deposition and modification of a flood layer on the northern california shelf lessons from and about the fate of terrestrial particulate organic carbon the 1995 flood of the eel river in northern california provided an opportunity to follow the short term history of riverine particulate matter on a continental shelf particulate organic carbon including both vascular plant debris and soil carbon was utilized as a tracer of the distribution and modification of the shelf flood deposit these components were sorted during initial emplacement of the deposit both in the river plume and in the benthic boundary layer during the 8 months following the flood lateral transport shallow burial and bioturbation contributed to spatial changes in the amount and character of carbon in the flood deposit study of the deposit suggests that this and previous flood layers may be preserved in the shelf and upper slope stratigraphic record as clay rich beds with relatively high carbon to nitrogen ratios and more negative 13c values than background non flood sediment concentrations of vascular plant debris are locally characteristic of such layers and may serve as distinctive stratigraphic markers investigation of organic carbon in the 1995 flood layer on the eel river shelf provides insight into the fate of terrestrial particulate carbon on continental margins in general flooding of the eel river and of similar river systems draining mountainous terrains introduces large quantities of terrestrial carbon to the marine environment and may favor the preservation of both terrestrial and marine carbon the abundant woody vascular plant debris discharged during floods is especially likely to survive oxidation and sulfate reduction in the shallower zones of the seabed this study reveals the dominant role that physical and biological processes may play in attenuating the terrestrial organic carbon signal on shelves over monthly to yearly time scales

evidence for reduced quartz cementation rates in oil filled sandstones when quartz rich sands are buried and heated pore space is gradually filled by precipitation of quartz cement from aqueous formation fluids here we examine whether the presence of oil in the pore space can retard or halt this loss of porosity by slowing or stopping quartz cementation the effect of oil fill on quartz cementation is examined by using the distribution of quartz cement in the brae formation deep water sandstone reservoir of the miller oil field north sea petrographic data demonstrate that sandstones from the oil zone have much less quartz cement and more porosity than sandstones from the water zone sandstones in both oil and water zones are compositionally and texturally identical and have been affected by a similar burial history kinetic modeling of the cementation process suggests that progressive oil charging has slowed quartz cement growth rates by at least two orders of magnitude halting it completely in the most extreme cases our data demonstrate that early oil charging in the crestal part of an anticline can preserve porosity in deeply buried sandstones this knowledge is especially relevant to porosity prediction for petroleum exploration in deeply buried sandstones

the effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer sand flume experiments and modelling summary this paper presents a new laboratory sand flume dataset on the propagation of groundwater waves in an unconfined sandy aquifer with a vertical boundary subject to simple harmonic forcing with a wide range of oscillation period from 10 7 s to 909 s the data is unique in that it covers a much wider range of non dimensional aquifer depths n d k where n is the porosity is the angular frequency d is the aquifer depth and k is the hydraulic conductivity than has been previously investigated both the amplitude decay rate and rate of increase in phase lag of the water table waves are observed to monotonically increase with increasing oscillation frequency increasing n d k this is in contrast to existing theoretical dispersion relations which predict 1 zero phase lag or standing wave behaviour and 2 an asymptotic decay rate as the frequency increases possible influences on the experimental data including sand packing measurement location finite amplitude wave effects unsaturated zone truncation and multiple wave mode effects are unable to explain the discrepancy the data was also compared against numerical solutions of richards equation with and without hysteresis and in both cases the same qualitative behaviour as the analytic solutions described above is found the discrepancy between data and predictions remains unexplained and highlights a knowledge gap that requires further investigation these findings relate directly to practical applications in the field of surface groundwater interactions such as the influence of wave forcing of coastal aquifers on contaminant transport sediment mobility and salt water intrusion all of which are influenced by the dispersion of the groundwater wave

genesis and depositional model of subaqueous sediment gravity flow deposits in a lacustrine rift basin as exemplified by the eocene shahejie formation in the jiyang depression eastern china abstract subaqueous sediment gravity flow ssgf deposits have recently been recognized as a major reservoir plays in lacustrine basins research on their genesis and depositional models are crucial to understand gravity flow evolution and the distribution of their deposits this study analysed ssgf deposits in the third member of the shahejie formation in the jiyang depression eastern china based on 3 d seismic data well log data and core observations the types and origins of ssgf the distribution patterns and depositional models of ssgf deposits have been investigated the dominant types of ssgf include muddy debris flows sandy debris flows high density turbidity currents surge like low density turbidity currents and quasi steady low density turbidity currents which are mainly caused by river floods and sediment failures the overall distribution of ssgf deposits is controlled by the sediment supplies basin structure and sequence stratigraphic framework paleotopography flood energy triggering mechanism and the slope angle of the delta front are also important ssgf deposits associated with river floods can be further subdivided into elongated and fan shaped deposits elongated sandstones are composed predominantly of bedload dominated and suspension load dominated hyperpycnal flow deposits the fan shaped sandstones can be subdivided into an inner fan a middle fan and an outer fan inner fan deposits are dominated by gully filling debrites middle fan deposits are composed predominantly of channel fill deposits while outer fan deposits consist of thin bedded and laterally extensive lobe intervals ssgf deposits triggered by sediment failures can be further subdivided according to their proximity to slumping proximal intermediate and distal parts the proximal deposits are composed predominantly of slide and slump deposits the intermediate deposits are dominated by sandy debrite tongues while the distal deposits are composed predominantly of thin bedded surge like low density turbidites this study offers some insight into the types origin of gravity flow as well as the distribution of their deposits in a lacustrine rift basin

contrasting styles of late jurassic syn rift turbidite sedimentation a comparative study of the magnus and oseberg areas northern north sea abstract contrasting types of sediment gravity flow and hemipelagite deposition are recorded by the late jurassic syn rift successions in the magnus and oseberg areas in the northern north sea in both areas the late jurassic rift interval was characterized by recurrent tectonic phases during the late oxfordian to early volgian the penguin halfgraben in the magnus area received a significant amount of coarse clastics and can be regarded as an example of a well fed deeper marine riftbasin periods with high rates of extensional faulting are characterized by isolated sediment gravity flow lobes which stack in an uneven albeit downdip shifting or backstepping manner the stratigraphic motif of these intervals is overall mud prone with coarse clastics represented by thick conglomerate sandstone mudstone aprons along the basin bounding masterfaults in contrast periods with low rates of extensional faulting are characterized by basinwide sheet like parallel layered sediment gravity flow packages which infill the riftbasin in a progradational manner from the middle volgian the penguin halfgraben became sediment starved and shows a similar development to the oseberg area in the oseberg area the late jurassic syn rift succession provides a typical example of a sediment starved deeper marine riftbasin sediment gravity flow deposition in this area is limited to periods of high rates of extensional faulting these coarser clastic depositional episodes mimic their counterparts in the penguin halfgraben being characterized by mud prone strata with localized isolated sediment gravity flow lobes and footwall derived clastic wedges along the basin bounding masterfaults in contrast to the well fed basins the intervening stages of tectonic quiescence in the sediment starved basins are characterized by basinwide blanketing of clay commonly of high source rock potential in both basins the rotational tilt packages can be subdivided into an early a climax and a late syn rotational interval based on the architecture of their contained facies tracts these depositional episodes reflect the temporal evolution of the riftbasins catchment areas and their linked depositional systems it is mainly the nature and amount of sediment supply during the following tectonic quiescence or post rift stages that determine whether the riftbasin remained sediment starved or became infilled simplified sequence stratigraphic models are of limited use in the analyses and lithology prediction of riftbasin infills as individual halfgrabens often have their own specific infill history and hence characteristic syn rift stratigraphic signature the main controls on the variability of these deeper marine syn rift sediment gravity flow hemipelagite packages are the style and rate of extensional faulting sediment supply the source area s sediment yield potential and calibre and the halfgraben configuration and location with respect to the main hinterland areas

sedimentation in marine impact craters insight from the ritland impact structure abstract this paper is intended to compare the sedimentary processes active in the ritland impact structure with the processes discussed from gardnos kardla lockne and chesapeake bay marine impact structures sedimentary processes e g rock avalanches slides and slumps debris and density flows turbidity and suspension deposition occur approximately in the same stratigraphical order in all these craters resulting in comparable crater infills the thickness and compositional variations can be explained by differences in crater size target lithology and water depth rock avalanches dominate in crystalline target impact sites with shallow water depth as observed in the ritland and gardnos craters impact into deeper water e g lockne does not reveal large scale gravity driven collapses of the transient sea floor cavity crystalline target sites with shallow water depth and thin sedimentary cover as in the ritland and gardnos impact sites resulted in elevated rim formations reducing resurge energy and yielded comparable reduced debris flow events impact into thick stratified sedimentary targets resulted in relatively weaker rim formation in kardla the related brim developments in the lockne and chesapeake bay impact structures can be reflected in multiple events of large scale debris flows resurge turbidites are observed in the kardla and lockne crater infilling successions turbidites in the ritland and gardnos are dominantly originated through later slope failure and reworking of the impact generated debris suspension dominated late post impact sedimentation within all the craters is largely controlled by their regional geological settings

sedimentology stratigraphic occurrence and origin of linked debrites in the west crocker formation oligo miocene sabah nw borneo abstract the west crocker formation oligocene early miocene nw borneo consists of a large 20 000 km2 submarine fan deposited as part of an accretionary complex a range of gravity flow deposits are observed the most significant of which are mud poor massive sandstones interpreted as turbidites and clast rich muddy sandstones and sandy mudstones interpreted as debrites an upward transition from turbidite to debrite is commonly observed with the contact being either gradational and planar or sharp and highly erosive based on their repeated vertical relationship and the nature of the contact between them these intervals are interpreted as being deposited from one flow event which consisted of two distinct flow phases fully turbulent turbidity current and weakly turbulent to laminar debris flow the associated bed is called a co genetic turbidite debrite with the upper debrite interval termed a linked debrite linked debrites are best developed in the non channellised parts of the fan system and are absent to poorly developed in the proximal channel levee and distal basin floor environments due to outcrop limitations the genesis of linked debrites within the west crocker formation is unclear based on clast size and type it seems likely that a weakly turbulent to laminar debris flow flow phase was present when the flow event entered the basin a change in flow behaviour may have led to deposition of a sand rich unit with turbidite characteristics which was subsequently overlain by a mud rich unit with debrite characteristics flow transformation may have been enhanced by the disintegration and incorporation into the flow of muddy clasts derived from the upstream channel floor channel mouth or from channel levee collapse lack of preservation of this debrite in proximal areas may indicate either bypass of this flow phase or that the available outcrops fail to capture the debris flow entry point establishing robust sedimentological criteria from a variety of datasets may lead to the increasing recognition of co genetic turbidite debrite beds and an increased appreciation of the importance of bipartite flows in the transport and deposition of sediments in deepwater environments

capillary effect on water table fluctuations in unconfined aquifers parlange and brutsaert 1987 derived a modified boussinesq equation to account for the capillary effect on water table dynamics in unconfined aquifers barry et al 1996 solved this equation subject to a periodic boundary condition their solution shows significant influence of capillarity on water table fluctuations which evolve to finite amplitude standing waves at the high frequency limit here we propose a new governing equation for the water table which considers both horizontal and vertical flows in an unsaturated zone of finite thickness an approximate analytical solution for periodic water table fluctuations based on the new equation was derived in agreement with previous results the analytical solution shows that the unsaturated zone s storage capacity permits water table fluctuations to propagate more readily than predicted by the boussinesq equation furthermore the new solution reveals a capping effect of the unsaturated zone on both the amplitude and phase of the water table fluctuations as well as the water table overheight due to the finite thickness of the unsaturated zone the capillary effect on water table fluctuations is modified mainly with reduced amplitude damping and phase shift

tidal dynamics of the water table in beaches tidal motions of the water table height inside a sloping beach are investigated via field measurements and theoretical considerations only the movements forced by the tide are considered so a beach with negligible wave activity was chosen for the field measurements the data show that even in the absence of precipitation the time averaged inland water table stands considerably above the mean sea level also the water table at a fixed point inside the beach is far from sinusoidal even though its variation is forced by an essentially sinusoidal tide this latter effect is due to the boundary condition along the sloping beach face which acts as a highly nonlinear filter the observed behavior of the water table is explained in terms of perturbation extensions to the classical deep aquifer solution one extension deals with the nonlinearity in the interior the other with the boundary condition at the sloping beach face

can dispersive pressure cause inverse grading in grain flows grain flows in the collisional regime are self regulated in such a way that dispersive pressure at every level tends to balance static pressure and so cannot promote the upward segregation of large particles in a steady flow le roux adds new insights to this analysis by pointing out that dispersive and static pressures would not balance in unsteady flows when shear strain rate increases in a grain flow dispersive pressure which is positively correlated to shear strain rate increases too and the gradient of dispersive pressure becomes higher than the gradient of static pressure as a consequence the grain flow expands thus lowering the dispersive pressure until the two gradients reequilibrate during the

an alternative boussinesq equation considering the effect of hysteresis on coastal groundwater waves abstract this paper presents an alternative boussinesq equation considering hysteresis effect via a third order derivative term by introducing an improved moisture pressure retention function this equation describes with reasonable precision groundwater propagation in coastal aquifers subject to dirichlet boundary condition of different oscillation frequencies test results confirmed that it is necessary to consider horizontal and vertical flows in unsaturated zone because of their variable influences on hysteresis hysteresis in unsaturated zone can affect the water table wave number of groundwater wave motion such as wave damping rate and phase lag oscillations with different periods exert different hysteresis effect on wave propagation truncation shrinkage of unsaturated zones also affects the strength of hysteresis these impacts can be reflected in the alternative boussinesq equation by adjusting the parameter representing the variation rate of moisture associated with pressure change as opposed to traditional computationally expensive hysteresis algorithms the present boussinesq equation is simple to use and can provide feasible basis for future coupling of groundwater and surface water models

topographic controls on the development of contemporaneous but contrasting basin floor depositional architectures abstract sediment laden gravity driven flow deposits on the basin floor are typically considered to form either discrete lobes that stack compensationally or packages of laterally extensive beds commonly termed sheets these end member stacking patterns are documented in several basinfills however whether they can coexist in a single basin or there are intermediate or transitional stacking patterns is poorly understood an analysis of depositional architecture and stacking patterns along a 70 km dip oriented transect in the upper broto turbidite system jaca basin south central pyrenees spain which displays disparate stacking patterns in contemporaneous strata is presented proximal and medial deposits are characterized by discrete packages of clean sandstones with sharp bed tops which exhibit predictable lateral and longitudinal facies changes and are interpreted as lobes distal deposits comprise both relatively clean sandstones and hybrid beds that do not stack to form lobes instead localized relatively thick hybrid beds are inferred to have inhibited the development of lobes hybrid beds developed under flows which were deflected and entrained carbonate mud substrate off a carbonate slope that bounded the basin to the south evidence for this interpretation includes 1 divergent paleoflow indicators and hummock like features in individual beds 2 a decrease in hybrid bed thickness and abundance away from the lateral confining slope 3 a carbonate rich upper division not seen in more proximal turbidites the study demonstrates the co occurrence of different styles of basin floor stacking patterns in the same stratigraphic interval and suggests that characterization of deep water systems as either lobes or sheets is a false dichotomy

water table waves in an unconfined aquifer experiments and modeling 1 comprehensive measurements are presented of the piezometric head in an unconfined aquifer during steady simple harmonic oscillations driven by a hydrostatic clear water reservoir through a vertical interface the results are analyzed and used to test existing hydrostatic and nonhydrostatic small amplitude theories along with capillary fringe effects as expected the amplitude of the water table wave decays exponentially however the decay rates and phase lags indicate the influence of both vertical flow and capillary effects the capillary effects are reconciled with observations of water table oscillations in a sand column with the same sand the effects of vertical flows and the corresponding nonhydrostatic pressure are reasonably well described by small amplitude theory for water table waves in finite depth aquifers that includes the oscillation amplitudes being greater at the bottom than at the top and the phase lead of the bottom compared with the top the main problems with respect to interpreting the measurements through existing theory relate to the complicated boundary condition at the interface between the driving head reservoir and the aquifer that is the small amplitude finite depth expansion solution which matches a hydrostatic boundary condition between the bottom and the mean driving head level is unrealistic with respect to the pressure variation above this level hence it cannot describe the finer details of the multiple mode behavior close to the driving head boundary the mean water table height initially increases with distance from the forcing boundary but then decreases again and its asymptotic value is considerably smaller than that previously predicted for finite depth aquifers without capillary effects just as the mean water table over height is smaller than predicted by capillarity free shallow aquifer models so is the amplitude of the second harmonic in fact there is no indication of extra second harmonics in addition to that contained in the driving head being generated at the interface or in the interior

stratigraphy and depositional setting of slurry and contained reflected beds in the marnoso arenacea formation langhian serravallian northern apennines italy this work presents the stratigraphy and facies analysis of an interval of about 2500 m in the langhian and serravallian stratigraphic succession of the foredeep turbidites of the marnoso arenacea formation a high resolution stratigraphic analysis was performed by measuring seven stratigraphic logs between the sillaro and marecchia lines 60 km apart for a total thickness of about 6700 m the data suggest that the stratigraphy and depositional setting of the studied interval was influenced by syndepositional structural deformations the studied stratigraphic succession has been subdivided into five informal stratigraphic units on the basis of how structurally controlled topographic highs and depocentres a consequence of thrust propagation change over time these physiographic changes of the foredeep basin have also been reconstructed through the progressive appearance and disappearance of thrust related mass transport complexes and of five bed types interpreted as being related to structurally controlled basin morphology apart from bouma like type 4 beds type 1 tripartite beds characterized by an internal slurry unit tend to increase especially in structurally controlled stratigraphic units where intrabasinal topographic highs and depocentres with slope changes favour both mud erosion and decelerations type 2 beds with an internal slump type chaotic unit characterize the basal boundary of structurally controlled stratigraphic units and are interpreted as indicating tectonic uplift type 3 beds are contained reflected beds that indicate different degrees of basin confinement while type 5 are thin and fine grained beds deposited by dilute reflected turbulent flows able to rise up the topographic highs the vertical and lateral distribution of these beds has been used to understand the synsedimentary structural control of the studied stratigraphic succession represented in the marnoso arenacea formation by subtle topographic highs and depocentres created by thrust propagation folds and emplacements of large mass transport complexes

linked debrites in sand rich turbidite systems origin and significance abstract the outer parts of a number of small late jurassic sandy deep water fans in the northern north sea are dominated by the stacked deposits of co genetic sandy and muddy gravity flows sharp based structureless and dewatered sandstone beds are directly overlain by mudclast breccias that are often rich in terrestrial plant fragments and capped by thin laminated sandstones pseudonodular siltstones and mudstones the contacts between the clast rich breccias and the underlying sandstones are typically highly irregular with evidence for liquefaction and upward sand injection the breccias contain fragments up to metre scale of exotic lithologies surrounded by a matrix that is extremely heterogeneous and strewn with multiphase and variably sheared sand injections and scattered coarse and very coarse sand grains often coarser than in the immediately underlying sand bed markov chain analysis establishes that the breccias consistently overlie sandstones and the character of the breccias and their external contacts rule out a post depositional origin via in situ liquefaction intrastratal flowage or bed amalgamation and disruption the breccias are interpreted as debrites that rode on a water rich sand bed just deposited by a co genetic concentrated gravity current as such they are referred to as linked debrites to distinguish them from debrites emplaced in the absence of a precursor sand bed the distinction is important because these linked debris flows can achieve significant mobility through entrainment of both water and sediment from beneath and they ride on a low friction carpet of liquefied sand this explains the paradox presented by fan fringes in which there are common debrites when conventional thinking might predict that deposits of low concentration gravity currents should be more important here in fact evidence for transport by low concentration turbidity currents is rare in these systems several possible mechanisms might explain the formation of linked flows but the ultimate source of both sandy and clast rich flow components must be in shallower water on the basin margin the debrites are not triggered from distal slopes flow partitioning may have occurred by upslope erosion and retardation of the mudclast charged portion of an erosional sandy density current partial flow transformation of a precursor debris flow and or hydraulic segregation and reconcentration of the flaky clasts and carbonaceous matter during transport linked debrites are not restricted to small sand rich fans and similar mechanisms may be responsible for the long runout of debris flows in other systems the recognition of a distinct class of linked debrites is of wider importance for facies prediction reservoir heterogeneity and even carbon fluxes and sequestration on continental margins

deposits of flows transitional between turbidity current and debris flow the relationship between submarine sediment gravity flows and the character of their deposits is poorly understood annular flume experiments were used to investigate the depositional dynamics and deposits of waning sediment laden flows decelerating fast 3 m s flows with fixed sand content 10 vol and variable mud content 0 17 vol resulted in only four deposit types clean sand with a mud cap that resembled a turbidity current deposit turbidite formed if the flow was turbulent when deposition began or if the muddy fluid had insufficient strength to suspend the sand the clean sand could contain structures if mud content was low 300 s ungraded muddy sand with a mud cap that resembled a debris flow deposit debrite formed if the flow became laminar before sand could deposit clean sand overlain by ungraded muddy sand and a mud cap formed either from a transitional flow or by late stage settling of sand from a muddy suspension these deposits resemble enigmatic submarine flow deposits called linked debrite turbidites the experiments provide a basis for inferring flow type from deposit character for submarine sediment laden flows

depositional features of co genetic turbidite debrite beds and possible mechanisms for their formation in distal lobated bodies beyond the base of slope ulleung basin east sea japan sea abstract a detailed analysis of the mr1 11 12 khz sonar images chirp 2 7 khz profiles core sediments and 14 c ages from the latest quaternary lobated bodies lb on the deep 2100 m water depth basin plain of the western ulleung basin reveals depositional features and context of co genetic turbidite debrite beds in the lb on the distal setting and a plausible mechanism for generating these beds eight lb are present in the basin plain ca 30 60 km beyond the base of slope and were generally deposited retrogressively older and more distal lb 1 4 have large dimensions 27 km long 15 25 km wide in contrast younger and less distal lb 5 8 are small 8 8 31 5 km long 1 2 12 km the muddier larger lb 1 and 2 were most likely originated from the relatively large scale sediment failures on the muddy upper slopes 350 400 m water depth between 18 5 and 20 0 cal ka b p on other hand the sandier smaller lb 6 and 7 were deposited between 17 0 and 17 5 cal ka b p probably by the relatively small scale sediment failures on the sandy uppermost slope shallower than 350 400 m water depth in lb 1 a lower sandy mud turbidite is transitional upward into an upper mud matrix debrite having small rounded mud clasts in contrast lb 6 exhibits a gradual upward change from a lower clay poor sandy turbidite to an upper clay rich sand matrix debrite with large interlocking mud clasts each mixed bed in lb 1 and 6 can represent a co genetic or linked turbidite debrite bed formed by the down dip flow transformation from turbidity current to debris flow at a point during the same event the abundant large scale up to 20 25 m deep 3 5 km long erosions of fine grained substrates near the base of slope area suggest that the down dip transformation was driven by incorporation of mud via erosional bulking by turbidity currents reaching the base of slope area the different clay sand content and size shape of mud clasts in the co genetic turbidite debrite beds between lb 1 and 6 imply that the composition sandy or muddy and dimension of initial turbidity current approaching the base of slope the volume of eroded masses from the fine grained substrates and the transport distance of sediment gravity flows from the erosional areas of muddy substrates can be all important factors controlling the depositional styles of co genetic turbidite debrite beds

return of the fan that never was westphalian turbidite systems in the variscan culm basin bude formation south west england thirty ve years ago harold reading stated 1963 p 69 the precise depositional environment of the bude sandstones is not easy to establish appropriately two of his former students are still arguing whether the environment was a storm affected shelf higgs 1986a 1987 1991 or a deep water fan burne 1969 1995 the paper by burne 1995 questions my shelf interpretation prompting this discussion burne and i agree that deposition took place offshore in a large westphalian lake with occasional marine connections based on faunal aspects and on the lack of evidence for emergence goldring seilacher 1971 lake bude of higgs 1986b 1994 we also agree that the majority of the sandstone beds are turbidites but whereas i argued for river fed turbidites on a shelf with storms accounting for both catastrophic rainfall hence sandy under ows and accompanying waves burne 1995 invokes slump generated turbidites on a deep water fan below storm wavebase the tectonic setting was the northern passive margin of a foreland basin higgs 1991 burne 1995 burne 1995 argues that all of the sedimentary structures interpreted by higgs 1991 as indicating shallow water deposition above storm wavebase can also occur in deep water turbidite settings these structures are quasi symmetrical ripples irregular cross lamination hummocky cross strati cation multidirectional tool marks and mud draped scours rare symmetrical wave ripples occur in the bude formation although burne 1995 p 130 points out that no convincing illustration of them has been published to date his italics in the following discussion i shall sequentially address these and other contentious issues raised by burne 1995 my intentions are threefold 1 to question the basis of burne s fan model 2 to reiterate evidence for my lake shelf model and 3 to explain that the shelf origin has been masked for decades by certain unusual facies characteristics including slurried and slumped beds formed in situ as seismites but widely misinterpreted as debris ows and slumps the shelf vs fan debate is not only interesting academically but also important economically because the easily accessible cliffs of bude are a magni cent natural laboratory in which to gather data for petroleum reservoir models

anatomy of turbidites and linked debrites based on long distance 120 x 30 km bed correlation marnoso arenacea formation northern apennines italy much of our understanding of submarine sediment laden density flows that transport very large volumes ca 1 to 100 km3 of sediment into the deep ocean comes from careful analysis of their deposits direct monitoring of these destructive and relatively inaccessible and infrequent flows is problematic in order to understand how submarine sediment laden density flows evolve in space and time lateral changes within individual flow deposits need to be documented the geometry of beds and lithofacies intervals can be used to test existing depositional models and to assess the validity of experimental and numerical modelling of submarine flow events this study of the miocene marnoso arenacea formation italy provides the most extensive correlation of individual turbidity current and submarine debris flow deposits yet achieved in any ancient sequence one hundred and nine sections were logged through a ca 30 m thick interval of time equivalent strata between the contessa mega bed and an overlying columbine marker bed correlations extend for 120 km along the axis of the foreland basin in a direction parallel to flow and for 30 km across the foredeep outcrop as a result of post depositional thrust faulting and shortening this represents an across flow distance of over 60 km at the time of deposition the correlation of beds containing thick 40 cm sandstone intervals are documented almost all thick beds extend across the entire outcrop area most becoming thinly bedded 40 cm in distal sections palaeocurrent directions for flow deposits are sub parallel and indicate confinement by the lateral margins of the elongate foredeep flows were able to traverse the basin in opposing directions suggesting a basin plain with a very low gradient small fractional changes in stratal thickness define several depocentres on either side of the verghereto high area the extensive bed continuity and limited evidence for flow defection suggest that intrabasinal bathymetric relief was subtle substantially less than the thickness of flows thick beds contain two distinct types of sandstone ungraded mud rich sandstone intervals record evidence of en masse debrite deposition graded mud poor sandstone intervals are inferred to result from progressive grain by grain turbidite deposition clast rich muddy sandstone intervals pinch out abruptly in downflow and crossflow directions in a fashion consistent with en masse debrite deposition the tapered shape of mud poor sandstone intervals is consistent with an origin through progressive grain by grain turbidite deposition most correlated beds comprise both turbidite and debrite sandstone intervals intrabed transitions from exclusive turbidite sandstone to turbidite sandstone overlain by debrite sandstone are common in the downflow and crossflow directions this spatial arrangement suggests either i bypass of an initial debris flow past proximal sections ii localized input of debris flows away from available sections or iii generation of debris flows by transformation of turbidity currents on the basin plain because of seafloor erosion and or abrupt flow deceleration a single submarine flow event can comprise multiple flow phases and deposit a bed with complex lateral changes between mud rich and mud poor sandstone

capillary effects on groundwater response to earth tides author s wang cy zhu ay liao x manga m wang lp abstract 2019 american geophysical union all rights reserved the response of unconfined aquifers to earth s solid tides earth tides has been used to study a number of hydrogeological environmental and ecological processes the traditional interpretation of such responses has been based on a model that assumes free flow of groundwater to the water table even though capillary effects have long been recognized to influence the response of coastal aquifers to ocean tides here we study the capillary effect on the response of unconfined aquifers to earth tides using a numerical procedure that couples groundwater flow and poroelastic strain in both the saturated and the unsaturated zones we show that when the water table rises to the surface and the capillary zone disappears the predicted tidal response is identical to that predicted by the traditional model but when the capillary zone is present when the water table falls below the surface the predicted amplitude ratio and phase shift depart notably from those predicted by the traditional model we apply the model to a field case where large seasonal changes of tidal response have been documented we show that the large seasonal changes in the tidal response may be due to the change of the water table from a capillary affected state to a capillary free state when the water table rises annually to the ground surface thus the omission of the capillary effects in the interpretation of the response of unconfined aquifers to earth tides may lead to incorrect inference of subsurface processes and properties

permian diamictites in northeastern asia their significance concerning the bipolarity of the late paleozoic ice age despite a lack of detailed sedimentologic analyses diamictites in the middle permian atkan formation were previously interpreted as glaciomarine and glacially influenced marine deposits this interpretation allowed this unit to play a prominent role in paleoclimatic and biogeographical reconstructions associated with presumed bipolar glaciation during the late paleozoic ice age lpia in this sense the lpia is considered to be a close analog to bipolar glaciation and climate change during the cenozoic here results are presented that challenge the glacigenic interpretation for these strata and negate interpretations of the bipolar nature of the lpia the 400 to 1500 m thick atkan formation was deposited in back arc basins associated with activity of the okhotsk taigonos volcanic arc along the leading edge of pangea as it drifted across the north polar circle the occurrence of tuffs volcanic clasts and glass shards indicate derivation from a nearby arc cooling and solidification of some clasts during sedimentation is suggested by the occurrence of clasts with embayments and protrusions that extend into the surrounding matrix clasts with columnar like jointing and alteration of the matrix surrounding some clasts ca tims dating of tuff zircons indicate a late capitanian age which is consistent with fossils within the strata bedded diamictites deposited as debrites dominate these diamictites which occur as tens of m thick downlapping packages that thicken then thin upward were deposited as prograding and abandoning sediment gravity flow fans chaotic and folded strata formed as slumps graded sandstones and conglomerates were deposited as turbidites and mudstones were deposited as mudflows low density turbidites and hemipelagic deposits striated clasts and outsized clasts piercing bedding were not observed in the study area strata above and below the atkan formation contain abundant graded beds and deep water trace fossils indicating deposition as turbidites the combination of debrites turbidites slumps volcanic grains clasts glass and tuffs and an absence of glacigenic indicators suggest that atkan strata were deposited in deep water basins associated with the development of the volcanic arc rather than due to glacial activity these findings are significant as they require reconsideration of current views of lpia glaciation and suggest that ice sheets were limited to gondwana

from marine bands to hybrid flows sedimentology of a mississippian black shale this study was funded by the natural environment research council nerc grant no ne l002493 1 within the central england training alliance centa consortium the study received case funding from the british geological survey nick riley carboniferous limited is thanked for sharing his expertise and assistance charlotte watts is thanked for providing field assistance nick marsh tom knott cheryl haidon and annika burns are thanked for offering expertise and laboratory assistance pete sadler university of california is thanked for compilation and provision of the background sediment accumulation rate dataset we thank all reviewers editor peir pufahl and elaine richardson editorial office for their valuable comments and advice which have significantly improved this manuscript

sediment flow and deformation sfd layers evidence for intrastratal flow in laminated muddy sediments of the triassic osawa formation northeast japan abstract thin chaotic layers containing abundant intraformational mud clasts are found in the offshore laminated mudstone of the triassic osawa formation in northeast japan the geometry and internal structures of the layers are somewhat similar to those of slump slide or debris flow deposits however the layers have both upper and lower erosional contacts projections of host sediments and mud clasts with planed surfaces are identified beneath the upper contact of the layers closely packed sheet form or ellipsoidal mud clasts are embedded in a poorly sorted fine to coarse grained sandy matrix some mud clasts are tightly folded or show imbricated stacking internal layering structures are also well developed in the layers the above features strongly suggest soft sediment deformation as horizontal displacement of sand and mud under buried conditions here we term these layers sediment flow and deformation sfd layers deformation layers with similar attributes have been identified by some prior authors as in the case of flow of liquefied and or fluidized host sand and clastic sill intrusion however the sfd layers described herein have more complex structure indicating advanced deformation occurrence of the sfd layers is stratigraphically limited to the uppermost part of the osawa formation which is overlain by sand rich submarine fan deposits the fukkoshi formation it suggests that the stress field caused by differential loading of overlying deposits facilitated intrastratal flow and sill intrusions of sand the vertical confinement was also controlled by the anisotropy in physical properties such as tensile strength of laminated mud and or conditions of gentle slope

tide induced fluctuations of salinity and groundwater level in unconfined aquifers field measurements and numerical model the responses of the fresh saline water interface fsi and the groundwater level gwl to the mediterranean sea tide were monitored in the coastal aquifer of israel modeled numerically and analyzed using cross correlation analysis different time lags between sea level fluctuations and hydraulic head and salinity fluctuations were detected for the fsi and the gwl at the fsi the time lag of hydraulic head behind the sea level is much shorter than the lag of the salinity at the same point surprisingly similar time lags behind the sea level were measured for both the hydraulic head at the gwl and the salinity at the fsi both at the same distance from the shoreline results from a numerical model simulating the flow and transport processes at the field scale agree with field measurements in both the gwl and the salinity in the fsi fluctuate almost simultaneously while the hydraulic head in the fsi reacts faster to sea level fluctuations the actual movement of the fresh water body which is controlled by the unsaturated flow in the capillary fringe capillary effect lags behind the pressure head fluctuations in the deeper parts of the aquifer which is controlled by saturated parameters of the aquifer the overall results agree with the conceptual mechanism suggested by levanon et al 2016 in which the effect of sea tide on the coastal groundwater system comprises two main processes 1 tidal fluctuations at the sea floor boundary which cause pressure wave propagation into the aquifer and 2 attenuation at the gwl due to the capillary effect which control also the change in the salinity and the actual movement of the fsi

upper pleistocene turbidite sand beds and chaotic silt beds in the channelized distal outer fan lobes of the mississippi fan cores from a mississippi outer fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized turbidite beds of graded sand and debris flow beds of chaotic silt off lobe basin plains lack siliciclastic coarse grained beds the basin plain mud facies exhibit low acoustic backscatter on seamarc ia sidescan sonar images whereas high acoustic backscatter characteristic of the lobe sand and silt facies the depth of the first sand silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes i e shallowest sand highest backscatter and youngest sublobe the high proportion 50 of chaotic silt compared to graded sand in the distal outer fan sublobes may be related to the unstable muddy canyon wall source areas of the extensive mississippi delta fed basin slope a predominace of chaotic silt in cores or outcrops from outer fan lobes thus may predict similar settings for ancient fans

hybrid event beds dominated by transitional flow facies character distribution and significance in the maastrichtian springar formation north west voring basin norwegian sea hybrid event beds comprising clay poor and clay rich sandstone are abundant in maastrichtian aged sandstones of the springar formation in the north west voring basin norwegian sea this study focuses on an interval informally referred to as the lower sandstone which has been penetrated in five wells that are distributed along a 140 km downstream transect systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings although individual beds were not correlated the lower sandstone shows an overall reduction of total thickness bed amalgamation sand to mud ratio and grain size in distal wells turbidites dominated by clay poor sandstone are at their most common in relatively proximal wells whereas hybrid event beds are at their most common in distal wells hybrid event beds typically comprise a basal clay poor sandstone non stratified or stratified overlain by banded sandstone with clay rich non stratified sandstone at the bed top the dominant type of clay poor sandstone at the base of these beds varies spatially non stratified sandstone is thickest and most common proximally whereas stratified sandstones become dominant in distal wells stratified and banded sandstone record progressive deposition of the hybrid event bed thus the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer this layer changed from non cohesive at the front through a region of transitional behaviour fluctuating non cohesive and cohesive flow to cohesive behaviour at the rear further spatial variation in the dominant type of clay poor sandstone at the bed base suggests that the front of the flow remained non cohesive and evolved from high concentration and turbulence suppressed to increasingly turbulent flow this is thought to occur in response to deposition and declining sediment fall out this research may be applicable to other hybrid event bed prone systems and emphasises the dynamic nature of hybrid flows this article is protected by copyright all rights reserved

inverse grading resulting from coarse sediment transport lag inverse grading in turbidites is conventionally ascribed to dispersive pressure caused by mutual collisions among grains within a traction carpet or grain flow the shearing traction carpet is supposed to become stratified with particle size increasing upward freezing of this traction carpet yields an inversely graded layer an alternative mechanism proposed here emerges from the fact that coarse sediment fractions are transported more slowly than fine fractions in a turbidity current a sufficiently heterogeneous mix of sediment sizes should undergo streamwise size segregation as the coarsest fractions lag behind if deposition begins before the coarsest fraction that will reach a particular station has arrived the lower part of the resulting deposit should be inversely graded a similar mechanism may produce inversely graded intervals in pyroclastic flow deposits because the head of a turbidity current typically travels only about 0 83 as fast as flow velocity in the body a short distance behind the head the coarsest grains able to keep up with the front of the flow are those having transport velocity v sed nearly equal 0 83 u body if coarser size fractions are available they will arrive later than the head permitting the development of inverse grading the proposed mechanism will not operate when the coarsest size fraction travels as fast as or faster than the head of the flow or when onset of deposition is delayed until after the coarsest size fraction has arrived assuming a logarithmic velocity profile below the maximum velocity streamline transport velocity can be calculated for particular sizes of suspended sediment and expressed as a fraction of flow velocity an upper limit for flow strength shear velocity can then be derived from the fall velocity of the coarsest grains at the base of an inversely graded interval u 4 w init where deposition of an inversely graded turbidite began immediately after passage of the head of the current u nearly equal 4 w init

steady periodic flow through a rectangular dam for unsteady free surface flow in a rectangular dam a simple integral relation which connects the pressure integral with the movement of the free surface is derived in the case of steady periodic movement driven by oscillating reservoir levels the time average of the pressure integral can be found which leads to an average discharge formula which is a generalization of the dupuit forchheimer discharge formula for periodic fluctuations of groundwater in a coastal aquifer in response to tidal oscillations a corollary is that the equilibrium water level far from the sea is equal to the root mean square of the sea level independent of the validity of the dupuit forchheimer assumptions

the vertical structure of turbidity currents and a necessary condition for self maintenance a simple numerical model predicts that properties of a turbidity current can vary significantly in the vertical direction particularly when more than one sediment size is in suspension each sediment size decreases in concentration with increasing distance from the bottom boundary at a rate which depends on its settling velocity the current velocity the entrainment coefficient and the bottom slope however it is shown that the details of the vertical distribution of sediment load do not necessarily greatly influence either the vertical structure of the hydraulic properties of the flow velocity stress or the bulk properties such as the entrainment coefficient at least when only one sediment size is in suspension the ability of a turbidity current to sustain itself is strongly dependent on the sediment load and an autosuspension criterion is obtained by taking into account the vertical structure of the currents the model turbidity currents often cannot maintain their sediment in suspension even when the bottom stress is greater than the critical stress of deposition for low concentration flows when this happens the concentration near the bottom increases without limit as the turbidity current evolves with time in real turbidity currents grain grain interactions which become important at high concentrations may at times cause the current to quickly deposit its near bottom sediment load this is suggested as a possible mechanism for the formation of the poorly sorted sediments frequently found in turbidites

sediment mass flow processes on a depositional lobe outer mississippi fan abstract seamarc 1a sidescan sonar imagery and cores from the distal reaches of a depositional lobe on the mississippi fan show that channelized mass flow was the dominant mechanism for transport of silt and sand during the formation of this part of the fan sediments in these flows were rapidly deposited once outside of their confining channels the depositional lobe is formed of a series of long narrow sublobes composed of thin bedded turbidites normally graded siliciclastic sand and silt 20 cm thick on average debris flow deposits soft clay clasts up to 5 cm in diameter in a siliciclastic silt matrix 48 cm thick on average and background sedimentation hemipelagic muds the mass flows most likely originated from slope failure at the head of the mississippi canyon or on the outer ontinental shelf and flowed approximately 500 km to the distal reaches of the fan with debris flow being the dominant flow type an analysis that uses the geometry of the confining channels and strength properties of the debris flow material shows that these thin debris flows could have traveled hundreds of kilometers on extremely small sea floor slopes at low velocities if the flowing medium behaved as bingham fluids and were steady state phenomena

field expressions of the transformation of debris flows into turbidity currents with examples from the polish carpathians and the french maritime alps various transformation mechanisms can generate turbidity currents from subaqueous debris flows different transformation mechanisms have been described and interpreted in the past from laboratory experiments and from deposits but the two approaches have not generally been linked this has made the genetic interpretation and comparison of deposits difficult in this paper a generic classification scheme of debrite turbidite couplets is proposed based on transformation mechanisms inferred from laboratory experiments five different flow types called a e herein and their resulting deposits are detailed but they are all part of a continuous spectrum and a mixture of types is likely to be found in the field type a flows are strong dense debris flows that undergo little transformation their deposit will be a debrite overlain by a thin turbidite which is separated from it by a clear grain size break type b flows are weaker and can develop waves at the debris flow turbidity current interface the deposit will be a debrite with a wavy top overlain by a turbidite that is thicker than for type a flows for type c flows the interfacial waves will grow so much that the debris flow disintegrates into separate parts the deposit will consist of debrite lenses encased in a turbidite type d flows will undergo even more mixing than type c flows so that the debrite parts will be mixed their deposit will be a turbidite with laterally varying areas of debrite characteristics near the bed type e flows will be so transformed that the debris flow character has disappeared and the flow is a turbidity current with high sediment concentration the deposit will be largely turbiditic the flow types and deposits will be illustrated with some examples from two field areas the polish carpathians and the french maritime alps

groundwater waves in a coastal aquifer a new governing equation including vertical effects and capillarity groundwater waves that is water table fluctuations are a natural phenomenon in coastal aquifers they represent an important part of the interaction between the ocean and aquifer and affect the mass exchange between them this paper presents a new groundwater wave equation because it includes the effects of vertical flows and capillarity the new equation is applicable to both intermediate depth aquifers and high frequency waves compared with the wave equation derived by nielsen et al 1997 the present equation provides a closer representation of groundwater waves in particular it predicts high frequency water table fluctuations as observed in the field a validation of the new equation has been carried out by comparing the analytical solutions to it with predictions from direct simulations using the numerical model sutra the effects of various physical parameters and their relative importance are also discussed

traction carpet stratification in turbidites fact or fiction abstract the spaced stratification that characterizes some thick deep water sandstones consists of a stack of layers 5 10 cm thick that are inversely graded at their base and structureless at their top these layers have been attributed to deposition from a succession of collapsed inertia layers traction carpets prior to collapse each layer was believed to have been maintained by shear from the overriding turbidity current this depositional model is based on the mistaken assumption that the distribution of shear stress in such a traction carpet is indistinguishable from the distribution of shear stress in a grain flow on a steep slope instead shear stress in an externally sheared traction carpet should be approximately constant from the top to the base of the layer and deposition sho ld be a gradual process leaving no record of sequentially active inertia layers inertia layers that do form under large turbidity currents are probably never as thick as 5 10 cm based on available data from shear cell experiments instead inertia layers are probably about 1 cm thick similar to the thickness of the inversely graded basal part of each layer in field examples of spaced stratification the rest of each inversely graded stratum probably forms due to rapid fallout from suspension the basal inversely graded 1 cm is believed to record strong shear that may accompany impingement on the bed of large turbulent eddies hence spaced stratification may not be a structure produced beneath steady flows but may record strong y fluctuating hydrodynamic conditions and vigorous burst sweep cycles in large turbidity currents

effects of unsaturated flow on hillslope recession characteristics recession flow analysis is usually conducted to infer hydraulic parameters of hillslope aquifers various boussinesq equation based models both linear and nonlinear have been used to analyze the recession curves for sloping aquifers with a focus on the long time recession behavior based on a modified boussinesq equation with capillarity incorporated we demonstrate the significant effect of unsaturated flow on the recession curve which result in three instead of two power law regimes with two transition points instead of one corresponding to the formation of a fully unsaturated zone at the adjacent area of the upslope boundary and across the whole domain respectively the results show that the power of the second and third recession regime is variable depending on the slope angles soil types and hillslope geometries the unsaturated flow effects also lead to the absence of drastic drop of formula presented at the transition between the first and second regime which was predicted by previous numerical models but has not been observed in the field or laboratory experiments these findings have important implications for recession flow analysis in studies of hillslope aquifers

modelling the permeability evolution of carbonate rocks abstract diagenesis is a major control on the distribution of porosity and permeability in carbonate rocks and therefore impacts fluid flow in the subsurface while changes in porosity can be directly related to diagenetic petrographic characteristics such as cement distribution and dissolution features quantifying how these textures relate to attendant changes in permeability is more challenging here we demonstrate for the first time how pore scale models representing typical carbonate sediments and their diagenetic histories can be used to quantify the evolution of petrophysical properties in carbonate rocks we generate 3d pore architecture models i e the spatial distribution of solid and pores from 2d binarized images representing the typical textural changes of carbonate sediments following hypothetical diagenetic pathways for each 3d rock model we extract the pore system and convert this into a network representation that allows flow properties to be calculated the resulting porosity and permeability evolution scenarios display several diagenetic tipping points where the decrease in permeability is dramatically larger than expected for the associated decrease in porosity the effects of diagenesis also alter the capillary entry pressures and relative permeabilities of the synthetic cases providing trends that can be applied to real rocks indeed values of porosity and absolute permeability derived from these synthetic 3d rock models are within the range of values measured from nature such diagenetic pathway models can be used to provide constraints on predicted flow behaviour during burial and or uplift scenarios using diagenetic back stripping of real carbonate rocks

effects of vadose zone on groundwater table fluctuations in unconfined aquifers summary above a shallow unconfined aquifer a considerable amount of water is stored in the vadose zone through water exchange with the underlying unconfined aquifer the vadose zone affects the groundwater table dynamics and overall behavior of the aquifer in this paper we examine tide induced groundwater table fluctuations in unconfined aquifers influenced by vadose zone of finite thickness under the condition of small aquifer thickness d compared with the groundwater wavelength l i e 2 d l 2 1 and small boundary oscillation amplitude a i e e a d 1 where 2 and e are two parameters an approximate analytical solution was derived to quantify systematically the vadose zone effects with a particular consideration of capping by the ground surface i e the upper boundary of the vadose zone depending on the extent to which the capillary rise is truncated by the ground surface the vadose zone enhances the groundwater table fluctuations in an unconfined aquifer however the mean groundwater table height and exchange between surface water and groundwater are reduced due to the presence of the vadose zone these effects are intensified with increased capillary rise but weakened as the vadose zone thickens this study provides a criterion for assessing the importance of vadose zone in modulating the response of unconfined aquifers to low frequency forcing oscillations such as tides

submarine channel response to intrabasinal tectonics the influence of lateral tilt lateral tilting is a common deformation style in extensional basins its influence on subaerial channels is to a degree understood and may be significant controlling the style of channel development and the resultant sand body architecture growth faulting and lateral tilting in turbidite channel systems have been demonstrated from three dimensional seismic data but the resultant architecture of channels within these settings has not yet been documented in the carboniferous of northern england a sand rich slope channel developed within a basin undergoing late stage extension underwent progressive and unidirectional migration toward a topographic low on a laterally tilting block the resultant sandstone body is wedge shaped in cross section and composed dominantly of sigmoidal lateral accretion deposits the channel returned to an axial course before undergoing lateral migration in the same direction creating a multistory multilateral channel sandstone body the repeated unidirectional migration combined with evidence of syndepositional deformation suggests that active tectonism strongly influenced channel evolution and deposition a model of submarine channel evolution in extensional basins is presented in systems where large displacements occur the channel system may avulse creating isolated sand ribbons which are connected updip where the lateral dip is always more influential than the regional dip the system may pond in the hanging wall syncline the model is compared to a subsurface channel within the pliocene of the nile delta slope which was influenced by syndepositional fault movement application of the outcrop derived model allows some simple architectural interpretations to be made

influence of hysteresis on groundwater wave dynamics in an unconfined aquifer with a sloping boundary in this paper the influence of hysteresis on water table dynamics in an unconfined aquifer was examined using a numerical model to solve richards unsaturated flow equation the model was subject to simple harmonic forcing across a sloping boundary with a seepage face boundary condition time series from both hysteretic and non hysteretic models were subject to harmonic analysis to extract the amplitude and phase profiles for comparison with existing sand flume data cartwright et al 2004 the results from both model types show good agreement with the data indicating no influence of hysteresis at the oscillation period examined t 348 s the models were then used to perform a parametric study to examine the relationship between oscillation period and hysteresis effects with periods ranging from 3 min to 180 min at short oscillation periods t 180 s the effects of hysteresis were negligible with both models providing similar results as the oscillation period increased the hysteretic model showed less amplitude damping than the non hysteretic model for periods greater than t 60 min the phase lag in the non hysteretic model is greater than for the hysteretic one for periods less than t 60 min this trend is reversed and the hysteretic model produced a greater phase lag than the non hysteretic model these findings suggest that consideration of hysteresis dynamics in richards equation models has no influence on water table wave dispersion for short period forcing such as waves t 10 s whereas for long period forcing such as tides t 12 25 h or storm surges t days hysteresis dynamics should be taken into account

tide induced seawater groundwater circulation in a multi layered coastal leaky aquifer system abstract mean groundwater levels of a multi layered coastal leaky aquifer system are considered the system consists of an unconfined aquifer a confined aquifer and a semi permeable layer between them both exact asymptotic solutions and approximate perturbation solutions are derived for multi sinusoidal component sea tide at inland places far from the coastline the perturbation solutions show a good agreement with the exact asymptotic solutions due to the watertable dependent transmissivity of the unconfined aquifer the mean groundwater levels of the aquifer system stand considerably above the mean sea level even in the absence of net inland recharge of groundwater and rainfall these lead to landward positive gradients of both the mean watertable and mean head in the region near the coastline which consequently results in a seawater groundwater cycle seawater is pumped into the unconfined aquifer by the sea tide and divided into two parts one part returns to the sea driven by the mean watertable gradient the rest part leaks into the confined aquifer through the semipermeable layer and returns to the sea through the confined aquifer driven by the mean head gradient the total discharge through the confined aquifer is significant for coastal leaky aquifer system with typical parameter values this seawater groundwater cycle has impacts on better understanding of submarine groundwater discharge and exchange of various chemicals such as nutrients and contaminants in coastal areas if the observed mean water levels in coastal areas are used for estimating the net inland recharge the enhancing processes of sea tide on the mean groundwater levels should be taken into account otherwise the net inland recharge will be overestimated

quantitative analysis of submarine flow deposit shape in the marnoso arenacea formation what is the signature of hindered settling from dense near bed layers abstract submarine sediment density flows are one of the volumetrically most important processes for sediment transport across earth the sediment concentration of flows that reach the deep ocean has never been measured directly and understanding these long runout flows remains a major challenge the miocene marnoso arenacea formation in the italian apennines is the only ancient sequence where individual submarine sediment density flow deposits single beds have been mapped out for more than 100 km down flow here we document the external shape and internal architecture of thirty two individual beds that record flow evolution and can be compared to deposit shapes in mathematical or experimental models the large number of beds allows modes of flow behavior to be identified larger volume turbidites are typically dominated by massive ta or planar laminated tb sandstone intervals that have a broad thickness maximum this shape is important because it suggests that massive and planar laminated sandstones record hindered settling from dense near bed layers which have high 10 by volume sediment concentrations previously some authors have inferred that planar laminated sandstones tb are deposited mainly by dilute flows the position of the broad thickness maximum moves basinward as the volume of sand in the flow increases this is consistent with mathematical modeling that suggests the position of the thickness maximum depends on flow thickness flow speed and sediment settling velocity as well as sediment concentration variations in seawater entrainment rate and local changes in seafloor gradient smaller volume turbidite sandstone intervals are finer grained and dominated by ripple cross lamination tc and have a near exponential decay in thickness that is consistent with deposition from a dilute sediment suspension the rate of near exponential thinning is controlled by sandstone volume in contrast turbidite mudstone intervals show an approximately linear increase in thickness with distance flows that entered the basin in opposite directions produced turbidite mudstone intervals that thicken towards the same location indicating that muddy turbidity currents can drain back over long distances to basinal lows

reversing buoyancy in turbidity currents developing a hypothesis for flow transformation and for deposit facies and architecture a turbidity current that contains fresher or otherwise less dense water than its surroundings may initially be denser than the ambient and propagate as a bottom hugging flow but later reverse in buoyancy as its bulk density decreases through sedimentation to become lower than that of the ambient seawater it is proposed that this reversal in buoyancy may be a significant mechanism controlling the structure and facies of turbiditic deposits buoyancy reversal followed by lofting may directly affect the relative distribution of fine and coarse material in the deposit while buoyancy reversal itself may mediate the transformation between dilute and highly concentrated suspension flows particularly in distal regions and thus lead to the formation of complex turbiditic beds in particular the generation of distal co genetic debrites may be expected similar transformations occur within dilute pyroclastic density currents where a mobile basal concentrated flow termed a surge derived pyroclastic flow develops through rapid sedimentation from the suspended load of the overlying surge the physical mechanisms involved in these processes are discussed leading to the proposal of some associated facies models these are compared with field data from the northern apennines with some striking similarities being noted as well as some differences on the basis of this discussion some directions are suggested for future experimental and modelling work on the topic

beach water table fluctuations due to wave run up capillarity effects high frequency beach water table fluctuations due to wave run up and run down have been observed in the field waddell 1976 such fluctuations affect the infiltration exfiltration process across the beach face and the interstitial oxygenation process in the beach ecosystem accurate representation of high frequency watertable fluctuations is of importance in the modeling of 1 the interaction between seawater and groundwater more important the effects on swash sediment transport and 2 the biological activities in the beach ecosystem capillarity effects provide a mechanism for high frequency water table fluctuations previous modeling approaches adopted the assumption of saturated flow only and failed to predict the propagation of high frequency fluctuations in the aquifer in this paper we develop a modified kinematic boundary condition kbc for the water table which incorporates capillarity effects the application of this kbc in a boundary element model enables the simulation of high frequency water table fluctuations due to wave run up numerical tests were carried out for a rectangular domain with small amplitude oscillations the behavior of water table responses was found to be similar to that predicted by an analytical solution based on the one dimensional boussinesq equation the model was also applied to simulate the water table response to wave run up on a sloping beach the results showed similar features of water table fluctuations observed in the field in particular these fluctuations are standing wave like with the amplitude becoming increasingly damped inland we conclude that the modified kbc presented here is a reasonable approximation of capillarity effects on beach water table fluctuations however further model validation is necessary before the model can confidently be used to simulate high frequency water table fluctuations due to wave run up

an analytical solution of groundwater response to tidal fluctuation in a leaky confined aquifer an analytical solution is derived to investigate the influence of leakage on tidal response in a coastal leaky confined aquifer system the analytical solution developed here is more general than the traditional solution obtained by ferris 1951 which can be regarded as a special case of the solution presented in this paper this solution is based on a conceptual model under the assumption that the groundwater level in the confined aquifer fluctuates in response to sea tide while that of the overlying unconfined aquifer remains constant this conceptual model is supported by numerous field studies by previous researchers which have demonstrated that the tidal response in an unconfined aquifer may be negligible compared to that in a confined aquifer the leakage has a significant impact on the tidal behavior of the confined aquifer hypothetical studies indicate that both tidal amplitude of groundwater head in the aquifer and the distance over which the aquifer can be disturbed by the sea tide will be considerably reduced because of the existence of leakage this analytical solution is used to investigate the tidal and piezometer data at the chek lap kok airport hong kong special administrative region people s republic of china

process controls on the development of stratigraphic trap potential on the margins of confined turbidite systems and aids to reservoir evaluation stratigraphic trapping at pinch out margins is a key feature of many turbidite hosted hydrocarbon reservoirs in systems confined by lateral or oblique frontal slopes outcrop studies show that there is a continuum between two geometries of pinch out configuration in type a turbidites thin onto the confining surface although the final sandstone pinch out is commonly abrupt and individual beds tend not to erode into earlier deposits in type b turbidite sandstones commonly thicken toward the confining slope and beds may incise into earlier deposits these two types may occur in combination to give a wide spectrum of pinch out characteristics our analysis suggests the principal control in determining pinch out character is flow magnitude with smaller flows producing type a and larger flows producing type b in areas of poor seismic control it can be difficult to assess either pinch out character or the proximity of wells to confining slopes because estimates of paleoflow magnitude can be made from core or high quality log image data however it is possible to make reasonable estimates of pinch out character even from wells such as exploration wells which may be placed conservatively away from the field margins furthermore systematic paleoflow variations and thickness trends are commonly seen in individual turbidite sandstones as they approach confining slopes for example dispersal directions indicate flow deflection parallel with the strike of confining topography beds thin toward type a onlaps and thicken toward type b onlaps these relationships can be exploited via analysis of vertical successions to constrain well position with respect to the slope similarly the presence location and frequency of locally derived debrites can provide information on the presence and proximity of confining slopes begin page 972

making a homogenite an outcrop perspective into the evolution of deformation within mass transport deposits abstract mass transport deposits mtds may show a variety of deformation aspects from poorly deformed layers to highly deformed and homogenized deposits as a result of the different kinds of mass transport processes involved in their evolution previous studies indicate that the downslope flow transformation of mtds is characterized by increasing disaggregation mixing and homogenization of a non to poorly lithified protolith which may ultimately generate a homogenite we here explore the role of deformation processes in the disaggregation and mixing of sediments that tend to lead to sediment homogenization and so may also control the evolution of mtds using the itarare group of the parana basin southern brazil as our case study we examine several types of structures in mtds with varying degrees of mass disaggregation and discuss the role of deformation process in the continuum homogenization of the sediment three deformational facies df 1 df 2 and df 3 were identified and interpreted as recording varying stages of homogenization of sediments disaggregation and mixing within the incipient mature and evolved flows respectively these different stages show transitional aspects that indicate a continuum homogenization the comparison between structural assemblages and the amount of matrix in the three different deformational facies indicates a close relationship between styles of deformation and the homogenization expected for mass flows the processes that promoted disaggregation include boudinage faulting layer parallel shearing and marginal deformation of intrabasinal clasts while mixing processes that generate matrix include shearing and liquefaction fluidization of sediments

redefining the waitemata basin new zealand a new tectonic magmatic and basin evolution model at a subduction terminus in the sw pacific 1 the early miocene waitemata basin has long been described as an interarc intra arc basin formed between twin chains of arc volcanoes in northland new zealand however deep marine polymict volcaniclastic conglomerates within the basin reveal tectonic and magmatic signals that are not evident from neighboring volcanic edifices the conglomerates were deposited by high density turbidity currents and debris flows and include single sediment cycle megaclasts of lava these basaltic lavas have ocean island basalt oib like geochemical affinities and are precisely dated at 20 ma by 40ar 39ar methods their age and the occurrence of subordinate clasts derived from an ophiolitic nappe to the north indicate the basin postdates the initiation of collision in the wider region contemporaneous calc alkaline volcanism did occur some 250 km nw of the basin however the conglomerates lack clasts of calc alkaline arc affinities indicating an absence of arc like volcanism in the vicinity of the basin recent tectonic models for the sw pacific region and mantle tomography highlight the importance of wholesale slab detachment in driving early miocene calc alkaline volcanism and basin development although such models provide a slab window for the eruption of nonarc oib like magmas they would not explain their localized occurrence at the proposed leading edge of the tear waitemata basin rather than progressively along the entire length of the detachment northland as seen in other detachment settings in addition oib like volcanism predates the adjacent calc alkaline volcanism on the margin of the basin a transition that is the opposite of that found at other slab detachment settings the occurrence of oib like volcanism is better explained by a lateral slab termination in the vicinity of the waitemata basin that allowed asthenospheric derived magmas to erupt the basin is inferred to have developed in response to asthenospheric upwelling and associated lithospheric extension or deformation associated with a slab termination zone this study highlights the importance and potential of combined geochemical geochronological and sedimentological studies of conglomerates in reconstructing the geodynamic setting of a basin

beds comprising debrite sandwiched within co genetic turbidite origin and widespread occurrence in distal depositional environments co genetic debrite turbidite beds occur in a variety of modern and ancient turbidite systems their basic character is distinctive an ungraded muddy sandstone interval is encased within mud poor graded sandstone siltstone and mudstone the muddy sandstone interval preserves evidence of en masse deposition and is thus termed a debrite the mud poor sandstone siltstone and mudstone show features indicating progressive layer by layer deposition and are thus called a turbidite palaeocurrent indicators ubiquitous stratigraphic association and the position of hemipelagic intervals demonstrate that debrite and enclosing turbidite originate in the same event detailed field observations are presented for co genetic debrite turbidite beds in three widespread sequences of variable age the miocene marnoso arenacea formation in the italian apennines the silurian aberystwyth grits in wales and quaternary deposits of the agadir basin offshore morocco deposition of these sequences occurred in similar unchannellized basin plain settings co genetic debrite turbidite beds were deposited from longitudinally segregated flow events comprising both debris flow and forerunning turbidity current it is most likely that the debris flow was generated by relatively shallow few tens of centimetres erosion of mud rich sea floor sediment changes in the settling behaviour of sand grains from a muddy fluid as flows decelerated may also have contributed to debrite deposition the association with distal settings results from the ubiquitous presence of muddy deposits in such locations which may be eroded and disaggregated to form a cohesive debris flow debrite intervals may be extensive 26 x 10 km in the marnoso arenacea formation and are not restricted to basin margins such long debris flow run out on low gradient sea floor 0 1 may simply be due to low yield strength 50 pa of the debris water mixture this study emphasizes that multiple flow types and transformations between flow types can occur within the distal parts of submarine flow events

increased marine sediment suspension and fluxes following an earthquake earthquakes are commonly cited as one possible triggering mechanism for turbidity flows dense sediment water plumes that can transport large volumes of sediment great distances down slope in both marine and lacustrine settings1 2 3 4 5 6 heezen and ewing1 were the first to make such a suggestion attributing breaks in a sea floor telephone cable in the north atlantic ocean to turbidity flows generated by the 1929 grand banks earthquake anumber of workers have consequently used sedimentary turbidite records to reconstruct the earthquake histories of various regions2 7 8 here we present direct observations of a seismically induced turbidity flow measurements of light scattering and sediment fluxes in the cariaco basin indicate that the earthquake that occurred along the coast of northern venezuela on 9 july 1997 resulted in considerable downslope displacement of sediments probably 105 tonnes into the deep part of the basin in such a seismically active region this mechanism of sediment transport may be responsible for a significant component of the long term sediment accumulation in the basin furthermore this process may result in the sequestration in deep sea sediments of large amounts of carbon initially deposited at shallow depths

subaqueous sediment gravity flow deposits practical criteria for their field description and classification a new method for the description and classification of subaqueous sediment gravity flow deposits is proposed the classification scheme employs a convenient letter code and divides deposits individual beds into descriptive categories of two hierarchical levels facies and subfacies facies as the higher rank categories are distinguished chiefly on the basis of sediment type i e bed grain size texture a total of 13 facies have been distinguished g gravel gs gravel sand couplet gys gravelly sand s sand sm sand mud couplet ms mud sand couplet tm silt mud couplet mt mud silt couplet m mud mys muddy sand sym sandy mud myg muddy gravel gym gravelly mud subfacies as the lower rank categories are distinguished within the individual facies on the basis of the bed s internal structures the number of subfacies is unlimited and their labelling code includes particular facies symbols see above preceded by lower case letters denoting specific sedimentary structures and their vertical arrangement subfacies thus refer to the bed s intervals or divisions which are labelled as follows m massive unstratified and ungraded g graded unstratified and graded s plane stratified x cross stratified 1 parallel and or cross laminated q liquefied for example subfacies gsg graded to plane stratified gravel are gravel beds that have a lower graded interval and an upper plane stratified interval subfacies xg cross stratified gravel are gravel beds that are cross stratified throughout subfacies sls plane stratified to laminated sand are sand beds that have a lower plane stratified interval and an upper laminated parallel and or cross laminated interval

improvement of the hillslope storage boussinesq model by considering lateral flow in the unsaturated zone unsaturated flow is an important factor that affects groundwater motion among various drainage models the nonlinear hillslope storage boussinesq hsb model has been commonly used to predict water flux along a slope in this study we improved this model by considering lateral flow in the unsaturated zone using modified van genuchten functions we analytically expressed the concept of equivalent propagation thickness in the vadose zone this analytical expression was then incorporated into the hsb model to reflect two different stages of the drainage process and to simulate the hillslope drainage process more accurately the model results indicated that lateral flow has significant effects in the unsaturated zone during the hillslope drainage process even in sandy aquifers the amount of water contributed by the unsaturated zone is a key factor that enables a decrease in the water table during the middle and late stages of the process a comparison between the measured and simulated results based on both convergent type and divergent type hillslope drainage processes revealed that the thickness of the saturated zone decreases as the unsaturated flow increases this study emphasizes the necessity of considering unsaturated flow in the hsb model to improve the accuracy of predicting groundwater outflow rates and develop more accurate hydrographs the concept of equivalent propagation thickness also provides a criterion for assessing the importance of unsaturated lateral flow for future drainage research

contained reflected turbidity currents from the middle ordovician cloridorme formation quebec canada an alternative to the antidune hypothesis the parautochthonous cloridorme formation is a syn orogenic flysch succession that was deposited in an elongate foredeep basin as mainly lower middle fan outer fan and basin floor deposits the basin floor deposits about 1 5 km thick are confined to members 1 2 and 1 and are characterized by graded thick 1 10 m mud rich calcareous greywacke beds previously interpreted as deposits of concentrated muddy unidirectional turbidity currents that locally generated backset antidune lamination in internally stratified flows the dominant flow directions were from east to west but west to east transport also occurred as seen in the orientation of ripples climbing ripples flutes consistently overturned flames and grain imbrication we believe that the flows that deposited these thick calcareous greywacke beds reversed by roughly 180 one or more times during deposition of the lower sandy part of the beds flow reversals are consistent with the sharp grain size breaks and mud partings within sandy divisions measurement of grain fabric relative to stratification in the most celebrated antidune bedforms indicates flow from west to east thus the bedforms were produced by west to east migration of megaripples not by the upcurrent migration of antidunes the thick muddy beds were deposited by large volume muddy flows that were deflected and reflected from the side slopes and internal topographic highs of a confined basin floor much like the contessa and similar beds of the italian apennines large quantities of suspended mud were ponded above the irregular basin floor and settled to produce the thick silty mudstone caps seen on each bed because of their mode of emplacement we propose that these beds be called contained turbidites