Paleomagnetism of Peninsular Malaysia

Paleomagnetic results from Upper Jurassic to Paleocene rocks in Peninsular Malaysia show counter clockwise (CCW) rotations, while clockwise rotations (CW) are predominantly found in older rocks. Continental redbeds of the Upp er Jurassic to Lower Cretaceous Tembeling Group have a post folding remagne tization, giving a VGP at N54 degrees E29 degrees, corresponding to approxi mately 40 degrees of CCW rotation relative to Eurasia and 60 degrees CCW re lative to the Indochina block (Khorat Plateau). Samples from Cretaceous to Paleocene mafic volcanics of the Kuantan dike swarm and the Segamat basalts give VGPs at N59 degrees E47 degrees and N34 degrees E36 degrees, respecti vely. These Malayasian data are indistinguishable from the Late Eocene and Oligocene VGPs reported for Borneo and the Celebes Sea and are similar to t he Eocene VGPs reported for southwest Sulawesi and southwest Palawan. The o ccurrence of CCW deflected data over this large region suggests that much o f Malaysia, Borneo, Sulawesi, and the Celebes Sea rotated approximately 30 degrees to 40 degrees CCW relative to the Geocentric Axial Dipole (GAD) bet ween the Late Eocene and the Late Miocene, although not necessarily synchro nously, nor as a single rigid plate. These regional CCW rotations are not c onsistent with simple extrusion based tectonic models. CW declinations have been measured in Late Triassic granites, Permian to Triassic volcanics, an d remagnetized Paleozoic carbonates. The age of this magnetization is poorl y understood and may be as old as Late Triassic, or as young as Middle or L ate Cretaceous. The plate, or block rotations, giving rise to these directi ons are correspondingly weakly constrained. (C) 1999 Elsevier Science Ltd. All rights reserved.