西藏早古生代地层主要分布于喜马拉雅、冈底斯—念青唐古拉和羌塘—唐古拉—昌都三个地层区内。由于前奥陶系主要为片岩、大理岩等组成的浅变质岩地层,未发现任何化石,因此大部分地区尚未明确划分出寒武系。但西藏奥陶系和志留系在上述地层区内皆有分布,发育较全,岩性以碳酸盐类为主,少量碎屑岩,均含丰富的大化石和微体化石。 The early Paleozoic strata in Tibet are mainly distributed in the three stratigraphic zones of the Himalayas, Gangdise-Nyainqentanglha and Qiangtang-Tangula-Qamdo. Because the former Ordovician is mainly composed of shallow schist rocks, such as schist and marble, no fossils are found, so the Cambrian has not been clearly divided in most areas. However, the Ordovician and Silurian reservoirs in Tibet are all distributed and developed well in the above stratigraphic zones. The lithology is mainly carbonate with a few clastic rocks, all of which are rich in large fossils and microfossils.