The Bentong Suture in southwest Kelantan, Peninsular Malaysia

A newly constructed dirt road between Kampung Raja, Cameron Highlands, and Pulai, UIu Kelantan, crosses the Bentong Suture which here is at least 18 km wide. The eastern border zone of the suture consists of bedded chert containing an internal low-angle thrust and is separated from olistostrome to its west along a vertical fault. The western border zone comprises an igneous injection complex - several hundred metres wide - into the schist-phyllite component of the suture. This injection complex is the eastern fringe of the Titiwangsa granitoid complex. Rocks within the suture are thick packets of parallel to subparallel stratified olistostrome (types: with tuffaceous mudstone matrix, with tuffaceous phyllite matrix, and with phyllite matrix), thoroughly weathered, massive tuffaceous mudstone, well-bedded chert, phyllite, phyllite-schist and a serpentinite lens. The olistostromal packets contain bedding-parallel mylonite zones. The general strike is NW-SEdips are moderately steep to verticaldip inclinations are towards NE. Reverse faults and low-angle thrusts also indicate SW-vergence. Along two stretches of the road that crosses the suture, low-angle thrusting towards south represents a younger tectonic activity. The various rock types of the suture seem to occur as at least seven tectonic units. From west to east (or from stratigraphically lower to higher levels) a complete tectonic unit is composed of a systematic sequence of schist and phyllite, olistostrome with or without massive mudstone interval, and bedded chert. The recurring rock sequence in each tectonic unit suggests that the units are stacked rock assemblages or form an imbricated structure, presumably as result of collision between the continental lithospheric plate in the east with a Gondwana continental crustal sliver to the west of the suture. Subduction northeastward appears consistent with dominant southwest vergence that is shown by the outcrops. The tectonic units of the suture proper were probably crustal and supracrustal rocks occupying a marine - very likely oceanic - environment between the colliding continental lithospheric masses. The presence of serpentinite and abundance of volcanogenic material suggest that the particular marine environment also included an island arc