Evidence of topographic disequilibrium in the Subarnarekha River Basin, India: A digital elevation model based analysis

Cratonic areas experience complex process-response changes due to their operative endogenic and exogenic forces varying in intensity and spatiality over long timescales. Unlike zones of active deformation, the surface expression of the transient signals in relatively tectonically stable areas are usually scant. The Subarnarekha River Basin, in eastern India, is a prime example of a Precambrian cratonic landscape, overlain in places by Tertiary and Quaternary deposits. A coupled quantitative-qualitative approach is employed towards deciphering tectonic and geological influences across linear and areal aspects, at the basin and sub-basin scale. Within this landscape, the transient erosional signatures are explored, as recorded in the disequilibrium conditions of the longitudinal profiles of the major streams, which are marked by a number of waterfalls at structural and lithological boundaries. Mathematical expressions derived from the normalized longitudinal profiles of these streams are used to ascertain their stage of development. Cluster analysis and chi plots provide significant interpretations of the role of vertical displacements or litho-structural variations within the basin. These analyses suggest that a heterogeneous, piece-meal response to the ongoing deformation exists in the area, albeit, determining the actual rate of this deformation or its temporal variation is difficult without correlated chronological datasets.