Open-ocean, off-bank transport of fine-grained carbonate sediment in the northern Bahamas

SUMMARY: The contribution of fine-grained, bank-derived versus pelagic-derived carbonate sediment in periplatform oozes has been evaluated by means of a detailed, quantitative carbonate min ralogy study of 35 surface sediment samples from north of Little Bahama Bank. Our data indicate that large volumes of aragonite and magnesian calcite ar being exported along the open-ocean margin of Little Bahama Bank during the present high-stand of sea-level. Percentages of mud-size aragonite+magnesian calcite display a strong negative correlation (r =-0.912) with distance from the dge of the bank, whereas percentages of calcite show a strong positive correlation (+0.914). Immediately adjacent to the northern, windward margin of Little Bahama Bank, 86 ~ of the fine-grained carbonates are bank-derived. This value decreases in a linear fashion to 50 ~ bank-derived muds at a distance of 50 km from Little Bahama Bank. Direct seaward projection of our data suggests that fine-grained, metastable, shallow-water carbonate s diments are transported laterally at least 120 km from open-ocean bank margins. This has important implications for the global budget of CO2, the diagenetic potential of periplatform oozes, and the growth potential of carbonate slopes