isotopic constraints on the structural relationships between the lesser himalayan series and the high himalayan crystalline series garhwal himalaya nd and sr isotope systematics may provide important constraints on the location of major thrust systems that separate lithologically similar sedimentary sequences the potential of the technique is illustrated by this isotopic study of the main central thrust system of the himalaya nd isotope data from the garhwal himalaya indicate that metasedimentary rocks from the vaikrita group nd 14 to 19 correlate closely with those from the high himalayan crystalline series which constitutes the hanging wall lithologies of the main central thrust in contrast metasedimentary rocks from the munsiari group nd 23 to 28 show marked similarities to the lesser himalayan series in the footwall of the main central thrust sr isotopes support the correlations in that the vaikrita group shows partial reequilibration at 500 ma whereas the munsiari group has not undergone sr isotope homogenization since 1800 ma thus the vaikrita thrust that juxtaposes these two formations is recognized as the main central thrust in garhwal himalaya the thrust coincides approximately with the location of the kyanite isograd confirming that inverted metamorphism is characteristic of both hanging wall and footwall of the main central thrust along the tons thrust known locally as the srinagar thrust 50 km south of the main central thrust low grade quartzarenites with nd sr isotope and trace element characteristics typical of lesser himalayan formations have been emplaced on phyllites and siltstones with geochemical characteristics of the high himalayan crystalline series the field relationships most probably result from out of sequence thrusting in which lesser himalayan series rocks to the north were emplaced over low grade equivalents of the high himalayan crystalline series preserved in the external part of the orogen this study establishes the value of isotope data for lithostratigraphic correlations within orogenic belts

geomorphic response to seasonal variations in rainfall in the southwest united states the interaction of the north american monsoon with watershed hydrology and landscape response is evaluated by observing geomorphic characteristics of hillslopes hydrology and stream channels in two mountain ranges with contrasting intensity of precipitation the study compares watersheds in the hualapai and santa catalina mountains in arizona which are similar in lithology elevation tectonic setting vegetation and annual precipitation but differ in the proportion of precipitation received in summer thunderstorms the hualapai mountains receive most of their precipitation in winter whereas rainfall in the santa catalina mountains occurs mostly in summer drainages in the santa catalinas are more variable in local relief and exhibit much more exposed bedrock and higher drainage density the trunk channel of a major drainage in the santa catalina mountains has measured discharges several orders of magnitude greater than a channel draining a comparable area in the hualapai mountains the alluvial segment of the channel in the santa catalina piedmont additionally displays greater concavity smaller width to depth ratios and a larger caliber of bed material in contrast to conventional interpretation summer monsoonal precipitation is not primarily responsible for generating most of the discharges that modify channels in large scale drainages in the monsoonal climate regime of the santa catalinas small basins flood most often in summer whereas larger drainages exhibit peak discharges in response to low intensity winter precipitation we attribute the paradoxical discharge response of larger drainages to the small spatial scale of summer thunderstorms which fail to deliver enough precipitation to generate floods in these larger basins but do prime hillslopes by stripping colluvium and lowering hillslope infiltration rates making the large drainages more responsive to areally extensive winter storms

estimation of strain distribution using gps measurements in the kumaun region of lesser himalaya abstract the continuous process of continent continent collision between the indian and the eurasian plates has led to the formation of the himalayan range and continuously caused earthquakes in the region large earthquakes with magnitudes of 8 and above occur in this region infrequently releasing the elastic strain accumulated over years around the plate boundary geodetic measurements can help estimate the strain distribution along the fault system these measurements provide information on active deformations and associated potential seismic hazards along the himalayan arc in order to understand the present deformation around the plate boundary we collected gps data during three campaigns in the years of 2005 2007 at 16 sites in the kumaun region of the lesser himalaya horizontal velocity vectors estimated in itrf2000 are found to be in the range of 41 50 mm yr with an uncertainty level of the order of 1 mm yr the velocity field indicates that the present convergence of around 15 mm yr takes place in the kumaun himalaya further we estimate the strain components in the study area for understanding the currently active tectonic process in the region the estimated dilatational strain indicates that the northern part near the main central thrust mct is more compressional than the southern part maximum shear strain is mostly accommodated in the northern part too the maximum shear and dilatational strain rates are about 1 0 and 0 5 strain yr it is seen that the distribution of high shear strain spatially correlates with seismicity the maximum of extensional and compressional strains due to the force acting along the main central thrust mct in the nw se direction are found to be 0 4 and 0 1 strain yr respectively the maximum shear strain in the northern part of the himalaya appears to be associated with the convergence of the region proposed by other geophysical studies

neotectonically triggered instability around the palaeolake regime in central kumaun himalaya india mass wasting often results from the combined effect of tectonic and climate processes it has not only resulted in human casualties on large scale but has also ruined agricultural land and disrupted hydro power projects and other governmental as well as private property despite the belief that prevention is inevitably better than cure decrease in future hazards requires proper dissemination of knowledge to the himalayan inhabitants considering this we investigated a part of kumaun himalaya to understand the cause of cloud burst induced mass movements along the saryu river that took place on 18th august 2010 and subsequently on 12 14th september 2012 a number of quaternary faults e g dulam fault df dulam gadhera fault dgf and vongarh gason fault vgf in the zone of a major thrust berinag thrust in the studied sector are invariably active as evident by various geomorphic features e g saw cutting of host rocks immature topography deflecting river courses ponding of ancient drainage development of cascades formation of unpaired fluvial terraces and series of triangular fault facets the fragile lithology deep v shaped valleys accelerating erosion and incision with higher uplift due to tectonic upheaval along the active faults are also responsible for rainfall induced catastrophes in the region additionally morphometric analysis reveals that the saryu basin is elongated and tilted further the tectonic tilting and moderate to coarse drainage density may possibly be responsible for quicker runoff amplified erosion and subsequently increased flooding around the study area we infer that the area is not only controlled by topography but may also have been affected by the hydraulic factors such as climate in addition the drainage is dominated mostly by first order streams which seem to be indicative of higher chances of flooding as most of the water is concentrated in a single channel during monsoon season we believe that the similar studies done in the other sectors will be helpful in reducing not only the huge loss of life but may also help in protecting ongoing and huge hydropower and other developmental projects in this newly born state

formation of lava tubes and extensive flow field during the 1991 1993 eruption of mount etna detailed mapping during the 1991 1993 eruption of mount etna has shown that there is a relationship between tumuli ephemeral vents lava tubes and their parent lava flows during this eruption many tubes formed in stationary inflated a a lava flows ephemeral vents at the fronts of these stationary flows and above lava tubes fed secondary lava flows many of which subsequently developed new tubes the resulting complex network of tubes ephemeral vents and secondary flows was responsible for most of the widening thickening and lengthening of the 1991 1993 etna lava flow field the supply of relatively uncooled lava via tubes to distal parts of this flow field allowed lava to flow 3 km farther from the vent than the longest channel fed lava flow our observations suggest that lava tubes play a more important role in the formation of extensive a a flow fields on etna than has previously been recognized

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

toothpaste lava characteristics and origin of a lava structural type transitional between pahoehoe and aa toothpaste lava an important basalt structural type which illustrates the transition from pahoehoe to aa is particularly well displayed on the 1960 kapoho lava of kilauea volcano its transitional features stem from a viscosity higher than that of pahoehoe and a rate of flow slower than that of aa viscosity can be quantified by the limited settling of olivine phenocrysts and rate of flow by field observations related to the low angle slope on which the lava flowed much can be learned about the viscosity rheologic condition and flow velocity of lavas long after solidification by analyses of their structural characteristics and it is possible to make at least a semiquantitative assessment of the numerical values of these parameters

the roza member columbia river basalt group a gigantic pahoehoe lava flow field formed by endogenous processes we present studies on the physical volcanology of the 15 ma roza member of the wanapum formation in the columbia river basalt group the roza member represents a compound pahoehoe flood basalt lava flow field with an area of 40 300 km 2 and a volume of 1300 km 3 it consists of 4 major lava flows each composed of numerous decimeter to kilometer long pahoehoe lobes roza lavas feature a wide range of pahoehoe surface structures such as lava rise plateaus tumuli and surface breakouts and we illustrate that the lava morphology is inconsistent with previous proposals of rapid emplacement for these lavas an integral component of the roza flow field is the sheet lobe with internal structures identical to those of inflated pahoehoe sheet lobes from hawaii and iceland both at the same scale and at much larger scales we identify a three part division of the sheet lobes into basal crust lava core and lava crust which are interpreted as the equivalent to the bottom crust the liquid lava core and the surface crust of an active inflating pahoehoe lobe the upper lava crust grows continuously during lava emplacement and its growth rate can be approximated by conductive cooling this relationship is used to calculate the emplacement time for individual roza sheet lobes and to derive a first order estimate on the duration of the roza eruption the results indicate that the emplacement of individual roza lobes lasted for months to years and that the lava flow field was constructed over a period of at least 14 years we propose that the roza flows achieved great areal dimensions and thicknesses by inflation and endogenous growth as the lava flowed from vent to flow front it traveled under an insulating crust which maintained cooling rates of 0 1 c km and allowed for efficient transport of lava over distances up to 300 km

the occurrence vesiculation and solidification of dense blue glassy pahoehoe dense blue glassy pahoehoe occurs on the lower kalapana flow field of hawaii as limited breakouts at the base of tumuli and pressure rises or in localized depressions dense blue glassy pahoehoe differs from the more abundant spongy pahoehoe in that it has a distinctive silvery blue color a poorly vesiculated glassy outer selvage and lower extrusion temperature 10 c cooler the color of blue glassy pahoehoe may be attributed to the concentration of iron and magnesium at the surface whereas the golden color of the spongy pahoehoe is possibly the result of fluorine enrichment the outer margin of the dense pahoehoe consists of three layers developed in response to an increased cooling rate toward the surface the outer glass selvage is less than 1 cm thick containing minor amounts of chromite olivine plagioclase and augite inside the glassy rind is a 5 mm thick transition zone characterized by increasing numbers and sizes of quenched plagioclase crystals and augite clusters the interior of dense blue glassy pahoehoe is largely crystalline crystal size distribution csd theory demonstrates that the formation and textures of plagioclase pyroxene and oxides are related to the cooling rates growth rates g and nucleation rates j present in each layer of the dense pahoehoe in contrast to the outer selvage the crystalline interior typically contains numerous large coalesced vesicles as compared to the evenly vesiculated spongy pahoehoe the enigmatic contrast between the poorly vesicular outer glassy selvage and the vesicular interior has been attributed to both lower and higher vapor contents of the dense pahoehoe the higher density lower extrusion temperatures degassed outer glassy selvage well developed crystalline interior and fluorine deficient surface of dense blue glassy as compared to spongy pahoehoe indicate that blue glassy pahoehoe was stagnant long enough to exsolve considerable vapor in the lava tube system before extrusion

evolution of the himalaya abstract the compression and attendant deformation of a thick and vast sedimentary prism formed since early riphean times on the northern continental margin of the indian craton gave rise to the himalaya mountains as a result of convergence and collision of the indian and asian plates the oceanic trench sediments tectonically implanted with sea floor material and intimately associated with calc al kaline volcanics in the narrow sindhu tsangpo belt extending from kohistan through dras leh darchen mansarovar to shigatse and beyond represent the subduction island arc complex which developed south of the dynamic southern margin of the asian continent and was welded to the colliding indian plate during the late eocene to oligocene period this complex is fringed to the north by a wide zone of andean type granitic bodies the evolution of the himalayan orogen is closely connected with the development of the present day andaman nicobar indonesia island arc subduction system in the southeast and the makran ranges oman trench in the southwest the evolution of the himalaya was accomplished in four major phases of tectonic upheaval during the late cretaceous to palaeocene karakoram phase late eocene to oligocene malla johar phase middle miocene to pontian sirmurian phase and late pliocene to middle pleistocene siwalik phase while the karakoram phase marks the convergence of continents and the malla johar phase represents the collision and subduction it was during the sirmurian upheaval that the main tectonic features developed and the himalaya acquired its distinctive structural complexion

river profiles along the himalayan arc as indicators of active tectonics abstract longitudinal profiles along sixteen major transverse himalayan rivers add important constraints to models of active continental subduction and its evolution these profiles are characterized by a zone of relatively high gradient that cannot be associated with differential resistence to erosion in all cases the base of the zone of increased gradients correlates with 1 the topographic front between the lesser and high himalayas 2 the narrow belt of intermediate magnitude thrust earthquakes 3 the main central thrust zone mct these features define a small circle in the central portion of the himalayan arc these correlations suggest that the discontinuity in the river profiles and the other features are controlled by a major tectonic boundary between the rising high himalayas and the lesser himalayas no sharp increases in gradient are observed near the main boundary thrust mbt except on a few rivers such as the jhelum or kundar where the mbt lies close to both the mct and the seismic belt thus it is unlikely that the mbt is a major tectonic boundary the diversion of river courses along the mbt and around anticlines in the sub himalayas has probably been caused by aggradation near the rosion deposition boundary upstream of uplifts in the mahabharat range and sub himalayas a parallel is drawn between the himalayas and new guinea based on the hypothesis that continent arc collision of the type occurring in northern australia preceded continent continent collision in the himalayas the present sedimentary tectonic phase in new guinea resembles the subathu paleocene eocene phase in the himalayas incipient counterparts of the major himalayan structures including the mct and the mbt are recognized in new guinea the drainage patterns in the himalayas and in new guinea bear a similar relation to major structures this suggests that 1 the tectonic evolution of the himalayas has been rather uniform since early stages of collision and 2 the himalayan drainage was also formed at these early stages and is therefore antecedent to the rise of the high himalayas

structural evolution of the tethyan sedimentary sequence in the annapurna area central nepal himalaya the tethyan sedimentary sequence of central nepal has been affected by three phases of folding d1 d 2 and d4 with contrasting vergence interspersed by two major extensional events d3 and d5 the north verging second phase folds f2 are the dominant deformation features preserved in the studied area these d2 structures indicate a vertical structural zonation that is interpreted to mark a preserved d2 strain gradient increasing with depth to a presumed north verging decollement plane at an approximate depth of 10 km palinspastic bed length restoration of the sequence implies a minimum 43 shortening and a minimum 150 vertical thickening due to d2 deformation the d4 event overprints the d3 annapurna detachment and manifests itself as post peak metamorphic south verging kink folds and spaced crenulation cleavage in the structurally lowest level observed d4 is associated with thrust sense meter scale fault zones the youngest extensional event d5 marks the initiation and eventual southward propagation of the thakkhola graben a newly named northeast dipping normal fault the lupra fault is described in the early stages of extension the lupra fault may have acted as a southern termination of the graben system dropping down cretaceous rocks and high level structural features in its hanging wall it is suggested that as the extension progressed southward the lupra fault was itself down faulted in the graben and the extent of the thakkhola graben reached the present position of the annapurna detachment q 2003 elsevier ltd all rights reserved

active tectonics in the sierra nevada betic cordillera se spain insights from geomorphic indexes and drainage pattern analysis article i nfo the sierra nevada of the central betic cordillera is a 3000 m high mountain range surrounded by neogene quaternary sedimentary basins having been uplifted since late miocene times the southern and western mountain fronts of the sierra nevada are fault bounded while the northern one is an unconformity between the neogene quaternary sediments of the guadix baza basin and the metamorphic rocks of the nevado filabride complex we have carried out a geomorphic study by examining drainage patterns and characteristics of mountain fronts in order to reveal areal variations and styles of rock uplift mountain front sinuosity smf area altitude relations hypsometric curves and valley floor entrenchment differ significantly between the northern western and southern mountain fronts the lack of important faults along the northern sierra nevada mountain front together with the elevated topographic position of the guadix baza basin average altitude is around 1100 m points to similar uplift of both geomorphic units sierra and basin in a single large scale crustal block the asymmetry factors show systematic asymmetries at both sides of the lanjaron river probably due to the presence of an active nne ssw oriented antiform in the western sierra nevada finally river profiles indicate maximal river entrenchment in the western part of the sierra nevada probably related to the uplift of the footwall of the padul niguelas fault system therefore our geomorphic analysis suggests that the western part of the sierra nevada is tectonically active by means of a combination of normal faults along the mountain front and nne ssw oriented active folds which in turn likely have a gravitational origin related to the exhumation of the footwall of the normal fault system

tectonic footprints and landscape evaluation along kulur river valley kumaun lesser himalaya india abstract tectonic reactivation along the major boundary thrusts and subsidiary thrust faults in the himalaya during the quaternary period has resulted in the rejuvenation of the landforms considering the role of neotectonic activity in the hazardous kumaun region we aim to study the neotectonically formed landscape along the kulur river valley a non glacier fed tributary of the saryu river in the zone of the berinag thrust bt the field evidences encompassing a variety of geomorphic indicators e g unpaired fluvial terraces palaeo river channels alluvial fans active and stabilized landslides lineaments waterfalls alignment of springs deeply dissected hills straight meandering course of rivers streams v shaped valleys triangular fault facets and water logged river ponding along with integrated values of eight morphometric parameters and stream steepness index ks indices characterize the modification of landscape in the kulur river valley the computed morphometric parameters in the kulur river drainage and its tributaries show that the basin has been tilted and uplifted forming v shaped valleys along with deformed and disequilibrium longitudinal profile thereof suggesting it to be controlled by lithology and tectonics based on the response of active tectonics in form of geomorphic features and quantitative measurements of river channels the entire basin has been divided into three segments in which the northern and southern segments are active compared to the middle sector a possible nne ssw trending lineament fault running parallel to the kulur river has been observed in the upper catchment and is characterized by fluvial terraces river ponding and deflection and offsetting of drainage with rectangular pattern etc this may have given rise to the widening and straightening of river courses which provide the favorable room for river ponding resulting in deposition of about 2 m thick lacustrine mud deposit

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

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

p type and s type pahoehoe a study of vesicle distribution patterns in hawaiian lava flows abstract two main types of hawaiian pahoehoe lava p type pipe vesicle bearing and s type spongy are characterized their origin is inferred from features of the vesicle sizes and abundances particularly in their chilled margins which record frozen in the vesicle population at the time and place of solidification s type margins are distinctly more vesicular than p type porosity and vesicle size and range in s type margins are highest at the vent vesicle size reaches a minimum in medial areas and then increases while porosity decreases onto the flatter ground of the coastal terrace the vesicles are inferred to be part of the complement of bubbles that was present at the vent modified by loss and coalescence during travel in lava tubes the minimum porosity occurs on the coastal terrace and is the result of degassing during a longer residence time in lava tubes there the systematically lower porosity of p type margins than s type is attributed to a still longer residence allowing more time for bubble coalescence and loss p type pahoehoe is common only on flatter ground such as the coastal terrace it is found where tumuli and lava rises are widespread and where extensive networks of lava expansion clefts occur through which lava moving below the surface crust can lose gas without significant cooling additionally p type pahoehoe shows clear evidence that a strong inward movement and growth of bubbles took place from the outermost selvage into an inner selvage concentration zone a mechanism that might cause this inward movement is surface tension operating against deforming forces in the steep viscosity gradient of flow margins causing down gradient bubble translation inward movement does not usually occur in the upper crust of thick 2 m flow units because of the absence of strong deforming forces in the shallow velocity gradient there many of the larger bubbles that entered the inner selvage rose buoyantly to form pipe vesicles p type pahoehoe is characterized by sampled profiles across 20 flow units continued gas loss through surface clefts caused a general overall reduction in vesicle content within each flow unit to less than that in the upper crust and the pronounced depletion of vesicles from its lower half is attributed to scavenging by ascending pipe bubbles in a small proportion of flow units overall gas loss was small and a median gas blister fed by pipe bubbles developed instead

quantitative analysis of relative tectonic activity in the sarvestan area central zagros iran neotectonics is a major factor controlling landform development in tectonically active regions and it has significantly affected fluvial systems and mountain front landscapes in the sarvestan area of the central zagros iran the area is located along the simply folded belt of the zagros and is an outcome of the sw ne oriented tectonic conversion that initiated in the late cretaceous and strengthened during the early miocene due to the collision of the arabian and eurasian plates to assess tectonic activities in the area we analyzed geomorphic indices the stream gradient index sl drainage basin asymmetry af hypsometric integral hi valley floor width valley height ratio vf drainage basin shape bs and mountain front sinuosity j these indices were combined to yield the relative active tectonics index iat using geographic information systems gis based on iat values the study area was divided into four parts class 1 very high relative tectonic activity 1 0 in area class 2 high 20 0 class 3 moderate 67 0 and class 4 low 12 0 the results are consistent with field observations on landforms and geology

palaeoclimatic conditions in the upper pleistocene and holocene bhimtal naukuchiatal lake basin in south central kumaun north india abstract a 52 m thick upper pleistocene and holocene terrestrial succession in the bhimtal naukuchiatal basin south central kumaun himalaya india was studied using chronological palaeontological palynological and 13c measurements the section recorded evidence for climatic changes at least two phases of arid climate and one phase of humid climate were recognised preliminary palaeomagnetic studies revealed a reversal of polarity presumably correlatable with the mono lake excursion prior to this no reversal event in the upper pleistocene holocene terrestrial sediments of indian subcontinent is known a fossiliferous horizon discovered in the lower part of the section consisted of sorex and mus this is the only report of a late pleistocene micromammalian assemblage in the kumaun himalaya

geomorphic observations of rivers in the oregon coast range from a regional reconnaissance perspective abstract changes in long profile gradient gradient index pseudo hypsometric integral valley incision and sinuosity fractal dimension for rivers in western oregon were studied to determine their usefulness in assessing an hypothesis of differential uplift within the coast range all data were gathered from topographic quadrangles and geologic maps and so the results of this paper are limited to the description of river forms with only limited interpretations rivers were naturally divided into three groups those in the western coast range the eastern coast range and the klamath and cascade ranges and differences in river morphometry were generalized rivers in the western coast range had more divergent characteristics whereas those in the other groups were more similar within each group for example long profiles of western coast range rivers had diverse forms but in the other groups long profiles were similar within the group pseudo hypsometric integrals had a wide scatter in the western coast range but in the other ranges the pseudo hypsometric integral was more narrowly defined valley entrenchment and high sinuosity were common in the western coast range and were less visible in the eastern coast range these regional generalizations do not hold for the central coast range near 44 5 n where the yaquina and marys rivers are located in the eastern coast range the marys river is unique in that it has a convex bulge in its long profile does not have an increasing valley floor width to valley height ratio downstream and has a high sinuosity fractal dimension in the western coast range the yaquina river is unique in that it has a smoothly decreasing long profile has a very low pseudo hypsometric integral and does not have a decreasing valley floor width to valley height ratio downstream there may be many explanations for these observations but these observations are also consistent with tectonic interpretations that the central western coast range is the locus of synclinal tilting and that the entire oregon coast is experiencing landward tilting and uplift

identification of possible quaternary deformation in the northeastern mississippi embayment using quantitative geomorphic analysis of drainage basin asymmetry to investigate neotectonism in the mississippi embayment east of the new madrid seismic zone we identified geomorphic domains that show evidence of ground tilting during quaternary time transverse basin profiles were converted to two dimensional vectors that denote channel position with respect to basin divides these basin asymmetry vectors record the net direction and degree of lateral migration of trunk streams more than 2500 vectors were measured and spatially averaged within 400 km 2 bins this field of 300 mean vectors delineates several domains that show preferred directions of stream migrations possibly driven by ground tilting the timing of stream migration was interpreted using across valley distributions of quaternary alluvial terraces comparison of our mean vector field with subsurface structures suggests that some domain boundaries may be related to reactivated faults late quaternary activity is suggested for two northeast striking faults of the southeastern reelfoot rift margin we acquired two seismic profiles showing near surface faulting beneath scarps that follow the domain boundary associated with one of these northeast striking faults big creek fault zone reelfoot thrust seismicity ends on the south against this fault suggesting that the rift margin has dextral slip accommodating northeastward movement of the thrust hanging wall our vector field also suggests late quaternary movement on the reelfoot thrust and on two other northwest striking faults here termed the hatchie river fault and the wolf river fault several other weak domains may imply minor elements of neotectonism our results demonstrate that morphometric analysis of drainage basin asymmetry can be an effective reconnaissance tool within neotectonic settings

geomorphic evolution and neotectonics of the qianhe river basin on the southwest margin of the ordos block north china abstract the qianhe river basin is located at the convergence zone of the northeastern margin of the tibetan plateau netp the ordos block and the qinling mountains a tectonic geomorphology study of the qianhe river is significant for providing a deeper understanding of the tectonic transition between the netp and the ordos block and the dynamic relationship of these three tectonic units based on advanced spaceborne thermal emission and reflection global digital elevation model aster gdem data and geographic information system gis techniques four tectonic geomorphic indices the hypsometric integral hi stream length gradient sl drainage basin asymmetry af and drainage basin shape bs were calculated and analyzed geologic evidence from field surveys deformation measurements and fault slip rate estimates was also obtained to further discuss the tectonic activity and tectonic geomorphic evolution model through analytical comparisons we proposed that the variations in the applied geomorphic index values were not significantly affected by climate and lithology but indicated variations in related tectonic activity the geomorphic index value analysis suggested relatively strong tectonic activity in liupanshan mountain and longshan mountain and northwestward tectonic tilting of the southwest margin of the ordos block the actual mechanisms responsible for the observed variations in the qianhe river basin are the rapid uplift and northeastward extrusion of the qinghai tibetan plateau and the local tilting uplift of the southwestern ordos block

reconstruction of late quaternary climate and seismicity using fluvial landforms in pindar river valley central himalaya uttarakhand india abstract fluvial landforms in the pindar river valley are investigated to understand the role of temporal variability in the indian summer monsoon ism and the spatial changes in crustal deformation employing the conventional geomorphological and sedimentological concepts supported by optical dating three major phases of valley fill aggradation separated by phases on non deposition are discerned an oldest aggradation phase is dated to 33 5 ka during relatively strengthened ism corresponding to the later part of pluvial marine isotopic stage 3 mis 3 following this alluvial fan sedimentation impersistently continued during the declining phase of the ism until around 21 ka a second major aggradation phase 17 5 ka 13 ka occurred during the post lgm lateglacial strengthening of the ism in which contribution from tributary valleys overwhelmed the valley fill sedimentation a youngest aggradation phase dated to the middle to late holocene 8 ka 3 6 ka represents the transitional climate during which sporadic high sediment fluxes both from the upper catchment and tributary streams led to the development of fossil valleys abandonment of old channels the spatial variability in the incision uplift rate based on river strath terraces reveals that the terrain is undergoing differential crustal deformation two zones of relatively high crustal deformation are identified these are located in the vicinity of the main central thrust mct and is attributed to the activity along the transverse fault and the in the inner lesser himalaya for which the thrust propagated fold associated with regional north south compression is implicated the study suggests that fluvial landforms valley fill and strath terraces in the pinder river valley are genetically related to the multi millennial scale changes in the ism and spatial and temporal changes in the crustal deformation associated with regional compression

late quaternary tectonic landforms and fluvial aggradation in the saryu river valley central kumaun himalaya abstract the present study has been carried out with special emphasis on the aggradational landforms to explain the spatial and temporal variability in phases of aggradation incision in response to tectonic activity during the late quaternary in the saryu river valley in central kumaun himalaya the valley has preserved cut and fill terraces with thick alluvial cover debris flow terraces and bedrock strath terraces that provide signatures of tectonic activity and climate morphostratigraphy of the terraces reveals that the oldest landforms preserved south of the main central thrust the fluvial modified debris flow terraces were developed between 30 and 45 ka the major phase of valley fill is dated between 14 and 22 ka the youngest phase of aggradation is dated at early and mid holocene 9 3 ka following this several phases of accelerated incision erosion owing to an increase in uplift rate occurred as evident from the strath terraces seven major phases of bedrock incision uplift have been estimated during 44 ka 3 34 mm year 35 ka 1 84 mm year 15 ka 0 91 mm year 14 ka 0 83 mm year 9 ka 1 75 mm year 7 ka 5 38 mm year and around 3 ka 4 4 mm year from the strath terraces near major thrusts we postulate that between 9 and 3 ka the terrain witnessed relatively enhanced surface uplift 2 5 mm year

the kumaun and garwhal lesser himalaya india part 1 structure and stratigraphy our understanding of the geologic evolution of the himalaya remains incomplete particularly in regard to structural and geochronologic details of the proterozoic paleozoic lesser himalayan sequence we conducted an integrated field mapping geochronological study and geochemical analysis of the lesser himalayan sequence strata in the kumaun and garwhal himalaya of nw india 78 00 80 30 e structural observations reveal a systematic change in deformation styles from lower to higher structural levels in the main central thrust footwall in the south and at lower structural levels the main central thrust footwall is characterized by parallel folding and sparse development of axial cleavage quartz microstructures indicate that deformation occurred at temperatures below 350 c in contrast in the north and at higher structural levels close to the main central thrust deformation is characterized by replacement of original bedding the development of penetrative cleavage and schistosity locally folds are tight in places isoclinal and overturned the corresponding quartz microstructures indicate that deformation occurred above 350 c dating of detrital zircons from lesser himalayan sequence metasedimentary units and igneous zircons from schistose gneisses throughout the lesser himalayan sequence allow refinements to the stratigraphic framework first unlike has been observed in western nepal immediately west of our study area u pb zircon dating suggests the absence of paleoproterozoic strata in the ramgarh thrust hanging wall this suggests that the thrust cuts upsection laterally along strike second u pb detrital zircon dating suggests that metasedimentary strata in the ramgarh thrust hanging wall are correlative with basal units of the outer lesser himalayan sequence removing the necessity that the ramgarh thrust hanging wall was allochthonous with respect to its footwall lesser himalayan sequence units schistose gneisses with u pb ages of ca 1850 ma are older than lesser himalayan sequence units in the area suggesting that they are thrust emplaced lesser himalayan sequence basement we conclude that the ramgarh thrust is an out of sequence thrust postdating a folding event in its footwall the earlier proposal that neoproterozoic cambrian lesser himalayan sequence strata are the southern extension of the tethyan himalayan sequence requires that the tons thrust which separates the distal and proximal facies of the lesser himalayan sequence be a major south directed structure with a slip magnitude of 50 100 km

temperature constraints on the ginkgo flow of the columbia river basalt group this study provides the first quantitative estimate of heat loss for a columbia river basalt group flow a glass composition based geothermometer was experimentally calibrated for a composition representative of the 500 km long ginkgo flow of the columbia river basalt group to measure temperature change during transport melting experiments were conducted on a bulk sample at 1 atm between 1200 and 1050 c natural glass was sampled from the margin of a feeder dike near kahlotus washington and from pillow basalt at distances of 120 km vantage washington 350 km molalla oregon and 370 km portland oregon ginkgo basalt was also sampled at its distal end at yaquina head oregon 500 km comparison of the glass mgo content k 2 o in plagioclase and measured crystallinities in the experimental charges and natural samples tightly constrains the minimum flow temperature to 1085 5 c glass and plagioclase compositions indicate an upper temperature of 1095 5 c thus the maximum temperature decrease along the flow axis of the ginkgo is 20 c suggesting cooling rates of 0 02 0 04 c km these cooling rates substantially lower than rates observed in active and historic flows are inconsistent with turbulent flow models calculated melt temperatures and viscosities of 240 750 pa s allow emplacement either as a fast laminar flow under an insulating crust or as a slower inflated flow

regional analysis of bedrock stream long profiles evaluation of hack s sl form and formulation and assessment of an alternative the ds form the equilibrium form of the fluvial long profile has been used to elucidate a wide range of aspects of landscape history including tectonic activity in tectonic collision zones and in continental margin and other intraplate settings as well as other base level changes such as due to sealevel fluctuations the hack sl form of the long profile which describes a straight line on a log normal plot of elevation normal versus distance logarithmic is the equilibrium long profile form that has been most widely used in such studies slope area analysis has also been used in recent years we show that the sl form is a special case of a more general form of the equilibrium long profile here called the ds form that can be derived from the power relationship between stream discharge and downstream distance and the dependence of stream incision on stream power the ds form provides a better fit than the sl form to river long profiles in an intraplate setting in southeastern australia experiencing low rates of denudation and mild surface uplift we conclude that if an a priori form of the long profile is to be used for investigations of regional landscape history the ds form is preferable in particular the ds form in principle enables equilibrium steepening due to an increase in channel substrate lithological resistance parallel shift in the ds plot to be distinguished from disequilibrium steepening due to long profile rejuvenation disordered outliers on the ds plot slope area analysis and the slope distance ds approach outlined here are complementary approaches reflecting the close relationship between downstream distance and downstream catchment area copyright 2006 john wiley sons ltd

active tectonic influence on the evolution of drainage and landscape geomorphic signatures from frontal and hinterland areas along the northwestern himalaya india abstract the kangra re entrant in the nw himalaya is one of the most seismically active regions falling into seismic zone v along the himalaya in 1905 the area experienced one of the great himalayan earthquakes with magnitude 7 8 the frontal fault system the himalayan frontal thrust hft associated with the foreland fold janauri anticline along with other major as well as secondary hinterland thrust faults provides an ideal site to study the ongoing tectonic activity which has influenced the evolution of drainage and landscape in the region the present study suggests that the flat uplifted surface in the central portion of the janauri anticline represents the paleo exit of the sutlej river it is suggested that initially when the tectonic activity propagated southward along the hft the janauri anticline grew along two separate fault segments north and south faults the gap between these two fault and the related folds allowed the sutlej river to flow across this area later the radial propagation of the faults towards each other resulted in an interaction of the fault tips which caused the rapid uplift of the area rapid uplift resulted in the disruption and longitudinal deflection of the sutlej river channel fluvial deposits on the flat surface suggest that an earlier fluvial system flowed across this area in the recent past geomorphic signatures like the sharp mountain fronts along the hft in some places as well as along various hinterland subordinate faults like the nalagarh thrust nat the barsar thrust bat and the jawalamukhi thrust jmt the change in the channel pattern marked by a tight incised meander of the beas channel upstream of the jmt indicate active tectonic movements in the area the prominent v shaped valleys of the beas and sutlej rivers flowing across the thrust fronts with vf values ranging from

morphometric analysis and tectonic interpretation of digital terrain data a case study tectonic movement along faults is often reflected by characteristic geomorphological features such as linear valleys ridgelines and slope breaks steep slopes of uniform aspect regional anisotropy and tilt of terrain analysis of digital elevation models by means of numerical geomorphology provides a means of recognizing fractures and characterizing the tectonics of an area in a quantitative way the objective of this study is to investigate the use of numerical geomorphometric methods for tectonic geomorphology through a case study the methodology is based on general geomorphometry in this study the basic geometric attributes elevation slope aspect and curvatures are complemented with the automatic extraction of ridge and valley lines and surface specific points evans univariate and bivariate methodology of general geomorphometry is extended with texture spatial analysis methods such as trend autocorrelation spectral and network analysis terrain modelling is implemented with the integrated use of 1 numerical differential geometry 2 digital drainage network analysis 3 digital image processing and 4 statistical and geostatistical analysis application of digital drainage network analysis is empha sized a simple shear model with principal displacement zone with an ne sw orientation can account for most of the the morphotectonic features found in the basin by geological and digital tectonic geomorphology analyses copyright 2003 john wiley sons ltd

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

preservation of aeolian genetic units by lava flows in the lower cretaceous of the parana basin southern brazil the lower cretaceous geological record of the intracratonic parana basin in southern brazil comprises a thick succession of aeolian sandstones and volcanic rocks the intercalation between aeolian sandstone and volcanic floods allowed the preservation of distinct aeolian genetic units each genetic unit represents an accumulation episode bounded by supersurfaces that coincides with the base of lava flood events the entire package can be subdivided into a lower genetic unit which corresponds to aeolian sandstones preserved below the initial lava flows botucatu formation and an upper set of genetic units which comprises interlayered aeolian deposits and lava floods serra geral formation the lower genetic unit is up to 100 m thick its base is composed of ephemeral stream and aeolian sand sheet deposits that are overlain by cross bedded sandstones whose origin is ascribed to simple locally composite crescentic and complex linear aeolian dunes aeolian accumulation of the lower unit was possible as a result of the existence of a wide topographic basin which caused wind deceleration and a large sand availability that promoted a positive net sediment flux the upper genetic units comprise isolated sand bodies that occur in two different styles 1 thin lenses 3 m thick formed by aeolian sand sheets and 2 thick sand lenses 3 15 m comprising cross bedded cosets generated by migration and climbing of simple to locally composite crescentic aeolian dunes accumulation of the aeolian strata was associated with wind deceleration within depressions on the irregular upper surface of the lava floods the interruption of sedimentation in the lower and upper genetic units and related development of supersurfaces occurred as a result of widespread effusions of basaltic lava preservation of both wind rippled topset deposits of the aeolian dunes and pahoehoe lava imprints indicates that lava floods covered active aeolian dunes and hence protected the aeolian deposits from erosion thus preserving the genetic units

testing the tectonic significance of some parameters of longitudinal river profiles the case of the ardenne belgium nw europe the longitudinal profiles of 24 rivers of 3rd to 5th order have been analyzed in order to recognize the regional tectonic differentiation pattern of the ardenne a paleozoic massif of nw europe data collected exclusively from 1 25 000 topographic maps were used to define a set of parameters related to the geometry of the profile and proxies for river bedload and drainage area validation of the proxy defined for the bedload discharge ratio demonstrates its potential use for inter river comparison based on its value at the river mouth it is however inadequate to estimate the ratio changes along a given stream course this proxy has been computed to estimate the portion accounted for by hydrodynamic factors in the river bed profiling thus outliers to the correlation function linking it to the river bed gradient have been considered as undergoing other influences principally of lithologic or tectonic origin most indicative of the computed profile parameters are those related to the concavity of the profile four more or less regional longitudinal profile types are recognized which are partly determined by differential tectonic movement the combined analysis of all the parameters confirms the current uplift of the ne ardenne and points to a subsidence of the namur area with respect to its sw and se surroundings whether periglacial or tectonic in origin the upper pleistocene lowering of a local base level has also been identified in the famenne another conclusion of this study is that in order to evidence tectonic influences and to avoid any misinterpretation in a region of complex geologic and geomorphic history and moderate tectonic activity it is essential to consider a number of parameters and to consider their significance within the framework of detailed geologic setting and morphogenetic history

geomorphic indicators of active fold growth south mountain oak ridge anticline ventura basin southern california south mountain oak ridge near ventura california is an asymmetric anticlinal uplift forming at the present time above the active buried oak ridge reverse fault shortening along the oak ridge fault accumulated largely in quaternary time and is responsible for the growth and present topography of the westernmost 15 km of the ridge during the past 0 5 m y tectonic geomorphic analysis using several indices of active tectonics provides information concerning fold growth stream gradient indices are relatively high in the northern eroded fold scarp of the ridge a pattern consistent with the existence of active rapid slip on the oak ridge fault mountain front sinuosity along the northern slope of the anticlinal ridge roughly decreases from 2 to 1 toward the westernmost 10 km of observed surface folding valley floor width to valley height ratios along the northern flank of the ridge generally decrease westward from 1 5 to 0 5 values of the hypsometric integral along the northern flank increase significantly from 0 35 to 0 4 maximum 0 55 from east to west drainage density varies from 4 to 6 km km2 along both flanks of the south mountain oak ridge anticline entrenchment of streams into the southern backlimb of the fold along the westernmost 9 km of the structure decreases from 20 m to 1 m from east to west apparent backlimb rotation as measured by dip of strata along the westernmost 7 km of the fold decreases from east to west from 35 to 20 fold growth of the south mountain oak ridge anticline occurred during the past 0 5 ma following deposition of the saugus formation lateral and vertical fold growth were likely produced by westward decrease in fault slip along the buried oak ridge fault

topo europe from iberia to the carpathians and analogues abstract earth sciences are rapidly changing from largely descriptive to process oriented disciplines that aim at quantitative models for the reconstruction and forecasting of the complex processes in the solid earth prediction is highly relevant for the basic needs of humanity supply of water and resources protection against natural hazards and control on the environmental degradation of the earth intensive utilization of the human habitat carries largely unknown risks of and makes us increasingly vulnerable there is an urgent need for scientifically advanced geo prediction systems that can accurately locate subsurface resources and forecast timing and magnitude of natural hazards the design of such systems is a major multidisciplinary scientific challenge the quantitative understanding of the earth has made significant progress in the last few decades important ingredients in this process have been the advances made in seismological methods to obtain information on the 3d structure of the mantle and the lithosphere in the quantitative understanding of the lithospheric processes as well as the recognition of the key role of quantitative sedimentary basin analysis in connecting temporal and spatial scales quantitative understanding of the mass transfer by erosion and deposition as well as their feed back with crustal and subcrustal dynamics presents a new frontier in modern earth sciences this research bridges investigations on high resolution near surface time scales and the large scale long term approaches characteristic for the lithosphere and basin wide studies the essential step towards a 4d approach in space and time is a direct response to the need for a full incorporation of geological and geophysical constraints in the modelling of solid earth processes topo europe is a multidisciplinary international research program that addresses the interaction of processes inherent to the deep earth lithosphere and mantle with surface processes erosion climate and sea level which together shaped the topography of europe the objective of this programme is to quantify natural hazards by incorporating data interactive modelling focused on the lithosphere memory and neotectonics with special attention on the thermo mechanical structure of the lithosphere mechanisms controlling large scale plate boundaries and intraplate deformations anomalous subsidence and uplift and links with surface processes and topography evolution

extrusion vs duplexing models of himalayan mountain building 1 discovery of the pabbar thrust confirms duplex dominated growth of the northwestern indian himalaya since mid miocene ongoing himalayan growth is generally thought to be dominated by duplexing and or extrusion processes these models may be tested by reconstructing himalayan fold thrust belt growth since the middle miocene however our knowledge of basic structural geometry remains too fragmentary to resolve the issue even in areas with rich stratigraphic diversity such as the northwestern indian himalaya in this region a primary outstanding question involves the uncertain relationship of the berinag thrust and the tons thrust structures with displacements of 80 km and 40 km respectively the uncertain geometry and kinematics allow for the complete range of duplexing or extrusion processes for the integrated kinematic history since the middle miocene to address this issue field mapping and kinematic analysis were performed to reconstruct the deformation of the lesser himalayan sequence in the northwest indian himalaya our results reveal a new discovery a 450 m thick top to southwest shear zone termed the pabbar thrust the pabbar thrust placed the outer lesser himalayan sequence the tons thrust hanging wall directly on the berinag group the berinag thrust hanging wall this discovery requires that the berinag thrust and tons thrust are in fact the same structure and discrete duplexing processes dominated growth of the northwest indian himalaya for the past 10 15 million years along strike extension of these kinematics and corresponding geometries is consistent with the observed orogenic framework and resolves a stratigraphic continuity problem across the india west nepal border where prior work suggests that structures are continuous but stratigraphy does not match

geomorphic characteristics of landscape development and formation of lakes in the zone of munsiari thrust garhwal himalaya uttarakhand india abstract the present investigation is focused on imprint of tectonic perturbation along a major tributary known as the lastar gad gad river in southeast catchment of the mandakini river in garhwal himalaya based on morphotectonic studies across the watershed we recognized evidences of neotectonics along the jutogh munsiari thrust mt mct ii various geomorphic features e g ponding of streams and formation of lakes fluvio lacustrine deposits waterfalls stabilized and active landslide fans dissected hills paired and unpaired terraces fault scarps and offsetting of drainage pattern etc point to the active tectonics the field investigations are supported by computation of morphometric indices such as low values of valley floor width to valley height vf asymmetry factor af elongated and tilted river basin with narrow valley floor as well as higher bifurcation ratio rb and sinuosity parameters immature topography and landscape elongation and tilting of drainage basin and accelerated erosion all show that the basin is structurally controlled the uplift along the valley is further manifested by two significant indexes e g stream length sl and steepness index ks also the mud deposits lacustrine flats and swampy and soggy land within the valley suggest the existence of an ancient lake basin named as gethina palaeolake downstream of present day badanital lake the 14c ams radiocarbon chronology of the badanital lake core as well as gethina jagtoli palaeolake profiles indicate the formation of these lakes around 5 6 ka bp due to tectonic upheaval along the mt we assume that a huge landslide activity blocked the course of a small stream badani gad forming an ancient lake at gethina locality followed by deposition of a landslide fan on which was created the badanital subsequently the palaeolake basin was filled with sediments due to accelerated erosion from almost vertical hills in the catchment owing to this the gethina ancient lake was disappeared and the modern badanital lake shrank to its present state

geomorphological and seismological investigations in a part of western kumaun himalaya uttarakhand india abstract the kumaun himalaya in india is seismotectonically one of the most responsive sectors of the himalayan arc the region falls in the seismic gap and is frequently rocked by the earthquakes of low to medium magnitude in the present investigation the seismic data of the area were obtained by deploying a seismic network and an attempt is made to interpret the seismological data of the local events and their relation with the geomorphology and thrusts faults rejuvenation the epicentral distribution of the earthquakes defines a relatively narrow zone of seismicity a majority of earthquakes are confined to shallow depth with low stress drop and higher peak ground velocity pgv further the neotectonic investigations along the major river valleys indicate the neotectonic activity in the form of paired and unpaired terraces shifting of river courses fault scarps development of palaeolakes straightening of river channels and deep cut v shaped valleys from the geomorphological and seismological data the thrust and fault systems in the area are seismotectonically quite active even today some of the transverse faults viz dwarahat chaukhutia fault takula basauli fault sim gad valley tilora jyala fault kosi valley show spectacular tectonic landforms and seismicity as a matter of fact the nnw nw sse se trending faults are active in the region

analyzing the drainage system anomaly of zagros basins implications for active tectonics abstract morphometric analysis of hierarchical arrangement of drainage networks allows to evaluate the effects of external controls especially tectonics on basin development in this study a quantitative method for calculation of stream s hierarchical anomaly number is introduced morphometric parameters such as hierarchal anomaly index a percent of asymmetry factor paf basin shape bs basin length to mean width ratio bl bmw stream s bifurcation ratio rb bifurcation index r drainage density dd drainage frequency df and anticline s hinge spacing hs of 15 basins in zagros mountains were examined results show that the strong correlations exist between pairs a paf r 0 844 a bs r 0 732 a bl bmw r 0 775 a r r 0 517 paf bl bmw r 0 519 bs r r 0 659 bl bmw r r 0 703 hs a r 0 708 hs paf r 0 529 and hs bs r 0 516 the variations in trend of anticlines control the shape of basins so that where anticlines hinges become closer to each other in the downstream direction basin become narrower downward and hence the a increases the more uplifted northeastern anticlines cause the trunk river of the basins to migrate toward the younger anticlines in southwest and hence a increases because the trunk river receives a lot of first order streams data reveal that the rate of a is higher in elongated synclinal basins due to the decrease in the intensity of deformation from northeast toward southwest of zagros the hinge spacing of anticlines increases southwestwards data reveal that the variation in hinge spacing of anticlines strongly controls the basin s shape and tilting as well as the hierarchical anomaly of drainage system since the elongation and tilting of basins are associated with the variations in rates of folding uplift and hinge spacing of anticlines it can be concluded that the hierarchical anomaly of drainages in studied basins is controlled by the intensity of zagros tectonic activities

segregation vesicles gas filter pressing and igneous differentiation some vesicles in certain subaerial flows of basalt and basaltic andesite are partially filled with dark partly glassy segregation material the segregation material has about three times the concentration of k o tio and p o as the associated host rock therefore the segregation materials are inferred to be frozen residual liquids that migrated into the vesicles several possible processes for filling the vesicles are examined within the context of the cooling time implied by heat conduction the preferred process is one in which the residual liquid migrates through a porous and permeable but rigid network of interlocking crystals in response to a pressure gradient generated by vapor saturated crystallization as crystallization proceeds h o is concentrated in the residual liquid and gas this produces a higher pressure in the gas poor matrix than in the vesicles and forces liquid to migrate into the vesicles textural features suggestive of or consistent with the process include 1 vesiculation

geomorphic and sedimentary response of rivers to tectonic deformation a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings abstract rivers are extremely sensitive to subtle changes in their grade caused by tectonic tilting as such recognition of tectonic tilting effects on rivers and their resultant sediments can be a useful tool for identifying the often cryptic warping associated with incipient and smaller scale epeirogenic deformation in both modern and ancient settings tectonic warping may result in either longitudinal parallel to floodplain orientation or lateral normal to floodplain orientation tilting of alluvial river profiles alluvial rivers may respond to deformation of longitudinal profile by 1 deflection around zones of uplift and into zones of subsidence 2 aggradation in backtilted and degradation in foretilted reaches 3 compensation of slope alteration by shifts in channel pattern 4 increase in frequency of overbank flooding for foretilted and decrease for backtilted reaches and 5 increased bedload grain size in foretilted reaches and decreased bedload grain size in backtilted reaches lateral tilting causes down tilt avulsion of streams where tilt rates are high and steady down tilt migration combing where tilt rates are lower each of the above effects may have profound impacts on lithofacies geometry and distribution that may potentially be preserved in the rock record fluvial sedimentary evidence for past tilting is traditionally based on the assumption that depositional features reminiscent of modern fluvial tectonic effects are evidence for past tectonic effects where it is closely associated with historically active structures or where non tectonic causes cannot be invoked however caution must be exercised when using these effects as criteria for past or current tectonic warping as these effects may be caused by non tectonic factors these non tectonic causes must be eliminated before tectonic interpretations are made

origin of pegmatitic segregation veins within flood basalts subhorizontal veins and lenses of coarse grained rock composed of plagioclase augite and fe ti oxides in a glassy and vesicular mesostasis occur within several thick subaerial basalt flows in the columbia river basalt province of washington and in the eastern north american mesozoic basalt province the veins and lenses referred to as pegmatitic segregation veins are typically 1 10 cm thick and are enriched in fe ti k p cu zr ba and ree by a factor of about 1 1 to 3 over the host basalt al ca sr mg ni and cr are lower and si and na are typically unchanged we interpret the pegmatitic segregation veins as the product of residual melt carried in vapor bubbles from the lower crystallization front of partially crystallized flows to the crystal mush within the upper crystallization front movement through the elevated temperatures of flow interiors fused any crystal nuclei in the segregation melt diminished nucleation density during crystallization may partially account for coarse grain sizes in addition diffusion of ions to large rapidly growing skeletal crystals was probably enhanced by the viscosity reduction effect of water enrichment the water content of accumulated segregation melt may have increased whenever the escape of volatiles from partiallymore crystallized flows was temporarily sealed off under a rigid barrier of solidified basalt rupture of the barrier by downward propagation of columnar joints would allow the resumption of effervescence and any remaining partially crystallized segregation melt phase would be degassed and quenched into a glassy and vesicular mesostasis 59 refs 8 figs 2 tabs less

response of active tectonics on the alluvial baghmati river himalayan foreland basin eastern india active tectonics in a basin plays an important role in controlling a fluvial system through the change in channel slope the baghmati an anabranching foothills fed river system draining the plains of north bihar in eastern india has responded to ongoing tectonic deformation in the basin the relatively flat alluvial plains are traversed by several active subsurface faults which divide the area in four tectonic blocks each tectonic block is characterized by association of fluvial anomalies viz compressed meanders knick point in longitudinal profiles channel incision anomalous sinuosity variations sudden change in river flow direction river flow against the local gradient and distribution of overbank flooding lakes and waterlogged area such fluvial anomalies have been identified on the repetitive satellite images and maps and interpreted through dem and field observations to understand the nature of vertical movements in the area the sub surface faults in the baghmati plains cut across the river channel and also run parallel which have allowed us to observe the effects of longitudinal and lateral tilting manifested in avulsions and morphological changes

palaeoclimatic conditions in the late pleistocene wadda lake eastern kumaun himalaya india abstract an episode of neotectonic activity on an east west trending fault in the zone of active intracrustal north almora thrust in the eastern kumaun himalaya resulted in the formation of a lake around 36 000 yr b p a 13 m continuous sequence made up largely of carbonaceous mud represents the lake that disappeared around 10 000 yr b p due to the revival of neotectonic activity on the basis of radiocarbon dating it appears that the rate of sedimentation varied from time to time during the existence of the lake palaeomagnetic studies show normal polarity except for a major deviation in the upper part of the section palynological investigations testify to the occurrence of three temperate humid and at least two well defined arid climatic phases which are correlated with previously documented late quaternary climatic changes as recorded in the himalaya as well as in tibet around 10 000 yr b p widespread deposition of a tectonically induced debris flow occurred in the lake basin at the terminal stage of the lake s life the two events ca 36 000 and 10 000 yr b p thus seem to represent two major neotectonic events in the kumaun lesser himalaya

late quaternary intensified monsoon phases control landscape evolution in the northwest himalaya the intensity of the asian summer monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes terrestrial environments and marine sedi ment records however the mechanisms of long lived 2 5 k y intensified monsoon phases the related changes in precipitation distribution and their effect on landscape evolution and sedimen tation rates are not yet well understood the arid high elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal i e strength ened monsoon seasons analogous to present day rainfall anom alies enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure we as sociate landslide triggering during intensified monsoon phases with enhanced precipitation discharge and sediment flux leading to an increase in pore water pressure lateral scouring of rivers and ov ersteepening of hillslopes eventually resulting in failure of slopes and exceptionally large mass movements here we use lacustrine deposits related to spatially and temporally clustered large land slides 0 5 km 3 in the sutlej valley region of the northwest him alaya to calculate sedimentation rates and to infer rainfall patterns during late pleistocene 29 24 ka and holocene 10 4 ka inten sified monsoon phases compared to present day sediment flux measurements a fivefold increase in sediment transport rates re corded by sediments in landslide dammed lakes characterized these episodes of high climatic variability these changes thus em phasize the pronounced imprint of millennial scale climate change on surface processes and landscape evolution

geomorphic assessment of active tectonics in the acambay graben mexican volcanic belt spatial variations of quaternary deformation and tectonic activity of faults along the acambay graben are assessed using geomorphic and morphometric approaches the acambay graben is an east west trending structure of apparent quaternary age located in the central part of the mexican volcanic belt which gives rise to pronounced scarps over a distance of about 80 km continuing tectonic activity in the acambay graben is confirmed by recent well documented seismic episodes the intensity of active tectonics has been interpreted through a detailed geomorphic study of the fault generated mountain fronts and fluvial systems the combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity among the acambay graben faults geomorphic indices suggest a relatively high degree of tectonic activity along the venta de bravo and the acambay tixmadeje faults followed in order of decreasing activity by the pastores temascalcingo and tepuxtepec faults spatial variations within faults have also been identified suggesting a higher level of tectonic activity at the tips of the faults this pattern of variation in the relative degree of tectonic activity is consistent with field evidence and seismic data for the acambay graben geomorphic evaluation of the acambay graben faults suggests that the acambay tixmadeje and venta de bravo faults and specifically the tips of these faults and a central segment near the town of venta de bravo should be considered as areas of potentially high earthquake risk 1998 john wiley sons ltd

assessment of relative active tectonics southwest border of the sierra nevada southern spain abstract we present a new method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography indices used include stream length gradient index sl drainage basin asymmetry af hypsometric integral hi ratio of valley floor width to valley height vf index of drainage basin shape bs and index of mountain front sinuosity smf results from the analysis are accumulated and expressed as an index of relative active tectonics iat which we divide into four classes from relatively low to highest tectonic activity the study area along the southwest border of the sierra nevada in southern spain is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front the study area has variable rates of active tectonics resulting from the collision of africa with europe that has produced linear east west anticlinal forms as well as extension with variable vertical rates of normal faulting to about 0 5 m ky we test the hypothesis that areas of known relatively high rates of active tectonics are associated with indicatives values of iat

quaternary extensional and compressional tectonics revealed from quaternary landforms along kosi river valley outer kumaun lesser himalaya uttarakhand a portion of the kosi river in the outer kumaun lesser himalaya is characterized by wide river course situated south of the ramgarh thrust where huge thickness 200 m of the landslide deposits and two to three levels of unpaired fan terraces are present brittle normal faults suggesting extensional tectonics are recognized in the quaternary deposits and bedrocks as further supported by surface morphology trending e w these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini horst and fault scarps sackungen exposed due to cutting across by streams active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart at one of the sites the faults look like bookshelf faulting with the maximum displacement of 2 m and rotation of the quaternary boulders along the fault plane is observed at another site the maximum displacement measures about 0 60 cm thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit landslide debris fans and terrace landforms are widely developed the highest level of fan is observed 1240 m above mean sea level at some places the reworking of the debris fans by streams is characterized by thick laminated sand body along the south almora thrust and ramgarh thrust zones the valleys are narrow and v shaped where quaternary deposits are sparse due to relatively rapid uplift across these thrusts along the south almora thrust zone three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the rt and sat abandoned channel tilted mud deposits incised meandering deep cut v shaped valleys and strath terraces indicate rapid uplift of the area thick mud sequences in the quaternary columns indicate damming of streams a 10 km long north south trending transverse garampani fault has offset the ramgarh thrust producing tectonic landforms

tectono climatic influence on landscape changes in the glaciated durung drung basin zanskar himalaya india a geospatial approach abstract this study aims at assessing the tectonic and climatic responses to landscape changes transpired in the durung drung basin in the zanskar himalaya we used relevant geomorphic indices interpreted from aster dem satellite data and supplemented by the field observations to decipher active tectonics and resultant changes in the landscape a n s trending fault in the north of the basin was studied with the help of basin geometry which includes relative parameter length area relation form factor shape factor ratio elongation ratio circulatory ratio compactness coefficient and morphotectonic indices e g drainage basin asymmetry mountain front sinuosity hypsometric integral topographic symmetric factor to comprehend the geomorphic signatures of the active tectonics the geomorphic indices indicate upliftment and tilting of the basin the data on mountain front index and hypsometric integral reveal the uplift and high relief we propose that the western side of the basin is tectonically more active than eastern side suggesting active upliftment the convex nature of hypsometric curve and strongly elongated circulatory ratio reflect competing role of deformation by tectonics the results of mountain front index and hypsometric integral reveal high relief and uplift overall deglaciation of 12 91 was observed in the basin analysis of the meteorological data for the last century 1901 2017 indicate that increase in minimum and maximum temperature coupled with increase in liquid precipitation are probably the main drivers of glacier depletion we conclude that the drainage system of this basin is structurally controlled and overall landscape change is significantly influenced by the ongoing perturbations in the climate system

pahoehoe flows from the central parana continental flood basalts inflated and compound pahoehoe flows have been identified within the central parana continental flood basalts based upon their morphology surface features and internal zonation pahoehoe flow features have been studied at five localities in the western portion of parana state brazil ponte queimada toledo rio quiteria matel ndia and cascavel we have interpreted the newly recognized flow features using concepts of hawaiian pahoehoe formation and emplacement that have been previously applied to the columbia river basalt and deccan plateau surface features and or internal structure typical from pahoehoe lavas are observed in all studied areas and features like inflation clefts squeeze ups breakouts and p type lobes with two levels of pipe vesicles are indicative of inflation in these flows the thinner compound pahoehoe flows are predominantly composed of p type lobes and probably emerged at the end of large inflated flows on shallow slopes the presence of vesicular cores in the majority of compound lobes and the common occurrence of segregation structures suggests high water content in the pahoehoe lavas from the central pcfb more volcanological studies are necessary to determinate the rheology of lavas and refine emplacement models

geomorphic response of coastal streams to low intermediate and high rates of uplift medocino triple junction region northern california analysis of three dimensional morphological properties of 24 coastal drainage basins that have evolved in areas of low 3 m 1 000 yr rates of uplift near the mendocino triple junction mtj coastal northern california identified channel gradients as the best indicator of tectonism in the landscape lower order tributaries best reflect tectonically controlled differences the largest streams examined of third order are able to adjust to most base level change and maintain their profile form whereas lower order streams farther upstream tend to accumulate the effects of net base level fall and have steepest profiles in the areas of highest uplift rates variations in steepness of first order channel gradients indicate that 1 high uplift rates in the wake of the mtj have existed for at least 73 000 yr and 2 differential tilt of the region to the north and south of the current locus of highest uplift rate is occurring in association with regional uplift although first order streams are excellent indicators of areas of both high uplift rates and regional differential tilting they are less useful in distinguishing between areas of low and intermediate uplift rate analysis of the longitudinal profile of the main trunk stream of ten of the 24 drainage basins using the stream gradient index was more useful to categorize broadly the uplift rates and to distinguish between streams in low and intermediate uplift rate areas although the hypotheses tested herein do not identify the exact mechanism off uplift in the mtj region they do indicate that the nature of deformation is most likely regional tilt rather than crustal shortening with localized compressional folding and thrust faulting they also indicate that geomorphic responses trail in the wake of the uplift rate response caused by development of a slab window beneath the north american plate 1 maximum uplift rates occur 9 km south of the northern boundary of the slab window 2 maximum mean first order channel gradient occurs 16 km south of the northern edge of the slab window and 3 maximum drainage basin relief occurs 20 km south of the northern edge of the slab window associated lag times between passage of the southern edge of the subducted gorda plate slab and geomorphic responses are 160 000 yr for maximum uplift rates 290 000 yr for maximum channel gradients and 370 000 yr for maximum relief