Interpretation of regional gravity and magnetic data in Peninsular Malaysia


Author : M.H. Loke. C.Y. Lee, G. van KlinkenPublication : Bulletin of the Geological Society of MalaysiaVolume : 16Page : 1 – 21Year : 1983


Description

Bulletin of the Geological Society of Malaysia, Volume 16, Dec. 1983, pp. 1 – 21

 

Interpretation of regional gravity and magnetic data in Peninsular Malaysia

M.H. LOKE, C.Y. LEE, G. VAN KLlNKEN

School of Physics, Universiti Sains Malaysia, Penang

 

Abstract: A regional gravity survey covering the portion of Peninsular Malaysia between latitudes 2°N and 4°N was carried out to study the crustal structure. The total number of gravity stations obtained by Universiti Sains Malaysia is 450. Some aeromagnetic data covering mainly the southern half of the peninsula were also used in the interpretation.

In general, the gravity data reflect the regional geology of the area. A gravity maximum of up to 20 mgals, and a broad magnetic minimum with an amplitude of up to 30 gammas were obtained over the Central Belt. These anomalies may indicate a denser and more basic upper crust underlying the Central Belt. A gravity minimum with an amplitude of up to 50 mgals, was observed over the Main Range. A smaller gravity minimum, with an amplitude of 20 to 25 mgals, was also observed over the Eastern Belt granites. These anomalies are probably caused by the granite batholiths in these areas which have lower densities than the surrounding rocks.

The gravity values on both coasts of the peninsula are roughly the same. This indicates that the gross tectonic structure beneath both coasts may be similar. The anomalies over the Main Range and the Central Belt taper off towards the south in Melaka and Johore. This implies that the Main Range granite batholiths and the denser (possibly oceanic) crust beneath the Central Belt do not continue farther south into Johore. 

Most of these features seem to be best accounted for by the marginal basin tectonic model of Hutchison (1978), which postulates an oceanic crust underlying the Central Belt.