Great Bahama Bank Aragonitic Muds: Mostly Inorganically Precipitated, Mostly Exported

Abstract

Sr concentrations in aragonitic muds on the banktop and leeward slope of Great Bahama Bank (GBB) are greater than in the needles produced by codiacean green algae but the same as in precipitated sand-size ooids and other nonskeletal grains. Results of two-part and three-part mixing models suggest that chemically precipitated aragonite contributes an average of 55-78% of the clay-size aragonite; individual samples contain as much as 95% chemically precipitated aragonite. Nonskeletal aragonitic needles apparently are precipitated ubiquitously over GBB but accumulate on the banktop only leeward of Andros Island. Much of the mud produced on the bank is exported to deeper waters: the thickness of mud-dominated Holocene sediments on the leeward slope can reach 90 m, and the aragonitic lysocline around the Bahamas is depressed by nearly 1500 m.