Geomorphic evidence of unrecognized Balapur fault segment in the southwest Kashmir basin of northwest Himalayas

- Present investigation aims to explore the unrecognized segment of Balapur fault (BF) in SW Kashmir basin.
- Longitudinal profiles of all the rivers express consistent (NW-SE) hypsometric anomalies (Knickpoints/knickzones).
- Calculated stream gradient indices of each river are in agreement with the anomalies observed on the river profiles.
- The observed anomalies suggest that the strike of BF extends over significant distance (~ 95 km) in SW Kashmir basin.

The Balapur fault (BF) is a high angle thrust fault (reverse), dipping ~ 60° NE, with an established length of ~ 40 km striking NW-SE of the Kashmir basin. However, geomorphic traces suggest that the strike of the BF propagates beyond what has been documented previously. The present investigation aims to identify the unrecognized segment of the BF in the SW of the Kashmir basin using hypsometric variability in longitudinal profiles (knickpoints/zones), followed by validation through stream gradient index (SL) calculations of the rivers draining the area. The longitudinal profiles of all the streams indicate prominent and consistent anomalies in the upper and mid-reaches even on the coarse resolution data (Survey of India topographic maps - 1:50,000/40 m, DEM-SRTM 90 m). The profile anomalies in the upper reaches (hard rock zone) of the streams may be attributed to lithological contacts, i.e., Panjal trap agglomeratic slate-shale-limestone. However, the river profile convex segments and course deflection specifically in the mid-reaches (soft rock zone) are most likely associated with recent tectonic activity. Geomorphic signatures suggest that these anomalies coincide with the strike of the recognized segment of the BF. Moreover, the SL values of each stream express a clear agreement with the anomalies shown by the long profiles of the rivers. Hence, we infer that the strike of the BF extends for a significant distance (~ 95 km) over the northeastern flank of the Pir Panjal range in the NW-SE direction.