thermochronometry reveals headward propagation of erosion in an alpine landscape glacial erosion of mountain ranges produces spectacular alpine landscapes and by linking climate with tectonics influences a broad array of geophysical phenomena although the resultant landforms are easily identified the timing and spatial pattern of topographic adjustment to pleistocene glaciations remain poorly known we investigated topographic evolution in the archetypal glacial landscape of fiordland new zealand using u th he thermochronometry we find that erosion during the past 2 million years removed the entire pre pleistocene landscape and fundamentally reshaped the topography erosion focused on steep valley segments and propagated from trunk valleys toward the heads of drainage basins a behavior expected if subglacial erosion rate depends on ice sliding velocity the fiordland landscape illustrates complex effects of climate on earth s surface morphology

quaternary channel focused rapid incision in the phung chu arun river in central himalaya implications for a quaternary capture event abstract the phung chu arun river one of the few major trans himalaya rivers consists of a large drainage area captured in the northern slope of the himalaya and provides a key to understand tectonic surface processes and their interplay in topographic development of the himalaya in this study we carried out thermochronologic and topographic analysis along the phung chu arun river in central himalaya to reveal its incision development apatites from a downstream section along its major tributary yield very young fission track and u th he ages of 0 8 1 5 ma these cooling ages combined with previously reported data for higher elevations reveal an abrupt change of the slope in the age elevation plot suggesting an accelerated channel incision initiated at between 1 5 and 2 5 ma the age elevation relationship yields a high apparent exhumation rate aer of 2 6 3 8 mm a during quaternary which is spatially focused along the mainstream of the kharta chentang reaches and the associated nearby tributaries topographic analysis suggests that this channel focused incision acceleration was probably facilitated by a quaternary capture event in upper drainage of the palaeo arun river this capture event greatly enhanced the effective discharge draining southward causing an accelerated incision wave along the mainstream and tributaries of the palaeo arun river furthermore thrusting at physiographic transition zone is also required to sustain high channel gradient and the long term rapid incision channel morphology presenting common knick points in major tributaries suggests that the drainage basin in ama drime range area likely remain in pre steady state adjustment of this capture event

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

40ar 39ar dating of quaternary lavas in northwest iran constraints on the landscape evolution and incision rates of the turkish iranian plateau summary we report five new 40 ar 39 ar ages for basaltic lavas in the maku region of northwest iran between ca 1 87 and 0 40 ma which help constrain the tectonic and landscape evolution of this part of the turkish iranian plateau flows originated from the composite volcanoes ararat agridagi tend urekandyigitdagi ineasternturkey anatolia thesevolcanoesarewithin the turkish iranian plateau which is a consequence of the arabia eurasia collision but has a poorly constrained evolution and surface uplift history current plateau elevations are typically 1 5 2 km and relief between non volcanic summits and basins is typically on the scale of 1 km samples are from flows that passed along pre existing river valleys gorges were cut by re established rivers after the eruptions but the great majority of the local relief 95 per cent lies above the sampled flows and so most likely pre dates the volcanism gorge depths and lava ages allow local quaternary fluvial incision rates to be calculated which are 0 01 to 0 05 mm yr 1 these rates imply slow surface uplift of this part of the turkish iranian plateau during the quaternary we therefore constrain the generation of the great majority of relief in the study area to be pre quaternary and caused by the tectonic construction of the plateau rather than a subcrustal origin related to the quaternary magmatism

control of detachment geometry on lateral variations in exhumation rates in the himalaya insights from low temperature thermochronology and numerical modeling 1 the himalayan range is commonly presented as largely laterally uniform from west to east however geological structures topography precipitation rate convergence rates and low temperature thermochronological ages all vary significantly along strike here we focus on the interpretation of thermochronological data sets in terms of along strike variations in geometry and kinematics of the main crustal detachment underlying the himalaya the main himalayan thrust mht we report new apatite fission track aft ages collected along north south transects in western and eastern central nepal at the latitudes of the annapurna and langtang massifs respectively aft ages are consistently young 3 ma along both n s transects in the high relief zone of the higher himalaya and increase 4 to 6 ma toward the south in the lesser himalaya we compare our new data to published low temperature thermochronological data sets for nepal and the bhutan himalaya we use the full data set to perform both forward and inverse thermal kinematic modeling with a modified version of the pecube code in order to constrain potential along strike variations in the kinematics of the himalayan range our results show that lateral variations in the geometry of the mht in particular the presence or absence of a major crustal scale ramp strongly control the kinematics and exhumation history of the orogen

determining the effect of topography on isotherms in the shallow crust using low temperature thermochronometry in tunnels apatite u th he and fission track age determinations of samples from a 20 km long near horizontal tunnel in the hochalm ankogel dome eastern tauem window austria are presented in order to determine the role of paleo topography in perturbing isotherms in the shallow crust apatite fission track ages 26 8 ma show no systematic correlation with distance along the tunnel or elevation two age components in the fission track data indicate cooling through 120 c at approximately 20 ma and 80 c at approximately 6 ma surface and tunnel u th he ages 17 9 ma and 13 5 ma respectively are consistently younger than the equivalent fission track ages u th he ages vary systematically along the tunnel with older ages at the northern and southern tunnel portals and younger ages in the central section geological factors faulting lithology appear to have had little effect on this age distribution the u th he age pattern is inconsistent with rock cooling underneath the present day hochalm ankogel dome topography the age minimum is interpreted to coincide with a paleotopographic maximum in the hochalm ankogel dome and suggests that the 40 60 c isotherms were warped sufficiently to affect apatite u th he ages the tunnel apatite u th he ages match synthetic he ages derived from a two dimensional numerical model of landscape evolution integrating the thermal model results with the data allows the relief development to be constrained and we calculate that the present day hochalm ankogel dome topography was formed at 7 to 10 ma copyright 2007 by the american geophysical union

natural and anthropogenic hazards in karst areas an introduction the distinctive hydrology and landforms of karst create a very special environment although several types of karst have been identified worldwide a common thread is the dominantly subterranean drainage the paucity of water flowing at the surface a consequence of rapid infiltration underground through a network of discontinuities in the soluble rock mass results in two important but contrasting points the considerable value of karst water resources representing about 25 of the drinkable supply in the world is strongly counteracted by the ease with which human activities can negatively impact this precious resource the same narrow discontinuities and the larger dissolution conduits and karst caves are the main pathways through which potential pollutants may travel swiftly to regional groundwater bodies or directly to springs contaminants can be introduced by means of dispersed infiltration as well as from point sources and are frequently transmitted with minimal filtering this example just one of the many natural and or anthropogenic hazards that may affect karst areas illustrates the fragility of karst environments their high vulnerability is further expressed by a very simple concept that is true for many other environments but probably shows its best evidence in karst it is very easy to damage or destroy natural resources but restoration to a pristine situation is an extremely difficult and commonly impossible task where some degree of remediation is possible the economic cost is commonly very high since the early 1960s there has been a great deal of progress in understanding the processes and landforms of karst areas e g ford williams 1989 gillieson 1996 klimchouk et al 2000 gabrovsek 2002 there have also been several initiatives designed to translate theoretical knowledge into practical application for example work by the international geographical unions karst commission williams 1993 barany kevei gunn 2000 the iucn 1996 and the world bank vermeulen whitten 1999 however projects continue to fail and resources are lost or damaged owing to a failure in understanding the peculiarities of karst for examples see waltham et al 2005 hence there remains a strong need to develop appropriate techniques to manage karst landscapes and protect karst resources there are many human activities that intentionally or not produce severe impacts in karst often with irreparable damage for example in some regions land degradation has been intense with deforestation and overgrazing leading to soil erosion destruction of the epikarst and rocky desertification rehabilitation of these desert lands is extremely difficult although in some parts of the mediterranean reduction of grazing has been followed by a return of shrubs and small trees legislation and even more its practical enforcement still appears to be extremely inadequate at facing these problems even in well developed countries lack of laws and acts specifically devoted to karst is very common but even when legislation takes into account the complexity and peculiarity of karst the potential benefits deriving from these acts frequently remain on paper owing to a lack of enforcement and control by the authorities the best example is probably provided by the management of aquifers in carbonate rocks as this requires an understanding of the character and type of water circulation within the rock mass for many years the principles developed for non carbonate aquifers and the resulting methodologies created for groundwater vulnerability assessment have also been applied to karst environments however it has long been known that the planning and management of carbonate aquifers poses different problems to those encountered in non carbonate groundwater karst groundwater watersheds often do not coincide with topographic divides to indicate just one of the main differences between karst hydrology and those in other environments only in recent years have some significant efforts been produced to give due weight to the peculiarity of karst hydrology and hydrogeology for example the cost 65 1995 and subsequent cost co operation in science and technology programmes in europe and the report by eckenfelder inc 1996 in the united states

inversion of topographic evolution using low t thermal history a case study from coastal mountain system in southeastern china abstract the topographic evolution of a mountain system provides key information for understanding surface processes we present a new and relatively simple method to reconstruct two dimensional paleotopography composed of two steps 1 construction of thermal history using low temperature thermochronological data and 2 conversion of the thermal history into topographic evolution a new computer program low t topo was developed to perform the suggested conversion of thermal history to paleotopography this approach when applied to the coastal mountain system cms in southeastern china suggests an uneven topographic evolution along the changting zhangzhou section since the late cretaceous according to our modeling the se segment of the section was higher maximum peak elevation 3 8 km than the nw segment 3 4 km during 80 50 ma the modeling also suggests that both the se and nw segments experienced an initially higher exhumation rate of 0 14 km myr at 80 70 ma which steadily decreased to about 0 03 km myr at 40 ma since then exhumation rates stayed relatively low 0 05 km myr the elevation reduction in the cms since the late cretaceous played an important role introducing the warm and humid pacific air to the inland

the influence of burial heating on the u th he system in apatite grand canyon case study article history thermochronological data can constrain the cooling paths of rocks exhumed through the uppermost 1 2 km of earth s crust and have thus been pivotal in illuminating topographic development over timescales 0 1 ma however in some cases different methods have led to conflicting conclusions about timing of valley scale exhumation here we investigate the case of western grand canyon usa where different thermochronological datasets have been interpreted to record very different timings of canyon incision 70 ma versus 5 ma we present a method to assess key assumptions in these constraints and demonstrate that burial heating conditions of basement rocks in the mesozoic can result in incomplete annealing of radiation damage in apatite in turn this has a dramatic effect on the temperature sensitivity of the apatite u th he system and its ability to record post burial exhumation the possibility of incomplete annealing resolves the apparent conflict in time temperature paths inferred over the last 70 ma although it requires temperatures during burial that are lower than predicted by apatite fission track data a refinement of parameters that prescribe the kinetics of damage annealing and related control on 4 he diffusivity in apatite would account for this discrepancy specifically if alpha recoil damage anneals at a lower rate than fission tracks at a given temperature these effects will be important for any application of the apatite u th he system in geologic settings that experienced prolonged residence 10 ma between 50 150 c the approaches developed here provide means to assess these effects

rapid glacial erosion at 1 8 ma revealed by 4he 3he thermochronometry alpine glaciation and river incision control the topography of mountain ranges but their relative contributions have been debated for years apatite 4 he 3 he thermochronometry tightly constrains the timing and rate of glacial erosion within one of the largest valleys in the southern coast mountains of british columbia canada five proximate samples require accelerated denudation of the klinaklini valley initiating 1 8 0 2 million years ago ma at least 2 kilometers of overlying rock were removed from the valley at 5 millimeters per year indicating that glacial valley deepening proceeded 6 times as fast as erosion rates before 1 8 ma this intense erosion may be related to a global transition to enhanced climate instability 1 9 ma

uplift and cooling pathways derived from fission track analysis and mica dating a review definition of time and temperature pathways for episodes of lithospheric movement provides not simply a chronological framework for crustal dynamism but also permits estimation of rates of crustal cooling and uplift important aspects of such pathways are the constraints provided for timing of both plate collision and lithospheric extension classically rb sr and k ar mica ages have been used to delineate rates of cooling and exhumation in the central alps by comparison of the measured ages with estimates of temperatures for the retention of daughter isotopes similar use of fission track apatite and zircon ages has provided data for lower temperature intervals 100 and 200 c respectively recent detailed studies of the annealing kinetics of fission tracks in apatite yield more precise estimates of cooling rate and permit predictive modelling of age and length parameters for given t t pathways in continental collision zones fast episodic uplift in the western alps can be contrasted with contemporaneous monotonic uplift in the central alps additional examples may be seen in the tibet himalayan orogenic belt in the southern alps of new zealand and in the bolivian andes in divergent teceonic regimes the record of uplift associated with rifting has been recorded by fission track ages in the southeastern australian margin and around the red sea in an intra plate tectonic setting our current fission track reconnaissance study in the british isles is revealing a hitherto unrecognised thermal history for crystalline and sediment alike

exhumational variability within the himalaya of northwest india in the himalaya of chamba nw india a major orographic barrier in front of the greater himalayan range extracts a high proportion of the monsoonal rainfall along its southern slopes and effectively shields the orogen interior from moisture bearing winds along a 100 km long orogen perpendicular transect 28 new apatite fission track aft and 30 new zircon u th he zhe cooling ages reveal marked variations in age distributions and long term exhumation rates between the humid frontal range and the semi arid orogen interior on the southern topographic front very young elevation invariant aft ages of 4 ma have been obtained that are concentrated in a 30 km wide zone 1 d thermal modeling suggests a plio pleistocene mean erosion rate of 0 8 1 9 mm yr 1 in contrast aft and zhe ages within the orogen interior are older 4 9 and 7 18 ma respectively are positively correlated with sample elevation and yield lower mean erosion rates 0 3 0 9 mm yr 1 protracted low exhumation rates within the orogen interior over the last 15 myr prevailed contemporaneously with overall humid conditions and an effective erosional regime within the southern himalaya this suggests that the frontal dhauladar range was sufficiently high during this time to form an orographic barrier focusing climatically enhanced erosional processes and tectonic deformation there thrusting along the two frontal range bounding thrust the main central thrust and the main boundary thrusts was initiated at least 15 ma ago and has remained localized since then the lack of evidence for localized uplift farther north indicates either a rather flat decollement with no ramp or the absence of active duplex systems beneath the interior of chamba exhumational variability within chamba is best explained as the result of continuous thrusting along a major basal decollement with a flat beneath the slowly exhuming internal compartments and a steep frontal ramp at the rapidly exhuming frontal range the pattern in chamba contrasts with what is observed elsewhere along the himalaya where exhumation is focused in a zone 150 km north of the orogenic front in the nw himalaya preserved high himalayan crystalline nappes and lesser himalayan windows alternate on a relatively small scale of 100 km these alternations are closely correlated with the pattern of exhumation although the spatial distribution of high exhumation zones varies considerably between individual himalayan sectors all of these zones are closely correlated with locally higher rock uplift rates sharp topographic discontinuities and focused orographic precipitation suggesting strong feedbacks between tectonically driven rock uplift orographically enhanced precipitation and erosional processes

dating topography of the sierra nevada california using apatite u th he ages the upward motion of rock masses relative to the earth s surface has been documented for most of the main mountain belts using thermochronological and petrological techniques more fundamental to the physical processes of mountain building however is the motion of the earth s surface itself which remains elusive here we describe a technique for estimating the age of topographic relief by mapping the low temperature thermal structure imparted by river incision using the ages of apatites determined from their uranium thorium and helium contents the technique exploits horizontal variations in temperature in the shallow crust that result from range normal river drainages because cooling beneath ancient river valleys occurs earlier than beneath intervening ridges our results from the sierra nevada california indicate that two of the modern transverse drainages the kings and the san joaquin had developed deep canyons by the late cretaceous period suggesting that the high topography of the range is 50 60 million years older than generally thought

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

timing and rate of exhumation along the litang fault system implication for fault reorganization in southeast tibet the litang fault system that crosses the litang plateau a low relief surface at high elevation 4200 4800 m above sea level that is not affected by regional incision provides the opportunity to study exhumation related to tectonics in the se tibetan plateau independently of regional erosion combining apatite and zircon fission track with apatite u th he thermochronologic data we constrain the cooling history of the litang fault system footwall along two transects apatite fission track ages range from 4 to 16 ma ahe ages from 2 to 6 ma and one zircon fission track age is 99 ma these data imply a tectonic quiet period sustained since at least 100 ma with a slow denudation rate of 0 03 km ma interrupted at 7 to 5 ma by exhumation at a rate between 0 59 and 0 99 km ma we relate that faster exhumation to the onset of motion along the left lateral normal litang fault system that onset is linked to a lower miocene important kinematic reorganization between the xianshuihe and the red river faults with the eastward propagation of the xianshuihe fault along the xiaojiang fault system and the formation of the zhongdian fault such strike slip faults allow the sliding to the east of a wide continental block with the litang fault system accommodating differential motion between rigid blocks the regional evolution appears to be guided by the strike slip faults with different phases of deformation which appears more in agreement with an hidden plate tectonic model rather than with a lower channel flow model

cenozoic deformation and exhumation history of the central kyrgyz tien shan new low temperature thermochronological data from 80 samples in eastern kyrgyzstan are combined with previously published data from 61 samples to constrain exhumation in a number of mountain ranges in the central kyrgyz tien shan all sampled ranges are found to have a broadly consistent cenozoic exhumation history characterized by initially low cooling rates 1 c myr followed by a series of increases in exhumation that occurred diachronously across the region in the late cenozoic that are interpreted to record the onset of deformation in different mountain ranges combined with geological estimates for the onset of proximal deformation our data suggest that the central kyrgyz tien shan started deforming in the late oligocene early miocene leading to the development of several widely spaced mountain ranges separated by large intermontane basins subsequently more ranges have been constructed in response to significant shortening increases across the central kyrgyz tien shan notably in the late miocene the order of range construction is interpreted to reflect variations in the susceptibility of inherited structures to reactivation reactivated structures are also shown to have significance along strike variations in fault vergence and displacement which have influenced the development and growth of individual mountain ranges moreover the timing of deformation allows the former extent of many intermontane basins that have since been partitioned to be inferred this can be linked to the highly time transgressive onset of late cenozoic coarse clastic sedimentation

significant increase in relief of the european alps during mid pleistocene glaciations the effect of expanded glaciation on the relief of mountain ranges is debated chronometric and model data from the european alps suggest that relief in the rhone valley was enhanced as a result of the increased incision of the valley following the mid pleistocene climate transition

a bayesian approach to calibrating apatite fission track annealing models for laboratory and geological timescales abstract we present a new approach for modelling annealing of fission tracks in apatite aiming to address various problems with existing models we cast the model in a fully bayesian context which allows us explicitly to deal with data and parameter uncertainties and correlations and also to deal with the predictive uncertainties we focus on a well known annealing algorithm laslett g m green p f duddy i r gleadow a j w 1987 thermal annealing of fission tracks in apatite 2 a quantitative analysis chem geol 65 1 1 13 and build a hierachical bayesian model to incorporate both laboratory and geological timescale data as direct constraints relative to the original model calibration we find a better in terms of likelihood model conditioned just on the reported laboratory data we then include the uncertainty on the temperatures recorded during the laboratory annealing experiments we again find a better model but the predictive uncertainty when extrapolated to geological timescales is increased due to the uncertainty on the laboratory temperatures finally we explictly include a data set vrolijk p donelick r a quenq j cloos m 1992 testing models of fission track annealing in apatite in a simple thermal setting site 800 leg 129 in larson r lancelet y eds proceedings of the ocean drilling program scientific results vol 129 pp 169 176 which provides low temperature geological timescale constraints for the model calibration when combined with the laboratory data we find a model which satisfies both the low temperature and high temperature geological timescale benchmarks although the fit to the original laboratory data is degraded however when extrapolated to geological timescales this combined model significantly reduces the well known rapid recent cooling artifact found in many published thermal models for geological samples

uplift and denudation of the central alaska range a case study in the use of apatite fission track thermochronology to determine absolute uplift parameters apatite fission track thermochronology aftt on granitic samples collected in the central alaska range in conjunction with geologic constraints from basins to the north nenana basin and south cook inlet of the range is used to constrain the timing amount rate and pattern of surface uplift rock uplift and denudation since the late miocene the conversion from a thermal frame of reference apatite fission track data to an absolute frame of reference with respect to mean sea level which requires constraining the paleoland surface elevation the paleomean annual temperature and the paleogeothermal gradient is evaluated and shown to be viable in the context of an exhumed apatite partial annealing zone paz apatite ages at denali mount mckinley range from 16 ma near the summit 6 km elevation to 4 ma at 2 km elevation a distinctive break in slope in the apatite age profile at an elevation of 4 5 km also marked by a change in confined track length distributions marks the base of an exhumed apatite paz rock uplift and denudation are greatest at denali decreasing southward away from the mckinley strand of the denali fault system as shown by progressively older apatite ages 7 35 ma from a suite of samples along the kahiltna glacier a correlative decrease in topography occurs southward from the fault the central alaska range lies within an arc defined by the denali fault with the highest peaks including denali concentrated at the arc apex patterns of rock uplift and denudation within the central alaska range mimic topography between early and late miocene and possibly earlier the central alaska range was most likely an area of relative tectonic and thermal stability rock uplift denudation and mean surface uplift of the denali region began by the late miocene 5 6 ma being 8 5 km 5 7 km and 2 8 km respectively at average rates of 1 5 km m y 1 km m y and 0 5 km m y the amount of rock uplift denudation and surface uplift decreases to 3 km 2 km and 1 km at little switzerland some 45 km south of the denali fault we conclude that the topographic and rock uplift patterns of the central alaska range the shape and proximity of the mckinley strand of the denali fault to these patterns the timing of the onset of rock uplift and denudation at 5 6 ma and a significant change in relative plate motion between north america and the pacific plates circa 5 6 ma are all inherently related

effect of alpha damage annealing on apatite u th he thermochronology recent data on he diffusion challenge the temperature sensitivity of apatite u th he thermochronology the damage induced by recoil of u and th decay series during emission of particles recoil damage has been proposed to modify he diffusion properties through time however we propose that annealing of these irradiation defects may be an important phenomenon and may be significant in case of slowly cooled or reheated basement rocks to test this hypothesis we developed a quantitative model including an explicit treatment of recoil damage annealing and their effect on he diffusion kinetics and calibrate it against literature data our model is based on two hypotheses 1 helium is in equilibrium between an apatite crystal and its defects and 2 alpha recoil damage annealing can be described analogously to fission track annealing this model has been embedded into a monte carlo simulation of helium production ejection diffusion and applied to data from the french massif central a complex slowly cooled terrain with burial reheating where the thermal history has been constrained by previous fission track ft data including ft length distributions u th he ages are close to the ft ages from the same samples and are generally reproducible among replicates but some samples present he age dispersion that is not correlated with crystal size our model reproduces the massif central data very well except for three samples where he ages are older than corresponding ft ages we show that annealing of irradiation damage has an important impact on retentivity of helium and that the he content he is only a rough approximation of the damage level in particular our results show that independence of he ages on crystal sizes in case of reheated samples is a clear indication of the higher he retentivity induced by recoil defects and that an explicit treatment of defect annealing is required for a correct interpretation of u th he ages in such a case more generally a correlation with the crystal size can bring information on the thermal path only if the age of defects well represented by the fission track age is available due to the dependence of the partial retention zone on damages conversely in case of rapid cooling or for samples having low u and th contents damage effects can be ignored without significant effects on he ages

exhumation and relief development in the pelvoux and dora maira massifs western alps assessed by spectral analysis and inversion of thermochronological age transects 1 we have used dedicated sampling and analysis of apatite fission track aft and apatite u th he ahe thermochronological data sets in an attempt to quantify relief evolution and exhumation rates in the pelvoux and dora maira massifs western european alps a dual approach comparing spectral analysis and thermal kinematic model inversion was applied we sampled age elevation relationships at a range of topographic wavelengths along two north south transects crossing these massifs for the 40 km long pelvoux transect we report 35 new aft ages that range between 3 0 0 4 ma and 12 6 1 0 ma and 8 new ahe ages between 3 5 1 5 and 4 7 0 7 ma the dora maira transect spans a distance of 60 km and includes 28 23 new and 5 previously published significantly older aft ages which vary between 13 1 0 2 and 27 3 0 3 ma inferred exhumation rates of 0 7 km m y 1 since 8 ma in the pelvoux and only 0 1 km m y 1since 20 ma in dora maira are consistent between methods as well as with previous estimates although they are associated with large uncertainties due to imperfect sampling and analytical errors neither massif displays clear evidence for relief change during the intervals constrained by the data data from the dora maria massif suggest moderate recent relief increase whereas the results from the pelvoux are inconclusive but could imply relief decrease our study highlights the difficulties of applying thermochronology techniques to constrain relief changes we show that an unreasonable number of samples is needed to perform reliable spectral analysis of age elevation transects and discuss the overall limitations of both techniques to address relief evolution we suggest that a more efficient approach would be to apply thermal kinematic model inversion to relatively small study areas using spatially distributed sampling and multiple thermochronometer analyses per sample

sediment supply and channel morphology in mountain river systems 1 relative importance of lithology topography and climate 1 quantifying landscape scale variations in sediment supply to streams and rivers is fundamental to our understanding of both denudational processes and stream channel morpho dynamics previous studies have linked a variety of sediment supply proxies to climatic topographic or geologic factors but few have connected these directly to the characteristics of fluvial systems draining these landscapes here we correlate landscape controls on sediment supply to observed sedimentology and channel patterns through direct measurements of water and sediment fluxes in over 80 drainage basins ranging in area from 1 4 to 35 000 km2 in the northern rocky mountains usa these data show that the relative sediment supply defined by the bankfull sediment concentration is dominated by basin lithology while exhibiting little correlation to factors such as relief mean basin slope and drainage density bankfull sediment concentrations bed load and suspended load increase as much as 100 fold as basin lithology becomes dominated by softer sedimentary and volcanic rocks relative to basins with more resistant lithologies as bed load concentrations increase stream beds become less armored and bed load grain size coarsens at very high sediment concentrations bed surface subsurface and bed load grain sizes converge and a transition from single thread to to braided channel patterns is commonly observed

exhumation history of the aydin range and the role of the buyuk menderes detachment system during bivergent extension of the central menderes massif western turkey the central menderes massif western turkey is a prominent example of symmetrical exhumation of a core complex it comprises the bozda and aydin ranges which represent the footwalls of the north dipping gediz detachment and the south dipping buyuk menderes detachment respectively in contrast to the gediz detachment the role of the buyuk menderes detachment during late cenozoic extension and exhumation of the central menderes massif is less well resolved here we present results from structural and geological mapping as well as new fission track and u th he data to show that two low angle normal faults contributed to the exhumation of the aydin range our data indicate that the sustained activity of the buyuk menderes detachment since the early miocene is followed by the onset of faulting along the previously unrecognized demirhan detachment which is situated in the hanging wall of the buyuk menderes detachment in the latest miocene pliocene thermokinematic modelling of cooling ages from the footwalls of the buyuk menderes and demirhan detachments yielded exhumation rates of c 0 5 and c 0 4 km ma 1 respectively apatite fission track ages from the demirhan detachment indicate a slip rate of c 2 km ma 1 during the pliocene high angle normal faulting along the modern buyuk menderes graben commenced in the quaternary supplementary material further results of thermal history modelling are available at https doi org 10 6084 m9 figshare c 4392905

inversion of thermochronological age elevation profiles to extract independent estimates of denudation and relief history ii application to the french western alps abstract thermochronologic data collected along age elevation profiles are commonly interpreted as recording temporally variant but spatially constant exhumation rates however thermochronologic age elevation relationships are known to be perturbed by topographic effects and potential changes in relief which are neglected in the inherently 1 d interpretation commonly applied such data thus potentially record both the denudation and relief history of the sampled region but extracting this information is challenging in a companion paper we develop a methodology for rigorously interpreting thermochronologic age elevation profiles in terms of exhumation rates and relief development through time and to independently quantify the resolution of these constraints here we test this approach using a thermochronological dataset consisting of apatite and zircon fission track and u th he data collected at la meije peak in the pelvoux ecrins massif french western alps our data and models suggest a three phase exhumation history in the pelvoux ecrins massif including a pulse of rapid exhumation at 6 5 5 ma preceded and followed by more moderate rates of denudation in the order of 0 3 0 4 km myr 1 this rapid exhumation event appears to occur coevally in other external crystalline massifs in the alps but is not detected by qualitative inspection of the age elevation relationships both our synthetic results and inversion of the la meije data strongly suggest that apatite fission track age elevation relationships alone cannot resolve both denudation and relief histories independently and that multiple thermochronometers are required combining apatite fission track and u th he ages and particularly including fission track length data greatly improves the resolution of the inferred exhumation histories although denudation rates through time and the timing of rate changes are generally well resolved our data have insufficient resolution to satisfactorily constrain the relief history synthetic results reported in the companion paper suggest that the reason for this limitation is that relief increase through valley carving has been insufficient with respect to the regional denudation rates to be unambiguously extracted from the data

volcanic landforms and ore deposits metals and lithophile element deposits related to four types of high level magmatic systems each characterized at the surface by a distinct volcanic landform stratovolcano flow dome complex caldera and maar porphyry copper bearing stocks and base metal rich precious metal veins are known from the deeper central zones of andesitic stratovolcanoes precious and base metal veins and breccias as well as cu pb zn ag replacement orebodies and lithophile element mineralization were emplaced in the shallow parts of flow dome complexes tin beryllium uranium and fluorine mineralization in rhyolite flow domes may be a manifestation of subjacent porphyry molybdenum systems precious metal vein deposits are associated with ring fracture domes around resurgent calderas and moat sediments are known to carry dispersed silver or mercury uranium mineralization many large calderas appear to be relatively deficient in temporally related ore deposits possibly as a result of volatile dissipation during pyroclastic eruption modified journal abstract

apatite u th he thermochronometry using a radiation damage accumulation and annealing model helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal a quantity that varies over the lifetime of the apatite using recently published laboratory data we develop and investigate a new kinetic model the radiation damage accumulation and annealing model rdaam that adopts the effective fission track density as a proxy for accumulated radiation damage this proxy incorporates creation of crystal damage proportional to production from u and th decay and the elimination of that damage governed by the kinetics of fission track annealing the rdaam is a version of the helium trapping model hetm shuster d l flowers r m and farley k a 2006 the influence of natural radiation damage on helium diffusion kinetics in apatite earth planet sci lett 249 148 161 calibrated by helium diffusion data in natural and partially annealed apatites the chief limitation of the hetm now addressed by rdaam is its use of he concentration as the radiation damage proxy for circumstances in which radiation damage and he are not accumulated and lost proportionately from the crystal by incorporating the rdaam into the hefty computer program we explore its implications for apatite u th he thermochronometry we show how u th he dates predicted from the model are sensitive to both effective u concentration eu and details of the temperature history the rdaam predicts an effective he closure temperature of 62 c for a 28 ppm eu apatite of 60 m radius that experienced a 10 c ma monotonic cooling rate this is 8 c lower than the 70 c effective closure temperature predicted using commonly assumed durango diffusion kinetics use of the rdaam is most important for accurate interpretation of u th he data for apatite suites that experienced moderate to slow monotonic cooling 1 0 1 c ma prolonged residence in the helium partial retention zone or a duration at temperatures appropriate for radiation damage accumulation followed by reheating and partial helium loss under common circumstances the rdaam predicts u th he dates that are older sometimes much older than corresponding fission track dates nonlinear positive correlations between apatite u th he date and eu in apatites subjected to the same temperature history are a diagnostic signature of the rdaam for many but not all thermal histories observed date eu correlations in four different localities can be explained with the rdaam using geologically reasonable thermal histories consistent with independent fission track datasets the existence of date eu correlations not only supports a radiation damage based kinetic model but can significantly limit the range of acceptable time temperature paths that account for the data in contrast these datasets are inexplicable using the durango diffusion model the rdaam helps reconcile enigmatic data in which apatite u th he dates are older than expected using the durango model when compared with thermal histories based on apatite fission track data or other geological constraints it also has the potential to explain at least some cases in which u th he dates are actually older than the corresponding fission track dates

effect of alpine glaciation on thermochronometer age elevation profiles 1 low temperature thermochronometers are widely used to quantify exhumation histories typically by interpreting sample cooling age elevation relationships however the effects of specific geomorphic processes on age elevation profiles are seldom considered we integrate apatite u th he ahe apatite fission track and zircon u th he thermochronometry with numerical modeling to determine the effect of glacial erosion on an age elevation profile from the heavily glaciated southern coast mountains british columbia ahe data show a distinct break in slope in ageelevation between 1900 2100 m we interpret this break in slope as an acceleration of erosion associated with the onset ofalpineglaciation weusea3 dthermo kinematic modelto constrain pre and synglacial erosion rates results indicate a preglacial erosion rate of 0 4 mm yr that accelerated by a factor of 2 since 6 ma we propose that glacial valley widening and deepening are responsible for the observed nonlinear ahe age elevation profile citation densmore m s t a ehlers and g j woodsworth 2007 effect of alpine glaciation on thermochronometer age elevation profiles geophys res lett 34 l02502 doi 10 1029 2006gl028371

cenozoic thermal evolution of the central sierra nevada california from uth he thermochronometry apatite u th he cooling ages are reported for igneous apatite samples from the central sierra nevada and compared to published apatite fission track ages and track length data from the same mineral separates helium ages are youngest at low elevations and increase systematically toward higher elevations ranging from 43 to 84 ma at yosemite valley 32 to 74 ma at kings river canyon and 23 to 75 ma at mt whitney helium ages from high elevation samples are generally concordant with corresponding fission track ages while lower elevation helium ages are substantially younger cooling histories inferred from present laboratory derived fission track annealing and helium diffusion models do not match well suggesting that either helium diffusion rates or fission track annealing rates are miscalibrated at temperatures below about 60 c for geologic exposure periods unlike the fission track results the helium data do not indicate a very low geothermal gradient in the sierra nevada during early to middle tertiary time

estimating exhumation rate and relief evolution by spectral analysis of age elevation datasets extracting independent information on mean exhumation rate and the rate of surface relief change from thermochronometric datasets is essential to improve our understanding of the complex coupling between tectonics and surface erosion i e the time scale over which landforms react to changes in uplift rate and or climate a new method based on spectral analysis of age elevation data collected along one dimensional profiles is presented that provides independent estimates of the mean exhumation rate and the relative change in surface relief the results are shown to be independent of the assumed geothermal gradient the method is applied to an existing age dataset from the sierra nevada california and provides constraints on the evolution of the present day relief the spectral analysis demonstrates how current sampling strategies should be modified to optimize the tectonic and geomorphic information that can be retrieved from a thermochronometric dataset

constraining erosion rates in thrust belts insights from kinematic modeling of the argentine precordillera jachal section abstract kinematic restorations in fold and thrust belts which are a valuable tool for studying the deformational history of fold and thrust belts have been poorly used to understand erosion rates in this contribution we estimated the amount of eroded material in thrust belts via kinematic reconstructions we combined kinematic restitutions with the classic critically tapered coulomb wedge model following the assumption that at times when thrusting is triggered the surface slope was less than the angle required to reach self similar growth i e critical following conservative geometrical considerations we were able to compute a time varying coulomb wedge such unsteady wedge is used to calculate first order time dependent erosion rates which are compared to denudation and provenance results derived from other techniques we applied our model to the argentine precordillera at the jachal river section whose extensively studied outcrop data have let establish a well constrained episodic deformation of the thrust belt even though no kinematic model of the area had been presented so far our results show two contrasting erosion rates one prior to the movement along the last in sequence fault niquivil and one after 0 1 and 1 34 km myr respectively our findings indicate that the amount of eroded material might not always be directly proportional to cumulative slip in the thrust system as slip along niquivil thrust is only 22 of the total horizontal displacement though it produced most of the uplift and erosion our results are in striking accordance to long term erosion estimation proxies like u th he 10be and sedimentological studies which highlights the validity of the economical methodology herein proposed furthermore our kinematic model of the evolution of the argentine precordillera allows us to perform 2d flexural numerical modeling which suggests that tectonic loading seems to not be enough to reproduce basin geometry and that additional mechanisms such as dynamic subsidence or lithospheric mantle thickening among others would be required

the anthropogenic impact on mediterranean karst aquifers cases of some spanish aquifers mediterranean karstic aquifers are a major source of water supply for drinking water and agricultural use in semiarid areas the risk of causing an intensive exploitation is high leading to degradation processes of water quality not only due to limited agricultural activities developed on the karstic rocks being generally poorly developed soils but to the presence of deep evaporates which can be mobilised or because of being coastal aquifers where seawater intrusion can progress rapidly moreover karstic massifs constitute often positive reliefs that can generate barriers for civil works more and more saved by building sophisticated tunnels such works can affect the quantity and quality of the waters from the karst five examples of human impacts on some karst aquifers in se of spain are shown in this paper three of them with impacts on water quality and the other two correspond to the impact of tunnels in high speed trains drilling below the water table

quantitative constraints on the rate of landform evolution derived from low temperature thermochronology in recent years the nature of the complex interactions between the solid earth and the overlying atmosphere has been the subject of much debate england and molnar 1990 whipple et al 1999 braun et al 1999 does erosion play an important role in the dynamics of mountain building is there a strong feedback into the balance of forces at the crustal scale from mass transport by erosional and depositional processes at the earth s surface or does erosion passively react to changes in the earth s surface topography to shape mountains with tectonic forces originating in the underlying convecting mantle dominating the dynamics of plate interactions and crustal deformation at convergent plate margins the answers to these fundamental questions lie in our ability to determine the rate at which surface processes can react to tectonic forcing whipple et al 1999 where erosion is efficient the coupling will be strong as the rate of change of surface loading by mass transport will be similar to the rate of creation of topography by crustal deformation this may lead to a concentration of deformation and thus exhumation in regions of intense erosion koons 1990 willett et al 1993 beaumont et al 2001 koons et al 2002 2003 braun and pauselli 2004 where erosion is relatively inefficient mountain building is the result of a balance between internal driving forces and those originating from the deflection of an upper free surface there is no feedback from erosional processes low temperature thermochronology such as u th he he or fission track ft dating in apatite and zircon provides information on the rate at which rocks cool as they are exhumed towards the cold earth surface duddy et al 1988 warnock et al 1997 farley 2000 reiners and farley 1999 because the

rock uplift and erosion rate history of the bergell intrusion from the inversion of low temperature thermochronometric data the bergell intrusion european alps was one of the first locations where thermochronometry was used to resolve changes in erosion rate yet relating these changes to variations in climate or in local tectonics remains challenging one approach that enables changes in erosion rate to be related to changes in climate or rock uplift rate is to utilize landscape evolution models as topographic response to these forcing parameters is unique furthermore low temperature thermochronometric systems have the potential to resolve topography through time and thus topographic response we present new u th he data for samples collected across 2 km of relief from the bergell the ages range from 2 to 16 ma and define an age elevation with an apparent exhumation rate of 0 1 km myr in order to infer erosion rates we use a thermokinematic model to solve the heat equation in the crust track material points through time and predict thermochronometric data paleo topography and erosion rate are parameterized using the stream power model we find that rock uplift rates were 0 4 km myr from 25 to 20 ma and subsequently decreased to 0 05 km myr this results in a gradual decrease in erosion rate from rates of 0 4 to 0 1 km myr a recent increase in rock uplift rate at 4 ma to 0 6 km myr is required to explain the youngest ages and high topographic relief

constraints on the rate of post orogenic erosional decay from low temperature thermochronological data application to the dabie shan china we have investigated whether low temperature thermochronological datasets can be used to constrain the rate of surface evolution during the post orogenic phase of a mountain belt we use a numerical method to solve the heat transport equation in the earth s crust including the effects of a changing finite amplitude topography and the resulting flexural isostatic rebound we demonstrate that accurate estimates of the amount of relief loss can be obtained by applying a recently developed spectral method that is based on estimates of the relationship between age and surface elevation as a function of topographic wavelength we also show that the rate at which topography decays with time following cessation of tectonic activity can be constrained from estimates of exhumation rate derived from the slope of age elevation profiles collected across short wavelength topography using the neighbourhood algorithm to perform a thorough search through parameter space we are able to find a tectonomorphic scenario that predicts age distributions compatible with a thermochronological dataset collected in the dabie shan of eastern china by reiners et al american journal of science 2003 vol 303 pp 489 518 we demonstrate that in the dabie shan the mean topographic relief has decreased by a factor of 2 5 to 4 5 during the last 60 80 ma while the mountain belt experienced a mean exhumation rate of 0 01 to 0 04 km ma 1 we confirm the

linking slab break off hellenic trench retreat and uplift of the central and eastern anatolian plateaus abstract the central and eastern anatolian plateaus are integral parts of the world s third largest orogenic plateau in the past decade geophysical surveys have provided insights into the crust lithosphere and mantle beneath eastern anatolia these observations are now accompanied by recent surveys in central anatolia and new data constraining the timing and magnitude of uplift along its northern and southern margins together with predictions from geodynamic models on the effects of various processes on surface deformation and uplift the observations can be integrated to identify probable mechanisms of anatolian plateau growth a changeover from shortening to extension along the southern margin of central anatolia that is coeval with the start of uplift can be most easily associated with oceanic slab break off and tearing this interpretation is supported by tomography deep seismicity or lack thereof and gravity data based on the timing of uplift geophysical and geochemical observations and model predictions slab break off likely occurred first beneath eastern anatolia in middle to late miocene time and propagated westward toward cyprus by the latest miocene alternatively the break off near cyprus could have occurred in late pliocene to early pleistocene time in association with collision of the eratosthenes seamount continental fragment with the subduction zone uplift at the northern margin of central anatolia appears to result from crustal shortening starting in the late miocene or early pliocene which has been linked to the broad restraining bend of the north anatolian fault the uplift history of the interior of central anatolia since the late miocene is unclear although shortening there appears to have ended by the late miocene followed by ne sw extension this change in the deformation style broadly coincides with faster retreat of the hellenic trench as well as uplift of the northern and southern margins of central anatolia these different events throughout the plateau may be linked as faster retreat of the hellenic trench has been predicted to occur after slab break off which could have induced extension of central anatolia and helped to form the north anatolian fault through accelerated westward movement of anatolia relative to eurasia correlative geochronologic evidence that we summarize here supports the hypothesis that the geodynamic activity throughout the aegean anatolian domain starting in latest miocene to early pliocene time defines a series of events that may all be linked to slab break off

the topographic state of fluvially conditioned mountain ranges abstract the topography of mountain ranges reflects the competition of constructive and destructive processes driven by tectonics and climate respectively there is a vital debate whether the topography of individual orogens reflects stages of growth steady state or decay that is fueled by the million year time scales hampering direct observations on landscape evolution the superposition of various process patterns and the complex interactions among different processes hence there is a demand for sophisticated analysis tools to extract constraints on the long term evolution of orogens from their topography we review the field of orogen scale landscape evolution from a numerical perspective summarize the most prominent modelling concepts and their implications for the fluvially driven development of mountain topography and finally evaluate their applicability for understanding real world orogens following the concept of equilibrium a state where uplift rates are balanced by erosion rates and topography remains steady over time the erosional long term response of rivers and hillslopes can be mathematically formalised by the stream power and mass diffusion equations respectively based on a simple 1 dimensional model consisting of two rivers separated by a watershed we explain the influence of uplift rate and rock erodibility on steady state channel profiles and show the time dependent development of the channel drainage divide system dynamic drainage network reorganisation adds additional complexity and its effect on topography is explored on a two dimensional model river capture events and drainage divide migrations as expression of the ongoing drainage network reorganisation cause changes in topography until a stable network topology and hence full topographic steady state is achieved the long time spans needed for this drainage network optimization suggest that orogens on earth may never reach full topographic steady state in real world orogens we find evidence for premature mature and decaying topography as well as relief rejuvenation by analysing slope elevation distributions and trace the expression of crustal strain distorting drainage networks by applying the transform we conclude that modern concepts of landscape evolution allow sophisticated analyses of real world orogens but emphasize that unambiguous results are mostly derived from regions dominated by a limited number of interacting processes such as mountain ranges with limited or no glacial imprint this results in a high demand for techniques to disentangle the complex topography of real world orogens into the signals resulting from the individual land shaping processes

environmental and hydrogeological problems in karstic terrains crossed by tunnels a case study the construction of one of the high speed railway tunnels between malaga and cordoba south spain beneath the abdalajis mountains occasioned a series of hydrogeological problems with geotechnical and environmental impacts the double tunnel 7 300 m in length runs south to north across several lines of small calcareous mountains that have a highly complex structure beneath the jurassic limestones lie triassic clays and evaporites overlying the limestones is an essentially marly and limestone marl cretaceous series which culminates with miocene marls containing some organic matter these mountains have generated springs that are used for urban water supply and irrigation as well as drinking fountains in the surrounding villages the initial water level in the aquifer series varied from 400 to 650 m above sea level after drilling approximately 2 900 m and intercepting a fracture zone within the carbonate rocks a sudden water eruption occurred that reached a peak flow of 800 l s after a short while spring discharges dried up leading to a public protest in this paper we describe the geological and hydrogeological settings the development of the aquifer as the drilling operation proceeded the measures adopted and the responses subsequent to completion of the tunnel including the effect of rainfall on the recovery of water levels lastly a generalized estimate is made of how the system functions and a forecast is made for recovery of its equilibrium

relief history and denudation evolution of the northern tibet margin constraints from 40ar 39ar and u th he dating and implications for far field effect of rising plateau abstract how does the rising tibetan plateau affect its peripheral region the current understanding of the mechanism of orogenic plateau development is incomplete and thus no consensus yet exists in this regard however our new 40ar 39ar and u th he dataset presented in this study may shed some light on this issue 40ar 39ar dating on two vertical transects from the massif between nuomuhong and golmud indicates that the eastern kunlun range was built up and exhumated during the later triassic initially and a minimum overburden of 11 7 14 0 km has been eroded since 220 ma u th he age elevation relationships aers indicate a rapid exhumation event at 40 ma following a long period of slow exhumation phase from late mesozoic to early eocene time in this study two scenarios one assuming a single stage and the other assuming multiple stages of evolution history are modeled modeling of a multiple stage scenario is reasonable and is able to reflect the actual situation which reveals the entire denudation and relief history of the northern tibet from late mesozoic to the present time after prolonged denudation before 50 ma a low topography 0 17 times the relief of the present developed by 50 ma with an erosion rate of 0 013 0 013 0 025 mm yr the highest relief 1 82 times the relief of the present of the cenozoic time came into being at 40 ma with an erosion rate of 0 052 0 025 mm yr which was possibly a result of the collision between india and eurasia subsequently the relief steadily decreased to the present level due to continued denudation this suggests that deformation propagation from the continued convergence boundary between india and eurasia was insignificant after the construction of the highest relief this observation is broadly consistent with published accounts on the stratigraphic cooling and faulting histories of the northern tibet margin

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

inversion of thermochronological age elevation profiles to extract independent estimates of denudation and relief history i theory and conceptual model abstract we determine to what extent low temperature thermochronology data in particular from age elevation profiles provide independent and quantitative estimates on denudation rates and relief development thermochronological age elevation profiles have been widely used to infer exhumation histories however their interpretation has remained inherently one dimensional neglecting potential effects of lateral offsets between samples furthermore the potential effects of transient topography on crustal isotherms and consequently on thermochronological data have not yet been addressed in detail we investigate this problem with the aim of deriving independent estimates of both denudation rates and relief history from low temperature thermochronometers measuring the relative uncertainties on these parameters and finally constraining the timing of potential variations in denudation rate and or relief development we adopt a non linear inversion method combining the three dimensional thermal kinematic model pecube which predicts thermal histories and thermochronological ages from an input denudation and relief history with an inversion scheme based on the neighbourhood algorithm we use synthetic data predicted from imposed denudation and relief histories and quantitatively assess the resolution of thermochronological data collected along an age elevation profile our results show that apatite fission track aft ages alone do not provide sufficient quantitative information to independently constrain denudation and relief histories multiple thermochronometers apatite u th he ahe ages and or track length measurements combined with aft ages are generally successful in constraining denudation rates and timing of rate changes the optimum combination of thermochronometers varying with the input scenario relief change or varying denudation rates however relief changes can only be quantified and precisely constrained from thermochronological age elevation profiles if the rate of relief growth is at least 2 3 times higher than the background denudation rate this limited resolution is due to the depth of the closure isotherm between 70 and 110 c for the aft and ahe systems which only partly record topographic change new thermochronometers such as 4 he 3 he or osl that are sensitive to lower temperatures may be the key for resolving this issue

asynchronous miocene pliocene exhumation of the central venezuelan andes constraining the uplift and exhumation history of the venezuelan andes is critical for understanding the complex geodynamic evolution of northern south america we present new apatite fission track aft data from the sierra nevada de merida in the central venezuelan andes and compare the results with previously published aft data for the sierra la culata el carmen block to the north the aft data are combined with three dimensional thermal modeling to constrain the exhumation and relief history of both blocks which show significant differences the sierra nevada indicates exhumation rates of 1 7 km m y from ca 10 ma until 4 ma decreasing to 0 4 km m y from 4 ma to present the el carmen block in contrast underwent much more rapid recent exhumation with rates of 1 4 km m y since 4 ma the data suggest 4 km of relative rock uplift of the sierra la culata with respect to the sierra nevada since 4 ma and support significant uplift of basement blocks along major preexisting discontinuities during transpression in the northern andes linked to accretion of the panama arc and indentation of the maracaibo block rapid middle late miocene exhumation in the sierra nevada resulted from surface uplift that caused the late miocene deflection of the orinoco river inferred from the neogene sedimentary record

the influence of natural radiation damage on helium diffusion kinetics in apatite abstract stepwise degassing diffusion experiments on 39 different apatite samples using radiogenic 4he and proton induced 3he reveal a range in closure temperature tc from 50 to 115 c for a cooling rate of 10 c myr there is no correlation between helium diffusion and apatite chemistry including f cl ratio but the closure temperature is positively correlated with the radiogenic 4he concentration 4he in each sample we argue that 4he is a proxy for a sample s natural exposure to actinide radioactivity below the closure temperature and that helium diffusion in apatite is impeded by radiation induced damage to the apatite structure the kinetics must therefore be an evolving function of time measured diffusivities thus reflect a snapshot in time and cannot alone be applied to the thermochronometric interpretation of a given sample the effect of radiation damage on helium diffusion appears to far exceed other known controls on helium diffusivity including grain size our diffusion data are well described by a previously proposed quantitative model that consists of two arrhenius relations one for volume diffusion through undamaged mineral structure and one for release of helium from radiation damage traps the unknown parameters in this trapping model were determined from the diffusion experiments and allow us to develop a tentative mathematical function that relates diffusivity to temperature and 4he by inserting this function into a 4he production diffusion model we have explored how these results affect the interpretation of apatite u th he thermochronometry the model predicts that the effective 4he closure temperature of apatite will vary with cooling rate and effective u concentration eu and may differ from the commonly assumed tc of 70 c by up to 15 c the 4he partial retention zone will look similar to previous expectations but its depth will depend on accumulation time and on eu most notably samples subjected to reheating after accumulation of substantial radiation damage will be more retentive than previously expected these predictions are consistent with recent observations of unexpected apatite u th he ages in some settings

evaluating balanced section restoration with thermochronology data a case study from the central pyrenees we present a new method that can be used to quantitatively evaluate the consistency between balanced section restorations and thermochronological data sets from orogenic belts we have applied our method to a crustal scale area balanced cross section restoration along a profile in the central pyrenees this restoration is well constrained and supported by a wide variety of geological and geophysical data moreover an extensive thermochronological data set has been collected independently in the area we use the structural kinematic software 2d move to constrain a set of velocity fields that describes the kinematics of the central pyrenees using these velocity fields as input for the thermokinematic code pecube we derive predictions of the thermal history and a range of thermochronometric ages for the modeled area we find that the kinematic history of the belt as inferred from section balancing is in good agreement with the published thermochronological data high temperature zircon fission track and k feldspar ar ar data constrain the thermal structure of the belt as well as the timing of underplating low temperature apatite fission track and u th he data require late synorogenic sedimentary burial of the southern flank of the pyrenees between late eocene 40 ma to late miocene 9 ma times consistent with previous studies and imply that no such burial occurred on the northern flank

variable late neogene exhumation of the central european alps low temperature thermochronology from the aar massif switzerland and the lepontine dome italy 1 several recent studies proposed an important increase in exhumation rate in the western european alps since circa 5 4 ma in order to assess potential spatial differences in exhumation histories we present new apatite fission track aft and apatite u th he ahe ages from the central aar massif guttannen area switzerland and the western lepontine dome formazza area italy internal u th zoning in apatites explains alpha ejection corrected ahe ages that are older than the corresponding aft ages in this study a qualitative interpretation of aft and ahe age elevation relationships suggests a two phase 9 7 and 5 3 ma exhumation scenario affecting the central alps with a stronger expression of the pliocene signal in the formazza area however a quantitative evaluation of exhumation scenarios using the 3 d heat equation solver pecube highlights the existence of several other likely scenarios casting doubt on the validity of a qualitative interpretation of the age elevation relationships in formazza scenarios suggested by quantitative modeling include continuous denudation at a rate of 750 m ma and a one step exhumation rate change from 300 to 1000 m ma at 5 ma in guttannen they include continuous denudation at a rate of 400 m ma with valley deepening and two periods of higher exhumation rate increasing from 300 to 700 m ma repeatedly at 9 7 and at 5 3 ma contingent upon further flexural isostatic modeling the magnitude of exhumation recorded in the axial region of the alps since circa 5 ma does not appear sufficient to solely explain the denudation recorded in the north alpine foreland basin

preservation of contrasting geothermal gradients across the caribbean north america plate boundary motagua fault guatemala 1 strike slip plate boundaries juxtapose crustal blocks that may have different geodynamic origins and therefore different thermal structures thermo kinematic modeling of this type of strike slip plate boundary predicts an asymmetric signature in the low temperature thermochronologic record across the fault age elevation profiles of zircon u th he ages across the motagua fault a 500 km long segment of the transform boundary between the north american and caribbean plates document a sharp cooling age discontinuity across the fault this discontinuity could be interpreted as a difference in denudation history on each side of the fault however a low relief miocene erosional surface extends across the fault this surface has been uplifted and incised and provides a geomorphic argument against differential denudation across the fault by integrating magmatic volcanic and heat flow data age elevation profiles and thermo kinematic modeling we propose that large horizontal displacement along the motagua fault has offset a persistent geothermal asymmetry across the fault and explains both the age discontinuities and the age elevation patterns this study illustrates how thermochronology can be used to detect large strike slip displacements and more generally opens new perspectives in understanding the impact of nonuniform thermal structures on thermochronologic results

role of topography in isotherm perturbation apatite u th he and fission track results from the malta tunnel tauern window austria 1 apatite u th he and fission track age determinations of samples from a 20 km long near horizontal tunnel in the hochalm ankogel dome eastern tauern window austria are presented in order to determine the role of paleo topography in perturbing isotherms in the shallow crust apatite fission track ages 26 8 ma show no systematic correlation with distance along the tunnel or elevation two age components in the fission track data indicate cooling through 120 c at approximately 20 ma and 80 c at approximately 6 ma surface and tunnel u th he ages 17 9 ma and 13 5 ma respectively are consistently younger than the equivalent fission track ages u th he ages vary systematically along the tunnel with older ages at the northern and southern tunnel portals and younger ages in the central section geological factors faulting lithology appear to have had little effect on this age distribution the u th he age pattern is inconsistent with rock cooling underneath the present day hochalm ankogel dome topography the age minimum is interpreted to coincide with a paleotopographic maximum in the hochalm ankogel dome and suggests that the 40 60 c isotherms were warped sufficiently to affect apatite u th he ages the tunnel apatite u th he ages match synthetic he ages derived from a two dimensional numerical model of landscape evolution integrating the thermal model results with the data allows the relief development to be constrained and we calculate that the present day hochalm ankogel dome topography was formed at 7 to 10 ma

paleo geomorphology of the sierra nevada california from u th he ages in apatite new apatite u th he ages from the central sierra nevada california place limits on the morphology and evolution of longitudinal profiles of major transverse river drainages developed in the late cretaceous helium ages from a new orogen parallel constant elevation sample transect are relatively uniform 60 ma and not correlated with topography unlike those from a similar lower elevation transect approx 15 km to the west we interpret the marked difference in the two orogen parallel profiles to reflect a headward decrease in long wavelength transverse relief at the time of cooling consistent with either a concave up stream gradient typical of those observed near the headwaters of modern sierran trunk streams or a convex gradient like those found along slope breaks of eroding plateau edges from the san joaquin drainage we obtained a new helium age versus elevation profile which has a comparable slope to those previously reported for the yosemite valley kings canyon and mt whitney areas this new profile yields slightly older ages at a given elevation as expected from its position adjacent to the largest major drainage the age versus elevation profiles imply that the mean denudation rate of the region in the cenozoic was about 0 04 to 0 05 mm yr we show that long wavelength 70 km relief inferred from longitudinal helium age variations is a strong function of erosion rate such that even relatively subdued relief is detectable with helium age profiling provided that denudation rates were low using the rate implied by sierran age versus elevation profiles we infer long wavelength relief of 1500 500 m in the late cretaceous by analogy with modern orogenic plateaus this value of long wavelength relief suggests a cretaceous interior cordilleran plateau lay at an elevation of at least 3000 m

natural age dispersion arising from the analysis of broken crystals part ii practical application to apatite u th he thermochronometry abstract we describe a new numerical inversion approach to deriving thermal history information from a range of naturally dispersed single grain apatite u th he ages the approach explicitly exploits the information about the shape of the 4he diffusion profile within individual grains that is inherent in the pattern of dispersion that arises from the common and routine practice of analysing broken crystals additional dispersion arising from differences in grain size and in u and th concentration of grains and the resultant changes to helium diffusivity caused by differential accumulation and annealing of radiation damage is explicitly included in this approach we calculate the ingrowth and loss due to both thermal diffusion and the effects of ejection of helium over time using a finite cylinder geometry broken grains are treated explicitly as fragments of an initially larger crystal the initial grain lengths l0 can be treated as unknown parameters to be estimated although this is computationally demanding a practical solution to the problem of solving for the unknown initial grain lengths is to simply apply a constant and sufficiently long l0 value to each fragment we found that a good value for l0 was given by the maximum fragment length plus two times the maximum radius of a given set of fragments currently whole crystals and fragments with one termination are taken into account a set of numerical experiments using synthetic fragment ages generated for increasingly complex thermal histories and including realistic amounts of random noise 5 15 are presented and show that useful thermal history information can be extracted from datasets showing very large dispersion these include experiments where dispersion arises only from fragmentation of a single grain length 400 m and radius 75 m c 6 50 dispersion including the effects of grain size variation for spherical equivalent grain radii between 74 and 122 m c 10 70 dispersion and the combined effects of fragmentation grain size and radiation damage for eu between 5 and 150 ppm c 10 107 dispersion additionally we show that if the spherical equivalent radius of a broken grain is used as a measure of the effective diffusion domain for thermal history inversions then this will likely lead to erroneous thermal histories being obtained in many cases the viability of the new technique is demonstrated for a real data set of 25 single grain u th he apatite ages obtained for a gabbro sample from the bk 1 bierkraal borehole drilled through the bushveld complex in south africa the inversion produces a well constrained thermal history consistent with both the u th he data and available fission track analysis data the advantage of the new approach is that it can explicitly accommodate all the details of conventional schemes such as the effects of temporally variable diffusivity zonation of u and th and arbitrary grain size variations and it works equally effectively for whole or broken crystals and for the most common situation where a mixture of both are analysed for the routine application of the apatite u th he thermochronometry technique with samples where whole apatite grains are rare our experiments indicate that 15 20 single grain analyses are typically required to characterise the age dispersion pattern of a sample the experiments also suggest that picking very short crystal fragments as well as long fragments or even deliberately breaking long crystals to maximise the age dispersion in some cases would ensure the best constraints on the thermal history models the inversion strategy described in this paper is likely also directly applicable to other thermochronometers such as the apatite rutile and titanite u pb systems where the diffusion domain is approximated by the physical grain size