干旱区生态环境知识资源中心

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 27?cal. ka in the western Chihuahua Desert. Variations in the available water content at the sedimentair interface of the watershed, lake salinity and lake productivity are inferred from values of the chemical index of alteration (CIA), CaCO 3 and Corg, respectively. An abrupt increase in runoff at c. 24?cal. ka BP appears correlative with the Heinrich 2 (H2) event. Except for this event, diminished runoff between c. 27 and 19?cal. ka BP indicates lower annual precipitation (weak summer rainfall) during the Last Glacial Maximum. The deposition of chemically altered sediments between c. 25 and 22?cal. ka BP results from the higher sedimentwater interaction in the watershed owing to lower evaporation, cooler conditions and higher precipitation during the H2 event. Since 19?cal. ka BP the runoff has been characterized by high-amplitude fluctuations with intervals of reduced precipitation identified at c. 19, 18, 17.5, 1314, 11.5, 10, 7.5 and 3?cal. ka BP.