Apr 9, 2014 - http://www.searchanddiscovery.com/abstracts/html/2014/90189ace/abstracts/1840529.html ... Carbonate BuildUps at the Margin of a Very Wide.
24/02/2015 Tectonic, SeaLevel and Oceanographic Controls on the Distribution and Growth of Isolated Carbonate BuildUps at the Margin of a Very Wide Plat…
Tectonic, SeaLevel and Oceanographic Controls on the Distribution and Growth of Isolated Carbonate BuildUps at the Margin of a Very Wide Platform (NW Australia) Muhammad M. Saqab1, Julien Bourget1 and Mike Dentith1 1Centre for Petroleum Geoscience & CO2 Sequestration, School of Earth & Environment, University of Western Australia,
Perth, Western Australia, Australia April 9, 2014 Wednesday 11:30 A.M. AAPG Annual Convention and Exhibition, Houston, TX
Abstract Isolated carbonate buildups (ICBs) represent attractive hydrocarbon exploration targets. They are often seen as longterm transgressive features; but their distribution within basins and growth history can be difficult to predict as they respond to the interplay between various tectonic, eustatic, and oceanographic parameters. Here we use a 3D seismic megasurvey (18,000 km2) combined with well data to understand the timing and mechanisms of formation of tropical Quaternary ICBs in NW Australia. At presentday, these ICBs are typically 130 km wide and form clusters of ∼ 150 buildups, developing 2 to 85 km from the edge of a 650 kmwide continental shelf. The physiography of the area is analogous to some ancient carbonate systems that formed along very wide shelves and epeiric seas (i.e. DevonianCarboniferous buildups of the Caspian region). Results demonstrate that the structural evolution of the margin had a major impact on the distribution of the ICBs. Main fault activity commenced during the latest MioceneEarly Pliocene, corresponding to the initial collision of Australian Plate with Banda Arc. Fault activity peaked in the late Pliocene (∼3 Ma), and was associated with flexural reactivation of structural highs (uplift) and lows (subsidence) along the shelfmargin. Later, during the Quaternary, ICBs developed on the highs. This late Pliocene event is synchronous with the uplift of Timor. Penecontemporaneous signatures of ocean bottom currents (i.e. erosional surfaces, moats and contourite drifts) of early Quaternary age (∼2 Ma) suggest a change in oceanographic regime along the NW Australian margin. It is probable that the reactivation of the Australian margin and the uplift of Timor narrowed the path of the Indonesian Throughflow (ITF) warmwater current. Despite potentially good conditions for carbonate production (basement highs and warm water ocean currents), ICBs did not form until the MidQuaternary (ca. 0.90.6 Ma). This age corresponds to the onset of major sealevel fluctuations associated with repeated, highamplitude (+120 m) deglacial rises, longterm highstands and slow falls. Thus, we infer that the NW Australia ICBs formed due to: (1) structural shaping of the margin; (2) oceanographic changes, and; most importantly, (3) onset of repeated highamplitude transgressions reactivating the carbonate production along isolated highs following 4th5th order lowstand exposures and allowing catchingup carbonate morphologies to develop. AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014
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