The Improvement In The Studies Of Planktonic Foraminiferal Biostratigraphy In The Upper Cretaceous In Tingri, Tibet

The marine upper Cretaceous strata are well exposed in South Tibet,Tethyan Himalayas zone and the systematic stratigraphic framework had been established. However, the space between each two samples were always too wide which could result in low precision of the boundary of planktonic foraminifera zones and stage.With the improvement of related research resolution overseas, plenty of new data are accumulated, then the neccarity and importance of doing high precision planktonic foraminifera biostratigraphy research is emerged gradually.During the time clearing up the lithostratigraphic units, the paper abandoned three formation terms, which are Lengqingre,Xiawuchuba and Jiubao.They were initial established by fossils but not lithology, so the paper adopted an old lithostratigraphic units system according to the International Stratigraphic Guide, and in the same time reconfirmed the boundary of specific lithostratigraphic unit.Under the guidance of high resolution research of paleoceanography, we collected 699 samples in the 291 meters thick upper Cretaceous section of Gongzha,Tingri,the average density is 2 to 3 per meter, and the time space between each two samples is only 0.05Ma, the high density of sampling can greatly upgrade the level of stratigraphic research in Tingri,Tibet.After the samples were disposed and the fossils identified, eleven foraminiferal zones are established from the lower part to the upper part of the section, which are : Rotalipora reicheli, Rotalipora cushmani, Whiteinella archeocretacea ,Helvetoglobotruncana helvetica,Marginotruncana sigali,Dicarinella primitiva , Dicarinella concavata , Dicarinella asymetrica , Globotruncanita elevata , Globotruncana ventricosa, Globotruncana falsostuarti.Based on these zones,the paper also confirms the boundaries of Cenomanian, Turonian, Coniacian to Santonian and Campanian stages. These conclusions would be help to the related study of Upper Cretaceous in Tingri, Tibet.