Lesser Himalaya Research Articles

Evaluation of Active Tectonic Features of Nandakini River Basin, Lesser Himalaya, India by Using Morphometric Indices: A GIS Approach

Tectonic geomorphology has been evidenced as an essential tool to define and measure recent tectonic deformation. The Nandakini River originates from Nanda Ghunti glacier at 6886 m in Lesser Himalaya. It covers about ~551 km<sup>2</sup> basin area, with a fourth-order stream. It confluences with the Alaknanda River near Nand Prayag (at elevation 852 m), Chamoli district of Uttarakhand. The drainage pattern is predominantly dendritic in the study area. The morphotectonic indices are measured to know the tectonic activity of the drainage basin. Morphometric indices reflecting hypsometric Integral is 1.07, indicating a deeper incision and a slight erosion. The basin elongation ratio is 0.17, suggesting that the area is tectonically active. The drainage basin asymmetric factor (44) suggest tilting. In addition, the drainage basin shape (3.27) indicates the basin is tectonically strong, the transverse topographic symmetry factor (0.31) indicates the asymmetric nature, the valley floor width to valley height ratio is 0.54 shows the deep, narrow valleys, and Active V-shaped incision. Stream longitudinal profile showing the area tectonically influenced. The Sinuosity Index of 1.12 suggests that low sinuous nature. The Stream length-gradient Index is 10.64, indicating high tectonic activity in valleys and basin areas. The transverse profile helps to understand the tilting of the basin. The Surface profile shows irregularity, and the linear trend of the profile shows the tilting of the basin. River carrying capacity with large boulder-size sediment indicates youth stage and tectonically active environment. The morphotectonic indices suggest that the drainage basin was affected by the regional structures and the present tectonics.

Three-dimensional magnetotelluric signatures and rheology of subducting continental crust: Insights from Sikkim Himalaya, India

3D inversion of broad band MT data present variation of electrical signatures across the subducting Indian crust in Sikkim Himalaya. The vertical and horizontal geoelectric cross-sections are dominated by north-east dipping conductive zones. Two high conductivity zones (4–8 Ω m) at a depth of 5–18 km in Lesser Himalayan Domain (LHD) are explained by conductive mineral assemblage associated with abundant low saline and entrapped fluids. Another conductive feature (6–16 Ω m) in Main Himalayan Thrust Zone close to Main Himalayan Thrust ramp could have arisen from entrapment of CO2-H2O fluids and fluids released by metamorphic reactions. The high conductive anomaly (4–10 Ω m) at a depth of 5–16 km in Greater Himalayan Sequence (GHS) is caused by the presence of partial melts/aqueous fluids derived by present day fluid-absent melting of leucogranite source rocks. A combination of leucogranite intrusion, shear heating, and radiogenic heat production (4–17 μW/m3) are the heat sources for inferred partial melting. Though, the constrained melt fractions of 1.4–3.8% in GHS are lower than the estimation in south Tibet that might be due to the less intrusion of leucogranites. The obtained moderate viscosities of (104.19-105.49 Pa.s) from empirical relation with low melt and fluid fractions of 5–6 wt% in high conductive zone suggest viscous/ductile deformation and weakening mid-crust beneath northern Sikkim Himalaya. However, the estimated values of melt fractions and viscosities at mid-crustal depth of GHS are insufficient to develop a melt channel to flow southward between Main Central Thrust-1(MCT-1) and South Tibet Detachment (STD) envisaged by channel flow model.

Crustal study based on integrated geophysical techniques in the Northwestern Himalayas, Pakistan

The present research aims to explicate the tectonics of the northwest Himalayas, Pakistan, based on integrated gravity, magnetic and earthquake data. The raw gravity and magnetic data were processed, and seven isoanomaly maps were prepared for qualitative interpretation, whereas a gravity model was prepared along the selected profile for quantitative interpretation. The local earthquake data have also been used to identify the various seismogenic layers in the subsurface and to understand how seismicity relates to regional structural features. Three northwest‐trending thick‐skinned blind basement faults are identified from the present study, namely the Indus Kohistan Seismic Zone (IKSZ), Bagh Basement Fault and Hazara Lower Seismic Zone. The IKSZ is the tectonically most active among them and responsible for the 2005 Kashmir earthquake (Mw = 7.6) and 1974 Pattan earthquake (Mw = 6.2) in the region. The present study also delineated the prominent location of the Main Central Thrust in which the high‐grade metamorphic rocks of Higher Himalayan Crystalline thrust over low‐grade metamorphic rocks of Lesser Himalayas along this thick‐skinned fault. The field evidence such as ductile deformation, zone of inverted metamorphism, and brittle deformation also confirm this location. The sharp bending of the crystalline crust, as well as deep basement just south of Kohistan Island Arc (KIA), indicate that the high density and susceptibility rocks of this arc thrust on the leading margin of the Indian Plate along the Main Mantle Thrust. This thrust fault is a major suture zone separating the KIA in the north from the Indian Plate in the south. The other faults in the region exist in the sedimentary/meta‐sedimentary wedge and are thin‐skinned. It is inferred from the current investigation that the study area exhibits a composite style of deformation. Moreover, the gravity model combined with earthquake data suggested the existence of multiple décollement zones below the Hazara‐Kashmir Syntaxis. The model envisaged an increase in the thickness of the Indian Plate continental crust in the northeast direction.

Modelling of rainfall threshold for the initiation of landslides in lesser Himalayan region using THRESH

Modelling of rainfall threshold for the initiation of landslides in lesser Himalayan region using THRESH

Ordovician strata of the Indian subcontinent

Abstract Ordovician rocks of the Indian Tethyan Himalaya contain a conspicuous angular unconformity between mostly marine Cambrian and overlying terrestrial Ordovician strata, which is a record of the Kurgiakh Orogeny. This tectonic event is traceable across the Tethyan Himalaya from Pakistan to Bhutan. The Pin Formation in the Spiti Valley provides a high-resolution account of the marine depositional history, palaeontology and isotope geochemistry of Late Ordovician events. The middle (Takche) member is late Katian and the upper Mikkim Member is lower Silurian (Llandovery), based on an ozarkodinid conodont fauna. The Pin Formation records the Boda event, the last warming interval prior to Hirnantian glaciation. The δ 13 C carb chemostratigraphic data allow precise global correlation, and recognition of the Paroveja positive excursion, the last major excursion of the Katian. The Mikkim Member records a ‘lower HICE’ (Hirnantian isotopic carbon excursion) of the Katian–Hirnantian boundary interval. Palaeontological data indicate that there are no known fossils diagnostic of any Ordovician ages older than the Katian Stage in India. Evidence of Ordovician sedimentary rocks in the Lesser Himalaya is intriguing, but presently equivocal. The widespread absence of pre-Katian strata on the Indian subcontinent is due to erosion associated with the Kurghiak orogeny and delayed onlap onto topographically high areas.

MONITORING DECADAL PRECIPITATION VARIABILITY IN UPPERINDUS BASIN, PAKISTAN

Upper Indus Basin (UIB) is critical for Pakistan’s economy as it is glacial incomposition and snow melt that provides 80% of the fresh water to Indus River. Decadal fluctuationsin the precipitation in UIB during 1980-2010, using interpolation technique in Arc Map were exploredin present study. The results provided a positive correlation between the winter precipitation andsummer runoff in middle elevation basins of UIB. The map of decadal difference of mean annualrainfall (1980-2010), prepared in Arc Geographic Information System 9.0, revealed that around Gilgit,Skardu, Astore, Chilas and Bunji, was found the least difference in mean annual rainfall, i.e. of -1.68 to-2.14mm, whereas area around Kakul experienced maximum rainfall decadal difference ranged from-13.63 to -17.45mm. The study suggested that south of lesser Himalayan areas experienced maximum rainfall variability during the period 1980-2010, whereas, lesser variability in north of Himalayan areas inferred safer addition in fresh water in Indus from its glacial reserve.

Tectono-metamorphic transitions in the higher Himalayan sequence: A clue for Main Central Thrust (MCT) localization in Darjeeling-Sikkim Himalaya

This study recognizes a transition in the modes of ductile deformation across the Himalayan Crystalline Complex (HCC) from field and microstructural evidence. This transition leads to the Main Central Thrust (MCT) zone localization in the Darjeeling-Sikkim Himalaya. In the initial stage of crustal shortening (prior to ∼16 Ma), the HCC experienced temporally varying distributed ductile strains that produced regionally occurring planar fabrics and folds of three generations. Thereafter, the tectonic transition (from distributed to localized deformation) at ∼16 Ma occurred, forming the MCT zone in the HCC. This MCT zone (∼4–6 km thick) marks a diffuse metamorphic/rheological boundary between the hot HCC and the relatively colder Lesser Himalayan terrane to the south. The field data suggests that the base of compressed reverse paleo-isograds at the bottom of the MCT zone coincides with the transition of quartz creep mechanisms, from sub-grain rotation (SGR) to grain boundary migration (GBM). The present study documents the prograde metamorphic imprints to establish the P-T conditions of these multiple deformation episodes. Finally, this study presents a conceptual tectonic model, based on previous laboratory findings, to propose a two-stage tectono-thermal evolution of the Higher Himalaya.

LANDSLIDE MAPPING AND SPATIAL DISTRIBUTION ANALYSIS FROM MUZAFFARABAD TO LUAT AREA WITH CASE STUDY OF PLANG LANDSLIDE, LESSER HIMALAYAS, PAKISTAN

Landslides are one of the most dangerous and frequent natural hazards worldwide and in Pakistan, wreaking havoc on society and the economy. Susceptibility mapping, as well as geological and geotechnical investigations, are the focus of this study on the Plang landslide in Neelam Valley, Pakistan’s Lesser Himalayas. This landslide’s causes and solutions were determined by a combination of geotechnical soil testing, longitudinal profiles, geological mapping, seismicity, roadcut, and rainfall assessments. The greatest concentration of landslides (as measured by both number of occurrences and slope gradient) was found on slopes with a gradient of between 31 and 40 degrees (33.5%). Most landslides (33.75%) happened facing south-east, according to the spatial link between the number of landslides and the slope aspect. To determine landslip causes and triggers, geotechnical studies were conducted. Complex debris flow and slump failure characterize the Plang landslip. Sieve analysis, Atterberg limits, specific gravity and study of disturbed soil samples show that Plang landslip soils are silty sand to clayey sand with plasticity index (PI) of 4.4%. The study depicts that drainage network, anthropogenic activities along steep slopes, fragile geology, active faults, freeze, and thaw action are influential parameters which significantly contribute to the landslide events.

Impact assessment of magnesium in the ground soil and suspended particulate matter in the ambient air of Kumaun region of lesser Himalayas

Impact assessment of magnesium in the ground soil and suspended particulate matter in the ambient air of Kumaun region of lesser Himalayas

Detrital zircon, monazite and tourmaline reveal the magmatic and metamorphic history of the Himalayan orogen from Archean to present

The litho-tectonic structure of the Himalaya is the result of multiple orogenic cycles. However, its pre-Cenozoic history is not well understood, which limits our ability to constrain the stratigraphy, structure, and tectonism in the Himalayan orogen. This issue can be potentially addressed by detrital mineral geochronology and isotopic studies, which can be used to reconstruct the magmatic and metamorphic records from past to present. In this study, we collected three river sand samples from the central Himalaya, which originated from the interior of Ama Drime Massif (ADM), Greater Himalayan Sequence (GHS) outside of the ADM, and the boundary between the ADM and GHS, respectively, and then conducted a geochronological study of detrital zircon and monazite, and obtained detrital zircon Hf and tourmaline B isotope data. Detrital zircon of the river sand from the ADM only records the 1.9–1.7 Ga magmatic event, while age groups of 3.5–2.4, 1.1–0.7, and 0.6–0.4 Ga are observed in the GHS outside the ADM. Detrital tourmaline from the GHS has heavy B isotopic signatures with δ11B = −15‰ to −7‰, similar to the values for GHS leucogranites. Detrital tourmaline from the ADM has δ11B = −20‰ to −13‰, similar to the Lesser Himalayan Sequence (LHS). Integrating these results with previous metamorphic and thermochronological works, we interpret that the ADM represents deeply buried LHS rocks beneath the GHS, which underwent a significant uplift assisted by the detachments on its two sides during the Miocene. Furthermore, zircon Hf isotopic variations indicate that the north Indian margin was an active convergent boundary during the Paleoproterozoic, Neoproterozoic, and Paleozoic, in relation to supercontinent amalgamation. Detrital monazite records two major thermal events in the Cenozoic era. A large proportion of detrital monazite yield ages from 25 to 20 Ma, indicating that the collision entered a mature stage at this time, during which thickened Himalayan crust formed and widespread anatexis occurred. A tectonic style transition in the Himalayan hinterland from shortening that thickened the crust to extension that thinned it occurred during the middle to late Miocene (15–10 Ma) in the Himalaya.

Geology, Structure, Metamorphism and Deformation of Botechaur-Chaurjhari Area of Western Nepal

The Lesser Himalayan unit of the Nepal Himalaya, especially the western and central parts comprise numerous metamorphic crystalline thrust sheets occupying the cores of large synclinorium. Despite having complex geological settings, some areas in western parts of Nepal lack detailed geological mapping with credible information. This study aims to explore one least explored section; with emphasis on lithostratigraphy, structural setting, deformation, metamorphism, and magmatism. Detailed geological mapping along the Botechaur-Chaurjhari section revealed three tectonostratigraphic units separated by the Main Boundary Thrust (MBT) and the Mahabharat Thrust (MT); the Siwaliks (Middle Siwalik), autochthonous units of the Lesser Himalaya (Dandagaon Phyllite, Nourpul Formation and Dhading Dolomite) and the Lesser Himalayan Crystalline units (Kalagaon Formation and Chaurjhari Formation) from south to north respectively. From the microstructural analysis and measurements of shear sense indicators, the MT shows a top-to-the-south sense of shear indicated by asymmetric boudins, parasitic folds, and thrusting indications in blasto-mylonitic augen gneiss and asymmetric porphyroblast of garnet and the shearing in the garnet. The area also displays an inversion of metamorphism, supporting the development and existence of thrust. The metamorphic grade ranges from chlorite grade to kyanite grade having metamorphic facies assemblage of zeolite to amphibolite facies. Five phases of deformation (D1 to D5) are prevalent within the area, two of which (D1 and D2) belong to the pre-Himalayan (pre-Tertiary) orogeny and the rest of the deformation syn-to post-Himalayan.

Constraints on the timing of the India‐Asia collision and unroofing history of the Himalayan orogen using detrital zircon U‐Pb‐Hf and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks

AbstractCretaceous‐Miocene sedimentary rocks in the Nepalese Lesser Himalaya provide an opportunity to decipher the timing of India‐Asia collision and unroofing history of the Himalayan orogen, which are significant for understanding the growth processes of the Himalayan‐Tibetan orogen. Our new data indicate that detrital zircon ages and whole‐rock Sr‐Nd isotopes in Cretaceous‐Miocene Lesser Himalayan sedimentary rocks underwent two significant changes. First, from the Upper Cretaceous‐Palaeocene Amile Formation to the Eocene Bhainskati Formation, the proportion of late Proterozoic‐early Palaeozoic zircons (quantified by an index of 500–1200 Ma/1600–2800 Ma) increased from nearly 0 to 0.7–1.4, and the percentage of Mesozoic zircons decreased from ca. 14% to 5–12%. The whole‐rock 87Sr/86Sr and εNd(t = 0) values changed markedly from 0.732139 and −17.2 for the Amile Formation to 0.718106 and −11.4 for the Bhainskati Formation. Second, from the Bhainskati Formation to the lower‐middle Miocene Dumri Formation, the index of 500–1200 Ma/1600–2800 Ma increased to 2.2–3.7 and the percentage of Mesozoic zircons abruptly decreased to nearly 0. The whole‐rock 87Sr/86Sr and εNd(t = 0) values changed significantly to 0.750124 and −15.8 for the Dumri Formation. The εHf(t) values of Early Cretaceous zircons in the Taltung Formation and Amile Formation plot in the U‐Pb‐εHf(t) field of Indian derivation, whereas εHf(t) values of Triassic‐Palaeocene zircons in the Bhainskati Formation demonstrate the arrival of Asian‐derived detritus in the Himalayan foreland basin in the Eocene based on available datasets. Our data indicate that (1) the timing of terminal India‐Asia collision was no later than the early‐middle Eocene in the central Himalaya, and (2) the Greater Himalaya served as a source for the Himalayan foreland basin by the early Miocene. When coupled with previous Palaeocene‐early Eocene provenance records of the Tethyan Himalaya, our new data challenge dual‐stage India‐Asia collision models, such as the Greater India Basin hypothesis and its variants and the arc–continent collision model.

Bhumichula plateau: A remnant high-elevation low-relief surface in the Himalayan thrust belt of western Nepal

The Himalaya is known for dramatically rugged landscapes including the highest mountains in the world. However, there is a limited understanding of the timing of attainment of high elevation and relief formation, especially in the Nepalese Himalaya. Anomalous high-elevation low-relief (HELR) surfaces, which exhibit geomorphic antiquity and are possibly remnants of formerly widespread high-elevation paleosurfaces, provide a unique opportunity to assess the attainment of regional high elevation in the Himalaya. The Bhumichula plateau is one such HELR surface (4300−4800 m) in the western Nepalese Himalayan fold-thrust belt. The Bhumichula plateau is situated in the Dadeldhura klippe (also called the Karnali klippe), an outlier of Greater Himalayan Sequence high-grade metasedimentary/igneous rocks surrounded by structurally underlying Lesser Himalayan Sequence low-grade metasedimentary rocks. We assess the origin of the Bhumichula plateau by combining regional geological relationships and zircon and apatite (U-Th-Sm)/He and apatite fission track thermochronologic ages. The HELR surface truncates pervasive west-southwestward dipping foliations, indicating that it post-dates tilting of rocks in the hanging wall of the Main Central thrust above the Lesser Himalayan duplex. This suggests that the surface originated at high elevation by erosional beveling of thickened, uplifted crust. Exhumation through the ∼180−60 °C thermal window occurred during middle Miocene for samples on the plateau and between middle and late Miocene for rocks along the Tila River, which bounds the north flank of the Bhumichula plateau. Cooling ages along the Tila River are consistent with erosional exhumation generated by early Miocene emplacement of the Main Central (Dadeldhura) thrust sheet, middle Miocene Ramgarh thrust emplacement, and late Miocene growth of the Lesser Himalayan duplex. The most recent middle-late Miocene exhumation took place as the Tila River and its northward flowing tributaries incised upstream, such that the Bhumichula plateau is a remnant of a more extensive HELR paleolandscape. Alpine glaciation lowered relief on the Bhumichula surface, and surface preservation may owe to its relatively durable lithology, gentle structural relief, and elevation range that is above the rainier Lesser Himalaya.

Culinary Tourism: A new way for destination attraction in Almora, Kumaun Lessar Himalaya

Food plays significant role in tourism promotion. Tourist visit a great number of destination in the world but we observed that some places are prominent because of the peculiar local cuisine as we know that Punjab is famous for Makke di Roti or Sarso ka saag, Rajisthan for Daal baati churma, Bihar for Litti Chhokha etc. These all example shows that if we focus in our local food it’s may definitely increase the tourist influx. Uttarakhand 27th state of India situated in the mesmerizing environment of the oak and deodar canopy, snow filled mountains and chilly wind always attract thousands of tourist from the globe but local cuisine neglected till the present. Almora, an ancient hill station in Kumaun, lesser Himalaya and known as a cultural capital of Kumaun. It is not only rich in cultural heritage but also enriched with delicisious and healthy cuisine. Varieties of food are well known here at local level but the special cuisine is not popular as other Indian State cuisine. So the paper attempt to study about various famous cuisine of Almora and its surrounding through the which government develop and promote culinary tourism concept likewise other form of tourism. Culinary tourism paves the way for exploring the antique food which are hidden as the treasure. The present study is based on the survey of 300 purposely and randomly selected tourists from different tourist destination of Almora district.

Dominant role of deglaciation in Late Pleistocene–Early Holocene sediment aggradation in the Upper Chenab valley, NW Himalaya

AbstractSediment transfer from the interiors of the Himalaya is complex because the archives are influenced by both glacial and monsoonal cycles. To deconvolve the coupling of glacial and monsoonal effects on sediment transfer processes, we investigate the Late Pleistocene–Holocene sediment archive in the Upper Chenab valley. Optically stimulated luminescence (OSL) ages from the archive indicate major aggradation during ca. 20–10 ka. Isotopic fingerprinting using Sr-Nd isotopes in silt fractions together with clast counts in boulder-pebble fractions indicate a decreasing Higher Himalayan sediment flux in the archive with time. Decreasing clast size, increasing clast roundness, increasing matrix to clast ratio, and dominance of the Higher Himalayan sourcing unequivocally suggest strong glacial influence during the initial stages of the archive formation. This evidence also agrees with the existing retreat ages of glaciers in the Upper Chenab valley. Results of our study also show that the upper parts of the archive contain significant fluvial sediment contribution from the Lesser Himalaya, which suggests an active role of the stronger Indian Summer Monsoon (ISM) in the region during the Early Holocene. The apparent decrease in sediment supply from the Higher Himalayan sources could have been due to longer source-to-sink transport in the Early Holocene and/or increased hillslope flux from Lesser Himalayan sources.

Advanced Training Programme on Granites and Related Rocks and Field Workshop in Kumaun Lesser Himalaya

Advanced Training Programme on Granites and Related Rocks and Field Workshop in Kumaun Lesser Himalaya

Implications of garnet nucleation overstepping for the P–T evolution of the Lesser Himalayan Sequence of central Nepal

AbstractRecent studies have demonstrated that kinetic factors can significantly influence garnet nucleation, delaying its appearance with respect to the equilibrium predictions. Overstepping of garnet nucleation occurs in both contact and regional metamorphic settings, with extremely variable degrees: The factors controlling such highly variable degrees of overstepping are still unclear. This study focuses on garnet nucleation and growth in aluminous metapelites from the Barrovian inverted metamorphic pile of the upper portion of the Lesser Himalayan Sequence (Upper‐LHS; central Nepal), with the aim of (i) investigating if (and how) the bulk‐rock composition can influence overstepping of garnet nucleation and (ii) which are the implications of garnet nucleation overstepping for the P–T evolution of a Barrovian metamorphic sequence. Detailed petrographic, microstructural and compositional data are presented for six phyllitic schists, containing porphyroblasts of garnet, staurolite and/or kyanite. Their P–T evolution is constrained through thermodynamic forward modelling (i.e., isochemical phase diagrams combined with isopleth thermobarometry), assuming that equilibrium was attained at every stage of their metamorphic evolution. Comparison between the P–T conditions inferred for the growth of garnet core, the assemblages predicted to be stable at these P–T conditions and the modelled garnet‐in reaction boundary suggests that the studied samples have experienced different degrees of apparent thermal (ΔT) and/or baric (ΔP) overstepping of garnet nucleation. We suggest that the bulk‐rock MnO and CaO amounts might have influenced the apparent ΔT and ΔP overstepping of the garnet‐in reaction: more specifically, the higher the bulk‐rock MnO content, the more pronounced the apparent ΔT overstepping, whereas the lower the bulk‐rock CaO content, the greater the ΔP overstepping. However, rather than an effective delay of garnet appearance with respect to equilibrium predictions, the apparent ΔT overstepping of garnet nucleation could reflect the attainment of the critical 0.5% threshold of garnet abundance, below which garnet is not readily detected in thin section. Kinetic factors seem much less critical in controlling the growth of the garnet rim at peak P–T conditions, confirming that peak metamorphic conditions constrained through equilibrium approaches based on the composition of garnet rim and of the matrix assemblage can be considered as reliable. Overall, the P–T paths of the studied samples are characterized by prograde heating coupled with tectonic overload (peak‐P conditions of 9.5–10.5 kbar, 580–590°C), followed by heating during exhumation (peak‐T conditions of 8.2–8.9 kbar, 610–630°C), supporting those thermo‐mechanical models that predict a period of slowdown (or quiescence) of the Main Central Thrust activity.

Provenance and sedimentation age of the Proterozoic clastic succession of the Garhwal‐Kumaon Lesser Himalaya, NW‐India: Clues from U–Pb zircon and Sr–Nd isotopes

The paper presents data on the U–Pb chronology of detrital zircon grains and radiogenic isotopic composition (87Sr/86Sr, ɛNd) from the Proterozoic clastic successions of the Garhwal‐Kumaon Lesser Himalaya representing the extended northern Indian cratonic margin, NW India. The Proterozoic Lesser Himalayan Basin in Garhwal‐Kumaon Himalaya is divided into two sectors, namely, Inner Lesser Himalaya (ILH) and Outer Lesser Himalaya (OLH) by a tectonic boundary, namely the Tons Thrust (TT). Age distribution from inner and outer sectors of the Lesser Himalaya shows that the U–Pb chronology of most of these zircons provides Palaeoproterozoic (between 1.6 and 1.8 Ga) to Neoproterozoic (800 Ma) ages. The age data suggest sedimentation of the Rautgara Formation (Damtha Group) of ILH continued till the Neoproterozoic (~850 Ma), which was earlier regarded as ≤1.6 Ga. Tracking the detrital U–Pb zircon ages in the near adjacent cratonic parts point towards Aravalli Orogen as the major source region. Whole‐rock ƐNd(0) values for ILH rocks range from −37.6 to −14.6 and for OLH it ranges from −19.6 to −6.7. More negative ƐNd values along with dominance of Neoarchean‐Palaeoproterozoic ages in ILH indicates supply from more evolved protolith or recycled sources and less negative ƐNd values with major Neoproterozic zircon ages from OLH supports for less evolved source rock. The change from more negative ƐNd to less negative ƐNd values progressively upward the stratigraphy can be due to a shift in source with time. Both U–Pb zircon and ƐNd supports for a continuous sedimentation model, rule out the presence of ~500 Ma unconformity within the LH and argues for separate evolution of the Lesser Himalayan Basin on the trailing edge of the extended north Indian craton in “Columbia” configuration.

Newly discovered ca. 1.6 Ga K-bentonite layers from the Lakharpata Group in Nepal Lesser Himalaya: Implications for basin evolution during the Columbia breakup

• Zircon U-Pb age for newly discovered K-bentonite (ca. 1.6 Ga) constrained the deposition time of the Lakharpata Group. • The Lakharpata Group in Nepal Lesser Himalaya is coeval sediment with the Lower Vindhyan in India. • The Lakharpata Group was deposited in a passive continental margin basin during the Columbia breakup. The Lakharpata Group, a set of marine sediments with a thickness of over 5000 m, occupies the middle part of the Lesser Himalayan sequence and records important tectono-sedimentary evolution in the northern margin of the Indian continent. However, the duration of deposition and tectonic background of the Lakharpata Group are poorly defined. This study presents zircon U-Pb ages and Hf isotopes, as well as petrochemical data for the newly discovered K-bentonite layers in the Aru Formation, the upper part of the Lakharpata Group. Integrating the detrital zircon ages of the underlying metasedimentary rocks and the sedimentation rate of dolomite in the South China Block, we suggest that the Lakharpata Group was deposited during the late Paleoproterozoic to early Mesoproterozoic (ca. 1680–1580 Ma) rather than from Mesoproterozoic to Early Paleozoic as previously presumed. Stratigraphic correlations show the Lakharpata Group in Nepal Lesser Himalaya correlates to the Lower Vindhyan Supergroup, as well as to the Deoban and Rautgara formations in Kumaun Lesser Himalaya and the Baxa Group in Sikkim Lesser Himalaya, India. The Lakharpata Group comprises two depositional sub-sequences that record two transgression-regression sedimentary processes, which are comparable to the Lower Vindhyan. Geochemical and sedimentological studies suggest that the Lakharpata Group may represent the deposition of a passive continental margin basin during the breakup of the Columbia supercontinent.

Assessing the vulnerability of watersheds to environmental degradation in the lesser Himalayan region using satellite data and a series of models

The Lesser Himalayan watersheds are vulnerable to environmental degradation due to their unstable lithology and anthropogenic pressure. A Gaula watershed was considered for the vulnerability analysis using satellite data, compound factor (CF) and multi-criteria decision making (MCDM) based on Grey Relation Analysis (GRA) and Complex Proportion Assessment of Alternatives (COPRAS) models. For prioritzation, 29 variables (12 morphometric, 5 geologies, 6 soils, 5 land uses/land covers, and 1 slope) were selected and the MCDM methods were validated using indices of the percentage of change and intensity of change. A total of five sub-watersheds (SW) were delineated, SW2 reported highest drainage density (0.58). The sinuosity index of SW1, SW4, and SW5 have 1.33, 1.34, and 1.27, showing active tectonic activities. The COPRAS reported highest intensity of change (93.33), whereas GRA and CF reported percentage of changes were 86.66 and 80.0, respectively. Hence, these models are appropriate to investigate the interrelationships of different components.