Mapping of the Buried Paleochannels on the Terminal Fans in the Western Ganga Plain: A Geomorphological and Ground Penetrating Radar-based Approach

Abstract

Abstract Paleochannels are valuable tools for delineating tectonics, climate, anthropogenic activities, reconstructing the paleo-geography, and studying the geomorphological evolution of the alluvial plains. Paleochannels on the terminal fans provide crucial information regarding their geomorphic evolution in space and time. Furthermore, paleochannels could be a good source for groundwater exploration. Exposed paleochannels in the recent alluvial plains are mappable by remote sensing and field evidence. However, mapping becomes difficult due to burial in relatively older alluvial surfaces, and anthropogenic disturbances complicate the case. This paper deals with an integrated method of mapping the buried paleochannels in the terminal fans from the western Ganga plain. Paleochannels have been mapped on three Holocene terminal fans, using remote sensing and Google Earth images, and Cartosat DEM. As continuity of the entire length of paleochannels could not be traced by the above tools due to burial and intense anthropogenic modifications, aligned surface water bodies were helpful at places to ascertain their continuity. The ground penetrating radar (GPR) survey by bistatic antennae (100 MHz frequency in distance mode) detected the subsurface existence of these buried paleochannels up to a maximum depth of about 35 m. Field evidence of some of these buried channels was confirmed at few excavations by the presence of channel sand. A previous study of these terminal fans through optical stimulated luminescence (OSL) dating suggests that channel abandonment occurred between 4.7 to 2.3 Ka, coinciding with the period of the dry climate and intense surface faulting episodes in the Ganga plain.