Late Pleistocene and Holocene paleoenvironments at Plains of Sonoran Desert, based on fossil pollen content and geochemical analysis

Quaternary pollen-geochemical based-studies in Sonoran Desert are poorly documented. Two sedimentary profiles were studied at Félix Gómez, Sonora in the Plains of Sonoran Desert: Paleosols “La Cárcava” (335 cm depth) and “La Morita” (220 cm depth) covers the latest Pleistocene and all Holocene. The results of paleoenvironmental proxy analysis (fossil pollen, geochemical data, and radiocarbon ages), show a variation in Late Pleistocene conditions with high precipitations and low temperatures leading to an open forest vegetation ( Pinus sp., Quercus sp. and Poaceae) in the actual desert. From Late Pleistocene to Early Holocene increasing temperature and higher evaporation rates were constated with the establishment of tropical-desert vegetation. Recovering to wetter al cooler conditions appear in early Holocene with a woodland vegetation type-Chaparral ( Pinus , Quercus and Pteridophytes). In the middle-late Holocene the hottest conditions were recorded, with mostly herbaceous plants (Asteraceae and Chenopodiaceae). Finally, in the Latest Holocene (last 2,500 years) similar conditions to present days were documented (Chenopodiaceae, Asteraceae, Cactaceae and Fabaceae). • First paleoenvironmental record since Late-Pleistocene for the Plains of Sonoran Desert • Important changes in pine-forest and Thornscrub related to climate variability • The Bølling-Allerød was recorded with increasing of tropical vegetation • A Chaparral pine-forest was still detected during middle Holocene (8 to 6 Ka) • Geochemical reveals climatic variability well correlated with fossil pollen records