Paleosecular Variations 0-19,000 Years Recorded by Sediments from Escondido Lake (Argentina)

GOGORZA, C.S.G.; SINITO, A.M.; LIRIO, J.M.; NUÑEZ, H.; CHAPARRO, M.A.E.; VILAS, J.F.

PHYSICS OF THE EARTH AND PLANETARY INTERIORS

Elsevier

Lugar: Amsterdam (Holanda); Año: 2002 vol. 133 p. 35 - 55

0031-9201

Paleomagnetic and sedimentological studies carried out on four cores, about 11m long, from the bottom sediments of Escondido Lake (southwestern Argentina) are described. This lake is geologically related to the set of lakes of glacial origin located in western Patagonia. Using several magnetic studies, the predominance of pseudo-single/single domain magnetite as main carrier, as well as an increase of concentration and grain size with depth was determined. The pairs of magnetic susceptibility and intensity of remanent magnetization profiles show a good correlation with the sedimentological macroscopic descriptions, and also with those of shorter cores previously studied. The stability of the natural remanent magnetization was investigated by alternating-field demagnetization. Within-lake correlation was based on lithology, magnetic susceptibility and intensity of remanent magnetization, because the patterns of these parameters showed similarity for every core. Radiocarbon dating suggests higher deposition rates during the early stage of the lacustrine basin (Late Pleistocene). The transfer function depth–age also allowed constructing a secular variation record from south Argentina for the past 19,000 years. The declination and inclination logs show some anomalous directions at about 18,000 calibrated years.