Vegetation And Environment History Of Erlongwan Maar Lake Since The Late Stage Of Late Pleistocene

Northeast China has been identified as a key region for investigating the present and past climates because it is under the influence of the East Asian monsoon. So, more and more research carried on this place. In fact, before these studies, many previous works about paleoenvironment and paleoclimate since the late stage of the late Peistocene also had been done in this place. Most of them are focus on pollen analysis for peat and wetland. However, these studies are difficult to compare with other place on thousand and century scale because of lacking long continuous carriers and enough age datas.In our work, the sediment of Erlongwan maar lake (Jilin Province, northeast China) is the study object in investigating the change history of vegetation and climate. As a volcanic lake, maar has well closed catchment basin interrupting the inflow and outflow of water between maar lake and around outer water system, decreasing the entry of outer non-volcanic products. The sediments of maar lake, to the largest content, record paleoclimate changes. Furthermore, the maar lake has steady hydrology, special geological background, special geochemistry and geophysics conditions, which make it to be the most appropriate area of forming and preservative high-resolution sedimentary record.The sediment core of Erlongwan maar lake is 2391cm, and age is from 39.8cal.ka B.P. to present. All of age models in the paper are based on 17 AMS14C dates. Multi-proxy analysis of core sediments, which include pollen, organic carbonates content, water content, dry density, grain size, lithological character, has been applied to reconstruct the regional climate and vegetation variability since the late stage of late Peistocene. Furthermore, comparison study between Erlongwan maar lake and other regions has also been carried out in the paper.Vegetation history of Erlongwan maar lake has been reconstructed according to the pollen analysis since the late stage of late Peistocene. During 39.8～32.8 cal. ka B.P., there is coniferous forest. Later, between 32.8～16.1 cal. ka B.P., coniferous forest and birch forest develop in region. During 16.1～11.2 cal. ka B.P., there develop conifer broad-leaved forest. From 11.2 cal. ka B.P. to 5.3 cal. ka B.P., there is deciduous broad-leaved forest. After 5.3 cal. ka B.P.,conifer broad-leaved forest develop again in Erlongwan region.The paleoenvironment history of Erlongwan region since the late stage of late Peistocene can be generally divided into 8 periods and 13 phases. During 39.8～32.8cal.ka B.P., the climate is cold, humid. Later, between 32.8～24.4cal.ka B.P., climate is cold, slightly humid in prophase (32.8～27.2cal.ka B.P.) and cold, slightly dry at late phases (27.2～24.4cal.ka B.P.). During 24.4～21.4cal.ka B.P., environment change to cold, slightly humid. Later, in the stage of 21.4～16.1cal.ka B.P., there develop cold and dry climate. Between 16.1～11.2cal.ka B.P., temperature, humidity change greatly in Erlongwan region. In the prophase of this period (16.1～14.5cal.ka B.P.), temperature, humidity increase quickly. Later (14.5～13.1cal.ka B.P.), temperature decline, but climate in this phase is not as cold as in LGM. In last phase of the period (13.1～11.2cal.ka B.P.), climate change to cold and dry. During 11.2～5.3cal.ka B.P., there develop warm, humid environment, climate is temperate in prophase (11.2～9.8 cal.ka B.P.), and change to optimum environment after 9.8cal.ka B.P. in Erlongwan region. From 5.3 to 1.7cal.ka B.P., climate changed again, there is temperate in 5.3～4.1cal.ka B.P. and slight humidity in 4.1～2.5cal.ka B.P. and slightly dry in 2.5～1.7cal.ka B.P. After 1.7cal.ka B.P., temperature decline obviously, and from 0.83cal.ka B.P. to present, climate is cool and dry.Comparing the sediment record of Erlongwan maar lake with other high-resolution records, which come from ice core, spectrometer, near maar lake and peat, the history of vegetation and environment since the stage of late Peistocene is consistent except in the late stage of MIS3a. The multi-proxy of Erlongwan shows cold and humid climate in this period, which is different with warm and humid climate in Tibetan Plateau, and is also different with cool and humid in Loess Plateau.There also record some cold events with thousand or century scale in Erlongwan sediment core. Younger Dryas event in Erlongwan appears in 12.94～11.68cal.ka B.P, which has the same character and age comparing with ice core GISP2 and Hulu cave spectrometer, but it is earlier than Sihailongwan maar lake record about 200a. B?lling-Aller?d warm period appears at 14.87～12.94cal.ka B.P.in Erlongwan . In Holocene, organic carbonates content, water content and dry density record 6 cold events in Erlongwan sediment core, which appear in 0.3 cal. ka B.P., 1.8 cal. ka B.P., 4.5 cal. ka B.P., 7.9 cal. ka B.P., 9.4 cal. ka B.P., 10.0 cal. ka B.P., and have some difference in appearing age and times comparing with North Atlantic hematite-stained grains record. Among these cold events, 8.1～7.5cal.ka B.P.cold event is likely to respond 8.2 ka B.P. globe cold event in Erlongwan region, but it has not being document by pollen record in either Erlongwan maar lake nor Jinchuan peat. On the contrary, 4.0 ka B.P. cold event is a prevalent event in northeast China.