Abstract: Chronostratigraphy of Miocene Turbinitic Sequence of the Sabah Basin from Nannofossil Assemblages
M. R. Che Kob, M. Mohamed
The Sabah Basin, in offshore northwest Sabah, is basically 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 require special biostratigraphic analyses. Reliable age determination of Miocene strata in the Sabah Basin, especially in turbiditic sequences, has been achieved through quantitative nannofossil analysis. Foraminiferal assemblages in this type of sequence in the basin commonly indicate unreliable ages, which eemingly reflect undetected floods of older allochthonous forms masking younger autochthonous types. The quantitative analysis of nannofossils from sediments in seven wells clearly shows mixtures of nannofossils of different ages. These can be categorized into the more common occurrence of indigenous forms with fewer reworked older types. These data reflect the nature of sedimentary facies and support the turbiditic depositional model. The indigenous assemblages, when differentiated from the reworked assemblages, are then quite useful in determining the ages of these problematic Miocene sequences of the Sabah Basin.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994