Polar record of Early Jurassic massive carbon injection

Abstract

Keywords: Oceanic Anoxic Event, Pliensbachian-Toarcian, carbon isotope excursion, Arctic 30 climate, sea level changes 31 2 The Toarcian Oceanic Anoxic Event (T-OAE) (ca. 182 mya, Early Jurassic) represents one of 32 the best-recognized examples of greenhouse warming, decreased seawater oxygenation and 33 mass extinction. The leading hypothesis to explain these changes is the massive injection of 34 thermogenic or gas hydrate-derived 13 C-depleted carbon into the atmosphere, resulting in a >3 35 per mil negative carbon isotope excursion (CIE), accelerated nutrient input and dissolved 36 oxygen consumption in the oceans. Nevertheless, the lack of a precisely dated record of the T-37 OAE outside low latitudes has led to considerable debate about both its temporal and spatial 38 extent and hence concerning its underlying causes. Here we present new isotopic and 39 lithological data from three precisely dated N Siberian sections, which demonstrate that mass 40 extinction and onset of strong oxygen-deficiency occurred near synchronously in polar and 41 most tropical sites and were intimately linked to the onset of a marked 6‰ negative CIE 42 recorded by bulk organic carbon. Rock Eval pyrolysis data from Siberia and comparisons 43 with low latitudes show that the CIE cannot be explained by the extent of stratification of the 44 studied basins or changes in organic matter sourcing and suggest that the negative CIE 45 reflects rapid 13 C-depleted carbon injection to all exchangeable reservoirs. Sedimentological 46 and palynological indicators show that the injection coincided with a change from cold 47 (abundant glendonites and exotic boulder-sized clasts) to exceptionally warm conditions 48 (dominance of the thermophyllic pollen genus Classopollis) in the Arctic, which likely 49 triggered a rapid, possibly partly glacioeustatic sea-level rise. Comparisons with low latitude 50 records reveal that warm climate conditions and poor marine oxygenation persisted in 51 continental margins at least 600 ky after the CIE, features that can be attributed to protracted 52 and massive volcanic carbon dioxide degassing. Our data reveal that the T-OAE profoundly 53 affected Arctic climate and oceanography and suggest that the CIE was a consequence of 54 global and massive 13 C-depleted carbon injection. 55 56 57

Trochamminaas opportunist foraminifera in the Lower Jurassic from north Siberia

“…This interpretation is congruent with the context of relative sealevel fall in the Arctic palaeobasin during the Margaritatus Chron and the early Viligaensis Chron (Nikitenko & Mickey 2004). In conjunction with this eustatic fall, abrupt climatic cooling due to the presence of glendonites (calcite pseudomorph after ikaite) has been evoked for north-eastern Siberia (Kaplan 1976;Suan et al 2011). A sea-level fall has likewise been interpreted for the PliensbachianÁToarcian boundary in other regions, as well as a drastic cooling event during the last ammonite The topmost 1.5 m of the Pliensbachian records an improvement of environmental features evidenced by an enhanced abundance of foraminifera excepting opportunist Trochammina.…”

“…A condensed Antiquum Zone of a few centimetres characterizes the succession. The Falciferum Zone is represented by the Kurung Member, with finely laminated black shales, high values of total organic carbon (TOC, 6 wt.%) and a negative carbon isotopic excursion (Suan et al 2011). …”

“…In general, the T-OAE is characterized by a record of organic-rich sediments associated with a negative excursion in d 13 C (e.g., Jenkyns & Clayton 1997;Rö hl et al 2001;Hesselbo et al 2007;Hermoso et al 2009;Suan et al 2011), in a context of exceptionally warm conditions (e.g., McArthur et al 2000;Svensen et al 2007;Gó mez & Goy 2011;Suan et al 2011) and sea-level rise (e.g., Haq et al 1987;Hallam 2001;Nikitenko 2008Nikitenko , 2009). For the T-OAE, the genera of calcitic and aragonitic foraminifera identified as opportunists (r-strategists) in the Tethys Realm would include Lenticulina, Eoguttulina and Reinholdella (Nocchi & Bartolini 1994;Boutakiout & Elmi 1996;).…”

Palaeoclimatic oscillations in the Pliensbachian (Early Jurassic) of the Asturian Basin (Northern Spain)

“…This is why many authors point to this period as one of the main candidates for the development of polar ice caps in the Mesozoic (Price, 1999;Guex et al, 2001;Dera et al, 2011;Suan et al, 2011;Gómez and Goy, 2011;Fraguas et al, 2012). This idea is based on the presence, in the Upper Pliensbachian deposits of different parts of the World, of (1) glendonites; (2) exotic pebble to boulder-size clasts; (3) the presence in some localities of a hiatus in the Late Pliensbachian-earliest Toarcian; (4) the results obtained in the General Circulation Models, and (5) the Late Pliensbachian palaeotemperatures calculated and the assumed pole-to-equator temperature gradient.…”

“…Especially relevant are the latest Pliensbachian−Early Toarcian climate changes, which have been documented in many sections from Western Europe (i. e. Saelen et al, 1996;McArthur et al, 2000;Röhl et al, 2001;Schmidt-Röhl et al, 2002;Bailey et al, 2003;Jenkyns, 2003;Rosales et al, 2004;Gómez et al, 2008;Metodiev and Koleva-Rekalova, 2008;Suan et al, 2008Suan et al, , 2010Dera et al, 2009Dera et al, , 2010Dera et al, , 2011Gómez and Arias, 2010;García Joral et al, 2011;Gómez and Goy, 2011;Fraguas et al, 2012), as well as in Northern Siberia and in the Artic Region (Zakharov et al, 2006;Nikitenko, 2008;Suan et al, 2011). The close correlation between the severe Late Pliensbachian Cooling and the Early Toarcian Warming events, and the major Early Toarcian mass extinction indi- cates that warming was one of the main causes of this faunal turnover (Kemp et al, 2005;Gómez et al, 2008;Gómez and Arias, 2010;García Joral et al, 2011;Gómez and Goy, 2011;Fraguas et al, 2012;Clémence, 2014;Clémence et al, 2015;Baeza-Carratalá et al, 2015).…”