The Longyearbyen CO 2 storage project drilling and coring campaign in central Spitsbergen provided new insights on the shale-dominated Middle Jurassic to Lower Cretaceous Agardhfjellet Formation, which is the onshore counterpart to the Fuglen Formation and the prolific source rocks of the Hekkingen Formation in the Barents Sea. Logs of magnetic susceptibility, organic carbon content, organic carbon isotopes and XRF geochemistry on the cores, together with wireline logs, biostratigraphy and sedimentology, have made it possible to refine the interpretation of the depositional environment and to identify transgressive-regressive (TR) sequences. Several key sequence-stratigraphic surfaces are identified and suggested to be correlative in Central Svalbard, and four of them, although not necessarily chronostratigraphic, also to surfaces in the Barents Sea. Due to the nearly flat-lying thrust faults in the upper décollement zone of the West Spitsbergen Fold and Thrust Belt, there is some concern about the lateral correlation of the sequences within Spitsbergen. However, some of the TR sequence surfaces appear to be of regional importance and are recognised both onshore Svalbard and offshore on the Barents Shelf. The observations suggest a shallow-marine shelf depositional environment within an epicontinental sea with variable dysoxic, anoxic and oxic sea-floor conditions. The majority of the facies vary from outer shelf to transition zone or prodelta and lower shoreface/distal delta front. In one outcrop, proximal facies, i.e., delta front or middle shoreface, are recognised. In our study area the nearly 250 m-thick, fine-grained Agardhfjellet Formation is proposed to represent distal shoreline clinoforms and a precursor to the overlying forward-and southward-stepping wedge of the Valanginian Rurikfjellet Formation and the Barremian to Early Aptian Helvetiafjellet Formation.

No abstract

Abstract:The Late Jurassic Slottsmøya Member Lagerstätte on Spitsbergen offers a unique opportunity to study the relationships between vertebrate fossil preservation, invertebrate occurrences and depositional environment. In this study, 21 plesiosaurian and 17 ichthyosaur specimens are described with respect to articulation, landing mode, preservation, and possible predation and scavenging. The stratigraphic distribution of marine reptiles in the Slottsmøya Member is analysed, and a correlation between high total organic content, low oxygen levels, few benthic invertebrates and optimal reptile preservation is observed. A new model for 3D preservation of vertebrates in highly compacted organic shales is explained.

No abstract

The Agardhfjellet Formation (Middle Jurassic to lowermost Cretaceous) of Svalbard (Norwegian Arctic) is well known for its abundant and unique marine reptile fauna, of ichthyosaurs and plesiosaurs. In an attempt to reconstruct the palaeoecology and palaeoenvironment of the Agardhfjellet Formation, a study of the invertebrate fauna, geochemistry and stratigraphy was conducted. During this study numerous small vertebrate fossils were encountered. Only a few reports of Jurassic teleost from the Arctic were known previously, from the Agardhfjellet Formation on Svenskøya, Kong Karls Land, described as Leptolepis nathorsti, and at Lardyfjellet, East Spitsbergen. We describe more teleost material from the Kimmeridgian and Volgian of the Agardhfjellet Formation in central Spitsbergen and assign a new age, Kimmeridgian, to the original material. This new material also provides more information on the palaeoecology of the Jurassic of Svalbard, showing that fish were probably common in the pelagic fauna of central Spitsbergen together with the better known cephalopods, and could have been important elements of the diet of the marine reptiles.