Cambrian-Ordovician trace fossils of the Basissletta region, northeast Spitsbergen, Svalbard

Abstract

Trace fossils of the Cambrian–Ordovician sedimentary succession of the Basissletta region, northeast Spitsbergen, Svalbard, belong to three ichnoassemblages. The first one, composed of Monocraterion and Diplocraterion, belongs to the Skolithos ichnofacies and characterises sandstones of the Tokammane Formation (lower Cambrian: Terreneuvian) deposited in a shallow subtidal setting. The overlying carbonates with pseudomorphs after evaporites (uppermost part of Terreneuvian and the Cambrian Series 2) display abundant Balanoglossites. These beds were deposited in an oxygenated but hypersaline environment. The younger Ordovician carbonates of the Kirtonryggen Formation and the mixed carbonate-clastic deposits of the Valhallfonna Formation display a more diverse but poorly preserved trace fossil suite (Phycodes, Curvolithus, Planolites, Palaeophycus) typical of the archetypal Cruziana ichnofacies. Some parts of the succession are not bioturbated, and these are characterised by dark coloured fine-grained sediments with primary lamination. They were mostly deposited between the normal and storm wave base or below the storm wave base in oxic to anoxic environment.