1:250 000 Sumxi and Wenquan Sheets in Xizang and Xinjiang

Twenty-seven formation-scale and nine member-scale stratigraphic units, of which two are informal stratigraphic units, are established in the 1:250 000 Sumxi and Wenquan Sheets in Xizang and Xinjiang. Various fossils abound in most of the strata, especially abundant Early and Middle Devonian corals and brachiopods in the Lazhuglung Formation. The Lazhuglung Formation overlies unconformably the Ordovician and Silurian strata. Several important unconformities in northern Qiangtang are found to be intermediate between the Middle Triassic Heweitan Formation and its underlying strata, Heweitan Formation and its overlying Upper Triassic Keleqinghe Formation, Lower Jurassic Bagongbulansha Formation and its underlying Keleqinghe Formation, and Lower-Middle Jurassic Longshan Formation and Bagongbulansha Formation. Abundant Early Ordovician fossils are identified in the western part of Sanchakou. The Sanchakou Formation is redefined as the lowest fossil-controlled horizons in the Qiangtang region. The Silurian strata are recognized in the area north of the Lungmuco area. The Middle Jurassic Longshan Formation is used in the western and central parts of these Sheets. There exists a number of Neogene andesitic volcanic sedimentary basins named the Sumxi Formation, and three Paleogene continental basins named the Paleogene Mahuangshan Formation in the Shumuyingdi-Lungmuco-Duoliangshan zone. There occur larger-scale coral reefs that may be subdivided into reef base, reef frame, reef-front collapse breccias and inter-reef deposits. The platform Carboniferous-Permian strata are found in the Karakorum stratigraphic province, and glacial dropstone in the Upper Carboniferous Cameng Formation. The alkaline granites are observed for the first time in northern Qiangtang. The geochemistry and tectonic settings of the Palaeozoic diabase-porphyrite are also treated in detail. The additional discovery includes abundant Paleogene andesitic volcanic rocks arranged along the major faults. Other advances include the discovery of the gap-aligned NS-trending structural zones, and the examination of Lungmuco-Shuanghu fault, Altun fault and other NS-trending faults.