Depositional evolution of the Upper Carboniferous - Lower Permian Wordiekammen carbonate platform, Nordfjorden High, central Spitsbergen, Arctic Norway

This paper presents the first comprehensive study of the Wordiekammen carbonate platform on the Nordfjorden High, Central Spitsbergen. The Wordiekammen succession is divided into four depositional sequences bounded by subaerial exposure surfaces and consists of 12–84 m-thick wedgeshaped sequences being thickest in the distal area and thinner on the crest of the High. The uppermost Finlayfjellet Beds (Tyrrellfjellet sequence 2) represents in contrast a uniform sequence. The Wordiekammen Formation is composed of 11 depositional carbonate facies and three overprint facies which are grouped into 10 facies associations. Each association represents a predictable pattern of facies, 0.5–22 m thick, which is repeated many times producing a distinct cyclicity in the succession. The Wordiekammen Formation is composed of 50 depositional cycles, 21 cycles in the Kapitol Member and 29 cycles in the Tyrrellfjellet Member. Analysis of the well-dated Tyrrellfjellet Member indicates that the succession was controlled by mixed 100 kyr and 400 kyr cyclicity signals which are believed to be a reflection of eustatic sea-level fluctuation and tectonic instability. Allocyclic control on the deposition dominated the majority of the Wordiekammen succession, and an abrupt change in depositional style in the uppermost Finlayfjellet Beds is believed to reflect the break-down of the Gondwanaland ice sheets and the end of glacio-eustaic control. Four key lithological intervals and unconformities have been correlated across the Billefjorden Fault Zone to the time-equivalent succession in Bünsow Land. Based on the correlation, it is considered that the distal part of the Nordfjorden High towards the west and the carbonate platform on Bünsow Land reflected a similar geological setting while the up-dip and crestal part of the Nordfjorden High was a positive feature that divided the two carbonate platforms during sea-level lows. Finally, it is believed that the Nordfjorden High remained a homoclinal carbonate ramp up to at least Late Asselian times.

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