西藏札达盆地上新统古格组和托林组的厘定与层序地层划分  

Definition of the Pliocene Guge and Toling formations and sequence stratigraphic division in the Zanda basin, Tibet, China

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] 雷伟志[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,西藏拉萨850000

出　　处：《地质通报》2007年第8期984-995,共12页Geological Bulletin of China

基　　金：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);国家自然科学基金项目(编号:40572134)共同资助。

摘　　要：根据札达盆地剖面中地层的接触关系、沉积旋回、沉积体系和岩相岩性特征,可将上新统河湖相地层划分为2个组、5个沉积相、8个岩段。古格组(N22g)一岩段为砾岩,属河流相沉积;二、三、五岩段以细碎屑岩为主,属浅湖相沉积;四岩段以含粘土质细碎屑岩为主,属深湖相沉积。托林组(N21t)一、二、三岩段为一套砾岩、含砾中粗粒钙质长石岩屑砂岩和中细粒砂岩的碎屑岩,为典型冲(洪)积扇沉积物。ESR法和古地磁法测年结果表明,古格组形成时代为上新世晚期(4.40～2.47Ma);托林组形成时代为上新世早期(5.44～4.40Ma)。札达盆地为一同生断陷盆地,在上新世时期的构造运动过程中,盆地演化经历了水进体系域—湖泊扩张体系域—湖泊收缩体系域3个发展阶段。Based on the contact relationships, sedimentary cycles, sedimentary systems and lithofacies and lithologic characteristics of the stratigraphic section, the Pliocene fluvio-lacustrine sediments in Zanda basin are divided into 2 formations, 5 sedimentary facies and 8 lithologic members. The first lithologic member of the Guge Formation consists of conglomerate, belonging to fluvial deposits; the second, third and fifth members are dominated by fine clastic rocks, belonging to shallow lacustrine deposits; and the fourth member consists predominantly of clayey fine clastic rocks, belonging to deep lacustrine sediments. The first, second and third members of the Toling Formation consist of a sequence of clastic rocks including conglomerate, pebbly and coarse- and medium-grained, calcareous feldspathic litharenite and medium and fine sandstone, belonging to typical alluvial （diluvial） fan deposits. ESR. and paleomagnetic dating indicate that the age of the fluvio-lacustrine sediments of the Guge Formation is late Pliocene （4.40-2.47 Ma） and the age of the Toling Formation is early Pliocene （5.44-4.40 Ma） in the Zanda basin. The Zanda basin is a syngenetic downfaulted basin. Its evolution progressed through three stages： the transgressive systems tract, lake expansion systems tract and lake shrinkage systems tract during the Pliocene tectonic movement.

关 键 词：上新世 河湖相沉积 层序地层 古格组和托林组 札达盆地 西藏 

分 类 号：P534.622[天文地球—古生物学与地层学]