Relative palaeointensity and reservoir effect on Lake Esmeralda, Antarctica

Abstract

Four cores from the bottom sediments of Lake Esmeralda, Vega Island, Antarctica (60°48'S, 57°37'W) were studied. Analysis of rock magnetics indicates that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo-single-domain (titano-) magnetite with a small proportion of paramagnetic and antiferromagnetic minerals. The magnetic grain size of the samples is in the range of 1-5 μm and the variation of the interparametric ratios is less than one order of magnitude. Demagnetization of the natural remanent magnetization shows a stable remanent magnetization in most of the samples. Thus, the samples fulfil the necessary conditions to calculate relative palaeointensity (RPI) and the curves obtained correlated with global models enabling dating of the cores. The 250 cm of sediment recovered spans the last 10 200 yr bp. Finally, some samples with high organic matter content were dated by accelerator mass spectrometry 14C. By comparison with the age defined by the RPI curves, a reservoir effect of c. 5200 years is suggested for this region of Vega Island.