T283 Greenhouse to Icehouse Transition: Global Events of the Devonian, Carboniferous, and Early Permian II

Wednesday, 7 November 2018
1:30 PM - 5:30 PM
Room 140

GLACIO-EUSTASY AND δ13C ACROSS THE MID-CARBONIFEROUS BOUNDARY RECORDED IN CARBONATE SLOPE SUCCESSIONS IN THE EASTERN PALEO-TETHYS OCEAN (SOUTH CHINA)

Paper number: T283-8
Program: Technical Sessions
Time: 3:25 PM – 3:40 PM

Authors

  • Xiaoxu Tian Presenting Author
    CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing
  • Xiaoxu Tian Presenting Author
    University of Science and Technology of China, Hefei
  • Jitao Chen
    CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing
  • Le Yao
    CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing
  • Keyi Hu
    Centre for Research and Education on Biological Evolution and Environment, Nanjing University, Nanjing
  • Yuping Qi
    CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing
  • Xiangdong Wang
    Centre for Research and Education on Biological Evolution and Environment, Nanjing University, Nanjing
  • Xiangdong Wang
    CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing

Abstract

A positive carbonate δ13C excursion (by ~1.5–3.0‰) has been reported across the mid-Carboniferous boundary (i.e., Mississippian–Pennsylvanian boundary, MPB) from Euramerican epicontinental seas, coincident with climate cooling and Gondwanan glaciation at that time. Most of these studied MPB successions were, however, deposited in shallow-water carbonate platforms and experienced repeated subaerial exposure of variable duration. Therefore, these strata contain significant hiatus and their carbonate δ13C values might have been altered during meteoric diagenesis. During the mid-Carboniferous, the South China Block was located in the eastern Paleo-Tethys Ocean near the paleo-equator, which contains well-preserved carbonate slope deposits across the MPB. In this study, we investigated three carbonate slope sections (Naqing, Narao, and Dianzishang) in order to better understand the glacio-eustasy and δ13C changes across the MPB.

Four lithofacies are defined in the studied sections, including thin-bedded lime mudstones, laminated wacke-to packstones, normally graded packstones, and slumps, collectively suggesting a carbonate slope setting. High-resolution conodont biostratigraphy shows a complete evolutionary lineage of conodonts across the MPB, which, together with lithofacies analysis, suggests near-continuous deposition. Immediately above the MPB, the occurrence of normally graded packstones (~75 cm thick) in the Naqing section, and slump deposits in the Narao (~2 m thick) and Dianzishang (~5 m thick) sections, indicates a significant sea-level fall. Carbonate δ13C records show a consistent value of ~3‰ below the MPB in the Naqing and Narao sections, and both sections have an obviously positive shift in δ13C across the MPB (by~0.5–1.0‰), which is comparable to the coeval positive δ13C excursions recorded in Euramerica. The relatively small-amplitude shift in δ13C would have resulted from intensified upwelling in the South China Block where the studied sections were located during the MPB glacial peak. Well-preserved slope carbonates as well as well-mixed seawater suggest that the carbonate δ13C values recorded in the South China Block may represent a mean value of global dissolved inorganic carbon in the ocean during the mid-Carboniferous.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-319893

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