Biostratigraphy and paleoceanography of the Cretaceous seaway between Norway and Greenland

Abstract The narrow seaway between Greenland and Norway, in Cretaceous time was over 1500 km long and 300+ km wide, and partly of bathyal water depth during Aptian through Campanian. It received a large volume of fine-grained, siliciclastic sediments, with intercalated, gravity-flow sandstone wedges. As a conduit for heat transport between the low latitudes and polar region, Atlantic watermasses particularly affected the eastern, Norwegian margin of this seaway. Despite its high-latitude setting, calcareous and few siliceous planktonic microfossils thus play an important role in regional stratigraphy and facies analysis, and a majority of fossil events correlate to NW European basins. The eastern margin sedimentary succession may be subdivided in several broad lithologic units: (1) Thin, multicolored, marly sediments of Hauterivian–Barremian age, with a shallow marine Falsogaudryina /nodosariid/ostracod assemblage; (2) Dark mudstones and minor sands, Aptian-early Cenomanian in age, with an upper bathyal, agglutinated assemblage, and monotypic Hedbergella floods; (3) Thick mudstone facies with thin, slope-apron turbidite sands, and an impoverished benthic/planktonic assemblage of late Cenomanian–Coniacian age, deposited in an upper bathyal, oxic/dysaerobic environment. Where Turonian sedimentation rates are low, a planktonic foraminiferal assemblage with Whiteinella , Hedbergella , Dicarinella , and Marginotruncana occurs; (4) Grayish, laminated mudstones, Santonian–Campanian in age, with local sands in the north, a low diversity, middle to upper bathyal benthic/planktonic foraminiferal assemblage, and an Inoceramus prisms and radiolarian/diatom flood; a Campanian agglutinated foraminiferal bloom also is known from the Atlantic oceanic realm; (5) More marly sediments of Maastrichtian age, with a low diversity planktonic/benthic foraminiferal assemblage. Using the distribution of 1755 foraminiferal and dinoflagellate microfossil events in over 30 exploration wells, a RASC (Ranking and Scaling) probabilistic zonation served as a template to build a Cretaceous zonal model with 19 assemblage and interval zones, including over 100 events. Variance analysis ranks 72 events according to reliability in correlation. Three new index taxa include Uvigerinammina una and Ammoanita globorotaliaeformis (Albian), and Fenestrella bellii (Campanian). Widespread planktonic flood events occur in late Albian through early Cenomanian, early–mid Turonian, late Santonian–earliest Campanian and mid-Maastrichtian, the result of northwards shifts of warmer water masses, and disruptions in water stratification in the dysaerobic basins. An earliest Cretaceous hiatus separates Jurassic from Cretaceous strata. Ongoing block-faulting, coupled to thermal subsidence and global sealevel rise increased water depth in Aptian–Albian time from neritic to bathyal, and created sand accommodation space in dysaerobic, restricted settings. In Cenomanian–Coniacian time, sedimentation rates in the `central basin' increased 10-fold, whereas paleo waterdepth did not deepen. This relatively brief (less than 10 m.y.) tectonic episode, resulting in deposition of deep water sands, is tentatively linked to stress re-orientation in the Rockall area. A widespread upper Maastrichtian–Danian hiatus, the result of `shoulder' uplift, reflects `break-up', prior to the onset of Paleogene seafloor spreading in the Norwegian Sea.