Late Pleistocene and Holocene Palaeovegetational Changes at Alero El Puesto (AEP-1) Archaeological Site in the Northern Deseado Massif. Regional Palaeoenvironmental Implications and Early Human Occupation

Abstract

Interpretation of pollen data from Alero El Puesto (AEP-1) archaeological site at Piedra Museo locality (47° 53′ 42″ S, 67° 52′ 04″ W, 150 m a.s.l.), in the northern Deseado Massif, allows to improve the knowledge about the palaeoenvironmental conditions following the Last Glacial Maximum, and their relationship to the early human occupations. Two climatic events featured the late Pleistocene–early Holocene transition, the Antarctic Cold Reversal (ACR, ca. 14,600–12,800 cal BP), and the Northern Hemisphere Younger Dryas event (YD, ca. 12,900–11,700 cal BP). The vegetal palaeocommunities reconstructed from pollen records from the Deseado Massif region reflected abrupt changes related to both temperature and precipitation during these events. Cold and extremely arid conditions characterized the ACR, when vegetation was dominated by shrub steppes with Asteraceae subf. Asteroideae and dwarf shrub steppes with Ephedra. Meanwhile, the spread of grassland steppes with variable proportions of shrubs and dwarf shrubs, coeval with the YD, suggested a change toward warmer and slightly wetter conditions than before. The archaeological data showed an increase in the human use of space during this interval. After that, the trend of increasing temperature and decreasing effective moisture favored the development of a mosaic of shrubby steppes during the early Holocene. The floristically heterogeneous shrub steppes began to dominate the Deseado Massif during the middle and late Holocene. This vegetation reflected arid to semiarid conditions indicating rainfall spatial variation, runoff redistribution, and edaphic diversity. Plant palaeocommunities similar to the present-day ones were established in the north of the Deseado Massif after ca. 4000 cal yr BP, and in the south of this massif after ca. 2100 cal yr BP. Taken together, the palaeoenvironmental conditions recorded in the studied region are closely related to variations in the latitudinal position and/or strength of the westerlies that would have impacted the early human occupations.