Palaeoclimatic changes over the past 1 million years derived from lacustrine sediments of Heqing basin (Yunnan, China)

摘要

A 168-m long core of mostly fine-grained lacustrine sediments was recovered from Heqing Basin, Yunnan Province, southwestern China. The area is located at the south-eastern margin of the Tibetan Plateau and is mainly affected by the SW monsoon. Magnetostratigraphy of this core indicates that it spans the last one million years. Spectral analysis of carbonate and magnetic susceptibility (χ) and a rough correlation of χ with the marine oxygen isotope record suggest that the climatic record of this area is consistent with the global climatic pattern. Pollen data from HQ indicate alternations between temperate-arid and cold-humid climatic conditions, as a typical regional palaeoclimatic pattern. The highs and lows of χ can be related to warm and cold periods, respectively. Maghemite and magnetite dominate the magnetic mineralogy. Maghemite is distributed throughout the whole core, whereas magnetite occurs additionally in samples with higher χ deposited during arid periods. The magnetic and non-magnetic variations clearly show a change at 65 m (corresponding to ca. 410 ka) indicating a change in the depositional system related to a climatic and/or tectonic event.