spectrally based mapping of riverbed composition abstract remote sensing methods provide an efficient means of characterizing fluvial systems this study evaluated the potential to map riverbed composition based on in situ and or remote measurements of reflectance field spectra and substrate photos from the snake river wyoming usa were used to identify different sediment facies and degrees of algal development and to quantify their optical characteristics we hypothesized that accounting for the effects of depth and water column attenuation to isolate the reflectance of the streambed would enhance distinctions among bottom types and facilitate substrate classification a bottom reflectance retrieval algorithm adapted from coastal research yielded realistic spectra for the 450 to 700 nm range but bottom reflectance based substrate classifications generated using a random forest technique were no more accurate than classifications derived from above water field spectra additional hypothesis testing indicated that a combination of reflectance magnitude brightness and indices of spectral shape provided the most accurate riverbed classifications convolving field spectra to the response functions of a multispectral satellite and a hyperspectral imaging system did not reduce classification accuracies implying that high spectral resolution was not essential supervised classifications of algal density produced from hyperspectral data and an inferred bottom reflectance image were not highly accurate but unsupervised classification of the bottom reflectance image revealed distinct spectrally based clusters suggesting that such an image could provide additional river information we attribute the failure of bottom reflectance retrieval to yield more reliable substrate maps to a latent correlation between depth and bottom type accounting for the effects of depth might have eliminated a key distinction among substrates and thus reduced discriminatory power although further more systematic study across a broader range of fluvial environments is needed to substantiate our initial results this case study suggests that bed composition in shallow clear flowing rivers potentially could be mapped remotely

modeling decadal bed material sediment flux based on stochastic hydrology estimates of decadal bed material sediment flux and net storage are derived by driving sediment transport calculations with a stochastic hydrology model the resulting estimates represent the whole distribution of sediment flux based on natural variability in channel characteristics gradient width and bed grain size and the magnitude duration and interarrival time of flood events a procedure for calibrating a fractional sediment transport equation of a commonly used form to bed material grain size distributions bmgsds at cross sections is presented the procedure was applied to the sacramento river channel network to compute estimates of annual total and annual peak bed material discharges into and through the main stem over a 30 year period main stem bed material budgets were evaluated to identify reaches in states of net accumulation or scour simulations highlight large imbalances in sand and gravel storage throughout the sacramento river which can be explained by a combination of local hydraulics and bmgsds and for which there is at least some empirical support

weathering and evolution of soils formed on granitic glacial deposits results from chronosequences of swiss alpine environments abstract two soil chronosequences of mountainous ecosystems in switzerland served as the basis to calculate the accumulation of soil organic matter transformation of pedogenic fe and al and net losses of the main elements ca mg k na fe al mn and si by means of mass balance calculations elemental losses due to deglaciation and exposure to the weathering environment were calculated these mass balance calculations indicate that extensive mineral weathering resulted in significant leaching losses of si major base cations and al particularly from the upper horizons the losses are especially pronounced in the early stages of soil formation in most cases the exponential decay model incorporating an asymptotic or logarithmic regression model seems to provide a good description of weathering the greatest changes in the soil chemistry of these alpine soils on granitic host material occurred within the first 3000 4000 years of soil development later the weathering rates decreased rapidly and the overall depletion of elements nearly reached an asymptote we also found that the mean ratio of al t fe d al d fe t of the fine earth of the a e and b horizons is closely linked to the duration of soil development a very rapid decrease of this ratio also occurred at the beginning of soil evolution in order to reach asymptotic values after about 3000 years consequently this ratio could be a good indicator of the age of alpine soils furthermore there is a close relationship between the mass of organic c or n in the whole profile and the soil age the older the soil the higher the corresponding mass per unit area the chronofunctions presented give a first attempt of the chemical soil evolution in the alps however only little data has been available up until now regarding alpine soils and this fact inhibits a more detailed observation of the changes that have occurred over a period of 2000 8000 years of soil formation under similar climatic conditions

effects of lateral confinement in natural and leveed reaches of a gravel bed river snake river wyoming usa this study examined the effects of natural and anthropogenic changes in confining margin width by applying remote sensing techniques fusing lidar topography with image derived bathymetry over a large spatial extent 58 km of the snake river wy fused dem s from 2007 and 2012 were differenced to quantify changes in the volume of stored sediment develop morphological sediment budgets and infer spatial gradients in bed material transport our study spanned two similar reaches that were subject to different controls on confining margin width natural terraces vs artificial levees channel planform in reaches with similar slope and confining margin width differed depending on whether the margins were natural or anthropogenic theeffects of tributaries also differed between the two reaches generally the natural reach featured greater confining margin widths and was depositional whereas artificial lateral constriction in the leveed reach produced a sediment budget that was closer to balanced although our remote sensing methods provided topographic data over a large area net volumetric changes were not statistically significant due to the uncertainty associated with bed elevation estimates we therefore focused on along channel spatial differences in bed material transport rather than absolute volumes of sediment to complement indirect estimates of sediment transport derived by morphological sediment budgeting we collected field data on bed mobility through a tracer study surface and subsurface grain size measurements were combined with bed mobility observations to calculate armoring and dimensionless sediment transport ratios which indicated that sediment supply exceeded transport capacity in the natural reach and vice versa in the leveed reach we hypothesize that constriction by levees induced an initial phase of incision and bed armoring because levees prevented bank erosion the channel excavated sediment by migrating rapidly across therestricted braidplain and eroding bars and islands

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

spatial and temporal patterns in channel change on the snake river downstream from jackson lake dam wyoming abstract operations of jackson lake dam jld have altered the hydrology and sediment transport capacity of the snake river in grand teton national park prior research has provided conflicting assessments of whether the downstream river was perturbed into sediment surplus or sediment deficit in this paper we present the results of an aerial photo analysis designed to evaluate whether the history of channel change indicates either significant deficit or surplus of sediment that could be expressed as narrowing or expansion of the channel over time we analyze changes in braid index channel width channel activity and net channel change of the snake river based on four series of aerial photographs between 1945 and 1969 a period of relatively small main stem floods widespread deposition and up to 31 reduction in channel width occurred throughout the snake river between 1969 and 2002 a period of large main stem floods the style of channel change reversed with a decrease in braid index and an increase in channel width of up to 31 these substantial changes in the channel downstream from the dam primarily occurred in multithread reaches regardless of proximity to tributaries and no temporal progression of channel narrowing or widening was observed we demonstrate that channel change downstream from jld is more temporally and longitudinally complex than previously described

extractable fe and al in late pleistocene and holocene paleosols on niwot ridge colorado front range summary surface and buried paleosols on niwot ridge in the front range of colorado were analyzed for extractable fe and al to determine if their distributions would assist in the interpretation of past and present soil forming environments extractable fe and al distributions in surface and buried paleosols suggest that leaching is more pronounced in the older paleosols with a considerable difference in soil forming environment between pleistocene interstadial later pleistocene and postglacial paleosols using radiocarbon dated buried a horizons it appears that little pyrophosphate extractable fe and al have been translocated downward into these middle latitude alpine buried paleosols there is no evidence that the na pyrophosphate extractable fe and al were affected by degradation of organic matter following burial however the data suggest that some amorphous fe and al might have been affected by soil water movement over permafrost and by redistribution of preweathered sediments

effects of large floods on sediment transport and reach morphology in the cobble bed sainte marguerite river abstract sediment transport rates were estimated for two flood events on the cobble bed sainte marguerite river in the saguenay region canada morphologic methods were used to derive one set of estimates and a combination of the meyer peter and muller equation with a dimensionless sediment transport ratio after dietrich et al nature 340 1989 215 was used to derive another set of estimates both sets of estimates give consistent results for the first event which had a decade scale return period and for the second event which was the largest flood on record and had a century scale return period the transport occurring during the second event was an order of magnitude greater than that occurring during the first event despite this disparity in the transport intensity of the two events the channel morphology remained qualitatively similar the observed degree of channel stability is attributed to a change of channel pattern and the initiation of bed degradation following channel rectification in the 1960s

mobility of bed material in harris creek 1 the mobility of bed material is investigated in a small gravel bed river in which the bed is weakly bimodal in texture and relatively stable the bed surface remained intact throughout the freshet and scour was limited to small areas of the bed observations of bedload caught in pit traps and displacement of magnetically tagged particles during two spring freshets permit analysis of the mobility of each size fraction fractional transport rates plot up to three orders of magnitude below the reference transport rate suggested in the literature at low flows no size fraction was fully mobile at intermediate flows shear stress 27 pa sand was fully mobile while larger material remained partially mobile at high flows 43 pa the division between the full and partial mobility regimes occurred around 16 mm which remains finer than the median size of the subsurface material the largest material scarcely moves at mean annual flood magnetic tracers confirmed results obtained from the pit traps three distinct zones of mobility can be defined in fractional transport plots partial mobility full mobility and overpassing suspended critical shear stress for incipient motion varied over an order of magnitude a qualitatively similar result for bimodal sediment was reported by wilcock and mcardell 1993 incipient motion analysis based on the largest grain observed to move yielded an upper envelope implying transport similarity for sizes found on the bed surface and a lower envelope that corresponds with our nonsimilar entrainment criterion

joint isotopic mass balance a novel approach to quantifying channel bed to channel margins sediment transfer during storm events the important role of floodplains and the broader riparian zone in providing temporary storage for a large fraction of the annual sediment load of rivers is well established but this understanding is largely based on observations of the long term average behavior of the catchment here we combine measurements of the fallout radionuclides 7be and 210pb and the stable isotopes of hydrogen in water to quantify fine sediment mobilization and storage in a stream and its channel margins during individual intermediate sized storm events with recurrence intervals of a few months or less we demonstrate this method using five storm events in a small 15 km2 undeveloped gravel bedded tributary of the connecticut river usa we estimate that in each storm the mass of sediment deposited onto the margins accounts for almost 90 of the sediment mobilized from the bed with the remainder of the mobilized bed sediment transported downstream as suspended load the result that the bed is a net source of sediment to the stream and the margins a net sink is robust but estimates of the mass of material eroded from the bed and deposited on the margins are less certain the source of sediment to the bed remains unclear as consistent with earlier studies we observe only limited deposition of sediment to the bed during the storm events the suspended sediment is organic rich and thus its source may be associated with in channel organic decay between storm events understanding the coupled interactions between discharge magnitude and frequency and sediment resupply at the event time scale has important implications for stream restoration efforts seeking to connect the channel and the broader riparian zone and for the development of accurate sediment budgets and predictions of sediment flux from a watershed copyright 2015 john wiley sons ltd

a framework for modeling connections between hydraulics water surface roughness and surface reflectance in open channel flows this paper introduces a framework for examining connections between the flow field the texture of the air water interface and the reflectance of the water surface and thus evaluating the potential to infer hydraulic information from remotely sensed observations of surface reflectance we used a spatial correlation model describing water surface topography to illustrate the application of our framework nondimensional relations between model parameters and flow intensity were established based on a prior flume study expressing the model in the spatial frequency domain allowed us to use an efficient fourier transform based algorithm for simulating water surfaces realizations for both flume and field settings had water surface slope distributions positively correlated with velocity and water surface roughness however most surface facets were gently sloped and thus unlikely to yield strong specular reflections the model exaggerated the extent of water surface features leading to underestimation of facet slopes a ray tracing algorithm indicated that reflectance was greatest when solar and view zenith angles were equal and the sensor scanned toward the sun to capture specular reflections of the solar beam reflected energy was concentrated in a small portion of the sky but rougher water surfaces reflected rays into a broader range of directions our framework facilitates flight planning to avoid surface reflected radiance while mapping other river attributes or to maximize this component to exploit relationships between hydraulics and surface reflectance this initial analysis also highlighted the need for improved models of water surface topography in natural rivers

a model for garnet and plagioclase growth in pelitic schists implications for thermobarometry and p t path determinations numerical models of the progressive evolution of pelitic schists in the ncmnkfmash system with the assemblage garnet biotite chlorite staurolite plagioclase muscovite quartz h2o are presented with the goal of predicting compositional changes in garnet and plagioclase along different p t paths the numerical models support several conclusions that should prove useful for interpreting the p t paths of natural parageneses i garnet may grow along p t vectors ranging from heating with decompression to cooling with compression p t paths deduced from garnet zoning that are inconsistent with these growth vectors are self contradictory ii there is a systematic relation between garnet and plagioclase composition and growth such that for most p t paths garnet growth requires plagioclase consumption furthermore mass balance in a closed system requires that as plagioclase is consumed the remaining plagioclase becomes increasingly albitic inclusions of plagioclase in the core of garnet should be more anorthitic than those near the rim and zoned matrix plagioclase should have rims that are more albitic than the cores complex plagioclase textures may arise from the local variability of growth and precipitation kinetics iii a decrease of fe fe mg in a garnet zoning profile is a reliable indicator of increasing temperature for the assemblage modelled however there is no single reliable p monitor and inferences about p can only be made by considering plagioclase and garnet together iv consumption of garnet during the production of staurolite removes material from the outer shell of a garnet and may make recovery of peak metamorphic compositions and p t conditions impossible low peak temperatures typically recorded by staurolite bearing assemblages may reflect this phenomenon v diffusional homogenization of garnet affects the computed p t path and results in a clockwise rotation of the computed p t vector relative to the true p t path

sediment transport along lower fraser river 1 measurements and hydraulic computations a comprehensive program of sediment transport measurements was conducted along lower fraser river british columbia between 1966 and 1986 the data yield a detailed sediment budget annual total suspended loads at three stations are virtually identical averaging 17 106 tonnes year t yr 1 the suspended sand load is about 5 5 106 t yr 1 about one third of the total in the gravel bed reach of the river the sand behaves as wash load significant transport of gravel begins at agassiz at a discharge of about 5000 m3 s 1 the annual gravel transport was estimated to be about 0 23 106 t yr 1 only 1 of the total load all of this material is deposited in the reach upstream of mission at mission sands finer than 0 177 mm make up more than 50 of the suspended sand load but are virtually absent from the sand bed therefore a portion of the sand load at mission is wash load the total bed material load here was estimated to be 3 0 106 t yr 1 about 18 of the total sediment load virtually all of the bed material load was transported in intermittent suspension near the bed less than 5 occurring as bed load in the long term the suspended sand load upstream is approximately equal to the total sand load at mission however within individual years some of the sand is stored within the reach temporarily and then reentrained later

mapping gravel bed river bathymetry from space 1 understanding river form and behavior requires an efficient means of measuring channel morphology this study evaluated the potential to map the bathymetry of two clear flowing shallow 3 m deep gravel bed rivers 60 m wide from 2 m pixel worldview2 satellite images direct measurements of water column optical properties were used to quantify constraints on depth retrieval the smallest detectable change in depth was 0 01 0 04 m and the maximum detectable depth was 5 m in green bands but 2 m in the near infrared lower sensor radiometric resolution yields less precise estimates over a smaller range an algorithm for calibrating a band ratiox to field measurements of depth d proved effective when applied to spectra extracted from images r2 0 822 and 0 594 for the larger and smaller stream respectively or measured in the field r2 0 769 and 0 452 this procedure also identified optimal wavelength combinations but different bands were selected for each site accuracy assessment of bathymetric maps produced using various calibration approaches and image types indicated that 1 a linear d vs xrelation provided depth estimates nearly as accurate as a quadratic formulation 2 panchromatic and pan sharpened multispectral images with smaller 0 5 m pixels did not yield more reliable depth estimates than the original images and 3 depth retrieval was less reliable in pools due to saturation of the radiance signal this investigation thus demonstrated the feasibility as well as the limitations of measuring the bathymetry of clear shallow gravel bed rivers from space

on the interpretation of peak metamorphic temperatures in light of garnet diffusion during cooling abstract finite difference models of fe mg diffusion in garnet undergoing cooling from metamorphic peak conditions are used to infer the significance of temperatures calculated using garnet biotite fe mg exchange thermometry for rocks cooled from high grades where the garnet was initially homogeneous the calculated temperature tcalc using garnet core and matrix biotite depends on the size of the garnet the ratio of garnet to biotite in the rock vgarnet vbiotite and the cooling rate for garnets with radii of 1 mm and vgarnet vbiotite 1 tcalc is 633 700 and 777 c for cooling rates of 1 10 and 100 c ma for vgarnet vbiotite 1 and 4 and a cooling rate of 10 c ma tcalc is approximately 660 and 610 c respectively smaller and larger garnets have lower and higher tcalc respectively these results suggest that peak metamorphic temperatures may be reliably attained from rocks crystallized at conditions below tcalc of the garnet core provided that vgarnet vbiotite is sufficiently small 0 1 and that the composition of the biotite at the metamorphic peak has not been altered during cooling numerical experiments on amphibolite facies garnets with nominal peak temperatures of 550 600 c generate a well in fe fe mg near the rim during cooling maximum calculated temperatures for the assemblage garnet chlorite biotite muscovite plagioclase quartz using the fe fe mg at the bottom of the well with matrix biotite range from 23 43 c to 5 12 c below the peak metamorphic temperature for cooling rates of 1 and 100 c ma respectively maximum calculated temperatures for the assemblage garnet staurolite biotite muscovite plagioclase quartz are approximately 70 c below the peak metamorphic temperature and are not strongly dependent on cooling rate the results of this study indicate that it may be very difficult to calculate peak metamorphic temperatures using garnet biotite fe mg exchange thermometry on amphibolite facies rocks tmax 550 c because the rim composition of the garnet which is required to calculate the peak temperature is that most easily destroyed by diffusion

records of the evolution of the himalayan orogen from in situ th pb ion microprobe dating of monazite eastern nepal and western garhwal abstract in situ th pb monazite ages from rocks collected along two transects the dudh kosi everest eastern nepal and the bhagirathi river garhwal himalaya india perpendicular to the main central thrust mct suggest a striking continuity of tectonic events across the himalaya the youngest age reported in this study 5 9 0 2 ma mswd 0 4 from matrix monazite grains collected beneath the mct in the garhwal region is consistent with several age data from rocks at similar structural levels in central nepal providing support for widespread late miocene mct activity the lateral parallelism of orogenic events is further manifested by the 20 7 0 1 ma age of a high himalayan leucogranite from an injection complex that outcrops along the dudh kosi everest transect resembling ages of these bodies reported elsewhere the youngest monazite grain analyzed along the dudh kosi everest transect is 10 3 0 8 ma the absence of 7 3 ma monazite ages in eastern nepal may reflect a different nappe structure which obscures the reactivated ramp equivalent exposed in the garhwal and central nepal garnets from the mct hanging wall greater himalayan crystallines and footwall lesser himalaya display different major element zoning and the patterns are useful for constraining the location of the thrust system that separates the two lithologies pressure temperature paths for two upper lesser himalayan garnets that contain monazite inclusions indicate the utility of an in situ methodology to constrain the metamorphic evolution of the shear zone along the dudh kosi everest transect upper lesser himalayan monazite grains from three rocks record a clear signal at 14 5 0 1 ma mswd 8 4 and the 23 ma age that characterizes the hanging wall is notably absent monazites collected within a large scale greater himalayan crystallines fold yield the 14 ma age consistent with the structure forming due to mct related compression paleo mesoproterozoic 1407 35 ma matrix monazite grains are found within an augen gneiss unit located beneath the mct whereas cambro ordovician 436 8 548 17 ma inclusions are preserved within garnets of the greater himalayan crystallines the presence of 45 2 2 1 ma grains from lower structural levels of the greater himalayan crystallines indicates the unit realized conditions conducive for monazite growth during the eocene

metamorphic peak geothermobarometry in the furulund group sulitjelma scandinavian caledonides implications for uplift regional metamorphism in the sulitjelma area of the arctic scandinavian caledonides has produced a series of barrovian zones from chlorite through to kyanite in more aluminous pelites which transect the major lithological boundaries in a large nappe unit of the koli nappe complex the metamorphic zones are inverted and metamorphic grade increases westwards from the foreland to the hinterland the furulund group comprises a mixed sequence of originally flysch like sediments which crop out over the whole range of the observed barrovian zones but are usually too calcareous to develop the characteristic barrovian aluminous phases staurolite and kyanite instead above the garnet isograd the furulund group pelites and semi pelites have widely developed hornblende porphyroblasts in the common assemblage grt pl bt ms qtz hbl ep czo chl cal dol thermobarometric estimates of metamorphic peak p t conditions i e at maximum recorded temperatures from this assemblage using three different methods indicate a westward increase of both pressure and temperature over a distance of 14 km away from the garnet isograd towards the hinterland of the orogen independent of topographic level and without change in the common mineral assemblage the increased peak pressure in the west indicates greater initial burial and subsequent exhumation in the hinterland than towards the foreland restoration indicates that the furulund group has been subjected to substantial eastward bulk tilting after peak metamorphic conditions whilst this enhances the overturning of the metamorphic zones the amount of tilting was not sufficient to cause the overturning

microsampling lu hf geochronology on mm sized garnet in eclogites constrains early garnet growth and timing of tectonometamorphism in the north qilian orogenic belt

effects of jackson lake dam on the snake river and its floodplain grand teton national park wyoming usa in 1906 the bureau of reclamation created jackson lake dam on the snake river in what later became grand teton national park the geomorphic hydrologic and vegetation adjustments downstream of the dam have yet to be documented after a larger reservoir was completed further downstream in 1957 the reservoir release schedule from jackson lake dam was changed in a manner that lowered the magnitude and frequency of floods the stability of the snake river exhibited a complex response to the change in flow regime close to major tributaries the snake river increased in total sinuosity and rates of lateral channel migration away from the influence of tributaries the river experienced fewer avulsions and a decrease in sinuosity vegetation maps were constructed from 1945 and 1989 aerial photography and field surveys using these data we determined how vegetation is directly related to the number of years since each portion of the floodplain was last occupied by the channel the vegetation has changed from a flood pulse dominated mosaic to a more terrestrial like pattern of succession changes in the snake river and its floodplain have direct implications on bald eagle habitat moose habitat fish habitat safety of rafting and canoeing and biodiversity at the community and species levels

gravel transport and morphological change in braided sunwapta river alberta canada the relation between morphological change and patterns of variation in bedload transport rate in braided streams was observed by repeated daily topographic surveys over a 25 day study period in a 60 m reach of the proglacial sunwapta river alberta canada there are two major periods of morphological change each lasting several days and each involving the complete destruction and reconstruction of bar complexes bar complex destruction was caused by redirection of the flow and by downstream extension of the confluence scour zone upstream reconstruction involved accretion of unit bars on bar head flank and tail and in one case was initiated by disection of a large lobate unit bar high rates of sediment movement measured from net scour and fill of the cross sections coincided with these morphological changes sediment was supplied from both bed and bank erosion and patterns and distances of transfer were highly variable rates of transport estimated by matching upstream erosional volumes with downstream deposition were much greater than those estimated from either a step length approach or a sediment budget measurements of scour and fill and observations of morphological change indicate that step lengths virtual transport distances were typically 40 100m during a diurnal discharge cycle shorter step lengths occurred when transfer was confined to a single anabranch and longer steps involved channel changes at the scale of the entire reach sediment budgeting was used to describe the spatial patterns of sediment transport associated with the morphological changes and to estimate minimum daily reach averaged transport rates mean bedload transport rates correlate with discharge but with considerable scatter the largest deviations from the mean relation can be tied to phases of channel incision bank erosion scour hole migration bar deposition and channel filling apparently controlled by changes and fluctuations in sediment supply from upstream independent of discharge these are interpreted as field evidence of autopulses or macropulses in bedload transport previously observed only in laboratory models of braided streams

magnetic enhancement is linked to and precedes hematite formation in aerobic soil 1 soil formation usually increases magnetic susceptibility most often by increasing the concentrations of magnetite and maghemite which are two ferrimagnetic iron oxides here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite which is later transformed into hematite the iron oxide that gives red color to soil we show that the maghemite hematite ratio is influenced by the particular environment and the degree of soil development so it constitutes an effective tool for paleoenvironmental and planetary studies

sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads the rio grande in the big bend region of texas usa and chihuahua and coahuila mexico undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology thus it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change we analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form in this study physically based analyses suggest that channel change in the rio grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales channel narrowing is primarily caused by substantial deposition of sediment supplied to the rio grande during tributary sourced flash floods tributary floods have large suspended sediment concentrations occur for short durations and attenuate rapidly downstream in the rio grande depositing much of their sediment in downstream reaches long duration floods on the mainstem have the capacity to enlarge the rio grande and these floods released from upstream dams can either erode or deposit sediment in the rio grande depending upon the antecedent in channel sediment supply and the magnitude and duration of the flood geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long duration floods are most strongly controlled by spatial changes in flow strength largely through changes in channel slope however spatial differences in the in channel sediment supply regulate sediment evacuation or accumulation over time in long reaches greater than a kilometer

pedogenic gradients for iron and aluminum accumulation and phosphorus depletion in arctic and alpine soils as a function of time and climate pedogenically significant chemical extracts of iron aluminum and phosphorus are related mainly to time in chronosequences from baffin island canadian arctic the alpine sierra nevada and wind river range western united states the alpine khumbu glacier area himalaya nepal and the alpine southern alps new zealand based on the accumulation index for fe and al and the depletion index for p in each region the following ranking of chemical pedogenic development is obtained southern alps khumbu glacier area wind river range sierra nevada coastal baffin island inland baffin island the ranking mainly follows regional climate with the greatest accumulation and depletion to the warmest and wettest environment and the least accumulation and depletion in the coldest and driest environment

extractable fe and al as an indicator for buried soil horizons summary reddish brown and associated horizons from several buried soils were analyzed for dithionite oxalate and pyrophosphate extractable fe and al although these methods can be used with surficial soils they are not necessarily applicable to buried soils however on the basis of morphology and the fact that dithionite and oxalate extractable fe and al were always highest for the reddish brown horizon in each profile sequence it was concluded that these horizons were zones of pedogenic accumulation since pyrophosphate extractable fe and al essentially measures only the organic forms of pedogenic fe and al and organic compounds are usually subjected to further degradation after burial it is suggested that for buried soils dithionite and oxalate extractable fe and al are more meaningful comparisons with data in the literature giving typical ranges for the main types of soil horizons allowed both the classification of the profiles sampled and the recognition of past processes such as gleying which are not identifiable morphologically today

metamorphic discontinuities in the pennsylvania delaware piedmont evidence for early paleozoic assembly interpretation of the early paleozoic tectonic history of the appalachian piedmont is commonly complicated by post taconian deformation that has disrupted and obscured early paleozoic structure blocks that lie between zones where later deformation has been concentrated however may preserve evidence of taconian high grade metamorphism in these cases analysis of metamorphism allows an interpretation of the early paleozoic tectonic history of the block and its surrounding region a block of this type in the pennsylvania delaware piedmont includes three tectonic units 1 the basement cored massifs of southeastern pennsylvania with grenvillian gneiss unconformably overlain by the setters formation and cockeysville marble 2 the wilmington complex arc terrane and 3 the wissahickon group and associated metaigneous rocks a metamorphic gradient and inferred temperature inversion within the wissahickon group and a metamorphic discontinuity at the wissahickon group cockeysville marble contact are used t

sediment transport in a large impounded river the lower ebro ne iberian peninsula abstract the sediment transport of the highly regulated lower ebro river is estimated on the basis of a measuring programme carried out between 2002 and 2004 total sediment transport including both suspended load and bedload was measured upstream and downstream from the mequinenza and riba roja reservoirs with special attention to the transport during floods annual total load upstream from the dams is estimated at around 1 64 106 t of which at least 99 is transported in suspension annual total load downstream from the dams is estimated at around 0 45 106 t of which 60 is transported in suspension and the remaining 40 as bedload mean d50 bl in the range of 32 mm total load represents 3 of what was transported at the beginning of the 20th century in the delta plain sediment yield is three to four times lower below the dams a fact that is caused by the trapping of sediment within the reservoirs around 90 in the case of suspended sediment and 100 in the case of bedload as a consequence sediment that is transported downstream from the dams is all entrained from the riverbed and eroded from the banks the sediment deficit causes a mean riverbed incision of 30 mm per year as estimated from bedload measurements and by means of scour chains and painted pebbles located between the lowermost dam and the measuring section 28 km downstream since floods have been reduced on average by 25 but sediment supply from upstream has been reduced to almost nothing the river channel of the lower ebro river will continue exporting sediment both during floods 2000 m3 s mostly bedload and frequent high flows 1000 m3 s to 2000 m3 s making the incision progressive unless restoration steps are taken

geothermometry geobarometry and the al2sio5 triple point at mt moosilauke new hampshire the distribution of aluminum silicate minerals in pelitic schists constrains pressure and temperature conditions during the acadian orogeny to have been approximately those of the al 2 sio 5 invariant point thus providing an excellent opportunity to evaluate the internal consistency of a variety of published geothermometers and geobarometers with the al 2 sio 5 invariant point of holdaway 1971 four fluid independent equilibria yield p t estimates consistent with holdaway 1971 two fluid dependent equilibria yield internally consistent but unrealistically high temperatures our data are consistent with the conclusions that 1 only pyrope grossular mixing in the quaternary garnet system is significantly non ideal and 2 the activity coefficient for the anorthite component in plagioclase is approximately 2 at triple point p t conditions modified journal abstract

topographic and bioclimatic controls on soil paleosol morphogenesis in the norra storfjallet mountains sweden abstract retreat of the stabre glacier in the norra storfjallet mountains of northern sweden led to the emplacement of a broad expanse of glaciofluvial sediment a virtual blanket of debris interspersed with recessional and push moraines episodic mass wasting of the glaciofluvial moraine and loessic deposits yielded a pedostratigraphic succession of 14 c dated sub boreal and sub atlantic cryosols in soliflucted sediment that provide weathering data related to neoglacial perturbations whereas weathering within polygonal complexes yielded single profile one event cryosolic gleysols of similar age both provide a database of paleosol extremes controlled by topography and bioclimate together the paleosols provide a database of weathering of mixed amphibolitic gneiss trachytic lavas and granite weathering under two variable redox conditions one soliflucted sediment fully or partially aerated and free draining under a subaerial atmosphere with high redox potential the other polygonal soil partly reduced under the influence of an active layer of sporadic permafrost paleosols dated to the early neoglacial 3600 4200 cal 14 c yr bp have variable horizon development dependent upon landform associations and provide maximum ages for the second oldest moraine stillstand of ice retreat into the highlands on the arctic circle of sweden the cryosolic gleysol yields surprisingly high extractable fe and al suggestive of considerable redox fluctuations over the time of morphogenesis

evaluation of olivine spinel geothermometry as an indicator of thermal history for peridotites olivine and spinel in peridotites from the miyamori ultramafic complex and the ichinogemata crater of northeast japan show a systematic variation in the mg mg fe ratio which is correlated mainly with the grain size of spinel this correlation can be explained by a diffusion model assuming a semi infinite composite sphere under cooling or heating conditions in order to obtain absolute temperatures of thermal events the olivine spinel geothermometer is applied to pairs of spinel core and olivine core average composition the calculated temperatures range over two hundred degrees and have a systematic relationship with the grain size of spinel in the miyamori complex the calculated temperatures decrease monotonically with decrease in grain size of spinel whereas in the ichinomegata lherzolite nodule those of spinel smaller than 0 2 mm increase as the grain size decreases and those of spinel larger than 0 2 mm remain constant regardless of further increase in grain size these observations in the light of the diffusion model suggest that the miyamori complex may have cooled from higher than 800 c to lower than 600 c and that the lherzolite nodule from the ichinomegata crater may have been in equilibrium at 900 c before it was heated above 1 100 c for less than a few days these two examples indicate that olivine spinel pairs of peridotites do not always indicate an appropriate equilibration temperature we cannot interpret the supposed equilibration temperatures until the existence of isothermal stages in the thermal history of peridotites is established by carefully checking the chemical heterogeneity

influence of a dam on fine sediment storage in a canyon river glen canyon dam has caused a fundamental change in the distribution of fine sediment storage in the 99 km reach of the colorado river in marble canyon grand canyon national park arizona the two major storage sites for fine sediment i e sand and finer material in this canyon river are lateral recirculation eddies and the main channel bed we use a combination of methods including direct measurement of sediment storage change measurements of sediment flux and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport in order to evaluate the change in both the volume and location of sediment storage the analysis shows that the bed of the main channel was an important storage environment for fine sediment in the predam era in years of large seasonal accumulation approximately 50 of the fine sediment supplied to the reach from upstream sources was stored on the main channel bed in contrast sediment budgets constructed for two short duration high experimental releases from glen canyon dam indicate that approximately 90 of the sediment discharge from the reach during each release was derived from eddy storage rather than from sandy deposits on the main channel bed these results indicate that the majority of the fine sediment in marble canyon is now stored in eddies even though they occupy a small percentage similar to 17 of the total river area because of a 95 reduction in the supply of fine sediment to marble canyon future high releases without significant input of tributary sediment will potentially erode sediment from long term eddy storage resulting in continued degradation in marble canyon

changes in braided river morphology resulting from aggradation and degradation forty three experiments were completed in a large flume 1 8 x 18 3 m to examine the effects of sediment load sediment size and channel gradient on braided river morphology the laboratory results were supported by field research and analogs from the published literature subaerially exposed braid bars were formed by the dissection and further accretion of stalled linguoid dunes which are actively migrating bedforms bar forming processes and channel dynamics were the same in both sand and gravel bed channels however linguoid dunes stalled and were transformed into braid bars more frequently in gravel bed channels and therefore gravel bed channels were more intensely braided aggradation resulted in the development of more bars rather than in an increase in the size of preexisting braid bars the number of actively migrating linguoid dunes also increased with sediment load in the highly mobile sand bed channels conversely in degrading channels the number of braid bars decreased and average bar

accounting for uncertainty in cumulative sediment transport using bayesian statistics abstract that sediment transport estimates have large uncertainty is widely acknowledged when these estimates are used as the basis for a subsequent analysis such as cumulative sediment loads or budgets treatment of uncertainty requires careful consideration the propagation of uncertainty is a problem that has been studied in many other scientific disciplines in recent years bayesian statistical methods have been successfully used to this end in hydrology ecology climate science and other disciplines where uncertainty plays a major role their applications in sediment transport however have been few previous work demonstrated how deterministic sediment transport equations can be brought into a probabilistic framework using bayesian methods in this paper we extend this basic model and apply it to sediment transport observations collected on the snake river in wyoming usa these data were used previously to develop a 50 year sediment budget below jackson lake dam we revisit this example to demonstrate how viewing sediment transport probabilistically can help better characterize the propagation of uncertainty in the calculation of cumulative sediment transport we present the development of probabilistic sediment rating curves that rely on deterministic sediment transport equations and then show how these can be used to compute the distribution of sediment input and output for each year from 1958 to 2007 the bayesian approach described provides a robust way to quantify uncertainty and then propagate it through to subsequent analyses results show that transport uncertainty is quantified naturally in the bayesian approach making it unnecessary for modelers to assume some specified error rate e g 5 when developing estimates of cumulative transport further we demonstrate that a bayesian approach better constrains uncertainty and allows sediment deficit and surplus to be examined in terms of quantified risk

dams and geomorphology research progress and future directions dams impose changes of flow and sediment transfer that drive changes of channel form along the downstream regulated river these changes have been described for more than 50 years but process form relationships have only been advanced with the establishment of a conceptual framework during the 1970s and then the extension of monitoring data and advancement of remote sensing technologies particularly over the past 20 years this paper reviews these developments and identifies three influential themes i channel dynamics ii the role of riparian vegetation and iii channel change as the driver of ecological change changes can be rapid in semi arid regions but elsewhere relaxation periods may extend to millenia in these latter cases regime or steady state models should be replaced by models of transient states applied to the reach scale in order to respond to the needs of river managers over decadal timescales

downstream effects of impounding a natural lake the snake river downstream from jackson lake dam wyoming usa a sediment mass balance constructed for a 16 km reach of the snake river downstream from jackson lake dam jld indicates that river regulation has reduced the magnitude of sediment mass balance deficit that would naturally exist in the absence of the dam the sediment budget was constructed from calibrated bed load transport relations which were used to model sediment flux into and through the study reach calibration of the transport relations was based on bed load transport data collected over a wide range of flows on the snake river and its two major tributaries within the study area in 2006 and 2007 comparison of actual flows with unregulated flows for the period since 1957 shows that operations of jld have reduced annual peak flows and increased late summer flows painted tracer stones placed at five locations during the 2005 spring flood demonstrate that despite the reduction in flood magnitudes common floods are capable of mobilizing the bed material the sediment mass balance demonstrates that more sediment exits the study reach than is being supplied by tributaries however the volume of sediment exported using estimated unregulated hydrology indicates that the magnitude of the deficit would be greater in the absence of jld calculations suggest that the snake river was not in equilibrium before construction of jld but was naturally in sediment deficit the conclusion that impoundment lessened a natural sediment deficit condition rather than causing sediment surplus could not have been predicted in the absence of sediment transport data and highlights the value of transport data and calculation of sediment mass balance in informing dam operations copyright 2011 john wiley sons ltd

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

pressure temperature deformation time constraints on the south tibetan detachment system in the garhwal himalaya nw india a peculiar feature of the himalaya is the occurrence of a system of low angle normal faults and shear zones the south tibetan detachment system stds at the mountain crests the stds was active during syn convergent tectonics we describe the stds related sheared rocks along the dhauli ganga valley in the garhwal himalaya nw india where the malari granite reported as an undeformed igneous body cross cutting the stds occurs a detailed multidisciplinary study integrating field based microstructural petrographic and geochronological analyses was carried out on rocks along this valley we demonstrate how the non coaxial ductile portion of the stds affected the upper part of the greater himalaya sequence migmatite which experienced peak pressure p temperature t conditions of 0 9 1 1 gpa and 750 c at 24 ma this migmatite has been reworked structurally upwards leading to the formation of high t sillimanite bearing mylonites further upward medium t shearing deformed the malari granite and leucogranite dykes forming medium t mylonites ductile shearing was temporally constrained based on new in situ monazite datings and previously published ar ar geochronology between 20 15 ma we demonstrate that a preserved ductile to brittle spatial and temporal transition of the stds deformation exists with the brittle features overprinting ductile ones our data shed new light on the geological evolution of the stds in the nw himalaya with implications for the relationship and relative timing of partial melting granite emplacement and deformation along low angle normal faults

sediment supply and channel morphology in mountain river systems 2 single thread to braided transitions differences in sediment supply between single thread and braided channel types provide a long recognized though difficult to quantify pattern discrimination building on the results from our preceding paper we present a multiscale assessment of the sediment supply geomorphology and sediment transport characteristics of braided gravel bedded reaches in the northern rocky mountains usa first we present a quantitative theoretically based discriminant function that stratifies single thread and braided reaches on the basis of variations in bankfull sediment concentration and dimensionless discharge following the work of millar 2005 and eaton et al 2010 this function correctly classifies 50 of the 53 channel types where bed load concentrations are known second while channel pattern transitions are often linked to changes in slope field studies along sunlight creek wyoming show that downstream transitions between single thread and braided reaches are instead caused by valley constrictions and changes in the grain size of sediment from tributaries finally we demonstrate that the two dimensional variability in flow properties in braided reaches produces locally high values of shear stress and bed load transport yet bed load measurements and sediment transport calculations also show that sediment transport rates between adjoining braided and single thread reaches may be approximately equal where channels are near the pattern threshold and downstream variations in bank fortitude and channel constriction force pattern transitions taken together these results indicate that high bed load concentrations are fundamental to the braided channel planform and that braided channels likely reflect a quasi equilibrium state within watersheds with persistent high sediment supply

classification of geomorphological effects downstream of dams abstract the effects of dams on downstream geomorphology are reviewed and a typology is devised consisting of nine cases the classification can be seen as a further development of lane s balance between water discharge sediment load grain size and river slope depending on changes in released water flow and changes in released sediment load relative to the transport capacity of the flow it is possible to estimate resulting cross sectional geomorphology the longitudinal extent of changes and their variability with time and the tributary response to altered mainstream cross section changes are also discussed

prograde reactions and garnet zoning reversals in staurolite schist british columbia significance for thermobarometric interpretations an outcrop of staurolite bearing pelitic schist from the solitude range in the south western rocky mountains british columbia was examined in order to determine the nature of prograde garnet and staurolite producing reactions using information from garnet zoning and inclusion mineralogy although not present as a matrix phase chloritoid is present as inclusions in garnet and is interpreted to have participated in the simultaneous growth of garnet and staurolite by a reaction such as chloritoid quartz garnet staurolite h2o a garnet zoning trend reversal which is most pronounced with respect to almandine and grossular components is present in the outer core of garnets the location of the zoning reversal corresponds to the outer limit of chloritoid inclusions in garnet as there is no evidence for polymetamorphism the zoning reversal is interpreted to indicate continued garnet growth by prograde reaction s during a single metamorphic event after the exhaustion of chloritoid as a matrix phase metamorphic conditions recorded by mineral rim compositions are 550 600 c at 6 7 kbar because there is no evidence for partial resorption of garnet during production of staurolite we interpret these results to represent peak conditions

high resolution multiproxy records of sedimentological changes induced by dams in the sept iles area gulf of st lawrence canada abstract a multiproxy approach was performed on two sediment box cores sampled in the nw gulf of st lawrence in order to better understand the impacts of recent climatic or land use changes on the sedimentary regime in the proximal offshore zone multibeam and seismic surveys allowed for the careful selection of coring sites the chronology of the cores was established by 210 pb measurements and validated with coinciding historical weather events recorded in both cores confirming that the sediments are recent last 370 years the lithological variations in the cores were quantified using 1 stratigraphic markers and grain size measurements 2 high resolution x ray micro fluorescence xrf and 3 physical and magnetic tracers the grain size measurements allowed the identification of a major flood around ad 1844 4 years whereas a drastic decrease in variations and in the median grain size d50 occurred around ad 1900 highlighting the offshore impact of the sm1 dam construction on the sainte marguerite river in the early 1900s sedimentological variations have been investigated by wavelet analysis using xrf data and the sharp disappearance of high frequencies

solute partitioning under continuous cooling conditions as a cooling rate indicator a mathematical model is developed to describe the concentration profiles as a function of time of a solute dissolved in two coexisting finite phases under continuous cooling conditions a temperature dependent partitioning of the solute between the two phases is included the model relates to the use of experimentally determined solute profiles to infer the rates at which various rocks cooled the model employs finite difference equations and the thomas tridiagonal method to solve the appropriate differential equations describing the solute partitioning to illustrate the application of the model the partitioning of zirconia between coexisting ilmenite and ulvospinel is considered it is shown that cooling rates can be calculated not only from solute concentration profiles within the grains but also from the ratio of the solute concentrations at a given distance on both sides of the interface or from the ratio of the average solute concentrations in the two phases the cooling rates of a suite of apollo 15 elbow crater gabbros are calculated from measured ratios of concentrations at 10 m from the interfaces between the phases a comparison is made of calculated concentration ratios 10 m from the interface and cooling rates for equilibrium versus uniform initial concentrations it is shown that the elbow crater gabbros could not have had a uniform concentration profiles at the previously suggested initial temperature of 1350 k also considered are the effects of the initial temperature the grain sizes and the diffusion coefficients of zr in the phases on the calculated cooling rates finally suggestions are made for other systems where the present model can be applied to estimate the thermal histories of rocks

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

deformation and metamorphic history of the western blue ridge eastern blue ridge terrane boundary southern appalachian orogen 1 the western eastern blue ridge boundary involved formation by premetamorphic thrusting of an oceanic fragment accretionary wedge island arc upon laurentian basement and metasedimentary cover detailed outcrop scale mapping structural and petrographic analysis reveal both terranes experienced the same deformation at the same metamorphic grade early f1 and f2 isoclinal folds are overprinted by f3 open to tight folds f3 transposes s2 to an axial planar cleavage s3 the youngest penetrative feature prekinematic to synkinematic relative to s2 barrovian metamorphism attained kyanite grade in the western blue ridge wbr upper amphibolite facies in the eastern blue ridge ebr and anatexis in both terranes postkinematic m2b is characterized by appearance of fibrolite throughout the kyanite zone coarsening to granular sillimanite and identification of a kyanite sillimanite isograd in the wbr d3 strain was accommodated by dynamic recrystallization of quartz neocrystallization folding and basal slip of micas pressure solution of plagioclase folding of kyanite and fracturing of garnet scattered lower greenschist facies m4 static retrograde metamorphism resulted in replacement of kyanite and garnet by sericite and chlorite respectively although the juxtaposition of two lithologically distinct terranes implies a fault relationship polymetamorphism and deformation obliterated any microfabrics mineral assemblages or structures that might have developed during premetamorphic thrusting the boundary cannot be an extension of a continent scale dextral strike slip fault system inferred to have developed along laurentian margin in the devonian

colorado river sediment transport 1 natural sediment supply limitation and the influence of glen canyon dam analyses of flow sediment transport bed topographic and sedimentologic data suggest that before the closure of glen canyon dam in 1963 the colorado river in marble and grand canyons was annually supply limited with respect to fine sediment i e sand and finer material furthermore these analyses suggest that the predam river in glen canyon was not supply limited to the same degree and that the degree of annual supply limitation increased near the head of marble canyon the predam colorado river in grand canyon displays evidence of four effects of supply limitation 1 seasonal hysteresis in sediment concentration 2 seasonal hysteresis in sediment grain size coupled to the seasonal hysteresis in sediment concentration 3 production of inversely graded flood deposits and 4 development or modification of a lag between the time of a flood peak and the time of either maximum or minimum depending on reach geometry bed elevation analyses of sediment budgets provide additional support for the interpretation that the predam river was annually supply limited with respect to fine sediment but it was not supply limited with respect to fine sediment during all seasons in the average predam year sand would accumulate and be stored in marble canyon and upper grand canyon for 9 months of the year from july through march when flows were dominantly below 200 300 m3 s this stored sand was then eroded during april through june when flows were typically higher after closure of glen canyon dam because of the large magnitudes of the uncertainties in the sediment budget no season of substantial sand accumulation is evident because most flows in the postdam river exceed 200 300 m3 s substantial sand accumulation in the postdam river is unlikely

partial transport in a natural gravel bed channel 1 partial transport is documented in the gravel bed channel of carnation creek using magnetically tagged stones for four flood peaks the active proportion of surface grains was used to map streambed areas into distinct units of three different levels of grain entrainment in partially mobile regions of the bed the active proportion of surface grains declines with grain size as flow increases areas of partial transport grow at the expense of inactive areas and fully active areas replace areas with partial mobility approximately 25 50 of the bed remained in a state of partial mobility during a flood with a 2 year return period indicating that inactive regions of the bed surface typically persist from year to year during a flood with a 7 year return period surface grain entrainment was nearly complete indicating that full mobilization of surface grains is not a frequent event

evolution of a landslide induced sediment wave in the navarro river california a streamside landslide delivered 60 000 m3 of mixed size sediment to the navarro river a sinuous gravel bed channel drainage area 535 km2 at the end of the annual high runoff period in spring 1995 the deposit formed a 9 m high dam that partially breached within several hours but recessional flows entrained little material until the following high runoff season the landslide afforded the opportunity to measure the evolution of a sediment wave from its inception to near obliteration and particularly to test relative tendencies for translation and dispersion of a sediment wave in a natural gravel bed channel this study represents a simple case the wave originated from a single input the preexisting channel was relatively uniform and resistant banks prevented adjustments in width we surveyed channel topography over a 1 5 4 5 km reach centered on the landslide dam each year from 1995 to 1999 and we sampled bed material downstream of the dam in 1995 and 1997 landslide material was coarser than ambient bed material but all sizes were mobilized by subsequent peak flows abrasion of weathered and fractured graywacke sandstone landslide material was roughly an order of magnitude greater than the ambient river gravel the sediment wave dispersed and mostly disappeared within a few years with no measurable translation sediment filled the reservoir created by the eroding landslide dam until throughput of bed load was restored in 1998 the stationary wave crest eroded until in 1999 it was 1 m higher e mail dsutherl fs fed us than the preslide elevation as the wave profile flattened its detectable leading edge extended downstream from 620 m in 1995 to 1600 m in 1997 downstream advance of the wave was associated with coarsening of bed material the sediment wave created a longitudinal disturbance in sediment transport by using the dam as a reference datum of zero bed load transport we computed longitudinal variations in annual bed load and suspended sediment transport rates in 100 m increments downstream of the dam these longitudinal variations were controlled by scour and fill of the bed and by abrasion of bed load particles bed load transport rates in the first and second years after the landslide increased in the landslide vicinity and then decreased downstream as sediment deposited behind the advancing leading edge of the wave the location of peak bed load transport rate advanced from the first year 400 m to the second 800 m we used a physically based one dimensional model cui et al 2002b to hindcast annual changes in transversely averaged bed elevation over the study reach agreement between measured and predicted bed elevations was very good this result supports our conclusion that once emplaced sediment waves in gravel bed rivers tend to disperse with little or no translation

cation diffusion kinetics in aluminosilicate garnets and geological applications the compositional properties of garnet probably preserve the most extensive records of the pressure temperature time p t t history of metamorphic rocks there are a number of cation exchange and discontinuous reactions involving garnet that have been extensively used to decipher the p t conditions or p t paths of the host rocks as these were buried and exhumed e g ganguly and saxena 1987 spear 1993 however as metamorphic garnets commonly show compositional zoning the choice of composition within a zoned garnet to retrieve peak metamorphic conditions requires consideration of its diffusion kinetic properties dasgupta et al 2004 2009 as does the issue of whether the peak condition is at all preserved in the compositional property of a garnet of a given grain size e g spear 1991 ganguly and tirone 1999 tirone and ganguly 2010 diffusion kinetic modeling of the major element compositional zonings of garnets leads to important constraints on the time scales of metamorphic processes such as heating and cooling rates e g florence and spear 1993 ganguly et al 2000 faryad and chakraborty 2005 augue and baxter 2007 from which one may infer the burial and exhumation rates respectively e g ganguly et al 2000 faryad and chakraborty 2005 and time scales of deformation camacho et al 2009 in addition the presence of garnet in the source region of a basaltic magma imparts a characteristic signature often referred to as the garnet signature to its rare earth element ree pattern in addition to providing an important constraint on the depth of the source region of a basaltic magma since garnet is stable below 50 km depth in the earth s interior e g saxena and eriksson 1983 the ree pattern of basaltic magma with garnet signature is often used to infer

geochemistry and extractable fe and al in cold temperature soils of northwestern siberia the concentrations of major minor and trace elements in three cryosols from north western siberia were analysed to determine profiles of geochemical uniformity element mobility and the release and build up of extractable fe and al the scope of this study involves weathering processes over all or part of the lateglacial to the holocene epoch 10 ka bp q1 in a cold environment the variability of hf content in the horizons is likely silica induced and accounts for much of the concentration variation in the other elements the slight increases of mobile to immobile elements in the b horizons indicate trivial downward movement within the profiles iron and al extracts were investigated to elicit information regarding profile age and palaeoclimate extractable fe and al show slight increases relative to the total concentrations in the soil sola ah bw horizons lattice fe decreases in the ah bw horizons as a result of weathering and production of sesquioxides over time increases of ferrihydrite in the ah horizons and in the parent material of some profiles may indicate perched water tables at some time in the past possibly as sustained yearly water levels in the active layer free iron fed relative to total fe increases in the ah bw horizons compared with the lower horizons where the oxidation potential is weaker low total fe reflects reworked felsic rich deltaic and shallow marine deposits from the permian to the early tertiary thereafter emplaced by episodic flooding of glacial meltwater from the arctic urals and or the kara sea ice sheet organically complexed al alp uniformly low in all soils nevertheless shows trends indicating some downward movement a rather unique occurrence in arctic tundra soils as indicated by the slow increase of oxihydrites it may not be realistic to estimate the age of a profile by its physical characteristics however it appears possible to determine broad age ranges from the isotopic composition of water in soils organic carbon concentrations between and within soil profiles indicate it may be more prevalent in tundra soil than previously thought and may also play a significant role in uploading co2 to the atmosphere as warming and microbial activity q2 progresses copyright 2009 john wiley sons ltd

surface exposure dating of the great aletsch glacier egesen moraine system western swiss alps using the cosmogenic nuclide 10be egesen moraines throughout the alps mark a glacial advance that has been correlated with the younger dryas cold period using the surface exposure dating method in particular the measurement of the cosmogenic nuclide 10 be in rock surfaces we attained four ages for boulders on a prominent egesen moraine of great aletsch glacier in the western swiss alps the 10 be dates range from 10 460 1100 to 9040 1020 yr ago three 10 be dates between 9630 810 and 9040 1020 yr ago are based upon samples from the surfaces of granite boulders two 10 be dates 10 460 1100 and 9910 970 yr ago are based upon a sample from a quartz vein at the surface of a schist boulder in consideration of the numerous factors that can influence apparently young 10 be dates and the scatter within the data we interpret the weighted mean of four boulder ages 9640 430 yr including the weighted mean of two 10 be dates of the quartz vein as a minimum age of deposition of the moraine all 10 be dates from the great aletsch glacier egesen moraine are consistent with radiocarbon dates of nearby bog bottom organic sediments which provide minimum ages of deglaciation from the moraine the 10 be dates from boulders on the great aletsch glacier egesen moraine also are similar to 10 be dates from egesen moraines of vadret lagrev glacier on julier pass in the eastern swiss alps both the morphology of the great aletsch glacier egesen moraine and the comparison with 10 be dates from the inner vadret lagrev egesen moraine support the hypothesis that the climatic cooling that occurred during the younger dryas cold episode influenced the glacial advance that deposited the great aletsch glacier egesen moraine because of the large size and slow response time of great aletsch glacier we suggest that the great aletsch glacier egesen moraine was formed during the last glacial advance of the multiphased egesen cold period the kromer stage during the preboreal chron copyright 2004 john wiley sons ltd

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

deformation of garnets in a low grade shear zone elongated shapes of garnets in high grade metamorphic rocks have been explained as a result of plastic crystal flow or anisotropic growth in the case of low to medium grade metamorphic rocks a satisfactory explanation has not been proposed yet for elongated garnets we have studied elongated garnets grown under low grade metamorphic conditions in a shear zone with a composite planar linear fabric garnet shapes in three dimensions define oblate ellipsoids drawing on evidence from compositional x ray maps it can be deduced that growth zoning is truncated along the long borders of grains whereas subcircular garnets show non truncated concentric growth zoning this fact shows that selective dissolution along planes parallel to the foliation and the c surfaces can be claimed to be the main mechanism responsible for the deformation of the garnets under examination here more specifically dislocation enhanced dissolution which occurs at low temperatures and low dislocation mobility is arguably the mechanism responsible for partially dissolving the garnet grains selective dissolution is expected to yield plane strain oblate ellipsoids i e with a volume loss as measured in the elongated garnets however the rock as a whole has been deformed by plastic flow in a simple shear regime as shown by the existence of numerous shear criteria and the strain calculations performed 0 1997 elsevier science ltd

closing a sediment budget for a reconfigured reach of the provo river utah united states 1 we quantified all components of a fluvial sediment budget for a discrete flood on an aggrading gravel bed river bed load transport rates were measured at the upstream and downstream ends of a 4 km study area on the provo river utah during a dam controlled flood we also collected high resolution measurements of channel topography before and after the controlled flood for the entire reach topographic uncertainty in the digital elevation models dem was characterized using a spatially variable approach the net sediment flux provided unambiguous indication of storage sediment input to the reach 319 m3 exceeded output 32 m3 producing a net accumulation of approximately 290 m3 the difference between the scour and fill was also positive 470 m3 but uncertainty in the topographic differencing was larger than the observed net storage thus the budget would have been indeterminate if based on morphologic data alone although topographic differencing was not sufficiently accurate to indicate net storage it was able to demonstrate that internal erosion was a larger sediment source than the net sediment flux the magnitude of total erosion 1454 m3 and deposition 1926 m3 was considerably larger than net change in storage showing that internal sources and sinks were the dominant driver of channel change the findings provide guidance for the development of sediment budgets in settings in which one must choose between a morphological approach and the direct measurement of sediment flux

diffusion obstacles and opportunities in petrochronology many of the approaches in petrochronology are rooted in the assumption of equilibrium diffusion is an expression of disequilibrium the movement of mass in response to chemical potential gradients and isotopes in response to isotopic gradients it is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment conversely the effects of diffusion also provide opportunities for understanding rates processes and conditions experienced by rocks the enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals many resources cover these topics including rimg volume 72 diffusion in minerals and melts zhang and cherniak 2010 and several textbooks crank 1975 glicksman 2000 particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion brady and cherniak 2010 zhang 2010 as well as diffusion rates in feldspar cherniak 2010a accessory minerals cherniak 2010b garnet ganguly 2010 mica pyroxene and amphibole cherniak and dimanov 2010 and melts zhang and ni 2010 zhang et al 2010 rather than duplicate that material our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes to achieve this goal we emphasize key principles and illustrative examples quantitative interpretation of the effects of diffusion assumes predictability of numerous factors that may affect chemical or isotopic transport including temperature initial and boundary conditions water and oxygen fugacities activities of other components multiple mechanisms of diffusion and crystal chemistry coupling of the substitution of elements into different crystallographic sites additionally the extraction of meaningful ages durations of events and temperatures requires

crustal cooling rates inferred from homogenization of metamorphic garnets abstract a closed system diffusion model has been developed for describing homogenization of spherical crystals by chemical interdiffusion with the added knowledge of interdiffusion coefficients it is possible to model temperature time t t histories of particular rocks the model has been used to describe the homogenization of almandine rich garnets in a polymetamorphic terrane in southwestern new hampshire the results of the analysis indicate that the calculated cooling rates are controlled by the deformation history of the area in particular the folding of isotherms the proposed model is of general applicability to problems of cooling in metamorphic and subsolidus igneous rocks

the effects of topographic surveying technique and data resolution on the detection and interpretation of geomorphic change abstract change detection of high resolution topographic data is commonly used in river valleys to quantify reach and site scale sediment budgets by estimating the erosion deposition volume and to interpret the geomorphic processes driving erosion and deposition field survey data are typically collected as point clouds that are often converted to gridded raster datasets and the ultimate choice of grid resolution is left to the user this choice may have important implications for both the quantification and interpretation of geomorphic change here we used concurrent topographic data collected by terrestrial laser scanning tls and structure from motion sfm photogrammetry to quantify the influence of grid resolution and sampling technique on a the sediment budget and b the presence and role of geomorphic processes i e alluvial colluvial aeolian and fluvial transport driving topographic change at four sites along the colorado river in grand canyon arizona usa we found that while both techniques produced similar estimates for site scale sediment budgets the magnitude of detected topographic change was dampened at coarser pixel resolutions an overall decrease in the areal extent of erosion and deposition were observed respectively when coarsening pixel size from 5 cm to 1 m among all sites coarser resolution data tended to affect interpretation of landscape change along the margins of river valleys for example when changing from 5 cm to 1 m pixel resolution the inferred contribution of aeolian changes to total site scale geomorphic change increased in area by 7 9 whereas the inferred contribution of alluvial and colluvial processes decreased in area by 97 9 and 88 2 respectively more generally we found that coarsening pixel sizes disproportionately attributed geomorphic change to one or more of the most common processes operating at a site we also found that coarsening pixel resolution amplified the net sediment imbalance at the site scale driving the imbalance at erosional sites further into erosion and vice versa for depositional sites our results have implications both for point cloud data collection and for raster dataset processing we argue that selecting the finest obtainable resolution is not always warranted to accurately quantify and interpret geomorphic change because remote sensing technique topographic data resolution and analysis procedure can be optimized to capture the spatial scale of those processes driving landscape change however in landscapes at or near sediment equilibrium i e equal amounts of erosion and deposition the finest obtainable topographic data resolution is warranted to avoid amplifying sediment imbalance and erroneously inferring that sites are trending toward erosion or deposition

melt producing versus melt consuming reactions in pelitic xenoliths and migmatites abstract melt producing reactions have operated both in pelitic xenoliths and in pelitic migmatites but melt consuming reactions related to in situ melt crystallization are largely restricted to migmatites hence xenolith reaction textures may provide clues on the relative roles of both reaction types in migmatites a comparison of xenoliths and migmatites results in a catalogue of textural and chemical features some of which are argued to be diagnostic the results have implications for the identification of restite in igneous rocks and for the relative importance of prograde and retrograde processes in different domains of layered migmatites