Discovery of Early Devonian strata in northern Qiangtang, Tibet, and the establishment of the Pingshagou Formation

Although it is important to determine whether there exist sedimentary strata older than the Upper Permian in the northern Qiantang area in Tibet, there has been no report of such old strata in this area. During the geological mapping of the Mayigangri area, we discovered strata that contain the bivalves Eoschizodus roemeri (Beushausen), E. minor (Beushausen) , E. infiatus (Roemer), Actinodesma (Actinodesma) cf . maneiforme Sandberger, A . (Actindesma) cf . vespertilio Maurer, and the brachiopod Huananochonetes subquadratus Sun & Chen. These fossils indicate a late Early Devonian age (Emsian) , thus the strata represent the first discovered Lower Devonian rocks in northen Qiangtang, confirming the existence of strata older than the Upper Permian. A new stratigraphic term, the Pingshagou Formation , is introduced. The new data provide constraints on the tectonic, palaeogeographic, and palaeobiogeographic history of the north Qiangtang area in the Early Devonian.<br />