General geology and depositional environment of the semanggol formation in Kota Putra, Kuala Nerang Kedah Darul Aman

The study area lies within the coordinate of ‟ ” and E ‟ ” in ota utra, Kuala Nerang heading to the road connecting Thailand-Malaysia. Dominated by the clastic sedimentary rock of the Semanggol Formation formed at the early of Mesozoic era by the subduction of Sibumasu to the continental margin caused the seaward jump of trench depositing the conglomerate, Triassic chert and turbidite. This study aimed at determining the geology and depositional environment of the exposed outcrops of Semanggol formations in Kota Putra by using the methods of stratigraphic column. The field data shows the north part of the study area composed of thick sedimentary rock interbedded with thin layer of siltstone with the presence of planar cross bedding as the south part of the study area composed of interbedded thick layer of sandstone with the alternating of siltstone and shale showing coarsening upward sequence. The sedimentary structure identified at the north part of the study area are planar cross bedding and ripple mark in between the layer of mudstone and sandstone. The changes of lithology from south to the north part indicating the difference in the depositing environment which probably influenced by both fresh water and marine water as the meandering river meets the ocean phase. As the time flies, the near channel sand deposit by spill over sediments during floods will rise above the flood plain forming natural levees of meandering river. Tiny particles as mud are drifted and away and deposited farther in the environment where sandy to muddy grain mostly found combine with sedimentary structure identified in the study area indicating the depositional environment might be a mid tidal zone of the mud coastal line at the north part.