Naslov
The Jenkyns Event (early Toarcian OAE) in the Ordos Basin, North China

Autori
Jin, Xin ; Shi, Zhiqiang. ; Baranyi, Viktoria ; Kemp, David B. ; Han, Zhong ; Luo, Genming ; Hu, Jianfang ; He, Feng ; Chen, Lan ; Preto, Nereo

Izvornik
Global and Planetary Change (0921-8181) 193 (2020); 103273, 16

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Carbon isotopes ; Biomarkers ; Early Jurassic Lacustrine ; Palynostratigraphy

Sažetak
The early Toarcian (Early Jurassic) Oceanic Anoxic Event (T-OAE) or Jenkyns Event (~183 Ma) was marked by aglobally synchronous negative carbon-isotope excursion, large-scale organic carbon burial and widespreadoxygen depletion in the oceans. These features have been associated with volcanic activity of the Karoo andFerrar large igneous provinces. The Jenkyns Event is well investigated in the Tethyan Ocean, but its expressionin continental settings outside of Europe are still poorly understood. Here, the lacustrine Anya (AY) section in theNE Ordos Basin, North China, is studied for carbon-isotope geochemistry and palynology. Palynostratigraphyconstrains the age of the section to the Pliensbachian-Toarcian transition, and a positive trend inδ13C, inter-rupted by a pronounced negative carbon-isotope excursion, has been identified in bulk organic matter and long-chainn-alkanes. The negative excursion is the expression of the Jenkyns Event, and coincides with variable totalorganic carbon (TOC) content in lake sediments. The maximum TOC (~21.5%) values precede the most negativecarbon isotopes. A turnover from spore and seed fern-dominated palynological assemblages toClassopollissu-perabundance is coincident with the isotopic excursion and indicates clearly environmental perturbation.Biomarker data suggest that the organic matter was mainly sourced from higher plants. The magnitude of theToarcian excursion in the bulk organic matter of this section (~−12.5‰) is much larger compared to thattypically observed in marine and lake strata. Humidity-related fractionation effects in land plants and changes inplant groups might have contributed to the recorded magnitude. This magnitude is also larger than that of otherterrestrial records, and casts doubt on the use of terrestrial C-isotope data to constrain deep timepCO2.Nevertheless, ourfindings show that the Jenkyns Event is well-recorded in lacustrine facies of the Ordos Basin.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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