Normal fault growth influenced by basement fabrics: The importance of preferential nucleation from pre‐existing structures

Abstract

Reactivation of pre-existing intra-basement structures can influence the evolution of rift basins, yet the detailed kinematic relationship between these structures and overlying rift-related faults remains poorly understood. Understanding the kinematic as well as geometric relationship between intra-basement structures and rift-related fault networks is important, with the extension direction in many rifted provinces typically thought to lie normal to fault strike. We here investigate this problem using a borehole-constrained, 3D seismic reflection dataset from the Taranaki Basin, offshore New Zealand. Excellent imaging of intra-basement structures and a relatively weakly deformed, stratigraphically simple sedimentary cover allow us to: (a) identify a range of interaction styles between intra-basement structures and overlying, Plio-Pleistocene rift-related normal faults; and (b) examine the cover fault kinematics associated with each interaction style. Some of the normal faults parallel and are physically connected to intra-basement reflections, which are interpreted as mylonitic reverse faults formed during Mesozoic subduction and basement terrane accretion. These geometric relationships indicate pre-existing intra-basement structures locally controlled the position and attitude of Plio-Pleistocene rift-related normal faults. However, through detailed 3D kinematic analysis of selected normal faults, we show that: (a) normal faults only nucleated above intra-basement structures that experienced late Miocene compressional reactivation, (b) despite playing an important role during subsequent rifting, intra-basement structures have not been significantly extensionally reactivated, and (c) preferential nucleation and propagation of normal faults within late Miocene reverse faults and folds appears to be the key genetic relationship between contractionally reactivated intra-basement structures and rift-related normal faults. Our analysis shows that km-scale, intra-basement structures can control the nucleation and development of newly formed, rift-related nor-mal faults, most likely due to a local perturbation of the regional stress field. Because of this, simply inverting fault strike for causal extension direction may be incorrect, especially in provinces where pre-existing, intra-basement structures occur. We also 660 | EAGE COLLANEGA Et AL.

The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

“…These faults merging with the shear zone at depth (Fazlikhani et al, ; Figure ). Instances where preexisting heterogeneities locally perturbed the regional stress field have also been interpreted in the East African Rift (Corti et al, ; Philippon et al, ), the Gippsland Basin offshore Australia (Samsu et al, ), the Taranaki Basin offshore New Zealand (Collanega et al, ), and Thailand (Morley, , ). Although local faults may be misaligned with respect to the regional stress field, at the regional scale, overall rift kinematics do appear to be compatible with the extension direction (Corti et al, ; Philippon et al, ).…”

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

“…Since the Cenozoic, these terranes have been offset along the Alpine Fault, a major plate boundary and strike‐slip fault located along the spine of the South Island that has accommodated >450 km, and potentially >700 km, offset (Cooper et al, ; Lamb et al, ; Sutherland et al, ; Wellman, ). Due to this offset, the basement terranes of the South Island are also present beneath the North Island (Figure ) (Collanega et al, ; Mortimer et al, ; Muir et al, ). The basement terranes, which together comprise the Austral superprovince, are divided into Eastern and Western Provinces separated by the Median Batholith Zone (Mortimer et al, ).…”

“…This fault is associated with a series of fault blocks in its hanging wall and multiple embayments that incise into the footwall (Figures 4, 5, and 7). Similarly in the North Island, the boundary between the Median Batholith and Western Province terranes was also reactivated, forming the Cape Egmont Fault Zone (Collanega et al, 2018;Muir et al, 2000).…”

Jurassic to Early Cretaceous basin configuration(s) in the Fingerdjupet Subbasin, SW Barents Sea

“…Previously established tectonic fabrics affect fault growth during subsequent rift phases (Keep and McClay, 1997;Morley et al, 2004;Henza, Withjack and Schlische, 2011;Whipp et al, 2014;Collanega et al, 2018). In multiphase rifts, faults reactivate either by upward propagation of existing faults or by dip linkage, where new faults nucleate in the overburden of old faults before linking through breaching of a vertical relay zone (Baudon and Cartwright, 2008).…”