Magnetism of the Huguangyan Maar Lake sediments, Southeast China and its paleoenvironmental implications

Abstract

The Huguangyan (HGY) lake, a typical maar lake in the southeast of China, is sensitive to the evolution of the Asian monsoon system, including the East Asian summer monsoon (EASM) and the Indian summer monsoon (ISM). So far, the mechanism of how magnetic properties of the HGY lake sediments respond to climate changes has not been well determined. In this study, we performed a detailed mineral-magnetic analysis on the high-resolution HGY sediments. Results revealed that finer-grained magnetite (superparamagnetic and single domain magnetite mixed with a small amount of goethite and hematite) is the dominant magnetic mineral, which is consistent with the magnetic properties of the red weathered soils collected from the catchments, but differs greatly from that of the aeolian inputs. Therefore, magnetic minerals of the HGY sediments were originated mainly from the lake catchment, rather than the wind-blown dust inputs. Considering the high tephra wall (relative elevation of 10–20m) and great precipitation, surface runoff by rainfall is interpreted as the main process to transport red soils into the lake. The magnetic records of HGY sediments revealed that the summer monsoon was enhanced at the early Holocene and then declined abruptly at the mid-late Holocene (~5.5kyr cal. BP). This pattern strongly mimics the evolution pattern of ISM, but is inconsistent with the EASM. Thus, we suggest that the magnetic records from HGY have the great potential to investigate the evolution of ISM.