relationship between biofabric and petrophysics in coquinas insights on brazilian barremian aptian carbonates of the santos and sergipe alagoas basins coquinas are a sedimentary rock composed mainly of shells and their fragments with a carbonate or siliciclastic matrix these rocks exhibit a high range of porosity and permeability values that are related to depositional and diagenetic processes a series of coquina reservoirs were discovered in the campos and santos basins in the eastern margin of brazil and the understanding of the petrophysical properties of these rocks is essential for reservoir production in this work samples from the morro do chaves formation sergipe alagoas basin and the itapema formation santos basin were selected to identify the porosity vs permeability relationship according to the biofabric characteristics and porosity control the biofabric textures where classified into four groups according to taphonomic patterns and diagenetic modification i well sorted and preserved biofabric ii well sorted and altered biofabric iii unsorted and preserved biofabric and iv unsorted and altered biofabric the porosity control varies in all groups from depositional to diagenetic with distinct pore types pore sizes and pore connectivity that are located in different global hydraulic elements the analysis of the pore space was carried out through laboratorial measurements gas injection and by images from high resolution computed tomography from plug samples resulting in a pore network model where values of pore radius pore throat radius and coordination number were obtained the best values of porosity and permeability are related to well sorted altered biofabrics whereas the lowest values either with unsorted biofabrics with low pore connectivity or biofabrics that had the porosity reduced by compaction and cementation

interaction between pile groups and thrust faults in a physical sandbox and numerical analysis abstract for a bridge that straddles a fault line its pile group foundation can tilt or even fail during an earthquake event a small scale physical sandbox experiment is performed in this study to model a pile group subjected to thrust faulting and particle flow code pfc3d is adopted for numerical analysis the numerical analysis results are in good agreement with the sandbox test results with regard to the propagation path of the shear zone displacement of the pile cap and deformation patterns of the piles the propagation path of the fault rupture surface frs for the case with a pile group is different from that for the free field case the pile cap undergoes substantial rotation and displacement moreover adjacent piles can experience different deformation patterns producing different degrees of axial force and bending moments the piles in the shear zone can separate and the pile group can fail with increasing fault offsets the relative positions of the pile group and the fault show that the position of the pile foundation should be as far from the triangular shear zone as possible the development of the fault rupture surface is affected by the existence and location of the pile group the bending moment along the pile shaft is related to the passive earth pressure exerted by soil on the right side of the pile cap this behavior results in rotation deformation and displacement of the pile

measuring bluff erosion part 1 terrestrial laser scanning methods for change detection human activities influence watershed sediment dynamics in profound ways often resulting in excessive loading of suspended sediment to rivers one of the primary factors limiting our ability to effectively manage sediment at the watershed scale has been our inability to adequately measure relatively small erosion rates on the order of millimeters to centimeters per year over annual and sub annual time scales on spatially extensive landforms such as river banks and bluffs terrestrial laser scanning tls can be employed to address this need tls collects high resolution data allowing for more accurate monitoring of erosion rates and processes and provides a new opportunity to make precise measurements of geomorphic change on vertical landforms like banks and bluffs but challenges remain this research highlights challenges and limitations of using tls for change detection on river banks and bluffs including the presence of vegetation natural surface crenulations and difficulties with creating benchmarks and provides solutions developed to overcome these limitations results indicate that data processing algorithms for change detection can have a significant impact on the calculated erosion rates with different methods producing results that can vary by over 100 the most accurate change detection technique compares a point cloud to a triangulated irregular network tin along a set of vectors that accommodate bluff curvature this paper outlines a variety of methods used to measure bluff change via tls and explains the accompanying error analysis that supports these methods copyright 2012 john wiley sons ltd

erosion and channel changes due to extreme flooding in the fourmile creek catchment colorado abstract infrequent large magnitude geomorphic events generate quantifiable change on geologically short timescales and are crucial to understanding landscape evolution airborne lidar surveys and field measurements were used to investigate floodplain erosion and deposition along a 19 5 km reach of fourmile creek colorado that was devastated by severe flooding in 2013 that followed a 2010 wildfire 350 mm of rain fell on the fourmile catchment from september 9 15 2013 generating discharge that exceeded bankfull for 120 h at the orodell gage with local unit stream power 300 w m 2 throughout the study reach debris flows occurred on steep hillslopes and tributary channels in the most intensely burned areas lidar difference measurements and field studies highlight zones of local deposition along the study reach but demonstrate overall net erosion of 0 25 m for the 19 5 km reach of fourmile floodplain mainly by channel widening tributary junctions where debris flow sediment entered the floodplain and local decreases in unit stream power controlled some zones of deposition overall mass balance calculations show that a total sediment loss of 91 000 161 000 m3 from the fourmile creek floodplain and hillslopes which is broadly consistent with channel sediment flux estimates of 71 000 111 000 m3 measurements from the fourmile catchment demonstrate that floodplain erosion was a major source of sediment in the 2013 flood and demonstrate that infrequent events marked by long duration flooding and high total energy expenditure can account for a large fraction of total sediment transport in mountain streams

the effects of fire and water repellency on infiltration and runoff under mediterranean type forest abstract an investigation is being made into the relationship between forest fire and hillslope hydrology in the selva region of catalonia over a three year period at sites with a known fire history the major sites are on granite granodiorite or on sediments derived from these rocks at locations between santa christina d aro and santa coloma de farnes it appears that there is a general relationship between the type of organic profile found in a forest and the impact of fire in terms of loss of organic matter soil erosion hillslope hydrology and on the regeneration of the forest this paper summarises the results of about 150 rainfall simulation experiments and presents an overview of work carried out so far a major conclusion is that runoff processes are discontinuous and spatially structured due mainly to the effects of water repellency as a result of surface properties macropores hydrophobic behaviour and swelling four types of infiltration curve can be recognised at many locations infiltration increases with time during the early part of an experiment reaches a maximum value after about 30 minutes therupon subsequently decreasing this type of relationship can not be modelled with standard infiltration equations illustrations are given of sections through both burnt and unburnt soils to show how the hydrophobic effect influences water penetration it can be seen that infiltration patterns are similar for both burnt and unburnt soils and that micropores filled with organic matter are very important in conducting water through a water repellent surface layer the hydrophobic layer traps water in the bc horizon and prevents evaporation and loss by upwards capillary movement although the hydrophobic effects mean that small areas sometimes have a high runoff coefficient on larger areas there are many macropores and shrubs beneath which the soil is permeable and these trap runoff generated on the water repellent areas the main effect of fire is to illiminate the storage of water in the organic horizons several cm at first infiltration rates remain high but later these decrease as there is a reduction in porosity the sites having a moder type profile have better water retention properties more organic matter that survives the fire and a faster rate of vegetation recovery sites with a mor type profile can be degraded and erode if they are subject to disturbance the study provides another example of how on seemingly uniform slopes hydrological processes are structured by interactions with vegetation the patterns produced by these interactions survive the effects of fire

depositional model of early cretaceous lacustrine carbonate reservoirs of the coqueiros formation northern campos basin southeastern brazil abstract recent discoveries of giant hydrocarbon accumulations in coquinas and other lacustrine carbonate rocks of rift and post rift pre salt super sequences of the campos and santos basins have motivated a series of studies focused on understanding the genesis of these unique reservoirs an integrated petrologic sedimentologic stratigraphic seismic study of the coqueiros formation delineated the depositional model and evolution of reworked bioclastic rocks and other associated rocks deposited on the external high in the northern campos basin during the transition between late rift and sag stages bioclastic rudstones and grainstones with moderate to high shell reworking represent 65 of the samples described the following pieces of evidence point to a predominantly shallow lacustrine depositional environment dominated by storm currents i presence of high angle 14 longshore cross bedded rudstones ii limited occurrence of muddy sediments interbedded with thick packages of amalgamated bioclastic rudstones iii great lateral continuity of rudstone deposits devoid of matrix on the structural high consistent with processes of storm action on large expanses of shallow lakes iv deposits of massive rudstones with disorganized shells similar to the modern coastal bioclastic deposits of california and shark bay three sets of facies association are proposed i high energy facies composed of bioclastic rudstones and grainstones devoid of matrix deposited above the fair weather wave base fwb ii low energy facies composed of hybrid rocks with muddy or peloidal matrix and other fine grained rocks deposited below the fwb or in protected shallow environments iii an alkaline set composed of mainly magnesian clay ooids deposited in a more alkaline composition of lake water the evolution of the facies associations over time demonstrates an overall fall of the relative lake level high proportion of low energy facies associated with a deeper lacustrine environment occurs at the coqueiros fm base while at the top predominate high energy facies associated with a shallow lacustrine environment in addition to magnesian clay rich facies associated to restricted and alkaline water bodies paleocurrents suggest the activity of two main wind direction northwest and southeast over the external high that result in clean bioclastic facies with good reservoir potential on both flanks the knowledge of wind directions during the late barremian and early aptian in the northern campos basin is extremely important for targeting the best depositional facies for hydrocarbon accumulation in the coqueiros formation

how do sediment yields from post wildfire debris laden flows depend on terrain slope soil burn severity class and drainage basin area insights from airborne lidar change detection we derived a high resolution spatially continuous map of erosion and deposition associated with the debris laden flows triggered by the 2011 las conchas wildfire and subsequent rainstorms over a 197 km2 area in new mexico usa this map was produced using airborne lidar derived bare earth digital elevation models dems acquired approximately one year before and one year after the wildfire differencing of the pre wildfire and post wildfire and rainstorm bare earth dems yielded a dem of difference dod map that quantifies the magnitude of ground surface elevation changes due to erosion deposition within each 1 m2 pixel we applied a 0 3 m threshold filter to our dod to remove changes that could have been due to artifacts and or imperfect georeferencing the 0 3 m value for the threshold filter was chosen based on the stated accuracy of the lidar as well as a comparison of areas of significant topographic change mapped in aerial photographs with those predicted using a range of candidate threshold values for the dod filter we developed an automated procedure that accepts the dod map as input and computes for every pixel in the dem the net sediment volume exported through each pixel by colluvial and or fluvial processes using a digital routing algorithm an analysis of the resulting sediment volume map for the las conchas fire demonstrates that sediment volume is proportional to upstream contributing area after normalized by contributing area the average sediment yield defined as the sediment volume divided by the contributing area increases as a power law functions of the average terrain slope and soil burn severity class sbsc with exponents equal to approximately 1 5 our analysis quantifies the relationships among sediment yield average terrain slope and average soil burn severity class at the watershed scale and should prove useful for predicting the geomorphic response of wildfire affected drainage basins copyright 2014 john wiley sons ltd

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

normal fault rupture interaction with strip foundations observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed in some cases the rupture path appears to divert avoiding the structure such observations point to an interaction between the propagating rupture the soil and the foundation this paper i develops a two step nonlinear finite element methodology to study rupture propagation and its interaction with strip foundations ii provides validation through successful class a predictions of centrifuge model tests and iii conducts a parameter study on the interaction of strip foundations with normal fault ruptures it is shown that a heavily loaded foundation can substantially divert the rupture path which may avoid outcropping underneath the foundation the latter undergoes rigid body rotation often detaching from the soil its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center the average pressure q on the foundation largely dictates the width of such unsupported spans increasing q decreases the unsupported width reducing foundation distress the role of q is dual 1 it compresses the soil flattening fault induced surface anomalies and 2 it changes the stress field underneath the foundation facilitating rupture diversion however even if the rupture is diverted the foundation may undergo significant stressing depending on its position relative to the fault outcrop

interaction of piled foundation with a rupturing normal fault post seismic observations in the 1999 kocaeli earthquake in turkey have indicated that piled foundations may be less suitable than stiff mat foundations in defending a structure against a major nor

quantifying relationships of burning roughness and potential dust emission with laser altimetry of soil surfaces at submeter scales abstract decrease in surface roughness by the reduction of vegetation is one mechanism by which fire can promote aeolian transport in a variety of landscapes the extent to which fire might alter the roughness of the soil surface at fine spatial scales and the effect of this alteration on post fire aeolian response is not well known we examined relationships in the field between dust emissions and subcentimeter level soil surface roughness at submeter spatial scales with a terrestrial laser scanner and portable wind tunnel analog based on aeolian theory we hypothesized that observed relationships would differ from those determined in previous studies with laser altimetry at landscape scales meter kilometer length scales we examined four semiarid shrublands in southern idaho usa containing a distinct pattern of undershrub and interspace microsites including recently burned and unburned conditions mixed models were used to determine effects of burning on surface roughness and the response of dust emissions to changes in surface roughness results indicated that burned soil surfaces were rougher than unburned soil surfaces dust emissions were enhanced by increases in roughness on burned soil surfaces and in the absence of nonerodible roughness elements i e plants this finding is expectedly in contrast to previous work that demonstrated an inverse relationship between soil erosion and surface roughness determined with lidar light detection and ranging at landscape scales vegetated and unvegetated surfaces relationships of lidar derived roughness and aeolian emissions are scale dependent and vary with environmental factors of fire and vegetation these findings are integral for future research that attempts to parameterize model based predictions of aeolian emissions with lidar derived roughness

effects of rock fragments incorporated in the soil matrix on concentrated flow hydraulics and erosion rock fragments can act as a controlling factor for erosional rates and patterns in the landscape thus the objective of this study is to better understand the role that rock fragments incorporated into the soil matrix play in concentrated flow hydraulics and erosion laboratory flume experiments were conducted with soil material that was mixed with rock fragments rock fragment content ranged from 0 to 40 per cent by volume other treatments were slope 7 and 14 and flow discharge 5 7 and 11 4 l min 1 an increase in rock fragment content resulted in lower sediment yield and broader width of flow rock fragment cover at the soil surface i e surface armour increased with time in experiments with rock fragments flow energy was largely dissipated by rock fragment cover for more turbulent flow conditions when roughness elements were submerged in the flow hydraulic roughness was similar for different rock fragment contents in experiments with few or no rock fragments a narrow rill incised flow energy was dissipated by headcuts total sediment yield was much larger than for experiments with rock fragments in the soil adding just a small number of rock fragments in the soil matrix resulted in a significant reduction of sediment yield copyright 2007 john wiley sons ltd

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

evidence of debris flow occurrence after wildfire in upland catchments of south east australia abstract numerous reports of flash floods mud torrents and landslides in burnt landscapes of south east australia were only recently linked to debris flows and recognised as a significant process that warrant more detailed investigation this paper provides a systematic documentation of high magnitude erosion events after wildfire in south east australia focusing on small

centrifuge modeling of fault propagation through alluvial soils the behavior of alluvial deposits subjected to fault movements in the underlying bedrock is of major concern for critical structures located within fault zones an understanding of fault propagation through soils would assist in design of such structures but could also be utilized in geological interpretation of fault displacement history on the premise that alluvial fault morphology contains shear patterns characteristic of modes and rates of fault displacements a study was undertaken involving centrifugal and numerical models of reverse faulting this paper describes the centrifuge model testing performed to backup simultaneous numerical studies geognosis report 1980 which will be described elsewhere a comprehensive model test series under earth gravity conditions 1g involving reverse and normal faulting under different angles has recently been undertaken by cole 1979 however model tests performed under 1g conditions are limited to rather thin soil layers because of their inability to simulate realistic gravity stress conditions furthermore it is not possible to simulate faulting fast enough to include inertial effects with such models

illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar erosion following a wildfire is much greater than background erosion in forests because of wildfire induced changes to soil erodibility and water infiltration while many previous studies have documented post wildfire erosion with point and small plot scale measurements the spatial distribution of post fire erosion patterns at the watershed scale remains largely unexplored in this study lidar surveys were collected periodically in a small first order drainage basin over a period of 2 years following a wildfire the study site was relatively steep with slopes ranging from 17 to 30 during the study period several different types of rain storms occurred on the site including low intensity frontal storms 2 4 mm h 1 and high intensity convective thunderstorms 79 mm h 1 these storms were the dominant drivers of erosion erosion resulting from dry ravel and debris flows was notably absent at the site successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys the results show an evolution in geomorphic response such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre fire site morphology hillslope and channel roughness increased over time and the watershed armored as coarse cobbles and boulders were exposed the erosional response was spatially nonuniform shallow erosion from hillslopes 87 of the study area contributed 3 times more sediment volume than erosion from convergent areas 13 of the study area however the total normalized erosion depth volume area was highest in convergent areas from a detailed understanding of the spatial locations of erosion we made inferences regarding the processes driving erosion it appears that hillslope erosion is controlled by rain splash for detachment and overland flow for transport and quasi channelized erosion with the sites of highest erosion corresponding to locations with the lowest roughness by contrast in convergent areas we found erosion caused by overland flow soil erosion was locally interrupted by immobile objects such as boulders bedrock or tree trunks resulting in a patchy erosion network with increasing roughness over time

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

experimental investigation of reverse fault rupture propagation through wet granular soil abstract surface fault rupture has been previously investigated in dry cohesionless soil however wet granular soil has not been investigated in detail however apparent cohesion induced by intergranular water causes granular soil to behave differently than dry cohesionless soil field evidence shows that all soil that has been wetted will experience some degree of cohesion in the present study eight experimental faulting tests were conducted on sand in which the water content varied from 0 dry to 15 and the soil layer height ranged from 25 to 35 cm to determine the behavior of the wet sand a series of direct shear tests were carried out at low confining stress corresponds to stresses at different depth of the physical model the results showed that the shear band zone decreased in the wet specimens creating a sharp scarp at the surface the required normalized fault displacement for outcropping decreased significantly in these specimens and reached a minimum value at about a 5 water content the direct shear test results showed that the failure strain of the wet sand can be used for prediction of h0 h surface tension cracks at the hanging wall widened in the zone of distortion at the surface in the wet specimens other aspects of fault rupture also are discussed

modeling of the interactions between forest vegetation disturbances and sediment yields in the idaho batholith are investigated through numerical modeling the model simulates soil development based on continuous bedrock weathering and the divergence of diffusive sediment transport on hillslopes soil removal is due to episodic gully erosion shallow landsliding and debris flow generation in the model forest vegetation provides root cohesion and surface resistance to channel initiation forest fires and harvests reduce the vegetation vegetation loss leaves the land susceptible to erosion and landsliding until the vegetation cover reestablishes in time simulation results compare well with field observations of event sediment yields and long term averages over 10 000 years when vegetation is not disturbed by wildfires over thousands of years sediment delivery is modeled to be less frequent but with larger event magnitudes increased values of root cohesion representing denser forests lead to higher event magnitudes wildfires appear to control the timing of sediment delivery compared to undisturbed forests erosion is concentrated during the periods with low erosion thresholds often called accelerated erosion periods following wildfires our modeling suggests that drainage density is inversely proportional to root cohesion and that reduced forest cover due to wildfires increases the drainage density we compare the sediment yields under anthropogenic harvest and natural wildfire disturbances disturbances due to forest harvesting appear to increase the frequency of sediment delivery however the sediment delivery following wildfires seems to be more severe these modeling based findings have implications for engineering design and environmental management where sediment inputs to streams and the fluctuations and episodicity of these inputs are of concern index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 keywords sediment yield wildfires forest management hydrology

monitoring and modelling morphological change in a braided gravel bed river using high resolution gps based survey recent research in fluvial geomorphology has emphasized the direct monitoring of channel topography as a useful tool to better understand the interrelationship between river form and process and in particular to estimate bedload transport rates and reach scale sediment budgets until recently however this morphometric approach has been limited to comparison of repeatedly surveyed cross sections with the associated problems of low frequency sampling and an emphasis on cross stream as opposed to downstream morphological dynamics recent advances in analytical photogrammetry have however permitted the acquisition of data at sufficient resolutions to represent macroform 101 m and microform 10 m channel geometry in fully three dimensions while inherently spatially distributed the photogrammetric approach to land surveying is however restricted to observable areas of the channel and is thus of limited use in the subaqueous zone especially if flows are turbid or highly coloured this paper presents an alternative approach to the study of three dimensional morphological dynamics of a divided reach of the gravelly river feshie scotland in which topographic survey of both exposed and submerged areas of the reach was undertaken using the global positioning system gps survey results from two field programmes in 1998 and 1999 are presented in which a geotronics geotracer 2000 real time kinematic gps receiving unit was used to survey a 200 80 m reach rapid radial survey methods were employed permitting the collection of 2000 survey points per day giving a mean density over the 13 ha reach of 1 1 points per square metre a detailed assessment of survey errors and dem quality is presented and a limit of detection of c 10 cm proposed as an upper threshold for the identification of significant change between dems preliminary interpretation of channel dynamics in 1998 99 reveals relatively little change to the overall macroscale reach structure dem differencing techniques however highlight important local changes including the progradation of submerged bar fronts bar head aggradation and scour along major channel thalwegs and the erosion of fines from sloughs copyright 2000 john wiley sons ltd

a sediment transport model for incision of gullies on steep topography 1 we have conducted surveys of gullies that developed in a small steep watershed in the idaho batholith after a severe wildfire followed by intense precipitation we measured gully length and cross sections to estimate the volumes of sediment loss due to gully formation these volume estimates are assumed to provide an estimate of sediment transport capacity at each survey cross section from the single gully forming thunderstorm sediment transport models commonly relate transport capacity to overland flow shear stress which is related to runoff rate slope and drainage area we have estimated the runoff rate and duration associated with the gully forming event and used the sediment volume measurements to calibrate a general physically based sediment transport equation in this steep high shear stress environment we find that a shear stress exponent of 3 corresponding to drainage area and slope exponents of m 2 1 and n 2 25 match our data this shear stress exponent of 3 is approximately 2 times higher than those for bed load transport in alluvial rivers but is in the range of shear stress exponents derived from flume experiments on steep slopes and with total load equations the concavity index of the gully profiles obtained theoretically from the area and slope exponents of the sediment transport equation c m 1 n agrees well with the observed profile concavity of the gullies our results although preliminary because of the uncertainty associated with the sediment volume estimates suggest that for steep hillslopes such as those in our study area a greater nonlinearity in the sediment transport function exists than that assumed in some existing hillslope erosion models which calculate sediment transport capacity using the bed load equations developed for rivers

genesis and environmental significance of upper cretaceous shell concentrations from the cauvery basin southern india abstract upper cretaceous shallow marine calcarenites of the upper campanian maastrichtian kallankurichchi formation from the cauvery basin of southeastern india are rich in shell concentrations dominated by large bivalves with minor admixtures of brachiopods bryozoans and larger foraminifera rarely these concentrations occur as lenses or pavements but usually as beds 10 to 200 cm thick depending on the dominant skeletal elements five types of shell concentrations can be distinguished isognomon pycnodonte ceratostreon inoceramid platyceramus cataceramus and polyspecific concentrations these shell concentrations occur in various preservational states which reflect the gradual mixing and mechanical destruction of former communities analysis of the taphonomic signatures of their components and of the biofabric suggests that storm induced waves and currents reduced sediment input the settling behaviour of taxa and a high rate of production of biogenic hardparts were responsible in varying degrees for the formation of the various shell concentrations accordingly they can be classified as storm wave proximal tempestite and primary biogenic concentrations the shell concentrations formed below fair weather wave base in shallow subtropical low stress environments

physical and numerical modeling of hybrid foundations to mitigate seismic fault rupture effects abstractstrong earthquakes threaten civil structures through ground shaking and sometimes due to the outcrop of the causative fault a number of hybrid foundation schemes that have been found hel

seismic characterisation and origin of clinoforms in lacustrine depositional environments a case study from the cretaceous of the south atlantic

effect of storms during drought on post wildfire recovery of channel sediment dynamics and habitat in the southern california chaparral usa author s florsheim joan l chin anne kinoshita alicia m nourbakhshbeidokhti samira abstract current global warming projections suggest a possible increase in wildfire and drought augmenting the need to understand how drought following wildfire affects the recovery of stream channels in relation to sediment dynamics we investigated post wildfire geomorphic responses caused by storms during a prolonged drought following the 2013 springs fire in southern california usa using multi temporal terrestrial laser scanning and detailed field measurements after the fire a dry season dry ravel sediment pulse contributed sand and small gravel to hillslope channel margins in big sycamore creek and its tributaries a small storm in wy 2014 generated sufficient flow to mobilize a portion of the sediment derived from the dry ravel pulse and deposited the fine sediment in the channel totaling 0 60 m3 m of volume per unit length of channel the sediment deposit buried step pool habitat structure and reduced roughness by over 90 these changes altered sediment transport characteristics of the bed material present before and after the storm the ratio of available to critical shear stress t o t c increased by five times storms during wy 2015 contributed additional fine sediment from tributaries and lower hillslopes and hyperconcentrated flow transported and deposited additional sediment in the channel together these sources delivered sediment on the order of six times that in 2014 further increasing t o t c these storms during multi year drought following wildfire transformed channel dynamics the increased sediment transport capacity persisted during the drought period characterized by the longer residence time of relatively fine grained post fire channel sedimentation this contrasts with wetter years when post fire sediment is transported from the fluvial system during the same season as the post fire sediment pulse results of this short term study highlight the complex and substantial effects of multi year drought on geomorphic responses following wildfire these responses influence pool habitat that is critical to longer term post wildfire riparian ecosystem recovery

quantifying the time scale of elevated geomorphic response following wildfires using multi temporal lidar data an example from the las conchas fire jemez mountains new mexico abstract sediment yields commonly increase following wildfires in mountainous landscapes quantifying the magnitude and duration of elevated sediment yields following wildfires is important for quantifying the relative importance of wildfire affected versus non wildfire affected erosion in the long term evolution of landscapes and for understanding the processes of post wildfire erosion in this study we use bi annual terrestrial laser scanning tls surveys conducted over a 2 yr period together with repeat airborne laser scanning als surveys conducted over a 1 yr period to estimate the dependence of sediment yield on time following the high severity las conchas fire of 2011 within two small approximately 1 3 km 2 watersheds the dependence of sediment yield on time since the wildfire was quantified using dems of difference dods of the upland watersheds to measure erosion and of the adjacent piedmonts to measure the deposition of eroded sediment over the 2 yr study period sediment volume decreased linearly with time and sediment yield decreased exponentially with time in one watershed while the other watershed showed a more complex relationship with time influenced by the specific sequence of rainstorms that impacted that watershed both watersheds had a recovery time of approximately 1 yr suggesting that vegetation regrowth and the stabilization of incised valley bottoms were primarily responsible for the decline in sediment yield versus time following the wildfire multi temporal dods of the piedmonts show how they responded to the delivery of elevated sediment yields from the upland watersheds i e by 1 incision of the proximal portion of the piedmont triggering distal deposition 2 infilling of the incised channel and avulsion and 3 incision of the distal portion creating an incised channel connecting the proximal and distal ends of the piedmont the dynamic nature of incision aggradation and channel shifting on piedmonts following wildfires has important implications for post wildfire flood hazard assessments

critical shear stress for erosion of cohesive soils subjected to temperatures typical of wildfires received 26 february 2004 revised 15 september 2004 accepted 5 november 2004 published 22 january 2005 1 increased erosion is a well known response after wildfire to predict and to model erosion on a landscape scale requires knowledge of the critical shear stress for the initiation of motion of soil particles as this soil property is temperature dependent a quantitative relation between critical shear stress and the temperatures to which the soils have been subjected during a wildfire is required in this study the critical shear stress was measured in a recirculating flume using samples of forest soil exposed to different temperatures 40 550 c for 1 hour results were obtained for four replicates of soils derived from three different types of parent material granitic bedrock sandstone and volcanic tuffs in general the relation between critical shear stress and temperature can be separated into three different temperature ranges 275 c which are similar to those for water repellency and temperature the critical shear stress was most variable 1 0 2 0 n m 2 for temperatures 2 0 n m 2 between 175 and 275 c and was essentially constant 0 5 0 8 n m 2 f or temperatures 275 c the changes in critical shear stress with temperature were found to be essentially independent of soil type and suggest that erosion processes in burned watersheds can be modeled more simply than erosion processes in unburned watersheds wildfire reduces the spatial variability of soil erodibility associated with unburned watersheds by eliminating the complex effects of vegetation in protecting soils and by reducing the range of cohesion associated with different types of unburned soils our results indicate that modeling the erosional response after a wildfire depends primarily on determining the spatial distribution of the maximum soil temperatures that were reached during the wildfire

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

deformation of overburden soil induced by thrust fault slip abstract when the blind thrust fault slips due to earthquakes overburden soil strata may deform and fail leading to a development of a coseismic fault zone how overburden soil strata will deform or be faulted is an essential issue in the evaluation on the safety of ground underground infrastructures located near the potential plastic zone on the basis of previous work by cole and lade cole d a lade p v 1984 influence zones in alluvium over dip slip faults journal of geotechnical engineering 110 599 615 this research further explores the processes of thrust faulting within overburden soil and examines the influences of corresponding factors or parameters under a range of boundary conditions using physical models and numerical analysis for both small scale and full scale configurations factors explored include uplifting rate fault dip angle dilation angle of plastic flow young s modulus poisson ratio cohesive strength frictional angle scaling as well as the location of ground loadings applied on ground surface the experimental results indicate that although one major fault slip surface can be developed subsidiary faults may also form which requires special attention when defining stain patterns young s modulus and the dilation angle are the most influential parameters in our models a stiffer e leads to early fault propagation and the occurrence of back thrusts and causes more significant discrepancies in the deformation behaviors of models with different scales a greater dilation angle of the overburden soil leads to a wider fault zone the above mentioned phenomena highlight that a careful consideration of the applicable young s modulus and the dilation angle is essential in a proper simulation or prediction of the fault zone development for small scale physical models used to simulate the fault development for a full scale problem the stiffness of model soil should be properly scaled down which still requires further study

centrifuge modeling of reverse fault rupture propagation through single layered and stratified soil abstract many buildings have been built over active faults surface faulting as a main effect of earthquakes can cause damage such buildings properties of material over bedrock affect the pattern of rupture propagation through deposits and the width of the rupture zone on ground surface several researchers have primarily studied fault rupture propagation patterns on single layered granular soil however natural geologic deposits are rarely homogeneous and uniform but mostly consist of different layers in this study centrifuge model tests were conducted to investigate the patterns of reverse fault rupture propagation through single and double layered soil stratum it was observed that the soil type and sequence of layers affected the fault rupture propagation pattern as well as the surface rupture zone the results show that the width of deformation zone tends to decrease in stiffer soil in compare to softer soil these findings may help to produce a framework for predicting the occurrence and geometry of surface fault rupture zone that can help us to define a setback zone which is a major concern in building codes

centrifuge modeling of pile sand interaction induced by normal faulting abstractmany forensic studies conducted after catastrophic earthquakes revealed severe damages to pile foundations caused by bedrock fault movement the mechanism behind these pile foundation failures is not yet fully understood in this study two centrifuge model tests are carried out on a single pile and on a group of three piles in sand subjected to normal faulting the surface settlement profile and additional internal forces of the piles are measured the surface settlement profile in sand could be well fitted and predicted with a profile function error function the single pile which is located in a differential settlement zone is displaced and the pile top rotates toward the hanging wall inducing an additional bending moment along the pile the pile group is then forced to rotate toward the hanging wall because the three piles are well connected to the pile cap driven by the movement of the two additional piles and a pile cap in place the pile on the footwall side experiences greater displ

paleoseismic evidence for coseismic growth fold in the 1999 chichi earthquake and earlier earthquakes central taiwan abstract the 1999 chichi earthquake ruptured along previously unrecognized traces of the chelungpu fault because the traces were covered with thick bedded fluvial alluvial and colluvial deposits the earthquake created a 95 km long surface rupture and associated fault related fold scarps this study focused on the fault related fold at two locations where the fold scarp is characterized with trench excavation and shallow cored boring results the structural characteristics revealed by the two trench sites are consistent with a trishear fault propagation fold growth above a blind thrust several characteristics of the fold observed in the holocene deposits show smoothly rounded fold hinges unconformities onlapped structure and downward steepening of forelimb strata results from these structures suggest that the fold grows by progressive limb rotation of growth strata in sequential coseismic growth episodes the growth strata show several unconformable contacts as indicated by paleosoil horizons developed on event horizons based on the syntectonic sedimentary structure three events are revealed at the siangong temple site and two paleoearthquake events on the shijia site integration with the two trenches and the previous studies suggests the three paleoearthquake events occurred 300 430 710 800 and 1710 1900 yr b p these data on the two trench sites indicate that the average slip rate is 4 2 and 4 5 mm yr respectively

the evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances a wildfire and a historic flood abstract the transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape scale disturbances the first disturbance a high severity wildfire changed the catchment hydrology to favor overland flow which incised a colluvial hollow creating a channel in the same location this incised channel became armored with cobbles and boulders following repeated post wildfire overland flow events three years after the fire a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps an analysis of the step spacing shows that after the flood newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow prior to channelization this suggests that despite a distinct change in channel form roughness and bedform morphology the endogenous roughness periodicity was conserved variations in sediment erodibility helped to create the emergent steps as the largest particles d84 remained immobile becoming step features and downstream soil was easily winnowed away

post fire geomorphic response in steep forested landscapes oregon coast range usa abstract the role of fire in shaping steep forested landscapes depends on a suite of hydrologic biologic and geological characteristics including the propensity for hydrophobic soil layers to promote runoff erosion during subsequent rainfall events in the oregon coast range several studies postulate that fire primarily modulates sediment production via root reinforcement and shallow landslide susceptibility although few studies have documented post fire geomorphic response here we describe field observations and topographic analyses for three sites in the central oregon coast range that burned in 1999 2002 and 2003 the fires generated strongly hydrophobic soil layers that did not promote runoff erosion because the continuity of the layers was interrupted by pervasive discontinuities that facilitated rapid infiltration at each of our sites fire generated significant colluvial transport via dry ravel consistent with other field based studies in the western united states fire driven dry ravel accumulation in low order valleys of our sulphur creek site equated to a slope averaged landscape lowering of 2 5 mm given holocene estimates of fire frequency these results suggest that fire may contribute 10 20 of total denudation across steep dissected portions of the oregon coast range in addition we documented more rapid decline of root strength at our sites than has been observed after timber harvest suggesting that root strength was compromised prior to fire or that intense heat damaged roots in the shallow subsurface given that fire frequencies in the pacific northwest are predicted to increase with continued climate change our findings highlight the importance of fire induced dry ravel and post fire debris flow activity in controlling sediment delivery to channels

centrifuge and numerical modeling of normal fault rupture propagation in clay with and without a preexisting fracture abstractover the last few decades extensive research has been conducted to investigate fault rupture propagation induced by faulting through uncemented soil while it has long been realized that many natural soils are cemented relatively few publications have been devoted to investigating fault rupture propagation in cemented soil moreover preexisting fracture in soil may be reactivated during earthquakes and its influence on fault rupture propagation is not fully understood in this study three centrifuge model tests are reported on investigating fault rupture propagation induced by normal faulting in uncemented clay and cemented clay with and without a preexisting fracture preliminary numerical analyses of the centrifuge tests are also carried out to study the mechanism of fault rupture propagation in these three ground conditions ground deformation was dominated by a shear mechanism in uncemented clay and a shear zone along the projection of the bedrock fault plane was observed on the other h

evolution of a coquina barrier in shark bay australia by gpr imaging architecture of a holocene reservoir analog abstract the holocene hypersaline carbonate system in shark bay australia is represented by microbial deposits stromatolites and thrombolites and a supratidal coquina beach ridge system which overlies the pleistocene bibra formation and is prograding seaward since 4500 years ago over supratidal intertidal microbial deposits as a consequence of late holocene sea level fall and the high volume of bivalve shells available the extent internal architecture and ridge constructional types of coquina deposits in this world heritage area have not been previously investigated in detail by cores tied with geophysical images here we document external and internal architecture of the holocene coquina system in southeast hamelin pool showing three depositional units which comprise the ridge system construction 1 tabular layers complex 2 convex up ridges and 3 washover deposits bivalve skeletons represent almost the total amount of bioclasts with symmetrical semi circular formats and valve sizes 5 9 mm based on ground penetrating radar gpr images the number of prograding layers present in each transect line varies from 252 to 433 which when compared with the measured 14 c ages shows lateral growth of the system at average rates from 10 years per layer on proximal older sequences to 30 years per layer in the younger and thicker packages which display more gentle inclination and sub horizontal arrangement divergent orientation of tabular layers relates to changes in energy of currents and waves and involves time gaps and erosion after earliest crest construction the system experienced a decrease in sea level 3600 3000 14 c years bp that left behind a sequence of parallel tabular layers with dip angles 10 to

post fire thin debris flows sediment transport and numerical modelling the creation of a hydrophobic layer in the soil during res in semi arid environments inhibits the in ltration of rainfall this leads to increased rates of runoff and associated sediment transport when the hydrophobic layer is deposited beneath the soil surface a perched water table develops which may cause thin 1 2 cm hillslope failures that are distinguishable from features caused by rilling and sheet ow evidence for these failures was observed after a re near santa barbara california the amount of sediment eroded from some hillslopes was substantial with 290 kg of sediment per metre width of hillslope delivered to the valley oor the mechanics of these failures are examined with a numerical model that incorporates a stability analysis with subsurface ow routing along a typical hillslope pro le the model correctly predicts the location of the failures as well as the rainfall amount necessary to trigger them copyright 2003 john wiley sons ltd

post wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment chiricahua mountains arizona usa abstract flooding and erosion after wildfires present increasing hazard as climate warms semi arid lands become drier population increases and the urban interface encroaches farther into wildlands we quantify post wildfire erosion in a steep initially unchannelized 7 5 ha headwater catchment following the 2011 horseshoe 2 fire in the chiricahua mountains of southeastern arizona using time lapse cameras rain gauges and repeat surveys by terrestrial laser scanner we quantify the response of a burned landscape to subsequent precipitation events repeat surveys provide detailed pre and post rainfall measurements of landscape form associated with a range of weather events the first post fire precipitation led to sediment delivery equivalent to 0 017 m of erosion from hillslopes and 0 12 m of erosion from colluvial hollows volumetrically 69 of sediment yield was generated from hillslope erosion and 31 was generated from gully channel establishment in colluvial hollows processes on hillslopes included erosion by extensive shallow overland flow formation of rills and gullies and generation of sediment laden flows and possibly debris flows subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies winter freeze thaw led to soil expansion likely related to frost heaving causing a net centimeter scale elevation increase across soil mantled slopes by characterizing landscape form the properties of near surface materials and measuring both precipitation and landscape change we can improve our empirical understanding of landscape response to environmental forcing this detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood debris flow and sedimentation hazards used in post wildfire response assessments and land management and may help improve process based models of landscape evolution

centrifuge modeling of geotechnical mitigation measures for shallow foundations subjected to reverse faulting surface fault ruptures are particularly damaging to buildings lifelines and bridges located across or adjacent to active faults these structures should be designed in consideration of surface fa

re sedimented deposits in the rift section of the campos basin abstract an integrated petrologic sedimentologic stratigraphic seismic study of the lagoa feia group rift section of the campos basin has shown that rift sedimentation was dominantly intrabasinal carbonate and stevensitic deposits with siliciclastic deposits restricted to the proximity of graben border faults the bivalve bioclastic rudstones coquinas that constitute the rift reservoirs show commonly limited abrasion of the bioclasts and were deposited both on basement highs and lows throughout the rift section although in situ deposits of stevensite ooids and peloids occur dominantly at the base of the succession these particles are ubiquitous to the entire rift section mixed in variable proportion with siliciclastic and carbonate sediments the environmental conditions required for the formation of stevensite and the growth of bivalves are mutually exclusive as stevensite forms only at ph greater than 10 while bivalves cannot tolerate ph greater than 9 the common mixture of well rounded basaltic rock fragments with angular granitic gneissic rock fragments and feldspars in the sandstones and conglomerates indicates recycling of epiclastic deposits from the early rift section combined with first cycle contribution from the plutonic basement the studied cores show no evidence of subaerial exposure and there is a lack of bioturbation suggesting harsh environmental conditions the rift deposits are dominantly massive or faintly laminated with diffuse facies boundaries structures indicative of unidirectional or oscillatory flow are subordinate integration of seismic sedimentologic and petrographic evidence indicates that the campos basin rift section is formed mostly by re sedimented gravitational deposits the onset of the rift sedimentation occurred in synformal depressions where bivalve banks or stevensite ooids were formed in shallow lacustrine environments under variable alkalinity conditions with the development of half grabens and concentration of the tectonic activity along the border faults recurrent tectonic events promoted the mixing and gravitational re deposition of stevensitic clastic and bioclastic sediments in deeper fault bounded troughs large scale units hundreds of meters thick were generated by major tectonic events whereas compositional variations in the scale of meters were possibly a product of lake level climatic fluctuations thus due to syn rift and mainly to post rift erosion the neo aptian unconformity the preserved rift section of the lagoa feia group comprises mostly sediments deposited in the central troughs of the half graben structures marginal sediments were extensively eroded and re sedimented as gravity driven mixed deposits this new model constructed form the integration of seismic stratigraphic sedimentologic and petrologic data diverges substantially from the presently accepted model for the sedimentation of the rift section opening new possibilities for the exploration of campos basin as well as of similar settings as in the adjacent santos basin

rill erosion in natural and disturbed forests 1 measurements 1 rill erosion can be a large portion of the total erosion in disturbed forests but measurements of the runoff and erosion at the rill scale are uncommon simulated rill erosion experiments were conducted in two forested areas in the northwestern united states on slopes ranging from 18 to 79 we compared runoff rates runoff velocities and sediment flux rates from natural undisturbed forests and in forests either burned at low soil burn severity 10 months or 2 weeks post fire high soil burn severity or subject to skidding of felled logs the runoff rates and velocities in the natural sites 2 7 l min 1 and 0 016 m s 1 respectively were lower than those in all the disturbed sites 12 to 21 l min 1 and 0 19 to 0 31 m s 1 respectively except for the 10 month old low soil burn severity site where the velocity 0 073 m s 1 was indistinguishable from the natural sites the mean sediment flux rate in the natural sites also was very small 1 3 10 5 kg s 1 as compared to the rates in the disturbed areas 2 5 10 4 to 0 011 kg s 1 the hillslope gradient did not affect the runoff or sediment responses the sediment flux rates generally were greater in the initial stage of each inflow period than in the steady state condition but there was no corresponding transient effect in runoff rates rill erosion modeling implications based on these data are presented in part 2 of this study

filtering spatial error from dems implications for morphological change estimation abstract scour and fill estimation from digital elevation model dem subtraction or differencing is an increasingly common technique in morphological and sediment transport investigations the technique is commonly used to estimate scour and fill volumes and to produce scour and fill maps that provide process based information to geomorphologists accounting for sources of uncertainty within the dem is of critical importance dem error is spatially variable and has a tendency to be greater at breaks of slope such as bar and bank edges in the past however this has been achieved using a uniform error metric across the dem resulting in over conservative estimates of error in turn this has led to over conservative scour and fill volumes and incorrect process interpretation this paper applies a new approach that permits assessment of spatially distributed error across a dem the method is tested on a sequence of field surveys of the gravel bed river nent cumbria uk the results demonstrate some dramatic differences application of conventional techniques that account for mean error across a dem led to a 15 and 31 underestimation in scour and fill volumes respectively between july and october 1998 whilst for the october 1998 june 1999 subtraction 31 and 13 of scour and fill were underestimated respectively use of a uniform error across a surface captures less change in comparison to a spatially distributed approach furthermore the changes captured using a uniform error are biased toward areas of the channel that have more local topographic variability such as bar and bank edges in contrast the use of a spatially distributed approach provides information on change from flatter surfaces such as bar tops that would otherwise be missed this study also demonstrates that estimates of morphological change can be misleading in the absence of an error filter where the raw survey data is available it is recommended that sediment budgeting studies take account of the spatial variability of error in each dem involved in the subtraction

geographic gradients in the formation of shell concentrations plio pleistocene marine deposits gulf of california abstract shell bed coarse concentrations of invertebrate bioclastic material are rich sources of paleontologic and stratigraphic information studies often emphasize the relationship between shell bed formation and bathymetric gradients because many sedimentologic and ecologic factors that influence shell concentrating processes vary with water depth however shell bed formation is also influenced by factors that are not related to water depth shell beds in plio pleistocene marine sediments of the gulf of california mexico formed in less than 10 15 m water depth but under varying conditions of coastal topographic relief and tidal range sampling of shell beds focused on two regions the northern mainland coast and the southern peninsular coast shell beds in the northern mainland region 13 total formed along a macrotidal low relief coastline whereas shell beds in the southern peninsular region 27 total formed along a microtidal high relief coastline shell beds represent community beds 11 storm beds 3 beach berm beds 6 tidal channel bed 1 or current wave winnowed beds 19 the community beds represent biogenic concentrations the other four types represent sedimentologic concentrations sedimentologic concentrations formed either through short term concentrating events storm beds or long term dynamic bypassing beach berm beds tidal channel beds and current wave winnowed beds concentrations formed through dynamic bypassing are far more common 26 beds than storm concentrations 3 beds of the 26 concentrations formed through dynamic bypassing 10 cap major stratigraphic discontinuities representing temporal breaks ranging from 103 to 108 years the abundance and distribution of the five types of shell beds is significantly different between the two sampling areas the northern mainland coast is dominated by allochthonous beach berm beds capping linear beach ridges the formation of beach ridges in the north is favored by the wide shallow shelf representing a large reservoir for beach shells and sediment starved conditions resulting from the low topographic relief and periodic reductions in sediment supply from the colorado river delta beach berm beds are absent along the southern peninsular coast where coarse terrigenous sediment shed from adjacent highlands overwhelms shell input to the beach and the narrow steep shelf supplies the beach with few shells the southern peninsular coast is dominated by parautochthonous current wave winnowed beds and autochthonous community beds southern shell beds have undergone significantly less reworking winnowing and transportation than northern shell beds this is a function of both the relative weakness of tidal currents in the south and the relatively higher rates of terrigenous sedimentation along the rugged southern coastline which can bury shell concentrations relatively rapidly geographic variation in topographic relief and tidal range results in significant variation in the distribution and abundance of shell beds within these shallow marine sediments these variables have root tectonic cause relief reflects tectonic activity tidal range reflects basin configuration underscoring the potential utility of fossil concentrations for reconstructing earth history

effects of fire and ash on soil water retention despite the pronounced effect of fire on soil hydrological systems information on the direct effect of fire on soil water retention characteristics is limited and contradictory to increase understanding in this area the effect of fire on soil water retention was evaluated using laboratory burning and heating experiments in addition ash infiltration and ash incorporation experiments were performed to evaluate the effect of ash on soil water retention while heating soil to 200 c and below did not change soil properties burning and heating to 300 c and above increased bulk density clay and silt content and decreased organic matter and sand content burning and heating above 200 c decreased the amount of water stored at the nine tensions considered although the effect on soil water retention did not always increase with increasing temperature changes were largest for low tensions i e between saturation and field capacity 10 kpa heating to 200 c decreased the amount of plant available water but despite reducing the amount of water stored at evaluated tensions burning and heating to 300 c and above increased the amount of plant available water this may be caused by more complete combustion of organic matter at the higher temperatures and the production of ash direct incorporation of ash into soils did not alter soil texture but increased water retention from saturation to 310 kpa tension ash infiltration experiments interestingly had a similar effect despite the fact that very little ash washed into the samples results from these experiments contribute to understanding post fire changes in hydrological and erosion processes

processes of coastal bluff erosion in weakly lithified sands pacifica california usa abstract coastal bluff erosion and landsliding are currently the major geomorphic processes sculpting much of the marine terrace dominated coastline of northern california in this study we identify the spatial and temporal processes responsible for erosion and landsliding in an area of weakly lithified sand coastal bluffs located south of san francisco california using the results of a five year observational study consisting of site visits terrestrial lidar scanning and development of empirical failure indices we identify the lithologic and process controls that determine the failure mechanism and mode for coastal bluff retreat in this region and present concise descriptions of each process bluffs composed of weakly cemented sands unconfined compressive strength ucs between 5 and 30 kpa fail principally due to oversteepening by wave action with maximum slope inclinations on the order of 65 at incipient failure periods of significant wave action were identified on the basis of an empirical wave run up equation predicting failure when wave run up exceeds the seasonal average value and the bluff toe elevation the empirical relationship was verified through recorded observations of failures bluffs composed of moderately cemented sands ucs up to 400 kpa fail due to precipitation induced groundwater seepage which leads to tensile strength reduction and fracture an empirical rainfall threshold was also developed to predict failure on the basis of a 48 hour cumulative precipitation index but was found to be dependent on a time delay in groundwater seepage in some cases

combining bulk sediment osl and meteoric 10be fingerprinting techniques to identify gully initiation sites and erosion depths deep erosional gullies dissect landscapes around the world existing erosion models focus on predicting where gullies might begin to erode but identifying where existing gullies were initiated and under what conditions is difficult especially when historical records are unavailable here we outline a new approach for fingerprinting alluvium and tracing it back to its source by combining bulk sediment optically stimulated luminescence bulk osl and meteoric 10be 10bem measurements made on gully derived alluvium samples in doing so we identify where gully erosion was initiated and infer the conditions under which such erosion occurred as both 10bem and bulk osl data have distinctive depth profiles in different uneroded and depositional settings we are able to identify the likely incision depths in potential alluvium source areas we demonstrate our technique at birchams creek in the southeastern australian tablelands a well studied and recent example of gully incision that exemplifies a regional landscape transition from unchanneled swampy meadow wetlands to gully incision and subsequent wetland burial by post european settlement alluvium we find that such historic alluvium was derived from a shallow erosion of valley fill upstream of former swampy meadows and was deposited down the center of the valley incision likely followed catchment deforestation and the introduction of livestock which overgrazed and congregated in valley bottoms in the early 20th century during a period of drought as a result severe gully erosion was likely initiated in localized compacted and oversteepened reaches of the valley bottom

representative styles of deformation along the chelungpu fault from the 1999 chi chi taiwan earthquake geomorphic characteristics and responses of man made structures the chi chi earthquake provides dramatic evidence of the damaging effects of surface ground deformation to buildings lifelines and other facilities much of the building damage is associated with surface faulting and folding along the chelungpu thrust fault our detailed surveying at representative sites along the fault shows that the rupture commonly is a relatively simple 1 to 4 m high scarp with minor hanging wall deformation and localized but severe uplift folding and graben formation along the scarp crest for individual scarps the width of deformation is about 10 to 20 times the net vertical displacement distributed secondary faulting and folding on the hanging wall occurred as much as 350 m from the primary fault near the northern end of the rupture growth of a pre existing 1 km wide late quaternary anticline produced severe ground rupture along multiple thrusts and backthrusts but only minor tilting between fault strands the pattern of building damage coincides with the pattern of geologic deformation with severe damage along large fault scarps and lesser but still significant damage attributable to distributed secondary surface deformation on the hanging wall rupture related building damage on the footwall occurred next to the prerupture fault trace where the hanging wall bulldozed onto the footwall the width of this damage zone is related to the local horizontal shortening along the fault and generally is less than 10 m building zonation along reverse faults should account for this pattern of surface deformation in addition buildings with massive foundations locally influenced the style and location of near surface deformation producing variations in fault strike or accentuated secondary deformation on the hanging wall manuscript received 15 january 2001

vegetation and wildfire controls on sediment yield in bedrock landscapes steep rocky landscapes commonly exhibit high sediment yields and are especially sensitive to climate tectonics and wildfire predicting landscape response to these perturbations demands a quantitative understanding of erosion processes however existing models for hillslope sediment production and transport do not apply to landscapes with patchy soil and slopes that exceed the angle for sediment stability here we present field measurements in southern california usa which indicate that sediment storage on steep slopes is enabled by vegetation that traps sediment upslope we find that the storage capacity of unburned vegetation dams follows a geometric scaling model with a cubic dependence on effective plant width and an inverse dependence on local slope measured sediment volumes behind burned vegetation dams indicate a loss of at least 75 relative to unburned dams and when expanded to the catchment scale our measurements match records of postfire sediment yield from nearby retention basins contrary to existing models our observations indicate that wildfire induced sediment yield is driven by transient storage and release of sediment by vegetation dams rather than increased bedrock to soil conversion rates without a feedback between soil production and wildfire fire may play little role in long term landscape evolution and increasing fire frequency in response to climate change may not result in heightened sedimentation hazards due to supply limitations

sedimentation in large lakes processes associated with sedimentation in these lakes is in its infancy the large lakes of the world are precious resources that provide their nearby inhabitants with abundant fresh water food economical transpor tation and recreation they also provide additional benefits to the geologist unique paleoclimatic records and useful basins in which to test models of aquatic sedimentary processes this paper summarizes the global distribution oflarge lakes and focuses upon their geological attributes

interaction of shallow foundations with reverse faults a series of centrifuge model tests is reported that investigated the effects of foundation position on the interaction of reverse dip slip faults with shallow foundations resting on sand the model tests have allowed careful examination of both the soil and foundation deformation as a shear localization fault propagates through a 15 m thick sand layer for fault throws up to 5 m by comparing results of the tests with foundations present with those from a free field test the effect of the foundation on the faulting pattern has been observed directly the response of the foundation is very sensitive to the exact position of the fault and even when the fault emerged remotely from the foundation it sometimes caused significant foundation movements detailed results are presented for the tests and it is suggested that these results are used as 1 indications of likely foundation soil fault interaction mechanisms and 2 to allow future validation of numerical models for similar problems finally fou

fallout radionuclide tracers identify a switch in sediment sources and transport limited sediment yield following wildfire in a eucalypt forest abstract fire can alter sediment sources and transport rates in river basins changing landforms and aquatic habitats and degrading downstream water quality variability in the response between environments between fires and with time since fire makes predicting the catchment scale effect of individual fires difficult this study applies the fallout radionuclides 137cs and 210pbxs to trace the sources and transport of fine sediment through a river network following a wildfire of moderate to extreme severity in the 629 km2 eucalypt forested nattai river water supply catchment near sydney australia the tracer analysis showed that post fire erosion caused a switch in fine

post wildfire erosion response in two geologic terrains in the western usa abstract volumes of eroded sediment after wildfires vary substantially throughout different geologic terrains across the western united states these volumes are difficult to compare because they represent the response to rainstorms and runoff with different characteristics however by measuring the erosion response as the erodibility efficiency of water to detach and transport sediment on hillslopes and in channels the erosion response from different geologic terrains can be compared specifically the erodibility efficiency is the percentage of the total available stream power expended to detach remobilize or transport a mass of sediment erodibility efficiencies were calculated for the i initial detachment and for the ii remobilization and transport of sediment on the hillslopes and in the channels after wildfire in two different geological terrains the initial detachment efficiencies for the main channel and tributary channel in the granitic terrain were 10 9 and 5 4 and were similar to those for the volcanic terrain which were 5 5 and 1 1 no initial detachment efficiency could be measured for the hillslopes in the granitic terrain because hillslope measurements were started after the first major rainstorm the initial detachment efficiency in the volcanic terrain was 1 3 0 41 the average remobilization and transport efficiencies associated with flash floods in the channels also were similar in the granitic 0 18 0 57 and volcanic 0 11 0 41 terrains on the hillslope the remobilization and transport efficiency was greater in the volcanic terrain 2 4 than in the granitic terrain 0 65 however this may reflect the reduced sediment availability after the first major rainstorm 30 min maximum rainfall intensity 90 mm h 1 in the granitic terrain while easily erodible fine colluvium remained on the hillslope after the first rainstorm 30 min maximum rainfall intensity 7 2 mm h 1 in the volcanic terrain the erosion response in channels and on hillslopes of the granitic and volcanic terrains was similar when compared using erodibility efficiencies

autogenic microbial genesis of middle miocene palustrine ooids nullarbor plain australia abstract miocene palustrine ooids located in the nullarbor plain southern australia illustrate the importance of microbes and soil processes in the formation of these spherically laminated grains in pedogenic settings these particles are composed of dense minimicrite and include a wide assortment of microbially produced structures such biogenicity includes interpreted extracellular polymers eps algal filaments palygorskite and sepiolite nano fiber mats bacterial spores and meniscate fabrics ooid nuclei are peloids that are interpreted to have formed via microbial binding of lacustrine sediment in a subsequent palustrine environment both at the surface and inside underlying karst cavities the peloids are encapsulated in multigenerational micrite laminations that form the spherical cortex individual cortical laminae are made up of degraded minimicrite crystals and complex encrusting mats of palygorskite and sepiolite nano fibers cortex generation is interpreted to have been an annual process involving alternating soil hydration states in this conceptual model during the wet season ooids were covered in bacterial mucus that bound ions from solution and produced hydrated mg si gels that evenly surrounded the entire ooid gel dehydration during the following dry season resulted in precipitation of fibrous palygorskite and sepiolite succeeding seasonal variations in moisture produced numerous laminae that ultimately resulted in a multigenerational ooid cortex this annual microbial process provides a new mechanism involving an autogenic formation of ooids that may be applied to a wide variety of pedogenic sediments unlike the more common marine ooids that require constant movement to achieve cortical precipitation the process of grainification combined with microbially mediated mineral precipitation under different soil hydration states results in the in place formation of terrestrial ooids

hyperbolic spiral model for predicting reverse fault ruptures in sand based on centrifuge tests fault deformation can cause severe damage to structures located within the fault zones a logarithmic spiral model was developed by d a cole and p v lade in 1984 to predict the shapes and locat

paleoclimate of the kimmeridgian tithonian late jurassic world i results using a general circulation model abstract the kimmeridgian tithonian 154 7 145 6 ma middle and late late jurassic was a time of expanded continental rifting increased sea floor spreading and a relatively high eustatic sea level stand these processes collectively caused the fragmentation and flooding of the megacontinent pangea as well as the alteration of the global paleoclimate using a version of the community climate model ccm from the national center for atmospheric research we report two kimmeridgian tithonian paleoclimate seasonal simulations with geologically inferred paleotopography one using a co 2 concentration of 280 ppm pre industrial level and the other 1120 ppm increasing the co 2 four fold warms virtually the entire planet the greatest warming occurs over the higher latitude oceans and the least over the equatorial and subtropical regions simulation of a warmer planet with an elevated greenhouse effect fits the distribution of paleoclimatically sensitive faunas floras and sedimentary rocks model results indicate that sea ice was restricted to the high latitudes of the boreal and austral seas making landfall only in restricted areas the trade winds bring heavy rainfall in december january february to eastern gondwana and in june july august to the tethys sea margins a strong june july august monsoon occurs over southeast asia the distribution of coals correlates to precipitation sufficient to maintain gymnosperm forests and coastal areas where water saturated sediments are a result of eustatic high stands of sea level evaporites are localized to areas of negative precipitation evaporation runoff is restricted to regions of intense precipitation overall the 1120 ppm co 2 simulation provides a reasonable paleoclimate for the kimmeridgian tithonian and provides a standard until a ccm with oceanic heat transport a coupled atmospheric oceanic model or one with a finer grid cell configuration is available the results need further scrutiny in areas with more detailed geologic information

constraining the relative importance of raindrop and flow driven sediment transport mechanisms in postwildfire environments and implications for recovery time scales national geographic society proposal002929 2009 0046 1 national science foundation 02 39749 09 34131 u s geological survey usgs landslide hazards program

evolution of the surface deformation profile and subsurface distortion zone during reverse faulting through overburden sand abstract the 2d distinct element method was used to investigate the propagation of fault rupture traces through overlying sand during reverse faulting along a range of dip angles and at different vertical throws calibrated micromechanical material parameters were used in the numerical simulations which were validated through a comparison of the simulation results with those obtained from a centrifuge experiment involving acceleration at 80 g the gompertz sigmoid function with three parameters provided the best fit to the normalized surface deformation profiles obtained both from the numerical simulation and from centrifuge experiments the three parameters that characterized the gompertz sigmoid function were the normalized scarp height the maximum slope on the scarp and the location of the reverse fault outcropping a surface deformation profile slope of 1 150 was used as the setback criterion the normalized affected width and fault outcrop relative to the fault tip were determined for reverse faults having a variety of dips and throws the dip angle significantly affected the kinematic mechanism underlying reverse faulting at a given vertical throw the scarp height increased as the dip angle decreased in the cases of 45 as the dip angle decreased the location of the fault outcropping shifted toward the footwall and the maximum slope on the scarp increased the horizontal displacement played a significant role at low dip thrusts 22 5 30 37 5 a back thrust fault developed and an inverted triangle wedge formed in the subsurface

lacustrine carbonate reservoirs from early cretaceous rift lakes of western gondwana pre salt coquinas of brazil and west africa abstract barremian aptian lower cretaceous pre salt lacustrine carbonates host large petroleum reservoirs in south atlantic rift basins yet remain poorly studied in part due to the scarcity of lacustrine carbonate reservoirs throughout the geological record this review provides an integrated discussion of the current state of knowledge on the coquina play having been deposited in extensive rift lakes during the early stages of the opening of the south atlantic thick successions of coquina are recorded from the santos to sergipe alagoas basins and the kwanza to gabon basins on the brazilian and west african continental margins respectively coquinas exhibit similarities in depositional processes across the south atlantic however have distinct diagenetic histories and stratigraphic stacking patterns having been deposited in lakes with different geologies climates and water chemistries west african coquinas exhibit depositional characteristics that are indicative of deposition on distally steepened ramps and rimmed platforms and accordingly facies are somewhat different to those in brazilian basins which were deposited on low angle ramps as petroleum exploration continues into ultra deep waters on the brazilian and west african margins accurate facies models will be important for the predictability of carbonate reservoir intervals to this end onshore outcrop in the sergipe alagoas basin has revealed that the molluscan faunas have marine origins suggesting that facies patterns may be more complex than previously considered it is hoped that this review will provide the impetus for further research on the coquinas especially given the presence of poorly studied easily accessible onshore outcrops

post fire hillslope debris flows evidence of a distinct erosion process abstract after wildfire a hitherto unexplained erosion process that some authors have called miniature debris flows on hillslopes and that leave behind levee lined rills has been observed in some regions of the world despite the unusual proposition of debris flow on planar hillslopes the process has not received much attention the objectives of this study were to 1 accumulate observational evidence of hillslope debris flows hdf as we have defined the process to 2 understand their initiation process by conducting runoff experiments on hillslopes to 3 propose a conceptual model of hdf and to 4 contrast and classify hdf relative to other erosion and transport processes in the post wildfire hillslope domain hdf have been observed at relatively steep slope gradients 0 4 0 8 on a variety of geologies and after fire of at least moderate severity and consist of a lobe of gravel to cobble sized material 0 2 1 m wide that is pushed by runoff damming up behind it during initiation runoff moved individual particles that accumulated a small distance downslope until the accumulation of grains failed and formed the granular lobe of the hdf hdf are a threshold process and runoff rates of 0 5 l s 1 2 l s 1 were required for their initiation during the experiments the conceptual model highlights hdf as a geomorphic process distinct from channel debris flows because they occur on planar unconfined hillslopes rather than confined channels hdf can erode very coarse non cohesive surface soil which distinguishes them from rill erosion that have suspended and bedload transport on a matrix of slope and grain size hdf are enveloped between purely gravity driven dry ravel and mostly runoff driven bedload transport in rills

shell beds as tools in basin analysis the jurassic of kachchh western india skeletal concentrations are ubiquitous in bathonian oxfordian shallow water sediments of the pericratonic basins of kachchh and rajasthan western india by analysing the biofabric of the concentrations and the taphonomic signatures of individual components it is possible to distinguish between the final concentration process recorded by the biofabric and events taking place prior to final deposition recorded by taphonomic signatures the skeletal concentrations are grouped in nine genetic types ranging from fair weather wave concentrations to storm concentrations and condensed concentrations they mainly reflect biological and hydraulic processes and in some instances permit estimates of their duration and show a rough zonation along a bathymetric gradient plotted against the stratigraphic sections the skeletal concentrations show in accordance with other sedimentological data three orders of bathymetric trends the first two orders are shallowing deepening cycles which possibly correspond to eustatic changes in sea level the third order represents parasequences with a strongly asymmetric sedimentary record skeletal concentrations are a useful additional tool in basin analysis but are best used in combination with other data

prediction of spatially explicit rainfall intensity duration thresholds for post fire debris flow generation in the western united states abstract early warning of post fire debris flow occurrence during intense rainfall has traditionally relied upon a library of regionally specific empirical rainfall intensity duration thresholds development of this library and the calculation of rainfall intensity duration thresholds often require several years of monitoring local rainfall and hydrologic response to rainstorms a time consuming approach where results are often only applicable to the specific region where data were collected here we present a new fully predictive approach that utilizes rainfall hydrologic response and readily available geospatial data to predict rainfall intensity duration thresholds for debris flow generation in recently burned locations in the western united states unlike the traditional approach to defining regional thresholds from historical data the proposed methodology permits the direct calculation of rainfall intensity duration thresholds for areas where no such data exist the thresholds calculated by this method are demonstrated to provide predictions that are of similar accuracy and in some cases outperform previously published regional intensity duration thresholds the method also provides improved predictions of debris flow likelihood which can be incorporated into existing approaches for post fire debris flow hazard assessment our results also provide guidance for the operational expansion of post fire debris flow early warning systems in areas where empirically defined regional rainfall intensity duration thresholds do not currently exist

characterizing the primary material sources and dominant erosional processes for post fire debris flow initiation in a headwater basin using multi temporal terrestrial laser scanning data abstract wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce hazardous debris flows relative to shallow landslides the primary sources of material and dominant erosional processes that contribute to post fire debris flow initiation are poorly constrained improving our understanding of how and where material is eroded from a watershed during a post fire debris flow requires 1 precise measurements of topographic change to calculate volumetric measurements of erosion and deposition and 2 the identification of relevant morphometrically defined process domains to spatially constrain these measurements of erosion and deposition in this study we combine the morphometric analysis of a steep small 0 01 km 2 headwater drainage basin with measurements of topographic change using high resolution 2 5 cm multi temporal terrestrial laser scanning data made before and after a post fire debris flow the results of the morphometric analysis are used to define four process domains hillslope divergent hillslope convergent transitional and channelized incision we determine that hillslope divergent and hillslope convergent process domains represent the primary sources of material over the period of analysis in the study basin from these results we conclude that raindrop impact induced erosion ravel surface wash and rilling are the primary erosional processes contributing to post fire debris flow initiation in the small steep headwater basin further work is needed to determine 1 how these results vary with increasing drainage basin size 2 how these data might scale upward for use with coarser resolution measurements of topography and 3 how these results change with evolving sediment supply conditions and vegetation recovery