| Summary: | The most extensive Paleogene succession on Svalbard, in the Arctic north of Norway, is found in the Central Tertiary Basin of Spitsbergen. It consists of a clastic basin fill of mudstone, sandstone, coal and rare conglomerate beds. A coastal plain to shallow marine setting is suggested for the Late Paleocene Firkanten Formation, the lowermost unit of the Paleogene succession. This is the first comprehensive facies model, sequence stratigraphic analysis, and paleogeographic reconstruction of the Firkanten Formation, based on new borehole cores and field data. The facies analysis reveals that sedimentation occurred in a flat relief coastal plain environment with tidal, wave, and storm influence but only minor fluvial sediment input. Previous interpretations have described the Todalen Member, the lower part of the Firkanten Formation as delta plain deposits. The detailed sequence stratigraphic analysis and paleogeographic reconstruction show that the Firkanten Formation consists of parasequences combined into parasequence sets bounded by major flooding surfaces. The succession is dominated by aggradation in a step-wise transgressive setting. The general tectonic subsidence was at all times greater than any eustatic sea level fall since there are no relative sea level falls detected in the succession. The basin was formed as a depression in front of the West Spitsbergen Fold and Thrust Belt. Thick sections of coastal plain deposits of coal, carbonaceous shale, and other fine grained clastic sediments were deposited on the coastal plain, in mires and swamps that graded into tidally influenced lagoons. The coastal plain was protected from wave reworking by sandy barrier bars but was flooded during periods of increased relative sea level rise probably from eustatic sea level rise. The foreshore and shoreface deposits are characterised by fine grained sandstone and a few pebbly beds, making up the Endalen Member, the upper part of the Firkanten Formation. The foreshore was characterised by sandy barrier bars of long ...
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