A holocene lake-margin aeolian sequence from interior Tierra del Fuego, Argentina, and evidence for human occupation

A 20 m thick sequence of aeolian deposits and palaeosols, deposited above Tertiary marine sediments adjacent to the shallow, saline, ephemeral Laguña Arturo in interior Tierra del Fuego, is described. The sequence of nine aeolian units, 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 and Canidae sp. bones embedded within palaeosols, and organic matter content, radiocarbon dated from 9,951+/-59 y BP (11,304 cal BP) at the base of the sequence to 434 +/- 43 y 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. The evidence suggests that accumulation of the aeolian sediments occurred throughout most of the Holocene, and were sourced from deflation from the intermittently dry lake bed, as well as deposition of material transported by wind from more distant sources. Local acquisition of fine particles derived from the weathering and erosion of the basal Tertiary marine sediments may also have occurred. 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 aeolian 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 Laguña Arturo 1 (stone artefacts and animal bones) is confined to the upper part of the sequence, and is interpreted as a place for primary butchering and raw material acquisition.