Tectonic evolution of the Malay Peninsula inferred from Jurassic to Cretaceous paleomagnetic results

- A primary clockwise deflected direction is observed in Jurassic-Cretaceous red beds in Peninsular Malaysia.
- A secondary counter-clockwise direction is also recovered.
- Peninsular Malaysia experienced two-stage tectonic movements.
- The first stage is ascribed to the indentation of India into Asia starting 55 Ma.
- The second stage is ascribed to the collision of the Australian Plate with SE Asia.

A primary remanent magnetization is identified in the Jurassic-Cretaceous red bed sandstones of the Tembeling Group in Peninsular Malaysia. This high-temperature magnetic component is unblocked at 680-690 °C, revealing a clockwise deflected direction of Ds = 56.8°, Is = 31.6° (where ks = 8.5, α95 = 11.3° and N = 22) in stratigraphic coordinates. The primary origin of this component is ascertained by a positive fold test and a geomagnetic polarity reversal in the Kuala Wau section. Secondary remanent magnetizations are identified in the rocks of the Tembeling and Bertangga basins, which indicate a counter-clockwise deflection in the geographic coordinates (Dg = 349.1°, Ig = 15.3° where kg = 11.8, α95 = 5.1°, N = 72). The comparison with the expected paleomagnetic directions from the 130 Ma and 40 Ma Eurasian poles indicates two-stages of tectonic movement in the southern Malay Peninsula: (1) a clockwise rotation of 61.1° ± 11.9° accompanied by a 13.3° ± 8.1° southward displacement after the Cretaceous; and (2) a subsequent counter-clockwise rotation of 18.5° ± 5.0° to the present day position. The first stage of rotation is ascribed to tectonic deformation caused by the indentation of India into Asia after 55 Ma, while the second stage is attributed to the collision of the Australian Plate with SE Asia after 30-20 Ma. The present paleomagnetic results from the Jurassic-Cretaceous Tembeling Group thus reveal impacts of both of these collisions on SE Asia in general and on Peninsular Malaysia in particular.

245