Slope-to-basin stratigraphic evolution of the northwestern Great Bahama Bank (Bahamas) during the Neogene to Quaternary: interactions between downslope and bottom currents deposits

摘要

Multichannel high-resolution seismic data along the northwestern margin of the Great Bahama Bank (GBB), Bahamas, detail the internal geometry and depositional history of a Neogene-Quaternary carbonate slope-to-basin area. The stratigraphic architecture through this period evolves from (i) a mud-dominated slope apron during the Miocene, (ii) a debris-dominated base-of-slope apron during the Late Pliocene and then (iii) return to a slope apron with very short prograding clinoformal aprons during the Pleistocene. This geometric evolution was broadly constrained by the development of the Santaren Drift by bottom current since the Langhian. The drift expands along the northwestern GBB slope, forming a continuous correlative massive feature that shows successive phases of growth and retreat and influenced the downslope sediments distribution. Indeed, Late Pliocene deposits are confined into the moat, forming a strike-continuous coarse debrites belt along the mid-slope, preventing their free expansion into the basin. The occurrence of basinal drift that operated since 15 Ma showed a significant upslope growth around 3.6 Ma and is interpreted as resulting from the closure of the Central American Seaway which also coincides with a global oceanographic re-organization and climate changes in the Northern Hemisphere.