藏北羌塘中部冈塘错地区早古生代角石化石的变形特征及其意义

Deformation feature and significance of Early Paleozoic hornstone fossil in Gangtangcuo area, central Qiangtang, northern Tibet, China

研究区处于冈瓦纳大陆和欧亚大陆结合部位的南缘,龙木错-双湖-澜沧江缝合带从研究区北部通过。野外地质填图过程中发现,在研究区早古生代地层中发育丰富的角石化石。这套角石化石具有明显的韧性变形特征,角石化石体呈石香肠状,横断面具σ型剪切构造的特征。这些特征表明研究区经历了明显的构造置换作用,呈现"总体无序,局部有序"的格局,属于典型的非史密斯地层,该认识对于研究区地层的划分具有重要意义。

The study region is located in the southern edge of the Eurasian continent and Gondwana land, where the Longmucuo-Shuanghu-Lancangjiang suture passes by through the northern part. By means of field geological mapping, we found there are abundant hornstone fossils in early Paleozoic strata. These fossils have distinct features indicating ductile deformation, such as boudinage structure and σ—type shear structure in cross-section. It′s shown by all these features that this study area has experienced strong structural displacement, strata within this area display as generally in disorder but locally in order and belong to typical non-Smith strata. This understanding is important for stratigraphic division in the study area.