Study on Holocene environmental evolution based on grain size end-member model: A case study of two outcrop sections in Salawusu River Basin.

Samples from two outcrop sections, MGS1 and DGS1 of Milanggouwan and Dishaogouwan in the Salawusu River Basin, were studied in terms of grain size using end-member model. Results show that: 1) MGS1 layer particles are more concentrated, better sorting, and smaller skewness and kurtosis values than those of DGS1. Whereas in the upper part of the DGS1 section, the grain size of the paleodune is coarser, with better sorting and sharper peak, comparing with the lower lacustrine sediments. 2) Three end-member components, EM1 (end-member 1), EM2 (end-member 2) and EM3 (end-member 3), which reflect sedimentary dynamic characteristics, are extracted by end-member analysis. The EM1 indicates the hydrodynamic force with great variation, EM2 indicates transporting force by flowing water and EM3 indicates the depositional environment closely related to the wind activity. 3) According to the accumulation processes of MGS1 and DGS1 strata, a total of four climate periods can be identified, namely early warming period, Holocene peak period, fluctuating transition to cold period and unstable cooling period. Moreover, EM1 of MGS1 and DGS1 is basically consistent with both the sea surface temperature (SST) in the western tropical Pacific and global temperature trends during the Holocene, suggesting that the environmental fluctuations recorded by MGS1 and DGS1 can be correlated with each other.