OSL ages and pedogenic mode of Kobresia mattic epipedon on the northeastern Qinghai-Tibetan Plateau

Abstract

Kobresia mattic epipedon (ME) is widely distributed on the Qinghai-Tibetan Plateau (QTP) and alpine areas worldwide, which plays a pivotal role in maintaining regional ecological stability. However, the time of ME formation and development is still unclear, which limits the understanding of pedogenic mode of alpine soils on the QTP. In this study, the optically stimulated luminescence (OSL) dating method was used to determine 54 dating samples from 45 MEs on the northeastern QTP (NE-QTP), the deposition rate (DR) and mass deposition rate (MDR) of MEs were calculated based on the OSL sampling depth, OSL age and bulk density (BD). The provenance of ME parent materials was identified by the soil grain-size composition, elemental geochemistry characteristics and bleachability of luminescence signals analysis. The results show: (1) aeolian dust deposition played an important role of ME parent materials; (2) modern ME formed mainly in the Late Holocene (∼ 3 ka) and concentrated during ∼ 1.4–0.2 ka. It took average 0.9 ka for a majority thickness of ∼ 20 cm ME formation; (3) the average DR of MEs was 0.3 ± 0.04 mm·a−1, and MDR was 346.3 ± 45.9 g·m−2·a−1, which was close to the flux of modern atmospheric fallen dust; (4) the formation of most MEs followed an aeolian dust aggradation mode.