The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacustrine with marine influence in latter. sequence consists mainly siltstone, several intercalations fine-grained sand volcanic tuff. Based on well data, Mid-Upper sediments exist Basin deeper parts half grabens sub-basins. Hence, this implies age basin initiation at Mid-Eocene, rather than as tradition...