Late Jurassic – Early Cretaceous marine deoxygenation in Northeast Greenland

Abstract

The Upper Jurassic – Lower Cretaceous interval represents a prolonged marine deoxygenation period particularly in the Boreal–Arctic basins, the controlling factors of which remain poorly understood. Two drill cores totaling >450 m cover the Kimmeridgian–Barremian succession in contrasting locations in an evolving half-graben system (basin center and near the footwall crest) in Wollaston Forland, NE Greenland; they provide an exceptional ∼20 myr long window into paleoenvironmental development and changes in redox conditions within a detailed tectonostratigraphic framework. Synthesis of a multidisciplinary dataset including sedimentology, inorganic and previously published organic geochemistry indicates that, despite continuous black mudstone accumulation from the Kimmeridgian to the Ryazanian, sea floor anoxia was intermittent in the Kimmeridgian, whereas more sustained anoxia/euxinia occurred in the middle Volgian – early Ryazanian. Correlation to reported contemporaneous successions along the Greenland margin, indicate that protracted rifting and generation of localized sea-floor topography were among the major drivers both of sea-floor deoxygenation and current funneling and amplification during the Jurassic–Cretaceous transition. Consequently, distribution of seaway current activity and dysoxia, anoxia and euxinia varied spatially, allowing fully oxygenated and anoxic pockets to coexist. Supplementary material: [S1: Facies table, S2: Summary of geochemistry data, S3: Geochemistry raw data, S4: Sedimentological log from Store Koldewey] is available at https://doi.org/10.6084/m9.figshare.c.6442539