Bulletin of the Geological Society of Malaysia, Volume 43, Dec. 1999, pp. 417 – 432
Institute of Technology Petronas, 31750, Tronoh, Perak, Malaysia
Abstract: The recent study on the Sarawak Basin indicated that the formation, sedimentation and deformation of the basin were dominantly controlled by strike-slip tectonism. This finding seems to be inconsistent with the present available regional tectonic models including subduction (James, 1984) and southward thrusting (Untung, 1990) models where acceptance are already on the decline, judging from the recent publications. Although there are several publications on strike-slip lineaments in Sarawak, strike-slip tectonism was not regarded as one of the present tectonic models as the occurrences of strikeslip lineaments in Sarawak were only regarded as local phenomena.
This paper aims to further discuss the geological and geographical evidences for the presence of several major lineaments in the onshore area that could be used as evidences for strike-slip tectonism. Further, this will help in determining whether onshore Sarawak has experienced similar strike-slip tectonism as in the Sarawak Basin. The study has identified nine possible major strike-slip lineaments in onshore Sarawak which could be the extensions of the offshore lineaments.
On the basis of its configuration, it is proposed that north-west Borneo has undergone a series of strike-slip movements which are in NW-SE orientation and gradually changing to eastward direction. The lineaments are progressively younger to the east with several cross-cutting slips. The model with strike-slip movements that are associated with the localised counter clockwise rotation, is proposed to be a new Tertiary tectonic model for the whole onshore and offshore Sarawak.