| Marine isotope stage 5 (MIS 5, 130--80 ky BP) was the last major interglacial episode of earth's climate history. High-resolution climate archives of MIS 5 are available from Greenland ice cores, North Atlantic sediment cores, and low-latitude speleothems, but such records are lacking from the tropics. Sediments of the Cariaco Basin, located on the northern continental shelf of Venezuela and separated from the Caribbean Sea by several shallow (∼150 m) sills, provide high-resolution records of tropical climate variability. This dissertation focuses on a decadal to centennial-scale record of the geochemical composition of planktonic foraminifer shells and marine sediments from the Cariaco Basin over the time interval 145--73 ky BP, which encompasses the end of MIS 6 through the transition from MIS 5 to MIS 4, the entire interglacial event. Chapter I explores trace metal records from the planktonic foraminifera, Globigerinoides ruber; variability in Fe, Mn, U, Sr, and La primarily reflects the influence of diagenetic coatings, whose composition varied with changing chemical conditions of basin waters. At high interglacial sea levels, foraminifera experienced minimal diagenesis, but at low glacial sea levels an increase in carbonate ion concentration of basin waters caused elevated U and Sr relative to Mg, and, at intermediate water depths, periodic oxidation of basin waters caused pyrite formation in sediments. Chapter II is a detailed look at the structure of interglacial MIS 5, including millennial-scale events and the extreme warm interval, MIS 5e, with a particular focus on the SST record of these events. Millennial-scale variability in SSTs was linked with atmospheric methane in several intervals, and MIS 5e exceeded Holocene temperatures by 1.8 +/- 0.9 °C, averaging 28.4 +/- 0.5 °C from 128.2--118.4 ky BP. Chapter III looks specifically at the penultimate deglaciation, Termination II, and compares this glacial termination and the associated weak monsoon interval to the last deglaciation. During Termination II, the weak monsoon interval was characterized by an extreme cold interval from 135.7--129.0 ky BP, during which a southward shift of the ITCZ caused upwelling conditions to dominate in the Cariaco Basin. |
