28 matthew.reeve09@imperial.ac.uk 29 Corresponding Author 30 Harya D. Nugraha 31 harya.nugraha14@imperial.ac.uk 32 33 34 35 2 ABSTRACT 36Deep-marine deposits provide a valuable archive of process interactions between sediment gravity 37 flows, pelagic sedimentation, and thermo-haline bottom-currents. Stratigraphic successions can also 38 record plate-scale tectonic processes (e.g. continental breakup and shortening) that impact long-39 term ocean circulation patterns, including changes in climate and biodiversity. One such setting is 40 the Exmouth Plateau, offshore NW Australia, which has been a relatively stable, fine-grained 41 carbonate-dominated continental margin from the Late Cretaceous to Present. We combine 42 extensive 2D (~40,000 km) and 3D (3,627 km 2 ) seismic reflection data with lithologic and 43 biostratigraphic information from wells to reconstruct the tectonic and oceanographic evolution of 44 this margin. We identified three large-scale seismic units (SUs): (1) SU-1 (Late Cretaceous) -500 m-45 thick, and characterised by NE-SW-trending, slope-normal elongate depocentres (c. 200 km long and 46 70 km wide), with erosional surfaces at their bases and tops, which are interpreted as the result of 47 contour-parallel bottom-currents, coeval with the onset of opening of the Southern Ocean; (2) SU-2 48 (Palaeocene -Late Miocene) -800 m-thick and characterised by: (i) very large (amplitude, c. 40 m 49 and wavelength, c. 3 km), SW-migrating, NW-SE-trending sediment waves, (ii) large (4 km-wide, 100 50 m-deep), NE-trending scours that flank the sediment waves, and (iii) NW-trending, 4 km wide and 80 51 m deep turbidite channel, infilled by NE-dipping reflectors, which together may reflect an 52 intensification of NE-flowing bottom currents during a relative sea-level fall following the 53 establishment of circumpolar-ocean current around Antarctica; and (3) SU-3 (Late Miocene -54

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.

Mass-transport complexes (MTCs) are deposits of subaqueous mass flows, and comprise slides, slumps and debrisflows (Dott, 1963; Nardin, Hein, Gorsline, & Edwards, 1979; Posamentier & Kolla, 2003). MTCs are found along all continental margins, and can play a major role in sediment transfer from the continents to the deep ocean (e.g. Hjelstuen,

Contractional features characterize the toe domain of mass transport deposits. Their frontal geometry is typically classified as frontally confined or frontally emergent. However, it remains unclear how the style of frontal emplacement and contractional strain within a mass transport deposit vary along-strike. We use bathymetry and 3D seismic reflection data to investigate the lateral variability of frontal emplacement and strain within the toe domain of the Haya Slide in the Makassar Strait, offshore Indonesia. The slide originated from an anticline flank collapse and the toe domain is characterized by a radial fold–thrust belt that reflects southwestwards emplacement. The frontal geometry of the slide changes laterally. It is frontally confined in the south and is associated with a deep, c. 200 m b.s.f. planar basal shear surface. The frontal geometry gradually changes to frontally emergent in the west, associated with a shallow, c. 120 m b.s.f., c. 3° NE-dipping basal shear surface. Strain analysis shows c. 8–14% shortening, with the cumulative throw of the thrusts increasing along-strike westwards from c. 20–40 to c. 40–80 m. We show that even minor horizontal translation of mass transport deposits (c. 1 km) can result in marked lateral variability in the frontal geometry and strain within the failed body, which may influence their seal potential in petroleum systems.