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Foraminiferal distribution and biofacies of Late Triassic to Middle Jurassic sediments of the Kapp Toscana group have been investigated. The sand-shale sedimentary package of this group is widely distributed both in Svalbard and in the Barents Sea, where it comprises shallow marine, prodelta, delta front, delta plain and coastal plain deposits. In this study we apply micropaleontological data in combination with sedimentological and geochemical data such as lithology, organic carbon, and boron contents. This data base is applied to recognize, characterize and correlate specific depositional conditions within a marine to non-marine facies development. Therefore foraminiferal assemblages of the Juvdalen section in central Spitsbergen were quantitatively analyzed.
In central Spitsbergen, the Kapp Toscana Group is divided into three lithostratigraphic units. The Tschermakfjellet Formation (Middle-Late Carnian) is a shallow marine to prodelta shale-dominated unit showing an upwards coarsening development. Foraminiferal assemblages contain both calcareous and agglutinated species with intermediate diversity values indicating deposition under normal marine shelf conditions. The dominant genera are Lingulina, Vaginulinopsis and Astacolus. Upwards increasing deltaic impact is reflected by expanding proportion of agglutinanted taxa and decreasing diversity. The boron content attains maximum values in the basal shales but decreases upwards with increasing brackish conditions. The organic carbon content is generally low. Two biofacies are distinguished: a shallow marine replaced by a transitional one.
The De Geerdalen Formation (Late Carnian-Early Norian) is a succession of interbedded shales, siltstones and sandstones. The formation contains impoverished foraminiferal assemblages of agglutinated taxa with extremely low diversities. Several samples are barren. The organic carbon and boron contents are very low. These observations indicate deposition in highly brackish marginal marine waters and delta plain fresh water environments.
The Knorringfjellet Formation (Norian-Bajocian) is a condensed succession of shales and sandstones including extensive hiatuses. The foraminiferal association recorded in these deposits is composed only of agglutinated taxa and reveals low diversities with high dominance of Ammodiscus and Trochammina species. The foraminiferal test size is strongly reduced indicating growth under restricted environmental conditions. The organic carbon content is moderate to low, suggesting that oxygen was not a dominant restricting factor. Boron shows increasing values indicating increasing salinity compared to the underlying deposits. The biofacies of this formation indicates deposition under hyposaline bottom water conditions (in spite of salinity increase) with tendency to develop hypoxic conditions.
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