Grain-size Characteristics and Climate Variability in TMS5e Sequence of Tumen Section in Southern Tengger Desert,Northwestern China

The TMS5e sequence from the Tumen section, at the southern edge of Tengger Desert in the northwestern China, is synchronous with Marine Isotope Stage 5e （MIS5e）. It consists of 16 layers of aeolian dune sands, 11 layers of lacustrine loess-like facies, and 5 layers of lacustrine facies. The results of grain-size analysis shows that the pa- laeo-mobile dune sands, palaeo-fixed to semi-fixed dune sands and loess-like sandy loams are mainly composed of sands, ranging from 70% to 96%; their silt contents ranged from 4% to 20%, and their clay contents ranged from 1% to 5%; the climate under which the aeolian dune sands were deposited is similar to that under which modern mobile dune sands form, which is caused by the dominance of the cold, dry East Asian winter monsoon. In contrast, the lacustrine loess-like facies and lacustrine facies had a lower sand contents than those of the three aeolian dune sands, but have higher silt and clay contents, most of their sand content ranged from 30% to 60%, their silt contents ranged from 35% to 55%, and their clay contents ranged from 6% to 20%. The lacustrine loess-like facies and lacustrine facies formed under the influence of the warm, humid East Asian summer monsoon based on their similarity with modern sediments. The grain-size indicator Mz （mean grain diameter） and the SC/D value in the TMS5e sequence indicate climatic insta- bility at the southern edge of the Tengger Desert during MIS5e, with at least 14 fluctuations between a warm, humid climate and a cold, dry climate, divided into five stages： TMS5e5 （139 kyr to 129.3 kyr B.P.）, TMS5e4 （129.3 kyr to 124 kyr B.P.）, TMS5e3 （124 kyr to 119.5 kyr B.P.）, TMS5e2 （119.5 kyr to 116.5 kyr B.P.）, and TMS5el （116.5 kyr to 113.7 kyr B.P.）. These correspond roughly to MIS5e5, MIS5e4, MIS5e3, MIS5e2, and MIS5el, respectively, in the GRIP ice core data.

Quantitative reconstruction of the palaeoclimate of the Shahejie Formation in the Chezhen Depression,Bohai Bay Basin,eastern China

This paper uses pollen climate analysis and coexistence analysis to systematically analyze the climatic evolution of the Shahejie Formation in the Chezhen Depression,Bohai Bay Basin,eastern China and discusses the relationship between palaeoclimatic evolution and lake level rise.The results show that the sedimentary period of the Shahejie Formation in the Chezhen Depression had an overall temperature change trend from hot to cold and simultaneously experienced a dry and wet balance-wet-dry and wet balance-wet transition process.The climatic parameters of the Shahejie Formation in the Chezhen Depression include a mean annual temperature of 8.1℃-15.1℃,a mean coldest monthly temperature of-0.1℃-2℃,a mean warmest monthly temperature of 18.6℃-28℃,a mean annual precipitation of 389-1164 mm,a wettest monthly precipitation amount of 215-262 mm,and a driest monthly precipitation amount of 8-48 mm.Climate change is believed to affect the rise and fall of lake levels to some extent.The quantitative reconstruction of these climatic parameters allows researchers to more intuitively understand the geological background of the Chezhen Depression and guide the exploration and development of oil and gas resources.