Upper Paleocene radiolarians from the Yamdrok mélange, south Xizang (Tibet), China

Abstract

A rich assemblage of upper Paleocene radiolarians has been extracted from siliceous mudstones that locally form the matrix of the Yamdrok mélange in southern Tibet. Faunas include Bekoma campechensis, Lychnocanoma? costata, Orbula comitata, Orbula ducalis. Clathrocycloma parcum, Amphisphaera macrosphaera, Phormocyrtis turgida, Spongurus? regularis, and Dictyocephalus middouri, and correspond to the Bekoma campechensis Zone. This is the first discovery of upper Paleocene radiolarians from Tibet and provides a maximum age constraint on the timing of formation of the Yamdrok mélange, a unit postulated to have developed during collision of the northern margin of India with an intra-oceanic island arc system within Tethys.