HR: 0800h
AN: OS51B-1305    [Abstracts]
TI: Brunhes Evolution of the Belize Mixed Siliciclastic Carbonate Margin: Source to Sink Dynamics Relative to Glacial-Interglacial Sea Level Fluctuations
AU: * Olson, B E
EM: bolson@rice.edu
AF: Rice University Department of Earth Science, 6100 Main Street MS 126, Houston, TX 77005 United States
AU: Droxler, A W
EM: andre@rice.edu
AF: Rice University Department of Earth Science, 6100 Main Street MS 126, Houston, TX 77005 United States
AU: Dickens, G
EM: jerry@rice.edu
AF: Rice University Department of Earth Science, 6100 Main Street MS 126, Houston, TX 77005 United States
AU: Beaufort, L
EM: beaufort@cerege.fr
AF: CEREGE, CNRS Europole Mediterraneen de l'Arbois BP 80, Aix-en-Provence, 13545 France
AB: Mixed siliciclastic carbonate systems are developed on continental margins where significant volumes of terrigenous sand and mud interact with shallow water tropical carbonate barrier reefs and banks. These systems represent highly dynamic environments, directly influenced by sea level fluctuations and climatic changes. In current sequence stratigraphy models, neritic carbonates flourish, exporting sediments to the basins during sea level highstands, while siliciclastic input to the basins 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 3 km offshore the central Belize Barrier reef in the distal slope of Gladden Basin at 333 m of water depth by the R/V Marion Dufresne (IPEV). A robust chronology is established using high resolution planktic oxygen isotope stratigraphy, anchored by several nannofossil stratigraphic and tephrochronologic markers, as well as radiocarbon ages in the upper part of the core, and demonstrates that the core represents most of the Brunhes (about 0.7 My). The upper 26m of MD02 2532 penetrated five subunits of the distal portion of a sedimentary wedge, likely corresponding to interglacial intervals from Marine Isotope Stage (MIS) 11 to MIS 1 (Holocene), while the lower 11.7m recovered the upper portion of an underling subparrallel reflector seismic unit. Bulk carbonate percent values cyclically vary down the core; low values of 40 to 50% typically occur during the interglacial to glacial transitions, whereas high values of 70 to 80% typically occur at the glacial to interglacial transitions. The Holocene interval is characterized by the highest values observed in the entire core, reaching 82-83%. Calculated siliciclastic fluxes to the slope are greatest during early sea level regressions, whereas the lowest values occur during transgressions and early highstands. In contrast, carbonate fluxes are maximum during transgressions and early highstands. These results show that the late Quaternary is an ideal interval to determine the timing relative to sea level fluctuations of siliciclastic and carbonate sediment maximum fluxes into slope and basinal environments and, therefore, to test some basic sequence stratigraphic principles, because the timing and amplitude of the late Quaternary sea level fluctuations are independently well established.
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting