Stratigraphy and Radiocarbon Chronology of a Subaerially Exposed Holocene Coral Reef, Dominican Republic

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Abstract
A subaerially exposed coral reef records a period of marine conditions following earliest Holocene transgression into the technically active, subsea level Enriquillo Valley, Dominican Republic. Field mapping, detailed leveling of reef elevations, and I4C dating of fossil corals and mollusks reveal the following chronology of reef development in an unusual geologic and tectonic environment: (1) earliest Holocene ( yr B.P.) marine transgression and growth of oysters on an alluvial fan surface approximately 33 m below sea level (BSL); (2) colonization of reef corals at approximately 34 m BSL on the oyster shell deposits ( yr B.P.); (3) middle Holocene development of a typical Caribbean fringing reef in a protected environment ( to yr B.P.); (4) late Holocene sedimentation over the reef with fossil bivalves ( to yr B.P.) that record a gradual change from marine to brackish water that accompanied growth of shoreline thrombolitic stromatolites near present sea level; and (5) subsequent evaporation of Lake Enriquillo to its present level (March 1983) of 41.5 m BSL. The mid-Holocene reef crest corals (stage 3 above) are about 2 m higher than corals of similar age reported for reefs elsewhere in the Caribbean and western Atlantic. Apparent uplift is attributed to either deformation along thrust faults bounding the valley or underestimation of paleosea levels by previous reef studies in the Caribbean and western Atlantic. The Enriquillo Valley probably contains a record of post-glacial sea level rise extending more than 10,000 yr B.P. It may also contain a record of other sea level transgressions that invaded the valley in late Quaternary time. It is possible that this record could be recovered by drilling or coring the lake sediments.