the measurement and modelling of rill erosion at angle of repose slopes in mine spoil the process of rill erosion causes significant amounts of sediment to be moved in both undisturbed and disturbed environments and can be a significant issue for agriculture as well as mining lands rills also often develop very quickly from a single rainfall event to a season and can develop into gullies if sufficient runoff is available to continue their development this study examines the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogeneous mine spoil on an angle of repose slope it also examines the ability of the siberia erosion model to simulate the rill s spatial and temporal behaviour while there has been considerable work done examining rill erosion on rehabilitated mine sites and agricultural fields little work has been done to examine rill development at angle of repose sites results show that while the overall hillslope morphology was captured by the laser scanner with the morphology of the rills being broadly captured the characteristics of the rills were not well defined the digital elevation model created by the laser scanner failed to capture the rill thalwegs and tops of the banks therefore delineating a series of ill defined longitudinal downslope depressions these results demonstrate that an even greater density of points is needed to capture sufficient rill morphology nevertheless siberia simulations of the hillslope demonstrated that the model was able to capture rill behaviour in both space and time when correct model parameters were used this result provides confidence in the siberia model and its parameterization the results demonstrate the sensitivity of the model to changes in parameters and the importance of the calibration process copyright 2007 john wiley sons ltd

calibration and testing of upland hillslope evolution models in a dated landscape banco bonito new mexico 1 in this study we tested upland hillslope evolution models and constrained the rates of regolith production colluvial transport and eolian deposition over geologic time scales in a dated volcanic landscape in northern new mexico using field measurements of regolith thickness geochemical analyses of regolith bedrock and regional dust numerical modeling of regolith production and transport and quantitative analyses of airborne light detection and ranging lidar digital elevation models dems within this volcanic landscape many topographically closed basins exist as a result of compressional folding and explosion pitting during eruption the landscape has evolved from an initial state of no regolith cover at 40 5 ka to its modern state which has highly weathered regolith ranging from 0 to 3 m with local thickness values controlled primarily by topographic position our models constrain the maximum rate of regolith production in the study area to be in the range of 0 02 to 0 12 m kyr 1 and the rate of colluvial transport per unit slope gradient to be in the range of 0 2 to 2 7 m 2 kyr 1 with higher values in areas with more aboveground biomass we conclude that a depth dependent colluvial transport model better predicts the observed spatial distribution of regolith thickness compared to a model that has no depth dependence this study adds to the database of estimates for rates of regolith production and transport in the western united states and shows how dated landscapes can be used to improve our understanding of the coevolution of landscapes and regolith cover

on the nonuniqueness of sediment yield at the catchment scale the effects of soil antecedent conditions and surface shield the understanding of reasons leading to nonuniqueness of soil erosion susceptibility is still inadequate yet indispensable for establishing general relations between runoff volume and sediment yield to obtain relevant insights we performed a series of numerical simulations with a detailed hydrodynamic model using synthetic storms of varying intensity duration and lag time between events as representations of different hydrologic response conditions in a zero order catchment the design targeted to generate surface flow and perturb soil substrate by a first rainfall event creating a set of initial conditions in terms of flow and deposited sediment prior to the onset of a subsequent rainfall event due to the differential effect of re detachment and re entrainment processes on soil particles of varying sizes the deposited sediment mass formed shielding layer one of the essential results is that unless the initial condition of flow and sediment is identical the same volume of runoff can generate different total sediment yields and their variation can reach up to 200 the effect is attributed to two major conflicting effects exerted by the deposited initialization soil antecedent condition sediment mass erosion enhancement because of supply of highly erodible sediment and erosion impediment because of constrain on the availability of lighter particles by heavier sediment consistently with this inference long term simulations with continuous rainfall show that a peculiar feature of sediment yield series is the existence of maximum before the steady state is reached the two characteristic time scales the time to peak and the time to steady state separate three characteristic periods that correspond to flow limited source limited and steady state regimes these time scales are log linearly and negatively related to the spatially averaged shields parameter the smaller the rainfall input and the heavier a given particle is the larger the two scales are the results provide insights on how the existence of shield operates on erosion processes possibly implying that accurate short term predictions of geomorphic events from headwater areas may never become a tractable problem the latter would require a detailed spatial characterization of particle size distribution prior to precipitation events

toward process based modeling of geochemical soil formation across diverse landforms a new mathematical framework we present a mathematical model that integrates geochemical and geomorphic processes responsible for soils elemental and mineralogical evolution on diverse landforms eroding to depositional to level grounds this new model combines a hillslope sediment mass balance and a soil geochemical mass balance we model soils as the sum of a physically disturbed zone pdz and the underlying physically undisturbed but chemically altered zone caz the model considers processes including the production of pdz weathering front propagation mineral specific dissolution colloidal translocation and colluvial transport thus this study serves to 1 review preexisting models of pedogenic processes and to 2 offer a framework to integrate the geochemical and geomorphic processes active in soils we further discuss the implications of our model in 1 scaling chemical weathering reactions from mineral grains to pedons to soil catenas 2 understanding the emergence of geochemical soil catenas and 3 coupling physical and chemical weathering processes

observations of the internal tide in monterey canyon abstract data from two shipboard experiments in 1994 designed to observe the semidiurnal internal tide in monterey canyon reveal semidiurnal currents of about 20 cm s 1 which is an order of magnitude larger than the estimated barotropic tidal currents the kinetic and potential energy evidenced by isopycnal displacements of about 50 m was greatest along paths following the characteristics calculated from linear theory these energy ray paths are oriented nearly parallel to the canyon floor and may originate from large bathymetric features beyond the mouth of monterey bay energy propagated shoreward during the april experiment itex1 whereas a standing wave that is an internal seiche was observed in october itex2 the difference is attributed to changes in stratification between the two experiments higher energy levels were present during itex1 which took place near the spring phase of the fortnightly 14 8 days cycle in sea level while itex2 occurred close to the neap phase further evide

weathering rates of sandstone in a semi arid environment hunter valley australia the rate of sandstone weathering in the semi arid climate of the hunter valley new south wales australia has been estimated from observations of gravestone weathering in the area the gravestone data points to two distinct stages in the weathering process the first stage covering the first century of exposure is characterised by a relatively low recession rate of 0 5 mm 100 years this is followed by a second stage in which the rate of weathering increases sharply to ca 2 5 mm 100 years the non linear nature of the weathering trends over time suggests that during the first century of exposure structural changes took place within the sandstone material which lay the foundation for accelerated weathering after further exposure laboratory trials were also conducted to identify the effectiveness of different weathering processes in the decay of sandstone in this region of the four processes examined only the freeze thaw cycle produced a significant degree of mass loss and is therefore most likely a strong contributor to the weathering of sandstone in this region

channel movement and erosion response to rainfall variability in southeast australia intrinsic and extrinsic forces on the catchment and stream channel network drive morphological change separating individual forcings is difficult given the complexity of such nonlinear systems here a modelling approach is used to investigate the sensitivity of channel position and movement under a series of realistic rainfall scenarios for a catchment in southeastern australia the results demonstrate the sensitivity of the catchment to different rainfall patterns and how relatively small changes in rainfall can lead to much larger sediment outputs revealing sensitivity to subtle changes in climate channel movement occurs as an avulsion this is the first time such a process has been observed and modelled in an ephemeral stream environment and demonstrates fluvial geomorphic change at human time scales human intervention by rock lining channels was demonstrated to prevent the movement of the main channel overall the caesar landscape evolution and erosion model used in this study is able to replicate both erosion rates and the variation in past channel movement the modelling suggests that any landscape change is based on both internal and external forcing and that landscape history also plays a significant role here we demonstrate the potential to quantify many of the nonlinearities and thresholds in soil mantled catchments using a landscape evolution model copyright 2011 john wiley sons ltd

mixing at the head of a canyon a laboratory investigation of fluid exchanges in a rotating stratified basin 1 observations indicate that oceanic mixing is intensified near the head of submarine canyons how the presence of canyon walls affects the local production and distribution of mixed fluid is an open question these dynamics are addressed through rotating tank experiments which impose mixing at middepth at the closed end of a channel open to a larger body of water turbulence is generated in a linearly stratified fluid with initial buoyancy frequency n by means of a single bar oscillated with frequency the mixed fluid quickly reaches a steady state height h n 1 2 independent of the coriolis frequency f and collapses into the channel interior a small percentage of the fluid exported from the turbulent zone enters a boundary current the bulk forms a cyclonic circulation in front of the bar as the recirculation cell expands to fill the channel it restricts horizontal entrainment into the turbulent zone mixed fluid flux decays with time as t and is dependent on the size of the mixing zone and the balance between turbulence rotation and stratification the recirculation cell is confined within the channel and export of mixed fluid into the basin is restricted to the weak boundary current as horizontal entrainment is shut down long term production of mixed fluid relies more on vertical entrainment however the scalings indicate that short term dynamics are the most applicable to oceanic conditions

effects of vegetation change on interrill runoff and erosion walnut gulch southern arizona during the past 100 years grassland has been replaced by shrubland in many parts of the american southwest the effects of this vegetation change on interrill runoff and erosion are investigated by performing field experiments on small and large runoff plots located on contemporary grassland and shrubland hillslopes in walnut gulch experimental watershed the experiments indicate that the vegetation change causes runoff and erosion to increase in interrill areas by decreasing resistance to overland flow decreasing runon infiltration increasing the spatial heterogeneity of the plant canopy and possibly increasing the susceptibility of the soil to frost action increased runoff and erosion result in stripping of the soil a horizon the formation of desert pavement in intershrub areas and the development of rills fines remain and accumulate only under shrubs where they form islands of fertility shrubs are able to regenerate in these islands but it is difficult for any plants to become established in intershrub areas consequently there is an increase in the spatial heterogeneity of soil resources and this spatial heterogeneity is self perpetuating increasing spatial heterogeneity of soil resources is considered to be characteristic of the process of desertification

mean circulation and high frequency flow amplification in the sable gully abstract the sable gully a broad shelf break submarine canyon approximately 40 km east of sable island on the eastern scotian shelf separates banquereau and sable island banks unique among canyons on the eastern canadian continental shelf because of its depth steep slopes and extension far onto the shelf its ecological significance and increasing human pressures led to its designation in 2004 under canada s oceans act as the first marine protected area mpa in the atlantic region to improve the state of knowledge of the gully mpa a multi disciplinary field program was carried out in 2006 07 the physical oceanographic component consisted of the deployment april 2006 and recovery august 2007 of four current meter moorings and ctd surveys analysis of this 16 month mooring deployment demonstrates that the mean circulation above the canyon rim 200 m is characterized by a southwestward flow that appears unaffected by the canyon topography there is also some indication of the existence of an eddy at rim depth below 500 m the circulation is dominated by an upcanyon flow of order 0 02 m s 1 at the mooring array halfway between the canyon head and mouth the mean 200 m bottom transport towards the head of the gully was estimated as 35 500 m3 s 1 implying an upwelling velocity of 1 7 10 4 m s 1 14 m d 1 over the area results also show bottom intensified tidal flows and non linear constituents due to the interaction of k1 o1 m2 and s2 components along the thalweg of the canyon the strong overtides and compound tides observed in the gully make it unique among canyons further analyses provide evidence of enhanced mixing in the gully kv 180 10 4 m2 s 1 which is approximately 20 times that observed on the adjoining scotian shelf total variance of the currents in the gully is about 2 5 times greater than that observed on the nearby continental slope with an equivalent water depth

circulation near submarine canyons a modeling study circulation near a submarine canyon is analyzed with a numerical model previous theoretical work indicated that stratification controlled the interaction of coastal flow with canyons specifically the ratio of canyon width to the internal radius of deformation a wide canyon was thought to merely steer the flow while a narrow canyon would create substantial cross shelf exchange four cases are analyzed considering two directions of alongshore flow and two choices of initial stratification the weakly stratified case has an internal radius about equal to the canyon width while the strongly stratified case has one about 3 times the canyon width the direction of the alongshore flow is shown in this study to be the more important of the two factors in particular right bounded flow flow with the coast on the right looking downstream in the northern hemisphere leads to shallow downwelling in the canyon and weak exchange across the shelf break while left bounded flow creates upwelling at the head of the canyon and strong exchange between the ocean and shelf in left bounded flow upwelling dense water is pumped onto the shelf even for strong stratification however the stratification limits the vertical extent of the topographic influence so that the alongshore flow above the canyon is only weakly affected in the strongly stratified case with any level of stratification the surface temperature density is not modified at all by the flow interaction with the submarine canyon the important dynamics involve pressure gradients and coriolis acceleration and how they interact with the bathymetric gradients but not advection of momentum advection of density is clearly important in the upwelling cases finally continued upwelling onto the shelf acts as a drag mechanism and retards the alongshore coastal flow

the interaction between armouring and particle weathering for eroding landscapes the interaction between particle weathering and surface armouring and its effect on erosion has been investigated the effect of soil armouring is to decrease sediment transport with time by preferentially stripping away fine particles on the other hand the effect of weathering which breaks down the particles in the armour is generally believed to increase erosion by extending an existing armouring model armour and using a variety of published weathering mechanisms this interaction has been explored the model predicts that while this is generally true in some cases erosion can be decreased by weathering when the particles generated by weathering were approximately of equal diameter erosion increased while armouring decreased when weathering produced very fine particles by spalling erosion increased and armouring also increased when weathering produced a range of particles from fine to coarse the armour layer broke down and erosion decreased relative to the no weathering case this latter decrease in erosion was due to the high entrainment of coarser transportable materials from the bed decreasing the sediment transport capacity of the flow in these studies clear regimes could be identified where erosion was limited by either the energy of the flow alone i e transport limited or the rate of weathering weathering limited however for some mechanisms there was an interaction between the two which we called weathering transport limited copyright 2006 john wiley sons ltd

modelling landscape evolution geomorphology is currently in a period of resurgence as we seek to explain the diversity origins and dynamics of terrain on the earth and other planets in an era of increased environmental awareness yet there is a great deal we still do not know about the physics and chemistry of the processes that weaken rock and transport mass across a planet s surface discovering and refining the relevant geomorphic transport functions requires a combination of careful field measurements lab experiments and use of longer term natural experiments to test current theory and develop new understandings landscape evolution models have an important role to play in sharpening our thinking guiding us toward the right observables and mapping out the logical consequences of transport laws both alone and in combination with other salient processes improved quantitative characterization of terrain and process and an ever improving theory that describes the continual modification of topography by the many and varied processes that shape it together with improved observation and qualitative and quantitative modelling of geology vegetation and erosion processes will provide insights into the mechanisms that control catchment form and function this paper reviews landscape theory in the form of numerical models of drainage basin evolution and the current knowledge gaps and future computing challenges that exist copyright 2010 john wiley sons ltd

aeolian deposition and its effect on soil and vegetation changes on stabilised desert dunes in northern china abstract spatial and temporal patterns of aeolian deposition at shapotou northern china were studied on a chronosequence 0 12 29 and 37 years of stabilised desert dunes aeolian deposition markedly influenced soil and vegetation changes on the dunes the spatial pattern of aeolian deposition was studied using dust traps and measurements of the depth of aeolian accumulation mean deposition from august 1993 to july 1994 was 372 g m 2 and showed a complex spatial pattern determined by prevailing wind direction topography and shrub distribution contrasts between the topographic pattern of aeolian deposition trap data and accumulation thickness of aeolian deposits indicate that the measured pattern of aeolian deposition alone is insufficient to explain the pattern of accumulation an accretionary surface soil or grey sand containing much aeolian derived particles is developing on the stabilised dunes at a mean rate of 1 6 mm year rapid accumulation of aeolian particles significantly changed the surface environment increased moisture retention by the finer grey sand resulted in decreased moisture penetration and subsequent desiccation of the deeper dune sands this has led to vegetation changes with the deep rooted planted xerophytic shrubs declining from 12 to only 3 cover after 37 years of stabilisation the shrubs were replaced by a widespread microphytic crust and later by shallow rooted annual species which increased from 0 to approximately 12 cover over the same period the implications of projected increases in the dustiness of arid regions on the stability of desert dunes and vegetated desert margins are discussed stabilised dunes may become increasingly vulnerable to deflation with the progressive decline in shrub cover

high resolution swath sonar investigation of sand ridge dune and ribbon morphology in the offshore environment of the new jersey margin abstract sand ridges on the northeast us atlantic shelf form in the near shore environment most likely in response to storm driven flows as the holocene transgression has continued the ridges have been transferred to an offshore hydrodynamic regime where currents are not constrained by the coast and storms do not influence bottom currents as frequently or as strongly here we qualitatively and quantitatively investigate the morphology of offshore sand ridges and smaller scale features in an effort to place constraints on bedform development in these deeper waters a recent high resolution swath sonar survey mapped a portion of the new jersey shelf from 20 m water depth to the shelf break 120 m imaging both sand ridges and smaller scaled dunes and ribbons in far greater detail than has been previously possible using a robust statistical analysis we find that the gross morphology of ridges height width length does not change with depth beyond 20 m water depth and changes in ridge orientation generally mirror changes in regional contour orientation hence ridges have not continued to grow since transgression has brought them into the offshore hydrodynamic regime however on the inner shelf 20 m water depth to the mid shelf shore we do find evidence in the ridge shape which has an asymmetry opposite to that seen near shore and in the complex backscatter response that some important modifications to ridges are taking place at these water depths in contrast on the mid shelf from the mid shelf shore to the franklin shore ridges tend to have higher backscatter at the crests implying that these are largely winnowed relict features lineated smaller scale 100 500 m wavelength

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

upper jurassic reefs of smackover formation united states gulf coast the occurrence of reefs in the smackover formation an upper jurassic oxfordian sequence that has been recognized in the subsurface of the united states gulf coast requires a revision of existing depositional models that have been based exclusively on subsurface data gathered from nonskeletal carbonate reservoirs these reefal buildups are 10 to 130 ft 3 to 40 m thick commonly elongate and several square kilometers in plan they developed seaward of oolite shoals on paleostructures of three types that created subtle topographic highs on an otherwise ramplike sea floor 1 basement ridges 2 faulted basement highs and 3 upthrown salt cored fault blocks reef rubble zones have reservoir quality porosity throughout the smackover trend but reef framework is a ta get only where diagenesis has been favorable although only a few reefs have produced commercial hydrocarbons attractive porosities and permeabilities mean phgr of 15 mean k of 20 md result from freshwater leaching dolomitization or fracturing the biota forming smackover reefs is similar to that described for sponge and algal buildups and patch reefs from the late jurassic of europe reef framework is constructed by digitate and branching stromatolitic blue green algae tubiphytes sp and marine cements the biota varies through the smackover trend reefs in southern arkansas and northern louisiana are more diverse in these reefs encrusters and binders produce constructional microframework cavities on and between corals primarily actinastrea skeletal algae parachaetetes sp and cayeuxia sp lithistid and hexactinellid sponges bryozoans and hydrozoans the cavities are commonly filled with marine cements and geopetal sediments a vertical biotic zonation in cores of the reef interval suggests that the reef commu ity of organisms evolved through time the reefs are commonly underlain and overlain by subtidal peloidal lime packstones containing oncolites and scattered fossils and they can develop in close proximity to subtidal quartz sands

the longevity of hillslope soil in se and nw australia article i nfo the cosmogenic nuclide 10 be that is produced in the atmosphere and falls out in rainfall garden variety 10 be is used at a site in se australia and one in nw australia to estimate soil formation rates and natural erosion rates soil formation rates of 1 7 m ma are found at the se australian site while higher rates of 10 27 m ma are found in nw australia these are compared with estimates of modern erosion rates based on surveys of sedimentation in farm dams or 137 cs in hillslope soils in both cases modern erosion rates are markedly higher than either soil formation rates or natural erosion rates measured here at the nw australian site the 10 be data are complemented by measurements of in situ 36 cl in nearby limestone cuesta surfaces these show that the hard rock surfaces are eroding more slowly than the soils and that relief is therefore increasing in this landscape this contribution to a small but growing body of studies of the likely longevity of hillslope soils in australia shows that garden variety 10 be can be a very useful tracer but only if its transport both within the solum and saprolite is taken in account

oxfordian upper jurassic coral reefs in western europe reef types and conceptual depositional model comparative sedimentology and palaeoecology of oxfordian upper jurassic coral dominated reefs of england france italy and switzerland has been used to 1 identify and characterize different types of late jurassic coral reefs with regard to their litho and biofacies and 2 develop a depositional model for these reefs relating different reef types to each other within a palaeoenvironmental framework eight generic reef types and one associated reef facies are recognized these are i biostromal units dominated by platy microsolenids developed within clean limestone facies ii biostromal units dominated by platy microsolenids developed within marly facies iii reefal thickets dominated by tall dense phaceloid colonies developed within pure carbonate muds iv microbial coral reefs dominated by massive branching ramose and phaceloid colonies v large high diversity reefal units associated with large volumes of bioclastic material vi small species poor reefs developed within mixed carbonate siliciclastic facies vii microbial coral reefs dominated by massive colonies viii reefal thickets dominated by branching ramose colonies with widely spaced branches developed amongst sand shoals and coral debris channels and ix conglomerates rich in rounded coral fragments the reef associated facies the development of these different constructional and compositional reef types is interpreted as being primarily a function of light intensity hydrodynamic energy levels and sediment balance a conceptual depositional model based on these parameters can be used to predict the spatial and temporal distribution of different reefal carbonates and highlight sedimentological and palaeoecological trends in reef development

climate and surface properties hydrological response of small arid and semi arid watersheds abstract a positive relationship between annual rainfall and geomorphic processes runoff and erosion rates and environmental factors water regime soil and vegetation cover is often assumed for arid and semi arid areas with an annual rainfall in the range of 100 300 mm this assumption disregards the fact that changes along a climatic gradient at desert margins are not limited to purely climatic factors they are often accompanied by a parallel change in surface properties especially the relative extent of rocky or soil covered surfaces that differ greatly in their response to rainfall this raises the issue whether the change in surface properties along a climatic gradient enhances the assumed positive effects of rainfall increase or limits it the hypothesis advanced in this paper is that runoff generation and rate in arid and semi arid areas are primarily controlled by surface properties rather than by the absolute amounts of storm and annual rain amounts hydrological data collected at two instrumented watersheds located one in an arid rocky area and the second in a semi arid soil covered area support this hypothesis the implications of data obtained for runoff generation and flow continuity under changing climatic conditions are analyzed they point to the fact that the same regional climatic change may have different and even opposite effects on the hydrological response of different adjoining surface units this response is expected to be strongly controlled by the specific local surface conditions that prevailed in the area prior to the climatic change

the humped soil production function eroding arnhem land australia we report erosion rates and processes determined from in situ produced beryllium 10 10be and aluminum 26 26al across a soil mantled landscape of arnhem land northern australia soil production rates peak under a soil thickness of about 35 cm and we observe no soil thicknesses between exposed bedrock and this thickness these results thus quantify a well defined humped soil production function in contrast to functions reported for other landscapes we compare this function to a previously reported exponential decline of soil production rates with increasing soil thickness across the passive margin exposed in the bega valley south eastern australia and found remarkable similarities in rates the critical difference in this work was that the arnhem land landscapes were either bedrock or mantled with soils greater than about 35 cm deep with peak soil production rates of about 20 m ma under 35 40 cm of soil thus supporting previous theory and modeling results for a humped soil production function we also show how coupling point specific with catchment averaged erosion rate measurements lead to a better understanding of landscape denudation specifically we report a nested sampling scheme where we quantify average erosion rates from the first order upland catchments to the main sixth order channel of tin camp creek the low 5 m ma rates from the main channel sediments reflect contributions from the slowly eroding stony highlands while the channels draining our study area reflect local soil production rates 10 m ma off the rocky ridge 20 m ma from the soil mantled regions quantifying such rates and processes help determine spatial variations of soil thickness as well as helping to predict the sustainability of the earth s soil resource under different erosional regimes copyright 2009 john wiley sons ltd

cantor set model of eolian dust deposits on desert alluvial fan terraces available data show that eolian dust accumulation rates on desert alluvial fan terraces are often inversely proportional to the square root of the terrace age for a given area this temporal scaling is similar to that observed in fluvial and marine stratigraphic sequences in which a fractal distribution of hiatuses occurs i e a cantor set eolian dust accumulation on alluvial fan terraces is controlled by regional climatic influences on dust deposition e g dessication of pluvial lakes in the early holocene and local surface characteristics e g vegetation and pavement coverage that control dust preservation in order to interpret the observed scaling in terms of these relative influences i consider two end member models 1 a deterministic model in which dust deposition is controlled by cyclical climatic changes i e glacial interglacial cycles and in which no erosion occurs and 2 a stochastic model in which erosion and deposition take place with equal probability and magnitude during each time step i e a bounded random walk the observed temporal scaling is most consistent with the bounded random walk model suggesting that long term eolian dust accumulation is predominantly controlled by episodic changes in vegetation and pavement coverage over time and that eolian dust deposits are strongly punctuated by episodes of erosional reworking at a wide range of temporal scales

upper jurassic thrombolite reservoir play northeastern gulf of mexico in the northeastern gulf of mexico upper jurassic smackover inner ramp shallow water thrombolite buildups developed on paleotopographic features in the eastern part of the mississippi interior salt basin and in the manila and conecuh subbasins these thrombolites attained a thickness of 58 m 190 ft and were present in an area of as much as 6 2 km2 2 4 mi2 although these buildups have been exploration targets for some 30 yr new field discoveries continue to be made in this region thrombolites were best developed on a hard substrate during a rise in sea level under initial zero to low background sedimentation rates in low energy and eurytopic paleoenvironments extensive microbial growth occurred in response to available accommodation space the demise of the thrombolites corresponded to changes in the paleoenvironmental conditions associated with an overall regression of the sea the keys to drilling successful wildcat wells in the thrombolite reservoir play are to 1 use three dimensional seismic reflection technology to find paleohighs and to determine whether potential thrombolite reservoir facies occur on the crest and or flanks of these features and are above the oil water contact 2 use the characteristics of thrombolite bioherms and reefs as observed in outcrop to develop a three dimensional geologic model to reconstruct the growth of thrombolite buildups on paleohighs for improved targeting of the preferred dendroidal and chaotic thrombolite reservoir facies and 3 use the evaporative pumping mechanism instead of the seepage reflux or mixing zone models as a means for assessing potential dolomitization of the thrombolite boundstone

numerical study of the circulation in a steep canyon off the catalan coast western mediterranean we use a limited area fine resolution primitive equation model to carry out a case study of the circulation in the steep and narrow blanes canyon located off the catalan coast western mediterranean this area is characterized by a permanent along slope density driven current and strong northerly and easterly wind bursts in autumn in a first step the slope current is allowed to adjust to the bottom topography leading to a stationary circulation pattern which presents large vertical variations related to the canyon geometry in the surface layer the strong stratification allows the current to flow straight over the canyon rim ignoring bottom topography in the intermediate layer the canyon is wide and waters are isolated in a geostrophic anticyclonic eddy maintained by friction at the edge of the slope current in the deep layer the canyon is narrow and a topographic upwelling lifts bottom waters toward the canyon head in a second step the circulation is forced by easterly along shore with the coast on its right and northerly seaward 1 day wind bursts which induce significant vertical and cross shore motions steered by the bottom slope this ageostrophic circulation is substantially amplified in the canyon where the flow pattern presents large amplitude oscillations characterized by a downwelling upwelling during the easterly northerly wind burst followed by a rebound upwelling downwelling as the wind relaxes the upwelling induced by the northerly wind burst is capable of renewing waters trapped in the canyon eddy our results appear to be in fairly good agreement with in situ physical and biogeochemical data collected in blanes canyon and comparable canyons of the world ocean the three dimensional features obtained in this study can explain some of the observed patterns of larvae distribution and exchanges between the coastal zone and the open sea

how well can hillslope evolution models explain topography simulating soil transport and production with high resolution topographic data the morphology of hillslopes is a direct refl ection of tectonic forcing and climatic and biologic processes that drive soil production mobilization and transport soil transport on hillslopes affects river incision by providing tools for channel abrasion and controls the distribution of sediment that infl uences aquatic habitat although numerous hillslope transport relationships have been proposed over the past 60 years a comprehensive analysis of model predictions for a real landscape has not been performed here we use high resolution topographic data obtained via airborne laser swath mapping alsm to simulate the long term evolution of oregon coast range hillslopes and test three published transport models and a new model that accounts for nonlinear depth and slopedependent transport analysis of one dimensional steady state solutions for these four models suggests that plots of gradient curvature may be diagnostic for distinguishing model predictions to evaluate two dimensional model predictions for our fi eld site we assumed local steady state erosion for a 72 000 m 2 sequence of hillslopes and valleys after calibrating each of the four models we imposed constant base level lowering for cells within the valley network simulated 500 000 yr of soil production and transport and determined which transport model best preserved morphologic patterns that describe the current landscape form models for which fl ux varies proportionally with hillslope gradient generated broadly convex hilltops inconsistent with the sharp crested steep sided slopes of our study site whereas the two nonlinear slope dependent models produced convex planar slopes consistent with current hillslope form our proposed nonlinear slope and depth dependent model accounts for how soil thickness controls the magnitude of biogenic disturbances that drive transport this model best preserved the current landscape form particularly the narrow sharply convex hilltops characteristic of the oregon coast range according to our formulation which provides an explicit linkage for relating the distribution of biota to hillslope processes the degree of hilltop convexity varies nonlinearly with the ratio of erosion rate to maximum soil production rate highlighting the profound infl uence of soil depth on hillslope evolution

internal tides and mixing in a submarine canyon with time varying stratification abstractthe time variability of the energetics and turbulent dissipation of internal tides in the upper monterey submarine canyon msc is examined with three moored profilers and five adcp moorings spanning february april 2009 highly resolved time series of velocity energy and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring neap cycles however the onset of springtime upwelling winds significantly alters the stratification during the record causing the thermocline depth to shoal from about 100 to 40 m the time variable stratification must be accounted for because it significantly affects the energy energy flux the vertical modal structures and the energy distribution among the modes the internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals suggesting more reflection from up canyon early in the observational record turbulence computed from thorpe scales is greatest in the bottom 5

the influence of canyons on shelf currents a theoretical study the influence of submarine canyons on shelf currents is studied using the rossby adjustment method for a homogeneous inviscid fluid on an f plane the canyon in the model is assumed to have vertical edges and constant width the geostrophic flow around a canyon is found to be dependent upon two geometric parameters the ratio of the depth of the canyon to the depth of the shelf and the ratio of the width of the canyon to the rossby radius over the canyon moreover a single parameter determines most of the properties of the geostrophic state this parameter is called the canyon number and is a combination of the two basic geometric parameters in the geostrophic state an infinitely long flat bottom canyon will act as a complete barrier to an approaching shelf flow the approaching flow is asymmetrically diverted along the canyon and a net flux is generated to the left of the flow in the northern hemisphere if the canyon cuts a shelf between the shelf break and the coast and connects to a strait the geometry of juan de fuca canyon an in canyon out canyon current will be generated when the shelf break current flows keeping the shelf at its left right in the northern hemisphere if the canyon has a stepped or sloped bottom the geostrophic flow has a singularity where the step or slope meets the left canyon edge looking upcanyon in the northern hemisphere flow can cross the canyon edge through the singularity so the canyon is no longer a complete barrier to the approaching shelf flow in this case as above a net flux is generated to the left of the approaching shelf flow

soil production on a retreating escarpment in southeastern australia the functional dependence of bedrock conversion to soil on the overlying soil depth the soil production function has been widely recognized as essential to understanding landscape evolution but was quantified only recently here we report soil production rates for the first time at the base of a retreating escarpment on the soil mantled hilly slopes in the upper bega valley southeastern australia concentrations of 10 be and 26 al in bedrock from the base of the soil column show that soil production rates decline exponentially with increasing soil depth these data define a soil production function with a maximum soil production rate of 53 m m y under no soil mantle and a minimum of 7 m m y under 100 cm of soil thus constraining landscape evolution rates subsequent to escarpment retreat the form of this function is supported by an inverse linear relationship between topographic curvature and soil depth that also suggests that simple creep does not adequately characterize the hillslope processes spatial variation of soil production shows a landscape out of dynamic equilibrium possibly in response to the propagation of the escarpment through the field area within the past few million years in addition we present a method that tests the assumption of locally constant soil depth and lowering rates using concentrations of 10 be and 26 al on the surfaces of emergent tors

late jurassic coral microbial reefs from the northern paris basin facies palaeoecology and palaeobiogeography abstract during the late middle oxfordian patch reefs grew on the northern margin of the paris basin according to the facies analysis of the reef and inter reef sediments the environment was a warm clear and agitated sea with highly episodic sedimentation the bioherms were a short lived phenomenon during the third phase of regional reefal development sequence stratigraphically they are associated with a highstand system tract volumetrically and trophically dominant organisms were microbes now represented by massive clotted leiolite stalactitic hemispheroids with purely thrombolitic texture are restricted to open caves corals were of structural reef building importance due to their rapid upward growth the patch reefs are characterised by thickets of ramose corals which developed a very open framework in the vicinity of these patch reefs though in hydrodynamically higher energy environments grew thickets of more stoutly branched corals however they are rarely preserved in situ and are generally represented as abundant coral rubble the reef taxa are characterised by the notable absence of several groups e g oysters serpulids bryozoans pectinids occurring at other localities where reefs of similar age developed in similar environmental conditions the reefs also have strikingly modern aspects to them in particular the presence of cryptic elements within caves and a sponge dominated borer association dwellers belong to various life form types although encrusting taxa are exceedingly rare this may be explained by the presence of soft microbial films on most surfaces the palaeoecological analysis suggests that the major controls on faunal composition and high diversity were elevated nutrient levels highly episodic sedimentation and probably seasonal environmental disturbances structural and functional aspects of the reef community grazers trigger framebuilders borers trigger binders binders hamper borers allow ecological comparisons to be made with contemporaneous as well as recent reefs the unique combination of ecological factors resulted in a specialised previously undescribed community which differs from both tethyan and northern localities in various aspects these include cavities with cryptofauna prominence of grazing gastropods and high faunal diversity in a microbially dominated build up

microsolenid corals as rock formers in the corallian upper jurassic rocks of england summary microsolena thurmanni koby and m foliosa roniewicz scleractinia are important rock formers in the upper oxfordian stage of upware and to a lesser extent yorkshire

post mining landform evolution modelling 2 effects of vegetation and surface ripping computer simulations of the topographic evolution of the proposed post mining rehabilitated landform for the era ranger mine showed that for the unvegetated and unripped case the landform at 1000 years would be dissected by localized erosion valleys maximum depth 7 6 m with fans maximum depth 14 8 m at the outlet of the valleys valley form simulated by siberia has been recognized in nature this indicates that siberia models natural processes efficiently for the vegetated and ripped case reduced valley development maximum 1000 year depth 2 4m and deposition maximum 1000 year depth 4 8m occurred in similar locations as for the unvegetated and unripped case i e on steep batter slopes and in the central depression areas of the landform for the vegetated and ripped condition simulated maximum valley depth in the capping over the tailings containment structure was c 2 2 m by modelling valley incision decisions can be made on the depth of tailings cover required to prevent tailings from being exposed to the environment within a certain time frame a reduction in thickness of 1 m of capping material over tailings equates to c 1 000 000 mm3 over a 1 km2 tailings dam area this represents a saving of c 1 500 000 in earthworks alone incorporation of siberia simulations in the design process may result in cost reduction while improving confidence in environmental protection mechanisms copyright 2000 environmental research institute of the supervising scientist commonwealth of australia

mixing associated with sills in a canyon on the midocean ridge flank to close the global overturning circulation the production and sinking of dense water at high latitudes must be balanced elsewhere by buoyancy gain and upward vertical motion hydrographic and microstructure observations from the brazil basin in the south atlantic ocean indicate that most of the abyssal mixing there takes place on the topographically rough flank of the midocean ridge in previous studies it has been suggested that the high level of abyssal mixing observed on the ridge flank is primarily caused by breaking internal waves forced by tidal currents here the results from a detailed analysis of velocity hydrographic and microstructure data from a ridge flank canyon are presented two year long current meter records indicate that within the canyon there is a significant along axial mean flow down the density gradient toward the ridge crest five hundred meters above the canyon floor the kinetic energy in the subinertial band exceeds that associated with the semidiurnal tides by approximately a factor of 2 the mean dissipation of kinetic energy inside the canyon exceeds that above the ridge flank topography by approximately a factor of 5 the largest dissipation values were observed downstream of a narrow 1000 m high sill that extends across the full width of the canyon along the entire canyon there is a strong association between the presence of sills and along axial density gradients while there is no similar association between the presence of depressions and density gradients together these observations suggest that sill related mixing contributes at least as much to the diapycnal buoyancy flux in the canyon as tidally forced internal wave breaking which is not expected to be associated preferentially with sills while only 15 of the interfacial area between antarctic bottom water and north atlantic deep water in the brazil basin lie inside canyons the available data suggest that approximately one half of the diapycnal buoyancy fluxes take place there in comparison the region above the ridge flank topography accounts for about one third of the buoyancy fluxes the apparent importance of sill related processes for mixing in ridge flank canyons is therefore of global significance especially considering that such canyons occur on average every 50 km along 2 3 of the global midocean ridge system and that sills partially block the canyon axes every few tens of kilometers

late quaternary erosion in southeastern australia a field example using cosmogenic nuclides late quaternary rates of apparent soil production bedrock incision and average erosion are determined for the southeastern highlands of australia using in situ produced cosmogenic nuclide concentrations of 10 be and 26 al apparent soil production rates define a steep inverse exponential function of soil depth with a maximum of 143 m ma 1 under zero soil depth there were no observed soil depths between about 25 cm and zero however such that the maximum observed rate is about 50 m ma 1 the bredbo river catchment average erosion rate is 157 1mm a 1 and is similar to the average hillslope erosion rate of 167 1mm a 1 bedrock incision rates average 9 mma 1 and suggest that the higher rates of hillslope erosion may be in response to a pulse of incision perhaps generated by knickpoint propagation bedrock erosion rates inferred froma tor profile average 3 8 mma 1 with higher rates on other more weathered tor tops an aboveground tor profile of nuclide concentrations is consistent with a simple model of rapid stripping of the surrounding saprolite supporting the view that at least one episodic period of increased denudation has affected the landscape evolution of the highlands we test this hypothesis by using a simple landscape evolution model to reasonably predict the spatial variation of soil depth as well as the emergence of tors r 2001 elsevier science ltd and inqua all rights reserved

soil geomorphology the linkage of pedology and surficial processes geologists have made significant contributions to the discipline of pedology however until recently direct contributions came largely prior to 1935 as exemplified by those of powell and shaler during the late 19th century tandarich et al 1987 during much of the twentieth century geology and pedology have generally evolved along nearly separate pathways re integration of the two disciplines began slowly in the late 1950s and early to middle 1960s through the research and publications of ruhe 1956 1960 1964 richmond 1962 and morrison 1964 1965 1967 richmond s and morrison s research has provided much of the basis for the use of soils in the study of the stratigraphy of quaternary deposits in the western u s a birkeland 1984 the soil stratigraphic unit the geosol is a key component of the methodology developed by morrison geosols are presumed to have formed only during soil forming intervals interglacial or interstadial periods when climatic conditions were deemed optimal for rapid soil development recognition of soil stratigraphic units as geosols automatically conferred climatic as well as stratigraphic significance to buried soils this approach may have great utility in regions at higher latitudes that were characterized by extremes of climatic fluctuation during the qua ternary catt 1986 with little or no soil development during cold climate intervals a rather different approach involving the use of soils has been adopted by geoscientists conducting geomorphological research during the mid to late 1960s studies by researchers such as balster daniels hawley gile parsons and yaalon focussed on the nature of the relationships linking soils and landscape elements in many respects the philisophical approach to soil geomorphic research emphasized in the studies of these scientists strongly reflected the intellectual impact of jenny 1941 on the science of pedology this philosophy also strongly influenced the research of birkeland and following publication of birkeland s important textbook pedology weathering and geomorphological research 1974 a dramatic increase in the use of pedology in the geosciences occurred as researchers focussed on the study of landscape evolution in our view this emerging marriage of pedology and studies of surficial processes provides a critical framework for both the study of soil genesis and the study of evolution of and or stability of landscape elements

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

soil landscape response to mid and late quaternary climate fluctuations based on numerical simulations abstract we use a numerical dynamic soil landscape model to study one aspect of the spatio temporal soil landscape evolution process the effect of climatic fluctuations on soil grading distribution in space and time in response to the interplay between physical weathering and surface erosion soil mineralogical fluxes we simulate a synthetic soil landscape system over the middle and late quaternary last 400 ka the results show that 1 soil landscape response to climate change is non linear and highly spatially variable even at hillslope scale and 2 soil landscape adjustment to climate change can lag tens of thousands of years and is both spatially and temporally variable we propose that the legacy of past climatic condition i e last glacial maximum in modern soil landscape systems vary considerably in space this implies that the spatiotemporal uniformity in which soil is typically described in earth system modeling and analysis e g carbon cycle grossly underestimates their actual complexity

automatic landform stratification and environmental correlation for modelling loess landscapes in north otago south island new zealand the advent of quantitative soil landscape modelling techniques has seen the mapping of pedological phenomena placed on a more scientific footing in new zealand the spatial distribution of loess has a significant influence on soil properties and recent regional scale quantitative models have attempted to model the thickness and pattern of this important soil parent material here we apply two quantitative modelling techniques automatic landform stratification and environmental correlation to test and refine loess landscape models for a higher resolution study window in north otago south island field validation demonstrated that previously developed coarse scale models were moderately successful in predicting loess thickness but these models required refinement automatic landform stratification based on conceptual models of loess distribution was a good predictor of primary loess in the field 85 success but predicted poorly occurrence of colluvial and thin loess environmental correlation using nominal logistic regression with equal prior probabilities was a good predictor of primary loess in the field 70 success but predicted poorly occurrence of colluvial and thin loess quantitative loess landscape models need to be further refined using higher resolution terrain data derived from lidar and photogrammetric surveys in addition morphometric similarities between different loess landscapes needs to be addressed and the historical and spatial contingency inherent in loess landscape evolution incorporated in models for improved spatial prediction of loess parent materials

general patterns of circulation sediment fluxes and ecology of the palamos la fonera submarine canyon northwestern mediterranean abstract currents particle fluxes and ecology were studied in the palamos submarine canyon also known as the fonera canyon located in the northwestern mediterranean seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis on the canyon walls and on the adjacent slope additionally local and regional hydrographic cruises were carried out current data showed that mean near surface and mid depth currents were oriented along the mean flow direction ne sw although at 400 and 1200 m depth within the canyon current reversals were significant indicating a more closed circulation inside the canyon mean near bottom currents were constrained by the local bathymetry especially at the canyon head the most significant frequency at all levels was the inertial frequency a second frequency of about three days attributed to a topographic wave was observed at all depths suggesting that this wave was probably not trapped near the bottom the current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon the associated vertical velocity ranged between 10 and 20 m day and was constrained to the upper 300 m this latter feature together with other computations suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow in the canyon suspended sediment concentration downward particle fluxes chlorophyll and particulate c and n were significantly higher up canyon from about 1200 m depth than offshore defining along with the different hydrodynamics two canyon domains one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf slope front the higher near bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows during the deployment period the increase in downward particle fluxes occurred by mid november when a severe storm took place on the canyon walls at 1200 m depth suspended sediment concentrations downward particle fluxes chlorophyll and particulate c and n were higher on the southern wall than on the northern wall inversely to the current s energy this could be caused by an upward water supply on the southern canyon wall and or the mean flow interacting with the canyon bathymetry in the swimmers collected by the sediment traps the dominant species was an elasipod holothurian which has not been recorded in other canyons or elsewhere in the mediterranean indicating particular speciation

inverting topography for landscape evolution model process representation 3 determining parameter ranges for select mature geomorphic transport laws and connecting changes in fluvial erodibility to changes in climate

the long term stability of engineered landforms of the ranger uranium mine northern territory australia application of a catchment evolution model there is a need to assess the long term stability of engineered landforms associated with the rehabilitation of ranger uranium mine northern territory australia as it is a requirement that mill tailings must be contained for periods in excess of 1000 years the geomorphic model siberia is calibrated on hydrologic and erosion data collected by a combination of monitoring and rainfall simulation experiments on the waste rock dumps of ranger preliminary analysis of ranger s preferred above grade option suggests that erosion of the order of 7 to 8 m will occur on the structure in a period of 1000 years this depth of erosion may be sufficient to compromise the integrity of containment it is shown that siberia has significant advantages over steady state erosion models suggestions are made for the design that will enhance the stability of the structure and extend the structural life of the containment 1998 john wiley sons ltd

geological and computer modeling of upper jurassic smackover reef and carbonate shoal lithofacies eastern gulf coastal plain abstract reefs and carbonate shoals have long been known from the upper jurassic smackover formation in the gulf coastal plain however these carbonate lithofacies have unique acoustic properties that make them difficult to define using 3 d seismic reflection technology in the eastern gulf coastal plain microbial reef and shoal buildups occur on pre jurassic paleotopographic basement features on a carbonate ramp margin development of these buildups is a result of the interplay among paleotopography sea level changes and carbonate productivity geological and computer modeling indicates that smackover reef and shoal development is restricted to the flanks of high emergent relief structures while reef and shoal development occurred on the crest and flanks of low relief structures submergent for these submergent features modeling indicates that carbonate productivity during reef growth was significantly greater than during shoal development in addition to the initial paleorelief the rate of sea level rise the level of carbonate productivity and duration of reef growth appear to be critical factors in determining thickness and distribution of the reef lithofacies subsidence and compaction are minor factors shoal development is greatly influenced by reef distribution sea level changes level of carbonate productivity and duration of shoal deposition subsidence compaction and sediment redistribution are also factors modeling of parameters affecting reef and shoal development associated with pre jurassic paleohighs in combination with 3 d seismic reflection studies increases the chances of drilling a successful exploration well

shelf slope exchanges associated with a steep submarine canyon off calvi corsica nw mediterranean sea a modeling approach a three dimensional unsteady nonlinear high resolution model is used to investigate the impact of the calvi canyon nw corsica steep topography on the shelf slope exchanges as well as on the circulation in the calvi bay in homogeneous winter and early spring conditions a double coordinate system is considered in order to represent adequately the high depth gradients within the canyon the studied region is under the influence of the west corsica current flowing northeastward along the nw corsican coast right bounded flow model results show that the circulation in the calvi bay is determined by flow modifications in the canyon area the mean horizontal flow is deviated southwestward upstream of the canyon to form an anticyclonic gyre in the western part of the calvi bay within the canyon the circulation is cyclonic leading to an offshore flow downstream of the canyon around the canyon rim the cross shelf currents become important indicating that this region acts as a transition zone of high exchange between nearshore and offshore areas furthermore the canyon topography generates high downwelling upwelling and downsloping upsloping velocities responsible for an intense vertical transport of material in the area numerical runs are performed for typical prevailing wind conditions the wind is responsible for a drastic increase of cross shore transports between the bay and the canyon area 3 4 times larger than in the no wind case sw winds induce a further enhancement of cross shelf exchanges whereas the effect of n ne winds is to reduce exchange at the shelf break apart from the canyon head where an intense offshore flow occurs within the canyon high vertical velocities are shown to be associated with high cyclonic vorticity which is enhanced reduced by the n ne sw wind event a comparison between model results and measured distributions of nitrate and chlorophyll a concentrations in the area shows the role played by this specific hydrodynamics as a strong constraint on the coastal pelagic ecosystem

the effects of sediment transport weathering and aeolian mechanisms on soil evolution aeolian derived soils are found throughout the world soil evolution processes in aeolian dominated landscapes differ from processes in bedrock weathering landscapes by a number of key aspects including the lack of 1 soil production depth dependency 2 surface armoring and 3 grain size self organization in the soil profile we use here a soil evolution model marm5d to study the differences between aeolian and bedrock weathering dominated landscapes by analyzing soil evolution on a hillslope under various aeolian and bedrock soil supply settings subject to fluvial and diffusive sediment transport the model simulates spatial and temporal variation in soil particle size distribution psd and profile depth for each grid cell on the landscape as a function of physical weathering aeolian deposition and diffusive and fluvial sediment transport our results indicate that surface armoring plays a major role in soil evolution under bedrock weathering dominated conditions armoring reduces soil erosion and in conjunction with depth dependent soil production leads to steady state soil grading and depth and a relatively uniform soil distribution in contrast aeolian dominated landscapes tend to have considerable spatial variability in soil depth and psd our results also indicate that in contrast with diffusive transport which is assumed to be psd independent fluvial sediment transport is strongly influenced by the soil production mechanism aeolian or bedrock weathering based on the results presented here we propose that aeolian dominated landscapes are more responsive to environmental changes e g climatic and anthropogenic compared with bedrock weathering landscapes we further propose that this sensitivity may help explain the patchy soil distribution that is often observed in aeolian dominated regions

upper jurassic microsolenid biostromes of northern and central europe facies and depositional environment abstract microsolenid biostromes are a common and important reef type in many upper jurassic reefal sections comparative study of these biostromes in western europe allows the characterisation of this distinct biostrome type in terms of its taxonomic composition palaeoecology and sedimentary regime the biostromes are characterised by a coral community of relatively low generic diversity being dominated by the microsolenidae family of corals the coral skeletal biovolume is generally high and is overwhelmingly dominated by platy ecomorphotypes sedimentologically these biostromes developed in low energy marl and limestone regimes which were subject to low sedimentation rates and varying degrees of siliciclastic influx in contrast to the coral fauna the associated fauna shows a high generic diversity in particular a rich assemblage of echinoids and bivalves in addition the coral plates provide an ideal habitat for a well developed and strongly polarised encrusting and boring fauna top surfaces show limited post mortem encrustation by serpulids and cementing bivalves and are also bored by lithophagan bivalves the undersides of the plates show a highly developed and diverse cryptic fauna of serpulids thecidean brachiopods bryozoans calcareous sponges and sclerosponges it is concluded that the main control on the development of these biostromes was low light intensities though low energy level and low background sedimentation rates were also important it is suggested that relatively high nutrient levels may have also played a significant role the conditions for microsolenid biostrome development prevail in relatively deep water environments and hence these are the first coral dominated reefal structures to have developed in deeper water shallowing upward sequences the corals in these biostromes have adapted to these conditions by developing a strongly platy growth form but also reducing their growth rates substantially the microsolenids are particularly adapted to these environments in two ways 1 they secreted an extremely porous calcium carbonate skeleton which in environments where calcification rates are slow such as deep water environments is a distinct advantage 2 in response to the limited potential of phototrophy in these environments the microsolenids have developed a pennular septal structure which is suggested to be a means of improving heterotrophic feeding trophic analysis of the reef fauna reveals that the nutrient limitation model developed for present day coral reefs cannot be applied to these biostromes it is demonstrated that the microsolena and the present day agariciid leptoseris show a number of significant morphological and ecological similarities

soil development at snail s pace evidence from a 6 ma soil chronosequence on basalt in north queensland australia abstract in semi arid tropical australia basaltic lava flows with ages of 0 01 0 89 2 46 2 64 3 4 and 5 59 ma show a trend of progressive soil thickness increase of ca 0 30 m ma this rate is 10 to 1000 times slower than most soils on unconsolidated parent materials such as alluvium dune sand and glacial deposits reverse polarity magnetisation of pedogenic hematite in the lower b horizons of soils on the four oldest flows indicates acquisition of the remanence prior to the brunhes matuyama polarity transition at 0 78 ma preservation of such a reverse polarity implies that the remanence carrier pedogenic hematite has been unchanged by chemical weathering or physical disturbance by soil biota for at least 0 78 ma a conceptual model of soil development is presented which implies that prior to 0 78 ma soil weathering may have occurred to a greater depth because summer rainfall was significantly higher than present the extremely slow rate of soil formation implied from these basaltic soils in northern australia is a clear warning that agricultural use of such soils is unlikely to be sustainable against accelerated surface erosion

the marm spatially distributed soil evolution model a computationally efficient modeling framework and analysis of hillslope soil surface organization 1 hillslope surface armouring and weathering processes have received little attention in geomorphologic and hydrologic models due to their complexity and the uncertainty associated with them their importance however in a wide range of spatial processes is well recognized a physically based armouring and weathering computer model armour has previously been used to successfully simulate the effect of these processes on erosion and soil grading at a hillslope scale this model is however computationally complex and cannot realistically be applied over large areas or over long periods of time a simplified process conceptualization approach is presented named marm which uses a novel approach of modeling physical processes using transition matrices which is orders of magnitude faster we describe in detail the modeling framework we calibrate and evaluate the model against armour simulations and show it matches armour for a range of conditions the computational efficiency of marm allowed us to easily examine time and space varying relationships between erosion and physical weathering rates at the hillslope scale for erosion dominated slopes the surface coarsens over time while for weathering domination the surface fines over time when erosion and weathering are comparable in scale a slope can be weathering dominated upslope where runoff and therefore erosion is low and armouring dominated downslope in all cases for a constant gradient slope the surface armour coarsens downslope as a result of a balance between erosion and weathering thus even for weathering dominated slopes the surface grading catena is dependent on armouring through the balance between weathering and armouring we also observed that for many slopes the surface initially armours but after some period of time space and rate dependent weathering begins to dominate and the surface subsequently fines depending on the relative magnitude of armouring and weathering the final equilibrium grading of the slope may be finer or coarser than the initial conditions the results demonstrate the complexity of the evolution of surface grading and the balance between the armouring and weathering processes they also point toward inherent organization of surface grading on the hillslope driven by erosion even for extremely high weathering rates the implications for natural landforms are discussed we also plot and quantify for the first time a log log relationship between surface grading contributing area and slope for a range of weathering rates the results show that this log log relationship is robust the log log scaling is constant in space and true even for extreme weathering rates this has potentially important implications for soil geomorphology it suggests that an analytical solution can be found for soil grading catena this might allow us to more easily map soil distribution as a function of topographic characteristics

the design of post mining landscapes using geomorphic principles nature can provide analogues for post mining landscapes in terms of landscape stability and also in terms of the rehabilitated structure blending in with the surrounding undisturbed landscape in soil mantled landscapes hillslopes typically have a characteristic pro le that has a convex upper hillslope pro le with a concave pro le lower down the slope in this paper hillslope characteristic form is derived using the area slope relationship from pre mining topography at two sites in western australia using this relationship concave hillslope pro les are constructed and compared to linear hillslopes in terms of sediment loss using the siberia erosion model it is found that concave hillslopes can reduce sediment loss by up to ve times that of linear slopes concave slopes can therefore provide an alternative method for the construction of post mining landscapes an understanding of landscape geomorphological properties and the use of erosion models can greatly assist in the design of post mining landscapes copyright 2003 john wiley sons ltd

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

soil production in heath and forest blue mountains australia influence of lithology and palaeoclimate an erratum has been published for this article in earth surfaces processes and landforms 25 13 2005 1683 1686 recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth this contrasts with a long held assumption that maximum soil production occurs under a soil cover of finite depth sites in the blue mountains australia show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath covered spurs and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil the substrate varies from hard ferruginized sandstone to soft saprolite in situ 10be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but in contrast to other studies these sites do not show significant depth dependence of apparent soil production the pattern reflects both hardness variation in the rock substrate and the effect of late quaternary climatic change optically stimulated luminescence osl dating indicates that soil 30 cm depth is of holocene age whereas the deeper soil is substantially older the age break coincides with a stone line interpreted as a former surface lag deposit assuming that pre holocene soil depths were 30 cm less than today recalculated soil production tends to decrease with increasing depth soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic in the long term average rates of erosion and soil production decrease with increasing soil depth copyright 2005 john wiley sons ltd

turbulent mixing and exchange with interior waters on sloping boundaries abstractmicrostructure measurements along the axes of monterey and soquel submarine canyons reveal 200 300 m thick well stratified turbulent near bottom layers with average turbulent kinetic energy dissipation rates e 4 10 8 w kg 1 and eddy diffusivities k 16 10 4 m2 s 1 assuming mixing efficiency 0 2 to at least thalweg depths of 1200 m turbulent dissipation rates are an order of magnitude lower in overlying waters whereas buoyancy frequencies are only 25 higher well mixed bottom boundary layer thicknesses hn are an order of magnitude thinner than the stratified turbulent layer hn he because well stratified turbulent layers are commonly observed above slopes arguments that mixing efficiency should be reduced on sloping boundaries do not hold in cases of energetic internal wave generation or interaction with topography an advective diffusive balance is used to infer velocities and transports predicting horizontal upslope flows of 10 50 m day 1 extrapolating this estimate globa

evaluating the development of upper jurassic reefs in the smackover formation eastern gulf coast u s a through fuzzy logic computer modeling abstract a three dimensional 3d numerical stratigraphic model has been built to simulate the development of microbial reefs on a jurassic carbonate platform using fuzzy logic modeling methods the flexibility of the model allows for the examination of a large number of variables the relative importance of local environmental conditions and global changes on the frequency of reef development are examined relative to the temporal and spatial constraints from upper jurassic oxfordian smackover reef datasets from two alabama oil fields the fuzzy model simulates the deposition of reefs and carbonate facies by integrating local and global variables local scale factors include basement relief sea level change climate latitude water energy water depth background sedimentation rate and substrate conditions regional and global scale changes include relative sea level change climate and latitude the model confirms preexisting theories that background sedimentation rate water energy substrate relative sea level change and climate influenced the development of jurassic reefs additionally the model determines the degree of control each variable has on if where and when reefs develop the variables that control if reefs develop are the global parameters of climate and amplitude of sea level change the model specifies that the variables that influence the lateral distribution of reefs or where reefs occur are substrate water energy and background sedimentation rate the model also indicates a strong correlation between when reefs develop and the rate of sea level rise in all simulations reefs initially develop in conjunction with the greatest rate of sea level rise i e the inflection point on the sea level curve and reach peak development before the time of deepest water

stratigraphic architecture of upper jurassic oxfordian reefs in the northeastern gulf coast u s and the eastern paris basin france abstract the late jurassic was a major period of reef expansion many jurassic reefs are potential hydrocarbon reservoirs but their stratigraphic distribution has been difficult to predict examination of the stratigraphic architecture of oxfordian reefs in the northeast u s gulf coast and the eastern paris basin france affords a comparison of mixed coral algal sponge reefs versus microbial dominated reefs the smackover formation in the northeastern gulf coast contains microbial dominated reefs the smackover represents deposition during a major transgression and reefs occur within late transgressive system tract tst deposits reefs of mixed coral algae and sponges characterize the oxfordian of the eastern paris basin in the ardennes lorraine reefs appear after the maximum flooding event of a stratigraphic sequence and are maintained through the highstand systems tract hst deposition and into the overlying stratigraphic sequence in burgundy reefs occur in association with the maximum flooding event of the upper stratigraphic sequence dominated by platy microsolenids reef growth begins in the tst this interval is traditionally called the lower reef complex more diverse reef growth the upper reef complex continues above the maximum flooding event through the early hst reef growth ceases by deposition of the late hst with the introduction of grainstones and other high energy lithologies all reefs in this examination regardless of biota are associated with maximum flooding events the sequence stratigraphy of the oxfordian reefs in france and the gulf coast provides a framework for studying jurassic reefs of both mixed and microbial dominated assemblages

a physical explanation for an observed area slope elevation relationship for catchments with declining relief a general relationship between the contributing area slope and mean elevation of catchments with relief declining after a tectonic uplift event is presented this relationship is based on the continuity equation for runoff and erosion processes in the catchment the key hypothesis underlying this relationship is that as a catchment declines the nondimensionalized catchment approaches a constant form this hypothesis is verified for computer simulated catchments the area slope elevation relationship covers several cases catchments declining toward a peneplain catchments declining from a high slope dynamic equilibrium resulting from a high rate of tectonic uplift to a low slope one resulting from a lower rate of tectonic uplift and catchments declining from an elevated initial condition as for example in the decline of a mine spoil heap a previously published relationship between slope and area for catchments in dynamic equilibrium and based on runoff and erosion physics is shown to be a special case of this general relationship the new area slope elevation relationship is compared with data from simulated catchments and a field catchment it is thus shown that for declining catchments the area slope elevation relationship is a good predictor of catchment form for catchments with declining relief it is argued that the slope area elevation relationship is sufficient with the planiform drainage pattern to completely define the elevation properties of the catchment such as for instance the hypsometric curve

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

a physical explanation of an observed link area slope relationship an observed log log linear relationship between channel slope and contributing area is explained by the erosional physics that lead to catchment form it is postulated that tectonic uplift is in balance with the fluvial erosion down wasting that dominates catchment erosion and it is shown that this relationship results in the observed log log linear relationship at dynamic equilibrium in addition it has been observed that there are deviations from this log log linear relationship near the catchment divide with observed slopes being lower than those predicted from the relationship this is explained by noting that for small areas fluvial erosion effects are dominated by soil creep and rain splash modeled by diffusive physics the area at which this deviation from log log linearity occurs is that point on the hillslope at which diffusive physics like soil creep and rain splash begin to dominate fluvial erosion these predictions are confirmed by numerical simulations using a catchment evolution model

mean and tidal currents in baltimore canyon the mean and tidal current fields within baltimore canyon and on the shelf and slope around it were observed with instrumented moorings at 12 sites currents on the shelf are similar to those observed elsewhere over the northeastern u s outer shelf with mean flow southwestward at 10 to 15 cm s 1 parallel to the shelf break tidal current velocity in the direction of the major axis of the m2 ellipse over the shelf is about 9 cm s 1 currents within the canyon are complex mean flow near the bottom along the canyon axis is downcanyon at 5 cm s at a depth of 275 m but upcanyon at 7 cm s 1 at 600 m depth and negligible at depths of 1000 m and 1500 m at 50 m above the bottom mean flow at each of these sites is less than it is at 6 m above the bottom the m2 tidal currents in the canyon tend to be aligned with topography and have velocities ranging up to 22 cm s 1 maximum instantaneous current speeds were found near the bottom in the canyon axis with a peak speed for the entire survey of 106 cm s 1 near the bottom at the 275 m level

suspended particle movement in and around quinault submarine canyon abstract time and space dependent light transmission temperature salinity and velocity data obtained during two winter experiments in the vicinity of quinault submarine canyon are used to examine processes controlling subtidal cpd fluctuations in suspended particulate concentration in the region in particular local resuspension of particles by waves and currents horizontal advection and vertical advection data include time series from four to eight mooring locations as many as 16 current meters and 10 transmissometers on the shelf over the open slope and in the canyon during each experiment spatial distributions from five ctd transmission surveys and gravity wave information particle concentration in the bottom boundary layer at the shelf edge was dominated by resuspension events the mechanism for resuspension had a large inter annual variation in the first year wave induced resuspension dominated whereas in the second year current induced resuspension dominated the cut off depth for storm related resuspension was generally m subtidal advection across isobaths upwelling downwelling accounted for 20 of the variance in concentration fluctuations at the shelf edge in the bottom boundary layer horizontal advection of material suspended in the bottom nepheloid layer on the shelf resulted in the formation of shelf break depth intermediate nepheloid layers over the canyon in regions where the flow crosses isobaths the existence strength onshore offshore extent and vertical structure of such nepheloid layers at a given time in this asymmetrical canyon appear to be a function of the direction of flow over the outer shelf and over the upper slope in the canyon whether active resuspension is occurring over the shelf and the maximum resuspension depth and magnitude of the active resuspension event the frequency timing and magnitude of previous resuspension events spatial and temporal continuity magnitude and direction of flow over the open slope north and south of the canyon vertical settling and upwelling or downwelling related to the along isobath flow over the upper slope fluctuations in particle concentration below the shelf break depth over the canyon slope were controlled by vertical rather than horizontal advection vertical excursions by the water mass of 100 m occurred both as a result of isopycnal adjustment to the quasi geostrophic along isobath flow and as a result of semidiurnal tidal oscillations when an overhead nepheloid layer was present such water mass excursions produced concentration fluctuations at depths below the maximum depth of storm related local resuspension in open slope regions where strong inls intermediate depth nepheloid layers were absent the portion of concentration variance that could be explained by advective models with constant spatial gradients was almost negligible only one resuspension event was documented in the bottom boundary layer within the deep canyon bottom depth 1000 m suggesting that advection must account for the observed variance in particle concentration however the large scale gradients at these depths are sufficiently weak cf the smaller scale gradients or noise that advective control could only be demonstrated during the second winter experiment when velocities along the canyon axis were relatively large finally the data demonstrate that subtidal concentration fluctuations within 50 m of the canyon floor are correlated to those at the shelf edge this correlation reflects a correlation in the velocity field rather than a transfer of particles as might occur with a turbidity current

currents in monterey submarine canyon 1 flow fields of mean subtidal and tidal frequencies between 250 and 3300 m water depths in monterey submarine canyon are examined using current measurements obtained in three yearlong field experiments spatial variations in flow fields are mainly controlled by the topography shape and width of the canyon the mean currents flow upcanyon in the offshore reaches 1000 m and downcanyon in the shallow reaches 100 m amplitude isotherm oscillations and associated high speed rectilinear currents the 15 day spring neap cycle and a 3 day band are the two prominent frequencies in subtidal flow field neither of them seems directly correlated with the spring neap cycle of the sea level

jurassic sequence stratigraphy in the mississippi interior salt basin of alabama abstract three depositional sequences associated with cycles of relative sea level change and coastal onlap can be identified in the mississippi interior salt basin of alabama these depositional sequences are here designated the lzagc 3 1 lzagc 4 1 and lzagc 4 2 sequences and include callovian through kimmeridgian strata in the mississippi interior salt basin the lzagc 3 1 depositional sequence is bounded by a major composite basal unconformity developed on paleozoic and early mesozoic strata the sequence includes werner and louann evaporites transgressive deposits pine hill anhydrites and shales condensed section deposits and norphlet continental sandstones progradational highstand regressive deposits and represents the initial incursion of marine waters into the basin during the callovian in conjunction with early rifting of the gulf of mexico and subsequent sea level fall in the oxfordian the lzagc 4 1 depositional sequence is bounded by a lower type 2 unconformity associated with this fall in sea level this sequence includes norphlet marine reworked sandstones shelf margin deposits lower smackover packstones wackestones and carbonate mudstones transgressive deposits middle smackover carbonate mudstones condensed section deposits and upper smackover grainstones buckner anhydrites and middle haynesville carbonates clastics and evaporites progradational highstand regressive deposits smackover deposition was part of a major jurassic transgressive event in the gulf of mexico area the lzagc 4 2 depositional sequence is bounded by a lower type 2 unconformity in the kimmeridgian this sequence includes upper haynesville peritidal sandstones transgressive deposits upper haynesville carbonate mudstones and shales condensed section deposits and upper haynesville anhydrites shales and continental sandstones progradational highstand regressive deposits these sediments are overlain by the marginal marine to continental deposits of the cotton valley group in these depositional sequences progradational highstand regressive deposits are the principal petroleum reservoirs however shelf margin sandstones and transgressive carbonates also are reservoirs condensed section and in part transgressive deposits have the potential to be source rocks if subjected to proper depositional and burial conditions however only the lower and middle smackover carbonate mudstones were deposited and buried under conditions favorable for hydrocarbon generation and preservation an understanding of sequence stratigraphy can serve as an aid to identifying potential hydrocarbon exploration targets

a one dimensional model for simulating armouring and erosion on hillslopes 2 long term erosion and armouring predictions for two contrasting mine spoils this paper investigates the dynamics of soil armouring as a result of fluvial erosion for a non cohesive sandy gravel spoil from the ranger mine australia and a cohesive silt loam spoil from the northparkes mine australia using a model for hillslope soil armouring these long term predictions concentrate on the temporal and spatial changes of the spoil grading and erosion over 100 200 years for the flat cap regions 1 2 and steep batter edges 10 30 typically encountered on waste rock dumps the existence of a significant rock fragment fraction in the ranger spoil means that it armours readily while northparkes does not for ranger the waste rock showed reductions in 1 cumulative erosion of up to 81 from that obtained by extrapolating the initial erosion rate out 100 years and 2 the erosion year by more than 10 fold for northparkes reductions were less marked with the maximum reduction in erosion year being 37 after 200 years for ranger the reductions were greatest and fastest for intermediate gradient hillslopes for the steepest hillslopes the armouring decreased because the flow shear stresses were large enough to mobilize all material in the armour layer model uncertainty was assessed with probabilistic confidence limits demonstrating that these erodibility reductions were statistically significant a commonly used hillslope erosion model sediment flux 1 discharge m1 slope n1 was fitted to these predictions the erodibility 1 and m1 decreased with time which was consistent with our physical intuition about armouring at ranger the parameter m1 asymptoted to 1 5 1 6 while at northparkes it asymptoted to 1 2 1 3 at ranger transient spatial trends in armouring led to a short term 50 200 years in the future reduction in n1 to below zero under certain circumstances recovering to an asymptote of about 0 5 1 at northparkes n1 asymptoted to about 0 6 with no negative transients predicted the m1 and n1 parameters predicted for ranger were shown to be consistent with field data from a 10 year old armoured hillslope and consistent with published relationships between erodibility and rock content for natural hillslopes copyright 2007 john wiley sons ltd

periodic resuspension in baltimore canyon by focusing of internal waves high concentrations of particulate matter are frequently reported in submarine canyons this study demonstrates that in baltimore submarine canyon elevated concentrations result from periodic resuspension events the sloping bottom and v shaped topography of submarine canyons could accelerate tidal flows in the canyon axis sufficiently to cause resuspension which occurs predominantly at tidal frequencies however current meter and transmissometer data show that resuspension events are often associated with a borelike intrusion of cold water moving upslope near the canyon head an event that is consistent with the focusing of internal wave energy toward the canyon head at tidal frequencies hydrographic conditions for the focusing of energy are most favorable in late winter and early spring when stratification in the canyon is diminished direct observations reveal that the most pronounced resuspension events occur during those seasons bottom stresses generated in the canyon are sufficient to resuspend sediment along the axis at least between 200 and 800 m with little resuspension occurring deeper along the axis on the canyon walls adjacent slope or shelf during a resuspension event the sediment laden water is forced upcanyon then sloshes back down the canyon until it reaches a layer of higher density water detaches from the canyon floor and moves seaward along a density surface this is a means of transferring sediment and associated pollutants intercepted at the canyon head to deeper water across the shelf slope front over geologic time frequent resuspension and seaward transport may aid in the headward erosion of submarine canyons or at least inhibit their infilling during interglacial times

predicting the thickness and aeolian fraction of soils in upland watersheds of the mojave desert abstract soil thickness and soil texture and their spatial variability at hillslope scales are important inputs for hydrologic models recent studies have demonstrated that mechanistic models can accurately predict the spatial distribution of soil thickness in areas where soil thickness varies gradually along hillslope profiles to date however these models have not been tested in arid regions where soils are often thin and highly variable at small scales i e 1 10 m and where the influence of aeolian accretion on soil thickness and soil texture may be significant in addition most of the data available for the fraction of the soil derived from aeolian deposition which can serve as a proxy for soil texture originate from soils developed on stable depositional landforms data for aeolian fractions from upland soils are scarce in this study we developed and tested a numerical model for the prediction of thickness and aeolian fraction of soils in arid upland areas the model assumes a long term balance between the rates of soil production from bedrock aeolian accretion and soil erosion rates of soil production are quantified in the model using the exponential and humped soil production functions and soil erosion rates are quantified using the nonlinear depth and slope dependent transport functions assuming that only the upper soil horizons a b are capable of transport the rate of aeolian deposition is assumed to be spatially uniform we calibrated the three free parameters of the model at a site in the mojave desert with a granite lithology using a combination of 1 field measured data for soil thickness and 2 estimation of the aeolian fraction in the soil using laboratory analysis of immobile element concentrations we validated the model results in three nearby sites using a combination of measured soil thickness in soil pits and the presence absence of soil and laboratory analysis of the aeolian fraction of soil the study area is characterized by generally thin soils

late quaternary loess landscape evolution on an active tectonic margin charwell basin south island new zealand abstract loess deposits constitute an important archive of aeolian deposition reflecting wider patterns of glacial atmospheric circulation and more localised interactions between riverine source areas loess trapping efficiency and geomorphic controls on erosion rate conceptual models have been formulated to explain the coeval evolution of loess mantles and associated landscapes loess landscape models but none apply to areas of tectonically induced base level lowering this study uses an age sequence of alluvial fill terraces in the charwell basin north eastern south island new zealand which straddles the transpressive hope fault to investigate geomorphic controls on loess landscape evolution in an active tectonic region we hypothesize that the more evolved drainage networks on older terraces will more effectively propagate base level lowering by way of a greater areal proportion of steep and convex hillslopes and a smaller proportion of non eroding interfluves eventually as the proportion of interfluves diminishes and hillslope convexity increases terraces shift from being net loess accumulators to areas of net loess erosion we investigate the nature of erosion and the geomorphic thresholds associated with this transition morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo concave land elements the number of loess sheets and the thickness of loess increased across the three youngest terraces the next oldest ca 150 ka terrace remnant had the greatest maximum number of loess sheets 3 and loess thickness 8 m but the loess mantle was highly variable a detailed loess stratigraphic analysis and the morphometric analysis place this terrace in a transition between dominantly planar uniformly loess mantled landforms and loess free ridge and valley terrain exemplified by the oldest terrace remnant variations in thickness and preservation of loess sheets demonstrated spatially and temporally variable erosion during loess accumulation to test our hypothesis of loess persistence we calculated critical steady state hillslope curvatures from a soil transport model calibrated for the study area above which the uppermost loess sheet l1 max thickness 1 8 m should be completely eroded we compared loess distribution mapped in the field to values of slope curvature calculated from topographic surveys and found two of three critical curvature values had acceptable predictive ability where predictions failed this is probably due to transient responses related to active steam incision because all critical curvature values predicted presence of loess on the oldest terrace remnant where there is none we conclude that important factors other than morphometric ones are important in determining loess distribution in loess landscapes in active tectonic regions these may include internal changes to regolith affecting erodibility or vegetation or topographic interaction with wind patterns affecting loess trapping

a one dimensional model for simulating armouring and erosion on hillslopes 1 model development and event scale dynamics this paper presents an erosion model armour which simulates time varying runoff erosion deposition and surface armour evolution down a hillslope either as a result of a single erosion event or as the cumulative impact of many events over periods up to decades armour simulates sediment transport for both cohesive and non cohesive soil and dynamically differentiates between transport limited and source limited processes a variety of feasible processes for entrainment of different size classes can be modelled and evaluated against data the generalized likelihood of uncertainty estimation glue technique was used to calibrate and validate armour using data collected during rainfall simulator experiments at two contrasting sites 1 non cohesive stony sediments at ranger uranium mine northern territory australia and 2 cohesive silty sediments at northparkes gold mine nsw australia the spatial and temporal variations of model predictions within the individual runoff events showed that some entrainment processes could not model the spikes in concentration and subsequent depletion while the hiding model of andrews and parker best simulated the concentration trends for both calibrated and independent runoff events armour also successfully captured the coarsening of the surface material though small over the duration of the rainfall simulator trials this was driven by the depletion of the finest size class of the soil for a constant discharge armour simulated higher sediment flux at the start of the storm with the sediment flux and concentration diminishing with time for natural rainfall a power law relationship between sediment flux and discharge was observed the calibration exercise showed that sediment concentration and discharge alone are insufficient to calibrate all aspects of the physics in particular the armour depth this appears to be because the armouring during the short duration events is driven by depletion of the finest classes of the sediments diameters less then 62 5 mm which are not normally measured copyright 2006 john wiley sons ltd

the marm3d spatially distributed soil evolution model three dimensional model framework and analysis of hillslope and landform responses 1 we present a three dimensional landscape pedogenesis model marm3d matrices armour 3d which simulates soil evolution as a function of erosion and pedogenic processes the model simulates the discretized soil profile for points on a spatial grid the approach using transition matrices is computationally efficient and allows the simulation of large scale spatial coupling and long term soil evolution we study the effect of the depth dependent soil weathering rate i e the rate of soil particle breakdown and bedrock lowering rate i e the rate of conversion of bedrock to soil the difference in depth dependent weathering functions has a significant effect on the in profile soil properties through depth specifically particle size grading however the depth dependency has a relatively minor effect on the surface properties of the soil profile with all weathering functions generating very similar surface properties the surface properties were a function of the cumulative amount of weathering i e the integral of the weathering function over exhumation with finer surface grading for higher weathering rates soil thickness could be estimated without explicitly modeling soil thickness thickness was negatively correlated with surface median grain size as thickness decreases the surface grading coarsens this was driven by surface erosion where as surface grading coarsens erosion decreases and the soil deepens weathering and erosion interact to spatially organize the surface soil grading with a log log relationship between surface grading contributing area and local slope this relationship was independent of the weathering function this relationship might be useful for the spatial description of soil properties in digital soil mapping

flow near submarine canyons driven by constant winds circulation over coastal submarine canyons driven by constant upwelling or downwelling wind stress is simulated and analyzed with a primitive equation ocean model astoria canyon on the west coast of north america is the focus of this study and model results are consistent with most major features of mean canyon circulation observed in astoria canyon near surface flow crosses over the canyon while a closed cyclone occurs within the canyon upwelling prevails within the canyon and is larger than wind driven upwelling along the adjacent shelf break water rises from depths reaching 300 m to the canyon rim and subsequently onto the adjacent shelf onshore flow within the canyon is driven by the onshore pressure gradient force due to the free surface slope created by the upwelling wind and is enhanced by the limitation to alongshore flow by the canyon topography density gradients largely compensate the surface slope with realistic stratification but continual upwelling persists near the edges of the canyon within the upper canyon 50 150 m below the canyon rim a cyclone is created by flow turning into the canyon mouth separating from the upstream edge and advecting toward the downstream rim below this layer the cyclone is created by vortex stretching due to the upwelling downwelling winds create nearly the opposite flow in which compression and momentum advection create a strong anticyclone within the canyon momentum advection is found to be important both in creating strong circulation within the canyon and in allowing the surface flow to cross the canyon undisturbed model results indicate that astoria like submarine canyons produce across shore transport of sufficient volume to flush a continental shelf in a few 2 5 years

testing of the siberia landscape evolution model using the tin camp creek northern territory australia field catchment the siberia landscape evolution model was used to simulate the geomorphic development of the tin camp creek natural catchment over geological time measured hydrology erosion and geomorphic data were used to calibrate the siberia model which was then used to make independent predictions of the landform geomorphology of the study site the catchment located in the northern territory australia is relatively untouched by europeans so the hydrological and erosion processes that shaped the area can be assumed to be the same today as they have been in the past subject to the caveats regarding long term climate fluctuation a qualitative or visual comparison between the natural and simulated catchments indicates that siberia can match hillslope length and hillslope profile of the natural catchments a comparison of geomorphic and hydrological statistics such as the hypsometric curve width function cumulative area distribution and area slope relationship indicates that siberia can model the geomorphology of the selected tin camp creek catchments copyright 2002 environmental research institute of the supervising scientist commonwealth of australia

the potential roles of biological soil crusts in dryland hydrologic cycles biological soil crusts bscs are the dominant living cover in many drylands of the world they possess many features that can influence different aspects of local hydrologic cycles including soil porosity absorptivity roughness aggregate stability texture pore formation and water retention the influence of biological soil crusts on these factors depends on their internal and external structure which varies with climate soil and disturbance history this paper presents the different types of biological soil crusts discusses how crust type likely influences various aspects of the hydrologic cycle and reviews what is known and not known about the influence of biological crusts on sediment production and water infiltration versus runoff in various drylands around the world most studies examining the effect of biological soil crusts on local hydrology are done by comparing undisturbed sites with those recently disturbed by the researchers unfortunately this greatly complicates interpretation of the results applied disturbances alter many soil features such as soil texture roughness aggregate stability physical crusting porosity and bulk density in ways that would not necessarily be the same if crusts were not naturally present combined these studies show little agreement on how biological crusts affect water infiltration or runoff however when studies are separated by biological crust type and utilize naturally occurring differences among these types results indicate that biological crusts in hyperarid regions reduce infiltration and increase runoff have mixed effects in arid regions and increase infiltration and reduce runoff in semiarid cool and cold drylands however more studies are needed before broad generalizations can be made on how biological crusts affect infiltration and runoff we especially need studies that control for sub surface soil features such as bulk density micro and macropores and biological crust structure unlike the mixed effects of biological crusts on infiltration and runoff among regions almost all studies show that biological crusts reduce sediment production regardless of crust or dryland type copyright 2006 john wiley sons ltd

a catchment scale evaluation of the siberia and caesar landscape evolution models landscape evolution models provide a way to determine erosion rates and landscape stability over times scales from tens to thousands of years the siberia and caesar landscape evolution models both have the capability to simulate catchment wide erosion and deposition over these time scales they are both cellular operate over a digital elevation model of the landscape and represent fluvial and slope processes however they were initially developed to solve research questions at different time and space scales and subsequently the perspective detail and process representation vary considerably between the models notably caesar simulates individual events with a greater emphasis on fluvial processes whereas siberia averages erosion rates across annual time scales this paper describes how both models are applied to tin camp creek northern territory australia where soil erosion rates have been closely monitored over the last 10 years results simulating 10 000 years of erosion are similar yet also pick up subtle differences that indicate the relative strengths and weaknesses of the two models the results from both the siberia and caesar models compare well with independent field data determined for the site over different time scales representative hillslope cross sections are very similar between the models geomorphologically there was little difference between the modelled catchments after 1000 years but significant differences were revealed at longer simulation times importantly both models show that they are sensitive to input parameters and that hydrology and erosion parameter derivation has long term implications for sediment transport prediction therefore selection of input parameters is critical this study also provides a good example of how different models may be better suited to different applications or research questions copyright 2010 john wiley sons ltd and commonwealth of australia

flow modification and shelf slope exchange induced by a submarine canyon off the northeast spanish coast we present results from a study of the modifications induced by the short timescale response of a shelf break baroclinic jet to the presence of a downstream canyon the field site was the canyon of palamos located in the northeastern edge of spain to determine the short time scale variability of the area three intensive surveys were carried out at approximately 10 day intervals data indicate that the jet s location usually over the slope is subjected to significant onshore offshore displacements analysis of the data has shown the importance of a small scale temporal variability induced by river runoff and the climatology of the area this variability generates on off shore displacements of the jet which interacts with the head mouth of the canyon the different interactions with the canyon induced by these displacements produce different regimes of shelf slope exchange in the canyon domain that strongly modify the biomass patterns in the area