Loess accumulation in Harbin with implications for late Quaternary aridification in the Songnen Plain, Northeast China

The Harbin loess in Northeast China, located in the easternmost part of the Eurasian loess belt, has great potential to reconstruct the aridity history of the Songnen Plain and to reveal its dynamic process. However, the relationship between coupled tectonic-climate-drainage evolution and the aridification in the Songnen Plain is currently poorly understood. In this study, we present a high-resolution magnetic susceptibility, grain-size, trace element, Sr-Nd isotope, total organic carbon (TOC), and organic carbon isotope composition (delta C-13) record retrieved from the Harbin loess-paleosol sequences to reveal the aridification history in the Songnen Plain. These results reveal a long-term drying trend in the Songnen Plain since 0.46 Ma, indicating the birth of the Songnen Sandy Land at that time. Superimposed on the major aridification trend, two significant abrupt drying events were found at similar to 300 ka and similar to 380 ka. However, the climate in the Songnen Plain became wetter and warmer under the background of the long-term drought since 180 ka. The global ice/temperature changes, regional tectonics (i.e., uplift of the Songliao divide) and drainage change (i.e., river pattern shift in the Songnen Plain from endorheic to exorheic drainage, and termination of the Songnen paleolake) were collectively responsible for the aridification in the Songnen Plain. This study has further improved knowledge of the process of the aridification in Northeast China, which is of great significance to control land desertification and ecological imbalance.