High-resolution marine record of climatic change in mid-latitude Chile during the last 28,000 years based on terrigenous sediment parameters

Marine sediment cores from the continental slope off midlatitude Chile (33 degrees S) were studied with regard to grain-size distributions and clay mi neral composition. The data provide a 28,000-yr C-14 accelerator mass spect rometry-dated record of variations in the terrigenous sediment supply refle cting modifications of weathering conditions and sediment source areas in t he continental hinterland. These variations can be interpreted in terms of the paleoclimatic evolution of mid-latitude Chile and are compared to exist ing terrestrial records. Glacial climates (28,000-18,000 cal yr B.P.) were generally cold-humid with a cold-semiarid interval between 26,000 and 22,00 0 cal yr B.P. The deglaciation was characterized by a trend toward more ari d conditions. During the middle Holocene (8000-4000 cal yr B.P.), comparati vely stable climatic conditions prevailed with increased aridity in the Coa stal Range. The late Holocene (4000-0 cal yr B.P.) was marked by more varia ble paleoclimates with generally more humid conditions. Variations of rainf all in mid-latitude Chile are most likely controlled by shifts of the latit udinal position of the Southern Westerlies. Compared to the Holocene, the s outhern westerly wind belt was located significantly farther north during t he last glacial maximum. Less important variations of the latitudinal posit ion of the Southern Westerlies also occurred on shorter time scales, (C) 19 99 University of Washington.