Living in Andean dead ends: human-environmental interactions at the fringes of the Northern Ice Field.

MÉNDEZ, C.; DE PORRAS, M.E.; NUEVO DELAUNAY, A.; MALDONADO, A.; REYES, O.; MCCULLOCH, R.

Congreso; 20th Congress of the International Union for Quaternary Research (INQUA); 2019

Andean dead ends in Central Western Patagonia (CWP) represent ideal landscapes to address the differential role of hunter-gatherer occupations and human/environment interactions, yet they remain understudied. As marginally occupied areas, these are highly sensitive to changes in mobility and land use, and thus informative of human processes occurring at broader spatial scales. The sector bounded by the General Carrera/Buenos Aires (GCBA) and Cochrane/Pueyrredón (CP) lakes, the Baker River (BR) and the Northern Ice field (NIF) stands as a remarkable example of dead end. Our goal is to study human/environmental interactions by combining archaeological (occupational redundancy, variability in technology and subsistence, and changes in mobility) and paleoenvironmental (pollen, charcoal) records.Paleoenvironmental records based on pollen records located within the forest do not show major changes particularly during the Holocene due to the over-representation of Nothofagus pollen. However, those located at the forest-steppe ecotone further north (44.5°S; Lago Shaman and Mallín El Embudo) show the gradual development of the forest after 14ka peaking between 8-5ka as a response to higher humidity and unmarked seasonality, while the late Holocene was characterized by highly variable conditions. At 47°S, the pollen record of Mallín La Frontera, also in the forest-steppe ecotone, shows an initial amelioration in environmental conditions after ca. 8.2ka followed by a reversal to colder conditions between ca. 7.4-6.5 ka followed by variable climatic conditions up to 3.7ka. After 3.7ka and up to the present, a gradual shift to more stable and temperate conditions occurred. Mire pollen records within the forest at 47°S (Laguna Anónima and Mallín Casanova) show a decrease of forest pollen after 2ka.The spatial characteristics of the area east of the NIF and the distribution of known archaeological sites suggests geographical barriers such as the GCBA and CP Lakes, as well as the BR, acted as bounds constraining mobility during the Holocene. The initial exploration of this area occurred ca. 8ka as indicated by the earliest records of Alero Entrada Baker and sites south of the CP Lakes. This occurred once these environments became attractive to populations of eastern steppes. Cave sites, however prone to accumulate anthropogenic sediments and artifacts, are characterized by temporal discontinuities, with limited periods of sustained human presence during the late Holocene. FONDECYT 1180306, National Geographic Grant # HJ-150R.17