Summary of the geology of Gunung Jerai
Gunung Jerai is a mountainous region located in central Kedah, between the borders of Kuala Muda and Yan district. The highest point of Gunung Jerai is recorded to be 1217 meters and Gunung Jerai covers a total area of 86.4 square kilometers (Lee et al., 2004). According to Bradford (1972), the existence of Gunung Jerai can be related to the Jerai Formation and the Patani Formation.
The Jerai Formation, named after Gunung Jerai itself, is of Cambrian age with thickness of 1425 meters. Jones (1970) has divided the Jerai Formation into two members which are the lower member and the upper member. The lower member is near 900 meters thick and it consists of quartz-mica, schist and phyllite. Also present is the occasional amphibole and garnet-bearing schist. On the other hand, the upper member is 525 meters thick with made up of quartz arenite with infrequent presence of feldspar grit (Lee et al., 2004). The Jerai Formation is believed to have a shallow marine shelf depositional environment.…show more content… The Patani Formation is of Silurian age and the boundaries of this formation actually overlie the Jerai Formation. The thickness of Patani Formation is 1524 meters. Bradford (1972) has divided the Patani Formation into three facies which are argillaceous, arenaceous and calcareous. The lithology of Patani Formation consists of argillaceous sequence of shale and mudstone, commonly ferruginous and subject to lateritization and in places phyllitic or pyritiferous. A less extensive arenaceous facies of sandstones or orthoquartzite can also be found with the presence of limestone on Bidan Island. The Patani Formation is believed to have a deep gulf or geosynclinal basin depositional