four pleistocene formations in southwest british columbia their implications for patterns of sedimentation of possible sangamonian to early wisconsinan age semiahmoo and dashwood drifts were deposited during the penultimate glaciation and highbury sediments and muir point formation during the last interglacial these sediments are defined and described and stratotypes are established for them based on arboreal pollen assemblages lithologic similarity and relative stratigraphic position semiahmoo drift of the fraser lowland is tentatively correlated with dashwood drift of vancouver island stone provenance till fabrics glaciotectonic structures cross bedding and stone imbrication indicate that regional ice and meltwater flowed out of major fiords in the coast mountains and into the ancestral strait of georgia during the penultimate glaciation ice flowed southeastward against the east coast of vancouver island and down the axis of the strait pollen and molluscs in semiahmoo and dashwood fossiliferous muds give evidence of transition from glaciomarine to marine conditions at the close of the penultimate glaciation highbury sediments of the fraser lo

a glacier peak and mount saint helens j volcanic ash couplet and the timing of deglaciation in the colville valley area washington a late pleistocene volcanic ash couplet consisting of a glacier peak ash layer and an underlying mount saint helens j ash layer has been identified at three sites in the colville valley area of nor

computational simulation of seepage instability problems in fluid saturated porous rocks potential dynamic mechanisms for controlling mineralisation patterns abstract pore fluid flow associated with seepage instabilities can play an important role in controlling large mineralisation patterns within the upper crust of the earth to demonstrate this process two kinds of seepage instability problems in fluid saturated porous rocks are considered in this paper the first kind of seepage instability problem is caused by the temperature induced buoyancy of pore fluid so that it can be called the buoyancy driven seepage instability problem while the second kind of seepage instability problem is caused by chemical dissolution reactions that are commonly encountered in the upper crust of the earth so that it can be called the chemical dissolution driven seepage instability problem after the mathematical governing equations of and computational methods for these two kinds of seepage instability problems are introduced two numerical examples are used to elucidate how and why these two kinds of seepage instabilities can provide favorable places for the formation of large mineralisation patterns within the upper crust of the earth the related computational simulation results have demonstrated that 1 the convective pore fluid flow caused by the buoyancy driven seepage instability not only can dissolve minerals at the lower part of the upper crust but also can transport the dissolved minerals from the lower part to the upper part of the upper crust resulting in large mineralisation patterns near the surface of the earth s upper crust 2 the chemical dissolution driven seepage instability in fluid saturated porous rock can provide some favorable places such as finger like channels created by porosity enhancement in the porous rock for the formation of large mineralisation patterns within the upper crust of the earth

periodic jokulhlaups from pleistocene glacial lake missoula new evidence from varved sediment in northern idaho and washington newly examined exposures in northern idaho and washington show that catastrophic floods from glacial lake missoula during late wisconsin time were repeated brief jokulhlaups separated by decades of quiet glaciolacustrine and subaerial conditions glacial priest lake dammed in the priest river valley by a tongue of the purcell trench lobe of the cordilleran ice sheet generally accumulated varved mud the varved mud is sharply interrupted by 14 sand beds deposited by upvalley running currents the sand beds are texturally and structurally similar to slackwater sediment in valleys in southern washington that were backflooded by outbursts from glacial lake missoula beds of varved mud also accumulated in glacial lake spokane or columbia in latah creek valley and elsewhere in northeastern washington the mud beds were disrupted in places violently during emplacement of each of 16 or more thick flood gravel beds this history corroborates evidence from southern washington that only one graded bed is deposited per flood refuting a conventional idea that many beds accumulated per flood the total number of such floodlaid beds in stratigraphic succession near spokane is at least 28 the mud beds between most of the floodlaid beds in these valleys each consist of between 20 and 55 silt to clay varves lacustrine environments in northern idaho and washington therefore persisted for two to six decades between regularly recurring colossal floods from glacial lake missoula

modeling the effect of stratification on cemented layer formation in sulfide bearing mine tailings abstract reactive transport simulations have been applied to investigate possible effects of stratification on the potential of sulfide bearing mine tailings to form protective cemented layers the simulations are based on characteristic strata found at a german tailings site including sulfide enriched heavy mineral layers mica enriched silt layers and homogeneously mixed layers the simulated secondary phases jarosite gypsum amorphous ferric arsenate amorphous fe hydroxide alunite amorphous silica and kaolinite are similar to those observed in the field using scanning electron microscope analyses of cemented layers it has been observed that the pore area becomes disconnected if the porosity is decreased to values below 15 which would indicate a strong decrease in permeability stratification was found to play a crucial role in cemented layer formation cemented layers are absent or insignificant in systems with a homogeneous distribution of fe bearing sulfides they are extensively developed in systems with a an arsenopyrite rich layer or b a mica enriched layer situated immediately below an fe sulfide enriched layer the modeling results have clearly demonstrated that the key processes operating in scenario a are very different from the key processes in scenario b in scenario a the oxidation of arsenopyrite is followed by the precipitation of amorphous ferric arsenate which can be solely responsible for significant pore reduction in scenario b the presence of a large amount of reactive aluminosilicates e g biotite and ca bearing plagioclase immediately below the fe sulfide rich layer appears to be crucial key processes are extensive formation of acid rock drainage ard followed by enhanced ph driven weathering of aluminosilicates resulting in the accumulation of secondary phases directly below the fe sulfide rich layer in both scenarios a cemented layer is formed that effectively retards the further downward movement of the oxidation front the presented details on the role of stratification in the formation of cemented layers could be considered in the construction of mining heaps as a possible measure to stimulate natural attenuation

significant effect of sediment cohesion on delta morphology delta morphology is thought to be controlled by factors such as river discharge tides and waves numerical modelling shows that sediment cohesion also strongly influences the development of a delta s characteristics the morphologies of the world s deltas are thought to be determined by river discharge tidal range and wave action 1 more recently sea level rise 2 3 and human engineering4 have been shown to shape delta evolution the effects of factors such as sediment type and the overall amount of sediment carried by rivers are considered secondary4 5 6 in particular the role of sediment cohesion which is controlled by sediment size and type of vegetation is unclear here we use a numerical flow and transport model7 8 9 10 to show that sediment cohesiveness also strongly influences the morphology of deltas we find that holding all other factors constant highly cohesive sediments form bird s foot deltas with rugose shorelines and highly complex floodplains whereas less cohesive sediments result in fan like deltas with smooth shorelines and flat floodplains in our simulations sediment cohesiveness also controls the number of channels that form within the deltas and the average angle of bifurcation of those channels as vegetation generally acts as a cohesive agent we suggest that deltas that formed before the expansion of land plants in the devonian period should show fan like characteristics a finding consistent with the limited data from the sedimentological record11

expression of andic and spodic properties in tephra influenced soils of northern idaho usa abstract tephra from mount mazama crater lake has strongly influenced genesis and morphology of forest soils in the selkirk mountains of northern idaho characteristics associated with andisols and their intergrades are common in soils throughout the area in addition tephra influenced soils of the higher elevations exhibit properties of spodosols as well this study was initiated to examine development and relative expression of these properties along an elevational transect with its associated bioclimatic gradient this paper presents data from three soils that encompass the range in expression of andic and spodic properties found along this gradient cooler moister soils of the higher elevations have formed under subalpine fir forest and are strongly influenced by volcanic ash as indicated by color naf ph glass content and quantities of oxalate extractable fe al and si additionally podzolization processes have created e bhs horizon sequences in these soils within the last 6800 years the clay fraction of the very strongly acid e horizon is dominated by a well crystallized smectite mineral formation of an e horizon has effectively erased andic characteristics such as accumulation of short range order minerals sroms high naf ph and high p retention soils of the middle elevations have formed under western hemlock forest and also have significant ash influence these soils have properties transitional to those of the higher elevation spodosols and do not exhibit the overprint of podzolization processes eluvial horizons are absent although there has been significant accumulation of metal organic complexes and inorganic sroms in the upper horizons of these andisols soils of the lower elevations have developed under relatively warmer and drier conditions associated with the lower end of the western hemlock forest zone and have comparatively less volcanic ash influence the ash has been extensively mixed with coarse textured glacial drift and as a result these lower elevation soils lack the morphological or chemical properties associated with spodosol development but do exhibit weak andic characteristics

number and size of last glacial missoula floods in the columbia river valley between the pasco basin washington and portland oregon field evidence and radiocarbon age dating combined with hydraulic flow modeling provide new information on the magnitude frequency and chronology of late pleistocene missoula floods in the columbia river valley between the pasco basin washington and portland oregon more than 25 floods had discharges of 1 0 106 m3 s at least 15 floods had discharges of 3 0 106 m3 s at least six or seven had peak discharges of 6 5 106 m3 s and at least one flood had a peak discharge of 10 106 m3 s a value consistent with earlier results from near wallula gap but better defined because of the strong hydraulic controls imposed by critical flow at constrictions near crown and mitchell points in the columbia river gorge stratigraphy and geomorphic position combined with 25 radiocarbon ages and the widespread occurrence of the ca 13 ka radiocarbon years mount st helens set s tephra show that most if not all the missoula flood deposits exposed in the study area were emplaced after 19 ka radiocarbon years and many were emplaced after 15 ka more than 13 floods perhaps postdate ca 13 ka including at least two with discharges of 6 106 m3 s from discharge and stratigraphic relationships upstream we hypothesize that the largest flood in the study reach resulted from a missoula flood that predated blockage of the columbia river valley by the cordilleran ice sheet multiple later floods probably including the majority of floods recorded by fine and coarse grained deposits in the study area resulted from multiple releases of glacial lake missoula that spilled into a blocked and inundated columbia river valley upstream of the okanogan lobe and were shunted south across the channeled scabland

the southern limit of cordilleran ice in the colville and pend oreille valleys of northeastern washington during the late wisconsin glaciation the southern limit of the lobes of the cordilleran ice sheet in the colville and pend oreille valleys of northeastern washington during the late wisconsin fraser glaciation has been placed at widely different positions by various investigators the confusion that resulted in these different positions is due to the fact that both lobes at times terminated in glacial lakes and much of the terminal area of the pend oreille river lobe was swept by floods from glacial lake missoula evidence presented in this paper of the southern limit of these two lobes during the late wisconsin glaciation consists of i the southern limit of late wisconsinan till ii the southern limit of lateral meltwater channels iii meltwater channels whose headward areas coincide with the southern limit of late wisconsinan till and iv reconstructed ice surface profiles this evidence suggests that the southern limit of the colville lobe is represented by a moraine near the town of springdale whereas that of the pend oreille river lobe is near the town of newport the timing and extent of late wisconsinan deglaciation in the colville valley are provided by radiocarbon ages and late pleistocene tephras at sites upglacier from the terminal position these data demonstrate that the colville lobe had retreated at least 50 km by about 12450 bp in the pend oreille valley the presence of a glacier peak tephra layer near the town of ione indicates that the pend oreille river lobe had retreated at least 70 km prior to deposition of the tephra

hydrological connectivity in river deltas the first order importance of channel island exchange deltaic systems are composed of distributary channels and interdistributary islands while previous work has focused either on the channels or on the islands here we study the hydrological exchange between channels and islands and point at its important role in delta morphology and ecology we focus our analysis on wax lake delta in coastal louisiana usa and characterize the surface water component of hydrological connectivity through measurements of water discharge and hydraulic tracer propagation we find that deltaic islands are zones of significant water flux as 23 54 of the incoming distributary channel flux enters the islands a calculation of the travel times through a channel island complex shows travel times through the islands to be at least 3 times their channel counterparts a dye release experiment also indicates that travel times in islands are much longer that those within channels as dye remained in the island for the 3 8 day duration of the experiment additionally islands are more sensitive than channels to environmental forces such as tides which cause flow reversal and thus can increase travel times through the islands our work defines the hydrological network of a river delta to include not only the distributary channel network but also the interdistributary islands quantifies the implications of channel island hydrological connectivity to travel times through the system and discusses the relevance of our findings to channel mouth dynamics at the delta front and the potential for denitrification in coastal systems

precipitation in pores a geochemical frontier the purpose of this article is to review some of the recent research in which geochemists have examined precipitation of solid phases in porous media particularly in pores a few nanometers in diameter nanopores while this is a review it is actually more forward looking in that the list of things about this phenomenon that we do not know or cannot control at this time is likely longer than what we do know and can control for example there are three directly contradictory theories on how to predict how precipitation proceeds in a medium of varying pore size as will be discussed below the confusion on this subject likely stems from the complexity of the phenomenon itself one can easily clog a porous medium by inducing a rapid homogeneous precipitation directly from solution or have limited precipitation occur that does not affect permeability or even porosity substantially it is more difficult to engineer mineral precipitation in order to obtain a specific outcome such as filling all available pore space over a targeted area for the purposes of contaminant sequestration however breakthrough discoveries could occur in the next five to ten years that enhance our ability to predict robustly and finely control precipitation in porous media by understanding how porosity and permeability evolve in response to system perturbations these discoveries will likely stem at least in part from advances in our ability to 1 perform and interpret x ray neutron scattering experiments that reveal the extent of precipitation and its locales within porous media anovitz and cole 2015 this volume and 2 utilize increasingly powerful simulations to test concepts and models about the evolution of porosity and permeability as precipitation occurs steefel et al 2015 this volume a further important technique to isolate specific phenomena and understand reactivity is also microfluidics cell

provenance and deposition of glacial lake missoula lacustrine and flood sediments determined from rock magnetic properties abstract repeated outburst flooding from glacial lake missoula montana affected large areas of washington during marine oxygen isotope stage 2 29 14 ka we present the first high resolution rock magnetic results from two sites that are critical to interpreting these outburst floods and that provide evidence of sediment provenance glacial lake missoula the source of the floods and glacial lake columbia where floodwaters interrupted sedimentation magnetic carriers in glacial lake missoula varves are dominated by hematite whereas those in outburst flood sediments and glacial lake columbia sediments are mainly magnetite and titano magnetite stratigraphic variation of magnetic parameters is consistent with changes in lithology importantly magnetic properties highlight depositional processes in the flood sediments that are not evident in the field in glacial lake columbia hematite is present in fine silt and clay deposited near the end of each flood as fine sediment settled out of the water column this signal is only present at the end of the floods because the hematite is concentrated in the finer grained sediment transported from the floor of glacial lake missoula the only possible source of hematite 240 km away

regional reconstruction of subglacial hydrology and glaciodynamic behaviour along the southern margin of the cordilleran ice sheet in british columbia canada and northern washington state usa abstract subglacial landsystems in and around okanagan valley british columbia canada are investigated in order to evaluate landscape development subglacial hydrology and cordilleran ice sheet dynamics along its southern margin major landscape elements include drumlin swarms and tunnel valleys drumlins are composed of bedrock diamicton and glaciofluvial sediments their form truncates the substrate tunnel valleys of various scales km to 100s km length incised into bedrock and sediment exhibit convex longitudinal profiles and truncate drumlin swarms okanagan valley is the largest tunnel valley in the area and is eroded 300 m below sea level over 600 m of late wisconsin age sediments consisting of a fining up sequence of cobble gravel sand and silt fill okanagan valley landform substrate relationships landform associations and sedimentary sequences are incompatible with prevailing explanations of landsystem development centred mainly on deforming beds they are best explained by meltwater erosion and deposition during ice sheet underbursts during the late wisconsin glaciation okanagan valley functioned as part of a subglacial lake spanning multiple connected valleys few 100s km of southern british columbia subglacial lake development started either as glaciers advanced over a pre existing sub aerial lake catch lake or by incremental production and storage of basal meltwater high geothermal heat flux geothermal springs and or subglacial volcanic eruptions contributed to ice melt and may have triggered along with priming from supraglacial lakes subglacial lake drainage during the underburst s sheetflows eroded drumlins in corridors and channelized flows eroded tunnel valleys progressive flow channelization focused flows toward major bedrock valleys in okanagan valley most of the pre glacial and early glacial sediment fill was removed a fining up sequence of boulder gravel and sand was deposited during waning stages of the underburst s and bedrock drumlins in okanagan valley were enhanced or wholly formed by this underburst s subglacial lake development and drainage had an impact on ice sheet geometry and ice volumes the prevailing conceptual model for growth and decay of the cis suggests significantly thicker ice in valleys compared to plateaus subglacial lake development created a reversal of this ice sheet geometry where grounded ice on plateaus thickened while floating valley ice remained thinner due to melting and enhanced sliding with significant transfer of ice toward the ice sheet margin subglacial lake drainage may have hastened deglaciation by melting ice lowering ice surface elevations and causing lid fracture this paper highlights the importance of ice sheet hydrology its control on ice flow dynamics distribution and volume in continental ice masses

co2 injectivity in saline aquifers the impact of non darcy flow phase miscibility and gas compressibility a key aspect of co2 storage is the injection rate into the subsurface which is limited by the pressure at which formation starts to fracture hence it is vital to assess all of the relevant processes that may contribute to the pressure increase in the aquifer during co2 injection building on an existing analytical solution for immiscible and spatially varying non darcy flow this paper presents a mathematical model that accounts for combined effects of non darcy flow phase miscibility and gas compressibility in radial two phase displacements results show that in low permeability formations when co2 is injected at high rates non darcy simulations forecast better displacement efficiency compared to flow under darcy conditions this will have a positive effect on the formation co2 storage capacity this however comes at the cost of increased well pressures more favorable estimations of the pressure buildup are obtained when co2 compressibility is taken into account because reservoir pressures are reduced due to the change in the gas phase properties also non darcy flow results in a significant reduction in halite precipitation in the near well region with a positive effect on co2 injectivity in the examples shown non darcy flow conditions may lead to significantly different pressure and saturation distributions in the near well region with potentially important implications for co2 injectivity

coupled hydromechanical thermochemical processes in rock fractures the behavior of rock fractures under various coupled processes is reviewed under seven broad categories 1 hydromechanical processes 2 thermohydrologic processes 3 hydrochemical processes 4 thermohydromechanical processes 5 thermohydrochemical processes 6 hydromechanical chemical processes and 7 thermomechanical hydrochemical processes the state of the art and possible directions of further research in these coupled processes are discussed rock fracture behaviors considered include not only dilation closure shear and joint propagation but also changes in flow permeability and chemical sorption and retardation capabilities these properties are of critical concern in practical considerations of the rock mass as a medium to store and isolate chemical and radioactive wastes investigations of coupled processes in two fracture systems and multifracture systems are identified as important areas for future research the need to consider coupled processes in borehole testing procedures involving rock fractures is emphasized

delta allometry growth laws for river deltas 1 under projected scenarios of sea level rise subsidence and sediment starvation many deltas around the world are expected to drown delta growth dynamics which determine the ability of a delta to adapt to these changes are poorly understood due to the difficulty of measuring change in slowly evolving landscapes we use time series imagery of experimental numerical and field scale deltas to derive four laws that govern the growth of river dominated deltas land area grows at a constant rate in the absence of relative sea level change while wetted area keeps pace maintaining a constant wetted fraction over the delta surface scaling of edge lengths versus areas suggests delta shorelines are nonfractal even though the channel network is fractal consequently channel edge length which provides critical habitat grows more rapidly than delta area these laws provide a blueprint for delta growth that will aid in delta restoration and help predict how existing deltas will evolve

late pleistocene stratigraphy and implications for deglaciation and subglacial processes of the flathead lobe of the cordilleran ice sheet flathead valley montana usa abstract the flathead lobe of the cordilleran ice sheet advanced and retreated across the flathead valley a 90 km long by 15 25 km wide basin the glacier terminated at the southern end of the flathead valley during its last glacial maximum i used geologic mapping sedimentologic study and mapping from 3300 descriptive water well logs to define the stratigraphy of glacial and post glacial deposits in the flathead valley and to infer subglacial processes and retreat rates units in the 30 200 m thick stratigraphic sequence include deep sand and gravel proglacial alluvium diamicton till locally gravelly silt and clay coarse grained subaqueous deposits at recessional moraines and glaciolacustrine deposits and surficial sand and gravel outwash and holocene stream deposits a nearly continuous till overlies alluvium and is in turn directly overlain by glaciolacustrine deposits glaciolacustrine shoreline indicators at altitudes of 940 958 m show that the flathead lobe receded as a proglacial lake expanded in that range of altitudes this lake the ancestral flathead lake was impounded behind bedrock that was downcut 60 78 m since the late pleistocene glaciolacustrine deposits are as much as 180 m thick in discontinuous troughs that locally cut through till to alluvium and bedrock the troughs are mostly 1 5 km in width 6 25 km in length sinuous in plan view and undulatory in longitudinal profile the troughs extend below the elevation of flathead lake and have been below local base level since glaciation these characteristics point to incision by meltwater hydrostatically pressurized beneath the flathead lobe in subglacial tunnel channels sand and gravel at the trough bases and part of the glaciolacustrine fill in the troughs are subglacial deposits tunnel channels that terminate at recessional moraines suggest excavation occurred sporadically during deglaciation the distribution of glaciolacustrine silts indicates that the flathead lobe retreated and the ancestral flathead lake expanded by 87 km before the lake outlet stream could downcut its dam by 500 m year 1

regional significance of an early holocene moraine in enchantment lakes basin north cascade range washington abstract the upper enchantment lakes basin in the north cascade range of washington displays two moraine belts each recording an episode of glacier advance after the end of the last glaciation the inner belt the brynhild 0 1 to 0 5 km beyond existing glaciers postdates mount st helens wn tephra 450 yr old which lies only beyond the moraines the morainal surface is only slightly weathered is almost barren of lichens and is devoid of soil evidence suggesting that the brynhild moraines are no more than a century old the outer moraine the brisingamen 0 3 to 0 7 km beyond existing glaciers is weathered and is covered with large lichens on and behind the brisingamen moraine the mazama ash 6900 yr old is present beneath the mount st helens yn and wn tephras despite more than 7 millennia of weathering the rock surface behind the brisingamen moraine is measurably less weathered than the surface beyond which was last glaciated during the rat creek advance about 13 000 yr ago the age of the brisingamen moraine therefore is probably early holocene the brisingamen moraine evidently correlates with moraines near glacier peak near mount rainier in northeastern and central oregon in the southern canadian rockies and in the northern u s rocky mountains these regional effects suggest that a climatic episode of cooling or increased snowfall affected the entire region some time during the early holocene

lag of the fraser glacial maximum in the pacific northwest pollen and macrofossil evidence from western fraser lowland british columbia pollen and macrofossil evidence from two sites in northwestern fraser lowland reveals that abies lasiocarpa picea cf engelmannii forest and parkland grew there about 18 000 years ago under cold humid continental conditions taxus brevifolia was also a significant constituent of this forest this plant assemblage resembles the essf biogeoclimatic zone of subalpine elevations in the northern interior of british columbia 900 2250 m climate was probably cold with low to moderate rainfall and characterized by long cold wet winters and very short probably dry frost free summers mean annual temperature was depressed about 8 c and the tree line was probably 1200 1500 m lower than today fraser lowland was probably removed from pacific oceanic influence because the land sea interface was located on the continental shelf to the west of vancouver island and washington about the time of the last global glacial maximum global depression of sea level and quadra sand aggradation in the pacific northwest lo

recent decadal growth of the atchafalaya river delta complex effects of variable riverine sediment input and vegetation succession abstract the mississippi river delta plain has experienced substantial wetland loss from subsidence erosion and sea level rise threatening coastal communities and the ecosystems that support them the atchafalaya river the largest distributary of the mississippi river has one of the few prograding delta features along the 200 km deltaic coastline understanding changes in the atchafalaya river delta complex ardc development has critical implications for future prediction and management strategy for the mississippi river delta plain this study was organized to answer two major questions 1 how did development of the ardc respond to fluctuation in riverine sediment supply over the period 1989 2010 and 2 has vegetation succession helped stabilize subaerial land the study quantified annual total suspended sediment yields to the two ardc subdeltas atchafalaya river subdelta arsd and wax lake outlet subdelta wlsd classified delta land cover using satellite imagery over 5 year intervals into three classes barren land vegetation and open water and investigated the relationship of delta land change with sediment yield and vegetation succession over the entire 21 year study period we found a net land gain of 59 km 2 with the arsd accounting for 58 of this gain and wlsd 42 sediment yield to the subdeltas decreased from an average annual of 38 megatonnes mt for arsd and 18 mt for wlsd during 1989 1995 to an average annual of 24 mt for arsd and 17 mt for wlsd during 2004 2010 corresponding to the decrease in riverine suspended sediment concentration concurrently total land growth rate decreased from 2 4 km 2 y 1 to 1 6 km 2 y 1 for arsd and 3 2 km 2 y 1 to 0 6 km 2 y 1 for wlsd however the ardc had a net land loss of 2 1 km 2 during 1999 2004 because of tropical system effects in conjunction with the lack of large river floods defined as discharge 13 800 m 3 s 1 on average more than 60 of newly vegetated land remained vegetated in subsequent years and when compared with barren areas vegetated land was less likely 7 3 vs 32 to be converted to water indicating vegetative stabilization effect however during the period without a major flood vegetation buffering against tropical system erosion was limited this indicates that over the period 1989 to 2010 land growth of the ardc was dictated by large flood events

the magnetostratigraphy fission track dating and stratigraphic evolution of the peshawar intermontane basin northern pakistan the peshawar basin is situated along the junction of the northern margin of the indo gangetic foredeep and the southern margin of the hindu rush himalayan ranges during the late cenozoic southward encroachment of tectonic disruption into the foredeep terminated molasse deposition and delineated the peshawar intermontane basin through uplift of the attock range along the southern margin of the basin in this study magnetostratigraphy fission track dates on volcanic ashes and stratigraphic data are used to define the chronologic and stratigraphic evolution of the basin following a late miocene to pliocene interval of folding and thrusting of the preexisting molasse sediments deposition began in the peshawar basin by at least 2 8 m y ago subsequently 300 m of basin filling sediments accumulated at rates averaging 15 cm 1 000 yr northward progradation of alluvial fan deposits from the uplifted basin margin had begun by 2 6 m y ago and continued at an inferred rate of 2 cm yr proximal to the attock range in the south alluvial fan facies persisted until 0 6 m y ago contemporaneous sediments closer to the basin center demonstrate the presence of rapid facies transitions to extensive floodplain and shallow lacustrine depositional environments widespread intermontane basin sedimentation was terminated by accelerated uplift of the attock range after 0 6 m y ago subsequently during the brunhes chron catastrophic floods have periodically inundated the peshawar basin continuing tectonic deformation of the basin is indicated by uplifted flood deposits offset terraces and modern seismicity

ichnological evidence of jokulhlaup deposit recolonization from the touchet beds mabton wa usa abstract the late wisconsinan touchet beds section at mabton washington reveals at least seven stacked jokulhlaup deposits five showing evidence of post flood recolonization by vertebrates tracemakers are attributed to voles or pocket mice 1 3 cm diameter burrows and pocket gophers or ground squirrels 3 6 cm diameter burrows the mount st helens s tephra deposited between flood beds contains the invertebrate generated burrows naktodemasis and macanopsis estimates of times between floods are based on natal dispersal distances of the likely vertebrate tracemakers 30 50 m median distances 127 525 m maximum distances from upland areas containing surviving populations to the mabton area a distance of about 7 9 km tetrapods would have required at least two to three decades to recolonize these flood beds based on maximum dispersal distances invertebrate recolonization was limited by secondary succession and estimated at only a few years to a decade these ichnological data support multiple floods from failure of the ice dam at glacial lake missoula separated by hiatal surfaces on the order of decades in duration ichnological recolonization times are consistent with published estimates of refill times for glacial lake missoula and complement the other field evidence that points to repeated autogenically induced flood discharge

exploring the role of organic matter accumulation on delta evolution 1 we explore the role of plant matter accumulation in the sediment column in determining the response of fluvial deltas to base level rise and simple subsidence profiles making the assumption that delta building processes operate to preserve the geometry of the delta plain we model organic sedimentation in terms of the plant matter accumulation and accommodation space made for sediment deposition rates a spatial integration of the organic sedimentation added to the known river sediment input leads to a model of delta evolution that estimates the fraction of organic sediments preserved in the delta the model predicts that the maximum organic fraction occurs when the organic matter accumulation rate matches the accommodation rate a result consistent with field observations the model also recovers the upper limit for coal accumulation previously reported in the coal literature further when the model is extended to account for differences in plant matter accumulation between fresh and saline environments i e methanogenesis versus sulfate reduction we show that an abrupt shift in the location of the fresh salt boundary can amplify the speed of shoreline retreat

river channel lateral mobility metrics time scales and controls 1 alluvial river channels are intrinsically mobile we mapped channel planform extent in a series of experiments to measure instantaneous rates of channel motion loss of planform overlap with the original positions of the channels and reworking of the fluvial surface over which the channels moved these experiments comprise two aggrading deltas one subsiding delta that underwent cyclical base level changes and one braided channel system that was seeded with vegetation we find that the amounts of channel planform overlap and remaining unreworked fluvial surface area both decay exponentially with time and that these metrics and the instantaneously measured rates of channel motion scale predictably with one another in spite of the different time scales of the processes they record rates of channel planform change increase with increasing sediment flux and bed and planform irregularity and decrease with the establishment of riparian vegetation aggradation does not noticeably affect channel mobility but induces avulsions that allow the channels to more rapidly rework the fluvial surface additional findings include that 1 sediment flux in the braided experiment equals its rate of bar migration 2 channel widths are normally distributed with time and 3 we can use our channel mobility metrics to connect surface processes with the resultant fluvial stratigraphy

the process of sedimentation on the surface of a salt marsh abstract an unditched salt marsh creek drainage basin holland glade marsh lewes delaware has a sedimentation rate of 0 5 cm year 1 during normal storm free conditions the creek carries negligible amounts of sand and coarse silt of the material in the waters flooding the marsh surface over 80 disappears from the floodwaters within 12 m of the creek about one half of the lost material is theoretically too fine to settle even if flow were not turbulent however sediment found on spartina stems can account for the loss the quantity of suspended sediment that does reach the back marsh during these normal tides is inadequate to maintain the marsh surface against local sea level rise this suspended sediment is also much finer than the deposited sediments additionally remote sections of low marsh sections flooded by only the highest spring tides have 15 30 cm of highly inorganic marsh muds this evidence indicates that normal tidal flooding does not produce sedimentation in holland glade study of the effects of two severe storms of a frequency of once per year suggests that such storms can deposit sufficient sediment to maintain the marsh the actual deposition of fine grained sediments fine silt and clay appears to result primarily from biological trapping rather than from settling in addition this study proposes that the total sedimentation on mature marshes results from a balance between tidal and storm sedimentation storms will control sediment supply and movement on micro and meso tidal marshes and will have less influence on macro tidal marshes

the age of glacier peak tephra in west central montana at sheep mountain bog near missoula montana a late glacial tephra that probably fell in late summer is preserved as an 8 mm thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits sediment surrounding the ash was 14c dated to about 11 200 yr b p electron microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major element chemistry to those of glacier peak layer g previously considered to be about 12 000 yr old or older

holocene glacier fluctuations in the american cordillera abstract in many areas of the american rocky mountains colorado wyoming utah idaho montana cascade range washington oregon and the sierra nevada california radiocarbon ages suggest that ice receded to near present limits before 10 ka bp a pre altithermal readvance or stillstand left moraines ca 1 3 km beyond and ca 50 300 m below present glacier margins at one locality on glacier peak in washington these deposits are perhaps dated to the early holocene but in general these deposits are probably at least 10 ka old glacial advances during the altithermal ca 8 to 5 ka bp elsewhere are rare radiocarbon evidence for altithermal glacial advances in the colorado front range is questionable the earliest radiocarbon dated neoglacial advances occurred about 5 ka bp in the washington cascades moraines and related deposits believed to be of early neoglacial age i e 5 to 3 ka bp elsewhere are poorly dated for example moraines believed to date to the early neoglacial in colorado triple lakes and wyoming temple lake are actually late pleistocene age based on radiocarbon ages derived from lake sediments at the type localities although relative age data i e lichens rock weathering soils from many areas suggest a three fold neoglacial sequence little supporting radiocarbon evidence is available however tephrochronology distinguishes three neoglacial advances near mount rainier in washington in most mountain ranges of the western united states fresh unweathered sharp crested moraines usually adjacent to present ice margins or near headwalls in empty cirques date to the little ice age of the last several centuries however detailed photographic or other historical records of glacial fluctuations during the last century are rare and detailed mass balance studies rarer still whether or not pre little ice age glacial fluctuations in the american cordillera are synchronous must await better radiometric dating of local moraine sequences

late quaternary vegetation in the southwestern columbia basin washington abstract a 33 000 yr pollen record from carp lake provides information on the vegetation history of the forest steppe border in the southwestern columbia basin the site is located in the pinus ponderosa zone but through much of late quaternary time the area was probably treeless pollen assemblages in sediments dating from 33 000 to 23 500 yr b p suggest a period of temperate climate and steppe coinciding with the end of the olympia interglaciation the fraser glaciation ca 25 000 10 000 yr b p was a period of periglacial steppe or tundra vegetation and conditions too dry and cold to support forests at low altitudes aridity is also inferred from the low level of the lake between 21 000 and 8500 yr b p and especially after about 13 500 yr b p about 10 000 yr b p chenopodiineae and other temperate taxa spread locally providing palynological evidence for a shift from cold dry to warm dry conditions pine woodland developed at the site with the onset of humid conditions at 8500 yr b p further cooling is suggested at 4000 yr b p when pseudotsuga and abies were established locally

status of glacial lake columbia during the last floods from glacial lake missoula abstract the last floods from glacial lake missoula montana probably ran into glacial lake columbia in northeastern washington in or near lake columbia s sanpoil arm lake missoula floods dating from late in the fraser glaciation produced normally graded silt beds that become thinner upsection and which alternate with intervals of progressively fewer varves the highest three interflood intervals each contain only one or two varves and about 200 400 successive varves conformably overlie the highest flood bed this sequence suggests that jokulhlaup frequency progressively increased until lake missoula ended and that lake columbia outlasted lake missoula the upper grand coulee lake columbia s late fraser age outlet contains a section of 13 graded beds most of them sandy and separated by varves that may correlate with the highest missoula flood beds of the sanpoil river valley the upper grand coulee also contains probable correlatives of many of the approximately 200 400 succeeding varves as do nearby parts of the columbia river valley this collective evidence casts doubt on a prevailing hypothesis according to which one or more late fraser age floods from lake missoula descended the columbia river valley with little or no interference from lake columbia s okanogan lobe dam

prediction of velocity profiles and longitudinal dispersion in salt marsh vegetation to predict the behavior of solutes and suspended particles in wetlands it is necessary to estimate advection and longitudinal dispersion to better understand these processes measurements were taken of stem frontal area velocity vertical diffusion and longitudinal dispersion in a spartina alterniflora salt marsh in the plum island estuary in rowley massachusetts vegetation volumetric frontal area peaked at 0 067 6 0 007 cm 21 near 10 cm from the bed if the velocity profile in a dense emergent marsh canopy depends on the local balance between pressure forcing and vegetation drag the velocity will vary inversely with canopy drag i e velocity is minimum where the frontal area is maximum in fact the minimum velocity was observed at 10 cm from the bed the momentum balance therefore provides a way to predict the velocity profile structure from canopy morphology the vertical diffusion coefficient also depends on canopy characteristics such that the vertical diffusion coefficient normalized by the velocity and stem diameter had a constant value of 0 17 6 0 08 at this study site the canopy morphology also controls the longitudinal dispersion observed in this study to be 4 to 27 cm 2 s 21

formation dry out from co2 injection into saline aquifers 1 effects of solids precipitation and their mitigation f ormation d ry o ut from co 2 i njection into s aline a quifers p art 1 e ffects of s olids p recipitation and their m itigation karsten pruess 1 and nadja muller 2 earth sciences division lawrence berkeley national laboratory university of california berkeley ca 94720 shell international exploration and production b v exploratory research rijswijk the netherlands abstract injection of co 2 into saline aquifers may cause formation dry out and precipitation of salt near the injection well which may reduce formation porosity permeability and injectivity this paper uses numerical simulation to explore the role of different processes and parameters in the salt precipitation process and to examine injection strategies that could mitigate the effects the main physical mechanisms affecting the dry out and salt precipitation process include 1 displacement of brine away from the injection well by injected co 2 2 dissolution evaporation of brine into the flowing co 2 stream 3 upflow of co 2 due to gravity effects buoyancy 4 backflow of brine towards the injection point due to capillary pressure gradients that oppose the pressure gradient in the co 2 rich gas phase and 5 molecular diffusion of dissolved salt the different mechanisms operate on a range of spatial scales co 2 injection at constant rate into a homogeneous reservoir with uniform initial conditions is simulated in 1 d radial geometry to resolve multi scale processes by taking advantage of the similarity property i e the evolution of system conditions as a function of radial distance r and time t depends only on the similarity variable r 2 t simulations in 2 d vertical cross sections are used to examine the role of gravity effects we find that counterflow of co 2 and brine can greatly increase aqueous phase salinity and can promote substantial salt precipitation even in formations with low dissolved solids salt precipitation can accentuate effects of gravity override we find that injecting a slug of fresh water prior to commencement of co 2 injection can reduce salt precipitation and permeability loss near the injection well

thermohydrological conditions and silica redistribution near high level nuclear wastes emplaced in saturated geological formations evaluation of the thermohydrological conditions near high level nuclear waste packages is needed for the design of the waste canister and for overall repository design and performance assessment most available studies in this area have assumed that the hydrologic properties of the host rock are not changed in response to the thermal mechanical or chemical effects caused by waste emplacement however the ramifications of this simplifying assumption have not been substantiated we have studied dissolution and precipitation of silica in liquid saturated hydrothermal flow systems including changes in formation porosity and permeability using numerical simulation we compare predictions of thermohydrological conditions with and without inclusion of silica redistribution effects two cases were studied namely a canister scale problem and a repository wide thermal convection problem and different pore models were employed for the permeable medium fractures with uniform or nonuniform cross sections we find that silica redistribution in water saturated conditions does not have a sizeable effect on host rock and canister temperatures pore pressures or flow velocities

reactive geothermal transport simulations to study the formation mechanism of an impermeable barrier between acidic and neutral fluid zones in the onikobe geothermal field japan two types of fluids are encountered in the onikobe geothermal reservoir one is neutral and the other is acidic ph 3 it is hypothesized that acidic fluid might be upwelling along a fault zone and that an impermeable barrier might be present between the acidic and neutral fluid zones we carried out reactive geothermal transport simulations using toughreact xu and pruess 1998 and 2001 to test such a conceptual model mn rich smectite precipitated near the mixing front and is likely to form an impermeable barrier between regions with acidic and neutral fluids

geomorphology flood built land the southeastern us coastline is under threat as land subsides and sea level rises measurements of the 2011 mississippi river flood suggest that the river carries enough sandy sediment to offset some of this coastal drowning

flow and deposition in and around a finite patch of vegetation this laboratory study describes the flow and deposition observed in and around a finite patch of vegetation located at the wall of a channel two patch densities are considered with 2 and 10 solid volume fraction the velocity field measured in and around the patch by acoustic doppler velocimetry revealed three distinct zones first there is a diverging flow region at the leading edge of the patch where the flow in line with the patch decelerates and the bulk of the flow is diverted toward the open channel second there is a fully developed region within the vegetation where the velocity is uniform across the patch width and along the length of the patch third a shear layer forms at the interface between the patch and adjacent open channel the pattern of deposition in and around the vegetation was characterized by releasing 12 micron spherical glass particles and recording net deposition on a set of glass slides in the diverging region net deposition increases in the stream wise direction as the local velocity decreases in the fully developed region of the patch deposition decreases with longitudinal position as the concentration in the water column is depleted the deposition pattern is nearly uniform across the patch width consistent with the velocity field and suggesting that turbulent diffusive flux across the lateral edge of the patch is not a significant source of particles to the patch under the conditions studied here

reconstruction of rocks petrophysical properties as input data for reservoir modeling the worldwide increasing energy demand triggered studies focused on defining the underground energy potential even in areas previously discharged or neglected nowadays geological gas storage co2 and or ch4 and geothermal energy are considered strategic for low carbon energy development a widespread and safe application of these technologies needs an accurate characterization of the underground in terms of geology hydrogeology geochemistry and geomechanics however during pre feasibility study stage the limited number of available direct measurements of reservoirs and the high costs of reopening closed deep wells must be taken into account the aim of this work is try to overcome these limits proposing a new methodology to reconstruct vertical profiles from surface to reservoir base of i thermal capacity ii thermal conductivity iii porosity and iv permeability through integration of well log information petrographic observations on inland outcropping samples and flow and heat transport modelling as case study to test our procedure we selected a deep structure located in the medium tyrrhenian sea italy obtained results are consistent with measured data confirming the validity of the proposed model notwithstanding intrinsic limitations due to manual calibration of the model with measured data this methodology represents a useful tool for reservoir and geochemical modellers that need to define petrophysical input data for underground modelling before the well reopening this article is protected by copyright all rights reserved

an image based method for shoreline mapping on complex coasts 1 the ready availability of satellite and other images of the earth together with increasing societal interest in coastal processes and morphology make it desirable to have a consistent way of defining and mapping shorelines from images the obvious choice the land water interface is inadequate because it includes the back sides of islands and the edges of river and tidal channels that are not directly exposed to open water on complex coasts inclusion of these portions of the land water interface would significantly affect quantitative measures of shoreline geometry here we propose a method to map shorelines consistently while accounting for ambiguity the opening anglemethod oam uses a visibility criterion to define the shoreline first a region of unambiguous open water is defined next the shoreline is defined as the locus of points for which the sum of viewing angles extending to open water unobstructed by land exceeds a specified critical value shorelines defined by the oam follow the land water interface where the shoreline is unambiguous and in more complex cases oam shorelines are consistent with the idea that the shoreline is that part of the land water interface that is directly exposed to open water

ice streams of the late wisconsin cordilleran ice sheet in western north america abstract the late wisconsin cordilleran ice sheet cis of western north america is thought to have reached its maximum extent 2 5 106 km2 as late at c 14 5 ka most 80 of the ice sheet s bed consists of high mountains but its core zone sited on plateaux of the intermontane belt of british columbia and coterminous parts of the usa shows broad swaths of subglacially streamlined rock and sediment broad scale mapping from new digital imagery data identifies three subglacial bed types 1 hard beds of variably streamlined bedrock 2 drumlinized soft beds of deformation till reworked from antecedent sediment and 3 mixed beds of variably streamlined bedrock protruding through drumlinized sediment drumlins on soft beds appear to be erosional features cut into till and antecedent sediments and identify the catchment areas of paleo ice streams expressed downglacier as flow sets of megascale glacial lineations msgls grooved and cloned drumlins appear to record the transition from drumlins to msgls the location of paleo ice streams reflects topographic funneling of ice from plateau surfaces through outlet valleys and a soft bed that sustained fast flow rock cut msgls are also present locally on the floors of outlet valleys cis disintegrated in

reactive transport modeling in fractured rock a state of the science review abstract the field of reactive transport modeling has expanded significantly in the past two decades and has assisted in resolving many issues in earth sciences numerical models allow for detailed examination of coupled transport and reactions or more general investigation of controlling processes over geologic time scales reactive transport models serve to provide guidance in field data collection and in particular enable researchers to link modeling and hydrogeochemical studies in this state of science review the key objectives were to examine the applicability of reactive transport codes for exploring issues of redox stability to depths of several hundreds of meters in sparsely fractured crystalline rock with a focus on the canadian shield setting a conceptual model of oxygen ingress and redox buffering within a shield environment at time and space scales relevant to nuclear waste repository performance is developed through a review of previous research this conceptual model describes geochemical and biological processes and mechanisms materially important to understanding redox buffering capacity and radionuclide mobility in the far field consistent with this model reactive transport codes should ideally be capable of simulating the effects of changing recharge water compositions as a result of long term climate change and fracture matrix interactions that may govern water rock interaction other aspects influencing the suitability of reactive transport codes include the treatment of various reaction and transport time scales the ability to apply equilibrium or kinetic formulations simultaneously the need to capture feedback between water rock interactions and porosity permeability changes and the representation of fractured crystalline rock environments as discrete fracture or dual continuum media a review of modern multicomponent reactive transport codes indicates a relatively high level of maturity within the yucca mountain nuclear waste disposal program reactive transport codes of varying complexity have been applied to investigate the migration of radionuclides and the geochemical evolution of host rock around the planned disposal facility through appropriate near and far field application of dual continuum codes this example demonstrates how reactive transport models have been applied to assist in constraining historic water infiltration rates interpreting the sealing of flow paths due to mineral precipitation and investigating post closure geochemical monitoring strategies natural analogue modeling studies although few in number are also of key importance as they allow the comparison of model results with hydrogeochemical and paleohydrogeological data over geologic time scales

record of glacial lake missoula floods in glacial lake columbia washington abstract during the last glaciation marine oxygen isotope stage 2 outburst floods from glacial lake missoula deposited diagnostic sediments within glacial lake columbia two dominant outburst flood lithofacies are present within glacial lake columbia deposits a flood expansion bar facies and a finer grained hyperpycnite facies we conclude that the flood sediments have a glacial lake missoula source because 1 current indicators indicate westward flow through the lake and upvalley flow followed by downvalley flow in tributary valleys 2 no flood sediments are found north of a certain point 3 there is a dominance of belt purcell supergroup clasts in a flood expansion bar and 4 some of the finer grained beds have a pink colour reflective of glacial lake missoula lake bottom sediments a new radiocarbon age of 13 400 100 14c bp on plant detritus found below 37 flood beds helps constrain the timing of outburst flooding from glacial lake missoula

influence of sediment cohesion on deltaic shoreline dynamics and bulk sediment retention a laboratory study while boundary and forcing conditions influence the average location of a shoreline in deltaic systems internal morphodynamics can drive high magnitude deviations from the long term trend here we explore the role of sediment cohesion on these morphodynamics using physical experiments specifically we explore the role of sediment cohesion on the scales of autogenic shoreline transgressions and regressions results indicate that sediment cohesion enhances the time and space scales associated with autogenic cycles of channel formation elongation and abandonment in systems with high sediment cohesion this cycle can drive shoreline transgressions that produce flooding surfaces in the resulting stratigraphy which could be confused with surfaces produced by increases in sea level rise or subsidence rates enhanced channelization resulting from sediment cohesion also increases the pumping of fine grained sediment into the marine realm where it can bypass the delta foreset thus decreasing total delta sediment retention rate

paleomagnetic and tephra evidence for tens of missoula floods in southern washington paleomagnetic secular variation and a hiatus defined by two tephra layers confirm that tens of floods from glacial lake missoula montana entered washington s yakima and walla walla valleys during the last glaciation in these valleys the field evidence for hiatuses between floods is commonly subtle however paleomagnetic remanence directions from waterlaid silt beds in three sections of rhythmically bedded flood deposits at zillah touchet and burlingame canyon display consistent secular variation that correlates serially both within and between sections the secular variation may further correlate with paleomagnetic data from fish lake oregon and mono lake california for the interval 12 000 17 000 14 c yr b p deposits of two successive floods are separated by two tephras derived from mount st helens washington the tephras differ in age by decades indicating that a period at least this long separated two successive floods the beds produced by these two floods are similar to all of the 40 beds in the slack water sediment sequence suggesting that the sequence is a product of tens of floods spanning a period of perhaps a few thousand years

evidence of multiple late wisconsin floods from glacial lake missoula in badger coulee washington abstract catastrophic floods from glacial lake missoula entered the pasco basin in south central washington and backflooded its marginal valleys badger coulee one such valley contains beds of fine grained slackwater sediment deposited by these floods the slackwater sediment contains two ash layers of the mount st helens set s tephra about 13 000 yr old the ash was deposited on a ground surface developed atop slackwater sediment deposited during preash flooding evidence of the former ground surface includes the reworked ash inferred trace fossils stream and debris flow deposits slopewash and or eolian sediment and colluvium at the ash horizon these features and the ash were buried by slackwater sediment deposited during postash flooding nonflood subaerial deposits are not present atop other beds instead beds commonly are reversely graded across contacts suggesting that multiple beds were continuously deposited the exposed beds thus record at least two late wisconsin floods one preash the other postash the pre and postash floods may be correlative with earlier reported floods thought to have occurred 17 500 14 000 and 14 000 13 000 yr b p respectively

the channeled scabland a retrospective the channeled scabland of east central washington in the united states is a complex of anastomosing rock cut fluvial channels cataracts loess islands rock basins broad gravel deposits and immense gravel bars in the 1920s j harlen bretz demonstrated that the channeled scabland formed by cataclysmic erosion and deposition from pleistocene megaflooding derived from the margins of the cordilleran ice sheet particularly glacial lake missoula in western montana and northern idaho studies of this region and the high energy flood processes that generated it are stimulating a discoveries of similar megaflood related landscapes around the world and on mars b enhanced understanding of the processes involved in the fluvial erosion of bedrock and c the use of paleoflood indicators for understanding the magnitudes and frequency of flooding