Kunmingaspis(Trilobita) putatively from the Yunling collage, and the Cambrian history of the eastern Himalayan syntaxial region

Abstract

Faunal data provide critical constraints upon tectonic models, particularly in such areas of extreme structural complexity as the region adjacent to the eastern syntaxis of the Himalaya. Trilobites reported to have been collected from the Yunling collage at Yinchangou, northwestern Yunnan, are here assigned toKunmingaspis yunnanensisChang, 1964, and the concept of the genusKunmingaspisis reconsidered. Although there is debate about to the paleogeographic affinities of the Yunling collage, the apparent presence of this species supports previous arguments for faunal links between the Yangtze platform and the Himalayan margin during Early and Middle Cambrian time. A significant tectonic event of Late Cambrian/Early Ordovician age present in the western central Himalayan margin suggests that the Lhasa block collided with India at that time, but the northward extent of that block remains unclear. The recently discovered Late Cambrian trilobite fauna of Bhutan may hold the key to establishing faunal relationships between the Tethyan Himalaya, Sibumasu, and the Yangtze platform during this interval. No Cambrian sedimentary rocks are yet known from the Lhasa or Qiangtang blocks of Tibet and so there is no direct evidence for the existence of Cimmeria during the Cambrian Period.