Understanding the poorly-exposed Lahat and Lemat formations of the South Sumatra Basin using an outcrop analogue study

The Middle-Eocene to Late-Oligocene Lahat and Lemat Formations are present within the South Sumatran Basin. The deposits are poorly-exposed, and have been mainly described from subsurface data (core and seismic). The formations have been interpreted as having been deposited within basin margin alluvial fans and fluvial systems, which pass into contemporaneous lacustrine environments within the basin centre. Organic rich source rocks (coastal-coals and lacustrine-shales) have been identified at various horizons throughout the deposits. These lithologies are thought to produce approximately ten percent of hydrocarbons within the region, making the deposits an important part of the South Sumatran hydrocarbon play. An analogue study from the similar depositional systems of the Permian-aged Cutler Group, of the Paradox Basin, Utah, has been used to better understand the geology of the Lahat and Lemat Formations.