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TitleIntensive ocean anoxia and large d13Ccarb perturbations during the Carnian Humid Episode (Late Triassic) in Southwest China
AuthorZhang, Z T; Joachimski, M M; Grasby, S EORCID logo; Sun, Y
SourceGlobal and Planetary Change vol. 217, 103942, 2022 p. 1-11,
Alt SeriesNatural Resources Canada, Contribution Series 20210592
Mediapaper; on-line; digital
File formatpdf
AreaSouth China; Wolonggang; China
Lat/Long WENS 105.2500 105.5000 25.7500 25.5000
Subjectsenvironmental geology; geochemistry; Nature and Environment; pyrite; carbon isotopes; carbonate; Carnian; climate; Triassic
Illustrationslocation maps; photographs
ProgramGEM2: Geo-mapping for Energy and Minerals Western Arctic Sverdrup Basin
Released2022 10 04
AbstractThe Carnian Humid Episode (CHE) represents a dramatic dry to wet climate transition in the Late Triassic. Manifestations of this climate shift and its associated biological and environmental responses are not fully understood. Here, we carried out carbonate carbon isotope, trace metal, and pyrite framboid analyses at Wolonggang in southwest China to trace palaeoenvironmental changes during this critical interval. The CHE at Wolonggang is marked by the development of fine laminated carbonaceous siltstones and black shales overlying the intensely bioturbated Zhuganpo limestone deposited in the latest Julian 1. This lithological change is accompanied by two negative d13Ccarb excursions, a strong enrichment of redox-sensitive trace metals U and Mo, and the development of abundant small pyrite framboids with an average diameter < 5 um. The sedimentary and geochemical evidence collectively suggest a sharp decrease in carbonate production and a major carbon cycle disturbance, coinciding with the onset of intense ocean anoxia and the mass mortality of burrowing faunas. Unlike other areas in the western Tethys, the aftermath of the CHE at Wolonggang is characterized by long-lasting ocean anoxia, with weak carbonate production persisting at least to the late Tuvalian. This is evidenced by the deposition of finely laminated silty carbonates, marls, and carbonaceous siltstones with rare benthic fossils in the Wayao Formation. Our study suggests that anoxic-euxinic environments widely developed along the southwest margins of the Yangtze Platform and in the Nanpanjiang Basin, probably contributing to the loss of marine faunas during the CHE.
Summary(Plain Language Summary, not published)
This paper examines an event known as the Carnian Humid Episode that was a period of climate warming and enhanced rain fall that caused dramatic changes in patterns of sediment deposition. Understanding this time can provide insight into impacts of global warming as well as help develop models on resource deposits, specifically shales rich in critical minerals.

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