GLACIATION DURING THE PLEISTOCENE-HOLOCENE TRANSITION AND EARLY HOLOCENE IN THE MOUNTAINS OF CENTRAL MEXICO

Some mountains of the Transmexican Volcanic Belt peaking at >4200 masl (Iztaccíhuatl, Cofre de Perote, Malinche and Nevado de Toluca, ca. 19°N) display clear evidence of a glacier advance at the Pleistocene-Holocene transition lasting ca. 2 millennia, broadly within the Younger Dryas chronozone. Three of those mountains higher than 4400-4500 masl also show evidence of a short but distinctive advance at 9-8 ka, probably linked to the 8.2 ka event of the North Atlantic. Details are presented on the timing, extent and ELAs of each event, mostly from Iztaccíhuatl volcano (5250 masl). The chronology is supported on nearly 50 ³⁶Cl surface exposure ages. The mean ELA was positioned ca. 700 m (Pleistocene-Holocene transition) and ca. 550 m (9-8 ka) below modern values, which correspond to nearly 70% and 50% of the ELA descent during the LGM in central Mexico. Thus, both advances represent significant century-long cooling events for the northern tropics and support a hemispheric extent of the Younger Dryas and the 8.2 ka event.