西藏南部白垩纪—早第三纪钙质超微化石及其沉积环境  

CRETACEOUS--EARLY TERTIARY CALCAREOUS NANNOFOSSILS FROM SOUTHERN XIZANG(TIBET)AND THEIR SEDIMENTARY ENVIRONMENT

作　　者：徐钰林[1] 茅绍智[1] 

机构地区：[1]中国地质大学,北京100083

出　　处：《微体古生物学报》1992年第4期331-347,461-464,共17页Acta Micropalaeontologica Sinica

摘　　要：西藏南部岗巴—定日一带白垩系—下第三系海相地层发育完整,富含钙质超微化石。经研究,本文自下至上划分出5个钙质超微化石联合带(或带)及2个钙质超微化石组合,即:Ruciamolithusirregularis-Rhagodiscus angustu带(CC7),Prediscosphaera columnata-Eiffellithus turriseiffelii联合带(CC8—CC9),Microrhabdulus decoratus-Crearhabdus crenulatus联合带(CC10—CC11),Eiffellithus eximius-Micula decussata联合带(CC12—CC15),Lucianolithus cayeuxii-Quadrumgothicum联合带(CC16—CC21),Arkhangelskiella cymbiformis-Quadrum sissinghii组合(CC24—CC25)及 Coccolithus formosus-Discoaster sp.组合。依据钙质超微化石的属、种成份及组合特征,本文讨论了东山组、察且拉组、冷青热组、夏吾除波组、旧堡组、基堵拉组及遮普惹组地质时代的归属。通过钙质超微化石属、种成份及化石丰度、溶蚀程度的分析,推论了藏南地区白垩纪—早第三纪沉积环境演变及海水进退历史。Marine Cretaceous--Early Tertiary strata are exposed extensively in southern Xizang(Tibet). Samples containing calcareous nannofossils were collected from three sections,namely, the Gongzha Section (Dingri County), the Zongshan Section and the Zongpu Sec-tion (Gamba County). According to Sissingh's (1977) zonation, five calcareous nannofossilcombined zones (including one zone) and two calcareous nannofossil assemblages are estab- lished based on the first occurrence of marker species, namely, the Rucinolithus irregularis-Rhagodiscus angustus. Zone (CC7); the Prediscosphaera columnata--Eiffellithus turriseiffelii Combined Zone(CC8--CC9); the Microrhabdulus decoratus--Cretarhabdus crenulatus Combined Zone(CC10--CC11); the Eiffellithus eximius--Micula decussata Combined Zone (CC12--CC15);the Lucianolithus cayeuxii--Quadrum gothicum Combined Zone (CC16--CC21), theArkhangelskiella cymbiformis--Quadrum sissinghii Assemblage (CC24--CC25), and the Coc-colithus formosus--Discoaster sp. Assemblage. On the basis of the calcareous nannofossils,the formations can be dated as follows: Dongshan Formation, middle--late Aptian; ChaqielaFormation, Albian--early Cenomanian; Lengqingre Formation, middle Cenomanian--earlyTuronian; Xiawuchubo Formation, late Turonian--early Santonian; Jiubao Formation, ear-ly Santonian--early Campanian; Jidula Formation, early--middle Mastrichtian; and ZhepureFormation, middle Eocene. There was controversy about the age of the Jidula Formation; some authors dated it asLate Cretaceous (Mastrichtian) while others dated it as early Tertiary (Danian) based onforaminifers. The samples under study were collected from the lower part of the Jidula For-mation, which was dated early--middle Mastrichtian. The whole Jidula Formation, there-fore, is probably a suite of transitional strata form Mastrichtian to Danian. An attempt also has been made in reconstructing the Cretaceous--early Tertiary paleo-environments for the study area by means of calcareous nannofossil date (composition andrelative abundance as well

关 键 词：白垩纪 早第三纪 钙 超微化石 

分 类 号：Q913.653[天文地球—古生物学与地层学]