Rowley

NW Australia Offshore

Roebuck Geographic Basin

The Roebuck geographic basin is a depocenter of NW Australia margin, located between the Northern Carnarvon and the Browse depocenters, eastward of the Argo Abyssal plain and westward of the Canning geographic basin. It covers, approximately, 90000 km². As illustrated on this tentative geological interpretation, two geographic sub-basin (Rowley and Bedout) separated by a buried hill of the basement are recognized. These geographic sub-basins highlight two Mesozoic rift-type basins. In fact, above a pre-rifting infrastructure (Paleozoic or basement), Mesozoic rift-type basins were deposited. They are capped by the breakup unconformity, which emphasizes the end of a differential subsidence realm occurring, probably, near top Cretaceous. A relatively thin Cenozoic Atlantic-type divergent margin, mainly, characterized by a preponderant thermal subsidence, fossilizes the breakup unconformity. The proposed geological interpretation is not calibrated: the proposed ages are based on the stratigraphic signature of the area, i.e., they must be severely criticized (tested).

This tentative geological interpretation of a Canvas autotrace of a seismic line of Roebuck geographic basin corroborates, i.e., it does not falsify, the interpretation proposed on the previous autotrace. The Atlantic-type divergent margin is developed above the breakup unconformity. It is highlights the end of the lengthening of the Pangea continental crust and the onset of a seaward thermal subsidence associated with the oceanic expansion (sea floor spreading). The majority of the normal faults developed during the lengthening of the Pangea lithosphere die at the breakup unconformity. Such a geological feature is recognized on the majority of the seismic lines shot on this offshore as corroborated by the tentative interpretation of the next autotrace.

Here again, the extensional tectonic regime (σ₁ vertical) inducing the development of the rift-type basin, which predates the breakdown of the lengthened Pangea continental crust, ends at the breakup unconformity. Do not forget the proposed geological interpretation is not calibrated. The ages are based on the stratigraphic signature of the area, so they must be severely criticized (tested).