Upper Carboniferous cyclic shelf deposits, Kapp Kåre Formation, Bjørnøya, Svalbard: response to high frequency, high amplitude sea level fluctuations and local tectonism

Abstract

The upper Bashkirian-Moscovian Kapp KIre Formation is well-exposed in coastal cliff sections along the west coast of Bjørnøya, Svalbard. It is composed of stacked cycles of nixed siliciclastics and carbonates in the lower Bogevika Member and of cyclic shelf carbonates in the overlying Efuglvika Member. The uppermost Kobbebukta Member consists of shelf carbonates and syntectonic conglomerates and sandy turbidites. The shift in cycle types reflects an overall transgression of the region during the Moscovian combined with renewed tectonic activity and uplift of eastern Bjørnøya during the late Moscovian. Twelve carbonate facies and 6 siliciclastic facies are distinguished. The carbonate facies range from intertidal dolomitic mudstones with pseudomorphs after gypsum to subwavebase, intensely bioturbated wackestones. Most carbonates are deeper subtidal facies and shallow marine carbonate facies are only common in the transgressive part of mixed siliciclastic-carbonate cycles of the Bogevika Member. Incorporating the effects of high amplitude, high frequency glacioeustacy and active extensional tectonism, a dynamic model is developed to explain the spatial variability of facies observed within the Kapp Kke Formation. Observations from Bjørnøya are placed within the context of the regional structural and stratigraphic framework so that significance of the study to ongoing exploration efforts in the Barents Sea can be evaluated. Most important, our observations suggest that dolomitized, porous carbonate buildups are most likely to be found in the upper Moscovian succession in areas where accommodation space increased temporarily due to local tectonism.