site investigations to evaluate flow liquefaction slides at sand heads fraser river delta l ecoulement par liquefaction spontanee est un processus recurrent dans la progradation du delta du fleuve fraser une portion du delta a ete etudiee au moyen d essais de penetration au cone sismique et de resistivite et au moyen de l analyse spectrale de la methode des ondes de surface et de l echantiollonage de sol et de vapeur dans un effort pour determiner la stratigraphie du site l etat in situ et le degre de saturation afin explorer l enigme de l ecoulement par liquefaction spontanee un ensemble de capteur de pression interstitielle et d inclinaison a ete installe comme partie de l etude pour mesurer les effets de la vidange resultant du reflux de la maree les resultats ont indique que le lit de la mer a faible profondeur etait partiellement sature contenant un volume significatif de gaz methane qui affectait la reponse dynamique de la pression interstitielle durant le jusant une reduction de la contrainte effective atteignant 16 5 kpa a ete mesuree de meme qu un delai de 50 min entre le reflux de la maree et la reaction de la pression interstitielle ceci suggere que les effets de tampon sont un facteur significatif dans le declenchement de la liquefaction spontanee des sables l ches non viellis la ou ils reposent sur des pentes sous marines les resultats des essais in situ montrent que les sables nouvellement deposes du fleuve fraser ont une forte susceptibilite a l ecoulement par liquefaction

spatial analysis of channel belt stacking patterns metrics to discriminate between local and regional controls on deposition in the fluvial john henry member of the straight cliffs formation southern utah u s a the john henry member jhm of the straight cliffs formation exposed along the kaiparowits plateau provides a record of 6 my of coastal plain to marginal marine deposition to better understand the mechanisms influencing the alluvial architecture of the jhm a detailed quantitative characterization of the stratigraphic organization and stacking patterns of fluvial channel belt sandstone bodies was performed techniques of point pattern analysis were applied on three datasets consisting of 136 228 and 55 channel belts collected from two outcrops in bull canyon and one outcrop in rock house cove both localities are in the southwestern kaiparowits plateau the results reveal two major trends in the spatial organization of channel belts through time starting with a trend of decreasing channel belt clustering from the lower to middle stratigraphic interval followed by a reversed trend of increasing channel belt clustering in the upper interval furthermore up section changes in channel belt clustering exhibit strong similarities across the three outcrops as indicated by a correlation analysis based on dynamic time warping trends of consistent channel belt clustering in bull canyon and rock house cove are interpreted to be mainly the product of changing allogenic conditions influencing autogenic processes correlation of clustering trends with reconstructed paleo hydraulic conditions and previously measured architectural parameters suggests that significant channel belt clustering likely reflects the combined influence of two major factors 1 low aggradation rates driven by reduced accommodation and 2 high avulsion frequency where channels are deposited downstream of a backwater mediated nodal avulsion point a scale dependent clustering analysis using the k function indicates that channel belts are clustered at small length scales 10 to 50 m and random or uniform at larger length scales 60 m small scale clustering is interpreted to be the product of autogenic avulsion reoccupation where abandoned channels that are preserved as topographic lows serve as attractors to new avulsion paths and lead to channel persistence conversely the large scale pattern of randomness and or uniformity reflects periodic large scale shifts in the local depocenter as a result of avulsion driven compensational stacking of channel belts

interactions between axial and transverse drainage systems in the late cretaceous cordilleran foreland basin evidence from detrital zircons in the straight cliffs formation southern utah usa new detrital zircon geochronologic data from the straight cliffs formation of southern utah provide insight into the controls on stratigraphic architecture of the western interior basin during turonian early campanian time detrital zircon ages n 40 n 3650 derived from linked fluvial and shallow marine depositional systems of the kaiparowits plateau indicate the majority of zircons in fluvial strata were derived from the mogollon highlands 1 25 1 90 ga 67 of fluvial zircons with subordinate contributions delivered from the sevier fold and thrust belt 265 1250 ma 17 and cordilleran magmatic sources 81 265 ma 16 integration of these data with fluvial facies distributions petrography clast counts and evidence of magmatic arc sources from the mohave region of california implies the presence of a northeast flowing axial fluvial system this system was fed by rivers draining the mogollon highlands to the south and by transverse drainages from the sevier fold and thrust belt to the west compared to the fluvial deposits shallow marine sandstones have a greater proportion of sevier fold and thrust belt derived zircons 42 which were delivered via longshore currents from the north shallow marine samples also contain less mogollon input 44 compared to contemporaneous fluvial systems and similar input from the magmatic arc 14 although proterozoic zircons associated with the mogollon highlands are also present in the sevier fold and thrust belt several lines of evidence argue for a distinct southerly source for the straight cliffs formation these include 1 moderate proportions of feldspar and angular quartz grains in fluvial sandstones which favor a felsic intrusive source and 2 prominent 1 4 and 1 7 ga zircon populations the 1 4 and 1 7 ga peaks are the only dominant proterozoic peaks in samples from the straight cliffs formation whereas samples derived more directly from the sevier fold and thrust belt tend to have a broader distribution of proterozoic age peaks up section architectural trends in the straight cliffs formation are linked to trends in detrital zircon geochronologic data underscoring the likelihood of common drivers and controls the axial system depositing straight cliffs fluvial strata was primarily fed by drainages originating in the mogollon highlands during a pulse of tectonic activity in the maria fold and thrust belt and generally high subsidence rates in the foreland basin turonian santonian over time activation of the paxton duplex in the sevier fold and thrust belt early campanian exhumed proximal foreland basin strata and enabled drainage systems from the sevier fold and thrust belt to feed into the basin more prominently the results presented here underscore the potential significance of axial fluvial systems and their complex interplay with transverse drainage networks in foreland basins

the architectural variability of small scale cycles in shelf and ramp clastic systems the controlling factors many sedimentary successions are composed of metre to decametre scale cycles exhibiting various stratal architectures that depend on the complex interplay among several syndepositional controlling factors these controlling factors may produce extremely different stratal and facies architectures along relatively brief distances in the same basin but in contrast they also may form similar architectures in basins that experience a radically different tectonic setting the recognition of factors that controlled the architecture of small scale cycles therefore is very important to reconstruct the depositional history of sedimentary successions these factors include 1 the interplay between the rate of accommodation development and the rate of sediment supply a s 2 the amplitude and shape of the relative sea level curve 3 the position in the shoreface shelf system 4 the basin physiography 5 the shoreline trajectory 6 the climate driven environmental energy 7 the siliciclastic input vs carbonate production shoreface to shelf small scale cycles can be grouped into three main categories r cycles showing a dominant regressive interval t r cycles with transgressive and regressive intervals of similar thickness t cycles showing a dominant transgressive interval although some depositional settings may favour the deposition of a particular type of cycle these cycle motifs appear to be mainly controlled by the interaction of local and wider scale controlling factors for example t cycles may be present in both subsiding and uplifting settings depending on the interplay between the a s and the other factors cited above as a result r t r and t cycles may be recognized within the same depositional system these evidences suggest that care must be taken to apply general models that predict the stratal architecture of cycles mainly in function of the long term a s the correct prediction of the cycle architecture is important also for hydrocarbon researches as the thickness of potential reservoir deposits is the result of the interplay among factors discussed here

experimental results on the influence of gas on the mechanical response of peats direct observation of gas in peat layers generated by slow degradation in anoxic conditions raised concern in the netherlands about its potential impact on the geotechnical response of dykes foun

symmetrical and upward shallowing cycles in the middle devonian of new york state and their implications for the punctuated aggradational cycle hypothesis the middle devonian eifelian and givetian hamilton group in western and central new york composed largely of fossil rich marine shelf and slope facies is subdivisible into repetitive facies sequences of varying thicknesses minor cycles include 1 to 3 m thick upward coarsening shale to siltstone hemicycles resembling sixth order punctuated aggradational cycles pacs in central new york probably correlative 0 5 1 0 m shale to argillaceous nodular limestone couplets occur in western areas major cycles in western new york include subsymmetrical 3 to 5 m thick packages with medial limestone beds analogous to upper limestones of pennsylvanian cyclothems the center of each cycle marks a regressive maximum and grades vertically above and below into black shale or dark gray mudstone corresponding in a facies sense to cyclothemic core shales in the midcontinent pennsylvanian these widespread units appear to be allocyclic in nature and approximate fifth order transgressive regressive cycles based upon average unit thickness relative to the encompassing well zoned hamilton sequence correlations show that most key regressive events marked by limestones in western new york are expressed by equivalent siltstone or fine sandstone units in central new york most cycles which are nearly symmetrical in western new york grade eastward into 5 to 20 m upward coarsening pac motif hemicycles these asymmetric cycles apparently reflect rapid sediment aggradation to limits imposed by wave energy in a region of abundant sediment supply further minor shallowing was accompanied by winnowing and bypass of fine grained sediments generating condensed capping deposits of coarser silt and sand reworked shells and commonly phosphatic nodules ensuing sea level rises were accompanied by initial sediment starvation followed by sedimentation in deeper water hence asymmetrical upward shallowing hemicycles pacs appear to grade offshore into thin but symmetrical cycles both pac and symmetrical motifs are local responses to the same probably allocyclic sea level fluctuations we suggest that the pac motif is partially facies controlled being largely restricted to shallow shelf settings with relatively high rates of sediment accumulation

architecture and trace fossil characteristics of a 10 000 20 000 year fluvial to marine sequence se ebro basin spain abstract the eocene sant llorenc del munt fan delta complex lies on the southeastern edge of the ebro basin in ne spain alluvial fans and fan deltas prograded northwestwards from the catalan coastal range to form a series of clastic wedges that were interrupted by marine transgressions of period varying from 60 000 to a few hundred years resulting in a highly cyclic succession the cyclicity of the succession was controlled by a combination of syndepositional basin margin tectonics high sediment supply and eustatic sea level changes analysis of one of the component 25 40 m thick transgressive to regressive sequences 10 000 20 000 year duration shows that within its transgressive part the alluvial and coastal plain deposits are extensive and thickly developed whereas shoreline lithosomes are narrow and thin in the overlying regressive part the opposite relationship is documented the transgressive and regressive tracts thus have an overall landward expanding and seaward expanding geometry respectively six ichnofabrics have been documented in the succession ranging from nonmarine to offshore transition in origin these ichnofabrics are used to help define sequence boundaries flooding surfaces and maximum flooding surfaces as well as to increase the resolution of the stratigraphic analysis within the transgressive tract of the main sequence nonmarine deposits are separated from marine deposits by a steep landward inclined complex of wave ravinement surfaces successive ravinement surfaces have a vertical spacing of about a meter are offset landwards from each other by less than 100 m and diverge slightly from each other as they climb through the section these same erosion surfaces merge with each other basinwards causing the transgressive tract to thin significantly five high frequency sequences are recognized within the main sequence the middle one is nearly symmetrical the lower two are asymmetric and dominated by their transgressive tract and the upper two are asymmetric but dominated by their regressive tract

characteristics of a tonian reef rimmed shelf before the onset of cryogenian insights from neoproterozoic kunihar formation simla group lesser himalaya abstract the kunihar formation records evolution of a unique rimmed shelf during the tonian before the cryogenian marinoan glaciation of krol formation lesser himalaya the mixed siliciclastic carbonate system of neoproterozoic kunihar formation provokes interest for outcrop based facies analysis and sequence stratigraphy in order to frame a better understanding on the mechanism and control of its deposition the formation records a 450 m thick mixed siliciclastic carbonate rimmed shelf five facies associations have been identified peritidal fa1 lagoonal fa2 barrier island ooidal shoal fa3 reef complex fa4 and fore reef fa5 facies associations two systems tracts were delineated transgressive tst and highstand hst systems tracts tst is marked by dominant aggradation of stromatolitic carbonates while siliciclastic incursion surpassed carbonate deposition during highstand it conforms to the lower carbonate upper clastic model of mixed siliciclastic carbonates during the precambrian reef rimmed shelves were considered more abundant in the archaean and palaeo mesoproterozoic this study determines that development of rimmed shelves was more common during the neoproterozoic than previously speculated neoproterozoic reef rimmed shelves are concentrated more within the cryogenian and ediacaran period stromatolitic reef rimmed shelf of kunihar formation is the only rimmed shelf recorded in the tonian period till date increased microbial stromatolitic accretion was propelled by surge in nutrients due to chemical weathering of underlying tholeiitic basalt darla volcanics associated with the rifting of supercontinent rodinia with increasing interest of tonian cryogenian transition as a key period in both planetary and organic evolution kunihar formation represents a terminal reef rimmed shelf system that evolved due to microbial stromatolites in the absence of complex organisms subsequent to this cryogenian and ediacaran biota took over as the dominant reef builders

characteristics of the displacement of a landslide with shallow sliding surface in a heavy snow district of japan the displacement of a landslide with shallow sliding surface in a heavy snow district was automatically monitored for over 4 years by a newly developed displacement gauge meteorological properties meltwater and or rainfall mr water equivalent of snow and other factors were simultaneously observed pore water pressure was monitored but only for a limited period of time since the displacement of the landslide was too large statistical analyses showed that maximum daily displacements of each year were observed not in snow melting periods but immediately before or at the beginning of a snow cover period there are three types of annual variation pattern with peaks in mid november to mid december mid april and mid july the variation pattern of displacement from the beginning of march to the beginning of june showed the least total displacement of those three types therefore snow cover is likely to affect the displacement of a landslide detailed investigation of the landslide displacement during snow cover periods showed that the rate of displacement slowed as the snow cover deepened meaning a decrease in mr and increase in water equivalent of snow the displacement ratio for the unit antecedent mr effect during snow cover periods dropped when the snow started to accumulate on the ground in all 4 years the reduction was likely attributable to snow load since it was found to have a negative logarithmic relation with the water equivalent of snow changes in pore water pressure and the relationship between pore water pressure and displacement during the snow cover periods differed from those in the other periods therefore the displacement of a landslide that has a shallow sliding surface in a snowy region was considered to be affected by snow accumulation conditions especially water equivalent of snow

undrained responses of microbially desaturated sand under monotonic loading abstractdesaturation is a method for the mitigation of liquefaction of sand this method has gained increasing interest in recent years as it may become a more cost effective solution than many conventional methods in this paper a microbial denitrification process was adopted to generate nitrogen gas for desaturation of sand this approach offers several advantages first nitrogen gas does not dissolve in water easily second nitrogen gas is chemically inert third as the gas is generated in situ its distribution is also more uniform fourth the gas bubbles generated by the microbial process are tiny and thus the potential of escaping from the ground is less in this paper undrained triaxial compression and extension tests were adopted to evaluate the liquefaction behavior of sand desaturated using nitrogen under static monotonic loading conditions test results show that under an undrained axisymmetric condition when the degree of saturation of loose sand is reduced from 100 to a range of 95

tectonic control of high frequency depositional sequences with durations shorter than milankovitch cyclicity an example from the pleistocene paleo tokyo bay japan forcing mechanisms of high frequency depositional sequences in late cenozoic successions have commonly been interpreted in terms of glacio eustasy in contrast we demonstrate here the effects of local tectonics in the development of high frequency depositional sequences in a middle and upper pleistocene succession examples are from shallow marine and coastal deposits developed in the paleo tokyo bay japan and are based on a detailed chronostratigraphic framework constructed from dated volcanic ash beds within highstand successions of the glacio eustatic sequences we have mapped locally developed high frequency depositional sequences within areas that have undergone anticlinal uplift these high frequency depositional sequences pass laterally into parasequences overlying marine flooding surfaces in adjacent synclinal areas spatial variation in such stratigraphic features indicates local tectonic movements in the paleo tokyo bay area during rises and highstands of glacio eustatic sea level cycles the duration of such high frequency depositional sequences is estimated as 10 k y shorter than milankovitch cyclicity the present example indicates that local basin tectonics can be an important forcing mechanism of high frequency depositional sequences in pleistocene successions in an active margin basin

late cretaceous climate changes recorded in eastern asian lacustrine deposits and north american epieric sea strata abstract cretaceous climate data of the long lived cretaceous songliao basin sb in eastern asia is correlated and compared with the western interior seaway wis on the northern american plate in order to understand better the dynamics of the earth s past greenhouse climates nearly continuous late cretaceous terrestrial deposition in the songliao basin is represented by two cores totaling 2431 m in length the turonian maastrichtian age of the section is based on integrated stratigraphy and is comparable in age with upper cretaceous strata in the wis being consistent with global trends the dynamic late cretaceous climates of both the sb and wis gradually cooled from the warmest albian cenomanian time to the end of the maastrichtian with several intervening warm periods as did the global climate however regional differences existed the songliao basin climate was humid to semi humid warm temperate subtropical and the western interior seaway was in the humid warm temperate zone and experienced only moderate climatic changes the shifts of oxygen isotope data in the songliao basin were frequent and abrupt whereas wis records more gradual change affected mainly by fresh water runoff mixing with southern tethyan and northern arctic waters sedimentary cycles of eccentricity obliquity and precession bands are recorded in both the sb and wis basins the sedimentary cycles in the wis and sb are interpreted to be related to variations of the wet dry runoff cycles which indicate that orbital forcing played an important role in global climate change in late cretaceous the most favorable condition for organic carbon burial in both the sb and wis basin was bottom water anoxia regardless of the cause of the anoxia but the organic carbon burial rate was usually much higher in the songliao lake than in the wi epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric co 2 in both basins organic rich deposits formed during a rise in water level and incursion of saline waters the integration of paleoclimate data from cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the cretaceous greenhouse climate change and may provide insights for a future greenhouse world

the undrained shear strength of soils containing large gas bubbles measurements of undrained shear strength are reported from a series of triaxial tests on reconstituted soil samples containing large bubbles of methane gas the experimental results indicate that the undrained strength can be either increased or reduced by the presence of large gas bubbles depending upon the values of the consolidation pressure and the initial pore water pressure a conceptual model for soils containing large gas bubbles developed in the companion paper is analysed to provide theoretical predictions for the undrained shear strength the analysis leads to theoretical upper and lower bounds for the undrained strength which show good agreement with the experimental data the experimental and theoretical developments have led to a better understanding of the strength of soils containing large gas bubbles this could be of considerable benefit to the offshore construction industry if platforms pipelines and other structures are to be built in areas of gas bearing sediments l article pre

the undrained equilibrium behaviour of gassy sediments gassy soils are defined as those soils which contain a relatively large amount of gas dissolved in the pore fluid examples include the alberta oil sands marine sediments from deep ocean locations

the behavior of loose gassy sand methane gas found in loose deltaic deposits can contribute to the triggering of flow liquefaction of submarine slopes the behavior of loose gassy sand is studied in the laboratory using monotoni

evaluation of the in situ state of fraser river sand les glissements de type coulee par liquefaction sont des phenomenes qui arrivent souvent dans le delta de la riviere fraser du cote de sand heads ces ruptures n ont pas trouve d explication et leurs causes restent du domaine de la speculation l etude d un tel glissement ayant eu lieu en 1985 dans la riviere fraser a proximite de sand heads a ete entreprise en utilisant les concepts d etats stationnaires pour qu un glissement par coulee impliquant la liquefaction de depots de sables puisse prendre place le sable doit presenter un ramollissement lors du cisaillement non draine et les contraintes de cisaillement en place doivent etre superieures a la resistance non drainee mobilisable on a effectue des essais de laboratoire sur des echantillons reconstitues de sable de la riviere fraser de facon a etablir les parametres d etat stationnaire les specimens de sol ont ete prepares par compaction humide et pluviation dans l eau des mesures de vitesse de propagation des ondes de cisaillement ont ete utilisees pour evaluer l etat en place des depots de sable recents et non cimentes on a trouve que l etat en place des depots recents au voisinage de sand heads se situait du cote l che de l etat stationnaire ce qui correspond aux instabilites observees sur le site

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

late cretaceous fluvial megafan and axial river systems in the southern cordilleran foreland basin drip tank member of straight cliffs formation and adjacent strata southern utah u s a abstract the upper cretaceous lower campanian drip tank member of the straight cliffs formation in the grand staircase region of southern utah is an upward coarsening sandstone rich low sinuosity fluvial deposit in the cordilleran foreland basin the drip tank member thins from 75 m to 30 m eastward across the basin foredeep approximately parallel to its dominant eastward sediment dispersal direction and thins southward along the foredeep to as little as 17 m near its southern outcrop extent along modern cliff lines it overlies and underlies mudstone rich fluvial strata of the john henry member of the straight cliffs formation and lower member of the wahweap formation respectively both of which were deposited by northeast flowing rivers the john henry drip tank contact lies in an interfingering progradational stratigraphic transition from medium grained lenticular sandstone bodies to tabular coarse grained amalgamated sandstone bodies the contact with the overlying wahweap formation is locally a prominent surface of erosion or sediment reworking sandstone petrography and detrital zircon age populations of the strata indicate detrital sources in basement south of the foreland basin thrust sheets to the west and magmatic arc rocks to the southwest the uppermost part of the john henry member contains as much as 10 feldspar and abundant 1 84 1 60 ga detrital zircons derived from yavapai mazatzal basement rocks in the mogollon highlands the drip tank member ranges from quartzarenite to chert bearing sublitharenite with grenville 1 2 1 1 ga neoproterozoic and early paleozoic detrital zircons derived from proterozoic through jurassic strata exposed in the sevier orogenic belt lower member wahweap litharenites contain abundant thrust belt derived detrital carbonate grains absent from compositionally mature drip tank sandstones as well as a broad range of zircon ages the drip tank member constitutes deposits of a sand rich fluvial megafan or distributive fluvial system that displaced a subjacent but partly time equivalent axial fluvial system eastward as the megafan driven in part by seasonally high discharge fed by monsoonal precipitation prograded across the basin foredeep a thick amalgamated fan axis succession present in northern exposures contrasts with a thinner fan flank succession in southern localities tabular sixth order lithosomes each containing channels on the order of 7 m deep define three individual fluvial fans or fan lobes in the megafan system younger wahweap fluvial channels eroded uppermost drip tank deposits of the fan axis and fan flank transverse fan progradation across the foredeep recorded falling accommodation sediment supply in an aggradational to progradational systems tract erosion and reworking of the upper fan surface record decreased accommodation sediment bypass and erosion prior to reoccupation of the foredeep by the wahweap axial fluvial system the upper contact of the drip tank member is thus the primary sequence boundary in this multi component fluvial system and the lower wahweap represents transitional systems tract deposits accumulated as accommodation sediment supply increased

optimizing photogrammetric dems for glacier volume change assessment using laser scanning derived ground control points photogrammetric processing of archival stereo imagery offers the opportunity to reconstruct glacier volume changes for regions where no such data exist and to better constrain the contribution to sea level rise from small glaciers and ice caps the ability to derive digital elevation model dem measurements of glacier volume from photogrammetry relies on good quality well distributed ground reference data which may be difficult to acquire this study shows that ground control points gcps can be identified and extracted from point cloud airborne lidar data and used to control photogrammetric glacier models the technique is applied to midtre lovenbreen a small valley glacier in northwest svalbard we show that the amount of ground control measured and the elevation accuracy of gcp coordinates based on known and theoretical error considerations has a significant effect on photogrammetric model statistics dem accuracy and the subsequent geodetic measurement of glacier volume change models controlled with fewer than 20 lidar control points or gcps from sub optimal areas within the swath footprint overestimated volume change by 14 53 over a 2 year period dems derived from models utilizing 20 25 or more gcps however gave volume change estimates within 4 of those from repeat lidar data 0 51 m a 1 between 2003 and 2005 our results have important implications for the measurement of glacier volume change from archival stereo imagery sources

late cretaceous subsidence in wyoming quantifying the dynamic component the late cretaceous western interior basin of north america is generally considered to have been a retroarc foreland basin flexural backstripping of the stratigraphic record from 97 2 ma to 73 4 ma along a section perpendicular to the wyoming idaho salient of the sevier belt clearly demonstrates that there were components of subsidence in addition to those driven by the thrust and associated sediment loads the simulation demonstrates that the flexural foredeep is only 180 120 km wide and shows a forebulge located near the subsequent laramide rock springs uplift foredeep strata between the rock springs uplift on the east and the thrust front to the west were mostly involved in the eastward overlapping thrust belt or deeply truncated by inferred rebound after 78 5 ma the difference between the observed decompacted cumulative subsidence and the amount of subsidence that can be explained by simple flexural loading the residual subsidence increases from 800 m in eastern wyoming to 1 8 km near the thrust belt the westward thickening upper cretaceous sediment wedge filled the accommodation space generated by downward tilting to the west of the north american cratonic margin by underplating and mantle flow associated with the shallowly subducted farallon plate

elastic moduli of soils containing large gas bubbles a conceptual model for soils containing large gas bubbles is analysed to provide theoretical expressions for the drained and undrained elastic moduli experimental values of the undrained moduli measured in triaxial tests at large strains show little agreement with the theoretical predictions this lack of agreement is probably caused by concen trated local plastic straining which is likely to occur in soils containing gas bubbles at all but the smallest strains the undrained behaviour at very small strains as represented by acoustic measure ments of the compression wave velocity shows much better agreement with the theoretical predictions improved understanding of the small strain behaviour of soils containing large gas bubbles could he of considerable benefit to the offshore industry for predicting the deformation of foundations constructed on gas hearing sediments on analyse un modele conceptuel pour des sols cootenant de grandes bulles de gaz afin d obtenir des expressions theoriques pour l

seabed instability due to flow liquefaction in the fraser river delta les ruptures par liquefaction de depots de sables l ches peuvent representer une menace importante pour les structures cotieres on a evalue a partir des concepts d etats stationnaires les contributions possibles de divers mecanismes de declenchement lors d une rupture par liquefaction qui a eu lieu en 1985 a l embouchure du chenal principal de la riviere fraser parmi les mecanismes qui ont pu declencher le glissement par liquefaction en 1985 on a etudie la sedimentation les vagues de surface et les marees basses l analyse montre qu une sedimentation rapide genere des contraintes de cisaillement dans la pente mais ne pourrait pas faire demarrer des ruptures par liquefaction lorsqu on evalue l effet des vagues de surface et leur capacite a causer des glissements de type coulee profonde on trouve qu il ne s accumule pas de pressions interstitielles significatives dues aux vagues de surface pouvant exister dans la region les marees basses ne peuvent pas non plus declencher de rupture dans des sables submerges et completement satures l apparition de gaz provoque cependant la desaturation des sediments ce qui peut induire des pressions interstitielles residuelles pendant les marees basses on emet donc l hypothese que c est la combinaison de sediments l ches de faibles quantites de gaz et de marees basses qui favorise les ruptures par coulees liquefiees dans le delta ces ruptures conduisent a des glissements regressifs

liquefaction flow of submarine slopes under partially undrained conditions an effective stress approach the stability of submarine slopes is commonly assessed based on undrained soil response liquefaction flow may occur when pore pressure rise in soil elements under constant shear stress causes a reduction in effective stresses recent experimental studies have shown that a small net flow of water into an element results in additional pore pressure generation and further reduces its strength as a result soil elements can liquefy due to expansive volumetric strains that cannot be predicted by undrained analysis submarine deposits of the fraser river delta are known to contain high concentrations of methane gas tidal variations can cause unequal pore pressure generation with depth and time in these soils such changes reduce the effective stresses during low tides and may induce liquefaction flow of slopes due to partial drainage conditions an effective stress approach based on an elastic plastic stress strain relationship is presented to model liquefaction flow of sand a fully coupled analysis is carr

on the use of fredlund gas fluid compressibility relationship to model medium dense gassy sand behavior this paper presents the influence of gas bubbles trapped in a soil mass on the stress strain strength response of medium dense sands a hypoplastic constitutive sand model enhanced with the intergr

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

the potential of small unmanned aircraft systems and structure from motion for topographic surveys a test of emerging integrated approaches at cwm idwal north wales novel topographic survey methods that integrate both structure from motion sfm photogrammetry and small unmanned aircraft systems suas are a rapidly evolving investigative technique due to the diverse range of survey configurations available and the infancy of these new methods further research is required here the accuracy precision and potential applications of this approach are investigated a total of 543 images of the cwm idwal moraine mound complex were captured from a light b5 kg semi autonomous multi rotor unmanned aircraft system using a consumer grade 18 mp compact digital camera the imageswere used to produce a dsm digital surfacemodel of themoraines the dsmis in good agreement with 7761 total station survey points providing a total verticalrmse value of 0 517mand verticalrmse values as lowas 0 200mfor less densely vegetated areas of the dsm high precision topographic data can be acquired rapidly using this technique with the resulting dsms and orthorectified aerial imagery at sub decimetre resolutions positional errors on the total station dataset vegetation and steep terrain are identified as the causes of vertical disagreement whilst this aerial survey approach is advocated for use in a range of geomorphological settings care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy

the parasequence definition are transgressive deposits inadequately addressed abstract in only a few decades sequence stratigraphy has become one of the cornerstones of modern stratigraphy although the sequence is the principal stratigraphic unit parasequences are the fundamental composite building blocks by definition parasequences are typically upward shoaling successions that are bounded by flooding surfaces that form in response to relatively rapid rises of relative sea level in that definition little provision is made for significant transgressive deposition during the time of flooding but transgressive deposits do exist in the geological record because these deposits lie above the flooding surface and derive much of their sediment from transgressive erosion of the underlying progradational succession should the parasequence boundary not be moved from the u derlying flooding surface upward to the top of the transgressive unit by doing so the underlying progradational unit and the overlying transgressive unit would constitute one complete regressive transgressive succession nonetheless although appealing the typical inability to easily accurately and consistently identify the uppermost surface of the transgressive unit makes it an untenable surface for stratigraphic purposes as suggested by earlier workers therefore the flooding surface a readily identifiable surface that caps the progradational package and consistently underlies transgressive deposits is the most appropriate surface to bound the parasequence in any event to ignore transgressive deposits is to ignore an important component of the geological record a record that not only provides insight into transgressive depositional processes but also is one that can be economically important as a result transgressive deposits need to be included in the parasequence definition possibly only implicitly but certainly not explicitly excluded furthermore the notion that sequences typically indicate progradational deposition excludes examples where upward fining transgressive deposits related to upward deepening are present and lie below the upward shoaling progradational part of the same parasequence

sedimentary cyclicity in the marine pliocene pleistocene of the wanganui basin new zealand sequence stratigraphic motifs characteristic of the past 2 5 m y earth s climatic history since 2 5 ma has been controlled by milankovitch variations in the planetary orbit comprising alternate periods of glaciation and interglaciation with a dominant frequency of 41 000 yr concomitantly eustatic sea level has fluctuated 70 to 130 m causing rapid transgressions and regressions of the shoreline across the world s continental shelves the resulting sedimentary record is cyclothemic each cyclothem corresponding to a single climate and sea level cycle the wanganui basin new zealand contains a 2 km thick almost complete composite record since isotope stage 100 ca 2 5 ma in the form of 47 superposed cyclothems of shelf origin each cyclothem corresponds to an unconformity bound stratigraphic sequence and typically contains a transgressive systems tract sometimes a mid cycle shell bed a highstand systems tract and sometimes a regressive systems tract no advantage accrues from using transgressive regressive units rather than cyclothems and or sequences in description of the succession six basic sequence motifs represent deposition in locations between the shoreline and offshore shelf i e the hawera birdgrove turakina seafield castlecliff and rangitikei motifs a seventh the nukumaru motif which includes dominant coquina limestone represents deposition in shallow water areas of reduced terrigenous sediment on the flank of the basin the sequence motifs represented in any section change systematically in sympathy with basin scale changes in subsidence and sediment supply in contrast with the 41000 year length of individual glacioeustatic sequences these basin wide tectonic cycles have a periodicity of many hundreds of thousands to a few million years i e that of third or fourth order sequences of the exxon type this coupled with the restriction of strongly cyclothemic sediments to geological periods of known glacio eustasy permiancarboniferous pliocene pleistocene suggests that tectonic subsidence cycles rather than glacio eustasy are the driving forces behind the development of the third and fourth order unconformity bound sequences that are reported to occur throughout the stratigraphic record

high resolution monitoring of himalayan glacier dynamics using unmanned aerial vehicles himalayan glacier tongues are commonly debris covered and they are an important source of melt water however they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles observations of debris covered glaciers are therefore scarce and airborne remote sensing may bridge the gap between scarce field observations and coarse resolution space borne remote sensing in this study we deploy an unmanned aerial vehicle uav before and after the melt and monsoon season may and october 2013 over the debris covered tongue of the lirung glacier in nepal based on stereo imaging and the structure for motion algorithm we derive highly detailed ortho mosaics and digital elevation models dems which we geometrically correct using differential gps observations collected in the field based on dem differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial accuracy on average mass loss is limited and the surface velocity is very small however the spatial variability of melt rates is very high and ice cliffs and supra glacial ponds show mass losses that can be an order of magnitude higher than the average we suggest that future research should focus on the interaction between supra glacial ponds ice cliffs and englacial hydrology to further understand the dynamics of debris covered glaciers finally we conclude that uav deployment has large potential in glaciology and it may revolutionize methods currently applied in studying glacier surface features

eifelian givetian middle devonian high paleolatitude storm and wave dominated shallow marine depositional systems from the bidouw subgroup bokkeveld group of south africa abstract the sedimentology of the eifelian givetian middle devonian bidouw subgroup in the clanwilliam sub basin of south africa has been reassessed four distinct lithofacies associations are recognized a d and are representative of the deposits of offshore os offshore transition zone to distal lower shoreface otz dlsf proximal lower shoreface plsf and upper shoreface beach usf beach paleoenvironments these paleoenvironments are arranged as several t r controlled storm and wave dominated shallow marine depositional systems the presence of storm and wave dominated shallow marine depositional systems in the bidouw subgroup as well as the preceding emsian eifelian early middle devonian ceres subgroup provides an alternative explanation to storm and wave dominated delta and mixed wave and tide dominated delta models that have previously been proposed for the bokkeveld group sequence stratigraphic analysis of the bidouw subgroup suggests that although sedimentation occurred during two large scale second order transgressive events the succession was predominantly regressive third order and fourth order transgressive regressive t r sequences are more numerous with respect to the preceding ceres subgroup suggesting that the driver for t r cyclicity and relative sea level change was more active during the eifelian givetian than in the emsian eifelian of south africa these data are important since relative sea level change and its effects on paleoenvironmental change at high paleolatitudes during the devonian period are poorly known

effect of gas on the mechanical behavior of medium dense sands abstractthis paper presents the results of monotonic and cyclic triaxial tests performed on gassy medium dense sand specimens these sands are representative of conditions in a loose sand deposit that was densified using multiple blasting passes at a site in south carolina the equipment and laboratory testing procedures used to reproduce the postblast densification conditions observed at a field test are described in detail results of undrained and drained compression tests showed that the gassy specimen responses were bounded by the fully saturated drained and undrained responses the undrained test results showed that the presence of gas even in small amounts made the soil more compressible and restricted the buildup of excess pore water pressures as compared with those pressures observed in fully saturated specimens additionally the shear strengths of gassy medium dense sand specimens were similar to those observed in saturated loose sands sheared under drained conditions for a given cyclic s

geomorphological and sequence stratigraphic variability in wave dominated shoreface shelf parasequences physical stratigraphy within shoreface shelf parasequences contains a detailed but virtually unstudied record of shallow marine processes over a range of historical and geological timescales using high quality outcrop data sets it is possible to reconstruct ancient shoreface shelf morphology from clinoform surfaces and to track the evolving morphology of the ancient shoreface shelf our results suggest that shoreface shelf morphology varied considerably in response to processes that operate over a range of timescales 1 individual clinoform surfaces form as a result of enhanced wave scour and or sediment starvation which may be driven by minor fluctuations in relative sea level sediment supply and or wave climate over short timescales 10 1 10 3 years these external controls cannot be distinguished in vertical facies successions but may potentially be differentiated by the resulting clinoform geometries 2 clinoform geometry and distribution changes systematically within a single parasequence reflecting the cycle in sea level and or sediment supply that produced the parasequence 10 2 10 5 years these changes record steepening of the shoreface shelf profile during early progradation and maintenance of a relatively uniform profile during late progradation modern shorefaces are not representative of this stratigraphic variability 3 clinoform geometries vary greatly between different parasequences as a result of variations in parasequence stacking pattern and relict shelf morphology during shore face progradation 10 5 10 8 years these controls determine the external dimensions of the parasequence

architecture and formation of transgressive regressive cycles in marginal marine strata of the john henry member straight cliffs formation upper cretaceous of southern utah usa marginal marine deposits of the john henry member upper cretaceous straight cliffs formation were deposited within a moderately high accommodation and high sediment supply setting that facilitated preservation of both transgressive and regressive marginal marine deposits complete transgressive regressive cycles comprising barrier island lagoonal transgressive deposits interfingered with regressive shoreface facies are distinguished based on their internal facies architecture and bounding surfaces two main types of boundaries occur between the transgressive and regressive portions of each cycle i surfaces that record the maximum regression and onset of transgression bounding surface a and ii surfaces that place deeper facies on top of shallower facies bounding surface b the base of a transgressive facies bounding surface a is defined by a process change from wave dominated to tide dominated facies or a coaly shelly interval indicating a shift from a regressive to a transgressive regime the surface recording such a process change can be erosional or non erosive and conformable a shift to deeper facies occurs at the base of regressive shoreface deposits along both flooding surfaces and wave ravinement surfaces bounding surface b these two main bounding surfaces and their subtypes generate three distinct transgressive regressive cycle architectures i tabular shoaling upward marine parasequences that are bounded by flooding surfaces ii transgressive and regressive unit wedges that thin basinward and landward respectively and iii tabular transgressive lagoonal shales with intervening regressive coaly intervals the preservation of transgressive facies under moderately high accommodation and sediment supply conditions greatly affects stratigraphic architecture of transgressive regressive cycles acknowledging variation in transgressive regressive cycles and recognizing transgressive successions that correlate to flooding surfaces basinward are both critical to achieving an accurate sequence stratigraphic interpretation of high frequency cycles

sequence stratigraphy of sixth order 41 k y pliocene pleistocene cyclothems wanganui basin new zealand a case for the regressive systems tract this study is based on a late pliocene and early pleistocene approximately 2 6 1 7 ma succession about 1 km thick of 20 sixth order 41 k y duration cyclothems of shelf origin exposed in the rangitikei river valley in the eastern part of wanganui basin the cyclothems correlate with 18 o isotope stages 100 58 and each 41 k y glacialinterglacial stage couplet is represented by an individual depositional sequence comprising transgressive highstand and regressive systems tracts unlike most examples inferred from the stratigraphic record these systems tracts were deposited during phases of known sea level cycles indicated by the contemporary oxygen isotope ice volume curve because of the high rate of subsidence of wanganui basin glacioeustatic sea level falls during most cycles were not of sufficient magnitude to expose the outer shelf thus the rangitikei section provides an exceptional example of regressive strata deposited landward of the contemporary shelf break simple one dimensional modeling shows that moderate to high rates of basin subsidence 1 2 mm yr and low rates of sedimentation 0 2 mm yr during transgressions combined to produce an accommodation surplus at the relative highstand this surplus accommodation was infilled during the late highstand and ensuing fall partly by aggradational highstand systems tract shelf siltstone and chiefly by strongly progradational shoreface sediments of the regressive systems tract rangitikei regressive systems tracts are distinguished from forced regressive systems tracts sensu hunt and tucker 1992 by their different stratal geometry by definition forced regressive systems tracts display an erosional contact with the underlying highstand systems tracts and typically occur as a series of downstepped disjunct shoreline wedges stranded on the shelf and or slope in contrast regressive systems tracts exhibit a gradational lower contact above which parasequences are stacked in a strongly progradational pattern terminated by the superjacent sequence boundary cyclothems display two types of motif termed rangitikei dt depositional transgression and rangitikei nt nondepositional transgression which include the following architectural elements in ascending stratigraphic order 1 a basal sequence boundary that is coincident with either the transgressive surface of erosion which displays small scale up to 50 cm erosional relief and may be penetrated by the ichnofossil ophiomorpha or its deeper water correlative conformity 2 either a thick 5 30 m transgressive systems tract comprising a deepening upward nearshore to inner shelf mixed carbonate siliciclastic lithofacies succession depositional transgression or a thin 2 m transgressive systems tract comprising condensed fossiliferous facies deposited on the sediment starved offshore shelf nondepositional transgression 3 a sharp downlap surface separating condensed fossiliferous facies of the transgressive systems tract from terrigenous siltstone of the superjacent highstand systems tract 4 a highstand systems tract comprising a 10 20 m thick interval of aggradational shelf siltstone and 5 a thick up to 45 m progradational inner shelf to shoreface lithofacies assemblage ascribed to the regressive systems tract condensed shell beds are associated with intrasequence and sequence bounding discontinuities and together with the sedimentological and stratal characteristics of the sequences are important indicators of stratigraphic architecture four types of shell bed are associated with surfaces formed by four different types of stratal termination onlap backlap downlap and flooding surface shell beds cf kidwell 1991 are associated respectively with the transgressive surface of erosion apparent truncation at the top of the transgressive systems tract the downlap surface and local marine flooding surfaces a fifth shell bed type termed a compound shell bed forms in offshore environments where the downlap surface converges with the sequence boundary and elements of both the downlap and the backlap shell beds become mixed or superposed the shell beds mark zones of stratal attenuation and can be used as surrogates for seismic discontinuities when applying sequence stratigraphic concepts at outcrop scale

bedform and stratification characteristics of some modern small scale washover sand bodies washover sand bodies commonly develop along microtidal coastlines in beach barrier island or spit settings wave runup usually in conjunction with an abnormally high water level may overtop the most landward berm of the beach and the foredune crest if one exists to produce overwash and subsequent runoff across the more landward subaerial surface two main elements of the resulting deposit are the washover fan and runoff channel newly formed small scale washover deposits were examined along the outer banks north carolina near pt mugu california and at presque isle lake erie pennsylvania the fans were formed in response to unidirectional landward transport and the runoff channels in response to unidirectional flow usually in a landward direction but sometimes in shore parallel then seaward direction where overwash carried across the fan surface and entered a pond or lagoon a small scale delta microdelta developed in this case the washover fan consisted of two subfacies the wetted but subaerial part of the fan and the subaqueous washover delta flow associated with the development of the fan and runoff channel produced distinctive sets of bedforms and internal stratification high velocity discontinuous surges moving across the fan surface resulted in the development of a plane bed and subhorizontal to low angle landward dipping planar stratification which comprised the major part of the fan similarly rhomboid forms were produced by high velocity sheet flow across the fan surface where flow carried into a standing body of water delta type foreset strata developed for this case the lateral structural sequence was subhorizontal planar stratification merging landward into landward dipping delta tabular foreset strata in the runoff setting where flow became channelized and continuous both upper flow and lower flow regime currents were typical upper flow regime bedforms included antidunes standing waves and plane beds the most commonly observed lower flow regime bedforms included microdelta like bars low amplitude bars linguoid ripples and sinuous crested current ripple trains the sets of sedimentary structures comprising modern washover sand bodies provide criteria for the identification of similar deposits in ancient sediments and for more specific interpretation of the environment

modeling the topography of shallow braided rivers using structure from motion photogrammetry abstract recent advances in computer vision and image analysis have led to the development of a novel fully automated photogrammetric method to generate dense 3d point cloud data this approach termed structure from motion or sfm requires only limited ground control and is ideally suited to imagery obtained from low cost non metric cameras acquired either at close range or using aerial platforms terrain models generated using sfm have begun to emerge recently and with a growing spectrum of software now available there is an urgent need to provide a robust quality assessment of the data products generated using standard field and computational workflows to address this demand we present a detailed error analysis of sub meter resolution terrain models of two contiguous reaches 1 6 and 1 7 km long of the braided ahuriri river new zealand generated using sfm a six stage methodology is described involving i hand held image acquisition from an aerial platform ii 3d point cloud extraction modeling using agisoft photoscan iii georeferencing on a redundant network of gps surveyed ground control points iv point cloud filtering to reduce computational demand as well as reduce vegetation noise v optical bathymetric modeling of inundated areas and vi data fusion and surface modeling to generate sub meter raster terrain models bootstrapped geo registration as well as extensive distributed gps and sonar based bathymetric check data were used to quantify the quality of the models generated after each processing step the results obtained provide the first quantified analysis of sfm applied to model the complex terrain of a braided river results indicate that geo registration errors of 0 04 m planar and 0 10 m elevation and vertical surface errors of 0 10 m in non vegetation areas can be achieved from a dataset of photographs taken at 600 m and 800 m above the ground level these encouraging results suggest that this low cost logistically simple method can deliver high quality terrain datasets competitive with those obtained with significantly more expensive laser scanning and suitable for geomorphic change detection and hydrodynamic modeling

void ratio redistribution in undrained triaxial extension tests on ottawa sand water pluviated samples of ottawa sand were tested in monotonic undrained triaxial extension tests the specimens exhibited similar limited strain softening behavior and they all experienced ph

constitutive modeling of gassy sand behaviour the behaviour of loose gassy sand was investigated with the use of a constitutive model the constitutive model was modified from an existing model that focused on assessing the liquefaction of loose sands over a wide range of states and loading conditions the modifications involved taking into account the compressibility and solubility of the pore gas and liquids hilf s equation which calculates the pore pressure change in a gassy or unsaturated soil subjected to an applied total stress was incorporated into the model formulation the initial degree of saturation is needed for model prediction and the coefficient of volumetric solubility henry s constant was introduced as a new model parameter the modified model was used to predict the effect of gas on the undrained static behaviour of loose sand the laboratory results of saturated specimens were modeled and the predicted and observed behaviours were found to agree well results from gassy specimens were also predicted and again the model pred

cyclic liquefaction of loose gassy sand gas can be found in many soils but none more common than in seabed soils gas charged sediments are known to be widely distributed throughout the world s oceans numerous research programs have studied saturated soil response to cyclic loading however little is known about the behavior of gassy soils subjected to cyclic loading the response of loose gassy specimens subjected to cyclic loading was studied in a laboratory program triaxial tests were performed on specimens of reconstituted ottawa sand prepared to various gas contents and densities the specimens were consolidated and then sheared under undrained cyclic loading gas content was measured at the beginning and end of each test using time domain reflectometry the response of the gassy specimens has been shown to be influenced by the soil state and grain characteristics and the intensity duration and frequency of the cyclic loading the propensity of a soil to liquefy is represented by a cyclic resistance ratio defined as the cyclic stres

on the undrained unloading behaviour of gassy sands soils that contain large amounts of dissolved gas within the pore fluid are called gassy soils gassy soils are common in marine environments and it is important to further our understanding of the unloading behaviour of gassy soils because of their potential to initiate and propagate submarine slope failures this paper focuses on the pore pressure responses and volumetric strains of loose gassy sands under different undrained unloading stress paths in laboratory specimens special attention was given to the constant deviatoric stress q constant undrained unloading stress path as it simulates the stress condition imposed by tidal drawdown one of the potential triggers of landslides in gaseous marine sediments gas exsolution was observed when the pore pressure was reduced below the liquid gas saturation pressure upon further decreases in total stress the resulting pore pressure change was much less than the total stress change hence effective stress decreased rapidly and at a certain point the sa

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

interplay between shoreline migration paths architecture and pinchout distance for siliciclastic shoreline tongues evidence from the rock record facies geometry and key internal stratigraphic surfaces from eight cretaceous and eocene clastic shoreline tongues have been documented the regressive parts of all the studied tongues represent storm wave influenced strandplains deltas or fan deltas and the regressive shoreline trajectories varied from descending to ascending the transgressive parts of the tongues are dominated by either estuarine or coastal plain deposits the distance from the coeval up dip non marine deposits to the basinward pinchout of amalgamated shoreface sandstones measured along depositional dip is here termed the sand pinchout distance the study shows that the angle of regressive to transgressive turnaround defined by the angle between the regressive and subsequent transgressive shoreline trajectories and the process regime during turnaround largely control the sand pinchout distance the amount of transgressive erosion can also partly control the pinchout distance but this parameter was comparable for the different examples presented here if the type of depositional system at turnaround and the depth of transgressive erosion are constant small angles of turnaround are associated with large pinchout distances whereas larger angles of turnaround result in smaller pinchout distances the model developed allows sand pinchout distance to be predicted using data for the landward parts of shoreline tongues the dataset also shows that steeply rising aggrading shoreline trajectories tend to produce more heterolithic sandstone tongues than those formed by lower angle trajectories

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

facies architecture and geometry of landward stepping shoreface tongues the upper cretaceous cliff house sandstone mancos canyon south west colorado the campanian cliff house formation represents a series of individually progradational shoreface tongues preserved in an overall landward stepping system in the mancos canyon area the formation consists of four 50 to 55 m thick and 10 to 20 km wide sandstone tongues which pinch out landwards into lower coastal plain and lagoonal deposits of the upper menefee formation and seawards into offshore shales of the lewis shale formation photogrammetric mapping of lithofacies along the steep and well exposed canyon walls was combined with sedimentary facies analysis and mapping of the detailed facies architecture two major facies associations have been identified one comprising the mostly muddy and organic rich facies of lagoonal and lower coastal plain origin and one comprising the sandstone dominated facies of shoreface origin key stratigraphic surfaces were identified by combining the mapped geometry of the lithofacies units with the interpretation of depositional processes the stratigraphic surfaces master ravinement surface shoreface coastal plain contact transgressive surface maximum flooding surface and the sequence boundary allow each major sandstone tongue to be divided into a simple sequence consisting of a basal transgressive system tract tst overlain by a highstand system tract hst within each sandstone tongue a higher frequency cyclicity is evident the high frequency cycles show a complex stacking pattern development and are commonly truncated in the downdip direction by surfaces of regressive marine erosion the complexities of the cliff house sandstone tongues are believed to reflect changes in the rate of sea level rise combined with the responses of the depositional system to these changes synsedimentary compaction causing a thickness increase in the sandstone tongues above intervals of previously uncompacted lagoonal coastal plain sediments also played a role this study of the facies architecture geometry and sequence stratigraphy of the cliff house formation highlights the fact that there may be some problems in applying conventional sequence stratigraphical methods to landward stepping systems in general these difficulties stem from the fact that no single stratigraphic surface can easily be identified and followed from the non marine to the fully marine realm i e from the landward to the basinward pinch out of the sandstone tongues in addition the effects of synsedimentary compaction and changes in the shoreface dynamics are not easily recognized in limited data sets such as from the subsurface

effect of initial pore pressure on undrained shear behaviour of fine grained gassy soil many of the world reserves of fossil fuels are located at various water depths in fine grained sediment under the seabed the fine grained sediment contains relatively large biogas bubbles which has been posing challenges to the stability of offshore foundations supporting oil and gas platforms although fine grained gassy soil was found to exhibit different undrained shear strengths cu by altering the initial pore pressure ui relevant to water depth systematic studies concerning the effect of ui on undrained shear behaviours of the soil are still lacking this study reports a series of undrained triaxial tests aiming to compare and investigate the responses of reconstituted fine grained gassy soil with the same consolidation pressure p c but at a wide range of varying ui 0 1000 kpa the shearing induced excess pore pressure u in the gassy specimens highly depends on ui it can be either smaller than that of the saturated specimen with the same p c due to partial dissipation of u int

fast deformation of perennially frozen debris in a warm rock glacier in the swiss alps an effect of liquid water 1 surface movement internal deformation and temperature were monitored over 5 years on buz north rock glacier a small rock glacier located at the lower limit of the permafrost belt in the swiss alps the permafrost in the rock glacier mainly consists of pebbles and cobbles filled with interstitial ice two inclinometers installed at 4 and 5 m depths showed fast deformation with large seasonal and interannual variations while the permafrost temperatures remained almost at the melting point the movement of the inclinometers coincided with changes in the surface velocities the deformation rapidly accelerated during snowmelt periods whereas it gradually decelerated below a dry snow cover in winter the frozen debris was more deformable than typical glacier ice at the melting point these phenomena suggest that the frozen debris is permeable to snowmelt water the fast deformation should result from significant annual relocation of debris particles which probably creates a network of air voids in the frozen debris that eventually allows water infiltration the meltwater infiltration accelerates the deformation by reducing effective stress resulting in the reduced strength of the frozen debris the refreezing of the pore water which depends on the cooling intensity in winter decelerates the deformation the combination of these processes controls the temporal variations in the deformation