Supradetachment basins in necking domains of rifted margins: Insights from the Norwegian Sea

Abstract

Supradetachment basins at passive rifted margins are a key witness of majorcontinental extension, and they may preserve a record from which the amount and rates of extension and metamorphic core complex exhumation may be reconstructed. These basins have mainly been recognised in back-arc and orogenic collapse settings, with few examples from rifted margins. Using 2D and 3D seismic reflection, wellbore, and gravity anomaly data, we here characterise the threedimensional structural and tectonosedimentary evolution of a spoon-shaped supradetachment basin that was formed in the necking domain of a rifted margin, EAGE MUÑOZ-BARRERAetal.

Stratigraphic record of continental breakup, offshore NW Australia—Discussion

“…However, there is a tendency, which we believe to be erroneous, from interpreters to extend similar‐looking stratigraphic surfaces across and along these margins. This tendency is derived from the ‘syn‐rift’ literature, in which interpreters strive to recognise rift‐related tectonics systems tracts, separated by unconformities with seemingly regional expression, in contiguous extensional half‐grabens and grabens (see Nøttvedt et al, 1995; Prosser et al, 1993; Ravnås & Steel, 1998 as pioneer articles, but also Muñoz‐Barrera et al, 2021 for a more recent analysis of syn‐rift basins in deep‐offshore basins). The recognition of such systems tracts as being deposited during the continental rifting stage of margin evolution is valid, but many breakup‐related unconformities on distal continental margins reflect distinct geological settings, or have different ages to those where they were first defined on the continental shelf (e.g., Lei et al, 2019, 2020).…”

Low‐Angle Normal Faults on the NW Shelf of Australia: Implications for Late Paleozoic Rifting

“…(2013) (Figure 1b). The proximal and necking domains are now recognised as key elements of continental margin architecture that relay extension from areas of limited stretching to areas of significant thinning as manifested by a rapid change in crustal thickness from 30 to 10 km (McClay & Hammerstein, 2020; Muñoz‐Barrera et al., 2020, 2021; Peron‐Pinvidic et al., 2013).…”

“…Low-angle faults can be identified at the top-basement reflection on the Exmouth Plateau and are interpreted to have controlled the deposition of a thin layer of Late Paleozoic strata onto hyper-thinned crust (Figures 15 and S4 in Supporting Information S1). Observed stratigraphic onlaps against low-angle faults and basement ridges at the fault break-away (Figure S4 in Supporting Information S1) suggest a strong similarity to supra-detachment basins above low-angle fault systems of highly extended rift basins Deng, Ren, et al, 2020;Gillard, Manatschal, & Autin, 2016;Gillard et al, 2019Gillard et al, , 2015Lister & Davis, 1989;Muñoz-Barrera et al, 2021;Nirrengarten et al, 2018;Webber et al, 2020). Belgarde et al (2015) mapped the entire NW Shelf of Australia, showing that the "Westralian Superbasin" was formed during large-magnitude extension in the Late Paleozoic (Figure 16a).…”

“…Low‐angle normal faults (dip < 30°) and metamorphic core complexes have been widely recognised in many back‐arc and post‐orogenic settings such as the Basin and Range Province of western USA and Mexico (Brian Wernicke, 1985; Brian Wernicke & Axen, 1988; Lister & Davis, 1989), the Aegean (Jolivet & Brun, 2010; Lister et al., 1984), and the North Atlantic Caledonides (Fossen, 2010; Osmundsen et al., 2020; Wiest, Jacobs, et al., 2020; Wiest, Wrona, et al., 2020). Recent work shows that low‐angle normal faults play a critical role in shaping the style of rifting that leads to continental breakup, such as the South China Sea (Deng, Ren, et al., 2020), the Norwegian sea (Muñoz‐Barrera et al., 2021; Osmundsen & Ebbing, 2008; Osmundsen et al., 2020), and the Iberian margin (Lymer et al., 2019; Peron‐Pinvidic & Naliboff, 2020; Ranero & Pérez‐Gussinyé, 2010). The development of low‐angle normal faults has been explained either by flexural rotation of initially high‐angle normal faults to lower‐angles in response to tectonic unloading of hangingwall (Arca et al., 2010; Roger, 1988; Sandiford et al., 2021) or by reactivation of pre‐existing thrust faults catalyzed by high fluid flux and high pore fluid pressures resulting in long‐term fault zone weakening (Collettini et al., 2009; Morley, 2014).…”

“…High resolution seismic reflection data have been widely used as a powerful tool for the analysis of basinal and crustal scale structures by both academic and industry practitioners (Chauvet et al., 2020; Gans et al., 1985; Lymer et al., 2019; Sapin et al., 2021; Unruh et al., 2008). In particular, increasing amounts of high‐quality, dee p 2D/3D seismic reflection data and deep drilling on passive margins provides unprecedented imaging of deep crustal levels (Clerc et al., 2015; Deng, McClay, & Bilal, 2020; Deng, Ren, et al., 2020; Muñoz‐Barrera et al., 2021; Sapin et al., 2021) together with insights into the composition and structure of crystalline basement that often appears acoustically transparent due to low impedance contrast and seismic wave attenuation at depth (Allmendinger et al., 1987; Brown, 1991; Fazlikhani et al., 2017; Lenhart et al., 2019; Phillips et al., 2016). For instance, recent work using deep seismic reflection data in extensional terranes shows extensive igneous intrusion in the upper and lower crusts (Phillips et al., 2018; Wrona et al., 2019), inherited basement fabrics (Collanega et al., 2019; Fazlikhani et al., 2017; Osagiede et al., 2020; Phillips et al., 2016), and typically‐layered lower crust bounded at the base by a high‐amplitude Moho reflection and overlain by transparent upper crust with elevated geotherms (Allmendinger et al., 1987; Chauvet et al., 2020; Deng et al., 2020; Dong et al., 2020; Miller et al., 2005).…”