Palaeoenvironmental reconstruction of Paleocene deposits, Cenozoic Central Basin, Spitsbergen. A palynological investigation, with emphasis on dinoflagellate cysts

During the Paleogene, transcurrent motions between NE Greenland and Svalbard caused the formation of the Central Cenozoic Basin in Spitsbergen. The basin formation resulted in deposition of 7 sedimentary formations that cover Paleocene to Eocene time. This study is based on a drill core from Danzigdalen Svalbard, containing the three Paleocene formations: Firkanten -, Basilika -, and Grumantbyen Formations. This study provides a sedimentological description, coupled with palynological analysis on the Danzigdalen core. Qualitative analysis was limited by the poor preservation state and disappointing numbers of palynomorphs. However, 20 dinoflagellate cyst genera have been described and sporomorphs were divided into major morphological groups. The dinoflagellate cyst assemblages is dominated by the three genera Spiniferites, Cerodinium, and Deflandrea. Changes in the palynomorph assemblages reflect a shifting depositional environment, as well as changes in chemistry and nutrient availability of the water column. The distribution of gonyaulacoid dinoflagellate genera in the three formations, along with sedimentological observations, reflect a shift from a terrestrial and inner neritic environment (Firkanten Fm.) to outer neritic and oceanic environments (Basilika Fm.) and finally a return to inner neritic and shoreface environment (Grumantbyen Fm.). The dominance of peridinioid dinoflagellates in the Basilika Formation suggest that the formation was deposited in a nutrient-enriched brackish to hyposaline environment. Results from palynological analysis, including palynofacies, along with sedimentary observations have been compiled into a sequence stratigraphic framework and reveal two parasequences. The Firkanten Formation constitutes the first transgressive-regressive phase and the Basilika-Grumantbyen Formations the latter. The basin has been affected by a shortage of radiometric dates and palaeontological age determinations have suffered from a lack of useful fossil assemblages. 11 tuff beds have been documented within the studied interval. A single concordant age of 60.29 ± 0.29 has been retrieved from a tuff bed in the Basilika Formation (302.30 – 302.21 m depth in core), giving it a Selandian age. This supports Manum and Throndsen´s (1986) previous age determinations