Study On Newly Discovered Lacustrine Sedimentation Profile In Late Pleistocene Of Hexigten Town, Inner Mongolia Autonomous Regions, China

Hexigten is located in the east of Inner Mongolia Autonomous Regions, the junction of the Daxinganling Mountains and Yanshan Mountains which is a typical research area of the Quaternary environment change since the uplift of Daxinganling mountains and Yanshan mountains.This thesis originated from Hexigten Global Geopark planning and construction of the special fund projects. Based on outdoors practical measurement of Fushenghao lacustrine phase deposits profile, it carries out deposits grain size analysis and Magnetic susceptibility measurement. At the same time, with the help of implementing ¹⁴C,OSL,TL etc three different kinds of age judging to establish profile of age framework, then made further research on ancient climate and temporal sedimentary environment of research area since late Pleistocene .The main results are as follows:1. Through the outdoor detailed study of sedimentology and indoor particle size analysis, it deduces the deposits with thickness of 72.01 meters is lacustrine phase deposits. The discovery of Fushenghao lacustrine deposits profile provided a good material for the Quaternary sedimentary environments and paleoclimate research in the study area .2. It carries out grain size analysis for adopted 419 pieces samples, by analyzing each grain size distribution curve and grain size parameter and made climate feature research on profile. This profile experienced Warmer and wetter-Cold dry-Warmer and wetter three climate change stages from down to up.3. Explore the climate evolution discipline of the profile through research on the lacustrine sediments susceptibility. Volume magnetic susceptibility of all the test samples, then convert the test results into low-frequency magnetic susceptibility, and calculate the corresponding average annual temperature and average annual rainfall,and draw the curve with depth. The results showed that the profile of climate evolution can be divided into three stages and is consistent with the conclusion of particle size analysis 4. There are twenty-three samples from the profile to determine the age of strata (¹⁴C isotope age, OSL, TL). The results show that the profile was formed during the Late Pleistocene to early Holocene （33.68±2.86ka B.P. -8.37ka B.P）5.The evolution of the ancient climate from the Late Pleistocene (Qp^3-3) to the early Holocene （Qh¹） is divided into three stages by sedimentary features, grain size parameters and magnetic susceptibility, which is a warm and humid climate stage （33.68-26.24ka）, cold and dry climate phase （14.14-26.24ka） and warm and humid climate phases （14.14-8.37ka）.6. The results of study in Fushenghao profile is consistent with edimentary characteristics and division of climate phase of Daihai Lake. That is to say the division of paleoclimate evolution is of region comparability.