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A recovery brachiopod fauna occurs in the lower Niuchang Formation (upper Rhuddanian - lower Aeronian, Llandovery) of the Xinglongchang section, Meitan County, northern Guizhou Province, South China. Nine collections were made at the section, all of which are dominated by brachiopods, and three associations are recognized here and their paleoecology is discussed. Paleoenvironmental analysis shows a shallowing upward trend for the lower Niuchang Formation, although a global transgression was happening at that time. The balance between the global transgression and the regional Qianzhong Uplift guaranteed a stable environment for the formation of the Niuchang Formation and the recovery of brachiopods in South China after the end-Ordovician mass extinction. In addition to the traditional methods of principal component analysis and cluster analysis, a relatively new technique to paleontology, 'network analysis', is applied successfully in this study. It is suggested that network analysis could be used as one of the supporting methods in investigating brachiopod paleoecology. [ABSTRACT FROM AUTHOR]

The distribution pattern of early Telychian ( turriculatus-crispus graptolite biozone) red beds in the Eastern Yangtze Platform of South China is reconstructed based on regional geologic data. The red beds are developed in three areas, which are separated by regions without red deposition. The distribution pattern indicates that the Cathaysian Oldland was the provenance of sediment rich in ferric oxides, which are essential for the formation of red beds. Silurian marine siliciclastic red beds, both in China and worldwide, tended to develop during times of relatively low sea level. Coeval hematitic oolites that formed far from the coast may record a change from reducing to oxidizing conditions in the ocean. Furthermore, it is likely that a fall in global sea level, a transition from reducing to oxidizing conditions in the ocean, and a cooling climate, all of which were closely related to the early Telychian Valgu Event, promoted the global development of marine red beds during this period. [ABSTRACT FROM AUTHOR]

The Kuanyinchiao Formation (Hirnantian, Upper Ordovician), yielding the typical Hirnantia fauna, has commonly been accepted as representing cool-water sediments deposited during the glacial interval in the Hirnantian Global Boundary Stratotype Section and Point (GSSP) region of South China. Recent investigation reveals that the uppermost carbonate-dominated part of this formation yields a warm-water rugose coral fauna with Silurian affinities at many localities of northern Guizhou Province, which substantially differs from the underlying cool-water fauna. This suggests that these carbonates were probably postglacial warm-water sediments, rather than having formed during the Hirnantian glacial interval as previously thought. Such a conclusion is consistent with the evidence from the associated brachiopod fauna, i.e., the Dalmanella testudinaria - Dorytreta longicrura community, which is similarly distinct from the underlying typical Hirnantia fauna. The sedimentological data show warm-water features at the same level (e.g., the presence of oolitic grains), also supporting this new interpretation. [ABSTRACT FROM AUTHOR]

Previous studies of conodonts suggested that the upper member of the Xiushan Formation (late Llandovery) corresponds to the Pterospathodus eopennatus Superbiozone, but no data were obtained from the lower member in the Xiushan area. In this study, the entire Xiushan Formation was resampled from the Datianba section in the Xiushan area of Chongqing City on the Yangtze Platform in South China. In total, 40 samples were collected and processed. Fifteen of these samples contained identifiable conodont specimens. The present study indicates that the lower member and main part of the upper member of the Xiushan Formation correspond to the Pterospathodus eopennatus Superbiozone, while the top of the upper member probably correlates with the Pterospathodus celloni Superbiozone. [ABSTRACT FROM AUTHOR]

Enigmatic millimetre-scale micro-concretions with pseudocrystal faces and dominated by green clay minerals occur in unfossiliferous siliciclastic mudstone of the Lower Ordovician (479.0-466.0 Ma) Tonggao Formation, South China. The fossil-free mudstone unit is associated with local biodiversity decline. The mineralogy and mineral chemistry of these concretions were unknown previously, and this study comprises a preliminary investigation. The concretions are dominated by Fe-rich phyllosilicate minerals including glauconite and clinochlore, with minor quartz and traces of magnetite. The textural relations between the micro-concretions and the surrounding matrix, and the preservation of original mudstone laminations within the concretions, point to an origin during early diagenesis. The mineralogy and chemistry of these concretions are consistent with an origin in a restricted, hypersaline, relatively deep-water environment, in accordance with stratigraphical and paleonotological data. These micro-concretions provide clues for a stressed environment with poor water circulation and anomalies of salinity and oxygen. [ABSTRACT FROM AUTHOR]