Bulletin of the Geological Society of Malaysia, Vol 47, Dec. 2003, pp. 7-26
1lnstitute of Geophysics, University of Bergen, Allegt. 70, N-5007 Bergen, Norway
2Geophysics Program, School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia
3PRAD-PMU, Petronas Tower 1, Petronas Twin Towers, 50450 Kuala Lumpur, Malaysia
Abstract: A new theoretical framework, Global Wrench Tectonics, is employed for understanding the structural development of SE Asia, focussing particularly on the NW Borneo continental margin. The new theory, which is strongly aligned to principles of classical physics, shows that this structurally complex region is not one of geological ‘self-rule‘ but a direct product of the global dynamo-tectonic machinery. It can be shown that the Alpine tectonic revolution on Earth is the consequence of a certain westward wrenching of some outer planetary layering, governed by acceleration in spin rate and associated inertia forces. This global system give rise to continental rotations, and strong shear deformation, notably within the thin and fragile oceanic ‘lithosphere‘. The extensive NNE-SSW oriented foldbelt of the Indian Ocean is a major left-lateral shear zone, having formed in response to a significant northeasterly inertia-driven wrench displacement of a combined Antarctica/Australia block relative to Africa. This northward movement of Australia during the Alpine climax reactivated the old Indonesian Benioff Zone; the present Indonesian region started to attain its arcuate shape, and other structural effects from the Austral-Asia collision began to complicate the picture. A new dynamo-tectonic wave commenced in the early Miocene, and resulting from this global Neogene pulse Australia and environs underwent a 70 degrees of anticlockwise rotation, eventually docking with SE Asia to attain its present azimuthal orientation, in Upper Miocene-Recent time. This geographic juxtaposition of two originally widely separated regions gave rise to the Wallace Line, and a NW-directed stress field imposed significant tectonization in the Celebes Sea, the southern Sulu Sea, and North Borneo (Sabah). Australia‘s tectonic impingement with SE Asia caused a certain counterclockwise rotation of the eastern half of Borneo, and a marked thrust front and imbricated sedimentary wedge along the western continental margins of Sabah and Palawan evolved. The overall structural situation and basin development of the South China Sea region can apparently be readily accounted for within the framework of the new global theory.