ExxonMobil Exploration Company, United States

The origin of seismic reflections in slope deposits of a Miocene carbonate platform, offshore Sarawak, was studied using cores, well-log data, and two-dimensional seismic. This isolated carbonate platform has slope angles ranging from 2 to 25 degrees . Our interpretation of the seismic data is that the asymmetric and high-rising platform (250-300 m relief) has different stratigraphic character for the southern and northern flanks. The southern slope was characterized by bypass or erosion throughout the aggrading phase of platform development. It was subsequently buried by shale with downbending, onlapping beds that indicate terrigenous sediment transport from the south. An alternative is folding during tectonic deformation. On the northern flank, the shale already started to pile up during platform aggradation. Phases of erosional or bypass conditions were short and alternated with two phases formed when platform debris interfingered with surrounding shale. Shale intercalations can be recognized seismically by negative reflections that quickly lose amplitude away from the platform. Although the overall shape of the platform is probably related to an older structural pattern of the Luconia Province, the asymmetry of the platform architecture and the distribution of sediments are most likely the results of paleowinds.