Paleocene Radiolarian Faunas in the Deep-Marine Sediments Near Zhongba County, southern Tibet

Abstract

An upper Paleocene radiolarian-bearing succession (ZN1) located in the southern part of the north subzone of the Tethyan Himalaya is composed of siliceous siltstones and claystones. In this paper, 23 species belonging to 13 genera are reported. Three new species, Lychnocanium? pyramis Li and Matsuoka sp. nov., Lychnocanium? stypticum Li and Matsuoka sp. nov., and Pterocyrtidium sinense Li and Matsuoka sp. nov., are described. Radiolarian assemblages from this succession can be compared with the Bekoma campechensis Zone (RP6), indicating a time interval of 61.5–58.23 Ma, i.e., late Paleocene. The radiolarian assemblages from the Yamdrok melange, the Zheba section, and the Jiazhu section indicate that they are of the same age as those from the Zhinadibu 1 section. The lack of calcareous and coarse-grained terrestrial materials in the ZN1 section proves that the strata of this section were deposited in a relatively deep marine environment below the calcium carbonate compensation depth (CCD) and more distal to the continents during the late Paleocene. Coeval deepwater sediments near Saga were accumulated near the CCD.