桂西北过兴地区罗楼组牙形石Hindeodus parvus的发现及其地层学意义

The Discovery and Its Stratigraphic Significance of Conodont Hindeodus Parvus of Luolou Formation in Guoxing area of Northwest Guangxi

在1∶5万坡脚等幅区调工作中,于广西隆林过兴实测的罗楼组剖面,在第5层发现具有重要意义的牙形石Hindeodus parvus(Kozur and Pjatakova),目前国内外均以Hindeodus parvus首现作为三叠纪的开始;并在第4层发现晚二叠世最晚期的牙形石Hindeodus praeparvus(Kozur),4层上部发育较多晚二叠世后期的介形虫化石。由此表明,在过兴剖面罗楼组4层与5层间存在着一重要的地质界线即二叠系-三叠系界线,并由下而上划分出Hindeodus praeparvus和Hindeodus parvus两个牙形石带,分别代表上二叠统长兴阶最高层位牙形石带和下三叠统印度阶首个牙形石带。

In the 1∶50000 equal-amplitude regional survey of Pojiao,in the measured Luolou formation profile in Longlin,Guangxi,an important conodont Hindeodus Parvus(Kozur and pjatakova)was found on the 5 th floor.At present,the first appearance of Hindeodus parvus is considered to be the beginning of Triassic at home and abroad.The last conodont Hindeodus praeparvus(Kozur)was found in the 4 th floor,and there were many ostracods in the upper part of 4th floor.This shows that there is an important geological boundary between the fourth and fifth layers of Luolou formation in Guoxing section,it is the Permian-Triassic boundary.Two conodont zones:Hindeodus praeparvus and Hindeodus parvus,are divided from bottom to top.They represent the highest conodont zone in Changxing stage of Upper Permian and the first conodont zone in Indian stage of Lower Triassic respectively.