西藏晚白垩世晚Campanian期至早Maastrichtian期菊石群——中国最年轻的菊石群  

LATE CAMPANIAN TO EARLY MAASTRICHTIAN AMMONOID FAUNA OF LATE CRETACEOUS IN XIZANG ——THE YOUNGEST AMMONOID FAUNA IN CHINA

作　　者：孙亦因[1] 王义刚[2] 

机构地区：[1]中国科学院地质研究所,北京100029 [2]中国科学院南京地质古生物研究所,南京210008

出　　处：《古生物学报》2001年第1期20-30,共11页Acta Palaeontologica Sinica

摘　　要：记述产自西藏南部仲巴县的一个中国目前所知最年轻的菊石群 ,含 2科 4属 6种 ,其中 4新种。据菊石群面貌和它们所产出的层位可以划分出上、下两个组合带 :上部Pachydiscuscf.hidakaensis Libycoceraszhongbaense组合带 ;下部Manambolitescujiangdingensis M .pivaeteaui组合带。产菊石的曲贝亚组的下段和上段的中、下部(82F5 0及其以下层位 )为晚Campanian期 ,上段上部 (即 82F5 2及其以上层位 )为早Maastrichtian期。ThispaperdealswithanammonoidfaunafoundinZhongbaCountysouthernXizang(Tibet),whichistheyoungestammonoidfaunainageknowninChinaatpresent.Thefaunainvolves2families,4generaand6species(including4newspecies).Basedonthefeaturesofammonoidfaunaandtheverticaldistribution,anupperandalowerassemblagezoneshavebeendistinguished:TheupperassemblageZonePachydiscuscf.hidakaensis-Libycoceraszhongbaenseassemblagezone:only2genera,2speciesarefoundandthelatterisanewspecies.BasedonthefactthattheformerspecieswasoriginallyyieldedinearlyMaastrichtianbedsinHokkaido,Japan,whilethelatterissimilartoL.ismaelis,whoserangeisfromlateCampaniantolateMaastrichtian,theageofthisassemblageisreferredtoearlyMaastrichtian.ThelowerassemblageZoneManambolitescujiangdingensis-M.pivaeteautiassemblagezone:3genera,5speciesarefound.Inadditiontothetwomarkerspeciesofthezone,theothersareCoahuiliteszhongbaensissp.nov.,Libycocerastibetioumsp.nov.andL.zhongbaensesp.nov.BasedontheoccurrenceofgenusManambolitesbeingrestictedtomiddletolateCampanian,especiallythepresenceofM.pivaeteauibeingonlyfoundinlateCampanianbothinMadagascarandTunisia,itisappropriatetoassignthisassemblagezonetolateCampanian.Agesofthebedsyieldingammonoidsaresuggestedasfollows:QubeiyaFormation:Themajorpartofthelowermember,andlowerandmiddlepartofuppermembers(thebedsbelow82F50)canbeassignedtolateCampanian,whiletheupperpartoftheuppermember(82F52andthebedsabove)shouldbeearlyMaastrichtianinage.AsfortheoverlyingQuxiaFormationwithoutammonoidsitisinferredthatprobablyapartoftheearlyMaastrichtianandlateMaastrichtianareinvolvedbasedonthefindingsoflateMaastrichtianforaminifersandtheboundaryclaylayerwithiridiumanomaly,whichiscommonlyfoundatK-Tboundaryinmanyplacesthroughouttheworld.TheconsiderablepartoftheupperPadanaFormationunderlyingtheQubeiyaFormationisalsodeductedanddatedasearlyCampanianinagealthoughnofossilevidencehasbeenfound.

关 键 词：菊石群 晚CAmpAniAn期-早MAAstriChtiAn期 西藏 

分 类 号：Q915.818.4[天文地球—古生物学与地层学]