Masters Thesis

Geophysical and geochemical constraints on the age and paleoclimate implications of two Holocene lacustrine cores from the headwater region of the Claro River, Elqui Province, Coquimbo Region, Chile

A Holocene paleoclimate record for northern central Chile has been constructed using two lacustrine cores from the high-elevation Andes at ~30° S latitude. The 1.37-m Laguna Cerritos Blancos (LCB) core has been dated from 0-4.0 cal kyr BP using paleomagnetic secular variation (PSV) and 14C radiometric dating and the 5.53-m Laguna El Cepo (LEC) from 0-10.9 cal kyr BP using 14C radiometric dating. Coarser grain sizes, bimodal grain-size distributions, greater carbon and nitrogen weight percentages, and C/N ratios were found to co-vary suggesting increased storm activity and wet climate. The Holocene began with a wet period from ~10.9-9.5 cal kyr BP, then dry conditions beginning ~9.5 cal kyr BP with a transition to wetter conditions from ~8.3 until ~7.7 cal kyr BP. ~7.7-5.5 cal kyr BP is an arid period, then moisture and storm activity increase gradually from ~5.5 to ~4.9 cal kyr BP when conditions remain mildly dry until 4.4 cal kyr BP. Moisture and storm activity increase abruptly from ~4.0 cal kyr BP to ~3.8 cal kyr BP when moisture decreases gradually into a dry period from ~2.6 until 2.2 cal kyr BP wherein moisture and storm activity increase. A slight decrease in moisture after ~0.3 cal kyr BP is probably consistent with the current dry conditions in the study area. This paleoclimate record is consistent with others of the region. Accordingly, the wet periods with greater storm activity are likely caused by the prevalent influence of the westerlies, while stable and dry conditions are probably the result of the dominant influence of the Southeast Pacific anticyclone (SPA). Furthermore, the intervals of increased storm activity observed in the Chilean lake records correlate to a first order with short periods of global rapid climate change, including the 8.2 ka event.

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