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An ecological response to the Eocene/Oligocene transition revealed by the δ 13 C TOC record, Lanzhou Basin, NE Tibetan Plateau

Journal of Asian Earth Sciences, ISSN: 1367-9120, Vol: 159, Page: 74-80
2018
  • 10
    Citations
  • 0
    Usage
  • 11
    Captures
  • 0
    Mentions
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    10
    • Citation Indexes
      10
  • Captures
    11

Article Description

The Eocene/Oligocene (E/O) transition, corresponds to an abrupt global cooling, thought to have been one of the greatest temperature changes in the mid-Cenozoic Earth’s history. Sparse studies have successfully reconstructed the terrestrial ecological response to this temperature change. Here, we report results from the study of organic carbon isotopes (δ 13 C TOC ), together with n -alkanes biomarker analysis, in the Yongdeng Section, Lanzhou Basin, Northwest China, and discuss changes in δ 13 C TOC and their mechanisms. The results show that between 35.3 Ma and 31.0 Ma, δ 13 C TOC ranged from −26.72‰ to −21.27‰. The main change occurred at 33.4 Ma, when δ 13 C TOC became heavier by 3‰. At this time the long-chain n -alkane members (C 27, C 29 and C 31 ) were dominant, suggesting the most likely sources of organic matter were terrestrial plants. Combining these results with existing measurements of plant δ 13 C TOC and sporopollen data in adjacent areas, we infer that this change at 33.4 Ma might have been caused by an increase in gymnosperm content especially coniferous trees adapted to cold climates, which have a heavier δ 13 C TOC than that of the angiosperms, this would have been a response to the global cooling characteristic of this period.

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