Extensional fault and fold growth: Impact on accommodation evolution and sedimentary infill

Abstract

Extensional faults and folds exert a fundamental control on the location, thickness and partitioning of sedimentary deposits on rift basins. The connection between the mode of extensional fault reactivation, resulting fault shape and extensional fold growth is well‐established. The impact of folding on accommodation evolution and growth package architecture, however, has received little attention; particularly the role‐played by fault‐perpendicular (transverse) folding. We study a multiphase rift basin with km‐scale fault displacements using a large high‐quality 3D seismic data set from the Fingerdjupet Subbasin in the southwestern Barents Sea. We link growth package architecture to timing and mode of fault reactivation. Dip linkage of deep and shallow fault segments resulted in ramp‐flat‐ramp fault geometry, above which fault‐parallel fault‐bend folds developed. The folds limited the accommodation near their causal faults, leading to deposition within a fault‐bend synclinal growth basin further into the hangingwall. Continued fold growth led to truncation of strata near the crest of the fault‐bend anticline before shortcut faulting bypassed the ramp‐flat‐ramp structure and ended folding. Accommodation along the fault‐parallel axis is controlled by the transverse folds, the location and size of which depends on the degree of linkage in the fault network and the accumulated displacement on causal faults. We construct transverse fold trajectories by tracing transverse fold hinges through space and time to highlight the positions of maximum and minimum accommodation and potential sediment entry points to hangingwall growth basins. The length and shape of the constructed trajectories relate to the displacement on their parent faults, duration of fault activity, timing of transverse basin infill, fault linkage and strain localization. We emphasize that the considerable wavelength, amplitudes and potential periclinal geometry of extensional folds make them viable targets for CO2 storage or hydrocarbon exploration in rift basins.

Quantitative analysis of a footwall‐scarp degradation complex and syn‐rift stratigraphic architecture, Exmouth Plateau, NW Shelf, offshore Australia

“…How multiple depositional systems interact within a fault‐confined basin, and how those interactions evolve with the growth of associated structural elements (e.g. secondary faults and folds), is relatively understudied (Jackson, Gawthorpe, & Sharp, 2006; Lewis, Jackson, & Gawthorpe, 2015; Serck & Braathen, 2019; Sharp, Gawthorpe, Underhill, & Gupta, 2000). A better understanding of these processes is necessary to unravel the complexity of the ultimate depositional architecture of a hangingwall basin‐fill.…”

Architecture of growth basins in a tidally influenced, prodelta to delta‐front setting: The Triassic succession of Kvalpynten, East Svalbard

“…The evolution of growth faults is often related to the lateral and vertical linkage of fault segments (e.g. Cartwright, Mansfield, & Trudgill, ; Rotevatn & Jackson, ; Rykkelid & Fossen, ; Serck & Braathen, ; Tvedt et al, ; Walsh, Bailey, Childs, Nicol, & Bonson, ). Field‐ and seismic‐based studies and analogue modelling mainly show that extensional faulting tend to affect the delta top and upper delta front of the prograding deltaic system, whereas the lower delta front/prodelta can experience shortening and in some cases formation of gravity‐induced deep water fold‐and‐thrust belts (e.g.…”

Growth folds above propagating normal faults

“…Where the fault dip changes with depth, complex growth fold geometries may develop. For example, if a fault propagates through a mechanically layered sequence, 'flats' and 'ramps' may form in weak and strong layers, respectively, and forced folds may form at multiple stratigraphic levels Rotevatn and Jackson, 2014;Vasquez et al, 2018;Deng and McClay, 2019;Serck and Braathen, 2019). "Growth folds above propagating normal faults" by Coleman et al Fault throw, in contrast to fault dip, controls not only the fold geometry but also size.…”