Depositional environments of Lower Cretaceous (Ryazanian-Barremian) sediments from Wollaston Forland and Kuhn O, North-East Greenland

Lower Cretaceous sediments from the Wollaston Forland-Kuhn O area in North-East Greenland have been analyzed for stable carbon isotopes, total organic carbon (TOC) content, and major and trace elements, aiming at a lithological characterization and reconstruction of the depositional environments. The marine sediments of Ryazanian-Barremian age were deposited in North-East Greenland directly after a major Late Jurassic - earliest Cretaceous rifting event. The Lower Cretaceous post-rift sediments are composed of fossiliferous calcareous mud- and marlstones assigned to the Albrechts Bugt (upper Ryazanian - Valanginian) and Rodryggen (Hauterivian) Members. The calcareous sediments are commonly sandwiched between black mudstones of Late Jurassic-earliest Cretaceous (Bernbjerg Formation) and mid Cretaceous (unnamed formation) age. The carbon isotope curves present the first record for the Lower Cretaceous (upper Ryazanian - Barremian) of North-East Greenland. The Ryazanian - Hauterivian sediments are characterized by a mixture of terrigenous detrital matter (quartz, clay minerals, heavy minerals) similar to average shale, with varying CaCO3 concentrations. The Barremian black mudstones on the contrary have lower CaCO3 and higher clay mineral contents. The deposition of the Bernbjerg Formation took place under anoxic bottom water conditions. The depositional environment of the Albrechts Bugt and Rodryggen Members is characterized by well-oxygenated sea-floor conditions, hemipelagic sedimentation of fine-grained terrigeneous detrital matter, and biogenic carbonate settling. After this relatively short interval of carbonate sedimentation under oxic conditions, bottom waters were affected by dysoxic conditions, responsible for the burial of organic matter in the Barremian.