Stratigraphy in Billefjorden trough

Gipsdalen Group

• Gipshuken Formation: From 150- 250 m thick, these Artinskian carbonates and evaporites are widespread, stable shelf deposits (McCann & Dallmann, 1996).
• Nordenskioldbreen Formation: This is more recently known as the Wordiekammen Formation and consists of 200-250 m of platform carbonates of Kasimovian to Sakmarian age. A lack of thickness or facies changes across the Billefjorden fault zone in this unit suggests movement was over by then. In the field they appear as medium grey, well bedded carbonates.
• Minkinfjellet Formation: 0 - 350 m. Its distribution and absence on the Nordfjorden footwall block suggest this is part of the basin fill. Given the thickness of the underlying fill, compaction processes are inadequate to provide this accommodation space and so continued half-graben development can be inferred. They are interpreted to be open marine deposits of Moscovian age (Johannessen & Steel, 1992). Their restriction to the basin, however, suggests that water depths were not great enough to allow for footwall deposition.
• Ebbadalen Formation: Bashkirian age.
  • Odellfjellet Member: Up to 400 m thick of red, grey, and yellow conglomerates and sandstones, red shales and yellow dolomites. Johannessen & Steel (1995) indicate these are clastic wedges built out from the Billefjorden fault zone.
  • Trikolorfjellet Member: Gypsum/anhydrite (sabkha deposits intercalated with black/yellow limestones/dolomites. Some red sandstone and mudstone related to facies transition with Odellfjellet Member. According to Johannessen & Steel (1992) represents axial basin facies.
  • Ebbaelva Member: This is up to 200 m thick, and stretches across the basin. Grey-green shales intercalated with grey/yellow sandstones. Transitional with overlying formation with thin carbonates and evaporites. Braided stream, playa lake, barrier shoreline, sabkha and lagoonal facies all represented according to Johannessen & Steel (1992), and part of a transgressive tract. Douglas and Lamar (1995) suggest an slight angular unconformity exists at the base.
  • Hultberget Member: belongs in the Gipsdalen Group according to Johannessen & Steel (1992), and defined to only include about 150 m of continental red sandstones and interclated red siltstones. Thought to be ephemeral streams on alluvial fans.

Billefjorden Group: 0-450 m, Visean or older

• Svenbreen Formation
  • Hultberget Member: This belongs to Billefjorden Group according to McCann & Dallmann (1996). See above for description.
  • Sporehøgda Member: Little description exists of this unit. McCann & Dallmann (1996) note that is its often mapped as part of the lower Horbyebreen Formation. Lamar & Douglas (1995) describe them as fining upwards cycles of coarse pebble conglomerates to mudstones, with olive-gray to red-gray and red-brown coloration. Wackes are common, with possible Hecla Hoek lithics. Sedimentologically, this would possible represent inception of movement on the Billefjorden fault zone. They interpet these as high-sinuousity fluvial deposits.
• Hørbyebreen Formation: Upo to 450 m thick, these are described as fluvial Gjelberg & Steel (1981) indicate west flowing braided streams, and nearshore marine sandstones with minor shales, conglomerates and coal seams (McCann & Dallmann, 1995). Gjelberg & Steel (1981) indicate west flowing braided streams. Clasts are predominantly quartzite. Lithologically this is similar to the Orustdalen Formation of western Spitsbergen. Importantly these are found on both the foot and hangingwall of the Billefjorden fault zone.

Andree Land Group: Wood Bay Fm. A mixed and multi-colored sequence of clastics from shales to conglomerates. Cleavage and fairly complex deformation just W of the BFZ makes recognition of stratigraphic units more difficult. Lamar & Douglas (1995) describe lithologies and formational stratigraphy in much more detail. The interpretation is of coastal plain fluvial environments close to sea level with occasional flooding introducing estaurine and marine influences.

Basement: various schists, gneisses, amphibolites and minor quartzite and marble interbeds as part of the Atomfjella Group (McCann & Dallmann, 1996).