Pedogenesis- a likely process to explain the magnetic properties of the Late Pleistocene loess-paleosol sequence at Chenarli, northeastern Iran

Loess deposits of northern and northeastern Iran provide excellent sedimentary archives for understandingpast climate and environment changes in the continental interior. The loess records paleoenvironmentalchange in Iran over multiple glacial cycles, and helps to assess the extent to which key features of loessstratigraphy can be traced along the loess belt that crosses Eurasia, from Eastern Europe through CentralAsia to China (e.g. Frechen et al., ۲۰۰۹). Our approach aims at obtaining more detailed information aboutthe interaction between climate factors, pedogenesis process and magnetic signals of the studied section.In this study, we report rock magnetic properties of the loess and paleosols samples from the latePleistocene loess-paleosol sequences at Chenarli in northeastern Iran. Results and Discussions: The resultsprovide a model for understanding (post) pedogenic processes in relationship with (paleo) climate in thisregion. Temperature-dependent susceptibility (χ-T) curves of loess, modern soil and paleosols demonstratethe existence of detrital magnetite, as inferred from a susceptibility drop near ۵۸۵ °C. In contrast, asusceptibility loss at ~۳۰۰-۴۵۰ ◦C in the modern soil and paleosols of our study are probably caused by theconversion of ferrimagnetic maghemite to weakly- magnetic hematite. The only exception to this pattern isobserved at a Btb horizon of a paleosol at the depth of ۲۶m below surface. Furthermore, high anhystereticremanent magnetization (ARM)/isothermal remanent magnetisation (IRM) ratios of this paleosol coupledwith magnetic depletion in this paleosol, suggest a wet climate dominating during the marine isotope stage۵e in the area. Our results therefore are consistent with the previous studies (Sharifigarmdareh et al., ۲۰۲۰;Ghafarpour et al., ۲۰۲۱) which suggested that the formation of pedogenic maghemite-magnetite causemagnetic enhancement in modern soils and paleosols of northern Iranian loess-paleosol sequences.

کلیدواژه ها:

northern Iranian loess ، rock magnetism ، paleosols ، pedogenic maghemite-magnetite