A LATE QUATERNARY GEOCHEMICAL RECORD FROM THE PALEOAKE LA SALADA, SOUTHERN CHIHUAHUA DESERT, MÉXICO

The paleolake La Salada (N 23° 26’, W 102° 52’, 2061 m asl) is an ephemeral lacustrine basin located in the state of Zacatecas, northern Mexico and receives runoff mainly during the summer months by the North American Monsoon system. The sediments deposited in the basin provide information about the late Quaternary paleoclimatic variations from the southern part of the Chihuahua Desert. We studied magnetic susceptibility, multi-element concentrations, total organic carbon (TOC) and total inorganic carbon (TIC) contents and mineralogy of a 300 cm long sediment sequence collected from the basin margin in order to generate proxy records of runoff into the basin, lake water salinity, aeolian activity in the surroundings of the basin and water content in the sediment-air interface of the watershed. Radio carbon dates on bulk organic matter assign ages of 2420±30 ¹⁴C yr BP, 18,300±70 ¹⁴C yr BP, 25,850±130 ¹⁴C yr BP and 31,160±180 ¹⁴C yr BP at depths of 37, 59, 67 and 179 cm, respectively. Two different radio carbon analysis in the sediments at depths >200cm provided dates >43,500 ¹⁴C yr BP. Based on the stratigraphy and age model, we observed that the lake dried for an extensive period at ca.2.5, ca.28 and ca.36 cal kyr BP. The proxy indicator of runoff into the basin suggests millennial scale variation in precipitation in the surroundings. The basin received low runoff during the last glacial maximum (ca.21-28 cal kyr BP) and the runoff increased during ca.33 cal kyr BP and >50 cal kyr BP.