Impact of growth faults on mixed siliciclastic‐carbonate‐evaporite deposits during rift climax and reorganisation—Billefjorden Trough, Svalbard, Norway

Abstract

Fault‐controlled mixed siliciclastic‐carbonate‐evaporite depositional systems exhibit distinct sensitivity to tectonic and eustatic controls that are expressed in the sedimentary architecture. In the Upper Carboniferous Billefjorden Trough (Svalbard, Norway), up to 2,000 m of a warm and arid climate syn‐rift basin fill comprises such depositional systems, documented in this study with traditional field techniques supported by helicopter‐ and ground‐based LIDAR models. The basin evolved from siliciclastics‐dominated red beds and paralic units that filled a symmetrical basin, to a rift climax half‐graben with alluvial fans entering the basin along relay ramps of the master fault zone (Billefjorden fault zone). Faults located in the hanging wall dip‐slope prevented the progradation of coarser material to the eastern part of the basin. Later, structural reorganisation in the dipslope led to the cessation of easternmost faults with deformation focusing along one major lineament (Løvehovden fault zone) antithetic to the master fault zone. The basin subsidence became more symmetrical, with main central depocentre and shallower platforms near the basin flanks. Footwall anticlines from faults displacement gradients were sensitive to periodical exposure and recorded dissolution breccias and footwall synclines preserved evaporites coupled with shallow marine siliciclastic deposits. Concurrently, thick gypsum/anhydrite deposits in the basin centre reflect glacio‐eustatic lowstands, whereas evenly thick carbonate deposition characterises highstands. While most analysis of syn‐rift basin fill is based on siliciclastics deposits, we here demonstrate the complexity of tectonism versus eustatic sea level changes in a mixed carbonate‐evaporite syn‐rift deposits. Tectonic influence is ascribed to the deposition of alluvial fans that prograded from the master fault towards the basin centre. On the dipslope glacio‐eustatic signals outperformed tectonic influence on deposition. Sea level lowstands promoted deposition of red sabkha mudstones and gypsum/anhydrite, salinas evaporites or dissolution breccias, interbedded with highstand carbonate beds.

Impact of faulting in depocentres development, facies assemblages, drainage patterns, and provenance in continental half‐graben basins: An example from the Fanja Basin of Oman

“…Thorne et al, 2012), with sediment transport towards the lowest point in the landscape, being rerouted around topographic highs on the way. This pattern conforms well to an early‐rift scenario (Gawthorpe & Leeder, 2000; Smyrak‐Sikora et al, 2019, 2020, 2021) and, further acknowledges the observation of fault‐bound growth‐sections in the overlying Green Qahlah member.…”

The evolution of catchment‐depositional system relationships on the dip slopes of intra‐rift basement highs: An example from the Frøya High, Mid‐Norwegian rifted margin

“…The tectono‐sedimentary setting of dip slopes developed along the footwall of major faults is considerably different to that of immediate hangingwall systems such as fault‐scarp degradation‐related fans or rift‐margin deltas. Lower gradients and subsidence rates, of back‐tilted slopes in the footwall of major normal faults, lead to a greatly enhanced sensitivity to eustatic changes across broader, shallow landscapes compared with hangingwall depocentres and commonly host shoreline depositional systems (Bell et al, 2017; Fernández‐Blanco et al, 2020; Gawthorpe et al, 1994; Smyrak‐Sikora et al, 2021). However, the controls upon the spatial variability in the depositional environment and resultant stratigraphic architecture of dip slope shoreline systems in rift settings remains comparatively unclear, especially those flanking large intra‐rift basement highs (Muravchik et al, 2018; Nøttvedt et al, 2000).…”

Stratigraphic and Spatial Extent of HALIP Magmatism in Central Spitsbergen

“…70 km north of the borehole. Interestingly, no igneous intrusions were reported in recent field‐based studies from the Billefjorden Trough (Smyrak‐Sikora et al., 2018, 2021), though some igneous rocks of unknown age were reported from mine ventilation shafts in the vicinity of Pyramiden (Verba, 2015).…”

“…The Ellesmerian (locally called Svalbardian) compressional event affected Svalbard during the Late Devonian (Piepjohn, 2000). The Late Carboniferous was dominated by localized rifting along major north‐south trending tectonic lineaments, exemplified by the Billefjorden Trough filled with mixed siliciclastic‐carbonate‐evaporitic deposits, including the Ebbadalen Formation (Smyrak‐Sikora et al., 2018, 2021). A tectonically stable platform was established by the Permian and lasted until the Late Jurassic.…”