Ostracoda Biostratigraphy In Chuangde,Gyangze, Tibet

Southern margin of the Qinghai- Tibet Plateau is located in the eastern part of the Tethys Himalayan tectonic domain and is the collision belt between Indian plate and Eurasian plate. The Cretaceous marine strata are well preserved in southern Tibet, yielding abundant microfossils. Based on the micropalaeontology study, important evidence can be provided to explore the evolution of Neo-Tethys and Cretaceous palaeogeography and palaeoenvironment.Based on the sedimentary difference, Tethys Himalaya belt can be further divided into north and south sub-belts bounded by the Dingri-Dingjie-Gangba deep fault. During Cretaceous, Northern Tethys Himalaya sub-belt(typical by Kangmar and Gyangze areas) was largely in a slope-basin environment and marine red beds(CORBs) were also widespread in this area. Southern Tethys Himalaya sub-belt(typical by Gamba and Tingri areas) belonged to northern Indian passive continental margin.This thesis focuses on the ostracod biostratigraphy research of Chuangdexi section, Gyangze in northern Tethys Himalaya sub-zone.Abundant ostracodas yield from this section, which include 41 species of 24 genus, and five ostracoda biozones are recognized(in ascending order):①Xestoleberis eximia-Talicypridea ventricosa zone, ②Schuleridea shalayiensis-Candona longireniformis zone, ③Uroleberis inflata-Candoniella subcurvata-Argilloecia zone, ④Talicypridea occultaca-Bairdia acrocaudalis-Xestoleberis zone, ⑤Cypridopsis zhungaerensis-Cyclocypris cf. calculaformis zone.Based on the ostracod assemblages and planktic foraminifera from this section, the age of the measured strata of the Chuangdexi section in Gyangze is late Santonian-early Maastrichtian, and the age of the CORBs are defined as Campanian- early Maastrichtian. In addition, the rock characteristics of the red beds in Chuangde Formation are also analyzed in this thesis, which indicates that this area should be in a deep environment from slope to basin during Campanian- early Maastrichtian.