2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 166-5
Presentation Time: 2:00 PM

BASAL TRIASSIC (GRIESBACHIAN) CONODONTS FROM THE MICROBIAL LIMESTONE IN THE NANPANJIANG BASIN, SOUTH CHINA


BROSSE, Morgane, Paläontologisches Institut und Museum, Universität Zürich, Karl-Schmid-Strasse 4, Zürich, CH-8006, Switzerland, GOUDEMAND, Nicolas, Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, Zurich, 8006, Switzerland, FRISK, Åsa, Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala, SE 752 36, Sweden, BAUD, Aymon, BGC, Parc de la Rouvraie 28, Lausanne, CH-1018, Switzerland, BAGHERPOUR, Borhan, Paläontologisches Institut und Museum, Universität Zürich, Karl Schmid-Strasse 4, Zürich, CH-8006, Switzerland, GUODUN Sr., Kuang, Research Institute, Guangxi Regional Geological Survey, Nanning, 530023, China and BUCHER, Hugo, Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland

New Early Triassic (Griesbachian) conodonts were obtained from a high-resolution sampling of rocks from within and above the microbial limestone of the Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). In Wuzhuan, the microbial limestone is part of the basal Luolou Formation, which overlies the latest Permian peri-reefal shallow water limestone. These diversified conodont faunas allow the construction of a well-resolved conodont biozonation after the end-Permian mass extinction. Our results indicate the presence of five local maximal horizons (LMHs) based on maximal associations of conodonts faunas. The FO of Hindeodus parvus is four metres above the unconformable boundary between the late Permian Heshan Formation and the Early Triassic Luolou Formation. The youngest LMH from within the microbialite is characterized by the association of Isarcicella lobata, Isarcicella staeschei, Isarcicella isarcica and Hindeodus bicuspidatus. This association is also recognized in deeper water facies (e.g. Shangsi section, Sichuan), thus permitting correlation across contrasting bathymetries and facies within the South China Block. The youngest LMH in Wuzhuan is found ca. 2.5 m above the top of the microbial limestone and is characterized by Hindeodus postparvus. Hence, the entire microbialite limestone was deposited within the Griesbachian. Comparison of Wuzhuan with other sections in the Nanpanjiang basin indicates that the drowning of the earliest Triassic microbial limestones is diachronous, suggesting an overrinding local tectonic control on subsidence and bathymetry.

Session No. 166

T195. Extreme Environmental Conditions and Biotic Responses during the Permian-Triassic Boundary Crisis and Early Triassic Recovery I
Monday, 20 October 2014: 1:00 PM-5:00 PM
215/216 (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.418
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