Sediment Composition of periplatform sediments and calciturbidites around Pedro Bank, Southwestern Caribbean Sea
Spatial and temporal variations in the carbonate production and sediment export of the Pedro Bank carbonate platform were studied in response to the late Quaternary sea level fluctuations. A set of nine sediment cores were obtained from up- and downcurrent position to Pedro Bank to form a downcurrent offbank transect that covers the proximal toe-of-slope to a distal basinal setting. The sediments studied were deposited between 650 to 2520 meter below recent sea level, and reach back until oxygen isotope stage 9, i.e. until approximately 300-310 ky. The sediments recovered are rather uniform, and consist of foraminifer- and pteropod-bearing aragonite-rich mud- to wackstones. This typical periplatform lithology incorporates calciturbidites, which are of pelagic as well as neritic origin. The pelagic sourced turbidites are generally evident as fine tail-end turbidites, whereas the few neritic calciturbidites are present as coarse pack- to grainstones. The sediments were analysed on their ability to record the export patterns of neritic sediment from the shallow tops of Pedro Bank. Therefore mineralogical, sedimentological and geochemical analyses were performed. The aragonite and strontium content were found to be good indicators for variations in shallow-water sediment export. The geochemistry data, as well as the grainsize and component distribution patterns, were useful to differentiate between primary sediment input signals and secondary processes such as dissolution and preservation of metastable carbonates at the seafloor. This study shows that during the last 300 ky (1) sea-level fluctuations, but also the (2) ocean currents, (3) pelagic and neritic sediment production, (4) dissolution of metastable sediment constituents, and (5) input of non-carbonates have had a major control on the sediment dispersal, sediment deposition and composition, especially along the downcurrent margin, where main neritic export occurs. The mineralogical and grain-size composition documents this variability of periplatform sedimentation along the margins off Pedro Bank. In addition, it was found that also the seafloor morphology plays an important role for the spatial and temporal evolution of the periplatform sedimentation in the vicinity of Pedro Bank, which is situated in a tectonically active plate margin setting.