quantifying periglacial erosion in the nepal high himalaya abstract quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic distinguishing between periglacial and glacial rates is especially challenging in this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall we utilize a topographically well constrained debris covered glacier on the north slope of the annapurna range central nepal himalaya to quantify an average headwall retreat rate by measuring supraglacial debris depths from 0 1 to 2 4 m and average short term down valley transport rates of 17 m yr we calculate a yearly sediment flux of 5820 1990 m3 yr the supraglacial debris originates from the steep rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope perpendicular headwall retreat rate of 1 3 0 5 mm yr which corresponds to a vertical lowering rate of 0 42 0 16 mm yr and a horizontal retreat rate of 1 2 0 5 mm yr this rate is significantly greater than the steady state erosion rates that we determine for the valley ridge crests and sidewalls 0 08 0 03 mm yr and 0 20 0 05 mm yr respectively using concentrations of the in situ produced cosmogenic radionuclide 10be additionally 10be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long term supraglacial transport rate of about 10 m yr using this long term transport rate reduces our inferred headwall retreat and suggests that the up glacial bedrock slopes are eroding at roughly the same rate while our results do not quantify the rate of glacial erosion the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper marsyandi river that drains the study area suggesting that even glaciated catchments are not keeping pace with the rapidly down cutting rivers of the himalaya

boiling fluids in a region of rapid uplift nanga parbat massif pakistan abstract the nanga parbat massif of northern pakistan is currently undergoing rapid uplift 5 10 mm a 1 resulting in near surface elevated temperatures numerous quartz veins cut geologically young structures 100 c km 1 and the isotherms describe a giant pillar of heat above about 4 km fluid temperature is greater than conductive rock temperature in permeable zones which carry convecting boiling meteoric fluid

eocene tibetan plateau remnants preserved in the northwest himalaya in the northwest himalaya deeply incised mountain ranges contrast with high elevation low relief areas such as the deosai plateau in northern pakistan thermochronology data from the deosai plateau together with thermal history modelling suggest that this plateau along with other morphologically similar surfaces is a remnant of an eocene southwestern tibetan plateau

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

mountain environment and early human adaptation in nw himalaya india a case study of siwalik hill range and leh valley abstract prehistoric sites are reported from the entire length and breadth of india most of these are surface sites and invite less attention and significance compared to the few sites that are buried the systematic excavation of prehistoric sites has contributed to the understanding of typo technological evolution in the backdrop of time and space however the early artifact bearing sites in himalaya beyond the indo gangetic plains although open air sites hold significance in terms of understanding the extent of human colonization in himalaya in relation to climate the sporadic evidence of early humans in the siwalik ranges of jammu and along the indus river in the leh valley undoubtedly confirm the advent of early humans to this geographical realm when most of the area had tectonically stabilized and the more or less present day landscape and ecology had developed in the region with ameliorated climate for early human settlement

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

cosmogenic 3he in himalayan garnets indicating an altitude dependence of the 3he 10be production ratio to investigate the potential of using cosmogenic helium in garnet as a dating tool 3hec and 10bec have been measured within garnets and coexisting quartz respectively sampled in the himalayan range at various elevations comparison and correlation of 3hec and 10bec concentrations demonstrate that cosmogenic 3he is well retained in himalayan garnets and can thus be used in this mineral to quantify precisely earth s surface processes this in the case of recently cooled orogenic samples which contain limited amounts of non cosmogenic helium for these high elevation samples the exposure ages derived from 3hec using classical scaling factors lead however to an overestimation of 3hec ages compared to 10bec ages 0 1 to 28 ky by up to a factor of 2 additionally over the samples altitude range 3000 4622 m the theoretically invariant polar 3hec 10bec production ratio 22 5 increases with increasing elevation challenging classical models of production rate evolution to explain this observation we propose a new 3hec production mechanism based on the altitudinal dependence of the energy spectrum of cosmic rays and according to which neutrons or protons resulting from a first spallation reaction within the rock tertiary particles may have sufficient energy to induce an additional in situ spallation reaction producing a second 3h or 3he but insufficient energy to produce 10be the probability of such a mechanism increasing with altitude according to these observations we propose for future and ongoing studies to use the empirically determined attenuation length of 121 g cm2 for helium production at high altitude

neotectonics of the nanga parbat syntaxis pakistan and crustal stacking in the northwest himalayas the northwest termination of the himalayan arc is marked by two large antiformal structures termed syntaxes and a nw se zone of intermediate depth earthquakes which have yielded both strike slip and thrust sense fault plane solutions this contribution presents new structural data from the nanga parbat area the northern syntaxis one of the fastest rising portions of the orogen 7 mm yr 1 our studies show uplift related to syntaxis growth to be accommodated by structures located along its western margin fault kinematics in the southern part of the margin indicate nw directed thrusting along a shear zone and high level cataclastic faults termed the liachar thrust zone this carries amphibolite facies basement rocks out onto quaternary sediments further north along the western margin active faults are dominantly dextral strike slip oriented north south e g the shahbatot fault overprinting relationships suggest that the strike slip fault zone has migrated southwards into the nw directed thrust zone these relationships are consistent with the northwest termination of the arcuate himalayan thrust belt at a lateral tip generating folding and radial thrust directions faulting patterns at nanga parbat suggest that this tip zone has migrated southwards active faulting is now concentrated in the northwest continuation of the hazara southern syntaxis along a seismogenic strike slip and thrust zone these deep level tips lie on the crustal stacking thrusts which cut through the higher level sse directed thrusts of pakistan

sr and nd isotopes in river sediments from the ganga basin sediment provenance and spatial variability in physical erosion 1 sr and nd concentrations and isotope compositions in sediment of the ganga river from gangotri to rajmahal and its tributaries have been measured to determine provenance and the spatial variability in physical erosion among the ganga subbasins sr and nd in silicates range from 37 to 138 and from 10 to 36 g g with 87sr 86sr and nd of 0 7474 0 8428 and 25 5 to 15 5 respectively the results suggest that 65 of ganga mainstream sediments are derived from the higher himalayan crystallines highlighting intense physical erosion in this region the 87sr 86sr values of sediments in the gangetic plain show nearly identical trends during two seasons with a sharp and significant decrease at barauni downstream of gandak confluence this brings out the major impact of the sediment contribution from the gandak to the ganga mainstream model calculation suggests that about half of the ganga sediment at rajmahal is sourced from the gandak the erosion rates in the himalayan subbasins of the ganga range between 0 5 and 6 mm a where a is years with the gandak having the highest erosion rate high relief and intense precipitation over the headwater basins of the gandak appear to drive the rapid and focused erosion of this basin the results of this study and those in literature suggest that the eastern syntaxis brahmaputra the western syntaxis indus and the gandak have much higher physical erosion rates than the other himalayan basins focused erosion in the hot spots of these river basins contributes significantly to the global riverine sediment budget and influence regional tectonics

response of the ganges dispersal system to climate change a source to sink view since the last interstade the forcing of sediment dispersal systems by climate is widely accepted but there remains disagreement on the general responses to climate change such as how resulting signals propagate downstream and ultimately how they are preserved in the stratigraphic record towards a better understanding of these issues this paper presents a comprehensive overview of ganges dispersal system behavior since the last interstade which reveals major coeval responses to changes in the south asian monsoon at 3000 km from its mountain headwaters to deep sea fan the ganges dispersal system is immense and yet shows tight coupling between source area catchment basin and coastal and marine depocenters furthermore system wide responses and downstream transfer of the signal appear to occur at least as fast as current temporal resolution of 1 2 ky this tight linkage of source to sink components is considered a function of the southwest summer monsoon s overwhelming control on regional hydrology about 80 of the ganges discharge and 95 of its sediment load are delivered to the margin during only 4 months making the system extremely sensitive to this seasonal forcing in addition the regional scale and distribution of the monsoon weather system means that changes in atmospheric circulation affect the entire drainage basin rather than local subcomponents finally despite its present intensity strength of the summer monsoon has varied significantly over the past 150 ky under orbitally driven changes in insolation and global glacial boundary conditions the resulting changes in precipitation both well above and below modern values have forced system wide responses ranging from glacier advance retreat to sediment fluxes to the margin and deep sea fan the overall conclusions are 1 that this immense dispersal system responds to multimillennial scale 104 years climate change in a system wide and largely contemporaneous manner and 2 that major sedimentary signals can be transferred rapidly from source to sink with little apparent attenuation furthermore these acute responses to climate change have produced sedimentary stratigraphic features that diverge from traditional sequence models in their nature and timing

spatial patterns of late quaternary river incision along the northern tian shan foreland abstract river incision rate is widely used to track changes in tectonics or climate over time and space however the feasibility of utilizing the spatial variations of river incision to reconstruct past tectonic and climatic processes remains unclear here we focus on the spatial patterns of river incision along the northern chinese tian shan foreland three alluvial fans fp feh and flh are determined as the alluvial fan context of river incision and terrace classification providing the geomorphological framework across the foreland region four rivers i e the kuitun jingou manas and urumqi rivers from the western central and eastern part of the foreland are used to reconstruct the paleogeomorphology from the reference which is the best preserved terrace of each river system with ages clustering in different parts of the latest pleistocene early holocene the depth of incision constrained by the reference terrace of each river is obtained by comparing the present day topography and the reconstructed one the resulting profile of channel incision depth and rate of each analyzed river displays an overall decreasing downstream trend from the maximum where the river exits from the mountain range to zero such a trend has been attributed to the progressive lowering of the river gradient that was caused by the adjusted ratio of sediment input versus water discharge induced by climate change superimposing on the decreasing downstream trend an obvious step can also easily be observed onto the profile of channel incision of each river downstream of which channel incision is significantly less the step occurs near the thrust fault controlling growth of the outermost anticline through which each river cuts thereby implying the key role of local rock uplift in forming the river incision step the former observation implies that at the same timescale more river incision at the exit from the mountain range does not necessarily mean stronger climatic forcing of incision there we thus propose that in a foreland setting it should be the temporal pattern of river incision rather than its spatial variation that is helpful for unraveling the change in the forcing factor of downcutting

improving in situ cosmogenic chronometers new radiocarbon ages for sierra nevada deglaciation the first 10 be measurements from the laurentide terminal moraine and calculations based on paleomagnetic field strength have the potential to substantially improve the accuracy of cosmogenic age estimates specifically three new constraints apply to the interpretation of measured abundances of in situ produced cosmogenic 10be and 26al 1 a suite of minimum limiting radiocarbon dates indicates that the sierra nevada was deglaciated at least several thousand years earlier than assumed when nishiizumi et al 1989 first calibrated 10be and 26 al production rates based on polished bedrock surfaces in the range with retreat beginning by 18 000 cal yr b p and completed by 13 000 cal yr b p 2 concentrations of 10be in moraine boulders and glacier polished bedrock in new jersey show little variance 10 1 and can be used to calculate a preliminary 10be production rate integrated over the past 21 000 22 000 cal yr b p at 41 200 300 m altitude that is about 20 lower than currently accepted 3 calculations of the effect of past geomagnetic field strength variations on production rates suggest that the use of temporally averaged production rates may generate age errors of 20 however cosmogenic exposure ages can be corrected for this effect although the corrections currently are imprecise many previously reported late pleistocene 10be and 26al exposure ages are probably too young and are less accurate and less precise than implied by reported uncertainties the discrepancy between accepted production rates and those calculated from laurentide exposures when considered together with the sierran deglacial chronology and the model results suggest that correlations between cosmogenic and other numerical ages especially for brief events like the younger dryas and heinrich events will not be robust until temporal variations and the altitude latitude scaling of production rates are fully understood and quantified at levels comparable to current analytic uncertainties 3

revealing the pace of river landscape evolution during the quaternary recent developments in numerical dating methods during the last twenty years several technical developments have considerably intensified the use of numerical dating methods for the quaternary the study of fluvial archives has greatly benefited from these enhancements opening new dating horizons for a range of archives at distinct time scales and thereby providing new insights into previously unanswered questions in this contribution we separately present the state of the art of five numerical dating methods that are frequently used in the fluvial context radiocarbon luminescence electron spin resonance esr 230th u and terrestrial cosmogenic nuclides tcn dating we focus on the major recent developments for each technique that are most relevant for new dating applications in diverse fluvial environments and on explaining these for non specialists therefore essential information and precautions about sampling strategies in the field and or laboratory procedures are provided for each method new and important implications for chronological reconstructions of quaternary fluvial landscapes are discussed and where necessary exemplified by key case studies a clear statement of the current technical limitations of these methods is included and forthcoming developments which might possibly open new horizons for dating fluvial archives in the near future are summarised

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

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

in situ10be 26al exposure ages at meteor crater arizona a new method of dating the surface exposure of rocks from in situ production of 10be and 26al has been applied to determine the age of meteor crater arizona a lower bound on the crater age of 49 200 1 700 years has been obtained by this method

incision and differential bedrock uplift along the indus river near nanga parbat pakistan himalaya from 10be and 26al exposure age dating of bedrock straths abstract well preserved river cut bedrock surfaces straths abandoned by the progressive incision of the indus river in northern pakistan were dated using in situ cosmogenic 10 be and 26 al exposure age dating measurements on young and modern straths show no significant ingrowth of 10 be and 26 al implying that strath exposure ages closely approximate their abandonment age strath exposure ages range up to 65 ka and increase with height above the river the straths can be divided into two groups low straths dated at about 7 ka which yield very rapid bedrock incision rates 9 12 m ka and high straths 7 ka in age which yield somewhat slower incision rates 1 6 m ka incision rates for both groups increase by 1 3 m ka downstream toward an active reverse fault the raikot fault that forms the western border of the nanga parbat haramosh massif nphm the downstream increases in incision rates for the low straths mimic downstream increases in the modern gradient suggesting that bedrock incision rates have been proportional to stream power over the last 7 ka gradient increases are probably the result of the creation of knickpoints by bedrock uplift along the raikot fault the longitudinal profile and steep gorge of the indus river in the study area indicate that bedrock incision appears to keep pace with differential vertical motions between the nphm and surrounding regions thus the 1 3 m ka difference in incision rates likely reflects the differential bedrock uplift rate between the nphm and the skardu basin the differential incision rate is consistent with differential exhumation rates obtained from apatite fission track ages assuming geotherms of 80 90 c km in the nphm and 35 c km in the skardu basin this relation suggests that rapid bedrock incision of at least 1 3 m ka has persisted within the nphm for the last 0 5 ma the acceleration of incision rates throughout the study area since 15 ka is likely to be a climatic signal that records an increase in the discharge and or sediment load of the indus river in the study area related to deglaciation of the surrounding terrane

neotectonic study along mountain front of northeast himalaya arunachal pradesh india to study neotectonics the structural and morphotectonic aspects are studied along a part of mountain front region of northeast himalaya arunachal pradesh india unpaired river terraces are recognized near north of transverse burai river exit which is cut by an oblique fault across this fault fluvial terraces are located at heights of 22 7 and 3 m respectively on the left and right banks a water gap is formed along the river channel where the uplifted middle siwalik sandstone beds dipping 43 towards ene direction thrust over the quaternary deposit consisting of boulders cobbles pebbles and sandy matrix this river channel incised the bedrock across the intraformational ramghat thrust along which the rocks of the middle siwalik formation thrust over the upper siwalik formation recent reactivated fault activity is suggested north of the himalayan frontal thrust that forms the youngest deforming front of the himalaya the uplifting along the stream channel is noticed extended for a distance of 130 m and as a result the alluvial river channel became a bedrock river the relative displacement of rocks is variable along the length of strike slip faults developed later within the ramghat thrust zone longitudinal and channel gradient profiles of burai river exhibit knick points and increase in river gradient along the tapering ends of the profiles the study suggests active out of sequence neotectonically active thrusting along the mountain front neotectonics combined with climatic factor during the holocene times presents a virgin landscape environment for studying tectonic geomorphology

recently active contractile deformation in the forearc of southern peru abstract geomorphic and structural features of southern peru 14 18 s provide strong evidence for distributed crustal deformation along range sub parallel contractile structures we use in situ produced cosmogenic radionuclides in conjunction with field and remote mapping to determine the ages of geomorphic features and find 1 ancient surfaces 1 ma preserved as a result of very low surface erosion rates 2 young 30 ka low relief pediment surfaces developed during recent landscape modifications 3 active tectonic structures accommodating compressional stresses and 4 pleistocene river incision rates of 0 3 mm yr consistent with longer term rates in this region of southern peru the steep western wedge trench to arc area of the andean margin presently maintains the high topography of the altiplano through a combination of uplift and contractile deformation along steep east dipping faults and isostatic responses to the focused removal of large amounts of crustal material through canyon incision

the influence of bedrock geology on knickpoint development and channel bed degradation along downcutting streams in south central indiana geologic controls on knickpoint development and the mechanics of channel bed degradation were eluci dated by comparison of downcutting streams in south central indiana developed in lithologically homoge neous carbonate units and layered siliciclastic strata knickpoints formed in a single lithologic unit are stepped each step consists of a knickpoint face and tread the height of each step is equal to and controlled by bed thickness spatially knickpoints in homogeneous terrain are limited to jointed strata that dip 1 upstream or 2 downstream at angles less than the channel gradient knickpoints observed in lithologically layered strata are characterized by a single step in which resistant jointed rocks overlie and protect weaker units total knickpoint relief is influenced by thickness of the weaker strata knickpoints in layered siliciclastic strata are spatially limited to bedrock reaches produced by differential rates of channel incision knickpoint distribution is also influenced by joint

from gullies to mountain belts a review of sediment budgets at various scales this paper reviews the state of the art in the concept as well as in the application of sediment budgets in sedimentary research sediments are a product of mass dispersal at the earth surface and take part in global cycles sediment budgets aim at quantifying this mass transfer based on the principle of mass conservation and are the key to determine ancient fluxes of solid matter at the earth surface this involves fundamental questions about the interplay of uplift climate and denudation in mountain belts and transfer of sediments from the continents to the oceans as well as applied issues such as soil and gully erosion reservoir siltation and coastal protection first after introducing basic concepts relevant scales and methodologies the different components of quaternary routing systems from erosion in headwaters river systems glacial and paraglacial systems lakes deltas estuaries coasts shelves epicontinental seas and deep sea fans are discussed in terms of their sediment budget most suitable are sedimentologically closed or semi closed depositional environments e g alluvial fans lakes deltas and deep sea fans in a second step the dynamics of passive active and collisional tectonic settings and sediment budgets in related sedimentary basins are explored and new concepts of sediment portioning at large geodynamic scales are introduced ancient routing systems are more or less incomplete and may be intensively fragmented or destroyed in active tectonic settings in terms of sedimentary basin types rifts intracontinental and epicontinental settings are preferred objects of sediment budgets because of their persistence and relatively simple overall sedimentary architecture however closing basins such as foreland forearc retroarc piggy back and wedge top basins may provide excellent snapshots of orogenic sediment fluxes in a third step the large long lived routing systems of the amazon the ganges brahmaputra and the rhine are reviewed for each system estimates of either sediment volumes mass or sediment fluxes of continental and marine subsystems have been compiled in order to receive a complete routing in terms of mass conservation for specific time periods since the late glacial maximum as well as the cenozoic following lessons can be taken from these case studies i depositional centers and fluxes show strong shifts in space and time and call for caution when simply looking at subsystems ii the response times of these large systems are within the milankovich time interval thus lower than predicted from diffusion models iii cyclic routing of sediments in continental basins is much more dominated by climate human control than by eustacy and iv at long time scales ultimate sinks win over intermittent storage it is concluded from this review that the quantitative understanding of global sediment cycling over historic and geologic time and its response to allogenic forcing is still in its infancy and further research is needed towards a holistic view of sediment routing systems at various temporal and spatial scales and their coupling with global biogeochemical cycles this includes i to better determine response times of large routing systems by linking quaternary with cenozoic sediment budgets and continental with marine sub systems ii to combine advanced provenance techniques with sediment budgets in order to reconstruct ancient systems iii to study sediment partitioning at the basin scale iv to reconcile continental supply dominated sequence stratigraphy with the eustatic dominated marine concept and iv to account for non actualism of ancient systems with respect to their erosion and transport mode in particular during glaciations and pronounced arid intervals glacial and eolian sediment routing may cross over hydrologic boundaries of drainage basins thus challenging the principle of mass conservation

thermoluminescence measurements on shock metamorphosed sandstone and dolomite from meteor crater arizona 2 thermoluminescence age of meteor crater thermoluminescence tl dating measurements were performed on shock metamorphosed rocks from meteor crater arizona il ages were obtained for eight specimens four coconino sandstone and four kaibab dolomite which experienced sufficient shock heating during the impact to reset their preimpact tl postimpact radiation doses were determined for each shocked fragment from thermoluminescence measurements on quartz mineral separates effective radiation dose rates were calculated from concentrations of uranium thorium potassium and rubidium in the rocks and their burial environment and the distributions of these elements as determined by fission track and microprobe analyses cosmic radiation dose rates were estimated by altitude scaling of sea level data and were corroborated by tl dosimeter measurements at the crater the mean tl ages for the two rock types were reasonably concordant 50 400 2900 and 46 000 3100 years for sandstones and dolomites respectively the overall mean age 49 000 3000 years is significantly older than the 25 000 year age estimate based on the inferred correlation of the oldest pluvial episode at the crater with radiometrically dated 18o maxima

widespread aggradation in the mountainous catchment of the alaknanda ganga river system timescales and implications to hinterland foreland relationships abstract cut and fill type fluvial terraces are ubiquitous in the lesser himalayan zone of the alaknanda ganga ganges rivers system which flows perpendicular to himalayan lithotectonic units and traverses a steep climatic gradient lithofacies analysis of the sedimentary sequences of cut and fill terraces indicated that the valley aggradation took place via 1 channel bar development and excess sediment supply 2 debris flows composed of mixed rounded to sub rounded lithoclasts resulting from episodic high intensity rainfalls in the upper catchment or 3 debris flows or rockfalls generated by local landslides the luminescence chronology indicates that valley aggradation took place in two phases 49 25 ka and 18 11 ka the incision of the fill started soon after 11 ka paleoclimatic records from marine sediments indicate that the aggradation and incision in the alaknanda ganga river has oscillated in phase with global climatic variations glaciation deglaciation processes in the upper catchment produced huge amounts of sediment between 63 and 11 ka which was fluvially transferred to the lower valley via several cycles of erosion and deposition leading to extensive aggradation the climatic amelioration at 11 ka and the completion of deglaciation processes led to increased fluvial discharge and decreased sediment supply conditions conducive for incision of the alluvial fills records from the indo gangetic plain and the ganga delta demonstrate that the phase of aggradation was regional but that incision in the foreland started at least 2 3 ka later after 7 ka bedrock incision rates as calculated from dated alluvial covers of terraces that are separated by bedrock steps are spatially variable and fall within the range of rates reported from across the himalaya these estimated rates however are higher than the basin average erosion rates calculated using isotopic mass balance in riverbed sediments this study suggests that during the last 50 ka river dynamics in the himalayas were dominated by monsoon variability and the role of tectonic activity was limited to bedrock incision in few reaches only

cosmogenic 10be inferred lake level changes in sumxi co basin western tibet abstract most tibetan lakes are surrounded by conspicuous regressive shorelines attesting to high water levels in the past concentrations of the in situ produced cosmogenic radionuclide 10 be in bedrock from the three highest terraces surrounding sumxi co situated in western kunlun indicate that the highest lake level appeared before 10 000 11 500 yr and most likely between 11 000 and 12 800 yr younger ages for the two lower terraces imply regression of sumxi co during the early mid holocene the concurrency of the highest lake level with orbitally induced maximum northern hemisphere summer insolation suggests that the increase in water supply to sumxi co was most likely associated with increased recharge from melting glaciers we conclude that the enhanced indian monsoon during the early holocene did not penetrate the tibetan plateau and affect the northwestern part of tibet significantly

the incision variations of poiqu documented by the zhangmu landslide in the upper himalaya of tibet abstract aiming at the rate and causes of the incision variations in the upper himalaya orogenic belt of tibet a new method of incision rate estimation based on the analysis of the evolution of zhangmu landslide and its spatial and temporal relationship with the surrounding gullies is applied the research results are 1 the zhangmu landslide was an ancient huge landslide occurred at 24 2 2 4 ka bp consisting of an ancient bedrock landslide and subsequent deposit landslides with an area of 1 23 km2 and remaining volume of 23 4 106 m3 2 the fluvial incision rate shows variations in poiqu and its branch which may be controlled by the discharge and decreases from the poiqu 11 5 1 2 mm a to the tributaries from 4 8 0 5 mm a in the bangcundong gully to 2 4 0 2 mm a in zhangmu gully 3 the fluvial incision rate also shows temporal variations in the poiqu there are two periods of low rate and high rate incision processes in the poiqu while the section shape transforms from a gentle slope to a cliff in the low rate period from 24 2 ka bp to 10 0 ka bp in the poiqu valley the incision rate was 10 4 1 0 mm a while the high fluvial incision rate since 10 0 ka bp was 13 0 1 3 mm a 4 the fluvial incision promotes the landscape evolution and triggers the potential landslide in thousands of years

timing and mechanisms of central himalayan exhumation discriminating between tectonic and erosion processes the ability to deduce exhumation mechanisms from thermochronological data is hampered by the fact that assumptions on the thermal state of the lithosphere have to be made additional argumentation is generally required to discriminate between erosion controlled and tectonically induced exhumation this problem can be overcome by studying the spatial distribution of zircon and apatite u th he and fission track data in this work the variation of four different low temperature isotopic systems generating age trends along a sampling line is used to infer mechanisms of quaternary exhumation in the central high himalayan metamorphic belt observed zircon age trends with southwards increasing cooling ages from 0 5 to 1 7 ma are attributed to tectonically induced exhumation the uniform apatite cooling ages clustered c 0 5 ma are attributed to erosion

direct evidence for a steep geotherm under conditions of rapid denudation western himalaya pakistan recent fluid inclusion and 40 ar 39 ar cooling age data show that currently exposed basement rocks in the raikhot glacier valley of the nanga parbat haramosh massif pakistan himalaya were at temperatures of 350 50 c at depths of 6 2 km hydrostatic pressure correction these data imply the presence of a steep thermal gradient in the upper crust at 1 ma 29 100 c km and denudation rates over the past 1 0 m y of 3 6 mm yr providing independent corroboration of previous estimates of rapid denudation at nanga parbat 4 5 mm yr over 3 3 m y our data provide direct documentation of near surface compaction of isotherms under conditions of rapid denudation a result that has long been supported by thermal modeling

tectonic evolution of the himalayan syntaxes the view from nanga parbat acknowledgements i was introduced to the himalayas by mike coward in the mid 1980s and remain indebted to him for inspiring a career studying orogenic tectonics i also thank the numerous colleagues both from the uk and from peshawar university who were companions on many field campaigns especially around nanga parbat this contribution has been greatly improved by incisive reviews by tom argles and phaedra upton although of course the author takes full responsibility for the views presented here finally i thank peter treloar for inviting this review and for his patience while i put it together funding over the years this research has been variously supported by the uk s natural environment research council and the royal society published in himalayan tectonics a modern synthesis

relations between postglacial fluvial incision rates and uplift rates in the north island new zealand 1 fluvial incision rates are increasingly being used as a proxy for rock uplift rates for inland settings we test the validity of this approach by comparing incision rates and rock uplift rates along the hikurangi margin new zealand postglacial fluvial incision rates were calculated by measuring the difference in altitude between the last glacial maximum lgm terrace tread 18 2 calendar ka and the present river bed for 10 major rivers catchment areas 1400 5900 km2 incision rates have thus been measured over a half glacial cycle they also represent average rates over the last 18 kyr during which time variations are likely due to processes such as knickpoint retreat rock uplift rates have been estimated from 1 altitude differences between the treads of pairs of fluvial fill terraces 55 and 18 calendar ka assumed to have formed at the same altitude i e rock uplift relative to the geoid 2 present day altitudes of late neogene paleoshoreline marker horizons 1 6 5 7 ma i e rock uplift relative to sea level and 3 present day altitudes of neogene mudstones for which maximum depth of burial has been calculated from porosity i e rock uplift relative to sea level these rock uplift rates overestimate tectonic uplift rates because they do not take into account isostatic compensation due to erosion mean incision rates range up to 11 7 mm yr 1 and mean rock uplift rates range up to 4 1 and 0 9 mm yr 1 for the three methods respectively we have made some qualitative and semiquantitative observations about nontectonic controls on postglacial incision rates and find that localized influence only is exerted by rainfall base level and bedrock lithology while negative or no correlations are shown with lgm fluvial fill thickness and stream power incision rates and uplift rates display a rough correlation with incision rates typically 1 5 5 times uplift rates this relation suggests that tectonic uplift is likely to exert an important control on fluvial incision in the hikurangi margin

generality of drought flow characteristics within the arkansas river basin drought flow measurements from 11 river basins contained within and surrounding the cooperative atmosphere surface exchange study cases in the walnut river watershed in kansas were subjected to a recession slope analysis this analysis was based on the dupuit boussinesq groundwater formulation and made use of the historical streamflow daily values published by the u s geological survey the long and short term response features of the riparian aquifers were found to be practically identical to those observed in an earlier study in the washita river basin in oklahoma as both study areas lie within the osage section of the central lowland physiographic province these findings support the applicability of regionalization and scaling of low streamflow related basin characteristics within the same geomorphic domain

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

tectonic and climatic forcing on the panj river system during the quaternary surface processes involve complex feedback effects between tectonic and climatic influences in the high mountains of pamir the ongoing india asia collision provokes the development of east west trending mountain ranges that impose structural control on flow directions of the pamir rivers the evolving relief is further controlled by strong moisture gradients the decreasing precipitations from the southern and western margins of the pamir plateau to its center in their turn control the emplacement of glaciers chronologies of glacial records from the pamir plateau attest for strong climatic variability during the quaternary corresponding remnants of glacial advances suggest glacial morphodynamic restricted to 4 000 m a s l since marine isotope stage 4 the panj the trunk river of pamir deflects from the predominant westward drainage connecting its main tributaries at the western margin of the drainage basin the geometry of the river network and the pattern of incision characterize the panj as a composite river river reaches of indicated low incision coincide with west trending valleys parallel to domes and their bounding faults valley shape ratios reflect increased incision in north trending sections but do not match with changes in the catchment geometry or erodibility of rock types modelled riverbed profiles distinguish three panj reaches the upstream increase in convexity suggests successive river captures in response to local base level changes the northward deflected river reaches link the local base levels which coincide with the southern boundaries of the shakhdara and yazgulom dome and darvaz range we argue that tectonics plays a large role controlling the drainage system of the panj and hence surface processes in the pamir mountains

the early tertiary chemical remagnetization in the bakjisan syncline korea its geotectonic implications the bakjisan syncline is located in the northwestern part of the taebaeksan basin korea new paleomagnetic data for the upper carboniferous lower triassic pyeongan supergroup from the pyeongchang area on the west limb of the bakjisan syncline have been obtained and synthesized and compared with previous data from the jeongseon area on the east limb of the syncline a total of 350 specimens were collected from 21 sites to clarify the relationship between the spatial distribution of remagnetized areas and the thrust system in the taebaeksan basin the characteristic remanent magnetization chrm isolated from all samples was a remagnetized component acquired after tilting of the strata and carried by various magnetic minerals magnetite hematite and pyrrhotite from rock magnetic studies electron microscope observations and xrd analyses the pervasive remagnetization is interpreted to be associated mainly with a fluid mediated chemical remanent magnetization crm this is consistent with the results of previous work in adjacent areas the paleomagnetic pole position 88 3 e 83 9 n a95 4 9 from the pyeongan supergroup in the bakjisan syncline indicates that the timing of the remagnetization event is early tertiary times i e paleocene to eocene by comparison with reliable paleopoles from the korean peninsula early tertiary crms are also reported from previous studies of an adjacent region within the northwestern part of the taebaeksan basin in contrast a primary remanent magnetization was reported in the southeastern part of the taebaeksan basin this implies that the major thrust system the gakdong thrust which separates the two regions has caused them to experience substantially different geologic histories since deposition of the strata since many thrusts with ns trend are observed in the northwestern part of the taebaeksan basin compared with the southeastern region it appears that the remagnetizing fluids pervasively penetrated the northwestern part of the basin by utilizing the already well developed thrust system

channel incision in the rio atenguillo jalisco mexico defined by 36cl measurements of bedrock abstract the jalisco block of western mexico has undergone uplift in the tertiary in response to subduction tectonics the atenguillo river interior to the jalisco block has incised the bedrock units of the jalisco block including cretaceous ash flow tuff granite as well as younger volcanic lava flows to study incision rates knickpoint propagation and the uplift rate of the region samples from nine different points along the atenguillo channel were collected for 36 cl exposure age dating exposure ages along the length of the channel are high near the head of the basin where the river meanders in a broad plain ages are younger at the knickpoints and downstream where the river cuts deeply and forms a canyon incision rates measured at different points along the channel also correlate with channel slope and age low incision rates are measured in the oldest part of the channel near the head station b 2 5 mm year and just above the knickpoints station c 0 6 mm year and station g 1 4 mm year the incision rates are highest just below the knickpoints station f 2 4 mm year and farther downstream stations h and i 5 6 and 2 9 mm year respectively the high incision rates can be attributed to subduction related uplift of the jalisco block other features attributable to uplift are emergent paleoshorelines and uplifted marine sediments along the coast and relatively lower incision rates were measured north of the jalisco block

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

fluvial archives a valuable record of vertical crustal deformation abstract the study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms but also for identifying the nature of crustal deformation and its history in recent decades geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens here we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions the effects of horizontal deformation are not addressed channel long profiles have received considerable attention in the literature and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady state characteristics then we review the literature dealing with the transient response of rivers to tectonic perturbation through the production of knickpoints propagating through the drainage network inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories finally we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes as well as the erosional imprint of tectonic forcing sedimentary deposits such as fluvial terrace staircases are also considered as a classical component of tectonic geomorphology we show that these studies have recently benefited from rapid advances in dating techniques allowing more reliable reconstruction of incision histories and estimation of incision rates the combination of progress in the understanding of transient river profiles and larger more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation i e extrapolation of local data to entire profiles finally planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the dis equilibrium state of drainage systems across regional drainage divides

geochronology of pediment surfaces in southern peru implications for quaternary deformation of the andean forearc abstract the geomorphology of the andean forearc has historically been viewed as an old remnant of a late miocene planar landscape with no significant active structures accommodating quaternary deformation however the well preserved sequence of planation surfaces and strath terraces developed within the forearc of southern peru provide evidence of recent uplift along the western margin previously the abandonment of these surfaces was attributed to uplift of late miocene age however abrupt changes in topography and drainage incision within the pediment surfaces indicate recent deformation we use in situ produced 10be to determine the exposure ages of these abandoned surfaces in order to derive the spatial and temporal extent of this tectonic activity our new results in contrast to previous work yield pediment surface ages of 119 ka 203 ka 278 ka 549 ka and 1003 ka indicating a youthful morphology additionally these surfaces are affected by steeply dipping active faults producing localized deformation which can be quantified incision rates based on the exposure ages of abandoned strath surfaces are on the order of 0 04 0 3 mm yr the data set presented here not only suggests significant active deformation within the forearc but also highlights a sharp contrast between the style of deformation observed on the eastern and western margins of the andes while the general notion is that active deformation is localized in the subandean fold and thrust belt our data support an emerging view where active deformation is occurring in the western margin as well

observations on the role of lithology in strath terrace formation and bedrock channel width field observations from western washington and eastern tibet indicate a strong lithologic influence on strath terrace formation and highlight the response of bedrock channel width to spatial gradients in bedrock erodibility and or rock uplift rates measurements of local bedrock bed and bank erosion rates together with observations of the role of weathering processes on erosion of siltstones and sandstones illustrate a mechanism that underlies a conceptual model that predicts a strong lithological control on strath terrace formation direct measurements of bedrock erosion rates in lithologies susceptible to accelerated erosion upon sub aerial exposure show that lateral rates of bedrock bank erosion can substantially exceed vertical incision below the perennial flow level due to an asymmetry in erodibility between perennially submerged rock and rock exposed to cyclic wetting and drying on bedrock channel walls under such conditions the rapid weathering mediated lowering of bedrock exposed above baseflow promotes development of a beveled bedrock platform that could become a strath terrace upon abandonment in contrast to previous studies channel widths measured across a substantial gradient in lithology slope and long term erosion rates in eastern tibet do not follow conventional relations where channel width scales as a power law function of drainage area instead as they flow across a zone of rapid uplift these channels systematically narrow relative to the predicted width extrapolated from traditional power law relations field studies from a wide range of geological settings and lithologies support the interpretation that in general strath terraces tend to be more extensive in rivers flowing over weak sedimentary rock and tend to be poorly developed and or preserved where rivers flow over hard erosion resistant rock

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

rates of river incision across the main tectonic units of the pamir identified using optically stimulated luminescence dating of fluvial terraces calculated incision rates along the panj the main river of the pamir are used to investigate any influence by tectonics or climate on the architecture of the river the depositional ages of panj river terraces were calculated using optically stimulated luminescence osl dating of terrace sand fluvial incision rates were generated by integrating the terrace depositional ages with accurate kinematic gps measurements of terrace heights above the modern panj we investigated 16 terraces along the panj at the western pamir margin and one terrace from the vakhsh river to the north of the pamir the results reveal brief periods of fluvial deposition over the past 26 kyr the oldest panj terrace depositional ages coincide with early mis 2 and mis 2 1 glaciations on the pamir plateau younger terrace ages have no apparent link with glacial cycles terraces with varying heights above the modern panj at different localities yielded similar depositional ages this suggests that local conditions have determined fluvial incision rates combining all of the terrace measurements the average incision rate of the panj over the last 26 kyr has been 5 6 mm yr a high mean incision rate of 7 3 mm yr was calculated from terraces where the panj has cut a steep sided valley through the shakhdara dome significantly lower incision rates 2 3 mm yr were calculated from terraces where the panj flows along the southern boundaries of the shakhdara and yazgulom domes at those localities graded segments of the panj river profile and increased valley widths are indicative of local base levels downstream of the yazgulom dome river incision rates are generally lower 4 5 mm yr than the panj average however there is one exception where higher incision rates 6 mm yr were calculated upstream of the darvaz fault zone a major tectonic feature that forms the western boundary of the pamir the vakhsh river terrace to the north of the pamir yielded a lower incision rate 3 mm yr compared to the panj average variation in incision rates along the panj does not correspond to changes in rock type or river catchment area instead incision rates appear to have been primarily influenced by river capture across the southern and central metamorphic domes of the pamir wherever the panj cuts these domes it displays a convex river profile the combination of localized river profile convexity and changes in incision rates across the pamir domes indicates that the dome boundaries have been active recently

moraine dam related to late quaternary glaciation in the yulong mountains southwest china and impacts on the jinsha river abstract the yulong mountain massif is tectonically active during quaternary and contains the southernmost glacierized mountains in china and all of eurasia past glacial remnants remain preserved on the east and west sides of the yulong mountains a ridge of moraine protruded into the jinsha river at the daju basin damming the river and forming a lake at the head of the jinsha river cosmogenic 10 be and 26 al provide exposure age dates for the moraine based fluvial terraces left behind after the dam breached and for moraine boulders on both the eastern and western sides of the yulong mountains our results yield exposure ages for the terraces that range from 29 ka to 8 ka and a downcutting rate of 7 6 m ka the preservation of the remaining dam for over 10 000 years suggests stability of the moraine dam and gradual erosion of the dam during drainage of the dammed lake from the relationship between exposure ages and elevations of the fluvial terraces located in different walls of the daju fault we obtain a late quaternary dip slip rate of about 5 6 m ka for the daju fault the exposure ages of 10 2 ka and 47 ka for moraine boulders located in the east and west sides of the yulong mountains respectively coincide with warm periods in the late quaternary this implies that precipitation provides the major control for glaciations on the yulong mountains a domain of the southwest asian monsoon

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

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

late quaternary holocene landscape evolution of a monsoon influenced high himalayan valley gori ganga nanda devi ne garhwal the garhwal himalaya provides an excellent natural laboratory in which to examine landscape evolution in a monsoon influenced high mountain environment geomorphic and sedimentological analysis and 10be cosmogenic radionuclide crn surface exposure dating of moraines fans and river and strath terraces in the gori ganga valley of nanda devi ne garhwal indicate that fans and river terraces developed rapidly by debris flow and flood processes during periods of deglaciation these phases of high sediment transfer occurred at 1 2 4 5 and 7 8 ka fan incision rates subsequent to major times of resedimentation after each glacial advance are between 19 and 57 mm year this contrasts with bedrock incision rates based on mid holocene strath terraces of 5 mm year these rates indicate that despite episodes of rapid denudation and resedimentation linked to glacial activity in this region the background rates of denudation are similar to those for other regions of the himalaya averaging several millimeters per year furthermore these data show the importance of climatic controls on landscape evolution and suggest a strong monsoonal control on the dynamics of earth surface processes in this region

the effect of bedrock jointing on the formation of straths in the cache la poudre river drainage colorado front range the north fork poudre and poudre rivers have incised deep narrow canyons into precambrian age granite and gneiss along the colorado front range longitudinally discontinuous active strath surfaces and strath terraces are present along each river although the crystalline bedrock of the study area is resistant to weathering and erosion differences in joint spacing and orientation create significant differences in rock mass strength along each river the vertical spacing of active straths along the north fork poudre correlates strongly with the spacing of prominent subhorizontal joint surfaces strath terraces along the poudre river occur in areas of wider valley bottom upstream from a profile convexity especially wide segments with the greatest downstream extent reflect the locations of shear zones that create more densely spaced joints and lower rock resistance i interpret the absence of strath terraces in wider canyon segments downstream from the convexity to indicate that the poudre river is capable of laterally eroding the entire valley bottom as the river incises leaving behind only fill terraces upstream from the convexity in contrast lateral erosion has created canyon segments with wider valley bottoms but the entire valley bottom has not been lowered at the same rate leaving discontinuous strath terraces the poudre river is regionally unique in having relatively well developed strath terraces but strath terraces in other major drainages of the front range are also only present upstream from convexities in the longitudinal profile

glacier and landslide feedbacks to topographic relief in the himalayan syntaxes despite longstanding research on the age and formation of the tibetan plateau the controls on the erosional decay of its margins remain controversial pronounced aridity and highly localized rock uplift have traditionally been viewed as limits to the dissection of the plateau by bedrock rivers recently however glacier dynamics and landsliding have been argued to retard headward fluvial erosion into the plateau interior by forming dams and protective alluvial fill here we report a conspicuous clustering of hundreds of natural dams along the indus and the tsangpo rivers where these cross the himalayan syntaxes the indus is riddled by hundreds of dams composed of debris from catastrophic rock avalanches forming the largest concentration of giant landslide dams known worldwide whereas the tsangpo seems devoid of comparable landslide dams in contrast glacial dams such as river blocking moraines in the headwaters of both rivers are limited to where isolated mountain ranges intersect the regional snowline we find that to first order high local topographic relief along both rivers corresponds to conspicuously different knickzones and differences in the type and potential longevity of these dams in both syntaxes glacier and landslide dams act as a negative feedback in response to fluvial dissection of the plateau margins natural damming protects bedrock from river incision and delays headward knickpoint migration thereby helping stabilize the southwestern and southeastern margins of the tibetan plateau in concert with the effects of upstream aridity and localized rock uplift

cooling history of the nw himalaya pakistan fission track and 40ar 39ar cooling ages indicate that the late tertiary cooling history of the himalayan ranges of northern pakistan is largely a function of uplift and erosion interpretation of cooling ages which range from under 0 5 ma to over 80 ma suggests that during the late tertiary long term uplift rates at least doubled from under 0 2 mm yr to in some cases well over 0 5 mm yr uplift rates show strong and systematic regional variations as well which reflect the greater uplift of eastern and northern regions the association of very rapid uplift and erosion with the nanga parbat haramosh massif can be explained by a locally vigorous collision of india with eurasia near a promontory of indian crust the resultant rapid uplift of the nanga parbat haramosh massif reactivated the main mantle thrust melange zone with a reversed sense of motion discontinuities in the coolingage distribution along the main mantle thrust in the southern swat hazara region may be the result of the thermal effects of overthrusting

evolution of the santa cruz mountains california through tectonic growth and geomorphic decay i describe a strategy for modeling a specific large scale topographic feature that recognizes the discrepancy between tectonic and geomorphic scales and allows for important feedbacks between these processes in the geomorphic model the largest channel in each 4 4 km cell is explicitly treated the channel incision being driven by a stream power rule hillslopes internal to each cell respond rapidly to incision of the local channel prompting their treatment in the model as steady state forms i present analytic expressions for the local relief which is controlled by the local channel incision rate and rate constants associated with the dominant hillslope process either diffusive or landsliding initial conditions include any preexisting topography and a lightly etched a channel network the model is illustrated using the santa cruz mountains california i show that an earlier hypothesis that the santa cruz mountains are due to advection of topography past an uplift source related to a restraining bend in the san andreas fault remains viable when more specific geomorphic processes are considered the local tectonics are represented by crustal thickening necessitated by conservation of mass in the bend right lateral translation of crust with respect to the bend and flexural response to the distributed load the model produces reasonable geographic and statistical distributions of topography using rates of tectonic and geomorphic processes that are within the range of those measured locally this argues that this restraining bend is a long lived feature of the san andreas fault the slightly higher crest and shorter length of the southern santa cruz mountains may potentially be explained by slightly faster slip of the crust west of the fault with respect to the bend than of that to the east deflection is minimal beneath these relatively small mountains disallowing the interesting feedback of erosionally driven uplift the predicted pattern of exhumation could be used to guide the search for fission track sites that could aid in the testing of the model

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

landscape response to deglaciation in a high relief monsoon influenced alpine environment langtang himal nepal abstract significant glacial fluctuations and rapid paraglacial reworking of glacigenic sediments characterize the middle and late holocene of the langtang khola valley central nepal himalaya geomorphic mapping and beryllium 10 cosmogenic radionuclide crn dating of moraines and paraglacial fans were undertaken to test the existing paraglacial fan terrace and moraine chronologies the new dating compares favorably with prior studies that utilized radiocarbon adding additional support to the assumption that fan and terrace formation are strongly linked to deglaciation fan and terrace denudation rates are so rapid in this region averaging 33 mm yr that no depositional landforms older than 5 ka are preserved within 250 m of the valley floor in this region high rates of denudation during the late quaternary are driven by a combination of rapid tectonic uplift numerous glacial fluctuations and intense weathering driven by an active monsoon climate extensive reworking of glacigenic sediments in langtang during the latter half of the holocene is consistent with studies completed in other areas of the himalaya that are strongly influenced by the monsoon

longitudinal profile development into bedrock an analysis of hawaiian channels analysis of topographic maps of rivers incised into dated hawaiian lava flows shows that the long term average bedrock erosion rate along certain reaches is linearly related to stream power field observations suggest that two processes may control hawaiian channel downcutting 1 stream power dependent erosion including abrasion of the channel bed by transported particles and 2 step wise lowering caused by knickpoint propagation modeling results indicate that a simple stream power dependent erosion law predicts the straight to weakly convex longitudinal profiles characteristic of kauai channels but is insufficient to predict two other characteristic features the upslope propagation of knickpoints and the straight 5 8 channel slopes below the knickpoints thus more than this single transport law is apparently required to model bedrock channel incision field surveys also indicate that significant portions of the channel lengths below the knickpoints are mantled with large boulders we propose that

earth science river incision revisited a data set compilation suggests that measurements of river erosion into rock depend on the observation timescale casting doubt on whether terraces and other incised landforms faithfully record changes in climate and tectonics

middle late holocene river terraces in the erhjen river basin southwestern taiwan implications of river response to climate change and active tectonic uplift abstract we reconstruct the holocene river history of the erhjen river area 140 km 2 by correlating river terraces aided by 28 radiocarbon dates multiple terraces developed in the lower erhjen river since the middle holocene they converge downstream to the coastal plain the rates of channel incision into bedrock calculated from these terraces at yuehshihchieh are 7 8 mm year during ca 5 7 2 5 ka 5 cm year during 1 5 1 3 ka and 1 cm year since 1 ka the last is close to the average incision rate since middle holocene meanwhile only a single but wide middle late holocene paleo floodplain was developed in the upper erhjen river it was completely abandoned only after 0 8 ka likely following an episode of base level fall starting from the coastal plain based on the apparent downstream and upstream convergence of these dated terraces we identify a doming structure or anticline within the basin which results in a tilt rate of 10 6 to 10 7 per year in the lower erhjen river valley the major terraces here had different initial long profiles which implies that a critical graded long profile may not be a prerequisite for formation of a wide erosional terrace surface instead we propose that these terraces were initiated by a series of catastrophic rainfall events probably climatic related which brought a large amount of bedload from hillslopes to prevent the channel from incising when valley widening was facilitated by high discharge runoff we find that not only terrace surface formation but also channel incision can be strongly controlled by climatic driven discharge and bedload conditions as suggested by the contrast of bedrock incision rates we observe at yuehshihchieh apparently the climate and its effects on the landscape cannot be regarded as constant during the holocene even in a humid tropical area like taiwan however such a fluctuation of climate could only be recorded in a setting where rivers have a high tendency to incise so that multiple terraces can be created the lower erhjen river that is characterized by active tectonic tilting is an example of this setting

a signature of transience in bedrock river incision rates over timescales of 10 4 10 7 years measured rates of river incision into bedrock are commonly interpreted as proxies for rates of rock uplift see refs 1 and 2 for example and indices of the strength of climatic forcing of erosion over time see refs 3 and 4 for example this approach implicitly assumes that river incision rates are in equilibrium with external forcings over a wide range of timescales here we directly test this assumption by examining the temporal scaling of bedrock river incision from 155 independent measurements of river incision compiled from 14 sites of these sites 11 exhibit a negative power law dependence of bedrock river incision rate on measurement interval a relationship that is apparent over timescales of 10 4 10 7 years and is independent of tectonic and geomorphic setting thus like rates of sediment accumulation rates of river incision into bedrock exhibit non steady state behaviour even over very long measurement intervals non steady state behaviour can be explained by episodic hiatuses in river incision triggered by alluvial deposition if such hiatuses have a heavy tailed length distribution regardless of its cause the dependence of incision rate on measurement interval complicates efforts to infer tectonic or climatic forcing from changes in rates of river incision over time or from comparison of rates computed over different timescales

the quaternary uplift history of central southern england evidence from the terraces of the solent river system and nearby raised beaches abstract we have used fluvial solent river system and marine terraces to reconstruct the uplift history of central southern england in the case of the former we make the assumption that fluvial incision has been a direct response to surface uplift with its precise timing controlled by climatic forcing of fluvial activity such that height of terrace gravel above modern river is a consequence of uplift since deposition in the case of the marine sequence we take the height of interglacial raised beaches above a calculated contemporaneous sea level as a measure of uplift the calculation involving an adjustment from modern sea level using the deep oceanic oxygen isotope signal as an indication of global ice volume at the time of deposition this exercise requires some degree of dating constraint which is problematic for both environments the solent terraces have yielded little biostratigraphical evidence whereas the south coast raised beaches have either been poorly exposed in recent years or their ages have been controversial because of disputes between biostratigraphy and geochronological data we have supplemented the evidence available from these sources by using key aspects of the archaeological record as dating constraints in particular the first appearances of levallois technique a marker for mis 9 8 and of bout coupe handaxes mis 3 the first of these has been particularly useful in modelling of the middle pleistocene parts of the river terrace staircases of the solent system in undertaking this reappraisal we have noted several inconsistencies and disagreements between past correlation schemes for the terraces of the solent and its various tributaries we find that versions involving shallower downstream gradients in the main solent river are most likely to be correct and that revisions on this basis solve a number of problems in interpretation encountered previously our results show that most of this region has uplifted by 70 m since the late early pleistocene and by 150 m since the middle pliocene there being a high degree of consistency between uplift histories inferred for river terraces and marine terraces uplift rates increase gradually westward such that along the river frome at the western end of the hampshire basin 80 m of uplift since the late early pleistocene is indicated this variation is interpreted as a consequence of a regional scale variation in crustal properties about 80 m of uplift is also indicated on this timescale by raised beaches in the portsdown area and adjacent terraces of the river test and solent in the vicinity of the portsdown anticline to the north of southampton we interpret this as a consequence of 10 m of vertical slip in the past million years on the blind reverse fault beneath this anticline this dataset thus provides the first clear indication of measurable quaternary structural development in crustal basement in the onshore uk the solent has formed more than a single terrace per 100 ka milankovitch cycle leading us to attribute terraces to isotopic substages potentially improving upon the resolution available from sequences in which terraces formed once per cycle athough the first appearence of levallois technique was initially considered to date from the mis 9 8 transition based on evidence from the thames we found that there was a better modelling fit if this was taken as having occurred slightly earlier in mis 9b perhaps in association with the post mis 9e or 9c marine regression which could have permitted immigration into a previously insular britain of people versed in levallois technology

inner gorge slot canyon system produced by repeated stream incision eastern alps significance for development of bedrock canyons abstract many inner bedrock gorges of the alps show abrupt downstream changes in gorge width as well as channel type and gradient as a result of epigenetic incision of slot canyons many slot canyons also are associated with older gorge reaches filled with quaternary deposits the age of slot canyons and inner bedrock gorges however commonly is difficult to constrain for the inner bedrock gorge system of the steinberger ache catchment eastern alps active slot canyons as well as older abandoned gorge reaches filled with upper wurmian proglacial deposits record three phases of gorge development and slot canyon incision a 234u 230th age of cement of 29 7 1 8 ka in fluvial conglomerates onlapping the flank of an inner gorge fits with late wurmian valley bottom aggradation shortly before pleniglacial conditions in addition the age indicates that at least the corresponding canyon reach must be older during advance of ice streams in the buildup of the last glacial maximum lgm the catchment was blocked and a proglacial lake formed bedrock gorges submerged in that lake were filled with fluviolacustrine deposits during the lgm the entire catchment was overridden by ice during post glacial reincision streams largely found again their preexisting inner bedrock canyons in some areas however the former stream course was missed and a slot canyon formed the distribution of pleistocene deposits the patterns of canyon incision and the mentioned u th cementation age however together record a further discrete phase of base level rise and stream incision well before the lgm the present course of steinberger ache and its tributaries is a patchwork of 1 slot canyons incised during post glacial incision 2 vestiges of slot canyons cut upon an earlier middle to late wurmian cycle of base level rise and fall 3 reactivated reaches up to 200 m in width of inner bedrock gorge that are watershed at present and more than at least 30 ka in age and 4 abandoned sediment filled reaches of bedrock canyons that also must be older than 30 ka and that are exposed alongside the active streams multi cyclic bedrock canyon systems composed of reaches of markedly different ages may be common in mountain ranges subject to glaciations and or mass wasting

first indications of high slip rates on active reverse faults nw of damascus syria from observations of deformed quaternary sediments implications for the partitioning of crustal deformation in the middle eastern region recent research on rates of crustal shortening within the palmyra fold belt pfb in syria has drawn attention to the possibility that reverse faults near the city of damascus which adjoins the sw pfb have significant slip rates we infer that the damascus fault directly adjacent to the city has developed a throw of 2500 m and report the discovery of the en echelon bassimeh fault with a throw of 1000 m this fault being revealed by warping of the local bedrock and of a terrace of inferred late pleistocene age of the river barada we estimate that this set of faults became active circa 0 9 ma synchronous with changes to the pattern of faulting previously reported farther southwest in the northern jordan valley vertical slip rates on the bassimeh and damascus faults of 1 1 and 2 8 mm a 1 respectively are thus estimated we also infer that large historical earthquakes previously attributed to left lateral faulting farther west on the dead sea fault zone dsfz probably occurred on this set of reverse faults these faults thus represent a significant hazard to the city of damascus our observations indicate that as much as half of the northward motion of the arabian plate relative to the african plate may be absorbed by crustal shortening within the pfb potentially explaining the low slip rate recently measured geodetically on the northern dsfz in western syria

diagnostic heavy minerals in plio pleistocene sediments of the yangtze coast china with special reference to the yangtze river connection into the sea abstract this present study revealed five heavy mineral zones in the yangtze coastal borehole sediments ilmenite garnet and zircon suite of zone i of the pliocene characterizes the derivation of basaltic bedrock and local andesitic granitic rocks indicative limonite in the zone i sediments formed as alluvial fan facies shows strong chemical weathering the assemblage of amphibole straurolite kyanite and idocrase of metamorphic derivation together with a few zircon and tourmaline of andesitic granitic origin in zone ii represents the extension of sediment sources to the lower and middle yangtze basin in early pleistocene as the study area subsided also the braided to meandering riverine facies demonstrates a longer distance sediment transport few heavy minerals remained in zone iii of mid pleistocene when mottled thicker stiff mud occurred as the lacustrine facies suggesting a quasi coastal floodplain with lower capability of sediment transport heavy minerals appeared significant and continuous in zone iv of late pleistocene when changing to the shallow marine facies inferring much extended sediment sources to the upper yangtze hypersthene identified primarily in zone iv was closely associated with the er mei mountain tholeiite basalt of the upper yangtze heavy minerals of zone v remained almost the same as iv during holocene when the modern delta evolved the heavy minerals suggested the timing of the yangtze connection to the sea at ca 0 12 ma bp

synchronous anatexis metamorphism and rapid denudation at nanga parbat pakistan himalaya the nanga parbat haramosh massif of the western himalaya is a north trending half window of indian crust that provides spectacular exposures of precambrian basement gneisses that have been overprinted by himalayan metamorphism we report here petrologic data and u pb dates on zircon and monazite which document that nanga parbat gneisses underwent a pliocene pleistocene episode of high grade metamorphism and anatexis during an interval in which the nanga parbat massif was undergoing rapid denudation at mean rates of 5 mm yr we speculate that by initiating decompression melting this denudation may be at least partly responsible for the anatexis and high grade metamorphism

an episode of rapid bedrock channel incision during the last glacial cycle measured with 10be we use 10 be to infer when how fast and why the susquehanna river incised through bedrock along the u s atlantic seaboard one of the world s most prominent and ancient passive margins although the rate at which large rivers incise rock is a fundamental control on the development of landscapes relatively few studies have directly measured how quickly such incision occurs either in tectonically active environments or along passive margins exposure ages of fluvially carved bedrock strath terraces preserved along the lower susquehanna river demonstrate that even along a passive margin large rivers are capable of incising through rock for short periods of time at rates approaching those recorded in tectonically active regions such as the himalayas over eighty samples collected along and between three prominent levels of strath terraces within holtwood gorge indicate that the susquehanna river incised more than 10 meters into the appalachian piedmont during the last glacial cycle beginning 36 ka incision rates increased dramatically and remained elevated until 14 ka the northern half of the susquehanna basin was glaciated during the late wisconsinan however similar rates and timing of incision occurred in the unglaciated potomac river basin immedi ately to the south the concurrence of incision periods on both rivers suggests that glaciation and associated meltwater were not the primary drivers of incision instead it appears that changing climatic conditions during the late pleistocene promoted an increase in the frequency and magnitude of flood events capable of exceeding thresholds for rock detachment and bedrock erosion thus enabling a short lived episode of rapid incision into rock although this study has constrained the timing and rate of bedrock incision along the largest river draining the atlantic passive margin the dates alone cannot explain fully why or by what processes this incision occurred however cosmogenic dating offers compelling evidence that episodes of rapid incision into bedrock are tied to glacial cycles and changes in global climate these results and the methods we employ provide valuable insights into the nature of bedrock channel incision not only along the susquehanna river and passive margins but also across a wide range of settings around the globe because river incision into bedrock transmits the effects of changing climate and tectonics through fluvial networks to hillslopes comprehending when where and why rivers incise has important implications for the evolution of land scapes

dating sediment burial with in situ produced cosmogenic nuclides theory techniques and limitations abstract dating sediment burial over million year time scales is crucial in many areas of the earth sciences and archeology but is often difficult using traditional techniques sediment burial can be dated by the radioactive decay of cosmogenic nuclides provided that the sediment was exposed to cosmic rays prior to burial dating calculations are straightforward if sediment is buried deeply and rapidly enough to prevent cosmogenic nuclide production after burial however the analysis can be complicated by postburial production if sediment is insufficiently shielded from secondary cosmic ray nucleons and muons this paper discusses how buried sediments can be dated over timescales up to 5 myr using 26 al and 10 be in quartz

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

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

metamorphism and melting of the lithosphere due to rapid denudation nanga parbat massif himalaya the nanga parbat haramosh massif of the western himalaya has undergone a complex metamorphic and denudational history over the past 1 8 ga metamorphism in the tato region is characterized by a barrovian type metamorphism followed by partial melting and recrystallization along shear zones during nearly isothermal decompression while the massif was still at temperatures 550 c mineralogical and textural evidence for this path includes garnet zoning patterns late stage migmatization abundant cordierite both in schists and leucogranite dikes replacement of high pressure assemblages by low pressure assemblages and abundant low density inclusions thermobarometry on the nonmigmatized gneisses reveals conditions of 540 740 c at 7 1 13 1 kbar thermobarometry in the migmat ized rocks reveals final equilibration at 608 675 c at 3 9 6 8 kbar early fluid inclusions occur in quartz inclusions within garnet porphyroblasts that grew during decompression the last fluid inclusions to be trapped occur in microfrac

accuracy assessment of lidar derived dems of bedrock river channels holtwood gorge susquehanna river 1 we evaluate the accuracy of 1 m lidar derived dems of an exposed bedrock channel and use these high resolution terrain models to calculate erosional fluxes between four levels of strath terraces dated previously with 10be recent investigations into the timing rates and processes by which rivers incise their bedrock channels have greatly enhanced our understanding of landscape evolution however measuring channel geometries in 3 dimensions is difficult thus volumes of bedrock eroded during incision events are rarely considered although our analysis successfully demonstrates the proportionality between incision rates and erosional fluxes for terraces high above the channel floor in this gorge unusually high river flows on the date of acquisition inundated lower bedrock surfaces preventing accurate volume estimates to ensure optimal low flow lidar coverage for fluvial environments we discuss methods to improve the scheduling of data acquisition by using archived discharge records and predictive models based on real time data

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

late quaternary stream incision and uplift in the forearc of the cascadia subduction zone western oregon documentation of a latest pleistocene earliest holocene episode of strath formation and fluvial aggradation in the oregon coast range provides a datum from which long term bedrock stream incision rates are determined variations in long term incision rates probably reflect cumulative differential uplift in the forearc of the cascadia subduction zone although factors such as bedrock and climatic controls and isostatic adjustments to erosion obscure the precise relationship between surface uplift and stream incision patterns of differential incision are most striking near the latitude of newport where a steep gradient divides a region of higher rates 0 6 0 9 mm yr in the northern coast range from a region of lower rates 0 1 0 3 mm yr in the central coast range the steep incision gradient is nearly coincident with abrupt changes in marine terrace 80 125 kyr uplift rates the locations of quaternary faults and the southern flank of a saddle of low historic 40 70 years uplift the exact causes of these variable patterns of incision uplift are unknown analogies with uplift patterns in other subduction zones and comparisons with other neotectonic data in the region indicate that patterns of differential incision probably are caused by variations in permanent strain accumulation along the cascadia subduction zone such variations may be related to differences in seismic moment release during individual earthquakes to changes in plate geometry or rates of wedge accretion to segmentation of earthquake ruptures and or to deformation on active structures in the north american plate and accretionary wedge

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