Jiejunazhuo Formation: a Pliocene lithostratigraphic unit in the Coqen region, Xizang

The strata in the Coqen region, Xizang assigned to the Pliocene Wuyu Group in the Xigaze 1:1 000 000 Sheet consist of the lower volcanic rocks and upper sedimentary rocks. The former is assigned, on the basis of the isotopic ages obtained from the 1:250000 regional geological survey, to the Paleocene Dianzhong Formation, while the latter to the Lower Cretaceous strata in which the foraminifera such as Orbitolina occur. In addition, a sequence of continental clastic strata has also been newly identified in this area, which is named the Pliocene Jiejunazhuo Formation in terms of lithologic association, ESR dating and regional stratigraphic correlation.