Description
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 3D marine seismic survey acquired in late 2005 across the Torosa gas field. 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 3D 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). A 2D seismic line from Spectrumasa (0‐7000ms twt) provides regional control and allows for the interpretation and better understanding of sequence stratigraphic markers. Well logs obtained from the public domain Western Australia Petroleum Information System (WAPIMS) website allow for the generation of synthetic seismograms and help constrain lithological interpretations. 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. Eight distinct geomorphological stages in the evolution of this ~1500 m thick Oligocene to 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‐oceanic currents also play important roles. Earlier workers for example suggest that 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. These and other geomorphological observations are imaged beautifully in this volume of data.
