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

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The Jurassic/Cretaceous transition was accompanied by significant changes in palaeoceanography and palaeoenvironments in the Tethyan Realm, but outside the Tethys such data are very scarce. Here we present results of a study of the most complete section in the Panboreal Superrealm, the Nordvik section. Belemnite d 18 O data show an irregular decrease from values reaching up to '1.6 in the Middle Oxfordian and from '0.8 to (1.7 in the basal Ryazanian, indicating a prolonged warming. The biodiversity changes were strongly related to sea-level oscillations, showing a relatively low belemnite and high ammonite diversity during sea-level rise, accompanied by a decrease of the macrobenthos taxonomical richness. The most prominent sea-level rise is marked by the occurrence of open sea ammonites with Pacific affinities. Peak abundances of spores and prasinophytes correlate with a negative excursion in organic carbon d 13 C near the J/K boundary and could reflect blooms of green algae caused by disturbance of the marine ecosystem.

Реконструирована палеогеография Западной Сибири в мелу. Приведены и детально описаны па-леогеографические карты для отдельных веков мелового периода, которые отражают основные этапы формирования Западно-Сибирского осадочного бассейна. Представленный авторами набор карт пост-роен исходя из модели лавинного бокового заполнения в волжско-барремское время относительно глу-боководного морского бассейна в регрессивный этап крупного седиментационного цикла. Реконструи-рован рельеф и распределение внешних источников сноса терригенного материала. Палеогеография, мел, клиноформы, лавинная седиментация, Западно-Сибирский осадочный бассейн. For paleogeographic reconstruction of the West Siberian basin during the Cretaceous we used a set of pa-leogeographic maps, which were compiled for the main epochs of the Cretaceous period. The paleogeographic maps presented in this study suggest progradational fi lling of the deep basin with avalanche-type sedimentation during Volgian-Barremian regression. The paleorelief and provenance of terrigenous sediments were reconstructed. Paleogeography, Cretaceous, clinoforms, avalanch-type sedimentation, West Siberian sedimentary basin ВВЕДЕНИЕ Ранее была рассмотрена палеогеография юры [Конторович и др., 2013]. Юрский комплекс отло-жений Западной Сибири уникально обогащен, особенно породы волжского века (баженовская свита) органическим веществом и являлся главным генератором нефти и газа в Западно-Сибирском бассейне. В перекрывающем его меловом осадочном комплексе сформированы основные резервуары, содержа-щие значительную часть ресурсов нефти и газа этого уникального осадочного бассейна. При формиро-вании залежей углеводородов в меловом комплексе решающую роль играли процессы вертикальной миграции. Палеогеография мелового периода предопределила распределение в разрезе мела проницае-мых комплексов и флюидоупоров и в значительной степени их качество. Настоящая работа посвящена палеогеографии мелового периода. Юрский период в истории Земли закончился крупной (глобальной) трансгрессией. К концу волж-ского века на территории Западно-Сибирского осадочного бассейна сформировался глубоководный эпиконтинентальный морской бассейн. Максимальные глубины этого моря, по разным оценкам, дости-гали от 400 до 800 м