Onshore Jurassic of Scandinavia and related areas

摘要

Jurassic strata are extensively distributed in offshore areas of Scandinavia, but onshore exposures are mostly restricted to southern Sweden (Skane), the Danish island of Bornholm, East Greenland, northern Norway (Andoya) and Svalbard. The latest Triassic and Jurassic saw active tectonism in Scandinavia associated with the break-up of Pangaea and rifting in the North Atlantic region and the North Sea. Rifting and the gradual rise in sea level controlled the structural and sedimentological architecture of Scandinavian basins throughout the Jurassic. The Upper Triassic is represented by continental red beds (claystones and arkosic conglomerates) indicative of arid conditions (until the Norian) and by coal measures characteristic of humid conditions (in the Rhaetian). Early Jurassic sedimentation in the region was dominated by fluvial–estuarine systems. Basin subsidence combined with the supply of huge volumes of sediments led to the accumulation of thick sand units on vast coastal plains in the Early and Middle Jurassic. During the Late Jurassic, transgressions led to deposition of extensive marine mud, although sandstones are locally preserved. Paralic depositional environments prevailed during the Late Jurassic and into the Early Cretaceous in southern Scandinavia. Scandinavia hosts a rich Jurassic palaeontological record including fossil plants, sharks, dinosaur footprints, ammonites, belemnites, ichthyosaurs and pliosaurs. Miospores provide the primary tool for biostratigraphic subdivision and correlation of the continental Jurassic sediments, whereas ammonites, dinoflagellates and foraminifera are the main groups employed for marine biostratigraphy. However, much work remains to be completed to achieve a highly resolved zonation scheme that integrates both marine and terrestrial indices.