High-Resolution Marine Record of Climatic Change in Mid-latitude Chile during the Last 28,000 Years Based on Terrigenous Sediment Parameters

Abstract

Marine sediment cores from the continental slope off midlatitude Chile (33°S) were studied with regard to grain-size distributions and clay mineral composition. The data provide a 28,000-yr 14 C accelerator mass spectrometry-dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland. These variations can be interpreted in terms of the paleoclimatic evolution of mid-latitude Chile and are compared to existing terrestrial records. Glacial climates (28,000 -18,000 cal yr B.P.) were generally cold-humid with a coldsemiarid interval between 26,000 and 22,000 cal yr B.P. The deglaciation was characterized by a trend toward more arid conditions. During the middle Holocene (8000 -4000 cal yr B.P.), comparatively stable climatic conditions prevailed with increased aridity in the Coastal Range. The late Holocene (4000 -0 cal yr B.P.) was marked by more variable paleoclimates with generally more humid conditions. Variations of rainfall in mid-latitude Chile are most likely controlled by shifts of the latitudinal position of the Southern Westerlies. Compared to the Holocene, the southern westerly wind belt was located significantly farther north during the last glacial maximum. Less important variations of the latitudinal position of the Southern Westerlies also occurred on shorter time scales.

The topographic imprint of a transient climate episode: the western Andean flank between 15·5° and 41·5°S

“…Less extensive shifts of the Westerlies have occurred on shorter timescales in the recent geologic past, i.e. in Holocene (Lamy et al, 1999). In contrast, precipitation patterns of the plateau regions north of 27°S appear to be relatively stable over glacial-interglacial cycles (Garreaud et al, 2003).…”

“…Thus, northward-migrating (South) Westerlies may have reached these latitudes, intensifying precipitation during glacial and delivering sufficient moisture for glaciation in these threshold environments (e.g. Heusser, 1989;Lamy et al, 1999). This supports the notion that glaciation in large parts of the central Andes is moisture-controlled, which is in good agreement with results from Haselton et al (2002) who concluded that the Pleistocene snowline in the southern Altiplano-Puna Plateau is more sensitive to moisture increase than temperature.…”

Climate and marine carbon cycle response to changes in the strength of the Southern Hemispheric westerlies

“…Corroborating evidence comes also from marine sediments cores from the Chilean margin [Lamy et al, 1999;Stuut and Lamy, 2004]. The possible mechanism to explain the greater precipitation is an equatorward shift and/or an intensification of the Southern Hemisphere westerly winds and of the storm track [Garreaud, 2007].…”

Finding of a Holocene marine layer in Algarrobo (33°22'S), central Chile. Implications for coastal uplift

“…These data are in agreement with different studies that show evidence of an arid climate that prevailed in central Chile during the midHolocene, changing to cooler and wetter conditions at approximately 5700 cal yr BP. Evidence of a midHolocene dry climate comes from the study of grainsize distributions and clay mineralogies in sediment cores from the continental slope of central Chile at 33°S (Lamy et al, 1999) as well as from pollen analysis in Laguna de Aculeo (33°S) (Jenny et al, 2002;Villa-Martínez et al, 2003) and the Quintero II swamp forest (33°S) (Villa-Martínez and Villagrán, 1997).…”