--> ABSTRACT: Stratigraphy and Ages of Two 33 m Long, Bank-margin Cores From the Exuma Cays, Bahamas, by Paul J. Hearty, Don F. McNeill, Lynton S. Land, and Robert F. Dill; #91019 (1996)

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Stratigraphy and Ages of Two 33 m Long, Bank-margin Cores From the Exuma Cays, Bahamas

Paul J. Hearty, Don F. McNeill, Lynton S. Land, and Robert F. Dill

Two, 33m long, 6.3 cm diameter cores, Lee Stocking Island (Core M1) and Norman's Pond Cay (Core M2), show lithofacies changes in remarkable detail with ages ranging from late Pliocene to late Pleistocene. Core M1, at the northern end of LSI is one km west of the Exuma Sound bank margin. It has four soil-bounded, shoaling-upward sequences. Core M2, 0.5 km farther back on the bank has at least six soil-bound depositional sequences. Whole rock aminostratigraphy (AAR) and magnetostratigraphy provide age correlation between cores. (AAR) ratios from top to bottom in M1 ranged between 0.40 (St.5e) and 0.70 (St. 9 ?) The M2 core top (0.70) correlated with M1 at -25m. M1 shows a compressed (-) interval in a mainly normal (+) core polarity. Core M2 is (+) (-) (+) from the top to bo tom. U-series dates on corals at a depth of -25m in M1 yield a 257 ±19 Ka age. Sr isotope ratios are consistent with an age between 240 and 400 Ka. Coral molds of Stylopera spp. indicate Pliocene age in M2 at only -22m. Thus, Core M2 dates from late Pliocene (3 Ma) to Stage 9 (0.3 Ma), while M1 encompasses largely Stage 9 to Stage 5e (0.13 Ma) rocks. Stratigraphy shows rapid thickening of off lapping sedimentary sequences toward the bank margin and amphlication of seaward accretion since Stage 9. Early Pleistocene and Pliocene sequences at shallow depth in M2 suggests little subsidence has occurred during the past 2-3 Ma. M2 is 20m from a cave system extending below -90m. Cave wall rock below cored depths, has abundant fossil molds and additional paleosols. Cores and cave d ves demonstrate and record significant changes in sedimentary patterns responding to climate and sea-level fluctuations which in turn affected carbonate producing processes along the eastern margin of Great Bahama Bank.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California