Abstract
compositional variation of Pleistocene carbonate gravity deposits from the Exuma Sound Basin, Bahamas, was determined. Two types of gravity deposit were present in the cores of ODP Leg 101, Site 632A, i.e., calciturbidites and calcidebrites. In analogy with earlier studies, the compositional variations in the calciturbidites could be linked to different sources on the carbonate margin, i.e., platform interior, platform edge, and platform slope. Calciturbidites deposited during interglacial, sea-level highstands show a dominance of non-skeletal grains, largely derived from the platform interior, while calciturbidites of glacial, sea-level lowstands, show a dominance of skeletal platform-edge to platform-slope-derived grains. Thus, the calciturbidite composition can be used to reconstruct the position of absolute sea level. In addition, the mud content of the calciturbidites increased after Marine Isotope Stage 11. In contrast, the composition of the calcidebrites remained unaltered through time and showed a clear dominance of platform-edge-derived sediments during varying sea-level positions. The Bahamian carbonate platform is located in a tectonically stable passive-margin setting and the gravity-flow deposits were laid down in an environment exclusively controlled by eustatic sea-level fluctuations. This study shows that all types of gravity-induced carbonate deposits, calciturbidites, and calcidebrites, were deposited in response to global eustatic sea-level variations. The sediment composition could be linked directly to sediment input from specific facies realms along the carbonate platform margin. Hence, sediment composition analysis is a strong tool that may be used to discriminate between gravity-induced deposition triggered by eustatic sea-level changes and that related to tectonic events, when analyzing resedimentation processes in sedimentary basins.
Highlights
Sediment production and gravity flowsSediment production on flat-topped carbonate platforms and sediment export are affected by relative fluctuations in sea level that flood or expose the top of the platform
This study shows that all types of gravity-induced carbonate deposits, calciturbidites, and calcidebrites, were deposited in response to global eustatic sea-level variations
The Pleistocene calciturbidites of Exuma Sound show two different composition modes analogous to earlier studies of Haak and Schlager (1989) in their analysis of calciturbidites deposited in another Bahamian intraplatform basin, the Tongue of the Ocean
Summary
Sediment production on flat-topped carbonate platforms and sediment export are affected by relative fluctuations in sea level that flood or expose the top of the platform These sea-level variations may be either climate-induced or related to tectonic processes or a combination of both. Cyclic variations in the aragonite content of periplatform sediments deposited in the deep-water realm near flat-topped carbonate platforms, for example, could clearly be related to exposure and flooding of the shallow-water production areas, the ‘‘highstand shedding’’ model with high sediment production and export during sea-level highstands and low sediment production and export during lowstands in sea level (Droxler et al 1983; Mullins et al 1984; Reijmer et al 1988; Schlager et al 1994). Once transported off-bank, the sediments are transported down slope mainly by turbidity currents and debris flows (Mullins et al 1984)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
