The Baram Delta extends along the northwest coast and continental shelf of Borneo.
The Baram Delta is a river system located on the northwest coast of the island of Borneo that drains into the South China Sea. The river sources are mountains within central and southeastern Borneo that are politically part of Indonesia. The rivers drain through the Malaysian states of Sarawak and Sabah, and the Sultanate of Brunei. The Baram Delta has a triangular shape and extends in a northeast-southwest direction onshore and offshore of the coastal areas of Sarawak, Brunei and Sabah. It has two provinces: the East Baram Delta of Sarawak, called the Champion Delta in Brunei; and the West Baram Delta of Sarawak, called the Baram Delta in Brunei. The entire Baram Delta is an oil province both for Malaysia and Brunei.
Depositional Environment
Baram Delta sediments deposit in delta front and coastal systems. In a delta front, rivers carrying sediment from mountains inland empty their load into coastal waters. A delta grows, or pro-grades, seaward from a point on the coast. Finer-grained sediments deposit furthest offshore as the river advances. The system builds out so that fine-grained sediments deposit first followed by slowly coarsening, or larger-sized, grains. Tides, storms and coastal currents have transported and re-worked sediments along the coast. During earlier geological eras, tectonic uplift and rising sea levels forced the delta system back inland. Periods of crustal subsidence enabled the delta and sediment deposition to grow rapidly seaward. More than eight miles of sediment thickness accumulated in the Baram Delta since the beginning of the Lower Miocene period some 23 million years ago.
Setap
The oldest and lowest sedimentary sequence in the Baram Delta is the Setap Shale Formation. It consists of shale with occasional thin intervals of clay and sands. It lies mostly onshore of Brunei and part of Sarawak, where it is nearly 2 miles thick.
Belait
A four-mile thick layer of sandstones and clays---the Belait Formation---overlies the Setap Shale. This sequence contains some coal seams that are more than 12 feet thick.
Miri
The Miri Formation is a sequence of sands similar in age to the Belait Formation. The Miri overlies the Setap Shales in Brunei and is one of the reservoir sands of Brunei's Seria oil field.
Lambir
The Lambir Formation is similar in age to the Belait Formation. It consists of sandstones and shales with minor intervals of limestone.
Seria
The Seria Formation is a 1.2-mile thick sequence of sandstones that overlie the Miri Formation. Nodules of ironstone are common in these sands. Ironstone is ferrous oxide and ferrous carbonate mixture that is a type of iron ore.
Liang
The Liang Formations, similar in age to the Seria sequence, is a mixture of conglomerates and clays. A conglomerate is a mixture of cobbles, pebbles and boulders that were part of old river beds. Beds of lignite, an early form of coal, are abundant throughout the sequence.
Tags: Baram Delta, sediments deposit, Baram Delta Sarawak, Belait Formation, Borneo that, Delta Brunei