Three-dimensional seismic geomorphology and sedimentology of heterozoan and photozoan carbonate systems, Browse Basin, NW Australia
Final Report Abstract
During the Cenozoic, the carbonate succession of the Browse Basin on the North West Shelf of Australia developed from a non-tropical carbonate ramp to a tropical barrier reef system that finally drowned during the late Miocene. The morphologic development of this carbonate system was documented and analysed using an extensive two and three-dimensional seismic refraction dataset. The integration of this seismic dataset with geophysical and sedimentological well data allowed to identify the main factors controlling the carbonate system. The study focused on three aspects of carbonate platform development: 1) the role of sea-level change on slope erosion in non-tropical carbonates, 2) the turnover from a nontropical to a tropical carbonate platform and 3) the 3D documentation of a drowning reef sequence. Key outcomes of these study issues are: 1. The clinoform foresets of the non-tropical carbonate platform show different erosion patterns depending on the overall slope morphology. In the lower portion of the succession, the carbonate platform resembles a low-gradient distally steepend ramp, with a linear to sigmoidal slope curvature. The clinoform foresets of this ramp are dissected by larger channels and smaller gullies, evenly distributed along the clinoform front. During the later stages of platform development, the slope of the non-tropical carbonate platform steepens to form a distally steepend ramp with a concave-upward slope morphology. The clinoform foresets of this platform stage are relatively smooth, with numerous but small gullies. This cooccurrence of a change in platform slope morphology and the erosion pattern on the clinoform front could indicate that slope inclination is an important control on submarine channel systems. In contrast, sea-level falls and low-stands seem not to be the dominant control on submarine channel incision for the non-tropical carbonate system of the Browse Basin. 2. The onset of tropical reef growth in the Browse Basin in the Mid-Miocene can be interpreted as predominantly climatically controlled, whilst the subsequent reef evolution seems determined by a more complex interplay of regional subsidence, eustatic sea-level change and climatic and oceanographic variations. The influence of warm oceanic currents, e.g. the Leeuwin current seems to be an important controlling factor for the timing and distribution of reef growth. The interruption of the Leeuwin current flow in combination with global climatic cooling and third order sea-level variation are assumed to be the major contributing factors to the demise of the tropical reef system. 3. The Miocene section of the Browse Basin hosts with a length of >250 km one of the most extensive barrier reef systems in the Neogene record. Initial reef growth, forming several relatively small reef ridges, coincided with the transition into the Mid-Miocene climate optimum. A sequence boundary that was associated with sea-level fall after the Mid-Miocene climate optimum terminated the growth of the massive barrier reef of the second reef generation. After a phase of emergence in the inner platform area, reef growth is interpreted to have re-commenced in a slightly downstepped position during the initial phase of the earliest late Miocene sea-level rise. A continuation of transgression forced the reef front to retreat landwards. During this time the reef belt developed a pronounced reef front on the landward side, separating a strongly aggradational reef belt from a deeper lagoon. Further sea-level rise led to a second phase of backstepping and resettlement of reefs as isolated atolls above buried reefs of the first reef generation. Relic platforms survived until the Miocene/Pliocene boundary, before being subaerially exposed in the Messinian and subsequently drowned by a major Zanclean sea-level rise.
Publications
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(2008). The evolution of a Miocene barrier reef in NW Australia: Insights from a 4D-perspective. 26th IAS Meeting, Bochum, Germany
Rosleff-Sörensen, B., Reuning, L., Back, S. and Kukla, P.
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(2009). Seismic Expression of Sedimentary Processes on a Carbonate Shelf and Slope System, Browse Basin, Australia – Part I – Non-tropical Carbonates, Eocene to Lower Miocene. EAGE
Reuning, L., S. Back, H. Schulz, M. Hirsch, P. Kukla & J. Grötsch
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(2009). Tectonic vs. eustatic control on the 3D sedimentary architecture of a carbonate succession from Browse Basin, NW, Australia: An integration of well logs, 2D- and 3D-seismic data. EGU General Assembly
Rosleff-Sörensen, B., Reuning, L., Back, S. & Kukla, P.
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3D seismic geomorphology and sedimentology of the Chalk Group, southern Danish North Sea. Journal of the Geological Society, London, Vol. 168, 2011, pp. 1–13
Back, S., Van Gent, H., Reuning, L., Grötsch, J., Niederau, J., Kukla, P.
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Seismic geomorphology and growth architecture of a Miocene barrier reef, BrowseBasin, NW-Australia. Marine and Petroleum Geology (2011)
Rosleff-Soerensen, B., Reuning, L., Back, S., Kukla, P.
