Thrust tectonics on Brøggerhalvøya and their relationship to the Tertiary West Spitsbergen Fold-and-Thrust Belt

Abstract

The Tertiary fold-and-thrust belt on Brøggerhalvøya is characterized by a NE-vergent pile of nine thrust sheets. The sole thrust of the pile is located in Precambrian phyllites and climbs up-section to the northeast. Four lower thrust sheets consisting predominantly of Upper Palaeozoic sediments are overlain by two thrust sheets in the central part of the stack which contain a kilometrescale syncline and anticline. The fold is cut by juxtaposed thrusts giving rise to the formation of three structurally higher basement-dominated thrust sheets. A multiple-stage kinematic model is proposed including (1) in-sequence foreland-propagating formation of the lower thrust sheets in response to N-S subhorizontal bedding-parallel movements, (2) a change in tectonic transport to ENE and outof-sequence thrusting and formation of the kilometre-scale fold-structure followed by (3) truncation of the kilometre-scale fold and stacking of the highest basement-dominated thrust sheets by hindward-propagating out-of-sequence thrusting. The strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheets, reflecting a temporal change to a more transpressive regime. Thrusting was followed by (4) N-S extension and (5) W-E extension. Comparison of the structural geometry and kinematic evolution of Brøggerhalvøya with the data reported for the fold belt further south allows us to assume a coeval evolution with the fold belt. A latest Paleocene/Early Eocene age for the main phase of thrusting is suggested for the West Spitsbergen Fold-and-Thrust Belt; the main phases therefore pre-date the separation of Svalbard and Greenland due to right-lateral movements along the Hornsund Fault Zone. The fold belt's temporal evolution followed by the formation of the Forlandsundet Graben can be linked with the platekinematic framework in the span between latest Paleocene and Middle Eocene times.

A transpressional origin for the West Spitsbergen fold‐and‐thrust belt: Insight from analog modeling

“…In the model of Lyberis and Manby [1993], strike slip occurred in a second, separate phase and was associated with the opening of the Norwegian‐Greenland Sea. A rather similar evolution has been advocated by Saalmann and Thiedig [2002], who, based on observations on Brøggerhalvøya, proposed separate stages of compression‐dominated transpression followed by strike‐slip dominated transpression.…”

“…Here the strike of the structures (NW‐SE) and the shortening directions (initially and dominantly N‐NNE vergent, changing toward ENE) are deviating from the main trend of the WSFTB further south which strikes NNW‐SSE and parallel to the COB. These differences have been explained by the buttressing effect of the Nordfjorden block along the NW‐SE striking Kongsvegen Fault during dominantly WSW‐ENE contraction [ Bergh et al , 2000; Saalmann and Thiedig , 2002]. The Kongsvegen Fault bounds one of the en echelon Carboniferous grabens mapped by Steel and Worsley [1984], oblique to the main trend of the WSFTB but roughly coinciding with the orientation of thin‐skinned structures on northern Oscar II Land and Brøggerhalvøya.…”

“…Inversion in the eastern foreland province (zone 4) is characterized by thick‐skinned reactivation of Devonian‐Carboniferous basement faults [ Ringset and Andresen , 1988]. The anomalous strike of the belt in the Kongsfjorden area in the northwest has equally been explained by a preexisting basement structure [ Saalmann and Thiedig , 2002].…”

Analysis of structural trends of sub-sea-floor strata in the Isfjorden area of the West Spitsbergen Fold-and-Thrust Belt based on multichannel seismic data

“…Its development has been explained as a result of a time-constrained head-on collision between the Greenland and the Eurasian plate (Lyberis & Manby 1993a,b;CASE Team 2001;Saalmann & Thiedig 2002), whereas many researchers have advocated a mechanism related to transpression (Harland 1969;Lowell 1972) combined with strain partitioning (Faleide et al 1988;Maher & Craddock 1988). The latter model has gained support from Leever et al (2011a,b).…”

Seafloor expression and shallow structure of a fold-and-thrust system, Isfjorden, west Spitsbergen

“…1) developed in response to opening of the NorwegianÁ Greenland Sea (Talwani & Eldholm 1977;Srivastava 1985;Olesen et al 2007;Engen et al 2008;Gaina et al 2009). The evolution of the WSFTB has been explained as a result of a head-on collision between the Greenland and the Eurasian plates (Lyberis & Manby 1993a, b;Tessensohn & Piepjohn 2000, CASE Team 2001Saalmann & Thiedig 2002). An alternative hypothesis is that the fold-and-thrust belt reflects the contractional component of strain in a transpressional setting (Harland 1969;Lowell 1972;Faleide et al 1988;Maher & Craddock 1988).…”