Abstract

The Barcoo Sub-basin forms the southern part of the Browse Basin of Australia’s northwestern margin. Miocene reactivation of older Precambrian through Mesozoic-aged structures has resulted in a present-day complex right-lateral wrench zone. The fault system displays restraining and releasing bends separated by areas of almost pure strike-slip displacement, along its 180 km length. Reactivation and inversion varies along the system, with the southern end structurally highest, offsetting beds up to and including the seafloor. The location of restraining and releasing bends controls the occurrence of oil and gas shows in nine wells drilled in the sub-basin, with Neogene inversion causing trap leakage in a number of cases. Right-lateral motion on the Barcoo Fault system, in contrast to a proposed regional-scale left-lateral movement component on the northwestern margin as a whole, implies strong strain partitioning along the margin with regional tectonic control. We propose that the structural domain boundaries may be controlled in part by the location of the continental collision zone between the northernmost limit of Australian continental crust with the southernmost continental fragments of the Eurasian plate, in the vicinity of the island of Sumba.

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