structural and stratigraphie features and ers 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in nw alaska winter 1991 1992 changes in ers 1 c band synthetic aperture radar sar backscatter intensity from ice growing on shallow tundra lakes at three locations in nw alaska are described ice core analysis shows that at all lakes on the coast at barrow the ice whether floating or frozen to the bottom includes an inclusion free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth the clear ice may also be overlain by a discontinuous layer of bubbly snow ice backscatter is low 16 to 22 db at the time of initial ice formation probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar as the ice thickens during the autumn backscatter rises steadily once the ice freezes to the lake bottom regardless of the presence of forward scattering tubular bubbles low backscatter values of 17 to 18 db are caused by absorption of the radar signal in the lake bed for ice that remains afloat all winter the ice water interface and the tubular bubbles combine presumably via an incoherent double bounce mechanism to cause maximum backscatter values of the order of 6 to 7 db the saturates at 6 to 7 db before maximum ice thickness and tubular bubble content are attained a simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice during the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland this reversal may be related to the ice surface topography and wetness plus the effects of a longer cooler melt period by the coast time series of backscatter variations from shallow tundra lakes are a record of 1 the development of tubular bubbles in the ice and by association changes in the gas content of the underlying water and 2 the freezing of ice to the bottoms of the lakes and therefore lake bathymetry and water availability sar is also able to detect the onset of lake ice growth in autumn and the initiation of the spring thaw and thus has potential for monitoring high latitude lake ice growth and decay processes in relation to climate variability

greenland flow variability from ice sheet wide velocity mapping using radarsat synthetic aperture radar data we have mapped the flow velocity over much of the greenland ice sheet for the winters of 2000 01 and 2005 06 these maps provide a detailed view of the ice sheet flow including that of the hundreds of glaciers draining the interior the focused patterns of flow at the coast suggest a strong influence of bedrock topography differences between our two maps confirm numerous early observations of accelerated outlet glacier flow as well as revealing previously unrecognized changes the overall pattern is one of speed up accompanied by terminus retreat but there are also several instances of surge behavior and a few cases of glacier slowdown comprehensive mappings such as these at regular intervals provide an important new observational capability for understanding ice sheet variability

ocean forcing of the greenland ice sheet calving fronts and patterns of retreat identified by automatic satellite monitoring of eastern outlet glaciers 1 we have developed an automatic method to identify changes in the position of calving glacier margins using daily modis imagery application of the method to 32 ocean terminating glaciers in east greenland produced 26 802 margin positions for a 10 year long period 2000 2009 we report these high resolution data and show that the glaciers exhibit seasonal cycles with magnitudes of advance and retreat proportional to glacier width despite similar seasonality there is a distinct difference between the interannual trends of calving front positions north and south of 69 n all glaciers above this latitude showed very limited or no change when seasonality was excluded while glaciers south of 69 n retreated significantly between 2001 and 2005 2 3 km on average approximately 26 of the retreat of southern glaciers was regained by readvance from 2005 to 2009 to explain the latitudinal boundary of glacier dynamics we review basic climatic factors including summer and winter atmospheric forcing sea ice conditions and ocean temperature we conclude that the southern retreats were strongly influenced by warm oceanic conditions associated with increased transport of subtropical waters to the irminger sea and to fjords and coastal regions south of 69 n northern glaciers remained stable despite significant increase in runoff in this region because fjords at latitudes higher than 69 n are less exposed to subtropical waters the southern retreats illustrate sensitive behavior of calving glaciers and we hypothesize that the calving fronts retreated because they were exposed to rapid ice front melting

greenland marine terminating glacier area changes 2000 2010 area changes at 39 of the widest greenland marine terminating glacier outlets are measured in consecutive annual end of melt season moderate resolution imaging spectroradiometer modis scenes spanning ten annual intervals 2000 10 the rates of cumulative area change for glaciers and ice shelves are well represented by linear least squares fits r 0 99 and r 0 94 with average rates of 70 and 65 km 2 a 1 respectively collectively during this decade the 39 glaciers lost a cumulative area of 1368 km 2 more than three quarters of the total area change occurred north of 72 n the largest 11 year area change for a single glacier during the survey period is the 311 km 2 loss at humboldt glacier the largest annual change for a single glacier was extreme compared with the others where petermann glacier retreated 17 km between 3 and 5 august 2010 for the 10 year sample on average the count of glaciers retreating is twice that advancing a larger distinction is evident considering area change with the ratio of retreat and advance on average nine times the gain for glaciers with ice shelves we find no year with collective area gain the area change data from this study are posted at http bprc osu edu jbox data gac

sediment characteristics of an extreme flood 1993 upper mississippi river valley the 1993 mississippi river flood was notable for its high magnitude long duration summer occurrence and low sediment discharge a field survey of a 70 km long reach in the vicinity of quincy illinois revealed that the event was characterized by 100 yr flood had remarkably little sedimentological or geomorphological impact on the flood plain within the study reach because the transport effectiveness of floods in large drainage basins is influenced by event sequencing in the same manner as floods in small watersheds and the cohesive flood plain soils were not susceptible to erosion

longitudinal facies architectural changes of a middle holocene anastomosing distributary system rhine meuse delta central netherlands abstract longitudinal changes in channel planform and facies architecture occur over a 22 km long reach of an anastomosing middle holocene distributary system in the rhine meuse delta central netherlands a geological map and a sequence of cross sections show that the channel belt is characterized by sand body width thickness ratios which decrease within the study area from approximately 25 upstream to well below 10 downstream accompanied by a change in channel planform as indicated by a downstream increase of the number of crevasse splays the lithological composition of the sand body is relatively homogeneous but there is always a well developed fining upward sequence from sandy channel deposits to clayey natural levee deposits within channel vertical aggradation appears to have been restricted during most of the period of activity of the distributary system and since lateral accretion was also limited especially in the downstream part rapid accumulation of channel deposits seems to have occurred predominantly during the avulsion stage leaving a narrow and shallow residual channel as the last remnant the longitudinal change in channel pattern is mainly attributed to a downstream increase in the rate of ground water level rise that resulted from holocene sea level rise in the rhine meuse delta a rate of ground water level rise of 1 5 mm yr 1 is required for the creation of fully developed anastomosing fluvial systems ribbons with a width thickness ratio of

first demonstration of surface currents imaged by hybrid along and cross track interferometric sar this paper is concerned with the simultaneous measurement of terrain heights and currents using an airborne interferometric synthetic aperture radar insar for the first time a hybrid two antenna insar system with both along and across track baseline components is used to measure high resolution digital elevation maps dems and current fields in a wadden sea area coastal applications like the monitoring of sediment transport or the numerical modeling of morphodynamic processes require measurements of topography and currents classical in situ measurements of these parameters are both expensive and time consuming or even impossible if higher spatial resolution is required pure along track interferometers atis have demonstrated their ability to provide information on ocean currents while across track interferometric systems xtis have been successfully used to measure dems in this paper a hybrid system with both ati and xti components is used to acquire synoptic measurement for the first time an experiment with an airborne system taking data over a wadden sea area is presented demonstrating the potential of the technique a geometrical model is developed for the interferometric phase of hybrid insar systems this model combines ati and xti techniques using a baseline that spans between two antennas consisting of along track and across track components in this model both the effect of topography and the radial velocity of the water surface enter into the resulting interferometric phase to separate both components the system takes data of the respective scene flying two or more tracks with different flight directions e g antiparallel tracks this approach leads to a set of linear equations that has a unique solution for the along and cross track phase finally an additional phase bias has to be considered due to the radial velocity and the influence of squint this is caused by a misregistration effect between both antennas which is related to cross track imaging of surface motion the new insar technique is tested with data acquired during a campaign in february 1997 over the weser estuary at the german coast the airborne insar system aes 1 was used the interferometer configuration consists of two sar antennas separated by a mixed along track and cross track baseline two datasets acquired on antiparallel tracks are used the calculated velocities were compared with a hydrodynamic model operated by the federal waterway engineering and research establishment the experimental results agree well with the numerical model in particular the mean velocity of 0 7 ms sup 1 matches in both datasets deviations in the fine scale structure of the current field are discussed topographic analysis and validation are performed in a separate investigation the impact of surface gravity waves and wind drift which are known to cause significant artifacts in the ati phase under certain circumstances is discussed

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

estimation of discharge from three braided rivers using synthetic aperture radar satellite imagery potential application to ungaged basins analysis of 41 ers 1 synthetic aperture radar images and simultaneous ground measurements of discharge for three large braided rivers indicates that the area of active flow on braided river floodplains is primarily a function of discharge a power law correlation is found between satellite derived effective width we and discharge q where we is the water surface area within a braided reach divided by the reach length synthetic values of we and q generated from a cellular automata model of stream braiding display a similar power law correlation power functions that are fit through plots of we and q represent satellite derived rating curves that can subsequently be used to estimate instantaneous river discharge from space with errors ranging from tens to hundreds of cubic meters per second for ungaged rivers changes in relative discharge can be determined from satellite data alone to determine the shape and timing of annual flows in glacierized basins absolute discharge can probably be estimated within a factor of 2 more accurate estimates will require either 1 one or more ground measurements of discharge acquired simultaneously with a satellite image acquisition or 2 successful parameterization of known morphologic controls such as total sinuosity 5 p valley slope bank material and stability and braid channel hydraulic geometry values of total sinuosity 5 p derived from satellite imagery and field measurements from two rivers of braid channel width depth velocity water surface slope and bed material grain size indicate that while the shape of satellite derived we q rating curves may be influenced by all of these variables the sensitivity of flow area to changing discharge is most dependent upon the degree of braiding efforts to monitor river discharge from space will be most successful for intensely braided rivers with high values of total sinuosity subsampling of existing daily discharge records from the iskut river suggests that satellite return times of about 1 week are sufficient for approximating the shape and timing of the seasonal hydrograph in large glacierized basins although errors are large the presented technique represents the only currently available way to estimate discharge in ungauged braided rivers

controls on rapid supraglacial lake drainage in west greenland an exploratory data analysis approach the controls on rapid surface lake drainage on the greenland ice sheet gris remain uncertain making it challenging to incorporate lake drainage into models of gris hydrology and so to determine the ice dynamic impact of meltwater reaching the ice sheet bed here we first use a lake area and volume tracking algorithm to identify rapidly draining lakes within west greenland during summer 2014 second we derive hydrological morphological glaciological and surface mass balance data for various factors that may influence rapid lake drainage third these factors are used within exploratory data analysis to examine existing hypotheses for rapid lake drainage this involves testing for statistical differences between the rapidly and non rapidly draining lake types as well as examining associations between lake size and the potential controlling factors this study shows that the two lake types are statistically indistinguishable for almost all factors investigated except lake area thus we are unable to recommend an empirically supported deterministic alternative to the fracture area threshold parameter for modelling rapid lake drainage within existing surface hydrology models of the gris however if improved remotely sensed datasets e g ice velocity maps climate model outputs were included in future research it may be possible to detect the causes of rapid drainage

21st century evolution of greenland outlet glacier velocities earlier observations on several of greenland s outlet glaciers starting near the turn of the 21st century indicated rapid annual scale and large 100 increases in glacier velocity combining data from several satellites we produce a decade long 2000 to 2010 record documenting the ongoing velocity evolution of nearly all 200 of greenland s major outlet glaciers revealing complex spatial and temporal patterns changes on fast flow marine terminating glaciers contrast with steady velocities on ice shelf terminating glaciers and slow speeds on land terminating glaciers regionally glaciers in the northwest accelerated steadily with more variability in the southeast and relatively steady flow elsewhere intraregional variability shows a complex response to regional and local forcing observed acceleration indicates that sea level rise from greenland may fall well below proposed upper bounds

penetration depth of interferometric synthetic aperture radar signals in snow and ice digital elevation models of glaciated terrain produced by the nasa jet propulsion laboratory jpl airborne interferometric synthetic aperture radar insar instrument in greenland and alaska at the c 5 6 cm wave length and l band 24 cm frequencies were compared with surface elevation measured from airborne laser altimetry to estimate the phase center of the interferometric depth or penetration depth p on cold polar firn at greenland summit p 9 2m at c and 14 4m at l band on the exposed ice surface of jakobshavn isbrae west greenland p 1 2 m at c and 3 3 m at l band except on smooth marginal ice where p 15 5 m on colder marginal ice of northeast greenland p reaches 60 to 120 m at l band on the temperate ice of brady glacier alaska p is 4 2 m at c and 12 6 m at l band with little dependence on snow ice conditions the implications of the results on the scientific use of insar data over snow ice terrain is discussed

distal alluvial deposits in a foreland basin setting the lower freshwater molasse lower miocene switzerland sedimentology architecture and palaeosols the lower freshwater molasse untere susswasser molasse crops out over a wide area of the swiss molasse basin coarse grained alluvial fan conglomerates dominate in proximal basin areas along the alpine front these conglomerates pass northwards into sandstones and mudstones of an extensive northeastward draining meandering river system which ran parallel to the basin axis sedimentological study of outcrops quarry exposures and boreholes in the basal miocene aquitanian has permitted detailed facies analysis of this distal alluvial sequence the distal aquitanian is made up of distinct architectural elements characterized by their geometries and sedimentary structures each may be assigned to a particular depositional setting meander belt levees crevasse channels and splays overbank fines and palaeosols and lacustrine meander belt sandstones were deposited in mixed load channels with a dominant bedload component sandstones commonly comprise amalgamated and locally stacked ribbon bodies 2 15 m thick and 150 1500 m wide interbedded rippled laminated and mottled fine grained levee sandstones and siltstones form lenticular packages up to 3 m thick and 30 100 m across small scale crevasse channel sandstones 2 4 m thick and 5 10 m across pass laterally into metre scale medium to fine grained crevasse sandstone sheets rare laminated lacustrine siltstones occur only in the north east part of the basin floodplain mudstones and marls make up the remainder of the succession these display a variety of pedogenic features recording cyclical palaeosol development palaeosols show strong variations in morphology and maturity both laterally across the floodplain and downstream along the basin axis reflecting local variation in aggradation rate associated with proximity to alluvial channel courses as well as regional variation in subsidence and floodplain drainage analysis of the organization and distribution of the various sediment bodies permits reconstruction of the fluvial system and allows development of a model for the sedimentary architecture of the lower freshwater molasse in the study area integration of palaeosol studies into a well defined architectural framework assists recognition of areal facies belts and may aid location of sand prone sequences in the subsurface

what is a fluvial levee abstract fluvial levees are elevated partitions between channels and floodplains because of their character and position levees may provide critical controls on and insights into geomorphic processes that determine the distribution of water and sediment within river systems few studies have analysed the character distribution sedimentology and processes that form levees in modern depositional environments characterisation of levee deposits from the mississippi river continues to form the basis for most levee interpretations from the rock record this discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record and their associated inferences for river style this uncertainty reflects the lack of definitive sedimentological attributes for levee deposits their limited preservation potential and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies given these concerns it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern and ancient river settings

composition structure and evolution of a lacustrine carbonate margin dominated by microbialites case study from the green river formation eocene wyoming usa abstract during mid eocene times the northwestern margin of the gosiute lake wyoming has been characterised by the extensive development of a microbialite dominated carbonate sequence corresponding to the laney member of the green river formation thus providing a potential analogue for petroleum carbonate reservoirs developed in similar marginal lacustrine settings a detailed sedimentological study carried out on the little mesa plateau near labarge sw wyoming allows the reconstruction of 1 lateral and vertical facies variations of the carbonate sequence across the margin 2 development patterns of complex microbial bioconstructions and 3 the evolution of the margin through time the carbonate sequence up to 18 m thick starts with the deposition of sandy limestones which fill channels in the underlying siliciclastic unit of the cathedral bluff formation the increasing microbial contribution in the upper part of the sequence results in the development of large insect microbial build ups which represent up to 80 of the total volume of the carbonate deposits and which aggregated to form reef like geometries up to several tens of metres in diameter including bioherms spur and groove alignments and reef flat structures the initiation and development of the lacustrine carbonate platform was controlled both by the general lake expansion associated to the eocene climatic optimum and by local drainage diversions responsible for a new water inflow in the basin from the northern volcanic provinces short term lake level changes driven by high frequency climate fluctuations which are superimposed to this general transgressive trend may explain the discontinuous and polygenic growth of the individual insect microbial build ups the basin infilling by prograding alluvial volcaniclastic deposits originated from the northwestern volcanic province caused the rapid turn off of the marginal lacustrine carbonate factory during mid eocene time

rapid and synchronous ice dynamic changes in east greenland two major outlet glaciers in east greenland have suddenly begun to accelerate and retreat the speeds of kangerdlugssuaq and helheim remained steady during the 1990s despite progressive and substantial thinning but have abruptly increased within the last two years more than doubling ice flux to the ocean had it been an isolated example the comparable 1998 speed up of jakobshavn isbra in west greenland might have been explained simply by its chance retreat past a pinning point now that two further greenland outlets have exhibited similar behavior a common process seems likely a remarkable correspondence in the inter annual patterns of speed and ice front variation between kangerdlugssuaq and helheim implies a significant sensitivity to regional environmental factors the period of continued warming and thinning appears to have primed these glaciers for a step change in dynamics not included in current models we should expect further greenland outlet glaciers to follow suit copyright 2006 by the american geophysical union

lacustrine and fluvial deltaic depositional systems fort union formation paleocene powder river basin wyoming and montana the powder river basin is a laramide foreland basin that was filled by a combination of fluvial deltaic paludal and lacustrine sediments the depositional history of the fort union formation was unraveled in a regional subsurface study using data from approximately 1 400 geophysical well logs the depositional model developed from the subsurface study was tested by selective fieldwork the powder river basin originated as a structural and depositional basin in earliest middle paleocene as a result of rapid subsidence a lake lake lebo formed along the basin axis lake lebo documented in the mudstone of the lebo shale member spread rapidly to cover an area greater than 10 000 mi2 25 900 km2 during the middle through late paleocene lake lebo was filled peripherally by fluvial deltaic systems that are recorded in the coarser clastics of the tongue river member primary basin fill was from 1 the eastern margin by elongate deltas fed by suspended to mixed load fluvial systems issuing from the ancestral black hills and 2 the southwestern margin by mixed to bed load streams emanating from the wind river basin secondary fill was from th northwest by an elongate delta system fed by a suspended to mixed load fluvial system flowing from the bull mountain basin

the extreme melt across the greenland ice sheet in 2012 1 the discovery of the 2012 extreme melt event across almost the entire surface of the greenland ice sheet is presented data from three different satellite sensors including the oceansat 2 scatterometer the moderate resolution imaging spectroradiometer and the special sensor microwave imager sounder are combined to obtain composite melt maps representing the most complete melt conditions detectable across the ice sheet satellite observations reveal that melt occurred at or near the surface of the greenland ice sheet across 98 6 of its entire extent on 12 july 2012 including the usually cold polar areas at high altitudes like summit in the dry snow facies of the ice sheet this melt event coincided with an anomalous ridge of warm air that became stagnant over greenland as seen in melt occurrences from multiple ice core records at summit reported in the published literature such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the medieval warm period given its rarity the 2012 extreme melt across greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research

ice regime of the lower peace river and ice jam flooding of the peace athabasca delta the peace athabasca delta pad in northern alberta is one of the world s largest inland freshwater deltas home to large populations of waterfowl muskrat beaver and free ranging wood bison beginning in the mid 1970s a paucity of ice jam flooding in the lower peace river has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide a habitat for aquatic life in the pad region using archived hydrometric data and in situ observations the ice regime of the lower peace is described and quantified setting the stage for identification of the conditions that lead to ice jam flooding and replenishment of delta habitat the first such condition is the occurrence of a mechanical as opposed to a thermal breakup event second the river flow should be at least 4000 m3 s and third an ice jam should form within the last 50 km of the peace river the type of breakup event depends on the freeze up stage and spring flow the former has increased as a result of flow regulation and the latter has decreased owing to changing climatic patterns both trends tend to inhibit the occurrence of mechanical breakups and contribute to less frequent ice jam flooding potential mitigation strategies are discussed copyright 2006 crown in the right of canada published by john wiley sons ltd

remote sensing of temporal and spatial variations in pool size suspended sediment turbidity and secchi depth in tuttle creek reservoir kansas 1993 abstract four dates of landsat thematic mapper data from 1993 april 9 july 30 august 15 and september 16 were used to assess temporal and spatial patterns of lake area and dimensions of suspended sediment concentration in tuttle creek reservoir kansas in 1993 excessive precipitation in the big blue river basin and throughout much of the upper middle west led to widespread flooding rains produced substantial erosion sediment movement down the stream network and a runoff volume that filled tuttle creek reservoir a u s army corps of engineers flood control structure the april 9 data are from before the flood the july 30 data are from the time of maximum pool size and use of the emergency spillway and the august and september data document the declining pool sizes three separate analyses were performed on each of the four dates of thematic mapper data one set of analyses involved applying an existing physical model that uses at satellite reflectance for tm band 3 to estimate variations in suspended sediment turbidity and secchi depth throughout the reservoir maps of estimated parameters of water quality for the four individual dates were compared and analyzed to document spatial and temporal changes the second research method involved unsupervised classification erdas isodata algorithm of the data from the tuttle creek reservoir water areas were grouped into coherent classes for further spatial analysis using a two step or layered classification procedure for each date the third analysis used a gis overlay technique to compare the area of the water surface for each of the four dates with the flood pool as marked on u s g s 7 1 2 minute quadrangles comparisons document the major change in lake area between april and july the high levels of suspended sediment in mid summer and the decline in pool size and concentrations of suspended sediment by mid september the study illustrates the advantages of using remote sensing to assist in documenting a relatively short term environmental hazard this study also demonstrates the value of landsat thematic mapper data for use in mapping geographic variations in water area and quality in conjunction with a major flood event

greenland ice sheet surface properties and ice dynamics from ers 1 sar imagery c band synthetic aperture radar sar imagery from the european space agency s ers 1 satellite reveals the basic zonation of the surface of the greenland ice sheet the zones have backscatter signatures related to the structure of the snowpack which varies with the balance of accumulation and melt at various elevations the boundaries of zones can be accurately located with the use of this high resolution imagery the images also reveal a large flow feature in northeast greenland that is similar to ice streams in antarctica and may play a major role in the discharge of ice from the ice sheet

a relationship between alluvial backswamps and avulsion cycles an example from the willwood formation of the bighorn basin wyoming abstract stratigraphically limited intervals from the lower eocene willwood formation contain laterally extensive carbonaceous shales and ribbon sandstone networks associated with channel avulsion we present data from one such interval that documents the avulsion sequence vertical sections measured along the outcrop of this interval are similar and comprise a basal carbonaceous shale overlain by fine grained deposits on which weakly developed hydromorphic paleosols formed the paleosols enclose and are locally incised by ribbon sandstones some of which cut down to and partly through the carbonaceous shale the ribbons have width thickness ratios between 3 and 13 some ribbons cluster at a particular stratigraphic level which together with paleocurrent trends suggests that they formed channel networks sections are capped by yellow brown paleosols showing moderate pedogenic development we suggest that the carbonaceous shales developed in low lying topogeneous swamps in distal portions of the floodplain far from the trunk channel such a location set limits on the sediment that they received the mudrocks with weakly developed paleosols and associated ribbon sandstones are interpreted as crevasse splay complexes resulting from avulsion of the trunk river the ribbon sandstones represent ancient feeder channels of the avulsion complex the rapid influx of avulsion deposits appears to have been crucial to preserving the organic material and this study reveals an important and as yet uncharacterized link between trunk channel processes and the accumulation of organic rich deposits in distal alluvial swamps similar deposits are found in other stratigraphic units in the rocky mountain region and the development of these and other organic rich deposits should be reassessed in terms of channel avulsion

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

floodplain channel morphology and networks of the middle amazon river 1 floodplain channels are important components of river floodplain systems and are known to play a key role in hydrodynamic exchange and sediment transport the amazon floodplain exhibits complex networks of these channels and despite their potential importance to this globally important wetland system these floodplain channels are relatively unstudied the research presented here is the first systematic and detailed study of the network and morphologic characteristics of a large number of these channels in the middle reach of the central amazon river using analysis of data derived from landsat enhanced thematic mapper plus etm mosaic and field survey our findings show that the channels are ubiquitous their width varies widely and some of their characteristics can be fitted using power laws potentially much like the self similar or fractal like behavior hypothesized for other types of fluvial networks in all 96 of the floodplain channels are not wide enough to be represented well or at all in the 90 m shuttle radar topography mission data channel depths are tied closely to the local amplitude of the passing main river flood wave p value of 0 75 except where there are local runoff inputs which results in substantially deeper channels which provide preferential flow paths across the floodplain channel networks imply that areas of the floodplain function for large parts of the flood cycle as separate hydrogeomorphic land units here termed floodplain hydrological units fhus these hypothesized fhus also have distinct spatial and pattern characteristics and it is suggested here that their differences could provide the beginnings of a framework for understanding the detailed hydrodynamics of the floodplain in particular different types of fhus have differences in flood water source which will have important implications for biogeochemical studies of the wetlands

classification of hydrological regimes of northern floodplain basins peace athabasca delta canada from analysis of stable isotopes δ18o δ2h and water chemistry we used stable isotopes 18o and 2h and water chemistry to characterize the water balance and hydrolimnological relationships of 57 shallow aquatic basins in the peace athabasca delta pad northern alberta canada based on sampling at the end of the 2000 thaw season evaporation to inflow ratios e i were estimated using an isotope mass balance model tailored to accommodate basin specific input water compositions which provided an effective first order quantitative framework for identifying water balances and associated limnological characteristics spanning three main previously identified drainage types open drainage basins e i 0 4 n 5 characterized by low alkalinity low concentrations of nitrogen dissolved organic carbon doc and ions and high minerogenic turbidity include large shallow basins that dominate the interior of the pad and experience frequent or continuous river channel connection closed drainage basins e i 1 0 n 16 in contrast possess high alkalinity and high concentrations of nitrogen doc and ions and low minerogenic turbidity and are located primarily in the relict and infrequently flooded landscape of the northern peace sector of the delta several basins fall into the restricted drainage category 0 4 e i 1 0 n 26 with intermediate water chemistries and are predominant in the southern athabasca sector which is subject to active fluviodeltaic processes including intermittent flooding from riverbank overflow integration of isotopic and limnological data also revealed evidence for a new fourth drainage type mainly located near the large open drainage lakes that occupy the central portion of the delta but within the athabasca sector n 10 these basins were very shallow 50 cm deep at the time of sampling and isotopically depleted corresponding to e i characteristic of restricted and open drainage conditions however they are limnologically similar to closed drainage basins except for higher conductivity and higher concentrations of ca2 and na and lower concentrations of sio2 and chlorophyll c these distinct features are due to the overriding influence of recent summer rainfall on the basin water balance and chemistry the close relationships evident between water balances and limnological conditions suggest that past and future changes in hydrology are likely to be coupled with marked alterations in water chemistry and hence the ecology of aquatic environments in the pad copyright 2006 john wiley sons ltd

an improved mass budget for the greenland ice sheet extensive ice thickness surveys by nasa s operation icebridge enable over a decade of ice discharge measurements at high precision for the majority of greenland s marine terminating outlet glaciers prompting a reassessment of the temporal and spatial distribution of glacier change annualmeasurements for 178 outlet glaciers reveal that despite widespread acceleration only 15 glaciers accounted for 77 of the 739 29 gt of ice lost due to acceleration since 2000 and four accounted for 50 among the top sources of loss are several glaciers that have received little scientific attention the relative contribution of ice discharge to total loss decreased from 58 before 2005 to 32 between 2009 and 2012 as such 84 of the increase in mass loss after 2009 was due to increased surface runoff these observations support recentmodel projections that surface mass balance rather than ice dynamics will dominate the ice sheet s contribution to 21st century sea level rise

remote sensing of suspended sediment concentration flow velocity and lake recharge in the peace athabasca delta canada 1 the transport of fine sediment carried in suspension by water is central to the hydrology geomorphology and ecological functioning of river floodplains and deltas an extensive new field data set for the peace athabasca delta pad canada quantifies robust positive relationships between in situ suspended sediment concentration ssc and remotely sensed visible near infrared reflectance these relationships are exploited using spot and aster satellite images to map suspended sediment concentrations across the pad for four days in 2006 and 2007 revealing strong variations in water sources and flow patterns including flow reversals in major distributaries near daily monitoring with 276 modis satellite images tracks hydrologic recharge of floodplain lakes as revealed by episodic infusions of sediment rich water from the athabasca river the timing and magnitude of lake recharge are linked to springtime water level on the athabasca river suggesting a system sensitive to changes in river flow regime moreover recharge timing differentiates lakes that are frequently and extensively recharged from those recharged more rarely finally we present a first estimation of river flow velocity based on remotely sensed ssc though saturation may occur at velocities 0 6 m s viewed collectively the different remote sensing methodologies presented here suggest strong value for visible near infrared remote sensing of suspended sediment to assess hydrologic and sediment transport processes in complex flow environments field observations including nephelometric turbidity specific conductivity water temperature secchi disk depth suspended sediment concentration and water level are archived at the oak ridge national laboratory distributed active archive center for biogeochemical dynamics available at http daac ornl gov hydroclimatology guides pad html

fluvial architecture and paleoenvironmental evolution of the los colorados formation norian postrift stage of the ischigualasto villa union basin nw argentina

estimation of discharge from braided glacial rivers using ers 1 synthetic aperture radar first results using multitemporal ers 1 synthetic aperture radar sar satellite imagery and simultaneous ground measurements of streamflow a strong correlation r2 0 89 was found between water surface area and discharge for a braided glacial river in british columbia canada satellite derived effective width we was found to vary with discharge q as we 27 5q0 42 where we is defined as the total water surface area within a 10 km 3 km control section divided by the section length this area discharge rating curve yields instantaneous discharge estimates with a mean error of 275 m3 s for ground measured flows that ranged from 242 to 6350 m3 s

variations in fluvial deposition on an alluvial plain an example from the tongue river member of the fort union formation paleocene southeastern powder river basin wyoming u s a abstract the tongue river member of the paleocene fort union formation is an important coal bearing sedimentary unit in the powder river basin of wyoming and montana we studied the depositional environments of a portion of this member at three sites 20 km apart in the southeastern part of the basin six lithofacies are recognized that we assign to five depositional facies categorized as either channel or interchannel wetlands environments 1 type a sandstone is cross stratified and occurs as lenticular bodies with concave upward basal surfaces these bodies are assigned to the channel facies interpreted to be the product of low sinuosity streams 2 type b sandstone occurs in parallel bedded units containing mudrock partings and fossil plant debris these units constitute the levee facies 3 type c sandstone typically lacks internal structure and occurs as tabular bodies separating finer grained deposits these bodies represent the crevasse splay facies 4 gray mudrock is generally nonlaminated and contains ironstone concretions these deposits constitute the floodplain facies 5 carbonaceous shale and coal are assigned to the swamp facies we recognize two styles of stream deposition in our study area laterally continuous complexes of single and multistoried channel bodies occur at our middle study site and we interpret these to be the deposits of sandy braided stream systems in the two adjacent study sites single and multistoried channel bodies are isolated in a matrix of finer grained interchannel sediment suggesting deposition by anastomosed streams a depositional model for our study area contains northwest trending braided stream systems avulsions of these systems created anastomosed streams that flowed into adjacent interchannel areas we propose that during late paleocene a broad alluvial plain existed on the southeastern flank of the powder river basin the braided streams that crossed this surface were tributaries to a northward flowing basin axis trunk stream that existed to the west

changes in the areal extents of the athabasca river birch river and cree creek deltas 1950 2014 peace athabasca delta canada abstract deltas form where riverborne sediment accumulates at the interface of river mouths and their receiving water bodies their areal extent is determined by the net effect of processes that increase their extent such as sediment accumulation and processes that decrease their extent such as erosion and subsidence through sequential mapping and construction of river discharge and sediment histories this study examined changes in the subaerial extents of the cree creek and athabasca river deltas both on the athabasca river system and the birch river delta in northern canada over the period 1950 2014 the purpose of the study was to determine how when and why the deltas changed in areal extent temporal growth patterns were similar across the athabasca and birch river systems indicative of a climatic signal little or no areal growth occurred from 1950 to 1968 moderate growth occurred between 1968 and the early to mid 1980s and rapid growth occurred between 1992 and 2012 factors that affected delta progradation included dredging sediment supply isostatic drowning delta front bathymetry sediment capture efficiency and storms in relation to sediment delivered areal growth rates were lowest in the athabasca delta intermediate in the birch delta and highest in the cree creek delta annual sediment delivery is increasing in the cree creek delta there were no significant trends in annual sediment delivery in the birch and athabasca deltas there was a lag of up to several years between sediment delivery events and progradation periods of delta progradation were associated with low water levels of the receiving basins predicted climate change driven declines in river discharge and lake levels may accelerate delta progradation in the region in the changing ecosystems of northeastern alberta inadequate monitoring of vegetation landforms and sediment regimes hampers the elucidation of the nature rate and causality of ecosystem changes

changes in the velocity structure of the greenland ice sheet using satellite radar interferometry observations of greenland we detected widespread glacier acceleration below 66 north between 1996 and 2000 which rapidly expanded to 70 north in 2005 accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year as more glaciers accelerate farther north the contribution of greenland to sea level rise will continue to increase

the hydro geomorphologic complexity of the lower amazon river floodplain and hydrological connectivity assessed by remote sensing and field control abstract hydrological connectivity processes along the lower amazon river floodplain at lago miratuba floodplain lmf were analyzed based on remote sensing and field measurements connectivity processes are related to 12 geomorphic sub units of the floodplain that are interconnected at different stage thresholds through channelized and overbank flow paths while lakes act as reservoirs for flood waters local rainfall and water table saturation seepage hydrological connectivity processes along the floodplain happen through complex internal routings of water flows over space and time mainly along floodplain channels and breached levees the contribution of local recharge mainly rainfall was decoupled from river recharge river hydrological connection to floodplain because precipitations and local runoff also recharge the floodplain the hydrological connectivity of the 12 geomorphic units varied significantly from each other because the inundation and the floodplain connections with the river were initiated at specific river stage thresholds for each sub unit an interesting finding is that connections with the river for all units were initiated through channelized flows below the bankfull stage of the amazon river the connectivity processes over different geomorphic units are also not correlated with their minimum distance shortest lines from the river this implies that a flood pulse model largely concerned with lateral connectivity mostly through overbank diffusion only partially explains the complex hydrological connectivity processes at a regional scale along the complex lower amazon river floodplain thus for hydrological connectivity assessments in the amazon river floodplain reach by reach scale studies have to be carried out relating the hydro geomorphologic processes channelized flow routing paths overbank diffusion and local recharge to the internal geomorphic variability and complexity of the floodplain

flood hydrology of the peace athabasca delta northern canada this study conducted a systematic examination of the flood hydrology of the peace athabasca delta pad a complex and internationally important freshwater ecosystem located in northwestern canada three distinct zones of floodwater origin within the pad were discerned on the basis of the dominant hydrology and the topography represented by a digital elevation model dem 1 perimeter peace delta 2 perimeter athabasca delta and 3 central delta lakes analysis of the satellite image and dem derived flood maps of historically significant events combined with field data of open water and ice influenced flood stages revealed that ice jamming was the most effective and likely the only mechanism capable of recharging the highly elevated perimeter areas in the athabasca and peace deltas this supports the conclusion of previous studies that used hydrometric data external to the delta to infer inter delta flood conditions by contrast even the record open water flow to the peace delta could not generate overbank flow hydraulic simulation of the naturalized system no dam no weirs suggests that overbanking of the lower peace river would have been a rare occurrence without the effects of regulation both ice jam induced and open water high waters were found to recharge perched basins in the athabasca delta enlargement of the central delta lakes beyond the shoreline was determined to be an effective flood mechanism for filling low to mid elevation wetlands comparison of the observed and naturalized lake levels indicates that flow regulation of the peace river and addition of the weirs on delta outflow channels has depending on the year led to an increase or a reduction in the annual maximum potential of inland flooding via lake expansion copyright 2006 crown in the right of canada published by john wiley sons ltd

southwestward weakening of wyoming lithosphere during the laramide orogeny the mechanism of laramide deformation in the central rocky mountains remains enigmatic it is generally agreed that the deformation resulted from low angle subduction of the farallon plate beneath the north american plate during the latest cretaceous early eocene however recent studies have suggested the importance of slab removal or slab rollback in causing this deformation here we infer wyoming lithosphere structure and surface deformation pattern by conducting 2 d flexural subsidence modeling in order to provide constraints on the mechanism of laramide deformation we assume that wyoming lithosphere behaved as an infinite elastic plate subject to tectonic loading of mountain ranges and conduct 2 d flexural subsidence modeling to major laramide basins to document lithospheric stiffness and mountain load height our results show that the stiffness of wyoming lithosphere varied slightly in each basin during the 30 myr duration of the laramide deformation and decreased from northeastern wyoming te 32 46 km to southwestern wyoming te 6 9 km our results also imply that the increase of equivalent load height of major laramide ranges accelerated during the early eocene we propose that the bending stresses induced by the topographic load of the sevier fold and thrust belt combined with crust mantle decoupling initiated by the overthickened sevier hinterland and the end loads due to the low angle subduction at the western edge of the thick wyoming craton have caused the southwestward decrease of lithospheric stiffness in wyoming moreover we attribute the accelerated load height gain during the early eocene to both dynamic and isostatic effects associated with slab rollback

impacts of climate and river flooding on the hydro ecology of a floodplain basin peace athabasca delta canada since a d 1700 abstract multi proxy paleolimnological analyses on lake sediment cores from spruce island lake 58 50 82 n 111 28 84 w a perched basin in the northern peace sector of the peace athabasca delta pad canada give insights into the relative roles of flow regulation of the peace river and climatic variability on the basin hydro ecology results indicate substantial variability in basin hydro ecology over the past 300 years ranging from seasonal to periodic desiccation in the 1700s to markedly wetter conditions during the early 1800s to early 1900s the reconstruction is consistent with 1 dry climatic conditions that defined the peak of the little ice age and subsequent amelioration evident in conventional ring width and isotopic analyses of tree ring records located hydrologically and climatically upstream of the pad and 2 peace river flood history inferred from sub annual magnetic susceptibility measurements from another lake sediment record in the peace sector of the pad although regulation of the peace river for hydroelectric power generation since 1968 has long been considered a major stressor of the pad ecosystem leading to reduced frequency of ice jam and open water flooding and an extended period of drying our results show that current hydro ecological status is not unprecedented as both wetter and drier conditions have persisted for decades in the recent past under natural climatic variability furthermore paleolimnological evidence from spruce island lake indicates that recently observed dryness is part of a longer trend which began some 20 40 years prior to peace river regulation

fracture porosity creation and persistence in a basement involved laramide fold upper cretaceous frontier formation green river basin usa fracture hosted porosity and quartz distribution along with crack seal texture and fluid inclusion assemblage sequences in isolated bridging quartz deposits show that open fractures can persist through protracted burial and uplift in foreland basins fractures oriented at a high angle to current maximum compressive stress remain open and were weak mechanical discontinuities for millions of years even at great depth upper cretaceous frontier formation sandstones in the basement involved laramide table rock anticline eastern greater green river basin wyoming sampled by two horizontal wells cut parallel or nearly parallel to bedding and at a high angle to steeply dipping fractures have 41 5 m of rock in four cores at depths of 4538 4547 m cores intersect older e striking set 1 fractures are abutted by or locally cross cut by n striking set 2 fractures both sets contain quartz and porosity sequenced using quartz crack seal cement texture maps set 1 fluid inclusion assemblage fia trapping temperatures increase progressively from 140 to 165 c then decrease to c 150 c compatible with fracture opening over c 15 ma during rapid burial followed by uplift in eocene oligocene time set 2 opened at c 160 c probably near maximum burial after a period of quiescence set 2 reopened at c 5 ma at c 140 c on a cooling trajectory intermittent set 2 movement could reflect local basement involved fault movement followed after a pause by further set 2 reactivation in the modern stress field during uplift interpretations are sensitive to available burial thermal histories which have considerable uncertainty

remote sensing of volumetric storage changes in lakes three dimensional remote sensing promises a giant leap forward for surface water hydrology in much the same way that radar altimetry transformed physical oceanography however the complex geometries of small terrestrial water bodies introduce difficulties particularly with respect to trade offs between changing water depth and inundation area we use in situ measurements of water surface stage h dt and remotely sensed area a to compute time varying storage changes s in nine lakes of the peace athabasca delta canada despite their identical geomorphic setting regression slopes between h and a vary significantly between lakes primarily from a predictable area effect but also small bathymetric variations between basins on average lateral contraction expansion versus stage adjustment contributes as little as 7 versus 93 to as much as 76 versus 24 of overall storage change s we conclude that both surface area and h dt rather than just either alone must be measured to confidently estimate s from space copyright 2009 john wiley sons ltd

paleogeographic and paleotectonic setting of laramide sedimentary basins in the central rocky mountain region in the rocky mountain region between central montana and central new mexico sedimentologically isolated nonmarine basins were produced by basement deformation during the laramide orogeny within the area formerly occupied by a broad late cretaceous foreland basin in which laterally continuous marine facies had accumulated previously laramide structures of varying trend and scale reflect heterogeneity of crustal strain caused by shear between the continental lithosphere and an underlying subhorizontal slab of subducted oceanic lithosphere laramide basins include perimeter basins along the cratonic periphery of the arcuate laramide province axial basins along a north south intramontane trend and ponded basins located farther west closer to the overthrust belt twelve specific stratigraphic and sedimentologic criteria for the onset duration and termination of laramide deformation allow the chronology of basin development to be inferred independently for each basin maastrichtian initiation of laramide deformation was approximately synchronous throughout the laramide province but termination of laramide deformation was systematically diachronous from north to south between early and late eocene time widespread eocene erosion surfaces truncate syntectonic laramide sequences and are overlain by largely volcanic and volcaniclastic post laramide strata of eocene age in the north and oligocene age in the south fluvial depositional systems draining toward the great plains were dominant in perimeter and axial basins but ponded basins were occupied at times by large lakes that served as regional sediment traps paleocene drainages from ponded basins also led eastward toward the continental interior but partly interconnected lakes that developed within several ponded basins by mid eocene time were either closed hydrologically or else they drained westward into the tyee paleoriver of the pacific northwest

mid cenozoic stress evolution and magmatism in the southern cordillera texas and mexico transition from continental arc to intraplate extension orientations of dikes veins faults and slickenlines reveal the evolution of stress during eocene to miocene magmatism in the southern cordillera where most thoroughly studied by us in trans pecos texas magmatism began at about 48 ma shortly after the cessation of laramide folding dikes and veins that formed from then until about 32 ma strike dominantly east northeast this indicates that the least principal stress 3 was north northwest additional data suggest that the maximum principal stress 1 was east northeast the stress field changed to 1 vertical and 3 east northeast i e east northeast extension at least by 28 ma and probably by 31 ma dikes and veins that formed between 31 and 17 ma when all magmatism ceased in texas strike north northwest this change marks the beginning of regional basin and range extension however major normal faulting exclusively of high angle type did not begin until about 24 ma a similar stress change marked by a similar change in dike and vein orientations occurred throughout the southwestern united states and northern mexico the time of change is not well constrained in texas but available information allows it to have occurred at the same time thoughout the southern cordillera we suggest the earlier stress field is related to east northeast convergence between the farallon and north american plates the change in stress is approximately coincident with collision of the east pacific rise and paleotrench extension may be related to the change from a convergent to a transform margin along the western edge of north america the changes in the stress field are accompanied by changes in the sources and compositions of magmas erupted in texas contemporaneity of the changes in stress and magmatism indicates that they are related combined with regional age patterns paleostress and geochemical data indicate that pre 31 ma magmatism in the southern cordillera occurred in a subduction related continental volcanic arc subsequent magmatism occurred in an environment of intraplate extension of the basin and range province

interpreting paleo avulsion dynamics from multistory sand bodies abstract channel avulsion plays a significant role in building alluvial stratigraphy including fluvial sand bodies with through going erosion surfaces called multistory sand bodies msbs consequently msb characteristics may be useful for interpreting paleo avulsion dynamics from fluvial deposits here using a combination of literature review geometric modeling and field observations we explore the degree to which msb characteristics may be useful for interpreting paleo avulsion dynamics from ancient deposits we use published interpretations of msb origins to identify characteristics that are exclusively associated with avulsion related msbs and find that vertical story stacking irregular msb bounding surfaces and floodplain deposits that correlate with individual stories are attributes uniquely associated with avulsion origin msbs to evaluate how avulsion patterns may affect msb properties we use a 2d geometric model to build synthetic stratigraphy and compare characteristics for msbs formed under different avulsion patterns at a range of model aggradation rates avulsion patterns include random equal probability of a channel relocating anywhere across the model domain compensational channels avulse to the lowest elevation in the model domain at each time step and clustered where channel relocation is restricted to a zone near a previously occupied location model results show that at moderate to high aggradation rates msbs formed under clustered avulsion patterns can be differentiated from those formed via random and compensational avulsion patterns specifically msbs formed by clustered avulsion patterns have many stories and commonly contain remnant floodplain deposits we apply these insights to the well exposed lower williams fork formation upper cretaceous piceance basin colorado usa to demonstrate how they can be used in practice fifty four percent of lower williams fork msbs contain clear evidence for avulsion reoccupation 32 have characteristics suggesting intra channel belt origins and the remaining 20 have ambiguous evidence or insufficient exposure to permit confident process interpretations overall this study demonstrates that despite inherent challenges in eliciting information about avulsion dynamics from the stratigraphic record some msb characteristics can be interpreted as clear signals of paleo avulsion processes

miocene sedimentary evolution of the ne sw trending selendi and gordes basins w turkey implications for extensional processes abstract western turkey is one of the classic regions for the study of extensional processes in a recent interpretation the regional metamorphic basement the menderes massif was exhumed related to large scale extensional processes possibly during latest oligocene time regional scale ne sw trending basins including the gordes and selendi basins were created associated with this exhumation the ne sw trending basins are seen as regional scale corrugations 10 15 km across in the surface of an extensional detachment orientated parallel to the direction of extension the detached upper plate is represented by erosional remnants of unmetamorphosed tethyan ophiolitic melange we describe and interpret the gordes and selendi basins separately and then show that their sedimentary facies and evolution are very similar basal coarse alluvial fan deposits accumulated after extensional removal of the upper plate these basal sediments rarely exposed were rotated by up to 50 probably as a result of local extension or transtension later during the early miocene the gordes and selendi basins were infilled by a generally fining upward succession derived from the south based on palaeocurrent evidence coarse alluvial fan deposition was followed by the deposition of finer grained alluvial deposits from braided streams flowing northwards over a topographically subdued flood plain later deposition was within shallow ephemeral lakes after a possible change to a moister climate calc alkaline magmatism was initiated with the fall out of fine grained silicic ash followed by coarser grained tuff derived from local magmatic centres during early pliocene time the basins were dissected by e w extensional faults associated with the establishment of the modern pattern of westward drainage to the aegean sea we use the assembled sedimentary evidence to test alternative tectonic models for miocene basin formation in western turkey our preferred tectonic model emphasises the importance of deposition in regional basins created by exhumation of metamorphic basement that was previously assembled during early tertiary closure of the tethys ocean

a new high resolution digital elevation model of greenland fully validated with airborne laser altimeter data a new digital elevation model of the greenland ice sheet and surrounding rock outcrops has been produced at 1 km postings from a comprehensive suite of satellite remote sensing and cartographic data sets height data over the ice sheet were mainly from ers 1 and geosat radar altimetry these data were corrected for a slope dependent bias that had been identified in a previous study the radar altimetry was supplemented with stereophotogrammetric data sets synthetic aperture radar interferometry and digitized cartographic maps over regions of bare rock and where gaps in the satellite altimeter coverage existed the data were interpolated onto a regular grid with a spacing of 1 km the accuracy of the resultant digital elevation model over the ice sheet was assessed using independent and spatially extensive measurements from an airborne laser altimeter that had an accuracy of between 10 and 12 cm in a comparison with the laser altimetry the digital elevation model was found to have a slope dependent accuracy ranging from 1 04 1 98 m to 0 06 14 33 m over the ice sheet for a slope range of 0 0 1 0 the mean accuracy over the whole ice sheet was 0 33 6 97 m over the bare rock areas the accuracy ranged from 20 to 200 m dependent on the data source available the new digital elevation model was used as an input data set for a positive degree day model of ablation the new elevation model was found to reduce ablation by only 2 compared with using an older 2 5 km resolution model which suggests that resolution induced errors in estimating ablation are no longer important

limits to future expansion of surface melt enhanced ice flow into the interior of western greenland moulins are important conduits for surface meltwater to reach the bed of the greenland ice sheet it has been proposed that in a warming climate newly formed moulins associated with the inland migration of supraglacial lakes could introduce surface melt to new regions of the bed introducing or enhancing sliding there by examining surface strain rates we found that the upper limit to where crevasses and therefore moulins are likely to form is 1600m this is also roughly the elevation above which lakes do not drain completely thus meltwater above this elevation will largely flow tens of kilometers through surface streams into existing moulins downstream furthermore results from a thermal ice sheet model indicate that the 1600m crevassing limit is well below the wet frozen basal transition 2000m together these data sets suggest that new supraglacial lakes will have a limited effect on the inland expansion of melt induced seasonal acceleration key points greenland ice sheet meltwater volumes are increasing notably at high elevations low strain rates limit the likelihood of moulin formation at high elevations high elevation meltwater will reach an already wet bed at lower elevations

glacial lake mcconnell paleogeography age duration and associated river deltas mackenzie river basin western canada abstract glacial lake mcconnell lasted from 11 8 to 8 3 ka bp while occupying parts of the great bear great slave and athabasca lake basin the retreating laurentide ice front formed the eastern margin whereas low rolling hills formed the north west and south shorelines three major deltas were deposited at the mouths of the laird peace and athabasca rivers the total extent of all phases of the lake was 240 000 km 2 while the largest extent was 210 000 km 2 at 10 5 ka bp downwarping of the basin by glacial ice was the main cause of the lake whereas sediment blockage between jean marie river and fort simpson was secondary initially glacial lake mcconnell occupied the northwestern corner smith arm of the great bear lake basin and discharged through the hare indian river outlet by 11 5 ka bp the enlarged water body flowed out the great bear river but only for a short period of time the mackenzie river formed the third outlet near jean marie river at 11 ka bp and flow in the great bear river ceased until 9 ka bp at 9 9 ka bp glacial lake mcconnell was impacted by a major flood from glacial lake agassiz with a peak discharge of 2 7 10 6 m 3 sec flood water discharged from glacial lake mcconnell peaking at 0 35 0 57 10 6 m 3 sec and receding flow continued for 30 months the massive influx of floodwater into glacial lake mcconnell caused an abrupt increase of discharge which enlarged the outlet channel to between 6 and 13 km wide between fort simpson and jean marie river at 8 3 ka bp isostatic rebound ended the 3500 year old extensive lake by dividing it into the great slave lake and lake athabasca

labyrinthine facies architecture of the tortola fluvial system and controls on deposition late oligocene early miocene loranca basin spain abstract upper oligocene to lower miocene deposits of the tortola fluvial system loranca basin central spain display a labyrinthine stratigraphic architecture comprising isolated sandstone bodies embedded in mudstone and siltstone these sandstone bodies are subdivided into seven types which are interpreted to have formed in rivers with different discharges sediment yields and channel planform patterns on the basis of their characteristics and spatial distributions four facies zones are defined these formed a continuum along the tortola fluvial system profile each being characterized by specific depositional conditions and consequently channel pattern styles gravel rich braided streams dominated zone 1 down gradient these streams graded into wide sand dominated braided streams of zone 2 which contain large bedforms and were typified by significant discharge variations zone 3 comprises belts of mixed load dominated meandering and low sinuosity channels zone 4 represents distal floodplain areas at the toe of the fluvial system depositional conditions in a facies zone varied between an upper and lower bound or geomorphic threshold a crossing of the upper or lower threshold is indicated by relatively sudden but orderly lateral and vertical changes in channel pattern that in turn reflect superposition of facies zones a facies cycle is formed by superposition of two successive downstream facies zones superposition of facies zones is inferred to have been caused by changes in sediment supply and hydraulic regime and consequently the regional gradient of the system it is argued that the tortola fluvial system developed under a weak tectonic regime during the later stages of basin filling and was possibly affected by climatic changes changes in size of the facies zones typified the long term development of the tortola fluvial system and determined the three dimensional architecture of the succession

dynamic subsidence and uplift of the colorado plateau we use inverse models of mantle convection to explore the vertical evolution of the colorado plateau by satisfying multiple constraints seismic tomography stratigraphy in the western united states and great plains and other structural and volcanic data adjacent to the plateau the model provides predictions on the continuous history of colorado plateau vertical motion since 100 ma with the arrival of the flat lying farallon slab dynamic subsidence swept from west to east over the plateau and reached a maximum ca 86 ma two stages of uplift followed the removal of the farallon slab below the plateau one in the latest cretaceous and the other in the eocene with a cumulative uplift of 1 2 km both the descent of the slab and buoyant upwellings raised the plateau to its current elevation during the oligocene a locally thick plateau lithosphere enhances the coupling to the upper mantle so that the plateau has a higher topography with sharp edges the models predict that the plateau tilted downward to the northeast before the oligocene caused by northeast trending subduction of the farallon slab and that this northeast tilting diminished and reversed to the southwest during the miocene in response to buoyant upwellings

a complete map of greenland ice velocity derived from satellite data collected over 20 years while numerous maps of greenland ice flow velocity exist most have gaps in coverage and or accuracy is limited we processed a large volume of synthetic aperture radar sar and landsat 8 imagery collected between 1995 and 2015 to produce a nearly complete map of ice flow velocity for greenland at a far greater accuracy than most prior products we evaluated the accuracy of this map by comparing it with a variety of measured and estimated velocities for the slow moving interior of the ice sheet where estimates are determined from interferometric phase the errors are 2 m a 1 or better for coastal areas where estimates are determined entirely from speckle or feature tracking methods errors are 2 3 m a 1 which is in good agreement with the estimated formal errors especially for the slow moving majority of the ice sheet this map provides an important source of data for numerous types of glaciological studies

estimation of river discharge propagation speed and hydraulic geometry from space lena river siberia 1 moderate resolution imaging spectroradiometer modis derived measurements of lena river effective width we display a high predictive capacity r2 0 81 mean absolute error 60 90 km 2 3 time valley width satellite derived we q rating curves and hydraulic geometry b exponents converge upon stable values b 0 48 indicating transferability of the discharge retrieval method between different locations put another way at length scales exceeding 60 90 km all subreaches display similar behavior everywhere at finer reach length scales e g 0 25 1 km longitudinal extraction of b exponents represents the first continuous mapping of a classical hydraulic geometry parameter from space while at least one gauging station is required for calibration results suggest that multitemporal satellite data can powerfully enhance our understanding of water discharge and flow conveyance in remote river systems

factors affecting the accumulation of organic rich deposits in a modern avulsive floodplain examples from the cumberland marshes saskatchewan canada since the 1870s the saskatchewan river at the cumberland marshes east central saskatchewan canada has been undergoing progradational avulsion resulting in development of a 500 km2 avulsion belt the avulsion belt consists of an unstable network of active and abandoned channels splays and floodbasins some containing small shallow lakes fine grained deposits of varying total organic content toc are currently accumulating within floodbasins inside adjacent to and outside the avulsion belt the toc of these deposits depends on factors that control the amount of siliciclastic sediment received by floodbasins five factors that affect toc content are identified distance from an active channel position relative to the avulsion belt presence of alluvial ridges changes in local channel activity and developmental stage of avulsion a channel to basin trend of increasing toc is present at many locations reflecting greater suspended sediment loads received by near channel areas and locations within the avulsion belt generally accumulate sediment with lower toc than those adjacent to or outside the belt alluvial ridges locally act as barriers to floodbasin deposition and channel abandonment reduces suspended sediment to adjacent floodbasins both of which increase toc of sediment finally as avulsion wanes less siliciclastic sediment is distributed throughout the avulsion belt resulting in increased toc in the geological record such fine grained avulsion deposits are likely to appear as intervals of mudrock between thin beds of coal or carbonaceous shale formed from organic rich sediment deposited between avulsion events a succession that is common in many ancient alluvial strata

syntectonic burial and post tectonic exhumation of the southern pyrenees foreland fold thrust belt in the oligocene to earliest miocene the entire southern pyrenean foreland fold and thrust belt was backfilled and buried in up to 3 km of syntectonic continental conglomerates from the range9s own erosional debris then starting in the mid to late miocene the pyrenees were exhumed by erosional excavation to their present relief a model is proposed for this unusual development whereby late eocene oligocene tectonic uplift of the margins of the ebro basin raised local base level and blocked normal dispersal of erosional debris to adjacent oceans thus causing the basin to fill then backfill northwards across the entire southern flank of the pyrenees subsequent miocene rifting of the catalan mediterranean margin and the messinian salinity crisis lowered base level allowing the ebro river to cut headward capture the ebro basin and re excavate the pyrenees

a sar record of early 21st century change in greenland glaciers in greenland are changing rapidly to better understand these changes we have produced a series of seven synthetic aperture radar sar backscatter mosaics for seven winters during the period from 2000 to 2013 six of the mosaics were created using radarsat fine beam data and the seventh used alos palsar fine beam single polarization data the radarsat mosaics are radiometrically calibrated and capture changes in the backscatter coefficient related to melt and other events particularly the strong melting in the summer of 2012 comparison of features in the ascending orbit alos mosaic and the descending orbit radarsat mosaics indicate that in areas of smooth to moderate topography their locations are consistent to within a few 10s of meters the locations of features identifiable in the radarat mosaics which were collected with the same imaging parameters generally agree to within better than the 20 m posting of the data with such geometric accuracy these data establish a record of change in greenland for the early part of the 21st century thus providing a baseline that can be compared with new radar and optical data sets

late cretaceous evolution of the coqen basin lhasa terrane and implications for early topographic growth on the tibetan plateau the tectonic evolution of the lhasa terrane southern tibetan plateau played a fundamental role in the formation of the tibetan plateau however many uncertainties remain with regard to the tectonic and paleogeographic evolution of the lhasa terrane prior to the india asia collision to determine the early tectonic processes that controlled the topographic evolution of the lhasa terrane we analyze the cretaceous strata exposed in the coqen basin northern lhasa subterrane which comprises the langshan and daxiong formations the langshan formation unconformably overlies the volcanic rocks of the lower cretaceous zelong group and consists of similar to 80 m of orbitolina bearing limestones which were deposited in a low energy shallow marine environment micropaleontological analysis indicates that the langshan formation in the coqen basin was deposited from late aptian to early cenomanian times ca 113 96 ma the overlying daxiong formation similar to 1700 m thick consists of conglomerate coarse sandstone and siltstone with interbedded mudstone and represents deposits of alluvial fans and braided rivers the daxiong formation was deposited after the early cenomanian ca 96 ma and accumulated until at least ca 91 ma indicating accumulation rates of greater than 0 3 km m y 1 by combining paleocurrent data sandstone petrology detrital zircon u pb ages and hf isotope analysis we demonstrate that the daxiong formation was derived from lower cretaceous volcanic rocks and pre cretaceous strata in the northern lhasa subterrane during late cretaceous time two thrust systems with opposite vergence were responsible for transforming the northern lhasa subterrane into an elevated mountain range this process resulted in the evolution from a shallow marine environment langshan formation into a terrestrial depositional environment daxiong formation on the southern margin of the northern lhasa subterrane given the regional paleogeographic context we conclude that the daxiong formation in the coqen basin records local crustal shortening and flexure resulting in foreland basin development on the southern margin of the northern lhasa subterrane which implies early topographic growth of the northern lhasa subterrane in southern tibet prior to the india asia collision

calculation of river discharge and prediction of lake height from satellite radar altimetry example for the lake chad basin 1 the application of satellite radar altimetry to the determination of lake and river elevations has been used in numerous projects and is well validated here we show that with the aid of ground based information this technique can be extended to determine river discharge and predict downstream lake and marsh height the lake chad basin provides an ideal case study due to its well known hydrology and complex lake and marsh morphology and because prediction of lake and marsh height has been identified as potentially useful to people living in the region altimetric stage measurements from the topex poseidon satellite at the chari ouham confluence estimate river discharge about 500 km downstream at n djamena 10 days in advance r2 0 9562 via simple linear correlation methods the stage measurements successfully estimate the height of the permanent waters of the lake 600 km downstream 39 days in advance r2 0 9297 predicting the water height on the western marshes of the lake bed is poorer r2 0 7958 due to a change in response time of the local stage to the seasonal floods coincident with an observed increase in mean water level in the latter half of the 1990s before 1997 a 96 day phase lag results in the best fit r2 0 6463 after 1997 the best fit is obtained with a 66 day phase lag r2 0 8139 the excellent river discharge and lake height predictions show that altimetry is a useful tool where ground based data are difficult to obtain and where rapid water resource assessment is desirable

control on sediment and organic carbon delivery to the arctic ocean revealed with space borne synthetic aperture radar ob river siberia an important control on river biogeochemistry and sediment load is the process of water exchange between primary channels and the flood plain particularly in low r elief areas containing lakes ephemeral channels and other aquatic ecosystems flood plain exchange may be a dominant process on the lowland rivers of arctic russia which are among the world s largest in water discharge yet are strikingly deficient in their delivery of sediment to the arctic shelf temporal synthetic aperture radar sar amplitude and interferometric images of the ob river siberia reveal a time varying limnological network controlling water sediment and nutrient exchange between flood plain wetlands and the main channel the amount of hydrologic exchange decreases by one order of magnitude from june to september enhancing sedimentation over as much as 90 of the flood plain and enriching channel waters with colloidal organic carbon this observation combined with russian field measurements of water discharge and sediment load indicates that a major sediment sink on the lower ob flood plain may be responsible for the low amount of sediment delivery by the ob river to its estuary and the kara sea

large fluctuations in speed on greenland s jakobshavn isbrae glacier it is important to understand recent changes in the velocity of greenland glaciers because the mass balance of the greenland ice sheet is partly determined by the flow rates of these outlets jakobshavn isbrae is greenland s largest outlet glacier draining about 6 5 per cent of the ice sheet area and it has been surveyed repeatedly since 1991 ref 2 here we use remote sensing data to measure the velocity of jakobshavn isbrae between 1992 and 2003 we detect large variability of the velocity over time including a slowing down from 6 700 m yr 1 in 1985 to 5 700 m yr 1 in 1992 and a subsequent speeding up to 9 400 m yr 1 by 2000 and 12 600 m yr 1 in 2003 these changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter our observations indicate that fast flowing glaciers can significantly alter ice discharge at sub decadal timescales with at least a potential to respond rapidly to a changing climate

thick skinned tectonics and basement involved fold thrust belts insights from selected cenozoic orogens defining the structural style of fold thrust belts and understanding the controlling factors are necessary steps towards prediction of their long term and short term dynamics including seismic hazard and to assess their potential in terms of hydrocarbon exploration while the thin skinned structural style has long been a fashionable view for outer parts of orogens worldwide a wealth of new geological and geophysical studies has pointed out that a description in terms of thick skinned deformation is in many cases more appropriate this paper aims at providing a review of what we know about basement involved shortening in foreland fold thrust belts on the basis of the examination of selected cenozoic orogens after describing how structural interpretations of fold thrust belts have evolved through time this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics and emphasizes the key control exerted by lithosphere rheology including structural and thermal inheritance and local regional boundary conditions on the occurrence of thick skinned tectonics in the outer parts of orogens

ice sheet velocity mapping a combined interferometric and speckle tracking approach the first and second radarsat antarctic mapping missions amm 1 and 2 have now acquired interferometric synthetic aperture radar sar overmuch of the ice sheet the radarsat 24 day repeat cycle is nearly ideal for measuring slow ice motion e g 1 but application of sar interferometry is limited in faster moving areas with a 1day repeat period ers 1 2 tandem sar data are much better matched to fast motion but are not always available fortunately several authors have demonstrated the ability to measure velocity in fast moving areas by tracking sar speckle from image to image which works well even in the absence of visible features while these estimates have intrinsically lower resolution and poorer accuracy than direct phase measurements they serve well in areas where there are no data suitable for conventional interferometry this paper describes algorithms i have developed for merging interferometric and speckle tracking data from multiple swaths to form a single seamless mosaic of velocity at each point in the mosaic all the available data are combined to produce estimates of the velocity and the associated error this technique is demonstrated using radarsat data collected over lambert glacier antarctica during amm 1 and 2

changes in ice front position on greenland s outlet glaciers from 1992 to 2007 1 previous studies in greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss raising greenland s contribution to sea level rise we examined ice front changes of 203 tidewater glaciers land terminating glaciers and glaciers terminating with ice shelves to understand greenland glacier behavior over three periods 1992 2000 2000 2006 and 2006 2007 we observed synchronous ice sheet wide increases in tidewater retreat during 2000 2006 relative to 1992 2000 coinciding with a 1 1 c increase in mean summer temperature at coastal weather stations rates of retreat for the southeast and east slowed during 2006 2007 when temperatures were slightly cooler than the 2000 2006 average our work suggests that regional greenland tidewater retreat responds strongly to climate change with higher temperatures corresponding to increasing retreat and helps confirm a link between ice thickness velocity and ice front position

rapid retreat and acceleration of helheim glacier east greenland 1 a significant amount of the measured coastal thinning of the greenland ice sheet may be due to recent acceleration of outlet glaciers using remote sensing we measured two major periods of speedup on helheim glacier between 2000 and 2005 that increased peak speeds from approximately 8 to 11 km yr these speedups coincided with rapid retreats of the calving front totaling over 7 5 km the glacier also thinned by over 40 m from 2001 to 2003 retreat of the ice front appears to decrease resistance to flow and concentrates the gravitational driving force over a smaller area farther up glacier acceleration may be a delayed response to surface draw down and steepening of the glacier s main trunk if the 2005 speedup also produces strong thinning then much of the glacier s main trunk may un ground leading to further retreat citation howat i m i joughin s tulaczyk and s gogineni 2005 rapid retreat and acceleration of helheim glacier east greenland geophys res lett 32 l22502 doi 10 1029 2005gl024737

cretaceous eocene laramide landscape development and oligocene pliocene drainage reorganization of transition zone and colorado plateau arizona landscape development of central and northern arizona can no longer be ascribed mainly to events of miocene and pliocene age new information on the age and distribution of older cenozoic deposits has led to the recognition of a regional cretaceous paleocene surface of erosion that conforms to major elements of the present topography and to the recognition that a formerly thick deposit of gravel accumulated on this regional surface of erosion these relations cast new light on the history of evolution of the landscape and indicate a much greater age for the main landscape elements and a more complicated and prolonged history of erosion and deposition than has been previously supposed the timing of events postulated for development of drainage on the colorado plateau can now be compared and partly reconciled with events recognized in the adjacent closely related mountain region transition zone of central arizona as a consequence of late cretaceous paleocene laramide compression central and northern arizona underwent at least 1200 m of uplift documented by paleochannels cut into erosionally truncated paleozoic strata on the hualapai plateau of the southwestern colorado plateau during this time a highly irregular erosion surface was developed on proterozoic rocks across the transition zone south of the mogollon rim the scarp of the mogollon rim was eroded to its present height 600 900 m and an extensive stripped surface was developed on resistant upper paleozoic strata north of the rim deposition of several hundred meters of paleocene eocene rim gravels derived from highlands south and west of the region followed covering much of the cretaceous paleocene erosion surface nearly complete burial of the rim is suggested by the distribution of remnants of the rim gravels across the erosional scarps and on high plateau areas north of the rim a second increment of uplift apparently occurring in late eocene time and apparently recorded by a series of fission track cooling ages from the marble and grand canyons is inferred to have been responsible for ending deposition of the rim gravels for initiating differential uplift of contemporaneous deposits canaan peak and claron formations to their positions in the high plateaus of central utah and for causing the drainage reorganization required to explain the extensive removal of rim gravels from much of the region a southerly flowing ancestral verde river related to the drainage reorganization removed much of the older gravel cover from the transition zone of central arizona resulting in a younger regional erosion surface having 600 900 m of relief a surface closely approximating the cretaceous paleocene erosion surface late oligocene and early miocene rocks locally rest unconformably on remnants of rim gravels in the transition zone indicating that the second episode of regional erosion had been completed by late oligocene time north of the mogollon rim a west flowing ancestral colorado river is inferred to have become established on the rim gravels draining the interior parts of the colorado plateau and transporting detritus off the plateau exhumation of the mogollon rim and development of 600 900 m of topographic relief in the transition zone by an ancestral verde river system suggests the potential for a comparable coeval entrenchment of an ancestral colorado river in paleozoic strata north of the mogollon rim regional extension and volcanic activity ensued in late oligocene to pliocene time the oligocene erosion surface in the extensional basins of central arizona became largely concealed by miocene and pliocene deposits as the neogene climate became drier in late miocene and pliocene time perennial streams appear to have been lacking transport of detritus appears to have been principally by flash flooding little or no detritus appears to have been removed from the region and much of the precipitation presumably moved by groundwater flow through the deposits of aggradation a coeval episode of aggradation in the grand canyon is suggested by deposits that appear to have once choked much of the canyon if this event parallels the episode of late miocene and pliocene aggradation recorded east south and west of the grand canyon the colorado river could have been incised to its present level by late miocene time a return to wetter conditions in late pliocene time presumably was responsible for renewed erosion and reexcavation of older drainages and basins an understanding of this tertiary structural erosional and depositional history can be important for the geological analysis of geophysical transects across the region

prediction of discharge from water surface width in a braided river with implications for at a station hydraulic geometry 1 the total discharge of small braided rivers can be monitored nearly continuously using ground based orthorectified oblique images and a locally derived relationship between mean water surface width in a reach and total discharge with accuracy of the order of 10 the width discharge relationship is nearly linear over the normal range of summer flows measured in this proglacial stream the width discharge relation for a given location and channel configuration is transferable to adjacent reaches with different morphology with little loss in accuracy however the prospect of a more universal relation for braided rivers is remote because of differences in channel geometry and hydraulics between rivers the classical at a station hydraulic geometry exponent for width in this case is approximately 1 05 which is unique well above that observed in the few other braided rivers for which this has been derived and implies almost no change in mean velocity and depth with changing stage

large and rapid melt induced velocity changes in the ablation zone of the greenland ice sheet continuous global positioning system observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the greenland ice sheet within days ice velocity reacts to increased meltwater production and increases by a factor of 4 such a response is much stronger and much faster than previously reported over a longer period of 17 years annual ice velocities have decreased slightly which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input which results in a more or less constant ice flux over the years the positive feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades

avulsions channel evolution and floodplain sedimentation rates of the anastomosing upper columbia river british columbia canada ages of channels of the anastomosing upper columbia river south eastern british columbia canada were investigated in a cross valley transect by c 14 dating of subsurface floodplain organic material from beneath levees the avulsion history within the transect was deduced from these data and morphological stages in channel development were recognized additionally floodplain sedimentation rates were established the new data demonstrate that the upper columbia river is a long lived dynamic anastomosing system results show that anastomosis at the study location has persisted since at least 2700 cal years bp with avulsions occurring frequently at least nine channels have formed in the studied cross valley transect within the past 3000 years channel lifetimes from formation to abandonment appear to be highly variable ranging from approximately 800 to 3000 years log jams provoking avulsions and or silting up of old channels are proposed as reasons for this variability long term average floodplain sedimentation rates appear to be significantly lower than previously proposed by smith 1983 int assoc sedimentol spec publ 6 155 168 a long term 4550 years average of 1 75 mm per year after compaction was based on c 14 dates whilea short term sedimentation rate of 0 8 mm was determined for a single relatively small seasonal flood in 1994 using sediment traps however short term sedimentation rates vary considerably over the floodplain with levees aggrading up to four times faster than floodbasins channels of the upper columbia river anastomosed reach follow a consistent pattern in their development with each stage being characterized by different morphology and processes channel evolution comprises the following succession 1 avulsion stage in which a crevasse splay channel deepens by scour and levee sedimentation 2 widening and deepening stage in which bank slumping and bed scouring dominates 3 infilling stage in which either channel narrowing bank accretion or channel shallowing bed accretion takes place and 4 abandonment stage in which the residual remnant channel is filled exclusively by silt clay and organic material vertical stacking super imposition of active channels on recent channel fill sand bodies is a notable feature of the upper columbia river which suggests that reoccupation of residual channels is a common process

seasonal to decadal scale variations in the surface velocity of jakobshavn isbrae greenland observation and model based analysis 1 using new data we build upon the nearly two decade long record of observations from jakobshavn isbrae to investigate the processes driving its dynamic evolution while winter flow speed has not increased substantially over the last three winters there remains a strong seasonal variation in flow speed that coincides with a cycle of summer thinning and winter thickening we relate changes in glacier speed to geometry through variations in basal traction and horizontal stresses using ice flow models constrained by satellite and airborne observations these results suggest that the bed provides little flow resistance along the main trough within about 20 km of the terminus while the loss of buttressing from the retreat of grounded and floating ice likely contributed to the initial speedup other processes are of comparable significance at seasonal to decadal time scales from analysis of the models we hypothesize that thinning induced change in basal effective pressure is the dominant process influencing near terminus behavior while diffusive processes drive the upstream response the apparent need for the terminus to thin to near flotation before it can calve may limit the rate at which retreat occurs our analysis of the processes controlling the speed suggests little potential for further large acceleration thinning and elevated speeds may continue at rates similar to present however putting the glacier on course to retreat to the head of its deep trough in about a century at which point it likely would stabilize with a thinner terminus

high resolution correlation of the upper cretaceous stratigraphy between the book cliffs and the western henry mountains syncline utah u s a abstract exposures of upper cretaceous strata in the book cliffs have played a key role in the formulation of modern sequence stratigraphic concepts and yet correlations with time equivalent strata in nearby regions remain uncertain resulting in an incomplete understanding of regional paleogeography this study presents detailed high resolution correlations of the upper cretaceous stratigraphy between the book cliffs the wasatch plateau and the western henry mountains syncline in utah with emphasis on the campanian interval two newly acquired measured vertical sections at coal canyon near green river in the book cliffs and blind trail in the henry mountains inform the correlations which also incorporate the substantial body of previous research correlations are further constrained by vertical and lateral facies stacking patterns and changes in sediment dispersal directions at discrete stratigraphic horizons derived from paleocurrent measurements much of the campanian succession can be characterized as a single low frequency third order depositional sequence within which are nested numerous high frequency sequences while it is not possible to correlate every high frequency sequence recognized in individual outcrop areas we define four intervals numbered 1 4 in ascending stratigraphic order that we correlate across the entire region interval 1 basal campanian is represented by initially deltaic and later wave dominated shoreface strata of the star point sandstone and equivalent basal muley canyon sandstone interval 2 lower campanian comprises coastal plain facies passing eastward into shallow marine strata of the lower blackhawk formation and equivalent muley canyon sandstone interval 3 lower to mid middle campanian comprises a thick aggradational stack of coastal plain fluvial strata that pass eastward into coastal and shallow marine facies blackhawk formation and equivalent masuk formation interval 4 overlying a major facies dislocation third order sequence boundary comprises amalgamated sheet fluvial deposits of the lower castlegate sandstone and equivalent tarantula mesa sandstone during the early to middle campanian the northern wasatch plateau and western henry mountains regions were along depositional strike with respect to one another the book cliffs near green river were located obliquely down depositional dip from the western henry mountains region during the campanian these new correlations and the improved understanding of paleogeography that derive from them have the potential to inform basin scale stratigraphic interpretations to a greater extent than has been hitherto possible