GEOLOGY OF THE PENGKALAN HULU-BETONG TRANSECT ...

Permian as indicated by the presence of Anisopyge sp., Phillipsia sp. (trilobite) and
chonetid (brachipod) within the calcareous shale at Kampong Batu 2, Gerik (Mohd.
Shafeea Leman, Pers. Comm).
The Berapit formation (Kbr) overlies unconformably the steeper dipping and tightly
folded Kroh formation (SDkr).
The Nenering beds (Qnn) is well exposed along Kampung Ayer Panas-Kampung
Lalang road and along the Malaysian border route, covering an area of about 12 square
kilometres. It is made up essentially of gravelly, sandy and clayey layers. Generally, the
outcrop shows a broad syncline with its axis trending approximately NNW-SSE and
plunging NNW. The Nenering beds (Qnn) overlies unconformably the Berapit formation
(Kbr). Numerous sand filled gullies and channels can be seen through out this unit. Based
on grain size analysis of the Nenering beds (Qnn), Mohd Pauzi Abdullah (1992) indicated
that this sediment may be deposited in fluviatile environments (following the Moiola and
Waiser classification).
Young alluvial deposits of appreciable extent and thickness are present along the
valley of the Sungai Perak, Sungai Rui, Sungai Pengkalan Hulu and their larger
tributaries. The Recent deposits have been accumulated through fluviatile accretion in the
floodplains of the rivers. The best examples occur in the meandering lower reaches of
Sungai Rui, along the big loop of Sungai Perak opposite Kampung Kuala Rui, and south
of Pengkalan Hulu town. A simplified stratigraphic column of the Transect area on the
Malaysian side is shown in Figure 3. Simplified geological correlation of the Transect
area as compared to the geology of the Northern Peninsular Malaysia is summarised in
Figure 4.
The igneous rocks in the Transect area are represented by the granitic rocks of the
Main Range Granite Belt. The granites can be conveniently divided into three units
namely Rimba Telui granite (Trgrrt), Bintang granite (Trgrbt) and Damar granite (Trgrdm).
The Rimba Telui granite (Trgrrt) occurs as major proportion of the rock unit in the
Transect area, covering an area of approximately 560 square kilometres. It forms a large
batholith underlying the Kubang Pasu Formation (Ckp) in the western part of the Transect
area. The Bintang granite (Trgrbt) is exposed in the southwestern corner of the Transect
area. It is in contact with the Kubang Pasu Formation (Ckp), Gerik formation (Pgk) and
Kroh formation (SDkr). The Damar granite (Trgrdm) forms a rectangular block of
approximately 20 square kilometres in southwestern part of the Transect area. It intruded
into the Kroh formation (SDkr) and has introduced contact metamorphism along its
margin.
The Rimba Telui granite (Trgrrt) and Bintang granite (Trgrbt) are typically grey,
medium- to coarse-grained, porphyritic and invariably mottled with black biotite whereas
the Damar granite (Trgrdm) is characterized by grey, fine- to medium-grained, equigranular
granite, commonly containing both muscovite and biotite.
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