Application of grain size endmember analysis in the study of dust accumulation processes: A case study of loess in Shandong Province, East China

Abstract

Abstract The accumulation processes of loess in Shandong Province record atmospheric circulation changes in eastern China, which can be used to explore the varying characteristics of the East Asian monsoons and the evolution of the local environment. In this study, parameterized grain size endmember analysis is used to reveal the characteristics of sedimentary dynamics, material sources, and environmental evolution of a loess profile in Focun, Zibo City, Shandong Province, China. Optically stimulated luminescence (OSL) ages of the profile ranged from 3.02\u202f±\u202f0.45\u202fka to 100.99\u202f±\u202f13.58\u202fka. The grain size components of the sediments in the profile were divided into five endmembers. EM1 represents a mixed clay component of pedogenesis, EM2 represents a fine silt component transported by high-altitude westerlies, EM3 represents material that settled in the form of floating dust, EM4 represents a silt component transported by low-altitude near-source areas, and EM5 represents short-distance suspended materials transported under dust storms. Combined with a low frequency magnetic susceptibility (χlf) and chromaticity (a⁎), the characteristics of grain size endmembers indicate changes in sedimentary environments since the last interglacial (MIS 5). In MIS 5 the winter monsoon accumulation was low, with high accumulation during the summer monsoon, and an unstable climate. In MIS 4 the winter monsoon produced high accumulation, with low accumulation during the summer monsoon, and frequent dust storms. In MIS 3 the winter monsoon accumulation was low, westerly circulation and summer monsoon accumulation were high, and the climate was warm and humid. In MIS 2 the winter monsoon accumulation was high, summer monsoon accumulation was low, and the climate was dry and cold. In MIS 1 the westerly circulation and winter monsoon accumulation were low, summer monsoon accumulation was high, and the climate was warm and wet. This reflects the regional response to global climate change. This study shows that the parametric grain size endmember analysis method is feasible in studying the sedimentary dynamics, material sources and sedimentary environment of loess in Shandong Province.