New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north-east China and their implications for regional environmental change during the Mid-Pleistocene climatic transition

摘要

Little is known about the long-term climatic evolution of north-eastern (NE) China, because well-preserved terrestrial paleoenvironmental archives are scarce in this vast region. The extensive loess deposits in the Chifeng region are the thickest and most complete loess-paleosol sequence in NE China, and have significant potential for reconstructing the paleoclimate of the region. Here, we present new high-resolution magnetostratigraphic results from two loess-paleosol sections in the Chifeng region: the Sanbahuo (SBH) and Toudaojingzi (TDJZ) sections. The results demonstrate that both sections record the Brunhes normal polarity chron and the upper portion of the Matuyama reversed polarity chron. Based on these new results, the base of the TDJZ loess sequence is dated at ca. 1.22 Ma, representing the oldest known loess deposits in NE China. The initiation of loess accumulation in NE China was roughly synchronous with the large expansion of the Eurasian loess belt during the late Early Pleistocene (1.2-0.7 Ma), probably reflecting a widespread intensification of aridity in northern mid-latitudes. We suggest that global cooling during the Mid-Pleistocene climatic transition led to increased aridity and more favorable conditions for promoting the availability of silt for entrainment, transport and deposition. Copyright (C) 2016 John Wiley & Sons, Ltd.