西藏聂拉木中、晚侏罗世菊石组合划分及时代讨论

AMMONOIDS ASSEMBLAGES OF THE MIDDLE AND LATE JURASSIC FROM NIELAMU COUNTY, TIBET

黄亚平

Huang Yapin

地质矿产部石油地质中心实验室

Central Laboratory of Petroleum Geology, Ministry of Geology and Mineral Resources

藏南聂拉木地区有关侏罗纪的地层及古生物的研究,前人己有报导。本文对该区的中、上侏罗统菊石的组合特征,并结合邻区及国外有关地区的菊石组合及其时代,将本区的菊石进一步划分为五个组合及一个菊石层。同时,对其上下层位关系与时代分布也作相应的讨论。

The ammonoids described in the paper were collected from the middle and upper Jurassic in Nielamu County of southern Tibet in 1980 and 1981, Stratigraphically, these fossils can be divided into four assemblages and an ammonoids-bearing stratum as follows: 1. Macrocephalous-Indocephalous assemblage located at the basement of Menbu Formation, mainly consists of Macrocephalitidae, 2.Aulacosphinctoibes-Ptychophylloceras lalonglaensis assemblage derives from the middle and upper parts of Menbu Formation with few Katroliceras and Metagravesia genera etc, 3.Virgatosphinctes-Haplophylloceras pinque assemblage from the upper section of Xiumo Formation is characterized by plenty of Virgatosphinctes (sPP.). 4.Berriasella-Blanfordiceras assemblages at the lower part of Gucuo Formation are principally composed of Berriasellidae. Mayaitids-bearing stratum lies at the lower part of Menbu Formation, Based on the correlation analysis among the ammonid faunas and the other faunas from some parts of the world, it is considered the faunas in Tibet present a completed series from Callovian to Tithonian, It is interested that the Tithonian may be divided into three parts with three ammonoids-bearing strata of different features.

https://doi.org/10.11781/sysydz198504330