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

Intensification of the lacustrine methane cycle during the Toarcian Oceanic Anoxic Event

“…-32 ‰ at around 18.3 m, but low concentrations prevent determination of other δ 13 C values in the upper part of the section. These negative carbon isotope excursions (CIEs) of the compound-speci c δ 13 C values occur between ~ 11 and 17 m, which coincide with the palynological age (Classopollis torosa Oppel Zone) and the main phase of the T-OAE 20,21 . The magnitude of the negative CIE is ca.…”

“…These inferred high rates of aerobic methane oxidation are most likely related to an intensi cation of methane production by methanogens in the lake sediments. The T-OAE triggered global warming 24,33 and globally widespread organic matter burial -with a TOC maxima > 20 wt.% in the Ordos Basin 20 . Although we cannot rule out an in uence of local thermogenic methane, it is likely that the accumulation of organic-rich sediments at the onset of the T-OAE (Fig.…”

Reduced Marine Molybdenum Inventory Related to Enhanced Organic Carbon Burial and an Expansion of Reducing Environments in the Toarcian (Early Jurassic) Oceans

“…A more accurate naming system will also need to include environmental change that occurred on land. The term carbon cycle perturbations (CCPs) is useful in that it is more inclusive and also encompasses environmental change that occurs in terrestrial environments and does not require changes in local redox (e.g., Jin et al., 2020; Liu et al., 2020; Xu et al., 2017). Environmental change across these global carbon cycle pertubations may also be applicable to similar intervals across the entire Phanerozoic as evidence for widespread organic matter‐rich shales is not required since the deep sea records of these events are generally not well preserved.…”

“…As a result, the T‐OAE produced a geochemically unique signature in the stratigraphic record, with one of its hallmark characteristics being the widespread deposition of OC‐rich sediments throughout many European successions and other locations around the world (e.g., Jenkyns, 1988, 2010; Them, Gill, Caruthers, et al., 2017; and others). The T‐OAE is classically defined by a large (∼2‰ to 12‰), globally observed, negative carbon isotope excursion (N‐CIE) that occurs in lower Toarcian marine and terrestrial sediments that may interrupt a somewhat cryptic broad positive CIE (e.g., Hesselbo et al., 2000; Ikeda et al., 2018; Jenkyns & Clayton, 1997; Jin et al., 2020; Liu et al., 2020, 2021; Them, Gill, Caruthers, et al., 2017; Them et al., 2018). It has recently been suggested, however, that globally significant increases of expanded bottom‐water anoxia began at the Pliensbachian‐Toarcian (Pl‐To) boundary, well before (and was sustained well after) the classically defined OAE (Them et al., 2018), concomitant with the beginning of the main phase of the multi‐phased extinction event (e.g., Caruthers et al., 2013).…”

Dinosaur extinctions related to the Jenkyns Event (early Toarcian, Jurassic)

“…A decrease of 13 C fractionation during photosynthesis in C3 plants, confirms a turn to arid climate for emerged areas of Western Tethys during the Jenkyns Event (Rodrigues et al, 2019(Rodrigues et al, , 2021Ruebsam et al, 2020a). Other changes in terrestrial ecosystems affected diversity and composition of land plant assemblages (Slater et al, 2019;Jin et al, 2020) and an increase of wildfires in some areas (Baker et al, 2017). Dinosaur faunas underwent remarkable evolutionary changes during the Triassic-Jurassic transition (Benton, 1993;Brusatte et al, 2008aBrusatte et al, , 2008bAllen et al, 2019;Klausen et al, 2020;Novas et al, 2021;Langer & Godoy, 2022).…”