NOAA/WDS Paleoclimatology - La Alberca Lake, Guanajuato, Mexico 6,700 Year Geochemical Data

The relationship between climatic-environmental changes and its cultural implications in the Northern Mesoamerican Frontier is poorly understood, because of the lack of high-resolution well-dated records. In this work we present a high-resolution paleoclimate and paleoenvironmental reconstruction of the Northern Mesoamerican Frontier for the last 6700 yr BP, using laminated sediments from La Alberca maar lake, Guanajuato. For this purpose, we used different techniques such as X-ray fluorescence, microfacies analysis, magnetic parameters, bulk sedimentary d18O, d13C records and twelve AMS 14C ages. In Prehistory times, different climatic events are well defined. At around 5600 yr BP, our data indicate the end of Holocene Thermal Maximum and a subsequent decline of monsoon strength is observed. Variable hydrological conditions start to dominate around ~4400 yr BP consistent with the rise of latitudinal variations of the Intertropical Convergence Zone. A rise in sedimentation rate and increase in Amaranthaceae pollen percent occurred between ~225 CE- 600 CE are linked to the beginning of agricultural activities by the Chupicuaro Pre-Hispanic culture. In Historical times, during the Epiclassic period, we interpreted two drought events around ~700-790 CE and ~810-880, supporting the Armillas' theory that drastic climate events motivated the social changes and shift in the geographic position of Northern Mesoamerican Frontier. In the final part of the Postclassic period a pluvial interval is associated with the rise of Tarascan culture in the area. We propose that droughts and pluvial periods between 600 and 1500 CE are connected with SSTs variability of the Atlantic Basin.