Investigation of paleochannel identification using radar and optical images on placer deposits in Bangka Barat Regency, Indonesia

Abstract

This article is about a visual investigation of paleochannel identification using ALOS 2 PALSAR 2 (Advanced Land Observing Satellite 2 Phased Array type L-band Synthetic Aperture Radar 2) radar satellite image. The radar image has a higher layer-penetration ability than the optical image so that the characteristics of near-surface materials are possible to be detected, including the morphology of the abandoned river stream. The purpose of ancient channels investigation is to localize potential areas of tin placer deposits, including rare earth elements as associated minerals. This investigation was aided by LANDSAT 8 optical image and National Digital Elevation Model (DEMNAS) data. Visual identification has been performed based on the shape, color, pattern, texture, and position against other morphologies in the image. The criteria for paleochannels are the channels detected using ALOS 2 PALSAR 2 image but not in LANDSAT 8 optical image and DEMNAS data. Based on these criteria, eleven traces of paleochannels have been well identified. Their occurrences are generally associated with meanders, open areas, and near the coast. The detected paleochannels are generally purple to dark in the color composite of the ALOS 2 PALSAR 2 image. These detected rivers are in pink to purplish-green zones and have a random appearance.