Abstract
AbstractAn extensive, reprocessed two‐dimensional (2D) seismic data set was utilized together with available well data to study the Tiddlybanken Basin in the southeastern Norwegian Barents Sea, which is revealed to be an excellent example of base salt rift structures, evaporite accumulations and evolution of salt structures. Late Devonian–early Carboniferous NE‐SW regional extensional stress affected the study area and gave rise to three half‐grabens that are separated by a NW‐SE to NNW‐SSE trending horst and an affiliated interference transfer zone. The arcuate nature of the horst is believed to be the effect of pre‐existing Timanian basement grain, whereas the interference zone formed due to the combined effect of a Timanian (basement) lineament and the geometrical arrangement of the opposing master faults. The interference transfer zone acted as a physical barrier, controlling the facies distribution and sedimentary thickness of three‐layered evaporitic sequences (LES). During the late Triassic, the northwestern part of a salt wall was developed due to passive diapirism and its evolution was influenced by halite lithology between the three‐LES. The central and southeastern parts of the salt wall did not progress beyond the pedestal stage due to lack of halite in the deepest evaporitic sequence. During the Triassic–Jurassic transition, far‐field stresses from the Novaya Zemlya fold‐and‐thrust belt reactivated the pre‐salt Carboniferous rift structures. The reactivation led to the development of the Signalhorn Dome, rejuvenated the northwestern part of the salt wall and affected the sedimentation rates in the southeastern broad basin. The salt wall together with the Signalhorn Dome and the Carboniferous pre‐salt structures were again reactivated during post‐Early Cretaceous, in response to regional compressional stresses. During this main tectonic inversion phase, the northwestern and southeastern parts of the salt wall were rejuvenated; however, salt reactivation was minimized towards the interference transfer zone beneath the centre of the salt wall.
Highlights
The Barents Sea includes several stratigraphic units of Upper Carboniferous to Lower Permian Gipsdalen Group layered evaporitic sequences (LES) deposited in relatively shallow water depositional environments and arid climate conditions at a palaeo-latitude of ca. 30° N (e.g. Larssen et al, 2002; Stemmerik, 2000)
Semi-continuous, parallel to subparallel and medium amplitude seismic reflections interpreted as inter-bedded, mixed nonhalite and non-mobile lithologies, that is, anhydrite, gypsum of the Gipsdalen Group of Pennsylvanian to early Permian age. These seismic facies are mainly found at the hinged margin of the GU3 graben and are difficult to separate into evaporite layers L1 and L2
The transfer zone separating the GU2 and GU3 half-grabens was bordered by segmented normal faults with minor throws that were dipping towards the centre of the greater Tiddlybanken Basin. These geometries with overlapping/interference transfer zone in salt-free rifts, are common that is, in the northern part of Lake Tanganyika, East African Rift and the Gulf of Evvia (Burgess et al, 1988; Gawthorpe & Hurst, 1993; Morley et al, 1990; Rosendahl et al, 1986; Specht & Rosendahl, 1989; Versfelt & Rosendahl, 1989). We suggest that this arcuate transfer zone beneath the salt wall in the centre of Tiddlybanken Basin is the combined effect of a pre-existing Timanian lineament and the opposing geometrical arrangement of master faults M2 and M3 (Figure 10c) because extension along the thick-skinned master faults played an important role on the formation of the rift architecture
Summary
The Barents Sea includes several stratigraphic units of Upper Carboniferous to Lower Permian Gipsdalen Group layered evaporitic sequences (LES) deposited in relatively shallow water depositional environments and arid climate conditions at a palaeo-latitude of ca. 30° N (e.g. Larssen et al, 2002; Stemmerik, 2000). The Fedynsky High and the two depressions were influenced by transtension during late Devonian– early Carboniferous NE-SW regional extension (Hassaan et al, 2020) This event created NW-SE striking graben structures at the time when the Billefjorden Group (Soldogg, Tettegras and Blærerot formations; Figure 2) was deposited, and affected the Pechora Basin, eastern Barents Sea and the Olga-Sørkapp region (Klitzke et al, 2019; Stoupakova et al, 2011). Semi-continuous, parallel to subparallel and medium amplitude seismic reflections interpreted as inter-bedded, mixed nonhalite and non-mobile lithologies, that is, anhydrite, gypsum of the Gipsdalen Group of Pennsylvanian to early Permian age These seismic facies are mainly found at the hinged margin of the GU3 graben and are difficult to separate into evaporite layers L1 and L2. Semi-continuous to continuous, parallel to subparallel and medium to strong amplitude seismic reflections interpreted as inter-bedded, mixed non-halite and non-mobile lithologies, that is, anhydrite, gypsum of the Gipsdalen Group of Pennsylvanian to early Permian age
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