Sedimentology and facies distribution of the Upper Triassic De Geerdalen Formation in the Storfjorden area and Wilhelmøya, eastern Svalbard
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This study investigates sediments of the Upper Triassic De Geerdalen Formation, as it is exposed on eastern Svalbard. The De Geerdalen Formation was deposited during the Early Carnian to Early Norian, on the distal area of a shallow embayment on the northern margin of Pangea. It includes a wide range of depositional environments, ranging from offshore shallow marine, paralic delta front and shoreface to coastal plain environments. The aim of the study is to document and interpret the sedimentology of the formation and the spatial and temporal evolution of depositional environments, through detailed facies analysis. Fifteen facies and eight facies associations have been defined based on observations and outcrop data. These data were collected during a one-month field season in 2015 on eastern Spitsbergen, western Barentsøya and on Wilhelmøya. The interpretation presented here is based on previous research in neighbouring areas, as well as cooperation with other master students.From the measured sections, a strong fluvial dominance is observed on the northern part of Barentsøya and interpreted to reflect a proximal position to an eastern source compared to exposures further west and north. Waves and tides become increasingly dominant towards the west, particularly in the outcrops in the Agardhbukta area and represent more distal and transitional environments compared to the succession in the eastern exposures. The succession on eastern Spitsbergen and Wilhelmøya is mostly dominated by tidal and wave processes and reflect more distal depositional environments compared to the southern and eastern part of the study area. The De Geerdalen Formation shows a typical development of multiple coarsening upwards sequences that constitute parasequences normally associated with regressive depositional systems.