Stratigraphy of Middle Tertiary Rocks in Part of West-Central Florida GEOLOGICAL SURVEY BULLETIN 1092 This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission Stratigraphy of Middle Tertiary Rocks in Part of West-Central Florida By WILFRED J. CARR and DOUGLAS C. ALVERSON GEOLOGICAL SURVEY BULLETIN 1092 _ This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission 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. Geological Survey Library has cataloged this publication as follows: Carr, Wilfred James, 1926- Stratigraj)hy of middle Tertiary rocks in part of west- central Florida, by Wilfred J. Carr and Douglas C. Alver- son. Washington, U.S. Govt. Print. Off., 1959. iv, 112 p. maps (3 fold, in pocket) diagrs., tables. 25 cm. (U.S. Geological Survey. Bulletin 1092) This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission. Bibliography: p. 69-71. 1. Geology Florida. 2. Geology, Stratigraphic Tertiary. 3. Bor­ ings Florida. i. Alverson, Douglas Creighton, 1931- joint author, n. Title. (Series) [QE75.B9 no. 1092] G S 59-231 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. Price $1.25 (paper cover) Abstract..:_ _ __._-_.___..__-_-__-_____------__-___-..-..--_--_--___- 1 Introduction._-_________-_-___-__-__--__-___-----_...-_--,-_---__-- 2 Purpose and extent of work._-____-__--___---___-___-_---_------ 2 Previous work.________________________________________________ 4 Physiography __._.,___-.__. _________-_L ________________________ 4 Acknowledgments _-___.._._______-__--______.___.,__-_____--____ 5 Laboratory work...____.____._______________-________________________ 5 Procedures-..____--_.__.______.______.____.._______._-_______ 6 Evaluation of results..____________________________..___^__-___._ 7 Stratigraphy. ____;__._____-______-_______-___-.._______-__ __________ 8 Eocene rocks_-__-__-_-__-_.--_-____-__--________--__--_---___ 8 Ocala limestone.____,_--___---___-__-.__-_-__-_--_----_-_-_ 8 Oligocene rocks___.____________________________._ _____--_____-_ 0 Suwannee limestone..._--__---___.______-_____,.._____-____ 9 1 Miocene rocks__ -_____.-..__._____..___;_..._.__.-__._____-__ 14 Tampa limestone.___-_-____--______-__--.____,_-___-______ 14 Hawthorn formation._____._.._.____.______._._._____.__.__ 33 Post-middle Miocene rocks.____ ____________.:__-_____^_______. 48 Bone Valley formation._._____._______.__,_____...____._.___ 48 x Undifferentiated Miocene and Pliocene rocks___._____.^_-_._ 49 Weathering.__^_.._,_______.___ _.____....___.___..____.___.__._____ 50 Suwannee limestone___.-___-._-_-_-.^-_-_-_.-___--_--._--_-- 51 Tampa limestone..-______--__-__-___-_._-_.-_____.-_-_-__.__-_ 51 Hawthorn formation.____________________v-----_-_----------_-- 54 Post-middle Miocene rocks.--_-_______-_--____-____--____^_-___ 55 Date of weathering.________.____________._______ __'.___.__.___.._ 55 Petrographic comparisons______.________________:__ __._____'-__-^-__ 56 Geologic history.-__--__--__-_____-_._^.. T _ T _._--.-_.._._---______.__ 58 % Structure. __________-_____-__-____-_.__,:____________-_ _________ 58 _0cala uplift and distribution of Miocene rocks___ _-___-___-___ 58 Faulting. _i_._._-__.__________________L__j._ _______ _____ ____ 59 . Contact between the Tampa limestone and. the Hawthorn for- . mation____________.__________________________r_________ 60 .Structural features of Miocene rocks______.._________ _________ 62 ^ Sedimentation__ .______.______ ____________._^________^___.__'____ 63 Suwannee limestone____________ ___.__________-___-_-____ 63 Tampa limestone. ____ ____- _ _.-_-__ __-___--_______----_---__ 63 t Hawthorn formation__________________________________.____ 64 Sand and clay of the Miocene.__-___---_________--__--__-_-_ 65 Summary of geologic history.__,^_..__._____________________________ 66 Economic geology.__--________--_________--_-______-_.--_______.__ 67 * Phosphate and uranium.________.__________________ __________-_ 67 Limestone and dolomite._-_____---_.__-_____._______--_-_-_---- 68 "* Literature cited_________.________________________________________ 69 Exposures of the Suwannee and Tampa limestones and the Hawthorn for­ mation. ________________________________________________________ 72 Lithologic logs of core holes__-...-__-__-________._____-___--._____-_ 91 Index._...__..__._..._.._.._....___._______.__.........___._.____ Ill * ni IV CONTENTS ILLUSTRATIONS [Plates are in pocket] PIRATE 1. Geologic map and sections of parts of Hillsborough, Pasco, and Polk Counties, Florida 2. Map of west-central Florida showing location of sections, test holes, and outcrops - --- - 3. Map of west-central Florida showing structure contours on the base of the Hawthorn formation and the thickness of the Tampa limestone ............... Page FIGURE 1. Index .map of peninsular Florida____________..___--__-___ 3 -2. Sections through core holes in Hillsborough County. _______ 11 - 3. Section through core holes in Polk and Pasco Counties ._-__,. 14 4. Typical cumulative curves of sand for Ocala, Suwannee, and -Tampa limestones and Hawthorn formation________.^_^ 15 ; 5. Frequency distribution of fifth percentile value and sorting > coefficient in samples of Suwannee and Tampa limestones and Hawthorn formation______________________________ 16 ! 6. Frequency distribution of median diameter, percent sand, and » percent total insoluble material in samples of Suwannee and Tampa limestones and Hawthorn formation __________ 17 - 7. Petrographic and lithologic log of Davison Chemical Corp. churn-drilled well, Polk County____^________-_____-__-_ 18 8. Ranges of petrographic characters of formations in Davison ^ Chemical Corp. well, Polk County_________-__________ 19 9. -Ternary diagram of soluble and insoluble constituents of limestone samples^_^_^----__-----------_--__---__---_- 20 10. Sketch map and section of Tampa limestone at locality 26___ 22 -} 11. Diagram showing the relation between the four divisions of the Hawthorn formation;__;_____.____________________ 34 12. Diagrammatic sketch showing stratigraphic relations at lo­ cality 83___ - _-----______-______-______ 41 1 13. Diagrammatic sketch showing stratigraphic relations at ^ locality 13____._______________________ 42 14. Diagrammatic sketch showing stratigraphic relations at lo­ cality 24____________________________ 45 15. Diagrammatic sketch showing stratigraphic relations at lo­ cality 6______________________________ 46 16. Sections through core holes in Hillsborough County. _____ 47 TABLES Page TABLE 1. Distribution of fossils in the Suwannee limestone._____-___--_ 12 2. Distribution of fossils in the Tampa limestone_______-_ __-- 26 3. Distribution of fossils in the Hawthorn formation___________ 37 4. Summary of medians of petrographic characteristics._________ 57 STRATIGRAPHY OF MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA By WILFRED J. GARB and DOUGLAS C. ALVERSON ABSTRACT Petrographic studies of the Suwannee limestone (Oligocene), Tampa limestone (lower Miocene), and Hawthorn formation (middle Miocene) yielded data that are useful for correlation in a region where weathering has thoroughly altered, the rocks. Mechanical analysis of sand aided in the recognition of formations in weathered exposures. An efficient laboratory method for insoluble-residue and mechanical analysis of sand was developed. Preliminary work indicates that the kind and distribution of heavy minerals, clay minerals, and chert should also be valuable in any further stratigraphic studies of this area. Mapping of rocks of Oligocene and Miocene age in Hillsborough, Pasco, and Polk Counties has extended the known limits of the Tampa limestone northeast­ ward; some of the sand and clay previously mapped.as Hawthorn formation in northeastern Pasco County belongs to the Tampa. Sand of the Hawthorn formation is coarser than that of the Tampa, limestone. Although phosphate nodules are not normally present in the Tampa, they are abundant in places, particularly in Polk County. A contact between calcareous and noncalcareousparts of the Hawthorn was mapped in northern Hillsborough and Polk Counties. More than 50 new localities were examined. Structure contours on the base of the Hawthorn formation, and other evidence from well logs and surface exposures suggest an unconformity between the Tampa limestone and Hawthorn formation. A fault that brings rocks of Eocene age adjacent to the Suwannee and Tampa limestones is believed present in north­ western Polk County. The Suwannee limestone appears to be absent east of this structure. .-.. - . Weathering in this part of Florida results in local concentration of iron, phos­ phorus, alumina, and silica. Secondary chert and aluminum phosphate zones form where the parent material is favorable. Leaching forms a weathering profile of increasing solubility downwards, which typically contains,. from top to bottom, quartz sand, iron-stained clayey sand with chert'and iron and phos- phatic hardpans, blue-green sandy clay with local calcium phosphate nodules, and a thin zone of slightly calcareous clay passing abruptly into limestone. The presence of a substantial amount of secondary chert in a weathered section .is believed to be evidence that limestone was formerly