Lin Mu

Calibrating the End-Permian Mass Extinction

High-precision geochronologic dating constrains probable causes of Earths largest mass extinction. The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ13C over 90,000 years, and coincided with a δ13C excursion of −5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.

EARLY INDUAN (EARLY TRIASSIC) CEPHALOPODS FROM THE DAYE FORMATION AT GUIDING, GUIZHOU PROVINCE, SOUTH CHINA

Abstract An abundant and diverse Late Griesbachian (Early Induan) Wordieoceras-dominated cephalopod fauna occurs in the lower part of the Daye Formation at the Wenjiangsi section, Guiding County, Guizhou Province, South China. The cephalopod fauna consists of 17 species belonging to 10 genera, including two nautiloid species and 15 ammonoid species representing the families Ophiceratidae, Proptychitidae, Meekoceratidae, and Khangsariidae. One genus and five species are new: Vishnuites wenjiangsiensis, Pseudovishnuites guidingensis, Wordieoceras guizhouensis, Gyrophiceras subplicatum, and Hubeitoceras? Wangi.

Roadoceras (Permian Ammonoidea) from the Qubuerga Formation in the Mt. Everest Area in Southern Tibet

Abstract The Quberga Formation of the Selong Group in the Mt. Everest area in southern Tibet was previously assigned to Artinskian or Kungurian in age mainly based on an occurrence of an ammonoid species Uraloceras xizangense. However, a restudy on the previously and subsequently collected specimens of Uraloceras xizangense suggests that this species is re-assignable to Roadoceras xizangense, and therefore probably indicates an age between late Capitanian and early Wuchiapingian for the lower part of the Qubuerga Formation. Temporally, Roadoceras ranges from late Wordian to Wuchiapingian and was palaeobiogeographically distributed in the Palaeoequatorial and bi-temperate regions.