Vegetation and climate during the Holocene in Southwest Patagonia, Argentina

Abstract

Pollen analysis from archaeological sequences in the Lago Argentino area (Southwest Santa Cruz province, Argentina) are used to infer vegetation and climatic changes during the Holocene. These sequences are located in present-day grass and shrub steppes and in Andean desert. Comparison with modern pollen data and other fossil pollen sequences provides a regional analysis of Holocene vegetational changes and contributes to the understanding of the regional paleoclimatic history. The fossil records indicate that a grass steppe developed in the area at the beginning of the Holocene. According to the pollen spectra, a change to shrub steppe took place between 8500 and 3500 yr BP, suggesting drier conditions. The presence of grass steppe may relate to greater availability of moisture and decrease in temperature in the south of Lago Argentino from 3500 yr BP, and in the northern and eastern portions of the area from ca. 1000 yr BP onwards. In the high Andean zone a herbaceous-shrub steppe with Empetrum developed between 4500 and 3600 yr BP which indicates conditions colder than today. Towards 3600 yr BP an increase in Asteraceae, dominant up to 200 yr BP, indicates less availability of moisture. During the last 200 yr expansion of shrub steppe and decrease of the forest are documented. This period coincides with the increased European settlement of the region. The paleoenvironmental interpretation is related to human populations living in Southwest Patagonia since early Holocene times.