1:250 000 Dinggo and Gyamco Sheets in Xizang

The Late Permian fossils are collected from the limestones in the upper part of the Lower Carboniferous Riwancaka Formation in the Gangmarco area; the Middle Triassic fossils from the Middle Permian Lugu Formation on the eastern bank of the Chabo Lake, and the fusulinid and coral fossils in the Mopanshan region from the Jurassic Yanshiping Formation, where the Jurassic strata should largely be defined as the Permian strata. The discovery of the Early Triassic conodonts from the Upper Triassic Xiaocaka Formation in the Talikeganlishan area permits the modification of the Formation into the Lower Triassic Yingshuiquan Formation. A succession of volcanic rocks is found to overlie unconformably the Upper Triassic Xiaocaka Formation calcarenite. There is no angular unconformity between the previously Carboniferous Mushirebuka Group on the southwestern side of the Youyi gully and the pre-Devonian strata, both of which should be assigned to the same succession of strata in nature. There occur intermediate and acidic volcanic rocks and basalts in the Jianshan-Zougouyouchaco zone; andesite in the Xiaxiadinggou-Merze zone, and alluvial Pleistocene conglomerates in the Zexialong region. It is inferred that the Pleistocene ancient lakes once appeared in this region. Lithologically, the previously Kunchukeco, Jiazuobare and Xianqian massifs should be incorported into a giant batholith. The new findings include mica-rich S-type granites and garnet amphibole andesine gneiss as faults or blocks in the Darying region; granite gneiss in the area north of the Gangmarco fault in northwestern Gangmari, and blueschist as slices in the Gangmari region. Tectonically, the Gangmarco fault is believed to be a tectonic mélange zone, where the structural deformation appears in the upper, middle and lower levels of structures. The copper, iron, gold, gypsum and jade ore spots are delineated in the surveyed areas.