贵州关岭中三叠统坡段组沉积特征及其形成环境  

SEDIMENTARY CHARACTERISTICS AND ENVIRONMENTS OF THE PODUAN FORMATION OF MIDDLE TRIASSIC IN GUANLING OF GUIZHOU PROVINCE

作　　者：范嘉松[1] 吴亚生[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《古地理学报》2002年第1期67-74,T005-T008,共12页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金项目 (4 870 12 8)

摘　　要：贵州中三叠世碳酸盐台地边缘的“堤礁”向来受到人们的关注 ,并成为研究的热点。当前对台地边缘沉积的性质存在着不同的观点。某些人认为这些沉积是在浅水和扰动环境下形成的滩相沉积 ;而另外一些研究者则仍坚持它们代表典型的礁相沉积 ,因为它含有丰富的造架生物 ,如六射珊瑚、苔藓虫、钙质海绵和龙介类等。在贵州中部关岭县扒子场出露了一套巨厚的和属于台地边缘的中三叠统。扒子场在关岭县城的东南 ,直距约 2 2km。三叠系中下统沿着公路断面连续出露。中统包括安尼阶的坡段组及拉丁阶的垄头组和竹杆坡组。坡段组主要由砂砾屑 -生屑颗粒岩组成 ,约占全剖面的 2 / 3。它们形成于水流激荡的滩相环境。其他岩石为骨屑 -球粒粒泥岩和泥粒岩 ,约占全剖面的 1/ 3。根据该组的岩石结构、沉积构造和生物组分 ,坡段组代表由砂砾屑、生屑组成的粒屑滩 ,而非生物礁相沉积。仅在底部或下部出现少量的Tubiphytes—蓝细菌造礁骨架 ,组成局部的礁丘。The so called 'barrier reefs' along the Middle Triassic carbonate platform margin in central Guizhou Province have been subjected great attention for their origins, and became intensive targets of research. There are quite different views on the nature of platform margin deposits. Some people believed that these deposits be formed in shallow water, turbulent, bank or shoal environments rather than reefs, while other people still persisted that these deposits be typical reef facies deposits because they yield abundant framebuilding organisms, such as scleractinian, corals, bryozoans, calsisponges and serpulidal worms. During recent survey, extraordinarily thick, Middle Triassic deposits at the platform margin are magnificently exposed near the Pazichang, Guanling County,central Guizhou Province. The Pazichang is a small locality,approxmately spaced 22 km to the southeast of city of the Guanling County. The Lower and Middle Triassic rocks are uninterruptedly exposed in road cuts. The Middle Triassic includes Anisian Poduan Formation, and Ladinian Longtou Formation and Zhuganpo Formation. The rocks of the Poduan Formation are mainly intraclastic bioclastic grainstones formed in turbulent and agitated bank environments, and amount to about 2/3 of total thickness of the profile. Subordinate rocks of the Poduan Formation are skeletal peloidal wackestones and packstones, which amount to about 1/3 of total thickness in the same profile. Based on lithologic features and textures of these rocks and their fossils, these deposits are typical bank deposits with subordinate carbonate platform deposits rather than reef facies deposits, although some Cyanobacteria- Tubiphytes boundstones occured locally at the lower or bottom part of the Formation.

关 键 词：砂砾屑 台地边缘 坡段组 中三叠统 贵州 沉积特征 形成环境 

分 类 号：P512.2[天文地球—地质学] P534.51