贵州关岭三叠系竹杆坡组、小凹组头足类化石——兼论关岭生物群的时代

Triassic cephalopods from the Zhuganpo and Xiaowa Formations in Guan ling,Guizhou,with a discussion on the age of the Guanling biota

贵州关岭地区中、上三叠统竹杆坡组和小凹组产较丰富的头足类化石,计有11科19属37种,其中Enoploceras,Alloceratites,Sibyllites等属以及Trachycerasaon种系国内首次报道。自下而上可识别出(1)Xenoprotrachycerasprimum带;(2)Protrachycerasdeprati带;(3)Protrachycerascostulatum带;(4)Trachycerasmultituberculatum带;(5)Sirenitescf.senticosus带等5个菊石带。讨论了每个菊石带的特征,并与国外同期菊石带进行了对比,指出(1)带与欧洲拉丁期早期R.reitzi带相当,(2)和(3)带分别与拉丁期晚期E.curionii带和P.archelaus带相当,(4)和(5)带分别与欧洲早卡尼期早期T.aon带和北美的早卡尼期晚期Sirenitesnanseni带对比。关岭生物群产出层位与Trachycerasmultituberculatum菊石带层位一致,时代应为早卡尼期早期。

The Middle and Upper Triassic Zhuganpo Formation and Xiaowa Formation in the Guanling area,Guizhou,yield abundant cephalopods,including11families,19genera and37species.Among them,the Enoploceras,Alloceratites and Sibyllites and Trachyceras aon were first reported in China.Five ammonoid zones may be recognized,they are in ascending order:(1)the Xenop rotrachyceras primum Zone,(2)the Protrachyceras deprati Zone,(3)the Protrachyceras costulatum Zone,(4)the Tra chyceras multituberculatum Zone,and(5)the Sirenites cf.senticosus Zone.The characteristics of these ammonoid zones are discussed and correlated with international contemporaneous zones.The first zone in the Zhuganpo Formation may correspond with the Early Ladinian R.reitzi Zone in western Europe,the sec-ond and third ones are equivalent to the Late Ladinian E.curionii Zone and P.archelaus Zone respective-ly,the fourth one in the Lower Xiaowa Formation may be correlated with the early Early Carnian T.aon Zone in Europe,and the fifth one in the Middle Xiaowa Formation is equivalent to the late Early Carni-an Sirenites nanseni Zone in northern America.The horizon bearing Guanling biota may correspond with the Trachyceras multituberculatum Zone,which should be of early Early Carnian age.