Carbonate-platform response to the Toarcian Oceanic Anoxic Event in the southern hemisphere: Implications for climatic change and biotic platform demise

Zhong Han, Xiumian Hu (Corresponding Author), David B Kemp, Juan Li

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The Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) was a
profound short-term environmental perturbation associated with the largescale
release of 13C-depleted carbon into the global ocean-atmosphere
system, which resulted in a significant negative carbon-isotope excursion
(CIE). The general lack of characteristic T-OAE records outside of the
northern hemisphere means that the precise environmental effects and
significance of this event are uncertain. Many biotic carbonate platforms
of the northern hemisphere western Tethys drowned or shifted to nonskeletal
platforms during the early Toarcian. However, southern
hemisphere records of Toarcian carbonate platforms are rare, and thus the
extent and significance of biotic platform demise during the T-OAE is
unclear. Here we present high-resolution geochemical and sedimentological
data across two Pliensbachian-Toarcian shallow-water carbonate-platform
sections exposed in the Tibetan Himalaya. These sections were located
paleogeographically on the open southeastern tropical Tethyan margin in
the southern hemisphere. The T-OAE in the Tibetan Himalaya is marked by a
negative CIE in organic matter. Our sedimentological analysis of the two
sections reveals an abundance of storm deposits within the T-OAE
interval, which emphasizes a close link between warming and tropical
storms during the T-OAE event, in line with evidence recently provided
from western Tethyan sections of the northern hemisphere. In addition,
our analysis also reveals extensive biotic carbonate-platform demise by
drowning or changing to non-skeletal carbonates coincident with the onset
of the CIE. Taken together, our results suggest that rapid and pervasive
seawater warming in response to carbon release likely played a
significant role in sudden biotic carbonate platform demise, and
suppression/postponement of biotic platform re-development along the
whole tropical/subtropical Tethyan margin.
Original languageEnglish
Pages (from-to)59-71
Number of pages12
JournalEarth and Planetary Science Letters
Early online date7 Mar 2018
Publication statusPublished - 1 May 2018

Bibliographical note

We are grateful to Zhifei Liu for TOC and analyses at the Tongji University. We thank also Wei An, Bo Zhou and Shiyi Li for their assistance in the field, and Zhicheng Huang, Yiwei Xu and Weiwei Xue for their help in the laboratory, and Chao Chang, Tianchen He and Bolin Zhang for their helpful discussion. Hugh Jenkyns commented on a draft of the manuscript. We would also like to thank Editor Derek Vance, Christopher Pearce and two anonymous reviewers whose comments greatly improved the manuscript. This study was financially supported by the National Natural Science Funds for Distinguished Young Scholar in China (41525007) and the Chinese MOST 973 Project (2012CB822001). DBK acknowledges support of NERC Fellowship NE/I02089X/1. This is a contribution to the IGCP 655.


  • Toarcian Oceanic Anoxic Event
  • Tibetan Himalaya
  • carbon isotopes
  • storm deposits
  • carbonate platform
  • Southern Hemisphere


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