A dolomitization event at the oceanic chemocline during the Permian-Triassic transition

The Permian-Triassic boundary (PTB) crisis caused major short-term perturbations in ocean chemistry, as recorded by the precipitation of anachronistic carbonates. Here, we document for the first time a global dolomitization event during the Permian-Triassic transition based on Mg/(Mg+Ca) data from 2...

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Bibliographic Details
Published in:Geology (Boulder) 2018-12, Vol.46 (12), p.1043-1046
Main Authors: Li Mingtao, Li Mingtao, Song Haijun, Song Haijun, Algeo, Thomas J, Wignall, Paul B, Dai Xu, Dai Xu, Woods, Adam D
Format: Article
Language:English
Subjects:
alkaline earth metals
Anoxia
Asia
Calcium
carbonate rocks
Carbonates
carbonatization
Chemical precipitation
Chemocline
chemostratigraphy
China
Crystals
depositional environment
Dolomite
Dolomitization
Dolostone
Extracellular
Far East
Fossils
geochemistry
Geographical distribution
Geology
Lower Triassic
Magnesium
Marine environment
Mesozoic
metals
Microorganisms
Ocean currents
Oceanic analysis
Organic chemistry
paleo-oceanography
Paleozoic
Permian
Permian-Triassic boundary
Physical geography
Precipitation
Ratios
Recording
Reduction
sed rocks, sediments
Sedimentary petrology
sedimentary rocks
Seismology
South China Block
stratigraphic boundary
Stratigraphy
Sulfate reduction
Sulfates
Sulphate reduction
Tethys
Triassic
Upper Permian
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Summary:The Permian-Triassic boundary (PTB) crisis caused major short-term perturbations in ocean chemistry, as recorded by the precipitation of anachronistic carbonates. Here, we document for the first time a global dolomitization event during the Permian-Triassic transition based on Mg/(Mg+Ca) data from 22 sections with a global distribution representing shallow- to deep-marine environments. Ten of these sections show high Mg/(Mg+Ca) ratios bracketing the PTB, recording a short-term spike in dolomite formation. The dolomite consists mainly of micron-scale anhedral to subhedral crystals that are associated with abundant fossilized bacterial bodies and extracellular polymeric substances, suggesting that dolomite precipitation was induced by microbial metabolic activity. Sections showing a dolomite spike at the PTB are widely distributed geographically, but mostly encountered in mid-shelf to upper-slope settings. Because the dolomitization event coincided with a rapid expansion of oceanic anoxia and high rates of sulfate reduction, we hypothesize that it was triggered by enhanced microbial sulfate reduction within the oceanic chemocline.
ISSN:0091-7613
1943-2682
DOI:10.1130/G45479.1