Paleogeographic and paleoenvironmental evolution in northwestern Santa Cruz (Argentina), and its influence on human occupation dynamics during the late Pleistocene- early Holocene

Abstract

The climatic changes that occurred during the late Pleistocene-early Holocene in Patagonia generated a glacial retreat, which brought along with it the formation of proglacial lakes (in contact with ice) and periglacial lakes (in areas close to the glaciers). The bathymetric fluctuations of lacustrine systems throughout time have favored new areas available for population circulation and settlement. Our results showed the influence of ice masses on the palaeoenvironmental evolution with alternating glacial and proglacial environments: tillites, glacilacustrine/lacustrine environments, glacifluvial/fluvial environments, alluvial fans, and deltaic bodies. An initial diachronism was recorded in the formation of the paleolakes; the Lacustrine System Parque Nacional Perito Moreno (SL-PNPM) would have begun to form first, and then the Lacustrine System Pueyrredón – Posadas – Salitroso (SL-PPS). Between 12 and 11.7 kyr, in both sectors, the paleolakes would have reached their maximum areal extension. After 10 kyr, a regression and separation of the lacustrine systems until the acquisition of its current configuration was interpreted. This data coincides with archaeological sites located at lower elevations, closer to the current level of the coastline, both in the SL-PPS and the SL-PNPM areas. The palaeoenvironmental information indicated a synchrony in both areas in the evolution of the floristic landscape. The separation of lacustrine systems generated new available spaces and ecological niches for the establishment of vegetation which encouraged a greater heterogeneity in vegetation that could have been exploited by hunter-gatherer groups.