--> Abstract: Brunhes Evolution of the Belize Mixed Siliciclastic-Carbonate Margin Relative to Glacial-Interglacial Sea Level Fluctuations, by Brooke Olson, Andre Droxler, Gerald Dickens, and Luc Beaufort; #90039 (2005)

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Brunhes Evolution of the Belize Mixed Siliciclastic-Carbonate Margin Relative to Glacial-Interglacial Sea Level Fluctuations

Brooke Olson1, Andre Droxler1, Gerald Dickens1, and Luc Beaufort2
1 Rice University, Houston, TX
2 CEREGE,

Tropical mixed siliciclastic-carbonate systems develop on continental margins where significant volumes of terrigenous sediments interact with shallow water neritic carbonates. Directly influenced by sea level and climatic changes, mixed systems express dynamic sedimentary and foraminiferal histories. In current sequence stratigraphy models, neritic carbonates flourish, exporting sediments to the basins during highstands, while siliciclastic input is maximum during lowstands. In contrast, this study demonstrates that siliciclastic and carbonate sedimentation is not in phase with late Quaternary glacial-interglacial lowstand/highstand cycles on the central Belize margin.

This study is based on the analyses of a well-dated continuous 37.7 m long piston core, MD02-2532, collected on the distal slope 3 km offshore the central Belize Barrier reef by the R/V Marion Dufresne (IPEV). A robust chronology is established using radiocarbon ages and high resolution planktic oxygen isotope stratigraphy, anchored by several nannofossil stratigraphic and tephrochronologic markers, demonstrating that the core represents approximately the last 0.7 kyrs. Bulk carbonate percent values vary down the core with low values of 40 to 50% typically occurring during the interglacial to glacial transitions, high values of 70 to 80% typically occurring at the glacial to interglacial transitions, and Holocene values reaching 82-83%. Calculated siliciclastic fluxes to the slope are greatest during early sea level regressions, while the lowest siliciclastic and highest carbonate fluxes occur during transgressions and early highstands. Planktic foraminiferal assemblages vary corresponding to glacial-interglacial water mass changes, while benthic assemblages indicate water depth and paleoenvironmental changes as well as varying influences of carbonate and siliciclastic provinces.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005