Tectonic and oceanographic process interactions archived in Late Cretaceous to Present deep‐marine stratigraphy on the Exmouth Plateau, offshore NW Australia

Abstract

Deep‐marine deposits provide a valuable archive of process interactions between sediment gravity flows, pelagic sedimentation and thermohaline bottom‐currents. Stratigraphic successions can also record plate‐scale tectonic processes (e.g. continental breakup and shortening) that impact long‐term ocean circulation patterns, including changes in climate and biodiversity. One such setting is the Exmouth Plateau, offshore NW Australia, which has been a relatively stable, fine‐grained carbonate‐dominated continental margin from the Late Cretaceous to Present. We combine extensive 2D (~40,000 km) and 3D (3,627 km2) seismic reflection data with lithologic and biostratigraphic information from wells to reconstruct the tectonic and oceanographic evolution of this margin. We identified three large‐scale seismic units (SUs): (a) SU‐1 (Late Cretaceous)—500 m‐thick, and characterised by NE‐SW‐trending, slope‐normal elongate depocentres (c. 200 km long and 70 km wide), with erosional surfaces at their bases and tops, which are interpreted as the result of contour‐parallel bottom‐currents, coeval with the onset of opening of the Southern Ocean; (b) SU‐2 (Palaeocene—Late Miocene)—800 m‐thick and characterised by: (a) very large (amplitude, c. 40 m and wavelength, c. 3 km), SW‐migrating, NW‐SE‐trending sediment waves, (b) large (4 km‐wide, 100 m‐deep), NE‐trending scours that flank the sediment waves and (c) NW‐trending, 4 km‐wide and 80 m‐deep turbidite channel, infilled by NE‐dipping reflectors, which together may reflect an intensification of NE‐flowing bottom currents during a relative sea‐level fall following the establishment of circumpolar‐ocean current around Antarctica; and (c) SU‐3 (Late Miocene—Present)—1,000 m‐thick and is dominated by large (up to 100 km3) mass‐transport complexes (MTCs) derived from the continental margin (to the east) and the Exmouth Plateau Arch (to the west), and accumulated mainly in the adjacent Kangaroo Syncline. This change in depositional style may be linked to tectonically‐induced seabed tilting and folding caused by collision and subduction along the northern margin of the Australian plate. Hence, the stratigraphic record of the Exmouth Plateau provides a rich archive of plate‐scale regional geological events occurring along the distant southern (2,000 km away) and northern (1,500 km away) margins of the Australian plate.

Tectonic control on mass‐transport deposit and canyon‐fed fan system in the Ulleung Basin, East Sea (Sea of Japan)

“…Massive and/or repetitive mass‐wasting processes as documented in stage 1 can be caused by tectonic activities, resulting in MTD‐dominated sedimentation in the deep‐water environments (Figure 13b). This tectonic‐driven sedimentation pattern has been reported in many areas of the world (Frey Martínez et al., 2005; Gamboa, Alves, Cartwright, & Terrinha, 2010; Hampton, Lee, & Locat, 1996; Moscardelli et al., 2006; Nugraha et al., 2019; Pickering & Corregidor, 2005). In particular, in the fold‐and‐thrust belts, a variation of the source area, distribution, and geometry of MTDs could reflect the evolution of thrust faults and related folds (Festa, Ogata, Pini, Dilek, & Codegone, 2015; Ortiz‐Karpf et al., 2018).…”

“…The poor continuity and chaotic reflectors of this seismic facies indicate that rapid and non‐uniform deposition predominantly occurred. Many studies suggest that these seismic expressions derived from the MTD formed by slope deformational processes, including slide, slump and debris flow with plastic behaviour (Table 1; Brackenridge, Nicholson, Sapiie, Stow, & Tappin, 2020; Kim et al., 2020; Lee et al., 2001; Moernaut & De Batist, 2011; Nugraha, Jackson, Johnson, Hodgson, & Reeve, 2019; Pérez et al., 2016; Posamentier & Martinsen, 2011; Tournadour et al., 2015). SF2 is characterised by parallel and continuous well‐stratified reflections with high amplitude (Table 1).…”

The formation and implications of giant blocks and fluid escape structures in submarine lateral spreads

“…We adopt the seismic-stratigraphic framework of Nugraha et al (2018), which is based on their analysis of the Exmouth Plateau, c. 50 km SW of the study area (Figure 2a). Our study interval falls within SU3 of Nugraha et al (2018), within which we map four horizons based on the seismic continuity, amplitude, and frequency/spacing, as well as the seismic facies characteristics of the packages they bound. The lithology and geotechnical properties (i.e.…”

“…We divide the studied stratigraphic interval into three seismic units (SU-1-3). SU-1 is c. 500 m thick near the axis of the Kangaroo syncline, thinning westward and eastward to c. 200 m. SU-1 contains packages of chaotic, medium-to high-amplitude seismic reflections interpreted as stacked MTCs (Figure 3b-c) (Hengesh et al, 2012;Nugraha et al, 2018). SU-2 is thinner than SU-1, but also varies in thickness, being slightly thicker near the centre of the Kangaroo Syncline (c. 60 m) and thinning gradually westward and eastward to c. 30 m (Figure 3b).…”

“…Figure 1 Schematic diagram showing the classification of mass-transport complexes adopted in this study (modified from Nemec, 1990;Posamentier and Martinsen, 2011;Scarselli et al, 2013). Figure 3 a) Un-interpreted regional seismic section; b) Interpreted regional seismic section highlighting the key horizons and the seismic units the study area, note that the horizon H1 is the same horizon of Horizon C (see detail from Nugraha et al, 2018) which defines an unconformity of late Miocene (~9 Ma); c) Interpretation sketch of the regional seismic section.…”