An integrated approach to map certain palaeochannels of South India using remote sensing, geophysics, and sedimentological techniques

Abstract

Palaeochannels are important sources of groundwater, economic minerals, and placer deposits. They are also good repositories of palaeoclimate data. To exploit such resources, the first essential step would be to identify and map palaeochannels. This article presents a study in which multi-sensor (optical, thermal, and microwave) image data and satellite-derived digital elevation models (DEM)s of the northern coastal region of Tamilnadu state, south India, were analysed visually and digitally to recognize exposed and buried palaeochannels. Image-enhancement techniques such as linear contrast enhancement of optical data and fusion of microwave and optical image data brought out more information about the palaeochannels. Hill-shading techniques applied to the satellite-derived DEM, further added to the information content on the existence of the palaeochannels. The existence of the newly identified palaeochannels was verified by ground-based techniques such as field checks, sedimentological analysis, and electrical resistivity surveys. The presence of well sorted and rounded grains in the sediment samples and high apparent electrical resistivity values for the thick sandy subsurface strata in these locations confirmed the existence of palaeochannels which were interpreted from the images.