Ice-sheet control of continental erosion in central and southern Chile (36°-41°S) over the last 30,000 years

Bulk sediment chemistry from three Chilean continental margin Ocean Drilling Program sites constrains regional continental erosion over the past 30 000 years Sediments from thirteen rivers that drain the (mostly igneous) Andes and the (mostly metamorphic) Coast Range along with existing rock chemistry datasets define terrestrial provenance for the continental margin sediments Andean river sediments have high Mg/Al relative to Coast Range river sediments Near 36 S marine sediments have high Mg/Al (i e more Andean) sources during the last glacial period and lower Mg/Al (less Andean) sources during the Holocene Near 41 S a Ti rich source likely from coast-range Igneous intrusions is prevalent during Holocene time whereas high Mg/Al Andean sources are more prevalent during the last glacial period We infer that there is a dominant ice sheet control of sediment sources At 36 S Andean sourced sediment decreased as Andean mountain glaciers retreated after similar to 17 6 ka coincident with local oceanic warming and southward retreat of the Patagonian Forest and by Inference westerly winds At 41 S Andean sediment dominance peaks and then rapidly declines at similar to 19 ka coincident with local oceanic warming and the earliest deglacial sea level rise We hypothesize that this decreased flux of Andean material in the south is related to rapid retreat of the marine based portion of the Patagonian Ice Sheet in response to global sea level rise as the resulting flooding of the southern portion of the Central Valley created a sink for Andean sediments in this region Reversal of the decreasing deglacial Mg/Al trend at 41 S from 14 5 to 13 0 ka is consistent with a brief re advance of the Patagonian ice sheet coincident with the Antarctic Cold Reversal (C) 2010 Elsevier Ltd All rights reserved