Geochemistry of mudrocks in the Tertiary Central Basin of Spitsbergen, Norway - implications for provenance

Abstract

The Central Basin of Spitsbergen, Norway was developed by thrusting on the east side of the plate boundary between Greenland and Svalbard as an eastward migrating foreland basin.Sediment was derived during the Paleocene from a peripheral bulge east of the basin. Episodic uplift and erosion of the bulge repeatedly changed source area landward and basinward. During the Eocene, compressional tectonic regime became dominant between Greenland and Svalbard, and sediments source changed to the West Spitsbergen Orogen which was developing on the west side of the basin. In order to understand the relationship between provenance change and the tectonic history of the basin, geochemical analysis was performed for mudrocks of the Lower Paleocene Firkanten Formation, the Middle Paleocene Basilika Formation, and the Lower Eocene Frysjaodden Formation. In a discriminant function diagram using major element composition, Lower Paleocene mudrocks plotted in the field of recycled sedimentary provenance. Their significantly high SiO2 content (~81%) might be aresult of sedimentary recycling rather than extensive degree of weathering, considering that Spitsbergen was located in the arctic region and that CIA values (~78) are only slightly higher than those of PAAS (~75). Nearby Mesozoic and Paleozoic sedimentary rock terranes located east and north of the basin were the possible sediment source. Middle Paleocene mudrocks contain fresh feldspars, suggestive of crystalline source. They plotted on the boundary between felsic igneous and recycled sedimentary provenance field in a discriminant function diagram, with increased K2O and Na2O content, supported by the presence of distinctive peaks of K-feldspar and plagioclase on XRD data. Lower CIA values (~68) than Lower Paleocene mudrocks can also be interpreted as a result of provenance change from a sedimentary rock to a fresh igneous rock because of little climate change during the Paleocene. This result suggests that the bulge located cl