Contrasting Records of Deposition for Late Miocene Puerto Rican and Dominican Republic Carbonate Sequences

Diana Ortega-Ariza
University of Kansas, Department of Geology
Lawrence, KS, United States
[email protected]

Late Miocene Puerto Rican (PR) and Dominican Republic (DR) sequences are used to construct quantitative relative sea-level histories and compare the contributions of sea level, paleogeography, and oceanographic conditions in their development. ⁸⁷Sr/⁸⁶Sr isotopes indicate ages of 11 Ma (Tortonian) in PR and 6.2 Ma (Messinian) in DR. Three PR carbonate sequences, indicating relative sea-level fluctuations of 10’s of meters (minimums), are characterized by alternation of heterozoan and photozoan facies. Heterozoan facies were deposited in a shallow subtidal environment, with periods of intermittent higher energy and deeper water. Photozoan facies were deposited in a shallow to very shallow water environment. Three DR mixed carbonate-siliciclastic sequences, indicating relative sea-level fluctuations on the scale of at least meters (minimums), show dominance of photozoan facies, with heterozoan facies occurring locally. Photozoan facies were deposited in a mostly normal marine carbonate environment. Distribution of heterozoan and photozoan facies in both areas was controlled by relative sea-level fluctuations, and variation in nutrient flux regionally associated with gradual restriction (~10 Ma) and closure (~3 Ma) of the Central American Seaway in the Caribbean. PR sequences were deposited prior to and during initial restriction, and faced the open ocean with likely periodic upwelling (high nutrients) during transgressions. DR sequences characterized by photozoan facies were deposited later, as regional restriction increased, causing limited ocean circulation and less upwelling (low nutrients). Local proximal deposition of heterozoan facies is associated with runoff of siliciclastics (high nutrients).

AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects