Identification of The Subsurface Structure of The Lemukutan Islands at The Coast and Small Islands of The Western Part of Kalimantan Waters

Abstract

The Lemukutan Islands, located on the west coast of Singkawang, West Kalimantan, consist of four small islands: Lemukutan Island (the most significant island), Penata Besar, Kabung, and Penata Kecil. The purpose of this study is to reveal various occurrences of subsurface structures around the Lemukutan Islands based on bathymetry and subsurface data which is then compiled with observational data on the mainland of the islands. This information is expected to be input for interested parties in handling mitigation on the coast and small islands. Field observations found a strike-slip fault in the western part of Lemukutan, following the interpretation of DEM and Landsat 457 composite image data. This fault continues to the seabed even to Penata Besar Island in the east with a direction of N160° E. Phenomenon of the structure on the Penata Kecil, and Seluwas island is found on sandstone in the form of a crushed zone that shows the orientation of the block towards N230°E or to the southwest of Penata Besar Island. Traces of the structure are interpreted to have occurred after the Cretaceous period and are no longer active.