Palaeomagnetic Chronology and Paleoenvironmental Records of the Wuqi Paleolake of Late Neogene in the Northern Chinese Loess Plateau

Abstract

AbstractThe sequence of aeolian red clay and loess deposited in northern China since late Neogene is an ideal palaeoclimate recorder. A profile consisting of loess, lacustrine deposits and red clay was found at Wuqi County in the northern Chinese Loess Plateau. Preliminary investigations were carried out on the typical Tufosi section in order to provide the age constraints of the lacustrine deposits (namely the Wuqi paleolake). Rock magnetic results demonstrate that the magnetic carriers of the characteristic remanent magnetization of lacustrine deposits are mainly magnetite and hematite. The correlation between the magnetic polarity sequence of the Tufosi section and geomagnetic polarity time scale is very well. The age of the bottom of the section is 4.28 Ma B. P. approximately. The Wuqi paleolake formed at about 3.0 Ma B. P. and died out around 1.2 Ma B. P. The regional environment became colder and drier during this period as implied by the variations of lithology, magnetic susceptibility, grain size and sedimentation rates. The evolution history of the Wuqi paleolake can be divided into three stages: the paleolake was formed during the period of 3.0~2.5 Ma B. P. and the water body was relatively deep; the lake became shallow markedly as the result of paleoclimate change during 2.50~2.05 Ma B. P.; during 2.05~1.20 Ma B. P., reduction of the water body led to the extinction of the lake. Climatic deterioration in this region around 1.2 Ma B. P. was the main reason for the end of the Wuqi paleolake. Besides, the headward erosion of the North Luo River caused by regional tectonism was probably a factor, too.