tectonic control on 10 be derived erosion rates in the garhwal himalaya india erosion in the himalaya is responsible for one of the greatest mass redistributions on earth and has fueled models of feedback loops between climate and tectonics although the general trends of erosion across the himalaya are reasonably well known the relative importance of factors controlling erosion is less well constrained here we present 25 10 be derived catchment averaged erosion rates from the yamuna catchment in the garhwal himalaya northern india tributary erosion rates range between 0 1 and 0 5 mm yr 1 in the lesser himalaya and 1 and 2 mm yr 1 in the high himalaya despite uniform hillslope angles the erosion rate data correlate with catchment averaged values of 5 km radius relief channel steepness indices and specific stream power but to varying degrees of nonlinearity similar nonlinear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion and that twofold to threefold differences in annual runoff are of minor importance in this area instead the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock uplift pattern is largely controlled by the shortening rate and the geometry of the main himalayan thrust fault mht our data support a shallow dip of the mht underneath the lesser himalaya followed by a midcrustal ramp underneath the high himalaya as indicated by geophysical data finally analysis of sample results from larger main stem rivers indicates significant variability of 10 be derived erosion rates possibly related to nonproportional sediment supply from different tributaries and incomplete mixing in main stem channels

growth and deformation of the ladakh batholith northwest himalayas implications for timing of continental collision and origin of calc alkaline batholiths abstract the calc alkaline ladakh batholith nw himalayas was dated to constrain the timing of continental collision and subsequent deformation batholith growth ended when collision disrupted subduction of the tethyan oceanic lithosphere and thus the youngest magmatic pulse indirectly dates the collision both u pb ages on zircons from three samples of the ladakh batholith and k ar from one subvolcanic dike sample were determined magmatic activity near leh the capital of ladakh occurred between 70 and 50 ma with the last major magmatic pulse crystallizing at ca documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand tex

back analysis of an excavated slope failure in highly fractured rock mass the case study of kargar slope failure iran this paper examines the failure of kargar cut slope located at the south part of esfahan subway using analytical and numerical back analysis methods the excavated trench has 27 m depth with near vertical walls due to the space limitation around it the geology of the area comprises weathered and heavily jointed shale and sandstone overlaid by alluvium deposits despite the slope being supported by shotcrete and fully grouted rock bolts a catastrophic failure occurred at the east wall due to the uncertainty about the causes of failure initiation back analyses have been performed via both the limit equilibrium and numerical method for considering various probable mechanisms in the back analysis with limit equilibrium method the rock mass is assumed as an equivalent continuum and hoek brown failure criterion and geological strength index gsi are applied to calculate the shear strength parameters the results show that gsi value was 33 in the failed mass in the numerical back analysis the distinct element method is applied to study the contribution of rock joints to the failure and progressive rock mass strength degradation until failure the results show that threshold values of joint cohesion and friction were 0 2 mpa and 30 respectively also the modeled slip surface being step shaped agrees with the observed one

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

kita uebaru natural rock slope failure and its back analysis a large landslide occurred in kita uebaru or asato area of nakagusuku village in okinawa island japan on 10 june 2006 after a rainy period of about 9 days the total rainfall was 126 mm from june 8 till the time of the landslide this period this landslide destroyed several buildings and roads and the total travel distance of the landslide was about 110 m in this article the authors were concerned with the initiation conditions of kita uebaru landslide and post failure motions of the landslide body the observations made in the landslide area structural geology analyses and outcomes of geotechnical investigations are described first then possible causes of the landslide are investigated through back analyses using as inputs the geological structure and the strength properties of planes of discontinuities involved in the sliding processes the final part of the article is concerned with the simulation of post failure motions of the landslide body the results of the investigations and back analyses indicate that the failure plane was bi planar and the heavy torrential rainy period for about 3 days was the main cause of initiation of the landslide the mechanical model presented in this article was capable of capturing the overall features of the landslide body following the initiation of the failure

river drainage patterns in the new zealand alps primarily controlled by plate tectonic strain the persistence of dendritic drainage patterns implies that rivers reorganize after a tectonic perturbation preserving no long term record of that tectonic event numerical simulations of the evolution of drainage patterns in the southern alps new zealand however reveal rivers that resist reorganization and thus preserve a record of plate tectonic strain over 10 million years

importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem 1 fluvial erosion of bedrock occurs during occasional flood events when boundary shear stress exceeds a critical threshold to initiate incision therefore efforts to model the evolution of topography over long timescales should include an erosion threshold and should be driven by a stochastic distribution of erosive events however most bedrock incision models ignore the threshold as a second order detail in addition climate is poorly represented in most landscape evolution models so the quantitative relationship between erosion rate and measurable climatic variables has been elusive here we show that the presence of an erosion threshold when combined with a well constrained probabilistic model of storm and flood occurrence has first order implications for the dynamics of river incision in tectonically active areas first we make a direct calculation of the critical shear stress required to pluck bedrock blocks for a field site in new york second we apply a recently proposed stochastic threshold bedrock incision model to a series of streams in california with known tectonic and climatic forcing previous work in the area has identified a weak relationship between channel gradient or relief and rock uplift rate that is not easily explained by simpler detachment limited models the results with the stochastic threshold model show that even low erosion thresholds which are exceeded in steep channels during high frequency flood events fundamentally affect the predicted relationship between gradient and uplift rate in steady state rivers in a manner consistent with the observed topography this correspondence between theory and data is however nonunique models in which a thin alluvial cover may act to inhibit channel incision in the low uplift rate zone also provide plausible explanations for the observed topography third we explore the broader implications of the stochastic threshold model to the development of fluvial topography in active tectonic settings we suggest that continued field applications of geomorphic models including physically meaningful thresholds and stochastic climate distributions are required to advance our knowledge of interactions among surficial climatic and crustal processes

beyond threshold hillslopes channel adjustment to base level fall in tectonically active mountain ranges numerous empirical and model based studies argue that in general hillslopes and river channels increase their gradients to accommodate high rates of base level fall to date however few data sets show the dynamic range of both these relationships needed to test theoretical models of hillslope evolution and river incision here we utilize concentrations of 10 be in quartz extracted from river sand on the eastern margin of the tibetan plateau to explore relationships among short term 10 2 10 5 a erosion rate hillslope gradient and channel steepness our data illustrate nonlinear behavior and a threshold in the relationship between erosion rate and mean hillslope gradient confi rming the generalization that hillslopes around the world are limited by slope stability and cease to provide a metric for erosion at high rates 0 2 mm a the relationship between channel steepness index and erosion rate is also nonlinear but channels continue to steepen beyond the point where threshold hillslopes emerge up to at least 0 6 mm a demonstrating that channel steepness is a more reliable topographic metric than mean hillslope gradient for erosion rate and that channels ultimately drive landscape adjustment to increasing rates of base level fall in tectonically active settings

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

landscape form and millennial erosion rates in the san gabriel mountains ca abstract it has been long hypothesized that topography as well as climate and rock strength exert first order controls on erosion rates here we use detrital cosmogenic 10 be from 50 basins ranging in size from 1 to 150 km 2 to measure millennial erosion rates across the san gabriel mountains in southern california where a strong e w gradient in relief compared to weak variation in precipitation and lithology allow us to isolate the relationship between topographic form and erosion rate our erosion rates range from 35 to 1100 m ma and generally agree with both decadal sediment fluxes and long term exhumation rates inferred from low temperature thermochronometry catchment mean hillslope angle increases with erosion rate until 300 m ma at which point slopes become invariant with erosion rate although this sort of relation has been offered as support for non linear models of soil transport we use 1 d analytical hillslope profiles derived from existing soil transport laws to show that a model with soil flux linear in slope but including a slope stability threshold is indistinguishable from a non linear law within the scatter of our data catchment mean normalized channel steepness index increases monotonically though non linearly with erosion rate throughout the san gabriel mountains even where catchment mean hillslope angles have reached a threshold this non linearity can be mostly accounted for by a stochastic threshold incision model though additional factors likely contribute to the observed relationship between channel steepness and erosion rate these findings substantiate the claim that the normalized channel steepness index is an important topographic metric in active ranges

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

analysis of spalling failure in marble rock slope a case study of neyriz marble mine iran the expansion of the neyriz marble mine into deeper levels caused an unexpected failure particularly in the toes of lower benches this phenomenon can impact the overall stability of the quarry and results in undesirable environmental and technical consequences to understand the failure mechanism a comprehensive study including laboratory testing in situ field testing and theoretical analyses are carried out the theory of the brittle failure which was mainly developed based on the experiences gained during excavation in granite rocks is adopted and augmented in this study to explain the governing mechanism of failure mechanical properties of the marble are determined using conventional rock mechanics tests and the in situ stress field was evaluated using a modified under coring test analyzing the laboratory and field data with the available empirical criteria for brittle failure shows that the level of stress in the lower bench is high enough to initiate the brittle failure finally constitutive models developed for this failure mode are adopted in conjunction with numerical modeling to investigate the observed failure in the quarry two modeling strategies based on elastic and elastic plastic analyses are considered comparing the predicted failure surface with the observed failure profile it can be concluded that the brittle failure criteria can very well capture the failure mechanism in this marble quarry this shows that the criteria proposed to describe spalling failure around underground excavation in granite can be effectively employed for assessing the brittle failure in deep open cast and quarry mines in good quality rocks such as marble

was the younger dryas triggered by a flood draining of a huge lake into the northern atlantic may have triggered a cold period 12 900 years ago the route taken by the flood waters remains unknown

a generalized power law approximation for fluvial incision of bedrock channels 1 sediment flux is known to influence bedrock incision rates in mountain rivers although the widely used stream power incision model lacks any explicit representation of sediment flux the model appears to work in a variety of real settings we address this apparent contradiction using numerical experiments to explore the morphology of fluvial landscapes evolved with four different incision models three of which include the influence of sediment flux on incision rate the numerical landscapes have different spatial patterns of uplift and are at steady state we analyze these landscape using the common stream power approach which views incision rates to be primarily a function of the local channel gradient s and the upstream drainage area a we find that incision rates i for these landscapes are well described by an empirical power law equation i k am sn this equation is functionally equivalent to the widely used stream power model with the important distinction that the parameters k m and n are entirely empirical these parameters take on constant values within a single landscape but can otherwise be quite different between landscapes mainly due to differences in the pattern of rock uplift within the drainage in particular the parameters m and n decrease as the rate of rock uplift becomes more focused in the upland part of a mountain belt the parameter m is particularly important in that it describes the sensitivity of a tectonically active mountain belt to changes in precipitation or tectonic accretion it also defines how incision rates will change as the discharge becomes flashier

a fluvial record of long term steady state uplift and erosion across the cascadia forearc high western washington state six late quaternary river terraces preserved along the clearwater river in northwestern washington state provide a 140 ka record of long term incision and uplift across the western side of the cascadia forearc high terrace ages are constrained by weathering rind and radiocarbon dating and by correlation to dated coastal glacio fluvial deposits and the global eustatic curve the terraces overlie flat bedrock surfaces called straths which represent uplifted segments of the river channel bedrock incision is measured by the height of a strath relative to the adjacent modern river channel the straths along the clearwater show an upstream increase in bedrock incision ranging from 0 at the coast to a maximum of 110 m in the headwaters the incision at any point along the profile increases systematically with strath age the calculated incision rates range from 10 ky the clearwater river valley has maintained a steady state profile defined by a long term balance in the rates of incision and rock uplift upstream divergence of terraces is best explained by an increase in the rate of rock uplift from the coast toward the central part of the range these results are consistent with other evidence indicating a long term steady state balance between the accretionary influx and the erosional outflux for this part of the cascadia subduction wedge since 14 ma these results help show how terrace deposits form in tectonically active landscapes the dominantly fluvial clearwater drainage was forming straths while alpine glaciers were advancing in adjacent drainages in turn the straths were buried during the transition to interglacial times because of increased sediment supply due to local deglaciation and because of eustatic highstands that forced aggradation in the lower reach of the drainage and across the continental shelf as well the fluvial system shows strong forcing by the glacial climate cycle even so the river appears to have returned to the same valley profile during each cycle of strath cutting thus bedrock incision is clearly unsteady at time scales shorter than the glacial climate cycle 100 ky but appears to be relatively steady when averaged over longer time scales a simple kinematic model is used to examine how uplift of the cl our analysis indicates that the accretionary flux into the wedge occurs mainly by frontal accretion and not by underplating if accretion occurred entirely at the front of the wedge the present west coast should be moving to the northeast at 3 m ky relative to a fixed puget sound this prediction is in good agreement with offset of a 122 ka sea cliff preserved at the southwest side of the clearwater valley profile in this case the long term margin perpendicular shortening would account for 20 to 35 percent of the geodetically measured northeast southwest shortening across the olympic mountains

characteristics of steady state fluvial topography above fault bend folds 1 in steady state convergent orogens erosion balances lateral as well as vertical bedrock motions for simple geometrical reasons the difference between the total steady state erosion flux and its vertical component is up to 30 for typical fluvial slopes and bedrock streamline inclinations suggesting that lateral advection is also likely to be expressed topographically in order to understand these geomorphologic consequences we focus on steady state topography developed on active fault bend folds first we derive an analytical solution for the slopes of detachment limited streams that incorporates lateral advection next we conduct experiments using a numerical two dimensional landscape evolution model channel hillslope integrated landscape development model child incorporating linear diffusion on hillslopes and detachment limited stream channel incision above a fault bend fold the concavity and steepness indices of steady state long profiles are functions of bedrock velocity magnitude and direction streamflow direction and fluvial erosivity asymmetry of mountain range profiles varies as a function of fluvial erosivity or bedrock velocity only if we account for the lateral velocity component this asymmetry is equally sensitive to this lateral component fluvial incision and hillslope diffusion however the effect of diffusion on drainage divide position is significant only at high diffusivities short length scales low bedrock advection rates or relatively low fluvial erosivity thus in most mountain ranges and fault blocks drainage divide migration is expected to be dictated by stream channel erosion model results are shown to be consistent with topography in the siwalik hills nepal which overlie fault bend folds produced above the frontal fault systems in the himalayan foreland

seventeenth canadian geotechnical colloquium the effect of cohesion loss and stress path on brittle rock strength stress strain curves for brittle rocks show three characteristic stress levels crack initiation long term strength and peak strength damage controlled testing at low confining stresses has shown that the long term and peak strengths are sensitive to the amount of induced damage i e the greater the amount of damage the lower the long term and peak strengths these tests also showed that the brittle failure process is characterized by a loss of cohesion as friction is mobilized excavation of a circular test tunnel in massive brittle rock resulted in failure around the tunnel the back calculated strength for the failed rock around the tunnel is approximately one half of that measured in laboratory tests crack induced damage of lac du bonnet granite both in the laboratory and in situ begins when the load exceeds approximately one third of the unconfined compressive strength however the stress level associated with failure is a function of loading path in the laboratory where the loading path monotonically increases the ultimate strength of an unconfined sample is 225 mpa numerical studies suggest that in situ the loading path around the tunnel is more complex involving stress increase and decrease and stress rotation for this loading path failure initiates at a stress between 100 and 120 mpa conventional frictional failure criteria did not adequately predict the extent of brittle failure measured around the circular tunnel the results from the damage controlled laboratory tests and the microseismic monitoring carried out during tunnel construction indicate a constant deviatoric stress criterion is a reliable indicator for predicting the onset of damage this criterion was also found to give a reasonable prediction for the maximum depth of failure around the test tunnel the fundamental assumption in the constant deviatoric stress criterion is that at low confining stresses such as those which occur around underground openings the brittle failure process is dominated by cohesion loss

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

postglacial denudation of western tibetan plateau margin outpaced by long term exhumation the indus river one of asia s premier rivers drains the western tibetan plateau and the nanga parbat syntaxis these two areas juxtapose some of the lowest and highest topographic relief and commensurate denudation rates in the himalaya tibet orogen respectively yet the spatial pattern of denudation rates upstream of the syntaxis remains largely unclear as does the way in which major rivers drive headward incision into the tibetan plateau we report a new inventory of 10 be based basinwide denudation rates from 33 tributaries flanking the indus river along a 320 km reach across the western tibetan plateau margin we find that denudation rates of up to 110 mm k y 1 in the ladakh and zanskar ranges systematically decrease eastward to 10 mm k y 1 toward the tibetan plateau independent results from bulk petrographic and heavy mineral analyses support this denudation gradient assuming that incision along the indus exerts the base level control on tributary denudation rates our data show a systematic eastward decrease of landscape downwearing reaching its minimum on the tibetan plateau in contrast denudation rates increase rapidly 150 200 km downstream of a distinct knickpoint that marks the tibetan plateau margin in the indus river longitudinal profile we infer that any vigorous headward incision and any accompanying erosional waves into the interior of the plateau mostly concerned reaches well below this plateau margin moreover reported long term 10 6 yr exhumation rates from low temperature chronometry of 0 1 0 75 mm yr 1 consistently exceed our 10 be derived denudation rates with averaging time scales of 10 3 10 4 yr for our denudation data we report postglacial rates of downwearing in a tectonically idle landscape to counterbalance this apparent mismatch denudation rates must have been higher in the quaternary during glacial interglacial intervals

environment and paleoecology of a 12 ka mid north american younger dryas forest chronicled in tree rings abstract until now availability of wood from the younger dryas abrupt cooling event yde in n america ca 12 9 to 11 6 ka has been insufficient to develop high resolution chronologies for refining our understanding of yde conditions here we present a multi proxy tree ring chronology ring widths events evidenced by microanatomy and macro features stable isotopes from a buried black spruce forest in the great lakes area liverpool east site spanning 116 yr at ca 12 000 cal yr bp during this largely cold and wet period the proxies convey a coherent and precise forest history including frost events tilting drowning and burial in estuarine sands as the laurentide ice sheet deteriorated in the middle of the period a short mild interval appears to have launched the final and largest episode of tree recruitment ultimately the tops of the trees were sheared off after death perhaps by wind driven ice floes culminating an interval of rising water and sediment deposition around the base of the trees although relative influences of the continental ice sheet and local effects from ancestral lake michigan are indeterminate the tree ring proxies provide important insight into environment and ecology of a n american yde boreal forest stand

critical taper model of fold and thrust belts and accretionary wedges the fold and thrust belts and submarine accretionary wedges that lie along compressive plate boundaries are one of the best understood deformational features of the earth s upper crust although there is considerable natural variation among the many fold and thrust belts and accretionary wedges that have been recognized and explored several features appear to be universal in cross section fold and thrust belts and accretionary wedges occupy a wedge shaped deformed region overlying a basal detachment or decollement fault the rocks or sediments beneath this fault show very little deformation the decollement fault characteristically dips toward the interior of the mountain belt or in the case of a submarine wedge toward the island arc the topography in contrast slopes toward the toe or deformation front of the wedge deformation within the wedge is generally dominated by imbricate thrust faults verging toward the toe and related fault bend folding two north american fold and thrust belts that exhibit these features are shown in figure 1 neither of these two examples is tectonically active today the southern canadian fold and thrust belt was active during the late jurassic and cretaceous 150 100 ma whereas the southern appa lachians were deformed during the late carboniferous to permian alle ghenian orogeny 300 250 ma figure 2 shows two examples that are currently active the taiwan fold and thrust belt produced by the sub duction of the eurasian plate beneath the philippine sea plate suppe 1981 1987 and the barbados accretionary wedge produced by the sub

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

the role of climate and tectonics in aggradation and incision of the indus river in the ladakh himalaya during the late quaternary

timing and climatic drivers for glaciation across semi arid western himalayan tibetan orogen abstract mapping and forty seven new 10 be ages help define the timing of glaciation in the ladakh and pangong ranges in northwest india five new local glacial stages are defined for the ladakh range from oldest to youngest these include the ladakh 4 glacial stage at 81 20 ka the ladakh 3 glacial stage not dated the ladakh 2 glacial stage at 22 3 ka the ladakh 1 glacial stage not dated and the ladakh cirque glacial stage at 1 8 0 4 ka three local glacial stages are defined for the pangong range which include the pangong 2 glacial stage at 85 15 ka the pangong 1 glacial stage at 40 3 ka and the pangong cirque glacial stage at 0 4 0 3 ka the new 10 be ages are combined with 645 recalculated 10 be ages from previous studies to develop the first regional framework of glaciation across the dryland regions of the greater himalaya transhimalaya pamir and tian shan at the western end of the himalayan tibetan orogen nineteen regional glacial stages are recognized that are termed semi arid western himalayan tibetan stages swhts these include swhts 9 at 311 32 ka swhts 7 at 234 44 ka tentative swhts 6 at 146 18 ka swhts 5e at 121 11 ka swhts 5a at 80 5 ka swhts 5a at 72 8 ka swhts 4 at 61 5 ka swhts 3 at 46 4 ka swhts 2f at 30 3 ka swhts 2e at 20 2 ka swhts 2d at 16 9 0 7 ka swhts 2c at 14 9 0 8 ka swhts 2b at 13 9 0 5 ka swhts 2a at 12 2 0 8 ka swhts 1e at 8 8 0 3 ka tentative swhts 1d at 6 9 0 2 ka tentative swhts 1c at 3 8 0 6 ka swhts 1b at 1 7 0 2 ka and swhts 1a at 0 4 0 1 ka regional glacial stages older than 21 ka are broadly correlated with strong monsoons swhts that are 21 ka or younger have smaller uncertainties and broadly correlate with global ice volume given by marine oxygen isotope stages and northern hemisphere climatic events oldest dryas older dryas younger dryas roman humid period and little ice age

topographic advection on fault bend folds inheritance of valley positions and the formation of wind gaps drainage basins formed along the flanks of any individual linear mountain range or fault block are commonly observed to be self similar in planform uniformly spaced and in some cases aligned with drainage basins on the opposing flank data from the siwalik hills nepal illustrate this organization where drainage basins and valleys are aligned across the main divide we suggest that valley alignment is a consequence of advection of topography across the divide to explore this hypothesis numerical experiments were conducted using a landscape evolution model of a fault bend fold that simulates detachment limited stream incision and linear hillslope diffusion results show that the presence of incised valleys and a lateral component of bedrock motion are necessary and sufficient conditions for advection of relief across the divide a mechanism by which wind gaps form and valley spacing on the far side of a ridge is inherited from that on the near side this topographic inheritance is promoted by low rock erodibility low precipitation rates fast bedrock velocities and or intermediate fault dips

10be derived himalayan denudation rates and sediment budgets in the ganga basin abstract the himalayas represent the archetype of mountain building due to active continental collision and are considered in many studies as the locus of intense interactions between climate denudation and tectonics estimates of modern denudation rates across the entire range remain however relatively sparse in this study in situ produced cosmogenic 10 be concentrations were measured in detritic quartz in order to determine basin scale denudation rates for the central part of the himalayan range river sand was sampled over several years in the main trans himalayan rivers from the himalayan front to the ganga outlet in bangladesh the calculated 10 be denudation rates of the trans himalayan river basins range from 0 5 to 2 4 mm yr 1 average 1 3 mm yr 1 and vary by up to a factor of 3 between sampling years these denudation rates strongly contrast with the 0 007 mm yr 1 denudation rate of southern tributary basins draining the indian craton this work also shows that in the ganga basin no systematic evolution of average 10 be concentrations is observed during floodplain transfer implying that distal samples can be used to estimate the integrated denudation rate of the whole central himalayan range samples from the ganga in bangladesh display remarkably low variability in 10 be concentration implying an average himalayan denudation rate of 1 0 1 1 mm yr 1 however within the floodplain several samples suggest a recent perturbation of sediment transport dynamics with a recent increase in the relative sediment contribution from southern tributaries the himalayan sediment flux deduced from the 10 be denudation rate of the range is 610 230 mt yr 1 this flux is consistent within uncertainty with sediment fluxes derived from sediment gauging the similarity of the two flux estimates suggests that himalayan erosion fluxes have remained stable over the last centuries even if the large uncertainties associated with each method hamper more precise assessments

apparent osl ages of modern deposits from fabergstolsdalen norway implications for sampling glacial sediments the application of optically stimulated luminescence osl dating within glacial settings can be limited where sediments have not had their osl signal fully reset by sunlight exposure heterogeneous bleaching can result in age overestimations and although it is recognized that certain depositional settings are more likely to have experienced sufficient sunlight exposure to bleach the osl signal no comprehensive study has empirically investigated the processes of sediment bleaching or the variability in bleaching between deposits of the same type and within the same glacial catchment a suite of modern glacial and glaciofluvial sediments from fabergstolsda len southern norway have been analysed to explore the controls that sedimentary processes and depositional setting have on bleaching of the osl signal of quartz there is considerable variability in the residual osl ages of similar modern deposits which reflects high sensitivity of the osl signal to sediment source sedimentary process transport distance and depositional setting overdispersion values are greatest for the sediments which have been most heterogeneously bleached and these sediments have the lowest residual ages sampling strategies that incorporate sufficient consideration of the depositional framework of sample settings can minimize the effects of unbleached residuals on osl age determinations copyright 2013 the authors journal of quaternary science published by john wiley sons ltd on behalf of quaternary research association

squeezing river catchments through tectonics shortening and erosion across the indus valley nw himalaya tectonic displacement of drainage divides and the consequent deformation of river networks during crustal shortening have been proposed for a number of mountain ranges but never tested in order to preserve crustal strain in surface topography surface displacements across thrust faults must be retained without being recovered by consequent erosion quantification of these competing processes and the implications for catchment topography have not previously been demonstrated here we use structural mapping combined with dating of terrace sediments to measure quaternary shortening across the indus river valley in ladakh nw himalaya we demonstrate 0 21 m k y 1 of horizontal displacement since ca 45 ka on the stok thrust in ladakh which defines the southwestern margin of the indus valley catchment and is the major back thrust to the tethyan himalaya in this region we use normalized river channel gradients of the tributaries that drain into the indus river to show that the lateral continuation of the stok thrust was active for at least 70 km along strike shortening rates combined with fault geometries yield vertical displacement rates that are compared to time equivalent erosion rates in the hanging wall derived from published detrital 10be analyses the results demonstrate that vertical displacement rates across the stok thrust were approximately twice that of the time equivalent erosion rates implying a net horizontal displacement of the surface topography and hence narrowing of the indus valley at 0 1 m k y 1 a fill terrace records debris flow emplacement linked to thrust activity resulting in damming of the valley and extensive lake development conglomerates beneath some of the modern alluvial fans indicate a northeastward shift of the indus river channel since ca 45 ka to its present course against the opposite side of the valley from the stok thrust the integration of structural topographic erosional and sedimentological data provides the first demonstration of the tectonic convergence of drainage divides in a mountain range and yields a model of the surface processes involved

hoek brown parameters for predicting the depth of brittle failure around tunnels a review of underground openings excavated in varying rock masstypes and conditions indicates that the initiation of brittlefailure occurs when the damage index di expressed as theratio of the maximum tangential boundary stress to the laboratoryunconfined compressive strength exceeds approx0 4 when thedamage index exceeds this value the depth of brittle failure around a tunnel can be estimated by using a strengthenvelope based solely on cohesion which in terms of thehoek brown parameters implies that m 0 it is proposed that inthe brittle failure process peak cohesion and friction are notmobilized together and that around underground openings thebrittle failure process is dominated by a loss of the intrinsiccohesion of the rock mass such that the frictional strengthcomponent can be ignored for estimating the depth of brittlefailure an essential component in designing support for theopening case histories were analyzed using the hoek brownfailure criterion with traditional frictional parameter

late quaternary fluvial terraces of the romagna and marche apennines italy climatic lithologic and tectonic controls on terrace genesis in an active orogen abstract we synthesize a new fluvial terrace chronostratigraphy of the bidente and musone rivers cast within a broader european framework which forms the basis of a terrace genesis and river incision model for the northern apennines italy our model supported by terrace long profiles correlation to po foreland sediments 15 new radiocarbon dates and published numeric and relative stratigraphic ages highlights how drainage basin substrate drives concurrent formation of strath terraces in the bidente basin and fill terraces in the musone basin quaternary climate change paces the formative geomorphic processes through unsteady discharges of water and sediment in the weathering limited setting represented by the bidente basin siliciclastic detritus carves broad strath surfaces during glacial climates that are preserved as terraces as the river incises during the transition to an interglacial climate in contrast the transport limited and carbonate detritus dominated musone basin sees valleys deeply buried by aggradation during glacial climates followed by river incision during the transition to an interglacial climate incision of these rivers over the past 1 million years has been both unsteady and non uniform these and all po adriatic draining rivers are proximal to a base level defined by mean sea level and have little room for increasing their longitudinal profile concavities through incision particularly in their lower reaches despite periodic glacio eustatic drawdowns as a result the observed incision is best explained by rock uplift associated with active local fault or fold growth embedded in the actively thickening and uplifting apennine foreland

uplift shortening and steady state topography in active mountain belts we present a tectonic surface process model used to investigate the role of horizontal shortening in convergent orogens and the effects on steady state topography the tectonic model consists of a specified velocity field for the earth9s surface and includes a constant uplift rate and a constant horizontal strain rate which varies to reflect the relative importance of frontal accretion and underplating in an orogenic wedge the surface process model includes incision of a network of rivers formed by collection of applied precipitation and diffusive hillslope mass transfer three non dimensional parameters describe this model a ratio of the maximum horizontal velocity to the vertical velocity a peclet number expressing the efficiency of the hillslope diffusion relative to the uplift rate and a fluvial erosion number reflecting the fluvial incision efficiency relative to the uplift rate a series of models are presented demonstrating the resultant steady state landforms parameterized by these three numbers a finite velocity ratio results in an asymmetric form to the model mountain range although the magnitude of the asymmetry also depends on the peclet number topographic steady state is achieved faster for models with no horizontal component to the velocity field with finite horizontal velocity topographic steady state is achieved only at the scale of the entire mountain range even the first order drainage basins are unstable with time in the presence of horizontal shortening we compare our model results to topographic profiles from active mountain ranges in taiwan new zealand and the olympic mountains of washington state all these examples exhibit asymmetric topographic form with the asymmetry consistent with the polarity of subduction suggesting that horizontal tectonic motion is affecting the macro geomorphic form of these ranges

examination of surface exposure ages of antarctic moraines using in situ produced 10be and 26al concentrations of 10be t12 1 5 106 y and 26a1 t12 0 72 106 y have been determined by accelerator mass spectrometry ams in a suite of quartz samples taken from sandstone boulders in several moraines in arena valley a dry valley adjacent to the taylor glacier in the quatermain mountains southern victoria land east antarctica these isotopes are produced in surficial quartz by cosmic ray spallation of o and si the concentrations in these samples ranged from 6 1 105 to 3 0 107 at g 1 for 10be and from 9 4 106 to 1 2 108 at g 1 for 26a1 depending upon the extent of exposure at the surface analyses of 10be in several samples from a single moraine at altitudes ranging from 1300 to 1650 m permitted an estimation of the air attenuation pathlength of cosmic ray neutrons the value of 142 96 41 g cm 2 is consistent with other published values production rates of 17 6 4 at g 1 y 1 for 10be and 113 54 16 at g 1 y 1 for 26a1 at 1300 m and 87 s and a 26al 10be production ratio of 6 5 1 3 1 3 were calculated from the data these values correspond to sea level production rates at high geomagnetic latitude of 6 4 at g 1 y 1 and 41 7 at g 1 y 1 for 10be and 26a1 respectively consistent with determinations based on 11 ky glacially polished surfaces in the sierra nevada in california these production rates imply exposure ages for the various moraines ranging from 50 ky to 2 5 my in accordance with other geological evidence the 10be and 26al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of 3he examination of the 3he concentrations in conjunction with the present data set yields an estimate of 3he production of 230 8540 at g 1 y 1 corresponding to 85 31 15 at g 1 y 1 at sea level this is lower than previously reported values of 240 60 at g 1 y 1 and 190 at g 1 y 1 scaled to sea level and high geomagnetic latitude based respectively on volcanic flows less than 2000 years old at low latitude and samples collected from 14 400 year old volcanic flows this discrepancy is likely due to diffusive losses which may become significant up to 50 for surface exposure ages on the order of 2 0 my nevertheless the general correlations among the three isotopes suggest that 3he does not suffer gross losses through diffusion

hanging valleys in fluvial systems controls on occurrence and implications for landscape evolution 1 we document and characterize hanging valleys in a fluvially eroded landscape in eastern taiwan our conceptual model for the initiation of hanging valleys builds on a recently proposed model of bedrock incision in which erosion actually becomes less efficient on very steep channel gradients if a pulse of incision in the main stem outpaces the tributary response the gradients at tributary mouths may therefore pass a threshold value beyond which erosional efficiency declines giving rise to a mismatch between trunk and tributary erosion rates this mismatch is expected at junctions with small tributaries where a step function decrease in drainage area also leads to sharp contrasts in water and sediment flux between trunk and tributary channels the occurrence of hanging valleys in actively uplifting fluvial landscapes such as the central range of taiwan suggests that the most common parameterizations of bedrock erosion which typically assume a monotonic positive correlation between channel gradient and incision rate may be violated in very steep channels in addition hanging valleys could greatly increase the response time of landscapes to tectonic perturbations since catchments above these tributary mouths will be insulated from these perturbations until a new suite of processes e g weathering and rock mass failure wear through the hanging valley lip the results of this study underscore the need for a more complete understanding of bedrock erosion processes and the incorporation of process transitions and threshold conditions into landscape evolution models

the indus clastics forearc basin sedimentation in the ladakh himalaya india abstract the mid cretaceous to early tertiary clastic sediments of the indus group represent the forearc basin succession of the transhimalayan arc trench system in the late albian to early eocene a shallowing upward megasequence tar turbidites to nummulitic limestones and alluvial to deltaic sediments basgo and temesgam formations were deposited respectively on the southern and northern flanks of the basin clastic petrography points to provenance from the largely undissected volcanic cover of the massif with more important plutonic detritus recorded in the northern alluvial units after collision with the indian passive margin in the early eocene sedimentation in the whole basin was characterized by huge alluvial fans nurla formation and then by lacustrine deposits formed in an intermontane depression nimu formation a rapid change in petrographic and geochemical composition is recorded in post early eocene units with sharp increase in plutonic detritus and trace elements typically associated with ophiolites testifying to the uplift of both arc massif and subduction complex sources after collision with the indian passive margin the petrography of the indus basin clastics and the evolution of detrital modes compare well with volcano plutonic suites deposited in modern and ancient forearc basins the composition of sandstone units contained within the accretionary prism instead suggests provenance from an undissected magmatic arc and deposition in abyssal plain and trench settings nindam volcaniclastic turbidites reworking of arc derived sandstones took place in small basins perched on the accretionary trench slope the asian continental margin of the neotethys ocean was thus an active pacific type arc trench system until the eocene when it collided with india underwent polyphase fold thrust deformation and was finally uplifted several kilometers to form the indus suture zone of the himalayas

field calibration of sediment flux dependent river incision 1 bed erosion and sediment transport are ubiquitous and linked processes in rivers erosion can either be modeled as a detachment limited function of the shear stress exerted by the flow on the bed or as a transport limited function of the sediment flux capacity of the flow these two models predict similar channel profiles when erosion rates are constant in space in time but starkly contrasting behavior in transient settings traditionally detachment limited models have been used for bedrock rivers whereas transport limited models have been used in alluvial settings in this study we demonstrate that rivers incising into a substrate of loose but very poorly sorted relict glacial sediment behave in a detachment limited manner we then develop a methodology by which to both test the appropriate incision model and constrain its form specifically we are able to tightly constrain how incision rates vary as a function of the ratio between sediment flux and sediment transport capacity in three rivers responding to deglaciation in the ladakh himalaya northwest india this represents the first field test of the so called tools and cover effect along individual rivers

back analysis of a seismically induced highway embankment failure during the 1999 duzce earthquake an earthquake of magnitude 7 2 on the richter scale occurred on 12 november 1999 in the duzce bolu region of turkey the region was also hit approximately 3 months before during the devastating kocaeli earthquake of 17 august 1999 besides high casualties and damage to various engineering structures and buildings slope and embankment failures on the highway and the country roads occurred in this study the authors are concerned with the back analysis of an embankment failure that occurred on the four lanes e 5 highway connecting ankara to istanbul at bakacak in the bolu province during the 1999 duzce earthquake both pseudo dynamic and dynamic limiting equilibrium methods are used to back analyse the conditions for the initiation of failure and also displacement responses of the embankment during the earthquake shaking after having given a brief summary of the investigations on the post failure state the geology and geotechnical characteristics of the site and the dynamic limiting equilibrium method developed and used for analyses are described the results of the back analysis based on a pseudo dynamic approach revealed that the maximum ground acceleration to initiate the failure of the embankment was probably about 0 125 g on the other hand the application of a method for computing the displacement and velocity responses of the failed embankment showed that the failure was possible when the embankment was subjected to ground accelerations similar to that recorded at the duzce station in addition the computations also revealed that the time history of accelerations could be very important for the failure of slopes and embankments

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

neogene rejuvenation of central appalachian topography evidence for differential rock uplift from stream profiles and erosion rates abstract the persistence of topography within ancient orogens remains one of the outstanding questions in landscape evolution in the eastern north american appalachians this question is manifest in the outstanding problem of whether topographic relief is in a quasi equilibrium state decaying slowly over many millennia or whether relief has increased during the late cenozoic here we present quantitative geomorphic data from the nonglaciated portion of the susquehanna river drainage basin that provide insight into these end member models analysis of channel profiles draining upland catchments in the northern valley and ridge appalachian plateau blue ridge and piedmont provinces reveals that a large number of streams have well defined knickpoints clustered at 300 600 m elevation but not systematically associated with transitions from weak to resistant substrate cosmogenic 10 be inventories of modern stream sediment indicate that erosion rates are spatially variable ranging from 5 30 m myr above knickpoints to 50 100 m myr below knickpoints overall channel gradients normalized for drainage area scale linearly with catchment averaged erosion rates collectively regionally consistent spatial relationships among erosion rate channel steepness and knickpoints reveal an ongoing wave of transient channel adjustment to a change in relative base level reconstructions of relict channel profiles above knickpoints suggest that higher rates of incision are associated with 100 150 m of relative base level fall that accompanied epierogenic rock uplift rather than a change to a more erosive climate or drainage reorganization channel response timescales imply that the onset of relative base level change predates 3 5 ma and may have begun as early as 15 ma we suggest that adjustment of the channel network was likely driven by changes in mantle dynamics along the eastern seaboard of north america during the neogene

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

prediction of flash flood hazard impact from himalayan river profiles to what extent can we treat topographic metrics such as river long profiles as a long term record of multiple extreme geomorphic events and hence use them for hazard prediction we demonstrate that in an area of rapid mountain erosion where the landscape is highly reactive to extreme events channel steepness measured by integrating area over upstream distance chi analysis can be used as an indicator of geomorphic change during flash floods we compare normalised channel steepness to the impact of devastating floods in the upper ganga basin in uttarakhand northern india in june 2013 the pattern of sediment accumulation and erosion is broadly predictable from the distribution of normalised channel steepness in reaches of high steepness channel lowering up to 5 m undercut buildings causing collapse in low steepness reaches channels aggraded up to 30 m and widened causing flooding and burial by sediment normalised channel steepness provides a first order prediction of the signal of geomorphic change during extreme flood events sediment aggradation in lower gradient reaches is a predictable characteristic of floods with a proportion of discharge fed by point sources such as glacial lakes

magmatism and metamorphism in the ladakh himalayas the indus tsangpo suture zone abstract ladakh india provides a complete geological section through the northwestern part of the himalayas from kashmir to tibet within this section the magmatic metamorphic and geotectonic evolution of the northern himalayan orogeny has been studied using petrographic geochemical and isotope analytical techniques the beginning of the himalayan cycle was marked by large basaltic extrusions panjal trap of permian to lower triassic age at the northern margin of the gondwana continent indian shield these continental type tholeiitic basalts were followed by a more alkaline volcanism within the triassic to jurassic lamayuru unit of the gondwana continental margin lower jurassic to cretaceous oceanic crust and sediments ophiolitic melange s s accompany the triassic to cretaceous flysch deposits within the indus tsangpo suture zone the major structural divide between the indian shield high himalaya and the tibetan platform so far no relic of paleozoic oceanic crust has been found subduction of the tethyan oceanic crust during upper jurassic and cretaceous time produced an island arc represented by tholeiitic and calc alkaline volcanic rock series dras volcanics and related intrusives accompanied by volcaniclastic flysch deposits towards the tibetan continental margin subsequent to the subduction of oceanic crust large volumes of calc alkaline plutons trans himalayan or kangdese plutons intruded the tibetan continental margin over a distance of 2000 km and partly the dras island arc in the ladakh region the collision of the indian shield and tibetan platform started during the middle to upper eocene and caused large scale still active intracrustal thrusting as well as the piling up of the himalayan nappes the tectonically highest of these nappes is built up of oceanic crust and huge slices of peridotitic oceanic mantle spongtang klippe in the high himalayas the tectonic activity was accompanied and outlasted by a barrovian type metamorphism that affected triassic sediments of the kashmir nun kun synclinorium up to kyanite staurolite grade and the deeper seated units up to sillimanite grade cooling ages of micas are around 20 m y muscovite and 13 m y biotite towards the indus tsangpo suture zone metamorphism decreases with no obvious discontinuity through greenschist prehnite pumpellyite to zeolite grade remnants of possibly an eo himalayan blueschist metamorphism have been found within thrust zones accompanying ophiolitic melange in the suture zone

which dem is best for analyzing fluvial landscape development in mountainous terrains abstract regional studies of fluvial landforms and long term quaternary landscape development in remote mountain landscapes routinely use satellite derived dem data sets the srtm and aster dems are the most commonly utilised because of their longer availability free cost and ease of access however rapid technological developments mean that newer and higher resolution dem data sets such as alos world 3d aw3d and tandem x are being released to the scientific community geomorphologists are thus faced with an increasingly problematic challenge of selecting an appropriate dem for their landscape analyses here we test the application of four medium resolution dem products 30 m srtm aster aw3d 12 m tandem x for qualitative and quantitative analysis of a fluvial mountain landscape using the dades river catchment high atlas mountains morocco this landscape comprises significant dem remote sensing challenges notably a high mountain relief steep slopes and a deeply incised high sinuosity drainage network with narrow canyon gorge reaches our goal was to see which dem produced the most representative best fit drainage network and meaningful quantification to achieve this we used arcgis and stream profiler platforms to generate catchment hillshade and slope rasters and to extract drainage network channel long profile and channel slope and area data tandem x produces the clearest landscape representation but with channel routing errors in localised high relief areas thirty metre dems are smoother and less detailed but the aw3d shows the closest fit to the real drainage network configuration the tandem x elevation values are the closest to field derived gps measurements long profiles exhibit similar shapes but with minor differences in length elevation and the degree of noise smoothing with aw3d producing the best representation slope area plots display similarly positioned slope break knickpoints with modest differences in steepness and concavity indices but again best represented by aw3d collectively our study shows that despite the higher effective resolution of tandem x 12 m the aw3d 30 m data performs strongly across all analyses suggesting that it currently offers the greatest potential for regional mountain geomorphological analyses

distorted drainage basins as markers of crustal strain east of the himalaya extensive lithospheric deformation on the eastern margin of the india eurasia collision has brought three major rivers into exceptionally close proximity for over 300 km the salween mekong and yangtze rivers are only tens of kilometers apart 10 times closer than rivers of comparable length elsewhere in the world we view deeply incised river valleys as displacement markers that move with the underlying crust over time scales of at least tens of millions of years accordingly the close spacing of these major rivers and their nearly parallel trends reflect the large crustal strains near the eastern himalayan syntaxis these river characteristics are consistent with two primary phases of deformation in this tectonic setting ne sw shortening of 0 5 oriented radially from the eastern syntaxis followed by dextral shear strain of 6 1 along a north trending zone pervasive shearing of this magnitude throughout the 150 km wide region of anomalous drainage would account for 1000 km of northward motion of india relative to southern china directly east of this region another 1000 km of northward motion is likely to have been accommodated by pervasive shearing through a zone hundreds of kilometers wide finally we draw attention to the remarkable accord between the arcuate paths of each of the three great rivers in the broader southeastern tibet region and small circles that curve around the eastern himalayan syntaxis

using clast geometries to establish paleoriver discharges testing records for aggradation and incision from the upper indus river ladakh himalaya abstract river systems in the himalaya have been studied extensively to understand the processes driving periodic river valley aggradation and incision resulting due to rainfall high relief and ongoing deformation when climatic forces are considered the debate continues on whether wetter climatic intervals with localized glacier melting promote river aggradation through increased discharge and enhanced sediment load or instead it is during drier conditions that aggradation occurs through increased sediment to water ratio this study for the first time attempts to constrain discharge during periods of established river aggradation and incision over late quaternary here geometric data from imbricated gravels of channel fills are used to calculate paleodischarges during net river aggradation at 47 23 ka and preserved slack water deposits swds at 14 10 ka are used to constrain paleodischarges that occurred during net river incision catchment area normalized discharge derived from these valley fill sequences ranges from 0 78 to 3 26 10 7 m s 1 syn incision discharge estimates yielded normalized discharge values of 6 17 10 7 m s 1 are considerably higher than discharges estimated from periods of aggradation morphometric analysis chi slope and ksn along the indus river observed no relation with the paleodischarge this case study implies that net river incision in the upper indus river occurs predominantly during relatively wetter climatic conditions than the climate during aggradation

dynamic reorganization of river basins river networks evolve as migrating drainage divides reshape river basins and change network topology by capture of river channels we demonstrate that a characteristic metric of river network geometry gauges the horizontal motion of drainage divides assessing this metric throughout a landscape maps the dynamic states of entire river networks revealing diverse conditions drainage divides in the loess plateau of china appear stationary the young topography of taiwan has migrating divides driving adjustment of major basins and rivers draining the ancient landscape of the southeastern united states are reorganizing in response to escarpment retreat and coastal advance the ability to measure the dynamic reorganization of river basins presents opportunities to examine landscape scale interactions among tectonics erosion and ecology

evidence for late quaternary brittle deformation and back thrusting within the indus suture zone ladakh himalaya abstract although the tectonic evolution of the southern himalaya has been extensively studied relatively few studies have focused on potential neotectonic activity in the most hinterland part of himalaya north of the region that separates the southern edge of the tibetan plateau from the peaks of the higher himalayan range here we use a combination of new structural and geomorphic field data optically stimulated luminescence osl chronology as well as previously published seismicity and denudation rate dataset to suggest that the trans himalaya within the region of the indus suture zone isz is neotectonically active based on fault gouge tilted paleolake deposits and the chronology of deformed fluvial gravels constrained by osl dating the present study provides evidence for the tectonic activity along the isz between 78 and 58 ka the occurrence of two earthquakes of mw 4 0 and the focal mechanism solution of a shallow focus earthquake mw 3 0 depth 8 km near the town of upshi shows a pure thrust mechanism we suggest that this earthquake was likely associated with the upshi bazgo thrust a major structure which separates the mid miocene indus molasse from the cretaceous ladakh batholith it is envisaged that the fault and fold systems in the ladakh region such as the upshi bazgo thrust originated due to 1 acceleration in the northward movement of indian plate relative to the eurasian plate and 2 post collisional shortening parallel to plate convergence on account of this the eocene to miocene post collisional sedimentary sequences such as the indus molasse rode over the now extinct ladakh arc as it acted as a rigid body and formed a system of backthrusts which are neotectonically active

soft sediment deformation structures in the late quaternary sediments of ladakh evidence for multiple phases of seismic tremors in the north western himalayan region abstract the exposed quaternary sections of ladakh show evidence of seismicity during the late quaternary multiple levels of soft sediment deformation structures seismites are recorded from the quaternary sediments of the spituk leh along indus suture zone isz and the khalsar palaeolakes along shyok suture zone ssz and karakoraum fault kf the studied sections are a part of two major tectonically formed palaeolakes at 35 000 yr bp nine levels of seismites from spituk leh and eight levels from khalsar sections are recorded the deformed sediments comprise of clay silts and sand and are restricted to a single stratigraphic layers bounded by undeformed beds suggesting synsedimentary deformation the various deformational structures identified are simple and complex convolutes pinch and swell bedding microfolds and microfaults flame like structures pseudonodules clay diapirs ball and pillow structures pillar structures sedimentary dykes and mud lenses the release of stress along the isz ssz and kf may have been responsible for inducing seismicity in the area during the late quaternary times which may have caused liquefaction as a direct consequence of permanent deformation of ground surface due to earthquakes of large magnitudes 5 intensity the chronological data suggests release of stresses along isz ssz and kf in the form of earthquakes between 35 000 yr bp to approximately the last glacial maxima lgm as evident form the available chronology

expression of active tectonics in erosional landscapes understanding the manner and degree to which topography in active mountain ranges reflects deformation of the earth s surface remains a first order goal of tectonic geomorphology a substantial body of research in the past decade demonstrates that incising channel systems play a central role in setting relationships among topographic relief differential rock uplift rate and climatically modulated erosional efficiency this review provides an introduction to the analysis and interpretation of channel profiles in erosional mountain ranges we show that existing data support theoretical expectations of positive monotonic relationships between channel steepness index a measure of channel gradient normalized for downstream increases in drainage area and erosion rate at equilibrium and that the transient response to perturbations away from equilibrium engenders specific spatial patterns in channel profiles that can be used to infer aspects of the forcing these aspects of channel behavior lay the foundation for a series of case studies that we use to illustrate how focused quantitative analysis of channel morphology can provide insight into the spatial and temporal dynamics of active deformation although the complexities of river response to climate lithology and uplift patterns mean that multiple interpretations of topographic data alone will always possible we show that application of stream profile analysis can be a powerful reconnaissance tool with which to interrogate the rates and patterns of deformation in active mountain belts

large ancient earthquakes in the western issyk kul basin kyrgyzstan northern tien shan abstract new paleoseismological and archaeoseismological data from the western issyk kul basin of kyrgyzstan northern tien shan provide new insights on active fault in the actively deforming basement involved thrust system of central asia newly discovered fault scarps follow south and north dipping thrust faults which delineate the kyrgyz and kungey ranges bordering the issyk kul basin motion on these faults generated earthquakes with magnitudes 6 2 7 6 and msk 64 shaking intensities viii xi deformation observed in the zone of the toguz bulak fault results from two holocene earthquakes and another event that occurred about 8000 yr bp two more events at 13 000 and 3000 yr bp deformed the northeastern periphery of the kyzyl ompul uplift archaeoseismological research in the northern sary bulun settlement in the western periphery of the boz barmak uplift revealed traces of another earthquake of msk 64 shaking intensity i viii dating back to the 12th century the obtained data correlates well with results of previous paleoseismological and archeoseismological studies they show that in the northern tien shan there were clusters of strong earthquakes with ages of 14 13 8 4 3 ka ago and in the 11 12th centuries ad divided by periods of 4 5 ka we infer that coseismic slip on these faults may have formed a tectonic dam at the edge of the basin through growth of the boz barmak uplift and this dam ultimately deflected the chu river into its modern channel which bypasses the lake lacustrine sediments in the northeastern periclinal segment of the boz barmak uplift bear signatures of soft sediment deformation structures seismites corresponding to seven m 5 5 5 i vi vii earthquakes timed at about 20 000 yr bp

structural evolution and sequence of thrusting in the tethyan fold thrust belt and indus yalu suture zone southwest tibet regional mapping of a north south traverse from the india nepal china border junction to mount kailas in southwest tibet combined with previously published geochronologic and stratigraphic data is the basis for an incremental restoration of the tethyan fold thrust belt and deformation along the indus yalu suture zone from north to south the major structural features are 1 the indus yalu suture zone composed of five south dipping thrust faults involving rocks interpreted to represent parts of the former indian passive margin and asian active margin 2 the tethyan fold thrust belt composed of a dominantly north dipping system of imbricate thrust faults involving precambrian through upper cretaceous strata and 3 the kiogar jungbwa thrust sheet a linelength cross section reconstruction indicates a minimum of 176 km of north south horizontal shortening partitioned by the tethyan fold thrust belt 112 km and indusyalu suture zone 64 km sequential restoration of the cross section shows that the locus of shortening prior to the late oligocene occurred significantly south possibly 60 km of the indus yalu suture zone within the tethyan fold thrust belt and that a significant amount of unsubducted oceanic lithosphere was present south of the suture in southwest tibet until that time an implication of this result is that postcollision oligocene miocene high k calcalkaline magmatism may be explained by melting due to active subduction of oceanic crust beneath the kailas magmatic complex until the late oligocene a regional profile across the tibetan himalayan orogen from

global analysis of the stream power law parameters based on worldwide 10be denudation rates abstract the stream power law expressed as e kamsn where e is erosion rate lt 1 k is an erodibility coefficient t 1l 1 2m a is drainage area l 2 s is channel gradient l l and m and n are constants is the most widely used model for bedrock channel incision despite its simplicity and limitations the model has proved useful for topographic evolution knickpoint migration palaeotopography reconstruction and the determination of rock uplift patterns and rates however the unknown parameters k m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid which considerably limits the use and interpretation of the model in this study we compile a unique global data set of published basin averaged erosion rates that use detrital cosmogenic 10be these data n 1457 enable values for fundamental river properties to be empirically constrained often for the first time such as the concavity of the river profile m n ratio or concavity index the link between channel slope and erosion rate slope exponent n and substrate erodibility k these three parameters are calculated for 59 geographic areas using the integral method of channel profile analysis and allow for a global scale analysis in terms of climatic tectonic and environmental settings in order to compare multiple sites we also normalize n and k using a reference concavity index m n 0 5 a multiple regression analysis demonstrates that intuitive or previously demonstrated local scale trends such as the correlation between k and precipitation rates do not appear at a global scale our results suggest that the slope exponent is generally 1 meaning that the relationship between erosion rate and the channel gradient is nonlinear and thus support the hypothesis that incision is a threshold controlled process this result questions the validity of many regional interpretations of climate and or tectonics where the unity of n is routinely assumed

fluvial response to horizontal shortening and glaciations a study in the southern alps of new zealand 1 it has been postulated that a steady state between erosional and tectonic processes may develop in continental collision however it is not clear whether steady state conditions can be reached for all components of the landscape here we show using landscape evolution models and field evidence that a true geomorphic steady state may never be reached in the southern alps of new zealand the strong asymmetries in tectonic uplift and tectonic advection and the onset of glaciations constantly interact to prevent the landscape from reaching a topographic steady state evidence suggests that the first order geomorphology on the western side of the southern alps is controlled by orographic precipitation combined with extreme rates of tectonic uplift whereas the development of deep glacial valleys on the eastern side is initiated by differential uplift along large faults we also develop a first order equation governing the dynamics of the main divide to show that both tectonic advection and fluvial erosion efficiency control the position and the height of the main drainage divide using a two dimensional landscape evolution model we demonstrate that the transition from glacial to fluvial conditions at the end of the last glaciation led to substantial modifications of the landscape while the main trunk channels get slowly uplifted ridges are leveled down causing the relief to decrease hillslopes appear to be affected by fluvial processes which seem to be driven by incision of river tributaries this reduction of relief will probably never reach a steady state since warmer interglacial periods are substantially shorter than glacial periods

processes rates and time scales of fluvial response in an ancient postglacial landscape of the northwest indian himalaya both glacial and fluvial processes are key elements in molding landscapes in high mountain environments glaciers are highly efficient erosional agents and producers of sediment but are restricted spatially while rivers can transmit such signals through landscapes and flush this sediment out of mountain belts and into sedimentary basins however little research has focused on the manner in which these two agents of landscape change interact especially on longer time scales we analyze a suite of catchments that drain the previously glaciated ladakh batholith in the northwest indian himalaya which preserve the oldest known moraine succession in this mountain chain we describe and quantify the rates processes and time scales of postglacial recovery of the fluvial system across a previously unstudied time interval of 105 106 yr we demonstrate that glacial modification of the upper reaches of a catchment can have profound first order influence on the hydraulic scaling of the channel downstream where increasing degree of glacial modification systematically and nonlinearly elevates the channel concavities of downstream reaches above the expected value range of 0 3 0 6 we also demonstrate that the response time of these systems as they recover must exceed 500 k y which is longer than any previously reported estimate for recovery times from glaciations but is comparable with estimates from many tectonically perturbed landscapes

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

terrestrial cosmogenic nuclide surface exposure dating of the oldest glacial successions in the himalayan orogen ladakh range northern india terrestrial cosmogenic nuclide surface exposure dating of moraine boulders and alluvial fan sediments define the timing of five glacial advances over at least the last five glacial cycles in the ladakh range of the transhimalaya the glacial stages that have been identified are the indus valley glacial stage dated at older than 430 ka the leh glacial stage occurring in the penultimate glacial cycle or older the kar glacial stage occurring during the early part of the last glacial cycle the bazgo glacial stage at its maximum during the middle of the last glacial cycle and the early holocene khalling glacial stage the exposure ages of the indus valley moraines are the oldest observed to date throughout the himalayan orogen we observe a pattern of progressively more restricted glaciation during the last five glacial cycles likely indicating a progressive reduction in the moisture supply necessary to sustain glaciation a possible explanation is that uplift of himalayan ranges to the south and or of the karakoram mountains to the west of the region may have effectively blocked moisture supply by the south asian summer monsoon and mid latitude westerlies respectively alternatively this pattern of glaciation may reflect a trend of progressively less extensive glaciation in mountain regions that has been observed globally throughout the pleistocene

restoration and evolution of the intermontane indus molasse basin ladakh himalaya india abstract collision of the indian plate with the karakorum plate lhasa block during the eocene ca 55 50 ma created predominantly a s or sw verging thrust culmination across the himalaya during the late tertiary two molasse basins existed the siwalik bain formed in the late miocene to present on the indian foreland south of the himalaya and the mid eocene to late miocene indus basin along the indus suture zone north of the high himalaya the indus basin is approximately 2000 km long extending eastwards from ladakh across south tibet a balanced cross section along the zanskar river shows a minimum 36 km shortening in the eocene late miocene molasse and suggests that the minimum basin width was approximately 60 km in ladakh more than 2000 m of post eocene alluvial fan fluvial and fluvio lacustrine sediments accumulated in the ladakh sector with petrographies suggesting derivation mainly from the deeply dissected and uplifted northern granodioritic ladakh batholith aptian eocene with only minor amounts of debris derived from the deformed southern tethyan passive margin palaeocurrents show predominant e w axis parallel sediment transport with subordinate lateral input paths being preserved the indus molasse basin is deformed by numerous post eocene n directed backthrusts many of which cut the entire stratigraphy and therefore were active at least into late tertiary times

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

growth and lateral propagation of fault related folds in the siwaliks of western nepal rates mechanisms and geomorphic signature 1 we study the controls on drainage development in tectonically active regions using a numerical tectonic surface processes model combining tectonic uplift caused by fault related folding with erosion by fluvial incision hillslope diffusion and landsliding our model shows the fundamental control exerted by the dip of the detachment underlying the folds on drainage evolution when the detachment is horizontal the relative rates of tectonic uplift and fluvial incision control the evolution for a nonzero dip in contrast the lateral displacement gradient associated with fold propagation sets up a lateral slope behind the active structure which deflects the stream network we also demonstrate the importance of landsliding for the attainment of realistic and steady state topography in contrast discontinuous tectonic movements do not appear to influence the system we apply our model to the dundwa fault related fold ridge siwalik nepal we estimate a remarkably low mean propagation rate for different segments of the structure this finding together with the structure and morphology of the ridge leads us to propose that the ridge developed by linkage of several component segments the drainage evolution predicted when modeling this scenario compares favorably with field observations our models provide insights into the dynamics of fault related fold propagation in particular as a result of fault segment linkage estimates of propagation rate of these structures may be strongly scale dependent and the observed morphology and drainage patterns on fault related fold ridges may be controlled by fault geometry rather than by the relative rates of tectonics and surface processes

solutions of the stream power equation and application to the evolution of river longitudinal profiles 1 erosion by bedrock river channels is commonly modeled with the stream power equation we present a two part approach to solving this nonlinear equation analytically and explore the implications for evolving river profiles first a method for non dimensionalizing the stream power equation transforms river profiles in steady state with respect to uniform uplift into a straight line in dimensionless distance elevation space second a method that tracks the upstream migration of slope patches which are mathematical entities that carry information about downstream river states provides a basis for constructing analytical solutions slope patch analysis explains why the transient morphology of dimensionless river profiles differs fundamentally if the exponent on channel slope n is less than or greater than one and why only concave up migrating knickpoints persist when n 1 at migrating knickpoints slope patches and the information they carry are lost a phenomenon that fundamentally limits the potential for reconstructing tectonic histories from bedrock river profiles stationary knickpoints which can arise from spatially varying uplift rates differ from migrating knickpoints in that slope patches and the information they carry are not lost counterparts to migrating knickpoints called stretch zones are created when closely spaced slope patches spread to form smooth curves in distance elevation space these theoretical results are illustrated with examples from the california king range and the central apennines

cenozoic unroofing history of the ladakh batholith western himalaya constrained by thermochronology and numerical modelling abstract the ladakh batholith is part of the transhimalayan plutonic belt which crops out north of the indus suture zone we propose that the exhumation history of the ladakh batholith is linked to the tectonic magmatic and erosion history of the karakoram terrane and sw tibet we present new multiple low temperature thermochronometry data zircon u th he apatite fission track and apatite u th he to gain insight into the cooling history of the ladakh batholith and recognize key periods in the evolution of the region from the indus valley northwards the ages decrease across the batholith for all three thermochronometers applied a model is proposed in which magmatism in the ladakh batholith ceased in the late eocene and initial denudation was driven by topographic uplift caused by collision southward tilting of the batholith occurred in the late palaeogene this tilting resulted in an asymmetric topography with increasing elevation to the north strong erosion occurred in this northern region whereas the southern margin was affected by northwards thrusting of the indus molasse for the first time clear temporal and spatial variations in exhumation rate are identified in this region highlighting why sampling strategy is critical in documenting exhumation changes in active tectonic settings supplementary material sample co ordinates from the ladakh batholith sample preparation and fission track age measurements of apatite grains and grain size dimensions are available at http www geolsoc org uk sup18350

tertiary structural evolution of the gangdese thrust system southeastern tibet structural and thermochronological investigations of southern tibet xizang suggest that intracontinental thrusting has been the dominant cause for formation of thickened crust in the southernmost tibetan plateau since late oligocene two thrust systems are documented in this study the north dipping gangdese system gts and the younger south dipping renbu zedong system rzt west of lhasa the gangdese thrust juxtaposes the late cretaceous forearc basin deposits of the lhasa block the xigaze group over the tethyan sedimentary rocks of the indian plate whereas east of lhasa the fault juxtaposes the late cretaceous eocene andean type arc the gangdese batholith over tethyan sedimentary rocks near zedong 150 km southeast of lhasa the gangdese thrust is marked by a 200 m thick mylonitic shear zone that consists of deformed granite and metasedimentary rocks a major south dipping backthrust in the hanging wall of the gangdese thrust puts the xigaze group over tertiary conglomerates and the gangdese plutonics north of xigaze and west of lhasa a lower age bound for the gangdese thrust of 18 3 0 5 ma is given by crosscutting relationships the timing of slip on the gangdese thrust is estimated to be 27 23 ma from 40 ar 39 ar thermochronology and a displacement of at least 46 9 km is indicated near zedong the age of the gangdese thrust gt is consistent with an upper age limit of 24 ma for the initiation of movement on the main central thrust in places the younger renbu zedong fault is thrust over the trace of the gt obscuring its exposure the rzt appears to have been active at circa 18 ma but had ceased movement by 8 1 ma the suture between india and asia has been complexly modified by development of the gts rzt and locally strike slip and normal fault systems

susceptibility mapping of instability related to shallow mining cavities in a built up environment anthropogenic activities and urbanization frequently spread over areas underlain by unstable karst ground or man made cavities leading to potential risk situations for buildings infrastructure and population the roof of the cavities may rapidly propagate upwards eventually resulting in progressive ground settlement and or sudden collapse these processes are frequently accelerated or triggered by various human activities e g overloading water recharge water table decline in this paper the susceptibility to instability of artificial cavity networks under an urban area in apulia region southern italy was assessed and evaluated here there is dense network of underground quarries excavated for the extraction of massive calcarenite for building and ornamental stone that are currently affected by severe instability problems identifying the zones of the cavities most prone to instability is of great practical importance susceptibility models have been developed analyzing the statistical relationships between the cavity sections with evidence of instability and a number of predisposing factors mainly related to the 3d geometry of the voids roof thickness and the presence of overloads the models produced by the discriminant analysis and the logistic regression approaches were independently and quantitatively evaluated through the construction of roc curves although the two models are characterized by different input data treatment as the logistic regression allows using continuous and discrete variables or any combination of both types even if they do not have a normal distribution the roc curves highlighted for both methods a satisfactory congruence between the model results and the observed data consequently from the model performance analysis the two models were evaluated comparable in terms of result reliability the methodology should be considered as a general first level analysis for near surface underground cavities aimed at identifying critical cave sectors that can be the focus of more detailed analyses especially those associated with sensitive zone related to the presence of buildings roads and frequent presence of human activity

landslides associated with the colluvial soils overlying the natal group in the greater durban region of natal south africa in the last 25 years many of the landslides that have occurred in the greater durban region have been associated with the colluvial soils overlying the natal group most of which occurred during the very heavy rains of september 1987 subsequently a very heavy rainfall event in february 1999 also gave rise to landslides in fact prior to 1987 these colluvial soils were considered relatively stable a critical precipitation coefficient has been developed which included the cumulative precipitation up to a landslide event in addition an attempt has been made to establish a threshold value for triggering of landslides for the colluvial soils from a study of pluviometric data the results indicate that when a rainfall event exceeds 12 of the mean annual rainfall small scale landslides are likely to occur when a rainfall event is greater than 16 of the mean annual rainfall a moderate number of landslides take place major landslides are associated with rainfall events with intensities in excess of 20 of the mean annual precipitation an example of a landslide which occurred on the natal group due to construction operations is provided as well as an account of those which took place during september 1987 in the latter case most of the slides took the form of mudflows and were responsible for some of the worst damage which has occurred in the durban region the colluvial soils involved were relatively thin and therefore became quickly saturated by the heavy rainfall in some places the situation was further aggravated by liquefaction of the soils

rapid early miocene exhumation of the ladakh batholith western himalaya zircon apatite u th he and apatite fission track age data record a rapid cooling event in the ladakh batholith of northwest india ca 22 ma a combination of inverse and forward modeling of the data confirms this qualitative interpretation combining the thermochronometric data with structural evidence we propose that exhumation was due to south directed thrusting of the batholith along a north dipping structure coupled with erosion to bring the rocks to the surface the rapid exhumation recorded in ladakh is contemporaneous with exhumation of the high himalaya this focused surface denudation and structural shortening north of the indus suture zone in early miocene time implies that the actively deforming and eroding himalayan thrust wedge extended farther north than channel flow models currently predict

late quaternary valley infill and dissection in the indus river western tibetan plateau margin abstract the indus one of earth s major rivers drains large parts of the nw himalaya and the transhimalayan ranges that form part of the western tibetan plateau margin in the western himalayan syntaxis where local topographic relief exceeds 7 km the indus has incised a steep bedrock gorge at rates of several mm yr 1 upstream however the upper indus and its tributaries alternate between bedrock gorges and broad alluvial flats flanked by the ladakh and zanskar ranges we review the late quaternary valley history in this region with a focus on the confluence of the indus and zanskar rivers where vast alluvial terrace staircases and lake sediments record major episodes of aggradation and incision new absolute dating of high level fluvial terrace remnants using cosmogenic 10 be optically and infrared stimulated luminescence osl irsl indicates at least two phases of late quaternary valley infilling these phases commenced before 200 ka and 50 20 ka judging from terrace treads stranded 150 m and 30 40 m above modern river levels respectively numerous stacks of lacustrine sediments that straddle the indus river 200 km between the city of leh and the confluence with the shyok river share a distinct horizontal alignment constraints from irsl samples of lacustrine sequences from the leh spituk area reveal a protracted lake phase from 177 ka to 72 ka locally accumulating 50 m thick deposits in the absence of tectonic faulting major lithological differences and stream capture we attribute the formation of this and other large lakes in the region to natural damming by large landslides glaciers and alluvial fans the overall patchy landform age constraints from earlier studies can be reconciled by postulating a major deglacial control on sediment flux valley infilling and subsequent incision that has been modulated locally by backwater effects of natural damming while comparison with pleistocene monsoon proxies reveals no obvious correlation a late or post glacial sediment pulse seems a more likely source of this widespread sedimentation that has partly buried the dissected bedrock topography overall the long residence times of fluvial alluvial and lacustrine deposits in the region 500 ka support previous studies but remain striking given the dominantly steep slopes and deeply carved valleys that characterise this high altitude mountain desert recalculated late quaternary rates of fluvial bedrock incision in the indus and zanskar of 1 5 0 2 mm yr 1 are at odds with the longevity of juxtaposed valley fill deposits unless a lack of decisive lateral fluvial erosion helps to preserve these late pleistocene sedimentary archives we conclude that alternating 10 4 yr long phases of massive infilling and incision have dominated the late quaternary history of the indus valley below the western tibetan plateau margin

a statistical framework to quantify spatial variation in channel gradients using the integral method of channel profile analysis 1 we present a statistical technique for analyzing longitudinal channel profiles our technique is based on the integral approach to channel analysis drainage area is integrated over flow distance to produce a transformed coordinate which has dimensions of length assuming that profile geometry is conditioned by the stream power law defined as e kamsn where e is erosion rate k is erodibility a is drainage area s is channel gradient and m and n are constants the slope of a transformed profile in elevation space should reflect the ratio of erosion rate to channel erodibility raised to a power 1 n this quantity is often referred to as the channel steepness and represents channel slope normalized for drainage area our technique tests all possible contiguous segments in the channel network to identify the most likely locations where channel steepness changes and also identifies the most likely m n ratio the technique identifies locations where either erodibility or erosion rates are most likely to be changing tests on a simulated landscape demonstrate that the technique can accurately retrieve both the m n ratio and the correct number and location of segments eroding at different rates where model assumptions apply tests on natural landscapes illustrate how the method can distinguish between spurious channel convexities due to incorrect selection of the m n ratio from those which are candidates for changing erodibility or erosion rates we also show how given erosion or uplift rate constraints the method can be used to constrain the slope exponent n

estimation of rock mass deformation modulus and strength of jointed hard rock masses using the gsi system abstract rock mass characterization is required for many applications in rock engineering practice including excavation design support design stope design amongst others for these purposes it is necessary to obtain design input parameters such as deformation moduli and strength parameters for numerical modeling although such parameters can ultimately be determined from in situ tests at the preliminary design stage where access to underground is limited the practical way to obtain these parameters is to apply a rock mass classification system to characterize the rock mass and estimate the rock mass properties over the years many classification systems such as rqd rock mass rating q and geological strength index gsi systems have been developed amongst them the q system is widely used for rock support system design and the gsi system is used for estimating design parameters the gsi system is the only rock mass classification system that is directly linked to engineering parameters such as mohr coulomb hoek brown strength parameters or rock mass modulus however the application of the existing gsi system is hindered by the facts that the use of the system is to some extent subjective and requires long term experience in the present study a quantitative approach to assist in the use of the gsi system is presented it employs the block volume and a joint condition factor as quantitative characterization factors the approach is built on the linkage between descriptive geological terms and measurable field parameters such as joint spacing and joint roughness the newly developed approach adds quantitative means to facilitate use of the system especially by inexperienced engineers the gsi system is applied to characterize the jointed rock masses at two underground powerhouse cavern sites in japan gsi values are obtained from block volume and joint condition factor which in turn are determined from site construction documents and field mapping data based on gsi values and intact rock strength properties equivalent mohr coulomb strength parameters and elastic modulus of the jointed rock mass are calculated and compared to in situ test results the point estimate method is implemented to approximate the mean and variance of the mechanical properties of the jointed rock masses it is seen that both the means and variances of strength and deformation parameters predicted from the gsi system are in good agreement with field test data

very slow erosion rates and landscape preservation across the southwestern slope of the ladakh range india erosion rates are key to quantifying the timescales over which different topographic and geomorphic domains develop in mountain landscapes geomorphic and terrestrial cosmogenic nuclide tcn methods were used to determine erosion rates of the arid tectonically quiescent ladakh range northern india five different geomorphic domains are identified and erosion rates are determined for three of the domains using tcn 10be concentrations along the range divide between 5600 and 5700 m above sea level asl bedrock tors in the periglacial domain are eroding at 5 0 0 5 to 13 1 1 2 meters per million years m m y principally by frost shattering at lower elevation in the unglaciated domain erosion rates for tributary catchments vary between 0 8 0 1 and 2 0 0 3 m m y bedrock along interfluvial ridge crests between 3900 and 5100 m asl that separate these tributary catchments yield erosion rates 850 ky respectively these results highlight the persistence of very slow erosion in different geomorphic domains across the southwestern slope of the ladakh range which on the scale of the orogen records spatial changes in the locus of deformation and the development of an orogenic rain shadow north of the greater himalaya copyright 2014 john wiley sons ltd

asymmetric growth of the pyrenees revealed through measurement and modeling of orogenic fluxes orogenic asymmetry is ubiquitous in terms of topography structure and metamorphism but the relative influences of climate and tectonics in determining such asymmetry remain contentious this study demonstrates that for the case of the european pyrenees orogenic asymmetry is not defined by inherited structural asymmetry nor by orographic asymmetry of precipitation but is the simple consequence of the inherent tectonic growth of a doubly vergent orogen the pyrenees record approximately 60 myr of upper crustal accretion erosion and sedimentation that developed from late cretaceous to early miocene times approximately 165 km of plate convergence was accommodated by four phases of orogenic growth that can be summarized in terms of their generic orogenic development as follows 1 early inversion of passive margin extensional faults initiating the pro wedge 2 growth by a combination of frontal accretion and underplating to the pro wedge symmetrical and steady record of erosion and foreland basin sedimentation 3 cessation of pro wedge frontal accretion with propagation of the retro wedge deformation front 4 accelerated growth of pro wedge antiformal stack induced by underplating accelerated erosion over antiformal stack and increase in sediment discharge to pro foreland basin stabilization of outer pro wedge by sediment blanketing discrete element model experiments are used to explore the natural tendency of the system towards asymmetry model output demonstrates that during active frontal accretion to the pro wedge of an orogen the maxima in erosional denudation is offset towards the pro wedge relative to the maximum depths of exhumation this asymmetry is fundamentally driven by the progressive reduction in advection velocities of material within the orogen from the pro wedge into the retro wedge hence for an efficient erosional regime a dynamic coupling between erosion and structural uplift of the pro wedge will reduce activity of the retro wedge and hence drive asymmetry in terms of low temperature thermochronometry erosion and sedimentation the models also demonstrate the tendency for pro wedge growth through frontal accretion to slow however the cessation of frontal accretion as recorded by the south pyrenean thrust belt phases 3 and 4 requires additional forcing it is proposed that the thick wedge top sedimentation recorded at this time increased taper angles and hence stabilized the wedge accretionary influx into the orogen at this time was accomplished through underplating these processes governing asymmetry do not require a spatially variable climate or a laterally heterogeneous underthrust plate

sedimentology of the indus group ladakh northern india implications for the timing of initiation of the palaeo indus river the upper reaches of the indus river form a longitudinal network that drains a large portion of the western himalaya it plays an important role as a sediment routing system feeding the indus delta and submarine fan and has played a controlling role in the denudational history of the western himalaya given the rivers long term significance its timing of initiation remains poorly constrained the facies palaeocurrents and provenance of the post early eocene indus group preserved along the upper reaches of the modern indus reveal a history of fluvial deltaic and deep water sedimentation in an intermontane basin dominated by internal drainage hence the indus group is not considered to represent the deposits of a palaeo indus river as previously thought illite crystallinity values and apatite fission track dating of the indus group suggest that the succession was buried to temperatures of 155 280 c and that unroofing started in early miocene times and proceeded at 0 1 0 4 mm a 1 to the present the youngest sedimentary rocks preserved along the indus basin are early miocene in age from the tectonostratigraphically equivalent deposits around kargil to the west of the study area the transition from sediment accumulation to erosional unroofing in early miocene times coincides with accelerated regional unroofing of the high himalayas to the south and the initiation of the indus delta submarine fan to the west differential uplift between the northward thrusting of the zanskar and indus sedimentary succession against the undeformed ladakh batholith provides a mechanism for post early miocene initiation of a major longitudinal river hence early miocene times is believed to represent the earliest possible age of initiation of the palaeo indus river following this course

lateral migration of hillcrests in response to channel incision in soil mantled landscapes 1 we investigate lateral migration of hillcrests in response to vertical offsets or transient incision rates of channels bordering these hillcrests in soil mantled landscapes for hillslopes undergoing sediment transport that is linearly proportional to the slope the hillcrest offset distance is one quarter of the ratio of the vertical offset between the channels to the relief of the symmetric hillslope if channels are downcutting at different rates the speed of hillcrest migration will depend on the ratio of the downcutting rates and the density ratio which is the ratio of the bulk density of the bedrock to the bulk density of the soil the density ratio plays a fundamental role in determining the transient response of the hillcrest lower density ratios lead to faster transient responses to changes in channel downcutting rates other parameters that affect the transient response of the hillcrest are the magnitude of transient differences in downcutting between the two channels the time averaged incision rate and a ratio of the elevation of the hillslope to a length that characterizes the decay in soil production with increasing soil thickness different parameters will be important for different sediment flux laws the profile of soil thickness reacts to transient changes in downcutting at a different rate than surface topography hillslopes experiencing transient channel downcutting may have surface topography that is symmetric about the hillcrest but will at the same time have a soil thickness profile that is asymmetric

episodic fluvial incision of rivers and rock uplift in the himalaya and transhimalaya abstract seventeen strath terraces in northern india were dated using 10 be surface exposure methods ages range from c 7 to c 735 ka and provide fluvial incision rates of 0 02 0 003 to 2 6 1 9 mm a 1 on the northern side of the ladakh range incision rates are c 1 mm a 1 in the northern zanskar range they are 0 06 0 005 mm a 1 new and published incision rates in southernmost lahul range from 0 1 0 02 to 13 2 6 2 mm a 1 rates for ages 35 ka are 0 4 0 2 mm a 1 across the himalaya and transhimalaya holocene fluvial incision rates range from c 0 02 to c 26 0 mm a 1 whereas pleistocene incision rates are 5 mm a 1 many of the holocene incision rates exceed exhumation rates whereas pleistocene incision rates are comparable with exhumation rates this suggests that long term fluvial incision is in dynamic steady state with exhumation the temporal pattern for rates of fluvial incision is probably controlled by episodic incision linked to significant precipitation changes throughout the quaternary suggesting that strath terraces with ages 35 ka can be used for assessing long term rates of rock uplift in contrast rates of fluvial incision based on late glacial and holocene strath terraces reflect changes in monsoon intensity and deglaciation events by determining ages for multiple samples on flights of strath terraces it is possible to document changes in incision rate assess whether post abandonment transient shielding has occurred and help elucidate tectonic v climatic controls on their formation supplementary material tables ds1 4 for previously published data and recalculated ages for strath terraces and figures ds1 and ds2 showing plots of incision rates against time for the himalaya and transhimalaya are available at http www geolsoc org uk sup18454

asymmetrical erosion and morphological development of the central ladakh range northern india abstract variations in erosion were quantified across the topographically and morphometrically asymmetrical central ladakh range in nw india to elucidate erosion and sediment transfer processes across space and time and to gain insight into how mountains erode and evolve morphometric analysis and 10 be cosmogenic nuclide analysis of 14 fluvial sediment samples from active channels in six catchments conducted across the mountain range constrains 100 ka timescale erosion rates for catchments on the northern side of the mountain range and are between 56 12 and 74 11 m ma while catchments on the southern side of the mountain range to between 20 3 and 39 8 m ma for the last 300 ka maximum elevation from swath analysis across the range shows a strong correlation with the elas of 382 contemporary glaciers the higher erosion rate to the north likely relates to tectonic tilting of the central ladakh range and to active rock uplift on the northern side of the range along the karakoram fault morphometric analysis shows that the maximum and average elevations increase at nearly the same rate on a catchment scale across the central ladakh range with higher elevation on the northern side this suggests that greater erosion on the northern side of the range is not keeping pace with rock uplift moreover long term denudational unloading does not play a significant role in the tectonic tilting of the central ladakh range

quaternary geology tectonics and distribution of palaeo and present fluvio glacio lacustrine deposits in ladakh nw indian himalaya a study based on field observations abstract the ladakh region of the northwestern indian himalaya is rich in quaternary deposits but it has not received much attention previous quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available this article addresses the reconstruction of the palaeo lacustrine deposits and the present day lakes and their distribution in the ladakh region the region was under the influence of tectonic activity and cold climate during the late quaternary times tectonic activity at 50 000 years bp 35 000 years bp and 25 000 years bp has been recorded we report the presence of three major lakes in the region in the late quaternary these formed due to the damming of the indus river and its tributaries by debris avalanches initiated mainly by tectonic activity along the indus suture shyok suture and the karakoram fault these are the spituk leh palaeolake formed 50 000 years bp the lamayuru palaeolake dated to 35 000 years bp in the indus valley and the khalsar palaeolake 60 km in length in the shyok valley vast exposures of the palaeolake deposits ranging from 25 to 150 m in thickness are reported spituk section 25 m lamayuru section 110 m and khalsar 150 m and hundri 100 m and which have a wide lateral extent a glacial lake basin at bhaktpur city north of baralacha la is now completely filled the tsokar lake has been subdivided into smaller units now and the water level is lowering other lakes in the region e g pangong tso tso morari the twin kyun tso lakes are confined to the western side of the study area limited chemical weathering rapid erosion and cold climatic conditions in late quaternary times are suggested by the stable illite values in the lamayuru section four levels of palaeoseismic structures convolute structures sand dykes intraformational folds micro faulting are present in the khalsar section and at three levels in the tirit section at shyok nubra confluence palaeoseismic activity was also prevalent after 25 000 years bp as is evident from the three levels of palaeoseismic structures in the younger sediments