The Wilhelmøya Subgroup (Norian-Bathonian) is considered as the prime storage unit for locally produced CO 2 in Longyearbyen on the Arctic archipelago of Svalbard. We here present new drillcore and outcrop data and refined sedimentological and sequence-stratigraphic interpretations from western central Spitsbergen in and around the main potential CO 2-storage area. The Wilhelmøya Subgroup encompasses a relatively thin (15-24 m) siliciclastic succession of mudstones, sandstones and conglomerates and represents an unconventional potential reservoir unit due to its relatively poor reservoir properties, i.e., low-moderate porosity and low permeability. Thirteen sedimentary facies were identified in the succession and subsequently grouped into five facies associations, reflecting deposition in various marginal marine to partly sediment-starved, shallow shelf environments. Palynological analysis was performed to determine the age and aid in the correlation between outcrop and subsurface sections. The palynological data allow identification of three unconformity-bounded sequences (sequence 1-3). These sequences record intermittent deposition in the Early Norian, Early-Middle Toarcian, and Late Toarcian-Aalenian, interrupted by extended periods of erosion, bypass and/or non-deposition. The stratigraphically condensed development of the Wilhelmøya Subgroup in western central Spitsbergen is interpreted to be the result of very low subsidence rates coupled with a physiographic setting characterised by a very gentle depositional gradient. This facilitated rapid shoreline shifts in response to even relatively modest variations in relative sea level with considerable influence on the resulting depositional patterns. We present a revised depositional model for the regionally distinct Brentskardhaugen Bed at the top of the Wilhelmøya Subgroup involving condensation and partial reworking of a series of Upper Toarcian-Aalenian, high-frequency sequences. Coarse-grained extraformational fractions observed within conglomerates of the Wilhelmøya Subgroup are suggested to have been supplied from uplifted and exposed margins to the west (northern Greenland) and north (northern Svalbard).

1985: The Wilhelmeya Formation (Upper Triassic-Lower Jurassic) at Bohemanflya, Spitsbergen. Polar Research 3 n.s., 155-165. An 18.5 m thick shale sequence of Norian-Rhaetian age is described from the Bohemanflya-Syltoppen area (north of Isfjorden. central Spitsbergen). Lithological, petrographical and palynological analyses show that the sequence represents a marginal development of the lower part of the Wilhelmeya Formation. The depositional history at the Triassic-Jurassic transition is discussed in the light of this new evidence. The Wilhelmeya Formation was probably deposited during a weak marine transgression over an area of low relief. Low sediment supply and current and wave reworking of the sediments characterized the depositional conditions.

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Core samples from Well 33/9‐3, Norwegian North Sea, have been analysed sedimentologically, palynologically and micro‐paleontologically. The cores cover the Toarcian Drake Member of the Dunlin Formation, and nearly the whole thickness of the Middle Jurassic Brent Formation. The Drake Member is characterized by pro‐deltaic depositional conditions. In the Brent Formation, five members are recognized (from below): the Broom, Rannoch and Etive Members represent distributary mouth bar facies; while the Ness and Tarbert Members are recognized as interdistributary bay fill sequences. The composition of the kerogen assemblages is controlled by the changing energy regimes of the different depositional facies. Terrestrial plant débris are dominant throughout the studied interval. Marine palynomorphs are present in the Drake Member and in the lower part of the Broom Member. The development of rich, arenaceous foraminiferal assemblages in the Drake Member are interpreted as a response to shallow, pro‐deltaic conditions. Calcareous foraminifera constitute only a small, accessorial part of these assemblages.

A quantitative study of palynomorphs and palynodebris in a shallow core from the central part of Bjørnøyrenna, western Barents Sea, is presented. The core could be subdivided into a lower part characterized by a complete dominance of reworked plant debris of Mesozoic age and an upper part with considerable input of first cycle algal debris and dinoflagellate cysts. Two hypotheses are suggested to explain this radical change in palynodebris composition. Either it represents a transition from a situation with permanent ice to normal marine conditions, or the absence of first cycle plant debris in the lower part of the core is caused by a masking of this component due to extremely high input of glacially eroded material from the bordering shallow parts of the Barents Sea. The present study shows that palynodebris analysis may contribute important information to the study of composition and depositional environment of Quaternary marine sediments in the area.