Earth Planets Space, 51, 93–106, 1999 Holocene geomagnetic secular variations recorded by sediments

Paleomagnetic and sedimentological studies carried out on two short cores and nine long cores from the bottom sediments from Escondido Lake (south-western Argentina) are described. Rock magnetic analysis suggests that the main carriers of magnetization seems to be ferrimagnetic minerals, predominantly pseudo single domain magnetite. The presence of greigite, as diagenetic euxinic material, is also suggested. Calibrated ages were calculated from radiocarbon dating and a transfer function shortened depth-age is built, which suggests the existence of a hiatus, supported by the suggestion of previous palynological studies about the possible evidence of the younger Dryas cooling event seen in the Antarctic ice cores. The stacked inclination and declination curves and their standard deviations using arithmetical average after chronostratigraphic correlations are made. Inclination data show two well defined periods: a long period (about 7700 years) and a short one (between 2660 and 2900 years). Declination data show two intermediate periods (about 3600 and 2900 years respectively) and a long, although less reliable, period (about 10000 years). The longer periods may be related to dipolar variations, while the shorter periods may be associated to non dipolar variations. 1