Bulletin of the Geological Society of Malaysia, Volume 31, July 1992, pp. 107 – 111
1Sarawak Shell Berhad, Lutong, Miri, Sarawak.
2Dept. of Geology, University of Malaya, 59100 Kuala Lumpur.
Abstract: Three main rock types are found in the Rompin-Endau area. These are volcanics, igneous intrusives and sedimentary sequences. Metamorphic rocks occur only at Gunung Lesong. The volcanic rocks are referred to as the Jasin volcanics and represent the oldest rocks of the area, probably of Mid-Permian to Triassic age. Some of these rhyolites are also mylonitised. A granite batholith found on the western flank of the area can be termed a biotite-adamellite granite. This granite pluton which has intruded the volcanic rocks, is similar to those found in other parts of the Ulu Endau area and has been dated to be of Late Triassic Age.
On the eastern plateau, sedimentary sequences of sandstone, shale, siltstone and mudstone overly the volcanics. A similar sequence of sediment is seen capping the granite hill 1448 on the western side, forming a mesa. These sediments are referred to as the Tebak Formation which is of continental origin and exhibits subhorizontal dips. Plant fossils were recorded from light grey mudstone beds in the tributaries of Sungai Telentang, and a boulder of silicified wood was found in Sungai Anak Seladang on the western flank of Sungai Kinchin. The plant fossil has been identified as Frenelopsis malaina Ko‘ono, which is a foliage of a conifer plant, giving an age of Upper Jurassic – Lower Cretaceous. The silicified wood is also that of a conifer plant Araucarioxylon telentangensis Idris with a minimum age Late Triassic. A major fault trending 345-350° runs along Sungai Kinchin.