Spatio-temporal distribution of dust sedimentation rate of Tianshan loess since MIS3 and its implications

Eolian loess is an important archive for understanding Quaternary environmental changes. The sedimentation rate of loess, as an important proxy to environmental changes, is helpful to revealing atmospheric circulation and paleoenvironmental changes. With the application of various dating methods especially the high-accuracy Optically Stimulated Luminescence (OSL), sedimentation rate has been widely applied to the orbital-scale and millennial-scale paleoclimatic changes recently in the study of Chinese Loess Plateau (CLP). Central Asia is also one of the main distribution areas of world loess. This paper is specially devoted to the spatio-temporal distribution pattern of dust sedimentation rate of the Tianshan loess in order to provide a new horizon for understanding paleoclimatic patterns in Central Asia, where sedimentation rate has been poorly studied. Therefore, we collected the available geochronological data including OSL and ¹⁴C of the last glacial loess sections from the Tianshan Mountains of Central Asia in this paper, analyzed the reliability of age data and discussed spatial and temporal distribution pattern of the sedimentation rate. The results suggest that: (1) During the Last Glacial Maximum (LGM), sedimentation rate is relatively low in the west of Tianshan, but high in the Ili Basin. This spatial pattern of distribution is closely related to geographic and atmospheric conditions as well as proximal accumulation. (2) LGM and MIS3b are the main dust deposition stages since MIS3. In the Tianshan area, the sedimentation rate of MIS3b is higher than that of LGM. Since the solar insolation in the MIS3b stage is higher than that in the LGM stage, the westerly will bring more moisture from the Atlantic Ocean, Caspian Sea and Mediterranean Sea. In the Tianshan area, moisture is believed the main factor affecting glaciers. In this regard, the scale of glacier in the wetter MIS3b period is larger than that in the LGM period, and the intensified abrasion of the glaciers will bring in more fine particulate matters. (3) Sedimentation rate is low in Holocene, and the variations in sedimentation rate are similar to the 'westerly model'. We speculate that the amount of dust in the atmosphere is relatively low in Holocene. Dust is mainly deposited under wet climate since humidity is conducive to vegetation and helpful for dust to settle down. More moisture will result in higher sedimentation rate.