Late Quaternary Climatic Record in Western Equatorial Atlantic Sediment.

摘要

Ten cores contain successions of planktonic foraminiferal assemblages and sedimentary components that record late Quaternary climatic changes in the western equatorial Atlantic Ocean. The climatic cooling that began at the end of the last interglaciation and continued throughout the last glaciation led to the sequential disappearance of tropical forams and the incursion of cool-water species. Despite a twofold increase in cool equatorial species, a tropical climate prevailed throughout the last glaciation. Paleotemperature estimates indicate only a small (0.1 - 3.6 C) difference between glacial and postglacial winter temperatures. The coldest sea-surface temperatures occurred at about 73,000 B.P. Concurrently, calcareous remains underwent extensive dissolution. Faster water-mass circulation during the early part of the last glaciation as compared to the Holocene Epoch is postulated to account for the increased dissolution. Sea-level lowering (approximately 100 m) during the last glaciation and most of the last interglaciation allowed South American rivers to discharge large quantities of terrigenous sediment. Sea-level rise during the Holocene Epoch shut off the terrigenous-sediment supply to the deep sea, and the continental rise and abyssal plains became a regime of pelagic sedimentation.