U.S. Geological Survey Professional Paper 1603-I

Chap I-front.fm Page I Tuesday, July 11, 2000 9:35 AM U.S. Department of the Interior U.S. Geological Survey Foraminifera from Paleogene Sediments from the Millhaven and Millers Pond Cores, Screven and Burke Counties, Georgia By Thomas G. Gibson U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1603–I Prepared in cooperation with the U.S. Department of Energy and the Georgia Geologic Survey GEOLOGY AND PALEONTOLOGY OF FIVE CORES FROM SCREVEN AND BURKE COUNTIES, EASTERN GEORGIA Edited by Lucy E. Edwards Chap-I-contents.fm Page III Tuesday, July 11, 2000 9:36 AM CONTENTS Abstract .......................................................................................................................... I1 Introduction ....................................................................................................................1 Acknowledgments .................................................................................................. 2 Material and Methods .................................................................................................... 2 Biostratigraphy ............................................................................................................... 2 Paleoenvironmental Analysis.......................................................................................... 4 Millhaven Core................................................................................................................ 5 Ellenton Formation ................................................................................................ 5 Snapp Formation .................................................................................................... 8 Congaree Formation ............................................................................................... 8 Warley Hill Formation ........................................................................................... 9 Santee Limestone ................................................................................................... 10 Barnwell Unit ......................................................................................................... 10 Millers Pond Core ........................................................................................................... 10 Santee Limestone ................................................................................................... 11 Conclusions .................................................................................................................... 12 References Cited ............................................................................................................ 12 PLATE [Plate follows References Cited] 1. Nodogenerina, Pseudonodosaria, Globoconusa, Pyramidina, Pulsiphonina, Siphonina, Cibicides, and Pararotalia. FIGURES 1. Index map showing the Savannah River Site and the location of the Millhaven and Millers Pond test holes in Screven and Burke Counties, Georgia ............................................................................................................................ I2 2. A lithologic log and paleobathymetry of the Millhaven core .......................................................................................... 3 3. A lithologic log of the Millers Pond core......................................................................................................................... 4 TABLES 1, 2. Sedimentary characteristics of foraminiferal samples from the— 1. Millhaven core......................................................................................................................................................... I6 2. Millers Pond core .................................................................................................................................................... 11 III Chap I-new.fm Page 1 Tuesday, July 11, 2000 9:37 AM GEOLOGY AND PALEONTOLOGY OF FIVE CORES FROM SCREVEN AND BURKE COUNTIES, EASTERN GEORGIA Foraminifera from Paleogene Sediments from the Millhaven and Millers Pond Cores, Screven and Burke Counties, Georgia By Thomas G. Gibson1 ABSTRACT environments during the deposition of most upper Pale- ocene and Eocene beds, but an upper Paleocene dark clay interval contains assemblages suggestive of high-productiv- Paleocene and Eocene foraminifers were studied for biostratigraphic and paleoenvironmental analysis in cores ity and low-oxygen environments. from two test holes in the eastern Georgia Coastal Plain. The Millhaven test hole, located southeast of the Millers Pond test hole, is in the more downbasin position. In the INTRODUCTION Millhaven core, foraminifers are present in lower and upper Paleocene strata of the Ellenton Formation, lower middle Paleogene foraminifers from the Millhaven and Millers Eocene strata of the Congaree and Warley Hill Formations, Pond cores were examined during a study of the hydrogeo- upper middle Eocene strata of the Santee Limestone, and logic framework of easternmost Georgia across the river upper Eocene and questionable lower Oligocene strata of from the Savannah River Site in South Carolina (fig. 1). the Barnwell unit. Foraminifers were recovered only from This study examined foraminiferal assemblages both for upper middle Eocene strata of the Santee Limestone in the biostratigraphic placement of the strata and for interpreta- Millers Pond core. The Millers Pond site is the more west- tion of depositional environments. Foraminiferal assem- erly of the two sites and is in a more upbasin position. blages are discussed in a sample-by-sample format to Foraminifers are moderately to highly altered diagenet- provide the maximum amount of information from this area ically in many of the sandy or carbonate-rich intervals in where little foraminiferal information is currently available. these cores, and the alteration makes specific identifications difficult. Diagnostic planktonic species are found only in In the more easterly, and thus downbasin, Millhaven beds of early Paleocene age. Some benthic foraminiferal core, foraminifers are found both in Paleocene and Eocene species that have restricted regional biostratigraphic ranges strata. The specimens are well preserved in the more clayey are present. These species suggest placements for some strata, but most are highly altered in the more sandy and strata in the early part of the late Paleocene and in the mid- limy beds. In the more upbasin Millers Pond core, foramini- dle Eocene. fers are found only in the Santee Limestone of late middle Foraminiferal assemblages suggest that most upper Eocene age. These specimens occur in carbonate-rich, Paleocene and Eocene beds were deposited in shal- sandy sediments, and their tests are moderately to highly low-marine environments with water depths of less than altered diagenetically. 100 ft. Assemblages in a few intervals, however, suggest Some common and important stratigraphic marker somewhat deeper inner-middle to middle neritic environ- benthic species and one stratigraphically important plank- ments. Foraminiferal assemblages suggest well-oxygenated tonic species are illustrated by scanning electron micro- scope (SEM) photographs (pl. 1). A high degree of 1Retired from the U.S. Geological Survey. Present address: Depart- recrystallization within many assemblages, however, makes ment of Paleobiology, National Museum of Natural History, Smithsonian it difficult to obtain satisfactory pictures of many species, Institution, Washington, DC 20560–0121. particularly those from the middle Eocene. I1 Chap I-new.fm Page 2 Tuesday, July 11, 2000 9:37 AM I2 GEOLOGY AND PALEONTOLOGY OF FIVE CORES FROM SCREVEN AND BURKE COUNTIES, GEORGIA 82 O 30’ 82OO 81 30’ particles adhering to the specimens, chamber infillings, cal- careous overgrowths, or heavy recrystallization of the test wall. In these samples, the foraminifers were picked from GA. S.C. the entire sediment residue that remained after washing. Aiken The degree of diagenetic alteration of the foraminifers Upper Three in many samples makes it difficult to identify these speci- O S Runs Creek 33 30’ a v a mens to the species level. In addition, diagenetic alteration n n a h R i may have selectively removed certain taxa from the original v e Richmond r Barnwell foraminiferal assemblage. Because of these possible biases, Millers Pond Savannah Brier River Site samples were studied on a qualitative (species present or Creek absent) basis only. Jefferson In the Millhaven core, 23 samples from 5 Paleocene 33 O Burke Allendale and Eocene units contained foraminifers (fig. 2). In the Millers Pond core, only three samples from the Santee SOUTH CAROLINA Millhaven Limestone contained foraminifers (fig. 3). Sample depths Jenkins GEORGIA are recorded to the nearest 0.5 ft, except in the lower part of Screven the Millhaven core where sample depths are recorded to the 0 10 20 30 MILES nearest 0.1 ft. 0 10 20 30 KILOMETERS Illustrated specimens, other study specimens, faunal O 32 30’ slides, and foraminiferal concentrates are deposited in the Cushman Foraminiferal Collection at the U.S. National EXPLANATION Museum of Natural History (USNM), Smithsonian Institu- Millhaven Test hole site and informal name of site tion, Washington, D.C. Figure 1. Index map showing the Savannah River Site and the BIOSTRATIGRAPHY location of the Millhaven and Millers Pond test holes in Screven and Burke Counties, Georgia. Gohn (1988) summarized the early Cenozoic geology of the southern Atlantic Coastal Plain. This work contains ACKNOWLEDGMENTS numerous references to the

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