Tectonic Evolution and Sedimentation of Sabah (North Borneo), Malaysia

Allagu Balaguru
Exploration Division, Petronas Carigali Sdn Bhd, Kuala Lumpur, Malaysia

The diverse structural trend and depositional framework of Sabah (North Borneo) were contributed by several regional tectonic events occurred since the early Tertiary. At least three major episodes were linked to NW-SE compressions coinciding with the ongoing subduction of the proto-South Chine Sea during the Late Eocene, Early Miocene and Middle Miocene.

The Late Eocene tectonic deformation is characterized by folding and thrusting of basement rock and older paleogene sediments. The Paleogene regional tectonic setting of Sabah seems to be very complex with southeasterly subduction in the NW Borneo, and extension in the SE in the Celebes Sea and Makassar Strait.

The Early Miocene deformation is interpreted to mark a major tectonic event, causing formation of the mélanges, major uplift and erosion which produced the Base Miocene Unconformity. This was followed by a change in depositional environment from deep-water to a shallow deltaic setting.

The Late Early Miocene marked the NW-SE direction of rifting of the Sulu Sea interpreted to have rejuvenated the Central Sabah Basin with regional extension and subsidence, and initiated rift basins as part of the formation of the Sulu Sea in a back arc setting.

Middle Miocene collision of the Cagayan Arc and Palawan micro-continental block caused another Middle Miocene Unconformity has been referred to mark the Deep Regional Unconformity in Sabah.

The Late Miocene tectonic event marks another major folding and uplift which can be correlated as the Shallow Regional Unconformity of this region. This latest tectonic event probably caused by strike-slip faulting and transpressional fault movement which continued during the Pliocene to present day.

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