Channel-Levee Systems in a Tropical Carbonate Slope Environment and the Influence of Syn-Sedimentary Fracturing, Browse Basin, Australian Northwest Shelf

Abstract

The Miocene succession of the Browse Basin, Australian North-West-Shelf hosts one of the largest Neogene tropical paleo-barrier reef systems. This barrier reef existed from the middle to late Miocene, and the growth architecture and development of the system is reasonably well understood. In this talk, we present a high-resolution 3D seismic investigation of the slope system coeval with the barrier reef. The study includes two overlapping 3D seismic surveys that cover an area 2116 sq km and have a lateral resolution of 14 or 20 m. While most turbidite studies focus on siliciclastic systems, the Miocene slope-succession of the Browse Basin reveals channel and channel-levee complexes on a carbonate-dominated slope. We present, to date one of the only detailed geomorphological descriptions of the development of channel systems in the carbonate environment. The channels develop from an early stage with < 3 km channel length and < 70 m incision, to a mature stage in which single tributaries have merged to form larger channel-systems with channel lengths of 12 m to > 20 km and 150 m to > 200 m incision depth. Additionally, we present a detailed description of a deep-water, 10 km long channel-levee complex with levee widths of up to 850 m. At the clinoform breakpoint, syn-sedimentary deformation structures are developed, which are attributed to differential compaction through the progradation and aggradation of the steep-sloped margin. This leads to shear-stress concentration and brittle normal-faulting. In the Browse Basin, an extensive network of syn-sedimentary fractures and small faults with a throw of up to a few meters is located directly landward of the channel heads. We argue that these faults may initiate turbidity currents and directly relate the development of these faults to the initiation of channels. Further, channel fills and syn-sedimentary fractures potentially form conduits for fluid migration and hence are important for the understanding of hydrocarbon reservoirs in carbonate slope systems.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016