Abstract
Depositional geometries as imaged in seis- mic lines, logging data, and quantitative petrographic data were used to analyse the slope and toe of slope deposits of the Miocene distally steepened carbonate ramp of Great Bahama Bank. The shedding pattern along the slope of this ramp is more complex than it is along the slope of the Pliocene-Pleistocene flat- topped carbonate platform. Compositional changes and compositional trends of periplatform sediments correlate with the positions of geophysically-defined sequence boundaries. Two types of depositional sequences occur. The first sequence is characterised by laterally traceable sequence-internal reflections, whereas the second type contains major intrasequen- tial incisions. Erosional incisions and sedimentary infills of these canyons by turbidites formed during sea-level lowstands, as is indicated by the composition of the turbidites having a mixture of shallow-water and pelagic particles. Highstand turbidites are charac- terised by more extensive, laterally traceable geome- tries and by the occurrence of abundant shallow-water particles. In contrast to highstand turbidites shed from the Pliocene-Pleistocene flat-topped platform, shal- low-water components in highstand turbidites of the Miocene ramp are of skeletal origin. The stacking pat- tern of the periplatform deposits is controlled by sea- level fluctuations. Four orders of sea-level changes are distinguished. Third-order cycles are delimited by sequence boundaries, and fourth (100,000 a) order cycles govern the bundling of turbidites into packages. Fifth (40,000 a) and sixth (23,000 a) order cycles are recorded in the background sediments and resolvable with spectral analysis.
Published Version
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