Supplementary data for Devonian–Carboniferous extension and Eurekan inversion along an inherited WNW–ESE-striking fault system in Billefjorden, Svalbard.

Content: -S1: Description of the late Paleozoic sedimentary successions in central Spitsbergen from the literature. -S2: (a) Uninterpreted bathymetric data in Billefjorden and (b–d) associated zooms. -S3: Interpreted seismic sections in Billefjorden showing early Cenozoic duplexes and thrusts (yellow lines), bedding surfaces (dotted white lines) and potential multiples (dashed yellow lines). See Fig. 1 for location. (a) SSW-directed Cenozoic thrust between Phantomodden and Narveneset showing (from south to north) in the southern part a well-developed SSW-verging ramp anticline and an open, symmetric, NNE-tilted detachment/ramp anticline. (b) Top-west to top-west thrust sheet with minor reverse offsets. -S4: Uninterpreted seismic sections in Billefjorden. See S1 for location. -S5: Description and interpretation of the upper Paleozoic sedimentary successions on seismic data in Billefjorden. -Lower Devonian sedimentary rocks of the Siktefjellet and Red Bay and Andrée Land groups -Uppermost Devonian to Mississippian sedimentary rocks (Billefjorden Group) -Pennsylvanian to Permian sedimentary rocks (Gipsdalen Group) -Uppermost Mississippian to Lower Pennsylvanian Hultberget and Ebbadalen formations -Middle to lowermost Upper Pennsylvanian Minkinfjellet Formation -Uppermost Middle Pennsylvanian to lowermost Permian Wordiekammen Formation -Lower Permian Gipshuken Formation -S6: Depth conversion data including checkshot data from exploration well 7816/12-1 in Reindalspasset (upper left table; Eide et al., 1991), the depth of lithostratigraphic intervals from the well completion report (upper right table), the depth of formations of interest to the present study from the well completion report (middle right table), average velocities of stratigraphic intervals of interest to the present study from Gernigon et al. (2018; lower right table), and calculated stratigraphic thicknesses and depths, and fault offsets in Billefjorden based on velocities from well 7816/12-1 and from Gernigon et al. (2018; lowermost table). -S7: (a) Uninterpreted and (b) interpreted depth-converted seismic section NP-IS-85-05 through Billefjorden showing the main NNE-dipping shear zone (dashed yellow and grey-shaded), and some of the normal (red) and inverted brittle faults (black), and décollements and detachments (yellow) shown in Figure 4. Notice the gentle dip of the main shear zone. Abbreviation: GaF: Garmaksla fault. -S8: Bathymetric profiles across NNE–SSW-trending moraine ridges (up) and a fault-related escarpment (down). Notice the contrast between smooth, 2–3 meters high drops in bathymetry across moraine ridges (black arrows) and the abrupt 5 meter drop across the fault-related escarpment (red arrow). -S9: Bathymetric profiles across Billefjorden showing the N–S-trending ridge (red arrows). Location of the profiles is shown as white lines in supplement S1d. Notice the steep western flank and the smooth and gently east-dipping top and eastern flank of the ridge. -S10: Satellite images in (A) Narveneset and (B) Brimerpynten (see Figure 1B for locations) showing smooth, high-frequency, gently curving, NNE–SSW- to NNW–SSE-trending lineaments (dotted white lines) most likely representing sub-vertical bedding surfaces within Lower Devonian sedimentary strata (Dallmann et al., 2004a; Dallmann & Piepjohn, 2020) crosscut by discrete, linear to undulating, dominantly WNW–ESE-trending fault-related escarpments (red lines). The legend is common to A and B. -S11: Field photograph of WNW–ESE-striking brittle faults in Narveneset showing sinistral sense of shear. -S12: Decreasing tectonic activity from Early Devonian to early Permian times. -Early Devonian to Mississippian collapse and rift “initiation” phase -Latest Mississippian to earliest/Early Pennsylvanian “interaction and linkage” phase -Middle Pennsylvanian “through-going fault zones” phase -Late Pennsylvanian to earliest Permian latest- to post-rift phase -Conclusion -Figure 1 electronic supplement 12 -S13: (A) Calculation of the surface slope angles between Pyramiden and Yggdrasilkampen and Yggdrasilkampen and Asvindalen and of the altitude difference due to the normal dip angle (c. 145 m) and to Eurekan deformation (c. 330 m). (B) Illustration of the calculated surface slope angles (in red) in Billefjorden and of the potential WNW–ESE-trending fold (in fuchsia) along the Adolfbukta fault. Notice the significant altitude drop of the base of the Wordiekammen Formation between the Pyramiden Mountain (c. 850 meters) and northern Yggdrasilkampen (c. 375 meters). -S14: Outcrop photograph showing south-dipping and southwards thickening Lower Devonian strata of the Wood Bay Formation in Triungen in the hanging wall of the NNE-dipping Hugindalen Fault.