Spatio-temporal evolution of strain accumulation derived from multi-scale observations of Late Jurassic rifting in the northern North Sea: A critical test of models for lithospheric extension

Abstract

We integrate observations of lithospheric extension over a wide range of spatial and temporal scales within the northern North Sea basin and critically review the extent to which existing theories of lithospheric deformation can account for these observations. Data obtained through a prolonged periodofhydrocarbon exploration and production has yielded a dense and diverse data set over the entire Viking Graben and its anking platform areas. These data show how syn-rift accommodation within the basin varied in space and time with sub-kilometer-scale spatial resolution and a temporal resolution of 2{3 Myr. Regional interpretations of 2D seismic re ection, refraction and gravity data for this area have also been published and provide an image of total basin wide stretching for the entire crust. These image data are combined with published strain rate inversion results obtained from tectonic subsidence patterns to constrain the spatio-temporal evolution of strain accumulation throughout the lithosphere during the 40 Myr (170{130 Ma) period of Late Jurassic extension across this basin. For the rst 25{30 Myr, strain localisation dominated basin development with strain rates at the eventual rift axis increasing while strain rates over the anking areas declined. As strain rates across the whole basin were consistently very low (< 3x10 ;16 s ;1 ), thermally induced strength loss can not explain this phenomenon. The strain localisation is manifest in the near-surface by a systematic migration of fault activity. The pattern and timing of this migration are inconsistent with exural bending stresses exerting an underlying control, especially when estimates of exural rigidity for this area are Preprint submitted to Elsevier Science 31 January 2005 considered. The best explanation for what is observed in this time period is a coupling between near-surface strain localisation, driven by brittle (or plastic) failure, and the evolving thermal structure of the lithosphere. We demonstrate this process using a continuum mechanics model for normal fault growth that incorporates the strain rate-dependence of frictional strength observed in laboratory studies. During the nal 10 Myr of basin formation, strain accumulation was focused within the axis and strain rates declined rapidly. Replacement of weak crust by stronger mantle material plus crustal buoyancy forces can adequately explain this decline.

Tectonostratigraphy of a rift basin affected by salt tectonics: synrift Middle Jurassic–Lower Cretaceous Dutch Central Graben, Terschelling Basin and neighbouring platforms, Dutch offshore

“…Banham & Mountney 2013) and for clastic continental settings affected by brittle deformation (e.g. Gawthorpe & Leeder 2000;Cowie et al 2005). However, relatively little documentation on the impact of rifting and salt tectonics on shallowmarine settings has previously been published (Mannie et al 2016).…”

Influence of fault reactivation during multiphase rifting: The Oseberg area, northern North Sea rift

“…Furthermore, rift zones are featured by (iii) high levels of earthquake activity associated with active fault zones (e.g., Shudofsky et al, 1987;James and Tom, 1993) and (iv) a set of normal faults that are oriented perpendicular to the extension direction and mostly (but not necessarily) dipping basinward, with a variable percentage of strike-slip faults depending on the orientation rift axis relative to the extension direction (e.g., Gibbs, 1984;Bonini et al, 1997;McClay et al, 2002;Childs et al, 2003). Lastly, rift zones are typified by (v) the development of grabens or halfgrabens controlled by basin-bounding faults (e.g., Gupta and Scholz, 2000;Cowie et al, 2000Cowie et al, , 2005. Cowie et al (2005) presented a general model of fault evolution based on multi-scale observations of Middle-to-Late Jurassic extension of the northern North Sea: (i) a wide range of fault sizes formed during the extensional episode; (ii) present-day maximum fault throw increases towards rift axis; (iii) a preferred inward dip direction of large faults emerges as extension progressed and was accompanied by cessation of activity on outward dipping smaller-scale faults; (iv) maximum fault slip rate (or maximum strain rate) correlates with fault displacement (or β-stretching factor), as well as the duration of extension; and (v) the zone of active extension narrowed through time (from ~200 km to <50 km over 40 Myr).…”

“…Lastly, rift zones are typified by (v) the development of grabens or halfgrabens controlled by basin-bounding faults (e.g., Gupta and Scholz, 2000;Cowie et al, 2000Cowie et al, , 2005. Cowie et al (2005) presented a general model of fault evolution based on multi-scale observations of Middle-to-Late Jurassic extension of the northern North Sea: (i) a wide range of fault sizes formed during the extensional episode; (ii) present-day maximum fault throw increases towards rift axis; (iii) a preferred inward dip direction of large faults emerges as extension progressed and was accompanied by cessation of activity on outward dipping smaller-scale faults; (iv) maximum fault slip rate (or maximum strain rate) correlates with fault displacement (or β-stretching factor), as well as the duration of extension; and (v) the zone of active extension narrowed through time (from ~200 km to <50 km over 40 Myr). This systematic migration of fault activity indicates that strain localization dominates basin development with strain rates at the eventual rift axis increasing and strain rates over flanking areas declining.…”

Influence of fault reactivation during multiphase rifting: the Oseberg area, Northern North Sea rift

“…The Middle Jurassic -Early Cretaceous rift phase (e.g. Badley et al, 1988;Coward et al, 2003;Cowie et al, 2005;Roberts et al, 1995;Underhill and Partington, 1993) led to the superimposition of rift-related extension onto the thermally subsiding basin (e.g. Faerseth,1996;Roberts et al, 1995).…”