Aeolian sequence and the archaeological record in the fuegian steppe, Argentina

A 20 m thick sequence of aeolian deposits and palaeosols, deposited above Neogene marine sediments adjacent to the shallow saline ephemeral Lake Arturo in interior Tierra del Fuego, is described. A deposit of archaeological stone artifacts and bones, the Lake Arturo 1 archaeological site, is located in a deflation hollow near the top of the aeolian sequence. The sequence of nine aeolian deposits, including eight palaeosols and capped by the contemporary soil, provides evidence of environmental changes which have occurred during the Holocene in the cold Fuegian steppe, beginning as early as the Late Glacial-Early Holocene transition. A chronostratigraphy is provided by guanaco (Lama guanicoe) and Canidae bones embedded within palaeosols and organic matter content, radiocarbon dated from 9951 ± 59 BP (11,304 cal BP) at the base of the sequence to 434 ± 43 BP (471 cal BP) near the top. A tephra layer between Palaeosols 4 and 5 is interpreted from its geochemical fingerprint as the product of one of the mid-Holocene eruptions of Mt. Burney, located in the Southern Patagonian Andes. It is suggested that the accumulation of the aeolian sediments occurred throughout most of the Holocene, as a result of both local acquisition of fine particles derived from the weathering and erosion of the basal Neogene marine sediments, and deflation from the intermittently dry lake bed, as well as deposition of material transported by wind from more distant sources. The orientation of the aeolian deposits suggests a more northwesterly wind direction instead of the present westerlies. Weakly developed A horizons capping each of the sediment units suggest that the landscape was sensitive to environmental change, from more arid conditions when the aeolian deposits accumulated to brief periods of landscape stability when topsoil development occurred. Evidence of human occupation in Lake Arturo 1 is confined to the upper part of the sequence (ca 500 years BP) and is interpreted as a place for primary butchering and raw material acquisition.