Askeladden Delta Sequence (Palaeocene) on Spitsbergen - sedimentation and controls on delta formation

Abstract

Because of its coal potential the basal Tertiary Firkanten Formation on Spitsbergen has received much attention. The formation is an offset stacked (overall transgressive) sequence comprising at least eight coastaydeltaic units each of which has a regressive character and is 10 to 30m thick. The lowermost coal-bearing unit (Todalen Member) represents deltas which were largely fluvial- and tide-dominated while the upper unit deltas (Endalen Member) were wave-dominated:One of the transitional deltaic units, the Askeladden Sequence, has been examined in some detail along depositional dip (-15 km) and strike (-55 km). This unit represents wave- (tide)dominated delta conditions, and two main facies associations are recognized: 1. Delta front/shoreline deposits (Facies Association I). 2. Delta plain/coastal plain deposits (Facies Association 11). Askeladden sequence accumulated in a shallow, low-gradient embayment (Nordenskiold Land subbasin) open to the south and southwest. Periodic, strong longshore currents caused a net northwards transport of sediment. Tidal range is considered close to the micro/meso-tidal boundary, and estimates of ancient wave regime indicate overall moderate wave conditions, suggesting that the extensive wavereworking of the delta front/shoreline sands is related to relatively slow rates of fluvial input. Climate and tectonics are considered important contributory controls on sedimentation.