Tectonic constraints on watershed development on frontal ridges: Mohand Ridge, NW Himalaya, India
Introduction
Uplifting frontal ridges are a surface manifestation of active fault-related folds present in the hanging wall block of thrust faults in frontal parts of an orogen. They are one of the most conspicuous geomorphic features that mark the frontal parts of actively converging mountain belts (Mueller and Talling, 1997, Delcaillau et al., 1998, Delcaillau et al., 2006, Gupta and Ellis, 2004). Growth of these ridges is closely related to simultaneous development of transverse drainage systems (Gupta, 1997, Champel et al., 2002, Jones, 2004). Investigation of the drainage system can be therefore used as a key tool in deciphering the morphotectonic evolution of the landscape as a manifestation of the subsurface structure (Bull and Knuepfer, 1987, Keller and Pinter, 1996, Delcaillau et al., 1998, Burbank and Anderson, 2000, Jain and Sinha, 2005). The major components of a drainage system comprise the watersheds, stream network and long profiles of channels. Most of the previous studies pertaining to different aspects of geology have investigated the stream network and long profiles (Hack, 1976, Delcaillau et al., 1998, Delcaillau et al., 2006, Singh and Tandon, 2008); however, integrated studies of the three components are not available. The present study has been carried out in a part of the NW Himalaya along the Himalayan Frontal Thrust (HFT), to put forward an integrated understanding of watersheds, drainage network growth and long profile characteristics that can be used in active tectonic investigations. This manuscript provides a study of different aspects of a drainage system to decipher the nature of watershed growth in the backlimb and forelimb, and its relation with the fold development due to slip along an underlying fault (HFT in the present study).
Section snippets
Geology, tectonics and climate
The present study focuses on the Mohand frontal ridge in the NW Sub-Himalaya (Fig. 1). It is located on the hanging wall of the Himalayan Frontal Thrust (HFT). The Mohand ridge is composed of the Siwalik Group of rocks that are mainly fluvial sandstones, shales and conglomerates. The Siwalik Group are divided into Lower, Middle and Upper Siwaliks in that chronological order (Karunakaran and Ranga Rao, 1976). These rocks have been folded into an anticlinal structure popularly known as the
Methodology
The study utilizes a digital elevation model (DEM) that was generated using 20-m contour lines from the Survey of India (SOI) topographic maps at 1: 50,000 scale. The DEM was resampled to a pixel (cell) resolution of 20 m (same as the contour interval). The watersheds were extracted through spatial analysis tools provided in ArcGIS software. There are different algorithms available to delineate watersheds. The simplest and most commonly used is the eight-flow direction matrix (D8) suitable for
Morphometric parameters and results
Tectonic processes control fluvial processes through alteration of channel slope, which in turn causes variation in stream network, channel morphology and watershed development. Therefore, various morphometric parameters related to watershed area characteristics, drainage network pattern and channel slope variation are analyzed (Table 1). These morphometric parameters are a function of the geomorphic evolution of the watersheds. These parameters are subdivided into watershed related, stream
Asymmetric distribution of watersheds and dominant surface processes
The asymmetry across the ridge crest is characterized by watershed area and shape, drainage network parameters and long profile parameters, which is significantly different between the southern (forelimb) and northern (backlimb) flanks. The abnormally higher value of Rb1/2 in comparison with Rb2/3, as well as a larger number and longer length of first order streams highlight the development of numerous first order streams in the southern flank. It indicates the dominance of headward erosion
Conclusions
This study has demonstrated a direct relation between endogenic tectonic processes and surface processes which has resulted in different patterns in watershed shape and drainage network. The watershed shape parameters including area and the elongation ratio can be used with stream networks to evaluate tectonic processes that shape up the landscape. The asymmetric development of frontal ridges is related to difference in proximity of the frontal thrust (HFT). The watersheds closer to the frontal
Acknowledgements
The author is thankful to the Head, Department of Earth Sciences, Indian Institute of Technology, Roorkee for providing infrastructural support. The Department of Science and Technology (DST), New Delhi is thanked for financial support via Fast Track Young Scientist project grant no. SR/FTP/ES-52/2006 to carry out the present study. The authors are also thankful to Prof. Anne Mather and Prof. Bernhard Delcaillau for their reviews and critical comments that helped considerably to improve the
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2022, Journal of Asian Earth SciencesProgressive evolution of thrust fold topography in the frontal Himalaya
2021, GeomorphologyCitation Excerpt :The contrast in the average rock uplift rate between the south and north of the range has caused the southern flank to have greater relief (Barnes et al., 2011; Singh, 2008). There has been a debate over whether the Mohand Range is a fault-bend fold (Barnes et al., 2011; Kirby and Whipple, 2012; Mukhopadhyay and Mishra, 2004; Rao et al., 1974; Singh and Jain, 2009; Thakur, 2004) or a fault-propagation fold (Powers et al., 1998; Srivastava et al., 2016; Wesnousky et al., 1999). Recent studies have indicated that the Mohand Range is in fact a monocline related to a fault-propagation fold (Srivastava et al., 2018; Srivastava and Mukul, 2020).
Active transfer faulting in the NW Sub-Himalaya (India) observed by space-borne topographic analyses
2021, Quaternary InternationalSpatiotemporal variability of neotectonic activity along the Southern Himalayan front: A geomorphic perspective
2019, Journal of GeodynamicsInvestigating topographic metrics to decipher structural model and morphotectonic evolution of the Frontal Siwalik Ranges, Central Himalaya, Nepal
2019, GeomorphologyCitation Excerpt :The frontal ranges are better studied along the northwestern Himalaya in comparison to the central and eastern parts. The topographic growth, direction and rate of fault propagation, and drainage reorganisation due to the growth of frontal ranges is well documented for the Janauri, Chandigarh, and Mohand ranges in the NW Himalaya of India (Mugnier et al., 1999; Delcaillau et al., 2006; Singh and Tandon, 2008, 2010; Singh and Jain, 2009; Mukul, 2010, Mukul et al., 2014; Malik et al., 2010; Barnes et al., 2011; Srivastava et al., 2016). On the other hand, study of the frontal ranges along the central Himalayan front are very few and mostly restricted to the western part of the Nepal (e.g., Mugnier et al., 1999, 2005).