--> --> Recognition of Multiple Subaerial Unconformities in Cores: NW Great Bahama Bank, by D. K. Beach and R. N. Ginsburg; #90986 (1994).
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Abstract: Recognition of Multiple Subaerial Previous HitUnconformitiesNext Hit in Cores: NW Great Bahama Bank

David K. Beach, Robert N. Ginsburg

Shallow cores from nine locations across northwestern Great Bahama Bank contain multiple, often closely spaced, subaerial Previous HitunconformitiesNext Hit. These Previous HitunconformitiesNext Hit separate Plio-Pleistocene carbonate rocks into discrete depositional units. Interpretation of these and similar stacked Previous HitunconformitiesNext Hit in the Bahamas has been controversial. However, their recognition is crucial to understanding Plio-Pleistocene bank history and reflects a record of multiple sea-level changes.

Recognition of Previous HitunconformitiesNext Hit is based largely on petrographic evidence. This evidence includes diagenetic features produced by karstification, calichification, residual soil development, and erosion; as well as depositional features reflecting marked changes and/or hiatuses in sedimentation. Diagenetic features below Previous HitunconformitiesNext Hit include staining; dense laminated and/or unlaminated micrite; soil-zone pisoids; microcodium; needle-fiber cement; solution pipes; increased induration; rhizomorphs; macroborings; and microborings. Extensive but localized leaching commonly occurs overlying Previous HitunconformitiesNext Hit. Depositional features include marked facies changes; paleosol; and filling of solution pipes and vugs by overlying paleosol and sediments. Basal and capping sections of depositional units are often mud rich. Basal sections commonly contain lithoclasts (usually blackened) and abundant fossils (notably molluscs, including articulated bivalves, and corals, particularly Porites porites).

Using the observed features, all Previous HitunconformitiesNext Hit are ranked according to certainty of existence. Rankings do not necessarily equate to degree of alteration nor to relative length of exposure. Correlation of depositional units between core locations supports identification of Previous HitunconformitiesNext Hit. The methods used and evidence cited should be particularly applicable to recognition of subaerial Previous HitunconformitiesTop in other late Tertiary-Quaternary carbonates.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994