surface rupture of the 2005 kashmir pakistan earthquake and its active tectonic implications to provide a detailed record of a relatively rare thrust surface rupture and examine its active tectonic implications we have conducted field mapping of the surface rupture associated with the 2005 m w 7 6 kashmir earthquake despite the difficulty arising from massive earthquake induced landslides along the surface rupture we found that typical pressure ridges and warps extend northwestward for a distance of 70 km with a northeast side up vertical separation of up to 7 m neither the main frontal thrust nor the main boundary thrust is responsible for the earthquake but three active faults or fault segments within the sub himalaya collectively called the balakot bagh fault compose the causative fault although the fault exhibits substantial geomorphic expression of repeated similar surface ruptures only a part of it had been mapped as active before the earthquake the location of the hypocenter suggests that the rupture was initiated at a deep portion of the northern central segment boundary and propagated bilaterally to eventually break all three segments our obtained surface rupture traces and the along strike slip distribution are both in good agreement with results of prompt analyses of satellite images indicating that space geodesy can greatly aid in time consuming field mapping of surface ruptures assuming that the extensive fill terrace in the meizoseismal area was abandoned during 10 30 ka we tentatively estimate the earthquake recurrence interval and shortening rate on the balakot bagh fault to be 1000 3300 yr and 1 4 4 1 mm yr respectively these estimates indicate that the balakot bagh fault is not a main player of himalayan contraction accommodation graphic 1 selected field photographs and arcgis files of the mapped surface rupture traces and measured vertical separations are available in the electronic supplement to this article 1 embed inline graphic 1 gif

tectono geomorphic study of the karewa basin of kashmir valley abstract the karewa basin nestled between the pir panjal range and the great himalayan range in northwest india has been studied to understand its tectono geomorphic evolution on the basis of geomorphic indices and morphotectonic parameters supported by the field evidences satellite data topographic maps and digital elevation model dem were used to extract various parameters at various spatial scales four watersheds representative of the entire karewa basin were chosen for detailed studies on the basis of the researchable evidence of the complete sequence of the stratigraphic record and the preservation of geomorphic landscapes the integrated analysis of the geomorphic and morphometric data provides evidence of the relative variations in the tectonic activity among the watersheds geomorphic indices suggest a relatively high degree of tectonic activity along the pir panjal side of the karewa basin this variation in the relative degree of tectonic activity is consistent with the field evidence fault lineament locations and the landscape geometry of the karewa basin based on the results from this study it is suggested that late quaternary climate changes tectonic uplift and erosion of the pir panjal range and changing geometry of the karewa lake have played a key role in the evolution of the geomorphic landscape of the kashmir valley

slow spreading ridge axis tectonics evidence from the lizard complex uk abstract the east coast section of the lizard ophiolite complex cornwall u k preserves a series of interrelated extensional faults and dyke sets which indicate that the formation of this section of obducted oceanic lithosphere resulted from a combination of contemporaneous structural and magmatic events three dolerite dyke sets are evident the first two sets 1 and 2 are cut by and rotated on a series of ridge parallel extensional faults and shear zones later dykes set 3 cross cut the extensional faults these data indicate that both rotation and significant thinning in the region of 40 of this part of the oceanic lithosphere occurred prior to the final period of dyke injection the thinning of the lithosphere was the result of extension along the normal faults all of the dolerite dykes show morb characteristics although the late dykes set 3 are more primitive tending to be aphyric to sparse olivine phyric and show higher cr ni and lower zr values than the typically plagioclase phyric dolerite dykes sets 1 and 2 intruded prior to the ductile shearing event the more primitive dolerites post date the tectonism and indicate the lack of a significant magma chamber following a period of amagmatic extension the data are consistent with observations at present day slow spreading ridge axes and some mafic ultramafic ophiolite sequences and provide insight into the nature of ridge related structures and the interrelationships between tectonism and geochemical evolution of the dykes and record a mechanism listric faulting to account for the presence of peridotites and gabbros commonly dredged at slow spreading centres

discussion on shrimp u pb zircon dating of the exhumation of the lizard peridotite and its emplacement over crustal rocks constraints for tectonic models in this recent contribution nutman et al 2001 provide the first shrimp u pb zircon age data for the lizard peridotite and its immediate envelope and demonstrate the usefulness of ion microprobe geochronology in the unravelling of the complex thermo tectonic history inherent in the emplacement of such assemblages of plausibly oceanic rocks onto continental strata building on the research of cook et al 2000 the authors distinguish clearly between the lizard peridotite proper a mass of c 15 kbar mantle tectonite and the contiguous crousa downs complex of gabbro troctolite and sheeted mafic dykes emplaced into the peridotite following its exhumation and cooling thus although exhibiting many lithologies and structures characteristic of ophiolites the oceanic part of the lizard complex is clearly at least bipartite the studies of cook et al 2000 and nutman et al 2001 rationalize and clarify several problematic relationships in this extensively studied but still ambiguous suite we understand that the editorial handling of nutman et al s paper overlapped with the publication in this journal of our detailed account of the petrogenesis of the kennack gneiss which incorporates an evaluation of the tectonic context of this controversial unit on the basis of an idtims single zircon date sandeman et al 2000 we consider none the less that several aspects of the new contribution require comment these include nutman et al s interpretations of our earlier documentation of the petrology and age relationships of the kennack gneiss sandeman et al 1995 the man of war gneiss sandeman et al 1997 and the porthkerris plagiogranite clark et al 1998 b as well as our overview of the emplacement history of the lizard complex clark et al 1998 a an extended abstract cited but not referenced by nutman et al we employ herein the revised palaeozoic time scale of mckerrow

assessment of atmospheric propagation effects in sar images terrasar x the first civil german synthetic aperture radar sar satellite was successfully launched on june 15 2007 after 4 5 days the first processed image was obtained the overall quality of the image was outstanding however suspicious features could be identified which showed precipitation related signatures these rain cell signatures are thoroughly investigated and the physical background of the related propagation effects is provided in addition rain cell signatures from former missions like sir c x and the shuttle radar topography mission are provided for comparison during the commissioning phase of terrasar x a total of 12 000 scenes were investigated for potential propagation effects and about 100 scenes revealed atmospheric effects to a visible extent some of the particularly interesting events were selected and are discussed in greater detail an interesting case of data acquisition over new york will be presented which shows typical rain cell signatures and the sar image will be compared with weather radar data acquired nearly simultaneously within the same minute by comparing the images it can be clearly seen that reflectivities in the weather radar image of 50 dbz may cause visible artifacts in sar images furthermore in this paper we discuss the influence of the atmosphere troposphere on the external calibration of terrasar x by acquiring simultaneous weather radar data over the test site and the sar acquisition it was possible to flag affected sar images and to exclude them from the procedure to derive the absolute calibration constant thus it was possible to decrease the 1 sigma uncertainty of the absolute calibration factor by 0 15 db

isotope geochemistry and revised geochronology of the purrido ophiolite cabo ortegal complex nw iberian massif devonian magmatism with mixed sources and involved mesoproterozoic basement abstract in the purrido ophiolite cabo ortegal complex new u pb zircon dating of the amphibolite g03 8 by laser ablation inductively coupled plasma mass spectrometry confirms the existence of a dominant mesoproterozoic zircon population with a refined age of 1155 14 ma however the u pb zircon dating of two more amphibolite samples by sensitive high resolution ion microprobe has provided new ages of 395 3 ma and 395 2 ma respectively interpreted as the crystallization age hf isotope data for zircon show that most of the devonian zircons crystallized from a juvenile depleted mantle source the mesoproterozoic zircons have relatively juvenile hf isotopic composition reflecting some influence of an older component a few devonian zircon crystals show evidence of mixing with an older component represented by the mesoproterozoic zircons the whole rock sm nd isotope data indicate an important heterogeneity in the composition of the purrido amphibolites only compatible with the generation of their protoliths from two sources we interpret these puzzling data as resulting from the mixing of a devonian mantle derived magma with a mesoproterozoic basement these new data provide new perspectives in the interpretation of the most common ophiolites across the variscan suture in europe supplementary material analytical methods zircon u th pb shrimp analytical data zircon u th pb la icp ms analytical data zircon lu hf la mc icpms analytical data and whole rock sm nd isotope data are available at http www geolsoc org uk sup18449

evolution of the rheic ocean the rheic ocean which separated laurussia from gondwana following the closure of iapetus is arguably the most important ocean of the palaeozoic its suture extends from mexico to turkey and its closure produced the climactic variscan alleghanian ouachita orogeny that assembled the supercontinent pangaea following protracted cambrian rifting that represented a continuum from neoproterozoic orogenic processes the rheic ocean opened in the early ordovician with the separation of several neoproterozoic arc terranes from the continental margin of northern gondwana separation occurred along the line of a former neoproterozoic suture following the onset of subduction in the outboard iapetus ocean the timing of rift drift transition and drive for subsequent spreading was likely governed by slab pull accounting for the rapid rate 8 10 cm yr at which the rheic ocean widened during the ordovician the ocean broadened at the expense of iapetus and attained its greatest width 4000 km in the silurian by which time baltica had sutured to laurentia and the neoproterozoic arc terranes had accreted to laurussia closing iapetus in the process closure of the rheic ocean began in the devonian and was facilitated by northward subduction beneath southern baltica and southward subduction beneath northwest gondwana closure was largely complete by the mississippian as gondwana and laurussia sutured to build pangaea north africa colliding with southern europe to create the variscan orogen in the devonian carboniferous and west africa and south america suturing to north america to form the alleghanian and ouachita orogens respectively during the carboniferous permian the rheic ocean consequently plays a dominant role in the basement geology of southern europe in the appalachian ouachita orogeny of north america and in the palaeozoic sedimentary structural and tectonothermal record from middle america to the middle east with its closure the ocean brought about the assembly of pangaea and brought the palaeozoic era to an end

strike slip orogens an explanation for the hercynides the nature of oblique plate interactions is not yet well understood the oblique interaction of pacific and n american plates has resulted in large scale migration rotation and accretion of microplates intervening basins are ephemeral individually filled and deformed oblique motion results in zones of both compression and extension the latter may be sufficient to generate new oceanic crust and the former to obduct it both subduction and collision are restricted in time and space the resulting orogen is extraordinarily complex in detail the far more complicated hercynides are the result of dextral interaction between continental plates europe and africa the lateral variability of the orogen the major and long lived strike slip faults the bimodal volcanism and related ore deposits of the european trough the lizard ophiolite and its melanges the nw spanish ophiolites and the iberian pyrite belt are all explained using an oblique collision model in particular the generation deformation and obduction of ophiolites in oblique slip mobile zones is discussed

upper palaeozoic ophiolite generation and obduction in south cornwall the gramscatho flysch sequence of south cornwall including the melanges of the meneage formation and the lizard ophiolite are described in relation to the development of the gramscatho basin the timing and geotectonic evolution of this feature are considered in its regional context within the rhenohercynian zone of northwest europe this zone is interpreted as an intracontinental dextral transform system that developed during the devonian closure of the so called massif central ocean a basin and rise topography is attributed to extension and compression at offsets on major faults e w extension of the gramscatho pull apart basin in middle and upper devonian times is believed to have caused rifting and the development of ocean crust from which the lizard ophiolite was assembled in an oceanic setting at a ridge transform junction the meneage formation was generated as a result of intrabasinal uplift on transcurrent faults a major change of plate motions took place when the massif central ocean finally closed at the end of the devonian and the weak rhenohercynian zone became a site of crustal convergence from which thrust nappes were transported northwards foreland basins were sequentially developed and deformed by thin skinned tectonics as the system advanced northwards during the carboniferous

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

tectonic uplift and landslides triggered by the wenchuan earthquake and constraints on orogenic growth a case study from hongchun gully longmen mountains sichuan china abstract many uncertainties need to be taken into account to estimate the relationship between tectonic uplift the landslide volume triggered by the wenchuan earthquake and constraints on the orogenic growth of the longmen shan mountain in this research coseismic tectonic uplift landslides and postseismic debris flows in hongchun gully located at the earthquake epicenter have been studied field data aerial photographs and digital elevation data were used to estimate the quantitative relationship between the tectonic uplift and landslides debris flows and their constraints on the orogenic growth of the longmen mountains the coseismic tectonic uplift volume 667 104 m3 was more than the coseismic landslide volume 380 01 104 m3 only 57 of the volume of the tectonic uplift has been converted to the volume of landslides in hongchun gully indicating new uplift and orogenic growth of the longmen shan the volume of postseismic debris flows was 70 5 104 m3 indicating that 20 of the volume of coseismic landslides was converted into postseismic debris flows by heavy rainfall the volume of materials discharged by minjiang river the main river is 48 5 104 m3 indicating that only 13 of coseismic landslide sediments has been removed from the range by fluvial processes and at least 86 of landslide sediments still remain in the hongchun gully coseismic tectonic uplift volume exceeds coseismic landslides volume and the wenchuan earthquake caused new uplift and geomorphic growth of the longmen mountains this is not consistent with a previous conclusion that mass wasting triggered by the 2008 wenchuan earthquake exceeds orogenic growth and led to a net material deficit in the longmen shan region

ophiolitic mylonites in the lizard complex ductile extension in the lower oceanic crust ophiolitic rocks in the lizard complex southwestern england preserve fine examples of mylonitic schists within low angle amphibolite facies shear zones two prominent shear zones with type localities at carrick luz and porthoustock both have a footwall in the mafic ultramafic interface at the base of the oceanic crust the carrick luz shear zone shows mylonitized gabbro above peridotite mafic dikes both predate and postdate the shearing the porthoustock shear zone brings down higher oceanic crustal levels gabbro sheeted dike complex against ultramafic rocks and has an extensional geometry shear sense indicators show hanging wall movement directions different from those predicted by previous northward obduction models generation of these ophiolitic mylonites is interpreted instead as due to ductile extension at an oceanic spreading center

deformation pattern around the conjoining strike slip fault systems in the basin and range southeast nevada the role of strike slip faulting in basin formation and inversion within the extensional regime of the basin and range strike slip faults create a regional pattern of opposing sense of fault systems the relationship between these faults and other deformational features nearby is enigmatic this paper addresses a diverse assemblage of contractional and extensional structures reflecting local uplift and subsidence respectively at the junction of two large neogene strike slip faults in southeastern nevada the right lateral las vegas valley shear zone and the left lateral bitter spring valley fault of the lake mead fault system first a middle miocene lacustrine carbonate basin the bitter ridge lovell wash carbonate basin formed north of the strike slip faults second the lacustrine basin inverted locally while sediments accumulated south of the strike slip faults third the study area was deformed by north northeast trending high angle oblique faults with normal and left slip components the results both from field observations and numerical modeling of the intersecting strike slip faults show that the las vegas valley shear zone and the bitter spring valley fault may have produced the basin in the north and its intense contractional deformation as well as the southward shift of deposition during the inversion event we conclude that conjoining strike slip fault systems can promote localized vertical tectonics and lead to basin formation and uplift right next to each other subsequent inversion of the earlier basinal deposits however requires a reversal in the sense of slip across the las vegas valley shear zone and a change in the regional stress system

reconciling competing models for the tectono stratigraphic zonation of the variscan orogen in western europe abstract the late paleozoic variscan orogen in europe is the result of convergence and collision between laurussia and gondwana during closure of the rheic ocean the orogen is divided into tectonostratigraphic zones that have a distinct curvature ibero armorican arc iaa and record the late cambrian early ordovician opening of the rheic ocean the migration of terranes from the gondwanan margin towards laurussia as well as the closure of that ocean and development of the iaa three models have emerged to explain the distribution of tectonostratigraphic zones 1 indentation tectonics due to collision with laurussia by a ibero aquitanian promontory of gondwana during the devonian 2 development of the cantabrian orocline at ca 295 ma in the inner core of the iaa an interpretation supported by abundant paleomagnetic structural and geochronological data and 3 orogen scale modification due to large scale strike slip shear zones the indentor and orocline models 1 and 2 have been viewed as incompatible because the former requires curvature along the gondwanan margin prior to devonian collision with laurussia whereas the latter requires that the tectonostratigraphic zones were much more linear prior to bending at ca 295 ma recent data have rekindled the hypothesis that the cantabrian orocline is connected to a second orocline to the south central iberian orocline highlighting the possibility that inner gondwanan and outer laurussian zones of the ibero armorican arc may be structurally discordant with respect to each other implying that the geographic limits of orocline formation are presently unclear the two models can be reconciled if the geography of gondwana s leading edge was irregular but the tectono stratigraphic zones remained approximately linear within the inner zones of the putative ibero aquitanian indentor and ii deformation associated with initial collision was largely accommodated by sinistral sw iberia and dextral armorican massif motion along shear zones on either side of the promontory

geochemistry and u pb and 40ar 39ar geochronology of the man of war gneiss lizard complex sw england pre hercynian arc type crust with a sudeten iberian connection the man of war gneiss is a variably deformed meta igneous body that ranges in composition from gabbro to tonalite and comprises part of the basal structural slice of the lizard ophiolite complex sw england u pb dating of zircon demonstrates that the parental magmas crystallized in the earliest ordovician 499t s 3 ma but 40 ar 39 ar step heating analysis of amphiboles suggests that at least the northernmost zone of the gneiss was subjected to an amphibolite grade metamorphic event at c 374 ma probably associated with thrust emplacement of the ophiolite the gneiss exhibits major trace and rare earth element variations in conformity with an origin through partial melting of an amphibolitic source containing hornblende and plagioclase probably with minor garnet and zircon the elemental abundances and variations are characteristic of granitoids formed in supra subduction zone environments a granitoid sill within the adjacent old lizard head series schists previously inferred to be related to the man of war gneiss is trondhjemitic and exhibits higher sio 2 tio 2 and mgo but lower zr v ba and sr contents and therefore is probably not genetically related to the latter the sill may record local melting during ophiolite emplacement the man of war gneiss probably represents a structural inlier of pre hercynian basement incorporated in the hercynian nappes of sw england during nnw directed thrusting we emphasize the geological and geochronological similarities between variably deformed granitoid units of the lizard complex the sudeten massif of southern poland and the allochthonous complexes of northern portugal and nw spain these granitoid rocks may represent dispersed remnants of tremadoc arcs that formed oceanward from the northern margin of gondwana this is further convincing evidence that at this time eastern avalonia was separated from northern gondwana by an ocean basin that may have been connected with the tornquist sea

oblique convergence and slip partitioning in the nw himalaya implications from gps measurements we report gps measurements of crustal deformation across the kashmir himalaya we combined these results with the published results of gps measurements from the karakoram fault system and suggest that in the kashmir himalaya the motion between the southern tibet and india plate is oblique with respect to the structural trend we estimated this almost north south oblique motion to be 17 2 mm yr which is partitioned between dextral motion of 5 2 mm yr on the karakoram fault system and oblique motion of 13 6 1 mm yr with an azimuth of n198 e in the northwest southeast trending kashmir himalayan frontal arc thus the partitioning of the india southern tibet oblique motion is partial in the kashmir himalayan frontal arc however in the neighboring nepal himalaya there is no partitioning the entire india southern tibet motion of 19 20 mm yr is arc normal and is accommodated entirely in the himalayan frontal arc the convergence rate in the kashmir frontal himalaya is about 25 less than that in the nepal himalayan region however here the karakoram fault system accommodates about 20 of the southern tibet and indian plate convergence and marks the northern extent of the nw himalayan arc sliver the kaurik chango rift a north south oriented seismically active cross wedge transtensional fault appears to divide the sliver in two parts causing varying translatory motion on the karakoram fault on either side of the kaurik chango rift

siegenian generation of the lizard ophiolite u pb zircon age data for plagiogranite porthkerris cornwall the long controversial age of the lizard ophiolite is resolved by u pb dating of three single magmatic zircons from a plagiogranite dyke near porthkerris point this demonstrates that the axial oceanic crust was undergoing extensional ductile shearing mylonitization amphibolite facies metamorphism and probably anatexis at 397 2 2 ma in conjunction with published k ar 40 ar 39 ar and rb sr data for the complex this early devonian age predicates a protracted interval between intra oceanic magmatism and deformation on the one hand and obduction during late devonian northwestward displacement of the normannian high on the other

a model for the tectonic evolution of south cornwall a stratigraphy for south cornwall is combined with an analysis of the chronology of thrust nappe emplacement the resulting model suggests that northward overthrusting of nappes of flysch and olistostrome ophiolite and continental basement is related to the closure of an oceanic basin in south cornwall involving southward subduction throughout the devonian the subsequent continental collision between the normannian high and part of laurentia occurred in the upper devonian with deformatian continuing until late carboniferous times

constraints on the p t conditions and age of emplacement of the lizard ophiolite cornwall amphibole plagioclase thermobarometry and 40ar 39ar geochronology of basal amphibolites the basal slice of the lizard complex incorporates strongly foliated amphibolitic metabasites lower landewednack schists interpreted as the remnants of a dynamothermal aureole formed beneath the ophiolite during intraoceanic thrusting structurally overlying the basal slice and occurring predominantly within the overlying lizard peridotite is the kennack gneiss a controversial banded and gneissose unit comprising intimately mixed amphibolitic and granitic components interpreted to represent commingled melts thermobarometry of hornblende plagioclase pairs indicates that both the landewednack schists and the mafic component of the kennack gneiss recrystallized synkinematically at ca 600 c and 300 400 mpa three amphiboles two from the kennack gneiss and one from the landewednack schists yield disturbed 40ar 39ar age spectra characterized by low temperature overprinting but with good high temperature plateaux with ages of 366 1 4 2 364 2 4 8 and 359 8 7 4 ma respectively theoretical dif

tectonic evolution of kashmir basin in northwest himalayas abstract geomorphology has long been recognised as a key to evaluate the interplay between tectonics and landscape geometry in the regions of active deformation we use geomorphic signatures at varied spatial scales interpreted from srtm dem landsat etm data supplemented with field observations to review the tectonic evolution of kashmir basin in northwest himalayas geomorphic evidence is persuasive of a credible nnw sse trending dextral strike slip structure central kashmir fault ckf with the strike length of 165 km stretched centrally over the nnw sse length of the kashmir basin as a result of the strike slip motion and subsequent erosion significant deformation has taken place along the ckf in addition broad geomorphic architecture of the basin reveals typical pull apart characteristics hence we deduce that the kashmir basin has evolved as a pull apart quaternary sediment depression owing to the deformation along the central kashmir fault the spatial distribution pattern of seismic events neic catalogue 1973 2013 and gps measurements published collectively substantiate our geomorphic interpretations

transtension driving volcano edifice anatomy insights from andean transverse to the orogen tectonic domains abstract dykes and minor eruptive vents are not randomly distributed within tectonically controlled volcanic arcs which is reflected in the resulting morphology of stratovolcanoes as a first order approach regional stress field controls the spatial distribution and geometry of dykes and minor eruptive vents however favourably oriented pre existing weakness zones such as inherited fault systems parallel or close to parallel to the orogen scale shortening axis may reactivate and be the loci for magma migration within the upper crust in intra arc regions field mapping and satellite image analyses were used to establish the callaqui stratovolcano csv structural setting in the andean southern volcanic zone central southern chile geometrical and morphometric analyses of intravolcanic dykes and minor eruptive vents respectively yields a consistent model of dykes propagating and erupting into either 1 n 60 e 5 oriented inherited pre existing fractures in central portions of the volcanic edifice and or 2 regional stress controlled n 70 e 10 self propagating fractures at distal zones a wing crack like structural array of the intra volcanic dyke swarm documents a local right lateral transtensional setting driving the late pleistocene to holocene volcano building up process the latter plays a fundamental role in the progressive shaping of the csv elongated anatomy in space and time parallel dyking and fissural eruptions contribute to successive volcanic output in a predominant ene orientation on the other hand a prominent elongated relief enhances normal to the volcano elongation flank instability developing steeper flanks that could trigger sector collapses this may promote an increase in the extensional component reinforcing further parallel dyking and subsequent eruptions these results improve the understanding of the tectonic role in magma migration processes within the upper crust which is crucial to understand geothermal systems and to minimize hazards related to volcano instability

influence of geomorphic and anthropogenic activities on channel morphology of river jhelum in kashmir valley nw himalayas abstract the srinagar reach of the river jhelum in kashmir valley india exhibits complex meandering and variable width 47 180m and depth 0 76 6 09m the reach is characterised by sharp bends in the river course channel sinuosity linearity of meander bends linear truncation of braid bars and concavities and convexities in the river channel reflecting varied river geomorphic processes during the extreme hydrological event of september 2014 a large number of river breaches occurred along the river jhelum particularly in the srinagar stretch of the river due to the floodwaters overflowing the banks and the consequent bank erosion the flooding situation was aggravated over the years by anthropogenic influences like the extensive urbanization of the jhelum floodplains encroachment of river banks and siltation of water courses due to the deforestation in the catchment and the shrinkage of wetlands which usually act as sponge during the flooding events to establish a relationship between the geomorphic processes and anthropogenic activities on river morphology we used various geomorphic parameters and techniques like river profiling bathymetric profiling lateral entrenchment ratio water velocity sinuosity index supported by gps and other field measurements the impact of the geomorphic and human induced changes on the channel morphology was corroborated with the data from the river breaches that occurred during the 2014 flooding a few of which occurred at the locations where geological structures lineaments faults cut across the river banks based on the investigations from this study it is suggested that varied geomorphic processes and the unchecked anthropogenic activities in the vicinity and catchment have significantly impacted the channel morphology of the river jhelum in kashmir valley increasing the vulnerability of the srinagar city to flooding

multiple active spreading centres in the hot north fiji basin southwest pacific a possible model for archaean seafloor dynamics abstract the north fiji basin nfb in the southwest pacific is one of the most evolved back arc basins within the basin active spreading is taking place along several ridges some of which display the characteristics of spreading ridges observed in mature large oceans characterized by a range of spreading rates segmented accretion centres organized magnetic lineations and propagators for example however the great cumulate length of the spreading centres of the nfb relative to the basin s surface makes it an unique example among the world s oceanic basins we have reviewed a comprehensive body of geological geophysical and geochemical evidence multiple spreading centres of various trends high heat flow high geoid and slow upper mantle seismic velocities which collectively demonstrate that a hot upper mantle underlies the north fiji basin active upper mantle convection is the key process controlling the large crustal and lithospheric production in the nfb which would be thus largely independent from the evolution of even the largest structural features such as the vitiaz and new hebrides subduction zones petrological studies of the archaean greenstone belts have led to a similar picture for the entire earth during the archaean numerous short active ridges connected by unstable triple junctions would have at this time provided an efficient convective mechanism allowing for a large heat dissipation we propose that the presently active processes in the north fiji basin are modern analogues to archaean seafloor dynamics

fold cleavage relationships as indicator for late variscan sinistral transpression at the rheno hercynian saxo thuringian boundary zone central european variscides abstract the boundary between the rheno hercynian and the saxo thuringian zones of the european variscides is characterized by a ne sw striking late orogenic fold and thrust belt affecting the intervening rheic suture classical models used the first order strike of this zone as an indicator for perpendicular plate convergence i e nw se we present structural data from both sides of the suture focusing on fold cleavage relationships the statistical analysis reveals an orientation maximum of the youngest cleavage that deviates from the strike of the fold and thrust belt by c 22 the presence of clockwise transection of the folds by the cleavage up to 16 indicates pervasive sinistral transpression three types of fold cleavage relationships are observed ne trending folds i with or ii without a transecting cleavage and iii non transected ene trending folds we explain the occurrence of different fold cleavage types by strain partitioning due to nnw convergence obliquely to pre existent ne trending mechanical anisotropies in terms of plate tectonics we propose that the classical boundary of the rheno hercynian and the saxo thuringian zone represents an initial transform plate boundary that was finally affected by sinistral transpression

geomorphic evidence of unrecognized balapur fault segment in the southwest kashmir basin of northwest himalayas abstract the balapur fault bf is a high angle thrust fault reverse dipping 60 ne with an established length of 40 km striking nw se of the kashmir basin however geomorphic traces suggest that the strike of the bf propagates beyond what has been documented previously the present investigation aims to identify the unrecognized segment of the bf in the sw of the kashmir basin using hypsometric variability in longitudinal profiles knickpoints zones followed by validation through stream gradient index sl calculations of the rivers draining the area the longitudinal profiles of all the streams indicate prominent and consistent anomalies in the upper and mid reaches even on the coarse resolution data survey of india topographic maps 1 50 000 40 m dem srtm 90 m the profile anomalies in the upper reaches hard rock zone of the streams may be attributed to lithological contacts i e panjal trap agglomeratic slate shale limestone however the river profile convex segments and course deflection specifically in the mid reaches soft rock zone are most likely associated with recent tectonic activity geomorphic signatures suggest that these anomalies coincide with the strike of the recognized segment of the bf moreover the sl values of each stream express a clear agreement with the anomalies shown by the long profiles of the rivers hence we infer that the strike of the bf extends for a significant distance 95 km over the northeastern flank of the pir panjal range in the nw se direction

limit of strain partitioning in the himalaya marked by large earthquakes in western nepal great earthquakes in the himalaya are thought to occur mostly along the range front field mapping and radiocarbon dating reveal earthquake rupture on a previously unrecognized fault in the interior of the western himalaya which forms part of a key structural component of the mountain range implying that seismic risk evaluations should be revised

tectonics of strike slip restraining and releasing bends restraining and releasing bends are common but enigmatic features of strike slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation regional scale restraining bends are sites of mountain building transpressional deformation and basement exhumation whereas releasing bends are sites of topographic subsidence transtensional deformation basin sedimentation and possible volcanism and economic mineralization because restraining and releasing bends often occur as singular self contained domains of complex deformation they are appealing natural laboratories for earth scientists to study fault processes earthquake seismology active faulting and sedimentation fault and fluid flow relationships links between tectonics and topography tectonic and erosional controls on exhumation and tectonic geomorphology this volume addresses the tectonic complexity and diversity of strike slip restraining and releasing bends with 18 contributions divided into four thematic sections 1 a topical review of fault bends and their global distribution 2 bends sedimentary basins and earthquake hazards 3 restraining bends transpressional deformation and basement controls on development 4 releasing bends transtensional deformation and fluid flow

macroseismic intensity assessment of 1885 baramulla earthquake of northwestern kashmir himalaya using the environmental seismic intensity scale esi 2007 abstract kashmir has a long written history of 5000 years which provides a sketchy picture of historical earthquakes in all we collated details of 16 earthquakes from the historical scribes most of the earthquakes had their epicenters outside the kashmir valley the exceptions earthquakes with epicenters within the valley however caused severe damage to life and properties and were associated with ground ruptures and long periods of aftershocks among them only the 1885 event is adequately described we have analyzed environmental effects of this destructive earthquake which occurred in the northwestern kashmir himalaya along pir panjal range in the early morning 5 00 a m of 30 may 1885 using archival sources followed by field work the present attempt envisages applying the environmental seismic intensity scale esi 2007 for a macroseismic intensity assessment of the 1885 baramulla earthquake inferences primary and secondary reveal that the 1885 baramulla earthquake local intensity would have been vi x on the esi scale baramulla the macroseismic epicenter of the earthquake must have witnessed epicentral intensity of x on esi scale the intensity must have been variable severe at baramulla and less at srinagar because of the severity of damage decreased from nw to se

strain partitioning along the himalayan arc and the nanga parbat antiform shortening along the himalayan arc of continental convergence is approximately in the radial direction if the underthrusting foot wall block india is not deformed the hanging wall block tibet needs to stretch along the arc as suggested by radial grabens in southern tibet in contrast the nanga parbat haramosh massif and the western himalayan syntaxis are part of a 250 km long antiform that strikes in the radial direction northeast and verges northwest the nanga parbat antiform is the structural and topographic expression of arc parallel shortening that compensates for arc parallel extension in southern tibet this shortening is predicted to be as high as 12 mm yr

the emplacement of peridotites and associated oceanic rocks from the lizard complex southwest england upper mantle peridotites and associated oceanic rocks from the lizard complex south west england preserve evidence for a multistage geological history steeply dipping pre emplacement fabrics record high temperature 900 1100 c shearing and exhumation of the mantle peridotites apparently formed during localized ne sw rifting in a pull apart basin setting c 400 390 ma associated oceanic rocks landewednack amphibolites preserve a pre emplacement prograde brown amphibole bearing metamorphic assemblage and steeply dipping fabric thought to have formed as the newly formed oceanic crust was juxtaposed with newly exhumed hot mantle peridotite during ne sw rifting in both the peridotites and landewednack amphibolites steep pre emplacement structures are cross cut by low angle mylonitic fabrics thought to have formed during the initial phases of emplacement of mantle over crustal rocks in a partially intra oceanic setting c 390 375 ma the fabrics in peridotites and amphibolites exhibit retrograde mineral assemblages c 500 800 c with the amphibolites preserving two superimposed assemblages green amphibole titanite and colourless magnesio hornblende respectively that are thought to record progressive down temperature deforma tion during thrusting emplacement related structures in both the basal peridotites and amphibolites consistently dip at low to moderate angles nw with down dip lineations and kinematic indicators showing consistent top to the nw senses of shear syn emplacement magmatism is recorded by intrusions of foliated kennack gneiss anastomosing serpentine filled faults mark many existing low angle contacts between the peridotites and landewednack amphibolites and appear to represent the final lowest temperature 250 c stages of emplacement c 370 ma this study shows that dynamothermal aureoles in ophiolites may preserve evidence for tectonothermal events that pre date thrust emplacement

a genetic model of thrust bounded intermontane basin using scaled sandbox analogue models an example from the karewa basin kashmir himalayas india the himalayan mountain system has many depressions of regional dimensions which are found oriented mostly e w to ne sw mainly to the north of the main boundary fault mbf the karewa basin in the kashmir himalaya has sediments belonging to late neogene to quaternary formations which represent an almost 1 300 m thick succession of sand mud and gravels exposed in the river valleys and the plateau margins of the entire kashmir valley sandbox analogue experiments show a great variety of wedge shapes showing significant changes in the taper angles due to the change in basal friction between two pop ups or depressions pop down of significant dimensions develop along the strike of the growing wedge in order to maintain the critical angle these depressions initially receive material from the hinterland and later on from the foreland end of the wedge the depressions have developed due to the change in the surface slope of the wedge and receive the eroded material only from the adjacent upheaved portions of the wedge on continuation of the experiments in cases where the wedge is highly unstable these depressions are coupled with the wedge along with their sand fills the depositional history of the karewa sediments indicates a sequential evolutionary pattern of the basin and thus represents a natural analogue of the sandbox experiments

borehole sections through the traboe hornblende schists a cumulate complex overlying the lizard peridotite three borehole sections in the traboe area provide a partial section through a layered basic ultrabasic complex previously referred to as the traboe hornblende schists this complex though dismembered into thrust sheets shows an overall ne dipping stratigraphy with a generalized upward sequence from dunite and pyroxenite to gabbro and anorthosite the bulk composition of the ultramafic rocks is quite different from the dominantly lherzolitic composition of the main lizard peridotite the composition of the basic rocks is also markedly different from that of the landewednack hornblende schists with which they have previously been correlated the deformation and recrystallization of the rocks has been complex and locally intense producing a fine granular fabric in many rock types amphibolitization has affected many rock types to give assemblages dominated by hornblende mineral composition varies with position in the stratigraphic sequence and is consistent with crystallization of the complex from differentiating basic magma pulses

flood hazard assessment of upper jhelum basin using morphometric parameters morphometric parameters can be useful tools to provide general understanding of physical characteristics of drainage basin with respect to floods to evaluate the flood influencing factors in the upper jhelum basin we delineate the upper jhelum basin into ten sub basins followed by extraction of drainage network and morphometric parameters using advanced spaceborne thermal emission and reflection radiometer digital elevation model and topographic maps in geographic information system the overall flood potential was determined on the basis of compound value obtained for all morphometric parameters of each sub basin the analysis reveals that in general the northeastern segment of the upper jhelum basin reveals comparative higher flood potential than the southwestern segment the tributaries such as lidder veshav arapal arapat and bring exhibit greater potential to produce peak flows during rainfall events while the tributaries like dudhganga rambiara sandran romushi and sasara express moderate to low flood potential respectively the results of this study are likely to be very useful for effective flood hazard mitigation in upper jhelum floodplain

parallel thrust and normal faulting in peru and constraints on the state of stress abstract we present evidence for recent normal faulting in the cordillera blanca of peru along planes trending approximately n40 w parallel to the chain this type of faulting suggests that there is an important component of extension perpendicular to the chain and contrasts markedly with the underthrusting of the nazca plate on the west side of peru and with the folding and thrusting observed in the sub andes on the eastern flank of the chain these contrasting styles of deformation and associated stress fields can be explained by buoyancy forces due to the high mountains and crustal roots in so far as this explanation is correct the difference in elevation between zones of normal and thrust faulting can be used to place an upper bound of 500 bars on the average stress difference in the crust

redefining medlicott wadia s main boundary fault from jhelum to yamuna an active fault strand of the main boundary thrust in northwest himalaya abstract the mbt demarcates a tectonic boundary between the tertiary sub himalaya and the pre tertiary lesser himalaya south of the mbt another tectonically important fault extends from muzaffarabad and riasi in jammu kashmir to bilaspur and nahan in himachal medlicott and wadia had designated this fault the main boundary fault mbf in simla hills and jammu region respectively in between these two areas later workers gave local area names to the mbf as the riasi thrust in jammu palampur thrust in kangra bilaspur thrust in simla hills and nahan thrust in sirmur we have reviewed and established the tectonostratigraphic framework and physical continuity of the lower tertiary belt and the mbf the lower tertiary belt lying south of the mbt has characteristic tectonostratigraphic setting with discontinuous bodies of stromatolite bearing proterozoic limestone overlain with depositional contact by the paleocene lower part middle eocene marine subathu patala formation which in turn overlain by the upper oligocene lower miocene non marine dharamsala murree formation to avoid confusion with the mbt we designate collectively the mbf and related faults as the medlicott wadia thrust mwt the mwt extends east of hazara kashmir syntaxis to river yamuna covering a distance of 700 km further east of yamuna the lower tertiary belt pinches out and the mwt merges with the sensuo stricto mbt the proterozoic limestone represents the basement over which the lower tertiary sediments were deposited the limestone basement with its cover was detached by the mwt exhuming to the surface and thrusting over largely the siwalik group the reactivated balakot bagh fault causative fault for the 2005 kashmir earthquake extends southeast with right step to the riasi thrust the riasi thrust shows evidence of reactivation and active tectonic activity in jammu region it extends further east to the palampur thrust in kangra reentrant which lies within the 1905 kangra earthquake rupture zone the bilaspur thrust continuation of the palampur thrust shows active faulting south of simla hills between sataun and yamuna river these observations indicate that the mwt represents a southern strand of the sensuo stricto mbt and shows active faulting in some segments

coexisting tectonic settings the example of the southern tyrrhenian sea we performed geodetic strain rate analyses in southern italy using new gps velocities two dimensional strain and rotation rate fields were estimated and results show that most of the shortening is distributed in the northern sicily offshore extension becomes more evident and comparable with shortening on the eastern side of the same margin and greater in the eastern sicily offshore principal shortening and extension rate axes are consistent with long term geological features seismic reflection profiles show both active compressive and extensional faults affecting pleistocene strata we show evidence for contemporaneous extension and transtension in the cefalu basin combining geodetic data and geological features point to the coexistence of independent geodynamic processes i e the active e w backarc spreading in the hangingwall of the apennines subduction zone and shortening along the southern margin of the tyrrhenian backarc basin operated by the nnw motion of africa relative to eurasia

two stage collision exploring the birth of pangea in the variscan terranes abstract the variscan suture exposed in nw iberia contains a stack of terranes including two allochthonous units with continental affinity and gondwanan provenance upper and basal units separated by an ophiolite belt where the most common units show protolith ages at c 395 ma recent lu hf zircon data obtained from these ophiolites indicate interaction between the gabbroic magmas and old continental crust hence the ophiolites could not have originated in a deep ocean basin associated with a mature mid ocean ridge or intraoceanic subduction the tectonothermal evolution of the continental terranes bounding the suture zone records two consecutive events of deep subduction the upper units record an initial high p ultra high p metamorphic event that occurred before 400 390 ma while the basal units were affected by a second high p low to intermediate t metamorphic event dated at c 370 ma continental subduction affected the most external margin of gondwana and developed in a setting of dextral convergence with laurussia development of the two high p events alternated with the opening of an ephemeral oceanic basin probably of pull apart type in early devonian times this ephemeral oceanic domain is suggested as the setting for the protoliths of the most common ophiolites involved in the variscan suture current ideas for the assembly of pangea advocate a single collisional event between gondwana and laurussia in the carboniferous however the new evidence from the allochthonous terranes of the variscan belt suggests a more complex scenario for the assembly of the supercontinent with an interaction between the colliding continental margins that started earlier and lasted longer than previously considered based on modern analogs of continental interaction the development of complex collisions as here suggested for gondwana and laurussia during the assembly of pangea could have been the norm rather than the exception throughout earth history

deformation and emplacement of the lizard ophiolite complex sw england based on evidence from the basal unit the basal unit of the lizard ophiolite complex preserves evidence of a protracted deformation and accretion history the earliest recognizable events record the construction of ocean crust and the generation of the lizard ophiolite complex in a slow spreading ridge axis environment the initial stages of deformation involved the development of a sub horizontal crustal scale shear zone and its progressive deformation by ductile thrusting and folding subsequent deformation progressed with the out of sequence stacking of ocean lithosphere in which detachment initiated at mid crustal levels culminated in mantle decoupling as thrust slices were derived from progressively deeper crustal levels the progressive emplacement of a coherent slice of ocean lithosphere over previously accreted units and the generation of a dynamothermal aureole are consistent with models suggesting rapid overthrusting of young ocean lithosphere evidence from the dynamothermal aureole indicates that syn emplacement extensional collapse of the complex occurred in response to thrust loading foreland directed offsliding and lateral thrusting mark the final stages in the collapse of the complex

re interpreting the devonian ophiolites involved in the variscan suture u pb and lu hf zircon data of the moeche ophiolite cabo ortegal complex nw iberia new u pb zircon data of a mylonitic greenschist from the moeche ophiolite one of the mafic units involved in the variscan suture in the cabo ortegal complex nw of the iberian massif yielded an age of 400 3 ma consequently this unit can be considered one of the devonian ophiolites the most extended group of oceanic units in the variscan belt the mafic rocks show transitional compositions between n morb and island arc tholeiites although lu hf isotope signatures of its zircons clearly indicate contribution from an old continental source ehf values in the analysed zircons are negative generally below ehf 5 and thence they are not compatible with their generation from a juvenile mantle source accordingly the igneous protoliths were generated in a setting where juvenile mafic magmas interacted with an old continental crust the devonian ophiolites from the variscan suture have been repeatedly interpreted as remnants of the rheic ocean however the presence of a continental source in the origin of the mafic rocks of the moeche ophiolite allows discarding an intraoceanic setting for their generation at least for the nw iberian counterparts the tectonic setting for the devonian ophiolites of nw iberia is very likely represented by an ephemeral oceanic basin opened within a continental realm herein the real rheic ocean suture could only be located west of the terrane represented by the upper units of the allochthonous complexes apparently that suture is not represented in nw iberia

structure of the hanmer strike slip basin hope fault new zealand hanmer basin 10 x 20 km located in northern south island new zealand is evolving where two major segments of the dextral strike slip hope fault are projected to converge across a 6 to 7 km wide releasing step over the structural geometry and development of hanmer basin does not conform to traditional pull apart basin models the respective fault segments do not overlap but are indirectly linked along the southwest margin of the basin by an oblique normal fault the hope river segment terminates in an array of oblique normal faults along the northwestern basin range front and east west striking normal faults on the west hanmer plain faulted holocene alluvial fan surfaces indicate west hanmer basin is actively subsiding evolving under north south extension the conway segment along the southeastern margin of the basin terminates in a complex series of active fault traces small pop up ridges and graben depressions early basin fill sediments of pleistocene age are being folded elevated and dissected as the eastern part of hanmer basin is progressively inverted and destroyed by north south contraction the north margin of the basin is defined by a series of topographic steps caused by normal faulting outside of the area of the releasing step over these normal faults we interpret to reflect large scale upper crustal collapse of the hanging wall side of the hope fault new seismic reflection data and geologic mapping reveal a persistent longitudinal and lateral asymmetry to basin development four seismic stratigraphic sequences identified in the eastern sector of the basin thicken and are tilted southward with insequence lateral onlaps occurring to the north and east and also onto basement near the fault controlled basin margins the basin depocenter currently contains 1000 m of sediment adjacent to the south margin and is disrupted by faulting only at depth in the western part of the basin the sediment fill is thinner today the rate of basin deepening under transtension at the western end is matched by its progressive inversion and destruction under transpression in the eastern sector with the oldest basin fill now being recycled we propose a hybrid model for hanmer strike slip basin one in which geometric elements of a fault wedge basin downward and upward tipped spindle shaped ends are combined with those of a pull apart basin step over region between the major fault segments we also conclude that changes in fault geometry releasing and restraining bends and step overs at a variety of scales and over short distances control the development of the extensile and contractile parts of the basin and three dimensional basin asymmetry strain partitioning is complex and cannot be related simply to local reorientation of the regional stress field

allochthonous terranes involved in the variscan suture of nw iberia a review of their origin and tectonothermal evolution abstract nw iberia includes a rather complete section of a variscan suture where different terranes with continental or oceanic affinities appear with clear structural relationships three groups of terranes namely upper ophiolitic and basal units and a frontal tectonic melange appear in galicia in cabo ortegal ordenes and malpica tui complexes they constitute a huge allochthonous pile thrust over the iberian parautochthonous and autochthonous domains which represent the section of the gondwanan margin that escaped continental subduction during the variscan cycle considering the allochthonous character of the nappe pile and the strong deformation associated to the variscan collision there are problems to identify the original tectonic setting of the terranes and thence it is difficult to reconstruct the paleogeographic context during the variscan and pre variscan times in detail key features to perform any model for the variscan convergence should consider the existence of two different high p metamorphic events dated at c 400 and 370 ma respectively separated in time for the generation of mafic ultramafic sequences at c 395 ma which constitute the most common ophiolites described in the variscan suture some dynamic models developed in nw iberia have important problems to explain the observed tectonothermal evolution especially the older high p metamorphic event and the exhumation of deeply subducted transitional type sections on the other hand the recently discovered participation of an older continental crust in the generation of different protoliths of the middle devonian ophiolites makes difficult the interpretation of these ophiolites in relation to open wide oceanic domains this paper describes the distribution structure lithologies geochronology and chemical composition of the terranes involved in the variscan suture of nw spain the scope of this description ranges from detailed regional aspects to the discussion of the development of the variscan orogen in the context of the assembly of pangea a two stage collisional model affecting a wide gondwanan platform may explain most of the evidences in nw iberia the generation of a long pull apart basin probably occurred after the first collision where the devonian ophiolites were formed these ophiolites have been in general described in the context of the rheic ocean but according to the new existing data they do not seem related to this ocean but rather they were formed after its closure

tectonic inheritance and pliocene pleistocene inversion of the algerian margin around algiers insights from multibeam and seismic reflection data 1 the algerian margin has originated from the opening of the algerian basin about 25 30 ma ago the central margin provides evidence for large scale normal faults of oligo miocene age whereas transcurrent tectonics characterizes the western margin a set of nw se oriented dextral transform faults was active during basin opening and divided the 600 km long central margin into segments of 120 150 km the upper miocene plio quaternary and present day tectonic setting is however compressional and supports the occurrence of a margin inversion a process still poorly documented worldwide we show that the central algerian margin represents a rare example of inverted margin where the process of subduction inception is particularly well expressed and helps understand how extensional and transtensive structures are involved in margin shortening using multibeam bathymetry and multichannel seismic reflection sections from the maradja 2003 and 2005 cruises we evidence pliocene pleistocene shortening with contrasting styles along the margin between west khayr al din bank and east boumerdes dellys margin of algiers pre miocene structures such as basement highs and transform faults appear to control changes of the deformation pattern along this part of the margin resulting in different widths geometries and relative positions of folds and faults plio quaternary and active blind thrust faults do not reuse oligo miocene normal and transform faults during inversion but instead grow within the continental margin as testified for instance by the 21 may 2003 mw 6 8 boumerdes zemmouri earthquake at the foot of the continental slope and at the northern sides of basement highs interpreted as stretched continental blocks of the rifted margin the inherited structures of the margin appear therefore to determine this deformation pattern and ultimately the earthquake and tsunami sizes offshore the complex geometry of the fault system along the algerian margin suggests a process of initiation of subduction in its central and eastern parts

tectono geomorphic indices of the erin basin ne kashmir valley india abstract the present study aims to assess the tectonic activity in the erin basin ne kashmir on the basis of several relevant geomorphic indices and field observations we use digital elevation model srtm and survey of india soi topographic maps in gis environment to compute the geomorphic indices the indices i e convex hypsometric curve high hypsometric integral value h i 0 5 low basin elongation ratio eb 0 17 low mountain front sinuosity values s mf 1 08 average low valley floor width ratios vf 4 suggest that the area is tectonically active moreover prominent irregularities knickpoints knickzones along longitudinal profile of the erin river even in homogenous resistant lithology panjal trap and anomalous stream gradient index sl values reflect that the erin basin is dissected by two faults ef 1 and ef 2 with nnw sse and ssw nne trends respectively the results of this preliminary study further substantiate the recent gps studies which argue that the maximum strain is accumulating in the ne part of the kashmir himalaya

implications of channel flow analogue models for extrusion of the higher himalayan shear zone with special reference to the out of sequence thrusting the higher himalayan shear zone hhsz contains a ductile top to n ne shear zone the south tibetan detachment system lower stdsl and an out of sequence thrust oost as well as a top to n ne normal shear at its northern boundary and ubiquitously distributed compressional top to s sw shear throughout the shear zone the oost that was active between 22 ma and the holocene varies in thickness from 50 m to 6 km and in throw from 1 4 to 20 km channel flow analogue models of this structural geology were performed in this work a newtonian viscous polymer pdms was pushed through a horizontal channel leading to an inclined channel with parallel and upward diverging boundaries analogous to the hhsz and allowed to extrude to the free surface a top to n ne shear zone equivalent to the stdsu developed spontaneously this also indirectly connotes an independent flow confined to the southern part of the hhsz gave rise to the stdsl the pdms originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel the lower boundary of this faster pdms defined the oost the model oost originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began the genesis of the oost seems to be unrelated to any rheologic contrast or climatic effects profound variations in the flow parameters along the hhsz and the extrusive force probably resulted in variations in the timing location thickness and slip parameters of the oost variation in pressure gradient within the model horizontal channel however could not be matched with the natural prototype channel flow alone presumably did not result in southward propagation of deformation in the himalaya

fabric development in a middle devonian intraoceanic subduction regime the careon ophiolite northwest spain abstract a middle devonian suprasubduction zone ophiolite the careon unit northwest spain displays amphibolite facies ductile deformation fabrics related to the onset of the rheic ocean closure two different fabrics an early high t foliation and a subsequent lower t foliation each of which characterized by distinct deformation mechanisms have been identified in two distinct crustal scale shear zones of the same ophiolitic thrust sheet combined quantitative texture analysis by electron backscattered diffraction and time of flight neutron diffraction were carried out on the shear zones and correlated with micro and macrostructural data the results indicate that the regional lineation and shear zone kinematics east west top to the east represent fabrics developed essentially during the intraoceanic subduction of the rheic ocean and their orientation may be considered a reference vector for convergence models in this part of the variscan belt

hybrid tectonic character of the kashmir basin response to comment on coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya alam et al 2017 by shah 2017 abstract in general the genesis of the kashmir basin is being viewed as a result of compressional tectonics perhaps because of the reason that the basin is located in india eurasia convergence zone however there is no work that convincingly demonstrates how existing geomorphic architecture of the kashmir basin evolved due to thrust tectonics with answer to many questions alam et al 2015 proposed an extensional model for the development of the kashmir basin moreover based on deformation styles at varied spatial scales alam et al 2017 also suggested the co existence of dominant extensional and relatively feeble compressional deformations within the basin our model has been questioned by shah 2017 and here we provide more evidence to prove that kashmir basin is a pull apart basin

late quaternary climatic changes in the eastern kumaun himalaya india as deduced from multi proxy studies abstract an event of neotectonic activity on an ne sw trending subsidiary fault in the zone of e w running intracrustal boundary thrust south almora thrust in the champawat district of eastern kumaun himalaya resulted in creation of a lake at ca 21 5 bp the lake drained in the late holocene leaving behind a 5 0 m thick sedimentary sequence of mostly black and carbonaceous mud with a minor magnetic reversal between 20 5 and 19 7 ka bp at the base the profile studied by using multi proxies e g carbon isotopes pollen analysis palaeo and mineral magnetism and clay minerals has recorded globally well established abrupt climatic events in the last 20 000 years such as the lgm older dryas od younger dryas yd holocene warming 8 2 ka and 4 2 ka events most events estimated assuming a constant rate of sediment accumulation for similar lithologies may be related to the rapid changes in the local climate and albedo structure the itcz may have played a key role in controlling the behavior of the southwest monsoon from the lgm

space and time in the tectonic evolution of the northwestern iberian massif implications for the variscan belt recent advances in geochemical studies of igneous rocks isotopic age data for magmatism and metamorphism quantitative pressure temperature p t estimates of metamorphic evolution and structural geology in the northwestern iberian massif are integrated into a synthesis of the tectonic evolution that places the autochthonous

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late quaternary evolution of tista river terraces in darjeeling sikkim tibet wedge implications to climate and tectonics abstract 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

geochemistry of two associated ophiolites from the cabo ortegal complex variscan belt of nw spain two paleozoic ophiolites of different age mark the variscan suture in the cabo ortegal complex northwestern iberian massif the moeche and purrido allochthonous ophiolites are structurally located between an exotic terrane of continental affi nity basal units below and another terrane with arc affi nity upper units above the mafi c rocks of the moeche unit are greenschist with a composition typical of tholeiitic basalt their rare earth element ree concentrations range from 12 to 31 times the chondritic abundances with almost fl at chondrite normalized ree patterns la n yb n avg 0 83 and they have no signifi cant eu anomalies according to their contents in some immobile trace elements the geochemical composition of these metabasalts seems to be transitional between normal mid ocean ridge basalt n morb and island arc tholeiites their abundances in the most immobile trace elements with the highest discriminating power th nb ce zr ti and y normalized to an average tholeiitic n morb depict quite fl at patterns close to the average n morb concentrations although they are slightly enriched a small negative nb anomaly points to an origin linked to a subduction zone the purrido unit consists of amphibolites with compositions also equivalent to tholeiitic basalt ree compositions range from 6 to 22 times chondritic abundance with essentially fl at chondrite normalized ree patterns la n yb n avg 0 99 and very small positive eu anomalies eu eu avg 1 08 the abundance of some trace

the late cenozoic chronologic and stratigraphic development of the kashmir intermontane basin northwestern himalaya abstract the intermontane basin of kashmir developed within the thrust faulted southern margin of the himalayan range detailed lithostratigraphies magnetic polarity stratigraphies and fission track dates on enclosed volcanic ashes were determined at four separate localities in order to develop a chronology of the late cenozoic evolution of the kashmir basin the results indicate that sedimentation had commenced by about 4 m y ago since then over 1300 m of sediments have aggraded at inferred average rates varying from 16 to 64 cm per 1000 yr lacustrine and deltaic sediments dominate the kashmiri sequences and appear to respond sensitively to tectonic events along the basin margins conglomerates shed from the faulted basin margins at about 1 7 2 1 2 7 and 3 0 3 5 m y ago punctuate the predominantly low energy fluviolacustrine depositional record paleocurrent analyses indicate a switch from northeasterly derived conglomeratic facies to southwesterly derived ones about 1 7 m y ago this transition reflects enhanced activity along the main boundary thrust complex to the southwest and an apparent diminution of faulting along the northeastern margin of the basin in the pir panjal range 1400 3000 m of uplift at inferred rates of up to 10 mm yr 1 have terminated widespread sedimentation within the kashmir basin since the middle pleistocene

the kennack gneiss of the lizard peninsula cornwall sw england commingling and mixing of mafic and felsic magmas accompanying givetian continental incorporation of the lizard ophiolite the kennack gneiss comprises a suite of interlayered mafic and felsic igneous rocks that intruded the 397 ma lizard ophiolite complex cornwall at 376 4 1 7 ma u pb single zircon date and were shortly thereafter c 370 ma metamorphosed to the amphibolite facies weakly deformed examples at the type locality of kennack sands reveal net veining of the mafic by the felsic component dispersed enclaves of the former in the latter and flame like interfingering of the two features indicative of magmatic commingling and mixing the silicic components of the kennack gneiss range from granodiorite to syenogranite and from metaluminous to peraluminous the least silicic rocks being the most peraluminous they were generated through anatexis of a predominantly metasedimentary crustal source having trace element and isotopic compositions comparable to those of the devonian gramscatho group of south cornwall the mafic component of the gneiss includes members group 1 which are weakly enriched in light ree have minor negative ta nb p and ti anomalies in extended trace element plots and display primitive time corrected 143 nd 144 nd and 87 sr 86 sr values and others group 2 which are more strongly enriched in all incompatible trace elements exhibit more prominent negative ta nb p and ti anomalies and have isotopic ratios intermediate between group 1 mafic components and the associated felsic gneiss group 2 represents mixtures of group 1 and granitic melts whereas group 1 rocks are comparable to emorb and were probably generated through partial melting of a weakly enriched mantle source emplacement of two commingled magmas into the base of the lizard ophiolite one representing the products of crustal anatexis implies that the ophiolite was removed from its oceanic setting and was in the process of obduction in the givetian

comment on coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya by akhtar et al 2017 article in press

faunal evidence for oceanic separations in the palaeozoic of britain the faunal criteria for the recognition of the relative separation of old continents are 1 the contrast between shallow not deep water faunas off opposite shorelines 2 the recognition of deeper water facies surrounding the edges of continents and 3 the recognition of the disposition of ancient climatic belts these criteria are defined and used to assess the relative position of the various parts of what is now britain in the palaeozoic the iapetus ocean is well characterized by faunal differences from the cambrian until the lower ordovician but from caradoc times onwards these differences dwindle until by the latest silurian only the distribution of the ostracods separates the two sides of the ocean on faunal grounds in the early ordovician s british faunas are comparable with those from bohemia france and elsewhere to the s indicating connection with gondwanaland and these faunas differ from those in the baltic area a distribution which we attribute to a true ocean tornquist9s sea between n and s europe tornquist9s sea probably closed in the upper ordovician and from ashgill times onwards the s british and baltic faunas remained similar during the middle and late silurian there is evidence of increasing faunal distinction between britain the baltic area and north america on the one hand and southern europe and gondwanaland on the other indicating an opening rheic ocean which appears to have persisted until late carboniferous times

careon ophiolite nw spain suprasubduction zone setting for the youngest rheic ocean floor the careon ophiolite galicia nw iberian massif shows lithological and geochemical features suggestive of an origin in a suprasubduction zone setting as with other devonian ophiolites in the european variscan belt it was generated within a contracting rheic ocean this setting and the general absence of large silurian devonian volcanic arcs on both of the rheic ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north this subduction removed the older normal n mid oceanic ridge basalt morb oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere the careon ophiolite is a key element in understanding the evolution of the rheic ocean which was the main oceanic domain that closed during the paleozoic convergence of gondwana and laurussia preceding the assembly of pangea

seismic slip deficit in the kashmir himalaya from gps observations 1 gps measurements in kashmir himalaya reveal range normal convergence of 11 1 mm yr with dextral shear of 5 1 mm yr the transition from a fully locked 170 km wide decollement to the unrestrained descending indian plate occurs at 25 km depth over an 23 km wide transition zone the convergence rate is consistent with the lower bounds of geological estimates for the main frontal thrust riasi and balapora fault systems on which no surface slip has been reported in the past millennium of the 14 damaging kashmir earthquakes since 1123 none may have exceeded mw 7 6 therefore either a seismic moment deficit equivalent to a mw 8 7 earthquake exists or the historical earthquake magnitudes have been underestimated alternatively these earthquakes have occurred on reverse faults in the kashmir valley and the decollement has been recently inactive although this can reconcile the inferred and theoretical moment release it is quantitatively inconsistent with observed fault slip in kashmir

comparative evolution of the iapetus and rheic oceans a north america perspective abstract differences in the origin and evolution of the iapetan and rheic oceans profoundly affected the development of the ouachitan appalachian variscan orogen the iapetus ocean was initiated in the late neoproterozoic early cambrian by the separation of large continental landmasses laurentia baltica gondwana whereas the rheic ocean originated in the late cambrian early ordovician as the result of the separation of several ribbon continents collectively termed peri gondwanan terranes from the northern margin of gondwana compared to the classic passive margin developed along the laurentian margin of iapetus passive margin successions to the rheic ocean are more limited in extent during convergence both margins of the iapetus ocean developed western pacific type arc back arc systems whereas subduction of the rheic ocean was primarily directed beneath laurentia and was andean in style closure of iapetus involved a number of arc back arc accretionary events and had occurred by the middle silurian as a result of laurentia baltica collision to form laurussia and the accretion of the peri gondwanan terranes rheic ocean closure occurred in the carboniferous by way of continent continent collision between laurussia and gondwana with gondwana on the lower plate within iapetus the formation of ophiolites occurred early in the orogenic cycle and was followed soon after by obduction hp lt metamorphism and foreland directed thrusting that is intimately related to accretionary events these features dominate the northern appalachian orogen where ht lp metamorphism is attributed to post accretionary slab break off events in contrast hp lt metamorphism within the rheic ocean reflects a type subduction during laurussia gondwana collision and is rapidly succeeded by ht lp metamorphism attributed to orogenic collapse ophiolites are rare and were formed either very early early ordovician or very late devonian carboniferous in the evolution of the ocean the early ordovician ophiolites were not obducted until the carboniferous at least 100 million years after their protoliths were formed rheic ocean closure resulted in the formation of large scale bivergent structures within the orogen with symmetry changing on either side of the rheic suture comparison of the evolution of the iapetus and rheic oceans suggests that differences in rift configuration passive margin development and subduction zone geometry within the two oceans profoundly influenced the subsequent style of orogenesis within the ouachita appalachian variscan orogen

coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya abstract this paper presents a new interpretation of overlapping differential deformations and likely causes of the structural heterogeneity within the kashmir basin representing a prominent and distinctive strain feature in nw himalaya the broad geomorphic expression of the kashmir as an elongated nw se trending sedimentary trough is inconsistent with general compression governing structural trend and deformation pattern of 2500 km long himalayan frontal thrust zone in addition to the general extensional geometry there are prominent anomalous deformation features at varied spatial scales in the basins that imply dominance of extensional tectonics we infer that contrary to the overall compression dominant mechanism of the himalaya the apparent extensional geometry of the basin connotes orogen parallel extensional deformation pull apart triggered by oblique convergence in the nw himalaya moreover we construe that the comparatively younger contractile positive features in form of the geomorphic convexity push up accompanied by out of sequence reverse faulting balapur fault hereafter called as bf within the basin which is generally believed to be associated with the uplift along ne dipping southern thrust complex mbt mct possibly resulted due to the tectonic reversal positive inversion the presence of the compressional features within the locally predominant extensional setting is suggestive of the basin s hybrid character where variable tectonic regimes earlier extension and subsequent compression seem to be coexistent

response to the commentary by shah a a 2015 and further evidence supporting the dextral strike slip pull apart evolution of the kashmir basin along the central kashmir fault ckf abstract this research article provides added evidence in support of the already presented tectonic evolution model of the kashmir basin by alam et al 2015 which states that the local dextral strike slip structure embedded with the southern forefront thrust system mbt mct resulted in the development of the nnw sse oriented elliptical pull apart sedimentary trough kashmir basin simultaneously we respond to the argument of shah 2015 wherein the author expresses his concern about the tectonic evolution model proposed by alam et al 2015 the commentator shah 2015 merely based on assumptions 1 perfectly planar geometry of the central kashmir fault ckf 2 pure strike slip along the ckf and misinterpretations of the data tectonic geologic structural seismic geodetic and geomorphic makes extraneous criticism throughout the length of his commentary by referring copied text figures however alam et al 2015 projected the ckf as noticeably curvilinear major exhibiting complex strike slip tectonics dextral lateral and vertical motion moreover contradictory to the claim of shah 2015 the tectonic geologic structural seismic geodetic and geomorphic data is in complete agreement with the model proposed by alam et al 2015 hence in addition to complimentary evidence for the dextral strike slip pull apart evolution of the kashmir basin a detailed response is provided to the commentary of shah 2015

rheic ocean ophiolitic remnants in southern iberia questioned by shrimp u pb zircon ages on the beja acebuches amphibolites 1 the rheic ocean was a major oceanic domain between avalonia and gondwana in ordovician silurian times most of the paleozoic plate reconstructions assume that the rheic ocean suture lies within southern iberia coinciding with the contact between the south portuguese zone and the ossa morena zone this paper reports four sensitive high resolution ion micro probe shrimp u pb zircon ages from mid ocean ridge basalt morb featured rocks of the beja acebuches amphibolite unit which crops out along the boundary between the ossa morena and the south portuguese zone and is considered its most conspicuous suture unit the obtained ages range from 332 3 to 340 4 ma corresponding to the crystallization of the mafic protoliths these early carboniferous ages for the beja acebuches amphibolites imply that this unit can no longer be viewed as an ophiolite belonging to the rheic ocean suture since this oceanic domain was presumably closed in devonian times tectonic reconstructions joining in a single suture line the beja acebuches amphibolite unit in southern iberia to either the devonian lizard ophiolite in southern england or the root zone of the devonian ordovician ophiolitic units in northwest iberia must be therefore reconsidered because of the age difference we interpret the beja acebuches amphibolite unit to represent a narrow and very ephemeral realm of oceanic like crust that opened in early carboniferous times after total consumption of the rheic ocean we suggest that a mantle plume underneath southern iberia in early carboniferous times is the most plausible large scale geodynamic scenario for the formation of these morb featured rocks

intermontane basin development in the past 4 myr in the north west himalaya the through the combined use of magnetic polarity stratigraphy with fission track dating of volcanic ashes a new chronology spanning 4 myr has been developed for the intermontane basin of kashmir in the northwestern himalaya

tectonic imprints of landscape evolution in the bhilangana and mandakini basin garhwal himalaya india a geospatial approach abstract torrential rains landslides and seismic activity are the common factors that are causing unprecedented damage to life property and infrastructure in mandakini and bhilangana basins of garhwal himalaya owing to such conditions we demonstrate the feedback this landscape in garhwal himalaya in response to episodic tectonic uplift and monsoon precipitation we calculated conventional geomorphic parameters to access the tectonic deformation across the major thrusts and faults we further analyzed the normalized steepness index ksn chi and knickpoints along the longitudinal course of rivers additionally the study attributed to active nature of chail ramgarh thrust along the balganga valley as envisaged by five levels of unpaired fluvial terraces entrenched stream course river ponding active and stabilized landslide deposits etc moreover the flooding during the heavy rainfall events induced river toe cutting makes an effect on settlement over fluvial deposits therefore we suggested that the highly dissected and tilted basins with deep v shaped valleys and ongoing seismicity also fabricates the region more vulnerable for hazards which threaten the human lives

integrated geophysical techniques for subsurface imaging of active deformation across the himalayan frontal thrust in singhauli kala amb india abstract non invasive geophysical techniques employed across the himalayan frontal thrust hft at singhauli in the north western frontal himalaya to understand shallow subsurface geological structures and their nature in the context of active tectonics the combination of high resolution ground penetrating radar gpr electrical resistivity tomography ert and multi channel analysis of surface waves masw techniques with the different acquisition parameters found to be beneficial in gaining high resolution images of shallow subsurface geological structures the contact zone of resistivity obtained between 134 m suggests the juxtaposition of dissimilar lithological units explained as two faults dipping to the northwest related to the hft the average separation between fault 0 and fault i is 12m which in general agreement with the trench excavation survey the gpr radargram over a length of 45m show offset reflectors at a horizontal distance of 12 15m close to the active deformation zone the horizontal reflectors abruptly truncate across two northerly dipping planes the 2d vs section masw1 2 exhibited dipping attitude of the litho units with different velocity zones in the northeast direction which are also consistent with the local geological setting prominent liquefaction feature identified in the ert section specifically with the 1 and 1 5m electrode spacing show explicit expression of its existence due to contrasting resistivity ranging between 100 and 450 m a strong correlation has been established between the field based geological observations carried out earlier in this area through a trench excavation survey with the present work using geophysical techniques the integrated approach found to be highly beneficial in those areas where contrasting sub lithological units exist in terms of their physical properties this study argues for judicious use of the ert gpr and masw techniques to delineate shallow subsurface geology across various active faults in the himalayan terrain to comprehend the active deformation related to large magnitude paleoearthquakes and earthquake hazard assessment

thermal and tectonic evolution of the kashmir basin vis a vis petroleum prospects abstract investigation of the formation of peri atlantic basins and evaluation of the mechanism of lithospheric break up provide a guide for understanding the pre collision history of the himalayan region as an example the kashmir basin is discussed the present form of the kashmir basin is that of a graben bounded by two horsts the stratigraphic succession shows a complete record of shallow marine sedimentation from the cambrian to middle carboniferous in the upper carboniferous the depositional environment changed to continental type accompanied by large scale erosion especially on the western side and the deposition of agglomeratic slate and then in the lower permian by the panjal trap volcanism whilst the eastern side after this continental phase again subsided and received marine sediments until the end of the triassic the western side experienced repeated uplift and volcanism gravity and seismic data indicate the presence of high density material and a shallow depth of the moho beneath the basin and also the eruption of the panjal trap lava along two deep seated faults f1 and f2 on the flanking horsts with dips towards the present indus tsangpo suture after the upper carboniferous a continental phase is noted all over the himalaya this is thought to mark the initiation of the break up of the indian plate from the siberian cathysian block which finally occurred at the end of the triassic based on the stratigraphie and tectonic set up of kashmir in particular and the whole himalaya in general a model is presented to explain the formation of the kashmir basin good compatibility of the model with observed tectonic and stratigraphie aspects of kashmir and the whole himalaya is found the geothermal history of different strata in this basin indicates promising conditions for hydrocarbon generation a few of the more promising strata are identified for intensive investigations

active tectonics in the lesser caucasus coexistence of compressive and extensional structures detailed spot image analysis which completed field data and a microseismicity study was done on the central caucasian mountain belt georgia armenia and eastern turkey north of the front of the arabian collision in order to clarify the relationships between compression extension and volcanism in fact this region is characterized by relatively complex active tectonics associating both n s compressive e w thrusts and folds and e w extensional n s normal faults and dikes structures accompanied by considerable neogene to quaternary volcanism and ne sw left lateral and nw se right lateral strike slip faults these different structures are all intricately imbricated and can be observed at different scales the general layout implies an important variation in the stress state for instance this passes from a n s compression in the spitak earthquake fault zone to an e w extension at the aboul samsar volcanic axis these results agree well with the n s convergence between arabia and eurasia and the e w lateral expulsion of the anatolian and iranian blocks a detailed cartographic network of active structures was drawn and their kinematic relationships were specified in places recent offsets on strike slip faults were estimated at about 500 to 1000 m suitable sites for future determination of fault velocity displacements were also selected this study shows that some strike slip faults behave partly like faults which transform the e w extension of the n s striking normal faults into a n s compression along the e w thrusts one of the characteristics of this region is the continuous important volcanic activity at least from the jurassic until now this persistence evidences a lithospheric thinning which remained in spite of the recent arabian eurasian collision because of the e w extension linked to the opposite lateral expulsion of the anatolian and iranian blocks this geodynamic evolution can explain the juxtaposition and superimposition of volcanic structures and thrusts in a general compressive context

highly depleted oceanic lithosphere in the rheic ocean implications for paleozoic plate reconstructions the rheic ocean formed at ca 500 ma when several peri gondwanan terranes e g avalonia and carolinia drifted from the northern margin of gondwana and were consumed during the late carboniferous collision between laurussia and gondwana a key event in the formation of pangea several mafic complexes ranging in age from ca 400 330 ma preserve many of the lithotectonic and or chemical characteristics of ophiolites they are characterized by anomalously high end values that are typically either between or above the widely accepted model depleted mantle curves these data indicate derivation from a highly depleted hd mantle and imply that i the mantle source of these complexes displays time integrated depletion in nd relative to sm and ii depletion is the result of an earlier melting event in the mantle from which basalt was extracted the extent of mantle depletion indicates that this melting event occurred in the neoproterozoic possibly up to 500 million years before the rheic ocean formed if so the mantle lithosphere that gave rise to the rheic ocean mafic complexes must have been captured from an adjacent older oceanic tract the transfer of this captured lithosphere to the upper plate enabled it to become preferentially preserved possible mesozoic cenozoic analogues include the capture of the caribbean plate or the scotia plate from the pacific to the atlantic oceanic realm our model implies that virtually all of the oceanic lithosphere generated during the opening phase of the rheic ocean was consumed by subduction during laurentia gondwana convergence

comment on earthquake geology of kashmir basin and its implications for future large earthquakes by shah 2013 kashmir basin fault and its tectonic significance in nw himalaya jammu and kashmir india by shah 2015 kbf without any additional structural kinematic geologic or geomorphic data in support therefore this comment aims to clarify the confusions created by shah 2013 2015a and it is in this context we provide a review of the bf no active faults out of sequence thrusts tectonic discontinuities were known north of mbt or mct in the kashmir basin except a few nw se suspected fault segments with the collective length of 45 km along nw quaternary deposits mapped from aerial photographs and corona satellite images nakata et al 1991 and a south facing scarp delineated as a possible active fault using landsat satellite images yeats et al 1992 subsequent investigations revealed that the southwest facing scarp yeats et al 1992 is a high angle thrust fault reverse with an average northeast 60 dip and nw se strike length of 40 km ahmad 2010 madden et al 2010 2011 ahmad and bhat 2012 figs 1 2 3 the structure was named as bf because of its exposure on the left bank of rambiara river tributary of jhelum river at balapur village n 33 75 e 74 83 in shupiyan district of jammu and kashmir state india ahmad 2010 ahmad and bhat 2012 with an unknown depth the bf cuts across nw se unconsolidated karewa deposits plio pleistocene soft sediments devoid of gouge and breccia however rotated gravels at the fault contact have been marked ahmad and bhat 2012 stratigraphic relations show that the fault has uplifted the lower pleistocene methawoin member sand sandy clay clay silt and lignite bands of the lower karewa and juxtaposed it to the middle pleistocene shupiyan member gravels mostly composed of panjal trap fragments of the upper karewa bhatt 1989 subsequently the bf was firmly established by paleoseismic investigation and field data madden et al 2010 2011 ahmad et al 2013 ahmad 2014 an optically stimulated luminescence osl sample collected from fluvial deposits a few meters above the lower strath gives comment

the rb sr isochron age of the kennack gneiss and its bearing on the age of the lizard complex cornwall an acid vein from a borehole in the kennack gneiss has given a whole rock rb sr isochron age of 369 12 ma this is interpreted as a metamorphic age recording the time of emplacement of the lizard complex this emplacement in late devonian times was part of an early phase of the hercynian orogeny which also affected the gramscatho 9series9 of s cornwall

the structure of sw cornwall and its bearing on the emplacement of the lizard complex six phases of deformation can be recognized in the devonian metasediments to the n of the lizard complex the first two phases d 1 d 2 show a variety of orientations and styles but with a general n or nw vergence these phases while respresenting regional deformation events are considerably modified by the emplacement of the lizard complex there is a general increase in intensity of both d 1 and d 2 structures towards the lizard boundary this is accompanied by variation in the orientation of both early phases of deformation leading to a variety of interference patterns domains of oblique f 1 folds with axes trending n s are developed in the rocks immediately to the ne and nw of the lizard and are considered to have formed by differential nnw directed thrusting of slabs of the complex during the early regional deformation d 2 produced discrete shear zones ahead and below the lizard rocks and may have resulted from the gravitational collapse of the d 1 nappes the d 3 deformation post dates the lizard emplacement being related to the cornubian batholith subsequent phases represent essentially post batholith and hence post lizard emplacement deformation