Long-term Pleistocene aridification and possible linkage to high-latitude forcing: New evidence from grain size and magnetic susceptibility proxies from loess-paleosol record in northeastern China

- Chronostratigraphic analysis and chronology development of the loess deposits in NE China
- The > 63 μm fraction in the NYZG section could be regarded as a proxy for drying of deserts in NE China.
- The grain-size record reveals a long-term drying trend in NE China since ca. 1.0 Ma.
- A long-term aridification history was possibly driven by high-latitude climate changes.
- The spatial differences in magnetic susceptibility could be related to the changes in climatic sensitivity.

Loess deposits are regarded as good indicators of the inception and development of arid and semi-arid climate in central Asia and northern China during the late Cenozoic. In northeastern China extensive loess deposits are found surrounding the Horqin and Otindag sand fields, and they have great potential for reconstructing the long-term aridification history of the region. However, these loess deposits are currently poorly understood. Here, we present a high-resolution magnetic susceptibility (MS) and grain-size record spanning the last 1.0 Ma from a 36.6-m-thick loess-paleosol sequence at Niuyangzigou site (NYZG) in NE China. The grain-size record reveals a long-term drying trend in NE China since ca. 1.0 Ma, punctuated by two significant abrupt drying events at ~ 0.65 Ma and ~ 0.3 Ma. These results demonstrate a process of stepwise intensification of drying in NE China over the past 1 Ma, and lend support to the hypothesis that global ice volume/temperature changes were the major driver of the long-term aridification of Asian dust source areas. However, unlike the widely studied loess deposits on the central Chinese Loess Plateau (CLP), the MS record in paleosol units S1, S2 and S4 from the NYZG site do not show evidence of enhanced monsoon precipitation resulting from decreased global ice volume and the prolonged episodes of interglaciation after the Mid-Pleistocene Transition evident in the ice volume record. We hypothesize that this may be due to differences in the climatic sensitivity of the MS of Chinese loess deposits on a regional scale, rather than to in regional differences in monsoon intensity.