Response of sedimentary and pollen records to the 1933 Diexi earthquake on the eastern Tibetan Plateau

Abstract

Vegetation plays an important role in ecosystem stability in tectonically active regions such as the eastern Tibetan Plateau (ETP). To determine the response of mountain ecosystem to climate change and tectonic activity on the ETP, detailed analyses of chronology, pollen, grain size and magnetic susceptibility (SUS) were conducted on a lacustrine sequence from the upper reaches of the Min River. The results show that the lacustrine sediments are mainly transported by wind as those seismogenic dust at Diexi and Lixian. The fine–grained sediments (<20 μm) are background dust that was transported over a long distance, while the coarse-grained sediments (>20 μm) were transported from local to regional dust sources. Intriguingly, the sand fraction (>63 μm) suddenly increased by 10.4%, in response to the Diexi Ms 7.5 earthquake in 1933. The earthquake probably induced many large landslides and provided more sources of coarse particles close to the study area. Also, around 1933, coniferous pollen increased rapidly while herbaceous and aquatic plants decreased significantly, probably due to a marked change in the local hydrological conditions caused by the strong earthquake. The percentage of shrub pollen dominated by Hippophae, remained at a relatively high level, showing these plants to have great significance for ecological stability in tectonically active regions.