Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian-Spathian boundary in the Bac Thuy Formation, Vietnam

Toshifumi Komatsu, Reishi Takashima, Yasunari Shigeta, Takumi Maekawa, Huyen Dang Tran, Tien Dinh Cong, Susumu Sakata, Hung Doan Dinh, Osamu Takahashi

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

The Smithian-Spathian boundary is indicated by the first occurrence of the ammonoid Tirolites cf. cassianus in the Olenekian Bac Thuy Formation, northeastern Vietnam. The boundary is intercalated within organic-rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the An Chau and Nanpanjiang Basins on the South China Block. In Lang Son area, three conodont zones, Novispathodus ex gr. waageni, Novispathodus ex gr. pingdingshanensis, and Icriospathodus collinsoni, are recognized in the formation. The Smithian-Spathian boundary is intercalated within N. ex gr. pingdingshanensis conodont Zone. The positive excursion inδ13C with values increasing from around -2.3‰ to +5.7‰ was recorded in the uppermost Smithian Xenoceltites variocostatus ammonoid beds and N. ex gr. pingdingshanensis conodont Zone. The δ13C values decrease across the Smithian-Spathian boundary. These δ13C isotopic patterns are correlated with well-known positive excursions around the Smithian-Spathian boundary globally.

Original languageEnglish
Pages (from-to)65-74
Number of pages10
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume454
DOIs
Publication statusPublished - 2016 Jul 15

Keywords

  • Ammonoid
  • Anoxic to dysoxic facies
  • Biostratigraphy
  • Carbon isotopic excursion
  • Conodont
  • Lower Triassic
  • Smithian-Spathian boundary

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

Fingerprint Dive into the research topics of 'Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian-Spathian boundary in the Bac Thuy Formation, Vietnam'. Together they form a unique fingerprint.

Cite this