Cretaceous Micro-biostratigraphy In Tianba Area, Southern Tibet

The marine upper Cretaceous strata are widespred in the Tethys-Himalays belt, southern Tibet. Macrofossils being relatively scarce, the microfossiles are quite important for us to study the biostratigraphy of Cretacous in this area. A detailed biostratigraphic study has been made and a systematic systematic Cretaceous biostratigraphic framework have been established in the South Tethys-Himalayas subbelt, which is located south of the Tingri-Gamba fault. In contrast, a shallow and fragmentary biostratigraphic study has been made about the Cretaceous in the North Tethys-Himalayas subbelt, which is located north of the Tingri-Gamba fault. Especially, there is no any biostratigraphic work has been made about the Cretaceous in the Tianba area of Kangma. Therefore, it is relatively necessary for us to make a further biostratigraphic study on the Cretaceus of Tianba area in Kangma.This thesis based on the detailed fieldwork at the Cretacous strata in Tianba, Kangma. Three new sections were measures in this area. Based on its being in the same depositional basin and similar lithologic association with the Cretaceous strata of Gyangtze area, the Cretaceous of Tianba area can aslo be ascendingly indiveded into Jiabula, Chungde and Zongzhuo formations.No macrofossils have been discovered from the Cretacous Zongzhuo Formation of Tianba area. However, a boundant microfossils (mainly foraminiferas and radiolarian) are present this formation. From the Zongzhuo Formation the Tianba sections of a and b, six foraminiferal assemblages have been ascendinly recognized as (1) Lagena apiculata Zone, (2) Globotruncana elevata Zone,(3)Dorothia stephensoni Zone,(4) Trochamminave globigeriniformis Zone,(5) Dentalina catenula Zone and (6) Haplophragmoides trifolium Zone; And four radiolarian assemblages have been ascendinly recognized as (1) Xitus sp , (2) Cyrtocapsa campi , (3) Orbiculiforma renillaeformis and (4) Stichomitra compsa.In the Daba section, six foraminiferal assemblages have been ascendinly recognized as (1) Trochammina wetteri Zone, (2) Lenticulina carlsbadensis Zone, (3) Haplophragmoides trifolium Zone, (4) Haplophragmoides calcula Zone, (5) Globotruncana lapparenti Zone, and (6) Gavelinella pertusa Zone; And three radiolarian assemblages have been ascendinly recognized as (1) Paronaella solanoensis,(2) Amphipyndax stocki,and (3) Orbiculiforma renillaeformis. The microfossil assemblages indicate a Campanian-Maastrichtian age for the Zongzhuo Formation of Tianba area..