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GEOLOGICAL
4 major geological formations are found in this region: The lowest stratigraphic unit in the region is the Upper Cambrian - Machinchang Formation, a thick quartzite sequence with subsidiary shale, flag, subgreywacke, grit and conglomerate. These are the oldest strata which have so far been conclusively proved in West Malaysia. The Machinchang Formation covers northwest of Langkawi and a small area south of Bukit China in north Perlis. The Ordovician to Lower Devonian Setul Formation limestone which conformably overlying the Machinchang Formation covers the west of Perlis from where it extends north and west to Thailand. Made up of the Setul limestone formation, the Nakawan Range runs for 36km before entering Thailand's Thaleban National Park. Much of the limestone is dark grey in clour and is finely crystalline. Rock pinnacles, swallow holes, cliffs, dry valleys (wang) and grikes are common features of limestone while the rock is honey-combed by a labyrinth of caverns and interconnecting caves many of which harbour the site of subterranean streams. When Bukit China Granite which covers the northern end of the Nakawan Range, came in contact with the Setul formation during the development stage, significant mineralisation of caseterite occurred. Over thousand year, mineralised tin was washed underground by cave streams and became lodged inside cavities and passages. Wang Tangga and Wang Kelian are two enclosed limestone valleys lying approximately one and 3 miles northwest of Kaki Bukit in north Perlis. The floor of Wang Tangga is covered by alluvium which increases in thickness from a shallow surface veneer at the head of the valley to a depth of 40 feet at the foot. The alluvial surface is approximately 180 feet above sea-level and is flat in the vicinity of the river but rises on approach to the steep limestone slopes surrounding the wang. The Sungei Pelarit winds its way over the alluvium from where it disappears from a defile connecting Wang Kelian with Wang Tangga to where it disappears into a cave connecting Wang Tangga with the central Perlis valley. The floor of Wang Kelian is approximately 100 metre above sea-level and lies about 35 metres above that of Wang Tangga. The valley is reached through a limestone defile at the head of Wang Tangga. The gap was originally eroded by a surface river draining from Wang Kelian but this river now pursues an underground course. The valley is half a mile wide and 2 miles long and divides into two arms in its upper part of the easterly arm being known as Wang Burma. Tin mining operations have worked the greater part of the alluvium which holds rich pockets of cassiterit. A small hydraulic mine worked the upper part of the valley where between 12 and 20 feet of sandy gravels overlying weathered, brightly coloured, impure, banded limestone were exposed. The pebbles were composed almost entirely of quartzite and limestone. The alluvium near the foot of the valley was worked by a gravel-pump mine which exposed some 30 to 40 feet of brown to red, predominantly calyey alluvium overlying grey muddy limestone. The Late Devonian to Triassic Kubang Pasu Formation covers much of central and east Perlis and the part of north Kedah. It is composed of red and grey-coloured shale, mudstone and grey and brown interbedded quartzite . In north Perlis the Bukit China granite of Mesozoic age is associated with significant mineralization along its contact with the Setul Formation. This is responsible for the rich alluvial tin deposits found in the limestone caves of north Perlis. The other geological feature of the area is the Chuping limestone formation. Younger than the Setul formation by 200 million years, it gives rise to stalactites and staglamites and the rugged karst feature of the hills in Perlis. Over the past 500 million years, rain has caved caves out of the limestone hills and tunnels which runs for kilometres.
Resource from : Geological Survey Malaysia District Memoir 17 GEOLOGY AND MINERAL RESOURCES OF PERLIS, NORTH KEDAH AND THE LANGKAWI ISLAND. By C. R. Jones Published by Geological Survey Department, 1978.
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