Magnetic parameters and paleoclimate: A case study of loess deposits of North-East of Iran

Abstract

Environmental magnetism techniques enable us to reconstruct paleoclimate conditions in some deposition such as losses. The magnetic properties of minerals are used as proxies for environmental changes. For this study, loess/paleosol sequence of Kolet section at Neka, north-east of Iran were magnetically investigated. We applied environmental magnetism methods, to reconstruct paleoclimate changes. We investigated relationship between paleoclimate changes and environmental magnetism proxies like magnetic susceptibility (χ) variation. The laboratory techniques indicated the presence of main factor of magnetic property in loess/paleosol sequence, such as magnetite, maghemite and etc. We also estimated magnetically parameters (like SIRM, HIRM and etc.) to confirm concentrations of both aeolian and pedogenic particles versus variations of magnetic susceptibility enhancement. The χ values show prominent peaks for the three well developed soil and paleosol horizons, Recent Soil (S0), Upper Paleosol (S1) and Lower Paleosol (S2); which refer to warmer and wetter conditions. As result, we concluded that the increase/decreasing of magnetic susceptibility is coinciding with palaeosol/loess sequence, and probably with humid/arid conditions. Moreover, variations of magnetic susceptibility versus lithological column of Kolet section enabled us to recognize paleoclimatically periods known as interglacial/glacial cycles. We plotted variation of magnetic susceptibility (MS), Natural Remnant Magnetization (NRM), Frequency Dependent Susceptibility (χfd) and χfd% versus lithological plot of the loess profile to confirm loess/paleosol deposits of Kolet section bear magnetic particles. Then, we applied the obtained magnetic data as variation of magnetic susceptibility (MS) to indicate that there have been glacial/interglacial periods during over the past 50 ka. Hence, during this period of time, there are three major glacial occurrences in the study area. Also, we conclude there was no main glaciation occurrence since last 20.5 ka.