The DOUNCE (DOUshantuo Negative Carbon isotope Excursion) was marked by a significant shift in δ13Ccarb from ~+5‰ down to ~−12‰ in the upper part of the Ediacaran Doushantuo Formation of South China. As an equivalent event of the Shuram/Wonoka anomaly, the DOUNCE isthe largest negative δ13Ccarb excursion in geological history and denotes a global ocean oxygenation event (Figure 1). Consequently, it has been widely used as a chemostratigraphic tool for correlating the Ediacaran strata globally. Nonetheless, the DOUNCE exhibits variable stratigraphic expressions across sections and depositional environments, raising questions about its representation as a primary indicator of the Ediacaran seawater δ13C value. Such variability casts doubt on the reliability of the DOUNCE for global correlation, and its implications for the carbon cycle, oceanic oxygenation, and biological evolution during the Ediacaran period.
To elucidate the DOUNCE event as a synchronous global occurrence and a chemostratigraphic tool, Dr. Yinggang Zhang, a postdoc in Prof. Maoyan Zhu’s group at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, has compiled the “DOUNCEraq” database. This global-scale database currently includes 9375 valid δ13Ccarb analyses from 156 sections/boreholes documenting the DOUNCE/Shuram/Wonoka event (Figure 2).
The meta-analysis of DOUNCEraq highlights the global scope of the DOUNCE event and reveals the presence of an instant rise stage post the abrupt δ13Ccarb decline as an inherent feature of the DOUNCE pattern. Moreover, it also emphasizes the impacts of palaeolatitude, palaeocontinent, water depth, and lithology on the DOUNCE’s pattern and variability: (1) lower pre-DOUNCE δ13Ccarb values and smaller shift magnitudes within 30–0°N compared to the southern hemisphere; (2) compared to the shallower sections, deep-water sections exhibit lower pre-DOUNCE and DOUNCE nadir δ13Ccarb values with smaller shift magnitudes relative to shallower sections; (3) dolostones demonstrate lower pre-DOUNCE values, higher values at the DOUNCE nadirs, and smaller shift magnitudes compared to limestones (Figure 3). Such local impacts on the DOUNCE pattern provide important constraints on the causes of the DOUNCE event and could be explained within the DOC-oxidation hypothesis via regulating oxidants supply. Overall, the present meta-analysis enhances our understanding of the DOUNCE’s global stratigraphic expressions and provides important constraints on the DOUNCE causes.
This study was recently published under the title of “Meta-analysis of the DOUNCE event (Shuram/Wonoka excursion): Pattern, variation, causal mechanism, and global correlation” in the journal Earth-Science Reviews. This research was financially supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, China Postdoctoral Science Foundation, and the Jiangsu Funding Program for Excellent Postdoctoral Talent.
Article information：Zhang, Y. & Zhu, M., 2024. Meta-analysis of the DOUNCE event (Shuram/Wonoka excursion): Pattern, variation, causal mechanism, and global correlation. Earth-Science Reviews, 105000. https://doi.org/10.1016/j.earscirev.2024.105000
Figure 1. Ediacaran fossil ranges (panel A), key evolution events (panel B), and carbonate δ13C variations during the Ediacaran (panel C).
Figure 2. Palaeogeographic map ca. 570 Ma showing the approximate locations of all the DOUNCE entries. The location of each entry included in the DOUNCEraq is marked by a circle, colour-coded by water depth, and the entry numbers are collected and summarized in the rectangle of the palaeocontinent.
Figure 3. The magnitudes of the δ13Ccarb negative shift during the DOUNCE event. Entries are grouped by four grouping variables, in order: (A) palaeolatitude band, (B) palaeocontinent, (C) water depth, and (D) dominated lithology in the falling stage.
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