Geology of the Charleston Phosphate Area, South Carolina GEOLOGICAL SURVEY BULLETIN 1079 Geology of the Charleston Phosphate Area, South Carolina By HAROLD E. MALDE GEOLOGICAL SURVEY BULLETIN 1079 A detailed study of the area from which phosphate rock was first produced in this country UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U.S. Geographical Survey Library has cataloged! this publication as follows: Malde, Harold Edwin, 1923- Geology of the Charleston phosphate area, South Carolina; a detailed study of the area from which phosphate rock was first produced in this country. Washington, U.S. Govt. Print. Off., 1959. v, 105 p. illus., maps, diagrs., profile, tables. 25 cm. (U. S. Geological Survey. Bulletin 1079) Part of illustrative matter folded in pocket. Bibliography: p. 96-101. 1. Geology South Carolina Charleston area. 2. Phosphates South Carolina. i. Title: Charleston phosphate area, South Caro­ lina. (Series) [QET5.B9 no. 1079] G S 59-214 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price $1.75 (paper cover) CONTENTS Page Abstract.___-_-----_--_----___-__-___---_-__-_--____----_-_----__ 1 Introduction______________________________________________________ 2 Stratigraphy. ____-_---_--_-_-___-_-_____-_-__----_-_-__-__-____-_- 5 General features_-_____--__________-_-_-__-__-_-___-____-___- 5 Oligocene series_______-_-__--_____-_-_-__--__-_----__________- 7 Cooper marl_______________________________________________ 7 Name_ ______________________________________________ 7 Distribution._________________________________________ 7 Structural attitude________.___-__----_-__-_--_-______- 8 Thickness. _____________________________ 8 Outcrop._____-_-------_-_-_-_-----_-_.__-_.-____-__ 8 Lithologic character___________________________________ 9 Stratigraphic relations_________________________________ 10 Mode of deposition___________________.________________ 12 Fauna. ______________________________________________ 13 Character of the fauna.____________________________ 13 Fossils from the Cooper marl and nodular phosphate rock..________________.__________ 13 Correlation of the fauna_______-_________________-__ 19 Pollen, spores, and marine microfossils, by Estella B. Leo­ pold. ____________________________. 22 Age___-_-_-___-.-_-.__._.-______________ 25 Miocene series________________________________________________ 26 Lower Miocene(?) deposits_____________-_--__-___-_--____ 26 Distribution and Stratigraphic relations________________ 26 Fauna and age_______________________________________ 26 Hawthorn formation______.________________________________ 27 Duplin marl______________________________________________ 28 Name__________________________________ 28 Distribution __ _ ______________________________________ 28 Lithologic character__________________________________ 29 Stratigraphic relations________________________________ 29 Fauna____________________________________ 31 New collections from South Carolina_______________ 31 Character and age of the fauna____________________ 33 Correlation of the Raysor and Goose Creek marls of former usage________________-_________-_-_---_--_--___-_ 33 Pliocene series______________________________________________ 34 Waccamaw formation______________________________________ 34 Distribution and Stratigraphic relations_________________ 34 A new locality near Charleston________________________ 35 in IV CONTENTS Stratigraphy Continued Page Pleistocene series._______________-__________-__-_-_--_---_-_--- 36 Ladson formation_____________-______--_-_-______-----_-- 36 Name, subdivisions, and type section.___________________ 36 Phosphate member______________-__-_______-__-_---_-_ 39 General features_______________-----_------------ 39 Distribution and outcrop_____-__-__-_--_----._----_- 39 Lithologic character____--__-__..---_---------_---- 41 Stratigraphic relations_________--____________-_---- 44 Fine-sand member.._______-___-_____-_-_--__-____-_- 46 Distribution and outcrop_____-____-_--__--_---__-_- 46 Lithologic character and stratigraphic relations________ 47 Medium-sand member___________-____-_____________-__ 47 Distribution and outcrop________________-__-_-__--_ 47 Lithologic character and stratigraphic relations........ 47 Coarse-sand member..______-____-_______--_-_----___ 48 Mode of deposition._________--________-_----_-__-_-_-- 48 Fauna___________________________________________ 49 Pollen, spores, and marine microfossils, by Estella B. Leo­ pold____________________...._____________ 49 Relation to coastal terraces____________-__-____-_--__--_ 53 Sand on Tenmile Hill. ________________________ 54 Distribution and topographic expression..________________ 54 Lithologic character and stratigraphic relations__________ 54 Mode of deposition and age___ __ _______________ 56 Pamlico formation_____________-__________-_______-_----__- 57 Name and distribution_____________-________---._--_- 57 Lithologic character and stratigraphic relations__________ 57 Fauna and age____________________---__-_-__.--------- 59 Terrace deposits along Goose Creek_________________________ 61 General features____________________--___.-_-. 61 Relative age_____________________________________ 61 Phosphate rock____________________________________________ 62 Chemical relation of phosphate rock and Cooper marl______________ 62 Origin of the nodular phosphate rock_____________-___-____-_-- 70 Production and reserves-.--_________________________________ 71 Soils__________________________________.______-- 73 Distribution. _______________________________________ 73 Types of soils._______ ______________________________ 74 Soil with red mottling__________________________________ 74 Representative pronle__________----__-__-__-_-_---_--_~ 74 Characteristics of the profile. ___________________________ 75 Soil with brown hardpan__-.________________________----__- 76 Soil in loose sand_______________________________________ 78 Soil in imperfectly drained sand________________ __________.. 79 Age of the soils__________________________________________ 79 Geologic history___________________________ __ ________ 82 Tertiary period_______________________________________ 82 Pleistocene epoch______________________________________ 83 Logs of auger holes bored in the Ladson quadrangle_____.__ _____ 84 Selected bibliography _______ _____________________________________ 96 Index_________________________________________ 103 CONTENTS ILLUSTRATIONS [Plates 1-5 are in pocket] PLATE 1. Geologic map of the Ladson quadrangle, South Carolina. 2. Diagram showing the stratigraphy, structural attitude, and thickness of the Cooper marl. 3. Diagram of the Duplin marl in South Carolina. 4. Correlation of beds along the line of the F. B. McDowell, Jr., Tunnel. 5. Isometric diagram showing members of the Ladson formation. 6. Pamlico formation exposed in wall of borrow pit west of Page Goodrich______________________________________Facing 58 7. Soil with red mottling_________________________.Following 74 8. Discontinuous boundary between pale-yellow sand and brown hardpan in a soil with red mottling_ ___________-Following 74 9. Section of red mottled zone in a weathering profile developed in the Ladson formation___________________...Following 74 10. Horizontal surface in a red mottled zone__________Following 74 FIGURE 1. Index map showing location of the Ladson quadrangle.______ 3 2. Correlation of the Tertiary formations of South Carolina.____ 6 3. Index map of fossil localities________________________-_-- 16 4. Diagram showing percent of pollen, spores, and microfossils in the Cooper marl_____________________________________ 24 5. Representative sections of the Ladson formation ____________ 38 6. Map showing the approximate original distribution of phos­ phate rock in South Carolina_______________________---_ 40 7. X-ray diff ractometer pattern of phosphatic material _________ 43 8. Diagram showing percent of pollen, spores, and microfossils in the Ladson formation__________________________ 50 9. Graph of lime and silica in the Cooper marl and phosphate rock___________________________________ 62 10. Triangular diagram showing the relative amounts of CaO, P2Os, and CO2 in Cooper marl and phosphate rock ______ 63 11. Triangular diagram showing the relative amounts of calcium phosphate, calcium fluoride, and the total carbonates in Cooper marl and phosphate rock________________________ 66 12. Amounts of P.OB, F, and CaO in phosphate rock of the Charles­ ton area compared to amounts in fluorapatite_____________ 68 13. Sketch of weathering profile in Ladson formation....________ 81 TABLES TABLE 1. Invertebrate megafossils from the Cooper marl and phosphate rock nodules_________________________________________ 14 2. Foraminifera from the Cooper marl_______________________ 17 3. List of d-spacings of phosphatic material____________________ 44 4. Chemical analyses of rockS-__________________-_-_--------- 64 5. Percent of calcium phosphate, calcium fluoride, calcite, and dolomite. ________________._-_______...___ 67 GEOLOGY OF THE CHARLESTON PHOSPHATE AREA, SOUTH CAROLINA By HAROLD E. MALDE ABSTRACT The Charleston phosphate area, part of a district from which phosphate was produced from 1867 to 1938, lies northwest of Charleston, S. C., between the Ashley and Cooper Rivers. The exposed rocks are marine and range in age from Oligocene to Pleistocene. Soils and swamp debris obscure much of the area.