Approximately 90% of Sri Lankan landmass is thought to consist of high-grade metamorphic rocks of granulite facies extending to the top of the amphibolite facies. The rest of the landmass, which extends from the west to the north of the country as a narrow belt almost parallel to the coastal margin, consists of Cenozoic sedimentary rocks. Exploration work has shown that twoprospective offshore sedimentary basins accessible by current technology are situated in Sri Lanka, namely the Cauvery and Mannar basins.
Recent studies have also identified the existence of hydrocarbon potential parallel to the continental shelf margin of the country, spreading out from the south to the east and north. However, the water depth at this margin is over 4km and therefore at the limit of current exploration capabilities.