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ABSTRACT: The Effects of Holocene Sea Level Rise on the Diagenesis of Carbonate Eolianites, San Salvador Island, Bahamas

Kathleen S. White, Brian White

Fossil coral reefs of Sangamon age on San Salvador Island clearly show the diagenetic imprint of falling sea level that resulted from the onset of Wisconsinan glaciation. Controversy exists as to whether sea level reached modern levels in the interval between the end of the Sangamon and the beginning of the Holocene. A test for such a highstand of sea level is to check for a diagenetic imprint in rocks of Sangamon age that are at the appropriate elevation to have been affected by it. Extensive studies so far have revealed no such imprint. A possible explanation for this absence is that sea level rise leaves no diagenetic signature. On San Salvador Island, Holocene eolianites are being submerged in sea water for the first time by the Holocene transgression, and this situat on affords an opportunity to study the diagenetic effects of a sea level rise on carbonate rocks.

The eolianites were lithified in a nonmarine environment by calcite cement that exhibits vadose textures, but considerable porosity and permeability remain. Eolianite samples were collected along transects from the supertidal to shallow subtidal zones. Aragonite is present in more than half of the samples and from each of the zones. Aragonite

occurs mainly as isopachous, acicular crystals in intragranular, intergranular, and solution pores. Pleistocene eolianites of post-Sangamon age have the same kind of aragonite cements but show no signs of an earlier marine phase. These studies clearly demonstrate that a marine transgression does leave a diagenetic imprint on carbonate rocks. The implication of these results is that there has been no sea level highstand comparable to modern levels in the interval between the Sangamon and the Holocene.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990