Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment

Abstract

The Valsequillo Basin in Central Mexico has been of interest due to the presence of megafaunal remains and evidence for early human occupation, but research has been controversial. It has been suggested that extensive and deep lakes characterized the Early Pleistocene environment but sediment exposure is highly fragmentary and reliable dating has been difficult. Here we report, for the first time, Early Pleistocene palaeoenvironmental reconstructions using stable isotopes, diatoms, tephra and pollen. We studied several stratigraphic sections of mainly non-volcanic rocks, containing the 1.3-Ma Xalnene Ash as a stratigraphic marker. The isotope and other proxy data show that topographically low points in the basin were occupied by spring-fed, shallow water lakes during the Early-Mid Pleistocene, with a trend to drier conditions. The basin was a dynamic volcaniclastic environment during this period, with the production of the Toluquilla volcanic sequence and other rhyolitic-dacitic volcanic ashes interbedded with the lake sediments at the sections studied. There is no evidence from the sections for extensive and deep lakes before or after deposition of the Xalnene Ash. Wetter conditions in the basin during the Early Pleistocene would have made it attractive for megafauna.

Testing the Utility of Geochemical Proxies to Reconstruct Holocene Coastal Environments and Relative Sea Level: A Case Study from Hungry Bay, Bermuda

“…Measurements made at specific temperatures and times in the heating/cooling cycle provide insight on the type and maturity of organic material that is present, which may be diagnostic of depositional environments (e.g., Metcalfe et al, 2016). From these directly measured parameters, a series of additional, secondary parameters are calculated.…”

An inventory of phreatomagmatic volcanoes in the Trans-Mexican Volcanic Belt

“…It is exorheic and the stratigraphy is formed by a succession of sediments produced by fluvial and lacustrine dynamics interbedded with pyroclastic deposits as well as lava flows. Climate conditions in this basin used to be more humid than at present, and there is evidence that there were lacustrine conditions before the formation of the Toluquilla tuff cone in the Early Pleistocene, 1.30 ± 0.03 Ma (Feinberg et al, 2009;Metcalfe et al, 2016). This is the only PV reported in this basin, among several other monogenetic volcanos like scoria cones.…”

Aspectos paleobiológicos de dos ejemplares de Mammuthus columbi (Mammalia, Proboscidea, Elephantidae) del Pleistoceno de Puebla, centro de México

“…Este paleoambiente podría ser equiparado al existente durante el Pleistoceno en la Cuenca de Valsequillo, Puebla, zona que se ubica a tan sólo 78 km de barranca El Morillo y a 22 km de Sierra de Amozoc. La reconstrucción del paleoambiente de la Cuenca de Valsequillo indica predominio de vegetación abierta, pero con presencia de coníferas (Pinus, Quercus, Alnus), donde predominaba un clima de baja humedad, que alternaba episodios secos y fríos (Stevens et al, 2012;Pérez-Crespo et al, 2014;Metcalfe et al¸ 2016). Por consiguiente, es posible que este tipo de hábitat fuera común en el centro del estado de Puebla durante el Pleistoceno, favoreciendo el desarrollo de las poblaciones de M. columbi.…”