Middle to Late Triassic (Ladinian to Carnian) palynology of shallow stratigraphic cores 7831/2-U-2 and 7831/2-U-1, offshore Kong Karls Land, Norwegian Arctic

Abstract

During the Triassic, the Barents Shelf was situated on the northwestern corner of the Pangaea supercontinent as a large epicontinental seaway. Into early Late Triassic (Carnian), a major delta, prograding from the southeast towards the northwest, reached the Svalbard area. In 2005, the NPD drilled five shallow stratigraphic cores through Upper and Middle Triassic strata offshore Kong Karls Land, Svalbard. In the present study, the two oldest cores (7831/2-U-2 and 2-U-1) have been studied by applying palynology and palynofacies analyses. This contributes to the knowledge of the Triassic palynostratigraphy in the region and aids in the interpretation of the palaeoenvironment. The lowermost core 7831/2-U-2 comprises 13.3 meter of shale, correlated to the Botneheia Formation. The palynological samples from the oldest core yielded poorly preserved palynomorphs, dominantly bisaccate pollen, algae and acritarchs. The core is assigned to the late Ladinian age Echinitosporites iliacoides CAz based on the occurrence of the nominate taxon, confirming the preliminary interpretation of Vigran et al. (2014). The younger core (7831/2-U-1) spans 20.95 meter of the Tschermakfjellet Formation. Palynological analysis of the core reveals an upwards increase of spores, coupled with a decrease in bisaccate pollen and marine palynomorphs. Core 7831/2-U-1 is assigned to the early Carnian Aulisporites astigmosus CAz based on observations of A. astigmosus, again confirming the age assignment of Vigran et al (2014). These age interpretations are also consistent with published Re-Os dates (Xu et al., 2014), which place the Ladinian - Carnian (Middle - Late Triassic) boundary within the upper part of the core 7831/2-U-2, and constrain the overlying core 7831/2-U-1 to the earliest Carnian. The palynofacies analysis of this oldest core revealed a total dominance of amorphous organic matter (AOM), indicative of deposition in an anoxic environment. The palynofacies analysis of this youngest core revealed an increasing input of terrestrial organic matter. This is consistent with previous studies from the area, documenting the arrival of a prograding, early Carnian delta in the region. The study is part of a larger industry consortium under the FORCE umbrella, where the main aim is to further enhance the resolution of the Upper Triassic Series in the Norwegian Arctic region. The present study therefore provides an important input towards this overarching goal.