Sedimentology of Anak Datai of Machinchang Formation, Langkawi, Kedah

Anak Datai beach is composed of rocks dated Cambrian age making it the oldest rock found in Peninsular Malaysia. It is located in the Northwest of Langkawi Island. Anak Datai beach area covers several beds such as Anak Datai Bed, Temurun Bed and Tengkorak Bed of the Chinchin Member under Machinchang Formation.The objective of the project is to perform sedimentology study by describing the sedimentary facies along with the facies succession and its association to understand the sedimentary processes and environment.
For this project, sedimentary logs are created and used as the main data. There are six sedimentary logs constructed along the transect route which are mainly composed of sandstone with minor intercalations of silty and muddy layers. Based on the research done, generally it is coarsening upward succession of sandstone with thin intercalation of muddy and silty layers. The sandstone is classified as metaquartzite sandstone as it has undergone low metamorphism. From facies analysis, the study area is mainly made up of four facies such as trough cross-bedding sandstone, planar cross-bedding sandstone, parallel lamination sandstone and massive sandstone. All of the facies type identified suggesting upper shoreface as the paleo-environment of deposition for the study area with wave dominated environment. Petrographic analysis is also carried out in order to understand further about the rock in the area in terms of mineralogy properties. 12 samples were prepared and the samples were categorized according to the grain sizes of the quartz minerals. The main mineral observed in the samples is predominantly quartz with matrix composed of smaller crystals of quartz, clay and carbonaceous matter.