A millennial-scale late pleistocene-holocene palaeoclimatic record from the western chihuahua desert, mexico

摘要

We present elemental concentrations and magnetic susceptibility data from a new 270-cm-long sediment core collected from the western part of palaeolake Babicora and infer millennial-scale hydrological variations over the last 27cal. ka in the western Chihuahua Desert. Variations in the available water content at the sediment-air interface of the watershed, lake salinity and lake productivity are inferred from values of the chemical index of alteration (CIA), CaCO 3 and C org, respectively. An abrupt increase in runoff at c. 24cal. ka BP appears correlative with the Heinrich 2 (H2) event. Except for this event, diminished runoff between c. 27 and 19cal. ka BP indicates lower annual precipitation (weak summer rainfall) during the Last Glacial Maximum. The deposition of chemically altered sediments between c. 25 and 22cal. ka BP results from the higher sediment-water interaction in the watershed owing to lower evaporation, cooler conditions and higher precipitation during the H2 event. Since 19cal. ka BP the runoff has been characterized by high-amplitude fluctuations with intervals of reduced precipitation identified at c. 19, 18, 17.5, 13-14, 11.5, 10, 7.5 and 3cal. ka BP.