f Structural lineaments of onshore Sabah and their relationship to the regional geodynamics of Southeast Asia

The present structural elements of Sabah are the overprint of several phases and episodes of orogenies and geologic events. Several regional tectonic events have converged in this region since early Tertiary producing well developed compressional and extensional structures. The continued regional collision and movement have altered most of the old structures. The pre-existing structures such as regional transcurrent faults provide weakest zones for stress transfer and determined the movement vectors. The study of synthetic aperture radar (SAR) images of onshore Sabah indicated several prominent structural trends. These trends, which have imprinted and reactivated throughout geologic time, are mostly related to the regional geodynamic evolution of SE Asia. The prominent features observed on the onshore Sabah are the structural elements related to the counter-clockwise rotation. The study of the lineaments and their kinematics indicate that most part of the onshore Sabah involved in these rotations. The counter-clockwise rotation of SE Asia occurred since Early Miocene (Hall, 1996) or perhaps<br>earlier. It is believed to be related to the collision of the northward moving Indo-Australian plate with the Eurasian plate and the Philippine Sea plate. The collision has caused SE Asia region to protrude southeastward and the Philippine Sea plate to rotate in clockwise direction. This rotation caused the area in eastern margin of SE Asia to move in counter-clock wise direction. In general the onshore Sabah can be divided into four structural blocks, Western, Northwest, Central and Eastern blocks (Figure 1). All of these blocks seem to rotate as separate unit in counterclockwise direction. The boundary between these blocks appears as linear features which are mostly<br>related to the transpression movement. Associated with it is the push-up restraining bends, oblique thrust faults and en echelon drag folds.