quaternary tectonic response to intensified glacial erosion in an orogenic wedge active orogens are thought to behave as internally deforming critical taper wedges that are in rough long term equilibrium with tectonic influx and erosional outflux spatial and temporal variations in climate are therefore hypothesized to have a significant influence on denudation topography and deformation of orogens thereby affecting wedge taper however the impact of the most severe transition in northern hemisphere climate during the cenozoic era the onset of glaciation has hitherto not been empirically documented here we analyse the spatial patterns of denudation and deformation and their temporal variations in the heavily glaciated st elias orogen in southern alaska low temperature thermochronometry thermokinematic modelling and offshore seismic reflection and borehole data suggest that the global scale intensification of glaciation in the middle pleistocene epoch enhanced glacier growth and caused ice streams to advance to the edge of the continental shelf this led to focused denudation across the subaerial reaches of the orogen and burial of the actively deforming wedge toe by the eroded sediment we propose that this climatically driven mass redistribution forced a structural reorganization of the orogen to maintain critical taper our empirical results thus support decades of numerical model predictions of orogenesis and provide compelling field evidence for the significant impact of climate change on tectonics intense glaciation during the middle pleistocene epoch led to focused denudation and mass redistribution within the st elias orogen in southern alaska and resulted in structural reorganization of the orogen the tectonic response of this orogen to climate change is consistent with predictions of numerical models

evidence for eocene oligocene glaciation in the landscape of the east greenland margin assessing the onset and extent of northern hemisphere glaciation is required to understand cenozoic climate change and its impact on topography while the onset of accelerated cenozoic erosion is generally associated with the quaternary at mid latitudes some high latitude passive margins may have undergone earlier glaciation starting at 38 30 ma or even 45 ma here we document a rapid phase of exhumation in the east greenland margin between 68 n and 76 n starting at 30 5 ma the timing is coincident with the dramatic worldwide fall of surface temperature at the eocene oligocene transition our inference is based on apatite fission track and apatite helium data we suggest that a transition from an eocene fluvial to an oligocene glacial dominated landscape triggered a period of enhanced erosion this study provides the first onshore potential evidence of the onset of continental ice in east greenland margin at the eocene oligocene transition ca 34 ma contemporaneously with the onset of antarctica glaciation and erosion our interpretation is consistent with that based on the oldest ice rafted debris found in the sedimentary records offshore east greenland and implies that east greenland exhibits the oldest onshore record of cenozoic glacial erosion on earth

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

simple model for the recirculation velocity of open channel embayments abstracta simple theoretical model is presented in order to predict the recirculation velocity in river embayments also commonly referred to as eddies gyres cavities and dead zones this velocity is important as it sets the fundamental timescale of the motion in these ecologically important regions using only an equilibrium torque balance basic geometrical properties and resistance characteristics the eddy velocity is determined as a percentage of the freestream velocity the model is restricted to the single gyre case placing modest limits on the embayment aspect ratio the result compares favorably with recent experimental computational and field studies of river embayments

geomorphically driven late cenozoic rock uplift in the sierra nevada california geologists have long accepted that the sierra nevada california experienced significant late cenozoic tectonically induced uplift a flexural isostatic model presented here shows however that a large fraction of the primary evidence for uplift could be generated by the lithospheric response to coupled erosion of the sierra nevada and deposition in the adjacent central valley and therefore requires less tectonic forcing than previously believed the sum of range wide erosion and the resultant isostatic rock uplift would have lowered sierra mean elevation by 200 to 1000 meters since 10 million years ago and could also have increased summit elevations during the current period of relief production

quaternary environmental evolution in the south carpathians reconstructed from glaciokarst geomorphology and sedimentary archives abstract the carpathian island type glaciokarst has a great potential of preserving signals of past environments archived in cave deposits like speleothems and clastic infills we present here the geomorphology and structural control of several relict alpine caves and the surrounding glaciated marble karst in the f g ra mountains four truncated and partially unroofed caves remained on the ridge top of mu eteica mountain above the glacial cirque while a ponor cave that developed on the cirque bottom could be related to the last glacial period structural measurements and cave morphology showed that the conduits formed at the intersection of foliation planes and tectonic fractures on the ne sw and nw se directions cave development reflects three speleogenetic stages 1 texture and fabric controlled dissolution and distension 2 structurally controlled breakdown and 3 truncation unroofing and cave infilling with sediments slow diffuse dissolution was typical for the ridge top caves whereas m1 cave developed by pressure flow further we report the first u th speleothem ages related to the evolution of alpine caves and island glaciokarst in the south carpathians during the middle and late pleistocene dating results show a minimum estimated age of 560 ka for the ridge top caves and that speleothem deposition met optimal conditions only during warmer periods largely corresponding to interglacials stable carbon isotope values in speleothems range between 9 96 and 4 11 indicating the presence of plant and soil organic activity at the time of deposition in total five speleothem growth phases were distinguished during the last 560 ka we excavated the sediment infill of a ridge top doline down to a 2 m depth radiocarbon dating revealed that it was deposited during the late holocene and preliminary pollen analysis identified a plant assemblage dominated by grasses using the relationships between karst development glaciation and cave sedimentary archives we present a time slice chronology of alpine landscape evolution at 560 ka 400 ka 330 ka the last glacial period 70 12 ka and the late holocene our geomorphological isotopic and geochronological results also support the existing hypothesis that the south carpathians may have experienced at least two glacial phases during the pleistocene glacial erosion rate during the last glacial period and most likely during the penultimate glaciation averages around 0 6 mm yr 1

review of erosion dynamics along the major n s climatic gradient in chile and perspectives abstract chile is an elongated country running in a north south direction for more than 30 along a subduction zone its climate is progressively wetter and colder from north to south this particular geography has been used positively by a growing number of studies to better understand the relationships between erosion processes and climate land use slope tectonics volcanism etc here we review the erosion rates factors and dynamics over millennial to daily periods reported in the literature in addition 21 new catchment mean erosion rates suspended sediment and 10be are provided and previous suspended sediment derived erosion rates are updated a total of 485 local and catchment mean erosion rates are reported erosion rates vary between some of the smallest values on earth 10 5 mm a to moderate values 0 5 mm a compared to other active ranges this review highlights strong limitations concerning the quantification of local erosion factors because of uncertainties in sampling point location slope and rainfall data for the mean erosion rates e for the millennial and decennial catchments a model of the form e s 1 s 0 6 2 r with 0 3 0 8 accounts for 40 to 70 of the erosion variance confirming a primary role of slope s compared to precipitation rate r over this time scale over the long term this review points to the long 5 to 10 ma response time of rivers to surface uplift in north central arid chile over millennia data provide evidence for the progressive contribution of extreme erosion events to millennial averages for drier climates as well as the link between glacier erosion and glacier sliding velocity in this period of time a discrepancy exists between the long term offshore sedimentological record and continental decennial or millennial erosion data for which no single explanation appears still little information is available concerning the magnitude of variation of millennial erosion rates over centuries data show the variable role of groundwater in the dynamics of suspended load and document a decrease in erosion over hundreds of years probably associated with historical harvesting

valley formation by fluvial and glacial erosion cross valley profiles from the west slope of the olympic peninsula washington are used to investigate the relative effects of fluvial and glacial erosion on valley formation unlike most ranges where glaciers and rivers sequentially occupied the same valleys neighboring valleys in the olympic mountains developed in similar lithologies but were subject to different degrees of glaciation allowing comparison of the net effect of glacial and fluvial processes integrated over many glacial cycles upslope drainage area was used to normalize comparisons of valley width ridge crest to valley bottom relief and valley cross sectional area as measures of net differences in the mass of rock excavated from below ridgelines for 131 valley spanning transects valley width relief and cross sectional areas are similar for glaciated partly glaciated and unglaciated fluvial valleys with drainage areas of 10 km 2 but diverge downslope glaciated valleys draining 50 km 2 reach two to four times the cross sectional area and have to 500 m greater relief than comparable fluvial valleys partly glaciated valleys have intermediate dimensions at distances of 5 km from valley heads the cumulative upstream volume of rock removed to form valleys is two to four times greater in glacially incised valleys than in fluvial valleys the finding of strong differences in the net result of valley excavation by fluvial and glacial erosion supports the interpretation that alpine glaciers are more effective erosional agents than are rivers and implies that large alpine valleys deepened and enlarged in response to pleistocene glaciation

unravelling the moisture sources of the alpine glaciers using tunnel valleys as constraints a lack of archives has impeded reconstructions of moisture pathways for past glaciations in the european alps here we focus on the confluence area of two palaeoglaciers in the swiss plateau that were sourced on the northern aare glacier and southern sides valais glacier of the european alps we mapped tunnel valleys in the region using a drilling database based on which we inferred the relative extent of each glacier c 270 ka ago when the valleys were formed we then compared this situation with that of the lgm we found that while the valais glacier expanded farther into the foreland than the aare glacier during the lgm the opposite was the case c 270 ka ago we also found that lgm glaciers were non erosive in the distal foreland these contrasts in extents and erosional efficiencies imply differences in moisture pathways between the lgm and the time when the tunnel valleys were formed

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

response of glacial landscapes to spatial variations in rock uplift rate 1 the response of glaciated landscapes to rapid rock uplift driven by tectonic convergence is an important often neglected aspect of proposed interactions between plate tectonic processes and climate change rivers typically respond to more rapid rock uplift in part through increasing channel gradients in contrast the glacial buzzsaw hypothesis suggests that glaciers can erode as quickly as the fastest rock uplift rates 6 10 mm yr without any increase in mean elevations however it has not been established how this is achieved we examined moving window maps swath and longitudinal profiles hillslope relief and hypsometry for glacierized and formerly glacierized basins in areas of spatially variable rock uplift rate in the southern alps new zealand and around nanga parbat pakistan to determine whether glaciers have a specific response to rapid rock uplift the response of these glaciated landscapes to rapid rock uplift 6 10 mm yr comprises 1 modest steepening of the longitudinal profiles in smaller glaciated basins 2 maintenance of shallow downvalley slopes in larger glaciated basins 30 km2 southern alps 100 km2 nanga parbat 3 development of tall headwalls and 4 steepening of the basin as a whole dominated by hillslope lengthening around nanga parbat headwalls several kilometers high constitute 50 of the basin relief at rapid rock uplift rates although glaciers can incise the valley floor swiftly they cannot prevent headwalls from reaching exceptional heights the associated increase in mean distance between cirque heads i e a decrease in drainage density causes regional mean elevation to rise with increasing rock uplift rate however this is much less than the changes in elevation expected in unglaciated ranges

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

linking late pleistocene alpine glacial erosion and continental margin sedimentation insights from 40ar 39ar dating of silt sized sediment canterbury basin new zealand abstract quaternary climatic and eustatic cycles in mid latitude regions have led to more extensive alpine glaciations and continental shelf progradation respectively however the glacial influence on sediment fluxes to the ocean creating continental margin strata is poorly documented this contribution analyzes the provenance of fine sediment accumulating on the continental shelf during the late pleistocene to evaluate the influence of glacial cycles on sediment erosion and routing to the continental shelf taking advantage of the contrasting bedrock ages exposed across the southern alps new zealand we perform 40 ar 39 ar incremental heating on the bulk silt size sediment from three drill sites of iodp expedition 317 canterbury basin new zealand the results suggest that a large proportion of sediment accumulating on the continental shelf results from erosion within the main divide fault zone of the southern alps sediment 40 ar 39 ar age fluctuations over this time period suggest that bedrock with various 40 ar 39 ar cooling ages has been differentially eroded in the upper waitaki river catchment and mixed in the waitaki canterbury sediment routing system across shelf variations in sediment 40 ar 39 ar age reflect changing modes of sediment dispersal on the continental shelf fluvial material likely derived from the main drainage divide zone preferentially accumulates in the middle continental shelf whereas material representing erosion of older bedrock torlesse terrane located lower in the drainage basin is dispersed uniformly across the shelf the age signature of the muddy sediment accumulating on the continental shelf reflects late pleistocene landscape evolution of the southern alps and its influence on sediment dispersal to the continental shelf

the quaternary glaciations of switzerland with special reference to the northern alpine foreland summary 1 the quaternary glaciations of the swiss alpine foreland comprise at least five major glacial advances beyond the northern border of the alps within the time span of the classical chronology of the alps however only two full interglacials are known hitherto between the glacigenic accumulations this paucity of inter glacial records and the lack of radiometric dates causes problems in correlation of the swiss glacial sequence with neighbouring areas or with the deep sea oxygen isotope record 2 the thalgut section to the south of berne is the most complete lithogenetic quaternary succession available the discovery of pterocarya beanng inter glacial deposits there is of regional importance hoistein interglacial sensu welten this discovery implies that the most intensive erosion of the perialpine valleys must have taken place before the riss glaciation of the classical chronology this observation and the absence of glacigenic deposits at meikirch and niederweningen question the traditionally held view that the penultimate glaciation riss was the most extensive glaciation of the swiss alps the big event antedates the holstein interglacial sensu welten 3 during the early stages of the second before last glaciation mindel or even before that event a change in the morphogenetic behaviour of the swiss plain occurred predominant erosion of the main valleys is followed after that time by predominant accumulation of glacigenic glacilacustrine and fluvial and lacustrine sediments this morphodynamic change is most probably related to crustal movements because a change in fluvial or glacial dynamics alone cannot explain this evolution 4 traces of glaciations in the alpine foreland which antedate the fundamental morphogenetic change and the time period of the classical four glaciations are recorded in the cover gravels of ne switzerland and in the wanderblockformation of the northern tabular jura mountains but these events may be pre quaternary in age 5 a schematic chronology of the glaciations recorded in the quaternary sediments of the swiss alpine foreland is given in fig 6

nature of flow and turbulence structure around an in stream vertical plate in a shallow channel and the implications for sediment erosion 1 detailed knowledge of the dynamics of large scale turbulence structures is needed to understand the geomorphodynamic processes around in stream obstacles present in rivers detached eddy simulation is used to study the flow past a high aspect ratio rectangular cylinder plate mounted on a flat bed relatively shallow channel at a channel reynolds number of 2 4 105 similar to other flows past surface mounted bluff bodies the large amplification of the turbulence inside the horseshoe vortex system is because the core of the main necklace vortex is subject to large scale bimodal oscillations the presence of a sharp edge at the flanks of the obstruction fixes the position of the flow separation at all depths and induces the formation and shedding of very strong wake rollers over the whole channel depth compared with the case of a circular cylinder where the intensity of the rollers decays significantly in the near bed region because the incoming flow velocity is not sufficient to force the wake to transition from subcritical to supercritical regime in the case of a high aspect ratio rectangular cylinder the passage of the rollers was found to induce high bed shear stresses at large distances 6 8 d behind the obstruction also the nondimensional values of the pressure root mean square fluctuations at the bed were found to be about 1 order of magnitude higher than the ones predicted for circular cylinders overall this shows that the shape of the in stream obstruction can greatly modify the dynamics of the large scale coherent structures the nature of their interactions and ultimately their capability to entrain and transport sediment particles and the speed at which the scour process evolves during its initial stages

three dimensional numerical model for flow through natural rivers this paper presents a three dimensional numerical model for simulating flow through natural river reaches the model solves the reynolds averaged navier stokes rans equations closed with the standard ik e turbulence model large scale roughness and multiple islands are directly resolved by employing boundary fitted curvilinear coordinates in conjunction with a multiblock approach small scale bed roughness is accounted for using a two point wall functions approach calculations are carried out for flow through a 4 km stretch of the columbia river downstream of the wanapum dam for which detailed field and laboratory measurements were collected for a range of power plant operating conditions measurements at one operating discharge are employed to calibrate the small scale roughness distribution in the numerical model subsequently the calibrated model is validated by comparing the computed results with laboratory and field measurements for other discharge combinations these comparisons demonstrate the ability of the model to capture most experimental trends with remarkable accuracy

an investigation of the flow and scour mechanisms around isolated spur dikes in a shallow open channel 1 conditions corresponding to the initiation of the erosion and deposition process 1 the present study investigates the flow physics and the role played by the main coherent structures in the scouring processes around a vertical spur dike in a straight channel at conditions corresponding to the start flat bed of the scouring process large eddy simulation les is performed at a relatively low channel reynolds number re 18 000 in the range where most flume studies with clear water scour conditions are conducted similar to these studies the incoming flow is fully turbulent and contains realistic turbulence fluctuations visualization experiments are conducted to better understand the nature of the interactions between the dominant coherent structures playing a role in the erosion process it is found that the structure of the horseshoe vortex hv system at the base of the spur dike changes considerably in time and in vertical sections perpendicular to the trajectory defined by the axis of the main necklace vortex however its intensity is the largest at vertical sections situated around the tip of the spur dike it is in this region that the core of the main necklace vortex oscillates aperiodically between two preferred modes in one of them zero flow mode the necklace vortex is closer to the spur dike and more compact and the near bed jet flow beneath it is weak in the other one back flow mode a strong near bed jet flow convects the primary necklace vortex away from the spur dike and its core is more elongated and less compact this explains the large amplification by about 1 order of magnitude compared to the surrounding turbulent flow of the turbulent kinetic energy and pressure fluctuations inside the hv system in the region situated around the tip of the spur dike and the double peak distribution of the turbulent kinetic energy past the spur dike in the legs of the necklace vortex the intensity of the bimodal oscillations decreases such that they are not observed in spanwise sections situated at more than one channel depth behind the spur dike it is found that the legs of the horseshoe vortices can interact at times with the vortex tubes shed in the detached shear layer dsl and with the tip of the spur dike these events typically result in a significant change in the coherence of the hv system the largest bed shear stress values in the mean flow are present in the strong acceleration region near the tip of the spur dike but high bed shear stress values are also observed beneath the upstream part of the dsl the bed shear stress fluctuations around the local mean values can be very high especially in the region situated beneath the upstream part of the dsl at random times some of the vortices shed in the dsl merge or interact with eddies from the recirculation region this leads to an increase in their strength and to a large increase of the bed shear stress along their path

incised relict landscapes in the eastern alps abstract we investigate landscape evolution in a region of the alps that has escaped glacial erosion during periodic glaciations of the last million years the research is thus suited to investigate landscaping processes on a longer time scale at the eastern end of the alps morphometric analysis reveals the presence of incised relict landscapes in several regions in the koralpe range topographic analysis is interpreted in terms of the relict landscape being present on both sides of the eastward tilted koralpe block this suggests that the relict landscape is younger than the tilting of the range which is inferred to have taken place between 18 and 16 ma in the pohorje region a relict landscape is developed across the contacts of a 19 ma pluton we use apatite u th he thermochronology to constrain the possible age of the koralpe and pohorje relict landscapes the results indicate that the pohorje massif had cooled below 70 c by about 15 ma suggesting that the relict landscape must be younger consistent with the interpretation of the koralpe range these results suggest that many relict landscapes of the eastern alps may have formed after 15 ma in a period of tectonic quiescence and erosion however in both ranges channel profile projections show that about 387 105 m uplift and incision occurred subsequently this incision is likely to have occurred during the last 6 5 ma in response to the uplift of the whole region it testifies to a renewed and ongoing uplift event that is earlier than the glaciation periods but might easily be confused with impact of glacial erosion elsewhere in the eastern alps

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

glacial steady state topography controlled by the coupled influence of tectonics and climate glaciers and rivers are the main agents of mountain erosion while in the fluvial realm empirical relationships and their mathematical description such as the stream power law improved the understanding of fundamental controls on landscape evolution simple constraints on glacial topography and governing scaling relations are widely lacking we present a steady state solution for longitudinal profiles along eroding glaciers in a coupled system that includes tectonics and climate we combined the shallow ice approximation and a glacial erosion rule to calculate ice surface and bed topography from prescribed glacier mass balance gradient and rock uplift rate our approach is inspired by the classic application of the stream power law for describing a fluvial steady state but with the striking difference that in the glacial realm glacier mass balance is added as an altitude dependent variable from our analyses we find that ice surface slope and glacial relief scale with uplift rate with scaling exponents indicating that glacial relief is less sensitive to uplift rate than relief in most fluvial landscapes basic scaling relations controlled by either basal sliding or internal deformation follow a power law with the exponent depending on the exponents for the glacial erosion rule and glen s flow law in a mixed scenario of sliding and deformation complicated scaling relations with variable exponents emerge furthermore a cutoff in glacier mass balance or cold ice in high elevations can lead to substantially larger scaling exponents which may provide an explanation for high relief in high latitudes

effects of groyne layout on the flow in groyne fields laboratory experiments this research is aimed at finding efficient alternative designs in the physical economical and ecological sense for the standard groynes as they are found in the large rivers of europe in order to test the effects of various groyne shapes on the flow in a groyne field experiments were performed in a physical model of a schematized river reach geometrically scaled 1 40 four different types of schematized groynes were tested all arranged in an array of five identical groyne fields i e standard reference groynes groynes with a head having a gentle slope and extending into the main channel permeable groynes consisting of pile rows and hybrid groynes consisting of a lowered impermeable groyne with a pile row on top flow velocities were measured using particle tracking velocimetry the design of the experiment was such that the cross sectional area blocked by the groyne was the same in all cases depending on the groyne head shape and the extent of submergence variations in the intensity of vortex shedding and recirculation in the groyne field were observed the experimental data are used to understand the physical processes like vortex formation and detachment near the groyne head it is demonstrated that the turbulence properties near and downstream of the groyne can be manipulated by changing the permeability and slope of the groyne head it is also observed that for submerged conditions the flow becomes complex and locally dominated by three dimensional effects which will make it difficult to predict by applying depth average numerical models or by three dimensional models with a coarse resolution in the vertical direction

a mean residence time relationship for lateral cavities in gravel bed rivers and streams incorporating streambed roughness and cavity shape 2 accurate estimates of mass exchange parameters in transient storage zones are needed to better understand and quantify solute transport and dispersion in riverine systems currently the predictive mean residence time relies on an empirical entrainment coefficient with a range in variance due to the absence of hydraulic and geomorphic quantities driving mass exchange two empirically derived relationships are presented for the mean residence time of lateral cavities a prevalent and widely recognized type of transient storage in gravel bed rivers and streams that incorporates hydraulic and geomorphic parameters the relationships are applicable for gravel bed rivers and streams with a range of cavity width to length w l aspect ratios 0 2 0 75 shape and reynolds numbers re ranging from 1 0 10 4 to 1 0 10 7 the relationships equate normalized mean residence time to nondimensional quantities froude number re w l depth ratio ratio of cavity to shear layer depth roughness factor ratio of shear to channel velocity and shape factor representing degree of cavity equidimensionality one relationship excludes bed roughness equation 13 and the other includes bed roughness equation 14 the empirically derived relationships have been verified for conservative tracers r 2 of 0 83 within a range of flow and geometry conditions topics warranting future research are testing the empirical relationship that includes the roughness factor using parameters measured in the vicinity of the cavity to reduce the variance in the correlation and further development of the relationship for nonconservative transport

a numerical investigation of coherent structures and mass exchange processes in channel flow with two lateral submerged groynes 1 large eddy simulation is used to investigate the dynamics of the main coherent structures present in the flow around two vertical submerged groynes situated in a long flatbed open channel the mass exchange processes between the embayment region and the main channel are investigated by studying the ejection of a contaminant introduced instantaneously inside the embayment the instantaneous and mean structure of the horseshoe vortex system forming at the base of the upstream groyne and the bed shear distributions that determine the evolution of the scour in the groyne region are investigated it is found that the amplification of the bed shear stress in the accelerating region around the tip of the upstream groyne is around one order of magnitude larger relative to the mean bed shear stress in the incoming flow analysis of the instantaneous flow fields shows that the eddies that are shed inside the horizontal and vertical detached shear layers play an important role in controlling the mass exchange at the lateral and roof interfaces it is found that most of the pollutant leaves the embayment through the roof and bottom lateral sections the overall mass exchange process is qualitatively different and substantially accelerated compared to the case when the groynes are emerged however it is shown that similar to the emerged case the decay of the mass of contaminant within the embayment cannot be characterized by a unique value of the exchange coefficient used in simple dead zone theory models

multi approach quantification of denudation rates in the gulf of lion source to sink system se france abstract during the pliocene and the quaternary the gulf of lion the northern passive margin of the liguro provencal basin in the western mediterranean sea received sediments from a 120 000 km 2 drainage area constituted by several structural domains the denudation of mountainous areas source of this sedimentary supply results from complex interactions between tectonics climate morphology and rock erodibility in this study denudation rates from the present day and ranging back to the quaternary and the pliocene are quantified using four independent methods allowing an investigation over different time scales 1 compilation of present day measured sediment fluxes 2 determination of catchment scale cosmogenic denudation rates through measurements of in situ produced 10 be concentrations in sands sampled at the outlet of present day rivers 3 estimation of eroded volumes within catchments using a dem to quantify long term averaged quaternary denudation rates and 4 quantification of sediment volumes deposited within the marine realm of the gulf of lion the results obtained by these four methods are in agreement within the range of uncertainties the internal part of the alps exhibits significantly higher denudation rates 700 mm ka 1 than those estimated in the other structural domains 150 250 mm ka 1 in the foreland alps 100 mm ka 1 in the pyrenees and 55 75 mm ka 1 in the massif central the alpine domain provides at least 80 of the total eroded volume supplied towards the gulf of lion a quantitative geomorphological approach shows that denudation rates are controlled at the first order by catchment morphologies slope relief over different time scales suggesting glacial conditioning to be the main driver on denudation from the quaternary to present day throughout the pliocene quaternary a doubling of denudation rates related to the mid pleistocene revolution 0 9 ma is highlighted

controls of initial topography on temporal and spatial patterns of glacial erosion abstract here we investigate the influence of initial pre glacial topography on spatial and temporal patterns of glacial erosion using numerical surface process modelling including a higher order ice sheet model first we consider glacier dynamics when simulating glaciation in two real landscapes representing plateau type topography southeast australia and characteristic steady state fluvial topography southern taiwan we find that the different initial landscape configurations result in distinctly different ice configurations and patterns of basal sliding the sliding patterns are controlled by ice configuration and the resulting basal shear stresses and by the thermal properties at the base of the ice we then investigate how these characteristic patterns of basal sliding control glacial erosion and long term landscape evolution using synthetic representations of the two landscapes the two landscape configurations result in markedly different spatial and temporal patterns of glacial erosion however the resulting landscapes may have similar morphology irrespective of initial landscapes and glacial erosion patterns being significantly different the numerical experiments also suggest that in addition to basal temperature basal shear stress is important in restricting long term glacial erosion which is relevant for the preservation of landforms during glaciations specifically pre glacial landforms may be eroded although they are initially protected by cold based ice when the ice configuration promotes significant basal shear stress glacial erosion at the edge of a plateau like landscape in contrast pre glacial landforms may be preserved irrespective of the ice being warm based when low gradients in the ice surface act to limit basal shear stress

numerical investigation of flow hydrodynamics in a channel with a series of groynes the flow hydrodynamics in a straight open channel containing a multiple embayment groyne field on one of its sides is investigated numerically using large eddy simulation the vertical groynes are fully emerged the mean flow depth in the groyne region is about half that of the main channel and the length and width of the embayments are much larger than the mean depth in the embayment region the model is validated using mean velocity and turbulent fluctuations data collected at the free surface in a previous experimental study it is found that despite the fact that the flow inside the main recirculation eddy in the embayments can be characterized as being quasi two dimensional the flow inside the mixing layer region between the embayments and the channel is strongly nonuniform over the depth as this region controls the mass exchange processes between the groyne field and the main channel a three dimensional description of the flow in this area is essential the large scale eddies that populate the mixing layer can penetrate the embayment region over lateral distances of the order of the channel depth these eddies advect with them channel fluid inside the embayment eventually the channel fluid is mixed with the embayment fluid by the small scales the other main mixing mechanism is due to the injection of patches of high vorticity mixing layer fluid near the tip of the downstream groyne and their subsequent convection in the form of a wall attached jet like flow into the embayment first parallel to the downstream groyne face and then to the sidewall it is shown that on average most of the fluid leaves the embayment region via the top layer of the embayment channel interface upstream half and enters the embayment region at levels situated around the middepth practically over the whole length of the embayment of the interface surface this explains why the mass exchange coefficients are overestimated when predicted using methods that employ floating particles as a tracer the instantaneous bed shear stress inside the cavity is found to peak close to the downstream groyne face of each embayment and to show a high variability around the mean values due to the interaction of the mixing layer eddies with the tip of the groynes and the formation of the jet like flow parallel to the droyne face

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

glacial effects limiting mountain height the height of mountain ranges reflects the balance between tectonic rock uplift crustal strength and surface denudation tectonic deformation and surface denudation are interdependent however and feedback mechanisms in particular the potential link to climate are subjects of intense debate spatial variations in fluvial denudation rate caused by precipitation gradients are known to provide first order controls on mountain range width crustal deformation rates and rock uplift moreover limits to crustal strength are thought to constrain the maximum elevation of large continental plateaus such as those in tibet and the central andes there are indications that the general height of mountain ranges is also directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw here we use a global analysis of topography and show that variations in maximum mountain height correlate closely with climate controlled gradients in snowline altitude for many high mountain ranges across orogenic ages and tectonic styles with the aid of a numerical model we further demonstrate how a combination of erosional destruction of topography above the snowline by glacier sliding and commensurate isostatic landscape uplift caused by erosional unloading can explain observations of maximum mountain height by driving elevations towards an altitude window just below the snowline the model thereby self consistently produces the hypsometric signature of the glacial buzzsaw and suggests that differences in the height of mountain ranges mainly reflect variations in local climate rather than tectonic forces

tectonic control on rock uplift exhumation and topography above an oceanic ridge collision southern patagonian andes 47 s chile

modulation of outer bank erosion by slump blocks disentangling the protective and destructive role of failed material on the three dimensional flow structure the three dimensional flow field near the banks of alluvial channels is the primary factor controlling rates of bank erosion although submerged slump blocks and associated large scale bank roughness elements have both previously been proposed to divert flow away from the bank direct observations of the interaction between eroded bank material and the 3 d flow field are lacking here we use observations from multibeam echo sounding terrestrial laser scanning and acoustic doppler current profiling to quantify for the first time the influence of submerged slump blocks on the near bank flow field in contrast to previous research emphasizing their influence on flow diversion away from the bank we show that slump blocks may also deflect flow onto the bank thereby increasing local shear stresses and rates of erosion we use our measurements to propose a conceptual model for how submerged slump blocks interact with the flow field to modulate bank erosion

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

miocene paleotopography of the central alps abstract reconstructing surface elevation surface uplift and relief histories is fundamental to understanding the growth of mountain ranges to explore their topographic limits and relate these to the interplay between geodynamic and earth surface processes here we aim to quantify miocene paleoelevation of the central european alps through stable isotope paleoaltimetry the novelty of our approach which renders our analysis less sensitive to past climate change is that stable isotope proxies of identical age are analyzed from both the high internal parts of the alpine orogen and the adjacent foreland basin whereas the foreland basin was at or near sea level and traces the combined effects of upstream changes in rainfall amount and composition the high alpine site additionally records the effect of elevation on stable isotopes in precipitation we compare hydrogen isotopic ratios d in mica and chlorite that interacted with meteoric water along the simplon detachment a major normal fault that developed at high elevations with meteoric water compositions deduced from carbonate bearing paleosols of the north alpine foreland basin d values of muscovite 126 and chlorite 135 from the brittle hanging wall and of recrystallized muscovite 108 and biotite 140 from adjacent footwall mylonites provide unequivocal evidence for localized syntectonic meteoric water interaction along the simplon detachment detailed 40 ar 39 ar and fission track geochronology constrains the timing of isotopic exchange to ca 14 5 ma when the footwall mylonites passed through the ductile to brittle transition age equivalent oxygen isotope ratios 18 o measured within pedogenic carbonate from north alpine foreland paleosols that developed near miocene sea level serve as our low elevation point of reference 18 o values in these paleosols dated with ca 100 ka precision vary between 19 and 25 smow with average values of 20 at ca 14 5 ma using the relative differences between meteoric water compositions in the foreland basin and the high alpine simplon detachment our isotope data are consistent with a mid miocene minimum average elevation difference of 2350 700 500 m for the simplon region our results indicate that miocene alpine elevations were at least comparable to those of today and are likely to have acted as an important barrier to atlantic derived moisture transport into central europe and eurasia since that time

evaluation of the relative roles of global versus local sedimentary controls on middle to late pleistocene formation of continental margin strata canterbury basin new zealand determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy in this paper the relative contribution of these factors on continental margin evolution during the middle to late pleistocene is evaluated using samples from integrated ocean drilling program expedition 317 core logging biostratigraphy and quantitative x ray diffraction mineralogy are used to delineate continental shelf sedimentary systems major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of middle to upper pleistocene sequences however a preliminary chronology suggests that sequence boundary formation cannot be linked one to one with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles smaller amplitude higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply their stratigraphy is variable in time and across the shelf suggesting a strong influence of local sedimentary forcing in their formation changes in sediment composition after the middle pleistocene transition indicate that sediment transfer from onshore sources in the glaciated southern alps to the middle shelf occurred over a single 100 ka glacio eustatic cycle with an additional 100 ka lag before the mineralogical signal was preserved on the outer shelf this phenomenon is coincident with rapid shelf progradation in this basin suggesting a causal relation between across shelf sediment transport and margin progradation this is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the middle to late pleistocene this work shows that compositional changes in mud dominated successions can lead to a sequence stratigraphic interpretation and the identification of high frequency sequences which may not be possible using a conventional stratigraphic approach

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

low frequency equatorial waves in vertically sheared zonal flow part i stable waves abstract the mechanism by which a vertically sheared zonal flow affects large scale low frequency equatorial waves is investigated with two level equatorial plane and spherical coordinates models vertical shears couple barolinic and barotropic components of equatorial wave motion affecting significantly the rossby wave and westward propagating yanai wave but not the kelvin wave this difference results from the fact that the barotropic component is a modified rossby mode and can be resonantly excited only by westward propagating internal waves the barotropic components emanate poleward into the extratropics with a pronounced amplitude while the baroclinic components remain equatorially trapped a westerly vertical shear favors the trapping of rossby and yanai waves in the upper troposphere whereas an easterly shear tends to confine them in the lower troposphere as such their westward propagation is slowed down by both westerly and easterly shears when the strength of the vertical shear varies w

the relative efficiency and influence of glacial and fluvial erosion on tibetan plateau landscapes abstract driven by climate change periods of dominating glacial and fluvial erosion have both sculpted mountain ranges during the quaternary to understand the evolution of mountain landforms there is considerable interest in knowing which erosion agent leads to more incision how glacial thermal regime impacts erosion and landscape development and whether glacial erosion can result in increased relief to investigate the relative efficiency of glacial and fluvial erosion and the influence of glacial thermal regime on topography we compare two different mountain ranges the qionglai shan monsoonal temperate glaciation and lenglongling subcontinental glaciation in western china we use a 1 d model to construct presumptive fluvial longitudinal profiles if glaciation had not occurred and compare these with the actual glacial profiles to obtain relative incision rates of fluvial and glacial erosion results demonstrate that glacial incision is smaller than fluvial incision in lenglongling and larger than fluvial incision in the qionglai shan which may be influenced by different tectonics and glacier types topographic analysis of glacial and fluvial valleys with similar drainage areas show that glacial erosion results in valley widening local valley relief increase induced by isostatic uplift and slope gradient increase in lenglongling however there is no local valley relief and slope increase observed in the qionglai shan which may reflect slope process responses to threshold hillslope limiting the height above valley bottoms

4he 3he thermochronometry using classical diffusion theory we present a mathematical technique for the determination of 4he concentration profiles in minerals this approach should prove useful for constraining the low temperature cooling histories of individual samples and for correcting u th he ages for partial diffusive loss the calculation assumes that the mineral of interest contains an artificially produced and uniform distribution of 3he obtained by proton irradiation shuster et al earth planet sci lett 217 2004 19 32 in minerals devoid of natural helium this isotope allows measurement of he diffusion coefficients in minerals with measurable radiogenic he it permits determination of 4he profiles arising during ingrowth and diffusion in nature the 4he profile can be extracted from stepwise degassing experiments in which the 4he 3he ratio is measured the evolution of the 4he 3he ratio as a function of cumulative 3he released can be compared with forward models to constrain the shape of the profile alternatively we present a linear inversion that can be used to directly solve for the unknown 4he distribution the inversion incorporates a standard regularization technique to filter the influence of random measurement errors on the solution using either approach we show that stepwise degassing data can yield robust and high resolution information on the 4he profile profiles of radiogenic he are a sensitive function of the time temperate t t path that a cooling sample experienced thus by step heating a proton irradiated sample it is possible to restrict the sample s acceptable t t paths the sensitivity of this approach was explored by forward modeling 4he profiles resulting from a range of realistic t t paths using apatite as an example results indicate that 4he profiles provide rich information on t t paths especially when the profiles are coupled with u th he cooling ages on the same sample samples that experienced only moderate diffusive loss have 4he concentration profiles that are rounded at the edge but uniform in the core of the diffusion domain such profiles can be identified by nearly invariant 4he 3he ratios after the first few to few tens of percent of 3he have been extracted by step heating we show how such data can be used to correct u th he ages for partial diffusive loss

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

rapid exhumation in the western alps driven by slab detachment and glacial erosion identifying topographic and erosion rate response to tectonic and climatic forcing remains challenging this is in part because of the difficulty in isolating the respective roles of climate and tectonics here we exploit 2500 thermochronometric data points collected over several decades of research using a new inverse technique to image the space time evolution of erosion rate across the european alps over the past 35 m y the most striking feature of our results is a two to three fold increase in erosion rate over the past 2 m y exclusively within the western and central alps this increase appears to be controlled by the inferred high rock uplift rate due to the progressive detachment of the european slab under the western alps the similarity in mean elevation between the western and eastern alps indicates a surprisingly low topographic response to this differential tectonic forcing and points to the role of enhanced glacial erosion in response to surface uplift

pronounced northward shift of the westerlies during mis 17 leading to the strong 100 kyr ice age cycles abstract the mis 17 interglacial 715 675 ka marks the end of the mid pleistocene transition as intensified long and asymmetrical 100 kyr ice age cycles became eminently established increasing arrival of moisture to the northern hemisphere high latitudes resulting from the northwestward migration of the subpolar front and the intensification of the norwegian greenland seas ngs convection has been put forward to explain the emergence of this quasi periodic 100 kyr cycle however testing this hypothesis is problematic with the available north atlantic precipitation data here we present new pollen based quantitative seasonal climate reconstructions from the southwestern iberian margin that track changes in the position and intensity of the westerlies our data compared to changes in north atlantic deep and surface water conditions show that mis 17 interglacial was marked by three major changes in the direction and strength of the westerlies tightly linked to oceanographic changes in particular we report here for the first time a drastic two steps northward shift of the westerlies centered at 693 ka that ended up with the sustained precipitation over southern european this atmospheric reorganization was associated with northwestward migration of the subpolar front strengthening of the ngs deep water formation and cooling of the western north atlantic region this finding points to the substantial arrival of moisture to the northern hemisphere high latitudes at the time of the decrease in summer energy and insolation contributing to the establishment of strong 100 kyr cycles

the application of computational fluid dynamics to natural river channels eddy resolving versus mean flow approaches in the last decade as computing power has increased there has been an explosion in the use of eddy resolving numerical methods in the engineering earth and environmental sciences for complex geomorphic flows where accurate field investigations are difficult to perform and where experiments may be difficult to scale these numerical approaches are beginning to give key insights into the nature of these flows eddy resolving methods such as large and detached eddy simulation les des may be contrasted with the time averaged three dimensional simulations that only really began to be applied seriously in geomorphology fifteen years ago while the potential of les for geomorphology has been examined previously des is a relatively recent method that deserves further consideration in this paper we explain the method and then utilise examples from meander and confluence flows as well as flow near the bed of a gravel bed river to highlight the improvements to both the representation of the mean flow and to the representation of time varying processes that result from the use of les des some suggestions are provided for the future use of such techniques in geomorphology

investigation of two elemental error sources in boat mounted acoustic doppler current profiler measurements by large eddy simulations measurements of water discharge and flow velocities in riverine and tidal environments are commonly made with acoustic doppler current profilers adcps mounted on a moving boat this paper presents results of high resolution large eddy simulations les conducted to investigate two elemental error sources in adcp measurements from a moving boat one of these errors is due to the flow disturbance induced by the boat mounted adcp the other error is due to the lack of flow homogeneity in horizontal layers assumed by the adcp algorithm to compute orthogonal velocities from the measured radial velocities along the acoustic beams the first error is investigated by comparing les results for an undisturbed flow field with les results for a flow field disturbed by a boat mounted adcp the second error is investigated by comparing the velocities beneath the adcp simulated by les with virtual adcp velocities which are obtained by applying the adcp algorithm to les velocities data mined along the path of the acoustic beams of the virtual profiler the distribution of the reynolds stresses beneath the adcp estimated with the adcp algorithm from the virtual adcp velocity data are also compared with those obtained from the les solutions for both the undisturbed and adcp disturbed flows results show that the boat significantly disturbs the flow field and that the disturbed flow field is qualitatively different from the flow fields observed around an isolated adcp no boat

plio pleistocene increase of erosion rates in mountain belts in response to climate change here we review an ensemble of observations that point towards a global increase of erosion rates in regions of elevated mountain belts or otherwise high relief since the onset of northern hemisphere glaciation about 2 3 ma during that period of earth s history atmospheric co2 concentrations may have dropped and global climate cooled and evolved towards high amplitude oscillating conditions that are associated with the waxing and waning of continental ice sheets in the northern hemisphere we argue for a correlation between climate change and increased erosion rates and relief production which we attribute to some combination of the observed cooling onset of glaciation and climatic oscillation at orbital timescales in our view glacial erosion played a major role and is driven by the global cooling furthermore analyses of the sedimentary fluxes of many mountain belts show peaks of erosion during the transitions between glacial and inter glacial periods suggesting that the variable climatic conditions have also played a role

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

abrupt glacial valley incision at 0 8 ma dated from cave deposits in switzerland glacial erosion dramatically alters mountain landscapes but the pace at which glaciers carve a previously fluvial landscape remains poorly defined because long term valley incision rates are difficult to measure here we reconstruct the lowering history of the aare valley switzerland over the past 4 m y by dating cave sediments with cosmogenic 26al and 10be incision accelerated from 120 m m y to 1200 m m y at 0 8 1 0 ma at least 1 m y after the onset of local glaciation rapid incision may have been triggered by lowering of the equilibrium line altitude at the mid pleistocene climate transition

impact of current wave interaction on storm surge simulation a case study for hurricane bob 1 hurricane bob moved up the u s east coast and crossed over southern new england and the gulf of maine with peak marine winds up to 54 m s 100 mph on 19 20 august 1991 causing significant damage along the coast and shelf a 3 d fully wave current coupled finite volume community ocean model system was developed and applied to simulate and examine the coastal ocean responses to hurricane bob results from process study oriented experiments showed that the impact of wave current interaction on surge elevation varied in space and time more significant over the shelf than inside the inner bays while sea level change along the coast was mainly driven by the water flux controlled by barotropic dynamics and the vertically integrated highest water transports were essentially the same for cases with and without water stratification the hurricane induced wave current interaction could generate strong vertical current shear in the stratified areas leading to a strong offshore transport near the bottom and vertical turbulent mixing over the continental shelf stratification could also result in a significant difference of water currents around islands where the water is not vertically well mixed

the glacially overdeepened trough of the salzach valley austria bedrock geometry and sedimentary fill of a major alpine subglacial basin abstract overdeepened valleys are unambiguous features of glacially sculpted landscapes they result from erosion at the bed of the glacier and their size and shape is determined by ice dynamics and the characteristics of the underlying bedrock major overdeepened valleys representing vertical bedrock erosion of several hundreds of meters are characteristic features of many trunk valleys in the formerly glaciated parts of the alpine mountain belt the thick sedimentary fill usually hinders attempts to unravel bedrock geometry formation history and fill characteristics based on reflection seismic data and core logs from multiple deep drillings we construct a detailed bedrock model of the lower salzach valley trough one of the largest overdeepened valleys in the european alps the analysed overdeepened structure characterized by a strongly undulating topography two reaches of enhanced erosion can be identified and are suggested to be related to variations in bedrock erodibility and a triple glacier confluence the sedimentary fill shows clear characteristics of rapid infilling and subaqueous fan delta deposits indicate a strong influence of tributary streams associated surface lowering of the valley floor had a major impact on tributary stream incision but also on the available ice accumulation area at subsequent glaciations the extent to which fills of earlier glaciations have been preserved from erosion during the last glacial maximum remains ambiguous and demands further exploration to our knowledge the presented bedrock model is one of the best defined of any major overdeepened trunk valley

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

signatures of late pleistocene fluvial incision in an alpine landscape uncertainty regarding the relative efficacy of fluvial and glacial erosion has hindered attempts to quantitatively analyse the pleistocene evolution of alpine landscapes here we show that the morphology of major tributaries of the rhone river switzerland is consistent with that predicted for a landscape shaped primarily by multiple phases of fluvial incision following a period of intense glacial erosion after the mid pleistocene transition 0 7 ma this is despite major ice sheets reoccupying the region during cold intervals since the mid pleistocene we use high resolution lidar data to identify a series of convex reaches within the long profiles of 18 tributary channels we propose these reaches represent knickpoints which developed as regional uplift raised tributary bedrock channels above the local fluvial baselevel during glacial intervals and migrated upstream as the fluvial system was re established during interglacial periods using a combination of integral long profile analysis and stream power modelling we find that the locations of 80 of knickpoints in our study region are consistent with that predicted for a fluvial origin while the mean residual error over 100 km of modelled channels is just 26 3 m breaks in cross valley profiles project toward the elevation of former end of interglacial channel elevations supporting our model results calculated long term uplift rates are within 15 of present day measurements while modelled rates of bedrock incision range from 1 mm yr for low gradient reaches between knickpoints to 6 10 mm yr close to retreating knickpoints typical of observed rates in alpine settings together our results reveal approximately 800 m of regional uplift river incision and hillslope erosion in the lower half of each tributary catchment since 0 7 ma

linking the northern alps with their foreland the latest exhumation history resolved by low temperature thermochronology the evolution of the central alpine deformation front subalpine molasse and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the alps its latest exhumation history is poorly understood due to the lack of late miocene to pliocene sediments we constrain the late miocene to pliocene history of this transitional zone with apatite fission track and u th he data we used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data two investigated sections across tectonic slices show that the subalpine molasse was tectonically active after the onset of folding of the jura mountains this is much younger than hitherto assumed thrusting occurred at 10 8 6 5 ma and potentially thereafter this is contemporaneous with reported exhumation of the external crystalline massifs in the central alps the jura mountains and the subalpine molasse used the same detachments as the external crystalline massifs and are therefore kinematically coupled estimates on the amount of shortening and thrust displacement corroborate this idea we argue that the tectonic signal is related to active shortening during the late stage of orogenesis

coherent structures in the flow field around a circular cylinder with scour hole large eddy simulation les and laboratory flume visualizations were used to investigate coherent structures present in the flow field around a circular cylinder located in a scour hole the bathymetry corresponds to equilibrium scour conditions and is fixed in les the flow parameters in the simulation correspond to the experimental conditions in which the approach flow is fully turbulent detailed consideration is given to the interaction of the horseshoe vortex hv system within the scour hole with the detached shear layers formed from the cylinder and the near bed turbulence it is found that the overall structure of the hv system varies considerably in space and time though a large relatively stable primary necklace vortex is present at practically all times inside the scour hole the simulation captures the presence of bimodal chaotic oscillations inside the hv system as well as the sharp increase in the resolved turbulent kinetic energy levels and pressure fluctuations reported in prior experimental investigations high levels of the mean bed shear stress are observed beneath the primary necklace vortex especially over the region where the bimodal oscillations are strong as well as beneath the small junction vortex at the base of the cylinder it is also found that the detachment and advection of patches of vorticity from the downstream part of the legs of the necklace vortices can induce large instantaneous bed shear stress values when the critical bed shear stress value for sediment entrainment on a flat surface is adjusted for bed slope effects the les simulation correctly predicts that the distribution of the mean bed shear stress is consistent with equilibrium scour conditions

flow field complexity and design estimation of pier scour depth sixty years since laursen and toch abstractthis paper written to celebrate the 60th anniversary of the journal of hydraulic engineering presents a structured contemporary approach to scour depth estimation that matches design met

glacial hydrology and erosion patterns a mechanism for carving glacial valleys article i nfo article history most glacial erosion models assume that erosion rates are proportional to ice sliding velocity while recent studies have shown that water plays a major role in modulating sliding velocities the impact it might have on erosion rates is still unclear here we incorporate subglacial hydrology into a glacial erosion model that is based on a sliding rule our results explicitly highlight that adding subglacial hydrology has profound impacts on the temporal and spatial patterns of glacial erosion first it suggests that erosion might mainly occur during melting seasons when subglacial water pressure is large and effective pressure is low i e before the channels fully develop and reduce the water pressure at the ice bedrock interface which promotes sliding and erosion second the distribution of erosion is bimodal with a peak at the equilibrium line altitude and as we demonstrate enhanced erosion at much lower altitudes within the ablation area where water due to melting abounds this has important implications because it explains why glacial erosion can simultaneously

canyon incision and knickpoint propagation recorded by apatite 4he 3he thermochronometry abstract in many regions of the world deeply incised canyons demonstrate the net effects of physical processes active at earth s surface in response to surface uplift low temperature thermochronometry can constrain the timing and rates of bedrock incision which is necessary for relating canyon incision to surface uplift over geological timescales we analyzed four samples from the cotahuasi ocona canyon system in southwest peru using 4 he 3 he thermochronometry and we present a new inversion model to identify continuous low temperature cooling histories that are consistent with the observed data derived cooling histories limit the onset of fluvial incision to 13 to 8 ma this is in agreement with previously reported interpretations based on a three dimensional thermal model interpolation to a much larger set of conventional apatite u th he ages however because 4 he 3 he thermochronometry constrains an independent cooling history for each sample the results also permit testing of landscape evolution models with greater spatial variability in exhumation compared to those models that can be tested by a geographically scattered set of conventional u th he ages the different cooling histories of the four samples require asynchronous incision along at least part of the canyon system that is best explained by headward propagation of fluvial incision by knickpoint migration

helium trapping in apatite damage insights from u th sm he dating of different granitoid lithologies apatite u th sm he ahe thermochronometry is widely used to constrain thermal histories and rates of tectonic exhumation and erosion processes however data interpretation is often challenging especially when the thermal history includes extended residence time in the he partial retention zone heprz with highly dispersed dates revealing the complexity of diffusion processes in natural systems this study investigates chemical and physical factors that may have impacted he diffusion in apatite over long timescales in a context of protracted residence in the heprz nine samples from the ploumanac h pluton and north tregor armorican massif france were collected in granitoids differing in petrography and chemisty this area was chosen because these samples underwent a similar thermal history since 300 ma we report new u th sm he dates along with apatite fission track aft data as well as lithological and chemical characterization the results show dispersed u th sm he dates ranging from 87 7 to 291 23 ma whereas central aft dates vary from 142 6 to 199 9 ma current predictive models for he diffusion and fission track annealing in apatite could not reproduce the two datasets together however this apparent discrepancy gives insight into the parameters influencing he diffusion at geological timescales the data confirm that radiation damage enhances he trapping as the ahe dates are positively correlated to effective uranium eu concentration the he age dispersion for constant eu content cannot be explained just by variations in grain size or chemical composition to explore the potential influence of recoil damage trapping behavior and annealing kinetics on ahe dates we tested a new diffusion model from gerin et al 2017 given the expected model of the thermal history provided by aft inversion we investigated the influence of the trapping energy on ahe dates the ahe date variations can be explained only if the trapping energy evolves from one crystal to another increasing with the amount of damage for a given trapping energy minor variations in the recoil damage annealing rate can consistently explain most of the remaining dispersion of the ahe dates

glacial and periglacial buzzsaws fitting mechanisms to metaphors the buzzsaw hypothesis refers to the potential for glacial and periglacial processes to rapidly denude mountains at and above glacier equilibrium line altitudes elas irrespective of uplift rates rock type or pre existing topography here the appropriateness of the buzzsaw metaphor is examined alongside questions of the links between glacial erosion and elas and whether the glacial system can produce low relief surfaces or limit summit heights plateau fragments in mountains on both active orogens and passive margins that have been cited as products of glacial and periglacial buzzsaw erosion instead generally represent dissected remnants of largely inherited pre glacial relief summit heights may correlate with elas but no causal link need be implied as summit erosion rates are low cirque headwalls may not directly abut summits and on passive margins cirques are cut into pre existing mountain topography any simple links between elas and glacial erosion break down on passive margins due to topographic forcing of ice sheet growth and to the km scale vertical swaths through which elas have shifted through the quaternary glaciers destroy rather than create low relief rock surfaces through the innate tendency for ice flow to be faster thicker and warmer along valleys the glacial buzzsaw cuts down

glacial conditioning as an erosional driving force in the central alps unparalleled data availability in the european alps has led to an ongoing debate about the driving mechanism behind the concurrent patterns of surface denudation and modern rock uplift analysis of stream channels reveals that oversteepened stream segments are primarily located in landscapes with strong glacial inheritance this leads to a transient signal in the landscape with the result that erosion is spatially focused by a combination of glacial conditioning and lithologic controls we postulate that the effect of glacial forcing is a positive feedback cycle between erosion and rock uplift driving rapid rates of both in the alpine landscape this mechanism may explain the observed increases in sediment flux since the late pliocene

3d flow and sediment dynamics in a laboratory channel bend with and without stream barbs abstracta series of laboratory flume experiments were performed to study the effect of stream barbs on flow field dynamics and sediment erosion in a 135 mobile bed channel bend stream barbs also known as spur dikes or submerged groynes are low profile linear rock features that redirect high velocity flow away from the outer bank of channel bends unlike emergent groynes the submerged nature of these structures creates a unique combination of horizontal shear plunging type flow and vertical shear at the groyne tip spatially dense high frequency velocity data were collected and analyzed to describe the pattern and magnitude of three dimensional 3d velocity throughout the bend and in the vicinity of the stream barbs this paper demonstrates that the outer bank region particularly between barbs may still be at risk of erosion or even increased erosion greater than the same case without barbs if stream barbs generate excessive secondary velocities because of their size and layout that are op

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

coherent structure dynamics in turbulent flows past in stream structures some insights gained via numerical simulation large scale coherent vortical structures in natural streams and rivers dominate flow and transport processes and impact the stability of stream banks the diversity and abundance of organisms and the quality of running waters in aquatic ecosystems thus understanding and being able to model the dynamics of energetic coherent structures in such flows at ecologically relevant scales are crucial prerequisites for developing a science based ecosystem restoration framework we review recent progress toward the development of coherent structure resolving csr computational fluid dynamics techniques based on hybrid urans les modeling strategies for simulating turbulent flows in open channels with hydraulic structures csr simulations of the turbulent horseshoe vortex thsv past bed mounted piers explained the physical mechanism leading to the experimentally documented bimodal velocity fluctuations of the vortex and underscored the importance of the reynolds number as a key parameter governing the thsv dynamics simulations of high reynolds number flows past surface piercing groynelike structures in open channels revealed the complexity of the recirculating region at the upstream face of the groyne underscored the interaction of the flow in this region with the energetic shear layer shed from the point of separation at the upstream side wall and demonstrated the importance of flow depth in the vorticity dynamics of such flows the paper also identifies areas for future work and modeling challenges that need to be addressed for the computational tools to be able to accurately predict flow and transport processes in real life aquatic environments

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

spatial correlation bias in late cenozoic erosion histories derived from thermochronology the potential link between erosion rates at the earth s surface and changes in global climate has intrigued geoscientists for decades1 2 because such a coupling has implications for the influence of silicate weathering3 4 and organic carbon burial5 on climate and for the role of quaternary glaciations in landscape evolution1 6 a global increase in late cenozoic erosion rates in response to a cooling more variable climate has been proposed on the basis of worldwide sedimentation rates7 other studies have indicated however that global erosion rates may have remained steady suggesting that the reported increases in sediment accumulation rates are due to preservation biases depositional hiatuses and varying measurement intervals8 10 more recently a global compilation of thermochronology data has been used to infer a nearly twofold increase in the erosion rate in mountainous landscapes over late cenozoic times6 it has been contended that this result is free of the biases that affect sedimentary records11 although others have argued that it contains biases related to how thermochronological data are averaged12 and to erosion hiatuses in glaciated landscapes13 here we investigate the 30 locations with reported accelerated erosion during the late cenozoic6 our analysis shows that in 23 of these locations the reported increases are a result of a spatial correlation bias that is combining data with disparate exhumation histories thereby converting spatial erosion rate variations into temporal increases in four locations the increases can be explained by changes in tectonic boundary conditions in three cases climatically induced accelerations are recorded driven by localized glacial valley incision our findings suggest that thermochronology data currently have insufficient resolution to assess whether late cenozoic climate change affected erosion rates on a global scale we suggest that a synthesis of local findings that include location specific information may help to further investigate drivers of global erosion rates reported acceleration of erosion in mountainous landscapes during the late cenozoic is the result of combining thermochronology data with disparate exhumation histories thereby converting spatial variations in erosion rates into temporal increases

glacial erosion status and outlook glacier erosion rates range across orders of magnitude and much of this variation cannot be attributed to basal sliding rates subglacial till acts as lubricating fault gouge or sawdust and must be removed for rapid subglacial bedrock erosion such erosion occurs especially where and when moulin fed streams access the bed and are unconstrained by supercooling or other processes streams also may directly erode bedrock likely with strong time evolution erosion is primarily by quarrying aided by strong fluctuations in the water system driven by variable surface melt and by subglacial earthquakes debris bed friction significantly affects abrasion quarrying and general glacier flow frost heave drives cirque headwall erosion as winter cold air enters bergschrunds creating temperature gradients to drive water flow along premelted films to growing ice lenses that fracture rock and the glacier removes the resulting blocks recent subglacial bedrock erosion and sediment flux are in many cases much higher than long term averages over glacial cycles evolution of glacial valley form feeds back strongly on erosion and deposition most of this is poorly quantified with parts open to argument glacial erosion and interactions are important to tectonic and volcanic processes as well as climate and biogeochemical fluxes motivating vigorous research

parameterization of mean residence times in idealized rectangular dead zones representative of natural streams abstractthree dimensional reynolds averaged navier stokes modeling validated against experimental data is used to parameterize the flow features and time scales in idealized rectangular cavities for a wide range of width to length ratios 0 4 w l 1 1 and reynolds number based on the depth 5 000 rd 20 300 representative of isolated dead zones in small natural streams the flow features for this parameter range are similar to open cavity flows and consist of a mixing layer spanning the entire length of the dead zone together with a single main recirculation region the langmuir time scale ratio of dead zone volume to discharge based on the assumption of a well mixed dead zone is found to be a function of the mean rotation time scale inverse of average rotation rate within the dead zone the momentum thickness of the upstream boundary layer and the dead zone width the entrainment coefficient used to relate the exchange velocity to the average free stream velocity is shown to be directly related

transport of suspended sediments under the influence of bank macro roughness river restoration works often include measures to promote morphological diversity and enhance habitat suitability one of these measures is the creation of macro roughness elements such as lateral cavities and embayments in the banks of channelized rivers however in flows that are heavily charged with fine sediments in suspension such as glacier fed streams and very low gradient reaches of large catchment rivers these lateral cavities may trap these sediments consequently the morphological changes may be affected and the functionality of the restoration interventions may be compromised herein we analyse the influence of these macro roughness elements on the transport of fine sediments in the main channel laboratory tests with uniform flow charged with sediments in a channel with banks equipped with large scale rectangular roughness elements were carried out the laboratory experiments covered a wide range of rectangular cavity geometrical configurations and shallowness ratios the influence of key parameters such as flow shallowness geometric ratios of the cavities and initial sediment concentration was tested surface particle image velocimetry sediment samples and temporal turbidity records were collected during the experiments the amount of sediments captured by the cavities the temporal evolution of the concentration of sediments in suspension and the flow hydrodynamics are cross analysed and discussed it is shown that the trapping efficiency of the macro roughness elements is a clear function of the channel geometry and the shallowness of the flow

alpine sedimentology an introduction and tribute to albert matter and daniel bernoulli department of earth sciences eth zurich sonneggstrasse 5 ch 8092 z urich switzerlandintroductionswitzerland offers a rich variety of sedimentolog ical features despite the fact that the country iswithout direct contact to any ocean its sedimen tological richness is related to the alpine oro geny that not only assembled the sedimentaryproducts of different former depositional envi ronments but also created important relief whichtriggers many different sedimentary processes some still ongoing in this sense the term alpinesedimentology denotes the prodigious relationbetween alpine mountain building and sedimen tary processes and their products in the regionsimplicated in its dynamics the present specialissue assembles a variety of examples of ongoingresearch both on alpine deformed sedimentarysuccessions as well as on sedimentary processesrelated to the alpine orogeny in switzerland andelsewhere the contributions in this issue were for a large part presented at a symposium inhonour of the 75th birthday of albert matter anddaniel bernoulli in november 2011 they haveboth generously contributed to the eld of sedi mentological research in switzerland and it is forthis reason that this issue is dedicated to them alpine sedimentology andsedimentsswiss alpine sediments and sedimentary rocksrepresent a great variety of depositional settings which include formerly active and passive mar gins and range from continental and shallow marine environments to deep ocean basins inthe swiss alps they span the time range fromthe carboniferous capuzzo wetzel 2004 totoday and their highly metamorphic counter parts may go back all the way to the late pre cambrian von raumer neubauer 1993 the preserved sedimentary record documentsthe palaeotectonic and palaeogeographicchanges which assisted in shaping central eur ope and are summarized in table 1 weissert st ossel 2009 switzerland effectively assemblesthe remains of different oceanic basins thevalais and piemontais basins are all part of thealpine tethys and their bordering shelves which were progressively closed partly sub ducted folded and thrusted in the course of thealpine orogeny fig 1 the succession of differ ent palaeogeographic units aggregated in swit zerland may have been as large as 1000 km in anorth west south east direction according to pal aeotectonic reconstructions fig 1 the diffe rent composition and type of basement of theseunits dictated the formation of different tectono sedimentary units during the alpine orogeny figs 2 and 3 these units will be brie y treatedlater in this study and complemented by adescription of the different elds related toresearch on sedimentological phenomena inalpine depositional environments alpine deformed sedimentarysuccessionsbasement rocks and carboniferous andpermian graben in llsthe polymetamorphic crystalline basement pres ently underlying the sedimentary units of thejura mountains the molasse basin and the alps fig 3 was consolidated uplifted and erodedduring the late carboniferous and a series ofmostly east west oriented continental basinswas formed the graben structures were conse quently in lled with detrital and volcanogenicsediments and subordinate lacustrine sedimentsand coal deposits matter 1987 the sedimen

links between eccentricity forcing and the 100 000 year glacial cycle the 100 000 year glacial cycles are generally thought to be driven by the eccentricity of the earth s orbit statistical analyses of climate variability and orbital forcing over the past five million years indicate that the glacial cycles are the result of an internal climate oscillation phase locked to the 100 000 year eccentricity cycle variations in the eccentricity 100 000 yr obliquity 41 000 yr and precession 23 000 yr of earth s orbit have been linked to glacial interglacial climate cycles it is generally thought that the 100 000 yr glacial cycles of the past 800 000 yr are a result of orbital eccentricity1 2 3 4 however the eccentricity cycle produces negligible 100 kyr power in seasonal or mean annual insolation although it does modulate the amplitude of the precession cycle alternatively it has been suggested that the recent glacial cycles are driven purely by the obliquity cycle5 6 7 here i use statistical analyses of insolation and the climate of the past five million years to characterize the link between eccentricity and the 100 000 yr glacial cycles using cross wavelet phase analysis i show that the relative phase of eccentricity and glacial cycles has been stable since 1 2 myr ago supporting the hypothesis that 100 000 yr glacial cycles are paced8 9 10 by eccentricity4 11 however i find that the time dependent 100 000 yr power of eccentricity has been anticorrelated with that of climate since 5 myr ago with strong eccentricity forcing associated with weaker power in the 100 000 yr glacial cycle i propose that the anticorrelation arises from the strong precession forcing associated with strong eccentricity forcing which disrupts the internal climate feedbacks that drive the 100 000 yr glacial cycle this supports the hypothesis that internally driven climate feedbacks are the source of the 100 000 yr climate variations12

glaciations in response to climate variations preconditioned by evolving topography landscapes modified by glacial erosion show a distinct distribution of surface area with elevation hypsometry in particular the height of these regions is influenced by climatic gradients controlling the altitude where glacial and periglacial processes are the most active and as a result surface area is focused just below the snowline altitude yet the effect of this distinct glacial hypsometric signature on glacial extent and therefore on continued glacial erosion has not previously been examined here we show how this topographic configuration influences the climatic sensitivity of alpine glaciers and how the development of a glacial hypsometric distribution influences the intensity of glaciations on timescales of more than a few glacial cycles we find that the relationship between variations in climate and the resulting variation in areal extent of glaciation changes drastically with the degree of glacial modification in the landscape first in landscapes with novel glaciations a nearly linear relationship between climate and glacial area exists second in previously glaciated landscapes with extensive area at a similar elevation highly nonlinear and rapid glacial expansions occur with minimal climate forcing once the snowline reaches the hypsometric maximum our results also show that erosion associated with glaciations before the mid pleistocene transition at around 950 000 years ago probably preconditioned the landscape producing glacial landforms and hypsometric maxima such that ongoing cooling led to a significant change in glacial extent and erosion resulting in more extensive glaciations and valley deepening in the late pleistocene epoch we thus provide a mechanism that explains previous observations from exposure dating and low temperature thermochronology in the european alps and suggest that there is a strong topographic control on the most recent quaternary period glaciations