Geochemical Signatures of the Florida Pleistocene Deposits: Establishment of Baseline Geochemical Signatures for Modern and Ancient Coral Reef Systems

REE geochemistry in carbonate rocks has successfully been used for studying both modern oceans and palaeoceanography, with additional applications for investigating water-rock interactions in carbonate diagenesis. However, the study of REE geochemistry in ancient carbonate rocks requires the determination of the preservation of the REE signature through subsequent diagenesis. In previous studies REE signatures have been shown to be retained even during diagenesis. Preserved REE signatures patterns in the stabilized material closely reflect the original REE signatures of the vertebrates, corals and associated reef carbonates. Studies have suggested that original REE signatures may commonly be preserved in ancient limestone, thus providing support for the use of ancient marine limestone as proxies for marine REE geochemistry.

In this study, Pleistocene deposits with fossil vertebrates (when available) and invertebrates of the Anastasia formation, Miami Limestone and the Key Largo Limestone and similar modern reef tract environments were collected and analyzed for Rare Earth Elements (REE) and other trace elements (TE) to determine the conditions of the depositional environment and the extent or variation of the Geochemical signature in the studied Florida Formations. Modern samples were then compared to the REE signatures of the fossil material to determine the extent of diagenesis in the ancient samples of both vertebrates (bioapatite) and invertebrates (calcite).

Our recent research focuses on establishing a REE signature baseline for both modern sediments and Pleistocene formations in the Florida Keys, the Gulf and the east coasts of Florida. This data library potentially can be used for stratigraphic correlation, interpretation of ancient and modern environments and fossil provenience. In addition the resultant database can be used for a baseline to monitor changing conditions in the modern reef tract systems of Florida. Analysis of these carbonate deposits represent further expansion of a data library of REE signatures for the purpose of interpretation of both ancient and modern depositional environments.  

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California