Mid-late Holocene Climate Change In Kulun Lake Under The Background Of Neotectonic Movement

Kulun Lake is located on the Bashang Plateau,Guyuan-Zhangbei deep fault runs through the Kulun Lake area and plays a major controlling role.Since the Quaternary Period,Geological activities in this area are very active because of the Guyuan-Zhangbei deep fault,mainly uplift-denudation.But In the Kulun Lake and other basin areas,thicker sediments were deposited.A series of geological tectonic activities after the neotectonic movement created preconditions for the subsequent lake deposits.As an important information carrier of continental climate and environmental change,lake sediments have irreplaceable advantages in studying global change and regional response.The Kulun Lake is located at the Monsoon fringe,which is very sensitive to climate change.Based on the climatic proxies of grain size,loss on ignition and geochemical elements recorded in the lake sediment in Kulun Lake,and combined with high-precision AMS ¹⁴C dating,the climatic evolutions in the area during the past 4243years was reconstructed.The main conclusions are as follows:(1)The sedimentary core of Kulun Lake has a carbon reservoir age of about 1857 yr;The bottom age of the core is about 4243 yr BP,and the average sedimentary rate is 0.0613cm/year.(2)The results show that there are six stages in the process of climate evolution in Kulun lake since 4243 years.During the period of 4243 yr BP—3700 yr BP,the climate in Kulun lake area was relatively cold and dry;During the period of 3700 yr BP—3250 yr BP,the climate of Kulun lake changed to warm and humid.During the period of 3250 yr BP—2750 yr BP,the climate in Kulun lake was relatively cold and dry;During the period of2750 yr BP-2000 yr BP,the climate of Kulun Lake was mainly cold-dry,but it changed to warm-wet;Since 2000 yr BP,the climate in Kulun Lake is relatively warm and humid,but since 1000 yr BP,there have been several cold events.(3)In this region,there have been significant Fast-moving climate events in the four periods of 3750—3600 yr BP(E1)?2900—2750 yr BP(E2)?1050—750 yr BP(E3)?350—200 yr BP(E4).The 2900-2750 yr BP rapid change event corresponds to the 2.8kyr cold events,respectively;The 1050 yr BP-750 yr BP and 350 yr BP-200 yr BP events correspond to the Medieval Warm Period(MWP)and the Little Ice Age(LIA),respectively.(4)Through comparison with other research results,the climate changes in Kulun Lake area since the Middle and Late Holocene are consistent with those in other parts of Inner Mongolia.Climate change in the Kulun Lake region over the past 4,243 years may be mainly related to periodic fluctuations in solar radiation intensity and the north Atlantic ice raft event.