ADAMS, ANGELA K., and FRED T. MACKENZIE
Dept. of Oceanography, Univ. of Hawaii, Honolulu, HI

Abstract: Respiratory Carbonate Dissolution in Surficial Sediments of the Arabian Sea

The process of carbonate dissolution in surficial sediments overlain by waters supersaturated, or at nearsaturation, with respect to carbonate minerals is explored in the modern-day deep Arabian Sea. Previous studies of sedimen s from this region suggest that remineralization of organic matter in surface sediments may supply the acid necessary to dissolve the carbonate phases above the lysocline. This process, termed respiratory dissolution, has been proposed as a key component of recent controversial scenarios put forth to explain variations in atmospheric carbon dioxide levels during glacial times.

We have accumulated additional evidence for supralysoclinal dissolution of biogenic carbonates in the Arabian Sea based upon hydrographic, total alkalinity, dissolved inorganic carbon and dissolved calcium measurements. Specifically, an increase of approximately 1.0% in excess calcium is observed from surface to depth. These data suggest a significant dissolution of biogenic carbonate above the depth at which calcite should dissolve due to thermodynamic reasons. Water-column inorganic carbon system data, in the form of nonconservative alkalinity and excess calcium signals emanating from the sediments, suggest that most of the dissolution is occurring within surface sediments as opposed to within the water column itself. Estimates of in situ sedimentary supralysoclinal dissolution rates will be presented and the effects of this process on present-day oceanic carbonate budgets and carbonate paleo productivity estimates addressed.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas