late quaternary plume nepheloid and turbidite sedimentation and effect of the gulf stream near the tail of the grand banks newfoundland abstract cores collected from the tops of the fogo seamounts southwest of the grand banks of newfoundland contain considerable amounts of detrital clay the seamounts rise at least 1 km above the surrounding sea floor and are an unlikely place for sedimentation by turbidity currents sedimentological and micropaleontological evidence suggests that large amounts of detrital clay were injected into the system during glacial and interglacial stages by turbidity currents and surface sediment plumes the main source of sediment was the laurentian channel although some sediment was injected through the canyons around the grand banks surface sediment plumes were strongly influenced by the labrador current and by the surface circulation of the gulf stream fine grained sediments injected into the system by turbidity currents through the laurentian channel were probably trapped by the deep circulation of the gulf stream and dispersed to the northeast effects of the sediment drift induced by the deep gulf stream circulation is also reflected in an abrupt eastward bent of the depositional lobes of the laurentian fan and in the shape of the newfoundland ridge

subsurface lateral flow generation in aspen and conifer dominated hillslopes of a first order catchment in northern utah mountain headwater catchments in the semi arid intermountain west are important sources of surface water because these high elevations receive more precipitation than neighboring lowlands this study examined subsurface runoff in two hillslopes one aspen dominated the other conifer dominated adjacent to a first order stream in snow driven northern utah snow accumulation soil moisture trenchflow and streamflow were examined in hillslopes and their adjacent stream snow water equivalents swes were greater under aspen stands compared to conifer the difference increasing with higher annual precipitation semi variograms of shallow spatial soil moisture patterns and transects of continuous soil moisture showed no increase in soil moisture downslope suggesting the absence of subsurface flow in shallow 12 cm soil layers of either vegetation type however a clear threshold relationship between soil moisture and streamflow indicated hillslope stream connectivity deeper within the soil profile subsurface flow was detected at 50 cm depth which was sustained for longer in the conifer hillslope soil profiles under the two vegetation types varied with deep aspen soils having greater water storage capacity than shallow rocky conifer soils though swes were less under the conifers the soil profile had less water storage capacity and produced more subsurface lateral flow during the spring snowmelt copyright 2010 john wiley sons ltd

application of turbidite sedimentology to determination of thrust fault displacements in the carolina slate belt abstract discontinuities in the lateral variations of grain size bed thickness and internal sedimentary structures of classic turbidites are used to calibrate thrust fault displacements in the carolina slate belt the ugly creek thrust just east of albemarle north carolina has been determined to have a displacement of 11 7 19 6 km while the uwharrie thrust in the same area has a displacement of 19 6 29 5 km the method relies on the predictability of lateral change in a down paleocurrent direction of sedimentological parameters values of the various parameters from opposite sides of the thrust fault are cross plotted against their lateral down current distance from a common reference point or base line data from one side of the fault are shifted relative to that of the other along the lateral distance axis so as to construct by eye a curve that mimics a predetermined curve form for lateral change of the parameter the amount of shifting necessary to achieve this is equal to the apparent thrust displacement in the down current direction this is then trigonometrically related to the actual thrust displacement

marine geology of sohm basin canadian atlantic margin multichannel seismic reflection seismic refraction and magnetic anomaly data are used to interpret the mesozoic sea floor spreading history and subsequent sedimentary evolution of the sohm basin southeast of nova scotia observed m series mesozoic magnetic anomalies show that oceanic crust in the sohm basin was generated at very slow rates of sea floor spreading 5 15 mm yr half rates the slow spreading created very rough crustal topography but the crustal thickness and seismic velocity structure are typical of normal oceanic basement basement depths corrected for sediment loading fall below the predicted age depth curve in the anomaly m25 m4 interval these depth anomalies and an associated regional negative geoid anomaly suggest that the sohm basin is underlai by asthenosphere denser and possibly colder than normal correlation of seismic reflection profiles in the basin to regional seismic stratigraphy together with age constraints from reflection pinch outs on dated oceanic crust provides a chronology for interpreting the seismic sequences the jurassic to lower cretaceous sequences are similar in thickness and acoustic character to sequences observed along the united states atlantic margin suggesting that the new england seamount chain had little effect on sediment distribution patterns within the early western north atlantic basin upper cretaceous sediments in the sohm basin are thin probably because seaward transport of sediment was restricted by eustatic sea level rise and by a sedimentary ridge uplifted because of salt tectonics along the central and upper continental rise progradati nal sedimentary wedges and erosional unconformities characterize the tertiary and quaternary sedimentary record along the lower continental rise the prograding sequences generally correlate to sea level lowstands repeated episodes of erosion by abyssal currents are marked by seismic unconformities horizon au lower oligocene lm lower miocene mm middle miocene and l upper pliocene the deep currents also controlled local patterns of deposition and modified cross slope sediment transport and accumulation patterns thick supra horizon l sediments cover the sohm basin and reflect rapid sediment influx caused by glacio eustatic fluctuations in sea level during the quaternary

the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

is xrf core scanning a viable method for coral palaeoclimate temperature reconstructions abstract the use of x ray fluorescence xrf core scanning for continuous high resolution analysis of sr ca in corals is investigated here as a new method for analyzing coral material corals are valuable archives for generating high resolution palaeoclimate records of sea surface temperatures of the tropical oceans but traditional methods of analyzing coral geochemistry involve extensive subsampling and wet chemistry techniques to obtain high precision elemental records more recent developments of micro beam techniques have limitations in the length of core that can be scanned at any one time xrf core scanning provides a fast non destructive method of analyzing long sections of coral cores whilst maintaining a high sampling resolution here we apply this method to two modern corals from the sunda strait indonesia and one tree island great barrier reef australia we find that results show that xrf core scanning of corals produce sr ca records that capture the annual cycle particularly from reef sites with a large sea surface temperature range coupled density measurements of the coral skeleton also aid in increasing the utility of xrf measurements obtained from coral material although difficulties remain in reliably reconstructing interannual temperature variability using xrf sr ca determinations we recommend that xrf can provide a valuable method of quick and non destructive screening of coral material prior to more targeted analysis using traditional destructive geochemical analysis

latest pleistocene ice rafting events on the scotian margin eastern canada and their relationship to heinrich events piston cores from the continental margin off nova scotia show up to four discrete intervals of brick red sandy mud which are up to 20 cm thick the ages of these intervals are bracketed by several radiocarbon dates and three fall in the range 12 5 14 1 ka radiocarbon years with 0 4 kyr reservoir correction the youngest dates from 10 4 ka placing it within the younger dryas the distribution of the beds and their petrographic character indicate a source in the gulf of saint lawrence the grain size of these beds suggests that they comprise a coarse component transported by ice rafting that diminishes distally and a fine component that represents suspension fallout from a surface plume and resulting nepheloid layers graded brick red beds in some cores were probably redeposited from turbidity currents the lowermost bed on the laurentian fan and east scotian rise is immediately overlain by a carbonate rich interval that can be identified all around the margin of the grand banks this interval is correlated with detrital carbonate bed dc 1 in the labrador sea and heinrich event h1 in the north atlantic the sequential occurrence of the two beds suggests that they may be a response to the same trigger probably sea level rise but that the gulf of saint lawrence source was more easily destabilized

tracer and hydrometric study of preferential flow in large undisturbed soil cores from the georgia piedmont usa we studied the temporal patterns of tracer throughput in the outflow of large 30 cm diameter by 38 cm long undisturbed cores from the panola mountain research watershed georgia tracer breakthrough was affected by soil structure and rainfall intensity two rainfall intensities 20 and 40 mm hr 1 for separate cl and br amended solutions were applied to two cores one extracted from a hillslope soil and one extracted from a residual clay soil on the ridge for both low and high rainfall intensity experiments preferential flow occurred in the clay core but not in the hillslope core the preferential flow is attributed to well developed interpedal macrochannels that are commonly found in structured clay soils characteristic of the ridge site however each rainfall intensity exceeded the matrix infiltration capacity at the top of the hillslope core but did not exceed the matrix infiltration capacity at the middle and bottom of the hillslope core and at all levels in the clay core localized zones of saturation created when rainfall intensity exceeds the matrix infiltration capacity may cause water and tracer to overflow from the matrix into macrochannels where preferential flow occurs to depth in otherwise unsaturated soil

piezometric response in zones of a watershed with lateral preferential flow as a first order control on subsurface flow characterizing zones of a watershed based on the water table is used to understand and predict internal watershed processes in watersheds dominated by lateral preferential flow the water table response typically shows a distinct hydraulically limited pattern this response is characterized by a capping of the rising water table when the lateral preferential flow features are activated and subsurface flow still increases we expected that this response would be related to the contributing area since nearby hillslope excavations showed that the development of preferential flow network was positively correlated with the contributing area the watershed was stratified into three predetermined zones and installed 25 piezometers to measure the water table dynamics the objectives were 1 to characterize the water table runoff relationship 2 to prove preferential flow by observable characteristics and 3 to test the feasibility of identifying areas within a watershed that are dominated by lateral preferential flow watershed zones were not well defined and there was no strong relationship between the hydraulically limited response and observable watershed characteristics although zones might still be useful for grouping the hillslope processes the piezometric response may not be an appropriate indicator for mapping the watershed into areas with runoff dominated by lateral preferential flow copyright 2010 john wiley sons ltd

normalizing xrf scanner data a cautionary note on the interpretation of high resolution records from organic rich lakes x ray fluorescence xrf scanning of unlithified untreated sediment cores is becoming an increasingly common method used to obtain paleoproxy data from lake records xrf scanning is fast and delivers high resolution records of relative variations in the elemental composition of the sediment however lake sediments display extreme variations in their organic matter content which can vary from just a few percent to well over 50 as xrf scanners are largely insensitive to organic material in the sediment increasing levels of organic material effectively dilute those components that can be measured such as the lithogenic material the closed sum effect consequently in sediments with large variations in organic material the measured variations in an element will to a large extent mirror the changes in organic material it is therefore necessary to normalize the elements in the lithogenic component of the sediment against a conservative element to allow changes in the input of the elements to be addressed in this study we show that al which is the lightest element that can be measured using the itrax xrf scanner can be used to effectively normalize the elements of the lithogenic fraction of the sediment against variations in organic content we also show that care must be taken when choosing resolution and exposure time to ensure optimal output from the measurements

hillslope dynamics modeled with increasing complexity summary few studies have investigated how much model complexity is needed to simulate both the hillslope outflow and the internal hillslope dynamics we studied the influence of model complexity on simulations for the panola mountain trenched hillslope we analyzed the influences of the inclusion of bedrock permeability variable soil depth and preferential flow on modeled hillslope responses we found that without the inclusion of bedrock leakage the long term subsurface flow response measured at the trenchface and the threshold relation between total precipitation and total subsurface flow could not be simulated adequately individual events could still be represented acceptably showing the importance of long time series for model calibration and validation the use of spatially constant bedrock conductivity allowed us to simulate spatially variable bedrock leakage rates because of the spatially variable depths of saturation without variable soil depth the spatial variability of subsurface flow along the trenchface and its temporal dynamics during events could not be represented in addition the spatial patterns of saturation at the soil bedrock interface did not agree with the observed patterns and responses to smaller events were underestimated inclusion of preferential flow mainly influenced the distribution of the maximum saturation depths at the soil bedrock interface and increased peak flows and recessions soil moisture measurements were less useful for model validation for the panola hillslope than measurements of the spatial patterns of saturation and subsurface flow we plea for a new blue print for the set up of hillslope experiments such that their data is useful for studies on hillslope model complexity and for model validation and rejection

acoustic interpretation of quaternary sedimentation and erosion on the channelled upper laurentian fan atlantic margin of canada about 1000 km of single channel seismic reflection profiles from a 50 km 100 km area on the upper laurentian fan shows no evidence of the large slumps interpreted by previous workers in this area our detailed profile grid indicates that slump like masses are commonly in depositional continuity with definite autochthonous sediments and surfaces previously interpreted as slide planes are either facies changes or the result of valley wall erosion only a few small slump blocks of relatively consolidated sediment are found on the uppermost fan acoustic facies distribution shows a single early pleistocene fan valley crossing the northeast part of the survey area with thick overbank sediments to the southwest in the middle pleistocene this valley became incised its upper reaches then ceased to receive sediment and a new valley was cut extending southward from the upper slope and intercepting the lower reaches of the old fan valley this channel diversion was probably related either to the glacia

hillslope subsurface flow similarity real world tests of the hillslope peclet number 1 similarity analysis offers the ability to model hydrological response using quantifiable landscape descriptors it is possible to develop similarity indices based on analytical solutions to the governing dynamic equations brutsaert 2005 berne et al 2005 provide derivation of such a similarity index the hillslope peclet number of subsurface flow and saturation for hillslopes with exponential width functions they showed that the hillslope peclet number depends only on geometric properties of the hillslope their work was validated using laboratory experiments conducted on constructed hillslopes with homogeneous soil structure and varying bedrock slope angle this study applies the similarity analysis of berne et al 2005 to two data sets 1 the trench hillslope study at the maimai research catchment conducted by woods and rowe 1996 and 2 the isolated hillslope study near troy idaho united states conducted by brooks et al 2004 the maimai trench study was selected because it provides subsurface flow data from hillslopes with different planform geometries the troy hillslope study was selected because the experimental results of brooks et al 2004 provide an estimate of hydraulic conductivity consistent with the support scale of the hillslope we estimated the hillslope peclet number of the hillslopes on the basis of elevation data and reported values of average soil depth this hillslope peclet number quantifies the geomorphological control on how water moves through these hillslopes and creates a basis for comparison independent of hydraulic properties we then estimated the first and second moments of the characteristic subsurface response function of each hillslope on the basis of subsurface flow data to compare the empirical and theoretical moments the hydraulic properties saturated hydraulic conductivity and drainable porosity of the hillslopes were related using a base flow recession analysis then we were able to derive the dimensionless moments of the hillslopes observed characteristic response function using hydraulic conductivities reported in the literature the agreement between the observed and theoretical moments shows the promise of implementing the hillslope peclet number as a similarity parameter to describe first order hydrological response in humid environments

morphology of upper laurentian fan using gloria long range side scan sonar a long range side scan sonar gloria survey of the upper laurentian fan shows for the first time the regional geomorphology of this large and complex sedimentary body the channels of the upper continental slope coalesce on the upper fan to form four major fan valleys the largest of these eastern valley is u shaped in cross section and up to 25 km 15 mi wide with a large levee on the western flank that reaches a maximum height of more than 1 km 3 300 ft above the valley floor the remaining valleys western central and grand banks are typically more v shaped in cross section and are up to 5 km 3 mi wide extensive gullying is observed on the walls of all the channels sonographs of the floor of eastern valley show a strong linear fabric elongated parallel ith the valley walls that appears to be related to mesoscale relief on the valley floor at water depths between 3 500 and 4 100 m 11 550 and 13 530 ft two major fan valleys are created by the merging of the four major valleys of the upper fan both fan valleys are associated with large asymmetric levee complexes that reach heights of more than 500 m 1 650 ft above the valley floors the gloria data show evidence for several amphitheaterlike slump scars in the region of the 1929 earthquake epicenter however we see no evidence for movement of large coherent sediment blocks as postulated by earlier workers therefore we suggest that the turbidity currents that occurred after the 1929 earthquake may have formed by the coalescence of many small slumps rather than from a single large slump

braided and meandering submarine fan channel deposits tesnus formation marathon basin west texas abstract exposures of predominantly mid fan channel deposits from the tesnus formation upper mississippian lower pennsylvanian of west texas provide an opportunity to examine possible meandering and braided deposits in a single submarine fan system within the tesnus six fan related sedimentary facies are recognized i amalgamated sandstone without vertical thickness trends ii amalgamated sandstone with thinning upward trends iii massive matrix rich sandstone iv interbedded sandstone and shale v chaotic sandstone and shale and vi black mudrock and chert the arrangement of sedimentary facies the nature of facies contacts and sandstone geometries differ significantly for braided versus meandering channel deposits sheet like braided channel deposits commonly exhibit a more random facies ordering and abrupt facies transitions whereas pod shaped meandering channel deposits commonly possess a more orderly arrangement of facies from base to top facies i vi in sequential order with gradual facies transitions the aforementioned differences in channel deposit characteristics are believed due primarily to variations in the migrational history of the braided abandonment and rapid shifting versus meandering gradual erosion and migration channel networks

threshold relations in subsurface stormflow 2 the fill and spill hypothesis analysis of subsurface stormflow from 147 storms at the 20 m long trench in the panola mountain research watershed by tromp van meerveld and mcdonnell 2006a showed that there was a distinct 55 mm precipitation threshold for significant subsurface stormflow production this second paper in the series investigates the processes responsible for this threshold response we installed a dense spatial array of maximum rise crest stage gauges and recording wells on the hillslope and studied the temporal and spatial patterns of transient saturation at the soil bedrock interface and its relation to subsurface stormflow measured at the trench face results show that while transient groundwater developed on parts of the hillslope during events smaller than 55 mm it was not until more than 55 mm of rain fell before bedrock depressions on the hillslope were filled water spilled over microtopographic relief in the bedrock surface and the subsurface saturated areas became connected to the trench when connectivity was achieved the instantaneous subsurface stormflow rate increased more than fivefold compared to before the subsurface saturated areas were connected to the trench face total subsurface stormflow was more than 75 times larger when connectivity was achieved compared to when connectivity was not achieved the fill and spill hypothesis presented in this paper is a process explanation for the observed threshold behavior of tromp van meerveld and mcdonnell 2006a thereby linking patterns and processes

palaeoecology and sedimentology of the dysaerobic bedford fauna late devonian ohio and kentucky usa abstract oxygen deficient biofacies models rely on lithologic and paleontologic attributes to identify distinctive biofacies interpreted to reflect levels of oxygenation in anaerobic dysaerobic and aerobic parts of a stratified water column this study of the bedford fauna from the bedford shale of ohio and kentucky and from adjacent black shale units reports faunal distributions different from those predicted by the accepted models this study suggests that although oxygenation was an important factor that determined the taxonomic makeup of the fauna bacterially mediated nutrient recycling and substrate characteristics were more important than oxygenation in determining faunal distribution in the dysaerobic zone

subsurface lateral preferential flow network revealed by time lapse ground penetrating radar in a hillslope subsurface lateral preferential flow lpf has been observed to contribute substantially to hillslope and catchment runoff however the complex nature of lpf and the lack of an appropriate investigation method have hindered direct lpf observation in the field thus the initiation persistence and dynamics of lpf networks remain poorly understood this study explored the application of time lapse ground penetrating radar gpr together with an artificial infiltration to shed light on the nature of lpf and its dynamics in a hillslope based on our enhanced field experimental setup and carefully refined gpr data postprocessing algorithms we developed a new protocol to reconstruct lpf networks with centimeter resolution this is the first time that a detailed lpf network and its dynamics have been revealed noninvasively along a hillslope real time soil water monitoring and field soil investigation confirmed the locations of lpf mapped by time lapse gpr surveys our results indicated the following 1 increased spatial variations of radar signals after infiltration suggested heterogeneous soil water changes within the studied soil which reflected the generation and dynamics of lpf 2 two types of lpf networks were identified the network at the location of soil permeability contrasts and that formed via a series of connected preferential flow paths and 3 the formation and distribution of lpf networks were influenced by antecedent soil water condition overall this study demonstrates clearly that carefully designed time lapse gpr surveys with enhanced data postprocessing offer a practical and nondestructive way of mapping lpf networks in the field thereby providing a potentially significant enhancement in our ability to study complex subsurface flow processes across the landscape

hillslope threshold response to rainfall 1 a field based forensic approach summary hillslope threshold response to storm rainfall is poorly understood basic questions regarding the type location and flow dynamics of lateral subsurface flow remain unanswered even at our most intensively studied field sites here we apply a forensic approach where we combined irrigation and excavation experiments at the well studied maimai hillslope to determine the typology and morphology of the primary lateral subsurface flowpaths and the control of bedrock permeability and topography on these flowpaths the experiments showed that downslope flow is concentrated at the soil bedrock interface with flowpath locations controlled by small features in the bedrock topography lateral subsurface flow is characterized by high velocities several orders of magnitude greater than predicted by darcy s law using measured hydraulic conductivities at the site we found the bedrock to be moderately permeable and showed that vertical percolation of water into the bedrock is a potentially large component of the hillslope water balance our results suggest that it is the properties of the bedrock topography and permeability that control subsurface flow at maimai and the soil profile plays a less significant role than previously thought a companion paper incorporates these findings into a conceptual model of hydrological processes at the site to explore the generalities of whole hillslope threshold response to storm rainfall

late quaternary development of left bank dominant levees in the bounty trough new zealand abstract the bounty trough encompasses an extensive submarine channel system that arises on the otago fan complex off the south island new zealand and extends 1000 km eastward to feed a large fan on the 4500 m deep pacific ocean floor channels are bordered by prominent levees which on the steep otago fans are mainly narrow sandy ridges by comparison the gently sloping floor of the trough supports broad low relief muddy levees in most cases levees display preferential development on the left side of the channel facing down channel we argue this preference results not only from the coriolis deflection of channel full turbidity currents but also from bottom currents and centrifugal forces operating at channel bends basement relief and locally high sedimentation rates at channel confluences may also influence levee height piston cores reveal two distinct phases of levee growth related to late quaternary climatic cycles during glacial times rivers discharged directly into the bounty trough turbidity currents travelled and overspilled the entire length of the bounty channels thereby producing the main phase of asymmetric levee growth and terrigenous deposition such turbidite deposition was punctuated by bouts of hemipelagic sedimentation in interglacial periods river borne sediment was diverted away from the trough which became the site of predominantly pelagic sedimentation represented by a drape of foraminiferal nannoplankton ooze over channels and levees alike however levees on the otago fan complex still received terrigenous sediment presumably reworked from the adjacent continental shelf

laurentian fan morphology sediments processes and growth pattern thick sediment accumulations in deep water provide a new target in the search for oil and require an innovative approach to hydrocarbon exploration the laurentian fan is a large deep sea 2 000 to 5 000 m fan in the western north atlantic and has been the major depocenter off nova scotia since at least the early tertiary the main development of the present depositional and erosional fan morphology in the past 2 to 3 m y was closely related to onshore glacial history the slope above the fan has been the site of rapid sedimentation and consequent slumping a network of tributaries on the upper fan appears to feed three main channel systems incised up to 800 m between broad asymmetric levees these channels meander widely across the lower fan then die out abruptly and pass into a lobate suprafan differences between the laurentian fan and typical fan models result in part from the muddy nature of the sediment and the supply system the channels contain thick coarse gravels which probably grade distally into sandy lobes both should produce good reservoir bodies with suitable source and trapping mechanisms fine grained sediments were more important in fan construction interbedded turbidites contourites and hemipelagites are present in the late quaternary holocene sequence the distribution of these sediments and in particular the recognition of structural sequences textural trends and fabric types in the fine grained turbidites can be used to characterize particular parts of the fan environment the development of this approach should prove useful in future hydrocarbon exploration

how to model shallow water table depth variations the case of the kervidy naizin catchment france the aim of this work is threefold 1 to identify the main characteristics of water table variations from observations in the kervidy naizin catchment a small catchment located in western france 2 to confront these characteristics with the assumptions of the topmodel concepts and 3 to analyse how relaxation of the assumptions could improve the simulation of distributed water table depth a network of piezometers was installed in the kervidy naizin catchment and the water table depth was recorded every 15 min in each piezometer from 1997 to 2000 from these observations the kervidy naizin groundwater appears to be characteristic of shallow groundwaters of catchments underlain by crystalline bedrock in view of the strong relation between water distribution and topography in the bottom land of the hillslopes however from midslope to summit the water table can attain a depth of many metres it does not parallel the topographic surface and it remains very responsive to rainfall in particular hydraulic gradients vary with time and are not equivalent to the soil surface slope these characteristics call into question some assumptions that are used to model shallow lateral subsurface flow in saturated conditions we investigate the performance of three models topmodel a kinematic model and a diffusive model in simulating the hourly distributed water table depths along one of the hillslope transects as well as the hourly stream discharge for each model two sets of parameters are identified following a monte carlo procedure applied to a simulation period of 2649 h the performance of each model with each of the two parameter sets is evaluated over a test period of 2158 h all three models and hence their underlying assumptions appear to reproduce adequately the stream discharge variations and water table depths in bottom lands at the foot of the hillslope to simulate the groundwater depth distribution over the whole hillslope the steady state assumption topmodel is quite constraining and leads to unacceptable water table depths in midslope and summit areas once this assumption is relaxed kinematic model the water table simulation is improved a subsequent relaxation of the hydraulic gradient diffusive model further improves water table simulations in the summit area while still yielding realistic water table depths in the bottom land

quaternary development of channels levees and lobes on middle laurentian fan seismic reflection profiles from the middle laurentian fan show that the western fan valley has an abrupt eastward leftward hook at its terminus the right hand levee of this valley has been built across an older depositional surface in which numerous south trending channels developed before the abrupt bend formed this older channeled surface probably represents a complex depositional lobe deposit eastward deflection of turbidity current flow occurred after debris flow or slide deposits partly obstructed the valley near its termination or after aggradation of the lobe deposits this deflection produced an abrupt change in the valley trend through time the eastward growing part of the levee has migrated northward toward the axis of the channel this northward migrati n confines turbidity current flow against the levee of another valley immediately upfan this study documents progradation of muddy facies over sandy lobes thus providing conditions for an effective seal for any hydrocarbons accumulated in the lobe sands updip migration of hydrocarbons through valley fill sands that are contiguous with the lobes could be blocked locally by thick debris flow units or by fine grained turbidite fill in abandoned channels

late cretaceous cenozoic development of outer continental margin southwestern nova scotia the growth pattern for the outer continental margin of nova scotia during the late cretaceous and cenozoic was studied using seismic stratigraphy and well data sediment accumulation was broadly controlled by temporal changes in relative sea level but significant spatial and temporal changes in accumulation patterns were caused by changes in sediment supply rate morphology erosion by abyssal currents and salt tectonics a jurassic early cretaceous carbonate platform remained exposed until the late cretaceous and controlled the location and steepness of the paleoslope until the late miocene local erosion of the outer shelf and slope in the late paleocene early eocene produced chalky fans on the upper rise the relationship between erosion of the shelf in the late eoce e and early oligocene and abyssal current erosion of the upper rise in the oligocene is unclear seaward extensions of tertiary shelf edge canyons are poorly defined except for the eocene fans in the miocene abyssal currents eroded a bench on the upper continental rise subsequently sediments lapped onto and buried the paleoslope the lower rise above horizon au oligocene is composed of fans and olistostromes shed from halo kinetic uplift of the upper rise current eroded unconformities are common in the rise sequence but the only current deposit is a pliocene interval 300 m restricted to the lowermost rise pleistocene turbidity currents eroded the present canyon morphology

the role of lateral pipe flow in hillslope runoff response an intercomparison of non linear hillslope response the importance of lateral pipe flow on runoff generation in wet steep hillslopes has been described in many case studies from around the world however most hillslope studies are done in isolation and usually focus on the idiosyncrasies of individual hillslope characteristics and pipe flow response at a single site consequently the first order controls on pipe flow responses remain poorly understood we present a new intercomparison of pipe flow response to storm rainfall at four well instrumented sites panola georgia usa toinotani kyoto japan jozankei hokkaido japan and hakyuchi tokyo japan our objective was to minimize the complexities of lateral pipe flow on hillslopes by looking for commonality across different hillslope types despite the large differences between the study sites in topography climate soil type and soil matrix hydraulic conductivity we found several common pipe flow responses to storm rainfall 1 the relationship between total rainfall amount and total pipe flow volume was highly non linear at each site 2 initiation of measurable pipe flow was threshold dependent controlled by the total rainfall amount and the pre storm wetness 3 once significant pipe flow response occurred the maximum pipe flow rate was sensitive to the measured rainfall intensity and 4 the ratio of total pipe flow to total hillslope discharge for each site was constant regardless of total rainfall amount once the precipitation threshold for significant pipe flow response was reached we used these results to develop a decision tree to determine the general conditions necessary for significant pipe flow to occur the controls derived from our comparisons agree largely with the controls reported by the previous individual hillslope pipe flow studies in the literature the commonality of response between our four very different forested hillslope settings indicates that site intercomparison may be effective for extracting common first order controls on complex hillslope processes we argue that a decision tree may be a useful organizational framework to summarize and organize comparative analyses and may provide a structure for defining the hierarchy of process controls necessary for model development

turbiditic levee deposition in response to climate changes the var sedimentary ridge ligurian sea abstract article history received 31 may 2010received in revised form 25 october 2010accepted 25 october 2010available online 31 october 2010communicated by d j w piperkeywords last deglaciationoverbank depositsturbidity currentsvar sedimentary ridgeligurian sea the var turbiditic system located in the ligurian sea se france is an intermediate mud sand rich system theparticularityofthevardeep seafanisitssinglechannelwithabruptbendsanditsasymmetricandhyper developed levee on the right hand side the var sedimentary ridge long term sediment accumulation on thevar sedimentary ridge makes this an ideal target for studying the link between onshore climate change anddeep sea turbidite stratigraphy this paper focuses on the establishment of the rst detailed stratigraphy ofthe levee which is used to analyze the timing of overbank deposition throughout the last deglaciation mainresults indicate that high variability in turbidite frequencies and deposition rates along the var sedimentaryridgearedeterminedbytwomainparameters 1 theprogressivedecreaseoftheleveeheightcontrollingtheabilityofturbiditycurrentstospilloutfromthechannelontothelevee and2 climaticvariationsaffectingthedrainage basin in particular changes in glacial condition since late last glacial maximum to early holocene compared to other deep water areas this study con rms the ability of turbiditic systems to record pastclimatic events on millennial timescales and underlines the in uence of european deglaciation on theobserved decrease in turbidite activity in the var canyon the presence of a very narrow continental shelf andasingle largechannel leveesystemmakesthevarsedimentaryridgeauniqueexampleofclimate controlledturbiditic accumulations 2010 elsevier b v all rights reserved

a younger dryas varve chronology from the rehwiese palaeolake record in ne germany abstract the first 1400 year floating varve chronology for north eastern germany covering the late allerod to the early holocene has been established by microscopic varve counts from the rehwiese palaeolake sediment record the laacher see tephra lst at the base of the studied interval forms the tephrochronological anchor point the fine laminations were examined using a combination of micro facies and xrf analyses and are typical of calcite varves which in this case provide mainly a warm season signal two varve types with different sub layer structures have been distinguished i complex varves consisting of up to four seasonal sub layers formed during the allerod and early holocene periods and ii simple two sub layer type varves only occurring during the younger dryas the precision of the chronology has been improved by varve to varve comparison of two independently analyzed sediment profiles based on well defined micro marker layers this has enabled both 1 the precise location of single missing varves in one of the sediment profiles and 2 the verification of varve interpolation in disturbed varve intervals in the parallel core inter annual and decadal scale variability in sediment deposition processes were traced by multi proxy data series including seasonal layer thickness high resolution element scans and total organic and inorganic carbon data at a five varve resolution these data support the idea of a two phase younger dryas with the first interval 12 675 12 275 varve years bp characterised by a still significant but gradually decreasing warm season calcite precipitation and a second phase 12 275 11 690 varve years bp with only weak calcite precipitation detailed correlation of these two phases with the meerfelder maar record based on the lst isochrone and independent varve counts provides clues about regional differences and seasonal aspects of yd climate change along a transect from a location proximal to the north atlantic in the west to a more continental site in the east

spatial organization of soil depths using a landform evolution model 1 the evolution of soil depths is investigated by modeling the interaction between soil production and surface erosion within a landform evolution model an enhanced version of the landform evolution model siberia that incorporates a soil evolution module is used to simulate evolving landforms and soils depths over geologic timescales the spatial and temporal evolution of soil depths are examined at the hillslope scale though it is widely accepted among the geomorphology community that soil water enhances chemical physical and biological weathering processes its effect has not been explicitly included in published models of soil production the main scientific questions that we address are 1 what are the implications of incorporating soil moisture dependency in the soil production function and 2 what type of soil production dynamics is needed to generate a bedrock topography that has a different spatial pattern from that of the ground surface a range of physics for the soil production model is explored the effect of soil moisture is included using the wetness index obtained from drainage analysis of either surface elevations or the bedrock topography the results show that the various soil production functions that incorporate either a wetness index or subsurface flow depth based on the bedrock topography give rise to soils that self organize with well defined spatial patterns and bedrock elevations with spatial organization significantly different from that of the surface the model that incorporates the influence of subsurface water on soil production is able to naturally generate a soil production rate with a maximum value for a nonzero soil depth and overcomes an inconsistency of previously published humped soil production models

giant paleodictyon in eocene flysch abstract a giant paleodictyon gomezi with a maximum mesh diameter of 13 cm and covering more than 0 5 m2 occurs in the lower eocene flysch near zumaya the giant paleodictyon occurs with flute casts and therefore must have been produced deeply in the sediment the lengthening of mesh cells parallel and perpendicular to the flute casts implies changing current directions during trace production rows of elongate and offset mesh cells reflect the row by row production of the trace however the base line followed by the trace fossil producer meandering or spiral cannot be reconstructed because of incomplete preservation the extraordinary size of this giant paleodictyon contradicts the evolutionary trend of deep sea trace fossils toward optimization and miniaturization since similar large paleodictyon specimens occur in silurian flysch

soil distribution in valleys according to stream order abstract while much research has been done on predicting the occurrence of waterlogged soils in small catchments we need to improve our knowledge of the extension of these soils in large catchments the aim of this study is to analyse the extent of soils with redoximorphic features in the valley bottomland domain as a function of the stream order this study concerns a 10 000 km 2 catchment river vilaine armorican massif north western france where valley bottomland soils commonly associated with hydromorphic characteristics cover up to 20 of the basin area to describe the catchment organisation we used the stream order classification of strahler to test the behaviour of the topographic index in a large range of landscape morphological settings two methods were used to define the extent of the hydromorphic zone hz in each valley bottomland according to stream order i a field study based on mapping the hz according to the occurrence of redoximorphic features along 60 transects ii a modelling approach linking a dem derived topographic index to the digitized stream network of the river vilaine in view of the topographic factors progressive valley widening may represent an enhancing factor of hz extent thus simple topographic index modelling predicts an increase in waterlogging in high order channel settings orders 6 7 by contrast field mapping suggests that hz extent remains stable with increasing order and decreases significantly for high order settings orders 6 7 therefore topographic index modelling appears effective in upper catchment settings 1st 2nd and 3rd order on the contrary modelling efficiency is limited in high order settings where the indices prove to be inappropriate in such contexts interactions between adjacent hillslope and hz are of secondary importance along the longitudinal profile of the catchment soil material near the streams shifts from having a colluvial origin in low order to an alluvial origin in high order settings in high order settings the fine scale valley bottomland topography and the spatial organisation of deposits control waterlogging duration and possibly play a major role in hz extent finally the integration of stream order data should considerably improve the efficiency of modelling the spatial distribution of soils over large catchments

concentration discharge relationships during an extreme event contrasting behavior of solutes and changes to chemical quality of dissolved organic material in the boulder creek watershed during the september 2013 flood during the week of september 9 15 2013 about 44 cm of rain fell across boulder county colorado usa representing a very rare precipitation event the resultant stream flows corresponded to an extreme event not seen since the historical flood of 1894 for the boulder creek critical zone observatory bcczo this event provided an opportunity to study the effect of extreme rainfall on solute concentration discharge relationships and biogeochemical processes we measured weathering derived lithologic solutes ca mg na k and si and dissolved organic carbon doc concentrations at two sites on boulder creek during the recession of peak flow we also isolated four distinct fractions of dissolved organic matter dom for chemical characterization at the upper and lower sites all solutes had their highest concentration at peak flow at the upper site which represented a mostly forested catchment the concentrations of lithologic solutes decreased slightly during flood recession in contrast doc and k concentrations decreased by a factor of three at the lower site within the urban corridor concentration of lithologic solutes decreased substantially for a few days before rebounding whereas the doc and k concentrations continued to decrease additionally we found spatiotemporal trends in the chemical quality of dom that were consistent with a limited reservoir of soluble organic matter in surficial soils becoming depleted and deeper layers of the critical zone contributing dom during the flood recession overall these results suggest that despite the extreme flood event concentration discharge relationships were similar to typical snowmelt periods in this rocky mountain region

sandy submarine braid plains potential deep water reservoirs sandy submarine braid plains like their fluvial counterparts on land are sand rich depositional environments that may display excellent reservoir characteristics in terms of sediment volume porosity and permeability the submarine examples may be laterally associated with potential source rocks such as the fine grained levee deposits of deep sea channels a side scan sonar study of the central labrador sea revealed the existence of a more than 700 km long and up to 120 km wide submarine sand and gravel plain that has been supplied with sediment by high density turbidity currents possibly resulting from subglacial lake outburst flooding in the hudson strait the side scan imagery of parts of the plain displays a conspicuous streaky pattern of alternating high and low backscatter intensity high resolution 3 5 khz seismic profiles and 12 khz bathymetric profiles show that the pattern represents a furrow and ridge erosional or channel and bar depositional topography similar to a braided alluvial plain the furrows or channels have low acoustic backscatter are less than 10 m deep and are separated by ridges or bars having high backscatter some channels terminate in depositional lobes individual channels and bars or furrows and ridges are less than 100 m wide and can be followed up to 40 km downcurrent on sleeve gun seismic profiles the total sand thickness appears to be between 200 m proximal and 100 m distal piston cores from the plain recovered massive sand layers up to 4 m thick buried under 1 m of holocene hemipelagic ooze texturally the sands and gravelly sands display a trend of improving sorting with increasing mean grain size some very coarse grained samples are moderately well sorted and almost matrix free the flooding events that deposited the sands might be the submarine counterpart of heinrich events but need not be restricted to such events radiocarbon ages of about 10 k y from the base of the ooze overlying the youngest sand gave a minimum age for the sand that is similar to the age of heinrich event 0 estimates for the discharge volume of individual events are poorly constrained and range from 103 to 105 km3 braided channel patterns in deep water begin page 1500 sandy depositional environments are not restricted to high latitudes but also have been identified in various submarine fan settings in the lower latitudes for example the orinoco var and monterey deep sea fans and in the santa monica basin the largest examples however are known from high latitudes suggesting that melt water discharge from continental ice sheets may favor the formation of this habitat of giant sands in the deep sea the occurrence of sandy braided deep water environments having favorable reservoir characteristics in a variety of tectonic settings makes this type of environment a potentially interesting deep water target

current perspectives on the capabilities of high resolution xrf core scanners abstract the introduction and application of high resolution xrf core scanners has made an enormous contribution to palaeoclimate science over the last two decades these core scanners have become essential analytical tools for the investigation of sedimentary and other natural cumulative records of environmental change their widespread adoption by the environmental and geoscience communities has had a significant impact on the ability to systematically record high resolution chemical profiles in marine and lake sediments and soils the range of applications has broadened beyond sedimentology and palaeoclimatology and now extends into scanning samples of speleothems corals mumiyo mounds rocks sedimentary nodules archaeological artefacts tree sections and melt segregations other areas exploiting the capability of xrf core scanners are mineral exploration geotechnical characterisation soil remediation studies and carbon capture and storage research as a consequence of their ability to efficiently determine detailed non destructive elemental records in sediments and soils scientific papers published since the year 2000 now number more than 1000

hydrological processes letters topographic controls on subsurface storm flow at the hillslope scale for two hydrologically distinct small catchmetns controls on hillslope ow pathways are still not well understood despite the many di erent studies reported since the pioneering work of hewlett 1961 in a wide range of recent modelling studies it has been assumed that ow directions can be related to hydraulic gradients derived from surface topography this assumption leads to believable maps of predictions of soil saturation and is convenient because of the increasing availability of digital terrain maps dtms the validity of the resulting spatial patterns throughout the watershed however have not been fully assessed although see the discussion in beven et al 1995 and the recent studies of nyberg 1996 and crave and gascuel odoux 1997 this results from the di culty of obtaining adequate spatial coverage of hydrological variables and the scale problem of relating point measurements to predictions at the dtm grid scale recent hillslope analyses of soil moisture distributions have identi ed that ow paths do not necessarily converge to hollow regions anderson 1982 that they may require dynamic spatial representations barling et al 1994 and that their prediction using topographically derived indices have had mixed results burt and butcher 1986 moore and thompson 1996 spatial representations of topographically driven indices therefore need further exploration a possible way forward is to conduct more detailed studies of the dynamics of subsurface ow at the hillslope scale analysis of a natural hillslope combines integrated trench ow and point scale soil moisture measurements coupled with a detailed understanding of surface and subsurface features such data provide a more comprehensive assessment of the assumption used in many modelling studies that hillslope ow is controlled by surface topography in this letter we address the question of whether it is appropriate to use surface topography to describe hillslope ow paths or if it is not more appropriate to use subsurface gradients relating to the soil bedrock interface or the hydrologically impeding layer we present examples for two hillslopes in di erent hydrogeological climatic settings analyses of the distribution of topographic index patterns derived from digital terrain analysis for both surface and subsurface topography are related to observational patterns of subsurface storm ow along arti cial trench face sections

morphology and acoustic character of the antarctic wilkes land turbidite systems ice sheet sourced versus river sourced fans the wilkes land continental slope contains an intricate network of submarine canyons that on the continental rise develop into a series of channel and overbank deposits of turbidite systems we can define upper fan middle fan and lower fan provinces the wilkes land upper fans are characterized by large channels with relief up to 900 m distances between levee crests up to 18 km and channel floor widths up to 6 km middle fan channels also have high relief 300 m and locally interchannel areas exhibit mounded contourite style deposits with high relief up to 490 m within middle fan sediment mounds there are acoustic facies of channel overbank deposits from turbidity currents and of sediment waves from contour current sedimentation the lower rise is characterized by small shallow channels 50 75 m relief and by interchannel areas of low relief both characteristic of a lower fan environment the wilkes land turbidite systems show the following significant morphological differences compared to most river sourced fans 1 multiple large tributary channels across the upper and middle fan 2 channel relief several times greater 900 m than typical relief 100 200 m for channels on fans less than 300 km in diameter and 3 steep middle fan and lower fan gradients we interpret the differences in channel network patterns channel size and middle fan and lower fan gradients between the wilkes land fans and other fans to result from the continental ice sheet feeding glacial ice streams that reached the outer continental shelf at times of glacial maxima the wilkes land canyon channel network patterns are comparable with the high latitude laurentian fan and labrador sea channels the laurentian fan also has large upper fan channels with larger relief 800 m than typical relief 200 300 m expected for fans that are 600 km in diameter both the labrador sea and laurentian fan are fed by continental ice sheets at the shelf edge

un courant d eau continu peut il generer des turbidites resultats d experimentations analogiques abstract the arenite pelite or limestone marl alternations of turbiditic sequences are today considered as resulting from quasi instantaneous turbidite flows separated by long relatively calm periods i e background sedimentation during which marls or pelites are deposited this is the classical interpretation of the turbidity concept considering the frequent incoherency of the sequences as well as the presence of silts in the sometimes normally graded pelites we propose an alternative explanation for the origin of turbiditic deposits which emphasizies the continuous nature of turbidity flows rather than alternating mechanisms we therefore carried out experiments involving the reproduction of turbidites in a tank for the first time the turbiditic alternation of arenitic and pelitic facies has been formed from a continuous unidirectional current rather than from the intermittent currents usually used in previous experiments the arenite pelite alternations were produced by introducing a given quantity of sediment into the continuous flow at various stages the basin i e the tank occasionally undergoes turbiditic pulsations whereas the supplying current remains completely continuous the turbidity of the water current increases rapidly after sediment addition and decreases very slowly until all the sediment is deposited the procedure was repeated several times at lengthening intervals and with various quantities of sediment arenites and pelites were deposited in spite of the constancy of the current this situation corresponds well to that in a river in which the sediment load variations are controlled by variations in floods which subsequently enter the basin these experiments therefore demonstrate that turbidites can form under fluviatile type conditions the facies discontinuities within turbidites need not reflect drastic systematic variations in turbid flows but could result from turbidity variations within a continuous turbid flow because rivers are the main carriers of sediments from the continents to the basins they could be the cause of the turbidite formation such conditions could explain many sequential aberrations within turbidites such as intrasequence erosion pelitic laminae within ripple foresets and the high proportion of silts in the pelites between the turbiditic sequences these pelites should not be considered as background sedimentation but as the product of a genuine turbid flow such as that which produced the coarse deposits this model leads to significant modification of the sequence interpretation of turbiditic basins which will be much more linked to drainage systems rather than to a particular geodynamic context

quantitative reassessment of brick red lutites evidence from reflectance spectrophotometry abstract brick red lutites are distinctive bright red sediments deposited in the western north atlantic these unique sediments were derived from permo carboniferous outcrops in the canadian maritime provinces transported out the gulf of st lawrence through the cabot straits and redistributed by the western boundary undercurrent along the north american continental margin in this study we used fourteen cores taken off eastern north america to more precisely examine the input and depositional history of brick red lutites our study differs from previous studies in the manner in which the red sediment was identified unlike previous studies which used color charts to assess the presence of brick red lutites we used visible light reflectance spectrophotometry the primary mineral imparting a red color to brick red lutites is hematite experiments with known quantities of hematite in a matrix mineralogically similar to western north atlantic sediment indicate that the presence of hematite can be detected at weight percentages of less than 0 1 using spectral reflectance data we characterized the distribution of brick red lutites for two broadly defined time levels latest glacial and early holocene as expected the maximum input of brick red lutite was during late glacial time and input decreased reaching a minimum during the early holocene since the early holocene there has been little change in the distribution of this unique red sediment on the north american margin however our reflectance spectra indicate renewed accumulation of hematite rich sediment at the present time in the cabot straits

effects of catchment discretization on topographic index distributions summary digital elevation models dems are widely used in topographically based hydrology models most researchers dealing with dems have worked exclusively with either grid or contour based techniques intercomparisons of these techniques are empirical in nature few in number and limited to a small number of catchments we examine the relative effects of these techniques on the distribution of the topographic index ti for nine idealised hillslope types and eight natural catchments 4 4 83 km 2 in southeast australia in particular we investigate the underlying causes for the frequently observed increase in the ti with grid size a simple analytical model for a parallel planar hillslope indicates that median ti is asymptotic with respect to the number of grid cells and a linear function of grid size we demonstrate that the latter result holds for hillslopes with more complex geometry using a multiple flow direction algorithm we find that hillslope geometry and flow partitioning affect the spatial pattern of the ti and the rate of change m of median ti with grid size this makes it impractical to recommend general guidelines for the value of the directional parameter in flow partitioning algorithms for the natural catchments we show that median ti is also a linear function of grid size and that there is some evidence for a linear relationship between m and the inverse of the median topographic slope throughout the investigation we find that contour dems are less sensitive to changes in resolution than grid dems

channels echo character mapping and tectonics from 3 5 khz profiles distal bengal fan abstract the distal parts of the bengal fan are spectacularly affected by tectonic deformation related to the diffuse plate boundary between the indian and australian plates here we use 3 5 khz and 12 khz echosounder profiles seismic reflection profiles and piston core results to examine sedimentary processes and their relationships to tectonism within an area 78 82 e 0 6 s just to the south of ocean drilling program leg 116 sites echo character mapping was completed using echosounder data in conjunction with results from piston coring and a total of five different echo types have been recognised four of these fall into the echo character classification scheme developed by damuth 1980a whilst the fifth is believed to represent hemiturbidite deposits several types of submarine channel were also identified from echosounder data and a correlation between echo type and channel location can be seen their abundance erosional and or depositional nature together with a complex meandering and bifurcation pattern across a wide region of average gradient around 1 km are all features characteristic of a broad channel termination zone on a large elongate fan it is clear therefore that the bengal fan extends beyond 6 s active faulting in the area has led to the development of an irregular topography of low rounded hillocks that interfere with incoming turbidity currents this has resulted in ponding between highs rather than lobe construction thinning and pinching out of turbidites against the flanks of local relief flow lofting and hemiturbidite drape and common small scale slumping in some cases uplifted channel segments can be seen abandoned and partially filled

throughflow variability on a forested hillslope underlain by compacted glacial till this study examined the spatial and temporal variability of throughflow in a shallow forest oil in terms of the controls exerted by topography soil properties and the shape of the water table hillslope outflow was measured at nine troughs installed at a road cut and hydraulic head was measured at 37 piezometers installed to the confining till surface at the base of the soil at the lowest flows the distribution of throughflow across the hillslope conformed reasonably to the distribution of upslope contributing area computed from the topography of the confining basal till layer at higher flows however the distribution of throughflow shifted partly as a result of changes in the orientation in flow tubes as the piezometric surface changed at high flows surface topography appeared to provide a reasonable proxy for the shape of the water table shunting of water through discrete macropores however can apparently overwhelm topographic controls on throughflow at least for slope widths less than about 10 m effective hydraulic conductivities computed at the scale of the troughs varied over two orders of magnitude and displayed no consistent relationship with the thickness of the saturated layer estimates at the plot scale c 10 m hillslope width were far less variable and for higher flows displayed an approximately linear relationship with saturated zone thickness copyright 2000 john wiley sons ltd

variable boulder concentrations in drumlins indicating diverse accretionary mechanisms examples from western ireland abstract a variation of boulder concentrations are identified within the diamicton component of drumlins in western ireland these range from single casst boulder lags to diffuse boulder concentrations with an internal spread of up to 4 m the former may be attributed to selective lodgement processes thus being largely glacigenic in origin the latter which are frequently closely associated with sand layers display close similarity to debris flow deposits with the prominence of the clas concentrations being indicative of the fluid characteristics of the respective flows the presence of the different boulder concentrations within a single drumlin or within drumlins of close proximity is indicative of disparate processes contributing to drumlin formation within the local embayment of western ireland this may reflect a complexity of processes operating within a transitional zone between terrestrial and aquatic glacial environments

new techniques in sediment core analysis an introduction marine sediment cores are the fundamental data source for information on seabed character depositional history and environmental change they provide raw data for a wide range of research including studies of global climate change palaeoceanography slope stability oil exploration pollution assessment and control and sea floor surveys for laying cables pipelines and siting of sea floor structures during the last three decades a varied suite of new technologies have been developed to analyse cores often non destructively to produce high quality closely spaced co located downcore measurements characterizing sediment physical properties geochemistry and composition in unprecedented detail distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and in some cases even annual or subannual scales allowing detailed insights into the history of climate and associated environmental change these advances have had a profound effect on many aspects of the earth sciences particularly palaeoceanography in this paper we review recent advances in analytical and logging technology and their application to the analysis of sediment cores developments in providing access to core data and associated datasets and data mining technology in order to integrate and interpret new and legacy datasets within the wider context of sea floor studies are also discussed despite the great advances in this field however challenges remain particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods new data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large multi parameter datasets sophisticated yet simple to use searchable internet databases with universal access and secure long term funding and data products resulting in user defined data mining query and display so far pioneered in the usa and australia provide robust models for efficient and effective core data stewardship

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

plio pleistocene evolution of the var deep sea fan off the french riviera abstract the var deep sea fan was deposited during the pliocene and quaternary seaward progradation of the var delta within a steep sided flat floored basin formed during the messinian salinity crisis the prominent palaeo var canyon was cut on the slope at the same time following the early pliocene transgression var sediments were initially trapped in the coastal ria formed by sea level incursion of the head of the messinian valley by middle pliocene time gilbert type deltas had prograded to the break of slope modern coastline allowing coarse sediment to reach the basin quaternary coastal uplift and sediment supply from the glaciated alps resulted in a supply of coarse sediment to the fan by the braided var river throughout the quaternary even during sea level highstands such as the present in the earliest pliocene hemipelagic clays accumulated while coarse sediment was trapped in the var ria through the rest of the pliocene a leveed fan valley extended southward from the var canyon which periodically switched locations through avulsion to the east at about the beginning of the quaternary this eastward spillover channel became the main distributary and re occupation of the older south trending channels was blocked by rapid levee progradation and aggradation of mud waves by overbanking of turbidity flows on the var sedimentary ridge during the quaternary channel shifting to the north occurred the quaternary var fan has an unusually steep concave longitudinal profile compared with most passive margin fans the laurentian fan has a similar profile to the var both have a high levee and a gravel and pebble floored fan valley that is essentially a bypass zone compared with the aggradational channel levee systems with lower levees in most passive margin fans this is a consequence of the constant supply of coarse sand gravel and pebbles to the fan even during highstands of sea level the erosive capability of this coarse sediment in ignitive turbidity currents resulted in flushing out of the upper and middle fan valley system thick muddy turbidity currents probably resulting from slumping caused by canyon incision produced the prominent mud waves on the levee the concave longitudinal profile led to rapid sediment deposition at critical points in the valley system as a result of turbidity flow expansion this in turn promoted the development of a left hook in the valley system

the influence of topography on time and space distribution of soil surface water content the distribution of water content in time and space at the soil surface has been investigated on a small farmland catchment 1 3 km2 from four field surveys corresponding to different moisture statuses for each survey about 400 samples were collected at the soil surface at a depth of 5 cm along ten axes parallel to the greatest slope the relationship between the measurements and the topography has been analysed the structure of the data is well explained by a topographic index referring to the downslope conditions and defined as the elevation difference between the sample point and the stream point corresponding to the outlet of the water pathway derived from the digital elevation model dem this index can be considered as an hydraulic head at least for saturated conditions a threshold for this index allows two domains within the catchment to be distinguished an upper domain where the water content is nearly constant and varies slowly and a lower domain where moisture status increases and is highly variable the spatial distribution of these two domains is well correlated to the spatial distribution of the soils thus both topography and the spatial distribution of soil appear to control the spatial distribution of surface water content at the 1 km2 scale 1997 by john wiley sons ltd

gypsies in the palace experimentalist s view on the use of 3 d physics based simulation of hillslope hydrological response as a fundamental unit of the landscape hillslopes are studied for their retention and release of water and nutrients across a wide range of ecosystems the understanding of these near surface processes is relevant to issues of runoff generation groundwater surface water interactions catchment export of nutrients dissolved organic carbon contaminants e g mercury and ultimately surface water health we develop a 3 d physics based representation of the panola mountain research watershed experimental hillslope using the tough2 sub surface flow and transport simulator a recent investigation of sub surface flow within this experimental hillslope has generated important knowledge of threshold rainfall runoff response and its relation to patterns of transient water table development this work has identified components of the 3 d sub surface such as bedrock topography that contribute to changing connectivity in saturated zones and the generation of sub surface stormflow here we test the ability of a 3 d hillslope model both calibrated and uncalibrated to simulate forested hillslope rainfall runoff response and internal transient sub surface stormflow dynamics we also provide a transparent illustration of physics based model development issues of parameterization examples of model rejection and usefulness of data types e g runoff mean soil moisture and transient water table depth to the model enterprise our simulations show the inability of an uncalibrated model based on laboratory and field characterization of soil properties and topography to successfully simulate the integrated hydrological response or the distributed water table within the soil profile although not an uncommon result the failure of the field based characterized model to represent system behaviour is an important challenge that continues to vex scientists at many scales we focus our attention particularly on examining the influence of bedrock permeability soil anisotropy and drainable porosity on the development of patterns of transient groundwater and sub surface flow internal dynamics of transient water table development prove to be essential in determining appropriate model parameterization copyright 2010 john wiley sons ltd

dissecting the variable source area concept subsurface flow pathways and water mixing processes in a hillslope summary this study uses an instrumented trenched 0 5 ha hillslope in the southern tier of new york state usa to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope measurements of water fluxes in the trench upslope water table dynamics surface and bedrock topography and isotopic and geochemical tracers have been combined for a four dimensional space time characterization of subsurface storm flow responses during events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers with much 33 71 of the total discharge of the hillslope originating from deeper water flow below the fragipan during storm events with wet antecedent conditions and large rainfall amounts shallow lateral flow of event and pre event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events in addition mobilization of total dissolved phosphorus tdp with subsurface flow played a greater role than with overland or near surface flow during all events tdp loads were highest in the total discharge during peak flows 8 11 5 kg ha 1 d 1 except during the largest storm event when tdp concentrations were highly diluted these results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading

analysis of topographic and climatic control on rainfall triggered shallow landsliding using a quasi dynamic wetness index abstract a model for the prediction of both topographic and climatic control on shallow landslide initiation processes in hilly mountainous terrain is proposed the model develops upon a theory for coupled shallow subsurface flow and landsliding of the soil mantle previously proposed by montgomery and dietrich water resour res 30 1994 1153 the model uses a quasi dynamic wetness index to predict the spatial distribution of soil saturation in response to a rainfall of specified duration the rainfall predicted to cause instability in each topographic element is characterised by duration and frequency of occurrence the incorporation of a rainfall frequency duration relationship into assessment of landslide hazard provides a practical way to include climate information into estimation of the relative potential for shallow landsliding the model is applied to a mountain experimental basin where high resolution digital elevation data are available the cordon catchment 5 km2 in north eastern italy an inventory of landslide scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide locations with model predictions the model reasonably reproduces the observed distribution of landslides although spatial variability of soil properties and hydrologic complexities not accounted for by the model complicate prediction of where landslides occur within areas of similar topographic climatic control model predictions from the quasi dynamic model are compared with those provided by the steady state model water resour res 30 1994 1153 these results suggest that the quasi dynamic model offers significant improvement over the steady state model in predicting existing landslides as represented in the considered landslide inventory

millennial scale east asian monsoon variability of the last glacial deduced from annually laminated sediments from lake sihailongwan n e china abstract lake sihailongwan in jilin province ne china provides the first continuous and almost entirely seasonally laminated sediment record on the east asian mainland comprising the complete holocene the late glacial period and large parts of the last glacial sediment and palynological proxy data provide a finely resolved regional environmental history of the east asian monsoon a varve based chronology shl vc2 has been established for the last 65 000 years and allows a detailed comparison with other long regional and global palaeoclimate records vegetation density of the study area depends on the long run on precessionally forced insolation changes with superimposed millennial scale variability during the last glacial periodic increase of organic carbon content and thermophilous tree species like ulmus and fraxinus and contemporary decrease of shrub alnus precisely mirror millennial scale climatic variations primarily known from greenland ice cores as dansgaard oeschger cycles as well as late glacial period climate changes percentages of trees shrubs pollen and in particular lake productivity related data reveal substantial differences between interstadial intensities with those between 50 and 60 ka bp being more pronounced than the following ones