--> Characteristics of the Frontier Northern Houtman Sub-Basin Formed on a Magma-Rich Segment of the Western Australian Margin

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Characteristics of the Frontier Northern Houtman Sub-Basin Formed on a Magma-Rich Segment of the Western Australian Margin

Abstract

The northern part of the Houtman Sub-basin (Perth Basin) is adjacent to the Western Australian large igneous province of the Cuvier margin and the Wallaby Plateau. Recent studies have shown significant prospectivity for oil and gas of the southern Houtman Sub-basin. In the north however, few 2D seismic lines have been acquired to date. These limited data indicate continuation of the structural style, major sequences and potentially key petroleum systems elements from the south to the north. The significant increase in the amount of intrusive and extrusive magmatism in the northern part of the sub-basin imaged in seismic data is related to the transition from a magma-poor to magma-rich segment of the margin. The Houtman Sub-basin was formed during two stages of rifting. During Early Permian rifting, a complex network of north-south oriented half-graben were formed in the inboard parts of the basin. The second stage of rifting occurred in the Jurassic to Early Cretaceous and resulted in accumulation of up to 10 km of synrift section. In the Berriassian-Valanginian, an extensive system of dykes and sills formed in the seaward part of the basin. This heavily intruded area is adjacent to the Wallaby-Zenith Transform Fault and the Wallaby Saddle. During Valanginian breakup, this area was affected by volcanism and partially buried beneath the volcaniclastic Seaward Dipping Reflector Sequences of the Wallaby Saddle. The geometries of the outer Houtman Sub-basin are remarkably similar to those described off the Parana-Etendeka region on the Namibian margin. The geodynamic setting of both the Namibian and Western Australian volcanic margins are governed by large transform faults and complex rift propagation history. Data from the northern Houtman Sub-basin are consistent with results from recent numerical modelling of melt generation on rifted margins. The modelling suggests that crustal-scale transfer faults continuing as large transform faults on the oceanic crust act as rift propagation barriers and lead to excessive magmatism typical for volcanic margins. Due to the complex rift propagation history and volcanism continuing up to Early Aptian, the northern Houtman Sub-basin is likely to have experienced higher rates of heat flow affecting maturation of its source rocks. A new 2D seismic dataset over the northern Houtman Sub-basin acquired the Geoscience Australia in 2014–15 offers an opportunity to re-examine the petroleum prospectivity of this frontier basin.