe Rivers, including the low lying and intensively eroded parts of each county. The limestone lies near the surface in this section and as a rule the phosphate is mined out by dry mining, the limestone being exposed in the abandoned pits. Dredging, which is applicable in the southern part of the phosphate area, is not used in this section. ALACHUA COUNTY. The west central part of Alachua County is actively producing phos¬ phate; fourteen plants were operated in this county at the close of 1912. Pit No. 25 of the Central Phosphate Company, west of Clark, gave the following section : Pale yellow incoherent sands . 5 to 10 feet Red clayey sands . 5* to 10 feet Phosphate-bearing formation . 10 to 25 feet Limestone at bottom of pit. The phosphate matrix consists of gray sands, yellow, buff and blue clays, and phosphate rock. At one place in this pit a stratum of gray sand Id to 2 feet thick is seen interbedded with the phosphate reck. 34 FLORIDA STATE GEOLOGICAL SURVEY. The incline leading to a pit belonging to T. A. Thompson, near Neals, gave the following section : Pale yellow incoherent sands . 5 to 10 feet Red clayey sands . 7 to 10 feet Gray phosphate sands (exposed) . 15 feet The gray sands give place laterally to phosphate rock. Pit No. 2 of the Cummer Lumber Company is, perhaps, the largest single pit in operation in the hard rock phosphate section. This pit is reported to include at the present time about thirteen acres. Pit No. 5 of this company, one mile west of Newberry, gives an exposure of the sandstone and flint pebble conglomerate already referred to as occurring occasionally in the hard rock deposits. The pebbles are round and more or less flattened. They vary in size from very small pebbles to pebbles weighing five to seven pounds. In the pit of the Union Phosphate Company, at Tioga, a considerable number of rounded elongate siliceous boulders occur. These vary in size, the largest approximating a ton in weight. They are embedded in the phosphate-bearing matrix. The many other pits which are now being worked, or which have recently been abandoned, although varying much even within a single pit in details, are in general much the same as those described. The limestone in this county, as a rule', lies relatively near the sur¬ face. In most instances the limestone is encountered before or very soon after reaching the water level. The phosphate is thus largely worked out by dry mining and dredges are^rarely used. The limestone is encountered at varying depths. One pit may show a great deal of limestone projecting as peaks, while another pit of equal depth near by may scarcely reach the limestone. Some of the limestone peaks project 15 to 25 feet above the general level of the bottom of the pit. The phosphate-bearing matrix here, as elsewhere, fills up the irregularities in the limestone. The top surface of the limestone is, as elsewhere, entirely irregular. The red clayey sand called “hardpan” by the miners may be present or lacking in the pits of this section. The loose, pale yellow sand is practically always present, varying in thickness from 1 to 25 feet. MARION COUNTY. The plate rock deposit found in the vicinity of Anthony and .Sparr, in the north central part of Marion County, represents an eastward ex¬ tension of the phosphate-bearing formation. The relation of the phosphate matrix to the underlying limestone is the same as previously described. The limestone projects into the phosphate matrix as rounded peaks. Cir¬ cular depressions, similar in appearance to pot holes or to “natural wells,” ORIGIN OF THE HARD ROCK PHOSPHATES. 35 are frequent in this section. These are filled with the phosphate matrix. One of these depressions observed by the writer had been cut into, in the process of mining. This depression was about three and one-half feet in diameter at the top, fifteen feet deep and narrowed gradually to the bottom. Other depressions variable in diameter and in depth occur. The limestone lying near the line of the underground water level has usually a rough and jagged surface owing to solution by water in contact with the limestone. Above the water level the limestone has a smooth rounded surface, the shells and other fossils having been eroded off plane with the general rock surface. The plate rock beds show evidence of having been originally faintly stratified. Much of the stratification that originally existed, however, has been destroyed through repeated local subsidence as the underlying limestone was moved by solution. The stratification lines in the plate rock are frequently much curved and distorted owing to this irregular subsidence. The chief difference noted between the plate rock and the typical hard rock region is in the relatively large amount of fragmentary phosphate rock and the small amount of boulder rock. Flint and limestone boulders chemically formed are likewise absent or rare. The deposits at Standard and at Juliette, in the western part of Marion County, are similar in general character to the hard rock deposits as previously described. The mines in this section are dry mines and usually reach to the bottom of the phosphate formation in places en¬ countering the limestone. In the southwestern part of Marion County and in Citrus County the hard rock phosphate-bearing formation reaches its maximum thickness. The underlying limestone is ordinarily encountered at a considerable depth from the surface. Many of the phosphate pits in this section are worked as dry mines to the underground water level and afterwards as dredge mines to such depth as the dipper will reach. Some of the pits on higher lands are mined as dry mines only. The pit at the Dunnellon Phosphate Company plant No. 10 was one of the first pits regularly worked in the phosphate section and has been continuously in operation for the past twenty years. This mine is operated by a dredge. The bottom of the phosphate is not reached in this pit and the full thickness of the formation at this place has not been reported. citrus COUNTY. The conditions in Citrus County are in a general way similar to the conditions in the vicinity of Dunnellon, in Marion County. The under¬ lying limestone is occasionally seen in the pits in this section md is frequently reached by the dredge. The surface of the limestone wherever 36 FLORIDA STATF GEOLOGICAL SURVEY. seen projects as rounded peaks. There is on an average more clay to be seen in the phosphate formation in this section than in the northern part of the field. In a few instances, notably that of the pit in the Istachatta Phosphate Company, the water level is within a few feet of the surface and the phosphate formation is entirely submerged. Only the sands of the overburden are here visible. HERNANDO COUNTY. Phosphate is being produced in Hernando County in the vicinity of Croom. The mine in operation here is a dredge mine. The relation of the phosphate formation to the underlying limestone', as seen in an aban¬ doned pit several miles west of Croom, is the same as that in other parts of the phosphate section, the limestone projecting as rounded peaks. The material above the phosphate stratum consists largely of incoherent sands. The usual gray phosphatic sands, weathering purple on exposure, are seen surrounding the phosphate rock. In the mines near Croom a considerable amount of clay is associated with the phosphate. The preceding description of the phosphate-bearing formation is taken with but slight revision from a paper by the writer entitled “A Preliminary Report on the Florida Phosphate De¬ posits,” published in the Third Annual Report of the Florida Geo¬ logical Survey, 1910. The present paper, like the earlier one, is to be regarded as a report of progress in the investigation of the phosphate deposits and is not in any sense final. / ORIGIN OR THE HARD ROCK PHOSPHATES. 37 problems to be accounted for. Among the problems that must be accounted for in connection with the hard rock phosphate deposits of Florida are the follow¬ ing: (1.) The source of the miscellaneous materials that make up the formation, including sands, clays, flint pebbles, vertebrate and invertebrate fossils, silicified wood, flint boulders, limestone inclusions and phosphate rock in its varying forms. (2.) The intimate admixture in the formation of these diverse materials. (3.) The processes by which phosphate and flint boulders have formed. (4.) The limitation of the hard rock phosphate forma¬ tion to a characteristic well marked physiographic type of country. (5.) The localization within the formation of phosphate rock to such an extent as to form workable deposits. (6.) The forma¬ tion of the plate rock deposits. SUMMARY OF THE EXPLANATION OFFERED. The explanation offered, briefly summarized, is as follows : It is believed that the Upper Oligocene and probably some later formations, now' found on the surrounding uplands, formerly extended directly across the section that is. now the hard rock phosphate fields. The disintegration of these formations supplied the miscellaneous materials of which the deposits are made up. The mixing of the materials was brought about in part by stream action, which has resulted in a reworking and reaccumulation of the residual material from these formations, and in part by the local irregular subsidence such as is constantly going on in a lime¬ stone country. In some parts of the phosphate fields the lower¬ ing and mixing of the materials by solution of the underlying limestone has been the predominating factor, while elsewhere the reworking of the materials by stream action has predominated. It is probable that local bodies of water existed also in which the materials reaccumulated. The immediate source of the phosphoric acid is the phosphate, which was widely disseminated through the overlying formations. The fossils now found in the formation include those that were residual from the formations that have disintegrated, and those that were incorporated in connection with 38 FLORIDA STATE GEOLOGICAL SURVEY. the reworking and reaccumulation of the materials. The phos¬ phate and flint boulders are formed chemically through the agency of ground water. The formation containing the hard rock phos¬ phate is limited in its distribution to that section of the State in which formations carrying more or less phosphate have disinte¬ grated, overlying a limestone substratum, thus affording condi¬ tions favorable for the downward passage of rain water carrying phosphoric acid in solution. The phosphate thus removed from the surface formations is reaccumulated under these conditions in a concentrated form at a lower level. The phosphate deposits are localized within the formation because the formation itself is lacking in uniformity. Local variations, particularly the presence of clay lenses and other conditions which interfere with the free circulation of ground waters, favor the formation of phosphate boulders and thus result in a local deposit of phosphate rock of sufficient amount and purity to be of commercial value. The plate rock represents chiefly fragments of disintegrated boulders. ACKNOWLEDGMENTS. In presenting this view of the origin of the hard rock phos¬ phates the writer takes pleasure in acknowledging his indebted¬ ness to the many investigators who have contributed to a knowl¬ edge of these deposits. This indebtedness is not alone to those who have written on the origin of the phosphates, but equally to those who have contributed to an understanding of the geology of the State as a whole, and particularly of that part of the State in which these deposits are found. Only a few of these general publications can be mentioned at this time, although a full list is included in the bibliography which forms a part of the First Annual Report, of the State Geological Survey, 1908. The monograph on the Tertiary Fauna of Florida by Dr. W. H. Dali published in the Transactions of the Wagner Free Insti¬ tute of Science, 1890 to 1903, includes by far the most extensive study of the invertebrate fauna of the Florida formations that has yet been made, and to these investigations we are indebted for many fundamental facts regarding the succession of forma- ORIGIN OR THE HARD ROCK PHOSPHATES. 39 tions in Florida. In the present discussion the writer is particu¬ larly indebted to Dali's observations, recorded in Bulletin 84 of the United States Geological Survey, pages 109, 110 and 111, of remnants of the Upper Oligoeene formations (then classed as old Miocene) at Levyville, in Levy County, at Fort White, in Columbia County, and near Archer, in Alachua County. These localities lie west, north and east of the northward extension of the phosphate fields, and Dali, in the map which accompanies this report, represents the old Miocene as extending directly across the northern end of the hard rock phosphate area, with local exposures of the Vicksburg formation. These observations by Dali are accepted by the writer and form a part of his argument that the Upper Oligoeene (old Miocene) formerly extended across the phosphate fields as a whole. Messrs. George C. Matson and F. G. Clapp, in connection with cooperative work carried on by the United States Geological Survey and the Florida State Geological Survey, have added im¬ portant observations regarding the former areal extent of the Upper Oligoeene formations in Central Florida, remnants of these formations having been noted by them at many of the phosphate mines of Central Florida. Dr. T. W. Vaughan, of the United States Geological Survey, under whose supervision these co-opera¬ tive investigations were carried on, has given material assistance in determining the stratigraphic succession in Florida both by directing the field work and by the identification of fossils and of formations. Of the many other publications on the phosphates of Florida all of those of which a record has been obtained are listed in the bibliography, which follows this paper. In addition, those rela¬ ting directly to the origin of the hard rock phosphates are reviewed in connection with a discussion of the theories previously advanced ; reference to a number of the papers on the Florida phosphates is included in the notes in regard to the discovery, investigation and development of the phosphate deposits. In out¬ lining, on the accompanying map, the probable extent of the land pebble phosphates of Southern Florida the writer has utilized, 40 FLORIDA STATE GEOLOGICAL SURVEY. among other sources of information, maps of these deposits by Geo. H. Eldridge and by C. G. Memminger. DISCOVERY OF THE FLORIDA PHOSPHATE DEPOSITS. The knowledge of, or belief in the existence of phosphatic material in Florida seems to have been prevalent from an early date. Thus, in a paper by Pratt (1868) we find a reference to and an attempted explanation of the coprolite or guano-like deposits of Florida. The original of Pratt’s paper not having been available to me I have been unable to determine from the reviews of the paper whether Pratt’s reference is to phosphatic material known to occur in Florida or assumed to occur. From Professor J. M. Pickel (1890) we have a statement that “Dr. J. C. Neal, formerly of Archer, now of the Florida Agri¬ cultural Experiment Station at Lake City, discovered in Levy and Alachua Counties, in 1876, and tested chemically phosphatic rocks, which were in 1885 sent to the Smithsonian and analyzed quantitatively.” In 1880 Dr. Chas. U. Shepard writing of the phosphate deposits of South Carolina stated that they certainly extended in¬ to North Carolina on the north and probably as far south as. Florida. Aside from these references the first definite information of deposits of low grade phosphate rock in Florida seems to have been obtained incidentally in connection with the investigation of building stone made for the Tenth United States Census, 1880. The first samples of the phosphate rock were collected from a quarry being operated for building stone near Hawthorne, in Alachua County. This quarry had been opened by Dr. C. A. Simmons, of Hawthorne, in 1879. The samples were sent to Washington probably during the summer of 1880. The paper which gives the analysis of this rock bears the date, June 29, 1881. It is contained in the Proceedings of the United States National Museum for 1882, which were issued in 1883. Whether Dr. Simmons knew or suspected the phosphatic character of this ORIGIN OF THE HARD ROCK PHOSPHATES. 41 rock before the analysis by the Census Bureau is not known. However, soon after the analyses had been made, and as a result probably of these analyses, Dr. Simmons began operating a mill in which this rock was ground for agricultural purposes. These operations which were carried on during 1883 and 1884 (Mineral Resources for 1885), were undoubtedly the earliest attempts at mining and utilizing the phosphate rock of Florida. In 1881 Captain J. Francis LeBaron, while engaged by the government in making a preliminary survey for a proposed ship canal from the head waters of the St. Johns River to Charlotte Harbor, became interested in the water-worn pebbles and frag¬ ments of bones in the bed of Peace River. Samples of this material were sent to the Smithsonian Institution. Captain LeBaron obtained leave of absence from the Engineering Depart¬ ment in 1882 and 1883, with a view to interesting capital in the development of the phosphate. Finding many difficulties in developing this new industry, he subsequently accepted employ¬ ment in connection with the proposed Nicaragua Ship Canal. (Letter of May 23, 1911.) Returning in 1886, Captain LeBaron made further efforts to interest capital in the development of the phosphate but without success. During the early eighties, due probably to these and to other discoveries, interest became very active in the Florida phosphate, and new localities for the phosphate rock were reported in rapid succession. The volume on mineral industry by the United States Geological Survey for 1882, published in 1883, contains, page 523, reference to phosphatic marls occurring in Florida, in Clay, Alachua, Wakulla, Duval and Gadsden Counties. The volume for 1883 and 1884, page 793, reports that phosphate rock has been found in Florida, in Clay, Alachua, Duval, Gadsden and Wakulla Counties. In 1884 and during the early part of 1885 L. C. John¬ son made for the United States Geological Survey a somewhat careful examination of the phosphate deposits in Suwannee, Columbia, Alachua and Marion Counties. That the existence of phosphate rock in Florida was generally known at that time is evident from the fact that Johnson, from his own investigation and from samples sent to him, and from popular report as to tne 42 FLORIDA STATE GEOLOGICAL SURVEY. occurrence of phosphate, concluded that the phosphate deposits of Florida extended entirely across the State from the Georgia line through Hamilton, Suwannee, Alachua, Marion, Sumter, Polk and Manatee counties to Charlotte Harbor. (Mineral Re¬ sources for 1885, pp. 450-453, 1886.) During 1886 and 1887, owing doubtless to the efforts of Captain LeBaron and to the general interest in phosphates, care¬ ful investigations were made of the Peace Creek section by private interests. These investigations resulted in the purchase of lands and the initiation of mining operations in the river pebble district, the first shipment of Peace River phosphate having been made in 1888. The deposits that we now know as the Florida hard rock phos¬ phate were discovered in 1888 by Mr. Albertus Vogt. In May of this year Mr. Vogt, while deepening the well at his place, near Dunnellon, dug into a rich matrix of gravel, soft phosphate and sharks’ teeth. In June, 1888, a sample of this material was taken to Ocala and was there analyzed by R. R. Snowden and was found to be a high grade phosphate. The time of the discovery of the hard rock phosphate in Flor¬ ida has been variously given as spring of 1888, fall of 1888, and spring and fall of 1889. The dates given above are from a letter from Mr. Vogt of August 26, 1909. The discrepancies in the various publications as to the date of discovery probably came about from the fact that the discovery was not made known to the public at once. As soon as the existence of high grade phosphate rock was made generally known, prospecting became very active and the hard rock phosphate belt substantially as we now know it was quickly outlined. THE BEGINNING OF THE FLORIDA PHOSPHATE MINING INDUSTRY. As has been already mentioned the first attempt at mining and utilizing the phosphates of Florida was made by Dr. C. A. Simmons, of Hawthorne, in 1883. This plant, however, was not successful and was closed down in 1884. ORIGIN OR THE HARD ROCK PHOSPHATES. 43 The production of phosphate rock on a commercial scale in Florida began with the mining of the Peace Creek pebble deposits, probably in 1887, the first shipments having been made in 1888. The first company to operate on Peace River was the Arcadia Phosphate Company, organized by Mr. T. S. Morehead, of Philadelphia. The first shipments were to the G. W. Scott Manufacturing Company of Atlanta. (Millar, 1892, page 24.) Hard rock phosphate mining began one or two years later than river pebble mining, but developed much more rapidly. Accord¬ ing to Millar, the first of the hard rock mining companies to actually take the field was the Marion Phosphate Company, which broke ground near Dunnellon in December, 1889, and made a first shipment to Liverpool in April, 1890. The Dunnellon Phos¬ phate Company, which was probably the first company organized, began mining in February, 1890, and made their first shipment to London and Hamburg in May, 1890. Following the discovery of the hard rock phosphate deposits mining companies were organized in rapid succession. It is said that fully one hundred hard rock phosphate companies were organized in the United States, and that forty-one of these actually began operations. By the close of 1891 only eighteen companies were operating. At the present time, 1913, fourteen companies are mining hard rock phosphate. INVESTIGATIONS OF THE FLORIDA PHOSPHATE DEPOSITS. The chief official investigations that have been made of the Florida phosphates are those of the United States Geological Survey, the United States Census Bureau, the United States Com¬ missioner of Labor, the United States Department of Agricul¬ ture, and the Florida State Geological Survey. In addition, the reports of the State Chemist of Florida and of the State Experi¬ ment Station contain many analyses of Florida phosphate rock. Dr. J. Kost, during his brief term of office as State Geologist in 1886, also contributed towards the discovery of phosphate and the development of the industry. 44 FLORIDA STATE GEOLOGICAL SURVEY. The principal investigations made by the United States Geo¬ logical Survey are those by Johnson (1885, 1893),* Penrose (1888), Darton (1891), Dali (1892), Eldridge (1893), Matson (1909), Clapp (1909) ,. Vaughan (1909). In addition a number of other members of the National Survey have made notes on the Florida deposits in connection with the annual statements of the production of phosphate contained in the volumes on Mineral Industry. The Census Bureau investigations are those made by the Tenth Census in connection with the study of building stone, by which the low grade phosphates were discovered, and the report on mineral industries by the Eleventh Census. This latter report contains a chapter on the Phosphates of Florida by Edward Willis. The Sixth special report of the Commissioner of Labor, 1893, is devoted to the phosphate industry of the United States. A brief review of the Florida phosphate fields was given in 1911 by William H. Waggaman, of the Bureau of Soils of the United States Department of Agriculture. The investigations of the phosphate deposits by the Florida State Geological Survey, on which this paper is based, have been made at occasional intervals as opportunity was afforded since the organization of the Survey in 1907. The discovery of the hard rock phosphate in 1888 resulted in many private investigations of these deposits. Of these private investigators a number have made public reports while others unfortunately have made no permanent record of their investiga¬ tions. Among the earliest of these private investigators was Dr. C. U. Shepard, of Charleston, who examined the phosphates of the Withlacoochee River section in connection with the organiza¬ tion of the Dunnellon Phosphate Company in 1889 and 1890. Among others who examined the hard rock deposits during the first few years of mining operations and who have published their observations are Albert R. Ledoux (1890), Francis Wyatt (1890, *The numbers in parenthesis refer to the date of publication as listed In the bibliography, not necessarily to the year in which the investigations were made. ORIGIN OF THE HARD ROCK PHOSPHATES. 45 1891) , E. T. Cox ( 1890, 1891, 1892, 1896), Walter B. M. David¬ son (1891, 1893), N. A. Pratt (1892), C. C. Hoyer Millar (1891, 1892) , G. M. Wells (1896), E. W. Coddington (1896), L. P. Jumeau (1905, 1906). THEORIES PREVIOUSLY PROPOSED. The hard rock phosphates of Florida have interested all who have examined them, and many theories have been advanced to account for these remarkable deposits. In the following review these various theories are given as nearly as practicable in the order in which they are proposed. A strictly chronological order is, however, often impossible since when several papers appear during the same year it is difficult to determine which was first issued. Moreover some of the papers were evidently written some years before being printed. The paper by Dr. Albert R. Ledoux read before the meeting of the New York Academy of Science, January 27, 1890, and published in the transactions for 1890 is apparently the first account of the hard rock phosphate deposits that has been preserved. In this paper Dr. Ledoux offers no specific theory for the Florida deposits. Speaking of phosphates in general, how¬ ever, he notes the fact that within the rain belt, when guano deposits rest upon limestone the phosphoric acid is leached out and alters the carbonate of lime to phosphate. An instance is cited in this connection in which limestone in one of the South Pacific islands was believed to have been changed to phosphate to a depth of several feet within the period of twenty years. The phosphoric acid in this instance was leached by rainwater from recently deposited guano. The suggestion of the replacement of the carbonate of limestones under certain favorable conditions by phosphate is not offered by Ledoux as a new hypothesis, as this method of formation of certain of the phosphates had been dis¬ cussed by various previous writers. In a paper published in the New York Mining and Engineer¬ ing Journal for August 23, 1890, Francis Wyatt proposed the theory that the hard rock phosphates are due to the evaporation 46 FLORIDA STATE GEOLOGICAL SURVEY. of the Miocene waters which are assumed to have covered this section of the State. While submerged there was deposited upon the limestone, according to Wyatt, more especially in the cracks and fissures, a soft, finely disintegrated calcareous sediment or mud. As the seas dried up estuaries were formed in which were found great numbers of fish, mollusks, reptiles and marine plants. The formation of the phosphate is attributed to the reactions between the calcareous sediments and the decaying animal and plant life. Professor E. T. Cox, in a paper read before the Indianapolis meeting of the American Association for the Advancement of Science, August, 1890, expresses the view that the hard rock phosphates of Florida are derived from the mineralization of an ancient guano. His argument is that as the peninsula of Florida was elevated above the ocean the land bordering the sea on the west coast became the resting place for numerous aquatic birds and other animals. The humid character of the climate caused the soluble alkalies to be removed, leaving the less soluble phos¬ phate of lime. This accumulation of guano subsequently became mineralized, thus resulting in the hard rock phosphates. This theory is restated in papers subsequently published by Cox in 1892 and 1896. Professor Cox mentions two other views current at that time. These are stated as follows : “It is a well known fact that phos¬ phorous is an element and, like the element of iron, is almost universally distributed over the globe, and is found in all the living things thereon. Therefore, it is reasoned that it may, like iron, be accumulated in large beds by a natural law which governs the concentration of mineral masses. Again, it is suggested that phos¬ phoric acid, derived from mollusca, deposits from birds, fish and saurians, has filtered down and replaced the carbonic acid in the underlying limestone, converting it into phosphate of lime.” To the first of these suggestions Cox offers no objection. Of the second, however, he says, “Against the latter theory the phos¬ phate of lime very rarely contains any trace of organic remains, while the limestone on which it rests is rich in the casts of mollusca that are referred to the Eocene age. Then, again, in proximity to ORIGIN OF THE HARD ROCK PHOSPHATES. 47 the hard rock phosphate is a soft phosphate of lime that has the consistency of soft, plastic clay. This soft phosphate often under¬ lies the hard and is several feet in thickness.” Mr. N. H. Darton, writing in the American Journal of Science for February, 1891, considers guano as the most probable original source of the phosphate. The early Miocene is regarded as the probable time of deposition of the guano which by leaching supplied the phosphoric acid. Two processes in the formation of the rock are recognized. The first is the replacement of the car¬ bonate of lime by phosphate of lime ; the second is a general stalactitic coating on the massive phosphates and in the cavities. Whether or not the restricted distribution of the phosphate was connected with the genesis of the rock Darton regards as undeter¬ mined at that time. Mr. Walter B. M. Davidson contributed a brief paper on the origin and deposition of the Florida Phosphate, which was published in the Engineering and Mining Journal, Vol. 51, pp. 628-G29, 1891. This paper has not been available to the writer, but from a reference in a later paper it appears that Davidson at that time believed that the hard rock phosphate boulders were deposited in underground caverns and river beds in the Vicksburg Limestone. Among important early publications on the Florida phosphates is a paper by Dr. W. H. Dali, published in 1892. Dali’s account of the phosphate was given in connection with and was incidental to a general summary of the geology of Florida included in a monograph on the Neocene of North America by Dali and Harris (Bull. 84, U. S. Geol. Survey). In this report Dali expresses the belief that the phosphoric acid of the phosphate deposits was derived directly from bird guano. The local character of the bird rookeries determine the local occurrence of phosphate rock. The influence of local clay beds on the accumulation of workable deposits is also recognized (p. 135). Davidson, in a paper read before the American Institute of Mining Engineers at the Baltimore meeting in February, 1892, published in the Transactions, 1893, appears to derive the hard rock phosphates as residual material from the Vicksburg Lime- 48 FLORIDA STATE GEOLOGICAL SURVEY. stone. He says, page 12, “The phosphates of Florida, in all shapes, I derive from the leaching of the Vicksburg limestone, and in the same way I would account for the phosphates of the West India Islands. The phosphatic limestone of these islands has been subject to the leaching action of rains and atmosphere reactions, and the carbonate of lime has been carried away, leaving on the surface the more insoluble phosphate, and the iron and alumina. As in all limestones, the water eats away the rock unevenly, mak¬ ing pits and holes, and caves, and the phosphate of lime fills them up — either in an earthy form, or in the massive variety, which is described as coating the stalagmites and stalactities in the cave in Navassa.” Davidson believed that after the phosphate had accumulated in the pits and holes in the limestone, Florida was again submerged, allowing the sea sand to accumulate over and around the boulders. Pratt (1892) while conceding that the theory of a pure bird deposit, in localities favorable to the roosting of water fowl, more nearly covers the conditions of the problem as presented in all localities than any other so far advanced, considers that in the case of the Withlacoochee River deposits the evidence is all opposed to this theory. In this paper the theory is advanced by Pratt that the phosphate boulder is a true fossil, the boulder being the phosphatic skeleton of a gigantic foraminifera, while the soft phosphate is supposed to be the germ spores or bud of the animals or the com¬ minuted debris of the animals themselves.* Millar (1892) reviews the theories current at that time (pp. 115-117) and favors the view that guano is the most probable source of the phosphate. Whether the hard rock phosphates of Florida resulted from a superficial and heavy deposit of soluble guano, or from the con¬ centration of phosphate of lime already widely and uniformly dis¬ tributed throughout the mass of the original rock, or from both *The original of Dr. Pratt’s paper not being accessible to the writer thio review is based on the quotation from the paper included in the Phos¬ phate Industry of the United States by Carroll D. Wright, 1893, pp. 24-31, and in the Florida, South Carolina, and Canadian Phosphates by Millar, 1892, pp. 73-77 and 117. FLORIDA GEOLOGICAL SURVEY. PlETH ANNUAL REPORT. Piece of phosphate rock taken from large boulder and showing secondary deposition of phosphate in the form of layers on the bottom of the cavities and as stalactitic projections from the roof of the cavities. Natural size. EEORIDA GEOEOGICAE SURVEY. EIETH ANNUAI, Piece of phosphate rock from laminated boulder. From the collection of H. Bystra. FLORIDA GEOLOGICAL SURVEY. FIFTH ANNUAL REPORT. PL. 3. Fig. 1. — Sample of phosphate illustrating the formation of phosphate by the replacement process. The rock was clearly originally limestone of the Vicksburg formation, the form of the shells being well preserved. The carbonate has been replaced by phosphate, and the rock as shown by analysis is now a high grade phosphate. Natural size. Fig. 2. — Piece of phosphate rock showing secondary deposition in cavities and recementation of broken fragments. Collection of H. Bystra. Natural size. FLORIDA GEOLOGICAL SURVEY. FIFTH ANNUAL REPORT. PL. 4. Fig. 1. — Mastodon tooth from T. A. Thompson’s mine at Neals, Fla. This tooth has the gray phosphatic sands of the phosphate formation firmly adhering to it indicating that it came from the phosphate formation. Natural size. Fig. 2. — Mastodon tooth from T. A. Thompson’s mine, Neals, Fla. The gray phosphatic sands clinging to the tooth are evident in the photo¬ graph. This tooth shows very little wear. Natural size. FLORIDA GEOLOGICAL SURVEY. FIFTH ANNUAL REPORT. PL. 5. Fig. 1. — A fragment of mastodon jaw with two teeth in place from Neals, Fla. About one-half natural size. Fig. 2. — Teeth and foot bone of horse. The light colored tooth on the upper side at the left is from the Dunnellon Phosphate Company plant No. 5 at Hernando, in Citrus County. It has the phosphatic sands of the phosphate formation adhering to it. The lower tooth on the left is from the Franklin Phosphate Company mine, Newberry, Fla. (No. 1233). The upper tooth in the center is from the Camp Phos¬ phate Company, Blue Run mine, near Dunnellon (No. 1366). The lower tooth in the center is from Cullens River Mine, Dunnellon (No. 1444). The foot bone is from the Dunnellon Phosphate Company plant No. 6, near Dunnellon (No. 1302). All natural size. ’ Florida geological survey. FIFTH ANNUAL REPORT. PL. 6 Sharks’ teeth from the hard rock phosphate deposits. FLORIDA GEOLOGICAL SURVEY. FIFTH ANNUAL REPORT. PL. 7. Sharks’ teeth from the hard rock phosphate deposits. FLORIDA GEOLOGICAL SURVEY. FIFTH ANNUAL REPORT. PL. 8. Fig. 1. — Phosphate washer for hard rock phosphate, Cummer Phosphate Company, Alachua County. Fig. 2. — Drill for prospecting for hard rock phosphate, in use by the Southern Phosphate Development Company. The prospect holes are drilled through the phosphate formation to the underlying formation, the Vicksburg Limestone, which is reached at this locality at a depth of 75 to 100 feet. FLORIDA GEOLOGICAL SURVEY. View in the Plate Rock Phosphate Mine at Anthony, showing the very irregular top surface of the limestone after removal of the phosphate. ORIGIN OR THE HARD ROCK PHOSPHATES. 49 of these sources is regarded by Eldridge (1893) as a difficult question. Alteration of the limestone and precipitation of phos¬ phate from solution are both regarded as having been active in the formation of the primary phosphates. Phosphate boulders, Eldridge suggests, may have been formed by chemical precipita¬ tion of layer upon layer of phosphate, either on a surface exposed to the air or within a cavity in the limestone. By continued growth in the latter case the cavity would become filled with laminated or massive rock which upon the solution of the surrounding materials or the complete breaking down of the formation, as in later times, would result in a rounded body of phosphate of lime resembling a sea rolled boulder. Referring to phosphate of lime in sedimentary rocks Eldridge says (p. 18), “Its presence in sea- water; its broad distribution in both plant and animal life; its occurrence in rocks of all ages, even to the extent of economic value ; and its special presence in limestones, more particularly in Cretaceous and Tertiary lime¬ stones, are facts long recognized. Its occurrence in recent time in the form of leached and soluble guanos on many of the oceanic islands, and the phosphatization of the underlying strata, have also been noted by many authorities ; the last is by actual observation a tangible source, but the features first detailed point t» some other and more general origin of phosphate of lime than localized bird- deposits, or the but little more widely distributed accumulations of animal remains. Its presence in sea-water, after the manner of carbonate of lime, though in far smaller amount, is well established ; both materials are of general occurrence, and each play a prominent part in sea-life. The transfer of a consider¬ able percentage of phosphate of lime to localities having condi¬ tions favorable for its deposition, either in sediments, then settling, or on surfaces of rocks already laid down, has doubtless been accomplished in many cases through the instrumentality of animals secreting it. Oceanic currents may have assisted this accumulation. Again, southern waters, swamps, and lands give evidence of the presence in them of abundant life, secreting phosphate of lime and afterwards returning it to the beds on which this life rests.” 50 FLORIDA STATE GEOLOGICAL SURVEY. With regard to the plate rock phosphates of Marion County, Johnson (1893) assumes an original deposition of immense beds of guano. These beds after the leaching out of their carbonates and other soluble materials are believed tO' have become very compact, yet not entirely impervious to water. Small cavities in close contiguity became finally separated by mere plates and in this connection are called laminated rock. By disintegration the laminated rock is broken up into fragments, thus giving rise to the so-called plate rock. Still further disintegration, in the opinion of Johnson, results in the formation of soft phosphate. Johnson’s theory as to the origin of the phosphate as expressed in this paper is essentially the same as that advanced by Cox in 1890 to account for the phosphates as a whole. Johnson’s view that the plate rock results from the disintegration of laminated boulders had not previously been definitely advanced, although Willis includes a statement to this effect in his paper published in 1892. Lucius P. Brown (1904) regards it as possible that guano may have contributed in a minor degree to the enrichment in phos¬ phoric acid of the Florida limestones. The workable deposits of phosphate of lime, however, he regards as having been gathered up from miscellaneous sources in sedimentary rocks and concen¬ trated through the agency of underground water with more or less further concentration by mechanical means. Mr. P. Jumeau (1905) reviews the theories proposed to account for the origin of the phosphate rock, pp. 68-82. That the phosphate rock has accumulated chiefly from the leaching of guano is regarded by him as the most probable theory. DISCUSSION OF THEORIES. The theories offered by Wyatt, 1890, and by Pratt, 1892, are highly speculative and are based on assumptions for which nc proof is offered. Of this class also are some other theories that have appeared from time to time in newspaper and magazine articles. Davidson assumes that the phosphate rock existed originally in the Vicksburg Limestone and in its present form is merely ORIGIN OF THE HARD ROCK PHOSPHATES. 51 residual from the decay of that formation. In answer to this hypothesis it may be noted that while the Vicksburg Limestone is known by surface exposures throughout a large extent of the territory in the Gulf States, and by well borings to a considerable depth in Florida and elsewhere, it is strikingly free from inclu¬ sions of phosphate rock, such as would remain upon the disinte¬ gration of the limestone to form these phosphate deposits. Cox, in successive papers, argues that the phosphate rock is itself mineralized guano. This, likewise, was the view of Johnson (1893), as applied at least to the plate rock phosphates of Marion County. The fact that not a few of the phosphate boulders and pieces of rock have retained more or less well preserved evidence of their derivation from limestone sufficiently controverts this hypothesis, which is otherwise improbable. Darton (1891) and Dali (1892) each assume that guano is the immediate source of the phosphoric acid. Barton’s paper on this subject is brief and includes merely a statement of the probable origin of the rock. Dali, however, gives a clear state¬ ment of the guano hypothesis in its relation to the hard rock phosphates of Florida. It is even thought probable by Dali that each local deposit of hard rock phosphate may represent the loca¬ tion of an ancient bird rookery. The hypothesis of the origin of the phosphate from guano fails entirely to account for the jumble of materials with which me phosphate is associated. This, in the writer’s opinion, is the insurmountable objection to the bird guano theory, as developed by Dali. Of those who have written on the origin of the hard rock phosphate deposits of Florida, no one, with the exception of Eld- ridge, has taken sufficient account of the complexity of this forma¬ tion, or has seemed to appreciate that it is as necessary to account for the associated materials as for the phosphate itself. With the hypotheses proposed by Eldridge, however, the writer is un¬ able to agree. Whatever the original source of the phosphoric acid, whether from guano or from phosphate of lime, originally disseminated throughout the Vicksburg Limestone, the subsequent process, according to Eldridge, was the formation of a highly phosphatized 52 FLORIDA STATL GEOLOGICAL SURVEY. zone within and presumably at or near the surface of the Vicks¬ burg Limestone. This process Eldridge designates as the first period during which the primary phosphate was formed. To account for the condition in which the rock is now found and for the mixture of materials in the matrix Eldridge assumes that at a late period, probably at the close of the Pliocene, the peninsula of Florida was resubmerged and that during this resubmergence this phos¬ phate stratum was broken up, the pieces being removed more or less from their original location. To account for the associated sands, clays and other materials mixed with the phosphate rock he assumes that strong currents were running which washed in these complex materials. The phosphate that is now present in a finely divided condition and acts as a cementing substance for the gray sands was, he assumes, the ground up sediment from the hard rock which mixed with the sands as they were drifted into their present location. The writer’s hypothesis is based on observations by himself and others which lead to the conclusion that formations later than the Vickburg, formerly extended across the phosphate fields, and that these have now largely disintegrated. It is shown also that these formations, where now found intact, or as remnants on the surrounding uplands, are distinctly phosphatic. From these observations it is concluded that the matrix of the hard rock phos¬ phate deposits is the residue of the formations that have dis¬ integrated in situ, and that the phosphate itself is derived from the phosphate originally widely disseminated through these forma¬ tions, circulating waters being the agency by which the phosphate has been carried to its present location. The gray sands held to¬ gether by the finely divided phosphate, referred to by Eldridge, are a part of the residue from these earlier formations in which the sands occur under similar conditions. In the present paper it is not intended to discuss the source of the phosphate, which is found widely disseminated in the Upper Oligocene and some later formations, from which by solution and redeposition it has accumulated to form the workable hard rock deposits. The writer does not believe, however, that the bird guano theory will account for these widely disseminated phos- ORIGIN OF THF HARD ROCK PHOSPHATES. 53 phates, any better than for the intensely localized hard rock phos¬ phates. Upper Oligocene formations, which are throughout more or less phosphatic, attain in Florida a thickness of several hundred feet. Moreover these formations, except where disconnected by erosion, are continuous from the Apalachicola River, in West Flor¬ ida, to an undetermined distance beyond the point at which they disappear beneath later formations in Central Florida. It is in¬ conceivable to the writer that bird guano deposits could have been so uniformly scattered over so wide an area and through so great a thickness of sedimentary rocks. As regards the chemical changes involved in the formation of the hard rock phosphate there is much less disagreement among the different writers. Fedoux, Darton, Dali, Eldridge, Brown, Jumeau and others have recognized that phosphoric acid in solu¬ tion in water may and under favorable conditions does replace the carbonate of limestones thus forming calcium phosphate. Darton recognized the two processes, the first being the replace¬ ment of the carbonate by phosphate, and the second the subsequent coating over the surface and in cavities by phosphate thrown out of solution. Eldridge recognized the formation of boulders by replacement of carbonate by phosphate, and by precipitation from solution. The evidence of the formation of phosphate by the replacement of carbonate by phosphate is entirely incontrovertible, since, as has been previously stated, many of the boulders retain the original calcareous shells now phosphatized. The evidence of subsequent secondary deposition in the cavities is likewise obtained from the structure of the rock itself. The formation of boulders by precipitation seems probable from the structure of many of the boulders. Doubtless, as elsewhere stated, the replacement and precipitation have combined in the formation of many boulders. The chemical processes involved are more fully discussed else¬ where. Turning again to the explanation of the hard rock phosphate deposits offered by the writer, the key to the solution of the hard rock phosphate problems is found, in the writer’s opinion, in a study of the geological history of the State. The foundation rock in Central Florida is the Vicksburg Limestone of Lower Oligo- 54 FLORIDA STATL GEOLOGICAL SURVEY. cene age. In the hard rock phosphate section there is at present no formation, other than the phosphate itself, overlying the Vicks¬ burg. However, there are good reasons, as already stated, for believing that the Upper Oligocene and some later formations, now found on the uplands bordering the phosphate belt, formerly extended across this area. Upper Oligocene deposits are found at the present time bordering the phosphate belt on the north, east and south, while on the west outliers of these formations may still be found in Levy and in Hernando Counties.* Remnants, apparently, of these formations have recently been observed by the writer on the hills near Morganville, west of the phosphate area in Marion County. Further support of the view that the Upper Oligocene deposits formerly extended across the phosphate belt is found in the topog¬ raphy of the area. The phosphate country has been reduced in elevation more or less by underground solution. The phosphate deposits of Alachua County are found at an elevation of from 75 to 100 feet above sea, while passing to the east the plateau or uneroded section of this county rises to an elevation of 200 feet above sea. In Marion County the phosphates are found at an elevation of from 40 to 100 feet above sea, while both west and east of the phosphate belt, hills, the remnants of the former plateau, rise to an elevation of from 140 to 160 feet above sea. In Citrus County the hill country west of the phosphate area still retains a height of from 150 to 220 feet. The Upper Oligocene formations are found very generally on the east side of the phos¬ phate belt, while remnants, as already stated, are found on at least some of the hills on the west side of the area. Whether or not marine Miocene formerly extended across the present phosphate fields is undetermined. The character of the residue at some localities suggests Miocene material, although no actual proof of a former extent of the Miocene across this part of the State has yet been obtained. The marine Pliocene probably did not reach across this part of the State. Fresh water deposits of Pliocene and Pleistocene, however, are to be expected since "Florida Geological Survey, Second Annual Report, Map, 1909. ORIGIN OR THE HARD ROCK PHOSPHATES. 55 fresh water Pliocene deposits, the Alachua clays, containing remains of land vertebrates are found locally around the border of the phosphate area. These deposits were formed in small lakes and sinks, and similar deposits, doubtless, formed in the phos¬ phate area. The red sandy clays which form the surface deposits over practically all of the Northern and Central Florida probably extended across the phosphate area. Assuming the former areal extent of these later formations across what is now the phosphate belt of Florida, the solution of other problems connected with the hard rock deposits is much facilitated. As a result of the action of the weathering agencies these formations have disintegrated, their residue forming the phosphate matrix. The process of erosion and disintegration has been long continued, during which time the general surface level has been gradually lowered by the solution and removal of the underlying limestone. The lowering of the limestone here as else¬ where in limestone countries progresses not uniformly but irregu¬ larly, due to the formation of caves, sinks and underground channels. This irregular subsidence has resulted in the mixing of materials originally distinct. Sinks form in the limestone section of Florida by which material at the surface is lowered by the sudden caving of the earth. When these sinks are first formed the walls are vertical or nearly so. As a result of the caving at the sides together with the wash of surface material they fill up. By this process long continued the materials of different forma¬ tions become intimately mixed. The mixing of materials by underground solution and sub¬ sidence has been supplemented by stream action. While this area is at present practically without streams, yet local streams existed during the earlier stages of physiographic development. These local streams begin their development as soon as sinks are formed and when the stratigraphic conditions are favorable a stream enters each sink; working back from the sink the stream estab¬ lished in time a normal drainage system. These streams are known as disappearing streams since they enter sinks. As has 56 FLORIDA STATE GEOLOGICAL SURVEY. been explained in a previous paper,* the limestone country of Central Florida is gradually encroaching on the non-limestone country. These temporary streams make up one of the character¬ istic features of the physiography in the transition stage and num¬ erous examples of such streams are found in the partially eroded uplands bordering the phosphate fields. After being formed a sink is frequently filled up by the materials carried by the stream which enters it. In addition to local streams it is probable that considerable bodies of water existed from time to time in this section into which streams entered. The Pliocene was probably the time of the most active reaccumulation of the material which makes up the matrix of the phosphate deposits. Whether or not this area was partially submerged during the time of the reworking of the materials of this formation can possibly be determined by a careful study of the fossils. THE FOSSILS OF THE HARD ROCK PHOSPHATE DEPOSITS. Two distinct groups or lots of fossils are found in this forma¬ tion. The first of these includes those fossils, chiefly sharks’ teeth, that are residual from the formations that have disintegrated. The second group, of which there is a considerable fauna, chiefly land animals, includes those fossils that were incorporated in connec¬ tion with the reworking of the materials. The invertebrate fossils of this formation are contained for the most part in loose frag¬ ments of rock which represent inclusions from the underlying Vicksburg Limestone or remnants from later formations that have disintegrated. It should be borne in mind in this connection that the residual fossils do not necessarily all come from formations later than the Vicksburg. A part, possibly a majority, are residual from the Vicksburg itself. As already explained, the limestone is being constantly removed by solution and the fossils that it contained, if sufficiently resistant, remain as a part of the residue and hence ^'Fourth Annual Report Florida Geological Survey, page 33, 1912. ORIGIN OR THR HARD ROCK PHOSPHATES. 57 become incorporated in the phosphate deposits. Among the residual fossils are sharks’ teeth, which are obtained in numbers from every pit that is operated. It is frequently stated by the miners that the sharks’ teeth become more abundant as the under¬ lying limestone is approached near the base of the deposits. This statement is consistent with the view that many of the teeth are residual from the underlying limestone. The less resistant parts of the skeleton can not be expected to have persisted from these early formations in such abundance and such perfect state of pres¬ ervation as have the teeth. The residual fossils are of value to the geologist since from them it may be possible to determine from what particular forma¬ tions the materials of the matrix have been derived. The fossils included with the phosphate, not residual, indicate the age or time during which the reworking of the materials occurred. The fossils that were incorporated with the materials while they were being, reworked and redeposited are, as would be expected, of much later date than the residual fossils. Of these later animals comparatively fragile bones are frequently preserved. Whole skeletons, however, are rarely found in place. This may be due to the conditions under which they .were entombed, or possibly to the fact that the parts of the skeleton have been subsequently more or less dissociated by the subsidence of the materials due to the solution of the underlying limestone. From the fact that the formation of caves and sink holes in the limestone has continued to the present time it is evident that some comparatively recent fossils are likely to become included with the phosphate. Moreover local fresh water Pleistocene or recent surface deposits are likely to occur as a part of the overburden from which fossils may become mixed with the phosphate. Along the Withlacoochee River, which cuts through these deposits, also there has doubtless beep more or less shifting of the stream by which Pleistocene and recent remains are included with the phos¬ phate. These are conditions that must be borne in mind in making and in studying the collections. Of the fossils that are accepted as contemporaneous with the phosphate formation the best authenticated is a species of 58 FLORIDA STATE GEOLOGICAL SURVEY. mastodon, probably M. floridanus. This mastodon has been obtained in the hard rock phosphate section from the following mines: T. A. Thompson, Neals, Alachua County; Dutton Phos¬ phate Company, plant No. 22, Juliette, Marion County; Cullen River Mine, Dunnellon, and Dunnellon Phosphate Company, plant No. 5, Hernando, Citrus County. That the mastodon is actually imbedded in the phosphate bearing formation is not only vouched for by the miners who have personally taken specimens from the pits, but is evident from the specimens themselves, some of which have the gray phosphatic sands of the phosphate forma¬ tion adhering to them. Associated with the mastodon is found the small three-toed horse, Hippcirion. The remains of the horse have been obtained only from the picker belt, but notwithstanding the fact that they have gone through the washer, some of the teeth still have bits of the phosphate matrix clinging to them. The horse remains have been obtained from the following mines : Franklin Phosphate Company, mine No. 2, Newberry, and T. A. Thompson, Neals, both in Alachua County; Dunnellon Phosphate Company, plant No. 6, Dunnellon, Marion County, and Dunnellon Phosphate Company, No. 5, Hernando, Citrus County. A number of other fossils have been obtained, which remain to be deter¬ mined. Among these are teeth of an early camel from Dunnellon Phosphate Company, plant No. 5, Hernando, Citrus County, and Cullen River Mine, Dunnellon. From the plants working along and near the bed of the Withlacoochee River have been obtained a considerable number of fossils. Among these, in addition to the mastodon, camel and early horse, is the elephant, rhinoceros and a more recent horse, as well as a number of other forms, some of which appear to be com¬ paratively recent. It is evident that a mixing of fossils has occurred along the river due, possibly, to the shifting of the channel. SOURCE OF THE PHOSPHORIC ACID. The source of the phosphoric acid is believed to be from the various formations that have disintegrated in situ. The Upper Oligocene deposits are Very generally phosphatic throughout their ORIGIN OR THE HARD ROCK PHOSPHATES. 59 entire extent from the Apalachicola River, in West Florida, through Northern and Central Florida. The red sandy clays forming the surface deposits over much of Northern Florida and which prob¬ ably extended across the phosphate section overlying the Oligocene deposits, contained fragments from the granitic rocks and have doubtless contributed in the process of decay more or less phosphoric acid. AGENCY. The agency by means of which the phosphates were accumu¬ lated in their present form was ground water. The rainfall, which in Florida amounts to about 54 inches per annum, in passing through the surface materials dissolves a limited amount of the phosphate, which is carried to a lower level and is finally thrown out of solution in a. concentrated form. This process long continued results in the accumulation of workable phosphate deposits. RELATION- TO THE UNDERGROUND WATER LEVEL. It is probable that the ground water level has had an impor¬ tant bearing on the formation of the phosphate deposits. There is, as is well known, a definite relation between the ground water level and chemical reactions within the earth. The conditions above and below this level are radically different. Above the ground water level the movement of water following rains is free and solution is active; below this level the water stands or has a scarcely appreciable movement. Above the water level solu¬ tion is active, while below this level deposition frequently occurs. It is important to observe in this connection that the under¬ ground water level, in Central Florida, which has such a direct bearing on chemical deposition has not always remained the same. In former times when the surface stood at a higher level the water table was higher above sea than at present. In other words, a lowering of the general surface level by erosion was accompanied by a lowering of the water table. It thus happens that a locality which in one stage of physiographic development is favorable to the formation of phosphate rock, may in a subsequent stage, when 6b FLORIDA STATF GEOLOGICAL, SURVEY. conditions have changed, be favorable to the disintegration of these deposits. Moreover, any change in levels, either elevation or depression, affects the water level and hence modifies condi¬ tions. Such changes in elevation have undoubtedly occurred. For instance a rise ‘in elevation of 15 to 25 feet along the east side of Florida and a similar depression along the west coast as late as Pleistocene times is fairly well established. This, together with any further changes that occurred in the elevation of the peninsu¬ lar, must be taken into account in its bearing on the change of water level and the corresponding change in deposition, and dis¬ integration. It is not held that the accumulation of the rock in no case occurs above water level. In fact the secondary stalactitic deposits seen in many boulders evidently form as in caves above water level. The earth is a complex chemical laboratory in which chemical reactions take place in accordance with constantly changing conditions. THE FORMATION OF BOULDERS. The phosphate boulders have evidently been formed chemically through the agency of ground water. The boulders of silica are formed by a similar process by which silica taken into solution near the surface is redeposited at a greater depth. SILICA BOULDERS. Most of the flint or silica boulders were originally masses of limestone and still retain, in recognizable form, the shells and other fossils of which the limestone was originally composed. In these boulders the calcium carbonate has been replaced by silica. This process is common in nature. Petrification, another term for a similar process, is the slow removal in solution of the sub¬ stance of which an object is composed and its replacement by some other substance. In the case of petrified wood the wood has been removed and replaced by silica, calcium carbonate, iron car¬ bonate or whatever the petrifying agent may be. Silicified wood, silicified shells, silicified bone all refer to petrification in which silica was the petrifying agent. ORIGIN OR THE HARD ROCIC PHOSPHATES. G1 The boulders of silica are, therefore, masses of silicified lime¬ stone, the fossils originally present in the limestone having for the most part retained their form. PHOSPHATE BOULDERS. The phosphate boulders are formed either by replacement of the limestone or by precipitation from solution. PHOSPHATE BOULDERS FORMED BY THE REPLACEMENT PROCESS. Some of the phosphate boulders and pieces of rock are evi¬ dently formed by the replacement of the carbonate of the original limestone by phosphate. That this is true is proven by the fact that the shells and other fossils that made up the original lime¬ stone are sometimes well preserved, and from these shells it is possible to identify the particular formation from which the original limestone comes. Among the illustrations which accom¬ pany this paper will be found a photograph of a rock, which was originally pure limestone of the Vicksburg formation but is now changed, as shown by analysis, to a high grade phosphate. The shells and other fossils making up the limestone, which were originally calcareous, were subsequently phosphatized. Other¬ wise expressed, they have been petrified, phosphate being the petrifying agent. The collection of Dr. H. Bystra at Holder contains a piece of phosphate boulder, in which much larger shells are equally well preserved. While occasional phosphate boulders with fossils in a perfect condition of preservation are found as a rule the preservation of the fossils in the boulders is imperfect. It is probable, also, that in many boulders formed by replacement the fossils are entirely obliterated. PHOSPHATE BOULDERS FORMED BY PRECIPITATION. Many of the phosphate boulders are formed in part or entirely by precipitation of calcium phosphate from solution in water. This is probably the method of formation of the laminated boulders. It is probable that replacement and deposition from solution are both involved in the formation of many boulders. 62 FLORIDA STATE GEOLOGICAL SURVEY. SECONDARY DEPOSITION OF PHOSPHATE FROM SOLUTION. ■ In many boulders a secondary deposition from solution may be recognized. Practically all the laminated boulders show a rough mamilated or stalactitic undersurface of each lamina, while the top surface of the lamina next beneath show successive layers, separated by minute parting planes, indicating successive deposi¬ tion of phosphate from solution. This process is similar to that which takes place in caves where calcium carbonate is deposited to form stalactites and stalagmites, and is probably confined to boulders lying above the permanent ground water level. Many small pieces of rock were doubtless phosphatized without having assumed the boulder form. ORIGIN OF THE PLATE ROCK. The plate rock deposits represent a peculiar phase of the hard rock formation. It seems probable that the plate rock represents, in part at least, fragments of boulders that have disintegrated, as was suggested by Johnson in 1893. It has also been suggested that these plates may have been formed by finely' divided phos¬ phate mud settling as a sediment. As previously stated many of the boulders have a laminated structure. When such boulders disintegrate the laminae break up, giving rise to the flattened pieces to which the term plate rock is applied. In this connection it is interesting to observe that the plate rock occurs in those sections of the field in which the phosphate deposits now lie above the water level, and have been subjected to disintegrating influences. The plate rock deposits, as at Anthony and Sparr, form a comparatively thin cov¬ ering over the Vicksburg Limestone and represent, in the writer’s interpretation, the disintegrated remnant of an ordinary hard rock phosphate deposit. The gravel found mixed with the hard rock very possibly represents in part small bits of rock that have become phos¬ phatized and in part fragments of larger rocks. The soft phos¬ phate associated with the hard rock has very generally been ORIGIN OR THE HARD ROCK PHOSPHATES. Go regarded as resulting from the disintegration of the hard rock, although a part of the soft phosphate may be merely phosphatic clays. LOCALIZATION OF THE HARD ROCK DEPOSITS. The localized nature of the hard rock deposits within the formation is with little doubt explained by the variable character of the materials in which it occurs. As has been previously stated, the deposits of phosphate boulders are to some extent associated with local clay lenses. Such an association is a priori natural since clay interferes with the free circulation of the per¬ colating water. On the other hand, when the matrix is chiefly sands with uniform and open texture, through which the water moves readily, the conditions are not favorable for the chemical deposition of phosphate. However, occurrence of the rock can not be expected to follow too closely the structural conditions as now observed since, as has already been explained, the whole phos¬ phate producing section has been subjected to erosion by solution, which permitted irregular and intermittent local subsidence, thus thoroughly mixing the materials and moving them more or less from their original location. LIMITATION OF THE HARD ROCK PHOSPHATES. There yet remains the problem of the limitation of the hard rock phosphate to a particular and well recognized physiographic type of country. That the phosphate beds are so confined has long been apparent to those actively engaged in prospecting for and mining phosphate as well as to those who have investigated the deposits from a scientific standpoint. The accompanying map from the Fourth Annual Report of the Florida Geological Survey outlines in a general way the several physiographic types of the limestone section of Central Florida. In the light of what has previously been written, together with the legend, the map is largely self-explanatory. Four well defined physiographic types are recognized as follows : The Gulf Hammock Belt, The Hard 64 FLORIDA STATE GEOLOGICAL SURVEY. Rock Phosphate Belt, The Middle Florida Hammock Belt, and The Fake Region. Immediately adjacent to the Gulf coast, in northern Peninsular Florida and for a few miles inland, the limestone lies at or very close to the surface. The underground water level is near the surface, and numerous large springs of limestone water emerge from the rock and flow to the ocean. This coastal strip contains' numerous extensive calcareous hammocks and is known as the Gulf Hammock section of Florida. If formations later than the Oligocene limestones were formerly present over the Gulf Ham¬ mock area they have, with the exception of a slight residue of sand, disappeared. The Gulf Hammock section, west of Suwan¬ nee River, is underlaid by the Upper Oligocene limestones, while east of the Suwannee River the underlying formation is chiefly the Tower Oligocene limestone. Inland from the Gulf Hammock area, in Peninsular Florida, is found a strip of country over which formations of later age than the Tower Oligocene were clearly present in former times, although there now remains of these scarcely more than the mixed and complex residue. The strip of country of this type extends in well marked development from the southern part of Suwannee and Columbia Counties, roughly paralleling the Gulf coast to Hernando and Pasco Counties. This area includes the hard rock phosphate deposits, these deposits having accumulated by the processes elsewhere explained during the period of erosion through which this section has passed. Few lakes or streams are found in the hard rock phosphate belt, as the rainfall enters through the loose surface material and passes directly into the underlying limestone. The underground water level lies, as a rule, at a greater depth beneath the surface than in the Gulf Hammock country. Numerous sinks form, giving evidence of the continued active erosion by underground solution. The sur¬ face contour is rolling, there being no regularity of hills or valleys. Inland from the hard rock phosphate belt is found areas less affected by erosion, in which more or less of the formations that originally overlaid the Vicksburg Timestone may be identified in position. This type of country is known as the Middle Florida ~7. Pk - - .- -r. 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