SHEARER, MICHELLE C. and ANDRE W. DROXLER
Rice University, Houston, TX

Abstract: Intense Mid-Brunhes Carbonate Dissolution in Caribbean Quaternary Sediments: Neritic Carbonate Golden Age and Maximum NADW Production.

During interglacial Stage 11, a period 423-362 ky ago, sea level is estimated to have risen as far as 20 m above modern sea level. The Greenland and West Antarctic ice sheets would have had to collapse in order to explain such a dramatic sea-level rise. The overall warmer climate and this exceptionally high sea-level transgression flooding tropical paleofluvial plains and previously exposed carbonate banks would explain the worldwide establishment of modern barrier reefs and optimum production of carbonate banks. During Stage 11 the production of NADW had reached maximum values. To compensate for this large volume of water sinking in the North Atlantic, the flow of corrosive, nutrient-rich AAIW through the Caribbean also reached its optimum level.

Carbonate preservation proxies such as percent coarse fraction, percent foraminifer fragmentation, pteropod occurrence and fragmentation, fine aragonite and Mg-calcite accumulation rates, and d¹³C at ODP Sites 999 and 1000 suggest that the mid-Brunhes (interglacial Stage 11) is characterized by intense CaCO₃ dissolution from subthermocline to intermediate water depths. These intense mid-Brunhes dissolution conditions are interpreted to be linked to the strong inflow of AAIW into the Caribbean. Since this clear dissolution pulse is also observed globally at low latitudes from subthermocline to abyssal depths, these conditions could also be explained by basin to shelf carbonate fractionation related to the worldwide establishment of modern barrier reefs and optimum carbonate bank production.

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