The Caribbean carbonate crash at the middle to late Miocene transition and the establishment of the modern global thermohaline circulation
Roth, Joy Michele
Droxler, Andre W.
Master of Arts thesis
The Caribbean carbonate crash was a time of increased regional carbonate dissolution at the middle to late Miocene transition. It is marked by five dissolution episodes, occurring from 12-10 Ma, characterized by significant reductions in carbonate mass accumulation rates (CO$\sb3$ MAR). We determined carbonate content and CO$\sb3$ MAR for sites 998-1000 over the middle to late Miocene interval. Stable isotope composition of benthic foraminifers is used to track changes in deep water masses. Carbonate mineralogies are determined for the shallow site 1000 (927 m water depth) to detect dissolution of metastable carbonates at sub-thermocline depths. The geochemical changes during the carbonate period are similar to those that occur during the Caribbean Quaternary interglacial stages, times when Antarctic Intermediate Water (AAIW) filled the Caribbean to abyssal depths. The initiation of North Atlantic Deep Water (NADW) production during this period, possibly caused by the partial closing of the Isthmus of Panama and the opening of Pedro Channel (northern Nicaragua Rise), led to reorganization of global thermohaline circulation. The increase of return flow that passes through the Caribbean may have brought corrosive AAIW into the Caribbean, causing dissolution of carbonate sediment at the sea floor.
Geology; Physical Oceanography; Geochemistry