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

kinematic models of fluvial terraces over active detachment folds constraints on the growth mechanism of the kashi atushi fold system chinese tian shan during detachment folding the relationship between differential uplift and shortening depends on the mechanism of fold growth such as limb rotation or hinge migration and may vary over the lifetime of a fold thus neither long term shortening rates nor the present fold geometry unambiguously constrain the kinematics of fold growth where rivers cut through growing anticlines flights of abandoned fluvial terraces act as passive kinematic markers as shortening progresses the terraces become deformed and thereby preserve critical information about the kinematics and evolution of active fold growth to constrain recent fold growth across three detachment folds in the kashi atushi fold system in the sw tian shan china we surveyed flights of deformed terraces and compared them with geometric models of successively emplaced horizontal unconformities terraces across pregrowth strata deformed by hinge migration limb rotation and a combination of the two migration of angular hinges and curved hinge zones were also compared each kinematic model predicts both a distinct geometry for the deformed terraces and contrasting angular relationships between the terraces and the pregrowth strata notably limb rotation and migration of curved hinge zones result in progressively rotated terraces that cut across pregrowth strata whereas all limb lengthening models result in parallelism between pregrowth strata and terrace straths across much of the fold the kashi atushi terraces show clear evidence of abandoned axial surfaces concentrated deformation near the core of the folds and progressive tilting with age when compared to the model predictions the folds are likely growing by a combination of limb rotation in the tight cores of the folds and hinge zone migration of pregrowth strata across the flanks of the folds

thrust fault growth and segment linkage in the active ostler fault zone new zealand abstract thrust faulting is a fundamental mode of crustal deformation yet many of the key geometrical attributes of thrust faults and the controls on fault rupture growth and linkage remain poorly resolved numerous surface rupturing thrust faults cut through upper quaternary glacial outwash terraces within the ostler fault zone an active thrust system in the southern alps new zealand we use these deformed marker surfaces to define the three dimensional deformation field associated with their surface expression and to map displacement and length on 40 fault segments displacement transfer across two fault segment arrays occurs in distinctly different styles in one displacement is transferred between en echelon fault segments to produce a smooth linear displacement gradient in the other large scale folding and a population of small faults transfer displacement between two non overlapping fault segments with a residual displacement minimum within the transfer zone size distribution of fault segment length and maximum displacement follow a power law scaling relationship maximum displacement d max scales linearly with and represents 1 of segment trace length l d max l data from the segments of the ostler fault zone display similar scaling to a global fault dataset this similarity is surprising given that the observed displacements along the ostler fault represent only 20 ky of slip on fault segments that are likely to be many times older

interplay between faulting and base level in the development of himalayan frontal fold topography 1 fold topography preserves a potentially accessible record of the structure and evolution of an underlying thrust fault system provided we understand the factors that shape that topography here we examine the morphology and fault geometry of two active folds at the northwest himalayan front the chandigarh and mohand anticlines show the following patterns 1 most 60 70 growth in catchment size and relief across multiple scales is accomplished within 5 km of the fault tips 2 range scale relief is divided unevenly between the fold flanks because of base level contrasts 3 mean gradients of the uplifting catchments correspond to different flank averaged rock uplift rates 4 high hillslope scale relief coincides with areas of fast rock uplift and stronger lithologies and 5 existing relief represents only 15 of the total rock eroded since faulting began implying significant erosion the first order fold topography is developed quickly and asymmetrically as a result of fault generated rock uplift which sets the space available for the fold and the distribution of rock uplift rates with some modulation by base level which affects the erosional response of the landscape to the uplift a linear rate of growth in catchment relief with range half width correlates with catchment averaged rock uplift rate suggesting that this metric may be used to infer variations in fault dip at depth in these frontal fold settings high slip rates weak uplifting rocks and rapid erosion may combine to quickly limit the topographic growth of emerging folds and disconnect their morphology from the displacement field

topography relief and trmm derived rainfall variations along the himalaya 1 along the southern himalayan topographic front the indian summer monsoon modulates erosive processes and rates to investigate the influence of topography and relief on rainfall generation and resultant erosion we processed satellite rainfall amounts for the last 8 years 1998 2005 from the tropical rainfall measurement mission trmm based upon a spatial resolution of 5 5 km for the himalaya we identify 1 the spatial distribution of rainfall and 2 the large scale relationships between topography relief and rainfall locations our results show two distinct rainfall maxima along strike in the himalaya the first outer rainfall peak occurs along the southern margin of the lesser himalaya within a narrow band of mean elevation 0 9 0 4 km and mean relief 1 2 0 2 km the second discontinuous inner band typically occurs along the southern flank of the greater himalaya elevation and relief both 2 1 0 3 km

transient landscapes at fault tips 1 fault growth produces patterns of displacement and slip rate that are highly variable in both space and time this transience is most pronounced near fault tips where along strike displacement gradients vary in time as the fault array lengthens we use a set of statistical and field observations to quantify the response of catchments and their associated fans in three large normal fault arrays to transient patterns of displacement and slip rate catchments near the fault tips show distinct scaling of channel slope with drainage area compared with catchments near the strike center this scaling becomes uniform beyond about 10 km from the fault tips and is therefore like footwall relief largely decoupled from the fault displacement profile the estimated catchment response times to a change in slip rate also vary between fault tips and strike center the response times for tip catchments are much longer than the inferred time since fault activity began indicating that they are unlikely to be in equilibrium with the current fault displacement field this disequilibrium combined with the decoupling of slope area scaling from displacement indicates that landscapes are most sensitive to fault activity near fault tips active faults characterized by along strike variation in slip rate thus provide excellent opportunities to explore the transient response of landscapes to tectonic forcing

causes of recent himalayan uplift deduced from deposited patterns in the ganges basin the hypothesis1 that late cenozoic uplift of many of the world s mountain ranges was a response to climate change rather than to tectonic processes is based on the premise that enhanced erosion in an altered climate led to a reduction in both the total mass of a mountain range and its mean elevation this reduction was coeval with increased regional relief and with passive isostatic uplift of the remaining summits the hypothesis is difficult to evaluate because both climate and tectonic forces affect uplift in many active ranges in the absence of sufficient denudational and uplift data from the mountains themselves depositional patterns in adjacent basins may sometimes be used to distinguish between uplift arising from erosional or from tectonic processes in foreland basins uplift of the proximal basin and a reduction or absence of asymmetric subsidence are predicted responses to erosionally driven uplift2 here i show that patterns of sediment accumulation and the position of major rivers in the neogene gangetic foreland basin seem to have changed markedly in plio pleistocene times these changes lend support to the hypothesis that the importance of erosional unloading has increased in the himalayas during the past 4 myr

uplift and convergence along the himalayan frontal thrust of india along the himalayan thrust front in northwestern india terrace deposits exposed 20 to 30 m above modern stream level are interpreted to have been uplifted by displacement on the underlying himalayan frontal thrust a radiocarbon age limits the age of the terrace to 1665 215 calendar bc 3663 215 radiocarbon years before present yielding a vertical uplift rate of 6 9 1 8 mm yr in combination with published studies constraining the dip of the himalayan frontal thrust fault to about 30 in the study area the observed uplift rate equates to horizontal shortening across the himalayan frontal thrust of 11 9 3 1 mm yr and the slip rate of the himalayan frontal thrust of 13 8 3 6 mm yr this is similar to previously reported rate estimates along the himalayan arc based on displacement of older plio miocene age rocks or the much shorter records of geodesy and historical seismicity the similarity is consistent with the idea that convergence across the himalayan front has occurred at a relatively steady rate through time the seismic expression of this deformation includes several great m 8 historical earthquakes which due to lack of surface rupture during those events have been attributed to their occurrence on blind thrusts yet the occurrence of a possible fault scarp in the field area indicates that past earthquakes have been sufficiently large to rupture to the surface and produce coseismic scarps these observations suggest a potential for earthquakes along the himalayan frontal thrust larger than those observed historically

quantifying differential rock uplift rates via stream profile analysis despite intensive research into the coupling between tectonics and surface processes our ability to obtain quantitative information on the rates of tectonic processes from topography remains limited due primarily to a dearth of data with which to test and calibrate process rate laws here we develop a simple theory for the impact of spatially variable rock uplift rate on the concavity of bedrock river profiles application of the analysis to the siwalik hills of central nepal demonstrates that systematic differences in the concavity of channels in this region match the predictions of a stream power incision model and depend on the position and direction of the channel relative to gradients in the vertical component of deformation rate across an active fault bend fold furthermore calibration of model parameters from channel profiles argued to be in steady state with the current climatic and tectonic regime indicates that 1 the ratio of exponents on channel drainage area and slope m n is 0 46 consistent with theoretical predictions 2 the slope exponent is consistent with incision either linearly proportional to shear stress or unit stream power n 0 66 or n 1 respectively and 3 the coefficient of erosion is within the range of previously published estimates mean k 4 3 10 4 m 0 2 yr application of these model parameters to other channels in the siwalik hills yields estimates of spatially variable erosion rates that mimic expected variations in rock uplift rate across a fault bend fold thus the sensitivity of channel gradient to rock uplift rate in this landscape allows us to derive quantitative estimates of spatial variations in erosion rate directly from topographic data

lithologic and tectonic controls on bedrock channel form at the northwest himalayan front 1 recognition that channel form reflects a river s ability to erode rock and transport material has spawned stream power models that estimate incision patterns by approximating energy dissipation within a channel these models frequently assume that channel width scales as a power law with drainage area partly because drainage area is easily extracted from digital elevation models dems however this assumption is often confounded by local variations in rock strength and rock uplift rate that can cause channel constriction downstream here we investigate the morphological response to spatial changes in rock strength and rock uplift rate of 10 bedrock channels traversing the mohand range along the northwest himalayan front we present a new method to continuously measure and compare channel width slope and other hydraulic parameters that integrate satellite imagery and dem analysis our method corrects for an 13 overestimation of average channel gradient from a 90 m resolution dem that arises from short circuits of fine scale meanders we find that channels 1 narrow 1 km upstream from knickpoints formed by an increase in rock strength 2 adjust laterally more than vertically in response to downstream decreases rock erodibility and uplift rate and 3 meander where shear stresses are high and channel widths are low we attribute these results to a high ratio of sediment supply to transport capacity which enhances lateral erosion relative to vertical incision our results suggest that substrate strength and sediment supply substantially influence channel form and that channel width should be explicitly measured when interpreting tectonic signals from bedrock channel morphology

quantifying the slip rates spatial distribution and evolution of active normal faults from geomorphic analysis field examples from an oblique extensional graben southern turkey abstract quantifying the extent to which geomorphic features can be used to extract tectonic signals is a key challenge in the earth sciences here we analyse the drainage patterns geomorphic impact and long profiles of bedrock rivers that drain across and around normal faults in a regionally significant oblique extensional graben hatay graben in southern turkey that has been mapped geologically but for which there are poor constraints on the activity slip rates and plio pleistocene evolution of basin bounding faults we show that drainage in the hatay graben is strongly asymmetric and by mapping the distribution of wind gaps we are able to evaluate how the drainage network has evolved through time by comparing the presence size and distribution of long profile convexities we demonstrate that the northern margin of the graben is tectonically quiescent whereas the southern margin is bounded by active faults our analysis suggests that rivers crossing these latter faults are undergoing a transient response to ongoing tectonic uplift and this interpretation is supported by classic signals of transience such as gorge formation and hill slope rejuvenation within the convex reach additionally we show that the height of long profile convexities varies systematically along the strike of the southern margin faults and we argue that this effect is best explained if fault linkage has led to an increase in slip rate on the faults through time from 0 1 to 0 45 mm yr by measuring the average length of the original fault segments we estimate the slip rate enhancement along the faults and thus calculate the range of times for which fault acceleration could have occurred given geological estimates of fault throw these values are compared with the times and slip rates required to grow the documented long profile convexities enabling us to quantify both the present day slip rate on the fault 0 45 0 05 mm yr and the timing of fault acceleration 1 4 0 2 ma our results have substantial implications for predicting earthquake hazard in this densely populated area calculated potential mw 6 0 6 6 enable us to constrain the tectonic evolution of the graben through time and more widely demonstrate that geomorphic analysis can be used as an effective tool for estimating fault slip rates over time periods 106 years even in the absence of direct geodetic constraints

erratic shortening from balanced cross sections of the western himalayan foreland basin causes and implications for basin evolution abstract balanced cross sections from the western himalayan foreland foothill belt reveal a variation in shortening amounts from 22 to 71 3 over a lateral distance of 85 km the large variation may be attributed to the fact that the method of cross section balancing considers the initial layering as horizontal which is an unlikely situation in foreland basins simple trigonometric relationships are used to minimize the error in shortening estimates however the suggested corrections could not be applied to the himalayan foreland basin because of unavailability of the required data on initial basin geometry the study also indicates that shortening rates for the area based on these shortening amounts cannot be used for earthquake prediction

geometry and kinematics of main frontal thrust related fault propagation folding in the mohand range northwest himalaya abstract the main frontal thrust mft shapes the 2500 km long frontal himalayan arc between two syntaxes surprisingly the structural geometry and kinematics of the mft sheet remains poorly constrained along portions of this arc even though it is a major seismogenic plate boundary hazard that affects 53 million people living in the himalaya and roughly 600 million living in the combined himalayan drainage basin apollo 2017 here we integrate methods to constrain and quantify mft deformation and its associated topographic growth in the mohand range at the northwestern himalayan front we use a new structural data and trishear modeling to detail the mft related structural geometry across a portion of the range and confirm it to be a fault propagation fold with an exposed monocline in the hanging wall as previously hypothesized srivastava et al 2016 and b microstructural finite strain and grain size analysis from 11 transport parallel thin section samples of middle siwalik sandstones to propose that the fold formed by near surface 1 5 km frictional sliding and block supported cataclastic flow new luminescence dating of fault gouge and uplifted sand bodies indicate that mft activity is older 105 ka in the central compared to the western 15 ka mohand range implying that recent mft motion has been variable and segmented we next present boundary element method based dislocation modeling results along 3 transects to confirm that the along strike topographic growth is variable but consistent with the existing data and our interpretations balanced cross sections indicate that a maximum of 23 26 km2 area was eroded from the mohand range since folding began modern era estimates of minimum erosion from our dislocation modeling compared to existing topographic profiles suggest that 1 km2 erosion occurred in the range our integrated approach helps us to better constrain resolve reported inconsistencies and advance our understanding of mft related deformation topographic growth and erosion within the dehradun recess and across its outboard range front himalayan arc segmentation into salients and recesses likely impacts along strike earthquake rupture propagation thus it is important to understand how each segment behaves evolves and perhaps interrelates as part of a larger perspective towards evaluating active collisional wedge fronts and their potential seismic hazards

what sets topographic relief in extensional footwalls we use three large normal fault arrays in the northeastern basin and range province western united states to document catchment development and relief production during fault growth fault slip and slip rates increase systematically along strike from zero at the fault tips catchment relief and across strike range width both increase as slip accumulates but reach maximum values at a distance of 15 km from the fault tips and remain uniform along strike over much of the footwalls catchment outlet spacing also increases away from the fault tips but does not reach a uniform value and may vary by a factor of 5 6 along strike we infer that catchments first elongate in the across strike direction as slip accumulates and the range half width increases once the half width reaches its maximum value continued catchment growth is possible only by along strike capture which increases outlet spacing but not relief the close correspondence between catchment relief and range half width suggests that geomorphically limited hillslope and channel gradients are achieved within the 15 km tip zone thus the limiting factor in footwall development is the width of the range which is controlled by two external agents the geometry and spacing of the major faults and the elevations of base level on both flanks

controls on channel width in an intermontane valley of the frontal zone of the northwestern himalaya abstract channel width is an important parameter of the hydraulic geometry of a river and can be linked to the tectonic topographic lithologic and climatic controls in a particular reach as such variations in channel width can be the result of one or many factors acting at a specific location for the rivers flowing in the intermontane valleys along the frontal himalaya active tectonics plays a major role in controlling their geometry by providing the space energy and sediment dehra dun is an intermontane valley in the northwestern himalaya where the rivers have their source in the lesser himalaya and sub himalaya they show remarkable variability in the channel width along their course in this work we have attempted to identify and evaluate the relative importance of various controlling factors on the channel width of these drainage systems we selected 20 streams six north flank rivers nfrs two main axial rivers mars twelve south flank rivers sfrs flowing in the valley in the hilly stretches the nfrs flow over the lesser himalaya and the sfrs flow over the poorly consolidated upper siwalik gravelly sediments channel width in the mountainous region varies generally from 5 to 30 m the sfrs that have smaller catchments are relatively wider than the nfrs in the mountainous areas in the dun the width variation is mostly between 50 and 400 m the nfrs show widening in their middle stretches except for the tons river which is wide in its lower stretch channels widen as they cross the structural zones i e the main boundary thrust mbt the santaurgarh thrust st and the bhauwala thrust bt as a result of the change in the gradient across the structures large sediment supply generated by mass wasting processes from the weak zones i e fault related zones and uplifted surfaces make the river transport limited resulting in the deposition of the sediments consequently channel bed armoring in these gravel bed rivers protects the channel floor causing the erosive actions to be intensified on the banks in the dun where the channel banks consist of cohesive materials the bank erosion is found to be limited apart from these controls anthropogenic interventions and activities also impact the channel width in the valley the nfrs and mars are embanked at many places on the other hand most of the sfrs become indistinct before the confluence with the larger rivers because of farming related activities this study suggests that in the mountainous stretches the lithology and geologic structures exercise a primary control over the channel width whereas within the dun the sediment concentration channel bed armoring and the properties of bank materials act as the main controls

the structural evolution of active fault and fold systems in central otago new zealand evidence revealed by drainage patterns abstract central otago in new zealand is an area of active continental shortening in which a peneplain surface cut into schist has been deformed by folds which are developed above buried reverse faults we use the drainage patterns in this region to demonstrate various processes in fold and fault growth and interaction that would be difficult to identify by other means in particular we show 1 how simple asymmetric folds can develop into box folds 2 how apparently continuous ridges were formed by the coalescing of quite separate propagating fold and fault segments 3 evidence for the relative ages or relative uplift rates of adjacent structures and 4 evidence for the propagation direction of folds or faults as they grow the few quantitative estimates we obtain for fault propagation rates suggest an increase in length of 10 50 m per earthquake on faults about 20 km long these estimates are very uncertain but are similar in magnitude to an estimate made in nevada for a normal fault of similar size and are also similar to predicted estimates from theoretical growth models they raise the question of whether fault growth earthquake recurrence rates and climate change can interact to produce semi regular discrete features in an active landscape

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

structure and shortening of the kangra and dehra dun reentrants sub himalaya india surface geology oil well seismic reflection and magnetostratigraphic data are integrated to evaluate the structural style and the shortening rate at the himalayan front sub himalaya of northwest india the sub himalaya between the main boundary thrust and the himalayan frontal fault is the primary surface expression of shortening between the himalaya and the indian plate at certain locations the himalayan frontal fault is a blind thrust beneath anticlines of siwalik tertiary molasse parallel to the himalayan orogen the main boundary thrust is sinuous so the width of the sub himalaya ranges from 30 to 80 km where the sub himalaya is narrow nahan salient tertiary rocks are exposed in imbricate thrust sheets where the sub himalaya is broad kangra and dehra dun reentrants alluvium fills wide synclinal valleys duns seismic reflection data reveal that surface anticlines form in association with south vergent thrusts that root in a decollement at the base of the tertiary section reflection profiles and well data also indicate that the basement lithology changes northward from precambrian crystalline rocks beneath the indo gangetic plains to precambrian and cambrian metasedimentary rocks beneath the sub himalaya the sub himalayan decollement dips 2 5 northward beneath the kangra reentrant but it is steeper 6 beneath the dehra dun reentrant the kangra and dehra dun reentrants display fault propagation folds having steep limbs in the north and fault propagation and fault bend folds that have gently north dipping limbs in the south a balanced cross section of the kangra reentrant shows that a minimum of 23 km shortening has occurred since 1 9 1 5 ma yielding a shortening rate of 14 2 mm yr shortening has occurred at a rate of 6 16 mm yr across the dehra dun reentrant these data are similar to other published shortening rates and indicate that approximately 25 of the total india eurasia convergence at this longitude is accommodated within the sub himalaya given continued convergence and the presence of overpressured wells in the kangra reentrant the region is likely at risk from moderate and or great earthquakes in the future

evolution of quaternary alluvial fans and terraces in the intramontane pinjaur dun sub himalaya nw india interaction between tectonics and climate change quaternary alluvial fans in the tectonically active pinjaur dun an intramontane valley in the sub himalaya were deposited in front of the nalagarh thrust and were influenced both by tectonics and glacial climate fluctuations the surface morphology indicates that an earlier set of first order fans qf1 became entrenched and onlapped by a series of second order fans qf2 the younger fan segments were then cut by a pair of terraces t1 and t2 quartz optically stimulated luminescence dating establishes that the qf1 aggradational phase was initiated before 96ae 5 2 5ae3 ka and terminated after 83ae 7 1 6ae3 ka this was followed by a period of incision before qf2 fan deposition started at 72ae 4 1 3ae4 ka and continued until 24ae 5 4 ae 9k a sediment was deposited on the t1 upper and t2 lower terraces at 16ae 3 2 ae1 and 4ae5 ka respectively recording a return to overall degradation punctuated by minor deposition on terraces the period of incision separating the younger and older fan deposits coincided with enhanced sw monsoon precipitation the subsequent development of the qf2 fans and their progradation until 20 ka suggest erosional unloading of the thrust hangingwall during a tectonically quiescent phase toe cutting deposition of axial river and lacustrine facies and retreat of qf2 around 45 ka indicate fanward shift of the axial river due to tilting of the valley towards the ne in response to reactivation of the nalagarh thrust the cessation of qf2 deposition around 20 ka and the onset of through fan entrenchment suggest reduced sediment supply but relatively high stream power during the last glacial maxima lgm the prolonged stream incision since the cessation of qf2 deposition with only minor depositional phases at 16ae 3 2 ae1 and 4ae 5k a resulted from high water discharge and low sediment input during intensification of the sw monsoon and vegetation changes in the hinterland

drainage systems and the development of normal faults an example from pleasant valley nevada abstract drainage systems in regions of active extension contain information about fault zone structure and development and particularly about the lateral growth of individual fault segments that is difficult to obtain by more conventional means such as the dating of sedimentary material we investigate drainage fault interaction in pleasant valley nevada where a large normal faulting earthquake occurred in 1915 we find geomorphological evidence for a propagation increase in length of several km at both ends of one of the 1915 fault segments at one end we estimate the propagation rate to be about 50 m per earthquake this estimate is uncertain but is within the range predicted by theoretical models of fault growth drainage along the axes of half graben in this region may be influenced by the spacing of tilted fault blocks the highest valleys are also the narrowest whether the axial streams succeed in reaching lower neighbouring sinks depends on whether sedimentation rates are able to keep basins filled to the levels of the basement highs that separate half graben of opposite polarity a knowledge of modern drainage fault interactions may help predict drainage systems and the position of potential syn rift reservoir sediments in older extensional terrains where fault configurations but not facies distributions are known from seismic reflection surveys

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

on steady states in mountain belts the dynamic system of tectonics and erosion contains important feedback mechanisms such that orogenic systems tend toward a steady state this concept is often invoked but the nature of the steady state is commonly not specified we identify four types of steady state that characterize the orogenic system and illustrate these cases by using numerical model results and natural examples these types are 1 flux steady state 2 topographic steady state 3 thermal steady state and 4 exhumational steady state they refer to the erosional flux the topography the subsurface temperature field and the spatial pattern of cooling ages respectively models suggest that the topography will reach a steady mean form at the scale of an orogenic belt but perfect topographic steady state is unlikely to be achieved at shorter length scales thermal steady state is a precondition for exhumational steady state and in the case of temperature dependent deformation topographic steady state exhumational steady state is characterized by reset age zones spatially nested according to closure temperature as illustrated in natural systems from new zealand the cascadia accretionary margin and taiwan

footwall topographic development during continental extension 1 we examine the progressive development of footwall topography associated with a set of active normal faults in the northeastern basin and range province of the western united states fault length and displacement increase monotonically from northeast to southwest in the study area allowing us to track both variations in footwall morphology with increasing displacement and along strike changes in morphology on a single fault we show that patterns of catchment area footwall relief and catchment outlet spacing vary predictably and are related to the growth of the range bounding normal fault array in this semiarid region full parsing of footwall drainage area and removal of antecedent topography do not occur until fault arrays grow beyond two crustal scale segments multiple segment faults with lengths of up to 150 km have footwall relief that is limited to 1000 m in the center of the footwall and that decays to zero at the fault tips over a length scale of 15 km we hypothesize that this relatively uniform footwall relief is erosionally limited and reflects the efficacy of surface processes in removing footwall material in the center of the footwall if the fault array grows by relatively steady propagation of the tips we suggest that the 15 km length scale required to reach uniform relief is related to a timescale of relief generation by the fault tip propagation rate while such propagation rates are poorly known an average rate of 10 mm yr 1 would imply footwall relief generation over a timescale of 1 myr

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

geomorphic criteria to determine direction of lateral propagation of reverse faulting and folding fault related folds develop above active faults and as these faults propagate laterally so do the folds they produce geomorphic criteria useful in evaluating rates and direction of lateral propagation of active folds in the direction of propagation are 1 decrease in drainage density and degree of dissection 2 decrease in elevation of wind gaps 3 decrease in relief of the topographic profile along the crest 4 development of characteristic drainage patterns 5 deformation of progressively younger deposits or landforms and 6 decrease in rotation and inclination of forelimb all these criteria are consistent with lateral propagation but do not prove it the presence of more than one wind or water gap formed by the same stream however is strong evidence of lateral propagation rates of lateral propagation of folding may be several times the rate of uplift and fault slip lateral propagation of anticlinal folds allows for a new explanation of how drainage may develop across active fold belts development of drainage across an active fold belt is probably a function of relatively long structurally controlled drainage diversion parallel to fold axes and development of relatively short antecedent stream reaches around the nose plunge panel of a fold water and or wind gaps form as uplift drainage diversion and stream capture associated with fold growth continue

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

spatial variations in catchment averaged denudation rates from normal fault footwalls we test the spatial correspondence between rock uplift in active normal fault footwalls in the western usa and catchment averaged denudation rates from cosmogenic radionuclide crn analysis we find that denudation rates vary along strike depending on the fault length and displacement for the 18 km long sweetwater fault foot wall relief is largely inherited from the prefaulting topography and denudation rates are only partly reflective of fault displacement for the 130 km long wassuk fault all inherited topography has been removed by erosion in response to fault displacement denudation rates however show little along strike consistency and no correlation with catchment size or morphology we argue that in the early stages of fault growth crn derived denudation rates reflect inherited prefaulting relief with an overprint of fault controlled erosion in later stages of fault growth rates are decoupled from fault displacement through the impact of stochastic landsliding events and longer term measures of denudation such as low temperature thermochronometry that integrate over multiple earthquakes may provide a better record of spatial variations in rock uplift

active tectonics of himalayan frontal fault system in the sub himalayan zone the frontal siwalik range abuts against the alluvial plain with an abrupt physiographic break along the himalayan frontal thrust hft defining the present day tectonic boundary between the indian plate and the himalayan orogenic prism the frontal siwalik range is characterized by large active anticline structures which were developed as fault propagation and fault bend folds in the hanging wall of the hft fault scarps showing surface ruptures and offsets observed in excavated trenches indicate that the hft is active south of the hft the piedmont zone shows incipient growth of structures drainage modification and 2 3 geomorphic depositional surfaces in the hinterland between the hft and the mbt reactivation and out of sequence faulting displace late quaternary holocene sediments geodetic measurements across the himalaya indicate a 100 km wide zone underlain by the main himalayan thrust mht between the hft and the main microseismicity belt to north is locked the bulk of shortening 15 20 mm year is consumed aseismically at mid crustal depth through ductile by creep assuming the wedge model reactivation of the hinterland faults may represent deformation prior to wedge attaining critical taper the earthquake surface ruptures 240 km in length interpreted on the himalayan mountain front through paleoseismology imply reactivation of the hft and may suggest foreland propagation of the thrust belt

geomorphic evolution of dehra dun nw himalaya tectonics and climatic coupling abstract the dehra dun is a good example of a piggyback basin formed from the growth of the siwalik hills two large rivers the ganga and the yamuna and their tributaries deposit a significant part of their sediment load in the dun before they enter the gangetic plains this work documents the geomorphic complexities and landform evolution of the dehra dun through geomorphic mapping and chronostratigraphic investigation of the incised fan sections lesser himalayan hills inner and outer dissected hills isolated hills proximal fan distal fan dip slope unit floodplains and terraces are the major geomorphic units identified in the area isolated hills of fan material ihf proximal fan pf and distal fan df are identified as fan surfaces from north to south of the valley the osl based chronology of the fan sediments suggests that the ihf is the oldest fan consisting of debris flow deposits with a maximum age of 43 ka coinciding with the precipitation minima the proximal fan consisting of sheet flow deposits represents the second phase of aggradation between 34 and 21 ka caused by shifting of deposition locus downstream triggered by high sediment supply that exceeded the transport capacity the distal fan was formed by braided river deposits during 20 11 ka coinciding with the deglacial period the ihf pf and df surfaces were abandoned by distinct incision phases during 40 35 20 17 and 11 4 ka respectively a minor phase of terrace deposition in dehra dun was documented during 3 2 ka our results thus show that the evolutionary history of the alluvial fans in dehra dun was primarily controlled by climatic forcing with tectonics playing a minimum role in terms of providing accommodation space and sediment production

ductile thrusting in the himalayas shear sense criteria and stretching lineations the most useful criteria used for the determination of the sense of shear can be found in the huge himalayan ductile shear zone known as m c t they allow the determination of the sense of shear in relation with an unequivocal southward directed intracontinental thrust the various criteria analyzed at different scales of observation show the permanence of the shear flow regime throughout the metamorphic evolution however most of the observed shear criteria are due to late nappe emplacement postdating the climax of the metamorphism the most striking feature is the stretching lineation which is roughly normal to the thrust trace all along the belt it parallels everywhere the shear direction and thus indicates the transport direction of the nappes the observed radial pattern of stretch trajectories implies that the local motion does not correspond to the average plate convergence

integrated analysis of structures and landforms of an intermontane longitudinal valley pinjaur dun and its associated mountain fronts in the nw himalaya abstract frontal regions of the himalaya associated with topographic recesses are commonly marked by the development of intermontane valleys locally referred to as duns the relationship between structural evolution and landform development of an intermontane longitudinal valley pinjaur dun is explored to understand the role of tectonic processes on landform development the pinjaur dun has a length of 180 km it is divisible into a wider 20 km northwestern and a narrower 6 8 km southeastern segment the barsar thrust the nalagarh thrust and the himalayan frontal thrust form the mountain fronts in the area the proposed structural model integrates the transverse structures for e g ghaggar tear fault with the sequential development of imbricates in front of the main boundary thrust the pinjaur dun formed as a consequence of the fold thrust related uplift that formed the outermost siwalik hills most of the geomorphic units formed within the dun are the result of interactions between the imbricates such as the pinjaur thrust jhajara thrust and pinjaur garden fault these interactions also resulted in the development of a significant and prominent drainage divide between the jhajjara and the sirsa rivers of the pinjaur dun landform development and landscape evolution in this frontal region of the himalaya are a consequence of the interaction of thrust fold and transverse fault zone tectonics and constitute a record of transient 102

fault growth and landscape development rates in otago new zealand using in situ cosmogenic 10be abstract we use in situ cosmogenic 10 be measurements in quartzites to examine the growth and propagation rates of a late quaternary anticline forming above a blind reverse fault in central otago new zealand we obtain average uplift and propagation rates of 0 10 0 15 mm yr 1 and 1 0 2 0 mm yr 1 respectively over the last 450 000 yr though it is probable that growth occurred episodically with more rapid development in the periods 600 400 kyr and 200 100 kyr and relative quiescence between about 400 and 200 kyr ago these results quantify and confirm a qualitative analysis of the fault evolution based on geomorphology and drainage patterns we obtain minimum 10 be exposure ages of up to 750 000 yr for the quartzites some of the oldest ages obtained by this method outside antarctica which are made possible by the extremely low erosion rates of less than 0 6 mm kyr 1 in the resistant quartzites these rocks consequently provide an opportunity to study geomorphic and tectonic processes in this region over unusually long time periods

deformed streams reveal growth and linkage of a normal fault array in the canyonlands graben utah we use the deformation of streams by the growth of active normal faults within the canyonlands graben of southeastern utah to constrain the displacement evolution of a fault array during segment interaction and linkage coupling fault displacement data with geomorphic analysis of present day streams and paleostreams permits sequential reconstruction of a three segment fault array from initial component segments to its final displacement geometry our results show that although segment interaction causes enhanced displacement addition at overlap zones postlinkage displacement accumulation is significant and permits array equilibration to a displacement length ratio characteristic of a single fault evidence of stream disequilibrium indicates that this postlinkage displacement addition was rapid compared to that during the fault interaction phase

coalescence megafan multistorey sandstone complex of the late orogenic mio pliocene sub himalayan belt dehra dun india in the himalayan foreland basin a prominent multistorey sandstone complex in the middle siwalik subgroup is exposed along the southern flank of the dehra dun valley in the mohand anticline extending laterally for 40 km the middle siwalik subgroup consists of sandstone mudstone couplets 300 450 m thick in the lower part and the multistorey sandstone complex 900 1200 m thick in the upper which forms a gross coarsening upward sequence the major lithofacies are trough cross stratified sandstone planar cross stratified sandstone ripple drift laminated sandstone horizontal laminated sandstone and massive sandstone with subordinate amounts 20 of mudstone and conglomerate the multistorey sandstone complex is punctuated by several erosional surfaces over which abundant mud clasts are present the trough cross stratification exhibits a dominantly southward palaeoflow with much variation in the southeast and southwest quadrants however at outcrop level the palaeoflow data reveal internal consistency this spatial and temporal variability in palaeoflow direction indicates the existence of two major drainage systems of coalescing alluvial megafan type the estimated palaeochannel sinuosity is of the order of 1 04 to 1 23 with a return period of 4 to 8 103 years palaeoflow variability facies distribution frequent avulsion and the coarsening upward sequence collectively suggest the progradation of coalescing alluvial fans towards the south and southwest this was principally controlled by thrust movements and differential basin subsidence at the margin of the himalayan orogen

application of three fault growth criteria to the puente hills thrust system los angeles california usa abstract three dimensional mechanical models are used to evaluate the performance of different fault growth criteria in predicting successive growth of three echelon thrust faults similar to the segments of the puente hills thrust system of the los angeles basin california four sequential boundary element method models explore the growth of successive echelon faults within the system by simulating snapshots of deformation at different stages of development these models use three criteria 1 energy release rate 2 strain energy density and 3 navier coulomb stress to characterize the lateral growth of the fault system we simulate the growth of an echelon thrust fault system to evaluate the suitability of each of these criteria for assessing fault growth each of these three factors predicts a portion of the incipient fault geometry i e location or orientation however each provides different information in each model energy release rate along the westernmost leading tip of the puente hills thrust drops with growth of the next neighboring fault this result supports the overall lateral development of successive echelon segments within each model regions of high strain energy density and navier coulomb stress envelope at least a portion of the next fault to develop although the strain energy density has stronger correlation than navier coulomb stress to the location of incipient faulting in each model one of the two predicted planes of maximum navier coulomb stress ahead of the leading fault tip matches the strike but not the dip of the incipient fault plane recreating part of the fault orientation the incipient fault dip is best predicted by the orientation of the strain energy density envelopes around the leading fault tip furthermore the energy release rate and pattern of strain energy density can be used to characterize potential soft linkage overlap or hard linkage connection of echelon faults within the system

geomorphic evidence for tear faults accommodating lateral propagation of an active fault bend fold wheeler ridge california abstract wheeler ridge is the topographic expression of an actively growing fault bend fold developed in the hanging walls of a system of mostly north vergent blind thrusts the eastern tip of the fold system has migrated laterally by approximately 3 km during the last 120 ka perpendicular to the regional shortening direction comparison of surface topography and structural cross sections indicates that eastern wheeler ridge comprises three fold segments whose topographic expression steps southward towards the eastern end of the structure lateral propagation of the fold is associated with numerous tear faults expressed as fault scarps that face towards the eastern end of the fold we suggest that these tear faults accommodate earthquake related processes that collectively build plunge of the fold and lateral propagation on blind thrusts we envisage that the fold will grow primarily by thrust faulting events with similar displacement s along strike that are terminated abruptly at tear faults build displacement over multiple earthquake cycles and then step eastward to form a new tear fault formation of especially large tear faults is inferred to be in response to an increase in rock strength governed by lithology the high fault displacement vs length d l for wheeler ridge may be related to high strain rates across a restraining bend in the nearby san andreas strike slip fault system

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

spring water trace element geochemistry a tool for resource assessment and reconnaissance mineral exploration abstract geochemical data from 151 spring locations within the 37 000 km2 south nahanni river basin of the mackenzie mountains northwest territories were analysed as part of a reconnaissance assessment of mineral potential in this large and remote region statistical data analyses graphical methods and strategic grouping of springs according to geochemistry ph and temperature were used to identify regions with higher mineralization potential quickly and efficiently testing of internal consistency indicates that known world class deposits within the basin are readily detected but by different methods as different deposit types have different geochemical signatures a new 3 component approach was developed to analyze trace element data for signatures of mineralisation estimation of circulation depth and therefore maximum potential ore depth further refines the assessment of economic potential the depth of circulation of the spring waters ranged from 4 7 km to less than 200 m for the entire dataset in total 62 spring locations were identified as having anomalous trace metal content by one or more method approximately 40 of the dataset specifically 11 spring locations were classified as anomalous by all three methods and 17 by at least two methods and 34 by only one method

tectonic constraints on watershed development on frontal ridges mohand ridge nw himalaya india abstract uplifting frontal ridges are one of the most conspicuous geomorphic features that mark the frontal parts of actively converging mountain belts growth of these ridges can lead to the simultaneous development of a drainage system that is defined by watersheds stream network and long profiles of channels in the present study shape parameters of watersheds stream network characteristics and pattern of network growth shape of long profiles and the sl index have been investigated in a part of nw himalaya to understand the relationship between endogenic tectonic processes and exogenic fluvial processes this explains the tectonic control on drainage systems in the uplifting frontal ridge this watershed analysis was carried out using a digital elevation model dem and a number of anomalies have been identified and analysed the most striking is the asymmetric development of watersheds on either side of an almost straight ridge crest watershed asymmetry along the ridge crest is characterized by larger area and less elongated watersheds in the southern flank forelimb in comparison to the northern flank backlimb drainage network and long profile analysis establishes that the larger watershed area in the forelimb is due to dominance of headward erosion and its impact on drainage network growth dominance of headward erosion is due to slope variation in response to forelimb development along a fault related fold even through headward erosion has shifted the ridge crest it is parallel with the trace of the himalayan frontal thrust hft the parallel ridge crest with reference to the hft is indicative of the tectonic control of the hft on the development of the watersheds hence a well developed linkage between tectonic processes fold development and surface processes headward erosion is responsible for variation in watershed and drainage network pattern across the ridge crest the study also investigates the role of planform ridge curvature on watershed development the effect is more pronounced on an asymmetric ridge such as the mohand ridge than on a symmetric ridge

investigating topographic metrics to decipher structural model and morphotectonic evolution of the frontal siwalik ranges central himalaya nepal abstract the fold and thrust belt in the himalayan front is marked by the upliftment of the frontal outermost siwalik hills along the main frontal thrust mft these frontal ranges display distinct morphology with prominent curved stair stepped and overlapping segments in the central himalaya in this study we analyse the structural framework morphology growth and relative uplift rates of the frontal ranges in the central himalaya using various topographic metrics the results suggest that the frontal ranges are folds developed along six mft segments that have interacted to form the present day topography these segments are also overlapping in some areas thus resulting in stress partitioning we also identify a nw se trending pre existing tear fault in the region that forms barrier to the growth and propagation of the mft segments and the frontal ranges along it the uplift rates are generally lower on relatively older fault segments due to initiation of the younger overlapping faults it is supported by the results of the morphometric indices as the older and less active mft segments yield high mountain front sinuosity ratio 1 3 2 2 and valley floor width to height ratio 3 3 14 6 and low values of steepness index 0 2 0 8 and hypsometric integral 0 4 0 5 growing folds along the mft segments have resulted in the deflection of the narayani and the east rapti rivers we establish a model for the initiation and growth of various structural segments in the study area and the resultant drainage reorganisation

paleoseismic evidence of great surface rupture earthquakes along the indian himalaya 1 toward understanding the relationship between strain accumulation and strain release in the context of the mechanics of the earthquake and mountain building process and quantifying the seismic hazard associated with the globes largest continental thrust system we describe the late quaternary expression and paleoseismic evidence for great surface rupture earthquakes at six sites along the himalayan frontal thrust hft system of india our observations span a distance of 250 km along strike of the hft uplifted and truncated fluvial terrace deposits resulting from the holocene displacements on the hft are preserved along canyons of the ghaggar markanda shajahanpur and kosi rivers dividing the elevation of the bedrock straths at each site by their ages yields estimates of the vertical uplift rate of 4 6 mm yr which when assumed to be the result of slip on an underlying thrust dipping at 20 45 are equivalent to fault slip rates of 6 18 mm yr or shortening rates of 4 16 mm yr trench exposures reveal the hft to fold and break late holocene surface sediments near the cities and villages of chandigarh kala amb rampur ganda lal dhang and ramnagar radiocarbon ages of samples obtained from the displaced sediments indicate surface rupture at each site took place after a d 1200 and before a d 1700 uncertainties attendant to the radiocarbon dating currently do not allow an unambiguous definition of the capping bound on the age of the displacement at each site and hence whether or not the displacements at all sites were contemporaneous trench exposures and vertical separations measured across scarps at rampur ganda lal dhang and ramnagar are interpreted to indicate single event displacements of 11 38 m dividing the observed single event vertical components of displacement by the estimated longer term uplift rates indicates 1330 3250 or more years should be required to accumulate the slip sufficient to produce similar sized displacements surface rupture appears to not have occurred during the historical 1905 kangra mw 7 7 1934 bihar nepal mw 8 1 and 1950 assam mw 8 4 earthquakes which also occurred along the himalayan front yet we observe clear evidence of fault scarps and displacements in young alluvium and progressive and continued offset of fluvial terrace deposits along the hft we suggest on this basis and the size and possible synchroneity of displacements recorded in the trenches that there exists the potential for earthquakes larger than recorded in the historical record and with the potential to rupture lengths of the hft greater than the 250 km we have studied

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

new constraints on sediment flux dependent river incision implications for extracting tectonic signals from river profiles we present new field data from rivers draining across active normal faults that incise across the same lithology at the fault have been subjected to similar climatic regimes and tectonic settings and were perturbed by a well documented increase in fault slip rate ca 1 ma in spite of these similarities the rivers exhibit markedly different long profiles and patterns of catchment incision we use channel slope and hydraulic geometry data for each river to calculate bed shear stresses b and show that there is no simple relationship between peak b and the relative uplift rates across the faults u which differ by a factor of four the long term average sediment supply to each channel q s estimated from time averaged catchment erosion rates can explain the b versus u data if bedload modulates bedrock incision rate e in a strongly nonlinear way together these field data allow us for the first time to evaluate theoretical predictions of the role of sediment on river profile evolution and to quantify the magnitude of the effect in natural systems

growth of faults by accumulation of seismic slip the accommodation of large strains in the upper crust is largely achieved by the accumulation of displacement on faults observation shows that as a fault accumulates displacement it grows in size i e its surface area and its length increase here we address the question for an increase in the amount of displacement on a fault by how much would the length of the fault change it is argued by cowie and scholz 1992a that the displacement on a fault is linearly related to the length of the fault this simple result is expanded upon in this paper by assuming that a fault accumulates displacement by repeated earthquakes two different approaches are presented the first approach considers the balance that must be achieved between the energy available for deformation and the work involved in creating new fault surface area as the fault grows the available energy is provided by changes in strain energy when the fault slips the second approach is to construct a geometrical model for fault growth using the scaling relationship between the slip during a single earthquake and the length of the rupture the total displacement on a fault is the sum of the slips contributed by many earthquakes the usefulness of these two approaches is that the growth of a fault over geologic time can be described by parameters that can be obtained from earthquake and fault data the models presented here predict that 1 the maximum amount a fault can grow in a single earthquake that ruptures the entire fault is of the order of 1 of its previous length and 2 the work of faulting may account for 10 of the total energy available during an earthquake the energy lost from the system is accounted for by work done against friction and seismic radiation consequences of fault growth for the segmentation and thus seismogenic potential of a fault over geologic time are discussed using predictions of the theory

contemporary tectonics of the himalayan frontal fault system folds blind thrusts and the 1905 kangra earthquake the sub himalayan fold thrust belt consists of deformed late cenozoic and older deposits south of the main boundary thrust mbt in pakistan east of the indus river the sub himalaya comprises the potwar plateau and the salt range which is thrust southward over the jhelum river floodplain along the salt range thrust although an estimated 9 14 mm a 1 shortening has been taken up on the salt range thrust during the last 2 ma the range front scarp does not show signs of recent faulting shortening may be shifting southward to the lilla overpressured anticline which rises from the jhelum floodplain as a fault propagation fold farther east shortening is partitioned among several anticlines underlain by foreland and hinterland dipping blind thrusts southeast of the main deformation zone the pabbi hills overpressured anticline is best explained as a fault propagation fold throughout the potwar plateau and salt range thrusts and folds rise from a basal decollement horizon in eocambrian evaporites the pakistani part of the decollement horizon could generate large earthquakes only if these evaporites die out northward at seismogenic depths in india and nepal the sub himalaya is narrower reflecting the absence of evaporites and a steeper slope of the basement towards the hinterland the southern boundary of the sub himalaya is the himalayan front fault discontinuous because part of the shortening is expressed at the surface by folding broad alluvial synclinal valleys dun valleys are bounded on the south by rising barrier anticlines of siwalik molasse the 1905 kangra earthquake m8 produced uplift on the mohand anticline and the dehra dun valley suggesting that this earthquake occurred on a decollement horizon above basement downdip from the fold if so the kangra event is the largest known earthquake on a blind thrust expressed at the surface as a fold

a balanced cross section across the himalayan frontal fold thrust belt subathu area himachal pradesh india thrust sequence structural evolution and shortening abstract the structural evolution of the frontal fold thrust belt in the nw himalayas has been deciphered through the construction of a balanced cross section which incorporates all the tertiary and the precambrian sedimentary rock units belonging to the sub himalaya zone and the lesser himalaya zone respectively towards the foreland the structural geometry is rather simple with widely spaced thrust ramps and simple fault bend folds in the hangingwall in the central sector the structural geometry seen at the surface is essentially controlled by a thrust system that can be approximately described as a buried hinterland dipping duplex the structural geometry becomes extremely complex in the northeastern sector i e towards the hinterland owing to out of sequence thrusting low ramp spacing leading to dislocation of older thrusts and related structures by younger thrusts folded thrusts and breached horses stacked up horses occupied by lesser himalaya zone formations dominate the structural geometry in this sector an in sequence thrusting event followed by out of sequence thrusting in an approximately break back style best describe the structural evolution of the fold thrust belt in this area a total slip of about 96 km occurred along the detachment and the shortening partitioned within the fold thrust belt is about 72 km or about 71

late quaternary holocene evolution of dun structure and the himalayan frontal fault zone of the garhwal sub himalaya nw india abstract dun structures are common in the sub himalayan zone of the himalaya bounded by the main boundary thrust mbt and the himalayan frontal thrust hft they are broad synclinal longitudinal valleys formed as a consequence of the exhumation of the range front of the himalaya in the garhwal sub himalaya these structures have grown since 0 5 ma with the peak activity postdating 100 ka a series of out of sequence deformation structures have been identified within the mbt hft bounded dun structures they are identified on the basis of geomorphic post 100 ka stratigraphic and structural expressions with activity as young as the early holocene to the south of the range front of the himalaya uplift has been observed in the piedmont zone with peculiar active tectonic geomorphic expressions piedmont sediments of 15 5 ka determined by optically simulated luminescence osl have been affected by the above uplift the complete tectonic scenario has been analyzed and an attempt has been made to delineate the sequential evolution of these structures during the post 100 ka period late quaternary holocene in the himalayan range front

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

rock magnetic characterization of pedogenesis under high energy depositional conditions a case study from the mio pliocene siwalik fluvial sequence near dehra dun nw himalaya india abstract systematic rock magnetic studies accompanied by field investigations are presented for 51 pedogenic horizons from magnetostratigraphically constrained middle upper siwalik fluvial sequence 9 4 ma near dehra dun in the himalayan foreland basin hfb detailed sedimentologic studies infer predominantly proximal to distal alluvial fan setting with considerably high rate of sedimentation 55 cm ka paleosol profiles in the mohand rao mr section are commonly truncated by channel activity these paleosols display few rootlets diffused color contrast amongst variegated pedogenic horizons rare concretions intense gleying at places and frequent incursions by sand silt layers the mean mass specific magnetic susceptibility lf for pedogenic horizons is 0 95 10 8 m3 kg max 1 4 10 8 m3 kg min 0 5 10 8 m3 kg and the associated non pedogenic layers is 0 82 10 8 m3 kg max 1 2 10 8 m3 kg min 0 4 10 8 m3 kg the low frequency dependence of the susceptibility fd mean 2 and high coercivities bocr mean 425 mt of the pedogenic layers infer the absence of finer pedogenic superparamagnetic sp fraction that might have depleted during post depositional burial processes acquisition of isothermal remanent magnetization irm shows under saturation and gentle upward trend even at high applied fields 4000 mt advocating the predominance of hematite and goethite sympathetic variation in the total organic and inorganic carbon content with iron oxides stable under warm humid oxidative arid and cold restricted conditions confirm the sensitivity of the rock magnetic parameters to ambient climatic condition relative variations in goethite hematite and ferrimagnetic contents have been derived from ratios mainly based upon selective irm saturations and their coercivities these studies are validated by sandstone petrography and clay mineralogy for the same section however the variation in rock magnetic parameters shows a better amplification and allows relative quantification of the ambient climatic conditions the assemblage of iron oxides using the rock magnetic ratios of the pedogenic layers in these high energy conditions broadly infer the prevalence of semi humid to semi arid climate entirely during the late miocene to early pliocene period in the hfb with an increased seasonality during early pliocene the present approach envisages a great scope for quantitative database under the given setup of high energy conditions that are common in the mio pliocene hfb

earthquake recurrence and rupture dynamics of himalayan frontal thrust india the black mango fault is a structural discontinuity that transforms motion between two segments of the active himalayan frontal thrust hft in northwestern india the black mango fault displays evidence of two large surface rupture earthquakes during the past 650 years subsequent to 1294 a d and 1423 a d and possibly another rupture at about 260 a d displacement during the last two earthquakes was at minimum 4 6 meters and 2 4 to 4 0 meters respectively and possibly larger for the 260 a d event abandoned terraces of the adjacent markanda river record uplift due to slip on the underlying hft of 4 8 0 9 millimeters per year or greater since the mid holocene the uplift rate is equivalent to rates of fault slip and crustal shortening of 9 6 3 5 7 0 millimeters per year and 8 4 3 6 7 3 millimeters per year respectively when it is assumed that the hft dips 30 10

active tectonics at wheeler ridge southern san joaquin valley california wheeler ridge is an east west trending anticline that is actively deforming on the upper plate of the pleito wheeler ridge thrust fault system holocene and late pleistocene deformation is demonstrated at the eastern end of the anticline where salt creek crosses the anticlinal axis uplift tilting and faulting associated with the eastward growth of the anticline are documented by geomorphic surfaces that are higher and older to the west faulting and associated folding is propagating eastward as indicated by increases in both the degree of surface dissection and the degree of soil development from east to west distinct topographic areas having distinct degrees of surface dissection bounded by tear faults suggest that faulting and folding have propagated eastward in discrete segments numerical dates indicate 1 the anticline is propagating eastward at a rate of about 30 mm yr about 10 times the rate of uplift 2 folding was initiated about 400 ka 3 a prominent wind gap was formed during q3 time about 60 ka when an antecedent stream was defeated forcing the stream east around the nose of the fold today drainage through the ridge is by way of two antecedent streams water gaps east of the wind gap and 4 the rate of uplift at the easternmost and youngest past 1 k y part of the fold is at least 3 mm yr investigations of the tectonic geomorphology of wheeler ridge support the hypothesis that climatic perturbations are primarily responsible for producing geomorphic surfaces such as alluvial fan segments and river terraces tectonic perturbations deform the surfaces

landward migration of active folding based on topographic development of folds along the eastern margin of the japan sea northeast japan abstract the eastern margin of the japan sea northeast japan lies in a strongly compressional area and contractional deformation in the region is ongoing we reconstructed the temporal and spatial evolution of contractional deformation across the tohoku district on the eastern margin of the japan sea by using surface geologic and geomorphologic data we measured the distance from the fold hinge to the topographic ridge line in antiforms developed by surface uplift associated with fold growth under the e w to wnw ese compressional stress regime the topographic development of fold structures developed in the region since the pliocene is consistent with the activity of the folds when the folding that generates the uplift becomes inactive the topographic contrasts between hinge and ridge location can be remarkable spatial variations in this parameter are consistent with the systematic eastward migration of fold growth in the area the documentation of fold related topography thus provides important information for understanding the dynamics of folding along the eastern margin of the japan sea

landscape evolution at the margin of the basin and range streams erode new basins in extensional mountain ranges where tectonic asymmetry facilitates divide migration ranges in the northern basin and range of the united states form a space for time series that illustrates stream incision and divide migration following footwall uplift accelerating basin growth and changes in the amount and direction of volume loss during basin expansion stream erosion exceeds hillslope retreat which elevates summit plateaus

magnetochronology of the upper cenozoic strata in the southwestern chinese tian shan rates of pleistocene folding and thrusting abstract the southwestern chinese tian shan of central asia is an actively deforming part of the indian asian collision system paleomagnetic investigations of two plio pleistocene terrestrial successions provide the first detailed magnetostratigraphy for the upper cenozoic strata in this region paleomagnetic samples were collected from 358 sites within the atushi formation and xiyu formation across the atushi talanghe anticline near atushi thermal demagnetization behavior reversal and fold tests of paleomagnetic stability indicate that the characteristic remanence directions were acquired before tilting and folding of the strata a composite magnetostratigraphic section for this sequence correlates with the mammoth subchron to the jaramillo subchron between 3 3 and 1 07 myr of the geomagnetic polarity timescale of cande and kent j geophys res 100 1995 6093 6095 the mean declination 349 3 in the boguzihe section indicates a counterclockwise vertical axis rotation 11 2 during the past 1 4 myr the conglomeratic xiyu formation is time transgressive along its progradational contact with the underlying atushi formation across a map distance of 6 km the basal contact ranges from less than 1 0 myr in the ganhangou section to 1 9 myr in the boguzihe section to the southwest and to 2 8 myr on the northwest limb of the anticline northeastward lateral propagation and growth of the atushi talanghe anticline initiated at 1 4 myr in the boguzihe and 1 2 myr in the ganhangou the cross section in the boguzihe provides a conservative maximum estimate of shortening rate of 3 3 4 4 mm yr and uplift rate of 3 mm yr this rate represents about half of the geodetically determined shortening rate between the northern tarim basin and the kyrgyz tian shan wang et al acta seismol sin 22 2000 263 270 reiger et al earth planet sci lett 191 2001 157 165 during fold growth over the past 1 4 myr the crest of the atushi talanghe anticline eroded at an average rate of 2 6 2 7 mm yr

tectonic impact on the fluvial deposits of plio pleistocene himalayan foreland basin india abstract the himalayan foreland basin comprises a number of subbasins developed in various sedimentary environments during the plio pleistocene phases of himalayan orogeny this paper describes the evolutionary processes that led to the development of the himalayan foreland basin in the dehra dun and subathu subbasins the dehra dun subbasin essentially consists of conglomerate facies whereas subathu subbasin is primarily composed of sandstone mudstone intercalated with conglomerate the two subbasins were sites of braided river systems evidence from chronostratigraphy provenance and tectonic and climatic conditions suggests that differential tectonic movement sedimentation rate and basin subsidence coupled with climatic variation were responsible for the contrasting fluvial facies in these subbasins following the merger of the two subbasins at about 5 23 ma the conglomerate facies assemblage of the dehra dun subbasin passes laterally into a sandstone mudstone conglomerate facies assemblage of the subathu subbasin thickly bedded amalgamated sheet conglomerate of dehra dun subbasin has a high sedimentation rate 0 70 mm year between 5 23 and 4 8 ma with a slow rate of basin subsidence in contrast a slow sedimentation rate 0 39 mm year in coeval sediments of the subathu subbasin with relatively fast subsidence produced a succession of thick multistorey sandstone body with mature paleosols petrographic and clast composition data from dehra dun subbasin suggest that the detritus was derived from the pre tertiary lesser himalayan sequence lying in the north during an active tectonic phase of the main boundary thrust between 4 8 and 1 77 ma progradation of posttectonic conglomerate of the dehra dun subbasin continued during a quiescent phase of the main boundary thrust however as a consequence of partitioning of subathu subbasin along the intra foreland thrust interfingering of buff piedmont drainage and grey trunk drainage sandstones took place in contrast the syntectonic conglomerate of subathu subbasin originated from the uplifted proximal part of the foreland basin tertiary belt during the active phase of intra foreland thrust around 1 77 ma

decoding temporal and spatial patterns of fault uplift using transient river long profiles we present detailed observations of rivers crossing active normal faults in the central apennines italy where excellent constraints exist on the temporal and spatial history of fault movement we demonstrate that rivers with drainage areas 10 km2 and crossing faults that have undergone an increase in throw rate within the last 1 my have significant long profile convexities in contrast channels that cross faults that have had a constant slip rate for 3 my have concave up profiles and have similar concavities and steepness indices to rivers that do not cross any active fault structures this trend is consistent across the central apennines and cannot be explained by appeal to lithology or regional base level change the data challenge the belief that active faulting must always be reflected in river profiles instead the long profile convexities are best explained as a transient response of the river system to a change in tectonic uplift rate moreover for these rivers we demonstrate that the height of the profile convexity as measured from the fault scales with the magnitude of the uplift rate increase on the fault and we establish that this relationship holds for throw rate variation along strike for the same fault segment as well as between faults these findings are shown to be consistent with predictions of channel response to changing uplift rate rates using a detachment limited fluvial erosion model and they illustrate that analysis of the magnitude of profile convexities has considerable predictive potential for extracting tectonic information we also demonstrate that the migration rate of the profile convexities varies from 1 5 10 mm y and is a function of the slip rate increase as well as the drainage area this is consistent with n 1 for the slope exponent in a classical detachment limited stream power erosion law but could potentially be explained by incorporating an erosion threshold or an explicit role for sediment in enhancing erosion rates finally we show that for rivers in extensional settings where the response times to tectonic perturbation are long in this case 1 my attempts to extract tectonic uplift rates from normalised steepness indices are likely to be flawed because topographic steady state has not yet been achieved

the pinjaur dun intermontane longitudinal valley and associated active mountain fronts nw himalaya tectonic geomorphology and morphotectonic evolution abstract the himalayan orogenic belt formed as a result of collision tectonic processes shows abundant evidence of neotectonic activity active tectonics and the occurrence of historical earthquakes its frontal deformation zone is characterized in some segments by intermontane longitudinal valleys duns such frontal segments of the himalaya are marked by the occurrence of multiple mountain fronts in one such segment of the foothills of the nw himalaya the pinjaur dun is developed and marked by three mountain fronts mf1a and mf1b associated with the southernmost himalayan frontal thrust hft mf2 associated with the sirsa fault and mf3 associated with the barsar thrust along the southern margin of the relatively higher main part of the sub himalaya geomorphic responses to the tectonic activity of these and related structural features have been analyzed through the use of geomorphic indices drainage density stream longitudinal profiles drainage anomalies and hypsometric analysis also fault and fold growth and their expression on landform development was studied using a combination of surface profiles and field observations the values of valley floor width to height ratio v f for valleys associated with mf1 ranged between 0 07 and 0 74 and for valleys associated with mf2 ranged from 1 02 5 12 v f for the four major valleys associated with mf1b ranged from 1 1 1 7 the asymmetry factor for 26 drainage basins related to mf1a indicate these have developed under the influence of a transverse structure these results taken together with those obtained from the hack profiles and sl index values hypsometry drainage density and drainage anomalies suggest that the faults associated with the mountain fronts and related structures are active active tectonics and neotectonic activity have led to the formation of four surfaces in the pinjaur dun in addition an important drainage divide separating the sirsa and jhajara drainage networks also developed in the intermontane valley surface profile analysis helped in deciphering the growth history of the fault bend fold structures of the outermost siwalik hills the effects of tectonic activity on the proximal part of the indo gangetic plains are interpreted from the remarkable river deflections that are aligned linearly over tens of kilometers in a zone about 10 km south of the hft based on these integrated structural and tectonic geomorphological approaches a morphotectonic evolutionary model of the dun has been proposed this model highlights the role of uplift and growth history of the fault bend fold structures of the outermost siwalik hills on i the depositional landforms and drainage development of the pinjaur dun and ii valley development of the outermost siwalik hills importantly this study postulates the formation of an incipient mountain front that is evolving ahead of the hft and the outermost siwalik hills in the indo gangetic plains

sedimentology of plio pleistocene late orogenic deposits associated with intraplate subduction the upper siwalik subgroup of a part of panjab sub himalaya india abstract this study provides a detailed sedimentologic documentation of the lithofacies cyclicity sandbody geometry palaeoflow variability and depositional models of the youngest late orogenic deposits of the siwalik molasse these deposits represent one of the important examples of sedimentation in the zone of intraplate subduction of the himalayan collision belt lithofacies analysis has resulted in the recognition of four conglomerate facies massive matrix supported conglomerate crudely stratified conglomerate trough cross stratified conglomerate planar cross stratified conglomerate five sandstone facies erosional scour and fill pebbly sandstone medium to coarse grained sandstone fine to medium grained ripple drift laminated sandstone bioturbated calcareous fine grained sandstone and six mudstone facies parallel laminated bioturbated mudstone reddish brown massive mudstone variegated mudstone bluish grey to violet mudstone buff coloured mudstone pebbly mudstone in addition hard calcareous layers have been recognised as a separate facies state the deduced cyclic sequences of the tatrot and pinjor formations of the upper siwalik subgroup show fining upward characters from cs coarse sandstone to ms mudstone through fs fine sandstone and ss alternations of sandstone and siltstone the sandbodies of the tatrot and pinjor formations reveal a sheet like geometry and an internal dominance of inter storey scour surfaces the presence of intraformational debris mud drapes reactivation surfaces and a general fining upward of grain size indicates fluctuating hydrodynamic conditions with frequent channel abandonment and re occupation resulting in net vertical aggradation the dominant style of sedimentation both in the channel and overbank facies is through vertical aggradation data on the palaeoflow variability indicates that the upper siwalik subgroup can be subdivided into four and three sediment vector sequences in the khetpurali and ghaggar sections respectively the palaeodrainage pattern in the khetpurali section reveals a major influence of northerly drainage twice in the stratigraphic column the high percentage of overbank deposits in individual cycles the lack of vegetal debris organic poor palaeosol units and abundant syngenetic caco 3 activity warrant comparison with the modern anastomosed deposits described from arid central australia some intervals of the sequences are comparable to the sublinear subparallel drainages with local anastomosis of the modern piedmont zone of the himalaya the higher parts of the stratigraphic column indicate proximal braided stream deposits and finally proximal alluvial fan deposits syntectonic activity has controlled the deposition of the megasequences which are a response to episodicity in the activity of basin margin basin margin or basin margin intrabasin structures the vertical stacking of the siwalik megasequences appears to be episodic in character

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

recent fold growth and drainage development the janauri and chandigarh anticlines in the siwalik foothills northwest india the active growth of a fault and thrust belt in frontal zones of himalaya is a prominent topographical feature extending 2500 km from assam to pakistan in this paper kinematical analysis of frontal anticlines and spatial mapping of active faults based on geomorphological features such as drainage pattern development fault scarps and uplifted quaternary alluvial fans are presented we analyse the geomorphic and hydrographic expressions of the chandigarh and the janauri active anticlines in the nw india siwaliks to investigate the morphological scenario during the folding process we used spatial imagery geomorphometric parameters extracted from digital elevation models and fieldwork folding between the beas and sutlej rivers gives clear geomorphological evidence of recent fold growth presumably driven by movements of blind thrust faults structural style within the janauri and chandigarh anticlines is highly variable fault propagation folds pop up structures and transfer faults the approach presented here involves analysis of topography and drainage incision of selected landforms to detect growth of active anticlines and transfer faults landforms that indicate active folding above a southwest dipping frontal thrust and a northeast dipping back thrust are described along strike differences in ridge morphology are measured to describe the interaction of river channel patterns with folds and thrust faults and to define history of anticline growth the evolution of the apparently continuous janauri ridge has occurred by the coalescence of independent segments growing towards each other by contrast systematic drainage basin asymmetry shows that the chandigarh anticline ridge has propagated laterally from nw to se