Trace fossils are ancient fossilized structures created by the activities of organisms, such as tracks, trails, burrows, and borings. These fossils, known as ichnofossils or trace fossils, provide valuable insights into past sedimentary environments and can be used to reconstruct the paleoenvironment.
Turbidity currents play a crucial role in mixing stratified water bodies in oxygen-deficient basins. These density flows transport sediment and oxygen-rich water from shallow to deep basins, leading to significant changes in the chemistry and oxygen level of the deep-basin waters. However, direct evidence of turbidity current-induced oxygenation events in oxygen-deficient basins is scarce in the geological record.
In a recent study published in the Geological Journal, Assoc. Prof. Zheng Quanfeng and Prof. Cao Changqun from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS) conducted high-resolution sedimentological and ichnological studies on the upper member of the Talung Formation in China. The study aimed to reveal the dynamic process of turbidity current-induced benthic-marine oxygenation through the analysis of sequential ichnocoenoses.
The researchers observed that the studied interval consisted mainly of black shale sedimentation, indicating anoxic benthic marine conditions. However, within this interval, there were also rapid event sedimentation of fine-grained calciturbidite, which exhibited intense bioturbation and abundant primary burrows.
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Fig. 2 Vertically polished slab (a) and line drawing (b) of the studied interval. Credit: NIGPAS
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Fig. 3 Schematic drawings showing the ichnocoenosis succession and the dynamic process of turbidity current–induced benthic-marine oxygenations. Credit: NIGPAS
Based on their analysis, the researchers identified three successive ichnocoenoses within the calciturbidites. The early-phase Thalassinoides/Scolicia ichnocoenosis represented the climax of turbidity-induced oxygenation and had the highest oxygen level. The later-phase Planolites-Zoophycos ichnocoenosis indicated a relatively more reducing bottom-water condition. The latest-phase Zoophycos ichnocoenosis represented the lowest oxygen level.
The study demonstrated the effectiveness of turbidity currents in oxygenating bottom waters in oxygen-deficient basins and highlighted their significant impact on benthic communities.
More information: Quan‐Feng Zheng et al, Dynamic process of turbidity current‐induced benthic‐marine oxygenation evidenced by sequential ichnocoenoses: An example from a Late Permian oxygen‐deficient basin, Geological Journal (2023). DOI: 10.1002/gj.4837
Citation: Ichnocoenoses reveal dynamic process of turbidity current–induced benthic-marine oxygenation (2023, July 28) retrieved 29 July 2023 from https://phys.org/news/2023-07-ichnocoenoses-reveal-dynamic-turbidity-currentinduced.html
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