Application Of Geochemical Weathering Indices To Loess -Paleosol Sequences From Central Asia (Tajikistan)

Loess deposits are well known as repositories of information about climatic and environmental variations occurring over the Quaternary. Over the years, numerous weathering indices relating to the geochemical characteristics of loess sediments have been developed to provide insights into environmental changes through time. In this study, we characterize the major element chemistry of the uppermost 20 m of the Karamaidan loess deposit in Tajikistan, which spans the last full glacial cycle. We compare major element ratios (Al/Ti, Fe/Ti, and Al/Fe), together with ternary A-CN-K diagram and enrichment/depletion of the elements relative to the upper continental crust, down the Karamaidan sequence, and compare our results to other regional and supraregional loess deposits and their change through time. We investigate different weathering indices (A and B indices, PWI, bases vs. Al ratio, CIW, PIA, and YANG indices, WI-1, WI-2, and CPA and FENG) in order to identify those most applicable to our study. We compare our results magnetic susceptibility down the stratigraphic profile to derive a direct index for alteration of the deposit.