The Tertiary basins of the Sunda Shelf of SE Asia were formed in the ?Mid-to Late Eocene and accumulated thick intervals of syn-rift lacustrine and low salinity organic rich shales throughout the Late Palaeogene. Towards the end of the Oligocene and into the Early Miocene marine transgression occurred throughout the region. A change to deep open marine sedimentation followed by a general shallowing and deposition throughout the Neogene, of great thicknesses of marginal marine and paralic sediments. The syn-rift sediments are the most important hydrocarbon source rocks in this region, although precise dating of them is difficult due to the long-ranging nature of the palynomorphs and the paucity of the microfauna. However characteristics of the depositional environments and nature of the source rocks deposited within separate provincial basins that were wholly or partially landlocked can be assessed from a detailed examination of the isolated palynomorph and kerogen assemblages. A classification of lacustrine depositional environments within the region on this basis is presented.