Karl Bloor

Karl Bloor

Seismic geomorphology of Miocene carbonate sedimentation in the Browse Basin, North West Shelf, Australia

Karl Bloor
M.S. Candidate
Department of Geological Sciences
San Diego State University
Advisor Dr. David Kimbrough

Wednesday, May 8th, 2013
CSL 422, 8:00am

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ABSTRACT pdf
This study provides a geomorphological interpretation of Miocene carbonate sedimentation along the Scott Reef Trend in the Browse Basin of NW Australia using a high resolution marine 3D “Torosa” seismic survey. Miocene carbonate sedimentation in the Browse Basin occurs along a NE-SW trending structural high resulting from multiple phases of extensional and inversion tectonics. The Torosa data set was provided by Dr. Henry Posamentier with the permission of Woodside Energy and Chevron Energy Technologies Company. It consists of ~740 km2 of full-fold data from 900-2100ms two-way travel time (twt) (~750-2500m sub-sea vertical depth). The purpose of the survey was to help better understand the petroleum system which lies within deeper Jurassic sediments (below 2100ms twt). For regional control a 2D seismic line was acquired from Spectrumasa extending from 0-7000ms twt allowing for the interpretation and better understanding of sequence stratigraphic markers. Well logs obtained from the Western Australia Petroleum Information System (WAPIMS) website, a source for industry data in the public domain, allow for the generation of synthetic seismograms and helps constrain lithological interpretations.
Eight distinct geomorphological stages in the evolution of the massive ~1500 m thick Early to Late Miocene carbonate shelf depositional setting are recognized. These stages of carbonate sedimentation are mostly controlled and punctuated by cyclical regional sea level fluctuations. Relative sea level fall results in the karstification of the shallow water carbonate platform, and a relative sea-level rise drapes the karstified terrain with carbonate mud. Carbonate sedimentation then reestablishes during the period of relatively high sea-level and the cycle repeats itself. Sea-level fluctuations aren’t the only controls on this carbonate deposition, basin subsidence and changing paleo-ocean currents also play a large role. The Indonesian Throughflow which brings warm, low salinity water across the North West Shelf of Australia may be the key to initiation and final demise of topical carbonate sedimentation along the Scott Reef Trend (Rosleff-Sorensen et al., 2012). These and other geomorphological observations are imaged beautifully in this volume of data. In this unique area of the world cyclical shallow water tropical carbonate sedimentation existed for ~20 million years and now is covered by ~ 550m of Pliocene-recent carbonate muds and ~400m of water.