Late Jurassic and Early Cretaceous fine-grained siliciclastic formations from key Arctic localities have been analysed. In this study their mineralogical and geochemical (major, trace, REE elements) affinities have been compared and put into a sedimentological context. Compared to other regions the studied sections represent more ventilated and less anoxic conditions than other Late Jurassic black shale formations. The overall mineralogical and geochemical composition is rather similar in the studied sections. This homogeneous appearance reflects the well-developed circulation of the shallow epicontinental sea of the region. The suspended material was repeatedly homogenised before final deposition and appears today to be relatively similar in composition over this wide area. In contrast, a basaltic source rock component (Siberian Traps?) is evident in the Siberian section (Nordvik). On large parts of the sea floor anoxic conditions prevailed, and in the Nordvik region this, in combination with slow and very fine-grained clastic sedimentation and high algal production, resulted in the formation of phosphate concretions.
Fine-grained epicontinental Arctic sedimentation – mineralogy and geochemistry of shales from the Late Jurassic-Early Cretaceous transition