Fault activity, tectonic segmentation, and deformation pattern of the western Himalaya on Ma timescales inferred from landscape morphology

Abstract

The location and magnitude of Himalayan tectonic activity has been debated for decades, and several aspects remain unknown. For instance, the spatial distribution of crustal shortening that ultimately sustains Himalayan topography and the activity of major fault zones remain unknown at Ma timescales. In this study, we address the spatial deformation pattern in the data-scarce western Himalaya. We calculated catchment averaged, normalized river-steepness indices of non-glaciated drainage basins with tributary catchment areas between 5 and 200 km 2 (n = 2138). We analyzed the spatial distribution of the relative change of river steepness both along and across strike to gain information about the regional distribution of differential uplift pattern and relate this to the activity of distinctive fault segments. For our study area, we observe a positive correlation of averaged k sn values with long-term exhumation rates derived from previously published thermochronologic datasets combined with thermal modeling as well as with millennial timescale denudation rates based on cosmogenic nuclide dating. Our results indicate three tectono-geomorphic segments with distinctive landscape morphology, structural architecture, and fault geometry along the western Himalaya: Garhwal-Sutlej, Chamba, and Kashmir Himalaya (from east to west). Moreover, our data recognize distinctive fault segments showing varying thrust activity along strike of the Main Frontal Thrust, the Main Boundary Thrust, and in the vicinity of the steep topographic transition between the Lesser and Greater Himalaya. In this region, we relate out-of-sequence deformation along major basement thrust ramps, such as the Munsiari Thrust with deformation along a mid-crustal ramp along the basal décollement. We suggest that during the Quaternary, all major fault zones in the Western Himalaya experienced out-of-sequence faulting and have accommodated some portion of crustal shortening.

Clustering River Profiles to Classify Geomorphic Domains

“…For many decades, the study of river networks has been a core concept in geomorphic theory and research. Both the planforms and profiles of fluvial channels have been used to answer diverse problems, such as constraining changes in uplift rates (e.g., Kirby et al, 2003;Kirby & Whipple, 2001;Lavé & Avouac, 2001;Nennewitz et al, 2018), deducing throw rates from faulting (e.g., Whittaker et al, 2008), isolating patterns of drainage capture (e.g., Giachetta & Willett, 2018;Willett et al, 2014), detecting signatures of climate (e.g., Hobley et al, 2012;Roe et al, 2002;Ranjbar et al, 2018;Seybold et al, 2017), and quantifying the impact of different erosional processes on drainage networks (e.g., Bookhagen & Strecker, 2012;Clubb et al, 2016;DiBiase et al, 2010;Hooshyar et al, 2017;Neely et al, 2017;Olen et al, 2016;Stock & Dietrich, 2003).…”

Process inference from topographic fractal characteristics in the tectonically active Northwest Himalaya, India

“…Abbreviations: MP Dam = Maharana Pratap Dam; GS Dam = Govindsagar Dam; MFT = Main Frontal Thrust; ST = Soan Thrust; BrT = Barsar Thrust; JMT = Jwalamukhi Thrust; PT = Palampur Thrust; BT = Bilaspur Thrust; MBT = Main Boundary Thrust; MCT = Main Central Thrust. [Colour figure can be viewed at wileyonlinelibrary.com] 3573 CONTROLS ON FRACTAL GEOMETRY OF THE TOPOGRAPHY IN THE HIMALAYAS boundary of the Himalayan FTB across its strike (Nennewitz et al, 2018). South of the MFT, the Indo-Gangetic alluvial plain (IGP) is characterized by unconsolidated Quaternary alluvium.…”

Structural variations in basal decollement and internal deformation of the Lesser Himalayan Duplex trigger landscape morphology in NW Himalayan interiors

“…Already Nennewitz et al, (2018) had proposed a high basin-averaged ksn value of > 300 in the KW. Here in this study, we worked with a much-detailed DEM and stream-specific ksn allocation ( fig.…”

“…They used longitudinal stream profiles and stream-length index and identified unadjusted and steep stream segments at the transition from the Lesser to the Higher Himalaya along sixteen major Himalayan rivers, including the Chenab river passing through the Kishtwar-Jammu region. Similarly, a study by Nennewitz et al, (2018) also portrayed morphometric indices (basinwide steepness indices and topographic relief) across a large part of the NW Himalaya. Though the resolution of the analyses was coarse, the first-order results encourage us to explore the large drainage networks over the prospect study areas in much more detail and with a terrain data having finer resolution than 30m SRTM DEM used before.…”

“…Another pivotal question on the Himalayan wedge kinematics is about the structural pattern of the basal decollement. Based on the large-scale basinwide morphometric analysis, Nennewitz et al, (2018) have proposed that the million-year-timescale shortening achieved in the interior of the Himalaya near the Sutlej-Beas area in the eastern Himachal Pradesh is caused by accentuated rock uplift over a ramp at a mid-crustal depth of ~ 8-25 km on the MHT. In contrast, studies from the Dhauladhar Range in the northwestern Himalaya hints the presence of deep-seated crustal ramp on the MBT and yielded a shortening rate of 1.5-3 mm a -1 across the MBT over the last 8 Ma and absence of mid-crustal ramp (Thiede et al, 2017).…”