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Bureau of Mines Information Circular/1985 
 
 Phosphate Resource Potential for Borehole 
 Mining in the Southeastern Coastal Plain 
 
 By George H. Popper, Douglas J. Godesky, and James J. Giambra 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 75 
 
 ^/NES 75TH Atv^ 
 
 ma 
 
Information Circular 9043 
 
 Phosphate Resource Potential for Borehole 
 Mining in the Southeastern Coastal Plain 
 
 By George H. Popper, Douglas J. Godesky, and James J. Giambra 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 Donald Paul Model, Secretary 
 
 BUREAU OF MINES 
 Robert C. Morton, Director 
 
■M-f0't3 
 
 Library of Congiess Cataloging in Publication Data: 
 
 Popper, George H 
 
 Phosphate resource potential for borehole mining in the southeast- 
 ern coastal plain. 
 
 (Information circular ; 9043) 
 
 Bibliography: p. 14-15. 
 
 Supt. of Docs, no.: I 28.27: 9043. 
 
 1. Phosphates— Southeastern States. 2. Boring. 3. Coasts— South- 
 eastern States. I. Godesky, Douglas J. II. Giambra, James J. III. 
 Title. IV. Series: Information circular (United States. Bureau of 
 Mines) ; 9043. 
 
 'm2t5T4J4.^, [TN913] 622s [553.6'4] 84-600385 
 
;ONTENTS 
 
 Abstract • 
 
 Introduction 
 
 Acknowledgments • 
 
 Borehole mining < 
 
 Borehole mining system 
 
 Deposits suitable for borehole mining , 
 
 Environmental considerations , 
 
 Geology 
 
 Geologic history and phosphate genesis 
 
 Lithology 
 
 Resource data 
 
 Areal extent 
 
 Regional variability 
 
 Overburden , 
 
 Ore zone thickness , 
 
 Grade 
 
 Reserves-resources 
 
 Evaluation method 
 
 Resource estimate 
 
 Potential phosphate rock, product , 
 
 Conclusions 
 
 References 
 
 Bibliography 
 
 Appendix A. — Mining and benef iciation parameters 
 
 Appendix B. — General resource data 
 
 ILLUSTRATIONS 
 
 1. Study area, Southeastern Coastal Plain , 
 
 2. Borehole mining system , 
 
 3. Ancient environments of phosphate deposition , 
 
 4. Depositional basins of Southeastern Coastal Plain , 
 
 5. Isopach map, Hawthorn Formation in Florida , 
 
 6. Isopach map, Pungo River Formation in North Carolina..., 
 
 7. Classification system of mineral reserves and resources, 
 
 TABLES 
 
 1. Borehole mining phosphate resource potential , 
 
 B-1. Resource characteristics of identified deposit zones..., 
 B-2. Extent of environmentally sensitive areas , 
 
 Page 
 
 1 
 
 2 
 
 3 
 
 3 
 
 3 
 
 4 
 
 5 
 
 6 
 
 6 
 
 6 
 
 9 
 
 9 
 
 9 
 
 10 
 
 10 
 
 10 
 
 11 
 
 11 
 
 12 
 
 13 
 
 14 
 
 14 
 
 15 
 
 19 
 
 20 
 
 2 
 
 4 
 
 7 
 
 8 
 
 12 
 
 12 
 
 13 
 
 13 
 
 20 
 20 
 
- 
 
 UNIT OF MEASURE ABBREVIATIONS USED IN 
 
 THIS REPORT 
 
 g/cm^ 
 
 gram per cubic centimeter mi 
 
 mile 
 
 ha 
 
 hectare mt 
 
 metric ton 
 
 km 
 
 kilometer mtph 
 
 metric ton per hour 
 
 m 
 
 meter pet 
 
 percent 
 
 I 
 
PHOSPHATE RESOURCE POTENTIAL FOR BOREHOLE MINING 
 IN THE SOUTHEASTERN COASTAL PLAIN 
 
 By George H. Popper, Douglas J. Godesky, and James J. Giambra 
 
 ABSTRACT 
 
 The Bureau of Mines has evaluated the extent of phosphate resources 
 available for recovery by the experimental borehole mining method in 
 the Southeastern Coastal Plain of the United States. Phosphate re- 
 sources at overburden depths greater than 30 m are as a rule currently 
 unsuitable for recovery through conventional mining methods because of 
 economic, environmental, or technical considerations. In the identi- 
 fied deposit areas, borehole mining operations are projected to yield a 
 more favorable rate of return and to be environmentally more desirable 
 than conventional surface mining. Borehole mining resource estimates 
 presented in this study are preliminary and designed to serve as a ba- 
 sis for future resource evaluations, as the current data base is rela- 
 tively sparse and incomplete. The resulting resources have, therefore, 
 been classified as hypothetical and speculative and are subject to up- 
 dating as additional exploratory data become available. 
 
 Hypothetical and speculative resources amenable to borehole raining 
 are estimated to total about 385 billion metric tons (mt) of phosphate 
 matrix with a minimum in situ grade of 5 pet P2^5' With projected 
 borehole mining capabilities and current conventional benef iciation 
 procedures, this resource would make available approximately 64 billion 
 mt of phosphate rock product at an estimated grade of 30 pet P20 5* 
 
 ^Physical scientist, former Eastern Field Operations Center, Bureau of Mines, 
 Pittsburgh, PA (now with Office of Surface Mining, Reclamation and Enforcement, 
 Pittsburgh, PA) . 
 
 ^Geologist (now consulting geologist, Lewiston, ME). 
 
INTRODUCTION 
 
 This Bureau of Mines study is a prelim- 
 inary evaluation of the resource poten- 
 tial of deep bedded, on-shore phosphate 
 deposits projected to be suitable for 
 borehole mining. Most of these resources 
 are not commercially recoverable under 
 current mining and economic conditions. 
 However, as a result of diminution of 
 easily mined, near-surface resources, as 
 well as an increase in environmental con- 
 straints, a need was recognized to iden- 
 tify and evaluate deep-bedded phosphate 
 deposits; these deposits may be suitable 
 for recovery in the future using a com- 
 mercial borehole mining system. 
 
 The area of study comprises the South- 
 eastern Coastal Plain of the United 
 States as illustrated in figure 1. The 
 study area includes the on-shore deposits 
 of the Atlantic and Gulf Coastal Plains. 
 Because of the exceptionally large size 
 of the study area, limited amount of data 
 
 / iJomes 
 
 ) Petersburg ^^^^^..^^^f^n^ 
 
 /Virginia J^S^^^^-J^ ■ ^^^r 
 /_____ .i--^"^ f?>^^ ftf^ AlbermoMe Sound 
 
 ^^Cofie Hatteros 
 
 / Raleigh uy^ — 
 
 /^\ 'fiver 
 
 y North ^ / I'e^-^^'—^Xv,/ 
 
 .y^ Carolina v ^ / <:, '^ ^'•''"Z^ 
 
 ( ^ 'vC^ ^i/-"^ Cape Lookout 
 
 -■r- ' South Va^"? 
 C,_ Carolina <<V \\ 
 i j \ Columbia__t^ ^ 
 
 \ Georgia ^-^ /' '^ JiU'e, 
 
 \ / Augusla^i! ^ ^\ief 
 
 V ^ t^^H". •/- 
 
 M ,. y XO ^\% ^Charleston 
 
 i Macon f , o~^ M% "^ 
 
 Columbus (^\^ama^(, • Savannah 
 
 ■ ■ ' •. Jacksonville 
 
 Tallahassee ■ 
 
 Wilmington 
 Cope Fear 
 
 Atlantic Ocean 
 
 • Palm Beach 
 
 • Miami 60 120 mi 
 I h h 
 
 100 200 km 
 Scale 
 
 FIGURE 1. - Study Area, Southeastern Coastal Plain. 
 
 available on deep-bedded phosphates, and 
 the synthesis of current authoritative 
 interpretations of the data, the result- 
 ing tonnage estimates have been catego- 
 rized as hypothetical and speculative re- 
 sources. The distribution and estimated 
 tonnages of phosphate resources should 
 therefore be used as a basis for further 
 refined exploration and evaluation of 
 borehole minable deposits rather than as 
 a conclusive and final evaluation. 
 
 Previous investigations by the Bureau 
 have indicated that the experimental 
 borehole mining system should prove to be 
 an economically and environmentally at- 
 tractive method of recovering commercial 
 quantities of phosphate under certain 
 conditions (9).^ The principal condition 
 being that the phosphate deposit occurs 
 at a depth too great to be considered 
 economically recoverable by conventional 
 mining and existing technology. An addi- 
 tional attribute of borehole mining is 
 that it can be employed in areas where 
 conventional surface mining would be aes- 
 thetically or otherwise objectionable. 
 
 The feasibility of the borehole mining 
 system for recovering phosphate ore (ma- 
 trix) was field tested under a Bureau 
 contract (16). In the initial tests, 
 about 1,500 mt of matrix was recovered at 
 an overburden depth of 75 m. A prototype 
 borehole mining system, designed as part 
 of the contract, is the basis for the 
 borehole mining parameters used in the 
 present study. Although the prototype 
 system has not yet been built or tested, 
 the use of these design specifications 
 and parameters provides a preliminary 
 method for projecting actual mining re- 
 sults and resource recovery. Any inter- 
 pretation of mining and resource data 
 from this study should be utilized in 
 this context. 
 
 Test results of a conventional benefi- 
 ciation process to concentrate phosphate 
 matrix mined by borehole methods were 
 used to estimate the tonnage of potential 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references 
 preceding the bibliography. 
 
phosphate product. Matrix is the natural 
 occurrence of unbenef iciated phosphate 
 ore. It consists of the calcium phos- 
 phate mineral apatite with quartz, cal- 
 cite, and dolomite; clay and iron oxide 
 minerals comprise the gangue within the 
 matrix (_5) • Washing and double-stage 
 flotation are proposed to produce a mar- 
 ketable phosphate rock product. 
 
 The phosphate resource estimate pre- 
 sented in this report is based upon an 
 analysis and extrapolation of public, in- 
 dividual, and industry data. The data 
 base is relatively sparse and its quality 
 variable. An extensive bibliography is 
 included to serve as a source of current 
 phosphate resource information for the 
 Southeastern Coastal Plain and reflects 
 
 much of the background data and research 
 used in this study. 
 
 The location and configuration of an- 
 cient phosphate depositional environ- 
 
 ments were considered 
 factors controlling 
 of existing deposits, 
 were delineated and 
 thicknesses, grades, 
 signed to each area. 
 
 to be the primary 
 
 the distribution 
 
 Paleoenvironments 
 
 average deposit 
 
 and densities as- 
 
 Site-specif ic drill 
 
 hole data were utilized but are not pre- 
 sented here because their inclusion would 
 not be correlatable with the area deter- 
 minations as often the drilling record 
 was incomplete and extrapolation was nec- 
 essary. Resource calculations and esti- 
 mates were then made for three major 
 areas of phosphate deposition. 
 
 ACKNOWLEDGMENTS 
 
 Grateful acknowledgement is made to the 
 following individuals for their contribu- 
 tions of data and access to information, 
 which made this study possible: J. P. 
 Bernardi, exploration manager. Interna- 
 tional Minerals and Chemical Corp. , Bar- 
 tow, FL; R. C. Fountain, geological con- 
 sultant. Winter Haven, FL; H. Gill and 
 M. Hacke, U.S. Geological Survey, Dora- 
 ville, GA; R. B. Hall, Gardinier Corp., 
 Fort Meade, FL; V. J. Henry, chairman. 
 
 Geology Department, Georgia State Univer- 
 sity; Atlanta, GA; P. Huddleston, geolo- 
 gist, Georgia Geological Survey, Atlanta, 
 GA; J. A. Miller, U.S. Geological Sur- 
 vey, Atlanta, GA; S. R. Riggs, geologist. 
 Department of Geology, East Carolina 
 University, Greenville, NC; and T. M. 
 Scott, geologist, Florida Bureau of Geol- 
 ogy, Tallahassee, FL. The final opinions 
 and conclusibns expressed here, however, 
 only represent those of the authors. 
 
 BOREHOLE MINING 
 
 BOREHOLE MINING SYSTEM 
 
 Borehole mining is an experimental 
 method of mining that employs highly 
 pressurized water to form an ore slurry 
 at depth. To date, field tests have been 
 successful and additional industry pilot- 
 scale work is planned. Through use of 
 this technique, phosphate matrix can 
 be recovered from deep horizons with- 
 out requiring the removal of overbur- 
 den. The experimental borehole mining 
 system, as illustrated in figure 2, may 
 be carried out under either open- or 
 f looded-cavity conditions. In the pro- 
 posed borehole raining system, a borehole 
 mining tool is lowered to the phos- 
 phate horizon through a predrilled steel- 
 cased borehole. A rotating water jet on 
 
 the tool disaggregates the phosphate ma- 
 trix while a jet pump at the lower end of 
 the tool pumps the resulting slurry to 
 the surface. The slurry is then trans- 
 ported to a benef iciation plant by pipe- 
 line. The resulting cavity is backfilled 
 with waste material (tailings) from the 
 plant. 
 
 Application of the borehole raining sys- 
 tem is not limited by matrix depth (9). 
 Initial tests indicate that although 
 slurry recovery rates vary, 4 5 mtph of 
 matrix is a reasonable estimate of a com- 
 mercially obtainable mining rate. For 
 this evaluation, overall mining recovery 
 is estimated to be 66 pet. These figures 
 may vary depending upon site-specific 
 conditions, modifications in mining tech- 
 niques, or results of future tests. 
 
Beneficiation 
 plant 
 
 Tailings return 
 to backfill 
 
 Backfilled 
 material 
 (tailings) 
 
 FIGURE 2. - Borehole mining system. {Courtesy Flow Industries, Inc.) 
 
 Drilling and mining would be conducted 
 on a staggered grid pattern. The re- 
 sulting cavities are expected to be 
 bowl-shaped and about 18 m in diameter. 
 A spacing of approximately 21 m between 
 boreholes would leave a final barrier of 
 3 m between mined-out cavities. Antici- 
 pated borehole mining unit specifications 
 and operating parameters are summarized 
 in appendix A. 
 
 DEPOSITS SUITABLE FOR BOREHOLE MINING 
 
 Initial tests conducted for the Bu- 
 reau indicated that relatively competent 
 strata must immediately overlie phosphate 
 matrix in order to carry out successful 
 borehole mining under open-cavity condi- 
 tions. This was thought necessary in 
 order to avoid cavity collapse. Results 
 
 of subsequent tests suggested that it may 
 be possible to mine deposits where only 
 minimal lithologic differences exist 
 between the ore zone and the overburden 
 provided that the operation is carried 
 out under f looded-cavity conditions. 
 Some contrast in lithology must exist be- 
 tween the matrix and the overburden in 
 order to afford a bearing surface for the 
 water in the cavity. 
 
 Cavity roof conditions in the resource 
 areas identified were not determined as 
 part of this study. Future exploration 
 and tests may determine that some areas 
 must be deleted from the identified 
 resource areas if overburden conditions 
 are such that borehole mining would not 
 be successful. Site-specific tests will 
 have to be made to determine each depos- 
 it's suitability for borehole mining. 
 
Primary phosphate deposits, deposits 
 in which no appreciable reworking or 
 leaching have taken place, are more suit- 
 able for mining by the borehole method 
 than those in which secondary reworking 
 has taken place. Primary deposits tend 
 to be consistent in thickness and uniform 
 in the quality and distribution of the 
 matrix; these factors facilitate explora- 
 tion and make mining easier to plan. 
 
 When mining at depths shallower than 
 30 ra, conventional mining methods are es- 
 timated to yield higher rates of return; 
 at depths of 45 m and greater, it is an- 
 ticipated that borehole mining would be 
 the more economical method (_9 ) . In addi- 
 tion, the borehole technique is environ- 
 mentally less disruptive at all depths. 
 The rate-of-return threshold between con- 
 ventional and borehole raining, where 
 borehole mining is projected to yield a 
 higher rate of return, is estimated to 
 occur between 30 and 4 5m. The present 
 study evaluates the resource potential of 
 phosphate deposits at overburden depths 
 of at least 30 m. A precise deposit 
 depth at which conventional mining sys- 
 tems become economically inferior or 
 technically unfeasible has not been de- 
 termined for the deposits of this large 
 study area. A determination of that na- 
 ture would vary between mining zones and 
 conditions within the coastal plain, but 
 will most likely occur between 30 and 
 4 5 m. 
 
 ENVIRONMENTAL CONSIDERATIONS 
 
 The borehole mining system would elimi- 
 nate the need for the removal of overbur- 
 den. Site cleanup, revegetation, and 
 cavity backfilling are the only reclama- 
 tion procedures required. 
 
 In using the borehole mining system, 
 benef iciation waste is backfilled into 
 mined-out cavities and thus long-term 
 aboveground waste storage is avoided. 
 Water used in borehole raining and benefi- 
 ciation is recirculated within the sys- 
 tem. Initial tests suggest also that 
 ground water drawdown and surface subsi- 
 dence would be minimal or insignificant 
 
 (16). Applications of borehole raining in 
 areas of relatively shallow overburden 
 may have raore profound environmental 
 effects. 
 
 Borehole mining in the Southeastern 
 Coastal Plain would be directed toward 
 recovering phosphate from the Miocene 
 Hawthorn and Pungo River Formations. The 
 Hawthorn is underlain in many areas by a 
 thick section of carbonate rocks that 
 constitute the principal aquifer. Mining 
 of the basal Hawthorn Formation would 
 therefore have to be done along with mon- 
 itoring of any underlying aquifer (19). 
 
 A major regional source of ground wa- 
 ter for the study area is the Coastal 
 Plain aquifer, formed by limestones that 
 dip gently seaward and are covered by 
 imperraeable Miocene clays (1). Ground 
 water is not normally free to move 
 vertically through an aquiclude that con- 
 fines a ground water system. A clay 
 aquiclude 7 to 11m thick underlies the 
 Upper Miocene phosphate matrix found 
 southeast of Savannah, GA; the clay is 
 believed to be capable of locally pro- 
 tecting that aquifer from deleterious 
 effects of mining in that region (1). 
 Such favorable determinations would be 
 required in other deposit areas prior to 
 the initiation of any commercial mining 
 operations. 
 
 Borehole mining may not be possible or 
 desirable in areas such as barrier is- 
 lands, tidal marshes, flood plains, and 
 wildlife refuges, where environmental 
 damage can be severe or industrial usage 
 undesirable. In addition, urban areas, 
 military bases, major water areas, and 
 State and Federal forests are not consid- 
 ered likely mining zones because of land- 
 use conflicts. In order to get a more 
 reliable resource estimation, such areas 
 were deleted from the resource calcula- 
 tions wherever possible. Approximately 
 1.9 million ha was deleted from the ini- 
 tial resource area. An estimate of the 
 areas susceptible to environmental dam- 
 age or land-use controversy within the 
 identified deposit zones is given in 
 appendix B. 
 
GEOLOGY 
 
 GEOLOGIC HISTORY AND PHOSPHATE GENESIS 
 
 The Southeastern Coastal Plain of the 
 United States was the site of widespread 
 phosphate deposition during the Miocene. 
 Phosphate was deposited discontinuously 
 from Virginia to southern Florida on a 
 shallow marine shelf of low relief. Re- 
 sulting phosphate deposits occur in the 
 Miocene Hawthorn, Pungo River, and corre- 
 lative formations. Subsequent to deposi- 
 tion, there was little modification of 
 the Miocene sequence other than minor 
 ground water and sink hole development; 
 structural deformation was minimal (14) . 
 
 The deposition and distribution of 
 phosphate along the Atlantic Coastal 
 Plain was controlled by the availabil- 
 ity of phosphate from deep ocean cur- 
 rents, glacially and tectonically pro- 
 duced fluctuations in sea level, and the 
 paleogeomorphic setting ( 13 , 1 5) . Sig- 
 nificant precipitation and accumulation 
 of sedimentary phosphorites took place 
 only under appropriate combinations of 
 this complex set of tectonic and environ- 
 mental variables ( 14 ) . 
 
 Deposition was locally cyclic in na- 
 ture and attributable to the following 
 sequence of events. As a result of nor- 
 mal marine circulation, cold waters, en- 
 riched with phosphate from both organic 
 and inorganic sources, upwelled against 
 the eastern coastal margins. Longshore 
 currents transported the cold phosphate- 
 enriched waters southward along the 
 ancient coastline. Material deposited 
 during this time consisted primarily of 
 terrigeneous matter with subordinate 
 amounts of phosphate; resultant phosphate 
 concentrations are thin and of low grade. 
 As glaciers melted and the sea level 
 rose, cold, deep waters transgressed lo- 
 cal portions of the Atlantic coastal 
 shelf. Where these currents encoun- 
 tered topographically raised areas, sig- 
 nificant concentrations of phosphate 
 were deposited in the warmer shallower 
 waters. Phosphate accumulated in coastal 
 basins adjacent to the ancient topo- 
 graphic highs. Units resulting from 
 these conditions consist predominantly 
 
 of phosphate with terrigeneous material 
 subordinate. 
 
 As sea level continued to rise, the 
 axis of the ancient Gulf Stream veered 
 westward. Portions of the shelf were 
 thus flooded with warm Gulf Stream wa- 
 ters. As the cold, upwelling, phosphate- 
 producing environments were destroyed, a 
 discontinuous carbonate caprock was de- 
 posited instead. With the onset and de- 
 velopment of a new glacial period or tec- 
 tonic event, sea level fell and erosion 
 proceeded to remove portions or, in some 
 cases, even the entire thickness of the 
 previously deposited units (13). 
 
 The shape of the phosphate deposits in 
 the Southeastern Coastal Plain is direct- 
 ly related to the geomorphology at the 
 time of deposition. The troughs in which 
 the phosphate was deposited characteris- 
 tically were linear depressions or en- 
 trapment basins adjacent to associated 
 topographic highs (14). Phosphate depos- 
 its in these zones are thin along the 
 flanks of the arches and thicker toward 
 the axis of the trough. The ancient top- 
 ographic highs tend to be oriented either 
 northwest or northeast and are present 
 throughout the length of the phosphate 
 province. The phosphate-forming environ- 
 ments of the Southeastern Coastal Plain 
 are illustrated in figure 3. The struc- 
 tural controls are also shown. These 
 ancient features all influenced the pat- 
 terns of phosphate distribution by con- 
 trolling the formation and regional accu- 
 mulation of Miocene phosphorite. 
 
 LITHOLOGY 
 
 Phosphate occurs in the Southeastern 
 Coastal Plain as phosphorite, a sedimen- 
 tary rock containing at least 5 pet P2O5 
 (14). Phosphorites are composed in part 
 of phosphate particles that may range 
 from pebble to clay size. Generally, 
 phosphatic particles are associated with 
 quartz grains, carbonate grains, or clay 
 minerals. The phosphorite may be in- 
 terbedded with quartz sands, dolomite, 
 magnesium-rich clays, or diatomite. 
 
^^v^ 
 
 Mioce ne U pland 
 
 LEGEND 
 
 Areas suitable for borehole mining 
 Hawthorn- Pungo River 
 Formations - deep environment 
 
 Hawthorn -Pungo River 
 Formations- intermediate 
 environment 
 
 Howthorn -Pungo River 
 Formations- shallow 
 environment 
 
 Areas unsuitable for borehole mining 
 Phosphatic horizons 
 J absent, shallow, or discontinuous 
 
 Miocene Upland 
 
 ,--' Limit of borehole minability 
 
 ij_ Structure contours on the base 
 of the Hawthorn Formation, 
 depth in meters 
 
 40 80 
 
 1 ' ' 'i ' ' ^^-^-^ 
 100 
 
 Scale 
 
 120 
 
 -1 i_ ^ 
 
 mi 
 
 200 km 
 
 FIGURE 3. 
 14 and 11;. 
 
 Ancient environments of phosphate deposition (modified from references 
 
1 
 
 Aurora 
 Embayment 
 
 LEGEND 
 
 - Form lines, define the 
 shape of the ancient 
 basins. 
 
 1 
 
 200 km 
 
 South Florida 
 Embayment 
 
 FIGURE 4. 
 14 and 11). 
 
 Depositionol basins of Southeastern Coastal Plain (modified from references 
 
RESOURCE DATA 
 
 AREAL EXTENT 
 
 Phosphate occurs in Miocene strata 
 throughout the entire Southeastern Coast- 
 al Plain. Those strata having the great- 
 est resource potential for borehole 
 mining occur from northeastern North Car- 
 olina to southern Florida; they are 
 termed the Pungo River Formation in North 
 Carolina and the Hawthorn Formation in 
 South Carolina, Georgia, and Florida. 
 
 The delineation of phosphate deposits 
 of sufficient concentration, occurring at 
 depths of at least 30 m, has resulted in 
 the identification of three major deposi- 
 tional regions. These are illustrated in 
 figure 4. The primary regions for bore- 
 hole minable deposits are the Aurora Em- 
 bayment of North Carolina, a region lo- 
 cated eastward and downdip of the current 
 North Carolina phosphate fields; the 
 Southeast Georgia Embayment in Georgia 
 plus the Jacksonville Basin and St. Johns 
 Platform of northeastern Florida; and the 
 Central Florida Platform, Brevard Plat- 
 form, Osceola Basin, and Okeechobee Basin 
 of southeastern and central Florida. In 
 this report, these areas are respectively 
 designated as eastern North Carolina, 
 Southeast Georgia Embayment, and southern 
 Florida. 
 
 An area of about 7.1 million ha is un- 
 derlain by matrix considered suitable for 
 borehole mining. The extent of favorable 
 matrix within each area is presented in 
 appendix B. Specific exploratory data 
 that are the basis for the delineation of 
 the deposits and region boundaries range 
 from locally dense and reliable to sparse 
 and interpretive. Specific drilling, 
 mapping, geologic, and other explora- 
 tory data cannot be presented in a quan- 
 titative way in order to duplicate the 
 resource conclusions without the qualify- 
 ing interpretations by authorities on the 
 particular data. 
 
 Within each depositional region, indi- 
 vidual phosphate beds may not be contin- 
 uous over the entire area, yet suitable 
 matrix is assumed to exist throughout 
 each depositional environment. Specific 
 locations within a region may exhibit 
 multiple beds of matrix, whereas others 
 
 may contain only a single bed or no 
 matrix. The estimated average matrix 
 thicknesses presented are representative 
 of total combined beds, and published re- 
 gional interpretations and summary data. 
 The matrix thickness should not be misin- 
 terpreted to indicate blanket deposition 
 or deposits. 
 
 The potential for suitable phosphate 
 deposits north of Alberraarle Sound, NC, 
 was discounted because of the low phos- 
 phate and high glauconite content that 
 characterize the units of that area. 
 Miocene strata of southwestern Georgia 
 are probably not suitable as a potential 
 resource because of their low phosphate 
 content. Hard-rock phosphate deposits 
 overlying the Ocala Arch' in Florida are 
 too shallow and discontinuous. 
 
 No determination was made for the 
 region south of Lake Okeechobee, FL, 
 because reliable data on phosphate 
 bearing horizons in this area are not 
 available. Deep-bedded phosphate is al- 
 so reported to occur in small deposits 
 outside of the identified zones, but 
 data are sparse and the phosphorite is 
 thought to be of limited lateral extent 
 (Z). 
 
 REGIONAL VARIABILITY 
 
 Phosphate-bearing strata exhibit a re- 
 gional variability along the length of 
 the Southeastern Coastal Plain. The Mio- 
 cene section tends to thicken and deepen 
 eastward in North Carolina, Georgia, and 
 northern Florida; in southern Florida 
 the section becomes thicker and deeper 
 southward. 
 
 Generally, the percentage of carbonate 
 units increases southward toward southern 
 Florida where they represent the dominant 
 lithology. By contrast, the clastic 
 material content, mostly terrigeneous 
 sands, increases northward and consti- 
 tutes the dominant lithology in North 
 Carolina. Carbonates, however, are also 
 present in North Carolina where they 
 occur principally as caprock horizons 
 within the terrigeneous sequence. 
 
 Diatom content increases northward. 
 Glauconite appears in the Pungo River 
 
10 
 
 Formation and increases northward until 
 it becomes a major component of strata 
 north of Albemarle Sound, NC. 
 
 Near the ancient topographic highs or 
 ancient shore lines, the phosphorite is 
 characterized by erratic areal distri- 
 bution and a high P2O5 content. In the 
 deeper depositional environments, al- 
 though the phosphorite is thicker, the 
 P2O5 content of the pellets is lower, the 
 magnesium content is greater, and the 
 average grain size is smaller. The phos- 
 phorites in downdip areas have not been 
 modified by supergene weathering and 
 consequently have not been chemically 
 upgraded (14). Dolomite content tends 
 to increase toward the deeper portions 
 of the depositional basins; the equiva- 
 lent facies in shallow water consist of 
 magnesium-rich clays. 
 
 Phosphate differs in character across 
 the Southeast Georgia Embayment. Depos- 
 its of the Savannah area are similar to 
 those of North Carolina but distinctly 
 different from concentrations along the 
 west and south margins of the embayment 
 in south Georgia (6). Phosphate of the 
 Savannah area is characterized by dark 
 color, low pebble content, and high iron 
 and aluminum content. 
 
 In Florida, the southern extension of 
 the Central District contains vast re- 
 serves of relatively low P2O5 grade mate- 
 rial, contained predominantly within an 
 upper clastic section of the Hawthorn 
 Formation (8). In addition, the MgO con- 
 tent is relatively high. In this area 
 the clastic phosphorite overall grain 
 size decreases southward as the distance 
 from the source area increases. As with 
 most of the resource areas, the phospho- 
 rite beds of the Hawthorn in southern 
 Florida vary significantly in thickness 
 and distribution, and change facies rap- 
 idly both vertically and laterally, yet 
 the total upper clastic section has suf- 
 ficient vertical and horizontal continu- 
 ity to be considered a single unit (2). 
 
 OVERBURDEN 
 
 Formation and related matrix averages 
 over 30 m deep (4_) . No attempt was made 
 to determine the viability of the over- 
 burden for cavity support as this re- 
 quires site-specific evaluation. Initial 
 testing of the borehole mining system 
 indicated that mining must be conducted 
 in a flooded cavity in order to avoid 
 caving. Some contrast in lithology must 
 exist between the ore zone and over- 
 burden in order to afford a bearing sur- 
 face for the pressurized water in the 
 cavity. 
 
 ORE ZONE THICKNESS 
 
 Borehole mining may be applied to 
 ore zones as thin as 0.33 m; in this 
 study, all identified matrix was at least 
 0.33 m thick. Phosphorite zones gener- 
 ally range in thickness from about 0.33 
 to 6 m; in some instances they are 15 m 
 thick, rarely do they exceed 30 m (14). 
 Representative thicknesses are given in 
 appendix B for each depositional environ- 
 ment within a basin. 
 
 GRADE 
 
 A P2O5 content of 5 pcf^ was considered 
 the minimum grade necessary for a phos- 
 phatic bed to be classified as a po- 
 tentially minable zone of matrix. An 
 estimated average of 10 pet P2O5 was used 
 for the calculation of potential product 
 tonnages. Matrix currently being mined 
 in Florida has a feed grade of 10 to 
 15 pet P2O5 (20). 
 
 It is anticipated that the MgO content 
 of the matrix recovered in much of the 
 resource area will be higher than the 
 levels in matrix currently being recov- 
 ered in Florida and North Carolina. A 
 high-MgO content is primarily attribut- 
 able to the presence of dolomite grains 
 in the matrix. The inclusion of MgO in 
 phosphate flotation concentrate creates 
 problems during the production of phos- 
 phoric acid and other products. Most of 
 the remaining near-surface deposits in 
 
 In all cases , depth to the ore zones 
 evaluated in the present study is at 
 least 30 m. The maximum overburden depth 
 is over 200 m. In Florida, the Hawthorn 
 
 ^1 pet P2O5 X 2.184 = 1 pet BPL; BPL is 
 bone phosphate of lime, used to express 
 the phosphate content of matrix or bene- 
 ficiated product. 
 
11 
 
 central Florida contain higher than de- 
 sirable levels of dolomite (J^) . Thus, 
 the problems associated with high-MgO 
 content are not limited only to borehole 
 minable deposits. 
 
 Areas have not been eliminated from 
 the resource estimation because of high- 
 MgO levels, as benef iciation tests have 
 demonstrated that it is possible to re- 
 move up to approximately 93 pet of the 
 total MgO in matrix flotation feed (10). 
 Other methods of reducing the MgO content 
 such as blending and high-, low-grade 
 zone mining can also be utilized. Site- 
 specific benef iciation tests would 
 have to be conducted in order to evalu- 
 ate the potential amount of MgO in the 
 product. 
 
 Generalized P2O5 recoveries for benef i- 
 ciation of high-MgO matrix have been used 
 to estimate potential product tonnages 
 for such areas. Southern Florida has 
 been evaluated as a high-MgO resource 
 area since carbonates are the most sig- 
 nificant and extensive contaminant of the 
 Hawthorn phosphorites in that region (2). 
 
 Phosphate pebble is a minor constituent 
 of Hawthorn Formation elastics, making up 
 less than 7 pet of the total (2^, 8^). De- 
 posits of low pebble content are more 
 amenable to borehole mining and such rel- 
 atively low pebble contents are charac- 
 teristic of primary phosphate deposits. 
 Alteration by leaching is not extensive 
 in the deep bedded Hawthorn Formation and 
 equivalent strata. 
 
 RESERVES-RESOURCES 
 
 EVALUATION METHOD 
 
 Calculation of the resource estimate 
 was based upon two factors: the limits 
 of the environments of phosphate deposi- 
 tion and the physical characteristics of 
 the matrix in single or multiple beds 
 (i.e., areal extent, thickness, grade, 
 and density). Environments were deline- 
 ated based upon the existing structure 
 of the Miocene Basin. The environmental 
 depth limits (0, 50, 122 m) are those 
 suggested in reference 14 and are based 
 on structure contours at the base of the 
 phosphorite-bearing unit. The shallow 
 environment encompasses the area between 
 the 0- and 50-m contours. Since this 
 study is solely an investigation of deep- 
 bedded phosphates, only the area between 
 30 and 50 m was evaluated for the shallow 
 environment. The intermediate environ- 
 ment extends from 50 to 122 m, and the 
 deep environment is represented by units 
 below 122 m. These boundaries are only 
 an approximation of the Hawthorn bathym- 
 etry, for through time the environmental 
 limits must have shifted markedly across 
 the basin in response to fluctuations 
 in sea level. An attempt has been made 
 to account for such variations in this 
 evaluation. 
 
 The physical characteristics associated 
 with each environment were established 
 based upon a synthesis of published and 
 
 proprietary information, well data, 
 drillers logs of wash borings, core de- 
 scriptions, personal communications, and 
 projections of regional trends. Exten- 
 sive use was made of well logs and 
 isopach and structure contour maps. 
 Site- and test-specific geologic explora- 
 tory data used in this study have not 
 been duplicated lest they be misinter- 
 preted to indicate that the conclusions 
 are entirely quantitative and can be sub- 
 stantiated without significant regional 
 interpretation. 
 
 Hypothetical and speculative resource 
 areas were delineated based upon the den- 
 sity and reliability of data and con- 
 clusions of individuals most familiar 
 with the basins. Known variations in the 
 physical characteristics of the phosphate 
 zones within a specific environment were 
 used to project the matrix characteris- 
 tics into deposit areas with limited 
 data. Average deposit thicknesses were 
 developed for each depositional environ- 
 ment and then applied to the hypotheti- 
 cal and speculative resource areas. The 
 final resource estimation is based upon 
 the equation 
 
 r = a X 10,000 x t x d, 
 
 where r = in situ resource, mt , 
 
 a = resource area, ha. 
 
12 
 
 and 
 
 t = matrix thickness, m, 
 d = density, g/cm-^ 
 
 A density of 1.44 g/cm^ was used to 
 approximate the overall regional matrix 
 density. The regional data used in the 
 resource evaluations are presented in ap- 
 pendix B. As stated previously, within 
 each depositional region, single or mul- 
 tiple phosphate beds may not be continu- 
 ous over the entire area, yet sufficient 
 vertical and horizontal matrix continuity 
 is assumed to exist throughout each depo- 
 sitional environment for resource calcu- 
 lation requirements and recognition as a 
 minable unit. 
 
 The regional variation in thickness of 
 the Hawthorn Formation in North Carolina 
 and Florida is presented in isopach maps 
 (figs. 5-6). Isopach maps have been de- 
 veloped and presented with some variation 
 
 Contour interval = 50 m 
 
 .^■ 
 
 FIGURE 5. - Isopach map, Hawthorn Formation 
 in Florida (modified from and courtesy of Florida 
 Bureau of Geology, 1983). 
 
 by others (_5) . This variation can be 
 attributed to differences in the quality 
 and density of control data and varia- 
 tions in the interpretation of the Mio- 
 cene section. 
 
 RESOURCE ESTIMATE 
 
 The principles of the sedimentary phos- 
 phate resource classification system of 
 the Bureau and the U.S. Geological Survey 
 (18) were used in this study. According 
 to this system, the resources identified 
 here are classified as undiscovered, hy- 
 pothetical or speculative. The classifi- 
 cation system is presented in figure 7. 
 
 Hypothetical phosphate resources repre- 
 sent extensions of known phosphate bodies 
 that may reasonably be expected to exist 
 in the same region under analogous geo- 
 logic conditions. Hypothetical resources 
 are based upon drill hole data that have 
 been projected for distances greater than 
 1 .6 km. 
 
 Speculative phosphate resources occur 
 in favorable geologic settings where 
 phosphate discoveries have not been made 
 
 10 20 30 40 km 
 Scole 
 
 FIGURE 6. - Isopach map, Pungo River Formation 
 in North Carolina (modified from reference 12). 
 
13 
 
 production 
 
 ECONOMC 
 
 MARGINALLY 
 ECONOMK 
 
 SUB- 
 ECONOMIC 
 
 IDENTIFIED RESOURCES 
 
 Demonstrated 
 
 Measured Indicated 
 
 Inferred 
 
 reserve 
 
 base 
 
 UNDISCOVERED RESOURCES 
 
 Ptobobility range 
 
 Hypothetical 
 
 (of)- 
 
 Speculative 
 
 + 
 + 
 
 : EC-REE OF GEOLOGIC ASSURANCE 
 
 FIGURE 7, - Classification system of mineral 
 reserves and resources. 
 
 and drill hole data are not available. 
 If exploration reveals additional data 
 about the quality, grade, and quantity, 
 these hypothetical and speculative re- 
 sources would be reclassified as identi- 
 fied resources. 
 
 It is estimated that the Southeastern 
 Coastal Plain contains a hypothetical re- 
 source of 250.355 billion mt and a specu- 
 lative resource of 135.303 billion mt of 
 phosphate matrix projected to be suit- 
 able for recovery by a commercial bore- 
 hole mining system when developed. Re- 
 source data for each depositional zone 
 are presented in appendix B and are sum- 
 marized in table 1. The borehole-mining- 
 recoverable resources are estimated to be 
 165.234 and 89.300 billion mt of matrix 
 for hypothetical and speculative classes, 
 respectively . 
 
 POTENTIAL PHOSPHATE ROCK PRODUCT 
 
 The Bureau conducted benef iciation 
 studies on phosphate matrix mined by the 
 borehole technique (3). Standard double- 
 stage flotation, the primary beneficia- 
 tion method used by the phosphate indus- 
 try, yielded a P2O5 recovery of 91.0 pet 
 on ground ore. Standard washing with a 
 93-pct-P205 recovery and the 91.0-pct 
 flotation recovery are applied here to 
 approximate the recoverable phosphate 
 rock product in most of the study area. 
 For southern Florida, where matrix is an- 
 ticipated to have a relatively high MgO 
 content, results of other Bureau research 
 were used to approximate P2O5 recoveries 
 (10). For high-MgO matrix, scrubbing is 
 anticipated to yield approximately 76 pet 
 P2O5 recovery; flotation, is anticipated 
 to yield approximately a 75-pct-P205 
 recovery. Employing such benef iciation 
 procedures, the borehole mining hypo- 
 thetical and speculative recoverable re- 
 sources would make available 43.070 bil- 
 lion and 21.222 billion mt of phosphate 
 rock product, respectively, at an esti- 
 mated grade of 30 pet P205« The poten- 
 tial phosphate rock product can be ap- 
 proximated by the following equation: 
 
 P = t X g, 
 
 where p = product, mt , 
 
 / g2 
 
 TABLE 1. - Borehole mining phosphate resource potential, 
 Southeastern Coastal Plain, million metric tons 
 
 Primary deposit 
 
 In situ matrix 
 
 Recoverable matrix 
 
 30-pct-P205 rock product 
 
 regions 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Eastern North 
 Carolina 
 
 123,257 
 
 40,346 
 28,687 
 58,065 
 
 NAp 
 
 61,776 
 
 8,309 
 
 65,218 
 
 81,350 
 
 26,628 
 18,933 
 38,323 
 
 NAp 
 
 40,772 
 
 5,484 
 
 43,044 
 
 22,941 
 
 7,509 
 5,339 
 7,281 
 
 NAp 
 1 1 498 
 
 Southeast Georgia 
 Embayment 
 
 Northeast Florida'... 
 Southern Florida^.... 
 
 1,546 
 8,178 
 
 Total 
 
 250,355 
 
 135,303 
 
 165,234 
 
 89,300 
 
 43,070 
 
 21,222 
 
 NAp Not applicable. 
 
 Ix- 
 
 Northeast Florida is combined with Southeast Georgia Embayment to constitute 1 ma- 
 jor area of deposition. 
 
 High MgO benef iciation recoveries applied in southern Florida. 
 
14 
 
 and 
 
 t = in situ matrix, mt, 
 
 gl = matrix grade, pet P2O5, 
 g2 = product grade, pet P2O5, 
 r = process P2O5 recovery, pet. 
 
 Benef iciation parameters are summarized 
 in appendix A. The regional distribution 
 for the potential phosphate rock product 
 estimate is presented in table 1. 
 
 Another recent estimate of the hypo- 
 thetical resources for the study area 
 is about 14.27 5 billion mt of recover- 
 able phosphate rock (_5) . This figure 
 and others found in the literature 
 
 such as an estimate of 25 billion tons, 
 hypothetical phosphate resource in the 
 entire United States (17) , do not corre- 
 spond with the estimate in this study 
 because of differences in evaluation cri- 
 teria such as maximum depth to the ore 
 zones, deposit areas, and mining and 
 recovery methods. Also, such resource 
 estimates almost exclusively reflect sur- 
 face minable resources. At the other end 
 of the resource estimate spectrum, poten- 
 tial phosphate rock resources for the 
 Hawthorn Formation in Florida alone have 
 been estimated at 181 to 218 billion mt 
 and about 45 billion mt for an area from 
 northeast Florida through North Carolina 
 (4). 
 
 CONCLUSIONS 
 
 The Southeastern Coastal Plain of the 
 United States is estimated to contain 
 a hypothetical phosphate resource of 
 about 2 50 billion mt and a speculative 
 resource of about 135 billion mt of phos- 
 phate matrix in approximately 5.2 million 
 ha which is projected to be suitable for 
 the application of a commercial borehole 
 mining system when developed. With esti- 
 mated mining and benef iciation recov- 
 eries, this total resource would make 
 
 available approximately 64 billion mt of 
 30-pct-P2O5 phosphate rock product. This 
 enormous on-shore phosphate reserve po- 
 tential justifies continuation and expan- 
 sion of exploration programs and devel- 
 opment of a commercial borehole mining 
 system. The application of a commercial 
 borehole system would help to assure an 
 adequate long-term domestic supply of 
 phosphate with minimal effect upon other 
 resources and the environment. 
 
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15 
 
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 V. 177, No. 9, Sept. 1976, pp. 94-97. 
 
 Stuckey, J. L. North Carolina: Its 
 Geology and Minerals Resources. Dept. 
 Conserv. and Development, Raleigh, NC, 
 1965, pp. 430-437. 
 
 Sweeney, J. W. , and R. N. Hasslacher. 
 The Phosphate Industry in the Southeast- 
 ern United States and Its Relationship to 
 World Mineral Fertilizer Demand. BuMines 
 IC 8459, 1970, 76 pp. 
 
 U.S. Bureau of Mines, Staff. The Flor- 
 ida Phosphate Industry's Technological 
 and Environmental Problems, A Review. 
 BuMines IC 8914, 1983, 42 pp. 
 
 Valentine, P. C. Upper Cretaceous Sub- 
 surface Stratigraphy and Structure of 
 Coastal Georgia and South Carolina. 
 U.S. Geol. Surv. Prof. Paper 1222, 1982, 
 33 pp. 
 
 Weaver, C. E. , and K. C. Beck, Miocene 
 of the S. E. United States: A Model for 
 Chemical Sedimentation in a Peri-Marine 
 Environment. Sediment. Geol., v. 17, 
 234 pp. 
 
 Watson, T. Aquifer Potential of the 
 Shallow Sediments of the Coastal Area of 
 Georgia in Investigations of Alternative 
 Sources of Ground Water in the Coastal 
 Area of Georgia. GA Geol, Survey OFR 
 80-3, 1979, 30 pp. 
 
 White, W, A. The Geomorphology of the 
 Florida Peninsula. FL Geol. Survey Bull, 
 51, 1971, 164 pp. 
 
 Woolsey, J. R. , Jr. Neogene Stratig- 
 raphy of the Georgia Coast and Inner 
 
Coastal Shelf. Ph.D. Dissertation, Univ. 
 GA, Athens, GA, 1977, 222 pp. 
 
 Zellars, M. E. The Genesis and Occur- 
 rence of Tertiary Phosphorites in the 
 Southeastern United States. Min, Eng. , 
 V. 30, No. 12, Dec. 1978, pp. 1652-1656. 
 
 Zellars, M. E., and J. M. Williams. 
 Evaluation of Phosphate Deposits of 
 Georgia, North Carolina, and South Caro- 
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 tem (contract J0377000, Zellars-Williams , 
 Inc.). BuMines OFR 14-79, 1978, 65 pp. 
 
19 
 
 APPENDIX A. —MINING AND BENEFICIATION PARAMETERS 
 
 BASIC DEPOSIT ASSUMPTIONS 
 
 Matrix grade, pet: 
 
 P2O 5 10. GO 
 
 BPL 21.84 
 
 GENERAL BENEFICIATION PARAMETERS 
 
 MgO content 
 
 Low High 
 Recovery, pet: 
 
 Washing-scrubbing 93.0 76.0 
 
 Flotation 91.0 75.0 
 
 Overall benef iciation. . . . 84.6 57.0 
 Product grade, pet: 
 
 P2O5 30.00 30.00 
 
 BPL 65.52 65.52 
 
 BOREHOLE MINING UNIT-SPECIFICATIONS 
 AND OPERATING PARAMETERS 
 
 Average unit mining rate. . .ratph. . 45 
 
 Average cavity radius m.. 9.1 
 
 Cavity separation m. . 3.0 
 
 Borehole separation m.. 21.3 
 
 Mining recovery pet.. 66 
 
 
20 
 
 APPENDIX B. —GENERAL RESOURCE DATA 
 TABLE B-1. - Resource characteristics of identified zones 
 
 Region and depositional environment 
 
 Resource 
 
 area, ha 
 
 Av matrix 
 thickness , m 
 
 In situ 
 10^ 
 
 matrix, 
 mt 
 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Hypo- 
 thetical 
 
 Specu- 
 lative 
 
 Eastern North Carolina: 
 
 Shal low 
 
 97,700 
 256,900 
 263,900 
 
 NAp 
 NAp 
 NAp 
 
 6.1 
 12.2 
 18.3 
 
 NAp 
 NAp 
 NAp 
 
 8,582 
 45,132 
 69,543 
 
 NAp 
 
 Intermediate. ...........••••••••••• 
 
 NAp 
 NAp 
 
 Deep 
 
 Total 
 
 618,500 
 
 NAp 
 
 NAp 
 
 NAp 
 
 123,257 
 
 NAp 
 
 Southeast Georgia Embayment: ^ 
 
 Shallow 
 
 NAp 
 161,200 
 297,200 
 
 236,300 
 927,500 
 266,200 
 
 NAp 
 3.0 
 7.8 
 
 3.0 
 3.0 
 3.0 
 
 NAp 
 
 6,964 
 
 33,382 
 
 10,208 
 
 Intermediate. •••••••••••••••••••••• 
 
 40,068 
 
 Deep 
 
 11,500 
 
 Total 
 
 458,400 
 
 1,430,000 
 
 NAp 
 
 NAp 
 
 40,346 
 
 61,776 
 
 Northeast Florida: ' 
 
 Shallow 
 
 150,600 
 506,200 
 125,700 
 
 117,100 
 
 21,900 
 
 NAp 
 
 2.4 
 2.7 
 2.1 
 
 3.6 
 7.1 
 NAp 
 
 5,205 
 
 19,681 
 
 3,801 
 
 6,070 
 
 Intermediate. ...................... 
 
 2,239 
 
 Deep 
 
 NAp 
 
 Total 
 
 782,500 
 
 139,000 
 
 NAp 
 
 NAp 
 
 28,687 
 
 8,309 
 
 Southern Florida: 
 
 Shallow 
 
 108,000 
 548,900 
 235,100 
 
 32,700 
 172,900 
 656,900 
 
 3.8 
 4.2 
 5.6 
 
 3.8 
 4.2 
 5.6 
 
 5,910 
 33,197 
 18,958 
 
 1,789 
 
 Intermediate 
 
 10,457 
 
 
 52,972 
 
 Total 
 
 892,000 
 
 862,900 
 
 NAp 
 
 NAp 
 
 58,065 
 
 65,218 
 
 Southeastern Coastal Plain 
 
 2,751,400 
 
 2,431,500 
 
 NAp 
 
 NAp 
 
 250,355 
 
 135,303 
 
 NAp Not applicable. 
 'Northeast Florida is combined with 
 deposition. 
 
 Southeast Georgia Embayment to constitute 1 major area of 
 
 TABLE B-2. - Extent of environmentally sens 
 
 itive areas for depos 
 
 it zones. 
 
 hectares 
 
 
 
 Total 
 area 
 
 Environmentally sensitive 
 
 areas 
 
 Resource 
 
 Region and depositional environment 
 
 Coastal ' 
 
 Water^ 
 
 Managed 
 land^ 
 
 Urban" 
 
 area 
 
 Eastern North Carolina: 
 
 Shallow 
 
 118,500 
 360,400 
 332,300 
 
 (5) 
 (5) 
 
 19,500 
 
 100,200 
 
 63,700 
 
 
 
 
 
 2,800 
 
 1,300 
 3,300 
 1,900 
 
 97,700 
 
 Intermediate ........................... 
 
 256.900 
 
 Deep 
 
 263,900 
 
 Total 
 
 811,200 
 
 (5) 
 
 183,400 
 
 2,800 
 
 6,500 
 
 618,500 
 
 Southeast Georgia Embayment:^ 
 
 Shallow 
 
 Intermediate 
 
 Deep > 
 
 274,000 
 
 1,558,700 
 
 819,200 
 
 19,900 
 
 89,200 
 
 161,700 
 
 17,800 
 
 109,800 
 
 74,800 
 
 
 
 148,300 
 
 15,100 
 
 
 
 122,700 
 
 4,200 
 
 236,300 
 
 1,088,700 
 
 563,400 
 
 Total 
 
 2,651,900 
 
 270,800 
 
 202,400 
 
 163,400 
 
 126,900 
 
 1,888,400 
 
 Northeast Florida:^ 
 
 Shallow 
 
 356,400 
 648,900 
 207,100 
 
 800 
 31,700 
 52,700 
 
 42,000 
 63,100 
 12,000 
 
 45,200 
 
 16,200 
 
 
 
 700 
 
 9,800 
 
 16,700 
 
 267,700 
 
 Intermediate. 
 
 528,100 
 
 Deep 
 
 125,700 
 
 Total 
 
 1,212,400 
 
 85,200 
 
 117,100 
 
 61,400 
 
 27,200 
 
 921,500 
 
 Southern Florida: 
 
 Shallow 
 
 194,400 
 
 994,800 
 
 1,279,000 
 
 (5) 
 (5) 
 (5) 
 
 40,600 
 237,100 
 325,900 
 
 
 
 8,600 
 
 
 
 13,100 
 27,300 
 61,100 
 
 140,700 
 
 Intermediate 
 
 721,800 
 
 Deep 
 
 892,000 
 
 Total 
 
 2,468,200 
 
 (5) 
 
 603,600 
 
 8,600 
 
 101,500 
 
 1,754,500 
 
 Southeastern Coastal Plain 
 
 7,143,700 
 
 356,000 
 
 1,106,500 
 
 236,200 
 
 262,100 
 
 5,182,900 
 
 Includes barrier islands and tidal marshes. 
 
 Includes flood plains, lakes, rivers, and inland marshes. 
 ^Includes wildlife refuges and State and Federal forests. 
 
 Incorporated limits of major cities; military bases. ^Coastal areas excluded from initial area. 
 
 Northeast Florida is combined with Southeast Georgia Embayment to comprise 1 major area of deposi- 
 tion; data courtesy of and modified from S. R. Riggs, Department of Geology, East Carolina University, 
 Greenville, NC. 
 
 A-U.S. GPO: 1985-505-019/20,098 
 
 INT.-BU.OF MINES,PGH.,PA. 28088 
 
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