Griesbachian and Dienerian (Early Triassic) ammonoids from Qubu in the Mt. Everest area, southern Tibet

Abstract

The Permian–Triassic boundary (PTB) is defined by the conodont Hindeodus parvus at Meishan section D in the palaeotropical Tethyan region, where basal Triassic ammonoids are rare and poorly preserved. Here we describe some basal Early Triassic ammonoids from the lower part of the Kangshare Formation at the Qubu section in the Mt. Everest area in southern Tibet, China. Our study recognizes three distinct ammonoid zones, the Otoceras woodwardi, Ophiceras tibeticum, and Ambites zones in ascending order. The occurrence of Otoceras, a key basal Triassic taxon, is here documented for the first time in this area. The first occurrence of Triassic conodonts at Qubu indicates that the PTB is not higher than the level 0.81 m above the base of the dolomite unit of the Kangshare Formation, and the first occurrence of the ammonoid Otoceras woodwardi is 0.89 m higher up at the section. At Qubu, the Griesbachian–Dienerian boundary is placed between the Ophiceras tibeticum Zone and the Ambites Zone. Our work represents a valuable addition for the construction of a high resolution of Griesbachian and Dienerian ammonoid biozonations in southern Tibet and provides a framework for the basal Triassic correlation in the Mt. Everest area.