Late Quaternary drainage reorganization assisted by surface faulting: The example of the Katrol Hill Fault zone, Kachchh, western India

Abstract

AbstractDrainage reorganization on restricted temporal and spatial scales is poorly‐documented. We attempt to decode the relatively complicated mechanism of drainage realignment involving two small rivers that show structurally controlled, highly anomalous channel networks. We provide geomorphic and shallow subsurface evidence using ground‐penetrating radar (GPR) for the presence of a buried paleo‐valley flowing northward through the wind gap and surface faulting along the range bounding Katrol Hill Fault (KHF) which correlates with the previously known three surface faulting events in last ~30 ka bp. Most of the present river channels and the KHF zone are occupied by aeolian miliolite (local name) which is stratigraphic and lithologic equivalent of the Late Quaternary carbonate rich aeolianite deposits occurring in several parts of the globe. The history of drainage evolution in the study area comprises pre‐miliolite, syn‐miliolite and post‐miliolite phases. Geomorphic evidences show that the paleo‐Gangeshwar River flowed north through the wind gap and paleo‐valley, while the short paleo‐Gunawari occupied the saddle zone to the east of Ler dome prior to and during the phase of miliolite deposition which ended by ~40 ka bp. Southward tilting of the Katrol Hill Range (KHR) due to surface faulting cut off the catchment of the paleo‐Gangeshwar River. The abandoned catchment stream extended its channel eastward along the strike through top‐down process while the paleo‐Gunawari River extended its course westward by headward erosion (bottom‐up process). As the channels advanced towards each other they joined to produce the “S”‐shaped bend which formed the capture point. We conclude that multiple surface faulting events along the KHF in the last ~30 ka bp, resulted in uplift and tilting of the KHR which caused drainage realignment by river diversion, beheading and river capture. Our study shows that the complexity of drainage reorganization processes is more explicit on shorter rather than longer timescales.