Geo-electric resistivity evidence for subsurface palaeochannel systems adjacent to Harappan sites in northwest India

Abstract

It has been proposed that a major palaeo-river channel course, the Ghaggar-Hakra, flowed in the interfluve between the modern Yamuna and Sutlej rivers in the western Ganges basin during the Late Quaternary. This palaeochannel course has been associated with extensive Bronze-age Harappan civilisation archaeological sites that are located with the channel. The abrupt abandonment of urban centres at ∼3500 BP has been explained as a consequence of river diversion, although alternative explanations for cultural decline have also been offered. A major problem with earlier interpretations has been that little information exists on the geology of the palaeochannel system. Electrical resistivity soundings were used to map the large-scale geometry and architecture of the palaeochannel system. A thick and extensive sand body is present in the subsurface in parts of north-western Rajasthan, Haryana and Punjab. The dimensions of the palaeochannel bodies imply that these are the deposits of a large river system, though detailed sedimentological analysis is necessary to validate this. Two of the resistivity transects are close to important Harappan sites, Kalibangan and Kunal, suggesting a possible link to archaeological site distribution. However, detailed chronological constraints are required to establish such links. Nevertheless, this study reports the first geophysical evidence for the subsurface geometry of the palaeo-Ghaggar-Hakra river system.