The graptolite and conodont biostratigraphy of the latest Darriwilian, Sandbian and early and middle Katian succession on the Yangtze Platform is reassessed based on numerous new fossil collections and previously published data. At least at some localities, the lowermost Miaopo Formation is of pre-Nemagraptus gracilis Zone age (uppermost Pygodus serra and lowermost P. anserinus conodont zones). The rest of this formation (except for the uppermost part, which lacks diagnostic graptolites) has a diverse graptolite fauna of the N. gracilis Zone. The uppermost part of the Miaopo Formation contains few biostratigraphically diagnostic graptolites but the occurrence of conodonts of the Baltoniodus alobatus Subzone of the Amorphognathus tvaerensis Zone suggests equivalence with part of the Climacograptus bicornis graptolite Zone. The conodont succession of the Datianba Formation is virtually identical with that of the Miaopo Formation, confirming that these units are coeval. The lowermost part of the overlying non-graptolitic Pagoda Formation represents the upper A. tvaerensis Zone, and its upper part represents the A. superbus Zone. The occurrence of Dicellograptus elegans in the overlying Chientsaokou Formation (equivalent to the Linhsiang Formation in Yangtze Gorges region) suggests equivalence with the Pleurograptus linearis Zone in Scotland, which is consistent with the relatively non-diagnostic conodont fauna in these Chinese units. The biostratigraphic data are in good agreement with the δ13C chemostratigraphy and permit the establishment of precise correlations with the Baltoscandic and North American successions.

The Yangtze Platform preserves relatively thick carbonate successions and excellent fossil records across the Ediacaran–Cambrian boundary interval. The intensely studied Meishucun section in East Yunnan was one of the Global Stratotype Section candidates for the Precambrian–Cambrian boundary. However, depositional breaks were suspected in the section and the first appearance of small shelly fossils could not be verified. The Laolin section located in NE Yunnan is more continuous and shows great potential for global correlation of carbon isotope features across the Precambrian–Cambrian boundary. However, the stratigraphic framework and correlations were controversial. We studied and systematically sampled the Laolin section and present here new carbon isotope data for this section. The Laolin section consists of, in ascending order, the Baiyanshao dolostone of the Dengying Formation, the Daibu siliceous dolostone, Zhongyicun dolomitic phosphorite, lower Dahai dolostone and upper Dahai limestone of the Zhujiaqing Formation, and the black siltstone of the Shiyantou Formation. Our data reveal a large negative δ13C excursion (−7.2‰, L1′) in the Daibu Member, which matches the previously published data for the Laolin section, and a large positive excursion (+3.5‰, L4) in the Dahai Member, which was not shown in the published data. The excursion L1′ correlates well with the similarly large negative excursion near the first appearance of small shelly fossils in Siberia and Mongolia. Similar magnitude excursions are also known from Morocco and Oman, for which there are no robust fossil constraints but from where volcanic ash beds have been dated precisely at 542 Ma, thus confirming a global biogeochemical event near the Ediacaran–Cambrian boundary. Our data also indicate that deposition was more continuous at the Laolin section compared with the Meishucun section, where there are no records of a comparable negative excursion near the Ediacaran–Cambrian boundary, nor any comparable positive excursion in the Dahai Member. Therefore, the Laolin section has proven potential to be a supplementary Global Stratotype Section for the Ediacaran–Cambrian boundary on the Yangtze Platform.

The lower Meitan Formation (Floian, upper Lower Ordovician) at the Dajiaosi section, Zunyi District, northern Guizhou Province of South China, contains a moderately rich and diverse Sinorthis Fauna, with 22 species attributable separately to 15 families and seven orders of brachiopods. The fauna can be differentiated into three associations: the Paralenorthis serica, the Sinorthis typica, and the Tarfaya intercalare associations. These occupied a relatively wide palaeoecological range from lower BA3 to upper BA2 settings and from silty to clay substrate conditions. In South China, the Early Ordovician brachiopod radiation was marked by the diversification of the orthide-dominated Sinorthis Fauna, which first appeared and diversified in the middle part (relatively deep water) of the Upper Yangtze Platform in the Didymograptellus eobifidus Biozone, but rapidly declined in the succeeding Corymbograptus deflexus and basal Azygograptus suecicus biozones. During the latest Floian and early Dapingian, it expanded into comparatively shallow-water settings in the onshore direction (Changning area, southern Sichuan), offshore carbonate platform (Yichang, Hubei), and areas adjacent to the submergent Qianzhong Arch (such as the Zunyi area). The first appearance datum of the Sinorthis Fauna in shallower-water settings generally postdates that in the deeper-water environment in the central Upper Yangtze Platform, probably as a result of the fauna tracking a favoured BA3 setting during a gradual marine transgression.