Tectonic division and crustal shortening in the Coqen Basin,Xizang

The Coqen Basin,Xizang is the second large-scale marine basin only smaller than the Qiangtang Basin on the Qinghai-Xizang Plateau.Tectonically,the basement of the Coqen Basin may be divided into four first-order tectonic units,i.e.,northern depression,northern uplift,central depression and southern uplift,while the cover may be separated into five first-order tectonic units,i.e.,northern downwarped zone,northern thrust fault zone,central downwarped zone,southern thrust fault zone and southern downwarped zone.The shortening rates during the Late Cretaceous are estimated at about 24% on the basis of the balanced cross-section calculations.