GEOLOGY OF THE BATU MELINTANG-SUNGAI KOLOK TRANSECT AREA ALONG THE MALAYSIA – THAILAND BORDER By The Malaysian and Thai Working Groups A joint project carried out by Minerals and Geoscience Department Malaysia and Department of Mineral Resources, Thailand The Malaysia-Thailand Border Joint Geological Survey Committee (MT-JGSC) 2006 - ii - PREFACE This report together with its accompanying geological map on the scale 1:250,000 is the result of close cooperation between the Minerals and Geoscience Department Malaysia, and the Department of Mineral Resources, Thailand in resolving problems related to cross border geological correlation between Malaysia and Thailand. Fieldwork was carried out separately (July – August 2001) in the Batu Melintang and Sungai Kolok areas and then jointly checked (5-11 April 2002) by geoscientists from both Malaysia and Thailand, covering a total area of about 1,350 square kilometres along the common border. Problems on the discontinuity of time rock unit boundaries between the various rocks found in both sides of the common border areas have been satisfactorily resolved. Potential mineral deposits occur along the border areas but the present security situation, as well as environmental issues does not encourage the exploitation of these mineral deposits. Future increase in the price of minerals coupled with advances in mining technology may facilitate joint exploitation of these mineral deposits. Dr. Chu Ling Heng Mr. Somsak Potisat Director General Director General Minerals and Geoscience Department Department of Mineral Resources, Malaysia. Thailand. December 2003 December 2003 - iii - Geology of the Batu Melintang-Sungai Kolok Transect area along the Malaysia-Thailand border by The Malaysian and Thai Working Groups Executive Summary Detailed systematic geological mapping in the Batu Melintang-Sungai Kolok Transect area on scales of 1:100,000 and 1:250,000 (originally mapped on the scale of 1:50,000), was carried out independently by the working groups of Malaysia and Thailand covering individual territories within the Transect area i.e. during July-August 2001 and re-checked during November 2001. This was followed by detailed works on the Quaternary Geology in October 2001 and January 2002 (Malaysian side) followed by re-checking works during February 2002 (Thai side). A joint field check at selected localities along the Transect area by geoscientists from both Minerals and Geoscience Department Malaysia, and Department of Mineral Resources, Thailand was conducted in Thailand (5-7 April 2002) and in Malaysia (9- 11 April 2002). Problems on the discontinuity of time rock unit boundaries between the Paleozoic rocks to Quaternary deposits, and the extension of granitic rocks (including the mineral association), have been satisfactorily resolved. The oldest rocks, the Silurian-Devonian succession of the Tiang schist/Ban Sa formation (SDts/bs), consist mainly of medium- to thick-banded para-gneiss, augen gneiss with subordinate amphibolite schist, schist and hornfels. The main succession is exposed in the vicinity of Sungai Cherok (Malaysia) and at Khlong Ai Ku Sa (Thailand), in the western part of the Transect area. A smaller rock body is exposed near Sungai Golok (Malaysia), extending to the eastern side of the Ba Tu Ta Mong-Jeli granitic belt (Thailand). High-grade regional metamorphism (amphibolite facies) is obviously recognised by the presence of amphibole mineral group. No fossil assemblages were found and the thickness of the succession is indeterminable. The Carboniferous-Permian clastic rocks occur in the western and southeastern parts of the Transect area. The rock units in the western part are enclosed by two granitic belts, between the Kemahang Granite/Sukhirin granite (Trgrkg/su) and the Merah granite/Bu Do granite (Trgrmr/bd). The succession is subdivided into three formations, in ascending order: the Mangga formation (CPmg)/Ai Ka Po (CPak)/ Ka Lu Bi (CPkl) formations. The three formations are found to be stratigraphically equivalent and are known as the Mangga/Ai Ka Po/ Ka Lu Bi (CPmg/ak/kl) formations. The Mangga formation (CPmg) is well exposed in the upper reaches of Sungai Machang extending southwards to Kampung Gunung in the Batu Melintang area (Malaysia). It is represented by a low grade metamorphic sequence that can be subdivided into 4 facies: argillaceous facies (CPmgag), arenaceous facies (CPmgar), pyroclastic facies (CPmgpy) and calcareous facies (CPmgcl). The Ai Ka Po formation (CPak) or the arenaceous facies is exposed as a narrow N-S trending sharp ridge hill in Thailand. It is composed mainly of thin- to thick-bedded, tuffaceous sandstone, quartzite and metaconglomerates. The Ka Lu Bi formation (CPkl) or the argillaceous facies is gradational, fining upwards from the former formation. The succession, well exposed at low relief terrain (in Thailand), consists of cycles of thin- to medium-bedded, shales, sandstones and conglomerates with quartz vein and dyke in the lower part, and sharp, even, very thin bedded or rhythmic sequence of shales and siltstones intercalated with very fine-grained sandstones in the upper part. - iv - The Carboniferous-Permian clastic rocks in the southern part of the Transect area is known as Taku schist/ Buke Ta formation (CPtk/bt ). The Taku schist (CPtk) is well distributed in Malaysia, whereas the Buke Ta formation (CPbt) is locally distributed at Ban Buke Ta and Mae Nam Kolok (Thailand). These formations comprise predominantly schists which are wholly crystalline and generally completely schistosed. Mica schist is the main rock type, which consists of quartz-mica schist, mica-garnet schist and quartz-mica-garnet schist. Local deformation and low-grade metamorphism took place in the shear and contact zones and metamorphosed the original rocks to slate, phyllite, phyllitic shale and spotted slate. No fossil was found in these formations and the thickness of the succession is still indeterminable. However, evidences shown by the intrusion of the well-dated Triassic granite and the stratigraphic position of the rocks enabled the Working Groups to assume that the age of the rocks is Carboniferous-Permian. The Permian-Triassic succession of the Ai Ba Lo formation (PTrab) is confined to the northwestern part of the Transect area (in Thailand). It consists mainly of sharp, even, thin- bedded cherts with recrystalline radiolarian intercalated with stringering shale beds and rare volcaniclastic sediments. The succession obviously exhibits instability of the basin during the time of deposition because of igneous activities. Stratigraphically, the age of these chert strata is considered as belonging to the Permian-Triassic Period. The Permian-Triassic succession of the Telong formation (PTrtl) is confined to the central-south and central part of the Transect area (Malaysia), in Kampung Legeh and extends eastwards to the Tanah Merah area. The Telong formation consists mainly of argillite, low- grade metasedimentary and metavolcanic rocks, and can be divided into four facies: argillaceous (PTrtlag), arenaceous (PTrtlar), calcareous (PTrtlcl) and volcanic facies (PTrtlpy). No fossil so far was found in the Transect area. However, based on bivalves and foraminifera reportedly found in the similar lithology unit to the south of the Transect area, the age of this formation may be assumed as Permian-Triassic. The Triassic submarine fanglomerate, the Bu Yong formation (Trby), is unconformably underlain by the Carboniferous-Permian and Permian-Triassic rocks. It crops out in the central-northwestern part of the area, and consists of massive to thick-bedded, conglomerates, conglomeratic sandstones, with both matrix- and clast-supported types. Clasts are mainly of sandstones, quartz, cherts, and volcanic rocks. The Panau beds (Kpn) are locally exposed only at Bukit Panau and Bukit Jambul, about 10 km north of the Tanah Merah town, in the eastern part of the Transect area. Nonconformity between the Triassic granite and the overlying sandstone of the Panau beds can be observed at an abandoned rock quarry at the foothill of Bukit Panau. This rock unit is evidently younger than Triassic and is believed to be Cretaceous age based on plant fragments found in the fine- grained sandstone beds at the foothill of Bukit Panau. The unconsolidated sediments were deposited in both marine and non-marine environments and can be subdivided into 3 formations in ascending order: the Simpang Formation/Waeng formation (Qhsp/wg), Beruas Formation/Sungai Kolok formation (Qhbr/sk) and Gula Formation/Tak Bai formation (Qhgl/tb). The non-marine Pleistocene deposits consisting of Colluvium/Terrace and Former floodplain members of the Simpang Formation/Waeng formation (Qpspr/wg) are dominantly characterised by gravel, sand, silt, and laterite with abundant iron concretions. The marine Holocene sediments of the Gula Formation/Tak Bai formation are subdivided into 5 members (bottom to top): Bagan Datoh Member/Shallow marine member (Qhbdsmgl/tb), Teluk Intan Member/Tidal flat (Qhtitfgl/tb), Peat swamp member (Qhpstb), Matang Gelugor Member/ Old beach member (Qhmtobgl/tb) and Recent beach member (Qhrbgl/tb). However, the Peat swamp member is only exposed extensively in Thailand. The oldest beach ridge of Old beach member exposed 12 km from - v - the present shoreline at Ban Pa Wai, in the northern part of Sungai Padi District, Thailand. It is characterised by sand, gravelly sand, and silt. The non-marine Holocene sediments of the Beruas Formation/Sungai Kolok formation (Qhbr/sk) are subdivided