The Cretaceous of the Eastern Bangong--Nujiang Suture Zone (Tibet): Tectono--Sedimentation
Pujun Wang 1, Frank Mattern 2, Werner Schneider 3, Wanzhu Liu 1, Wenquan Tian 1, Cai Li 1 1.College of Earth Sciences, Jilin University, Chanchun, 130026 China 2.College of Geology, Berlin Free University, Berlin, D-12249 Germany 3.College of Geology, Braunschweig University, Braunschweig, D-38106 Germany
The ophiolite--bearing Bangong--Nujiang zone (BNZ) traversing central Tibet from east to west separates the Qiangtang block in the north from the Lhasa block in the south. The Cretaceous of the area includes Chuanba Formation (K 1c), Duoba Formation (K 1d), Langshan Formation (K 1l) and Jiangba Formation (K 2j). The K 1c is composed of black shale, sandy pelite, siltstone, sandstone, coal beds and volcanic rocks, mostly of shallow marine facies. The K 1d consists of terrestrial siliciclastics intercalated with some calcareous sandstone beds bearing Orbitolina sp. indicating marine influence. The K 1l is carbonate platform deposits of shallow marine and lagoon. The K 2j is characterized by terrestrial thick massive red conglomerate. An active margin related to B--subduction zone is considered to be the geological setting of the Cretaceous sedimentation.