210 D17. Recent Advances in Sedimentology and Stratigraphy

Wednesday, 18 October 2023
8:00 AM - 12:00 PM
329

APPLICATION OF CARBON ISOTOPE STRATIGRAPHY FOR REGIONAL CORRELATION OF NON-MARINE JURASSIC-CRETACEOUS TETORI GROUP IN JAPAN

Paper number: 210-14
Program: Technical Sessions
Time: 11:05 AM – 11:20 AM

Authors

  • Mayuko Kamimura Presenting Author
    Kanazawa University, Graduate school of Natural Sciene and Technology, Kanazawa, Ishikawa
  • Koichi Hoyanagi
    Institute of Science Shinshu University, Matsumoto, Nagano
  • Takashi Hasegawa
    Faculty of Geoscience and Civil Engineering, Kanazawa University, Kanazawa, Ishikawa

Abstract

Regional correlation of non-marine strata is much challenging comparing with marine one due to lithological lateral variations and the absence of reliable index fossils despite its crucial importance to understand terrestrial environmental transitions. In this study, we applied stable carbon isotope (δ13C) stratigraphy for preliminary regional correlation of the Tetori Group, a Late Jurassic to Early Cretaceous shallow marine and non-marine siliciclastic succession in Japan. Three sections of the Tetori Group were examined: Tamodani (26 horizons), Shokawa (47 horizons), and Itoshirogawa Logging Road (13 horizons).

δ13C curve was constructed for each section. Three samples per horizon were collected and analyzed from the Tamodani and Itoshirogawa Logging Road sections to realize horizontal variation in the δ13C values. The stratigraphic fluctuation of δ13C in the Tamodani section ranged within ~3.8‰, while the Shokawa section exhibited ~2.5‰. The Itoshirogawa Logging Road section displayed a fluctuation range as large as ~4.0‰. Majority of the values fell within the range between -23‰ and -24‰ for each section.

A notable character in δ13C curves was the high values exceeding -22‰ in the upper parts of the Tamodani and Itoshirogawa Logging Road sections coupled with underlying low values of -25‰ in the middle parts of the Tamodani and Itoshirogawa Logging Road sections. The upper part of the Shokawa section also showed similar low values.

After this study, we learned following issues are fundamental for further study of non-marine sequence including correlation with δ13C curve: (1) Collecting at least three samples per horizon to evaluate horizontal variation and track stratigraphic fluctuation of δ13C values; (2) Selecting multiple sections encompassing longer time-stratigraphic interval would be beneficial for capturing global δ13C trends; (3) Identifying conspicuous δ13C events as correlation markers would be crucial. We perceived the importance of information from other correlation techniques (i.e. radiometric dating and paleomagnetism) for international correlation and age identification. The application of δ13C stratigraphy to non-marine sequences in other regions, particularly continental East Asia, is eagerly awaited for regional and global correlation.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-392362

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