General Geology and Sedimentology of Pasir Tengkorak Beach, Machinchang Formation, Langkawi, Northwest Malaysia.

Machinchang Formation (Cambrian time) in Langkawi is the oldest rock formation in Peninsular Malaysia that is abundantly exposed at some parts of the island. It is divisible into three members; Hulor Member, Chinchin Member and Jemurok Member. This paper focuses on the outcrop found on the Tengkorak Bed from Tengkorak Beach which belongs to Chincin Member. The objective is to describe and interpret the sedimentary facies of found on Tengkorak Beach outcrop by doing sedimentary logging and petrography studies. Tengkorak beach (±200m thick) has a coarsening upward succession and consists of five sedimentary facies which are thick-bedded blocky sandstone, medium to thick planar cross-bedded sandstone, medium to thick horizontal planar laminated sandstone, medium thick-bedded siltstone and thin beds of mudstone. Pasir Tengkorak beach outcrop is sandier towards the top possibly due to increase in sediment input and the effect of sea level change. Petrography studies show that most of sandstone contains very fine to medium quartz grain size with some iron oxide minerals. The minerals generally are medium sorted and have subangular shape. Overall, outcrops in this area are thought to be deposited in deltaic environments ranging from river mouth to lower prodelta zone.