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ABSTRACT: Great Bahama Bank Aragonitic Muds: Ubiquitously Precipitated, Mostly Exported

J. D. Milliman, D. Freile, R. P. Steinen, R. J. Wilber, R. B. Halley

Strontium contents of aragonitic sediments from the bank top, bank edge, and leeward slope of Great Bahama Bank (GBB) have considerably higher Sr contents (0.90-0.98%) than those produced by codiacean green algae (0.79-0.89%). A simple two-part mixing model indicates that precipitated aragonite (Sr contents of 0.95-100%) must contribute at least 60-70% of the aragonitic muds, codiacean algae producing the remainder. As other aragonite producers on the bank (mollusks and, to a lesser extent, corals) have much lower Sr contents, this computation is conservative.

Such aragonitic muds are produced ubiquitously throughout GBB, but they accumulate only in the relatively quiescent environment leeward of Andros Island. Most muds are exported via normal currents and storms to the leeward slope of GBB (water depths 150-300 m), where Holocene accumulations can reach 90 m in thickness. In fact, more than 90% of the mud produced on GBB is exported from the bank top, a point that has dramatic consequences on the aragonitic lysocline and compensation depths of surrounding waters.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990