Abstract: During his geological excursions to Gansu and Xinjiang Provinces in 1920s—1930s Professor Yuan Fuli carried out a tremendous amount of pioneering work on stratigraphy and paleontology with many discoveries. He proposed such stratigraphic units as the Pingliang graptolites beds, the Chouniugou formation, the Shiqiantan marl (fm), the Dalongkou beds (fm), the Donghongshan beds (fm) and Shaofanggou beds (fm), which are still valid today and are retold briefly as follows. Besides, the present article also explains Yuan's stratigraphic observations in East Gansu, Northwest Gansu and Eastern Junggar. The Pingliang graptolites beds. These beds were discovered in Ordovician shale in 1923 at Guanzhuanggou, 10 km southwest of Pingliang County and the graptolites identified by A. W. Grabau consisting of 12 species in 7 genera as follows: Climacograptus bicornis Hall, C. parvus Hall, Didymograptus sagitticaulis Gurley, D. serratulus Hall, Dicellograptus divaricatus (Hall), Nemagraptus exilis (Lapw.), N. gracilis (Hall), Dicranograptus cf. furcatus (Hall), D. clingani Carruthers, Diplograptus (Glyptograptus) angustifolius (Hall), D. (G.) teretiusculus (His.) var. kansuensis Grabau var. nov., Orthograptus whitfieldi (Hall). These graptolites confirm an early Middle Ordovician age. The Chouniugou formation. This formation exposed some 35km southwest of Wuwei County is marked as bed 4 in the Chouniugou section and the rich fossils (Productus giganteus maximus M'Coy, P. giganteus depressa Chao, P. undulatus Defrance, P. elegans M'Coy) indicate for the first time the presence in China of Early Carboniferous Viscan stage. The Shiqiantan marl (fm). The formation developed around the Permian dormal structure near Shiqiantan ca 100km northeast of Qitai is divisible into the upper greenish grey thin-bedded marl and the lower reddish dense limestone. It had been assigned to the Permo-Carboniferous (Yang, 1948), the Permian (Artinskian, 1952 in Yuan, 1956) and Middle-Upper Carboniferous (Wu et Zhao, 1982). The Dalongkou beds (fm). Being exposed at Dalongkou, south of Santai, Jimsar County, this formation is composed of black shale, grey limestone, bluish shale, brown grey sandstone and conglomerate. According to Estherids and corals (Desmiophyllum) it contains, a Late Permian age could be assigned to it. The Donghongshan beds (fm). The formation was divided into 3 beds (Yuan, 1935), the uppermost of which is red argillaceous shale and reddish brown argilla- ceous sandstone and yields theromorphous reptiles (Dicynodon, Pelecosaurus—Chasmatosaurus, Lystrosaurus) which give an early Early Triassic age. The same formation was revised in 1956 into two portions, the lower containing fossil plants (Thinnfeldia n. sp., cf. Otozamites sphenozamioides, Equisetites sp.) and bivalves (Palaeomutela cf. keyserlingi), while the upper bed yielding theromorphous reptiles (Dicynodons, Lystrosaurus, Chasmatosaurus). The Shaofanggou beds (fm). This formation assigned orginally to the late Early Triassic (Yuan, 1935) is composed of various clastics (conglomerate, sandstone, shale, etc.) and divisible into 4 beds with bed 4 yielding silicified wood and the upper fish bed; in 1956 some revision was made with the addition to bed 2 Sinosemionotus urumchii, all belonging to the Middle Triassic. Stratigraphic observations in E. Gansu. These were restricted to a narrow strip stretching through central eastern Gansu and consist of Precambrian, Paleozoic (Ordovician Pingliang shale, Carboniferous Chuangou series, the Permian Chedipo series), Mesozoic (Jurassic Aganzhen series, Cretaceous Liupanshan series) and the Cenozoic (Pliocene) Suzikou series (Pliocene or earlier), Guide series, Pleistocene conglomerate, lacustrine marl, loess). Carboniferous stratigraphy of NW Gansu. Carboniferous strata are well represented by various sections in Wuwei County (Chouniugou), Yongchang County (Hongshanyao, Lijiachuan), Shandan County (Xinhe), Gaotai County (Megou-Heishixia, and Yaogou). Their subdivision and correlation are summarized in Table 1 in the Chinese text. The stratigraphy of E. Junggar. (A) Along the meridian through Qitai County there are developed 6 "groups" of rocks, namely: (1) slightly metamorphosed sedimentaries, e. g. Schist and quartzite at Tashan in the north as well as phyllite and slate north of Nanminsui; (2) the Devonian? tillite; (3) the Lower Carboniferous limestone (e. g. Shuanjingzi); (4) the Lower Permian thin-bedded marl and shale (e. g. Shiqiantan); (5) the Mesozoic (Triassic, Jurassic, and Cretaceous) and (6) various kinds of igneous bodies. (B) At Dalongkou, Santai, Jimsar County there was exposed the Lower Triassic Donghongshan formation, in which theromorphous reptiles (7 almost complete skeletons) were discovered. The succeeding formations consist of Gangou formation (Middle-Upper Triassic), the Lower Suixigou formation (Rhaetic), the Middle Suixigou formation (L. Jurassic), Upper Suixigou formation (Middle or Upper Jurassic), Xindi formation (Cretaceous) disconformable with the latter and the Pliocene Fuyuan formation disconformably overlying the Xindi formation. From the foregoing it may be noted that in the early Part of this century Prof. Yuan Fuli had carried out pioneering geological explorations to Northwest China and laid down a good foundation for stratigraphy and palaeontology, including in particular such discoveries as the Carboniferous Visean stage in Gansu and the Theromorphous reptiles in Xinjiang (E. Junggar). Hence, his contributions to Chinese Geoscience are well acknowledged and appreciated by all concerned.