Bulletin of the Geological Society of Malaysia, Volume 49, April 2004, pp. 111 – 117
Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia, 43600 Bangi
Abstract: The pre-Tertiary of continental SE Asia, the Indosinia and Sundaland tectonic blocks, most probably hosts a number of brecciated impact structures with good reservoir properties. Hydrocarbons that migrated or re-migrated during the Tertiary may have accumulated in such structures where top seal is present and these structures therefore constitute a potential hydrocarbon play. In the known sedimentary basins of Sundaland, the pre-Tertiary lies too deep or too shallow to be of commercial interest to the petroleum industry. The shallow basement has been considered to possess less proven trap styles of the stratigraphic and “buried hills” categories. Very recently, three areas onshore Peninsular Malaysia were proven products of meteorite impacts. Their definitive features of shock metamorphism comprise multi-directional cleavage in quartz crystals, mosaicism in their optical extinction, and suevite breccia in association with circular topography. About several dozen of circular features have been identified in the peninsula and study is in progress to ascertain their nature. The peninsular area constitutes less than 15 per cent of the pre-Tertiary expanse of Sundaland. The presence of more impact structures in pre-Tertiary Sundaland is undeniable. In addition, the wide offshore areas of shallow basement (>1 km deep) bordering the petroleum basins are worth exploring for this new play.