Magnetic properties of aeolian deposits in Paleolithic sites in Korea and correlation with the Chinese loess-paleosol sequence

Abstract

We report here data on the pH, electrical conductivity (EC) and environmental magnetic properties (χlf, χfd, χARM, IRMs at different field strengths) of modern tropical lateritic soils from Aribail, Miyapadavu and Uliyathadka, all in the Kasaragod District of Kerala, southern India. This study aims to characterize the rock magnetic properties of lateritic soils that formed under tropical high-rainfall conditions and determine the effects of pedogenesis on soil magnetic properties in comparison with temperate soils. The profiles may be divided into two or three zones based on differences in magnetic mineral concentration, grain size and mineralogy. There is no magnetic enhancement of topsoil in any of the profiles studied. As the lateritic rocks in the region are ferruginous, the lateritic soils developed over them contain significant amounts of coarse grained lithogenic magnetite as well as hematite. Because of the presence of this ‘laterite-derived’ magnetite and hematite, the lateritic soils have much higher susceptibility values when compared to temperate soils. The upper zone is characterized by a higher proportion of lithogenic grains and the lower zone by superparamagnetic (SP) grains. This is probably because of iron reduction and dissolution of fine magnetic grains at the profile-top because of the excessively high rainfall (average = ~ 3500 mm/year) in the region. The slight increase in χlf and SIRM values toward the top of the Aribail and Miyapadavu profiles is due to the presence of coarse magnetic grains. This characteristic is common to all the three profiles irrespective of the topography. Compared to pre-monsoon samples, post-monsoon samples exhibit an increase in the proportion of SP grains. However, the magnetic grain size of lateritic soils from the three locations is similar to that of temperate soils.