Morphology and orientation of paleochannel and its relationship to basement ridge in the western Ganga Plain

Abstract

This study investigates the morphology of ancient fluvial systems in the Ganga–Yamuna interfluve and examines the potential influence of basement topography, specifically the Delhi–Haridwar Ridge (DHR), on their evolution. Using LANDSAT-8 false-colour composite imagery, Topographic Wetness Index (TWI) maps, SRTM DEM, and borehole lithological data, two distinct types of paleochannels were identified: type 1, characterized by anastomosing patterns and type 2, exhibiting meandering forms. These paleochannels, with an average width of approximately 2.1 km, indicate the presence of a larger river system that was abandoned likely during a halted megafan-building event between the Late Pleistocene-Holocene. The borehole lithology analyses reveal four lithofacies associations (LA-1 to LA-4) indicating different depositional environments under different tectonic and climatic conditions. LA-1 may represent the basal depositional unit consisting of coarse sand and gravel, indicating high-energy braided river system, and may imply the lateral migration of the major rivers across the megafan surface and likely interpreted as relict channel deposits. Orientation analysis using azimuthal extraction techniques revealed that both the paleochannels and the DHR share a predominant NNE–SSW trend. Statistical correlation using the chi-square test yielded values between 9 and 18, below the critical threshold of 28, thereby supporting the hypothesis that the basement topography significantly influenced paleochannel development. This study underscores the importance of subsurface structural features in shaping ancient drainage systems and offers new insights into the tectonic and geomorphic evolution of the Ganga Plain.