AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Tectonic Control of Sedimentary Architecture on Giant Continental Shelves: An Example from the Bonaparte Basin (North-West Australia)
(1) Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia.
Giant continental shelves (up to 3000 km in width) were widely developed during Palaeozoic and Mesozoic times. These depositional environments produced major hydrocarbon resources, including some of the giant fields of NW Africa (Mann et al., 2003). The Bonaparte basin (north-west Australia) represents a rare recent to modern analogue for these shelves and can provide major developments in our understanding of these mega geological end members. 3D seismic, high-resolution and conventional 2D seismic were used in combination will well data, to generate a detailed study of the shelf-edge stratigraphy and structure. This resulted in the recognition of the main phases of deformation and an understanding of their control on sedimentation from the Late Oligocene (onset of Australia’s collision with the Banda Arc) to the present-day. Our observations are consistent with the regional model of a partitioned collision-induced deformation (Harrowfield et al., 2003), but we further demonstrate that both left-lateral strike-slip tectonics and flexure-induced basement topography reactivation controlled the location and nature of the Neogene sediment depocenters along the northern Bonaparte shelf. Along the deformation phases, the Late Pliocene / Early Pleistocene transition has been marked by a major tectonic pulse that ultimately shaped the giant continental shelf architecture. It lead to the creation of structurally-controlled depositional settings including a large, > 100 m deep intrashelf basin and a series of pull-apart basins at the shelf-edge. These structurally-controlled features strongly affected the stratigraphic architecture of both the central basin and shelf-edge areas. Similar patterns of tectonic control on sediment distribution have been recognized in the Gondwana sequences of the North African platform (Boote et al., 1998). The Bonaparte shelf provides some keys to evaluating the importance of tectono-sedimentary relationships along giant continental shelves, and hence could be used to better understand its ancient counterparts.