Late Quaternary lacustrine paleoenvironment in the centre of lake Cuitzeo

Abstract

A 27-m-long drilled core taken from Lake Cuitzeo, central Mexico, preserves a late Quaternary paleoenvironmental record of the center of the lake. Radiocarbon dating of the upper third of the core indicates an age of about 42,000 yr B.P.; an extrapolation of sedimentation rates from the upper part of the core suggests an age of approximately 120,000 yr B.P. at the base of the core. We studied diatom species and their abundance in the core that show Lake Cuitzeo fluctuated in water depth and chemestry. For approximately 110,000 to 17,000 yr B.P. Staurosira spp. was the abundant specie in the lake, suggesting that the center of the lake had open, either fresh and alkaline waters. During same late Pleistocene episode, two short episodes of high-water evels are indicated by the abundance of Stepanodiscus spp. and  Aulacoseira spp. taxa. One of these periods was from about 44,000 to 42,000 yr B.P. and the other about 19,000 to 17,000 yr B.P. From about 8,000 yr B.P. to the present, conditions in the center of Lake Cuitzeo became more alkaline, with Cyclotela meneghinians dominating the diatom assemblages. Th presence of C. meneghiniana in abundance suggests that the lake envolved into a shallower, more turbid environment. Three volcanic ash layers are preserved in the core. Approximate ages of eruption and deposition of these ashes is 25,000 yr B.P., 35,000 yr B.P. and 120,000 yr B.P. Results of this study show that environments in Lake Cuitzeo fluctuated in the late Quaternary but prevaling low lacustrine levels. During the late Pleisticene climatic conditions were generally more humid than during the Holocene. Similar trends are recognized elsewhere in the nearby Pátzcuaro and Zacapu lake.