Shyok Valley Research Articles

A glaciotectonic landform in the Shyok valley, Trans-Himalayan Karakoram Range, India

Abstract This study reports and discusses the first case of glaciotectonic landforms in the Shyok valley of the Trans-Himalayan Karakoram Range, Ladakh, where a large decomposed granite megablock (8.2 km2) along with underlying diamicton is thrust over the unconsolidated Quaternary glaciofluvial sediments along a fault gouge zone near the village of Khalsar. The absence of deformation signatures below the fault gouge indicates that the brittle fault acted as a décollement surface under frozen conditions along which the glaciotectonic megablock was translated. The other deformation features include slickensides, ductile shear, thrust propagation fold noses, clastic dykes and rafts of granite and slate within the diamicton sediments. These features indicate a subglacial glaciotectonic nappe origin of the landform. The presence of juxtaposed brittle to ductile deformation fabric, clastic dykes and the superimposition of deformed decomposed granite and diamicton over the undisturbed fluvial sediments indicates a permafrost glacial margin and proglacial environment under sufficient subglacial hydrodynamic conditions for the entrapment and transportation of the glaciotectonic megablock. The deformation fabric consistently shows a southeast orientation, indicating an advancing glacier motion from northwest to southeast. The Siachen Glacier which formerly flowed down the Nubra valley is the most likely cause of the Khalsar glaciotectonic landform.

Hydro-chemical Characteristics of Melt Water Draining from Glaciers of Rongdo Basin, Shyok Valley, Ladakh

Abstract Physico-chemical parameters of meltwater of 20 water samples from glaciers of Rongdo basin, Shyok valley are presented here. The concentration of cations and anions of the two valleys were found in the order Ca>Mg>Na>K and HCO3>SO4>Cl>NO3 respectively. Significant altitudinal variation was found in major ions as indicated by the increase of TDS of glacial melt and stream water samples downstream. Gibbs plot shows chemical weathering of the rock forming minerals as the main cause for contributing ions to the melt water. The dominant order of hydrogeochemical water types identified is Ca-HCO3, is due to the water rock interaction which leads to the easy dissolution of carbonate and silicate minerals. However, few glacial melt and stream water have the influence of precipitation and meltwater runoff on chemistry. The hot spring falls in Na-HCO3 type, a typical of deeper groundwater influenced by ion exchange processes. Scatter plots of HCO3+SO4 vs. Ca/Na Plot and Ca/Na vs. HCO3/Na clearly indicates that the weathering of carbonate and silicate play a dominant role on groundwater chemistry. Two chloro-alkaline indices indicate reverse exchange reaction between Na+, K+, Mg2+and Ca2+. The physical parameters and major ions are within the permissible concentrations as per WHO and BIS indicating water is good for drinking and domestic purposes. The groundwater is suitable for irrigation as per the quality parameters and plots including EC, sodium percent (Na%) and sodium adsorption ratio (SAR).

Inverted dune swales, Hunder, Ladakh, India

ABSTRACT The Hunder Dunes occur in the Shyok valley, Ladakh region, north-western India. These barchanoid and transverse dunes consist of sand reworked from the seasonally exposed beds of the river. Wind direction is strongly uni-modal from the northwest and is controlled by valley orientation. We observed small (10–20 m long, 5–10 m wide, and up to 1.5 m high) ellipsoidal mesas in the swales between dunes, composed of sand deflated from the Shyok River system. The mesas have a tiered, wedding cake appearance with concave upper surfaces. We interpret these mesas as inverted swale deposits consisting of stacked cycles of sediment. The cycles range from 40 to 50 cm in thickness and are composed of a from bottom to top, deposits of prior dunes, high energy fluvial deposits with climbing ripples, pool sediments with symmetrical wave ripples, and desiccation-cracked mud drapes over the ripples indicating final drying out of the pool. Up to four cycles of deposition were present in the mesas. The inverted swales are being both exhumed from beneath and buried underneath migrating dunes. Inverted swale deposits provide a record of historical depositional processes and biological communities active at the site.

Tectonics and Evolution of the Trans-Himalayan Mountains and Nagaland Ophiolite Belt

Scientific investigations in the Trans-Himalayan and Nagaland ophiolite belt during the period 2011-2015 incorporated various geological and geophysical aspects of evolution of these mountains, including large-scale tectonics of the Indian Plate, its sub-surface configuration, structure and metamorphism. Certain remote areas of Karakoram along the upper Shyok valley and Nagaland were covered for their metamorphism and high pressure metamorphism of ophiolite belts, respectively.

Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau: A >100 k.y. chronology from the Shyok Valley, Karakoram

Some of the largest and most erosive floods on Earth result from the failure of glacial dams. While potentially cataclysmic ice dams are recognized to have repeatedly formed along ice-sheet margins, much less is known about the frequency and longevity of ice dams caused by mountain glaciers, and their impact on landscape evolution. Here we present field observations and results from cosmogenic nuclide dating that allow reconstructing a >100-k.y.-long history of glacial damming in the Shyok Valley, eastern Karakoram (South Asia). Our field observations provide evidence that Asia’s second-longest glacier, the Siachen, once extended for over 180 km and blocked the Shyok River during the penultimate glacial period, leading to upstream deposition of a more than 400-m-thick fluvio-lacustrine valley fill. ^(10)Be-depth profile modeling indicates that glacial damming ended with the onset of the Eemian interglacial and that the Shyok River subsequently incised the valley fill at an average rate of ∼4–7 m k.y.^(–1). Comparison with contemporary ice-dammed lakes in the Karakoram and elsewhere suggests recurring outburst floods during the aggradation period, while over 25 cycles of fining-upward lake deposits within the valley fill indicate impounding of floods from farther upstream. Despite prolonged damming, the net effect of this and probably earlier damming episodes by the Siachen Glacier is dominated by glacial erosion in excess of fluvial incision, as evidenced by a pronounced overdeepening that follows the glaciated valley reach. Strikingly similar overdeepened valleys at all major confluences of the Shyok and Indus Rivers with Karakoram tributaries indicate that glacial dams and subsequent outburst floods have been widespread and frequent in this region during the Quaternary. Our study suggests that the interaction of Karakoram glaciers with the Shyok and Indus Rivers promoted valley incision and headward erosion into the western margin of the Tibetan Plateau.

Heterogeneity in glacier response in the upper Shyok valley, northeast Karakoram

Abstract. Glaciers in the Karakoram show long-term irregular behaviour with comparatively frequent and sudden advances. A glacier inventory of the upper Shyok valley situated in northeast Karakoram has been generated for the year 2002 using Landsat ETM+ and SRTM3 DEM as baseline data for the investigations and subsequent change analysis. The upper Shyok valley contained 2123 glaciers (larger than 0.02 km2 in size) with an area of 2977.9 ± 95.3 km2 in 2002. Out of these, 18 glaciers with an area of 1004.1 ± 32.1 km2 showed surge-type behaviour. Change analysis based on Hexagon KH-9 (years 1973 and 1974) and Landsat TM/ETM+ (years 1989, 2002 and 2011) images had to be restricted to a subset of 136 glaciers (covering an area of 1609.7 ± 51.5 km2 in 2002) due to adverse snow conditions. The area of the investigated glaciers, including the 18 surge-type glaciers identified, showed no significant changes during all studied periods. However, the analysis provides a hint that the overall glacier area slightly decreased until about 1989 (area 1973: 1613.6 ± 43.6 km2; area 1989: 1602.0 ± 33.6 km2) followed by an increase (area 2002: 1609.7 ± 51.5; area 2011: 1615.8 ± 35.5 km2). Although the overall change in area is insignificant, advances in glacier tongues since the end of the 1980s are clearly visible. Detailed estimations of length changes for individual glaciers since the 1970s and for Central Rimo Glacier since the 1930s confirm the irregular retreat and advance.

Mantle-derived arc related mafic enclaves and host orthogneiss from the Shyok Suture Zone of NE Ladakh, India: An evidence of magma-mixing

The Shyok valley in the northern Ladakh is a linear NW-SE trending suture zone (Shyok Suture Zone) and separates two distinct terranes, the southern continental margin of Eurasian Plate to north, and Ladakh magmatic arc to south. The crustal growth in the Shyok Suture Zone (SSZ) can be explained by two stage melting process involving the generation of orthogneiss (OG) with mafic enclaves (ME) (pre-collision), and temporal evolution towards increasingly more evolved felsic magmas during reworking processes (post-collision). In this paper, the geochemistry of various ME and host OG that fall within the Shyok‐Darbuk corridor of the suture zone are discussed. The field, petrographic and geochemical data suggest that the ME and host OG are genetically related. The ME has formed by low degree of partial melting of a garnet-bearing source or from the partial melting of a basaltic source with a clinopyroxene‐garnet eclogite as residue. The LILE and LREE enrichment of ME have been influenced by mantle‐magma interaction during the passage of the hydrous primary arc-magma through the overlying lithosphere. The likely interpretation for the genetic linkage of ME and host OG is explained through the mixing of coeval mafic (enclave) and felsic melts, resulting in hybrid magma. Besides, several geochemical lines of evidence suggest that fractional crystallization of the resultant hybrid magma had played a complementary role in the evolution of these rocks.

Quaternary glaciation in the Nubra and Shyok valley confluence, northernmost Ladakh, India

Three glacial stages (Deshkit 1, Deshkit 2 and Dishkit 3 glacial stages) are identified in the Nubra and Shyok valleys in northernmost Ladakh, northwest India, on the basis of geomorphic field mapping, remote sensing, and 10 Be terrestrial cosmogenic nuclide surface exposure dating. The glacial stages date to ∼ 45 ka (Deshkit 1 glacial stage), ∼ 81 ka (Deshkit 2 glacial stage) and ∼ 144 ka (Deshkit 3 glacial stage). A mean equilibrium line altitude depression of ∼ 290 m for the Deshkit 1 glacial stage was calculated using the area accumulation ratio, toe-to-headwall ratio, area–altitude, and area–altitude balance ratio methods. Comparison of glaciation in the Nubra and Shyok valleys with glaciations in the adjacent Central Karakoram of northern Pakistan and northern side of the Ladakh Range of northern India indicates that glaciation was synchronous on Milankovitch timescales across the region during MIS-6, but differed greatly in extent, with more extensive glaciation in the Karakoram than the morphostratigraphically equivalent glaciation on the northern slopes of the Ladakh Range. This highlights the strong contrast in the extent of glaciation across ranges in the Himalaya–Tibetan orogen, necessitating caution when correlating glacial successions within and between mountain ranges.

K-Ar ages of biotite and muscovite from Pangong metamorphic complex, Shyok suture zone, India: Implications for the youngest post-collision metamorphic event in Ladakh Himalaya

The garnet-kyanite-staurolite and garnet-biotite-staurolite gneisses were collected from a locality within Lukung area that belongs to the Pangong metamorphic complex in Shyok valley, Ladakh Himalaya. The kyanite-free samples have garnet and staurolite in equilibrium, where garnets show euhedral texture and have flat compositional profile. On the other hand, the kyanite-bearing sample shows equilibrium assemblage of garnet-kyanite-staurolite along with muscovite and biotite. In this case, garnet has an inclusion rich core with a distinct grain boundary, which was later overgrown by inclusion free euhedral garnet. Garnet cores are rich in Mn and Ca, while the rims are poor in Mn and rich in Fe and Mg, suggesting two distinct generations of growth. However, the compositional profiles and textural signature of garnets suggests the same stage of P -T evolution for the formation of the inclusion free euhedral garnets in the kyanite-free gneisses and the inclusion free euhedral garnet rims in the kyanite-bearing gneiss. Muscovites from the four samples have consistent K-Ar ages, suggesting the cooling age (∼ 10 Ma) of the gneisses. These ages make a constraint on the timing of the youngest post-collision metamorphic event that may be closely related to an activation of the Karakoram fault in Pangong metamorphic complex.

Quaternary geology, tectonics and distribution of palaeo- and present fluvio/glacio lacustrine deposits in Ladakh, NW Indian Himalaya—a study based on field observations

The Ladakh region of the northwestern Indian Himalaya is rich in Quaternary deposits but it has not received much attention. Previous Quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available. This article addresses the reconstruction of the palaeo-lacustrine deposits and the present-day lakes and their distribution in the Ladakh region. The region was under the influence of tectonic activity and cold climate during the late Quaternary times. Tectonic activity at ∼50,000 years BP, ∼35,000 years BP and ∼25,000 years BP has been recorded. We report the presence of three major lakes in the region in the late Quaternary. These formed due to the damming of the Indus river and its tributaries by debris avalanches initiated mainly by tectonic activity along the Indus Suture, Shyok suture and the Karakoram Fault. These are the Spituk–Leh palaeolake formed ∼>50,000 years BP; the Lamayuru palaeolake dated to 35,000 years BP in the Indus valley and the Khalsar palaeolake > 60 km in length in the Shyok valley. Vast exposures of the palaeolake deposits ranging from >25 to 150 m in thickness are reported—Spituk section (>25 m); Lamayuru section (>110 m) and Khalsar (>150 m) and Hundri (∼100 m) and which have a wide lateral extent. A glacial lake basin at Bhaktpur city, north of Baralacha La, is now completely filled, the TsoKar lake has been subdivided into smaller units now and the water level is lowering. Other lakes in the region (e.g., Pangong Tso, Tso Morari, the twin Kyun Tso lakes) are confined to the western side of the study area. Limited chemical weathering, rapid erosion and cold climatic conditions in late Quaternary times are suggested by the stable illite values in the Lamayuru section. Four levels of palaeoseismic structures (convolute structures, sand dykes, intraformational folds, micro faulting) are present in the Khalsar section and at three levels in the Tirit section (at Shyok, Nubra confluence). Palaeoseismic activity was also prevalent after 25,000 years BP as is evident from the three levels of palaeoseismic structures in the younger sediments.

Tectonic forcing of longitudinal valleys in the Himalaya: morphological analysis of the Ladakh Batholith, North India

Longitudinal valleys form first order topographic features in many mountain belts. They are commonly located along faults that separate tectonic zones with varying uplift histories. The Indus Valley of Ladakh, northern India, runs northwestwards following the boundary between the relatively undeformed Ladakh Batholith to the north–east and the folded and thrusted Zanskar mountains to the south–west. In this region the Shyok Valley, on the northern side of the batholith, approximately parallels the course of the Indus. This study investigates geomorphic variations in transverse catchments that drain the Ladakh Batholith, into the Indus and Shyok rivers. The batholith has been divided into three zones based on varying structural characteristics of its northeastern and southwestern boundaries. Morphometric analysis of 62 catchments that drain into the Indus and Shyok valleys was carried out using three digital datasets, and supported by field observations. Morphometric asymmetry is evident in the central zone where the Shyok valley is considered tectonically inactive, but the Indus Valley is bound by the northeastwardly thrusting Indus Molasse and the batholith. In this zone the catchments that drain into the Indus Valley are more numerous, shorter, thinner and have lower hypsometric integrals than those that drain into the Shyok. By linking these observations with the regional geology and thermochronological data it is proposed that high sediment discharge from the deformed Indus Molasse Indus Valley has progressively raised base levels in the Indus Valley and resulted in sediment blanketing of the opposing tectonically quiescent catchments that drain southwestwards off the batholith. The Indus Molasse thrust front has propagated at least 36 km towards the Ladakh Batholith over the last 20 Ma. Hence it is proposed that this long term asymmetric structural deformation and exhumation has forced the Indus longitudinal valley laterally into the Ladakh Batholith resulting in the morphometric asymmetry of its transverse catchments.

First find of the Early Permian Lower Gondwana plant remains and palynomorphs from the Chhongtash Formation (Upper Shyok valley), eastern Karakoram, India

A sedimentary sequence mainly consists of black shale, siltstone, calcareous sandstone and dark argillaceous limestone overlying pillow lava and thinly bedded limestone of the Chhongtash Formation near Chhongtash locality (Upper Shyok valley, eastern Karakoram, India) contains abundant, but poorly preserved plant fossils and palynomorphs probably referable to the Early Permian or Late Asselian (~275 Ma) interval. The plant fossils and associated palynological assemblages of eastern Karakoram show a marked similarity to the marine Lower Gondwana assemblages of the Salt Range and Talchir-Karharbari assemblages of Central India. Based on the present discovery it is suggested that, before the accretion of Cimmerian microplates to the Eurasian continent, the Karakoram microplate in its incipient state was not far from the Salt Range and located along the northern margin of the Indian subcontinent as Peri-Gondwanan microplate.

Geological evidence against the Shyok palaeo-suture, Ladakh Himalaya

Evolution of the Ladakh Himalaya is related to the Cretaceous–Tertiary subduction of the Indian oceanic plate below the southern margin of the Eurasian plate along the Indus suture zone1–11. The plate tectonic reconstruction suggests two stages of subduction due to the presence of a pre-Cretaceous suture along the Shyok valley12,13. This hypothesis is based on there being ophiolite belts in the Indus and Shyok valleys. The Indus suture zone is well established but there have been insufficient data on the Shyok suture to confirm the existence of the palaeo-suture. I have studied the Saltoro hills, in the western part of the Shyok valley, and report here the salient geological features. With a few exceptions, the igneous and sedimentary rocks indicate that the Indus and Shyok sutures had the same Cretaceous–Oligocene history. However, the volcanic eruption during the deposition of post-Oligocene molasse in the Saltoro hills of the Shyok valley is the youngest igneous activity in the whole of the Ladakh Himalaya. Hence the geological evidence described here does not accord with the theory of palaeo-suture.