sub aerial denudation of passive margins regional elevation versus local relief models abstract variations in denudation rates which are an important factor in the modification of the sub aerial topography of passive margins have frequently been modelled as being proportionate to regional elevation to be valid this assumption requires that mean slope gradient and the related property of local relief show a strong positive relationship to regional elevation since slope angle is a primary determinant of denudation rate analysis of the relationships between these variables based on the 1 250 000 scale topographic map coverage of southern africa demonstrates that regional modal elevation explains only 0 5 of the variance in mean sine slope gradient and only 0 14 of the variance in local relief measured over 15 15 areas these results demonstrate that regional elevation cannot be used to predict denudation rates for passive margins such as those of southern africa where a dissected coastal zone is separated from a high interior plateau by a major escarpment on the basis of a previous regression analysis relating local relief to sediment and solute transport by rivers the data for southern africa indicate denudation rates of 80 m ma 1 over much of the coastal zone and 1 across most of the elevated interior extrapolation of these results over geological time however necessitates either assumptions about the local relief of palaeotopography or independent evidence of long term denudation rates

late quaternary river incision rates and rock uplift pattern of the eastern qilian shan mountain china abstract the uplift rate and pattern of the qilian shan mountain which lies in the northeast margin of the tibetan plateau are key to understanding the dynamics of crustal deformation in the northeastern tibetan plateau in this work late quaternary terraces in seven river valley sections in the eastern qilian shan mountain are studied to determine terrace abandonment ages by osl optical simulating luminescence and terrace heights by gps global positioning system surveys river incision rates since 76 ka bp are calculated ranging from 0 37 mm a to 1 49 mm a distribution of river incision rates shows that higher river incision rates 0 85 1 49 mm a are located at the rivers upstream reaches where mean mountain elevation is 4000 m and relatively lower incision rates 0 32 0 62 mm a are located at the mountain front where the mean mountain elevation is

the spatial distribution of precipitation and topography in the qilian shan mountains northeastern tibetan plateau abstract the mutual interrelation of orographic precipitation pattern and topography is key to understanding the competing role of tectonics and climate in landscape evolution however the relationship between precipitation and topography across arid to semiarid orogens has received little attention because of limited data availability as a global successor to tropical rainfall measuring mission trmm the global precipitation measurement gpm extends precipitation measurements to mid and high latitudes since 2014 in this study we process one year of gpm precipitation with a spatial resolution of 0 1 0 1 across the arid to semiarid qilian shan mountains to examine the spatial correlation between topography and precipitation though short this data set provides reasonable precipitation when compared with other weather station relevant estimates we then use nine orogen perpendicular swath profiles to examine the influence of topography on precipitation distribution through the range the results show that precipitation variation displays a significant elevation control with precipitation peaks in the high elevation mountain interior we further compare the gpm precipitation with elevation and local relief within each swath extent the results show that precipitation uniformly increases with increasing elevation for nine swaths which is consistent with the elevation controlled precipitation pattern we find precipitation and local relief are positively correlated for five swaths but not for the remaining four swaths based on published data for uplift and erosion we suggest that the presence or absence of such a correlation indicates whether mountains are in topographic steady state or in a transient state of relief production

observed tidal currents outside block island sound offshore decay and effects of estuarine outflow 1 an array of moored profiling current meters on the inner continental shelf 15 65 m deep is used to investigate tidal currents outside the block island sound and long island sound estuarine system the m2 constituent dominates due to near resonant semi diurnal estuarine response vertical mean m2 currents rotate clockwise in time in ellipses elongated toward the estuary mouth with little sensitivity to complex local bathymetry semi major axes decay sharply offshore 55 to 20 cm s over 10 km in agreement with the nearly inverse square radius dependence of a kinematic theory estimated tidal volume exchange out of block island sound to the south is 2 9 105 m3 s observed vertical structure of m2 ellipses in the deepest 10 20 m amplitude decay ellipse flattening major axis turning clockwise phase advance is generally captured well by optimally fit frictional solutions despite the fact that they omit bathymetry and include stratification only indirectly through its influence on eddy viscosity in the upper water column vertical structure varies seasonally mid depth ellipses enlarge in spring near surface ellipses are larger smaller than optimal fit solutions in fall winter spring observed seasonal average estuarine outflow includes surface intensified coriolis deflected mean flow that strengthens and spreads farther offshore in spring richardson numbers based on moored hydrographic profiler records suggest spring stratification suppresses deep eddy viscosities which in frictional solutions can explain mid depth ellipse enlargement an inviscid theory for mean flow modifications due to ambient vorticity of estuarine outflow currents is shown to be the most plausible explanation for observed seasonal changes in near surface tidal ellipses

geomorphic evidence for northeastward expansion of the eastern qilian shan northeastern tibetan plateau abstract the eastern qilian shan is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located within the transition zone between the mainland tibetan plateau and the alax block active deformation affecting the topography in this region can be quantified based on geomorphic indices therefore we applied the geomorphic indices hypsometry and stream power incision model to evaluate the tectonic deformation pattern of the eastern qilian shan hypsometric curves and s a plots of the selected seven rivers were determined hi values of every single sub basins were also calculated the results show that the local topographic evolution of the eastern qilian shan is in pre steady state and will soon reach its equilibrium state according to the analysis of regional climate condition e g rainfall and glaciers distribution and fault characteristics it is suggested that abundant glacial snowmelt water sustains fluvial incision and tectonic deformation from sustained northeastward expansion of the tibetan plateau is the main reason for the landscape growth combining the research of the deep electric structure beneath the gulang boundary zone we claimed that the eastern qilian shan even the northeastern tibet has been growing and expanding northeastward since the middle miocene and its leading edge now is the hexibao sidaoshan fault on the premise of synthetically considering the western and middle parts of the qilian shan it is suggested that the hexibao sidaoshan fault area will rise into a mountain in 1 2 ma

climatic control on rapid exhumation along the southern himalayan front abstract along the southern himalayan front shf areas with concentrated precipitation coincide with rapid exhumation as indicated by young mineral cooling ages twenty new young 80 of the annual precipitation aft cooling ages reveal a coincidence between rapid erosion and exhumation that is focused in a 50 70 km wide sector of the himalaya rather than encompassing the entire orogen assuming simplified constant exhumation rates the rocks of two age vs elevation transects were exhumed at 1 4 0 2 and 1 1 0 4 mm a with an average cooling rate of 40 50 c ma during pliocene quarternary time following other recently published hypotheses regarding the relation between tectonics and climate in the himalaya we suggest that this concentrated loss of material was accommodated by motion along a back stepping thrust to the south and a normal fault zone to the north as part of an extruding wedge climatically controlled erosional processes focus on this wedge and suggest that climatically controlled surface processes determine tectonic deformation in the internal part of the himalaya

climate tectonics and the morphology of the andes large scale topographic analyses show that hemisphere scale climate variations are a first order control on the morphology of the andes zonal atmospheric circulation in the southern hemisphere creates strong latitudinal precipitation gradients that when incorporated in a generalized index of erosion intensity predict strong gradients in erosion rates both along and across the andes cross range asymmetry width hypsometry and maximum elevation reflect gradients in both the erosion index and the relative dominance of fluvial glacial and tectonic processes and show that major morphologic features correlate with climatic regimes latitudinal gradients in inferred crustal thickening and structural shortening correspond to variations in predicted erosion potential indicating that like tectonics nonuniform erosion due to large scale climate patterns is a first order control on the topographic evolution of the andes

late cenozoic relief evolution under evolving climate a review abstract the present review paper is an attempt to summarize quantitative evidence of late cenozoic changes in topographic relief different meanings of the word relief as it is commonly used and detail the metrics used to quantify it we then specify methodological tools used to quantify relief change primarily low temperature thermochronometry and terrestrial cosmogenic nuclides and analyze published evidence for different regions our review first shows that relief changes and rates of changes are more important at mid than high or low latitudes and appear to be insensitive to mean precipitation rates it also show that relief change is positive relief increases in most of the reported cases 80 we subsequently define two functional relationships between relief and erosion depending on the chosen definition of relief and propose a conceptual model of landscape memory we conclude following others that erosion rates depend non linearly on relief evolution itself being a function of the spatial distribution and rates of erosion the relief increases documented in this review may be to erosion rate increases during the same timescales lastly we discuss the importance of glacial and periglacial processes on late cenozoic relief and erosion rate changes and stress the importance of frost shattering and glacial erosion at mid and high latitudes

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

using slope area and apatite fission track analysis to decipher the rock uplift pattern of the yumu shan new insights into the growth of the ne tibetan plateau abstract studies have shown that the growth of the qilian shan the northeastern margin of the tibetan plateau started 10 ma ago however when and how it expanded northwards is still under debate here we focus on the rock uplift pattern of the yumu shan an active fault related fold in the hexi corridor north to the qilian shan normalized channel steepness achieved from the analysis of river longitudinal profiles shows a spatially variant rock uplift pattern with higher rates in the middle part and lower rates towards the west and east tips the compression of the mountain is typically accommodated by fault fold related shortening and vertical thickening apatite fission track thermochronology reveals that the growth of the yumu shan started 4 ma ago similar to the work on active tectonics combining the onset ages of the growth of the qilian shan 10 ma laojunmiao anticline 3 4 ma baiyanghe anticline 3 4 ma wenshu shan 4 5 ma and heli shan 2 ma we draw an conclusion that the ne margin of the tibetan plateau initiated growth in the mid miocene and expanded to the hexi corridor and to the south of the alxa block in the early pleistocene

unmixed loess grain size populations along the northern qilian shan china relationships between geomorphologic sedimentologic and climatic controls abstract grain size analysis provides a useful tool in reconstructing aeolian transport processes and allows deductions about environmental evolution however the sedimentological mechanisms driving the investigated imprint are often underrepresented in the interpretation of loess sections and may therefore lead to erroneous conclusions we present a study from the north eastern margin of the tibetan plateau qilian shan hexi corridor in which 11 mainly holocene loess sections up to 2 20 m depth and a set of surface samples were analysed for their grain size distribution a three end member mixing model yields grain size populations with modes of 63 m 33 m and 9 m respectively representing the major contributing transport processes from different sources these processes were identified in short term suspension and saltation from fluvial storages low level suspension driven by dust storms and high level suspension from distant sources sedimentology supply availability site specific geomorphology distance to potential sources and climate conditions such as effective moisture controlling dust trapping vegetation covers set up a complex system loess deposition and preservation depend on these steering factors large sediment supply from the last glacial cycle became available for deflation during early holocene moisture optimum this phase is represented by a high contribution of the coarsest grain size population in the late glacial early holocene loess record when climate amelioration allowed the establishment of a dust trapping vegetation cover comparable to mis 3 conditions the mid holocene loess deposits formed under more stable landscape conditions represented by much lower contributions from local sources accordingly relative contribution of far travelled dust was at its climax during the mid holocene the late holocene exhibits a relative increase in dust storm contribution which is in accordance to increasingly drier climatic conditions hence this study suggests a thorough consideration of the different system components when interpreting grain size records obtained from loess deposits

constraints on water reservoir lifetimes from catchment wide 10be erosion rates a case study from western turkey the functionality and retention capacity of water reservoirs is generally impaired by upstream erosion and reservoir sedimentation making a reliable assessment of erosion indispensable to estimate reservoir lifetimes widely used river gauging methods may underestimate sediment yield because they do not record rare high magnitude events and may underestimate bedload transport hence reservoir lifetimes calculated from short term erosion rates should be regarded as maximum values we propose that erosion rates from cosmogenic 10be which commonly integrate over hundreds to thousands of years are useful to complement short term sediment yield estimates and should be employed to estimate minimum reservoir lifetimes here we present 10be erosion rates for the drainage basins of six water reservoirs in western turkey which are located in a tectonically active region with easily erodible bedrock our 10be erosion rates for these catchments are high ranging from 170 to 1040 t km2 yr when linked to reservoir volumes they yield minimum reservoir lifetimes between 25 5 and 1650 360 years until complete filling with four reservoirs having minimum lifespans of 110 years in a neighboring region with more resistant bedrock and less tectonic activity we obtain much lower catchment wide 10be erosion rates of 33 to 95 t km2 yr illustrating that differences in lithology and tectonic boundary conditions can cause substantial variations in erosion even at a spatial scale of only 50 km in conclusion we suggest that both short term sediment yield estimates and 10be erosion rates should be employed to predict the lifetimes of reservoirs

paleoclimatic record from the clay mineralogy of quaternary sediments of drill core dwj from jiudong subbasin western hexi corridor nw china the thick sedimentary deposits of the jiudong subbasin in the western hexi corridor of nw china can potentially provide important records of climate change in arid and semiarid areas subject to the interaction of the east asian summer monsoon easm and the westerlies here we present the results of a study of the clay mineralogy of the sediments of drill core dwj from the jiudong subbasin the clay minerals consist mainly of illite followed by chlorite kaolinite and smectite the clay mineral assemblages are used to define four paleoclimatic stages since 1 8 ma 1 during 1 8 1 2 ma the climate was relatively cold and arid 2 during 1 2 0 9 ma it was relatively warm and wet with strongly seasonal precipitation 3 during 0 9 0 3 ma there was a long term trend of cooling and drying and 4 during 0 3 0 1 ma the climate was warmer and wetter than during the previous period with strongly seasonal precipitation the paleoclimatic record of the jiudong subbasin since 1 8 ma is consistent with records from the tengger desert and typical monsoonal areas this suggests that the easm penetrated into the central regions of the north qilian shan and zhangye jiudong subbasin during 1 2 0 9 and 0 3 0 1 ma

coastal countercurrent and mesoscale eddy formation by tidal rectification near an oceanic cape abstract cape st james is an extensive triangular shaped promontory located in a tidally energetic region at the southern tip of the queen charlotte islands approximately 150 km off the mainland coast or british columbia several years of oceanographic data collected in vicinity of the cape reveal a regional circulation characterized by a strong 0 50 m s 1 coastal current along the western continental margin and respective clockwise and counterclockwise rotating mesoscale baroclinic eddies to the west and south of the cape the coastal current flows counter to the prevailing winds while the anticyclonic eddy to the west of the cape is a particularly intense feature that appears consistently in avhrr imagery of the region the structure of the mean flow combined with the marked o 0 1 0 m s 1 low frequency current variability at fortnightly and monthly tidal periods plus significant coherence at fortnightly periods between low frequency currents and demodulated tidal flow suggests that rectification o

the distribution of active rock uplift in the interior of the western qilian shan ne tibetan plateau inference from bedrock channel profiles abstract the distribution of rock uplift rates in the interior of the western qilian shan is not yet fully resolved which limits our knowledge about the uplift pattern and landscape evolution in the northeastern tibetan plateau the stream power incision model suggests that the spatially differential rock uplift rate usually can exert a primary control on channel gradient thus providing a powerful approach to map the rock uplift pattern of active orogens here we analysed the river longitudinal profiles in the western qilian shan and found a spatially differential pattern with higher steepness indices along the parallel ranges e g the danghe nanshan daxue shan tuolai shan and the northern qilian shan but lower values in the intramontane basins comparison of steepness indices to variations in lithology and annual precipitation revealed limited correlation of channel gradient with lithologic resistance and climate in this landscape we also observed no systematic relationship between steepness indices with drainage area sediment flux or channel concavities we argued that the systematic changes in channel steepness indices are tectonically controlled rather than the consequence of variable sediment flux climate or lithology thus the normalized channel steepness pattern of the western qilian shan could reflect that the rock uplift is largely restricted to mountain ranges bounded by active thrust faults and imply distributed cenozoic crustal shortening by comparing the nne ssw directed elevation swath profiles and the channel steepness pattern we concluded that tectonic uplift rate should be higher in the northern qilian shan than in the internal ranges thus our study provides geomorphic evidence to favor both distributed crustal shortening and asian mantle lithosphere underthrusting as the primary mechanisms to explain the landscape evolution in the ne tibetan plateau

controls on decadal erosion rates in qilian shan re evaluation and new insights into landscape evolution in north east tibet abstract available data from the qilian shan in north east tibet suggested that decadal scale erosion rates were closely correlated with local topographic gradient but not with climatic factors however a climatic change to more arid condition was proposed to explain the discrepancy between short term and long term erosion rates in order to re evaluate the topographic tectonic and climatic influences on erosion we adopted five parameters slope mean local relief historical cumulative seismic moment runoff coefficient of variation and fault density to study 11 drainage basins in north east tibet our results showed that terrain gradient rock fracture density and rainstorm intensity had strong influence on erosion rates while 60 year cumulative seismic moments of historical earthquakes showed weaker correlations there was a spatial variation in the erosional mechanisms across the basin with detachment limited dominance around the ridges slope 20 and deposition dominant in the flat areas the variation may lead to the discrepancy between short term and long term erosion rates in general our study supports the bath tub model for low relief intermountain basins hence providing new insights into the landscape evolution of the qilian shan in northeastern tibetan plateau

late pleistocene holocene slip rate of the zhangye thrust qilian shan china and implications for the active growth of the northeastern tibetan plateau 1 we derive a slip rate for a thrust at the central qilian shan mountain front by combining structural investigations satellite imagery topographic profiling luminescence dating and 10be exposure dating the seismically active zhangye thrust transects late pleistocene alluvial fan deposits and forms a prominent north facing scarp the fault consists of two segments that differ in orientation scarp height and age a series of loess covered terraces records the uplift history of the western thrust segment loess accumulation on all terraces started at 8 5 1 5 kyr and postdates terrace formation gravels from the highest terrace yielded a 10be exposure age of 90 11 kyr which dates the onset of faulting with a displacement of 55 60 m derived from fault scarp profiles this yields a vertical slip rate of 0 64 0 08 mm yr 1 along the eastern thrust segment three 10be ages from the uplifted alluvial fan constrain that faulting started at 31 5 kyr together with a displacement of 25 30 m this leads to a vertical faulting rate of 0 88 0 16 mm yr 1 a dip estimate of 40 to 60 for the fault plane combined with lower and upper limits of 0 6 and 0 9 mm yr 1 for the vertical slip rate gives minimum and maximum horizontal shortening rates of 0 4 and 1 1 mm yr 1 across the zhangye thrust our results are consistent with geologic and gps constraints which suggest that nne directed shortening across the northeastern tibetan plateau is distributed on several active faults with a total shortening rate of 4 to 10 mm yr 1

geomorphic controls on andean denudation rates abstract to predict erosion rates throughout the andes we conducted a multiple regression analysis of the sediment discharge from 47 drainage basins in the bolivian andes and various topographic climatologic and geologic parameters these mountainous basins are typically large 17 81 000 km2 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm mean 11 000 end document km2 often have decades of measurement data on daily water and sediment discharge and display an extraordinary range of denudation 0 01 6 9 mm yr

higher erosion rates in the himalaya geochemical constraints on riverine fluxes the modern erosion rate of continental scale mountains is difficult to estimate and is usually based on measurement of the suspended load flux of rivers combined with assumptions about river bedload transport and sedimentation in flood plains these two parameters are very difficult to measure directly in continental scale basins in this paper we examine the chemical composition of the suspended load bedload and dissolved load of the ganga and brahmaputra rivers and compare them with the average composition of himalayan source rocks a mass balance equation of erosion fluxes shows that a si rich component is needed in addition to suspended and dissolved load fluxes to account for the composition of the source rock it corresponds to bedload sediment and flood plain deposits which are enriched in quartz by mineral sorting during transport the combined budget of si al and fe in the river system allows us to estimate this si rich flux by this method the total himalayan erosion is estimated to be twice the measured flux of suspended load the comparison between the brahmaputra and the ganga shows that the eastern himalaya has a higher erosion rate 2 9 mm yr than the western himalaya 2 1 mm yr this is likely the result of the higher runoff in the brahmaputra basin the intensity of the monsoon acts as a first order control of the erosion rate in the range

miocene cooling in the northern qilian shan northeastern margin of the tibetan plateau revealed by apatite fission track and vitrinite reflectance analysis apatite fission track and vitrinite reflectance data from phanerozoic rocks of the northern qilian shan and jiuxi basin at the northeastern margin of the tibetan plateau show a complex thermal history with multiple paleothermal events peak paleotemperatures reached in the middle cretaceous suggest that hydrocarbon generation occurred in the basin at that time paleozoic mesozoic samples show evidence of a middle tertiary cooling episode between 20 and 10 ma this thermal fingerprint is significant because stratigraphic evidence for miocene exhumation is overwhelmed by spectacular pliocene pleistocene deformation and erosion we interpret the miocene cooling as recording initial exhumation of the northern qilian shan earlier than other models have proposed i e after 6 5 ma miocene cooling is broadly coincident with cenozoic uplift and exhumation recorded elsewhere in the tibetan tarim region

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

temporal variations in supraglacial debris distribution on baltoro glacier karakoram between 2001 and 2012 distribution of supraglacial debris in a glacier system varies spatially and temporally due to differing rates of debris input transport and deposition supraglacial debris distribution governs the thickness of a supraglacial debris layer an important control on the amount of ablation that occurs under such a debris layer characterising supraglacial debris layer thickness on a glacier is therefore key to calculating ablation across a glacier surface the spatial pattern of debris thickness on baltoro glacier has previously been calculated for one discrete point in time 2004 using satellite thermal data and an empirically based relationship between supraglacial debris layer thickness and debris surface temperature identified in the field here the same empirically based relationship was applied to two further datasets 2001 2012 to calculate debris layer thickness across baltoro glacier for three discrete points over an 11 year period 2001 2004 2012 surface velocity and sediment flux were also calculated as well as debris thickness change between periods using these outputs alongside geomorphological maps of baltoro glacier produced for 2001 2004 and 2012 spatiotemporal changes in debris distribution for a sub decadal timescale were investigated sediment flux remained constant throughout the 11 year period the greatest changes in debris thickness occurred along medial moraines the locations of mass movement deposition and areas of interaction between tributary glaciers and the main glacier tongue the study confirms the occurrence of spatiotemporal changes in supraglacial debris layer thickness on sub decadal timescales independent of variation in surface velocity instead variation in rates of debris distribution are primarily attributed to frequency and magnitude of mass movement events over decadal timescales with climate regional uplift and erosion rates expected to control debris inputs over centurial to millennial timescales inclusion of such spatiotemporal variations in debris thickness in distributed surface energy balance models would increase the accuracy of calculated ablation leading to a more accurate simulation of glacier mass balance through time and greater precision in quantification of the response of debris covered glaciers to climatic change

geomorphic and tectonic process rates effects of measured time interval analysis of the original numerical components of diverse geomorphic and tectonic process rates indicates that process rate is not independent of measured time interval this implies that direct comparison of geologic process rates measured over variable time intervals may not be valid and that conclusions based on those comparisons regarding changes in rates through geologic time may be misleading in some cases calculation of statistically derived scaling functions is one approach that can be used to account for this measurement interval bias and to improve comparisons of geologic process rate data when this approach is used a 10 4 or 10 5 yr variation in the measured time interval accounts for approximately one order of magnitude change in the measured process rate the magnitude of the correction can substantially affect conclusions of studies that compare uncorrected process rates calculated from variable time intervals

spring summer frontogenesis at the mouth of block island sound 2 combining acoustic doppler current profiler records with a general circulation model to investigate the impact of subtidal forcing 1 the use of a one layer inverse model to improve the fidelity of a three dimensional primitive equation model is explored in the region just south of block island sound in the middle atlantic bight the inverse model based on the theory of bennett and mcintosh produces a solution to the linear shallow water equations that minimizes model data misfit and the resulting open boundary velocity variance the massachusetts institute of technology general circulation model is configured regionally and includes realistic tidal forcing surface warming and wind stress as well as climatological buoyancy gradients between the estuary and the shelf a 15 day record from two acoustic doppler current profiler moorings deployed in spring 2000 south of the entrance of block island sound allows assessment of the forward model and provides data to improve subtidal boundary conditions model data misfit decreases notably for both the depth averaged and vertically sheared flow indicating that improvements to the depth averaged circulation positively impact the three dimensional circulation in this shallow shelf environment the role of wind stress in modulating the position of the buoyant plume that characterizes the regional hydrography is also examined a distinctly three dimensional circulation is observed with a growing offshore plume at the mouth of the sound during northward stress followed by rapid alongshelf advection during periods of southwestward or weak winds although on the timescales considered here wind stress forcing dominates the buoyancy driven motion it is overwhelmed by the tidally driven rectified flow just south of montauk point which provides the inshore boundary of the front even in downwelling favorable conditions

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

active faulting mountain growth and erosion at the margins of the tibetan plateau constrained by in situ produced cosmogenic nuclides abstract the india asia collision zone is a key area for understanding continental plateau formation and mountain building two fundamental questions in this context are how the northeastward motion of india is partitioned between strike slip and thrust faults and how mountain building is counteracted by erosion cosmogenic nuclides allow us to address these questions because they provide age constraints on tectonically offset landforms and constraints on erosion rates after considerable debate on whether or not major strike slip faults move at high rates of up to 20 30 mm yr and absorb most of the continental deformation it now appears that the three largest faults altyn tagh haiyuan kunlun have millennial slip rates of no more than 8 13 mm yr consistent with rates of elastic strain accumulation determined by geodetic methods furthermore a significant portion of the lateral slip on these faults is transferred to thrust faults within the collision zone both observations indicate that the eastward tectonic escape of material along these faults is less important than often assumed with respect to mountain building and erosion cosmogenic nuclide studies show that thrust faults at the northeastern and eastern margins of tibet qilian shan longmen shan have vertical slip rates of 0 3 to 2 mm yr while catchment wide erosion rates vary from 0 02 to 1 0 mm yr with high relief areas eroding significantly faster than the plateau interior and growing mountains in the foreland the deeply incised regions have apparently reached an erosional steady state in which rock uplift is balanced by erosion river terraces at active mountain fronts document repeated changes between sediment deposition and fluvial incision during the quaternary incision and terrace formation occurred predominantly at glacial interglacial transitions but also during interglacial periods hence flights of terraces at the fault bounded mountain fronts record the interplay between sustained rock uplift and a temporally variable climate

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

uplift driven climate change at 12 ma a long δ18o record from the ne margin of the tibetan plateau carbonates from fluvial and lacustrine sediments were sampled from multiple measured sections in the linxia basin of western china based on textural and mineralogical evidence lacustrine carbonates are primary precipitates from lake water a 29 million year record of the oxygen isotope composition of meteoric water is inferred from the n 18 o values of these carbonates this inference is based on the most negative n 18 o values in the lake carbonates which represent lake waters that have experienced the least evaporative enrichment carbonate n 18 o values a proxy for rainfall n 18 o are v310 5x throughout the interval of 29 12 ma at 12 ma there is a shift to 39x a value that remains into the pliocene this implies a major reorganization of atmospheric circulation patterns and a shift to more arid conditions at the ne margin of the tibetan plateau with the post 12 ma system similar to that of today the 12 ma event may represent the time at which the tibetan plateau achieves sufficient elevation to block the penetration of moisture from the indian ocean or south pacific into western china the period of greatest aridity is from 9 6 to 8 2 ma a time interval which agrees well with other climate records 2003 elsevier b v all rights reserved

denudation intensity and control in the chinese tian shan new constraints from mass balance on catchment alluvial fan systems tectonics and climate are usually seen as the main controlling factors of denudation rates which seem to rise with the tectonic activity and to decrease when the climate becomes drier however the low denudation rates observed in semi arid to arid contexts are generally measured on orogenic plateaus where the respective influence of the flat relief and the dry climate cannot really be unravelled the chinese tian shan was chosen as a case study in the northern piedmont of this mountain range a series of well preserved quaternary alluvial fans offer the opportunity to perform a mass balance study at the scale of several catchment areas and several hundreds of thousands of years based on a geometrical reconstruction of these fans the volumes of sediments exported out of 10 drainage basins during the middle late pleistocene from 300 to 12 kyr and the holocene from 12 kyr to present have been estimated from these volumes an average denudation rate of 135 m myr was determined in the tian shan range for the last 300 kyr in agreement with other mass balances performed in the same area the typical denudation intensity of the northern tian shan is thus of a few hundred meters per million years at most regardless of the space and time scales considered from a comparison with denudation rates in other mountain ranges throughout the world we suggest that a dry climate can dramatically limit the denudation intensity even in active orogenic systems with a high topographic gradient like the tian shan as a result the time required to reach equilibrium between denudation and rock uplift in these systems could be extremely long i e of more than several million years copyright 2016 john wiley sons ltd

has focused denudation sustained active thrusting at the himalayan topographic front the geomorphic character of major river drainages in the himalayan foothills of central nepal suggests the existence of a discrete west northwest trending break in rock uplift rates that does not correspond to previously mapped faults the 40 ar 39 ar thermochronologic data from detrital muscovites with provenance from both sides of the discontinuity indicate that this geomorphic break also corresponds to a major discontinuity in cooling ages samples to the south are proterozoic to paleozoic whereas those to the north are miocene and younger combined these observations virtually require recent pliocene holocene motion on a thrust sense shear zone in the central nepal himalaya 20 30 km south of the main central thrust field observations are consistent with motion on a broad shear zone subparallel to the fabric of the lesser himalayan lithotectonic sequence the results suggest that motion on thrusts in the toe of the himalayan wedge may be synchronous with deeper exhumation on more hinterland structures in central nepal we speculate that this continued exhumation in the hinterland may be related to intense sustained erosion driven by focused orographic precipitation at the foot of the high himalaya

controls on spatial variations of glacial erosion in the qilian shan northeastern tibetan plateau abstract understanding interactions between topography and glacial erosion is a key to advancing knowledge of mountain landscape evolution and is often hampered by the lack of quantitative data for glacial erosion here we examine spatial variations in glacial erosion in the qilian shan using a power law model y axb fit to cross profiles of glacial valleys we further analyze the impacts of glacial dynamics topography and lithology on the degree of glacial erosion using qualitative and quantitative methods although the distribution of glacial erosion is controlled by the combined effects of glacial dynamics topography and lithology average glacier size or ice flux and mean slope above the equilibrium line altitude are dominant controls in addition the topographic data analyzed through a b fr diagram suggests two opposite types of glacial valley cross profile development temperate maritime glacier valleys are mainly dominated by overdeepening while continental glacier valleys are mainly dominated by a widening process although this varies with lithology

transient eddy formation around headlands eddies with length scales of 1 10 km are commonly observed in coastal waters and play an important role in the dispersion of water borne materials the generation and evolution of these eddies by oscillatory tidal flow around coastal headlands is investigated with analytical and numerical models using shallow water depth averaged vorticity dynamics eddies are shown to form when flow separation occurs near the tip of the headland causing intense vorticity generated along the headland to be injected into the interior an analytic boundary layer model demonstrates that flow separation occurs when the pressure gradient along the boundary switches from favoring accelerating to adverse decelerating and its occurrence depends principally on three parameters the aspect ratio b a where b and a are characteristic width and length scales of the headland h cda where h is the water depth cd is the depth averaged drag coefficient and uo a where uo and are the magnitude and frequency of the far field tidal flow simulations with a depth averaged numerical model show a wide range of responses to changes in these parameters including cases where no separation occurs cases where only one eddy exists at a given time and cases where bottom friction is weak enough that eddies produced during successive tidal cycles coexist interacting strongly with each other these simulations also demonstrate that in unsteady flow a strong start up vortex forms after the flow separates leading to a much more intense patch of vorticity and stronger recirculation than found in steady flow

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

dating of erosion surface and terraces in the eastern qilian shan northwest china the actively deformed foreland of eastern qilian shan mountains contains well preserved geomorphic features such as erosion surfaces river terraces and tectonically uplifted alluvial fans providing suitable archives for research on regional tectonic activities and palaeoclimatic changes these geomorphic surfaces are well dated by using a combination of magnetostratigraphy electron spin resonance thermoluminescence infra red stimulated luminescence radiocarbon dating and correlation with the well established loess palaeosol sequences of china our results show that the erosion surface formed about 1 4 ma ago and the age of river terraces is 1 24 ma 820 860 ka 780 ka 420 440 ka 230 250 ka 140 ka 60 ka and 10 ka respectively valley incision rates of e 0 09 0 25 m ka 1 have been identified the repetitive stratigraphic and geomorphic pattern of these terraces indicates the fluvial sedimentation incision cycles are tightly associated with the 100 ka glacial interglacial climatic cycles copyright c 2006 john wiley sons ltd

themis high resolution digital terrain topographic and thermophysical mapping of gusev crater mars 1 we discuss a new technique to generate high resolution digital terrain models dtms and to quantitatively derive and map slope corrected thermophysical properties such as albedo thermal inertia and surface temperatures this investigation is a continuation of work started by kirk et al 2005 who empirically deconvolved thermal emission imaging system themis visible and thermal infrared data of this area isolating topographic information that produced an accurate dtm surface temperatures change as a function of many variables such as slope albedo thermal inertia time season and atmospheric opacity we constrain each of these variables to construct a dtm and maps of slope corrected albedo slope and albedo corrected thermal inertia and surface temperatures across the scene for any time of day or year and at any atmospheric opacity dtms greatly facilitate analyses of the martian surface and the mola global data set is not finely scaled enough 128 pixels per degree 0 5 km per pixel near the equator to be combined with newer data sets e g high resolution imaging science experiment context camera and compact reconnaissance imaging spectrometer for mars at 0 25 6 and 20 m per pixel respectively so new techniques to derive high resolution dtms are always being explored this paper discusses our technique of combining a set of themis visible and thermal infrared observations such that albedo and thermal inertia variations within the scene are eliminated and only topographic variations remain this enables us to produce a high resolution dtm via photoclinometry techniques that are largely free of albedo induced errors with this dtm themis observations and a subsurface thermal diffusion model we generate slope corrected maps of albedo thermal inertia and surface temperatures in addition to greater accuracy these products allow thermophysical properties to be directly compared with topography

the influence of slope angle on final infiltration rate for interrill conditions abstract despite numerous studies the relationship between slope angle and infiltration rate remains unclear under different experimental conditions new processes may be introduced which influence the relationship the presence of rills for example may significantly affect the relationship between slope angle and infiltration rate so distinct relationships may exist for rill and interrill areas the objective of this study was to investigate the influence of slope angle on infiltration rate for an interrill area with a surface crust the experiment was carried out in a laboratory using simulated rainfall and soil trays designed to limit the processes to those found in interrill areas slope angles ranged from 1 5 to 21 5 infiltration was calculated from the overland flow rate and microtensiometers and micromorphological analysis were used to characterise the seals infiltration rate decreased with increasing slope angle image analysis of pore characteristics in the affected layer and subseal pressure head measurements indicated there were no differences in seal characteristics between slope angles the results showed that sealing intensity did not vary with slope angle and the dominant influence of slope angle on infiltration rate resulted from changes in overland flow depth and surface storage the results also suggest that small changes in seal hydraulic conductivity with microrelief play an important role in the infiltration process

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

tidal modulation of estuarine plumes abstract off an estuary mouth the nonlinear transfer of vorticity from the oscillating onshore offshore tidal currents to the mean field generates a pair of counter rotating eddies that flows seaward near the center axis of the inlet and landward on both sides the coriolis deflection strengthens the anticyclonic eddy but weakens the cyclonic one a seaward sloping shelf enhances these eddies but a seaward sloping estuary weakens them these tidal residual eddies strengthen and hasten the expansion of a river forced plume off an estuary mouth but weaken and retard the development of the coastal jet farther downcoast to lowest order this is the primary effect of tides on an estuarine plume in a coupled estuary shelf system tidal effects on the subtidal river forced circulation inside the estuary are secondary

low slip rates and long term preservation of geomorphic features in central asia in order to understand the dynamics of the india asia collision zone it is important to know the strain distribution in central asia whose determination relies on the slip rates for active faults1 2 3 4 5 many previous slip rate estimates of faults in central asia were based on the assumption that offset landforms are younger than the last glacial maximum 20 kyr ago 6 7 8 9 10 11 in contrast here we present surface exposure ages of 40 to 170 kyr obtained using cosmogenic nuclide dating for a series of terraces near a thrust at the northern margin of the tibetan plateau combined with the tectonic offset the ages imply a long term slip rate of only about 0 35 mm yr 1 for the active thrust an order of magnitude lower than rates obtained from the assumption that the terraces formed after the last glacial maximum our data demonstrate that the preservation potential of geomorphic features in central asia is higher than commonly assumed

decoupling of erosion and precipitation in the himalayas the hypothesis that abrupt spatial gradients in erosion can cause high strain rates in active orogens has been supported by numerical models that couple erosional processes with lithospheric deformation via gravitational feedbacks1 2 3 most such models invoke a stream power rule in which either increased discharge or steeper channel slopes cause higher erosion rates spatial variations in precipitation and slopes are therefore predicted to correlate with gradients in both erosion rates and crustal strain here we combine observations from a meteorological network across the greater himalaya nepal along with estimates of erosion rates at geologic timescales greater than 100 000 yr from low temperature thermochronometry across a zone of about 20 km length spanning the himalayan crest and encompassing a more than fivefold difference in monsoon precipitation significant spatial variations in geologic erosion rates are not detectable decreased rainfall is not balanced by steeper channels instead additional factors that influence river incision rates such as channel width and sediment concentrations must compensate for decreasing precipitation overall spatially constant erosion is a response to uniform upward tectonic transport of greater himalayan rock above a crustal ramp

modern erosion rates in the high himalayas of nepal abstract current theories regarding the connections and feedbacks between surface and tectonic processes are predicated on the assumption that higher rainfall causes more rapid erosion to test this assumption in a tectonically active landscape a network of 10 river monitoring stations was established in the high himalayas of central nepal across a steep rainfall gradient suspended sediment flux was calculated from sampled suspended sediment concentrations and discharge rating curves accounting for solute and bedload contributions the suspended sediment fluxes were used to calculate watershed scale erosion rates that were then compared to monsoon precipitation and specific discharge we find that in individual watersheds annual erosion rates increase with runoff in addition our data suggest average erosion rate increases with discharge and precipitation across the entire field site such that the wetter southern watersheds are eroding faster than the drier northern watersheds the spatially non uniform contemporary erosion rates documented here are at odds with other studies that have found spatially uniform long term rates 10 5 10 6 yr across the pronounced rainfall gradient observed in the region the discrepancy between the modern rates measured here and the long term rates may be reconciled by considering the high erosional efficiency of glaciers the northern catchments were much more extensively glacierized during the pleistocene and therefore they likely experienced erosion rates that were significantly higher than the modern rates we propose that in the northern watersheds the high rates of erosion during periods of glaciation compensate for the low rates during interglacials to produce a time averaged rate comparable to the landslide dominated southern catchments

tectonic uplift in the northern tibetan plateau since 13 7 ma ago inferred from molasse deposits along the altyn tagh fault abstract in response to the collision of india with asia thick molasse deposits were shed off the high evolving edge of the northern tibetan plateau providing great potential for understanding the relationships between mountain building rock denudation and sediment deposition a precise knowledge of the initial accumulation of the molasse deposits is important for understanding uplift history along the northern margin of tibet field investigations indicate that thick neogene sediments in the piedmont depression zones of the altun mountains are strongly deformed in a fold and thrust system indicating crustal shortening and thickening in the late cenozoic detailed magnetostratigraphic studies of the molasse deposits along the altyn tagh fault show that the accumulation of coarse conglomerate began ca 13 7 ma ago the source material of the deposits changing at the same time together with the remarkable increase in the sedimentation rate after 13 7 ma we attribute the accumulation of the conglomerates to the tectonic uplift along the northern edge of the tibetan plateau a process that continued until at least 9 ma ago

magnetostratigraphy of deep drilling core sg 1 in the western qaidam basin ne tibetan plateau and its tectonic implications abstract the qaidam basin is the largest intermontane basin of the northeastern tibetan plateau and contains a continuous cenozoic sequence of lacustrine sediments a 1000 m deep drilling sg 1 with an average core recovery of 95 was carried out in the depocenter of the chahansilatu playa sub depression in the western qaidam basin aimed to obtain a high resolution record of the paleoenvironmental evolution and the erosion history stepwise alternating field and thermal demagnetization together with rock magnetic results revealed a stable remanent magnetization for most samples carried by magnetite the polarity sequence consisted of 16 normal and 15 reverse zones which can be correlated with chrons 1n to 2an of the global geomagnetic polarity time scale magnetostratigraphic results date the entire core sg 1 at 2 77 ma to 0 1 ma and yielded sediment accumulation rate sar ranging from 26 1 cm ka to 51 5 cm ka maximum sars occurred within the intervals of 2 6 2 2 ma and after 0 8 ma indicating two episodes of erosion which we relate to pulse tectonic uplift of the ne tibetan plateau with subsequent global cooling

seasonal variation of a coastal jet in the long island sound outflow region based on hf radar and doppler current observations 1 surface current hf radar and velocity profile observations obtained as part of the front resolving observational network with telemetry front project over an approximately 2 year period are used to describe the seasonal variability of a coastal jet in the long island sound outflow region the jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter the current jet is coincident with a band of high summer frontal probability and apparently arises from the interaction between long island sound outflow and larger scale alongshore currents on the shelf the jet reaches peak strength in summer transport of 0 07 sv and is weak or non existent in winter flow is strongest near the surface and weakens with depth with only moderate seasonal variations in the vertical shear the relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth averaged momentum balance the depth averaged pressure gradient is partitioned into a steric component evaluated from the hydrography and a non steric component that is estimated as the residual of the computed terms in the momentum equation the depth averaged momentum balance is found to be approximately geostrophic in the across shore direction the seasonal variability in the jet arises due to the shifting balance between buoyancy driven flow that is always downshelf but intensifies somewhat in summer and wind driven flow which dominates in winter when wind stress becomes strongly upwelling favorable

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

minimal climatic control on erosion rates in the sierra nevada california climate is widely thought to regulate erosion rates but the relationships among precipitation temperature and erosion rate have remained speculative because long term erosion rates have been difficult to measure we used cosmogenic nuclides to measure long term erosion rates at climatically diverse sites in the sierra nevada california spanning 20 180 cm yr in annual precipitation and 4 15 8c in mean annual temperature average erosion rates vary by only 2 5 fold across these sites and are not correlated with climate indicating that climate only weakly regulates nonglacial erosion rates in mountainous granitic terrain

the topographic controls on the decadal scale erosion rates in qilian shan mountains n w china abstract the relationships between climate topography and erosion are significant in understanding landscape evolution in order to study this relationship in a tectonically active landscape the details of 11 drainage basins were collected from qilian shan mountains decadal scale erosion rates including the mechanical load and solute load contributions are estimated in natural conditions the calculated erosion rates show that the average erosion rate of qilian shan mountains is about 0 08 mm yr while the variation of annual erosion rates within each basin is significant the changes of topography and climate which potentially control erosion rates are also employed in this paper for correlating analyses correlation analyses indicate that erosion rates are more closely correlated with topographic variables such as mean local relief and mean slope than all of the climatic variables and mean local relief and decadal scale erosion rates show a linear relationship in these tectonically active mountains however some topographic variables like basin area and elongation ratio exert limited influence on erosion rates while others such as basin elevation basin relief and basin roughness show poor correlation the results indicate that topographic control like aspects of the local terrain steepness plays the most important role in spatial distribution of decadal scale erosion rates throughout qilian shan mountains under topographic control some climatic variables like discharge and runoff however could account for the significant variation of annual erosion rates in individual basin when comparing erosion rates on different timescales we found that the decadal scale erosion rates are lower than the long term river incision rates as well as the exhumation rates during early and middle miocene the change to more arid climatic condition since the middle miocene combining with tectonic uplift should attribute to the inconsistent erosion rates over different timescales in qilian shan mountains

focused modern denudation of the longmen shan margin eastern tibetan plateau we use river sediment load data to map the pattern of modern denudation across the longmen shan margin of the tibetan plateau suspended sediment load with corrections of bed load and solute load contributions is used to calculate watershed averaged denudation rates decadal erosion is spatially heterogeneous and seasonally modulated by monsoon flows which account for 80 90 of the sediment load enhanced denudation occurs in a 50 km wide band on the hanging wall of the longmen shan and huya fault zones reaching 0 5 0 8 mm yr these rates are similar to kyr scale rates deduced from cosmogenic 10be and to myr scale rates from low temperature thermochronology the sediment flux derived erosion rates decrease with increasing distance plateauward to less than 0 05 mm yr at a distance 200 km northwest of the foot of the longmen shan the gradient in precipitation across this margin alone cannot explain the one order of magnitude spatial difference in erosion rather the river sediment load data delineates a zone of relatively rapid denudation around active faults that carry the longmen shan in their hanging wall from the similarity of denudation rates measured over myr kyr and decadal time scales we propose that erosion of the longmen shan margin has approached a flux steady state the erosional efflux is balanced by advection of rock toward the longmen margin above the 20 nw dipping ramp of the margin bounding fault our results suggest that high amounts of landslide material mobilized by earthquakes such as the mw 7 9 2008 wenchuan event are gradually removed by rivers smoothing sediment flux over time our results also suggest that caution should be exercised when interpreting young cooling ages as evidence of the initiation of plateau uplift advection of an already high plateau into the belt of higher erosion rate at the longmen shan could also give rise to an abrupt cooling history

spring summer frontogenesis at the mouth of block island sound 1 a numerical investigation into tidal and buoyancy forced motion 1 the generation and underlying dynamics of late spring temperature and salinity fronts at the mouth of block island sound in the mid atlantic bight are examined using a three dimensional general circulation model the model is forced by tidal velocities at its outer boundaries an estuary shelf salinity gradient and surface warming runs representing the period from 18 april to 23 may 2000 are investigated through direct examination of the model results and diagnostic calculations that isolate individual processes three mechanisms are identified as significantly contributing to the location and structure fronts observed in this region vertical mixing produces the necessary horizontal temperature structure within and near block island sound but the southern frontal boundary is further affected by the subtidal circulation which is divided into two components defined using a momentum budget analysis tidal currents over the complex bathymetry leads to nonlinearly rectified flows including a headland eddy south of montauk point circumscribing this feature is a baroclinically adjusted buoyant outflow from the long island sound estuary while modifications to the buoyancy forcing can modify the frontal position it necessarily remains offshore of the tidally driven circulation analysis of the salinity anomaly fluxes indicates that both tidal and mean advection are responsible for the overall transport of buoyancy

correlation of himalayan exhumation rates and asian monsoon intensity although most data suggest that the india eurasia continental collision began 45 55 myr ago the architecture of the himalayan tibetan orogen is dominated by deformational structures developed in the neogene period 23 myr ago the stratigraphic record and thermochronometric data indicate that erosion of the himalaya intensified as this constructional phase began and reached a peak around 15 myr ago it remained high until 10 5 myr ago and subsequently slowed gradually to 3 5 myr ago but then began to increase once again in the late pliocene and pleistocene epochs here we present weathering records from the south china sea bay of bengal and arabian sea that permit asian monsoon climate to be reconstructed back to the earliest neogene these indicate a correlation between the rate of himalayan exhumation as inferred from published thermochronometric data and monsoon intensity over the past 23 myr we interpret this correlation as indicating dynamic coupling between neogene climate and both erosion and deformation in the himalaya although the india eurasia collision initiated 50 myr ago major deformation and exhumation of the himalaya did not begin until the early neogene 23 myr ago this coincides with the increased intensity of the asian monsoons as indicated by weathering records from the south china sea bay of bengal and arabian sea and hints at a dynamic coupling between climate and both erosion and deformation in the himalaya

uranium comminution age tested by the eolian deposits on the chinese loess plateau abstract the u 234 238 u ratio of fine particles can record the time since their separation from bed rock because of the disruption of uranium series equilibrium introduced by the recoil of daughter 234 th nuclei precursor of 234 u out of particle surfaces during the decay of 238 u application of the uranium comminution age method which has great potential in tracing production and transportation of sediments is however complicated by the weathering dissolution of u 234 depleted particle surfaces the difficulty in determining the fraction of recoiled nuclei and the precipitation of exogenetic u 234 here we minimize these complications by using a newly developed precise size separation using electroformed sieve and a chemical protocol that involves reductive and oxidative leaching eolian deposits collected from the chinese loess plateau clp were used to test the validity of our method possible effects of weathering dissolution were also evaluated by comparing samples with different weathering intensities the results show decreasing 234 u 238 u ratios in fine eolian particles with increasing sedimentation age agreeing well with the theoretical prediction of the comminution age model this successful application of the uranium comminution age approach to the eolian deposits on the clp is also aided by a stable dust source the low weathering intensity the lack of consolidation and the well defined age model of the deposits a transportation time of 242 18 ka was calculated for the eolian deposits which indicates a long residence time and thus extensive mixing of the dust particles in source regions partly explaining the stable and homogeneous composition of the eolian dust over glacial interglacial cycles

magnetostratigraphy of drill core sg 1b in the western qaidam basin ne tibetan plateau and tectonic implications the qaidam basin is an ideal archive to study long term climate and erosion histories at the ne tibetan plateau we present a magnetostratigraphic study of the 723 m deep drill core sg 1b of lacustrine sediments at the jianshan anticline in the western qaidam basin the polarity sequence shows 18 normal and 19 reverse polarity zones which can be readily correlated with chrons c1n c3br of the geomagnetic polarity time scale 2004 gpts 2004 dating the core at about 7 3 1 6 ma the resulting mean sediment accumulation rate sar between polarity boundaries ranges from 6 5 to 30 4 cm ka 1 high sars occur within the intervals of 7 3 6 0 5 2 4 2 and 3 6 2 6 ma indicating three episodic phases of higher erosion from the derived variation of sars and previous results we conclude that growth strata at the jianshan anticline started to develop at similar to 1 6 ma by limb rotation all this we relate to pulse tectonic uplift of the ne tibetan plateau and fault propagation folding in the qaidam basin

fronts stratification and mixing in long island and block island sounds spatial patterns of bulk stratification in long island and western block island sounds observed near the fall equinox of 1978 show a strong correlation r 0 79 with contours of the h u3 stratification index derived from tidal stream and depth charts the index delineates stratified transitional and mixed regions with apparent good accuracy with the marginally stratified frontal zones being characterized by log10 h u3 1 5 m 2 s3 these results and theoretical considerations suggest that the index may be a useful parameter in corroborating and predicting frontal boundaries in other moderately stratified estuaries where local buoyancy fluxes are derived from fresh water sources

semi automated classification of exposed bedrock cover in british columbia s southern mountains using a random forest approach abstract knowledge of the spatial distribution of exposed bedrock eb is essential for natural resource inventories environmental monitoring and landscape evolution modelling this paper presents a method for the use of a random forest rf classifier and legacy land data to locate areas of eb in a mountainous landscape of southern british columbia canada eb map accuracy increased from 48 to 88 with the use of rf models in comparison to the legacy land cover maps reducing the total number of predictor variables from 43 to 17 had a negligible effect on prediction accuracy meaningful relationships between eb predictions and important predictor variables were observed in partial dependence plots these findings emphasize that substantial improvement in eb map accuracy is possible with a limited number of predictor variables and interpretation of such maps is improved where the relationships between specific predictor variables and predicted classes can be observed and evaluated

downstream variation in stream power abstract stream power has a significant influence on many form and process attributes of the fluvial system using a similar approach to that suggested by d m lawler in 1992 and 1995 a model is developed to explore how stream power might vary in the downstream direction based on the assumption that the longitudinal profile of the river has an exponential form no particular discharge is necessarily specified but near bankfull flows are regarded as significant morphologically and one such discharge is the focus here total stream power per unit channel length qs is predicted to peak at an intermediate location the position of which depends on the ratio b where b and are the downstream rates of change of discharge and slope respectively if b is a relatively conservative quantity then the form of the longitudinal profile and in particular its degree of concavity will have the major influence on the position of maximum stream power specific stream power w is even more sensitive to and is expected to peak closer to the headwaters about half way between source and the location of the stream power maximum although this will depend on how channel width w varies with distance from source the model is tested along three connected streams of different size in the catchment of the river trent taking advantage of a relationship between mean annual flood and link magnitude which enables this near bankfull discharge to be estimated at any point within the network the model is verified in so far as stream power does attain a mid basin maximum but the observed and predicted locations of the maxima do not always correspond largely because of the distinctive variation in discharge and especially slope along individual pathways for example maximum power lies far downstream along the trent because of the large increase in mid basin discharge associated with a series of large closely spaced tributaries the importance of slope is borne out by the near headwater locations for specific power maxima which tend to be further upstream than predicted along all three rivers as a result of the steepness of upper reaches the variety of geomorphic settings produces deviations from expectation which has implications for the movement and storage of material in the fluvial system

evidence for nonlinear diffusive sediment transport on hillslopes and implications for landscape morphology steep soil mantled hillslopes evolve through the downslope movement of soil driven largely by slope dependent transport processes most landscape evolution models represent hillslope transport by linear diffusion in which rates of sediment transport are proportional to slope such that equilibrium hillslopes should have constant curvature between divides and channels on many soil mantled hillslopes however curvature appears to vary systematically such that slopes are typically convex near the divide and become increasingly planar downslope this suggests that linear diffusion is not an adequate model to describe the entire morphology of soil mantled hillslopes here we show that the interaction between local disturbances such as rainsplash and biogenic activity and frictional and gravitational forces results in a diffusive transport law that depends nonlinearly on hillslope gradient our proposed transport law 1 approximates linear diffusion at low gradients and 2 indicates that sediment flux increases rapidly as gradient approaches a critical value we calibrated and tested this transport law using high resolution topographic data from the oregon coast range these data obtained by airborne laser altimetry allow us to characterize hillslope morphology at 2 m scale at five small basins in our study area hillslope curvature approaches zero with increasing gradient consistent with our proposed nonlinear diffusive transport law hillslope gradients tend to cluster near values for which sediment flux increases rapidly with slope such that large changes in erosion rate will correspond to small changes in gradient therefore average hillslope gradient is unlikely to be a reliable indicator of rates of tectonic forcing or baselevel lowering where hillslope erosion is dominated by nonlinear diffusion rates of tectonic forcing will be more reliably reflected in hillslope curvature near the divide rather than average hillslope gradient

mountain erosion over 10 yr 10 k y and 10 m y time scales we used cosmogenic 10 be to measure erosion rates over 10 k y time scales at 32 idaho mountain catchments ranging from small experimental watersheds 0 2 km 2 t o large river basins 35 000 km 2 these long term sediment yields are on average 17 times higher than stream sediment fluxes measured over 10 84 yr but are consistent with 10 m y erosion rates measured by apatite fission tracks our results imply that conventional sediment yield measurements even those made over decades can greatly underestimate long term average rates of sediment delivery and thus overestimate the life spans of engineered reservoirs our observations also suggest that sediment delivery from mountainous terrain is extremely episodic sporadically subjecting mountain stream ecosystems to extensive disturbance

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

a simple theory for the fate of buoyant coastal discharges abstract a simple theory that predicts the vertical structure and offshore spreading of a localized buoyant inflow onto a continental shelf is formulated the theory is based on two competing mechanisms that move the buoyant fluid offshore 1 the radial spread of the lighter water over the ambient water being deflected by the coriolis force and producing an anticyclonic cyclostrophic plume and 2 offshore transport of buoyant water in the frictional bottom boundary layer that moves the entire plume offshore while maintaining contact with the bottom the surface expression of the cyclostrophic plume moves offshore a distance ys 2 3g h0 2i 2g h0 2i 1 2f where g is reduced gravity based on the inflow density anomaly h0 is the inflow depth i is the inflow velocity and f is the coriolis parameter the plume remains attached to the bottom to a depth given by hb 2l ih0f g 1 2 where l is the inflow width both scales are based solely on parameters of the buoyant inflow at its source there

uplift driven valley incision and river terrace formation in southern england outside the limits of middle pleistocene glaciation the river basins of southern england contain long cenozoic terrestrial sedimentary records of greatest importance are the river terrace sequences which contain biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary however trends in valley development cannot easily be accommodated within the framework of quaternary climatic change it is argued in this paper that episodic incision and terrace development result from uplift a consequence of the interplay between continuing alpine orogenic movements and erosion driven isostasy using a simple linear model height age an uplift rate of ca 7 cm ka 1 is estimated for the terrace sequence in the upper thames valley this preliminary model is evaluated using the records of adjacent basins 1997 john wiley sons ltd

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

geomorphic expressions of collisional tectonics in the qilian shan north eastern tibetan plateau abstract the qilian shan north eastern tibetan plateau is an area of active deformation caused by convergence in the india eurasia collision zone geomorphic indices capture the landscape response to competition between tectonics and climate reflecting the spatial distribution of erosion we use geomorphic indices hypsometric integral hi normalised channel steepness ksn elevation relief ratio zr and surface roughness sr to identify areas of active deformation and erosion highlight landscape variations and we interpret the results for potential tectonic and climatic drivers high hi 0 15 ksn 100 and low zr 0 15 and ksn 100 values in the eastern region are attributed to thrust parallel rivers in this region excavating wide valleys between the faults the east west precipitation variation across the qilian shan 500 mm yr to

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

catchment wide denudation rates at the margin of ne tibet from in situ produced cosmogenic 10be terra nova 23 42 48 2011 abstract we present denudation rates for catchments in the qilian shan and two mountain ranges in its foreland which differ markedly in elevation and catchment morphology catchments with mean slope angles below 25 yield 10be derived denudation rates 200 mm ka 1 and have narrow and symmetric slope frequency distributions which become broader as the mean slope angle increases denudation rates for catchments with mean hillslope angles steeper than 25 range from 100 to 800 mm ka 1 field observations suggest that these higher and more variable rates are the result of erosion by bedrock landslides which contribute to mass transport on the hillslopes six catchments aligned along the mountain front of the central qilian shan have reached threshold values of slope and relief these basins also show remarkably similar slope frequency distributions with negative skewness and a pronounced peak at a slope angle of 30 35 we hypothesize that these catchments have attained an erosional steady state

tectonic geomorphology of the qilian shan in the northeastern tibetan plateau insights into the plateau formation processes abstract we examined the regional scale topography of the qilian shan on the northeastern margin of the tibetan plateau longitudinal profiles and geomorphometric indices such as slope local relief and channel steepness reveal that the qilian shan was developed as a local plateau with high relief steep marginal ranges and interior low relief topography landscape mapping across this local plateau revealed spatially varied origins of the low relief landscape in the qilian shan north of the haiyuan fault universal massive intermontane aggradation was identified however the low relief plateau to the south of the haiyuan fault was dominated by relict erosional surfaces even though accompany basin filling still contributes the geomorphologic contrasts led us to integrate both the basin filling processes and antecedent low relief erosional surfaces into a new insight into the development of the qilian shan plateau in the northeastern tibet our present study highlights that explanation for the low relief plateau formation needs to consider the complex geological evolution of the qilian shan and the tibetan plateau itself

geometry and late pleistocene slip rates of the liangdang jiangluo fault in the western qinling mountains nw china abstract two groups of faults striking in different direction nww trending and nee trending within the western qinling mountains play important roles in the tectonic deformation and the transference slip along the east end of the east kunlun fault we investigated the fault geometry and kinematics properties in the area based on the displacements of landforms and optically stimulated luminescence osl dating techniques the late pleistocene slip rates along the liangdang jiangluo fault were determined to be 0 43 0 13 mm a thrust and 0 71 0 18 mm a left lateral strike slip we also investigated some other faults and obtained characteristically low slip rates these slip rates are consistent with decadal gps observations despite previous studies that point to a systematic decrease in the left lateral slip rates from 10 mm a to

millennial scale erosion rates in three inland drainage basins and their controlling factors since the last deglaciation arid china abstract in the regions surrounding the qinghai tibet plateau changes in erosion rates have been linked to the tectonics climate and topography over different time scales to understand the mechanisms governing the changes of erosion rates it is important to study erosion rates by different methods and for different time scales in inland drainage basins deposition rates of terminal lake sediments can indicate basin wide erosion rates at the millennial scale this paper presents three lake records of the last deglaciation and holocene huahai lake zhuye lake and yanchi lake from the hexi corridor north of the qilian mountains in arid china organic matter terrestrial pollen concentrates seeds grasses and plant debris are used for conventional and ams 14 c dating on the basis of 66 radiocarbon dates lithology and grain size we infer relatively high basin wide erosion rates during the last deglaciation and early holocene in the three drainage basins when the three lake sediments were seriously affected by reworking the deposition rates were an order of magnitude or greater in these lakes during the last deglaciation and early holocene than during the mid to late holocene during the transition period of the last glacial interglacial cycle significant climatic changes occurred in east and central asia corresponding to the strengthening of the asian summer monsoon and to increasing effective moisture in arid central asia which can have strong impacts on basin wide erosion rates north of the qinghai tibet plateau moreover melting glaciers in the qilian mountains probably also contributed to the high basin wide erosion rates at the same time tectonic activity was not recognizable in the study area during that period in the arid and semiarid regions surrounding the qinghai tibet plateau dramatic changes in erosion rates appear during the transition periods of the glacial interglacial cycles which illustrate the climatic controls on erosion rates at this time scale

climatic limits on landscape development in the northwestern himalaya the interaction between tectonism and erosion produces rugged landscapes in actively deforming regions in the northwestern himalaya the form of the landscape was found to be largely independent of exhumation rates but regional trends in mean and modal elevations hypsometry frequency distribution of altitude and slope distributions were correlated with the extent of glaciation these observations imply that in mountain belts that intersect the snowline glacial and periglacial processes place an upper limit on altitude relief and the development of topography irrespective of the rate of tectonic processes operating

rates of continental erosion and mountain building the first objective of this work was to obtain values for the rates at which continental erosion can smooth out or remove the topographic expression produced by orogeny the dominant part is played by mechanical erosion which acts most strongly in regions of large topographic expression chemical erosion depends strongly on precipitation or runoff in individual river drainage basins but because most continents have very similar average rainfall chemical erosion is fairly uniform for continental sized areas and will succeed in planing down all continents to a level peneplain if given enough time the exception to this rule is australia which has a very low chemical erosion rate because of its dryness the time constants for mechanical and chemical erosion so obtained vary between about 30 and 300 my depending on the continent and the assumptions made mountain building occurs throughout the geological time scale but at a non uniform rate although there will not be a balance between erosion and mountain building over a short time scale due to the non uniform rate of mountain building the long term situation must be that the two phenomena should balance out it is shown that the freeboard of continents will respond to the long term balance between mountain building and erosion an expression has been derived for the average continental elevation in which the rate of mountain building depends on the rate of radiogenic heat production within the earth it is shown that relatively small changes in average elevation above sea level of a few hundred metres are predicted to have occurred since the beginning of the proterozoic as mountain building is predicted to decrease on average with time because of the reduction in internal heat generation and as erosion is dependent on the average elevation this average elevation will decrease slowly through time the opposite of what some workers have predicted a more complicated model of mountain building is then investigated in which one component of mountain building has a sinusoidal signal the oscillations in average elevation depend on the period of the sinusoid being smaller for shorter periods finally an average continental elevation is derived using a list of real orogenic events although this list of orogenies is incomplete there is some indication that the actual continental elevation as seen in the flooding history of the continents is similar to that derived in this paper

plio quaternary stepwise drying of asia evidence from a 3 ma pollen record from the chinese loess plateau abstract a 3 ma pollen record was obtained from a continuous red clay loess paleosol sequence at chaona in the central chinese loess plateau clp the record shows a permanent change of a domination of typical cupressaceae forest vegetation representative of an ecological environment with a relative warm and humid climate during 3 0 2 6 ma to largely steppe vegetation under dry climate conditions after 2 6 ma the later is further manifested itself as steppe to forest or forest steppe spruce forest mostly mesophilous herbs between 2 6 ma and 1 5 ma forest steppe pine grass between 1 5 ma and 0 95 ma open forest steppe mesophilous and xeromorphic herbs pine between 0 95 ma and 0 5 ma and steppe xeromorphic herbs after 0 5 ma suggesting a process of stepwise aridification in central asia at the late pliocene and the quaternary

differential rock uplift along the northeastern margin of the tibetan plateau inferred from bedrock channel longitudinal profiles abstract bedrock channel profile analysis is a robust reconnaissance tool for examining the rates and patterns of deformation in active orogens here steepness and concavity indices were extracted from bedrock channels draining the northern qilian mountains based on the universal shear stress incision model the profile analysis reveals a systematic spatial distribution of steepness and concavity indices the average steepness index for channels draining the western part is approximately 1 6 times higher than that for the eastern part through empirical calibration of erosion coefficient k the influence of channel width rock strength discharge and sediment flux are identified and an approximately 1 1 1 2 times difference in k values is found between the west and east under the hypothesis that lithologic resistance and sediment flux have no contribution correlating profile analyses with parameter calibration an approximate 2 3 times increase in the rock uplift rate is found from the eastern part to the western part of the orogen the integration of this study with previous work in the eastern part of the mountains indicates that cross strike 2 4 times and along strike 2 3 times differential rock uplift both exist in the northeastern margin of the tibetan plateau in addition the abnormal values of concavity are apparently associated with the channels transecting large thrust fault zones thus the shortening deformation may play a dominant role in controlling the differential rock uplift through folding and thrusting of the northeast directed thrust faults across the northeastern margin of the tibetan plateau

late neogene magnetostratigraphy in the western qaidam basin ne tibetan plateau and its constraints on active tectonic uplift and progressive evolution of growth strata abstract the qaidam basin as the largest intermontane basin of the ne tibetan plateau is the ideal place to provide constraints on depositional and tectonic patters to determine its tectonic deformation history and progressive evolution of growth strata we conducted paleomagnetic study on the late neogene stratigraphic section in the western qaidam basin a magnetostratigraphic study of the well exposed 805 m qigequan section at the qigequan anticline in the western qaidam basin reveals twelve pairs of normal and reversed polarity zones which can be readily correlated with chrons c1n 3ar of the geomagnetic polarity time scale gpts from this correlation we can conclude that the shizigou and the qigequan formations were formed at 6 9 ma 2 5 ma and 2 5 0 4 ma respectively accumulation rates determined from our chronology together with the occurrence of unconformities suggest four phases of tectonic uplift which began at about 3 6 ma 2 5 ma 1 1 ma and 0 8 ma the results also suggest that offlap growth strata according to the limb rotation model on the anticlinorium started to occur at 8 2 ma they progressively become younger from the frontal region of the altyn tagh mts 8 2 ma to the southwestern basin 2 5 ma and to further east of the qaidam basin

what factors control mechanical erosion rates mechanical erosion rates are important factors in understanding how continents evolve mechanical erosion is much faster than chemical erosion especially for highly elevated regions of the earth s surface it is a principal way in which mountain ranges are removed exposing deep metamorphic roots which comprise much of the older portions of the continental masses in addition there has to be a long term balance between erosion and mountain building a new data set allows us to explore in greater detail some of the many factors which control mechanical erosion rates the most important factors are some expression of the average slope of a drainage basin some measurement of the amount of water available for erosion some environmental measurements and also a measurement of basin length for which we have no good explanation the estimate of global mechanical erosion rate obtained here is considerably lower than those obtained by some other workers some of whom have concentrated on the fact that smaller river basins tend to get eroded faster than larger basins and it is mainly smaller basins which have not been measured and which are therefore not allowed for by simple arithmetic averaging of observed erosion rates it is shown here that although smaller basins are eroded faster this is mainly because they are steeper than larger basins we also show that extrapolation of current data to smaller basins does not work because the observed continental area which is draining to the ocean cannot be attained by the simplest extrapolation scheme

holocene millennial scale erosion and deposition processes in the middle reaches of inland drainage basins arid china in inland drainage basins many studies have been conducted regarding the geomorphologic evolution processes in the upper and lower reaches few of them have been done on the middle reaches which are the pivotal areas connecting the erosion effects of the upper reaches and the deposition processes in terminal areas in this study we presented a millennial scale study from middle reaches of the shiyang river and the shule river drainage basins during the holocene several sedimentary sections are selected to calculate millennial scale erosion and deposition rates results show that the middle reaches of the shiyang river and the shule river are characterized by deposition processes in the early and middle holocene but erosion processes prevailed during the late holocene at the same time the sedimentary facies grain size geochemical proxies and pollen proxies of the sediments from middle reaches of the two drainages were used to complement the erosion and deposition rates which are good for understanding the environment background during the geomorphologic evolution processes besides the main factor affecting the basin wide geomorphologic evolution is millennial scale climate change and the responses of the middle reaches to climate change are different from those of the upper and lower reaches