GEOLOGY OF THE PENGKALAN HULU-BETONG TRANSECT ...

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many common characteristics to share with other parts of the Bintang granite (Trgrbt).
Although the exact age of the Damar granite (Trgrdm) is still remain uncertain, it is inferred
to fall within the Triassic period. It is believed that the Batu Puteh/Pa Ret Tu granite
(Trgrbp/pr) and Kawi granite (Trgrkw) had been formed by the magmatic differentiation of
the Rimba Telui/Si Nakhon granite (Trgrrt/sn). Therefore, the emplacement of the Batu
Puteh/Pa Ret Tu granite (Trgrbp/pr) and the Kawi granite (Trgrkw) probably took place
during the Triassic period or younger.
On the Thai side, the granites exposed in the Transect area can be correlated with the
Songkhla and Satun granites. Cobbing et al. (1992) reported the age of emplacement for
the Songkhla and Satun granites, which are classified in the Main Range granitoids, as
Triassic period, based on radiometric age determination by Rb/Sr isochron technique.
Therefore, the emplacement of granitoids in the Transect area may have been happening
in the Triassic.
4. STRUCTURAL GEOLOGY AND TECTONICS
4.1 Introduction
The structural geology of the Transect area corresponds to the regional tectonic pattern
of the Peninsular Malaysia and Southern Thailand. However, detailed mapping carried
out within the Transect area revealed that, in places, the local structures appear to have a
slight variance as compared to the regional pattern. Peninsular Malaysia and southern
Thailand were formed as a result of collisions between the Sibumasu (Shan Thai) to the
west and Eastmal-Indosinia (Indochina) blocks to the east. This collision was
accompanied by a major tectonic event during Late Triassic, resulting in the deformation
of rocks in the region. The continent-continent collision had caused uplifting and faulting
along the N-S direction. On the other hand, the formation of N-S trending fault zones had
caused a widespread deposition of post-collision sediments in an approximately N-S
longitudinal basin. However, the major structure of the Palaeozoic strata in this area may
have been destroyed by the influence of younger Cretaceous granite intrusions and multidirection
fractures were generated as a result. Finally, younger NE-SW and NW-SE
fractures, which can be prominently observed in both igneous and sedimentary host rocks,
may have been resulted from the movement of the major fault in the Transect area.
4.2 Folding
The Lower Paleozoic rocks in the Transect area are generally folded into series of
broad fold structures which are characterized by steeply dipping limbs. A pattern of closeset
minor folding can be seen superimposing the primary structures, especially in the less
competent horizon. The NE-SW and N-S trending fold axes are sub-parallel to the long
axis of the Peninsular Malaysia. On the Malaysian side, the synclinal and anticlinal axes
can be recognised in the valleys of Ayer Bungur and Sungai Kuak, respectively. Other
minor folds are present with small magnitude.