assessing aeolian beach surface dynamics using a remote sensing approach a remote sensing technique for assessing beach surface moisture was used to provide insight into beach surface evolution during an aeolian event an experiment was carried out on october 21 2007 at greenwich dunes prince edward island national park canada during which cameras were mounted on a mast on the foredune crest at a height of about 14 m above the beach maps of beach surface moisture were created based on a calibrated relationship between surface brightness from the photographs and surface moisture content measured in situ at points spaced every 2 5 metres along a transect using a delta t moisture probe a time sequence of maps of surface moisture content captured beach surface evolution through the transport event at a spatial and temporal resolution that would be difficult to achieve with other sampling techniques such as impedance probes erosion of the foreshore and berm crest resulted in an increase in surface moisture content in these areas as the wetter underlying sediments were exposed flow expansion downwind of the berm crest led to sand deposition and a consequent decrease in surface moisture content remote sensing systems such as the one presented here allow observations of the combined evolution of beach surface moisture shoreline position and fetch distances during short term experiments and hence provide a comprehensive rendering of sediment erosion and transport processes

seagrass wrack induced dune formation on a tropical coast banc d arguin mauritania abstract the banc d arguin mauritania is a shallow water area with mudflats bordering on the sahara desert mass depositions of seagrass litter were observed on some parts of the shore soil profiles of the low dune formations separating the flood debris zone from the desert showed that layers of seagrass detritus in various stages of decay extended under the dune formations the tentative mechanism of dune formation involving the interacting processes of beaching of seagrass litter and wind blown transport of desert sediment in a seaward direction is described this role in dune formation adds a new element to the significance of seagrass vegetation for the coastal environment

signatures of climate vs sea level change within incised valley fill successions quaternary examples from the texas gulf coast abstract the passive margin texas gulf of mexico coastal plain consists of coalescing late pleistocene to holocene alluvial deltaic plains constructed by a series of medium to large fluvial systems alluvial deltaic plains consist of the pleistocene beaumont formation and post beaumont coastal plain incised valleys a variety of mapping outcrop core and geochronological data from the extrabasinal colorado river and the basin fringe trinity river show that beaumont and post beaumont strata consist of a series of coastal plain incised valley fills that represent 100 kyr climatic and glacio eustatic cycles valley fills contain a complex alluvial architecture falling stage to lowstand systems tracts consist of multiple laterally amalgamated sandy channelbelts that reflect deposition within a valley that was incised below highstand alluvial plains and extended across a subaerially exposed shelf the lower boundary to falling stage and lowstand units comprises a composite valley fill unconformity that is time transgressive in both cross and down valley directions coastal plain incised valleys began to fill with transgression and highstand and landward translation of the shoreline paleosols that define the top of falling stage and lowstand channelbelts were progressively onlapped and buried by heterolithic sandy channelbelt sandy and silty crevasse channel and splay and muddy floodbasin strata transgressive to highstand facies scale architecture reflects changes through time in dominant styles of avulsion and follows a predictable succession through different stages of valley filling complete valley filling promoted avulsion and the large scale relocation of valley axes before the next sea level fall such that successive 100 kyr valley fills show a distributary pattern basic elements within coastal plain valleys can be correlated with the record offshore where cross shelf valleys have been described from seismic data falling stage to lowstand channelbelts within coastal plain valleys were feeder systems for shelf phase and shelf margin deltas respectively and demonstrate that falling stage fluvial deposits are important valley fill components signatures of both upstream climate change vs downstream sea level controls are therefore interpreted to be present within incised valley fills signatures of climate change consist of the downstream continuity of major stratigraphic units and component facies which extends from the mixed bedrock alluvial valley of the eroding continental interior to the distal reaches wherever that may be at the time this continuity suggests the development of stratigraphic units and facies is strongly coupled to upstream controls on sediment supply and climate conditions within hinterland source regions signatures of sea level change are critical as well sea level fall below the elevation of highstand depositional shoreline breaks results in channel incision and extension across the newly emergent shelf which in turn results in partitioning of the 100 kyr coastal plain valleys moreover deposits and key surfaces can be traced from continental interiors to the coastal plain but there are downstream changes in geometric relations that correspond to the transition between the mixed bedrock alluvial valley and the coastal plain incised valley channel incision and extension during sea level fall and lowstand with channel shortening and delta backstepping during transgression controls the architecture of coastal plain and cross shelf incised valley fills

paleosols and associated channel belt sand bodies from a continuously subsiding late quaternary system po basin italy new insights into continental sequence stratigraphy previous sequence stratigraphic work has emphasized the key role of paleosols and associated sand dominated fluvial bodies as key features for interpreting alluvial architecture the temporal resolution of the ancient record is however insufficient to fully explain the complex relationship between soil formation and the evolution of fluvial systems under changing sea level and climate conditions in this paper we present a detailed record of paleosol channel belt relationships reconstructed from the subsurface of a rapidly subsiding region po plain italy that spans almost all of the last glacial interglacial cycle 120 k y the studied succession preserves a systematic bipartite zonation into a thick paleosol bearing segment close to the basin margin and a sand dominated interval with vertically amalgamated channel belts in an axial position individual paleosols are weakly developed and represent key stratigraphic markers that can be traced basinwide into adjacent essentially contemporaneous unconfined channel belt deposits unlike conventional models of late quaternary alluvial coastal plain systems no persistent incised valley was established in the po system during the last glacial interglacial cycle continuous accommodation was the key depositional control on alluvial stratigraphy during the prolonged 90 k y phase of late pleistocene sea level fall which led to the deposition of a thick dominantly aggradational alluvial succession the development of shallowly incised short lived valley systems took place only at the transition to glacial stages associated with substantial sea level drop marine oxygen isotope stage mis 3 2 transition and possibly mis 5 4 transition this study shows that in rapidly subsiding settings with high rates of sedimentation incised valley systems may be replaced by aggradationally stacked essentially nonincised fluvial bodies in these cases overbank packages bounded by immature paleosols represent the most likely alternative to the highly weathered interfluve paleosol predicted by classic sequence stratigraphic models fourth order sequence boundaries and lower rank erosional surfaces may be easily confused at the 100 k y scale and transgressive surfaces defining the onset of retrogradation may become the most readily identifiable sequence stratigraphic surfaces

aeolian sediment transport on a beach surface moisture wind fetch and mean transport abstract temporal and spatial changes in wind speed wind direction and moisture content are ubiquitous across sandy coastal beaches often these factors interact in unknown ways to create complexity that confounds our ability to model sediment transport at any point across the beach as well as our capacity to predict sediment delivery into the adjacent foredunes this study was designed to measure wind flow and sediment transport over a beach and foredune at greenwich dunes prince edward island national park with the express purpose of addressing these complex interactions detailed measurements are reported for one stormy day october 11 2004 during which meteorological conditions were highly variable wind speed ranged from 4 ms 1 to over 20 ms 1 wind direction was highly oblique varying between 60 and 85 from shore perpendicular and moisture content of the sand surface ranged from a minimum of about 3 by mass to complete saturation depending on precipitation tidal excursion and storm surge that progressively inundated the beach the data indicate that short term variations i e minutes to hours in sediment transport across this beach arise predominantly because of short term changes in wind speed as is expected but also because of variations in wind direction precipitation intensity and tide level even slight increases in wind speed are capable of driving more intense saltation events but this relationship is mediated by other factors on this characteristically narrow beach as the angle of wind approach becomes more oblique the fetch distance increases and allows greater opportunity for the saltation system to evolve toward an equilibrium transport state before reaching the foredunes whether the theoretically predicted maximum rate of transport is ever achieved depends on the character of the sand surface e g grain size slope roughness vegetation moisture content and on various attributes of the wind field e g average wind speed unsteadiness approach angle flow compression boundary layer development moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface all other things being equal the rate of sediment transport over a wet surface is lesser than over a dry surface on this beach the moisture effect has two important influences a in a temporal sense the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place and b in a spatio temporal sense shoreline excursions associated with nearshore processes such as wave run up storm surge and tidal excursions have the effect of constraining the fetch geometry of the beach i e narrowing the width of the beach because saturated sand surfaces such as found in the swash zone will only reluctantly yield sediments to aeolian entrainment the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach under these constrained conditions the transport system begins to shut down unless wind angle becomes highly oblique thereby increasing fetch distance in this study maximum sediment transport was usually measured on the mid beach rather than the upper beach i e closer to the foredunes this unusual finding is likely because of internal boundary layer development across the beach which yields a decrease in near surface wind speed and hence transport capacity in the landward direction although widely recognized in the fluid mechanics literature this decrease in near surface shear stress as a by product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology

sequence stratigraphy in lacustrine basins a model for part of the green river formation eocene southwest uinta basin utah u s a abstract in the middle green river formation of central nine mile canyon uinta basin utah several lacustrine dominated intervals 10 m thick comprise aggradational carbonate parasequence sets and a progradational clastic parasequence maximum flooding surfaces are best identified within profundal oil shale that caps some of the clastic parasequences these lacustrine transgressive systems tracts therefore exhibit parasequence stacking patterns unlike typical marine sequences two types of sequence boundary are identified type a sequence boundaries display evidence for a basinward shift in facies across a regionally mappable surface that is an angular or rarely parallel unconformity and they typically juxtapose amalgamated braided fluvial channel sandstone late lowstand systems tract onto the profundal oil shale they also bound depositional sequences that show a distinct asymmetry being dominated by transgressive systems tracts 5 80 m thick highstand systems tracts are less than 4 m thick and may be removed completely by erosion on overlying sequence boundaries other surfaces satisfy only some of the standard criteria of sequence boundaries and are termed type b sequence boundaries type a sequence boundaries mark pronounced base level falls following times when the uinta lake had merged with a lake in an adjacent basin to form a much deeper lake such merging permitted the establishment of a new threshold at higher elevation following lake level balancing type b sequence boundaries are interpreted as marking base level falls from a barely merged lake or a lake that had an outflow over a 200 m stratigraphic thickness type a sequence boundaries are more common upsection indicating that with time a pluvial climate became more pronounced or that the adjacent lake was more easily filled type a sequence boundaries also become angular rather than parallel unconformities upsection suggesting increased tilting of the basin margin over time

diffusion of light hydrocarbons in subsurface sedimentary rocks in a deep core hole penetrating paleocene age strata on spitsbergen island diffusive transport of light hydrocarbons from a siltstone into an adjacent sandstone unit is strongly supported by regular patterns of concentration changes which are controlled by molecular type size and structure individual molecular species are ranked in sequence of increasing effective diffusion coefficients benzene and toluene appear to have anomalously high transportation rates these observations are significant with respect to an evaluation of the role of diffusion processes for hydrocarbon migration

influence of high water levels on aeolian sand transport upper beach dune evolution on a macrotidal coast wissant bay northern france abstract aeolian sand transport measurements and detailed topographic surveys were carried out during 1 year along a macrotidal upper beach dune system experiencing rapid coastal retreat aeolian transport measurements coupled with wind records showed extreme spatial and temporal variability along a spatially limited upper beach sector analysis of wind velocity rainfall and water level showed that aeolian sand transport may occur all year long on the upper beach with the most energetic conditions occurring during winter and spring analysis of volume change revealed that aeolian sedimentation on the upper beach occurred only during the summer period while the rest of the year was characterised by upper beach and dune scarp erosion this erosion due to storm events combined with high water levels completely eliminated summer aeolian sand accumulation our results show that aeolian transport and upper beach dune evolution on this macrotidal beach is strongly controlled by the magnitude and frequency of occurrence of high water levels this study illustrates the fact that upper beach dune evolution cannot be completely understood and satisfactorily modelled if only potential aeolian sand transport is considered

sequence response to syndepositional regional uplift insights from high resolution sequence stratigraphy of late early pleistocene strata periadriatic basin central italy abstract this paper deals with the depositional sequences that occur within the uppermost part of the plio pleistocene periadriatic basin fill in the southern marche region central italy the succession is an early pleistocene easterly dipping clastic wedge showing an overall shallowing trend from slope clays to shallow marine and non marine deposits comprising two major sequences namely qmb and qmc analysis has provided new insights into i the nature of sedimentary facies and facies associations occurring within the upper part of qmb and qmc ii the gradual contact within qmb between regressive littoral deposits rld and underlying deep marine blue clays iii the composite origin of the emilian surface which is a widespread erosional unconformity separating qmb from qmc iv the cyclothemic pattern of qmc composed of downstepping small scale depositional sequences v the role played by synsedimentary uplift on the stacking pattern of small scale sequences and their internal architecture up to three small scale depositional sequences have been recognised within qmc qmc1 qmc2 and qmc3 they are up to 50 m thick and defined by previously unrecorded lower rank regionally extensive surfaces facies organization indicates that as a rule in ascending stratigraphic order each small scale sequence may includes a distinctive basal unconformity surface that can be traced from incised valleys to associated interfluves an incised valley fill a transgressive surface of marine erosion a transgressive systems tract a highstand systems tract a regressive surface of marine erosion and an attached falling stage systems tract in proximal positions the small scale sequences are dominated by transgressive and highstand systems tracts with incised valley fills and falling stage systems tracts absent or volumetrically much less significant in relatively basinward locations where the regressive surfaces of marine erosion converge with the lower sequence boundary the falling stage systems tract may represent the entire depositional sequence high frequency sequences display a distinctive stacking pattern and form a tectonically induced forced regressive sequence set underlain by a composite tectonically enhanced regressive surface of marine erosion formed by the lateral connection of lower rank sequence boundaries

theoretical and measured aeolian sand transport on a barrier island louisiana usa over the past 100 years the isles dernieres a low lying barrier island chain along the coast of central louisiana usa has undergone more than 1 km of northward beach face retreat with the loss of 70 of its surface area the erosion results from a long term relative sea level rise coupled with day to day wind and wave action that ultimately favours erosion over deposition at a site in the central isles dernieres 8 days of wind and beach profile measurements during the passage of one winter cold front documented aeolian erosion and deposition patterns under both onshore and offshore winds for offshore winds the theoretical erosion rate based on wind shear velocity closely matched the measured erosion rate for onshore winds the theoretical rate matched the measured rate only after being corrected by a factor that accounted for beach face morphology in late february 1989 a strong cold front moved into coastal louisiana that cold front stalled over the gulf of mexico resulting in 4 days of strong northerly winds at a study site on the isles dernieres during those 4 days the wind moved sand from the backshore to the upper beach face when the cold front finally moved out of the area the wind shifted to the south and decreased in strength the onshore wind then restored some of the upper beach face sand to the backshore while increased wave activity moved the rest into the nearshore the theoretical estimate of 1 28 m3 m 1 for the rate of sand transport by the northerly wind compares well with the measured backshore erosion rate of 1 26 m3 m 1 which was determined by comparing beach profiles from the start and end of the period of northerly winds the theoretical estimate of 0 04 m3 m 1 for the rate of sand transport by the southerly wind however is notably less than the measured rate of 0 45 m3 m 1 the large discrepancy between the two rates can be explained by a difference in the shear velocity of the wind between the beach face where the erosion occurred and the backshore where the wind stress was measured using an empirical relationship for the wind shear drag coefficient as a function of coastal environment the theoretical estimate for the rate of sand transport by the southerly wind becomes 0 44 m3 m 1

aeolian sediment transport and morphologic change on a managed and an unmanaged foredune sediment transport and short term morphologic change were evaluated at a site where sand fences are deployed and the beach is raked managed site and a site where these human adjustments are not practiced unmanaged site data were gathered across the seaward portion of a low foredune when winds blew nearly shore normal at mean speeds 8 9 to 9 3 m s 1 data from traps revealed sediment transport rates at unvegetated portions of the foredune crest 40 2 to 43 5 kg m 1 h 1 were greater than on the backshore 4 9 to 11 2 kg m 1 h 1 due to onshore decreases in surface moisture and speed up of the wind passing over the foredune data from erosion pins indicate sediment input to the dune was 1 48 m3 m 1 alongshore at the managed site and 1 25 m3 m 1 at the unmanaged site the unmanaged site had deposition at the dune toe erosion at mid slope and deposition at the crest deposition occurred at mid slope on the managed site near a partially buried 0 58 m high fence with a porosity of about 65 deposition at partially buried wrack on the upper backshore and dune toe at the unmanaged site was about twice as great as deposition in this zone at the managed site results indicate that 1 the seaward slope of the foredune can be a more important source of sand to the lee of the crest than the beach 2 wrack near the toe can decrease transport into the foredune 3 a scour zone can occur on the foredune slope above the wrack line 4 a fence placed in this location can promote deposition and offset scour but fences can restrict delivery of sediment farther inland evaluation of alternative configurations of fences and strategies for managing wrack is required to better determine the ways that humans modify foredunes copyright 2012 john wiley sons ltd

effects of time dependent moisture content of surface sediments on aeolian transport rates across a beach wildwood new jersey u s a a one day field investigation on an unvegetated backbeach documents the importance of surface sediment drying to aeolian transport surface sediments were well sorted fine sand moisture content of samples taken in the moist areas on the backbeach varied from 2 9 to 9 2 per cent lack of dry sediment inhibited transport prior to 08 50 by 09 10 conspicuous streamers of dry sand moved across the moist surface barchan shaped bedforms 30 to 40 mm high and composed of dry sand moisture content 0 10 per cent formed where sand streamers converged the surface composed of dry sand increased from 5 per cent of the area of the backbeach at 09 50 to 90 per cent by 12 50 mean wind speeds were beetween 5 6 and 8 6 m s 1 at 6 m above the backbeach corresponding shear velocities were always above the entrainment threshold for dry sand and below the threshold for the moist sand on the backbeach measured rates of sand trapped by vertical cylindrical traps increased during the day relative to calculated rates the measured rate of sand trapped on the moist foreshore was higher than the rate trapped on the backbeach during the same interval indicating that the moist foreshore moisture content 18 per cent was an efficient transport surface for sediment delivered from the dry portion of the beach upwind measured rates of sand trapped show no clear relationship to shear velocities unless time dependent surface moisture content is considered results document conditions that describe transport across moist surfaces in terms of four stages including 1 entrainment of moist sediment from a moist surface 2 in situ drying of surface grains from a moist surface followed by transport across the surface 3 entrainment and transport of dry sediment from bedforms that have accumulated on the moist surface and 4 entrainment of sand from a dry upwind source and transport across a moist downwind surface 1997 john wiley sons ltd

seismic modeling of gas chimneys we propose a simple acoustic model explaining the main features of gas chimneys the main elements of the model consist of gas diffusing from a connected fracture network and into the surrounding shale creating an inhomogeneous gas saturation the gas saturation results in an inhomogeneous fluctuating compressional velocity field that distorts seismic waves we model the fracture network by a randomwalk process constrained by maximum fracture length and angleofthefracturewithrespecttothevertical thegassaturation is computed from a simple analytical solution of the diffusion equation and pressure wave velocities are locally obtained assuming that mixing of shale and gas occurs on a scalemuchsmallerthanseismicwavelengths syntheticseismic sections are then computed using the resulting inhomogeneous velocity model and shown to give rise to similar deterioration in data quality as that found in data from real gas chimneys also synthetic common midpointcmpgathers show the same distorted and attenuated traveltime curves as those obtained from a real data set the model shows clearly thatthefeaturesofgaschimneyschangewithgeologicaltime a model parameter in our approach the deterioration of seismicwavesbeingsmallestjustafterthecreationofthegas chimney it seems likely that at least some of the features of gas chimneys can be explained by a simple elastic model in combinationwithgasdiffusionfromafracturenetwork

a chronostratigraphic framework for the upper jurassic morrison formation western u s a the attached document is the authors final accepted submitted version of the journal article you are advised to consult the publisher s version if you wish to cite from it

the dynamic effects of moisture on the entrainment and transport of sand by wind abstract there is an increasing awareness of the influence of surface moisture on aeolian entrainment and transport of sediment existing wind tunnel studies have shown the impact of a limited range of moisture contents on entrainment thresholds but similar investigations are lacking in the field the research reported here investigated the influence of changes in surface moisture content on sand entrainment and transport on a meso tidal beach in anglesey north wales high frequency 1 hz wind velocities measured with hot wire anemometers were combined with grain impact data from a sensit monitor and mass flux measurements from a standard sand trap surface and near surface moisture contents were assessed gravimetrically from surface sand scrapes and also directly by using a thetaprobe critical threshold values for entrainment were specified using a modified form of the time fraction equivalence method stout j e zobeck t m 1996a establishing the threshold condition for soil movement in wind eroding fields proceedings of the international conference on air pollution from agricultural operations mwps c 3 kansas city 7 9 february 1996 pp 65 71 results indicate a time dependent change in dominant control of the sand transport system from moisture to wind speed dependent upon the moisture content of the surface sediment this interchange between controlling parameters on both entrainment and transport was very sensitive to prevailing moisture conditions and took place over a period of minutes to hours under conditions experienced in the experiments presented here the critical moisture threshold for sediment entrainment was determined to be between 4 and 6 higher than the 1 4 specified in previous wind tunnel experiments furthermore a moisture content of nearly 2 where moisture was adhered to transported sediment appeared to have little or no impact on the rate of sand flux

sequence stratigraphic analysis of cenomanian greenhouse palaeosols a case study from southern patagonia argentina abstract the aim of this contribution is to analyse extrinsic i e tectonics climate and eustasy and intrinsic i e palaeotopography palaeodrainage and relative sedimentation rates factors that controlled palaeosol development in the cenomanian mata amarilla formation austral foreland basin southwestern patagonia argentina detailed sedimentological logs facies analysis pedofeatures and palaeosol horizon identification led to the definition of six pedotypes which represent histosols acid sulphate histosols vertisols hydromorphic vertisols inceptisols and vertic alfisols small and large scale changes in palaeosol development were recognised throughout the units small scale or high frequency variations identified within the middle section are represented by the lateral and vertical superimposition of inceptisols vertisols and hydromorphic vertisols lateral changes are interpreted as the result of intrinsic factors to the depositional systems such as the relative position within the floodplain and the distance from the main channels that condition the nature of parent material the sedimentation rate and eventually the palaeotopographic position vertical stacking of different soil types is linked to avulsion processes and the relatively abrupt change in the distance to main channels as the system aggraded the large scale or low frequency vertical variations in palaeosol type occurring in the mata amarilla formation are related to long term changes in depositional environments the lower and upper sections of the studied logs are characterised by histosols and acid sulphate histosols and few hydromorphic vertisols associated with low gradient coastal environments i e lagoons estuaries and distal fluvial systems at the lower boundary of the middle section a thick palaeosol succession composed of vertic alfisols occurs the rest of the middle section is characterised by vertisols hydromorphic vertisols and inceptisols occurring on distal and proximal fluvial floodplains respectively the palaeosol succession for the mata amarilla formation can be analysed within a sequence stratigraphic scheme considering changes in depositional environments in relation to accommodation supply conditions the results contrast with classical models mainly in that the palaeosols of the mata amarilla formation are relatively well developed throughout the whole sequence including transgressive periods of relatively high aggradation rate also even when during regressive episodes when a thick palaeosol succession that marks the sequence boundary is developed in the classical models the lack of incised valleys in this succession led to the preservation of thick palaeosol successions during lowstand conditions the vertical and lateral palaeosol distribution identified in the mata amarilla formation could be eventually extrapolated to other sequences deposited during climate optimums

reconstructing a mid cretaceous landscape from paleosols in western canada abstract the albian stage of the mid cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates a late albian landscape surface that developed during a regression and subsequent sea level rise in the western canada foreland basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the paddy member of the peace river formation reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies utilizing continental sphaerosiderite proxy records the paleosols developed in estuarine sandstones and mudstones and they exhibit evidence of a polygenetic history upon initial exposure and pedogenesis the paddy member developed deeply weathered well drained cumulative soil profiles later stages of pedogenesis were characterized by hydromorphic soil conditions the stages of soil development interpreted for the paddy member correlate with inferred stages of pedogenic development in time equivalent formations located both basinward and downslope upper viking formation and landward and upslope boulder creek formation on the basis of the genetic similarity among paleosols in these three correlative formations the paleosols are interpreted as having formed along a single continuous landscape surface results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions sphaerosiderites in the paddy member paleosols are used to provide proxy values for meteoric 18o values at 52 n paleolatitude in the cretaceous western interior basin the meteoric 18o values are used to refine existing interpretations about the mid cretaceous paleolatitudinal gradient in meteoric 18o values and the mid cretaceous hydrologic cycle

constraints on aeolian sediment transport to foredunes within an undeveloped backshore enclave on a developed coast abstract landforms present in undeveloped beach enclaves located between properties developed with houses and infrastructure are often left to evolve naturally but are influenced by the human structures near them this field study evaluates how buildings and sand trapping fences change the direction of wind approach reduce wind speed and restrict fetch distances for sediment entrainment thereby reducing the potential for aeolian transport and development of dunes in enclaves field data were gathered in an 80 m long 44 m deep beach enclave on the ocean shoreline of new jersey usa comparison of wind characteristics in the enclave with a site unaffected by buildings revealed that offshore winds in the enclave are reduced in strength and altered in direction by landward houses increasing the relative importance of longshore winds vertical arrays of anemometers on the foredune crest foredune toe and berm crest in the enclave revealed increasing wind speed with distance offshore with strongest winds on the berm crest vertical cylindrical traps on the foredune crest foredune toe mid backshore berm crest and upper foreshore revealed the greatest rate of sediment transport on the berm crest sediment samples from the beach and from traps revealed limited potential for aeolian transport because of coarse grain sizes strong oblique onshore winds are common in this region and are normally important for transporting sand to dunes the length of an enclave and the setback distance on its landward side determine the degree to which sediment delivered by oblique winds contributes to dune growth the landward edge of the enclave defined by a sand fence near the dune toe is sheltered along its entire length from winds blowing at an angle to the shoreline of 25 or less a foredune set back this distance in an enclave the length of an individual lot about 20 m would be sheltered at an angle of 57 or less reducing the opportunity for dune building by onshore winds reduced potential for aeolian transport in enclaves implies that human actions may be required to build dunes artificially to protect buildings and roads from storm overwash

landscape and depositional controls on palaeosols of a distributive fluvial system upper cretaceous brazil abstract the stratigraphic record of distributive fluvial systems is commonly characterised by frequent and complex interstratification of palaeosols among channel and overbank deposits however current models focus primarily on sedimentation and pay only limited attention to palaeopedogenesis thereby failing to incorporate important palaeoenvironmental and stratigraphic information this study proposes a pedosedimentary model for distributive fluvial systems that depicts and accounts for two palaeopedogenetic trends one downdip in relation to distality from the fan apex and one along strike in relation to distance from active channel belts palaeosols are reported in detail from an upper cretaceous succession of the bauru basin southeastern brazil through the application of macro micromorphological and geochemical studies combined with facies and architectural element analyses of sediments in the downdip palaeopedogenetic trend the proximal zone of the depositional system is characterised by a dominance of well drained inceptisols that develop on amalgamated channel fills in the medial zone inceptisols occur interlayered with overbank deposits containing entisols and poorly drained vertisols the distal zone preserves more mature and poorly drained inceptisols developed on deposits of overbank and sporadic distal channel fills these pedotypes show an increase in maturity and hydromorphism moving away from the apex to the fan toe this is likely linked to i the progressive approach of the topographic surface to the water table and ii the average increase in distance to an active channel belt in distal locations the along strike palaeopedogenetic trend culminates in poorly developed palaeosols in floodplain regions that correspond to topographic depressions located between channel belts and which were subject to recurrent floods because palaeopedogenesis in the floodplain region is penecontemporaneous to sedimentation pedotypes show an increase in maturity bioinduced calcification and hydromorphism with distance from the active channels they pass laterally from entisols and inceptisols near active channels to vertisols away from active channels conversely following avulsion abandoned channel belts remain as topographically elevated alluvial ridges located at some distance from the newly active channels and positioned above the water table and this leads to the development of better drained and better developed inceptisols relative to pedotypes of the floodplain region overall both palaeopedogenetic trends demonstrate the overriding controls of topography sedimentation rate and parent material on pedogenesis with only minor climatic influence this work offers a novel pedosedimentary model for distributive fluvial systems and highlights the palaeoenvironmental significance of palaeosol trends providing new constraints for the recognition of distributive fluvial systems in the rock record

aeolian sediment transport on a human altered foredune changes in wind speed and sediment transport are evaluated at a gap and adjacent crest of a 2 to 3 m high 40 m wide foredune built by sand fences and vegetation plantings on a wide nourished fine sand beach at ocean city new jersey anemometer masts cylindrical sand traps and erosion pins were placed on the beach and dune during two obliquely onshore wind events in february and march 2003 results reveal that 1 changes in the alongshore continuity of the beach and dune system can act as boundaries to aeolian transport when winds blow at an angle to the shoreline 2 oblique winds blowing across poorly vegetated patches in the dune increase the potential for creating an irregular crest elevation 3 transport rates and deflation rates can be greater within the foredune than on the beach if the dune surface is poorly vegetated and the beach has not had time to dry following tidal inundation 4 frozen ground does not prevent surface deflation and 5 remnant sand fences and fresh storm wrack have great local but temporary effect on transport rates temporal and spatial differences due to sand fences and wrack changes in sediment availability due to time dependent differences in surface moisture and frozen ground combined with complex topography and patchy vegetation make it difficult to specify cause effect relationships effects of individual roughness elements on the beach and dune on wind flow and sediment transport can be quantified at specific locations at the event scale but extrapolation of each event to longer temporal and spatial scales remains qualitative copyright 2006 john wiley sons ltd

topographic changes associated with coastal dune blowouts at island beach state park new jersey topographic changes in two blowouts located in island beach state park new jersey usa were monitored over the winter of 1981 1982 elevation changes were measured with erosion pins and sediment traps placed at comparable locations in each blowout monitored the amount of sand moved by the wind discrete wind events were identified from regional data and morphological data for the intervals with the highest onshore and offshore wind speeds are examined in detail vegetation is the primary influence on the development of the two blowouts blowout a is characterized by eroding sidewalls a stable base and an accreting blowout rim high rates of sediment transport occur through the blowout throat which results in accretion on the vegetated rim this blowout is an active sediment transfer system vegetation causes a large amount of deposition in the throat of blowout b as vegetation was buried over the winter the area of deposition migrated inland sidewall erosion also occurred in blowout b little change was recorded on the blowout rim blowout b is a recovering system where sediment is delivered to the blowout floor from the beach by onshore winds and from the blowout rim by offshore winds where it is stabilized by vegetation the development of foredune blowouts is governed largely by vegetation cover on the dune crest and by sidewall erosion during offshore and onshore winds blowout recovery depends on vegetation growth and sediment deposition in the throat and on the role of the sidewalls as sources of sediment which is deposited elsewhere within the system foredune blowouts are dynamic systems in which positive feedbacks in sediment availability and vegetation growth lead to a cycle of development and closure

foredune morphodynamics and sediment budgets at seasonal to decadal scales humboldt bay national wildlife refuge california usa abstract coastal foredunes are shore parallel ridges that form in the backshore and their morphodynamics are controlled partly by seasonal and spatial variations in the coastal onshore sediment budget that in turn are driven by oceanic and atmospheric processes and interactions including regional wave and wind regimes climatic variability events e g enso sediment availability beach characteristics e g width slope and vegetation type and cover in the backshore previous studies on shoreline change in northern california report only broad rates of erosion and accretion related to regional meteorological regimes this study presents a more detailed multi decadal to seasonal account of shoreline response and foredune morphodynamics along a 2 5 km stretch of coast in the humboldt bay national wildlife refuge hbnwr analysis of historical aerial photography 1939 2014 reveals trends in shoreline position that are coupled with more detailed assessments of foredune morphodynamics and seasonal scale volumetric changes from cross shore topographic profiles these findings set the historical context of foredune morphodynamics and allow exploration of the implications of seasonal meteorological variation on long term 75 year foredune evolution and development at the hbnwr dsas describes maximum foredune progradation in the north up to 0 51 m a 1 and maximum foredune retreat in the south up to 0 49 m a 1 aerial photograph analysis 2004 2014 shows statistically significant larger erosive features in the southern zone than in the northern and central zones seasonal volume calculations from cross shore profiles indicate statistically significant differences in alongshore transect elevation and foredune volume with larger elevations and volumes in the northern and central zones than in the southern combined with evidence of seasonal bidirectional littoral drift these data support a north to south gradient in sediment availability foredune position and resulting stages of established foredune development seasonal storm energies and climate forcing events introduce variability in erosive patterns but support the persistence of alongshore developmental stages future research should explore foredune morphodynamics on a smaller spatial scale and changes related to the presence absence of multiple vegetation assemblages

trends in research on beaches and dunes on sandy shores 1969 2019 abstract trends in research on morphologic changes on beaches and foredunes on sandy shores are identified from the 1960s to the present research during this period evolved from early descriptive explanation and classification of profile change to instrumented field investigations to modelling of landform change at larger scales research efforts have become increasingly more collaborative with increasing use of field instrumentation data acquisition systems and remote sensing rich datasets are resulting in more comprehensive computational models human altered systems are of increasing interest but knowledge of these systems lags far behind knowledge of natural systems research is becoming more relevant to societal needs as the vulnerability of coastal populations increases the need for investigation of understudied or unexplored environments including human altered ones is ongoing many basic research issues remain but future studies would profit from the development of new models rather than validating or reconfiguring old models collaboration between geomorphologists and engineers may open up research opportunities particularly in modifying beaches and dunes built for shore protection to provide natural values in restricted space application of models to enhance knowledge of effects of sea level rise and coastal storms would be useful to managers developing resiliency plans

reconstructing last glacial maximum and younger dryas paleolandscapes through subsurface paleosol stratigraphy an example from the po coastal plain italy abstract paleosols are commonly used to reconstruct ancient landscapes and past environmental conditions through identification and subsurface mapping of two pedogenically modified surfaces formed at the onset of the last glacial maximum lgm and during the younger dryas yd cold event respectively and based on their lateral correlation with coeval channel belt sand bodies we assessed the geomorphic processes affecting the po coastal plain during the late pleistocene 30 11 5 cal ky bp the 3d reconstruction of the lgm and yd paleosurfaces provides insight into the paleolandscapes that developed in the po alluvial plain at the transitions between warm and cold climate periods the lgm paleosol records a stratigraphic hiatus of approximately 5 kyr 29 24 cal ky bp whereas the development of the yd paleosol was associated with a climatic episode of significantly shorter duration both paleosols dissected by apennine rivers flowing from the south dip towards the north east where they are replaced by fluvial channel belts fed by the po river the lgm channel belt sand body reflects the protracted lateral migration of the po river at the onset of the glacial maximum it is wider 24 km and thicker 15 m of the fluvial sand body formed during the yd the northern margin of lgm po channel belt deposits was not encountered in the study area in contrast a spatially restricted paleosol identified in the north at the same elevation as the southern plateau may represent local expression of the alpine interfluve during the yd event this study highlights how 3d mapping of regionally extensive weakly developed paleosols can be used to assess the geomorphic response of an alluvial system to rapid climate change

miocene forebulge development previous to broken foreland partitioning in the southern central andes west central argentina 1 in the distal region of the modern flat slab segment in the southern central andes an unusual stack of middle miocene paleosols together with regional upwarping and normal faulting indicate episodic aggradation and condensed sedimentation contemporaneous with the principal stage of foreland basin development associated with foreland flexure farther to the west these features are consistent with development of a forebulge zone during the early stages of a proposed asymmetric foreland basin system sedimentary thickness farther east and far from the cordilleran tectonic loads suggests accommodation and preservation driven by nonisostatic dynamic subsidence regional overlapping relationships and basin modeling suggest that the modern broken foreland present sierras pampeanas can be interpreted as a reactivation of a formerly partitioned broad forebulge

experimental measurements of the diffusion parameters of light hydrocarbons in water saturated sedimentary rocks i a new experimental procedure an automatic experimental set up has been developed for the determination of diffusion parameters of hydrocarbon gases through water saturated rock samples diffusive flow of hydrocarbons through rock slices is monitored by gas chromatography experiments are carried out according to the time lag method yielding diffusion coefficients solubility coefficients and diffusion permeabilities diffusion coefficients down to 10 12 m2 s 1 10 8 cm 2 s 1 may be determined routinely on rock samples of 2 10 mm thickness maximum errors in diffusion coefficients are estimated around 20 and reproducibility was found to range between 10 and 20 specific features of this set up are automatic sampling and data acquistion high sampling frequency and maintenance of water saturation of the rock samples throughout the experiment

foredune accretion under offshore winds experiments carried out at magilligan strand on the north coast of ireland suggest that topographic steering of offshore winds is an important facet of the aeolian sediment transport system at this location a five day study 18 22 june 2005 investigated the pattern of airflow over the foredune while simultaneously collecting data on sediment flux a simple instrument setup was used to characterise the airflow a sonic anemometer was placed at the dune crest with another on the mid beach horizontal traps electronic and integrating measured sediment flux on the supra tidal beach results show that offshore wind flow deviated from its original direction in the lee of the dune seaward of foredune the change in direction was not a simple steering of flow to a singular new direction but rather flow separation resulting in turbulent multidirectional flow including reversal traps located at the foot of the dune scarp recorded sediment transport during events forced by offshore winds data from sediment traps wind and observational evidence have been used to argue that sedimentation was occurring in this zone when budgeting for sediment movement within beach dune systems it is important to take into account the effect of secondary airflow patterns during offshore winds and their role in constructive processes of foredune formation particularly in post storm recovery c 2008 elsevier b v all rights reserved

palaeosols and sequence stratigraphy of the lower permian abo member south central new mexico usa the relationship between palaeosols and sequence stratigraphy is tested in the lower permian abo member south central new mexico by comparing interfluve and fluvial terrace palaeosols with palaeosols that developed within lowstand fluvial deposits interfluve and fluvial terrace palaeosols consist of primary pedogenic features including vertical root traces vertic structures stage ii and iii pedogenic calcite and translocated clay argillans which are cross cut or replaced by low aluminium goethite gley colour mottling sparry calcite veins and ankerite the polygenetic character of the palaeosols is consistent with initial development for several thousand to tens of thousands of years on well drained interfluves or fluvial terraces followed by waterlogging due to invasion by a rising water table that locally may have been brackish in contrast lowstand fluvial sediment that filled incised valleys contains only rooted and vertic palaeosols whose immaturity resulted from high aggradation rates palaeosols similar to those in the abo member have been recognized in other ancient strata and when combined with highresolution correlation provide evidence for interpretation of sequencestratigraphic surfaces and systems tracts

geochemical characterization of natural gas a physical multivariable approach and its applications in maturity and migration estimates gas geochemistry has recently been shown to enhance information regarding the geological history of hydrocarbons in this paper graphical representations of physico chemical processes affecting the chemical and isotopic signatures of natural gases are exemplified these diagrams are based on experimental studies and the use of basic statistics to extract significant and synthetic parameters from the geochemical data from 11 chemical and isotopic ratios a statistical analysis pca yields two very important parameters the first parameter using mainly the c2 fraction of the gas relates to maturity and the second parameter involving the proportions and d13c values of methane indicates mainly segregative migration positive values of the second parameter indicate that gases accumulated far from their source whereas negative values correspond to residual gas pools after leakage of a part of the fluids a tentative reconstruction of the gas history has been performed in two brazilian basins the espirito santo basin and part of the reconcavo basin the espirito santo basin is located on the passive continental margin of the atlantic ocean and the reconcavo basin corresponds to an intracontinental aborted rift in both cases the source rocks are mainly lacustrine with thermal maturities ranging between the oil window and the beginning of the gas window results show that in the reconcavo basin a major fault the mata catu fault acts as a drain for hydrocarbon migration at the basin scale associating a major isotopic fractionation to the gas migration with a clear correlation between isotope fractionation and the distance of migration in the espirito santo basin this segregation appears in the platform sediments to a lesser extent and is absent in the gas pools located in the paleocanyons filled with turbidites this long distance migration in the platform sediments suggests that a hydrocarbon kitchen is located offshore

effects of beach raking and sand fences on dune dimensions and morphology abstract raking beaches to remove wrack natural and human litter to enhance recreational use and using sand fences to build and stabilize dunes are common practices on developed shores but their effects on the landscape are not well understood managers in avalon nj ceased using sand fences and raking in a portion of beach in 1991 providing the opportunity to evaluate evolution of natural and managed dune systems over a 19 year period topographic and vegetation characteristics were evaluated on 15 transects within 5 sites in a managed area where raking and sand fences are still used and at 15 transects within 5 sites in a naturally evolving unmanaged area raking and deploying fences in the managed area restricted the size of the cross shore zone in which aeolian accretion occurred but resulted in greater dune crest heights than in the unmanaged area crest heights of the foredune in the managed area ranged from 4 45 m to 5 27 m crest heights in the unmanaged area ranged from 3 02 m to 4 27 m dune volume and beach volume were greater on average in the unmanaged area and the dune was wider mean of 72 m versus 40 m and had an additional ridge the unmanaged area had 35 more species and contained a greater percentage of all species encountered in the study area than the managed area 88 compared to 65 more species occurred in the swales than any other of the cross shore habitats and most of these species were observed in the deeper wider swales in the unmanaged area removing wrack from the beach prevents incipient dunes from forming thus reducing the number of dune crests and size of swales that create topographic variability and increase the number and types of habitats for flora and fauna suspension of raking can allow the dunes to build seaward while producing a greater variety and number of habitats but seaward growth does not mean that the height of the dune will increase substantially and fences may be needed to build an initial dune ridge for flood protection thereafter a policy of not raking in specially designated zones would be a good compromise between the need to accommodate nature and beach recreation

short term beach dune sand budgets on the north sea coast of france sand supply from shoreface to dunes and the role of wind and fetch abstract three experimental plots covering the transition from the upper beach to the dune on the north sea coast of france were monitored at various intervals over a period of 18 24 months via high resolution terrain surveys in order to determine inter site sand budget variability as well as patterns and processes involved in sand exchanges between the upper beach and dune the wind regime consists of a fairly balanced mix of moderate 80 of winds are below 8 m s onshore offshore and shore parallel winds sustained dune accretion over several years depends on the periodic local onshore welding of shoreface tidal banks that have developed in the storm and tide dominated setting of the southern north sea the only site where this has occurred in the recent past is calais where bank welding has created a wide accreting upper beach sand flat at this site significant sand supply from the subtidal sand bank reservoir to the upper beach flat occurred only once over the 18 month survey following a major storm the bulk of the sand deposited over this large flat is not directly integrated into the adjacent embryo dunes by onshore winds but is progressively reworked in situ into developing dunes or transported alongshore by the balanced wind regime thus resulting in alongshore stretching of the embryo dune system the leffrinckoucke site near belgium shows moderate beach dune mobility and accretion while the wissant site exhibits significant upper beach bedform mobility controlled by strong longshore currents that result in large beach budget fluctuations with little net budget change to the detriment of the adjacent dunes accretion at these two sites which are representative of the rest of the north sea coast of france is presently constrained by the absence of a shore attached sand bank supply reservoir while upper beach dune sand exchanges are further limited by the narrow wave affected upper beach the intertidal morphology of bars and troughs which segments the aeolian fetch and the moderate wind energy conditions the balanced wind regime limits net sand mobilisation in favour of either the beach or the dune and may explain the relatively narrow longshore morphology of the dune ridges bounding this coast

sediment supply from shoreface to dunes linking sediment transport measurements and long term morphological evolution a significant problem in current coastal research is the understanding of linkages between morphological phenomena occurring on different temporal and spatial scales morphodynamic processes in the nearshore typically exhibit nonlinear behaviour and consequently phenomena which occur on short temporal event scales as e g observed during field experiments have generally been difficult to upscale to provide an understanding of the long term behaviour of the coast on the time scale of seasons or decades this paper documents a persistent onshore migration of nearshore bar features over a period of 3 decades using a set of cross shore profile surveys from a barrier on the danish north sea coast the observed behaviour is consistent with experimental data obtained during weeklong field campaigns when sediment transport and bar migration were found to be landward directed during high energy dissipative conditions hydrodynamic and sediment transport processes leading to onshore bar migration and eventually welding of the bars are documented to provide an explanation for the observed long term evolutionary trends in addition bar welding and the resulting intertidal bar formation represent an onshore sediment storage which is subsequently available for aeolian transport observations on aeolian sediment transport indicate that transport rates and sediment supply to the foredunes critically depend on the presence of dry sand sources as represented by well drained intertidal bars measurements of long term accretion rates in foredunes indicate that volumes deposited on the crest and lee slope of the dunes are in reasonable correspondence with volumes supplied to the subaerial beach through the process of bar welding hence the data suggest that a persistent onshore directed sediment supply occurs from the shoreface across the surf and intertidal zones and into the dunes of the investigated barrier

gas accumulations in oligocene miocene reservoirs in the alpine foreland basin austria evidence for gas mixing and gas degradation two petroleum systems are present in the eastern austrian sector of the alpine foreland basin whereas oil and thermogenic gas in mesozoic and eocene reservoir rocks have been generated beneath the alps in lower oligocene source rocks relative dry gas in oligocene miocene clastic rocks deposited in the deep marine basin axial channel system puchkirchen channel is interpreted as microbial in origin detailed investigations of the molecular and isotope composition of 87 gas samples from 86 wells representing all producing fields with oligocene and miocene reservoir rocks suggest that the presence of pure microbial gas is rare and limited mainly to the northern basin flank e g kk field all other fields contain varying amounts of thermogenic gas which has been generated from a source rock with oil window maturity a relation with the underlying thermogenic petroleum system is obvious upward migration occurred along discrete fault zones e g h field or through low permeability caprocks local erosion of lower oligocene sediments the principal seal for the thermogenic petroleum system as well as a high percentage of permeable rocks within the puchkirchen channel favored upward migration and mixing of thermogenic and microbial gas all gas samples in oligocene miocene reservoirs are biodegraded biodegradation and the formation of secondary microbial gas resulted in gas drying therefore the gas samples analyzed in this study are relative dry despite significant contributions of thermogenic hydrocarbons biodegradation probably continues at present time the degree of biodegradation however decreases with depth

micromorphology and sequence stratigraphy of the interfluve paleosols from the ganga plains a record of alluvial cyclicity and paleoclimate during the late quaternary

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

millennial scale depositional cycles from the holocene of the po plain italy the holocene depositional history of southeastern po plain on time scales of 103 yr is reconstructed based upon integrated sedimentological and micropalaeontological analyses of nine continuously cored boreholes about 40 m deep major palaeoenvironmental changes include the rapid landward migration of a barrier estuary lagoon system during the early middle holocene transgressive systems tract tst followed by extensive delta progradation in the last 6000 yr highstand systems tract hst detailed facies analysis of cores combined with the identification of 12 microfossils benthic foraminifer and ostracod associations allow an ultra high resolution sequence stratigraphic framework to be reconstructed particularly eight small scale high frequency cycles about 3 5 m thick and spanning intervals of time of about 1000 yr can be physically traced throughout the study area interpretation of these cycles which are invariably bounded by sharp flooding surfaces and generally show internal shallowing upward trends parasequences indicates that relative sea level changes during the holocene were episodic and punctuated by rapid phases of sea level rise followed by periods of stillstand or decreasing sea level rise from seaward to landward locations parasequence boundaries document beach barrier migration bay head delta abandonment and increasing accommodation in the coastal plain the ensuing phases of sea level stillstands resulted in the progressive filling of the newly formed accommodation space through beach progradation extensive mud deposition in behind barrier lagoonal estuarine and marsh deposits and aggradation in bay head delta systems at the head of estuaries eustacy appears to be the major controlling factor of the retrogradational stacking pattern of parasequences within the tst by contrast a complex interplay of eustacy sediment supply and subsidence with an increasing influence of autocyclic mechanisms such as channel avulsion and delta lobe abandonment controlled facies architecture within the hst the maximum flooding surface cannot be assumed to be synchronous its timing being strongly dependent upon local variations in sediment influx and subsidence this study shows that the micropalaeontologic characterization of mud prone coastal plain and estuarine successions in terms of water depth and salinity can lead to very accurate sequence stratigraphic interpretations allowing identification of parasequence boundaries that may not be detected by conventional stratigraphic approach

diffusion model for predicting reservoir gas losses abstract a numerical one dimensional model has been developed to describe the influence of the evolution of geological parameters on the diffusive losses of gas from a reservoir a theoretical model of these phenomena is presented based on the equation of mass transfer through porous media and on the thermodynamics of the gas water system the numerical model aims to predict gas losses over geological time and the distribution of free gas within the caprock and the overlying sediment the equilibrium concentration of gas is calculated by a modified henry s law for the water phase and the lee kesler method for the gas phase the diffusion coefficients are functions of temperature and pressure the equations are solved by a control volume method and the numerical integration scheme is discussed the model can handle any kind of boundary conditions as well as gas phase migration pathways through the caprock the model is applied to a typical north sea field caprock the distribution of methane is calculated in different geological hypothesis

light hydrocarbon diffusion in a caprock abstract concentration profiles for light hydrocarbons c 2 c 7 were obtained by geochemical analysis of closely spaced samples from a caprock shale overlying a commercial size gas condensate accumulation interpretation of these data suggests that considerable diffusive transport of light hydrocarbons has occurred from the reservoir accumulation into the caprock a simple one dimensional diffusion model was used in order to quantify these transport processes evaluation of the analytical data with this model yields estimates for the duration of the diffusive transport and thus the maximum age of formation of the hydrocarbon accumulation in the reservoir alternatively if this age can be estimated from geological evidence the order of magnitude of effective light hydrocarbon diffusion coefficients in shale caprocks can be obtained

gas saturation and co2 enhancement potential of coalbed methane reservoirs as a function of depth the influence of moisture temperature coal rank and differential enthalpy on the methane ch4 and carbon dioxide co2 sorption capacity of coals of different rank has been investigated by using high pressure sorption isotherms at 303 318 and 333 k ch4 and 318 333 and 348 k co2 respectively the variation of sorption capacity was studied as a function of burial depth of coal seams using the corresponding langmuir parameters in combination with a geothermal gradient of 0 03 k m and a normal hydrostatic pressure gradient taking the gas content corresponding to 100 gas saturation at maximum burial depth as a reference value the theoretical ch4 saturation after the uplift of the coal seam was computed as a function of depth according to these calculations the change in sorption capacity caused by changing pressure temperature conditions during uplift will lead consistently to high saturation values therefore the commonly observed undersaturation of coal seams is most likely related to dismigration losses into adjacent formations and atmosphere finally we attempt to identify sweet spots for co2 enhanced coalbed methane co2 ecbm production the co2 ecbm is expected to become less effective with increasing depth because the co2 to ch4 sorption capacity ratio decreases with increasing temperature and pressure furthermore co2 ecbm efficiency will decrease with increasing maturity because of the highest sorption capacity ratio and affinity difference between co2 and ch4 for low mature coals

aeolian transport rates across raked and unraked beaches on a developed coast wind characteristics and aeolian transport were measured on a naturally evolving beach and dune and a nearby site where the beach is raked and sand trapping fences are deployed the beaches were composed of moderately well sorted to very well sorted fine to medium sand the backshore at the raked site was wider and the foredune was more densely vegetated and about 1 m higher than at the unraked site wind speeds were monitored using anemometers placed at 1 m elevation and sand transport was monitored using vertical traps during oblique onshore alongshore and offshore winds occurring in march and april 2009 inundation of the low backshore through isolated swash channels prevented formation of a continuously decreasing cross shore moisture gradient the surface of the berm crest was dryer than the backshore making the berm crest the greatest source of offshore losses during offshore winds the lack of storm wrack on the raked beach reduced the potential for sediment accumulation seaward of the dune crest during onshore winds and the higher dune crest reduced wind speeds and sediment transport from the dune to the backshore during offshore winds accretion at wrack seaward of the dune toe on the unraked beach resulted in a wider dune field and higher narrower backshore although fresh wrack is an effective local trap for aeolian transport wrack that becomes buried appears to have little effect as a barrier and can supply dry sand for subsequent transport aeolian transport rates were greater on the narrower but dryer backshore of the unraked site vegetation growth may be necessary to trap sand within zones of buried wrack in order to allow new incipient foredunes to evolve copyright 2010 john wiley sons ltd

aeolian sand transport over complex intertidal bar trough beach topography aeolian sand transport on macrotidal beaches with complex intertidal bar trough topography ridge and runnel beaches was assessed from experiments in northern france that involved measurements of wind speed saltation surface moisture contents and rates of sand trapping across surveyed portions of the upper beach profile beaches exhibiting intertidal bars and troughs are much more complex topographically than simple reflective or dissipative beaches furthermore the intertidal bar trough morphology commonly exhibits strong cross shore variations in the moisture contents of the beach surface and in patterns of bedform development the results of four 30 minute experiments conducted along topographically surveyed portions of the upper beach dune toe profile show that troughs act as extremely efficient sand interceptors because of their permanently saturated state which also inhibits sand mobilisation troughs thus limit or segment the dry fetch during conditions of intermittent saltation flow lines inferred from the wind profiles suggest that complex interactions at the boundary layer are generated by the bar trough topography troughs systematically appear to be characterised by air expansion while bar faces generate ramp wind acceleration for onshore winds and sometimes immediate downwind deceleration for offshore winds these effects may also contribute to cross shore variations in the rates of sand trapping finally a simple conceptual model of effective fetch development integrating the effects of the spring neap tidal range and of gross bar trough morphological variability over time is proposed for bar trough beaches the model highlights the key theme of fetch segmentation induced by cross shore differentiation in the moisture contents of the beach surface hinged on the complex topography of multiple bars and troughs

onshore to offshore anatomy of a late quaternary source to sink system po plain adriatic sea italy abstract in understanding the evolution of siliciclastic systems late quaternary analogs may enable reliable predictive models of facies tract architecture the po plain adriatic sea system where a wealth of research has been conducted during the last 20 years represents one of the most intensively investigated late quaternary successions with the aid of a chronologically well constrained stratigraphy paleoenvironmental evolution is tracked for the first time from fluvial to deep marine realms over 1000 km in length vertical stacking trends onshore and stratal terminations offshore are the key observations that allow identification of surfaces with sequence stratigraphic significance systems tract boundaries in the distinct segments of the system recurring motifs in stratigraphic architecture showing tight coupling of sedimentary responses among source area catchment basin and coastal and marine depocenters reveal a cyclicity driven by glacio eustatic fluctuations in the milankovitch band due to high rates of subsidence middle pleistocene forced regressive systems tracts are exceptionally expanded and the mis5e mis2 interval late pleistocene preserves a nearly continuous record of fourth order 100 kyr stepwise sea level fall the stratigraphic architecture of last glacial maximum deposits highlights the genetic relations between channel belt development pedogenesis and sediment delivery to the lowstand delta through narrow incised valley conduits the late glacial holocene succession records the last episode of sea level rise and stabilization through well developed patterns of shoreline transgression regression tst hst that can be readily traced updip from offshore to onshore locations architectural styles across the whole system reflect a dominance of allogenic forcing in the tst as opposed to a predominantly autogenic control on stratigraphic development in the hst external drivers of facies architecture were also effective on millennial timescales the younger dryas cold reversal which marks the transgressive surface on land records a short lived episode of subaqueous progradation that is correlative onshore with widespread immature paleosol development and small sized channel belt formation quantitative assessment of sediment budgets over different time intervals requires precise positioning of the key bounding surfaces based on this approach we outline for the first time over the entire po adriatic basin an estimate of the sediment volumes stored in each systems tract

the effect of wind gusts moisture content and fetch length on sand transport on a beach this paper reports on an analysis of instantaneous sediment transport in relation to wind gusts moisture content and fetch length from a field study carried out at skallingen denmark wind speeds were measured with cup anemometers and instantaneous sediment transport with vertical traps coupled to electronic balances moisture content was measured gravimetrically using samples taken along a beach profile at intervals of 1 to 2 h sediment transport and wind speeds were sampled at 1 hz and a 5 s running mean was used to smooth the data from the trap because of limitations of the balance resolution three measures of the threshold of sediment motion the intermittency threshold minimum threshold and maximum threshold were explored using data from five runs carried out on october 26 2000 the intermittency threshold and maximum threshold were largely insensitive to wind speed but varied spatially along the fetch distance the minimum threshold increased significantly with increasing mean wind speed as a result of reduced time for drying of the surface layer examination of time series for instantaneous wind speed and sediment transport for a number of runs on october 26 and november 6 2000 showed close agreement between fluctuations in wind speed and fluctuations in sediment transport cross spectral analysis of instantaneous wind speed and sediment transport for one run on each day where there was continuous transport showed high coherence between the two variables over a range of frequencies from 0 2 hz to 0 01 hz plots of all non zero instantaneous sediment transport values versus wind speed show considerable scatter in general transport rates are highest for traps located further from the upwind non erodible boundary i e along the fetch best fit power relationships show r2 values generally ranging from 0 4 to 0 6 and exponents ranging from 4 5 to 6 94 i e much higher than the traditional value of 3 found in most transport equations traps located close to the upwind boundary had lower r2 values and exponents 2 5

maturity related compositional changes in the low molecular weight hydrocarbon fraction of toarcian shales abstract compositional changes in the light hydrocarbon content of sedimentary rocks and petroleum are known to reflect their maturation history the present contribution comprises the study of the low molecular weight hydrocarbon fraction in core samples of lower toarcian age posidonia shale lias the samples series collected by shallow borehole drilling in the hils syncline lower saxony basin northern germany represents an excellent petroleum source rock type ii kerogen of a wide maturity range mean vitrinite reflectance rm between about 0 5 and 1 5 about 30 compounds in the c2 c7 molecular range were determined quantitatively using a combined thermovapourization capillary gas chromatography method both quantity and composition particularly of the c7 hydrocarbon fraction are discussed in relation to vitrinite reflectance values measured at five locations rm 0 48 0 66 0 68 0 88 and 1 45 correlations between rm and paraffin naphthene concentration ratios are described also the isomer concentration ratios of 2 methylhexane 3 methylhexane and of trans to cis 1 2 dimethylcyclopentane are clearly related to the maturity of the organic matter

beach fetch distance and aeolian sediment transport an experiment was conducted to examine the influence of fetch distance on aeolian sediment transport on a natural sand beach at benone strand county londonderry northern ireland the site consisted of a wide dissipative beach approximately 150 m wide at low tide and 80 m wide during high tide surface moisture levels and hence dry fetch distance were dictated by both local groundwater from a stream outlet across the beach as well as local tidal levels an abundant dry sediment supply was available during the experiment high resolution 1 hz measurements were made of wind speed and direction along with sediment flux wind velocity ranged from 2 1 to 8 1 m s 1 during the study second order polynomial sand transport equations were derived from the wind speed and trap results with r2 values of better than 0 93 for all data when the data were sorted into velocity bins of 1 m s 1 there was no discernible relationship between fetch distance and sand transport with a measured fetch distance range of 10 58 m available during the experiment results show that fetch distance is unimportant when an adequate sand supply is available however it is suggested that fetch may restrict the development of steady state transport under sediment limited conditions sediment availability is thus identified as a key variable in aeolian transport studies on natural beaches

coalescent valley fills from the late quaternary record of tuscany italy abstract three prominent incised valley fills of post last glacial maximum age are described from the northern tuscan coast of italy stratigraphic correlation of core data along a cross section transversal to the present fluvial channel axes enables identification of a suite of genetically related valley bodies that fill the incisions made up by arno serchio and camaiore stiava rivers during the last glacial interglacial cycle the valley fills display different shapes and size but remarkably similar facies architecture valley bodies range between 5 and 10 km in width and between 30 and 45 m in thickness with width thickness ratios of about 100 300 above a lowstand and early transgressive gravel fluvial deposit the three incised valley fills display a distinctive succession of coastal plain to estuarine facies dated to about 13 8 cal ka bp radiocarbon dates document that the three valleys were active simultaneously accommodation space was rapidly created during transgression and then filled under conditions of very high sediment accumulation about 1 cm y in contrast to the more common deepening upward trend recorded by the latest pleistocene early holocene valley fill successions worldwide sedimentation in the tuscan valleys equalled or even exceeded the rate at which accommodation was created thus leading to an aggradational rather than backstepping stacking pattern of high frequency millennial scale parasequences above the valley fills and on the interfluves a thin deepening upward succession of nearshore deposits marks the rapid change from aggradational to retrogradational depositional style this is invariably overlain by a characteristic shallowing upward motif of prograding deltaic and coastal facies the maximum flooding surface which can be tracked across the whole study area on the basis of subtle palaeontologic indicators is shown to represent an almost isochronous surface dated to about 7 8 cal ka bp through examination of large scale geometry and facies attributes of the valley fills including the relationships between valley bodies and interfluves this study represents an example of how adjacent river systems with significantly different characteristics may respond simultaneously in a consistent manner to rapid changes in sea level and climate conditions

the effect of sedimentary redbeds on coalbed methane occurrence in the xutuan and zhaoji coal mines huaibei coalfield china abstract the lithologies and permeabilities of caprocks have significant effects on coalbed methane cbm preservation to study the controlling effects of redbeds deposits on cbm occurrence in the xutuan and zhaoji coal mines of the huaibei coalfield in china the variations in mineralogical composition microstructure pore structure permeability and diffusion among the redbeds caprock samples neogene clay rock and ordinary coal measure strata sandstone mudstone and siltstone have been investigated the results indicate that redbeds are porous rocks with weaker sealing capabilities than coal strata caprocks allowing cbm to escape from the coal seam the formation of the lithological properties of the redbeds is closely related to their mineralogical composition and diagenesis redbeds are mainly composed of illite 57 64 calcite 25 33 quartz 6 12 muscovite 3 8 and pyrite

clay coatings from a modern soil chronosequence a tool for estimating the relative age of well drained paleosols abstract blue light optically stimulated luminescence osl dates obtained from upland and terrace soil profiles in southeastern mississippi have been used to generate a model for illuvial clay accumulation in deeply weathered subtropical soils e g ultisols the illuvial clays developed in upland vs alluvial terrace soils of southeastern mississippi are distinct in terms of thickness and total volume of translocated clay the coatings in the mississippi soils are also an analogue for clay coatings observed in mid cretaceous paleosols of north america many of the cretaceous paleosols had a polygenetic history the relative age of the well drained phase of pedogenic development characterized by illuvial clay accumulations may be estimated using the model generated from the mississippi soils as many of the mid cretaceous paleosols mark unconformities it would be beneficial to estimate the duration of the hiatuses three geomorphic surfaces characterize the landscape of southeastern mississippi uplands stream cut terraces and modern alluvium the present floodplain has poorly developed soils and lacks illuvial accumulations soils developing in the uplands have abundant and prominent illuvial clay coatings up to 2 mm thick while the terraces have minor clay coatings less than 1 mm thick

formation and behavior of aeolian streamers received 5 december 2004 revised 31 march 2005 accepted 9 june 2005 published 7 september 2005 1 field experiments were conducted to determine the characteristic spatial and temporal dimensions and behavior of aeolian streamers and to identify the processes responsible for their formation an instrument array that included anemometer towers piezo electric transport sensors safires and hot film probes was deployed to measure streamers and airflow dynamics on both a coastal dune and a desert sand mound in california aeolian transport occurs predominantly in the form of families of intertwining and bifurcating streamers while under intense wind forcing more complex patterns of nested streamers and clouds with embedded streamers develop the streamers display a characteristic width of approximately 0 2 m and an average lateral spacing of about 1 m these dimensions appear to be independent of mean airflow characteristics the observations and measurements of streamers under different environmental conditions suggest that bed surface control in the form of differentiation in moisture content grain size or microtopography is not a necessary condition for the formation of streamers the results show little correlation between possible streamwise vortices or burst sweep events and streamers it is proposed that streamers are generated by near surface gusts that originate from large eddies propagating to the ground from higher regions of the boundary layer these elongated and stretched eddies scrape across the surface and initiate saltation along their path this concept accounts for the characteristic size and spacing of streamers their rapid propagation and the fast response of saltation to wind speed fluctuations

spatial variability of palaeosols across cretaceous interfluves in the dunvegan formation ne british columbia canada palaeohydrological palaeogeomorphological and stratigraphic implications a basic sedimentological and palaeopedological framework is now in place for non marine sequence models the variability of interfluve palaeosols has not however been systematically documented nor have the stratigraphic implications of that variability been incorporated into sequence models interfluve palaeosol variability in the deltaic dunvegan formation ne british columbia canada is investigated for which a detailed allostratigraphic and palaeogeographic framework has been developed based on abundant well 2300 logs and outcrop 60 sections control regionally extensive valley fills and interfluves have been mapped in coastal plain deposits over an area of about 50 000 km 2 this palaeogeographic framework permits interfluve surfaces exposed in outcrop to be located in terms of distance from the margins of coeval valleys the micromorphological geochemical and mineralogical characteristics of five representative sequence bounding palaeosols located from 250 m to more than 15 km from coeval valley margins are described these interfluve palaeosols are similar to modern alfisols and all record i aggradation on an alluvial coastal plain ii a subsequent static and or degradational phase related to valley incision nondeposition and soil thickening and iii a final aggradational phase related to valley filling and renewed sedimentation across the coastal plain within this overall template however variations in palaeosol thickness redoximorphic features illuvial clay content and geochemistry suggest developmental control by hydrological characteristics that were influenced by both the nature of the underlying alluvial sediments and distance from the valley margin the presence of mature interfluve palaeosols with complex developmental histories suggests that landscape dissection may have been related to terrace development associated with valley incision palaeosols closer to valley margins are thicker contain more illuvial clay and display characteristics suggesting better drained conditions relative to those palaeosols that developed further from valley margins subsequent deposition on interfluves also reflects distance from valleys with those sites close to valleys accumulating cumulic soils with evidence of brackish groundwater whereas far from valleys 10 15 km groundwater was fresh and clastic supply minimal encouraging peat formation variations in drainage and palaeotopography during landscape dissection resulted in different palaeosol development styles on interfluve surfaces that can be shown on the basis of physical correlation to have the same geomorphic age these observations support the concept of the soil forming interval as a basis for pedostratigraphic correlation in ancient terrestrial deposits palaeosol variability on interfluves is to be expected and recognition and documentation of this variability is an important prerequisite to palaeogeomorphological palaeoclimatic and sequence stratigraphic interpretations

micromorphology and stable isotope geochemistry of historical pedogenic siderite formed in pah contaminated alluvial clay soils tennessee u s a abstract alluvial clay soil samples from six boreholes advanced to depths of 400 450 cm top of limestone bedrock from the chattanooga coke plant ccp site were examined micromorphologically and geochemically in order to determine if pedogenic siderite feco3 was present and whether siderite occurrence was related to organic contaminant distribution samples from shallow depths were generally more heavily contaminated with polycyclic aromatic hydrocarbons pahs than those at greater depth the upper 1 m in most boreholes consisted of mixtures of anthropogenically remolded clay soil fill containing coal clinker cinder grains and limestone gravel most layers of coarse fill were impregnated with creosote and coal tar most undisturbed soil below 1 m depth consisted of highly structured clays exhibiting fine subangular blocky ped structures as well as redox related features pedogenic siderite was abundant in the upper 2 m of most cores and in demonstrably historical 100 years old soil matrices two morphologies were identified 1 sphaerosiderite crystal spherulites ranging from 10 to 200 m in diameter and 2 coccoid siderite comprising grape like clusters of crystals 5 20 m in diameter the siderite formed in both macropores and within fine grained clay matrices indicates development of localized anaerobic low eh conditions possibly due to microbial degradation of organic contaminants stable isotope compositions of the siderite have 13c values spanning over 25 7 to 18 vpdb indicating fractionation of dic by multiple microbial metabolic pathways but with relatively constant 18o values 4 8 0 66 vpdb defining a meteoric sphaerosiderite line msl calculated isotope equilibrium water 18o values from pedogenic siderites at the ccp site are from 1 to 5 per mil lighter than the groundwater 18o values that we estimate for the site if confirmed by field studies in progress this observation might call for a reevaluation of low temperature siderite water 18o fractionations investigations at the ccp site thus provide valuable information on the geochemical conditions under which siderite can form in modern soils and thus insight on controls on siderite formation in ancient soils

carbonate lake deposits associated with distal siliciclastic perennial river systems abstract the genesis of thick accumulations of carbonate lake deposits on the siliciclastic floodplains of perennial rivers situated below the regional spring line requires 1 a significant source for calcium in the watershed and 2 a protected area to accumulate calcite the phanerozoic record of fluvial deposits shows that anastomosing rivers with carbonate rich provenance situated in distal areas below the spring line are the best environments for floodplain accumulation of significant carbonate lake deposits anastomosing rivers exist below the regional spring line and have isolated flood basins generally protected from bedload by high levees receiving suspended and dissolved load during flooding events numerical modeling to test the rate of accumulation for these carbonate sediments was performed using stratigraphic data from the pennsylvanian succession containing floodplain limestones of the stewart quadrangle of athens county in ohio usa limestone volumes for six limestone units upper pittsburgh fishpot sewickley benwood arnoldsburg uniontown and waynesburg limestones were calculated with the assumption of overland input of dissolved calcite from carbonate source areas in comparing the calcium input rate to the amount of calcium calculated from limestone unit volumes overland transport of calcium ions not spring input can supply sufficient ions to accumulate thick carbonates over the short lifetime of floodplain lakes within anastomosing river systems

spherulitic siderites in the holocene coastal deposits of korea eastern yellow sea elemental and isotopic composition and depositional environment abstract siderite concretions are recovered from both freshwater unit ii and tidal unit i deposits in the holocene macrotidal flat of kyunggi bay west coast of korea siderites from both units show a spherulitic and well rounded texture and well developed equant rhombs on the external surfaces the size of the concretions in unit ii 50 150 m in diameter is normally larger than that in unit i 10 20 m the siderites in unit ii are chemically pure and highly enriched in fe whereas those of unit i are relatively impure and distinctly zoned demarcating high mn up to 69 1 mol in the core and high fe up to 75 9 mol in the margin within siderites of unit i substitution for fe by ca and mg reaches up to 20 3 mol mean 15 1 mol and 16 1 mol mean 12 6 mol respectively bulk 18 o values 0 7 to 1 3 peedee belemnite pdb for siderites in unit i are relatively higher than those 7 1 to 0 5 pdb in unit ii regardless of units siderite 13 c values 21 3 to 11 2 pdb are persistently low indicating microbially mediated precipitation at shallow burial depth extensive mn ca and mg substitution coupled with enrichment of 18 o in the siderites of unit i seems to reflect marine influence during the holocene transgression the occurrence of early diagenetic siderites provides supporting evidence on the depositional environment marine vs non marine of the holocene muddy coastal deposits of korea eastern yellow sea

late quaternary depositional architecture of po and tevere river deltas italy and worldwide comparison with coeval deltaic successions abstract po and tevere rivers form two of the most important deltas of the whole mediterranean area detailed investigations have been carried out in the last decade beneath the present delta plains of these two river systems using borehole data correlation with the aid of radiocarbon dates and other dating methods pollens archaeology a detailed sequence stratigraphic framework has been constructed in both areas especially for the last glacial interglacial cycle regional subsidence combined with short term sea level fluctuations of relatively high amplitude played a fundamental role in creating subtracting accommodation during the long phase of falling sea level which followed the tyrrhenian substage 5e transgressive event a discontinuous record of this phase is present in the subsurface of the po plain whereas poor or no preservation has been detected in the tevere area progradational lowstand wedges accumulated during the last glacial maximum mostly in the central part of the basins far from the present deltas and are lacking in the study areas where a hiatal surface is invariably recorded below the transgressive deposits glacioeustasy exerted a major control on sedimentation in both areas during the latest pleistocene holocene sea level rise infilling of fluvial valleys and rapid landward migration of barrier lagoon systems in the context of wave dominated estuaries characterized the transgressive phase in both po and tevere systems in place drowning and transgressive submergence mechanisms of barrier migration were effective predominantly between 13 5 and 9 ka bp in contrast shoreface retreat was dominant in the late transgressive phase the maximum flooding surface mfs can be traced physically from continental to marine deposits and has similar characteristics in the po and tevere river systems being marked by peat layers or lagoonal deposits at landward locations and by distinctive lithological characteristics and micro and macrofossils assemblages basinwards above the mfs the early highstand systems tract records initially the filling of the lagoons followed by the rapid progradation of wave dominate delta systems and flanking strandplains autocyclic processes such as distributary channel avulsion delta lobe abandonment and local subsidence due to sediment compaction were the fundamental controlling factors on sedimentation during deposition of the hst the stratigraphic architecture of the post glacial po and tevere delta complexes closely resembles the basic facies successions documented from coeval deposits of wave dominated and wave influenced clastic coasts both locally within the mediterranean area and in other parts of the world our study emphasizes however some additional features and major differences with previously published depositional models including i the development of backstepping wave dominated estuaries during transgression ii consistent changes through time in the mechanism of barrier migration iii a later construction of the delta systems with respect to what traditionally considered

a high resolution micromorphological record of the late quaternary paleosols from ganga yamuna interfluve stratigraphic and paleoclimatic implications abstract this study reports the micromorphological record of a continuous set of samples from paleosol bearing intervals of two subsurface cores of 50 m depth representing typical pedosedimentary sequences of the ganga yamuna interfluve in the western ganga plains micromorphology microstructures rhizocretes fe mn features pedogenic carbonate illuvial clay coatings and relict pedofeatures was used to characterize pedogenic processes in the 13 paleosols in the iitk core and the 10 paleosols in the bhognipur core formation of these paleosols took place through incipient to moderate weathering on relatively stable surfaces of the ganga yamuna interfluve over the last 100 ka these paleosols range in character from simple ones having weakly developed pedofeatures to mature paleosols with strongly developed pedofeatures and are similar to modern entisols inceptisols alfisols and vertisols of the ganga plains pedosedimentary evolution in the two interfluve successions differs in terms of stratigraphic stacking of paleosols types of paleosols and heterogeneous nature of sediments in the northern part the iitk interfluve core is marked by a thick mature paleosol with a strongly developed argillic bt horizon at 41 45 m depth and weakly developed paleosols in the remaining part of the core the mature paleosol represents a major discontinuity when prolonged pedogenic activity took place on stable surfaces with little or no deposition on the other hand thin simple thick cumulic paleosols with weakly developed pedogenic features even with some preservation of sedimentary laminations indicate short stratigraphic breaks in rapidly aggrading sediments in the southern part the bhognipur core is marked by the heterogeneous nature of sediments with a predominance of cratonic sediments in the lower part and the himalayan sediments in the upper parts in contrast the iitk core shows a himalayan source throughout the entire interfluve succession in the bhognipur region is marked by rapid sedimentation and short pedogenic intervals of weakly developed paleosols excepting one mature paleosol with well developed argillic bt and vertic bss horizons at 10 14 m depth this mature paleosol possibly formed synchronously with a mature paleosol from the northern part of this interfluve the mature paleosol in both the cores represents a major stratigraphic break of 8000 10 000 years when prolonged pedogenesis occurred over large areas of the ganga yamuna interfluve following regional degradation and local gullying in response to climate change from sub humid to semi arid conditions during the mis 5 4 transition

alluvial pedogenesis in pleistocene and holocene mississippi river deposits effects of relative sea level change comparison of pleistocene and holocene soils developed in mississippi river meander belt deposits in louisiana illustrates the influence of relative sea level change on pedogenesis holocene and pleistocene meander belts have similar landscape morphologies lithofacies and soil characteristics and probably formed under similar hydrologic regimes the pleistocene avoyelles prairie meander belt is now terraced but it was originally graded to a lower relative sea level position than the holocene flood plain holocene alluvial soils are generally weakly expressed cumulative profiles with abundant redoximorphic features and formed on an aggrading flood plain with a shallow fluctuating water table the soil morphology varies with respect to landscape position and overbank lithofacies pleistocene alluvial paleosols show evidence for two stages of pedogenesis during the first stage of pedogenesis water table fluctuations and flood plain aggradation produced profiles with color mottles iron and carbonate nodules and weak b and c horizons similar to holocene flood plain soils the second stage of pedogenesis occurred after the avoyelles prairie was terraced and the regional water table fell a minimum of 30 m improved soil drainage created oxidizing and acidic conditions removed free carbonates dehydrated iron oxides and transformed clay minerals this stage produced pleistocene profiles with brighter matrix and mottle hues lower ph values larger and harder iron nodules and greater kaolinite contents than comparable holocene flood plain soils the primary influence on regional water table lowering in the southern lower mississippi valley was relative sea level fall mississippi river flood plain lowering adjacent to the avoyelles prairie most likely occurred between the end of oxygen isotope stage 3 and the maximum period of valley entrenchment during oxygen isotope stage 2 water table fall affected pedogenic processes a minimum of 400 km upvalley of the continental shelf margin pleistocene mississippi river paleosols represent excellent analogs for interpreting ancient alluvial paleosols formed during episodes of base level fall and valley incision as fluvial entrenchment terraced the meandering avoyelles prairie a pedogenic threshold was crossed that altered the pathway of chemical weathering the complexity of a multiple step pedogenic history also highlights the fact that interpretation of relative profile development as a function of time can be problematic

continental sequence stratigraphy of the upper triassic norian rhaetian chinle strata northern new mexico u s a allocyclic and autocyclic origins of paleosol bearing alluvial successions abstract two age equivalent upper triassic fluvial successions deposited on the continental interior of the southwestern united states were evaluated using an adapted marine stacking pattern analysis methodology a three tier cyclic hierarchy is present in the strata at both study areas meter scale fining upward fluival aggradation cycles facs comprise fluvial aggradational cycle sets facsets 4 15 m thick avg 8 4 m facsets in turn stack into four fluvial sequences 26 48 m thick avg 41 m within these sequences transgressive systems tract equivalents te are characterized by channel sands and associated minor overbank deposits and relatively immature paleosols i e high rates of deposition whereas highstand to falling stage systems tract equivalents hfe are dominated by overbank muds and relatively well developed paleosols i e lower rates of deposition these two fluvial successions which are 200 km apart contain age equivalent fluvial sequences that record similar histories of deposition and pedogenesis sequence 1 contains only an incomplete hfe sequence 2 includes both the te and hfe sequence 3 is an hfe and sequence 4 contains only a te fluvial sequences likely accumulated in response to pulses of source area uplift and or basin subsidence which resulted in changes in accommodation conversely higher frequency facs and facsets that occur within sequences do not correlate between study areas and are likely the products of autocyclic processes such as channel avulsion floodplain aggradation and channel migration these results suggest that regionally significant tectonic episodes may be discernible in suspended load fluvial deposits that accumulated over a broad area

offshore aeolian sediment transport across a human modified foredune concepts derived from previous studies of offshore winds on natural dunes are evaluated on a dune maintained for shore protection during three offshore wind events the potential for offshore winds to form a lee side eddy on the backshore or transfer sediment from the dune and berm crest to the water are evaluated as are differences in wind speed and sediment transport on the dune crest berm crest and a pedestrian access gap the dune is 18 20 m wide near the base and has a crest 4 5 m above backshore elevation two sand trapping fences facilitate accretion data were obtained from wind vanes on the crest and lee of the dune and anemometers and sand traps placed across the dune on the beach berm crest and in the access gap mean wind direction above the dune crest varied from 11 to 3 deg from shore normal no persistent recirculation eddy occurred on the 12 deg seaward slope wind speed on the berm crest was 85 89 of speed at the dune crest but rates of sediment transport were 2 27 times greater during the strongest winds indicating that a wide beach overcomes the transport limitation of a dune barrier limited transport on the seaward dune ramp indicates that losses to the water are mostly from the backshore not the dune the seaward slope gains sand from the landward slope and dune crest sand fences causing accretion on the dune ramp during onshore winds lower the seaward slope and reduce the likelihood of detached flows during offshore winds transport rates are higher in access gaps than on the dune crest despite lower wind speeds because of flatter slopes and absence of vegetation transport rates across dunes and through gaps can be reduced using vegetation and raised walkover structures

geochemical characteristics of tight gas and gas source correlation in the daniudi gas field the ordos basin china abstract the molecular composition stable carbon and hydrogen isotopes and light hydrocarbons of the upper paleozoic tight gas in the daniudi gas field in the ordos basin were investigated to study the geochemical characteristics tight gas in the daniudi gas field displays a dryness coefficient c1 c1 5 of 0 845 0 977 with generally positive carbon and hydrogen isotopic series and the c7 and c5 7 light hydrocarbons of tight gas are dominated by methylcyclohexane and iso alkanes respectively the identification of gas origin and gas source correlation indicate that tight gas is coal type gas and the gases reservoired in the lower permian shanxi fm p1s and lower shihezi fm p1x had a good affinity and were derived from the p1s coal measure source rocks whereas the gas reservoired in the upper carboniferous taiyuan fm c3t was derived from the c3t coal measure source rocks the molecular and methane carbon isotopic fractionations of natural gas support that the p1x gas was derived from the p1s source rocks the differences of geochemical characteristics of the c3t gas from different areas in the field suggest the effect of maturity difference of the source rocks rather than the diffusive migration and the large scale lateral migration of the c3t gas seems unlikely comparative study indicates that the differences of the geochemical characteristics of the p1s gases from the yulin and daniudi gas fields originated likely from the maturity difference of the in situ source rocks rather than the effect of large scale lateral migration of the p1s gases

sand composition changes across key boundaries of siliciclastic and hybrid depositional sequences abstract sand composition of arenite successions is sensitive to a suite of factors operating between initial grain production and final diagenesis on a variety of spatial and temporal scales seven allogenic factors the relative importance of which relies upon the complex interaction between tectonics eustasy and climate play a decisive role in dictating petrofacies distribution within siliciclastic to hybrid depositional sequences these factors include i tectonic exhumation ii physical and chemical rock breakdown iii change in sediment flux iv change in source basin physiography v shelf colonization by organisms vi generation of chemical grains and vii volcanism autogenic processes may locally have a considerable influence on the type and amount of sediment supplied to the basin thus interfering with the external control based upon literature data a conceptual framework of expected compositional changes across the key surfaces for sequence stratigraphic interpretation is outlined two case histories from the miocene shelf to turbidite deposits of the northern apennines and the quaternary alluvial to nearshore succession of the adriatic coast respectively are used as references to illustrate how arenite petrofacies changes can be framed into a sequence stratigraphic scheme on multiple timescales

the biomass of macro and interstitial fauna on clean and wrack covered beaches in western australia the benthic faunal spectrum including bacteria protozoans meiofauna wrack epifauna and macrofauna was quantitatively surveyed on two modally reflective moderate energy western australian beaches the more exposed beach had coarser sand no intertidal macrofauna and a poor interstitial fauna the less exposed beach had a large deposit of wrack totalling 161 kg m 1 dry mass concentrated on the lower shore the amphipod allorchestes compressa was abundant in the fresh wrack comprising most of the macrofauna there were also fairly abundant small epifauna on the wrack dry biomass of macrofauna epifauna meiofauna protozoans and bacteria was 0 0 15 4 and 180 g m 1 on the more exposed beach and 160 3 112 9 and 901 g m 1 on the less exposed beach with wrack on the latter beach there was an inverse correlation between meiofaunal densities and the densities of protozoans and bacteria suggesting grazing by the former on the latter on both beaches meiofauna was concentrated in the mid to upper beach protozoans near the surface and bacteria in the mid to lower beach it is estimated that bacteria are responsible for most of the secondary production on both beaches

recognition of interfluve sequence boundaries integrating paleopedology and sequence stratigraphy in shallow marine and coastal plain strata sequence boundaries are easily recognized at the base of incised valley fills between valleys however it is more difficult to recognize sequence boundaries where they are expressed as interfluve paleosols we suggest that interfluve paleosols can be most reliably identified using a combination of 1 stratigraphic position 2 field observations such as thickness structure color and degree of rooting and 3 micromorphological features such as bioturbation fabric clay coatings ferruginous features and siderite and barite only micromorphology permits recognition of temporal changes in drainage surface stability and protracted pauses in sedimentation that typify these surfaces this three part approach has been successfully employed to identify interfluve sequence bounding paleosols in the cenomanian dunvegan formation in alberta and british columbia canada

floodplain palaeosols of the cenomanian dunvegan formation alberta and british columbia canada micromorphology pedogenic processes and palaeoenvironmental implications

flow dynamics over a foredune at prince edward island canada time averaged windspeed profiles at eight locations over a relatively high 8 m vegetated topographically simple foredune were measured using cup and ultrasonic anemometry during an onshore wind event in may 2002 the experiment was part of a largerstudyonthesedimentarydynamicsofabeach dunecomplexinthegreenwichdunes princeedwardisland pei canada the foredune is vegetated with ammophila breviligulata and vegetation density ranged from 0 on the foredune ramp to upward of 70 at the dune crest topographic forcing and resulting flow acceleration was observed distinctly in windspeed profiles and linear speedup occurred for all elevations above the vegetation canopy a distinct inflection point is evident in normalized windspeed profiles over the dune indicating a net momentum sink below the vegetation canopy top and systematic speed down within the vegetation was observed up the foredune stoss slope wind speed profile structure was consistent for the range of incident wind speeds measured a comparison of normal and slightly oblique incident winds indicated that for similar approach winds wind speeds are consistently higher during oblique flow conditions the implications for foredune morphodynamics and sedimentation are discussed d 2004 elsevier b v all rights reserved

the effects of surface moisture on aeolian sediment transport threshold and mass flux on a beach this paper presents results from a study designed to explore the effects of beach surface moisture and fetch effects on the threshold of movement intensity of sand transport by wind and mass flux the experiment was carried out over a period of five weeks at greenwich dunes prince edward island canada in may and june 2002 moisture content was measured with a delta t moisture probe over a 50 m by 25 m grid established on the beach measurements of wind speed and direction were made with arrays of cup anemometers and a two dimensional sonic anemometer transport intensity was measured at a height of 2 4 cm above the bed using omnidirectional saltation probes which count the impact of saltating grains on a piezoelectric crystal anemometers and saltation probes were sampled at 1 hz sand transport was measured with vertical integrating sand traps over periods of 10 20 minutes results show that where there is a considerable supply of dry sand the saltation system responds very rapidly 1 2 s to fluctuations in wind speed i e to wind gusts where sand supply from the surface is limited by moisture mean transport rates are much lower and this reflects in both a reduction in the instantaneous transport rate and in a transport system that becomes increasingly intermittent threshold wind speed is significantly correlated with an increase in surface moisture content near the upwind end of the beach fetch but the relationship is not significant at the downwind end where sediment transport is initiated primarily by saltation impact from upwind mass flux increases with increasing fetch length and the relationship is described best by a power function further work is necessary to develop a theoretical function to predict the increase in transport with fetch distance as well as the critical fetch distance copyright 2007 john wiley sons ltd

wind blown sand on beaches an evaluation of models five models for predicting rates of aeolian sand transport were evaluated using empirical data obtained from field experiments conducted in april 1994 at a beach on inch spit co kerry republic of ireland measurements were made of vertical wind profiles to derive shear velocity estimates beach slope and rates of sand transport sediment samples were taken to assess characteristics of grain size and surface moisture content estimates of threshold shear velocity were derived using grain size data after parsing the field data on the basis of the quality of shear velocity estimation and the occurrence of blowing sand 51 data sets describing rates of sand transport and environmental conditions were retained mean grain diameter was 0 17 mm surface slopes ranged from 0 02 on the foreshore to about 0 11 near the dune toe mean shear velocities ranged from 0 23 m s 1 just above the observed transport threshold to 0 65 m s 1 rates of transport ranged from 0 02 kg m 1 h 1 to more than 80 kg m 1 h 1 these data were used as input to the models of bagnold bagnold r a 1936 the movement of desert sand proc r soc london a157 594 620 kawamura kawamura r 1951 study of sand movement by wind translated 1965 as university of california hydraulics engineering laboratory report hel 2 8 berkeley zingg zingg a w 1953 wind tunnel studies of the movement of sedimentary material proc 5th hydraulics conf bull 34 iowa city inst of hydraulics pp 111 135 kadib kadib a a 1965 a function for sand movement by wind university of california hydraulics engineering laboratory report hel 2 8 berkeley and lettau and lettau lettau k and lettau h 1977 experimental and micrometeorological field studies of dune migration in k lettau and h lettau eds exploring the world s driest climate university of wisconsin madison ies report 101 pp 110 147 correction factors to adjust predictions of the rate of transport to account for the effects of slope and moisture content were calculated using the models of bagnold bagnold r a 1973 the nature of saltation and bed load transport in water proc r soc london ser a 332 473 504 and belly belly p y 1964 sand movement by wind u s army corps eng cerc tech mem 1 washington d c 38 pp respectively none of the models was able to produce a strong correspondence between measured and predicted rates of transport best results were obtained using the bagnold and zingg models and the kadib model was the least viable of this group the influence of sediment moisture content appeared to be the critical factor in degrading model viability overall none of the models is adequate for general applications to coastal aeolian environments where moisture content complications tend to override the predictive competence of the simple transport formulations c 1998 elsevier science b v