西藏阿里札达盆地下更新统香孜组地层厘定与层序地层划分  

REDEFINITION OF THE EARLY PLEISTOCENE QANGZE FORMATION AND SEQUENCE STRATIGRAPHIC DIVISION IN THE ZANDA BASIN,NGARI,TIBET

作　　者：朱大岗[1] 孟宪刚[1] 邵兆刚[1] 杨朝斌[2] 韩建恩[1] 余佳[1] 孟庆伟[1] 吕荣平[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]西藏自治区国土资源厅,拉萨850000

出　　处：《地质力学学报》2006年第4期406-415,共10页Journal of Geomechanics

基　　金：国家自然科学基金项目(批准号:40572134);中国地质调查局项目<青藏高原第三纪重点古湖泊环境演变序列>(任务书编号:科[2005]005-02;工作项目编码:1212010511902)资助

摘　　要：根据札达盆地香孜组河湖相地层剖面的接触关系、沉积旋回、沉积体系和岩相岩性特征，可将札达盆地下更新统香孜组河湖相地层划分为2个沉积相、3个岩段。香孜组一、二岩段为一套砾岩夹砂岩的粗碎屑岩，属典型的冲（洪）积扇沉积物；第三岩段为砾岩与砂岩互层，属冰水冰缘相沉积。ESR法和古地磁法测年结果表明，札达盆地香孜组河湖相地层的形成时代为早更新世早期（2．68—1．36Ma）。札达盆地为一同生断陷盆地，在后期重新复活的过程中，盆地只经历了冲积体系域和水进体系域。冲积体系域形成于札达盆地早更新世早期重新复活层序发育的早、中期，水进体系域形成于札达盆地早更新世早期重新复活层序发育的晚期。Based on the contact relationships, sedimentary cycles, sedimentary systems and lithofacies and lithologic characteristics of the stratigraphic section, the fluvio-lacustrine sediments of the early Pleistocene Qangze Formation in the Zanda basin are divided into 2 sedimentary facies and 3 lithologic members. The first and second members of the Qangze Formation consist of a sequence of coarse clastic rocks of conglomerate with sandstone, belonging to typical alluvial （diluvial） fan deposits. The third member consists of alternating beds of sandstone and conglomerate, belonging to glaciofluvial and paraglacial deposits. ESR and paleomagnetic dating indicates that the age of the fluvio-lacustrine sediments of the Qangze Formation in the Zanda basin is earliest Pleistocene （2.68-1.36 Ma）. The Zanda basin was a syngenetic downfauhed basin, which only experienced the alluvial systems tract and transgressive systems tract in the process of its reactivation in the late stage. The alluvial systems tract was formed in the early and middle stages of development of the reactivated stratigraphic sequence in the early part of the early Pleistocene, while the transgressive systems tract was formed in the late stage of development of the reactivated stratigraphic sequence in the early part of the early Pleistocene.

关 键 词：早更新世 河湖相沉积 层序地层 札达盆地 西藏 香孜组 

分 类 号：P534.631[天文地球—第四纪地质学] P539.2[天文地球—古生物学与地层学]