Paleomagnetism as a means of dating geological events

The Cenozoic tectonic evolution of Southeast Asia reflects the complex interactions of rifting, subduction, continental collision, and large-scale continental strike-slip faulting.

The island of Borneo is at the leading edge of several continental blocks that protrude from Southeast Asia as a wedge into the Indo-Australian and Philippine Sea plates (Fig. There are two end members of tectonic models for Borneo (Figs.

1) that accommodates the movement of Palawan during of the opening of the South China Sea.

1B, 1C): collision-extrusion (Briais et al., 1993; Replumaz and Tapponnier, 2003) and subduction-collision (Hamilton, 1979; Lee and Laver, 1995; Hall, 1996).

These models differ in four principal aspects: (1) the mechanism responsible for rifting and seafloor spreading in the South China Sea ca.

Mean Ch RM directions for seven locations between Kota Kinabalu and Keningau (declination, dec 12°–19°; inclination, inc –22°–23°) indicate minor clockwise rotation and modest tilting, whereas two locations near Tenom (dec 321°–345°, inc –6°–24°) record counterclockwise rotation and modest tilting.

Although we cannot precisely date the age of remagnetization, the results of fold tests from 4 locations, interpreted within the regional structural framework, strongly indicate that remagnetization occurred between 35 and 15 Ma, the waning stages of the Sarawak orogeny to an early phase of the Sabah orogeny.