Lacustrine ostracodes from the Chihuahuan Desert of Mexico and inferred Late Quaternary paleoecological conditions
The abundance and distribution of ostracodes in the upper 865 cm of a sediment core recovered from Babícora paleolake allows reconstruction of paleoecological conditions in the western Chihuahuan Desert by inferring variations in temperature and salinity of the lake water over the last ca. 72 cal kyr BP. The ostracode assemblage consists of five species (Candona patzcuaro Tressler, Cypridopsis vidua Brady, Limnocythere bradburyi Forester, L. platyforma Delorme and L. Ceriotuberosa Delorme), and its abundance varies between 0 and 1441 valves/g. Low ostracode abundance suggests the presence of dilute lake water (salinity>100 ppm) with abundant fresh water inflow into the basin prior to ca. 57 cal kyr BP. During ca. 57-49 cal kyr BP salinity remained low (>100 ppm), but the water column was characterized by cold temperatures (>4 °C). Sediments of this zone have higher organic carbon content. Conditions were optimal for ostracode productivity (abundance of 44-1441 valves/g) during ca. 49-29 cal kyr BP, and this zone indicates fluctuating temperature (5-32 °C) and salinity (100-100,000 ppm). A warm water column (>13 °C) and salinity of >500 ppm are inferred during ca. 29-12 cal kyr BP. Sediments of the last 12 cal kyr BP lack preserved ostracodes, and precipitation of authigenic calcite indicates periodic desiccation of the lacustrine basin during the Holocene. The inferred paleoecological conditions in the western Chihuahuan Desert are synchronous with other proxy-based late Quaternary paleohydrological and paleoclimatic information obtained from southwestern USA and northern Mexico.