CRETACEOUS BIVALVE BIOGEOGRAPHY IN QINGHAI-XIZANG PLATEAU

The Cretaceous marine deposits in Qinghai Xizang Plateau develop mainly in six belts, extending from east to west. The fossil bivalves occur chiefly in five epoches, namely Berriasian, Aptian Albian, Cenomanian Turonian, Coniacian Santonian and Campanian Maastrichtian. Palaeobiogeographically, the Yarlung Zangbo River Suture Zone was the main controller for the distribution of the Cretaceous bivalves. During Early Creataceous, the bivalves Retroceramus, Nototrigonia, Maccoyella, Eyrena etc. emerging in the Himalayan area, south of the Yarlung Zangbo River Suture Zone, were similar to those contemporaries from Australia, Antarctica, East Africa and South America, belonging to the Gondwana Land; but Gervillaria, Caestocorbula, Myopholas, Trigonioides etc., from the north of the suture zone, were the elements limited in the northern margin of the Tethys and eastern Asian. Undoubtedly, there existed a deep and vast ocean, namely the Tethys Ocean, between the south and north of the suture zone then. In Late Cretaceous, the bivalves of these two areas gradually mixed as a result of the narrowing of Tethys Ocean. Up to Maastrichtian, the reef building rudists of warm water type, widespead in the Tethyan Realm since Late Jurassic, had emerged at last in the Himalayan Area, such as Bournonia, Praeradiolites, Biradiolites etc. According to the present materials, the bivalve biogeographical units are divided, and the northward drifting process of the Indian Subcontinent is expounded.

Project Supported:

Clc Number:

Q915.653