Annual laminations in the sediments of Hongfeng Lake, China

Abstract

Hongfeng Lake is an eutrophic freshwater artificial reservior. It began to restore water in 1960. Three sediment cores were taken from beneth about 25 m of water in the center of Hongfeng Lake in May 1991. The stratigraphy of the three cores was easily matched by using prominent marking horizons and characteristic seqnences of laminations. In three layer samples studied, diatom and other algae taxa appear in repeating sequences. The presence of laminations may reflect either the regular changes of physical-chemical conditions within the lake or the variation in the intensity of erosion and transport of material from the catchment, part iculaly where instability in the lake-water system has occurred as a result of human activities. The laminations were mainly caused by seasonal variation of environmental conditions, particularly climate. Unlike most of the previous examples, they have been formed at most recent sediments, in a small freshwater lake in the eastern slope of the Qinghai-Xizang Plateau, China in a subtropical climate, which is mainly controlled by southeastern and southwestern monsoon. It is believed that it’s the first reported instance of laminated lake sediments from China.