Chronostratigraphic framework and paleoenvironmental interpretation of the Holocene loess-paleosol sequence in the Luoyang Basin, Central China

Abstract

Abstract The loess-paleosol sequences in the Loess Plateau are major paleoclimatic archives which document the evolution of East Asian Monsoon (EAM) during the Quaternary glacial-interglacial cycles. A complete Holocene loess-paleosol sequence was identified by detailed field investigations in the Luoyang Basin, which is located at the southeastern margin of the Loess Plateau, Central China. Laboratory analysis including magnetic susceptibility, hygroscopic water, grain-size distribution, geochemical elements characteristics, AMS 14C dating, Bacon age-depth modelling and stratigraphic correlations have been carried out. Our results show that the stratigraphic sequence, from top to bottom, is topsoil (TS), recent loess (L0), mid-Holocene paleosol (S0), early Holocene transitional loess (Lt) and Malan loess (L1). The intensity of weathering and pedogenesis varies significantly in different layers and presents such a tendency of S0 > L0 > Lt > L1. This indicates four distinct stages in the EAM evolution: 1) an extreme dry-cold climate with strengthened East Asian winter monsoon (EAWM) during the last glacial period, 2) an episode of gradual transition to the warm-humid climate with intensive East Asian summer monsoon (EASM) in the early Holocene (11,500–8500 yr BP), 3) a warm-humid climate affected by intense EASM in the mid-Holocene (8500–3100 yr BP), and lastly 4) an episode of gradually shifting to dry-cool climate with weakened EASM (3100–0 yr BP). These results provide basic data for exploring the Holocene weathering and pedogenesis and paleoenvironmental evolution in Central China.