Oblique reactivation of lithosphere-scale lineaments controls rift physiography – the upper-crustal expression of the Sorgenfrei–Tornquist Zone, offshore southern Norway

Abstract

Abstract. Pre-existing structures within sub-crustal lithosphere may localise stresses during subsequent tectonic events, resulting in complex fault systems at upper-crustal levels. As these sub-crustal structures are difficult to resolve at great depths, the evolution of kinematically and perhaps geometrically linked upper-crustal fault populations can offer insights into their deformation history, including when and how they reactivate and accommodate stresses during later tectonic events. In this study, we use borehole-constrained 2-D and 3-D seismic reflection data to investigate the structural development of the Farsund Basin, offshore southern Norway. We use throw–length (T-x) analysis and fault displacement backstripping techniques to determine the geometric and kinematic evolution of N–S- and E–W-striking upper-crustal fault populations during the multiphase evolution of the Farsund Basin. N–S-striking faults were active during the Triassic, prior to a period of sinistral strike-slip activity along E–W-striking faults during the Early Jurassic, which represented a hitherto undocumented phase of activity in this area. These E–W-striking upper-crustal faults are later obliquely reactivated under a dextral stress regime during the Early Cretaceous, with new faults also propagating away from pre-existing ones, representing a switch to a predominantly dextral sense of motion. The E–W faults within the Farsund Basin are interpreted to extend through the crust to the Moho and link with the Sorgenfrei–Tornquist Zone, a lithosphere-scale lineament, identified within the sub-crustal lithosphere, that extends > 1000 km across central Europe. Based on this geometric linkage, we infer that the E–W-striking faults represent the upper-crustal component of the Sorgenfrei–Tornquist Zone and that the Sorgenfrei–Tornquist Zone represents a long-lived lithosphere-scale lineament that is periodically reactivated throughout its protracted geological history. The upper-crustal component of the lineament is reactivated in a range of tectonic styles, including both sinistral and dextral strike-slip motions, with the geometry and kinematics of these faults often inconsistent with what may otherwise be inferred from regional tectonics alone. Understanding these different styles of reactivation not only allows us to better understand the influence of sub-crustal lithospheric structure on rifting but also offers insights into the prevailing stress field during regional tectonic events.

Segmentation of Rifts Through Structural Inheritance: Creation of the Davis Strait

“…It should be noted that it is indeed unexpected that applying a North Atlantic Craton mantle suture (Figure 3b) in the presence of an extension field that is relevant in velocity and orientation to the Paleogene (Figure 4) would produce appropriate rift dynamics for the Davis Strait system ( Figure 6). However, the study here complements a growing body of work that highlights the potential of the mantle lithosphere to play an important role in tectonic processes (Pysklywec & Beaumont, 2004;Babuška & Plomerová, 2013;Jourdon et al, 2017;Salazar-Mora et al, 2018;Phillips et al, 2018;Balázs et al, 2018;Heron et al, 2019).…”

“…Numerous previous studies have shown the potential for mantle lithosphere structures to control the evolution of shallow tectonics (Balázs et al, 2018;Heron et al, 2019;Jourdon et al, 2017;Pysklywec & Beaumont, 2004;Phillips et al, 2018;Salazar-Mora et al, 2018;Schiffer et al, 2018), highlighting a deep genesis for lithosphere-scale deformation (e.g., Holdsworth et al, 2001;Vauchez et al, 1997). Reactivation of features formed through previous collisional or rifting events (Wilson, 1966) is well established and thought to occur along well-defined, preexisting structures such as faults, shear zones, or lithological contacts (Holdsworth et al, 1997).…”

Terrane Boundary Reactivation, Barriers to Lateral Fault Propagation and Reactivated Fabrics: Rifting Across the Median Batholith Zone, Great South Basin, New Zealand

“…Lithosphere-scale structures often localize strain, as indicated by tectonic events repeatedly localizing in highly deformed orogenic belts surrounding more stable cratonic continental interiors. These belts may control the location of rift systems and, to some extent, continental breakup (e.g., Dore et al, 1997;Heron et al, 2019;Paton et al, 2016;Phillips et al, 2018;Ring, 1994;Thomas, 2006;Thomas, 2018;Tommasi & Vauchez, 2001;Wenker & Beaumont, 2016;Wilson, 1966). The distribution of different crustal rheologies and their associated strength variations, such as between distinct crustal terranes or between igneous batholiths and adjacent terranes, may inhibit fault nucleation and propagation in some areas while promoting it in others (Critchley, 1984;Howell et al, 2019;Koopmann et al, 2014;Magee et al, 2014;Peace et al, 2017).…”

Pre-inversion normal fault geometry controls inversion style and magnitude, Farsund Basin, offshore southern Norway

“…2b) 105 Heeremans et al, 2004;;Wilson et al, 2004;Phillips et al, 2017;Malehmir et al, 2018). However, no Carboniferous-Permian fault activity is identified in the Farsund Basin (Phillips et al, 2018), although some pre-upper Permian faulting, likely related to Carboniferous-Permian extension, occurred in the Norwegian-Danish and Egersund basins (Skjerven et al, 1983;Jackson and Lewis, 2013) (Fig. 2, 3).…”