Publications

The stratigraphic successions in the Pattani, Malay, Penyu, West Natuna and Nam Com Son Basins show many features in common, with a generalised succession driven by regional tectonics. In each basin a Late Eocene and Early Oligocene synrift phase was followed by postrift deposition from the Late Oligocene onward. The Early and Middle Miocene was characterized by variable degrees of inversion and also by extension in Nam Con Son Basin, followed by regional subsidence during the Late Miocene and Plio-Pleistocene. Accurately dating and correlating these successions has proved problematic since marine index fossils are of limited occurrence. However, using an integrated multidisciplinary sequence biostratigraphic approach tied to lithologies and seismic, it is possible to divide the succession into discrete genetic packages, which can be considered as stratigraphic sequences and can be correlated across the entire region.This paper describes a sequence stratigraphic succession from the Nam Con Son Basin in Vietnam. The sequences closely parallels sequence biostratigraphic frameworks previously proposed for the West Natuna (Morley et al 2003) and Malay Basins (Shamsuddin and Morley, 2006), but with the Nam Con Son Basin being at the distal end of the basin succession this area has more marine influence than other basins and this permits the age of stratigraphic packages to be better constrained using marine fossils. The Nam Con Son formational sequence succession can thus be placed within a relatively tight chronostratigraphic framework, allowing direct comparison with global sea level changes as suggested from Oxygen isotope data. By using a simple flexible numerical terminology for the sequences, it is thought that these can be utilized across the region.It is concluded that in addition to tectonics, global sea level change plays a major part in determining the formational succession across this region. In particular, the Cau and its lateral equivalents, the Barat Shale in West Natuna and Trengganu Shale in Malay Basin, relate to the Late Oligocene thermal and eustatic maximum. Similarly, the Mang Cau Formation, equivalent in part to the Terumbu carbonates and the Malay Basin holomarine seismic groups H and F, tie to the mid Miocene thermal and eusatatic maximum.The paper demonstrates the need for international cooperation in order to properly understand the stratigraphy of this important hydrocarbon producing region which extends across several national boundaries.Keyword: Sequence biostratigraphy, Nam Con Son Basin, Cau, Mang Cau, Barat Shale