Search

This is the first record of Cornulites sp. as an epibiont on brachiopods from the middle Ashgill, Late Ordovician, of the South China Palaeoplate. Twenty-one cornulitid specimens were found attached to the brachiopod shells of Altaethyrella zhejiangensis and Ovalospira dichotoma. Both the location of cornulitids and their orientation on the brachiopod shells indicate a possible commensal relationship between the cornulitids and their hosts.

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. Des micro-concretions enigmatiques d'echelle millimetrique, avec des faces pseudocristallines et dominees par des mineraux argileux verts, se trouvent dans des mudstones siliclastiques non fossiliferes de la Formation de Tonggao de l'Ordovicien inferieur (479,0-166,0 Ma), dans le sud de la Chine. L'unite mudstone sans fossile est associee a un declin de la biodiversite locale. La mineralogie et la chimie des mineraux de ces concretions n' etaient pas connues anterieurement et la presente etude comprend une investigation preliminaire. Les concretions sont dominees par des mineraux phyllosilicates riches en Fe, incluant la glauconite et le clinochlore, avec un peu de quartz et des traces de magnetite. Les relations texturales entre les micro-concretions et la matrice environnante ainsi que la preservation des laminations originales du mudstone a l'interieur des concretions signalent une origine au debut d'une diagenese. La mineralogie et la chimie de ces concretions correspondent a une origine dans un environnement aqueux limite, hypersalin et relativement profond, ce qui concorde avec les donnees stratigraphiques et paleontologiques. Ces micro-concretions fournissent des indices qu'il s'agissait d'un environnement perturbe avec une mauvaise circulation d' eau et des teneurs anormales en sel et en oxygene. [Traduit par la Redaction], Introduction The Lower Ordovician (479.0-466.0 Ma) Tonggao Formation in Guizhou, South China (Fig. 1), contains abundant microconcretions of clay minerals, which occur in the largely unfossiliferous units of siliciclastic deposits [...]

High-resolution [delta][sup.13]C data of organic carbon from a continuous section of the Late Ordovician-Early Silurian reveal two positive [delta][sup.13]C excursions that are associated with the mass extinction in South China. The first stratigraphic [delta][sup.34]S measurements on pyrite tied to well-established biostratigraphy indicate a large perturbation of the sulfur cycle, consistent with major sea-level changes related to the glaciation. The elevated [delta][sup.34]S values of pyrites and a large, short-lived negative [delta][sup.34]S excursion of ~20[per thousand] associated with the decay of the glaciation suggest deep-water anoxia during the Hirnantian Stage, in contrast to the conventional view that the global oceans were oxygenated. We suggest that deep-water anoxia may have contributed to the Late Ordovician mass extinction in South China and possibly elsewhere.

Seventeen trilobite species belonging to 16 genera and 13 families are systematically documented from the Houping Formation (upper Dapingian-lower Darriwilian, Middle Ordovician) at the Datangkou and Dacao sections, Chengkou, northern Chongqing. Of these, a new species, Mioptychopyge chengkouensis sp. nov., is established and described. New morphological information is provided for previously known species on the basis of new specimens. Two trilobite associations based on faunal composition and dominant forms are distinguished from the Houping Formation, in ascending order, the Agerina Association (from the lower and middle members) and the Nileus-Illaenus Association (from the upper member). The Agerina Association lived in an inner shelf margin environment with carbonate substrate above storm wave base (<70 m deep), whereas the Nileus-Illaenus Association developed in a shallow outer shelf environment below storm wave base (>70 m deep), indicating a rise of relative sea level corresponding to the early Darriwilian transgression. The cluster and nonmetric multidimensional scaling analyses of the trilobites in the formation show that the fauna had a strong endemicity to South China and a close biogeographic connection with east Peri-Gondwana, especially Tarim, Annamia and central Iran. [ABSTRACT FROM AUTHOR]

Abstract: Brachiopods from the lower Tonggao Formation (Floian, late Early Ordovician) of Sandu, southeastern Guizhou Province, represent a deep-water benthic shelly fauna from the Jiangnan Slope facies of the South [...]

Abstract: Systematic and statistical study of brachiopods from the Dawan Formation of the Yichang area, western Hubei Province, central China, indicates that, at generic and specific levels, the α diversity [...]