Geophysical and geochemical constraints on the age and paleoclimate implications of Holocene lacustrine cores from the Andes of central Chile

A Holocene paleoclimate record was constructed using two lacustrine cores from the high-elevation Chilean Andes at 30 ̊S latitude. Coarser and more poorly sorted grain-size distributions and higher C/N ratios were interpreted as evidence for increased storm activity. Wet conditions prevailed from 10.8 to 9.5k cal a BP, then transitioned to dry conditions from 9.5 to 5.7k cal a BP interrupted by stormy conditions from 8.3 to 7.6k cal a BP. Wet conditions returned from 5.7k cal a BP to the present, interrupted by aridity from 4.1 to 2.2k cal a BP. This paleoclimate record is consistent with others from the region. The wet periods were probably caused by the influence of the Southern Westerlies, while dry conditions resulted from the influence of the Southeast Pacific Anticyclone. The increased storminess from 8.3 to 7.7k cal a BP may have been sourced from latitudinal shifts in the Intertropical Convergence Zone and subsequent weakening of the Westerlies, allowing the incursion of convective storms from east of the Andes. This sequence of events is consistent with synoptic conditions during modern easterly sourced storm activity. It is also consistent with modeling studies of the effect on the Southern Hemisphere of the rapid cooling of the North Atlantic Ocean during the 8.2-ka event.

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