中亚哈萨克斯坦南部VA黄土剖面过去～25000a来沉积地层特征  

Sedimentary strata record in VA loess section from the southern Kazakhstan during past 25 000 a

作　　者：冉敏[1,2] 杨奇丽[1] 黄昌庆[1] 

机构地区：[1]兰州大学西部气候与环境变化研究院,甘肃兰州730000 [2]新疆大学资源与环境科学学院,新疆乌鲁木齐830000

出　　处：《干旱区地理》2013年第6期979-986,共8页Arid Land Geography

基　　金：国家自然科学基金(40671190)资助

摘　　要：选取位于中亚哈萨克斯坦中南部的VA剖面作为研究对象，剖面厚7m，野外采样以及实验分析间距均为5cm。在AMS^14C测年基础上，综合野外地层考察和实验室指标（包括磁化率、碳酸盐、有机质和粒度）分析，结果表明：I：该剖面过去～25000^14CaBP以来地层主要可以分为五个地层单元：（1）～26000^14CaBP-～22000^14HCaBP，河流作用过的黄土层；（2）～22000^14CaB-～19000^14CaBP，潜育化的黄土层；（3）～19000^14HCaBP-～10000^14CaBP，弱土壤层；（4）～10000^14CaB-～5000^14HCaBP，典型的黄土层；（5）过去～5000^14CaBP以来，土壤层。II：将VA剖面与欧洲区以及东亚区黄土沉积对比发现：研究区过去～25000^14CaBP以来地层沉积与欧洲黄土沉积类似，全新世地层序列与东亚区具有反相位关系：中亚区早全新世为黄土沉积，晚全新世发育土壤层，说明研究区过去25000^14Ca以来主要受西风带和地中海气候控制，具有西风区气候特征。III：VA剖面MIS2记录到的潜育化黄土层以及弱土壤层显示研究区在MIS2时段气候相比东亚区更为湿润。The loess-covered area of Central Asia is surrounded by other three loess areas, including European loess area, Siberia loess area and Chinese Loess Plateau. Therefore, the loess deposits in Central Asia is of great sig nificance in clearifying the similarities and differences of loess deposits between Central Asia and other loess areas and in understanding the regional climate importance in terms of loess deposition and paleosol development. Clima tologically, Central Asian arid zone is affected by the Asian monsoon and the westerlies, understanding the regional paleoclimate change allows us to clarify the interacting history of the Asian monsoon and the westerlies. This paper focused on a loess section （VA section） in central Asian, combined with field investigation and laboratory analysis （grain size, magnetic susceptibility, total organic matter and carbonate content）, based on AMS ^14C dates, construct ed the strata sequence in VA section during past -25 000 a. The results indicate that the strata sequence in study ar ea during past -25 000 a BP can be divided into five units ： ① -26000 ^14C a BP--22 000 ^14C a BP, a fluvially-al tered loess deposition layer; ② -22 000 ^14C a BP--19 000 ^14C a BP, a weakly-gleyed loess deposition layer; ③ 19 000 ^14C a BP--10 000 ^14C a BP, an accretionary entisol layer; ④ -10 000 ^14C a BP--5000 ^14C a BP, a major loess deposition layer; ⑤ past -5 000 ^14C a, a typical mollisol layer. Furthermore, the regional comparison of loess strata in Central Asia and Europe indicates that the VA section loess is similar to the Europe loess during the past - 25 000 ^14C a BP and there is a converse phase relationship between VA loess strata and East Asian loess strata dur ing the past -25 000 ^14C a BP. Based on the VA loess section, the predominant gaciation between -25 000 and - 10 000 ^14C a BP suggested that the last glacial climate in the Central Asia domain was constantly wetter than that in the East Asia domain.

关 键 词：中亚干旱区 地层 黄土 MIS2 全新世 

分 类 号：P642.131[天文地球—工程地质学] P512.2[天文地球—地质矿产勘探]