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The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its aftermath. However, the age of the microbialite event remains controversial. New conodont collection across the Permian-Triassic (P-T) transition from Dajiang (Guizhou Province, South China) in this study enable us to discriminate four conodont zones, in ascending order, they are: Hindeodus parvus zone, Isarcicella lobata zone, Isarcicella isarcica zone and Hindeodus sosioensis zone. The age of microbialite in the P-T transition at the Dajiang Section is considered to be within the Hindeodus parvus zone and thus to clearly post-date the main extinction crisis. Reviewing the age of onset of microbialites throughout the Tethyan regions reveals two different ages: a Hindeodus changxingensis zone age is dominant in south-western and westernmost Tethys, whilst most other regions show microbialite deposition began in the Hindeodus parvus zone. Our investigation also indicates that two conodont changes occur at this time: an increase of hindeodid species immediately following a sequence boundary and the mass extinction, and a phase of extinction losses in the earliest Triassic Isarcicella isarcica zone during highstand development. [ABSTRACT FROM AUTHOR]

Examines the relation between central Guizou and Yichang uplifts present in central Guizou to western Hubei in China. Stratigraphic evidence of the uplifts; Mechanism of the central Guizou and Yichang uplifts.

Peloids are major contributors to modern and ancient limestones, although their origins are not yet comprehensively understood. Upper Permian to Lower Triassic carbonate successions are well preserved at the Bangeng area in Guizhou Province, South China, where microbialites (thrombolites), coccoidal microbes and peloids are preserved together. These peloids are classified into three types (Peloid-A, B, C) that typically occur together along with coccoidal microbes and restricted bioclasts in a variety of microenvironments. Peloid-A is most common and exhibits close relationship with coccoidal microbes. Peloid-A1 has spherical grain and a size range typical for coccoidal microbes (10–60 μm in diameter), whereas Peloid-A2 is marked by larger spherical and subrounded grains with diffuse margins, ranging from 70 to 200 μm in diameter. Peloid-A1 is in part produced by the complete micritic filling in coccoidal microbes by their metabolic activities, whereas Peloid-A2 is related to the calcification of a colony of coccoidal microbes by their metabolic activities, or simply to the aggregation of individual peloids and coccoidal microbes. Peloids of this type might also originate from other carbonate precipitation processes. Peloid-B is derived merely by micrite filling in ostracodes and gastropods skeletons, whereas Peloid-C is of micritized-bioclast origin. These peloidal origins do not explain those of all environments and ages. Peloids are polygenetic in origin, irrespective of the presence of coccoidal microbes. However, it is emphasized that the peloids formed after the end-Permian extinction are dominated by microbes related ones. Those kinds of peloids might have occurred repeatedly and predominantly, especially in severely deteriorated environments such as those after the end-Permian mass extinction. [Copyright &y& Elsevier]