Preliminary rock-magnetic and paleomagnetic studies on sediments from Laguna Chaltel (Patagonia, Argentina)

PEDRO PALERMO; MARÍA A. IRURZUN; C. S. G. GOGORZA; A. M. SINITO; MICHAEL FEY; C. OLHENDORF; B. ZOLITSCHKA

Tandil

Congreso; Segunda Reunión Bienal de la Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo (LatinMag); 2011

LatinMag - UNCPBA

We have performed paleomagnetic and rock magnetic studies on six short sediment cores from Lake Chaltel (Patagonia, Argentina) (49º57´S 71º06´W). Measurements of intensity and directions of Natural Remanent Magnetization (NRM), magnetic susceptibility (k), isothermal remanent magnetization, saturation isothermal remanent magnetization (SIRM), back field and anhysteretic remanent magnetization at 100 mT (ARM100mT) were performed and several associated parameters calculated (ARM100mT/k and SIRM/ ARM100mT). Also, as a first estimate of relative magnetic grain-size variations, the median destructive field of the NRM (MDFNRM), was determined. Stability of the NRM was investigated by alternating-field demagnetization (AF). Most of the samples show no systematic change in the direction of their remanent magnetization during AF demagnetization; few of them have a viscous magnetization, which could easily be removed by AF demagnetization at about 10 mT. Rock magnetic properties document that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo-single domain magnetite. A total of nine samples was dated by AMS 14C techniques at the Poznan Radiocarbon Laboratory, Poland. Radiocarbon ages were calibrated with the southern hemisphere calibration curve (SHCal04, McCormac et al., 2004) using the software CALIB 5.0.1 (Stuiver and Reimer, 1993; Stuiver et al., 2005) and are given as calibrated years before present (cal. BP). A basal age of 4616 cal. BP is obtained for the core CHA-04-4.The NRM as well as declination and inclination logs of the characteristic remanent magnetization for all samples as function of calibrated ages were obtained.