Paleoenvironmental implications of magnetic measurements on sediment core from Kunming Basin, Southwest China

Abstract

Mineral magnetic measurements have been made on a long sediment core from Dianchi Lake, Southwest China. They have been used for sediment stratigraphy, for bulk lithological classification and for detailed particle-size-based characterisation. These results are set alongside those derived from geochemical, granulometric and pollen analysis to reconstruct the environmental processes recorded in the radiocarbon dated sediment column. It is suggested that the variations of magnetic properties in this sediment core are mainly the result of changes in particle size constitution or organic content, implying shifts in the sedimentary environment. Three distinctive stratigraphic horizons, with several subdivisions, have been identified on the basis of the magnetic measurements. They are coincident with the pollen assemblage zones, indicating the different climatic periods in the Kunming Basin since late Pleistocene times. This paper proposes that a major shift in sedimentation, from lake to reedswamp, occurred in approximately 10 000–12 000 BP, in response to climatic change.