Cretaceous lithostratigraphy and sedimentary environment in the Ulan Ul Lake area,northern Qiangtang

The Cretaceous sections in the Ulan Ul Lake area,northern Qiangtang,are described in details.The Cretaceous in the area is divided into the Cuojuri Formation and Sangqiashan Formation.Sedimentary facies analysis indicates that the Cuojuri Formation in the Ulan Ul Lake area is composed of alluvial to fluvial deposits and highly varied in lithology and thickness and that the Sangqi ashan Formation is composed of lacustrine and lake deltaic to fluvial deposits.It is proposed that the Cuojuri Formation is Early Creta-ceous in age and the Sangqiashan Formation is Early to Late Cretaceous in age.