Facies and depositional processes of Lower Cretaceous carbonates, Danish Central Graben.

The Lower Cretaceous Tuxen (lower Hauterivian – upper Barremian) and Sola (upper Barremian Albian) Formations in the Danish Central Graben (North Sea) constitute one of oldest chalk successions recorded globally, but have received little attention with regards to sedimentary facies depositional processes. This study presents first comprehensive carbonate analysis succession, retrieved from seven drill cores Valdemar Adda Fields. A total 50 are identified, based on a continuum six lithologies ranging marlstone tuffaceous siltstone sandstone that display eight different structures or fabrics, two redox-associated lithological color variations (green red) Field. record: (i) bioturbation homogeneous sediment during fully oxygenated benthic conditions low sedimentation rates; (ii) similar process heterogeneous contrasts permitting visible burrows form, perhaps due rhythmic alternation between pelagic (clay-poor) hemipelagic (clay-rich) sedimentation; (iii) suspension settling dysoxic anoxic bottom-water conditions; (iv) patchy cementation shallow sea bed incipient hardground formation; (v) reworking bioclasts intraclasts by bottom wave-induced currents cohesive debris flows; (vi) pressure solution late burial diagenesis; (vii) shear deformation intense plastic unlithified limited lateral displacement; (viii) silicification diagenesis. distribution indicates active tectonism took place prior onset anoxia resulted deposition Munk Marl Bed, which Field was followed tectonic waning repeated anoxia. constituted basinal depocenter flanked east an early inversion high characterized condensation bypass. Fischschiefer Member represents return prevailing anoxia, consistent global records Aptian Oceanic Anoxic Event 1a (OAE-1a).