Late Palaeozoic sedimentology and stratigraphy of NE-Svalbard

Changes in climate and sea level and their effects on depositional processes, environments and biotic associations will be monitored in a number of lithostratigraphical sections. Outcrop investigations are combined with facies studies (interpretation of sedimentary structures, lithologies, microfacies), age determinations (fusulinids, conodonts, palynology) and geochemical analyses (13C/18O, 87Sr/86Sr, TOC, XRF, XRD). Correlated to the existing stratigraphic scheme of central Spitsbergen, the results are expected to form an important contribution to the understanding of the overall palaeogeographic development of Svalbard during the Carboniferous and Permian.

During the Late Palaeozoic, the depositional area of Svalbard was located at the northern margin of Laurasia and drifted from a subtropical location (ca. 25°N) to a more boreal position (ca. 50° N). During the continuous northward drift, changes in the depositional environments and processes, sea level and biotic associations are recorded in the strata.

During the Early Carboniferous, the palaeogeography of Spitsbergen was marked by a number of depressions. Terrestrial deposits of the Billefjorden Group (Tournaisian-Viséan) are preserved mainly in later formed half-graben structures, uncomfortably overlying Devonian Old Red Sandstone deposits or older basement rocks. They consist of fluvial, lacustrine and coal-bearing swamp deposits, formed under a humid, equatorial climate.

Part of the investigation will focus on the stratigraphy and sedimentology of basal sediments with uncertain age and affiliation, which crop out locally in the Lomfjorden area. Age determinations will be carried out by palynology. Facies investigations and geochemical analyses should reveal the depositional history of the strata and enable the amalgamation of the successions with the established lithostratigraphic scheme of Svalbard.

In the Late Carboniferous, a general sea-level rise was accompanied by the transition to a semi-arid climate and the onset of extensional tectonics. A number of north-south trending half-grabens developed all over Spitsbergen. The mixed siliciclastic-calcareous sediments of the Gipsdalen Group (Serpukhovian-Artinskian) comprise local terrestrial red beds, which laterally and vertically grade into marginal-marine evaporites (sabkha sequences) and shallow-marine shelf carbonates rich in fusulinids, corals, brachiopods and gastropods. In connection with the progressive transgression, faulted margins of positive areas were gradually submerged and carbonates were deposited with an unconformity upon basement rocks.

The project concentrates on the basal red-bed successions, which are exposed on Nordaustlandet (Hårbardbreen Formation) and in the Lomfjorden area (? Malte Brunfjell Formation), as well as on carbonate platform sequences of the upper part of the group (Wordiekammen, Gipshuken formations). Facies investigations and palaeoecological studies on fusulinids, enabling a precise biostratigraphic resolution of the upper part of the strata, are expected to reveal further insight into the timing of the transgression, as well as the sedimentary and palaeogeographic development.

After a short hiatus, the sediments of the Tempelfjorden Group (Artinskian-Kazanian) were deposited subsequent to another major transgression, accompanied by a transition to temperate climates, resulting in a fundamental facies change. Under stable platform conditions, a uniform sedimentation of cool-water carbonates, cherts and siliciclastics, some of which were extensively silicified, occurred. The biota changed from chlorozoan- to foramol-related biotic associations, dominated by brachiopods, bryozoans and siliceous sponges. Basal bioclastic limestone breccias (Vøringen Member) are interpreted as shoreline deposits, formed with the transgression of barrier sequences over the warm-water platform- and sabkha-sequences of the Gipsdalen Group. Upwards, the sediments grade into spiculitic shales, glauconitic siltstones to sandstones and cherts, deposited in low-energy, oxygenated-bottom environments below the wave base.

Detailed facies and palaeontological investigations are expected to clarify the lithostratigraphic arrangement of the group and the correlation of local, so far informal members. Additionally, climatic and sea-level fluctuations will be recorded in order to resolve the sequence stratigraphic architecture of the strata.