Preliminary environmnetal magnetism study of a holocene eolian sediments and paleosols sequence in Tierra del Fuego (Argentina)

ORGEIRA, M.J.; CORONATO, A., VÁSQUEZ, C.A.; PONCE, F.; EGLI, R.; HONORATO, MR

Foz de Iguzaú

Congreso; Meeeting of the Americas; 2010

American Geophysical Union

he studied sequence is located in the northern region of Isla de Tierra del Fuego, Argentina (53°42´48.6"S;68°18´20.3"W), altitude 71 m asl. It comprises a succession of 20 m of eolian silty-fine sand-clay sediments with 8 paleosols layers interbedded. Radiometric data of the intermediate paleosoil 5 and its overlying tephra layer (ca. 5,8 yr B.P. and ca 3,2 yr B.P., respectively) allow to infer that the eolian deposition and the edaphic processes started during the Early-middle Holocene. The mean annual rainfall in the area is 383 mm and the mean annual temperature of 5.2°C. The sequence is located in a large area of low pressure under the effect of both the westerlies and the Polar Front. Wind frequency is daily, with and average rate of 25 km/h with frequent periods of higher speeds. The influence of Antarctic air produces short periods of colder and drier climate. The studied sequence is located in the semiarid Fuegian steppe where "Festuca gracillima" (coirón) is the dominating specie. This contribution includes preliminary environmental magnetism results of 93 samples collected along the sequence. These results include VSM measurements at room temperature and some measurements of susceptibility at high and low temperatures in selected samples. The results discussed here, together with those of other climatic proxies being carrying on, will define the climate variability occured in the southern extremity of the Americas . Based on our study we hope to contribute to the knowledge of the southern hemispheric atmospheric circulation variability along the recent geological times.