西藏羌塘盆地东南缘晚白垩世—古近纪砾岩层砾组特征及其地质意义  

Gravel fabric characteristics of the Late Cretaceous-Paleogene conglomerate layers in southeast Qiangtang Basin,Tibet,and their geological significance

作　　者：陆露[1] 钱程[2] 赵珍[1] 吴珍汉[1] 叶培盛[3] 

机构地区：[1]中国地质科学院,北京100037 [2]沈阳地质矿产研究所,辽宁沈阳110034 [3]中国地质科学院地质力学研究所,北京100081

出　　处：《中国地质》2014年第3期879-892,共14页Geology in China

基　　金：中国地质调查局国土资源大调查项目(1212011221111;1212011120185;1212011120182)资助

摘　　要：通过对环绕聂荣微陆块分布的晚白垩世—古近纪砾岩层的沉积特征和砾组特征分析,结合区域地质情况,阐述了砾岩层的性质、成因、来源、搬运方式及其所反映的构造背景等。研究表明,本套砾岩层为近—中距离搬运的冲洪积作用的产物,砾岩层砾石成分复杂,含量各异,分选性好,其古水流呈现单一水流特征,水动力条件相对较稳定,砾性和砾向分析指示砾石主要来源于聂荣微陆块、班公怒江缝合带以及其周边高山地区,反映冲积为主、洪积为辅的山前或山麓水系分布的沉积特征。结合区域资料综合分析,晚白垩世时期,聂荣微陆块北部地区发生隆升,形成东北高西南低的古地理格局;进入古近纪时期,在继承先前的古地理构造格局基础上,测区整体隆升。由此推断,晚白垩世时期青藏高原的隆升遍布班公—怒江缝合带以北地区,古近纪时期青藏高原整体发生隆升。Based on an analysis of gravel fabric characteristics of conglomerate layers around the Late Cretaceous-Paleogene Amdo microcontinent in southeast Qiangtang Basin of Tibet,this paper elaborates characteristics,origin,source,transport way and tectonic background of the conglomerate in combination with the regional geology.Studies show that conglomerate layers are alluvialproluvial products that have experienced short-middle distance transportation.The gravels have the characteristics of complex composition,different constitutents and good sorting.The paleocurrent of the statistical points possesses the characteristics of a single flow direction,and the condition of hydrodynamic force is relatively stable.The analytical results of the compositional features and orientations of the gravel reveal that the gravels were derived from Amdo microcontient,Bangongnujiang suture zone and their surrounding mountains,indicating the sedimentary features of the piedmont water system formed by alleviation and subsequent proluvial action.In combination with regional geology,the authors hold that in the Late Cretaceous the north of Amdo microcontient experienced uplifting and formed the palaeogeographic pattern which was higher in the northeast and lower in the southwest,and in Paleogene,the study area which preserved the previously palaeogeographic pattern was subjected to integral uplifting.It is thus concluded that the uplifted area of Tibet occurred in the north of Bangongnujiang suture zone in the Late Cretaceous,and Tibet experienced uplifting as a whole in Paleogene.

关 键 词：砾组分析 白垩纪—古近纪 隆升 羌塘盆地 

分 类 号：P588.212.5[天文地球—岩石学] P534[天文地球—地质学]