numerical model predictions of autogenic fluvial terraces and comparison to climate change expectations terraces eroded into sediment alluvial and bedrock strath preserve an important history of river activity river terraces are thought to form when a river switches from a period of slow vertical incision and valley widening to fast vertical incision and terrace abandonment consequently terraces are often interpreted to reflect changing external drivers including tectonics sea level and climate in contrast the intrinsic unsteadiness of lateral migration in rivers may generate terraces even under constant rates of vertical incision without external forcing to explore this mechanism we simulate landscape evolution by a vertically incising meandering river and isolate the age and geometry of autogenic river terraces modeled autogenic terraces form for a wide range of lateral and vertical incision rates and are often paired and longitudinally extensive for intermediate ratios of vertical to lateral erosion rate autogenic terraces have a characteristic reoccurrence time that scales with the time for relief generation there is a preservation bias against older terraces due to reworking of previously visited parts of the valley evolving spatial differences in bank strength between bedrock and sediment reduce terrace formation frequency and length favor pairing and can explain sublinear terrace margins at valley boundaries age differences and geometries for modeled autogenic terraces are consistent in cases with natural terraces and overlap with metrics commonly attributed to terrace formation due to climate change we suggest a new phase space of terrace properties that may allow differentiation of autogenic terraces from terraces formed by external drivers

effect of channel bifurcation on residual estuarine circulation winyah bay south carolina the residual circulation pattern of winyah bay the fourth largest estuary on the eastern coast of the us is examined using stationary and shipborne current measurements during periods of low freshwater discharge the estuary has a complex morphology with a single channel and narrow banks at the river entrance and the bay mouth and a bifurcated channel system main and western channels respectively in the middle part that appears to affect the residual circulation overall the upper single channel morphology and middle dual channel morphology parts of the estuary exhibit a baroclinic residual circulation the presence of bifurcated channels in the middle part of the estuary modifies the typical gravitational circulation the near bed landward directed residual flow is stronger in the deeper main channel than the shallower western channel this is the result of the fact that the magnitude of residual flow scales with the water depth of the channel and it is also influenced by the opposing patterns of channel alignment in the northern and southern junctions analytical modeling confirms that the observed residual currents in the upper and middle estuary are density induced in the lower estuary residual flow is directed seaward throughout the water column of the channel while in the adjacent shoals the residual flow is directed landward suggesting that in contrast to the upper and middle estuary the residual flow near the mouth is barotropic controlled by the tides and the channelbank morphology 2005 published by elsevier ltd

quantifying postglacial sediment storage at the mountain belt scale sediment storage is an often neglected term in sediment budgets despite being the crucial link between rates of erosion and sediment yield mountain belts in particular host large valley fills that modulate fluxes of water and sediment buffer the geomorphic coupling between hillslopes and river channels reduce local valley relief and protect bedrock from fluvial incision here we propose a region growing algorithm based on a slope gradient criterion to automatically extract areas of postglacial fluvial and lacustrine valley fills from digital topography at the mountain belt scale applying this method to the european alps we find that the size frequency relationship of 17 766 individual sediment storage units expressed by either area or volume follows a power law over four and five orders of magnitude with scaling exponents 1 77 and 1 71 respectively we show that 90 of the area covered by sediment storage is in the lower quartile of the mountain belt9s elevation and below the median local relief on average low gradient valley fill occupies 6 of the studied drainage basins this fraction increases with basin size likely reflecting the larger accommodation space of trunk valleys generated by multiple glacial interglacial cycles comparison with sediment storage mapped in the southern alps new zealand indicates that rates of uplift and precipitation control the extent and spatial distribution of sediment storage at the mountain belt scale

experimental compaction of quartz sand at low effective stress and temperature conditions experiments have been carried out on dry and fluid saturated quartz sands to investigate the behaviour during compaction under diagenetic conditions and to evaluate the importance of stress induced solution transfer 9pressure solution9 as a compaction mechanism the experiments were performed at temperatures t in the range 150 350 c applied effective stresses e up to 20 7 mpa and pore fluid pressures p 1 of 12 5 and 15 5 mpa using material with a grain size d in the range 20 100 m and an initial porosity of 45 52 dry quartz sands underwent significant compac tion during the loading stage but showed very little compaction creep once full load was achieved i e essentially time independent compaction in contrast fluid saturated material at constant applied effective stress showed substantial time dependent compaction i e creep with increasing temperature there is a decreasing number of grains in the wet compacted sand which show intragranular cracks and an increasing number of grains which show dissolution features at contacts with adjacent grains in addition there is a decreasing dependence of the volumetric strain rate on e with both increasing volumetric strain e v and increasing e and a decreasing dependence of on e v with increasing temperature these observations suggest that for wet quartz sand a gradual change might occur from compaction creep controlled by time dependent microcracking at t 250 300 c to compaction creep controlled by stress induced intergranular solution transfer at t 300 350 c

geomorphological response of fluvial and coastal terraces to quaternary tectonics and climate as revealed by geostatistical topographic analysis geostatistical topographic analysis is widely recognized as a useful tool for the statistical reconstruction of planar geomorphic markers from relict surfaces this work is aimed at improving the geostatistical approach used in previous works and developing a method for evaluating the incision rates of rivers in their lower catchments during the late quaternary we chose the major valleys of the adriatic foothills central italy affected since late miocene by a differential tectonic uplift which is still active in particular i we applied the geostatistical analysis to reconstruct the original top surfaces of fluvial to coastal terrace bodies at the metauro river and cesano river mouths ii we performed correlations between the height distribution of the alluvial terrace sequences and the quaternary climatic curve to estimate the average long term fluvial incision rates in the lowermost reaches of the metauro cesano misa and esino rivers the obtained averaged incision rates have been interpreted also in the light of the stream length gradient index sl index steepness index ks and concavity index as proxies of the stream power per unit length results confirm that geostatistical and terrain analysis of topographic and geometric arrangements of fluvial and coastal terraces is an effective tool in detecting geomorphic and tectonic factors inducing perturbations on planar geomorphic markers in particular we better delineated the surface geometry and boundaries of well developed coastal fans at the mouths of the metauro and cesano rivers already recognized in previous works through sedimentological morphostratigraphic and chronological data moreover we found evidence for cut and fill phases that took place during and immediately after the river aggradation of the late quaternary glacial periods despite the slope area analysis evidenced a widespread influence of the regional differential uplift on single river basin configuration we observed some space and time variability of averaged incision rates for adjacent valleys mainly explained by physiographic configuration and dynamics of drainage network copyright 2011 john wiley sons ltd

terex toolbox for semi automated selection of fluvial terrace and floodplain features from lidar terraces and floodplains are important indicators of near channel sediment dynamics serving as potential sediment sources and sinks increasing availability of high resolution topography data over large areas calls for development of semi automated techniques for identification and measurement of these features in this study we introduce a novel tool that accommodates user defined parameters including a local relief threshold selected by a variable size moving window minimum area threshold and maximum distance from the channel to identify and map discrete terrace and floodplain surfaces each of the parameters can easily be calibrated for a given watershed or reach subsequently the tool automatically measures planform area absolute elevation and height relative to the local river channel for each terrace polygon we validate the tool in two locations where terrace maps were previously developed via manual digitization from lidar and extensive field mapping campaigns the tool is also tested on six different types of rivers to provide examples of starting selection parameters and to test effectiveness of the tool across a wide range of landscapes generally the tool provides a high quality draft map of terrace and floodplain surfaces across the wide range of environmental conditions for which it has been tested we find that the tool functions best in catchments where the terraces are spatially extensive with distinct differences between the terrace and floodplain the most challenging environments for semi automated terrace and floodplain mapping include steep catchments with dense riparian vegetation and very small terraces 10 m2 in areal extent we then apply the tool to map terraces and floodplains in the root river watershed southeastern minnesota and generate exceedance plots for terrace heights these plots provide a first pass analysis to indicate the tributaries and reaches of the river where terraces constitute a significant source of sediment copyright 2013 john wiley sons ltd

changes in quartz solubility and porosity due to effective stress an experimental investigation of pressure solution experimental compaction of quartz sand was conducted in semistatic flow through systems at 150c to examine the chemical and physical processes associated with pressure solution pore fluid chemistry and porosity were monitored through time to investigate the role of effective stress on silica solubility and compaction rate the concentration of silica in the pore fluid varied directly with effective stress at constant pore fluid pressure but not in a linear fashion increases in silica were not transient and could be partially reversed by removal of the effective stress porosity decreased steadily under constant nonzero effective stress at 150c but remained essentially constant under identical loading conditions at room temperature initial compaction rates increased linearly with effective stress deformed samples show indented contacts with fractures and dissolution features healed microfractures and a decrease in average grain size multiple mechanisms pressure solution subcritical crack growth crack healing appear to operate at grain contacts during compaction the authors interpret long term time dependent compaction accompanied by stress induced changes in fluid chemistry as evidence for pressure solution

automated mapping of land components from digital elevation data an algorithm for automating the mapping of land components from digital elevation data is described land components are areas of relatively uniform slope and aspect and often correspond with ridge crests shoulders head slopes back slopes or foot slopes aspect regions which generally span from stream to ridge are first identified by generalizing an aspect map derived from digital elevation data the aspect regions are then split successively into land components by grouping pixels above or below an automatically determined contour of elevation or distance from stream the contour approximates a slope break the land components mapped in this way give a complete polygonization of a hilly landscape and are a reasonable approximation of manually mapped land components

kinetics of pressure solution at halite silica interfaces and intergranular clay films pressure solution is widely regarded as a potentially important deformation mechanism along crustal faults and during aliagenesis yet the mechanisms and kinetics of this process remain highly controversial to better understand the fundamental factors controwing the rates of pressure solution at the grain to grain scale we conducted experiments in which convex halite lenses were pressed against fiats of fused silica in brine fluid pressures were maintained at 0 1 mpa temperatures and mean contact normal stresses ranged from 8 3 o to 90 2oc and 0 5 to 13 5 mpa respectively the geometry and growth rate of the contact spot between the two lenses and the rate at which the lenses approached one another convergence were monitored using reflected light interferometry and transmitted light photomicrography convergence occurred when halite and silica lenses were pressed together in brine halite silica experiments no undercutting was observed and dry control experiments indicated negligible dislocation creep convergence rates in experiments at 50 2oc ranged from 0 01 to 0 05 m d depending on mean normal stress and contact spot radius the data are consistent with intergranular pressure solution ips rate limited by diffusion through an intergranular film with a very high diffusion coefficient 10 5 10 7 cm2 s the data further suggest that the diffusion coefficient and or thickness of this film increases with decreasing normal stresses at least for normal stresses less than about 4 mpa as no island channel boundary structures were observed we propose that this film consists of a continuous layer of strongly adsorbed i e structured water that is maintained between the halite and silica lenses during deformation convergence rates in similar experiments conducted at a constant load of 0 11 n but at 8 3 o 50 2 o and 90 2oc were approximately constant at a given normal stress and contact spot size the cause of this temperature insensitivity is unknown but might result from changes in interphase boundary structure or thickness with increasing temperature that are sufficient to offset the expected thermal activation an experiment was also conducted in which a halite lens was pressed against a fused silica fiat coated with an 0 8 m thick film of na montmorillonite in brine this clay film produced an approximately fivefold increase in convergence rates over those observed in a halite silica experiment conducted without clay at the same load and temperature the strong sensitivity of ips rates both to contact spot radius and to the presence of second phases along grain boundaries suggests that fine grained clay rich fault gouges and multiphase granular aggregates should be particularly susceptible to pressure solution creep in the middle to upper crust

formation of lateral patterns in rock properties by dolomitization evidence from a miocene reaction front bonaire netherlands antilles abstract petrophysical and geochemical properties of dolomites may exhibit a nested set of lateral patterns typically at the scales of a few meters to 20 m this study assesses whether those lateral patterns are inherited from the limestone precursor or formed during dolomitization sampling was done across a preserved limestone to dolomite reaction front in grainstones of the miocene seroe domi formation bonaire netherlands antilles post dolomitization diagenetic overprinting in the two rock types is absent or minimal two 65 m lateral transects were drilled at 30 cm spacing in two separate beds porosity permeability and geochemical 18o 13c mn sr and na analyses were performed on all 287 recovered samples and 287 thin sections were point counted for petrographic attributes variography shows that dolomite abundance and porosity contain three scales of lateral variability much of the signal is random sample to sample noise as 65 of the total spatial variance occurs at 30 cm spacing however porosity and dolomite abundance also exhibit a short scale correlation length of 3 7 m and a long range oscillatory pattern hole effect at 16 m both of which are also periodic trace elements mn sr and permeability exhibit short range correlation to 5 8 m but no long range pattern mole mg and 13c show increasing variance with distance and all other dolomite attributes exhibit no spatial patterns no limestone attributes show evidence for any short range or long range oscillatory patterns this indicates that the lateral patterns in dolomite abundance porosity permeability sr and mn contents were not inherited from the limestone precursor dolomitization is interpreted to be the cause of the observed spatial patterns as that is the only geologic process that has affected the dolomite but not the limestone on the other side of the front geochemical self organization during the dolomitization process is suggested to be the mechanism by which the spatial patterns in the dolomites emerge a model for that self organizing process is proposed that involves positive feedbacks between precipitation dissolution textural properties reaction rates carbon transport and the evolving flow field relative to mississippian permian and eocene dolomites that have been studied previously the seroe domi dolomites have similar porosity variance at 30 cm spacing and hole effects with slightly greater wavelengths and much larger magnitudes any differences are interpreted to be related to diagenetic history the older dolomites have been affected by burial diagenesis and or weathering which would likely increase sample to sample variability therefore increasing short scale randomness decreasing the magnitude of hole effects and shortening wavelengths of hole effects the lateral patterning formed by dolomitization may thus not be as strongly expressed in ancient dolomites that have complex burial histories

a gis method to identify flat surfaces and restore relict fluvial long profiles from terrace remnants gives new clues on how large basins respond to endorheic exorheic transitions duero basin iberian peninsula this is an mite contribution spanish government plan estatal de investigacion cientifica y tecnica y de innovacion cgl2014 59516 pr2011 0044 gis technical support was funded by the spanish ministerio de economia y competitividad under grant pej 2014 a 93258 lrr is funded by the marie curie clarin cofund programme reference aca 17 19 ficyt principality of asturias

native copper formation in mine prop wood from cyprus illustrates displacive growth by force of crystallization abstract a long standing issue in the study of metamorphic rocks concerns the question in how far replacement of the protolith assemblage during the growth of metamorphic porphyroblasts is accompanied by the additional operation of a displacive mechanism due to an alleged crystallization force exerted by the growing porphyroblast whilst in few cases a component of displacive growth can be corroborated unequivocal criteria to identify such displacements are lacking it follows that the concept of a so called crystallization force is surrounded by uncertainties on the viability and operation of displacive growth in natural systems we investigate the growth of cu porphyroblasts in a sample of mine prop wood from a bronze age copper mine in cyprus the pit prop became infiltrated with copper saturated polluted mine water during collapse of an ancient mine gallery the microstructures associated with the copper porphyroblasts strongly indicate displacive growth whilst the matrix wood has not been affected by any externally imposed deformation we suggest that the displacement microstructures associated with the copper porphyroblasts substantiate the existence of crystallization forces

the pliocene and quaternary fluvial archives of the rhine system abstract the river rhine is one of the few major fluvial systems that connect the areas of the alpine glaciers and scandinavian ice sheet and so provides a key for correlating the two glacial areas in northern and middle europe the fluvial sequences of the rhine valley include at least 11 pleistocene terraces in the lower rhine area 2 pliocene and 12 pleistocene terraces in the middle rhine area resulting in 15 different pliocene and pleistocene terraces based on the correlation between lower and middle rhine the formation of fluvial terraces is significantly influenced by climatic and tectonic processes the terrace staircases are a result of uplift in the middle rhine area and the southern part of the lower rhine area whereas subsidence in the northern part of the lower rhine area resulted in buried stacked sequences magnetostratigraphic data provide chronological constraints for the terrace deposits in the lower rhine embayment and middle rhine region the matuyama brunhes boundary is a reliable marker horizon for the upper terrace fluvial deposits exposed in the karlich clay pit in the middle rhine area the first appearance of volcanic heavy mineral grains in the terrace sediments in loess and soils can be correlated from the middle rhine area through the lower rhine embayment to the netherlands the first occurrence of nordic components in terrace sediments of the lower rhine area is known from gravel on top of the kempen krefeld beds and so are younger than the holsteinian but older than the penultimate glaciation in the lower middle rhine area 40ar 39ar dating of tephra layers intercalated in the aeolian and fluvial sediments provide age constraints the upper pleistocene aeolian sediments overlying the terrace deposits have been dated by luminescence methods and the tephra from the laacher see eruption 12 860 bp is present in the younger lower terrace deposits

application of self organizing map and srtm data to characterize yardangs in the lut desert iran abstract yardangs an exclusive landform due to intensive wind erosion cover a large area in the hyper arid lut desert of iran this paper presents a new approach using self organizing map som as unsupervised algorithm of artificial neural networks for analysis and characterization of yardangs nowadays the shuttle radar topography mission srtm with 3 arc sec data approximately 90 m resolution and nearly world wide coverage provides uniform good quality data the srtm 3 arc sec data were re projected to a 90 m utm grid bivariate quadratic surfaces with moving window size of 5 5 were fitted to this dem the first derivative slope steepness and the second derivatives minimum maximum curvature and cross sectional curvatures were calculated as geomorphometric parameters used as input to the soms 42 soms with different learning parameter settings e g initial and final radius number of iterations and the effect of random initial weights on average quantization error were investigated a som with a low average quantization error 0 1040 was used for further analysis feature space analysis morphometric signatures three dimensional inspection auxiliary data like landsat etm and high resolution satellite imagery from quickbird facilitated the assignment of semantic meaning to the output classes in terms of geomorphometric features results are provided in a geographic information system as thematic maps of landform entities based on form and slope e g yardangs ridge corridors valley or planar areas the results showed that all yardangs and corridors were clearly recognized and classified by this method when their width was larger than the dem resolution but became unrecognizable if their width is much smaller than the grid resolution the identified yardangs and corridors are aligned nnw sse parallel to the prevailing direction of the strong local 120 days wind and cover about 31 and 42 of the study area respectively the results demonstrate that som is a very efficient tool for analyzing aeolian landforms in hyper arid environments that provides very useful information for terrain feature analysis in remote regions

the digital elevation model of italy for geomorphology and structural geology abstract the geomorphological setting and main geo structural features of the central southern italian peninsula have been investigated by creating and analyzing a digital elevation model dem and derived slope aspect and shaded relief images the dem has been assembled from the mean heights archive provided by the italian geological survey for the whole country the elevation data exhibit a grid mesh spacing of 7 5 latitude and 10 longitude firstly three different methods for calculating from a dem slope and aspect are discussed the four contiguous right triangles the maximum downward gradient and the bicubic spline first derivative the resulting maps have been compared with each other at regional scale and for a small area with a slope map obtained by using classical techniques the main goal of the comparison has been the choice of the best technique for the computation of the digital slope map of italy the four contiguous right triangles method yields better results both at local and at regional scale and is being used to create from the dem a slope map and a shaded relief of the whole country which will be published by the italian geological survey secondly the integrated analysis of dem derived slope digital map and shaded relief has permitted verification for the italian peninsula of the trends of already mapped fractures and faults and detection of previously unmapped structures showing morphological evidence the analysis of 1520 regional structural features has showed that the morphological setting of the studied area is strictly related to the tectonics about 90 of the mapped faults and folds are detectable on the shaded relief which proved to be the most useful byproduct of the dem for morphological analysis

nature and origin of authigenic k feldspar in precambrian basement rocks of the north american midcontinent authigenic k feldspar occurs in alteration profiles in uppermost precambrian igneous and metamorphic basement rocks of the midcontinent the k feldspar is widespread and has been identified in six states the profiles occur directly below the cambrian precambrian unconformity and range from about 1 to 8 m in thickness authigenic k feldspar occurs throughout the profile the k feldspar is monoclinic or triclinic by x ray diffraction of end member composition and may compose 63 of rock volume much of the k feldspar formed by replacement of primary feldspar a sample of wholly authigenic k feldspar from altered basement in southern illinois gives a k ar data of 549 plus minus 18 ma early cambrian this data is in agreement with early cambrian rb sr dates for potassic alteration of uppermost precambrian basement in ohio dated authigenic k feldspars from both ohio and illinois give identical delta sup 18 o values of 17 5 suggesting formation from a very similar fluid concordancy of both dates and delta sup 18 o values suggests that the k feldspar formed during an episode of potassic alteration during early cambrian time that affected much of midcontinent north america the dates and delta sup 18 o values for k feldspar when considered together do not fit any of the hypotheses presented here

geochemistry of tectonically expelled fluids from the northern coast ranges rumsey hills california usa tectonic compression has created abnormally high pressure on deep basinal fluids causing their expulsion from areally exposed upper cretaceous rock along the eastern margin of the california coast ranges the fluids emerge as near neutral perennial sodium chloride springs at high elevations with flow rates as high as 10 l per min higher spring discharges are more common around the exposure of a west vergent fault propagation fold axis spring waters range from 1000 to 27 000 mg l tds the least saline water 18o 7 5 closely represents local meteoric water that mixes with saline fluid 18o 5 3 and forms a slope of 3 5 on a d vs 18o plot a na 125 to 8000 mg l vs cl 150 to 17 000 mg l plot shows a linear dilution trend that extends close to but below the values for modern seawater calcium 75 3000 mg l is considerably enriched relative to seawater and forms a nonlinear trend with chloride in detail the na deficit defined by the difference between the measured na content and the na concentration on a hypothetical seawater dilution line is approximately balanced by the ca excess similarly defined by the seawater dilution line this relationship strongly suggests that the fluid is diluted seawater that is being modified by active albitization of plagioclase at different depths simultaneous b and 18o enrichment of the fluids accompanied by deuterium depletion further suggest that the seawater modification is influenced by clay diagenesis bicarbonate and sio2 concentrations show an inverse correlation with cl with most waters being saturated or slightly oversaturated with calcite and quartz at the discharge temperatures some freshwater springs with near meteoric stable isotope values may represent mixing of young groundwater from perched aquifers but in many cases the freshwater springs emerge along the same structures and have the same perennial nature as the saline fluids and expulsion of an older fresh groundwater component that is under abnormal fluid pressures cannot be ruled out basinal fluids elsewhere commonly show dilution trends with local meteoric water and in the case of the rumsey hills some of the dilute saline waters may indicate deep penetration of meteoric water 1 km in the pleistocene before the latest tectonic uplift geothermometry of the spring waters maximum 90 c suggest an origin from as deep as 4 0 km this depth is consistent with the depth of the core of a fault propagation anticline below the surface of the rumsey hills developed by active internal deformation of an east tapering wedge beneath the southwestern sacramento valley active tectonic compression causes near lithostatic fluid pressures in the shallow subsurface below the rumsey hills and volume strain within the core of the anticline that results in upward expulsion of the saline fluids from the indicated depths

implications of replacement for reaction transport modeling abstract mineral replacement in rocks consists of growth of guest mineral and dissolution of host the two reactions are coupled by the grain grain stress generated by growth of the guest grain in a rigid or very viscous rock in which it has initially no available room this stress self adjusts to make the volumetric rates of guest growth and host dissolution equal to each other which accounts for the volume conservation typical of replacement volume preservation during replacement is required by conservation of mass and momentum as well the two reactions are also simultaneous and proceed by a sequence of many tiny alternating increments where these increments are small enough internal textural details of the host grain or grain aggregate are morphologically preserved as ghost textures by the replacement the strong variation of mineral reaction rates with stress required by replacement is evidenced also experimentally reported widespread replacement in many rocks laterites diagenesis of siliciclastics and carbonates metasomatic ores metamorphic rocks and hydrothermal alteration warrants creating water rock reactive transport models that predict when and where in a system replacement should take place current geochemical models implicitly view replacement as sequential uncoupled dissolution of host and growth of guest this sequence of reactions may also occur in rocks but crucially differs from replacement implications of replacement for water rock reaction modeling include 1 balancing of replacement reactions on volume 2 use of helmholtz rather than gibbs free energies of minerals involved in replacement 3 taking account of the strong stress dependence of mineral growth and dissolution rates in rocks and 4 taking account of possible accommodation of growth by local deformation as well as pressure solution of the host rock and of the effect of strain rate growth rate on local rock viscosity

matrix rheology effects on reaction rim growth i evidence from orthopyroxene rim growth experiments the rim forming reaction quartz olivine orthopyroxene is used to investigate the effect of matrix rheology on rim growth rates orthopyroxene rim growth around olivine grains in quartz matrix is compared to rim growth around quartz grains in an olivine matrix at constant p t within one single capsule orthopyroxene rims grow faster around quartz clasts in olivine matrix than around olivine clasts in quartz matrix fourier transform infra red spectra indicate that the entire samples are water saturated because of water adsorption on the reactant grain surfaces the increased orthopyroxene growth rates in olivine matrix as opposed to quartz matrix are interpreted in terms of matrix rheology where in the two different matrix inclusion arrangements the olivine matrix behaves softer and the quartz matrix more rigid the strain energy associated with accommodation of the negative reaction volume is higher for the quartz than the olivine matrix and reduces the free energy that drives orthopyroxene rim growth growth textures in both kinds of orthopyroxene rims indicate that the diffusivity of mgo slightly exceeds the diffusivity of sio2 the relative mobility of mgo and sio2 at given p t fh2o seems to be controlled by energy minimization during orthopyroxene growth at the compressive ol opx interface our experiments provide evidence for two previously overlooked effects relevant to rim growth reactions in metamorphic rocks i diffusivity along chemical potential gradients to reaction sites is a function of rheology and ii the relative diffusivity of components during reaction rim or corona growth is a function of local volume changes at the rim s interfaces

an automated method to extract fluvial terraces from digital elevation models the vesdre valley a case study in eastern belgium abstract fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled directly or indirectly the quaternary incision of rivers terrace long profiles are usually retrieved from sparse traces of ancient floodplains preserved in the present topography however when these traces classically collected from topographic maps aerial photographs and field analyses are too few the inferred profiles may be questionable yet the now available high quality and high resolution digital elevation models dems offer an opportunity to increase greatly the quantity of information usable to reconstruct terrace profiles therefore the purpose of this study was to develop a new dem based method of terrace recognition in order to create a larger database and better constrain the profile reconstruction moreover particular procedures of image and numerical processing were defined to fully automate the analysis basically our method relies on the production of bivariate scatter plots depicting the relation between slope and relative altitude i e the altitude above the current alluvial plain for all pixels of successive sections of the valley for each scatter plot the curve of the lowest slope values observed at every relative altitude is smoothed and its minima are assumed to locate the altitudes of the terrace elements preserved in the section we successfully tested this method in the vesdre valley incised in the ne ardenne massif e belgium notably identifying fault deformation of the profiles the main advantages of our approach are its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of many rivers over extended regions

diagenetic replacement controlled by force of crystallization many diagenetic replacements in sedimentary rocks occur along thin solution films between the authigenic and host phases rather than conventionally invoking bulk pore water undersaturation for host phase dissolution we propose that many diagenetic replacements occur by a force of crystallization controlled replacement mechanism whereby nonhydrostatic stresses resulting from authigenic crystal growth are principally responsible for host phase dissolution this model explains diagenetic features such as the restriction of host phase dissolution to authigenic host crystal contacts and euhedral authigenic crystal faces in planar contact with unreplaced host phases as well as the relative replacement tendencies of some common authigenic minerals

connectivity among straits of the northwest pacific marginal seas 1 the connectivity among straits of the northwest pacific marginal seas is investigated with a primitive equation ocean circulation model simulated for 10 years from 1994 to 2003 over the simulation interval the temporal and spatial means and variations of the model sea surface temperature are comparable to those of the satellite sea surface temperature the model transport through the straits shows good agreement with the available observations and a high seasonality in the taiwan strait the korea strait and the soya strait but relatively low seasonality in the tsugaru strait the kuroshio and taiwan warm current twc are two sources of water flowing through the korea strait the volume transport in the korea strait is dominated by the kuroshio in winter 83 and by the twc in summer 66 relative to the transport through the korea strait the transport percentages of the tsugaru strait connecting to the northwest pacific ocean are 79 in winter and 65 in summer the seasonality of the korea strait transport is positively correlated with the cross strait wind stress the drifter experiments show that it takes about 4 months for most of the drifters deployed in the taiwan strait to enter the korea strait and more than 2 months to travel from the korea strait to the tsugaru and soya straits

episodic potassic diagenesis of ordovician tuffs in the mississippi valley area cambrian ordovician strata of the mississippi valley have been extensively modified by potassic diagenesis ordovician vitric tuffs are altered to k feldspar and illite rich mixed layer illite smectite i s both of which have been dated by k ar rb sr dates for k feldspar support its reliability as a k ar clock despite a dislocation density of 10 sup 9 10 sup 10 cm sup 2 age data document three paleozoic episodes of potassic diagenesis which have mean ages of 396 ma early devonian for k feldspar of the upper mississippi valley umv 362 ma late devonian for i s of the umv and 265 ma permian for i s of missouri devonian dates from the umv correspond to times of wide spread epeirogeny in the us midcontinent and diagenetic episodes are attributed to regional flow of basinal brines caused by ground water recharge on uplifted arches potassium for k feldspar may have come from the michigan basin and k for illite may have come from the east central iowa basin k feldspar and i s of the umv are in oxygen isotopic disequilibrium indicating that the k feldspar crystallized from fluid that was either warmer or had lower delta sup 18 o values than that of the i s permian illitization apparently records northward movement of warm saline fluid as a result of the ouachitamore orogeny less

comment on geochemistry of tectonically expelled fluids from the northern coast ranges rumsey hills california usa by m l davisson t s presser and r e criss

forcing mechanisms and hydrodynamics in loch linnhe a dynamically wide scottish estuary abstract hydrodynamic conditions in loch linnhe a dynamifcally wide estuary on the west coast of scotland are primarily influenced by wind forcing freshwater input and tides winds in the region are orographically steered along the axis of the estuary due to surrounding mountains a large rainfall catchment area results in a large freshwater inflow into loch linnhe which in turn produces low salinity waters at the head of the estuary this combined with a connection to the open sea with coastal salinities leads to salinity gradients in the horizontal and vertical even though a range of observational programmes have focussed on loch linnhe the literature still lacks an evaluation of its physical dynamics here we present a first description of the hydrodynamics in loch linnhe based on observations wind stress predominantly influences the surface layer especially at low frequencies and with a stronger influence than tides during neap tides the buoyancy driven flow due to the large river runoff influences the circulation independent of wind stress seasonal spring autumn and interannual 2011 2012 variability of water masses occur especially in the surface layer tides are dominated by the semi diurnal constituent m 2 with tidal ellipses aligned in the along estuary direction and a stronger influence during spring tides compared to wind an evaluation of dimensionless numbers reveal laterally and vertically sheared exchange flows compared to other scottish estuaries loch linnhe is wide enough to be influenced by the earth s rotation and demonstrates an enhanced freshwater outflow along its north western coast as the freshwater is diverted to the right in the direction of the flow these observed patterns are important for the sustainable environmental management of this socio economically valuable region e g through their relevance to aquaculture pathogen transmission patterns a thorough understanding of the dynamics of the system is essential for a successful evidence based marine planning framework

experimental diagenesis exploratory results we conducted experiments in which a granular mixture of quartz and labradorite was deformed in compression at elevated temperatures 200 350 c and pressures 100 mpa in the presence of deionized water following initial consolidation of the material by application of the loads at room temperature a second hydrothermal phase of consolidation was observed when the temperature was increased with the loads fixed the strain rate during this hydrothermal consolidation decayed approximately exponentially with time and was accompanied by only minor porosity reduction the sample permeability decreased rapidly during the hydrothermal consolidation and continued to decrease following cessation of the deformation the rate of this self sealing process was a complex function of temperature scanning electron microscopy and microprobe analysis of the indurated post experimental material showed albitization of the feldspar especially in highly deformed regions analysis of post experimental fluids show that si in solution increased with increasing flow and temperature fluid rock equilibrium was not achieved within the short durations of the experiments 50 60 hours our interpretation is that deformation occured by grain boundary sliding aided by solution and reaction at high stress contacts and sealing occurred by precipitation in low stress regions in the throats of pores

rate laws for water assisted compaction and stress induced water rock interaction in sandstones mineral water interactions under conditions of nonhydrostatic stress play a role in subjects as diverse as ductile creep in fault zones phase relations in metamorphic rocks mass redistribution and replacement reactions during diagenesis and loss of porosity in deep sedimentary basins as a step toward understanding the fundamental geochemical processes involved using naturally rounded st peter sand we have investigated the kinetics of pore volume loss and quartz water reactions under nonhydrostatic hydrothermal conditions in flow through reactors rate laws for creep and mineral water reaction are derived from the time rate of change of pore volume sand water dissolution kinetics and flow rate independent steady state silica concentrations and reveal functional dependencies of rates on grain size volume strain temperature effective pressure confining minus pore pressure and specific surface areas together the mechanical and chemical rate laws form a self consistent model for coupled deformation and water rock interaction of porous sands under nonhydrostatic conditions microstructural evidence shows a progressive widening of nominally circular and nominally flat grain grain contacts with increasing strain or equivalently porosity loss and small quartz overgrowths occurring at grain contact peripheries the mechanical and chemical data suggest that the dominant creep mechanism is due to removal of mass from grain contacts termed pressure solution or solution transfer with a lesser component of time dependent crack growth and healing the magnitude of a stress dependent concentration increase is too large to be accounted for by elastic or dislocation strain energy induced supersaturations favoring instead the normal stress dependence of molar gibbs free energy associated with grain grain interfaces

petrography and composition of authigenic feldspars oligocene frio formation south texas abstract detrital feldspar assemblages 1 to 4 km burial depth in oligocene sandstones from south texas are extensively altered by dissolution in some samples cementation in secondary pores principally by albite but also by authigenic k feldspar and other minerals occurs subsequent to the dissolution and can lead to wholesale replacement textures solid state diffusion of cations has not been important in the replacement process information from conventional light microscopy sem examination and back scattered electron imaging suggests that relative rates of dissolution versus replacement varied widely among different detrital grains through time even on the scale of a thin section dissolution of detrital feldspars and precipitation of relatively pure albite and k feldspar take place ver a large depth interval and thus can be markedly separated in time vacuolized albite occurring as irregular veins within detrital grains is associated with little visible secondary porosity and forms when precipitation is rapid relative to dissolution of the detrital grain more rapid dissolution results in formation of larger scale intragranular secondary pores commonly filled by subsequent precipitation of clear albite within the former grain volume electron microprobe analyses show that the composition of vacuolized albite and authigenic k feldspar deviate somewhat from ideal compositions presumed typical for authigenic feldspars regardless of their cause these subtle variations in composition have important ramifications for basin scale mass balance calculations requiring accurate estimates of the volume of authigenic feldspar

insights into the dolomitization process and porosity modification in sucrosic dolostones avon park formation middle eocene east central florida u s a abstract the avon park formation middle eocene in central florida u s a contains shallow water carbonates that have been replaced by dolomite to varying degrees ranging from partially replaced limestones to highly porous sucrosic dolostones to less commonly low porosity dense dolostones the relationships between dolomitization and porosity and permeability were studied focusing on three 305 m long cores taken in the city of daytona beach stable isotope data from pure dolostones mean 18o 3 91 v pdb indicate dolomite precipitation in eocene penesaline pore waters which would be expected to have been at or above saturation with respect to calcite nuclear magnetic log derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals beds and formations at the crystal scale dolomitization occurs in a volume for volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass carbonate is passively scavenged from the formation which results in no significant porosity change at the formation scale moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization which demonstrates the intimate association of the dolomitization process with carbonate dissolution the model of force of crystallization controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the avon park formation and elsewhere 1 volume for volume replacement at a crystal scale 2 coupled growth of dolomite crystals and dissolution of host calcium carbonate matrix and 3 automorphic replacement by euhedral dolomite crystals the force of crystallization model also does not require an influx of externally derived water that is undersaturated with respect to calcite to dissolve calcite a fact that could simplify diagenetic models of porosity generation in dolostones the later addition of external carbonate can result in a substantial reduction in porosity by the precipitation of dolomite cement which could convert a high porosity sucrosic dolostone into a dense paleozoic type dolostone

quaternary tectonics in the northern ardennes belgium abstract a number of nw se or nnw sse trending radial faults are recognized on the northern slope of the ardenne massif they have been active since the oligocene as depicted by deformations of planation surfaces and other morphological features the study of river terraces demonstrates their quaternary activity with vertical movements ranging from 4 to 10 m during the late quaternary this fault activity is related to the opening of the lower rhine embayment

computer assisted discrimination of morphological units on north central crete greece by applying multivariate statistics to local relief gradients traditional manual methods have been employed for decades to measure geomorphometric properties from topographic maps such measurement techniques tend to be tedious and time consuming and the designated landform elements cannot be easily overlaid on any digital map and imagery for further applied research this study deals with a new quantitative geomorphometric procedure based on the multivariate statistical analysis of local topographic gradients within a part of northcentral crete this method employs sets of computer algorithms that automatically extract and classify geomorphometric properties from digital elevation models dems this was done by evaluating the morphological setting around each pixel of the dem along the eight azimuth directions isodata unsupervised classification was implemented to generate 10 morphometric classes showing the spatial distribution of areas with a similar geomorphic scenario results revealed that this approach permitted a quick estimation of the spatial distribution of morphologically homogeneous terrain units it also demonstrated the ability of the delineated landform elements to be superimposed on any digital map and imagery for further investigation this became apparent during the examination of the relationship between the geomorphological units and the land cover land use types in the study area both relative association and the dominant land cover land use types in relation to geomorphological units are presented d 2003 elsevier b v all rights reserved

soil production and hillslope transport in mid latitudes during the last glacial interglacial cycle a combined data and modelling approach in northern ardennes

mineral growth in rocks kinetic rheological models of replacement vein formation and syntectonic crystallization abstract we model three cases of coupling between mineral growth kinetics and mechanical response of the rock i dispersed spherical crystals growing by replacement in a hydrostatically stressed elastic rock ii growth of veins or vein networks accommodated by viscous relaxation of surrounding rock and iii syntectonic crystallization in a rock undergoing bulk pure shear such models for the microscopic environment of mineral growth together with additional assumptions or knowledge about rheological behavior and aggregate geometry provide refined estimates of the behavior of a macroscopic volume element which could be combined with geochemical reaction transport models crucial in the models are the various consequences pressure solution creep fracturing of the local stress that is necessarily generated by mineral growth in rocks other than in pores in the first model the dispersed spherical crystals of mineral a are assumed to grow within a spherical volume of rock consisting of mineral b the mineralized zone mz itself embedded in elastic rock the macroscopic stress in the mz and the far field stress in the surrounding rock are uniform and hydrostatic mineral growth of the a crystals is driven by supersaturation with respect to mineral a is accommodated by replacement of b grains and leads to an expansion of the mz described by an infinitesimal strain the radial growth rate of a spherical crystal of mineral a with replacement of mineral b is da dt k a r tln a k b v 0 b k b v 0 b k a v 0 a where ka and kb are kinetic constants r is the gas constant t the temperature in kelvin and v0a and v0b are specific volumes reference saturation states of mineral a a 1 and host mineral b b 1 are specified at the far field hydrostatic stress 0 the microscopic environment of each crystal of a is modeled by a representative volume element rve consisting of a sphere of mineral a embedded in a spherical shell of mineral b in each rve stress is neither uniform nor hydrostatic the model links the local microscopic stress with the macroscopic stress in the mz and surrounding rock the second model refers to veins that make room for themselves by growing not to veins that form by cementation of previously opened or opening cracks if the growth of mineral a as propagating veins or as an interconnected vein network takes place by deformation and expansion of the mz with the deformation itself driven by the stress arising from the supersaturation driven growth the surrounding rock undergoes deformation and is treated as viscous the rate of growth in vein width w is dw dt 2 k a rtln a sv 0 a 1 m where m 16 kav0ac2 3b3 is the medium viscosity c is the vein radius and each vein is treated as centered in a spherical rve of radius b s is an effective tensile stress required for vein propagation for a vein network in which veins surround equant polyhedra of rock of radius b we set c b and drop the term in s for simplicity veins may also widen by replacement the ratio of vein widening by expansion to that by replacement is dw dt expansion dw dt replacement 3 b 16 3 b 16 k a v 0 a k b v 0 b k b v 0 b k a v 0 a both mechanisms of accommodation contribute equally when 3b 16kbv0b at higher viscosity replacement is dominant the incipient growth of a cylindrical crystal with circular cross section in a medium deforming in pure shear simulates syntectonic crystallization both dissolution and deformation of the host accommodate growth in the model the crystal tends to grow faster in the direction of maximum rate of extension in this direction the host mineral may either dissolve to accommodate growth or precipitate to form a pressure shadow accommodation by host dissolution is greatest in the direction of maximum rate of shortening

mineralogic and stable isotope studies of hydrothermal alteration at the jinchuan ni cu deposit china the jinchuan intrusion hosts one of the largest magmatic ni cu sulfide deposits in the world net textured and disseminated pyrrhotite pentlandite and chalcopyrite are found in olivine rich rocks 60 80 vol that occur as a northwest southeast striking dike olivine in the intrusion has been variably converted to mixtures of serpentine and fine grained magnetite interstitial pyroxene and minor plagioclase have been altered to mixtures of chlorite amphibole epidote clinozoisite na rich feldspar and lesser amounts of calcite although the interstitial net texture of sulfide minerals surrounding olivine grains is preserved up to 30 vol percent of sulfide minerals are replaced by magnetite serpentine and chlorite an external origin for mg and si needed for the isovolumetric replacement of sulfides cannot be discounted but a local origin related to olivine and pyroxene alteration is favored serpentine and chlorite may be enriched in cu and ni but the enrichment can account for less than 1 percent of the metals lost during the replacement of sulfide minerals by silicates and oxides some of the metals and sulfur that were removed from the net textured sulfide assemblages have been redeposited on a centimeter scale in fine ribbons and veins within serpentine chlorite and amphibole sulfur isotope values of the pyrrhotite pentlandite chalcopyrite assemblage at jinchuan fall in the range of 2 to 8 per mil with over 80 percent of the values between 2 and 2 per mil immediate country rocks in the jinchuan area are precambrian granitoids schists and marbles with sulfur concentrations less than 100 ppm although the 34 s values of the main sulfide assemblage at jinchuan are in the range that is characteristic of mantle derived sulfur assimilation of sulfur from unexposed country rocks cannot yet be discounted secondary pyrite occurs in veins and stringers and rarely as a replacement of pyrrhotite and is characterized by 34 s values between 7 and 27 per mil the strongly negative 34 s values of secondary pyrite are thought to be a result of oxidation of primary magmatic sulfide assemblages and partial reduction of aqueous sulfate oxygen and hydrogen isotope values of silicate minerals suggest that at least two fluids have been involved in the hydrothermal alteration at jinchuan the 18 o values of plagioclase amphibole and serpentine all suggest the involvement of a fluid with a 18 o value between 2 and 5 per mil at 300 to 400 c the d values of amphibole and one population of serpentine suggest a d value for the fluid in the range of 45 to 63 per mil these values are consistent with the involvement of evolved seawater or a metamorphic fluid in the early stages of alteration the possible involvement of evolved seawater in hydrothermal alteration is consistent with a rift setting for the emplacement of the jinchuan intrusion however the wide range in serpentine d values computed d of the fluid 45 to 103 suggest either that serpentinization involved a mixture of evolved seawater and or metamorphic water and meteoric water or more likely that serpentine continued to exchange hydrogen isotopes with late stage meteoric waters after it formed

morphometric analysis and tectonic interpretation of digital terrain data a case study tectonic movement along faults is often reflected by characteristic geomorphological features such as linear valleys ridgelines and slope breaks steep slopes of uniform aspect regional anisotropy and tilt of terrain analysis of digital elevation models by means of numerical geomorphology provides a means of recognizing fractures and characterizing the tectonics of an area in a quantitative way the objective of this study is to investigate the use of numerical geomorphometric methods for tectonic geomorphology through a case study the methodology is based on general geomorphometry in this study the basic geometric attributes elevation slope aspect and curvatures are complemented with the automatic extraction of ridge and valley lines and surface specific points evans univariate and bivariate methodology of general geomorphometry is extended with texture spatial analysis methods such as trend autocorrelation spectral and network analysis terrain modelling is implemented with the integrated use of 1 numerical differential geometry 2 digital drainage network analysis 3 digital image processing and 4 statistical and geostatistical analysis application of digital drainage network analysis is empha sized a simple shear model with principal displacement zone with an ne sw orientation can account for most of the the morphotectonic features found in the basin by geological and digital tectonic geomorphology analyses copyright 2003 john wiley sons ltd

terra rossa genesis implications for karst and eolian dust a geodynamic thread abstract although terra rossa has long been thought to form by residual dissolution of limestone and or by accumulation of detrital mud ash or dust on preexisting karst limestones we present conclusive new field and petrographic evidence that terra rossa forms by replacement of limestone by authigenic clay at a moving metasomatic front several centimeters wide the red clay s major chemical elements al fe and si probably come from dissolved eolian dust the replacement of calcite by clay exhibits a serrated microstylolitic texture that helps prove that replacement happens not by dissolution precipitation as conventional wisdom has it but by pressure solution of calcite driven by the crystallization stress generated by the growth of clay crystals the acid produced by the isovolumetric replacement of limestone by clay quickly dissolves out additional porosity permeability in an adjacent slice of limestone within the front triggering a reactive infiltration instability that should theoretically

automatically derived catchment boundaries and channel networks and their hydrological applications abstract a method of generating drainage networks and catchment boundaries from gridded ground elevation data a digital terrain model is presented the method includes an algorithm for coping with localised low points in the data the paper suggests two objective ways of comparing the conventionally mapped with the automatically generated drainage network emphasis is placed on the way that this approach is capable of benefiting a variety of hydrological applications in particular the automatic estimation of flow statistics from catchment characteristics

geomorphometric analysis for characterizing landforms in morelos state mexico landforms can be described and quantified into simple relief elements by parametrization of digital elevation model dem in this research we investigate the use of morphometric parameters and a new classification scheme to characterize selected elemental forms associated with landforms we apply and test this methodology on a geomorphologically diverse region located in central mexico these simple elements are known as morphometric classes and include ridge plane channel pit peak and pass these classes correspond to real entities and are of practical significance the morphometric classes were grouped according to their areal parameters ridge plane and channel and pointed parameters pit peak and pass which can be used to form the basis of a system of characterization and classification of landforms landform elements display statistically significant compositional differences with respect to their proportions of morphometric classes this in turn can be plotted onto a diagram of characterization and classification known as a double ternary diagram dtd which comprises both areal and pointed parameters and any combination thereof the dtd is useful for studying geomorphological processes wherein areal and point values and properties have expressions which are topographically quantifiable

long term fluvial archives in nw france response of the seine and somme rivers to tectonic movements climatic variations and sea level changes the seine and the somme are the two main rivers flowing from northwestern france into the channel during the pleistocene cold stages both rivers were tributaries of the river manche which was exporting sediments into the central deeps of the channel the river seine has a very well developed terrace system recording incision that began at around 1 ma the same age is proposed for the beginning of the main incision in the somme valley on the basis of morphostratigraphy pedostratigraphy palaeontology palaeomagnetism and esr datings the uplift rate deduced from analysis of the seine and somme terrace systems is of 55 to 60 m ma since the end of the lower pleistocene the response of the two rivers to climatic variations uplift and sea level changes is complex and variable in the different parts of the river courses for example the evolution of the lower seine system is influenced by uplift and climate changes but dominated by sea level changes in the middle seine the system is beyond the impact of sea level variations and shows a very detailed response to climatic variations during the middle and upper pleistocene in a context of uplift the somme valley response appears to be more homogeneous especially in the middle valley where the terrace system shows a regular pattern in which incision occurs at the beginning of each glacial period against a general background of uplift nevertheless the lower somme valley and the palaeo somme in the channel area indicate some strong differences compared with the middle valley influence of sea level variations and probably differences in rates of tectonic uplift between the channel and the present continent the differences in the responses of the two river valleys during the pleistocene are related to differences in the size of the fluvial basins to the local tectonic characteristics to the geometry of the platform connected to the lower parts of the valleys and to the hydrodynamic characteristics of each river finally it is shown from these examples that the multidisciplinary study of pleistocene rivers is a very efficient tool for the investigation of neotectonic activity

legacy sediment storage in new england river valleys anthropogenic processes in a postglacial landscape abstract legacy sediment associated with erosion from land clearing is a common feature in river valleys of the unglaciated mid atlantic piedmont region here we quantify the volume of legacy sediment storage in three watersheds in new england a formerly glaciated region with similar history and intensity of forest clearing and milldam construction during the seventeenth to nineteenth centuries we combine field observations of bank stratigraphy radiocarbon dating and mapping of terraces and floodplains using lidar digital elevation models and other gis datasets the 68 km2 south river watershed in western massachusetts exhibits the most extensive evidence for legacy sediment storage we visited 18 historic dam sites in the watershed and found field evidence for up to 2 2 m of fine sand and silt legacy sediment storage at 14 of the sites in the 555 km2 sheepscot river watershed in coastal maine we visited 13 historic dam sites and found likely legacy sediment up to 2 3 m thick at six of the dams in the 171 km2 upper charles river watershed in eastern massachusetts we investigated 14 dam sites and found legacy sediment up to 1 8 m thick at two of them stratigraphically we identified the base of fine grained legacy sediment from a change to much coarser grain size gravel at most sites or to glacial lacustrine or marine deposits along the sheepscot river we observed cut timbers underlying historic sediment at several locations likely associated with sawmill activities only at the charles river were we able to radiocarbon date the underlying gravel layer 1281 1391 calibrated ce at no site did we find a buried organic rich holocene soil in contrast to the field relations commonly observed in the mid atlantic region we use lidar elevation data to map planar terrace extents in each watershed estimate thickness of remaining legacy sediment found stored behind breached or removed milldams and estimate volumes of remaining legacy sediment storage in valley bottoms for entire watersheds the maximum volume of stored legacy sediment estimated for the south sheepscot and upper charles watersheds is 2 5 106 m3 3 7 106 m3 and 2 6 104 m3 respectively these volumes of legacy sediment can be translated to an equivalent thickness of soil eroded from each watershed 37 mm 7 mm and 0 2 mm respectively we attribute the variation in presence and thickness of legacy sediment at the new england sites to the existence or absence of upstream sediment supply in the form of thick glacial deposits and to sinks such as lakes and wetlands along valley bottoms of the three study watersheds the south river has the most extensive glacial sediments fewest sinks and the most legacy sediment in storage along the river corridor

multiple precursors of secondary mineralogical assemblages in cm chondrites we report a petrographic and mineralogical survey of tochilinite cronstedtite intergrowths tcis in paris a new cm chondrite considered to be the least altered cm identified to date our results indicate that type i tcis consist of compact tochilinite cronstedtite rims surrounding fe ni metal beads thus confirming kamacite as the precursor of type i tcis in contrast type ii tcis are characterized by complex compositional zoning composed of three different fe bearing secondary minerals from the outside inwards tochilinite cronstedtite and amakinite type ii tcis present well developed faces that allow a detailed morphological analysis to be performed in order to identify the precursors the results demonstrate that type ii tcis formed by pseudomorphism of the anhydrous silicates olivine and pyroxene hence there is no apparent genetic relationship between type i and type ii tcis in addition the complex chemical zoning observed within type ii tcis suggests that the alteration conditions evolved dramatically over time at least three stages of alteration can be proposed characterized by alteration fluids with varying compositions 1 fe and s rich fluids 2 s poor and fe and si rich fluids and 3 s and si poor fe rich fluids the presence of unaltered silicates in close association with euhedral type ii tcis suggests the existence of microenvironments during the first alteration stages of cm chondrites in addition the absence of mg bearing secondary minerals in paris tcis suggests that the mg content increases during the course of alteration

automated classification of landform elements using object based image analysis this paper presents an automated classification system of landform elements based on object oriented image analysis first several data layers are produced from digital terrain models dtm elevation profile curvature plan curvature and slope gradient second relatively homogenous objects are delineated at several levels through image segmentation these object primatives are classified as landform elements using a relative classification model built both on the surface shape and on the altitudinal position of objects so far slope aspect was not used in classification the classification has nine classes peaks and toe slopes defined by the altitudinal position or the degree of dominance steep slopes and flat gentle slopes defined by slope gradients shoulders and negative contacts defined by profile curvatures head slopes side slopes and nose slopes defined by plan curvatures classes are defined using flexible fuzzy membership functions results are visually analyzed by draping them over dtms specific fuzzy classification options were used to obtain an assessment of output accuracy two implementations of the methodology are compared using 1 romanian datasets and 2 berchtesgaden national park germany the methodology has proven to be reproducible readily adaptable for diverse landscapes and datasets and useful in respect to providing additional information for geomorphological and landscape studies a major advantage of this new methodology is its transferability given that it uses only relative values and relative positions to neighboring objects the methodology introduced in this paper can be used for almost any application where relationships between topographic features and other components of landscapes are to be assessed

karst driven flexural isostasy in north central florida deformed marine terraces can be used to explore a region s uplift history trail ridge is a marine terrace in north florida that is nearly 80 meters above modern sea level and contains quaternary marine fossils a fact that is inconsistent with estimates of paleo sea level history since the early pleistocene this implies that the terrace has experienced uplift since its formation as well as non uniform deformation recorded by the warping of its previously horizontal state the florida carbonate platform located on the passive margin of eastern north america is a setting where non tectonic influences e g isostatic adjustment dynamic topography can be examined we present a single transect numerical model of vertical displacement derived from elastic flexure to assess the influence of karst driven isostatic uplift on present day topography of trail ridge in north florida flexural modeling predicts elevations in central florida not observed today most likely because surface erosion and karst cavity collapse have obliterated this high topography older subsurface stratigraphic units however display the arched profile predicted from flexural modeling mass loss calculated by differencing modeled topography and observed topography was found to be 6 75 1012 kg since emplacement of trail ridge uplift rates assuming karst driven flexural isostasy alone using previously estimated ages of trail ridge of 0 125 1 4 3 or 3 5 ma were found to be 0 535 0 048 0 022 and 0 019 mm yr respectively a more likely explanation of uplift includes contributions from dynamic topography and glacial isostatic adjustment which should be further explored with more advanced geophysical modeling

potassic diagenesis of cambrian sandstones and precambrian granitic basement in uph 3 deep hole upper mississippi valley u s a abstract the mt simon sandstone cambrian in core from hole uph 3 in northwestern illinois contains three distinct diagenetic zones a zone with k feldspar overgrowths characterizes the upper 51 m of mt simon sandstone an intermediate underlying sericite zone is about 126 m thick and a lowermost feldspar zone is about 87 m thick authigenic k feldspar in the mt simon sandstone occurs in several modes overgrowths rhombs penetration twinned crystals chert like aggregates surrounded by coarser k feldspar mosaics of anhedral to euhedral crystals and as replacements of microcline sericite i s occurs as pore filling aggregates of minute flakes quartz overgrowths are common throughout these three diagenetic zones k feldspar was the first to form closely followed by quartz then by ericite and lastly possibly by a second addition of quartz overgrowth the upper 6 1 m of precambrian granite gneiss basement exhibits similar potassic alteration to the overlying mt simon sandstone the uppermost 2 5 m of the basement rock is a probable weathering profile in which pedogenic clays were replaced by sericite i s and chlorite sericite in the basement rock was likely formed during the same episode as in the mt simon sandstone based on 18o values authigenic k feldspar occurs as pore fillings overgrowths replacements of microcline and intergrown with phyllosilicate below the profile it partially replaces plagioclase similar potassic alteration of the mt simon sandstone of uph 3 occurs in cores of both uph 1 and 2 indicating a lateral extent of about 7 km a k ar date of 394 6 6 ma was obtained from authigenic k feldspar of the basal mt simon sandstone this early devonian age is within the range of ages from authigenic k feldspar in ordovician tuffs of the upper mississippi valley suggesting that the k feldspar is the product of a single regional diagenetic event k ar dates of 271 3 4 6 ma 254 4 4 6 ma and 214 1 4 6 ma were obtained from authigenic sericite of the mt simon sandstone the devonian age for the k feldspar and permian ages for the sericite are nearly coeval with times of uplift of the findlay and pascola arches respectively these diagenet c episodes are attributed to regional migration of basinal brines caused by groundwater recharge on these uplifted arches potassium for both the k feldspar and sericite possibly came from the michigan and illinois basins respectively devonian and permian dates for potassic diagenesis possibly coincide with two episodes of pb leaching of basement rocks at 400 ma and 260 ma thus the potassic fluids may have leached pb and zn from precambrian basement particulary paleosols and then formed upper mississippi valley pb zn deposits

reactive transport modeling an essential tool and a new research approach for the earth sciences abstract reactive transport modeling is an essential tool for the analysis of coupled physical chemical and biological processes in earth systems and has additional potential to better integrate the results from focused fundamental research on earth materials appropriately designed models can describe the interactions of competing processes at a range of spatial and time scales and hence are critical for connecting the advancing capabilities for materials characterization at the atomic scale with the macroscopic behavior of complex earth systems reactive transport modeling has had a significant impact on the treatment of contaminant retardation in the subsurface the description of elemental and nutrient fluxes between major earth reservoirs and in the treatment of deep earth processes such as metamorphism and magma transport active topics of research include the development of pore scale and hybrid or multiple continua models to capture the scale dependence of coupled reactive transport processes frontier research questions that are only now being addressed include the effects of chemical microenvironments coupled thermal mechanical chemical processes controls on mineral fluid reaction rates in natural media and scaling of reactive transport processes from the microscopic to pore to field scale

precipitation sealing and diagenesis 1 experimental results during burial and diagenesis of granular aggregates significant permeability reduction may be induced by the formation of low temperature authigenic minerals to quantitatively assess the importance of this process we have conducted a series of hydrothermal flow through experiments using deionized water and labradorite quartz sand all experiments were conducted in a modified triaxial apparatus configured to allow continuous permeability measurements under most of the conditions tested significant permeability reduction is observed with no concurrent decrease in porosity the overall permeability reduction sometimes exceeds 1 order of magnitude over 4 days and is positively correlated to temperature and deviatoric stress scanning electron microscope observations together with data from additional experiments show that the observed permeability reduction is entirely a result of secondary mineral growth si and al concentrations in the postexperiment fluids are also correlated to temperature and stress confirming the link between the chemical state of the system and permeability behavior in all experiments permeability reduction is fastest early and levels off in the late stages to explain the permeability behavior as a function of time a conceptual model is developed in which precipitation of authigenic minerals is rapid at early times while dissolution of quartz and labradorite is most active as the system approaches equilibrium the components necessary for secondary mineral formation are liberated at a lower rate thereby causing precipitation to slow although authigenic mineral formation does not reduce total pore space in these experiments there is a reduction in effective porosity which results in permeability reduction

dem based morphometry as a tool for reconstructing primary volcanic landforms examples from the borzsony mountains hungary a complex application of digital elevation model dem derivatives is presented for a highly degraded volcanic area the miocene borzsony mountains hungary we propose unconventional geometrical and mathematical transformations of the original dem data in order to enhance the topographic features of the volcanic relief that stem from the primary landforms it is the actual ridges that represent the least degraded surfaces of an original hypothetical volcanic cone therefore the statistical dem properties such as ridge pattern 1 slope angle distribution 2 and higher order slope derivatives 3 should be strongly correlated with the paleosurface automated creation of a ridge pattern image is based on the local histogram of the dem and helps to outline the original surface remnants a local slope angle histogram may point out structurally coherent parts of the original cone for instance tectonic displacements or large scale sector slumping does not affect the slope angle histogram of the original relief evaluating the ridge maps and slope aspect maps of the borzsony mountains allows various cone sectors to be identified and connected to the original volcano structural elements finally the polar coordinate transformed pct image 4 centered on a hypothesized eruptive vent enhances the original radial valley pattern in the case of multiple eruptive centers and or post eruptive tectonic modifications the radial pattern is changed which may be evidenced in the pct image in fact the pct image analysis for the borzsony mountains suggests a complex post eruptive tectonic scenario the presented methods can be recommended to infer the original configuration of highly degraded volcanic structures with poorly known tectonic and erosional history

silica diagenesis origin of inorganic and replacement cherts abstract silicification of originally non siliceous sediments affects a wide variety of rock types and materials and ranges from minor to pervasive partial and minor chertification occur mostly in phanerozoic carbonates carbonate bearing sandstones evaporites and fossil wood the source of the silica is predominantly biogenic in petrified wood the silicification mechanism is a permeation or void filling process not a replacement in this example the sequence of silica phase transformation is the same as that in deep sea siliceous sediments in many silicified rocks particularly in certain carbonates the transformation sequence is different from that in radiolarites or diatomites the chemical environment and conditions of early diagenetic chert formation in shallow water carbonates are delineated by the general mixing model of knauth 1979 but remain unknown for most other types an exception are the flint nodules and bands of the english chalk a detailed geochemical study of the paramoudra flint structures by clayton 1986 provided remarkable insight into the replacement process seven different recurring silica fabrics have been recognized in chert replaced carbonates including equigranular microcrystalline quartz or microquartz and megaquartz and fibrous types chalcedony quartzine or length slow chalcedony lutecite zebraic chalcedony and microflamboyant quartz among the latter quartzine and microflamboyant quartz are common in but by no means restricted to chert replaced evaporites for which milliken 1979 recognized a sequence of seven quartz fabrics as a single criterion only anhydrite inclusions in megaquartz quartzine or microflamboyant quartz provide unequivocal evidence for an evaporite precursor the relative timing between silicification and well established diagenetic carbonate reactions shows that virtually all theoretically possible sequences occur chertification of carbonate host sediment thus may take place during early intermediate or late diagenesis and even during anchimetamorphism pervasive to complete silicification has been described in lacustrine pedogenic and hydrothermal volcanogenic rocks and occurs on the scale of individual beds members or entire formations it may affect some of the aforementioned rock types too for example carbonates the source of the silica is predominantly inorganic chert formation in these environments includes direct chemical silica precipitation from solution through a gel stage magadi type cherts result from the conversion of the hydrous sodium silicate magadiite into microcrystalline quartz which has occurred in east african rift valley lakes such as lake magadi in late pleistocene time they are closely related to directly precipitated inorganic cherts which have been observed in alkaline environments of playa lakes silcretes originate from weathering and soil forming processes under climatic and environmental conditions conducive to the formation of duricrusts and laterites in more humid climates however non weathering profile silcretes occur which have been distinguished from weathering profile silcretes four to five different silcrete fabric types have been established including the 1 grain supported or quartzitic 2 floating terrazzo 3 matrix albertinia and opaline and 4 conglomeratic types in volcanic edifices silicification related to hydrothermal activity occurs 1 along the ascent routes of the fluids vents within the volcanic complexes 2 in isolated ponds and depressions on the sea floor where the fluids discharge mostly in the median rift valley of mid ocean ridges and 3 in geothermal areas on land associated with spreading lineaments volcanic islands arcs transform faults or continental hot spots attention has focussed on the associated base metal concentrations and less on the silicification and accompanying iron enrichment processes the precambrian banded iron formations may be indirectly or directly related to hydrothermal volcanic processes the origin of these cherty iron formations certainly requires more than one genetic model and at present remains a major unresolved problem despite massive efforts to tackle it

dynamic model of the genesis of calcretes replacing silicate rocks in semi arid regions abstract in both pedogenic and groundwater calcretes calcium carbonate precipitates in voids or displacing other grains or replacing underlying parent silicates replacement textures are widespread in pedogenic calcrete many calcretes also contain magnesium layer silicates and minor chert we present a reaction transport model that accounts for the genesis of replacement in calcretes and for their mineralogy replacement is difficult to account for geochemically because it requires simultaneous removal of large amounts of silicates and import of also large amounts of caco 3 in the model the genesis of replacement is directly related to seasonally alternating dry wet climates and to appropriate groundwater or circulating soil water compositions in a dry season water evaporation causes caco 3 and sepiolite or attapulgite to precipitate if groundwater contains enough mg 2 sepiolite precipitation by the chemical divide mechanism depletes sio 2 aq resulting in the dissolution of parent silicates in the following wet season sepiolite dissolves fast and silica and cations are flushed away by rainwater making room for caco 3 precipitation in the next dry season as climate cycles repeat caco 3 is accumulated and silicates are removed the sepiolite or attapulgite or mg smectite serves as a temporary storage of silica between seasons if the groundwater contains too little aqueous mg then the model predicts growth of calcium carbonate without removing silicates thus producing void filling and or displacive textures instead of replacement the model consists of a set of nonlinear partial differential equations taking account of mass conservation dispersion advection rainwater infiltration evaporation and the kinetics of mineral reactions the hydrodynamics of unsaturated media is applied in determining water flow in calcrete profiles wet dry seasonal changes are incorporated by alternating the upper boundary conditions the model successfully produces the mineral and textural zonation observed in many calcretes namely at the bottom of the profile the parent rock is first replaced by sepiolite only part of which is in turn replaced by calcite whereas at the top of the calcrete the sepiolite is itself completely replaced by the calcite which appears to directly replace the parent rock the model can produce calcrete near the earth s surface well above the water table low p co 2 intensive evaporation and long dry seasons all are predicted to produce thicker calcretes calcretes constitute an effective geochemical tool that via replacement removes parent silicate rocks and shapes the landscape of semi arid countries the model herein provides a mechanism that accounts for the efficiency of replacement in removing silicates

an automated method to extract fluvial terraces from lidar based high resolution digital elevation models the oiartzun valley a case study in the cantabrian margin abstract combined climatic and tectonic conditions controlled the quaternary incision of rivers and the fluvial terraces are the most significant landforms to untangle their evolutionary history increasing availability of high resolution topography data over large areas offers an opportunity to increment greatly the quantity and the quality of information feasible for the development of semi automated techniques for identification and characterization of these features in this study we apply a methodology based on demoulin et al 2007 for the detection of fluvial terraces in digital elevation models dem with the novelty of using dems derived from high resolution lidar data that are processed using geographical information system gis routines the method is based on the recognition of slope variations and change of sign of profile curvature across the hillslopes considering scatter plots over valley segments of given length every minimum of slope value as a function of either distance to or elevation above the base of the valley is considered a possible terrace remnant the compilation of these slope minima retained within the successive segments covering the whole length of the valley will finally provide a two dimensional plot of terrace remnants in respect to the present day long profile of the river we successfully tested this method in the oiartzun valley in the eastern area of the cantabrian margin western pyrenees where terrace maps were previously developed via aerial photo interpretation and field mapping campaigns despite the highly erosive nature of the cantabrian fluvial systems the poor preservation of fluvial landforms and the abundant vegetation cover our method obtained good results due to its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of fluvial valleys and their comparison

baroclinic two layer flow induced by extreme discharge from a dam in a narrow channel abstract long term current observations were taken in the narrow noryang channel during extreme discharge and small discharge periods from a river dam the noryang channel connects the west gwangyang and east jinju bays in southern korea jinju bay is relatively isolated from the open sea by many islands whereas gwangyang bay is connected to the open sea through a wide deep channel jinju bay is closer to the river dam than gwangyang bay the residual mean flow in the channel over the observation period showed a baroclinic two layer flow as in an estuary during the large discharge period whereas barotropic flow was present during the small discharge period during the large discharge period the upper layer of water flowed continuously westward whereas the lower layer flowed eastward hydrographic data observed along the channel showed that gwangyang bay water was relatively saline and heavier during the large discharge period this spatial difference in water density might be the result of a large inflow of discharge into jinju bay and relatively strong mixing between the water in gwangyang bay and the open sea the salinity in the more isolated jinju bay was lower simple analytical model calculations showed that horizontal density difference during the large discharge period could drive the surface current flow westward whereas that of the dense water of the lower layer in gwangyang bay flowed eastward through the noryang channel

an automated approach to the classification of the slope units using digital data abstract digital elevation and remote sensing data sets contain different yet complementary information related to geomorphological features digital elevation models dems represent the topography or land form whereas remote sensing data record the reflectance emittance or spectral characteristics of surfaces computer analysis of integrated digital data sets can be exploited for geomorphological classification using automated methods developed in the remote sensing community in the present study geomorphological classification in a moderate to high relief area dominated by slope processes in southwest yukon territory canada is performed with a combined set of geomorphometric and spectral variables in a linear discriminant analysis an automated method was developed to find the boundaries of geomorphological objects and to extract the objects as groups of aggregated pixels the geomorphological objects selected are slope units with the boundaries being breaks of slope on two dimensional downslope profiles each slope unit is described by variables summarizing the shape topographic and spectral characteristics of the aggregated group of pixels overall discrimination accuracy of 90 is achieved for the aggregated slope units in ten classes

on the crystallisation pressure of gypsum we estimate the crystallisation pressure of gypsum quantitatively with reference to the geological context of the gypsum keuper formation the formation contains sulphatic claystones which have the property of swelling in the presence of water and have caused substantial structural damage to the linings of several tunnels in switzerland and germany the swelling of these rocks is attributed to the transformation of anhydrite into gypsum which occurs via the dissolution of anhydrite in pore water and the precipitation of gypsum from the solution this simultaneous dissolution precipitation process happens because the solubility of gypsum is lower than that of anhydrite under the conditions prevailing after tunnelling and it does not cease until all of the anhydrite has been transformed the elementary mechanism behind the development of the macroscopically observed swelling pressure is the growth of gypsum crystals inside the rock matrix if a crystal is in contact with a supersaturated solution but its growth is prevented by the surrounding matrix it then exerts a so called crystallisation pressure upon the pore walls in the present paper the crystallisation pressure is calculated by means of a thermodynamic model that takes coherent account of all relevant parameters including the chemical composition of the pore water and pore size variations in these parameters lead to a very wide range of crystallisation pressures from zero to several tens of megapascals by using the results of mercury intrusion porosimetry and chemical analyses of samples from three swiss tunnels however we show that the range of predicted values can be reduced significantly with the help of standard project specific investigations

sediment supply base level braiding and bedrock river terrace formation arroyo seco california usa in many settings rivers alternate between carving wide valley bottoms straths and cutting narrow gorges over time thereby creating longitudinally continuous paired bedrock strath terraces along valleys strath terraces are used ubiquitously in geomorphology and tectonics however how and why they form remain poorly understood here we focus on arroyo seco in the central california coast ranges where we test hypotheses for strath planation and subsequent strath terrace formation several lines of evidence indicate that strath planation is triggered by braiding in bedrock channels in particular hydraulic modeling reveals that the width of arroyo seco s most recently formed terrace is comparable to the width of currently braided channel reaches additionally a comparison of currently braided reaches to abandoned bedrock meander cutoffs shows that braided channels have valleys that are several times wider than single thread meandering bedrock channel reaches lastly in locations where the modern channel is currently braided terraces are poorly preserved suggesting that evidence for past episodes of braiding in the form of paired strath terraces is apparently largely destroyed by subsequent episodes of braiding field observations combined with mapping of terrace levels using an objective light detection and ranging lidar based terrace identification algorithm reveal that temporal variation in tectonic uplift rate sea level and or alluvial cover along the river cannot explain strath planation and subsequent terrace formation in arroyo seco rather our results provide evidence that aggradation and degradation of alluvial sediments downstream of the reliz canyon fault result in impulsive base level forcing of arroyo seco s bedrock channel strath abandonment and terrace formation apparently occur as incision into downstream alluvial sediments propagates upstream into bedrock braiding and planation of straths in contrast occur during intervals of low vertical incision rate associated with downstream aggradation or immediately following pulses of vertical lowering triggered by downstream incision of alluvial sediments

partial eclogitisation of gabbroic rocks in a late precambrian subduction zone zambia prograde metamorphism triggered by fluid infiltration gabbros and eclogites occur closely associated in a 200 km long and up to 40 km wide area of the zambezi belt in central zambia this area is interpreted to represent part of a late precambrian suture zone with the mafic rocks being relics of subducted oceanic crust gradual stages of prograde transformation from gabbro to eclogite are preserved by disequilibrium textures of incomplete reactions this resulted in kyanite omphacite bearing assemblages for eclogites that have al poor bulk compositions undeformed eclogites typically preserve features of a former gabbroic texture reflected by replacements of plagioclase and magmatic pyroxene by eclogite facies minerals textures of deformed eclogites range from sheared porphyroclastic to porphyroblastic relics of magmatic pyroxene are common and complete eclogitisation occurred only in millimetre to centimetre scale domains in most of the rocks no evidence for prograde blueschist or amphibolite facies mineral assemblages was found in eclogites in contrast the fine grained intergrowth of omphacite garnet kyanite and quartz which replace former plagioclase or was formed in the pressure shadow of magmatic pyroxene relics indicates that eclogitisation might have affected the gabbroic protoliths directly without any significant intervening metamorphic reactions eclogitisation took place under p t conditions of 630 690 degreesc and 26 28 kbar suggesting a large overstepping 10 kbar of reaction boundaries eclogitisation was initialised and accompanied by a channelised fluid flow resulting in veins with large subhedral grains of omphacite kyanite and garnet the gabbro to eclogite transformation was enhanced by a fluid which allowed the necessary material transport for the dissolution precipitation mechanism that characterises the metamorphic mineral replacements the process of eclogitisation was limited by reaction kinetics and dissolution precipitation rates rather than by the metamorphic p t conditions even though ductile deformation occurred and equilibrium phase boundaries were overstepped the infiltration of fluids was necessary for triggering the gabbro to eclogite transformation

millennial lag times in the himalayan sediment routing system abstract any understanding of sediment routing from mountain belts to their forelands and offshore sinks remains incomplete without estimates of intermediate storage that decisively buffers sediment yields from erosion rates attenuates water and sediment fluxes and protects underlying bedrock from incision we quantify for the first time the sediment stored in 38 000 mainly postglacial himalayan valley fills based on an empirical volume area scaling of valley fill outlines automatically extracted from digital topographic data the estimated total volume of 690 242 452 km 3 is mostly contained in few large valley fills 1 km 3 while catastrophic mass wasting adds another 177 31 km 3 sediment storage volumes are highly disparate along the strike of the orogen much of the himalaya s stock of sediment is sequestered in glacially scoured valleys that provide accommodation space for 44 of the total volume upstream of the rapidly exhuming and incising syntaxes conversely the step like long wave topography of the central himalayas limits glacier extent and thus any significant glacier derived storage of sediment away from tectonic basins we show that exclusive removal of himalayan valley fills could nourish contemporary sediment flux from the indus and brahmaputra basins for 1 kyr though individual fills may attain residence times of 100 kyr these millennial lag times in the himalayan sediment routing system may sufficiently buffer signals of short term seismic as well as climatic disturbances thus complicating simple correlation and interpretation of sedimentary archives from the himalayan orogen its foreland and its submarine fan systems