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

Recent integrated studies of Mesozoic reference sections of the Anabar area (northern Middle Siberia, Laptev Sea coast) and the reinterpretation of all the previous data on a modern stratigraphic basis permit considerable improvement of the bio-and lithostratigraphic division and facies zoning of Jurassic and Cretaceous sediments in the region. Analysis of abundant paleontological data allows the development or considerable improvement of zonal scales for ammonites, belemnites, bivalves, foraminifers, ostracods, dinocysts, and terrestrial palynomorphs from several Jurassic and Cretaceous intervals. All the zonal scales have been calibrated against one another and against regional ammonite scale. Reference levels of different scales useful for interregional correlation have been defined and substantiated based on the analysis of lateral distribution of fossils in different regions of the Northern Hemisphere. It provides the possibilities to propose and consider parallel zonal scales within the Boreal zonal standard for the Jurassic and Cretaceous periods. A combination of these scales forms an integrated biostratigraphic basis for a detailed division of Boreal-type sediments regardless of the place of their formation and for the comparison with the international stratigraphic standard as far as a possible use of a set of reference levels for correlation.

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