华北板块北缘东段上三叠统的若干特征

SOME CHAR ACTERISTICS OF THE UPPER TRIASSIC ON THE EASTERN PART OF THE NORTHERN MARGIN OF NORTH CHINA PLATFORM

位于华北板块与古蒙古洋板块的交接处、金银别河至白水滩一带的一套变质的陆相碎屑岩,前人命名为白水滩组,时代归属早侏罗世。80年代末笔者在此进行1∶5万区域地质调查,在该地层中采到了Neoclamites sp.,Cycadocarpiclium sp.,Uniohuang bogouensis(?)等重要分子,同时发现其被二长花岗岩(U—Pb 192.7Ma)侵入,暂与小营子组对比,将其时代归属为晚三叠世。该套地层分为上下两段,即下部砾岩段和上部砂岩段;地层褶皱形态复杂,断裂构造发育,新老地质体相互推覆掩盖,构成独特的地质景观。

A suite of epimetamorphic continental clastic rocks located in contact zone between the North China plate and the paleoMongolia ocean plate in the Jinyinbie river-Baishuitan area named Baishuitan Formation by former geologists, was considered as Early Jurassic in age. Neocalamites sp., Cycadocarpidum sp., Unio Huang bogouensis (?) and others were eoleeted during regional geological survey in the late 1980s. At the same time, we found that this Formation was intruded by the adamellites (u—Pb 192.7Ma), named a Xiaoyingzi Formation, and the times is considered as later Triassic. The strata are divided into two members, i.e.; lower conglomerates and upper conglomerates. The strata display complex fold form, with the developed faulted structures and the interpenetrating and napping of the neoand old—geological bodies resulted in formation of unique geomorphic features.