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SUBSURFACE GEOLOGY OF THE ST. CROIX CARBONATE SYSTEM PHASE II Ivan P. Gill Dennis K. Hubbard May, 1987 Agreement No. 14-08-0001-G1258 Technical Report No. 28 Caribbean Research Institute University of the Virgin Islands St. Thomas, U.S.V.1I. 00802 Technical Report No. MG-4 West Indies Laboratory Teague Bay, St. Croix U.S. Virgin Islands 00820 SUBSURFACE GEOLOGY OF THE ST. CROIX CARBONATE SYSTEM , , PHASE II Ivan P. Gill Dennis K. Hubbard Agreement No. 14-08-0001-G1258 Technical Report No. 26 Caribbean Research Institute University of the Virgin. Islands St. Thomas, U.S.V.I. . 00802 The research on which this report is based was financed . in part by the United States Department of the Interior, Geological Survey, through the Virgin Islands Water Resources Research Center. Contents of this publication do not necessarily reflect. the views and policies of the U. S. Department of the Interior; nor does mention. of trade names or commercial products constitute their endorsement by the the United States Government. we ABSTRACT “Seven new test holes were drilled into St. Croix's central carbonate plain with a rotary drill! ria. Cumulative drilling for this phase of the project exceeded 750 feet, and brought the total number or test -holes for the project. to fourteen. These test holes allow lithologic: and biostratigraphic correlation ina “north to south transect from Krausses Lagoon to Estate St. John and in a west to east transect trom Estate Hesselbera to Estate-Pearl. , The drilling establishes tne existence or a probable Pliocene reef and shallow-water facies trend that cims the western and southern coastlines or the ‘central plain. The greatest thickness ot Pliocene sediments occurs in a subsidiary graben block in the ‘south coast industrial area. . The northern and western boundaries otf the Pliocene Graben can be interred from ‘core data. The Pliocene post-Kinashil} carbonates are less extensive than the Miocene Kingshitl: Limestone, but. are generally more permeable. Dolomitization in the Pliocene carbonates rims what was.the coastline of Krausses Lagoon betore industrial development moditied the shoreline in tne 1960s. The geographical distribution of the dolomite Suggests a hydrologic correlation between Krausses Lagoon and the formation. of dolomite. The stable isotopic: composition: ot the dolomite suggests the > “possibility ofa dolomitizing fiwid with elevated salinity. Structural. mapping.on the upper surtace or. the - Miocene Jealousy Formation indicates marked upwarping under the carbonate nighlands. This structural’ upwarping coincides with the greatest isopach thickness ot tne Kingshill Limestone. The patterns suggest a basin. opening to the south, but with a depocenter located under the present position of the carbonate highlands. There is a greater degree of. structural complexity in the central plains region than was previously supposed. ; , Micropaleontological evidence suggests that the Jealousy Formation ~ Kingshill Limestone contact is time-transoressive within the Miocene. Both units were deposited in deep. water, perhaps at depths greater than 1000 m. Despite. the marked color. change, there are surprisingly few mineralogic or paleontological} differences between the Jealousy Formation and the Kingshill Limestone, and the contact between the two tormations does: not imply significant paleobathymetric change. oe a i ACKNOWLEDGEMENTS This: project has been made possible through the etforts of many people and the cooperation ot numerous agencies.. Funding was provided by the United States Department of tne Interior through the Virgin Islands Water Resources Research Center; SOHIO. Chevron, .and Shell field research grants: grants trom Dr. David Epy and Champlin Petroleum, and the Applied Carbonate Research Program, the Department of Geology and the . Basin Research InStitute at Louisiana State University. Initial field work was funded by grants from the Geological Society of: America and the American ~ Association of Petroleum Geologists, The drilling would not have been possible without the aid and cooperation of Mr. Ken Eastman and the statt ot Sar ibbean Drilling Services. Access to exposures and drill sites for this phase of the project was freely given by the staff of Martin Marietta-Corporation, in particular G. Bennewith. and J. Savage, as well as H. Kerr, 0. Schjang and the Women’s Coatition of St. Croix. Cooperation during this phase. of work was extended by several agencies of the Virgin Islands and Federal Governments: the Department of Public Works, the V. 1. Planning Office, the Department of Natural Resources, and Mr..H. Rodrigues and the manbucket crew of tne V. I. Water and Power Authority (St. Croix). , : Field work for this phase of the project was aided generously by Y. Bordeaux, A. Hunt and J. Massare. Report preparation was aided by E. Babin, A. Brunett, -and C. Van.de burgh... Strontium isotopic work was generously ‘donated by R. Koepnick. and the Mobil Field Research Laboratory. Geophysical logging gear was loaned by Argonne National Laboratory courtesy. of Mr. R. Bowen and Dr. L. McGinnis. Special thanks are owed. to -K. Carter, N. Martinez, K. Myers and M. Price for sample preparation and micropaleontological work,. and to Sam Reed and T. Poche for thin section preparation. ~Micropaleontological determinations were done by P. McLaugh! in and W. van. den Bold, and the authors benefitted from discussions with R. Ferrell, R. Koepnick, E. Manning, P. McLaughlin, C. Moore, D. Nummedal, R. Pilger, B.. Sen Gupta, M. Simms, W.. van den Bold and S. Wendtler.. S. Frost contributed enthusiasm,. samples and. ideas regarding the: carbonate section of. St. Croix. it. . We appreciate the. support and advice of the staff ot the U. S. Geological Survey, Puerto Rico, in particular Mr. F. Gomez-Gomez and Mr. A. Zack. Logistical support.and management was provided by the Staff ofthe West Indies Laboratory, and the program was administered by Dr. H. Smith of the Water Resources Research Center of the University of the Virgin Islands. One of the authors, Gill, is supported on a fellowship from the Loulsiana State University Alumni _. Federation and the Department of Geology, and his lab _-work is supported by Dr. C..H. Moore and the staffs of the Applied Carbonate Research Program, the Basin Research Institute and the Department of Geology of Louisiana State University. The staffs of the Applied Carbonate Research: Program and Department of Geology of 7 Louisiana State University, and the staff of the West Indies Laboratory were invaluable in providing both tield ‘and laboratory assistance throughout. the project, TABLE OF CONTENTS — Abstract i re i 2 Acknowledgements cee ete we eee Table ot Contents vbals a eens iene eee’ ‘List of Figures aaa ewe ee dee te Introduction benhueSeahaeaweubess Geologic Settina vas be vers ba es PrevioUS WOCK eevee ee ee eee eee ese Hydrogeology — we ke BAPE Geology : bee ea ae vente “Methods _ vee eee ele ee see eiee eee apie eels ‘Results | bed adewe een ee deals ee bees Summary of test hole sampling ° . > . : ° ° Jealousy Formation (Oligocene-Miocene> Biostratigraphic Age Structure Lee were es Depositional Environment: Mineralogy = ....e..ee. Kingshill Limestone .........+ SErUCtULe wee eee eee eee Stratigraphy see ee eae —Biostratigraphy and paleobathymetry | . « * ° . e ° ° ° ii iv vi a a a . 46 Post-Kingsnill Carponates (Pliocene? . o8 ° . . . ° . . ° . . . 47 Sedimentology aa - oe ° 4b Stratigraphy | .. o seek oe . we . . . ol Structure. . . ° ° . . . e . . 56 Biostratigraphy « 56 Dolomitization and diagenesis ve . Cr ee ° o8 Conclusions cee ee ee ow - hr . ae ew ee we ree . e 6l References 7 ee ee eee oe ae eee eee ee ee eee . . 64 Appendix . Figure Figure Figure ‘Figure Figure Figure Figure. Figure Figure Figure Figure Figure Figure. Figure 14. LIST OF FIGURES L. t. Croix location map and study area 2. Generalized geologic map of St. Croix:... 3. Locations of Phase If test. holes Na aeelee 4. Locations of test holes: and data points | _ for Phases Ioand- IT... eee. cee ew eee ee 5. Structure map: top of Jealousy Formation. ....4. elev a ae e aleve sie wees eke eee! 6: Locations of cross sections A-A’, B-B: 7. Cross section A-A’: Krausses Lagoon to dudiths Fancy ..seeeees eee ee eee &. Cross section B-B’:.Hesselberg to Pear i 9, ~ Tsopach map: Kingshill. Limestone ....... 4 ‘10. Distribution of carbonate lithotacies, t. Croix Central Plain .e eevee eeeeees oe Ll. Cross section locations: C-C’, D-D’ ... 1z. Cross section ‘D- D’: Estate Fairplain to ue Pearl! aa ee a eae ee bbe bolas ogee eee aa 13. Cross” section C- c -Krausses Lagoon to Spanish TOWN ..eee ee aessiebienies ste . Facies map: south coast industrial area’. OVis 44 ay 52. SS 54 a5 i ar ae Information on previous work 15 contained in the first report <Gil1 and Hubbara, 19864) and the reager is referred to that report for additional detail. Complementary information on groundwater chemistry is contained within a second report (Gill and Hubbara, 1986b?. Since this project is part of an on-going doctoral research effort, results of longer-tecm analyses are expected to add to or modify the conclusions given in this report. As turther data . become availab } e, every effort will be made to. contribute this information to the public comain. a re 66 65 19° LS mt e00 200° i ATLANTIC va OCEAN yoo? ee? oe CENTRAL CR ey x AMERICA CARIBBEAN VIRGIN ISLANDS oe FT a ak” ee * ZA a o° or PUERTO RICO aoe Gore ST.CROIX oo? O06 BASIN pie e° — TROUGH Be a ( ST 100 | SOUNDINGS IN & 20° 40 a ven + + + + + Aa +7 +4 + +7 oP oo + 4 eS Noo 4 +/ ev +7 of + a+ + + 4% 14 +c +7 “s N+ + + ba ed »* + ALA CORES: Bi B7 BISA \*) 1 2 3 4 Villa La Reine. (Type Section, Deep Basin) . Evans Highway (Basinal) MILES Hess Oil (Reef / Near Reef) +t Cretaceous Volcanoclastice and intrusives: te) 1 2 Figure 1 pt. Cros location. map and study area. packground geology and the other lithologic units are discussed in the previous report on subsurface geology CGi1l and Hubbard, 1986a) and in the references cited therein. PREVIOUS WORK Hydrogeo] oay © Barly geologic interpretation and grounawater data are found in a publication by Cederstrom (19809, whicn contains the results and interpretations of the / _ exploratory drilling program of the Civilian Conservation Corps. and others, in “1939, More recent Work and recomienaat ions are round in U.S. Geologic Survey publications by Robison (1972), Hendrickson (1963) and a detailed publication by Jordan (1975). Nore recent publ ications dealing specifically with. groundwater issues are Buros (1976), Black, Crow ana o Bidsness, Inc. (1976), and’ the recent reports’ by Geraghty and Miller Inc. (1983a and p>. Buros (1976) deals primarily with a wastewater treatment and oe recharge project” in the Golden Grove section ‘of the “island. Black, Crow and Eidsness 1976) deal with the entire island water system, including siddace rundEt water catchment and desalination, Geraghty and Miller (1983a and bd address strictly groundwater issues, and _ make specific recommendat ions regarding maintenance of © oe the public wel] fields, governmental, organization and — aquisition of geologic data. See . 1 Geology © The overall geology ot St. Croix is summarized.in a doctoral. dissertation-and later publications by Whetten (e.g. .1966, 1974). More detailed work on the depositional environments and petrology of the carbonate. rocks i'n particular was done by Gerhard et al. -¢1978) and ‘Mul ter et al: C1977. These papers outline. the. deposition: ‘ot the carbonate units in a-. rs fault- bounded Seaway and define the type section ot the Kingshill Limestone at Villa La Reine. Biostrati- : Graphic work commériced. in the 1920s with ‘Kemp Gy 926 ty .e 2 “Mare recent work is. that of van den Bold C1970), wea and Low (1976), Multer et al. (1977) and Liaz (1982). — “The nomenclature. ot the carbonate 4 units on Ste " croix has changed over the years and, a short note will help to clarity matters. ‘The name "Kingshill Series" was used- by Kemp (1926) to describe the entire Tertiary * "+ section of St. Croix. Cederstrom (1950) used the terms. "Kingshill Marl" to differentiate the carbonates from ; the underlying: clays of the: Jealousy Formation. “gi scovered during: the deep drilling of 1938- 39. “Whetten (1966, 1974) followed the usage of Cederstrom (1950, above? as did Multer et-al. C1977), whereas van den Bold ¢1970) referred to the unit as the "Kingshill Formation". 10 Gerhard et al. (1978) sugeestec formalizing tne name to "Ks ngsnill Limestone" to include the variety ot facies “included. in the unit, and: suggested the type “section at villa ba Reine (Outcrop 1, Fig..d>. This usage has been. adopted for. this report, cand in the | pub] ications since Gerhard et. al. C1978). EB The depositional. models. suggested by. Multer et al. 1977) and Gerhard et al. ©1978) are accepted. as the ‘pasis for this report... ‘Our findings differ from or add to the papers cited above in the following ways: 1). We discuss the post-Kingshill limestones as a distinct unit, and are concerned primarily with the rocks found in the southeastern section of the central plains area. 2 For the purpose of this report, we chose the boundary between the basinal hemipelagic. = ‘carbonates and the floods ot benthic foraminifera as the formation break between the Kingshill! Limestone and. the post Kingshill carbonates. _Tnis break is recognizable’ in core samples and can be “seen in Qutcrop 2 (Fig. 1. It occurs at approximately the Miocene-Pliocene poundary, and is described in detail by Lidz 1962). The benthic” packstones and. grainstones: are ‘included in ‘the “¥ingshill Limestone by, Gerhard et al. (1978>. Li 3> . The Jealousy Formation is a deep basing) uit. containing almost entirely planktic forams, ratner ‘than the estuarine and shal low-water unit proposed in the reports listed above. The Jealousy ~ Formation was deposited in water ‘depths comparable to the pelagic portions of the Kingshil! Limestone. 4) The Jealousy Formation exposed in outcrop along the Northside Range (Whetten, 1966) does not correspond to the lithologies encountered in the subsurface (Fig. 2). We suggest that these exposures be mapped as Kingshill! Limestone. 5). The Jealousy Formation / Kingshil! Limestone “contact is abrupt, put does not imply sudden’ deepening to basinal conditions as suggested by Gerhard and others (1978). We suggest that the basin floor was already at least 1006 meters deep es . before the onset of Kingshill! Limestone , deposition. - 6 The age ot the Jealousy Formation is common] y. “listed as Oligocene, based on work by Cushman (1946). ‘However, Todd and Low (1976) and this report van den Bold, pers. comm., 1986) show no evidence of sediments older than early Middle Miocene. Due to the great thickness of Jealousy Formation sediments, however, there is little ‘doupt that the Jealousy Formation clays extend into the bligocene. Part’ of the discrepancy is. due to the revision of the Miocene 7 Oligocene boundary atter Cushman: s (1946) report, and misinterpretation of Todd and. Low 61976). ?> The fault boundaries of the Kingshill basin were probably active prior to, and spanned through: the time of Kingshill Limestone deposition. 6) Faulting in the southeastern section of the carbonate plain cuts through post-Kingshi 1! deposits and thus implies significant faulting in- the carbonate section at least into the Pliocene. 9) The geometric and structural relationships of _ the Kingshill Limestone and Jealousy Formation units may imply Tertiary-age compressional stress in the northern part of the Kingshill basin. The timing and cause of this deformation is stills “eonjectural, and it must be reconciled with the primarily tensional nature of the norma fault systems in the Kingshil1 basin. . 10) Reefal and lagoonal limestones rim the southern and western coastlines of St. Croix, and 13 overlie the Kingshill Limestone. These imply significant shal lowing of the depositional basin. and the establishment of Pliocene coral reets along its southern and western margins. 11) The greatest thickness of the post-Kingsnil! limestones occurs in the south coast industrial area. ‘The faulting in this area served: a) to allow the area to serve as a depocenter dur ing the Pliocene; or b) to preserve the shallow-water deposits from erosion during the subsequent uplift of St. Croix; or both. 14 ~ METHODS | The cross- sections in this report are based ‘on. test holes drilled both in Phase Tr and. Phase II of the. ‘deilling program, as well as water-wel | drilling logs ‘and records from previous reports and governmental files. Records from other reports and drilling logs. are summarized and described in Gill and Hubbard C1986a). The contact between the Kingshill Limestone and the underlying blue clay of the Jealousy Formation was selected as a stratigraphic marker due to its | “abruptness, geologic importance, and unmistakability to. untrained observers. Eight test holes were drilled with a rotary drilling rig capable of sampling to several hundred ‘feet; the total drilling footage for Phase II exceeded 756 ft. Friable or unconsolidated sediments were sampled at five or ten foot intervals with a split- spoon sampler; well-lithified mareriel Was ‘coliected. with a ‘diamond- -bit. core barrel. an additional” seven ‘cores. drilled in 1981 for Martin . Marietta Alumina were donated to the project during “Phase I by Caribbean Drilling Services, and provided data on the carbonate units underlying the southeastern portion of the central plain. “Several test holes | ‘drilled in 1983 for Tippetts, Abbott, McCarthy and Stratton ‘Inc. in the Limetree Bay area provided - “information on the submarine geology seaward of the — Hess and Martin Marietta industrial plants. Samples from one of these test holes was. donated to the proyect during Phase I. _ Unconsolidated sediments were sieved ito. -oravel-. sand- and mud-range size fractions. Further size: analysis was not undertaken due to signiticant aggregation of carbonate grains and other diagenetic alteration. Whole-grain counts and minefalogical analysis by X-ray diffraction provided data on grain origin and composition. Thin sections were prepared from: ‘consolidated material and loose grain mounts, and “Mere: used for mineralogical and facies: analysis. Biostratigraphic work was undertaken on the sana- size fraction (> 63 um) of, unaltered or little altered foram-rich material. As in Phase I, test holes were geophysical ly ‘logged with a portable gamma logging. units in cases where hole collapse did not interfere, the: test holes were also. logged with a portable spontaneous potential and resistivity unit. | The gamma logging was done ‘through the steel auger that served as casing during the drilling process. | Wer log: recoras have. been combined. with, sample. logs and Gata ‘trom test “holes: drilled curing this. project. tae) produce the cross sections and. gtructural “intormation in this report.” Summary of Test Hole Sampling “In this report, the terms “test hole", ‘test well’ and "poring" are considered synonymous, and reter to a drilled hole trom which geologic samples or information has been retrieved. These terms are distinguishea trom wells drilled specifically for water. A total of seven test holes were drilled during Phase II. In addition to the data gathered trom tnese ~ test holes, map locations are shown for a water wel! drilled during this project, can engineering boring “taken north of Fredericksted, and several engineering borings taken vest. of the present Alexander Hamil! ton ‘Airport runway «Pig, a Material from the latter holes was. donated by ‘Caribbean. Drilling Services. All test wctag ds isd Bueing Phase ike an -on Figure 3; the complete ‘data base “including | inforitgt lon-aquired during Phase 1 is shown - on Figure | a. Detailed sample logs of Phase II test holes are_ listed in the Appendix. Test hole M7 is located on the southernmost extension of Martin Marietta property (Fig. 4>. Tne “poring reached 270 | feet subsurface (=265 ft msl.» penetrating carbonate Jagoonal sediments, alluvium, and 18 Penn M10 == M13 FD *¢ P< Ae Ms M14 (ost? Mi2 3 M9 @PAlo M11 PA2,7,8 M7? @ TEST HOLE SAMPLES Ta 2 MI rie 2 KM Figure Locations ot Phase I] test holes. post ingspd carbonates . Split- spoon samples were taken: at % foot “intervals” to 166 ft subsurtace. then at “40 foot. intervals to 230. ft. subsurface - 225 ft ms). Due to hole collapse, no samp] ing was possiple past 230 ft subsurface, but the hole was extended with a rock pit to 270. ft subsurface c 268. et ms}> to determine indurated ‘carbonate layers were present. whether any The upper 170 feet.of sediment consists of alluvium and lagoonal carbonates, from.top to pottom: shallow-water carbonate ‘lagoonal sands | and silts, fiuvially, derived estuarine sediments, “mangrove: muds, 49 =2== = == Pe “=< diol = sos ss a = =-7 un tn 4 4 4 eq 4 s s Ss > Ny NS NY Ow = S Ny —- &, Ny > NS S tt Ne > ene . ga ° SS “J \ \ S » Ny NY .) NY NY Ny iN Ay \\ wt u ff 4 4 a id 2 + IW 4 + Ka 4 4 ”. Locations of test holes and data points. for Phases | and ll. ‘and alluvium derived poth from terrigenous ~ siliciclastics and reworked Pl locene garbonates: Bel ow. the alluvium, friable post-Kingshill carbonates extend from 170 £t to 230 ft subsurface (“165 to.-é2e5 tt ms|> and are pervasively dolomitized past 2u6 ft subsurtace c-195 #t msl>. No zones of extensively indurated carbonates were encountered -in this hole despite the presence of a 30 - ‘to 40 ft thick cemented layer present in Holes M6 and By to the north. The post-Kingshil | carbonates “presumably extend to the end of the boring at 2 270 ft ‘subsurface, but samp] ing was impossible past 230 feet subsurface (-225 ¢t msl) due to hole collapse ‘CAppendix?. Tess hole. NB is located on. “Estate Spanish Town northeast of the ‘Annaberg ruins at Martin Marietta, ~ with a maximum depth: Of: 95 ft «+70 ft msi, Fig. 4). Test Hole M&S penetrated 65 feet of Pliocene carbonate strata consisting of triable shal low- ‘derived. bioclastic packstones representing a benthic foraminiferal, - coralline algal and coral assemblage. Past 65 ft subsurface (40 #t.msl>, the drilling was characterized by 30 ft of alternating layers of cemented and non-cemented limestone representing the Kingshill Limestone deep-water facies. = Petrograph-!. fcally, the Kingshill Limestone in this well rs ‘characterized by a lithic clast, planktic foraminiferal packstone facies. The transition from the post-Kingshil] to the Kingshill Limestone was also detectable on. the .gamma logs. Spl it-spoon samples were taken at five-foot intervals, with the indurated layers ‘of the Kingshill Limestone being difficult to penetrate with the split-spoon sampler (Appendix). Test Hole N@ was drilled on the south coast of St. Croix directly south of the Amerada Hess oj] vefinery. - The hole lies” in the Krausses Lagoon area within. the ‘extension of the, borders: ot Blessing Estate (Fig. 4).0 This location, as well as. the. M6 and M7 locations. would have been. “seaward ot the pre-industrial | development Shoreline, and the top several teet of ss ‘material is composed of artificial fill from the “alumina plant and oil refinery development. “Split ~spoon “samples were taken at fiver foot intervals - from 0 to 110 ft subsur face EO to -190 ft isl>, ana at ten ft intervals from 110 to. 180 tt subsurface (-100 to -170 ft ms}. Diamond bit core samples were taken from. an indurated limestone and dolomitic layer from 182 to 194 ft subsurface, and split-spoon samples were cetrleved below this: layer. trom 194 ft to the end ot RN hole at 200 tt subsurface (-190 ft msl). . The upper 150 feet of. No were composed of _-alternating alluvium, organic- rich mangrove swamp muds, and carbonate lagoonal sands and silts. The alluvial material in the upper 150 feet subsurface were composed “primarily of muds, sands and gravels of terrigenous material weathered from the Cretaceous siliciciastics, and were. presumably deposited by. ephemeral: fluvial activity. In several intervals within the. alluvium, “Individual or ‘aggregated planktic foraminifera form. a signiticant component of an otherwise siliciclastic sand fraction. We interpret these forams as being cemented in-situ within the Kingshill Limestone, ang then eroded from Kingshill Limestone exposures iniand of the lagoon. The cementation. within the foram tests. ‘evidently provides enough strength for the tests to survive ‘the weathering and transport processes. From 160° ft “subsurface to the end of Test Hole Moo at 200 ft subsur face (- 150 to -190 ft ms}, “the boring penetrated post-Kingshill carbonate material composed of moderately cemented, benthic foram/coralline algal dominated packstones, At 160 ft subsurface, the equant calcite spar cement is rounded, and the preservation is ; poor, implying leaching. Similar textures are observed 23 in modérn. exposure surfaces” -on St. Croix, suggesting that the upper ‘Surface of the post- Kingshill carbonates — in this boring have. péeh exposed to - subaerial processes. or meteoric waters. “Samples from the diamond bit coring samples at ig2 ft subsurface C-l?re ft ms} show excellent textural ‘preservation, and geopetal ‘structures that are consistent with the present orientation of the core. The geopetal Structures imply that the micrite fibl ot the foram tests has not been disturbed since burial. and. that the. tests have. not been. redeposited since cementation. — Nummulitid foram tests and other flattened biociaats are orientéd sub-horizontal ly in several cases, suggesting either that the tests were” reworked by currents or: that they remain ina depositional position of highest initial ‘stability. core recovery from 162 ee fe subsurface C-172 5 to -177 ft ms!) was greater than 90% | Past 187 ft subsurface, core recovery was ‘poor, and the samples: swore: extremely friable due to dolomi tization. Split- “spoon. samples. beneath ‘the dolomitic layer contain dolomitic material as well as rounded lithic sand and gravel. The lithic sand and oravel in this case are contamination caused by hole collapse. Dolomi tic strata extend from ca. 186 ft subsurface to the. bottom 24 ot the hole at 200: ft subsurface (-176 to -190 tt ms! , Appendix). | Test hole HILO is located in Estate St. Jonn on the site of the old airfield south of Judiths Fancy (Fig. 4). Drilling reached a max imum depth of 105. teet- subsurface ¢-190 ft msl>, penetrating alluvium, | Kingshill Limestone and Jealousy Formation clays. ‘The top 30 feet of material consists of weathered alluvium, with the Kingshil! Limestone acting as primary ‘source ‘for alluvial material. ‘Much of the alluvial sand- size material ‘consists of cemented spherical planktic forams presumably reworked from surrounding Kingsniil , | imestone exposures. Below 30 ¢t subsurface (55 ft msi the boring penetrated Kingshill Limestone facies consistina of. "pelagic foraminiferal packstones alternating with. lithic pebble conglomerates. The lithic pebbles appear to be reworked ‘Cretaceous Mount Eagle Group: materia! such as the Judi ths Fancy Formation exposed inthe neighboring Northside Range. The lithic rounded pebble “conglomerate facies of the Kingshil) Limestone appears -mainiy, in | neighbor ing outcrops in the north portion ot ste Croix.. Below the conglomerate facies, the Kingshill Limestone consists of a planktic foram wacke-packstone. The Kingshill Limestone / “Jealousy Formation contact occurs. within: aZgft sprit- spoon sample. and “occurs at 86 ft subsurface (-4 ft msl>.. The Jealousy - Formation clays at this location consist of uniform arey-blue, planktic foram-rich clays. Neither the ‘Kingshill Limestone nor the Jealousy Formation clays are indurated close to the formation contact, and foraminifera washed from the samp les are clean and show little to no alteration. The total thickness of Jealousy Formation in this. area, as in the rest of St. Croix, is unknown due to lack of penetration by drilling CAppendix). “Test Hol e 11 is located in Estate Hesse iperg close: > ‘to Westend Sal tpond (Fig. 4). This hole, a) though. geographically removed trom the rest. ot the borings, establishes the existence of. shallow. reef and near-— reet “tacies on, the western side of the island. | Spl it-spoon samples were taken at 5 ft intervals to. a total depth of 55 ft subsurface (-45 ft ms} ). The upper samples show leached and micritized bioclasts, rounded equant spar, and in some cases, algal?) tubules: Indicating subaer ial weathering. Samples from 10 to 1S ‘feet contain abundant coral-derived bioclasts and coral binding. of reef material. Below 20 feet subsurface, <-10 ft ‘ms\> the 26. fossil bioclast aseémb lage is very similar co tne - post-Kingshil) facies along ‘the southern coast ot the centrai piain, containing dominantly bentnic roram ana coralline algal assemblage. In this area, shallow carbonate banks and near-reet deposits were Succeeded py scleractinian reef growth. Chronological correlation between strata penetrated py Mid and the shal low-water deposits e|sewhere in the post-Kingshil} carbonates is speculative. However. samples trom test holes to tne west ot the Airport runway - (PAZ 17, 8 and 10; Fig. 4> end” reports in Gerhard et al. (197 78> indicate that shal low- water deposits extend. at. least as tar west as Estate Carlton. shal low- marine facies outcrop in Feeder icksted. and. are found in test ‘borings afi ited to. the ‘north of Fredericksted cthis| report). It is likely that these facies are time- -correlative with the , ~“post-Kingshill facies on the south coast, and that reet growth extended around the perimeter of the islana during the Pliocene. Test Holes t2, 13 :and 14 were drilled in Estates Grasava Garden, Castle Coakley and Cottage, “respectively. Sampling was done by split spoon at 5 ft intervals and extended to a maximum depth of 15 £t CFig. 40. Elevations: ot. the tops of these borings are N) ~J 20, ‘110 and vo ft ms! for M12, Mis and M14, “respectively. “The purpase*ét. these test holes was to investigate the mineralogy and distribution of ‘shallow ¢actes in-areas of poor outcrop control. All. three bor ings shoved the eftects ot subaer ial exposure and. calichification in the shal lowest samples, and contained bioclastic packstones dominated by benthic foraminifera and coral line algae. The strata penetrated by these bor ings correspond to the post-Kingshil} facies. ‘No dolomitization has eeeurred “in any of these samples. ‘Test Holes PAT, 8 and 160° are. located tothe. west of. the existing airport runway and were drilied to: ‘a maximum depth of 15 tt subsurface (Fig. 4). ‘Despite their. shallow depth, these holes” confirm “the existence | of post- ‘Kingshill carbonate. deposition along the Southern margin of ‘the ‘islana to the west. of the . airport. | Samples from these wells contain a ‘foram- algal dominated ploclastic packstone facies “eyptzes of the post Kingshill. Test Hole FD was drilled just north of the town ot “Header ioested (Fio. 4>. . ‘The samples available. were collected by diamond bit ‘drilling from 43. 5S to 45 ft - ‘subsurface (ca. -38.5 to ~40 ft msl). — Bioclasts within the core pieces are dominated by external molds ot. 2B gastropods and pelecypods, and include external molds of tragmented’ solitary mussid corais similar to ‘Antillea bilobata. It the coral identitication is “correct, it would place these strata within the Pliocene “CS. Frost, pers. comm. 1986). The nature of the biofacies implies a shallow lagoon system and ‘confirms the presence of a Pliocene shallow-water carbonate system extending to the north of Fredericksted. In addition to the holes listed above, trom-which sample data are available, well logs and recoras from the VI Dept of Public Works, Cederstrom (1950) and- a Hendrickson (1963) provided data on the depth of tne Kingshill Limestone / Jealousy Formation contact. _ “Information on the depth to the underlying Jealousy Formation clay and general rock lithology were used to ‘construct geologic cross-sections, isopach and structure maps in areas where rock’ samples are not ‘available. Jealousy Formation (Oligocene-Miocene? ‘The Jealousy Formation underlies the entire. central plain of the island, and can be considered the hydrologic basement. The transition from yellowisn marls of the Kingshill Limestone to bluish clays of the 2? Jealousy Formation is marked and abrupt. Well oriilers almost invariably stop after reaching the clays, and the boundary is well marked on their drill logs. The “Jealousy Formation contains a rich planktic. foraminiferal assemblage that allows for. paleoenvironmental analysis and biostratigraphic. correlation. The type section for the Jealousy Formation is considered to be the deepest penetrating test wel | drilled by the Civilian Conservation Corps in 1939. . ‘This well penetrated more than 1400 ft of Jealousy Formation sediments with amaximum depth. of penetration of 1506 £t subsurface (Cederstrom, 1950). The formation exceeds the 1506 foot depth of penetration ot their: deepest well, and gravity surveys indicate that it may be is much as 6600 ft (2000 m) thick (Shurbet et ale, 19562. Conglomeratic deposits are noted at various depths in the deepest hole drilled by the CCC, but were not encountered in the holes drilled for this project. None of the test holes drilled. for this project in either Phase I or Phase II penetrated more than 25 ft of Jealousy Formation clays. More information on the Jealousy Format ion is contained in the report for Phase 30_ I of this proyect and the references cited therein (Gill and Hubpard 1986a>. Bbiostratigqraphic Age. Descriptions and drill! logs from the 1939 test wells are contained in Cederstrom, 1950). Attempts to stratigraphically date -the Jealousy Formation date back to Cushman (1946) who was updated by Todd and Low <1976). ‘Todd’ and Low (1976) placed tne age ‘of the Jealousy Formation between early and middle Middle Miocene, or approximately between 13 and 15.5 million years betore present. The “age determined by Todd and Low (1976) depended on the ~ Yoeation of the well and the position of the sample within the well. Uncertainties in interpretation arise "trom the fact that the samples used were well cuttings, which are subject, to potential contamination and ; uncertainties otf. depth: particularly in deep wells.- . sionetaviavésnng determinations ot the Jealousy "Formation done at Louisiana State University, however, give ‘similar results. -P. McLaughlin and Wi van den “Bold analysed several. samples of Jealousy Formation taken for. this project CP. Mclaughlin and We van den Bold, ‘pers. comm. ,. 19877: 7 Test Hole M1, Sample 12, 105 ft: late N9 - early. N10; ca. 15.5 ma. . 31 Test ma. Te M2, Sample 24 14 14.6 ma. ‘Test Hole M10, Sample H 15.4 ma. The Kingshill Limestone poundary lies between sample ‘Ml, 15+Z20 cm above sample 24 - 20 ft above sample HS in Tes “These findings imply that th Kingshill Limestone boundary ‘that the Jealousy Formation Miocene stratigraphic unit. this. unit, there is little d Format ion extends into the 0 stated in the Phase I report Format ton as Oligocene in ag Hubbard, 1986a> 2). Structure. The nature 7 Kingshil) Limestone contac “unambiguous, and is used in "datum for that reason. It i drillers on St. Croix as am Mi. Samp le 16, 147 tt: late N8; ca. 16.3 -4, 167 ft: Nii - Nl2; ca S; 105 ft: early N1G;3 ca. 7 Jealousy Formation s 12 and 16 in Test Hole aodn Test Hole MZ, and ca. t Hole Miu <Appendix>. e Jealousy Formation / ¥s° time-transgreSsive, “and should be considered a ‘Due to the thickness ot oubt that the Jealousy ligocene. However. as” , labeling the Jealousy e is misleading (Gill and of the Jealousy Formation. tis abrupt and , this report as a subsurtace S used similarly by wel) arker of the lower boundary ce of potable water recovery. ‘Cross-section maps and structure map of. the upper Jealousy Formation. surtace | were prepared for this report using the Jealousy Formation as a datum. ‘The surtace of the Jealousy Formation is characterized by three general trends ‘Fig. 5S): 1) deepening toward the north and south coasts of St... Croix; Z> a marked upbowing of the surface beneath the highlands ‘in. the northern section of. the central plain; B a ‘pronounced rise. in the Jealousy Formation ‘elobe to the fault boundary imposed by the Northside. _ Range (Fig. 5). “Benavior of the Jealousy Rormat fon: surtace. close to the eastern fault boundary is unknown because of. ‘poor we! ] control. Similarly, behavior oft the, Jealousy Format ion surface in the southeastern ‘coastal section is not known ‘due to faulting in- the area, which places the upper surface of the “Jealousy Formation beyond the 7 reach of. deiiiing. Depth to the Jealousy Formation in this region is deeper than -260 ft ms], the deepest penetration of drilling in. the area (Fig. 5). o NO 27 oy | eee ey mity y ith om yl \! ae al Vy by 4h Wf “+ ar Vy Ny yh Vy VV A ly 7 hey i vl os hy in ae py yl vy a) | F/, fly pA Cyt vy] gl 407 a) tl V/s 1fO of}! 4 Ztth Yi SMA o! — Aut 471 ~~ ee “tt Os ft = 4d N\ ‘vo Ne” NNO \ NN XY ‘6 \ \o Md, NON od NOY rw \ to \ 1 \ Ay BAY bo \ \ Figure 5. Structure map: top of the Jealousy Formation. The topography of the Jealousy Formation surface can be explained by: 1? an erosional unconformity between the Kinashnil} Limestone and the Jealousy Formation; tw Nv -pasement topography: 3) tectonic deformation;. ad ditterential compaction of the thick clay sequence. A final possibility is that the marked color contrast between the Jealousy Formation and the Kingsmill Limestone ‘does not ‘reflect any significant change in age, deposition or mineralogy. In this case, “the two units would. represent a continuous record ot “deposition, and the cause and significance OF the ‘color change is. unknown. The strongest evidence supports the notion that the contact represents a time- transgressive or erosional boundary that nas been. deformed ‘py tectonic compression. ‘Depositional Environment. In contrast to earlier work, we suggest that the. Jealousy Formation represents a deep- -water ‘pelagic unit. Benthic foraminifera in | test hole samples from both. phases of drilling. imply ‘depths comparable to continental slope conditions. 35 Benthic foraminiferal assemblages with large “components of Cassiaulina supglobosa and Cibicites. wuellersdorti occur in Several upper Jealousy Formation samples and imply depths exceeding 1006 m. and possibly “approaching 2000 m (P. McLaughlin, pers. comm. 1987) | Although tentative at this point, these depths are three to six times greater than previous estimates | (Multer et al., 19773 Gerhard et al., 1978; Liaz. 19823 Gill and Hubbard, 1986a). The foraminiferal ‘assemblages in the Jealousy Formation are similar to the Kingshill Limestone assemblages in immediately overlying samples. Minekaloay: The mineralogy of the Jealousy ‘Formation is dominated by calcite, with significant components of quartz, feldspars and clay minerals. “Based on semi-quantitative estimates by powder mount X-ray diffraction, calcite comprises almost 90 percent of the sample, with: six to seven percent of the. sample peing composed. ot quart: and teldspar and the remaining four percent. composed of clays and other minerals. ‘However, these components are not largely different either quantitatively or qualitatively than the: overlying Kingshill. Limestone. “Surprisingly, it is” apparent ‘that despite the marked color. and textural ‘contrasts, the transition from the Jealousy Formation to the Kingshi!] Limestone does. not enta?i a larae. change. in-either mineralogy or depositional — environment. Kingshill Limestone --Reterred to as the Kingshill Mar] when described by Cederstrom (19502, the unit was renamed the Kingshil! Limestone by Gerhard et al. (1978). The more recent label. recognizes the axtetence ot a wide variety ot lithologies within the unit, and will-be used nere. . The geologic setting ot the Kingshil} Limestone is one of deep basinal deposition. The lithologies within ~ the: unit: consist of alternating. layers ot planktonic. deposits and beds of shal low- derived debris brought by ‘sedinent-oravity flows... The appearance of the unit in outcrop. is: one Of chythmic bedding with individual beds alternating between positive and negative reliet. Individual. beds are generally packstones and | " wackestones, end contain clasts of sand- through boul der- -sized material. -Boulder-sized clasts are generally transported coral heads mixed with finer debris. The type section. for the Kingshil 1 Limestone is the Villa La Reine outcrop (Outcrop 1, Fig. 13 and Gerhard et al., 1978). “The “Kingshi li Limestone. is hydrological ly important due to the. large number of water wells ideal into be aha its wide lateral extent. water. yield # from the Kingshill Limestone is highty variapie (Cederstrom, 19503 Jordan, 1975). The Kingshill “Limestone is bounded on. the: east and west. by normal “faults contacting the Cretaceous Siliciclastic units. “Structure. “The contact between the Kingsh1} 1 ‘Limestone and the Cretaceous rocks” is described asa “fault by Whetten (1966) and Multer et al. 977, a “cone lusion we follow here. “Evidence from the eastern “Kingshil] Limestone Cretaceous rock ‘contact in the ohilis. at Estate Work and Rest - implies that basin faulting has occurred during or . after. Kingshill - Limestone deposition, in addition to the faulting that. ~ presumably tormed the depositional basin. «Gill ana “Hubbard, 1986a). | - The contact against the Northside — Range is less obvious due to alluvial cover (Fig. 2). - @erhard et ‘al. C1978) suggest with some evidence that there was less. displacement along. this. northern fault ' boundary than along the eastern margin just discussed. Locations of cross-sections drawn through the. central plain are ‘mapped in Fig. (6. Cross section A - AS Fig. 72> shows the marked upbowing of the Jealousy Formation and Kingshil] Limestone strata under. the’. 38 aoe wa 4 ea ® 27h \° or & yay ay o° Q ~wo* @—B an O TEST HOLE. SAMPLES ews ees 2 Mi 4 LOG INFORMATION ese 2 KM Figure 6 Locations ot cross sections A-A’, B-B highlands close to. the northern coast. The Jealousy Formation 7 Kingshill Limestone contact was reached in two test holes: Mz and Mio, the latter drilled during Phase II of. this. project. The Jealousy Formation contact has not -peen reached by the drill bit along the south coast due to normal faulting within the carbonate section there €Gill and Hubbard 1986a). 39 PEAK HEIGHT | FE] PLIOCENE POST -KINGSHILL LIMESTONE FED] MIOCENE KINGSHILL LIMESTONE [==] MIOCENE JEALOUSY FORMATION [G25] CRETACEOUS SILICICLASTICS Figure 7. Cross Section A-H': Krausses Lagoon to Judiths Fanty.. = ae 2 tc -f2 o. a © ,a2 < < ibe — © < ~~ x ; OX | . ° o f=] & So oe ° a a. e o NS . . . = “Ul : ; . , 5 os UETE ARMM ONT OTRATAT Ot COTE TITTT. : ELE aes A\ : ~ © = Ss = AUC iN <r T T °o a o me w ai The. Kingshill Limestone is ‘unconformaply “overiain b by Pliocene carbonates. along the southern coast < ot ‘the ‘island. The contact 1s erosional as expressed in outcrop CLidz, 1982; Gill.and Hubbard, 1986a), and may parallel a fault boundary between Test Holes MS.and MB (Fig. Jo. If the contact between Holes MS and M6 is fault controlled, this boundary would , delineate the northern hingeline of the fault block whose western border: is the norma! fault that runs ‘northward petween Test Holes Ml and M4 (Fig. 43. Cross. section B - Be (Fig. 8) fs drawn ‘on a west to ‘east ‘transect ‘trom Estate Hesselberg to Estate Pearl. The Jealousy Formation under hes: the Kingshill ‘Limestone: across. ‘most oft the south coast oft ‘St. Croix: ‘The position. of the Kingshill] Limestone 7 Jealousy Formation contact 1s “unknown west ot Estate Williams ‘De light due, to poor. core control, and east ot Estate. “Anguilla « due. ‘to faulting within the Tertiary section between Test Holes Mi and. M4. Similarly, the thickness and geometry of the Kingshill Limestone west. of _ Williams Delight is speculative due to poor core control. Stratigraphy. The thickness of the Kingshill} Limestone is reported by Cederstrom C1950) to range 4l rN aa ae Toor} — 1 ( ore oe Ee e- 9 e '| Qtr itd oe adansienentese Become mmm! t > i iD oo sig 0 sIHI! ow IReGlr I poo yk ee eacas piaaas ieee aa H iz = if + —j | LER isiam@e 4 — erat ‘| Sal = pa || ' ! | bbe | li! I a0 eel tl Hy 1 | | ae i al Hi! l | | | || | bE | a Pit, — | ae \| | amen wu fea) | Nh r\ | NI atl Vo! NU —— | ES | | 1 \ | eeeeraciaies Hh faa) { Figure 6. Cross Section B-B': Hesselberg to Pear! “trom 0 to 600 teet. the larger fioure referring to ‘extrapolated thickness in the carbonate highlands ot the Rattan Hill ‘area. In tact, actual max imum . thickness of the Kingshill Limestone is petween 400 and 500 ft in the ‘carbonate. highlands due to upwarping of ‘the underlying Jealousy Formation (Fig. De Thickness , patterns ot the Kingshill Limestone are “shown on an isopach map in - Figure> 9, and reveal three major trends: 1) pinching out toward the north and northwest margins oft the passin: 2 pronounced thickening in. the carbonate highlands close to the northern coast. of St. croix: 3? gentle thickening toward the south ‘ot tne basin, Interupted. by post- depositional faulting along” the south coast (Fig. 926. Well. control for thickness of the. Kingsnil) “Limestone section is poorest within the faulted “section ot post- “Kingshill carbonates, on. ‘the south coast, and ‘to the. west of Estate Williams Delight. In general, Kingshill Limestone ‘thickness patterns follow the. "trends shown by the Jealousy Format ion structure map (Fig. 5). If deformation is ignored, the Kingshill ‘Limestone isopach patterns imply a basin opening to the 43 gs TED CH em cay, ey ct. mg N '< easy on ‘ Ue Wy Py A Ny 4, Wie ey ON a A AALGT WY INN 4%, \ S/O 4 YF 4 79 74 feo Ni SS > Ma A, N= dios cf 7 nt i we ice} als sy VY Fly) I og? 4 we aly vy fio Le) fe) nul é “yt 7° Why fay sy ry yh High it 2? it NN it ra S277 \* Wee <S tre plty NY of ty + syd 7 oN CAS SSS STs Ss = to 9 SY 7 NN yb v> NV 6 ess sa? NX Xo ‘ = 2 777 >O5 \ VN ar Se Tod ° ox \ oN ar! 71 Ne VA \yy\\ Volo Vy Via —— \ aa \ a-N \ 3 ne? Se yl © Q\ \o \ ML? , F igure 9. Isopach map: Kingshill Limestone. south but deepest in the section occupied by tne carbonate highlands. tt should be noted that only three ot tne 14 teat notes drilled ‘Specifically tor this croject eohtact- Jealousy Formation clays: Test Holes Mi, M2 and M10 at Fairplain, Bonne Esperance and St: John respectively (Fig. 4). The other holes, drilled for the most part nthe ‘southern coast, penetrate extensive thicknesses of limestone. The majority of this material is , Pliocene carbonate deposition and the total] thickness of Kingsnil! Limestone in the southeastern region 1s “still unknown. Based on extrapolation in our cross-section, t though, we estimate a Kingshill Limestone thickness in the southern coast industrial area ot 146 to 180 feet (Fig. 8). 5 Blostratioraphy and. paleobathymetry. Samples of “Kingshill Limestone material from Test Hole’ Mi: yield planktic. foram assemb| ages corresponding to the base of the ‘NLO zone cP. McLaughlin, W. van den Bold, pers. _comm., 1987). This” places the base. of the Kingsh il) Limestone in the early Middle Miocene (ca. 15. 5 ma), in good agreement. with. the outcrops studied by Lidz (1982). Benthic foram assemblages close to the Kingshill Limestone / Jealousy Formation boundary are’ 45. very similar to the assemblages found in the upper. Jealousy Formation, implying two points: 1) water depth at the time of Kingshil1 Limestone deposition may. have been on: the order of 1000 ~. 2000 m rather than 600 --700 m (Multer et al., 197?; Lidz, 1982). 2> the Jealousy Formation / Kingshill Limestone transition does not represent a major change in paleoenvironment or paleobathymetry.. Post-Kinashill Carbonates (Pliocene) ‘In most early reports, Pliocene sediments sre lumped together with the rest of the St. Croix carbonates as the Kingshill Marl, and are treated similarly by Lidz (1982): Gerhard et al. (1976) “mentioned a péssible younger age for this part ot the section, but did hot separate it trom the Kingshill Limestone. Behrens (1976) and Frost (pers. comm., 1986) suggested two formations, the Annaberg and Blessing formations. We feel the Pliocene rocks are ‘different enough to be segregated from the Kingshill Limestone, put should be treated as one unit for this report. These strata will be referred to here as the. 46 post-Kingshil1 or Pliocene. carbonates, prior to. formalization of formation names. The post-Kingshi il icatbohates. are the most | consistently permeable and porous ot central plain sedimentary units. They are extensively utilized as an aquifer by commercial and- industrial concerns and are the source of water for at least one public wel] field ‘(Barren Spot). Despite this, the geometry of the unit, its facies and diagenesis are the least understood, , partly due to the lack ot the well logs and exposures. The age of this unit is based on unpubl ished work. by G. Behrens. (1976) and.s. Frost <pers. comm. , 1986), “using scleractinian fossils; on correlation to Lidz: (1982) Miocene-Pliocene boundary determinaton in the ‘Evan's Highway outcrop (Fig. 19; and on field work carried out for this report. Sedimentology. -In most hydrogeological reports and. some well logs, the post-Kingshill is reterred to as a calcarenite. While adequately descriptive for visual inspection and general well logging, tne term can also be applied to many parts of the Kingshill Limestone. and should not be inferred to be unique to ; this unit. Sediments in. the post-Kingshill range from sandy muds to the more common silty sands with gravel generally referred to as a calcarenite. 47 Petrographic ally. the post-Kingshil) carbonates are’ ‘dominantly a benthic foraminiteral, “coralline algal packstone, with significant. quantities of reer and skeletal clasts. The dominance of material derived. from shallow water distinguishes this unit from the “underlying Kingshill Limestone facies of deep-water foraminitera] debris. ~ Stratuacaphy. The Pliocene carbonates are: bounded below and laterally by the Kingshill Limestone. The presumed lateral extent ot both the Pliocene carbonates and ‘the Kingshill. Limestone: is shown “in map > view in Figure “10 with the greatest thickness of Pliocene accumulation occurring within a subsidiary fault plock. ‘Based on samples from: test holes west. ‘of the airport runway, north ot Fredericksted, and from Test Hole Mll | (Fig. 10), shal llow- water carbonate environments stretched along the south, coast of St. Croix, wrapped around the Southwest Point. area, and extended north of. Fredericksted (Fig. 10). The lower boundary and lateral extent of the Pliocene carbonates is poorly controlled west of Test Hole Ml. (Fig: 4). “For this reason, unit thicknesses of — ‘the Pliocene carbonates west of Test. Hole Mi are™ speculative (Fig. 8). Within the fault-bounded Pe Od /— |= = — [ 7. aat [— {[-— T— =A Ant TT Zool: — [| YT —]f- T-T a es A , A 1 boa PT Tae. ; . aaj Lt te fe Te : Pa a ED Oe CS 3 2ot-—Te Ts TT eee] = T= tT » wt — fo Te Ty To 1 aPeh = 1 peso ee oa ee Ly - | -— TO Te Pe — Eredlo } p Seay all [— TT — T= 1 “ 5 KINGSHILL LIMESTONE . . fea POST-KINGSHILL LIMESTONES. (ONDIFFERENTIATED). : { moa a 2 MI © TESTHOLES .- oo me , " (ALLUVIAL COVER NOT SHOWN) - N Figure 10, Distribution or carbonate lithofacies, St. Croix central plain. industrial area on the southern coast, core control is tar more extensive. — We place the lower boundary of tne post-Kingsni i ‘carbonates at the transition between the an plankton-dominated sediments of the Kingshil) Limestone “and the onset of floods of benthic foraminifera and “skeletal depris. This boundary is one that is detectable in the subsurface and can be seen in outcrop. In outcrop, the transition can be seen in the ‘Evans Highway exposure less than one mile to the west: a9 of Test Hole Ma «Fig. 1). The erosional uncontormity in this outérop was’ placed at approximately the Mio-Pliocene boundary by Lidz (1982), and corresponds to our Kingsnill Limestone / post-Kingshil| carbonate contact. Based on our core material, we assign the lower boundary of. the post=+ Kingshill facies to 145 ‘feet: below. sea’ level in Test Hole M4 (Fig. 8). The transition is marked by a change in dominance from the deep -water planktic fauna of the “Kingshill Limestone to the “shal low-der ive benthic fauna oft the post- -Kingshil1 tacies. The core material from Test Hole M4 indicates: that. in most of the area studied on the south coast, the. post- Kingsh it) facies extend tor. at least 185 teet subsurface. Subunits within the Pliocene carbonates: generally. correspond to. three catagories: es Sechdn agveiatn algal, bioclastic packstones; 2) scleractinian, bioclastic packstones and grainstones; a) molluscan, coralline algal, solitary coral packstones. 50 “These correspond to bank, reef. and }agoon deposits 3 all three types exist. in, the southeastern ‘section of the “ basin and on the western coast near Fredericksted (Fig. 10). - Structure. Cross-section. locations for the southeastern basin area are shown in Figure lb. The “western margin: of the greatest thickness ot --post- Kingshil] carbonates lies against a fault contact “near. Fairplain. “Test. Hol e M1 ‘reacnes Jealousy — Formation clays. at -98 ft ms) (Fig. 42>. Test nole M4, less | than, 600 ft to the east, does not contact Jealousy Formation material despite penetration to 962. #¢. below sea. level. “Similarly, waSa, drilled 200 ft ‘to the east — of M1 in 1939 (Gil and pubpard, 19868). strikes Jealousy Format ion sediments more than 80.: teet deeper than the contact in Test Hole. M1, “indicating a steeply “dipping fault zone. “The presence of a: ‘fault. at this location is "supported by the. ‘Miocene- -Pliocene contact in the Evans siglo outcrop: to. the west <Lidz, i982; Fig. 1, this report). in this outcrop, the: ‘Kingshill y oe : post- -Kingshil! “contact is elevated 80 tt above. sea. Si oe a rr a a ae ae -o" a ow \* o7& eo” B » %o AS ~~” p~ oO Wc O: TEST HOLE. SAMPLES fee ed 2. MI See 2 KM 2 LOG INFORMATION Figure 11 Cross section locations: C-t', D-D level In- the cores. drilled:on Martin Marietta this contact is not. reached until property, approximately 180 ft below sea level setting a minimum fault displacement of 260 feet. The Evan’s Highway outcrop mentioned above displays a noticably anticlinal form dipping into the fault zone Faulting through these ‘strata implies: significant tectonic activity after deposition of both the ‘Kingsnill Limestone 52 bt VIEW TO NORTH D’ 100- M4 MS p 4 Mt ao? B87 M9 SL47 pe -— - of 1005 \\t - f= ~ew 7 ~N ie . PnP OD my et ee om NN wna a VERT: EXAG. 2X = rns FEE} Pliocene POST “KINGSHILL LIMESTONE —_ 2000 {.: fd MIOCENE KINGSHILL LIMESTONE MIOCENE JEALOUSY FORMATION : Figure Lz. Cross section D-b': Estate Fairplain to Fearl. and post-Kingshill carbonates, and thecefore extends the time of fault activity into the Pliocene. The Kingshill Limestone and the Pliocene carbonates dip seaward in the southeastern area of the basin (Fig. 13) and are overlain by lagoona| muds and ‘alluvium of Krausses Lagoon and Limetree Bay. The Kingshil] Limestone / Pliocene contact dips steeply 55 WEST. VIEW ms Cc “a Cc 100 4 ms ort od ME BT st 4 NO f= 100 a fa se ln = i A = FP oA papal: — ae a 3 ar eet a a Ae - f— VERT. EXAG 2X (Zc) QUATERNARY ALLUVIUM Ed PLiocENE POST-KINGSHILL LIMESTONE ee 2000 ft. GEG MioceENE JEALOUSY FORMATION Cross section C-C‘: Kraussés. Lagoon to Spanish Town. Figure 13 between the Ms and: MS test noles. The. topograpny and drainage in. an east west line are Anterupted and the lateral extent area of interuption corresponds to the of the reetal facies CFig 14), We suggest that the northern boundary of the reefa!l facies in this area corresponds to the extension ‘of the post- Kingshil) Limestone fault. ‘found: between. Test Holes Mi and M4 CFig 14) o4 we Be e @ Ow > 44 te foc 2250 Ona ce mo 3a Is feo OQ Ow CZs <e eo ae ae 50 Bu CC ( aa ow zw ( 5,a ne) cz or Nn 20 wS eo? wal a <a x, wi O uw es as n= UNV e £5 ew a 5 czy 4 Ld ee cy oa “Ss eo a0 ce ay ®c 2° ow =O) ek& ¢ 6 SY C-¢ CK as S CC <\,. CX —~ OOS med ae} ‘as BEY. v eoo eo ®@ °. FX =< Z TY onl Figure 14. Facies map: South coast industrial area. Biostratioraphy. The Pliocene carbonates are _ generally highly porous and, recrystallized, and ao net. yield recognizabl e. forams for: biostratigraphic correlation. © The plostratigraphic age oft tne ‘Post "Kingshill carbonates is inferred from: 1> stratigraphic correlation to the post- Kingsnill + Kingsnil.l Limestone contact in the Airport- -Penetentiary ‘outcrop (Fig. 1) determined by Lidz. (1982) to lie close to the Mio- Pliocene boundary: 2) the presence of solitary Mussid corals sucn 4s Antillea bilobata and Teliophyllia grandis that went extinct close to the PILOT Pleistocene boundary: (5S. Frost, pers. comm. , 1986). Dolomitization and diagenesis. The Pliocene © carbonates show patchy areas of Blteration to dolomite. with Test Holes ‘MS, M4, MS. M7, M9 and B7 intersecting subsurface areas of ‘dolomitization CFige 1a. The geographic. distribution of dolomi tization tol lows the pre- -~development shore! ine of Krausses Lagoon (Fig. 14) and the subsur face trend follows: the alluvium / - post- -Kingsh i carbonate contact (Fig. 1s). No ‘dolomite has been detected elsewhere in the areas a drilled for this project, or elsewhere on St. Croix. 56 , The dolomitization, as indicated by strontium isotopic techniques, most likely occurred during the Pliocene. Stable isotopic analyses suggest that -meteoric processes are unlikely culprits. tor the dolomitization. We suggest that hypersaline conditions could have been responsible for the dolomitization, and ‘that Krausses Lagoon may be a remnant Tertiary feature. Subsurface dissolution, as evidenced by voids _ during drilling, do occur in the Pliocene carbonates. Voids have not been identified in the Kingshill) Limestone. Adequate water flow for’ significant ‘dissolution probably does exist today, as evidenced by "flowing artesian conditions encountered during the. drilling of Test Hole M7 ‘Fig. 4). -CONCLUSIO NS. L. The south shore and western end ot St. Croix are underlain by carbonates that represent significantly different facies than the Kingshil! Limestone and are Pliocene En ages Tnese deposits represent considerable shal lowing of the: basin. and range from in-place reefs to transported benthic foraminiteral sands. These deposits, classitied simply as post-Kingshil) carbonate ‘in this report, should be > split from the Kingshill] Limestone and put ‘into one or two separate formations. 2, The post-Kingshill carbonates represent three major facies: lagoon, bank and reef... Al) tnree.tacies are represented on the westend as “well “as the. south-central coast. a 3. An area extending from Estate Judith s Fancy to Estate Colquehoun was mapped by Whetten (1966) as tne. Jealousy Formation (Fig. 2>.- Exposures in this area are “completely unlike the Jeatousy Formation sampled in the subsurface and are similar to Kingsnil| Limestone exposures in neighboring areas. We suggest © that these exposures be mapped as the Kingshill Limestone. 4. The northern section of Kingshill Limestone deposition is. characterized by extensive deposition. ot 58 rounded-pebble conglomerate tacies. This tacies is found both in outcrop: and subsurface in Test Hole Miu. 5. The contact between the Kingshil] Limestone and the underlying Jealousy Formation clays .1is unambiguous and abrupt. However, analyses undertaken in Phase II of this project show that despite the color change between the formations, the mineralogic content , and foraminiteral fauna of the two formations are very Similar. - 6. The Kingshill! Limestone / Jealousy. Formation contact forms an unculating surface that upwarps ana crudely follows the present island topography. The ~— Kingshit] Limestone does not thin over these upwarps. and there 1s some evidence. for ‘folding in. the carbonate section. over Jealousy Formation topographic highs. We submit that this 1s evidence for deformation during Kingshill. or post-Kingshil] time. 7. The Cretaceous rock / Kingshill Limestone contact on the eastern margin ‘of ‘the basin ‘shows — evidence ot fault brecciation, structural dip and ‘abrupt, nondepositional contact. lf true, this suggests that activity along tne basin margin fault blocks. was not completed prior to ‘Kingshill Limestone 59 deposition and continued at least through Kingshi 1} time. 68. A fault of 260 feet minimum displacement cuts through the ‘post-Kingshi 11 carbonates on the soutn shore extending the range of tectonic deformation well into the Pliocene. A curvilinear extension of this fault runs east - west ‘between Test Holes Ms and Ms, segregating facies ot the post- Kingshill carbonates ana cimming the outline of both Krausses Lagoon and the Pliocene + reet tract. “Evidence for this tault includes. disrupted drainage, disrupted topography and lateral -€acies transition. 60 REFERENCES Behrens, G.. K., 1976, Stratigraphy, sedimentology and paleoecology of a Pliocene reef tract: St. Croix, U.S. Virgin Islands: unpubl. Masters thesis, Northern Illinois University, 93pp. Black, Crow and Eidsness, Inc., 1976, A water management plan for St. Croix, U. S. Virgin Islands, Gainesville, Florida: Black, Crow and Eidsness, Inc. Buros, 0. K., 1976, Wastewater reclamation Proyect, St. Croix, U. S. Virgin Islands, Report No. EPA-600/2-76-134, Cincinnati: Environmental Protection Agency. Cederstrom, D. J., 1950, Geology and groundwater resources of St. Croix, U. S. Virgin Islands: U. ' §S. Geological Survey Water Supply Paper 1U67, 117 Pp. Cushman, J. A., 1946, Tertiary foraminifera from St. Croix, Virgin Islands: U.S. Geological Survey ‘Professional Paper 210- A 17 pp. Folk, R. FP... 1974, The Petrology of Sedimentary ROCKS, . Austin: Hemphi 11 Publ. Co., 173 PP. Frost ; S. H. and. Bakos, N. A., 1977, Miocene pelagic biogenic sediment production and diagenesis, St. Croix, U. S. Virgin Islanas: Palaeogeograpny,: Palaeoclimatology, Palaeoecology, v. 22, Pp. (137- 177i. Done , Geraghty and Miller, Inc, 1983a, Report on current — groundwater conditions in the U. S. Virgin Islands, Syosset, ‘New York: Geraghty and Miller Inc., 89-pp. “Sty clulee eee -----, 1983b, Groundwater management plan for the U. S. Virgin Islands, Syosset, New York: Geraghty and Miller, Ine., 86 pp. Gerhard, L. C., Frost, S. H., and Curth, P. J., 1978, “Stratigraphy and depositional setting,- Kingsnil| Limestone, Miocene, St. Croix, U. S. Virgin Islands: Amer. Assoc. Petrol. Geol. Bull., v. 62, - no. 3; -p. 403-418. mt, - : Gill, I. EF. and Hubbard, D. K., 1985, Subsurtace sedimentology of the Miocene-Pliocene Kingshill Limestone, St. Croix, U.S.V.I., in P. Bb. Creveilo and P. M. Harris, eds., Deep Water Carponates: ‘Buildups, Turbidites, Debris Flows and Chalks, Tulsa, OK: Soc. Econ. Paleon. Mineral. Core Workshop No. 6, p. 431-460. ~-------4----------------, 1986a, Subsurtace geology of the St. Croix carbonate rock system: Caribbean Research Institute Technical Report 26, ‘College of the Virgin Islands, 86 pp. OO pened een en en nc enon nec scsrcncn, 1986b, Groundwater rs geochemistry of the St. Croix carbonate aquifer system: Caribbean Research Institute Technical Report 27, College of the Virgin Islands, SY pp. ‘Hendrickson, G. E., 1963, Ground water for public. supply in St. Croix, Virgin Islands: U. 5S. | ‘Geological Survey. Water-Supply Paper. 1663-0, er “Jordan. D. G., 1975, A survey of the water resources ot St. Croix, Virgin Islands: U.S. Geological Survey _ Open-File Report, Caribbean District, San Juan, 51 pp. Kemp, J. F., 1926, Introduction and review ot the literature on the Geology of the Virgin Islands: — New York Acad. Sci., Scientific Survey of Porto Rico and the Virgin Islands, v. 4. pt. 1, p. 3-693 -efted by Cederstrom, D.. J., 1950, Ground water. resources of the U. S. Virgin Islands: U.S. . Geological Survey Water Supply Paper 1067, 117 pp. Lidz, B. H., 1982, Biostratigraphy and paleoenvironment ‘of Miocene-Pliocene hemipellagic limestone, | “Kingshill Seaway, St. Croix, U.S. Virgin Islands: J. Foram. ‘Res., v. 12, p. 205-233. Multer, H. G., Frost, S. H. and Gerhard, L. C., 1977, Miocene "Kingshil] Seaway" |- a dynamic carbonate basin and shelf model, St. Croix, U.S... Virgin 329-352. Islands: in Frost, S. H., Weiss, M.-P. and Saunders, J. B. Ceds.>, Reefs and Related ‘Carbonates--Ecology. and Sedimentology: Amer. Assoc. Petrol. Geol. Studies in Geology No. 4, P. , 62 7 Robison, T. W.. 1972, Ground water in central St. U “S. Virgin Islands: U.S Geol. Survey croix. Open-File Report, Caribbean District, 18 pp. Shurbet, G. L., worzel, J. L. and Ewing, Me, 1956, Gravity measurements in the Virgin Islands: Geo} Soc. Amer. Bul} ’ Vv 67, p.. 1529-1536. Todd, R., and Low, D., 1976, Smaller toraminitera trom. deep wells on Puerto Rico and St. .Croix: Geological Survey Professional Paper 863, 5S& pp. van. den Bold, W A » 1970, Ostracoda oft the Lower and St. Martin and: Middle Miocene.of St. Croix, Anguilla: Caribbean Journal nos. 1-2, p Of Se1ence, v. iu, 35-61. Whetten, J. T., 1966, The geology of St. Croix, U S. Virgin Islands: Geol. Soc. of Amer. Memoir 98, Pp “177-239. » 1974, Field guide to the geology of St. Croix in Guidebook to the Geology and Eco logy ot some Marine and Terrestria! Environments, St. Croix, U. S. Virgin Islands: West Indies Laboratory Special Publication No. S, p. ley" 14s. 63 ee a ae 64 Textu re- e a mdst wkst pkst orst a5 Qn AZaANY Key catter tou Wot Wout to Wel] Log Abbreviations Folk, 1974) sandy, Sand siity, Silt. ‘gravelly, Gravel muddy, Mud . clayey, Clay We slightly gravelly sandy Mud u - sanay. Gravel: mudstone wackestone .packstone . Grainstone Sample Designation Ched ss) “ab hs TS Color bk br bu gn OY or re tn wh ate i ou wou tou. Wow Welt oe | ee sample no. 12 split spoon ‘sample ‘diamond: bit. sample hoilow.stem auger sample . thin. section made from this sample. black brown. - blue green grey. orange - red tan “white yellow light dark Key to Well Litholoay — b. toram. calc cmtd CBS frags “Pith Ls. — Mn Pp. foram rol ‘recov. rk ske |] spl. howe Hou dl now Wow WW. i} Log Abbreviations. (continued? benthic foraminifera calcareous | cemented carbonate fragments lithic _ limestone | _ Manganese. planktic foraminifera rubble — recovery ‘core recovery) rock : skeletal sample Ov ON. | TEXTURES TEST HOLE M7: KRAUSSES. LAGOON 80 90 100° -wh. (g)zS; Halimeda’ and mollusk fragments (ca. 80%); reworked Pliocene (2) LS age : “GRAIN TYPES STRUCTURE - Maximum Depth:.270 ft . dominant (50%) Drilled:-15-Oct 86 ; : sbundents (11-80%) SITY. \ (HOSTER | 2 tere BAS? Lp wleleler PORO : “oo Teann BA ELEY Le DEPO| SZ\2 4 %. TYPE : DESCRIPTION . erve Eletsl2).]_ 3 £13 | wore El >| 0.20% Wixey/ “pm 7 lloleleicisislelste om _|ras above; 18 inch recov. * _|-as above; 18 inch. recov. Lagoonal sands and muds Bioclastic debris -gn-wh: mottled (g)sC° blows: 8,9,15 Other = 4 a “gy-bn stiff sM a blows: 14,16,20 S - - ‘oo | |-wh loose (z)gS: i CO3 aggregates . blows: 5,4,3 E ~CO3 bn-tn gM; recov. =6" z yo bl. ent.#14, 18, 220 3 ~gy-gn M (cale?) : . ~ blows: 8,14,22 j-stiff olive gn ‘2C w/rd. . “streaks; recov.=10"; blows= 14 15 205 03 clasts re- | ; rhed’LS . Lap. i ‘\-gntwh marbled soft. (g)2C ; yess \a blows: 2,5,5 1 r \ C03: clasts: Ls age. : usyss?- -wh gM, calc. oo Tyee te pea gravel We. i Cee -biows:. 8,612 a4 (16)ss0 -wh, rd stained calc. mC | a. 90m, blows: 15,14,15 ~ g To ¢ aca @ re - ce * La7)ss a Jr. s = vee %e =gntbn (g)s sM z 4 f8)ss , zones of C03 pebbles © a: toi oe. continued CONTINUED © | - . ; LEGEND ; : UTHOLOGY FABRICS *: POROSITY TPES GRAIN TYPES STRUCTURES ae Oe cdsione m= Molde . B. Foram = Benthic Foraminitera A\s atid limestone pkst-pockstone t=Primory interporticle . S|. her { bed whst-wackestone X=lIntererystolline P. Foram m Planktic Foraminifera = izonto s dol kst-mudss V=Vogoy Coral = Coral _ =| wavy lominations marl FeFrocure C.Algee = Coraline Algae =|. groded: bedding ; : Ech = Echinoderm 4 : . sond ‘Mol = Molluek LE | frocture. clay Pelold =. Pelold fp |. bioturbated Lithig = /LithicGrain Ld “Other ; TEXTURES | foo . . ; _ GRAIN. TYPES LITHOLOGYSTRUCTUR .| TEST HOLE M7 (continued) ’. dominant (960%) : ; . : ° : abundant (14-60%) _ common (2~10%) | Vx POROSITY: . es : o tare (0-1%) " = ee Pe ener EVs! lel | fy] | [DEO os 0} | O10 % TYPE DESCRIPTION. oteilste Profs oa WYi<Xlo neon . fan | ae Sl<|<|<l2l=|2 INTRP SS E} 39 #0 20 30 xe v4 slolojolulsielsls . . 100 Las above: gn + bn’ (g).sM : y : C03 pebble zones: : 5 gn + bn marbled 2M : 3 <u . - sed “110 Bi fod 9 ° » ’ i D> we i : oe) 120 - - : z 2 \ Fen-bn (s)gM ~ : 2 : a . ~ es . . : n N ; -bn mS; terrigenous G + 6 Zs o}d- reworked. planktic. forams. V1} > @ a 130 & 9 ‘Lbn sM to. bn coarse S$: a8 blows: 12,14,20 S48 > ok Ftan sM, minor C03 g ae ‘hd layer - &§ cS) 140 blows: 16,39,61 Roam — ~~ r-rd-br sM; minor C03 g 3° blows: 12,20,21 ° KV hd hes recov.=12" ° br + wh'mS+G (calc G) bal plows: 28,157,refusal [i ; . i) bn mS+G;, . silieielastic , 3 ~Tecov.= 2" E -dk br ang G 5 . : Sal > EI rt = alt. br.+ wh ce SM 4 tH calc. and silic. oo : . G=C03 age tceweckad LS) een + wh LS mS+G : . : emtd. C03 288 G did ¢ ao] we o. oD aed L-wh mG: LS G si . ORT S65 Ow 9.0 | Ew a eo o> en : : . “To oa | ond L-py-wh mS+G . x 33 ang. LS G o 3 et a Coal a | - |continveD en LEGEND FABRICS POROSITY TYPES : GRAIN TYPES STRUCTURES ae relator een crernorticle B. Forem = Benthic Foreminifera As ime wkst-wockestone - Ko tmercrysallne - P: Foram se Planktic Foreminifora = horizontal beds kst-mud V=Vouggy - a : Coral == Coral | a wovy lominations F=Frocture C.Atgae = Coraline Algae fe} groded bedding Ech = Echtnoderm — Mol = Mollusk | RE | froctre Pelold = Peloid - & bioturboted Lithte = .LithicGrein Le : ‘Other =. Other : TEXTURES [GRAIN TYPES GY i eran ae : dominant LITHOLOGYSTRUCTUR TEST HOLE M7 (continued) a atundent (11-80%) : : _ _ _— . . . “common (2-.10%) . . zo POROSITY os | [Mup oo rere (O- 1%) > og cleteie ; _| ; ; .|SAND =: E Ee © DEPO wr oO] ol a} ao gy: |TYPE]| DESCRIPTION — .- GAVE S/o} slot Plofs . So «8 SE sae : | - * eo LE PET S| sts] slSfele| [INTRP O° =I 90 2.90 ixky, 26 076 Hislelolalelsielsis6 } adau |+wh LS. mS -+-G" ; : i ; : blows: 28,32,31 _ dolomite (ca.100%) .-.- ' o |: artesian: flow € . i ww 2. ev -wh LSS + G; minor gn C & recov. 9", rest collapse 7 ‘blows; 31,88, refusal £6 . oe e v nN ow _ uw fm E ey IS -as.above . 2 -| ° < blow: 31,29,refusal _ a j recoy. 9", rest’ collapse. . w » : . |-as above; hole caving ale ° & rockbit drilling to 270 ft 3 no spls,. hole collapses 2 easily . : oo . : a> ‘{oalt. layers G+. S(?):. me either gravel layers or gh layers of cmtd C03 ‘ee . ‘ a +lose return. water flow Avoid; ca. 1.5 ft. dian. -2.voids.ca. 1 ft. diam. 270 : ~ END TEND. OF HOLE Se a _ . LEGEND a foe “LITHOLOGY FABRICS” POROSITY TYPES. * . GRAIN TYPES STRUCTURES, Py . : Gest-groinstone m= Moldic : B. Foram =m Benthic Foraminifera. nore . limestone pkst-pockstone t=Primary interparticle - oO ; Lol, horizontal bed: : ieee’ whst-wockestone X=Intercrystalline . P. Foram a Planktic Foraminifera * pees - : dolomite mkst-moditone V=Vugoy Coral. = Coral : wovy lominations. EEE ment F=Frocuure . C.Algae = Coralline Algae wi Jding Ech =. Echtnoderm : rend Mol = Moltusk fracture clay. Pelold = Pelold ; bioturboted Lithic ‘= -LithicGrain Other = Other ‘TEXTURES| =. TEST HOLE. M8\(Spenish Town) 9 “GRAIN: TYPES - LITHOLOGYSTRUCTUR Maximum Depth: 95 ft. : dominant (950%), : ao “Drilled: 27 Oct 86) 7 -hundént (11-86%) = POROSITY / Soy rare co-1%) TE ~ 5 * olalsisls|[ 9 [TYPE|| © DESCRIPTION. | 1] | lsle[ enol bo g Ssegisl| * anak Eye) s)Zle|<|s]2 2] |INTRP] a i 1020 90 MIXF y ole Slsfelslelslé 28,63 ooo ete Packed Amphistigina tests as above as above; recov.: 12” : er ai a ale . | BC: 30,59,refusal 2c . as above; recov.: 12" las above loose or zS+G, LS recov. 6” ° as above hd layers: ss cuts cylindri- cal pieces . - tn-or LS zS+G BC: 10, 12,18; recov. 9"~ : = “| fede! Jas above: recov.: 18" bbe | a i 1 Tor BC: 13,19,13 micritization common Pliocene LS: shelf foram-algal: deposits as above *® void as above o! ies a | wie | C: 40,38,504 = Pei age in planktic forams ; {od cmid. layer i aa t LS. 26 . "Bc: 183+ (refusal) emtd layers , as above; recov. 6" BC: refusal. : a emtd. layers from 60-95 ft tan LS; BC: refusal emtd. layers F as above me | Be Sige eos | | i} aed Cal 7 ° a av 73 : i) vA WwW oo aa awd me @ ~ a Oo as above og nD oOo oo aaa as above 23 c.. cal 2] so - r = Lal as above . oa ia . | “TT blows 70, 150+(refusal). ; : glauconitic : as above; blows: 51,44,99 END OF HOLE . : __ LEGEND ve : . LITHOLOGY FABRICS POROSITY: TYPES : GRAIN TYPES : ” STRUCTURES t-greinst = Moldi : : : . >| eross-beddi Orsi-gromstone m= Moldic ; B. Foram = Benthic Foraminifera | Ne ibe limestone. pkst-packstone - 1=Primory interparticle : ; =" herizontel wkst-wockestone X=intererystolline P. Foram m. Planktic Foraminifere = izontol beds dolomite » mkst-mudstone V=Vuggy . Coral = Coral. cae beminations = : ; Ime ny | mart : fF Fracture ; C.Algee = Coraltine Algae © 0 fe or sdding Ech = Echinoderm {___1 : sond “Mol = Mollusk LE | trocture cley . : : Peloid = . Pelold. > bioturbeted Lithic = | LithicGrain _—— Other = Other af “SP TEXTURES) 0. TEST HOLE N9- (KRAUSSES: LAGOON) oe GRAIN TYPES. » LITHOLOGYSTRUCTURE . : Maximum Depth: 200 Ft ° : dominant. (960%) ; : : : “Drilled: .29 Oct 86 : - abundant (11-50%) ——_— - —— oe - common (2-10%) =x : POROSITY ar . cee (0-.1.%) DEPO es : - - - . ecje oT EE % olalslsis|[— q [TYPE|| . DESCRIPTION SElz1E] | lelel- 85 B OPS eIo . o aa ele clele| sle}e]2] NTRP ie 290 MIXFY, elelo[o{wlslei5lo ()ss ; organic debris and tan 2S+G S wees BC: 5,5,3 ga ~~ aw (2)ss mcr _dk bu-gy. 2S+M; org. rich Earet BC: 1,2,1 wos — co 2 Th (3)ss . woody.org. debris grading =. . downward to gy-bn C and fede re tan ¢ : s (4) ss Jiquid tn 2S, cale., BC: 7 r 8 : = : ; We i9s C03 clasts are re- r a oe . | worked Pliocene: o (5)ss— : . : top: liquid wh mS - : é —— . btm: stiff tan. gM; blows: a 655,45 3 - et (6)ss..° 4 Q dee: tn SM - stiff tn M < BC:0 : K (ss : y _ no récovery;. fluid, un- & consol... matl. (8)ss : tan zS; loose, calc. BC: 1) i a . . “12,14; LS clasts show | : : weath, rhinds; algal tub- (9)ss : ule pens ! tan to brick re SM; blows: oe 7, | 13,11,12._ 7 (10)ss - olive 3,15 Cc. wpb mottling & oo . . |: 8 (11)ss as above $ BC: 12;12,19 i . 0 (12)ss._ a ; as. above ar . _— : BC: -6,9,13 : _Lg%.rewkd pl. forans | Q3)ss_ tn-wh sC -W/bk mottling BC: 10,12,17 (14)ss .. Pde tn sC3 s=calc. : ; Ty Pad gntbn marbled ‘st 15)ss : 7 : 15,17,17 0 — . a Sal (16)ss ; bn_zS_ gfe eases (Si+C03). a eo 8 : . F . BC: a aan (17)ss a ers sG, Si4C03 a vee : . ce <2? . ) ws : - a (18)ss br ans-sM, —_. y 27,7410: + et _ 3 (19)ss : br mS+G 2 cont. _ ual ; CONTINUED ~ ; : : LEGEND : : . LITHOLOGY FABRICS POROSITY” TYPES GRAIN TYPES - .- STRUCTURES - wer : 9rs1-grainstone M=Moldic - B. Foram = Benthic Foraminitera: AS sheild limestone pkst-packstone : {= Primory interporticle : = . whst-wockestone ” X= Intererystolline P. Foram wz Planktlc Foraminifera == | horizontol beds dolomite mkst-mudstone V=Vuggy’ * Coral =. Coral ca wovy laminations mart : : FeFrocture C.Aigee. = Coralline Algae . [== | graded bedding Ech = Echinoderm t+ send Mol. = Mollusk 2S] frocture clay ; Retold z= Pelold : <p bioturbated Lithic = LithicGraln — Other =. Other ] TEXTURES. LITHOLOGYSTRUCTURE oe TEST HOLE: M9- (continued)... 160 170 “180 190 200 - ‘GRAIN TYPES... dominant: (050%) abundant (11-60%) on 2. Common (2-10%) . POROSITY MUD e rears. (O- 1%) : oy eiterten , sano fed |ELE] | o DEPO ARR Ar % TYPE}) DESCRIPTION | - gAvtLL_ilels|s|e Pl oped Bees} 3) roa : > 1p {£l Elel<| c/s} e| 2] fIntRe 90 20 90. ree v/ 262.0 75 |lolelolofulsletsls ; ; dk bn zS+C oe ri : lithic grains (terrig.) 95% . , n : C03 gravel =. 25% 2 4570, rfel. 2 o v 6 bn, (m)sG, Si x BC: 16,40,99 a an] « 3 a ™ bn sM; BC: 9,12,16 tapes r | lithi¢. gvl w/ wthd. srhinds tn Be gi i 13,2 30, 35 Fluvial and Estuarine Deposits bn (s)mG; Si, minor cop BC: 45,63,rfsl top = brick re (g}sM . © “ybtm: wh sG, LS (27)ss ‘tz ZZIL br sM, loose calc S$, mS+G BC: 11,12,19 leached, rnd eqnt spar exp. surf? 4mS w/ cale zS$+G layer BC: 11,31,20 (31)DB xvoid 2 loose br, wh,gy, BC: 97,73. BP med LS - Dolostone, 922 recov. . Superb text. preservation ‘geopetals common as above, friable; 49% recov. nummulitid. pkst) Pliocene carbonate (32) DB cmtd. layer ends ca. 189 ft mS+G; G =-Si +C03 Shallow Bank and Slope: Foramalgal Deposits ; ; : ; LEGEND ; UTHOLOGY FABRICS POROSITY TYPES | GRAIN TYPES J-grainston = i : limestone wat pockstone te Pony interporticle B. Foram m Benthic Foraminitera wkst-wockestone - X= Intercrystolline P. Foram wm. Planktic Foraminifera dolomite mkst-mudstone * V=Vuggy Coral = Coral mari F=Frocture C.Algae =~. Coraline ‘Alone Ech = Echinoderm song Mol = Mollusk clay Petoid =. Petold Lithic = LithicGrain Other = Other STRUCTURES —. _ “eross:bedding - horizontal beds wovy lominetions groded bedding frocture . oN “TEXTURES: a, er 3 GRAIN TYPES”. F . ae TEST HOLE M9.. (continued). dominant o% LITHOLOGYSTRUCTUR “ sbungant (11-80%) a : e : : “ ‘, common (2-10%) xz. ‘ : ; POROSITY : : ey, (O-1%) DEPO io i e,e< ae, es fbb dd ° j AVL si5l-18 2 Stn = . CARAS TYPE DESCRIPTION 8 sf] Oo] OLS sis . 25 9 SIZE] ® | mo LUT El </e| lS] 12| [INTRP oe, HEEFT LL 1 20 90 brixey ; ve 26 60.76 |icielololulsielsiojl 00 (34)ss Me lefele wh. zS+G, clean €03 : a A BC: -15,20,23 4 END OF CORE’ 4 4 4 ae ; LEGEND a ; LITHOLOGY, ~ FABRICS “POROSITY TYPES GRAIN TYPES. _ STRUCTURES _ oct mackstore M=Moldic sicko” B. Forem: = Benthic Foraminifera as : fi : St-packstone = Pri ert ita . eo i imestone wkst-wockestone Ke interchstoline : P..Foram m= Planktic Foraminifera horizontal beds dolomite: mkst-mudstone V=Vuggy .. Coral = Coral wovy lominations mar! | F=Frocture C.Algae = Coraltine Algae gioded bedding Ech = Echinoderm : sond Mol = Mollusk fracture clay -Pstotd = Pelold bioturbated Lithic = LithicGralin Other Other Perens YpTRUCTURE a - |” TEST HOLE MIO (ST. JOHN) © eee osew) LITHOLOGYSTRUCTURE "Maximum Depth: 105 ft | BP stoncent Cr1-s0%)) 7 ms . . Drilled: O7-Nov 86 ce ; -eommon: (2-10%) = |x. POROSITY i ; cog rare ~(0-1%) PO cr % Parra Pore EB] DESCR Zoe. os 8A ele| fe de DEP aoe : VE Pref e| stolid Eo SiBEB|] TYPE], DESCRIPTION, | ie =/2}E/2] <]<[3/ 2] 2| |intRP| “S 0, {El = 20 9 MIXFY hentia 26:6 76 1 iclejoiolulsiel alo. (ss : : lt br sZ, minor C03 m snes | BC: 9,12,15 > 10 : : : 7 ; 2 (2)ss_ | lt tn sM;.BC: 9,16,17 Eile ————- p- forams dominant: prob. > _— rewkd. a wen layered tn 6M, dk Si G 3 (308s : BEES, 14,15" 5 a teal 20 foe ; | ; } : (4)ss. - ; | “|Itn_2zC w/patchy wh Z 7 : : : | BC: 811,12 7 |} des. : -fevzgn (Z)eCs 6 = Si + LS a | ° im a ss] | aE (PIs : , yss . ; sM + cmtd layers, = Kingshill : : ‘LS; BC: 20,3 38, 22 (7)ss— - : as above; BC: 17,26,27 (8)ss as above; BC: 46,140 (rfsl) oT fe eri 5s — ; : rewkd-CO3 agg common; one : v — dolomite agg. 3° ()ss— ee a ee] ] | das above; BC: rfsl ~ * 50) : = an : S) eM; = dk bn si ia 610) ss): Foyt PEELE TL Pep8:?155 635 46 ® . ° r 7 eo] ; ts: ; | “fla ereds ‘eomtd ste, sM , eer ; mire (11) #8 - | P*ber 36, 133,74 ay tye) ye : a Milse : pee a : - : C03 ie ghallow bioclast : ra 60k. ft fo. . : aséblg;P:B =.2 yo. (zyss y 7 77 ; las above, BC: 13,27, 36 a4 . °. ou : vo} ; to z- " Py. . | : 4s above: lith. sebb. cong. | ze C13) 8, mane BC: 37,10, 764 P e 6 - rae Tee i ° : pn bn (g) si; BC: -13,15,27 E og. M14) ss : : : co age: shallow-water : a en on | : asSblg,. intraclasts Z (15)ss j : : hyrd:. tn sigh pebb cong. ° orn ae bn + z pol. : “Ber 39566, 76" 4 (16)ss |. ni i Paed diy tn sM, + gr-bn sM : . oe LLLP de 1,814+(r£si) of: (17) ss | - kop 1.1 ft: tn sC,P:B =53- : : btm 1.1 fet By- -bn sC (foram r : “rich)3 PiB = 45 ; a : 7 (18)ss J : : bn sC, foram-rich eS ° : . . : cde [ BCs 18,31, 31° est . - ~ nal . 19)ss ]. . “as ‘above OWE . } : aes os : . Ste 100 —— : . Sw FABRICS POROSITY TYPES : a: GRAIN TYPES. ° __srructurts Past pechstore . penne rerporticle 8B: Foram-= Benthic Foreminifera.- = = interpartic! . : ma i wkst-wockestone - Xelotererpsllive : P. Foram w= Planktic Foraminifera horizontel beds kst-mud “VW=Vugoy oo : -. “Coral = Coral wavy lominations - ~F=Frocture i C.Algae = Corailine Algae groded bedding Ech = Echinoderm . Mol = Moltusk frocture Peloid = Pelold bioturboted Lithic, = LithicGrain Other ==. Other - TEXTURES |. coe OE GRAIN TYPES | LITHOLOGYSTRUCTUR . TEST HOLE M10 (continued). : dominant (0%) — : : ° 7 - . nf abundant (11-80%) i : : : . . common. (2-10%) =x. POROSITY. . : MUD ean ne (0-4%) DEPO ars ~ ~ - . . ele © . . . 52. % olalslslsi— a [TYPE DESCRIPTION 5}51<18 Bleols |}. co — oO fojmcit- 4 ae . : wfuelfeicl. ela} « Ko, 6, HL EPSTSI FL) 45 20 a0 : : : [ebst<retslepe| | LINTRP . th bale IXFEY, ; ; elelfololw{sio{aie 100 (20)ss° gy-bn sC, stiff, plastié * fs > BC: 20,34, 34 is P:B = 59 : . as above, P:B = 20 1 END END: OF HOLE 110 4 4 4 4 4 _ LEGEND mca UTHOLOGY. FABRICS -" POROSITY.TYPES . GRAIN TYPES STRUCTURES : Orst-groinstone me oldie interporticle 8B. Foram «= Benthic Foraminifera A\ ee . . = Primo inter; = . 5 whst-wackestone - “Xe Intererystolline PL Foram m Pianktic Foraminifera == | horizontal beds dol. kst-mudsior V=Vuggy Coral = Coral [=| “ wavy laminations mart F=Frocture C.Algae ..=. Coralline Algae == | gr bedding - Ech = Echinoderm t—-—— . sond Mol = Motivek RE | frocture clay Pelotd = Pelold fp bioturbsted Lithic =. LithicGretn ———. Other =. Other — DL cemenans ca neat ne pment don, eens marae Sarees mupeer | TEXTURES “GRAIN TYPES fo Other = Other cel TEST. HOLE MI 1 (HESSELBERC) : LITHOLOGY, aun — dominant. (960%) LITHOLOC STRUCTUR Maximum Depth: abundant’ (11-50%) _ : aan sity Driiled: - _ o . | Yoo common .(2-10%) | ; . “POR , . . ‘[muo. Bigeas fo rare. (o-1%) wef epee : Pan : SAND faced | E £ ‘8 DEPO DO}. O11]. oy, TYPE . DESCRIPTION. oRVL it esl otal: F]olel Bsa posta we PELE] Ett 2] <|s]2| 2] |INTRP =| 3 [290 20-30 WIxF 2560 78 | lolol Slolalsiel|Slo HS-spl; no penetration. w/ss ; re-or + rk flour S high wthrd microspar o me clasts;algal tubules me Tv rdsh tn sG; BC: 44,80,46 gal " 7 " 5 var. -pres. os ‘ : = tn-or emtd LS S$ + G oven ie ee f . I & . — . | - : : : 4 emtd. lyr ca. 1 ft thick , rock,bit drilling from 20- ’ 1 N wh emtd LS: $+; BC: 15, a a . tf. 22,15 me | q ; rock bit to 30 ft, void ood. . : ; as above; BC: 8,5,10 . SC | | voids | od: 3S as above; BC: 15,23,23 | “g | a zo : : . qo 3. . : is] as above; BC: 15,55,70 8 (7) void: 42-43.5 ft e as above; BC = rfsi rc Tr {a 1 : a 3 . . cal | o : . Oo . : . 1. o . . 7 : as above; BC: 79,180,85+" 4. _ (rfsl) : : oS. ‘Pas above; BC: 33,79,21 7 : b texture obliterated by “Ed : i M ° [ b clay. mineralization = : END OF HOLE — 70 90 a LEGEND "LITHOLOGY FABRICS | POROSITY TYPES. | GRAIN TYPES _STRUCTURES _— . Qrst-groinstone M= Moldic ; B. Forem. = Benthic Foraminifera A\d am s | fimestone pkst-pockstone . J= Primary interporticle oo, Lo Loe . == herizontal beds whst-wockestone X= Intercrystaliine “P. Foram m Planktic Foraminitere = Senile - dolomite. mkst-mudstone V=Vugoy Coral. = Coral = wavy laminations =. mart © F= Fracture C.Algae = Coralline Algae’ = o 4 bedding Ech =. Echinoderm +——— send Mol =: Molluek [RE | frocture clay Pelold = ‘Pelotd efp | bioturboted : : Lithtc =. LithicGrain. — LJ fe: ov TEXTURES} 9... > TEST HOLE M12 (CASSAVA GARDEN) GRAIN TYPES. - i . > Total Depth: 1 dominant (60%) [LITHOLOG STRUCTURE | prdlled: 8 Dec 86. aa " gbungent (117608) . : - ve common (2-10%) ROSITY : MUD hy | ° rere (0~4%) Fog tle POROSIF) sano kecd |ELEL fel |{DEPO f=. % olelslslsl[— 4 (TYPE! DESCRIPTION orvel 4) 5} 5/218] | lz} e]s fe o OSS ° . 2d . * {J2{"] Slefelslslele INTRP SL ELF 90.2090 MIxFY . 78 | islelstojelslelslolt is a “TT: : : : uw o (l)ss. wh emtd LS, 25+G ° . oo ; dominantly ‘un 1D bioclasts ; ec | algal tubules éa 10 T) wo” B (2)ss as above; BC: 16 total i 5 (3)ss— as. above; BC: 34,9,8 ra i i | a 20 “| - END END ‘OF HOLE 30 4 : ; — = LEGEND ~ " UTHOLOGY FABRICS POROSITY TYPES ; GRAIN TYPES _smucturts woe : vee : cross-bedding rt-grainstone. M=Moldic - B. Foram = Benthic Foraminifera NE . pkst-pockstone t= Primary intecporticle 7: : == horizontal beds wkst-wockestone X=lntercrystolline P.Foram m= Planktic Foraminifera = kst-emud: V=Vugay Coral = Corel. = wavy fominotions - F=Frocture ¢ —— , ; cty C.Algae = Coraltine Algae === | greded bedding Ech = .Echinoderm ee Mol = Mollusk . | RE | frocture Pelold = Peloid : > | . bioturboted Lithic | = LithieGratn bj Other =" Other -. TEXTURES : TEST ROLE MJ3 (CASTLE. COAKLEY) " - 7 Jen : dominant .(50% . /STRUCTUR Maximum Depth: 15 ft spundant: (11-80%) . : oon : Drilled: 8 Dec 86 “Bemmon. (2210%) Se A oe : ° ° |e : G- 4%) fBo pe oe LD ee POROSITY. oY, de, tere ¢ ) DERO epee - _ : e-e © , ¢ er % Pir ered rose — rye. © o : : SR, | | TYPE DESCRIPTION Jeloisio Zlels fer o Sagi]. & i MIE} Si<ie)s/2/£)2] |INTRP] NO. RP EPS 1 20 Wixry olel{olojulsletsto : (1)ss.q° re-or mod emtd LS, z2S+G i i te . BC: 22,14,17 wt +t a3. 10 ; oo : (2)ss as above a : BI . 8 a ne void hae : — L no penetration - cmtd layer Bo . FREND END OF HOLE 20 5 . 1 ad ag. og vo 4 a 7 4 : oo s al s #. a 7 a “s 4 =z . vos “f ~@. s . : 4 * ‘@ “ : LEGEND : 5 % UTHOLOGY FABRICS POROSITY TYPES _ GRAIN. TYPES’. ___ STRUCTURES o F oie wockstone M= Moldic ile B. Foram «= Benthic Foraminifera [NE] : imest 3!-pockstone 1= Pri interportic Lo wee ‘ va . — wkst-wockestone.” X=lntercrystalline P. Foram.== Planktlc Foreminttera ‘erizontal bees a dolomite mkst-mudstone V=Vuggy Coral vs. Coral wavy laminations “mart F=Frocture © C:Aigae = . Coraliine Algae groded bedding : Ech = “Echinoderm : - sond Mol = Mollusk “fracture 31 clay Peloid — == Pelold bioturbated : Lithic = -LithicGratn 2 Other Other “GRAIN TYPES ~~] TEXTURES | ae Sines GRAIN TYPES ‘ 1 EST. HOLE. M14 OTTAGE) s - ‘ LITHOLOGYSTRUCTUR T OLE.M : AC TTAGE) “dominant 50%) a Maximum Depth: 15. ft abundant (11-50%) pe ss “ Drilled:-8 Dec 86. - ; - : 5 . 2 : common (2-10%) zo POROSITY . oyare (O-1%) S| fetes pee bees erel te DEPO urs O| 8] ©) alo % TYPE DESCRIPTION s{olo} oe Profs. fa [o} O|Uxcjxts . Bye] l= olz=le No, oO =fElsal> ; . : {"/s1<1 5) 5/2] 214 INTRP < | : [90 20 90 MIXxFy elofololwislalsio : = 10t 4 (lyss mod lith LS, re-or + tn z2S+G cs 1 (2)ss as above a f END END OF HOLE La : 30: 4 oo LEGEND . ; UTHOLOGY FABRICS POROSITY TYPES. GRAIN TYPES: STRUCTURES wee] t-groinst = . : s-beddi . ciateccktone pecia snterporticle B. Foram = Benthic Foraminifera As sen ™" whst-wockestone X= Intereryttolline P. Foram ‘m Planktic Foraminifera = | horizontal beds dol kst-mud Ve woo Coral. = Coral ZS | wovy lominations . = Fracture C.At ii . mail : gee =. Coralline Algee aa] gr ing 4 ch = Echinoderm b—— * Mol = Mollusk es fracture clay’ Pelold z= Pelold > bioturbated Lithle. = LithieGratn. a Other = Other