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Identifying active faults in alluvial plains with varying sedimentation rates, erosion, and extensive anthropogenic modifications is challenging. In tectonically active foreland basins, tectonics outweighs other controlling factors and produces a set of key fluvial geomorphic markers that are critical for precisely locating active faults. This study employs several key tectonic fluvial morphometric parameters, seismically induced soft-sediment deformation structures (SSDS) as seismites, and the displaced rocks of the Siwalik mountains to mark the surface positions of a buried basement fault system, namely the Great Boundary Fault (GBF) beneath the alluvial cover of the Indo-Gangetic foreland basin. The Great Boundary Fault (GBF) is a NE-SW trending, oblique-slip, branching reverse basement fault running from peninsular India to the Sub-Himalayas. About 400 km length of its NE segment is buried under thick sediments of the Indo-Gangetic foreland basin. This fault's surfaceward propagation deforms the overlying sediments via a network of subsidiary faults, resulting in 20 km wide broad fault zones. The extreme flatness of the Ganga plain conceals the primary faulting evidence but tectonic fluvial geomorphic signatures, the SSDS, and the laterally displaced Siwalik rocks, including south-verging thrusts at the frontal Himalayas, provide collective evidence of neotectonic activity along both fault branches. The primary objectives of this study are to characterise the GBF's buried segment in the Ganga plain through the geomorphic signatures and SSDS, to elucidate its extension up to the Main Boundary Thrust (MBT), and to understand the surfaceward propagation mechanism of its reverse faults through the alluvial-fills. Tectonic geomorphic parameters such as sinuosity spectra and knickpoints were analysed using ArcGIS and Matlab. Meander scar mapping was carried out using Google Earth Pro and Landsat imagery within ArcGIS to characterise the pattern of avulsions and adjustments of the floodplain linked to the tilting directions of the fault blocks. Fourteen prominent knickpoints of 4 to ≥6 m height were derived from the river profiles across the fault zone. Rivers on the up-thrown block possessed low sinuosity (as low as 1.1), whilst those on the down-thrown block had higher sinuosities (up to 3.1), indicating active uplift and rapid subsidence. The deflection of multiple river courses (Ganga, Ramganga, Burhiganga, Sot, Pangaili, and Deoha) and the presence of asymmetrical meander-belts demonstrate an eastward tilting of the tectonic block. The occurrence of liquefaction-induced SSDS close to the GBF corroborates its recent seismogenic nature. Field observation suggests these SSDS are likely related to the Usawan paleo-earthquake (estimated magnitude of 6.5–7.2), epicentered near the GBF. Based on the geometry and the venting characteristics, a new type of SSDS has been recognized, and the term "liquefaction vents" has been proposed for it. Their association with the other types of SSDS that are characteristically formed by >6.5 magnitude earthquakes suggests it is the minimum magnitude of earthquake required for the formation of liquefaction vents. The regional seismic record suggests a significant number of both large and moderate earthquakes around this fault. Finally, we synthesise the results to propose a growth model for the propagation of reverse faulting from the underlying basement bedrock through to the alluvial sediments and the surface of the Ganga plain. [Display omitted] • The Great Boundary Fault is a dextral strike-slip dominated reverse basement fault. • Sinuosity spectra, knickpoints, meander scars & offset streams demarcate the fault. • Liquefaction structures suggest an unreported large paleo-earthquake at Usawan. • Geomorphic signatures & seismites decipher reactivation of the Great Boundary Fault. [ABSTRACT FROM AUTHOR]

Himalaya is an active fold and thrust belt formed due to continent-continent collision between the Eurasian and Indian plates. It comprises a 3000 km long chain of mountains that span ∼1000 km across, with major boundary thrusts viz., Main Central Thrust (MCT), Main Boundary Thrust (MBT) and the Main Frontal Thrust (MFT). MFT is marked as mountain front and is the most active thrust; however, evidence of tectonic activity along MCT and MBT also exists. Tectonic activity along MFT created uplifted terraces which now serve as geomorphic archives of past tectonic events. The present study focussed on a glacial-fed river Sankosh that originates in northern Bhutan, and crosses MCT, MBT and MFT before joining the Brahmaputra River in Assam. Due to tectonic uplift, the river shows a deflection at MFT, incising and thus forming four levels of strath terraces. Luminescence chronology, geomorphic studies and analysis of satellite images suggest four levels of terraces T4 (highest level, 195 m asl), T3, T2 and T1 (lowest level, 120 m asl). The quartz was found insensitive for luminescence dating, and thus fading corrected Infra-Red Stimulated Luminescence (IRSL) ages on feldspar minerals were measured that provided ages of 143-77 ka (T4), 65-36 ka (T2) and 35-14 ka (T1), respectively. The T3 terrace was present only on the right bank of the river and could not be accessed. These ages accord with other studies at the Chalsa and Malbazar, North Bengal (west of the study area) and this regional disposition of similar ages suggest that these formed during glacial-interglacial periods. The strath terraces indicate a time-averaged tectonic uplift with a 0.5 mm/year rate over the past 150 ka. [ABSTRACT FROM AUTHOR]

Abstract: The Kashmir Valley or the Jhelum basin is an intermontane-basin in NW Himalaya bounded by the Pir Panjal Range in the south and southwest and the Great Himalayan Range in the north and northeast. The valley is marked by active major thrust boundaries in its south and southwestern parts. Remote sensing studies and morphometric analysis suggest neo-tectonic activities and the formation of tectonic terraces due to uplift on the major thrust boundaries in NW Himalayas. The quartz from freshly eroded mountain belts is usually found to show very poor luminescence sensitivity and thus not suitable for optical dating. Similar problems occurred with the quartz from the Srinagar Basin. Due to this, feldspar was selected as a natural dose meter for dating tectonically uplifted terraces in an active and dynamic belt of the NW Himalayas. We report here for the first time the luminescence characteristics of quartz and feldspar minerals from the study area. However, feldspar also shows poor luminescence sensitivity, although enough to perform optical dating. Athermal fading was observed in all the feldspar samples, which was corrected using ‘g’ values; a large scatter was found in the g values, probably due to intermixing of feldspar grains from varying source rock types and also due to poor luminescence sensitivity. An average g value correction to the mean paleodose was found to agree if compared with the thermo-luminescence date of loess deposit dated earlier. The ages show that the terrace formation started taking place at ∼100ka in the southwestern part of the Jhelum basin and continued with pulses at 50ka and 11ka towards the northwestern part. [Copyright &y& Elsevier]

The study presents the Late Quaternary glaciation history of monsoon-dominated Dokriani Glacier valley, Dingad basin, central Himalaya, India. The basin is tested for the mechanism of landforms preservation in high relief and abundant precipitation regimes of the Higher Himalaya. Field geomorphology and remote sensing data, supported by Optical Stimulated Luminescence (OSL) dating enabled identification of five major glacial events of decreasing magnitude. The oldest glacial stage, Dokriani Glacial Stage I (DGS-I), extended down to ∼8 km (2883 m asl) from present-day snout (3965 m asl) followed by other four glaciations events viz. DGS-II, DGS-III, DGS-IV and DGS-V terminating at ∼3211, 3445, 3648 and ∼3733 m asl respectively. The DGS-I glaciation (∼25–∼22 ka BP) occurred during early Marine Isotope Stage (MIS) −2, characterized as Last Glacial Maximum (LGM) extension of the valley. Similarly, DGS-II stage (∼14–∼11 ka BP) represents the global cool and dry Older Dryas and Younger Dryas event glaciation. The DGS-III glaciation (∼8 ka BP) coincides with early Holocene 8.2 ka cooling event, the DGS-IV glaciations (∼4–3.7 ka BP) corresponds to 4.2 ka cool and drier event, DGS-V (∼2.7–∼1 ka BP) represents the cool and moist late Holocene glacial advancement of the valley. This study suggests that the Dokriani Glacier valley responded to the global lowering of temperature and variable precipitation conditions. This study also highlights the close correlation between the monsoon-dominated valley glaciations and Northern Hemisphere cooling events influenced by North Atlantic climate. [ABSTRACT FROM AUTHOR]

• The Moradabad fault (MF) was mapped in the Ganga basin and the Himalaya. • Its doubted-extension into the Himalaya resolved from geomorphological and field studies. • This is neotectonically active, triggered by the Himalayan tectonics. • The geomorphic impression shows the signs of compression in the up-thrown block of the fault. • Normal faults are developed at the releasing bend. The present study focuses on the neotectonic perspective of a subsurface basement fault, i.e., the Moradabad Fault (MF) in the Ganga basin. This is a ∼163 km long NE-SW trending prominent pre-Himalayan subsurface structure that participated in many phases of tectonic movement during and after the Himalayan orogeny. At present, it is deep-buried under the alluvium, and frequent geomorphic readjustments are seen in the fluvial archives around this fault. The datasets presented here include tectono-geomorphological analysis, transverse-tectonic analysis, previous seismic records from the earthquake catalogs and the associated seismites, and the Ground Penetrating Radar (GPR) studies. The available geological maps limit the northern end of the MF at the Himalayan front, and further northward, it is marked as lineaments. However, the recent geological evidence such as the river alignment, river confluence, landslides, faceted spurs, triangular facets, truncated spurs, fault scarps, structural terraces, and the alignment of the low to moderate magnitude seismic events having parallel trends with the MF may conclude that it is not just a matter of coincidence. However, these features are likely aligned due to the post-Himalayan reactivation-regeneration of the basement structures. It is, therefore, argued that these linear structures showing active deformation are the extension of the MF into the Himalayas, and hence the lineament terminology for these structures should be abolished. The MF has a curved fault-line with the existence of the releasing bend in a transtensional regime. The up-thrown block shows the signs of compression, evidenced by the geomorphological signatures. The fault-bend is characterized by oblique deformation may be accommodated by oblique-slip faulting or dip-slip fault displacements. Tectonic geomorphological characteristics, morphostratigraphic record, GPR data, seismic events, and the basement contour model suggest the Moradabad fault is neotectonically active and is influenced by the Himalayan tectonics. [ABSTRACT FROM AUTHOR]

The Himalayan front exhibits varying convergence rates along its length. This study examines the morphotectonic evolution of the landforms in an intermontane valley (viz., Chitwan dun) present in a relatively rapidly converging segment of the Himalaya. Using field investigations, geomorphic analysis, and geochronology, we demonstrate that five geomorphic levels have developed in the past >112 ka. Four major phases of aggradation occurred in the Chitwan, i.e., >112 ka, ~112–>70 ka, ~70–25 ka, and ~18–11 ka. Tectonic activity on the Jharahi (JHT) and Belani thrusts (BT) at >112 ka and >70 ka respectively resulted in the uplift of the geomorphic units to Level 5 and Level 4. Continuous aggradation in the valley occurred between 70 and 25 ka (Level 3); the tectonic activity during this period is marked by the reactivation of the West Chitwan thrust (WCT) and the Central Churia Thrust (CCT). The Level 3 surfaces were abandoned during the LGM (25–18 ka) and subsequently incised. Enhanced monsoon in the post-LGM period favored aggradation of the Level 2 and 1 geomorphic units. The Level 2 surfaces were abandoned due to activity on the Danda (DT) and Shaktikhor Thrusts (ST) whereas the Level 1 landforms were incised due to climatic changes in the Holocene. Comparing the results of this study with other parts of the Himalaya, we infer that despite variable tectonic convergence rates, major aggradation and incision cycles are uniform. This suggests that Late Quaternary climatic perturbations have strongly influenced the fluvial systems across the Himalaya. However, the role of tectonics is also manifested in the form of multiple levels of surfaces and terraces. • Surfaces, fans and terraces in the Chitwan dun (Central Himalaya) investigated. • Landform mapping, surveying, facies analysis and OSL dating applied. • Dated landforms record spatial-temporal patterns of landscape evolution from ~112 ka. • Chitwan dun landscape evolution records distinct tectonic and climatic events. • Climate-landform associations appear regionally synchronous across the Himalaya. [ABSTRACT FROM AUTHOR]

Terraces in the Himalayas are important geomorphic archives which preserve the signature of tectonics and past environment. Terraces in eastern part of the Himalayan fold and thrust belt have not received much attention of the geologists. A geochemical approach using luminescence dating has been applied to understand the evolution of paired and deformed terraces between major thrust boundaries of the eastern Himalayas, on the either banks of the Tista River in Darjeeling-Sikkim-Tibet wedge. These terraces are located at the confluence of Tum Thang khola and the Tista River. Three levels of terraces are present in general and also in the study area. The terrace T3 was formed during last interglacial period and the T2 terrace during last glacial maximum (LGM) and in the humid phases after LGM. The top section of T2 terrace (∼2.5 m thick) was formed in the transition phase (arid to humid) after Younger Dryas event. The region has experienced several deformational events, (i) one after 45 ka which raised the T3 terrace to its present level, (ii) another one after 11.9 ka which raised the T2 to its present level and this event is also associated with the shifting of the Tum Thang khola, and (iii) the region is still tectonically active as shown by the warping of the T1 and T0 surfaces, which are of recent origin. These terraces have complex input of sediments from Higher Himalayan Crystalline (HHC) rocks and from locally present Lingtse granites. [ABSTRACT FROM AUTHOR]

Abstract: Determining the frequency, magnitude and causes of large floods over long periods in the flood-prone Himalaya is important for estimating the likelihood of future floods. A thousand year record (with some information from 2600 years ago) of the frequency and some estimates of velocities and discharges of large floods has been reconstructed in the Upper Ganga catchment, India, using written reports, litho-stratigraphy and sedimentology, and dated by optical and radiocarbon methods. In the Upper Ganga catchment rainfall triggers large landslides that dam rivers and release large amounts of water when they burst, thereby amplifying the effects of rainfall. The large floods in the catchment may be the result of landslide dam bursts rather than glacial lake bursts, and these are likely to continue and possibly worsen as the monsoon intensifies over the next century. However preliminary information suggests that the recent devastating flood of June 2013 was the result of heavy rainfall not landslide dam bursts. The frequency record is non-random and shows a high frequency between AD 1000 and AD 1300 (omitting uncertainties), then a low frequency until a cluster of floods occurred about 200 years ago, then increased frequency. This temporal pattern is like but not identical with that in Peninsular India, and both appear to be the result of variations in the monsoon. [Copyright &y& Elsevier]