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CAROLINA GEOLOGICAL SOCIETY Guidebook for 1992 Annual Meeting Pages 59-62 NANNOFOSSIL BIOSTRATIGRAPHY AND SEQUENCE STRATIGRAPHY OF MIDDLE TO UPPER EOCENE STRATA IN THE SOUTHWESTERN SAVANNAH RIVER SITE AND ADJACENT AREAS OF GEORGIA Richard A. Laws, W. Burleigh Harris and Victor A. Zullo Department of Earth Science University of North Carolina at Wilmington Wilmington, N.C. 28403 INTRODUCTION Core VSC-4 (Figure 1, 2) contains a relatively complete middle to upper Eocene stratigraphic section typical of the southwestern Savannah River Site and adjacent areas of Georgia. The core is at an elevation of 156.7 feet; and penetrates a Cenozoic section of almost 500 feet; the Cretaceous Tertiary boundary is placed at a depth of 494.6 feet. Paleogene stratigraphic units recognized in the core include the Paleocene Ellenton Formation, an upper Paleocene/lower Eocene Un-named unit, the middle Eocene Congaree Formation, Warley Hill () Formation and Blue Bluff Marl, and the upper Eocene Utley Limestone Member of the Clinchfield Formation, the Griffins Landing Member of the Dry Branch Formation and undifferentiated Barnwell Group sands. We will focus our attention on the middle to upper Eocene section which extends from the surface to a depth of 325 feet at the base of the Congaree Formation (see Figure 2). Figure 1. Location of cores and outcrops. Lithostratigraphy The Congaree Formation extends from 325 to 236 feet depth and comprises clean, coarse, pebbly, Fe-stained quartz sand with occasional kaolin lithoclasts at the base grading upward into fine to medium clean quartz sand with occasional thin gray to green clay beds. The contact with the underlying intensely weathered kaolinite of the un-named unit is sharp, is characterized by local concentrations of reworked coarse sediments, and represents a regional unconformity. From 236 to 218.6 feet depth interbedded calcareous sand and sandy molluscan-mold grainstone may correlate to the Warley Hill Formation. The contact with the underlying Congaree is subtle and is marked by a change in sand size and the addition of calcareous material. The Blue Bluff Marl extends from 218.6 to 136 feet depth and consists of impure micrite or argillaceous, silty to sandy micrite becoming clayey at the top. The contact with the underlying Warley Hill Formation is picked where sand suddenly decreases in quantity and size; it represents a regional unconformity. The Utley Limestone in 21 feet thick in the core and comprises a sandy, molluscan-mold biosparudite. Thin interbeds of calcareous quartz sand are present in the Utley. The contact with the underlying Blue Bluff Marl is quite distinct and represent a major regional unconformity that is mapped over the area. The Griffins Landing Member extends from 45 to 115 feet depth and consists of sandy calcareous and kaolinitic clays containing large Crassostrea. The contact with the underlying Utley Limestone is sharp and represents a regional unconformity. We assign the remainder of the core from the top of the Griffins Landing at 45 feet to the surface to undifferentiated Barnwell Group sands and clays (see Figure 2). Biostratigraphy Poorly to well preserved calcareous nannofossils occur in the interval from 76 to 256 feet depth, (i.e. mid Congaree Formation through mid Griffins Landing Member). Preservation is best in the Blue Marl and Griffins Landing Member which includes the Middle-Upper Eocene boundary. Table 1 presents a list of calcareous nannofossil species recorded from the lithic units included in this study. That list was compiled from examination of samples from cores VSC-3, VSC4, VG-7, and VG-8. Figure 2 shows the occurrence of selected age-diagnostic nannofossils in VSC-4. Range of calcareous nannofossils for the purpose of correlation are taken from Perch-Nielsen (1985). “NP” zones refer to the zonation of Martini (1971) as described in Perch-Nielsen 59
Richard A. Laws, W. Burleigh Harris and Victor A. Zullo Figure 2. Middle to upper Eocene lithostratigraphy, biostratigraphy, and sequence stratigraphy of core VSC-4. Asterisks represent location of calcareous nannofossil samples. Solid dots indicate the occurrences of each species. (1985). “CP” zones refer to the zonation of Okada and Burkry (1980) as described by Perch-Nielsen (1985). One sample from calcareous beds in the upper Congaree Formation contains moderately well preserved nannofossils. The sample at 237 feet contain Lophodolithus mochlophorus which has a last occurrence (LO) in NP 15. Several nannofossils including Reticulofenestra umbilica and R. reticulata which first appear in the sample from 225 feet (Warley Hill) may have first occurrences in NP 16. However, the definitive taxa Chiasmolithus gigas and Rhabdosphaera gladiu do not occur in these samples, and therefore, we cannot separate NP 15 and NP 16. Samples 60
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CAROLINA GEOLOGICAL SOCIETY FIELD T
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CONTENTS Road Log and Outcrops in t
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W.C. FALLAW, VAN PRICE, AND WALTER
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Page 16 and 17: SOUTHEASTERN ATLANTIC COAST REGIONA
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Page 60 and 61: NANNOFOSSIL BIOSTRATIGRAPHY AND SEQ
Page 64 and 65: DINOFLAGELLATE CYSTS OF EOCENE STRA
Page 68 and 69: RADIOCARBON DATES OF PEAT IN UPPER
Page 72 and 73: HYDROSTRATIGRAPHY OF THE SAVANNAH R
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Page 78 and 79: PETROLOGY AND POROSITY PERMEABILITY
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Page 82 and 83: PAUL HUDDLESTUN Figure 1. Location
Page 84 and 85: PAUL HUDDLESTUN REFERENCES Herrick,
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