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The Sabah Basin, Eastern Malaysia is a Neogene trench-associated sedimentary basin filled with progradational cycles of marine and coastal sediments that display spectacular arrays of facies changes. The strata also show a decreasing intensity of deformation resulting from an interplay of subsidence due to local extension and compression due to crustal convergence. Consequently, age determinations and correlation of these strata create various problems that reqwre special biostratigraphic methods. More reliable age-determinations of Miocene strata in the Sabah Basin, especially in turbiditic sequences, have been achieved through quantitative nannofossils analysis. Foraminiferal assemblages in this type of sequences in the basin commonly indicate unreliable ages which seemingly reflect , undetected floods of older, allochthonous forms masking lesser preserved younger autochthonous type. The analyses of nannofossils from sediments in five wells also show mixtures of nannofossils of different ages. Analysis of nannofossils abundance allow the recognition of the more common occurrence of indigenous forms as compared to fewer reworked older types. The abundance pattern thus reflects the nature of sedimentary facies and support the turbiditic depositional model. The dominant indigenous assemblages, as differentiated from the reworked assemblages through quantitative analysis are then quite useful in determining the ages of this problematic Miocene sequence of the Sabah Basin.

The growth architecture, faulting and karstifications of the Miocene carbonate build-up in Central Luconia Province, offshore Sarawak, Malaysia were studied using an integrated 3D seismic and calibrated with core and well-logs. A high resolution well-to-seismic tie was obtained through the application of climate stratigraphic approach. This calibrated 3D seismic data were then analyzed using sequence stratigraphy and seismic attributes analyses. The RMS (Root Mean Square) attribute displays the best build-up morphology image that distinctively disseminates zones withinbuildup and interbuildup areas. Spectacular arrays of facies heterogeneities across the buildup were also observed. The facies range from back reef lagoonal and reef front to off-reef facies. The calibrated seismic facies analysis reveals the association of the reservoirs with the mounded reefal and progradational facies. Evidence for porosity and permeability enhancements through karstification was also observed. The extraction of seismic attributes at different stratigraphic levels of the buildup shows progressive growth architecture of the build-up from Early Miocene to Late Miocene. The carbonates were accumulated in two major sequences. The initial growth corresponded to a major sea level rise in the Early to Middle Miocene. The build-up was then subaerially and repeatedly exposed, and finally drowns during a major sea level rise at the beginning of the Pliocene. Generally, three main factors controlled the growth and the architecture of the buildups; tectonics, relative sea level changes and also the paleowind direction.

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