Tectonic constraints on watershed development on frontal ridges: Mohand Ridge, NW Himalaya, India

doi:10.1016/j.geomorph.2008.11.001

Geomorphology

Volume 106, Issues 3–4, 15 May 2009, Pages 231-241

https://doi.org/10.1016/j.geomorph.2008.11.001 Get rights and content

Abstract

Uplifting frontal ridges are one of the most conspicuous geomorphic features that mark the frontal parts of actively converging mountain belts. Growth of these ridges can lead to the simultaneous development of a drainage system that is defined by watersheds, stream network and long profiles of channels. In the present study, shape parameters of watersheds, stream network characteristics and pattern of network growth, shape of long profiles, and the SL index have been investigated in a part of NW Himalaya to understand the relationship between endogenic tectonic processes and exogenic fluvial processes. This explains the tectonic control on drainage systems in the uplifting frontal ridge. This watershed analysis was carried out using a Digital Elevation Model (DEM) and a number of anomalies have been identified and analysed. The most striking is the asymmetric development of watersheds on either side of an almost straight ridge crest. Watershed asymmetry along the ridge crest is characterized by larger area and less elongated watersheds in the southern flank (forelimb) in comparison to the northern flank (backlimb). Drainage network and long profile analysis establishes that the larger watershed area in the forelimb is due to dominance of headward erosion and its impact on drainage network growth. Dominance of headward erosion is due to slope variation in response to forelimb development along a fault-related fold. Even through, headward erosion has shifted the ridge crest; it is parallel with the trace of the Himalayan Frontal Thrust (HFT). The parallel ridge crest with reference to the HFT is indicative of the tectonic control of the HFT on the development of the watersheds. Hence, a well developed linkage between tectonic processes (fold development) and surface processes (headward erosion) is responsible for variation in watershed and drainage network pattern across the ridge crest. The study also investigates the role of planform ridge curvature on watershed development. The effect is more pronounced on an asymmetric ridge, such as the Mohand ridge, than on a symmetric ridge.

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 R_b1/2 in comparison with R_b_2/3, 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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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).
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Morphostructural evidence of Late Quaternary tectonics at the Po Plain-Northern Apennines border (Lombardy, Italy)
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The landscape of foreland basins adjacent to active mountain ranges evolves under the control of basinward tectonic propagation of the structural fronts, in competition with climate dynamics. The resulting palimpsest landscapes record the sequence of geomorphic evolutionary steps, and the spatial-temporal relations between the active geological processes. However, a precise evolutionary sequence is hard to decipher from low-relief settings, like the wide alluvial plains worldwide. About these topics we investigate the sequence of tectonic- and climate-driven processes which shaped the palimpsest landscape of a large Quaternary foreland basin, the Po Plain in Northern Italy. Above the average glacio-fluvial and alluvial plain of the basin, Late Quaternary intra-basin reliefs emerge, owing to syndepositional ramp folding and uplift driven by N-wards propagation of the outermost thrust fronts of the active N-Apennine chain.
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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).
The fold-and-thrust belt in the Himalayan front is marked by the upliftment of the Frontal/Outermost Siwalik Hills along the Main Frontal Thrust (MFT). These frontal ranges display distinct morphology with prominent curved/stair-stepped and overlapping segments in the central Himalaya. In this study, we analyse the structural framework, morphology, growth and relative uplift rates of the frontal ranges in the central Himalaya, using various topographic metrics. The results suggest that the frontal ranges are folds developed along six MFT segments that have interacted to form the present day topography. These segments are also overlapping in some areas, thus, resulting in stress partitioning. We also identify a NW-SE trending pre-existing tear fault in the region that forms barrier to the growth and propagation of the MFT segments and the frontal ranges along it. The uplift rates are generally lower on relatively older fault segments due to initiation of the younger overlapping faults. It is supported by the results of the morphometric indices as the older and less active MFT segments yield high mountain front sinuosity ratio (1.3–2.2) and valley floor width to height ratio (3.3–14.6), and low values of steepness index (0.2–0.8) and hypsometric integral (0.4–0.5). Growing folds along the MFT segments have resulted in the deflection of the Narayani and the East Rapti rivers. We establish a model for the initiation and growth of various structural segments in the study area and the resultant drainage reorganisation.

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Tectonic constraints on watershed development on frontal ridges: Mohand Ridge, NW Himalaya, India

Abstract

Introduction

Section snippets

Geology, tectonics and climate

Methodology

Morphometric parameters and results

Asymmetric distribution of watersheds and dominant surface processes

Conclusions

Acknowledgements

Geomorphology

Geomorphology

Geomorphology

Geomorphology

Journal of Structural Geology

Geomorphology

Geomorphology

Geomorphology

Journal of Structural Geology

Adjustments by Charwell river, New Zealand, to uplift and climatic changes

Geomorphology

Tectonic Geomorphology

Growth and lateral propagation of fault-related folds in Siwaliks of western Nepal: rates, mechanisms and geomorphic signature

Journal of Geophysical Research

Himalayan drainage patterns and origin of fluvial megafans in Ganges foreland basin

Geology

Does the topography of actively growing folds mimic fold structures? The case of Mohand anticline, Frontal Himalaya

Geophysical Research Abstracts

Studies of longitudinal stream profiles in Virginia and Maryland

USGS Professional Paper

Stream profile analysis and stream gradient index

USGS Journal Research

Erosional development of streams and their drainage basins

Geological Society of America Bulletin

Tectonic controls on drainage evolution and development of terminal alluvial fans, southern Pyrenees, Spain

Terra Nova

Status of exploration for hydrocarbons in the Himalayan region: contribution to stratigraphy and structure

Geological Survey of India

Active Tectonics: Earthquakes, Uplift and Landscape