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Palaeomagnetic data from Late Glacial glaciolacustrine sediments at Rio Corintos, Chubut, Argentina

1990; Elsevier BV; Volume: 64; Issue: 2-4 Linguagem: Inglês

10.1016/0031-9201(90)90031-r

1872-7395

Luis A. Beraza, J. F. Vilas,

Pleistocene-Era Hominins and Archaeology

The characteristics of the Pleistocene glaciations in Patagonia have been partially solved. On the basis of the moraine extent and the varve-counting method, and by analogy with the Weichselian Glaciation in Scandinavia, Caldenius (1932) established a pattern of Patagonian glaciations which has remained acceptable. Palaeomagnetic studies of glacial sediments have been started with the aim of testing this correlation. A 78-m Late Glacial glaciolacustrine sequence was studied and sampled at Rio Corintos, Chubut Province, Argentina (43 ° 10′ S, 71 ° 15′ W). Approximately 1089 varves were counted; they were thought to have been deposited between 25 000–13 000 years BP. The samples showed strong and stable values of remanent magnetization. Magnetite was identified as the carrier of the remanence. Magnetic susceptibility and intensity were recorded and the expected variations according to grain size were obtained. Recorded declination values oscillated from 30 ° W to 15 ° E, and inclination values from −8 ° to − 56 °. This shift can be attributed to the secular variation of the geomagnetic field. Declination and inclination values were smoothed using a stratigraphic window which covered 40 varves. Assuming that a single varve implies that one year has passed, the secular variation curve can be presented against a scale-time which spans approximately 1200 years. The corresponding VGP path showed 100% clockwise motion in the region of northern Canada. A correlation with other VGPs recorded in Lago Buenos Aires for Late Glacial varves has been established.