PALEOENVIRONMENTAL CONDITIONS AT THE BAJIO DURING THE LAST GLACIAL MAXIMUM

The maar of Valle de Santiago is located in the state of Guanajuato to the south of the City of Salamanca, at the northern limit of the Mexican Volcanic Arc. It is present near the border between arid northern México and tropical to subtropical high pressure climatic systems that dominate the central and southern Mexico.

The rainfall distribution is controlled in part by the latitudinal migration of the InterTropical Convergence Zone (ITCZ) bringing humid air mass from the Gulf of México and the Caribbean and the westerly winds that carry moisture from the Pacific. This work intends to reconstruct the environmental conditions in the Bajio region during the last 22,000 cal years BP,

A 14.5 m core collected from the central part of the maar. The chronological control is provided by 4 differe nt 14C dates. According to the age model, the sediment sequence covered the late Pleistocene and the base of the sedimentary sequence has been assigned an age of 22000 cal year BP. The inferred changes in climatic conditions based on the stratigraphy, TIC-TOC, and pollen of the sedimentary deposits of the maar Rincón de Parangueo showed lower lake levels associated to dry phases (13000, 14500-15000, 16500-17000, 18500, 19500 and 20000 cal year BP) and humid phases (14000, 16300 and 17000 - 17500 yr Cal BP) with important terrigenous input at 14000, 15000 and 19000 cal year BP, respectively. The observed vegetation during the Last Glacial Maximum (18,500 to 22,000 yr Cal BP) suggested a dense cloud forest in the surroundings of the maar, inferring colder and wetter conditions in the Bajío.