呼伦贝尔高平原全新世早晚期砂、土楔及其古气候环境意义  

HOLOCENE SAND AND SOIL WEDGES ON THE SOUTH-CENTRAL HULUN BUIR HIGH PLAIN IN NORTHEAST CHINA

作　　者：金会军[1] 常晓丽[1] 郭东信[1] 杨思忠[1] 何瑞霞[1] 

机构地区：[1]中国科学院寒区旱区环境与工程研究所冻土工程国家重点实验室,兰州730000

出　　处：《第四纪研究》2011年第5期765-779,共15页Quaternary Sciences

基　　金：国家重点基础研究发展规划项目(973项目)"北半球冰冻圈变化及其对气候环境的影响与适应对策"(批准号:2010CB951402和2010CB951404);中国科学院战略性先导科技专项项目(碳专项)的子课题"大暖期与盛冰期的中国冻土"(批准号:XDA05120302)资助

摘　　要：砂、土楔等楔状构造是多年冻土曾经存在的可靠证据,其与多年冻土及年均地、气温度的关系也是重建古冰缘环境的依据。在呼伦贝尔高平原中南部的乌尔逊河、辉河、新巴尔虎东旗和鄂温克旗发现大量砂、土楔及伴生的冻融褶皱。通过对其形态、规模及围岩(土)结构分析,并根据楔内充填物及围土的^(14)C定年结果判断,砂楔形成于早全新世(约10.0～7.5kaB.P.),当时研究区年平均气温为-6.5～-7.0℃;土楔形成于晚全新世(约2.3～2.0kaB.P.),其时年平均气温为-5.0～-5.5℃。这表明,早全新世更为干寒,风沙堆积活跃,多年冻土分布广泛;进入晚全新世后,气候转暖,呼伦贝尔气温与现今大兴安岭北部(即满归以北)的年半均气温(-5.0～-5.4℃)大体相当。据此推测,当时呼伦贝尔高平原的冻土发育程度与满归以北地区现今大片多年冻土状况相似。早全新世砂楔(脉)形成时期气温比现今大兴安岭北部低1.5～2.0℃。依此可见,早全新世该区多年冻土地温低于现今大兴安岭北部的地温(-1.5～-2.0℃),冻土厚度超过80～100m。The Hulun Buir High Plain（ HBHP） （47040＇ -49~40＇N, 114~30＇ - 121~20＇E;550 -750m a. s. 1. ）is in the piedmont and denuded areas in a transition zone from semi-arid to semi-humid elimate zones in the northwest region of Northeast China, where regional environments are sensitive to elimate changes. Sinee the Last Glaeiation Maximum, a series of environmental changes, such as lake level fluctuations and peat development, alternate deposition of aeolian sands and paleosols, as well as the concurrent shifts in the southern and lower limits of permafrost. In order to better understand the changes of the southern limit of permafrost, field investigations were organized for the past permafrost and periglaeial remains in the Xing＇anling Mountains in Northeast China in 2007 and 2008. From June to August in 2007, large numbers of sand and soil wedges and involutions were identified on the first terraces of the Wu＇erxun and Hui＇he rivers in the Xinba＇ er＇ hu West Banner,and in Xinba＇ er＇ hu East Banner and Ewenke Banner on the South-Central HBHP. The shapes, scales, sedimentary structures of these wedge structures and involutions and their host strata, and nearby topography and surface conditions were carefully observed and recorded. In the profiles, generally 2m to 4m in the exposed height, soils were sampled at intervals of 0.2 -0.4m in vertical strata and analyzed for data on grain size distribution,pollens,and 14C dating. Their ages were estimated on the basis of their relative positions in strata and their 14C dating. Analysis and cross-examinations indicate that these sand wedges were formed during the Early Holocene （ca. 10.0 -7.5kaB. P. ）when the mean annual air temperatures were about -6.5 - -7.0℃ in the study region, whereas these soil wedges were formed during the Late Holocene （ ca. 2.3 - 2.0kaB. P. ） when mean annual air temperatures were about -5.0 -5.5℃. It was colder and drier during the Early Holocene, when aeolian action and deposition prevailed and permafrost o

关 键 词：呼伦贝尔高平原 砂、土楔 早 晚全新世 古气候和冰缘环境 冻土地温和厚度 

分 类 号：P532[天文地球—古生物学与地层学]