Naga Hills Research Articles

Platylomia kohimaensis n. sp.a new cicada species (Hemiptera: Cicadidae) from the Naga Hills in the Eastern Himalayas.

A new cicada species, Platylomia kohimaensis n. sp., belonging to the Platylomia radha group is described from the Naga Hills in the eastern Himalayas. It is a dusk singing, large-sized cicada that calls for a short window during the evening twilight hours. Timbalisation is in the form of a continuous and regular cackling. Photographs of adult male and female along with genitalia illustration and distribution map are provided. A sonogram along with Acoustic Identification Card is also provided.

Multistage melt impregnation in Tethyan oceanic mantle: Petrochemical constraints from channelized melt flow in the Naga Hills Ophiolite

Ophiolitic sequences obducted onto continental margins allow field based observations coupled with petrochemical interrogations of upper mantle lithologies thereby aiding evaluation of compositional heterogeneity of oceanic mantle, depletion-enrichment events and geodynamic conditions governing oceanic lithosphere formation. The Naga Hills Ophiolite (NHO) suite preserves a segment of the Neotethyan oceanic lithosphere encompassing a package of mantle and crustal lithologies. This paper for the first time reports the occurrence of melt flow channels traversing the mantle section near Molen of the NHO and presents a comprehensive study involving chromite-spinel chemistry, bulk rock major, trace and PGE geochemistry to understand the petrogenesis and evolution in a geodynamic transition from mid oceanic ridge (MOR) to suprasubduction zone (SSZ). The spinel chemistry of peridotitic melt channels depicts both MOR-type and SSZ signatures underlining a transitional tectonic frame. Chromite chemistry and high Al2O3/TiO2 ranging from 15.98–35.70 in concurrence with low CaO/Al2O3 ranging from 0.03–0.53; and chondrite normalised LREE > MREE < HREE patterns confirm the influx of boninitic melts into the refractory mantle. The boninitic signature shared by melt channels and host rock invokes a geochemical and geodynamic transition from anhydrous melting of depleted mantle to hydrated fluid flux melting resulting in boninitic melts, that subsequently impregnate and refertilise the fore arc mantle wedge in a SSZ regime at the nascent stage of subduction. The high Ba/Nb, Ba/Th, and Ba/La for the studied peridotites highlight the influx of subduction derived fluids in the supra subduction mantle. Further higher Zr/Hf and Nd/Hf with respect to primitive mantle values in concurrence with lower Nb/Ta suggest progressive refertilisation due to fluid- and melt-driven metasomatism of the refractory fore arc mantle wedge. The chondrite normalised PGE patterns suggest positive Ir and Ru anomalies stipulating the source to be refractory while enriched Pt and Pd underpins the mobilisation of these elements by subduction derived fluids and melts. The elevated abundances of PPGEs than IPGEs as cited by PPGE/IPGE > 1; and Pd/Pt avg. 0.85 for melt channels and 0.84 for host peridotites indicate fluid-fluxed metasomatism of fore arc mantle wedge with a S-undersaturated trend coupled with boninitic affinity. The mineral, trace, REE and PGE chemistry collectively emphasizes that the mantle peridotites of the NHO formed in a transitional geodynamic tectonic setting caused by fore arc extension during subduction initiation followed by rejuvenation by subduction derived fluids and boninitic melts, which typically are of the SSZ tectonic regime. The harzburgitic melt channels and host rock are refractory in nature, reflecting multiple episodes of melt extraction of about 5–15% and ~10–20% respectively from a spinel peridotite mantle source. The occurrences of these melt channels indicate segregation and percolation of melt through porous and channelized network in upper mantle peridotites.

Middle Jurassic arc reversal, Victoria–Katha Block and Sibumasu Terrane collision, jadeite formation and Western Tin Belt generation, Myanmar

AbstractMyanmar is occupied by the N-wards continuation of the Sunda arc and by the Shan Plateau and its continuation through Yunnan into Tibet. Our new tectonic interpretation of the ophiolite–flysch belts, world-famous jadeite and tin deposits in Myanmar west of the Salween adopts previous proposals that, before 450-km post-early Oligocene dextral displacement along the Sagaing Fault, the ophiolite belt in NE Myanmar continued through the topography that is now located west of the fault in the Indo-Burman Ranges. Differences in cross-section through Mogok and the Shan Scarps are reconciled by the recently proposed emplacement, in our view during Permian time, of the Mogok Metamorphic Group onto the Slate Belt to form Sibumasu. We argue that during Early Jurassic time a Neo-Tethys ophiolite nappe was obducted over turbidites on Sibumasu’s passive western margin. Following reversal in tectonic polarity, the remaining Neo-Tethys subducted E-wards generating the 113–128 Ma Mondaung Arc. During ocean closure the Victoria–Katha Block and its Triassic flysch subducted beneath Sibumasu, resulting in jadeite veins in overlying serpentinite that ascended in the subduction zone and were exhumed at Hpakant and Nat Hmaw, bordering the Jade Mines Uplift. Subduction of the Indian Ocean since Albian time generated the Popa–Loimye arc, while extensional faulting led to uplift of the Indo-Burman Ranges and to the formation of the Western Tin Belt granites. Tectonic effects in Myanmar of the India–Asia collision may be confined to the Disang thrust belt in the Naga Hills.

Reconstruction of Middle Miocene Surma Basin as Two Arcs Derived Sedimentary Model: Evidence from Provenance, Source Rock Weathering and Paleo-Environmental Conditions

Surma Basin in Northeast India is characterized by a thick Cenozoic sedimentary succession that initiated due to the collision between Indian and Burmese plates. Variability in the litho-association of a thick sedimentary column in this robust terrain represents the distribution and deposition of enormous sediments that supplied throughout the entire basin evolution, especially during the Middle Miocene. This makes Middle Bhuban sandstone as the best aspirant for this study. Miocene Bhuban sandstones collected from parts of Aizawl and Champhai Districts of Mizoram, NE India have been studied for the whole rock geochemistry to understand the nature of source rocks, probable source areas and paleoclimatic conditions. The geochemical behavior of studied sandstones represent a felsic nature (TiO2/Zr: 15.03–37.09; La/Sc: 1.80–6.52, La/Co: 0.39–5.48, Th/Sc: 0.56–2.05; Cr/Th: 4.19–28.00; Al2O3/TiO2: 13.13–28.09), fractionated granitoid provenance [(La/Lu)N: 15.06–22.25; (La/Yb)N: 14.09–19.96; (La/Sm)N: 3.17–3.99; (Gd/Yb)N: 2.00–2.84] and moderately weathered sediments (CIA: 65; CIW: 73; PIA: 69; WIP: 41; ICV: 0.87; Rb/Sr: 1.07). The deposition of these sediments took place in an oxic condition (sharp positive Ce anomaly) during a regressive phase with contribution from various granitoid plutons. Synthesizing the data available for different plutons around the Himalayan and Indo-Burmese Ranges (IBR), they show close similarity with Middle Bhuban geochemical signatures. Ladakh granite, Yangbajin granite and Jirong Granodiorite of Himalaya along with Wuntho-Mt. Popa and Banmauk granitoids are the most influential sources of the Surma sediments before the cessation of Paleo-Irrawaddy and then Paleo-Brahmaputra River courses. This is also evident by the paleo-current directions of sediments from various parts of the Surma Basin. Rise of Shillong plateau, Mikir massif and Naga hills in the north and IBR in the east caused the flow migration and lithological changes. Therefore, the present study ultimately invokes a significant supply of the sediments from the granitoids of neighbouring Indo-Burmese arc in the east in addition to their contribution from the Himalayan ranges in the north.

THE FIRST MAJOR CHALLENGE AGAINST THE BRITISH COLONIALISM BY THE NAGAS: 1879-1880 A CRITICAL APPRAISAL

The Nagas since time immemorial were never under any foreign powers. They lived in a state of nature where any principality that ever encompassed them was rudimentary, unscathed and the purest that nature could provide them. Their primordial worlds had endured for generations until the modern century without being bothered and unaware of what was happening around them. British Colonialism had shaken the world entirely right to its core; altering every fundamental structures in it. Nagas however continued to live in a state of perpetual bliss on this side of the 'promised land'. Not before long, the ray of the British Empire inltrated into the Naga territory and disturbed their ethnic environment. What another considered as a convenient expansion of power; turn out to be the abrogation of existence for the other. In the light of this argument, we shall pursue in studying and observing the underlying factors that led to the Nagas challenging the powerful British authority over the Naga Hills, and the consequences that followed

Micropalaeontological and Geochemical Evidence of the Late Jurassic Radiolarians Cherts of Naga Ophiolite Hill, Nagaland, Northeast-India

We analyzed the radiolarian assemblages (pelagic sediments) and geochemical studies of 15 samples collected from Meluri district Nagaland, Naga Hills Ophiolite belt (NHO) and it consists of the Flysch Naga-Arakan-Yoma trough beyond the Indo-Myanmar border. It reflects one of the many components of the Himalayan Orogenic systems of Tethyan oceanic crust discovered in Nagaland at Meluri district of India and they have very well-preserved studies and can be identified to Upper Jurassic (Kimmeridgian-mid-Tithonian). As well as a continuous sequence of Kimmeridgian-mid-Tithonian, five radiolarian assemblages have been identified in this study. This is so far the first recovery of pelagic sediment assemblages (Radiolarians) from the Naga Hills Ophiolite complex. Samples of Naga Hills Ophiolite belts fell in the Sublitharenite, Litharenite, and Fe-shale Fe-sand area, and the A-CN-K diagram indicates that these sediments in the source region were exposed deep to moderate weathering conditions. In the discriminant plot, the Naga Hill-Ophiolite-Chert samples occupy the field of origin of the sediment quartzose, and the log (K2O/Na2O) versus SiO2 samples fall into the active continental marginal field, and only one sample falls into an island arch, suggesting that the tectonic framework of the Naga Hills-Chert samples was deposited in the active continental margin and the diagrams K2O/Al2O3 and MgO/Al2O3 illustrated the tectonic setting of the marine environment from Naga Hill Ophiolite Chert. Such findings have been consistent with the current geology of Naga Hills in the province of Nagaland.

Easterine Kire Iralu’s Mari: A Historical Narrative of the Forgotten Battle of Kohima

Most of the Indians now have forgotten that Kohima was the scene of an Allied victory in the World War II; the victory was so decisive that it changed the contours of the war in Asia. In this significant battle of Kohima, the Japanese force tried to enter India from Naga Hills, advancing progressively into Asia after the success of their Burma campaign in 1941-42. But in Kohima they were defeated convincingly by the British Allied Forces which were helped by local inhabitants in the battle. The Japanese had broken down equally by disease and hunger thus left their plan to enter in India. The Battle of Kohima often refers by Nagas as a ‘forgotten battle’ and its heroes as the ‘forgotten heroes’. Easterine Kire Iralu’s Mari stands as a distinct novel as it commemorates the forgotten Battle of Kohima of 1944. The novel is a fascinating love story set in the midst of this war. It is an enchanting tale of Iralu’s aunt Khrielievu Mari O’ Leary who was engaged to a British sergeant Victor. The novel is written in form of a diary which Mari maintained during the war meticulously registering every event of her life. Mari is not just a story of a young girl falling in love but it’s a story of all those people who lived that war- time. This paper examines the impact of the battle of Kohima on the culture, identity and traditional values of Naga society which the writer has described in the backdrop of Mari’s life journey in the novel.&#x0D;

Tectono-magmatic evolution of Tethyan oceanic lithosphere in supra subduction zone fore arc regime: Geochemical fingerprints from crust-mantle sections of Naga Hills Ophiolite

The Naga Hills Ophiolite (NHO) belt in the Indo-Myanmar range (IMR) represents a segment of Tethyan oceanic crust and upper mantle that was involved in an eastward convergence and collision of the Indian Plate with the Burmese Plate during the Late Cretaceous-Eocene. Here, we present a detailed petrological and geochemical account for the mantle and crustal sections of NHO, northeastern India to address (i) the mantle processes and tectonic regimes involved in their genesis and (ii) their coherence in terms of the thermo-tectonic evolution of Tethyan oceanic crust and upper mantle. The NHO suite comprises well preserved crustal and mantle sections discretely exposed at Moki, Ziphu, Molen, Washelo and Lacham areas. The ultramafic-mafic lithologies of NHO are mineralogically composed of variable proportions of olivine, orthopyroxene, clinopyroxene and plagioclase. The primary igneous textures for the mantle peridotites have been overprinted by extensive serpentinisation whereas the crustal section rocks reflect crystal cumulation in a magma chamber. Chondrite normalised REE profiles for the cumulate peridotite-olivine gabbro-gabbro assemblage constituting the crustal section of NHO show flat to depleted LREE patterns consistent with their generation from depleted MORB-type precursor melt in an extensional tectonic setting, while the mantle peridotites depict U-shaped REE patterns marked by relative enrichment of LREE and HREE over MREE. These features collectively imply a dual role of depleted MORB-type and enriched arc-type mantle components for their genesis with imprints of melt-rock and fluid-rock interactions. Tectonically, studied lithologies from NHO correspond to a boninitic to slab-proximal Island Arc Tholeiite affinity thereby conforming to an intraoceanic supra subduction zone (SSZ) fore-arc regime coherent with the subduction initiation process. The geochemical attributes for the crustal and mantle sections of NHO as mirrored by Zr/Hf, Zr/Sm, Nb/Ta, Zr/Nb, Nb/U, Ba/Nb, Ba/Th, Ba/La and Nd/Hf ratios propound a two-stage petrogenetic process: (i) a depleted fore arc basalt (FAB) type tholeiitic melt parental to the crustal lithologies was extracted from the upwelling asthenospheric mantle at SSZ fore-arc extensional regime thereby rendering a refractory residual upper mantle; (ii) the crust and upper mantle of the SSZ fore arc were progressively refertilised by boninitic melts generated in response to subduction initiation and slab-dehydration. The vestiges of Tethyan oceanic lithosphere preserved in NHO represent an accreted intra-oceanic fore arc crust and upper mantle section which records a transitional geodynamic evolution in a SSZ regime marked by subduction initiation, fore arc extension and arc-continent accretion.

The Forgotten Chindits – 23 British Infantry Brigade

In March 1944 Japan launched its Operation U Go offensive which resulted in the well documented battles of Kohima and Imphal in north east India. At the same time 23 British Infantry Brigade was finalising Long Range Penetration training before participation in Operation Thursday, the second Chindit campaign that was already underway in north eastern Burma. That plan was changed, and the brigade was diverted to operate in the mountainous Naga Hills to protect the eastern flank of Kohima and disrupt Japanese supply lines from Burma. Much has been written about Burma, Kohima, Imphal and the two Chindit operations, but surprisingly little on the activities of 23 British Infantry Brigade in 1944. This article seeks to redress some of that imbalance by considering: how the brigade prepared for the Long Range Penetration role; how it operated in the Naga Hills; how those operations differed to Operation Thursday; and finally, if this was an effective use of the brigade.

Resurfacing of deeply buried oceanic crust in Naga Hills Ophiolite, North-East India: Petrofabric, microstructure and seismic properties

We have studied the microstructure, texture and seismic anisotropy of a foliated blueschist-eclogite rock in the Naga Hills Ophiolite (NHO) complex, North-East India. The rock is composed essentially of omphacite, sodic amphibole (glaucophane), sodic-calcic amphibole (barroisite), phengite, and garnet, and represents oceanic crust that experienced Neo-Tethyan subduction and metamorphism before it resurfaced and accreted in the ophiolite. Omphacite and glaucophane show weak shape preferred orientation (SPO), while phengite displays a strong SPO. The Crystallographic Preferred Orientation (CPO) of omphacite is characterized by the [001]-axes gridle within the foliation, and the (010)-poles concentrated sub-perpendicular to the foliation. For glaucophane, the [001] axis aligns parallel to lineation and the [100] axis and (110) pole plunge perpendicular to foliation. These CPOs correspond to SL-type fabrics, related to plane strain deformation geometry. Based on our analysis, we propose that the observed texture had developed from plastic deformation through dislocation creep. Employing the textural data, we have presented the seismic anisotropies of the individual minerals, blueschist-eclogite domains and discussed their contributions in the bulk-rock anisotropy. The calculated bulk-rock seismic anisotropies, AVP and AVS, of the rock are 12.8% and 8.1%, respectively, which correlate with the observed seismic anisotropy of the subducting oceanic crust.

From pathways to roadways: Issues and challenges of road transport in Nagaland

AbstractModern transport was introduced in the Naga Hills by the British, initially to conquer the Hills, and then, the same was expanded to retain the conquered Hills. The colonial roads, however, even at the beginning of the 20th century were still largely of “bridle paths.” Significant capacity expansion in roads came only post‐statehood. However, the state of transport in Nagaland, even today, is still characterized by myriad issues and challenges. Against this backdrop, and in the light of a stagnant, regionally skewed underdeveloped economy of the province, it is imperative to invest in transport infrastructure and services. A survey of literature on “transport and development” shows that investment in transport in an economy like that of Nagaland brings about huge returns.

New freshwater mussel taxa discoveries clarify biogeographic division of Southeast Asia

While a growing body of modern phylogenetic research reveals that the Western Indochina represents a separate biogeographic subregion having a largely endemic freshwater fauna, the boundaries of this subregion are still unclear. We use freshwater mussels (Unionidae) as a model to reconstruct spatial patterns of freshwater biogeographic divides throughout Asia. Here, we present an updated freshwater biogeographic division of mainland Southeast Asia and describe 12 species and 4 genera of freshwater mussels new to science. We show that the Isthmus of Kra represents a significant southern biogeographic barrier between freshwater mussel faunas of the Western Indochina and Sundaland subregions, while the Indian and Western Indochina subregions are separated by the Naga Hills, Chin Hills, and Rakhine Yoma mountain ranges. Our findings highlight that the freshwater bivalve fauna of Southeast Asia primarily originated within three evolutionary hotspots (Western Indochina, Sundaland, and East Asian) supplemented by ancient immigrants from the Indian Subcontinent.

Eocene foraminifers of the Naga Hills of Manipur, Indo-Myanmar Range (IMR): Implications on age and basin evolution

The Disang Group incorporates the oldest Cenozoic clastic sedimentary rocks that crop out in a series of NNE–SSW trending ridges and valleys throughout much of the Naga Hills. The stratigraphic position of this unit is not well constrained due to a paucity of definitively recognisable, in situ fossils. We report forty-four species attributable of twenty-eight genera. Based on our new reported foraminiferal assemblages, we refine the age and paleoenvironmental interpretations for the Upper Disang Formation. We recognize Planktonic Foraminiferal Zones E14-16 correlative to upper middle Eocene to upper Eocene in the Upper Disang Formation within the Naga Hills. A basin model for this lithological unit involving an upper bathyal bathymetry, rapidly shallowing in a restricted basin with slump deposits where anoxic conditions prevailed is proposed based on field observations, foraminiferal assemblages, and published data.

Variability of orographic architecture of Indo-Burmese Ranges (NE India): constraints from morphotectonic and lineament analysis

Activeness of the tectonic and related sub-surface processes control the surface features that lead to variations in topography and lithostratigraphy. To understand the role of active tectonics in shaping the topography, morphotectonic and lineament studies are important. In this study, geological categorization has helped understand the orogenic evolution of the Indo-Burmese Range (IBR), NE India. This is an arcuate hill range that shows many unique topographic characteristics that incited to categorise the entire IBR into different tectonically active domains: Northern (Changlang district of Arunachal Pradesh); Naga Hills; Cachar and Manipur; and Southern (Mizoram). The Northern and Southern domains are more active than the others. Lineament analysis also indicates the presence of active features in the region with NW–SE, NE–SW, ESE–WNW trends are being common. The Northern and Naga Hills domains have mostly E–W younger lineaments whereas the Cachar and Manipur domains rather show N–S younger trends. The Southern Mizoram domain shows a dominance of older N–S lineaments with younger NW–SE lineaments. These variations result from differential stress conditions, i.e. Indian Plate movement and westward stress from the Burma Plate. This study shows how overall variations in tectonic settings can be related to the orogenic evolution.

Salt Trade in Goalpara District During Colonial Period

Salt is an essential commodity for human beings, and its demand has been increasing in the markets since the early days. There was no information regarding salt production in Assam during the precolonial and colonial periods. On the other hand, small salt brines existed in places like Sadiya, Burhat and Naga hills, but they were unaffordable. At that time, people used Khar, the burn ashes of certain trees which produced a salty taste instead of ready-made salt. The salt became a symbol of wealth which helped people maintain a high status in the society of Assam as well as in the Goalpara district. The salt of Bengal became very famous because of its affordability—its supply was also available at Goalpara in the colonial period. Thus, Goalpara became the centre of salt trade of the north-eastern frontier countries. This article will attempt to highlight the salt trade and its significance in the colonial period.

Interpretation of gravity anomaly to delineate thrust faults locations at the northeastern part of India and its adjacent areas using source edge detection technique, tilt derivative and Cos(θ) analysis

The Northeast India and its adjacent areas converge among the three different plates, viz. Eurasia, India and Sunda plates. The tectonic interaction of Northeast India and underlying dynamics of the Himalayas as well as the Indo-Burma Ranges might cause the Assam Syntaxis. The area of study is located between latitude 23°–28°N and longitude 88°–96°E and situated in one of the most seismically active tectonic provinces in the world with seismic zone-V. This area had demonstrated several thrust faults activities and tectonic evident accomplishments during the recent past. The complicated geotectonic setups inspirits various smaller magnitude earthquakes, and the current seismicity shows seismic activities are still enduring in the Shillong Plateau, Arakan-Yoma fold belt, Bengal Basin, Naga Hills, Mikir Hills, Upper–Lower Brahmaputra Valley and Mismi Hills of Himalayan foothills. It is imperative to obtain wide-ranging learning tectonic configuration, thrust faults delineation for improved geoscientific study. Parts of the areas are extremely unreachable, and very limited thrust faults were marked by studying GIS map received from the various agencies and field geological study. During the past studies, most of the prominent lineaments/thrusts are marked; however, many active and hidden thrust faults are still unidentified. Seismic data can provide better information about the thrust faults locations, but due to small number of seismic data, the information is not adequate. In this paper, attempt has been made to study and reinterpret the available ground gravity data of northeastern parts of India for understanding thrust fault locations using various applications of gravity derivatives like analytical signal, horizontal gravity gradient, tilt derivative, horizontal tilt angle derivative and Cos(θ) analysis. Source edge detection technique has also been premeditated to categorize thrust fault locations. It is understandable that the low gravity is observed at Assam Valley which contributed sediment accumulations and higher gravity anomaly observed at Shillong Plateau and Bengal Basin containing denser formations. Bouguer gravity data is used after isostatic correction assuming Airy’s isostasy root depth model and first-order trend removal using least square technique. The derived thrust fault locations from the present study are superimposed with the existing thrust-fault locations for correlation. Some additional thrust faults are narrated which are not previously mapped. It is also suggested that Brahmaputra Thrust, Dauki Fault, Naga Thrust, Disang Thrust and Kopili Fault have key responsibility for high seismicity and tectonic movement causing upliftment and depression that encouraged some anticlockwise rotation in the area.

Tectonic Evolution of the Western Margin of the Burma Microplate Based on New Fossil and Radiometric Age Constraints

AbstractResults of biostratigraphic and geochronological investigations in eastern Nagaland and Manipur, NE India, provide new constraints on the tectonic evolution of the western margin of the Burma microplate. U/Pb zircon ages indicate that the Naga Hills ophiolite developed in a suprasubduction zone setting as part of an intraoceanic island arc developed during late Early Cretaceous (mid‐Aptian) time and is younger than similar rocks exposed along the Indus‐Yarlung Tsangpo suture zone. Radiolarian microfossils provide Jurassic and Cretaceous age constraints for Tethyan ocean floor sediments that were subducted beneath the forming ophiolite. Timing of the emplacement of these rocks onto the passive margin of eastern India is constrained by Paleocene/Eocene radiolarians in sediments over which the ophiolitic assemblage has been thrust. Previously undated schists and gneisses in the Naga Metamorphics are of Early Ordovician age, and their sedimentary protolith was most likely derived from sources in the south of Western Australian and East Antarctica. After Barrovian‐style metamorphism, these rocks were uplifted and eroded becoming an important source of detritus shed into the Eocene Phokphur Formation. This unit also contains abundant clasts sourced from the disrupted basement of the Naga Hills ophiolite, which it overlies. It also contains Permo‐Triassic‐aged detritus eroded off an enigmatic source that was possibly a continental convergent margin arc system somewhere along the northern margin of Gondwana.

Morphotectonic aspects in a part of Naga-Schuppen belt, Assam-Nagaland region, Northeast India

The Belt of Schuppen is an important tectonic element of the Assam-Arakan basin. It is a narrow belt of thrust slices in southeastern boundary of the Assam valley. The Naga Schuppen Belt, consisting of eight or more imbricated thrusts, occurs between the Naga and Disang thrusts. This present study encompasses an area of 4,720 sq km along the Assam-Nagaland border. The Dikhow River, which is a seventh order basin, originates from Naga Hills flowing through a total length of 240 km in the Assam valley and reaches the Brahmaputra. In this study, the morphotectonic analysis of the Dikhow River was carried out to understand the role of active tectonics of the Naga Hills in Nazira-Naginimora areas of Assam and Nagaland respectively. The parameters such as asymmetric factor (AF), transverse topographic symmetric factor (T), and stream length gradient index (SL) were computed. Absolute AF values shows asymmetric to highly asymmetrical shape of the basins (range III-IV) which is also supported by T values. Anomalous SL values were obtained wherein major lineament and tectonic features are present. This indicates that the study area is tectonically active. Further, in the Assam valley it has been observed in the bank stratigraphy of Dikhow River that the Quaternary sediments are deformed. This deformation of the soft older alluvium indicates that the area is undergoing deformation during post Pliocene time. This evidence demands the morphotectonic evaluation of the aforesaid area to demarcate the tectonic activeness of the region in post Pliocene times.

Japanese invasion, war preparation, relief, rehabilitation, compensation and ‘state-making’ in an imperial frontier (1939–1955)

ABSTRACTThis paper looks at the history of state-making in an entangled imperial frontier. The northeastern frontier of British India was a mosaic of princely states, administered and un-administered territories. The presence of the colonial state in the region was contentious, marked by violence on one hand and philanthropy on the other. The Japanese invasion of the region during World War Two had several unintended ramifications. Wartime and post-war developments produced institutions and social experiences which facilitated the process of state-making in the region. Relief and Rehabilitation project of the colonial state, and later distribution of monetary compensation was not merely governed by moral or legal obligations but was part of a larger project of imperialist reconquest in Asia after the surrender of the Japanese with Manipur and Naga Hills as the base. This project also provided the postcolonial Indian state with institutions to continue the process of state-making of its own.

Melt-rock interaction and fractional crystallization in the Moho transition Zone: Evidence from the cretaceous Naga Hills Ophiolite, North-East India

The Moho Transition Zone (MTZ) within the suboceanic lithosphere records an episode of multiple magmatic exchanges between the underlying mantle and the overlying oceanic crust. This study investigated a fossilized MTZ from the Naga Hills Ophiolite (NHO) by characterizing its lithology and describing the petrogenesis of various rock types. Like the other well-studied MTZs around the world, the NHO MTZ has an association of dunite, wehrlite, clinopyroxenite and gabbroic rocks. The dunite formed by crystal fractionation from an olivine-normative basaltic melt that successively crystallized olivine-gabbro, gabbro and oxide-gabbro. Our study of the wehrlite provides evidence of melt-mantle interactions that lead to the formation of replacive dunite, later impregnated with clinopyroxene saturated melt. The melt percolated through the replacive dunite and re-equilibrated with the olivine to some extent. The clinopyroxenite formed simultaneously with the wehrlite as a crystal mush in pockets from clinopyroxene saturated melt. In summary, the major and trace element mineral chemistry of the NHO MTZ rocks documents their evolution through melt-rock interaction and fractional crystallization. Clinopyroxene played an important role in the evolution of NHO MTZ, particularly the formation of wehrlite and clinopyroxenite. There is no direct evidence for the involvement of water in the formation of the MTZ rocks. However, the presence of primary hydrous phases in the evolved rock types and the signatures of early crystallization of clinopyroxene prior to plagioclase in the initial cumulates, discernible from a positive Sr anomaly, suggest the hydrous nature of the parent melt. Therefore, the NHO possibly represents a fragment of oceanic lithosphere that had its origin above a subduction zone and was later incorporated within a mountain belt during terminal closure of the Neo-Tethys Ocean.