transgressive sand bodies on the maresme continental shelf western mediterranean sea abstract three large scale elongate asymmetrical sand bodies lie beyond the shoreface of the straight sandy coast of maresme barcelona in the northwestern mediterranean sea they are found on the continental shelf at water depths of 15 30 m 35 80 m and 95 113 m they are typically 12 20 m thick 1000 2000 m wide and trend parallel or subparallel to the coast for a distance of up to 24 km slopes on the steep offshore side vary between 3 and 20 while the shoreward slopes are gentler the shallowest sand body is modern in dynamic equilibrium with present conditions the other two however are relict bodies built up during the last postglacial rise in sea level development of these sand bodies occurs in the shoreface environment and in a space time evolution they show a punctuated but nearly continuous nature in the way that their preservation during the holocene transgression occurs only in specific locations on the continental shelf they begin growing on pleistocene scarps with offshore slopes and their growth pattern is mostly controlled by the sediment supply flow distribution and rate of sea level rise the formation of these sandy bodies is related to winter storms and southwesterly flows which cause large volumes of sediment to be transported downshelf and offshore by downwelling bottom currents generated by coastal set up the result is sand movement onto and across the sand body surface down to water depths of 15 20 m the thick sandy lenses of the maresme shelf are interpreted as topographically induced lee side sand bodies and not primarily as sand ridges in the classic sense the occurrence of these bodies on a low energy shelf may be significant for the interpretation of the geological record

sedimentology of coarse clastic beach ridge deposits essex southeast england abstract the distinction of cheniers from other types of beach ridge can often be problematic the stratigraphy sedimentology and geomorphological development of sand and gravel rich beach ridges at three sites on the northern essex coast england were determined using ground penetrating radar gpr ground truthing trenches and auger holes and historical aerial photograph analysis the 900 mhz gpr system used achieved a maximum vertical resolution between 0 02 and 0 06 m there was good correspondence between the radar stratigraphy obtained from time migrated radar reflection profiles and the nature and form of bounding surfaces sets of lamination beds and bedsets observed in trenches data for one of the study sites colne point illustrate a complex beach ridge stratigraphy and sequence of development that confirms they are not true cheniers instead the ridges form part of both retrogradational and progradational barrier spit sequences chenier designation at the other two study sites foulton hall and stone point is more straightforward as the beach ridges lie at the junction between actively eroding mudflat and saltmarsh however despite the distinction between the barrier spit beach ridges and the cheniers the same types of deposit are recognised in both indicating similar formative processes washover sheet deposits consist of low angle

winter storm induced hydrodynamics and morphological response of a shallow transgressive shoal complex northern gulf of mexico abstract using extended deployments during seasons of low and high discharge from the atchafalaya river meteorological hydrodynamic and bottom boundary layer parameters were monitored from tiger and trinity shoal complex off louisiana coast usa during winter storms the surface current speed measured at both shoals exceeded 0 5 m s and the entire water column followed the prevailing wind direction the current speed close to the bottom exceeded 0 3 m s during high energy northerly winds the mean water level in the shoal complex increased during southerly winds and decreased during northerly winds such that the difference between wind set up and set down exceeded 0 7 m in tiger shoal and 0 6 m in trinity shoal during high energy frontal passages the swell height was inversely correlated with mean water level and increased during pre frontal phase and decreased during post frontal phase of winter storms the sea short waves height responded quickly to wind direction and speed and within a few hours after the wind shifted and blowing from the north the sea height increased during both deployments bimodal wave frequency spectrum was observed during wind veering from southerly to northerly when both sea and swell intensities were significant the tiger shoal bed sediment texture transformed drastically from mud to shell and shell hash assemblage within a period of two weeks during the december 2008 deployment backscatter signal intensity from a pulse coherent acoustic doppler profiler pcadp and its velocity estimates were used to determine the vertical extend and timing of mud resuspension and their eventual flushing out from the shoal environment when exposed to high energy winter storm passages the computed time frame for a total transformation of bottom sediment texture from muddy bottom to shell and shell hash assemblage was supported by the combined wave and bottom current induced shear stress at shoal bed the bed samples collected from tiger shoal before and after the deployment in spring 2009 consisted of more than 80 shell and shell hash which again confirmed a stable bottom as predicted from the pcadp data however the fine sand and mud dominated bed at trinity shoal was highly dynamic and experienced a few cm of ephemeral sediment deposition during the passage of each cold front as revealed from the analysis of acoustic backscatter data from the pcadp suspended sediment concentration estimated from optical backscatterance sensors obs and pcadp were in good agreement during low river discharge events in december 2008 but significantly diverged during the spring 2009 deployment when a high suspended sediment load was discharged into the shelf from the atchafalaya river and subsequently pushed farther offshore into the deployment sites by wind induced strong currents during the passage of cold fronts

micropaleontological documentation for early holocene fall of relative sea level on the atlantic coast of nova scotia the presence of a marsh sequence between two shallow water marine deposits in an offshore core from lunenburg nova scotia indicates fall of relative sea level followed by rise of relative sea level the marsh sequence is now 27 m below datum level with a c 14 date of 7 070 yr b p this sequence suggests that the glacial forebulge migrated through this area 7 000 yr ago that 27 m of submergence has occurred since then and that prior to 7 000 yr b p the site was characterized by low amplitude emergence this is at present the only sequence where the entire regression transgression record is preserved along this coast the accuracy required to demonstrate this can be obtained only by using established marsh foraminiferal zonations

a model of coastal evolution in a transgressed thermokarst topography canadian beaufort sea abstract the coast of the southern canadian beaufort sea consists of bluffs of ice bearing quaternary sediments and of spits and barrier islands enclosing more or less completely lagoons and complex embayments formed by the breaching of thaw lakes the study of the evolution of this coast developed in a thermokarst topography and of the shallow stratigraphy of the inner continental shelf has resulted in the development of a conceptual model of coastal evolution five stages have been defined in this model which form an idealized continuum of coastal evolution according to the model the formation of embayments spits and barrier islands is primarily controlled by the pre existing topography relative sealevel rise and local sediment supply sealevel rise over a topography of thermokarst basins formed in ice bearing sediments leads to the formation of embayments and rapidly eroding headlands from which spits develop geomorphic evidence suggests that barrier islands mainly form by spit breaching or by erosion of tundra islands breached lake basins act as sediment sinks and may restrict the development of coastal accumulation features spits and barrier islands are rapidly retreating landward the mean retreat rates being 2 2 m a 1 and 3 9 m a 1 respectively on an annual time scale spits and barrier islands retreat in response to episodic storm generated overwash events but on a geologic time scale relative sealevel rise in the major forcing mechanism of landward migration while retreating landward these coastal accumulation features may be drowned and possibly partially preserved in breached lake basins during the holocene transgression the shoreface has undergone erosional retreat partly eroding the pre existing topography but preserving the bottom of some breached thaw lakes and lagoons which are now overlain by a transgressive sand sheet on the inner shelf our observations provide the basis of a semi quantitative model of shoreline changes for the barrier coast of the canadian beaufort sea which relates coastal stability to bluff erosion ground ice content sediment texture offshore sediment supply wave energy volume of breached lake basins relative sealevel rise and regional slope

riverine sediment inflow to louisiana chenier plain in the northern gulf of mexico abstract the louisiana chenier plain is a geomorphologic extension of the mississippi deltaic plain highly influenced by sediments originating from the mississippi river with the mississippi river unable to avulse closer to the plain local riverine sediment resources are integral to maintaining the physical and ecological integrity of the estuaries and marshlands to gain insight into the sediment resources this study assessed two decades 1990 2009 of discharge and total suspended solids tss of four rivers sabine river calcasieu river mermentau river and vermilion river that flow into the chenier plain the study quantified long term sediment delivery analyzed seasonal and inter annual trends of sediment transport and investigated the effect of hydrometeorological conditions on sediment yields total sediment delivery from the rivers over the 20 year period was 6 86 10 6 tonnes with the sabine river contributing 62 of the sediment load the sabine river also showed a significant decreasing trend p 0 03 in annual sediment yield long term trends of sediment loads in all the rivers were influenced by their discharge not their tss concentrations annual mean sediment load was 342 950 tonnes with higher sediment loading during the winter and spring months and lower during the summer and fall months annual sediment inflow has the capacity to create 2 3 10 7 m 2 of land to the depth of 1 cm but most of this sediment is unable to reach the coastline the greatest asset that these rivers provide for the chenier plain is sediment and freshwater for restoration of marsh lost to salinization or inundation

internal architecture and evolution of bioclastic beach ridges in a megatidal chenier plain field data and wave flume experiment beach ridges in macrotidal environments experience strong multi annual to multi decennial fluctuations of tidal inundation the duration of tide flooding directly controls the duration of sediment reworking by waves and thus the ridge dynamics flume modelling was used to investigate the impact of low frequency tidal cycles on beach ridge evolution and internal architecture the experiment was performed using natural bioclastic sediment constant wave parameters and low frequency variations of the mean water level the morphological response of the beach ridge to water level fluctuations and the preservation of sedimentary structures were monitored by using side view and plan view photographs results were compared with the internal architecture of modern bioclastic beach ridges in a macrotidal chenier plain mont st michel bay france surveyed with ground penetrating radar the experimentally obtained morphologies and internal structures matched those observed in the field and the three ridge development stages identified in ground penetrating radar profiles early transgressive late transgressive and progradational were modelled successfully flume experiments indicate that flat bioclastic shapes play a key role in sediment sorting in the breaker zone and in sediment layering in the beach and washover fans water level controls washover geometry beach ridge evolution and internal structure low water levels allow beach ridge stabilization and sediment accumulation lower on tidal flats during subsequent water level rise accumulated sediment becomes available for deposition of new washover units and for bayward extension of the beach ridges in the field low frequency water level fluctuations are related to the 4 4 year and 18 6 year tidal cycles experimental results suggest that these cycles may represent the underlying factor in the evolution of the macrotidal chenier coast at the multi decadal to centennial time scale

structure and development of shell cheniers in essex southeast england investigated using high frequency ground penetrating radar abstract the stratigraphy and internal structure of contemporary shell cheniers on the southern essex coast england were investigated using a high frequency 900 mhz ground penetrating radar gpr system the cheniers lie on the seaward edge of laterally eroding saltmarshes at the junction with the tidal flats four main types of chenier are recognised each with a characteristic morphology and dynamic status migrated radar reflection profiles obtained from each of the chenier types achieved a sub decimetre vertical resolution ground truthing data demonstrate that the radar profiles accurately delineate the subsurface stratigraphy and sedimentary structure of the cheniers interpretation of the radar stratigraphy derived from the radar reflection profiles allows various deposits to be identified these have resulted from overwashing overtopping sedimentation across the whole of a seaward dipping beachface or berm ridge welding onto the upper beachface each chenier is characterised by a different spatial arrangement of these four basic depositional units the results from the gpr surveys support the hypothesis that each of the chenier types represents a distinct phase in the development of these contemporary coastal landforms however a simple model involving a linear progression through chenier types 1 4 with time appears inappropriate instead two main evolutionary pathways are proposed with the sequence of development being principally controlled by the nature of the cheniers longer term sediment budgets

pleistocene shoreline ridges from tide dominated and wave dominated coasts northern gulf of california and western baja california mexico abstract the arid climate of northwestern mexico preserves pleistocene beach deposits forming linear shoreline parallel ridges on the coastal plains of sonora northern gulf of california and the vizcaino peninsula of baja california beach deposits represent both cheniers northern gulf and beach ridges vizcaino peninsula they formed during pleistocene sea level highstands most commonly during oxygen isotope stage 5e 125 ka the ridges are 0 5 to 5 0 m thick 100 m wide and 1000 m long coarse grained with common low to high angle cross stratification and are dominated by bivalve shells ridges from the tide dominated northern gulf of california and the wave dominated western vizcaino peninsula differ in underlying lithology size profile and shell fragmentation northern gulf ridges progradationally overlie deltaic or marsh deposits are smaller median thickness 1 4 m median width 25 m median length 300 m typically have a seaward dipping upper surface and a linear crest on the landward side and have low levels of fragmentation of large bivalve shells in contrast vizcaino ridges disconformably overlie bedrock on wave cut terraces are larger median thickness 3 3 m median width 100 m median length 2000 m typically have a landward dipping upper surface and a linear crest on the seaward side and contain beds of extensively fragmented large bivalve shells these differences are interpreted to reflect contrasting processes of ridge formation in the two regions the ridges of the tide dominated northern gulf are true cheniers transgressive beach deposits produced during episodes of clastic starvation associated with shifts in colorado river delta deposition they are modified primarily through episodic washover processes during high tides and storms the ridges of the wave dominated vizcaino peninsula are regressive beach ridges developed on highstand wave cut terraces they are modified primarily through continuous wave accretion to the beach face and secondarily by washover processes

the geomorphology of the mississippi river chenier plain abstract the chenier plain of the mississippi river is a shore parallel zone of alternating transgressive clastic ridges separated by progradational mudflats the term chenier is derived from the cajun term chene for oak the tree species that colonizes the crests of the higher ridges the mississippi river chenier plain stretches 200 km from sabine pass texas to southwest point louisiana and ranges between 20 and 30 km wide with elevations of 2 6 m the timing and the process of formation could be re evaluated in the light of new chronostratigraphic findings in the mississippi river delta plain the stratigraphic relationship between the teche and lafourche delta complexes and ship shoal offshore indicates that these delta complexes belong to different delta plains that developed at different sealevels it appears that the teche delta complex is associated with the late holocene delta plain which developed 7000 to 3000 yrs b p when sealevel stood 5 6 m lower than present a regional transgression occurred between approximately 3000 bp and 2500 yrs b p leading to the transgressive submergence of the late holocene delta plain producing the regional teche shoreline the timing of this transgression conforms to the age of the most landward ridge in the chenier plain the little chenier little pecan island trend which dates at about 2500 yrs b p this ridge trend was originally interpreted as representing the teche delta complex switching event with the landward holocene pleistocene contact representing the high stand shoreline the implication of this new interpretation is that the little chenier little pecan island trend represents the high stand shoreline a continuation of the teche shoreline separating the late holocene and recent delta plains and that the holocene pleistocene contact represents the leading edge of the marshes transgressing onto the prairie terrace significant mudflat progradation seems to require a westerly position of the mississippi river but the numerous different forms and ages of cheniers do not correspond well to the timing of major delta complex switching progradation of the chenier plain appears to be associated with building of the recent delta plain and not the teche complex of the late holocene delta plain the occurrence of individual ridges appears to be primarily tied to delta lobe switching within the lafourche complex and variations in sediment supply from local rivers the recent development of the atchafalaya delta complex to the west is the closest position of an active distributary to the chenier plain since sealevel stabilization a new episode of rapid mudflat progradation is thus taking place

shelly cheniers on a modern macrotidal flat mont saint michel bay france internal architecture revealed by ground penetrating radar abstract the relationship between short term morphodynamics and internal structure of shelly chenier ridges is investigated using ground penetrating radar and core x ray analysis complemented with a comparison of aerial photographs these cheniers are located on the uppermost part of a macrotidal flat in mont saint michel bay north western france they actively migrate landward over the salt marshes by washover processes when they are submerged during the coincidence of spring tides and enhanced wave activity the architecture of the cheniers is imaged using high frequency radar antennas 400 mhz to 2 6 ghz three types of cheniers are recognized featuring differences in morphology and internal structure the altitude of the banks on the tidal flat relative to the level of tidal flooding as well as local sediment supply seem to be important forcing parameters in chenier development and stages of evolution on a multi annual time scale evolution of this chenier system is influenced by a combination of the 18 year and the 4 year tidal cycles superimposed on wave activity during minima of the 18 year cycle spring tide level is globally lower on the tidal flat allowing salt marsh progradation and chenier ridge development during peak periods of the tidal cycle former barriers are reworked by wave action and experience onshore migration associated with salt marsh erosion the 4 year tidal cycle coupled with enhanced wave activity is probably responsible for the deposition of large washover units observed in gpr reflection profiles

sea level sediment supply and coastal changes examples from the coast of ireland abstract sediment supply and pre existing shoreline morphology are crucial factors in controlling coastal changes due to sea level rise using examples from both southeast and northeast ireland it can be shown that sea level change may trigger a sequence of events which leads to both static and dynamic shoreline equilibrium cliff erosion and longshore sediment movement in east co wexford has led to injection of sediment onto the shelf and the growth under both wave and tide regimes of linear offshore shoals these shoals now control the pattern of shoreline erosion and provide a template for possible stepwise evolution of the coast under any future sea level rise in contrast the nearby coast of south co wexford comprises a series of coarse clastic barriers moving monotonously onshore via overwash processes here the behavior of the barrier is conditioned by the antecedent morphology of both the beach face and stream outlet bedforms finally the rock platform coast of co antrim presents a far more resistant shoreline to incident marine processes yet even here there is strong evidence of present process control over so called raised platforms and embayments it is concluded that coastal sediment supply and dynamics together with coastal morphology and its interaction with waves present a far more complex variety of sea level indicators than is normally acknowledged

ichnology and sedimentology of a mud dominated deltaic coast upper cretaceous alderson member lea park fm western canada abstract current depositional models largely promote the perception that all open coastal distal sea proximal land gradients are reflected by upward coarsening grain size trends and that shoreline deposits are represented by prominent sand bodies although commonly the case significant departures from this model may occur when the availability of coarser sediment calibers sand sized and larger is limited this is especially true where alongshore sediment transport influenced depositional systems are associated with rivers that supply abundant suspended sediments underestimating the role of grain size segregation may lead to misinterpretations of energy levels and water depths especially in some shale dominated sedimentary units the upper cretaceous alderson member lea park fm is an up to 180 m thick gas charged shale unit that we interpret as an ancient analogue for modern offshore and mud dominated deltaic coasts sedimentological and ichnological data collected from 27 cores indicate that much of the sediment volume of the alderson member was deposited in relatively shallow water under the influence of tidal and wave processes in a deltaic coastal setting characteristic features reflecting these depositional affinities include 1 increased proportions of terrestrially derived organic matter 2 indications of thixotropic to soupy substrates e g fluid mud coupled with rapid depositional rates 3 an impoverished ichnological signal planolites dominated suites 4 micro laminated shale 5 shale on shale erosional contacts 6 scour and fill structures and 7 intervals of low angle cross stratification the interpretation of relatively shallow water settings is also supported by recurring root bearing horizons glossifungites ichnofacies demarcated transgressive surfaces of erosion and conglomeratic surfaces at particular stratigraphic levels the deposits are interpreted to include offshore subaqueous deltas muddy shoreface and or tidal flat and aggradational muddy coastal plain chenier plain sub environments the results of this study improve our knowledge of ichnological and sedimentological characteristics of shallow marine shale units and are potentially useful for recognition of similar nearshore mud prone deposits elsewhere

arsenic and metal mobility from au mine tailings in rodalquilar almeria se spain in the old mining area of rodalquilar mine wastes soil and sediments were characterized and the results revealed high concentration of au ag as bi cu fe mn pb se sb and zn in tailings and sediments the contaminant of greatest environmental concern is as the mean concentration in the tailings was 679 9 and 345 mg kg in the sediments of playazo creek the groundwater samples from the alluvial aquifer showed high concentration of al as cd fe hg mn ni pb se sb and zn and very high concentration of chloride and sulfate which were above the concentration defined in the european standards for drinking water the presence of as in groundwater may be caused by the oxidation of arsenian pyrite the possible as desorption from goethite and ferrihydrite and the jarosite dissolution groundwater concentrations of cd fe mn and possibly cu were associated with low values of eh indicating the possible dissolution of oxy hydroxides of fe and mn the mobility of metals in the column experiments show the release of al fe mn cr cu ni v and zn in significant concentrations but below the detected values in groundwater however as cd sb se pb and au are generally mobilized in concentrations above the detected values in groundwater the possible mass transfer processes that could explain the presence of the contaminants in the aquifer and the leachates was simulated with the phreeqc numerical code and revealed the possible dissolution of the following mineral phases jarosite natrojarosite arsenian pyrite alunite chlorite kaolinite and calcite

shoreface translation and the holocene stratigraphic record examples from nova scotia the mississippi delta and eastern australia abstract classic descriptive models of barrier sedimentation have been developed with data from the atlantic and gulf coasts of the united states these models are dominated by low to moderate rates of relative sea level rsl rise and wave energy barriers respond by landward recycling of sediment through the mechanism of shoreface retreat sedimentation processes on the central coast of new south wales n s w australia consist of rapid rsl rise in early holocene times followed by a stillstand since 6500 b p wave energy is relatively high year round and sand sources for barrier formation are only found on the inner shelf barrier sedimentation on the central coast of n s w exhibits a thick composite sequence composed of a basal marine transgressive sand overlain by regressive beach and dune facies the louisiana coast surrounding the mississippi delta is underlain by compacting deltaic muds which generate very rapid rates of rsl rise the louisiana coast experiences low wave energy punctuated by high energy tropical and extra tropical storm events barrier sediments accumulate from the erosion of deltaic headlands and undergo a transformation from subaerial barrier island systems to subaqueous shoals located on the inner shelf drumlins experience coastal erosion on the eastern shore of nova scotia and provide a sediment source for compartmented estuary mouth barriers an ongoing moderate rise of rsl results from the passage of a glacial forebulge wave energy is intermediate between louisiana and n s w and displays a seasonal pattern dominated by frequent winter storms coastal barrier sedimentation is episodic consisting of a period of beach ridge progradation followed by barrier destruction and re establishment further landward the three contrasting sedimentary sequences found in examples from louisiana n s w and nova scotia indicate that presently available sedimentation models from locations such as the middle atlantic or texas coasts of the united states may only represent well documented regional case studies a true generalised coastal sedimentation model is required which can identify the parameters controlling vertical and horizontal translation of the depositional surface and provide relationships between these parameters which quantitatively predict the genesis distribution and geometry of coastal sedimentary facies

late quaternary evolution of coastal sand barriers port stephens myall lakes area central new south wales australia abstract the geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of newcastle new south wales n s w australia in order to determine modes of deposition and the degree to which marine and estuarine deposits can be correlated and dated each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur in four of the bays dual sand barriers comprising an inner barrier and an outer barrier provide the framework for correlation between embayments six stages are recognized in the deposition of late quaternary sediments in this area i pre last interglacial involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes ii last interglacial stage during which inner barriers were formed iii last glacial reworking of barrier and dune sands by westerly winds iv postglacial marine transgression during which the outer barriers were initiated v mid holocene stage following cessation of sea level rise ca 6000 6500 yr b p on this coast and involving progradation of outer barriers in some embayments and vi late holocene episodic eolian reworking of dune complexes and outer barriers the relatively high wave and wind energy as well as the tectonic setting of the central n s w coast results in somewhat different geomorphic histories from barrier island coasts in north america and europe

influences of relative sea level rise and mississippi river delta plain evolution on the holocene middle amite river southeastern louisiana abstract the holocene geomorphic history of southeastern louisiana s middle amite river is recorded in the stratigraphy of three alloformations identified in decreasing age as the watson wat denham springs ds and magnolia bridge mag the wat meander belt formed by at least 9000 yr b p when sea level was lower and the amite river was tributary to a larger ancestral drainage basin the ds became an active meander belt by at least 3000 yr b p in response to relative sea level rise and eastward progradation of the mississippi river delta plain the mag developed its meander belt in part during the european settlement of the drainage basin and is now attempting to adjust to modern anthropogenic influences geomorphic influences on the middle amite river floodplain have temporal and spatial components that induce regional and local scale effects regional extrinsic influences caused meander belt avulsion that produced alloformations however local influences produced intrinsic geomorphic thresholds that modified channel morphology within a meander belt but did not induce alloformation development base level influences of the relative sea level rise and the mississippi river delta plain were so dominant that the effects of possible climate change were not recognized in the holocene amite river system

coastal morphodynamics and chenier plain evolution in southwestern louisiana usa a geomorphic model abstract using 28 topographic profiles air photo interpretation and historical shoreline change data coastal processes were evaluated along the chenier plain to explain the occurrence distribution and geomorphic hierarchy of primary landforms and existing hypotheses regarding chenier plain evolution were reconsidered the chenier plain of sw louisiana classified as a low profile microtidal storm dominated coast is located west and downdrift of the mississippi river deltaic plain this late holocene marginal deltaic environment is 200 km long and up to 30 km wide and is composed primarily of mud deposits capped by marsh interspersed with thin sand and shell rich ridges cheniers that have elevations of up to 4 m in this study the term ridge is used as a morphologic term for a narrow linear or curvilinear topographic high that consists of sand and shelly material accumulated by waves and other physical coastal processes thus most ridges in the chenier plain represent relict open gulf shorelines on the basis of past movement trends of individual shorelines ridges may be further classified as transgressive regressive or laterally accreted geomorphic zones that contain two or more regressive transgressive or laterally accreted ridges are termed complexes consequently we further refine the chenier plain definition by otvos and price otvos e g and price w a 1979 problems of chenier genesis and terminology an overview marine geology 31 251 263 and define chenier plain as containing at least two or more chenier complexes based on these definitions a geomorphic hierarchy of landforms was refined relative to dominant process for the louisiana chenier plain the chenier plain is defined as a first order feature 5000 km2 composed of three second order features 30 to 300 km2 chenier complex beach ridge complex and spit complex individual ridges of each complex type were further separated into third order features chenier beach ridge and spit to understand the long term evolution of a coastal depositional system primary process response mechanisms and patterns found along the modern chenier plain coast were first identified especially tidal inlet processes associated with the sabine calcasieu and mermentau rivers tidal prism and quantity of littoral transport mtotal are the most important factors controlling inlet stability greater discharge and or tidal prism increase the ability of river and estuarine systems to interrupt longshore sediment transport maintain and naturally stabilize tidal entrances and promote updrift deposition thus prior to human modification and stabilization efforts the mermentau river entrance would be classified as wave dominated sabine pass as tide dominated and calcasieu pass as tide dominated to occasionally mixed hoyt hoyt j h 1969 chenier versus barrier genetic and stratigraphic distinction am assoc petrol geol bull 53 299 306 presented the first detailed depositional model for chenier genesis and mudflat progradation which he attributed to changes in mississippi river flow direction i e delta switching caused by upstream channel avulsion however hoyt s model oversimplifies chenier plain evolution because it omits ridges created by other means thus the geologic evolution of the chenier plain is more complicated than channel avulsions of the mississippi river and it involved not only chenier ridges i e transgressive but also ridges that are genetically tied to regression beach ridges and lateral accretion recurved spits a six stage geomorphic process response model was developed to describe chenier plain evolution primarily as a function of i the balance between sediment supply and energy dissipation associated with mississippi river channel avulsions ii local sediment reworking and lateral transport iii tidal entrance dynamics and iv possibly higher than present stands of holocene sea level consequently the geneses of three different ridge types transgressive regressive and laterally accreted typically occur contemporaneously along the same shoreline at different locations

complex coastal change in response to autogenic basin infilling an example from a sub tropical holocene strandplain thick bay fill sequences that often culminate in strandplain development serve as important sedimentary archives of land ocean interaction although distinguishing between internal and external forcings is an ongoing challenge this study employs sediment cores ground penetrating radar surveys radiocarbon dates palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes notably a reduction in wave energy in response to coastal embayment infilling in coastal evolution and shoreline morphodynamics following a regional 2 to 4 m highstand at ca 5 8 ka the 75 km2 tijucas strandplain in southern brazil built from fluvial sediments deposited into a semi enclosed bay holocene regressive deposits are underlain by fluvial sands and a pleistocene transgressive regressive sequence and backed by a highstand barrier island the strandplain is immediately underlain by 5 to 16 m of seaward thickening fluvially derived holocene age basin fill mud several trends are observed from the landward oldest to the seaward youngest sections of the strandplain i the upper shoreface and foreshore become finer and thinner and shift from sand dominated to mud dominated ii beachface slopes decrease from 11 to ca 7 and iii progradation rates increase from 0 4 to 1 8 m yr 1 hydrodynamic modelling demonstrates a correlation between progressive shoaling of tijucas bay driven by sea level fall and sediment infilling and a decrease in onshore wave energy transport from 18 to 4 kw m 1 the combination of allogenic sediment supply falling relative sea level and geology and autogenic decrease in wave energy due to bay shoaling processes drove the development of a regressive system with characteristics that are rare if not unique in the holocene and rock records these findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts furthermore this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems

variable response of coastal environments of the northwestern gulf of mexico to sea level rise and climate change implications for future change the results from nearly three decades of marine geological research in the northwestern gulf of mexico are compiled in an effort to understand those factors e g sea level rise sediment supply subsidence antecedent topography that influenced coastal evolution during the last eustatic cycle 120 ka to present armed with this information we evaluate coastal response to variable sea level rise of the holocene and accelerated rise during historical time to gain a better understanding of how the coast is likely to respond to future changes the early holocene evolution of northwestern gulf of mexico bays was punctuated by rapid and possibly synchronous flooding events that are interpreted as resulting from episodes of rapid sea level rise two of these events one between 8 4 and 8 0 ka and the other between 7 4 and 6 8 ka were associated with known episodes of ice sheet retreat in north america and antarctica respectively during the middle and late holocene the east texas and western louisiana coasts experienced episodes of stability and growth followed by rapid shoreline retreat while the central texas coast remained relatively stable this variability in coastal response to sea level rise resulted mainly from differences in sediment supply and the highly irregular antecedent topography on which coastal environments formed sand that nourished the evolving east and south texas as well as westernmost louisiana coasts was derived mainly from transgressive ravinement of deltas that were formed during the falling stage of sea level mis5e mis2 the loci of these deltas controlled the spatial variability of this offshore sand supply sand supply to the central texas coast has been dominated by converging longshore currents and throughout the middle to late holocene was large enough to keep pace with sea level rise moreover sand supply from rivers has varied considerably in response to climate change during the early holocene when the average rate of linear sea level rise was 4 2 mm yr the brazos colorado and rio grande rivers all formed deltas on the inner continental shelf today only the brazos contributes enough sediment to the gulf of mexico to form a delta but its sand delivery is minimal a reversal from late holocene growth of western louisiana east texas and south texas barrier islands and peninsulas to erosion occurred during the last 2 0 ka after the rate of sea level rise began to decelerate the actual timing of this reversal was diachronous across the coast and was caused by a decrease in sediment supply once offshore sand sources were bypassed by the landward advancing shoreface transgressive ravinement differences in the exact timing and rate of retreat also reflect variability in the offshore profiles of these barriers and their thickness which results from the underlying relief on the pleistocene surface the late holocene was also the time of chenier plain development in western louisiana and east texas that was marked by localized differences in growth and retreat the current rate of eustatic sea level rise in the northern gulf of mexico is in the range of 2 0 and 3 0 mm yr and is approaching rates of the early holocene this is on average about five times the long term rate of the past 4 0 ka this larger rate is associated with an increase in coastal erosion in historical time relative to long term rates current rates of gulf shoreline erosion are approaching rates of the early to mid holocene and the rate of retreat of some barriers is not sustainable core transects off central texas reflect a late holocene history of shoreface progradation but the modern shoreline is currently eroding albeit at slower rates than elsewhere along the coast overall the sand supply needed to sustain the gulf shoreline is lacking likewise baylines are experiencing erosion rates that are faster than the late holocene average and bayhead deltas are at the tipping point of catastrophic retreat spatial variability in erosion rates highlights the importance of factors such as sediment supply subsidence and anthropogenic influences on coastal evolution tropical storms and hurricanes while exerting the most noticeable coastal change merely exacerbate overall shoreline retreat and migration along the entire northwestern gulf coast the impact of human intervention to natural processes is particularly evident primarily due to alterations in river discharge and sediment supply to the coast interruptions in along shore and cross shore sand transport and increases in rates of subsidence through fluid withdrawal compared to natural changes that took place during the holocene the impacts of human activity have been virtually instantaneous the geological record indicates that the ongoing increase in the rate of sea level rise coupled with diminished sediment supply and human intervention will continue to severely impact the low gradient coastal environments of the northwestern gulf of mexico

morphological evolution of a mud capped dredge pit on the louisiana shelf nonlinear infilling and continuing consolidation abstract buried sandy paleo river channels on the continental shelf can be accessed through dredging for the restoration of beaches and barrier islands which are under the threat of land loss and rising sea levels however our knowledge on post dredging evolution of paleo river channels is still very limited in this study we focus on infilling rate sediment acoustic characteristics slope change and surficial morphology all of which have implications for the management of seafloor oil and gas infrastructure bathymetric data collected during nine bathymetric surveys over 13 years were used to study the long term changes of the peveto channel dredge pit which is 5 km offshore of holly beach in western louisiana usa this pit was constructed in 2003 and was completely infilled in or before 2016 initial pit infilling rates began at 214 cm year from 2003 to 2004 and then rapidly decreased to an average rate of only 33 cm year from 2006 to 2016 this corresponds volumetrically to 418 753 and 80 816 m3 year for the same intervals pit wall margins displayed small lateral migration moving

barrier and lagoon coast evolution under differing relative sea level regimes examples from ireland and nova scotia abstract although the coasts of southern ireland and eastern nova scotia possess many basic similarities especially in terms of geology glacial history sediment character resistance to erosion and wave and tide regimes there is a fundamental contrast in holocene sea level history in ireland recent the past 4000 years sea level rise has been limited to less than 1 mm year by contrast the atlantic coast of nova scotia has been experiencing sea level rises up to three to five times greater over the same period under these markedly differing relative sea level rise regimes barrier and lagoon evolution has varied considerably in ireland barrier lagoon form is controlled by local basement expression particularly through the emergence of headlands creating largely closed sediment systems and the requirement to maintain cross shore drainage it is this latter factor that leads to a simple four fold categorization of the irish barriers and lagoons from freshwater seepage to open tidal environments the nova scotian examples are associated with rapidly moving erosional fronts with local basement control relegated to a subordinate role at the expense of rapid changes in sediment supply barriers can both grow and decay under these conditions subject to certain critical but as yet ill defined thresholds simultaneously forcing development and destruction of adjoining lagoons these major differences also find expression in sedimentary sequences

sedimentary processes over an intertidal flat a field investigation at hythe flats southampton water uk the sedimentary processes acting over an intertidal flat hythe uk located in southampton water hampshire uk are investigated on the basis of hydrodynamic morphological and sediment transport field measurements bed level changes patterns of suspended sediment transport and shell movement over the tidal flats were examined in order to identify sediment transport pathways and salt marsh mudflat morphological changes overall sediment transport patterns at hythe can be described in terms of suspended sediment and bedload shell transport the hydrodynamic complexity of the tidal flow over the flats determines the patterns of suspended sediments transport during the young flood phase tidal currents present a sw orientation shoreward about 1 h into the flood a change occurs and the currents start flowing in a se direction estuary mouthward this veering of the tidal current controls the hydrodynamic pattern over the mudflat inducing sediment transport towards the estuary mouth conversely shell tracer experiment showed a net landward movement shells are transported over the mudflat deposited at the base of the cliff and eventually transported over the salt marsh where they form extensive chernier deposits shell transport rates can reach up to 0 7 m tide over the upper mudflat shell movement over the salt marsh on cheniers occurred only during storms up to 3 m in a storm event shell induced erosion can become an important parameter on morphological changes of a coastal area shell transport and deposition over the salt marsh surface can contribute to vegetation deterioration as shell deposits migrate over the marsh surface as a result the seaward limit of the salt marsh showed deteriorated vegetation which leads to scouring and consequent surface lowering in terms of bed level changes no seasonal pattern was observed a relationship between mudflat bed erosion and cliff retreat is suggested during periods of high cliff erosion there was a tendency for the mudflats to be stable and conversely mudflat bed erosion was greatest when cliff retreat rates were lowest hence morphological characteristics of hythe intertidal area appear to be controlled by a combination of prevailing hydrodynamic conditions and shell transport over the salt marsh

maintenance of the shoreface by wave orbital currents and mean flow observations from the long island coast waves and currents were observed for a total of 36 days in august 1976 and 1977 calculations of wave transport of sediment using a bagnold equation for transport and second order stokes theory show that wave orbital current asymmetry results in landward sediment transport in 10 m or less water depth but does not significantly effect transport at greater depths calculations of sand transport using the madsen grant formulation show that during a 36 day observation period sediment in less than 10 m of water generally moved landward into the breaker and then along coast with the wave driven littoral flow the calculations show that below 10 m the generally upwelling coast parallel mean flow did not move sediment however during two days of a mild summer northeaster storm a downwelling coastal jet developed with 60 cm sec sup 1 maximum current the calculations show that if this flow had been combined with the intense wave regime of the succeeding several days sediment would have been entrained across the lower as well as the upper shoreface movement would have been offshore and alongshore such storm transport is believed to be typical of the more intense winter storms and to be responsible for the erosionalmore shoreface retreat that has caused up to a kilometer of shoreline retreat on the long island coast in the last century less

abstract geologic framework processes and rates of subsidence in the mississippi river delta plain abstract since the 1930 s louisiana has lost an estimated 3 950 km2 of coastal wetlands and barrier islands the loss of these coastal lands resulted primarily from subsidence and erosion rather than the draining and filling of wetlands more than 40 of the coastal wetlands in the u s are found in louisiana and 80 of our nation s total wetland loss occurs here at alarming rates beach erosion rates exceed 10 m yr and the rate of wetland loss is currently measured at 75 km2 yr the causes of louisiana s coastal land loss include delta switching storm impacts man s impacts on this deltaic system and high rates of subsidence recent studies indicate that the highest subsidence and coastal land loss rates occur where the underlying holocene sediments are the thickest this relationship suggests that subsidence through the consolidation and settlement of these young deposits is of primary importance to the coastal land loss problem found in louisiana to understand the role of subsidence in louisiana s coastal land loss problem requires a knowledge of the late quaternary history of the lower mississippi river of the infilling of its incised valley during the holocene transgression and of the processes of delta switching end of record last page 644

origin of amazon mudbanks along the northeastern coast of south america abstract seismic profiles sediment cores and water column measurements were collected along the northeastern coast of brazil to examine the origin of mudbanks in the amazon coastal mud belt these 10 60 km long shore attached features previously had been observed to migrate along the 1200 km coast of the guianas in response to wave forcing chirp 3 5 khz seismic profiles of the shoreface and inner shelf located two mudbanks updrift of the previous eastern limit in french guiana 210 pb geochronology shows that these two banks are migrating to the northwest over a relict mud surface in 5 20 m water depth the mudbanks are 3 4 m thick and are translating over a modern shoreface mud wedge deposited by previous mudbank passage in

late devensian and holocene relative sea level changes on the isle of skye scotland uk detailed litho and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the isle of skye scotland uk reveal evidence for several changes in relative sea level during the late devensian and holocene at the start of the record relative sea level in the area was high at ca 12 500 14c ca 14 800 cal yr bp but then fell reaching a low point during the younger dryas at ca 11 000 10 000 14c ca 13 000 11 600 cal yr bp when a rock platform correlated with the main rock platform was formed in the early middle holocene relative sea level was rising by ca 8000 14c ca 8800 cal yr bp and in northeast skye a lagoonal surface correlated with the main postglacial shoreline was formed at ca 6600 14c ca 7500 cal yr bp by the late holocene relative sea level was again falling but a rise registered at at least two sites began probably before ca 4000 14c ca 4500 cal yr bp and a second lagoonal surface in northeast skye correlated with the blairdrummond shoreline was formed although by ca 3000 14c ca 3200 cal yr bp relative sea level in the area had resumed its downward trend the pattern of relative sea level changes disclosed is compared with evidence elsewhere in scotland

the times are always changing the holocene saga the popular notion that the natural world maintains an invariant balance without perturbation by industrial civilization is invalid environmental changes in the aftermath of pleistoceneglaciationweredramaticandpervasive and continued in varying guise throughout the holocene interglacial which has been coincident in duration with the rise of modern human cultures holocene conditions have been influenced by the progress of physical processes and biotic migrations set in motion by deglaciation by climaticfluctuations still poorly understood and by the behavior of aboriginal peoples who achieved widespreadmanipulationoftheirevolvingenvironments even as they learned to adapt to them because cumulative holocene environmentalchangesarelargelyirreversible future sustainability of the human condition is dependentuponfurtherandwiserdevelopment of human culture all hopes for return to an irretrievable past are quixotic

the geysers clear lake area california thermal waters mineralization volcanism and geothermal potential manifestations of a major thermal anomaly in the geysers clear lake area of northern california include the late pliocene to holocene clear lake volcanics the geysers geothermal field abundant thermal springs and epithermal mercury and gold mineralization the epithermal mineralization and thermal springs typically occur along high angle faults within the broad san andreas transform fault system that forms the western boundary of the north american plate in this area the young volcanic rocks overlie mesozoic marine rocks of the great valley sequence which have been thrust above the coeval franciscan complex and penecontemporaneously dropped back down along low angle detachment faults many of the waters of the region are nonmeteoric as defined by their isotopic signature one type of isotopically shifted water emerges from or near great valley sequence rocks and is the most chloride rich it is interpreted to be evolved connate in origin a second type evolved meteoric water has moderate chloride contents high boron contents and high b cl ratios and is found locally in franciscan rocks notably at the sulphur bank mercury mine where it probably results from near closed system repeated boiling of meteoric water in host rocks that also contribute organic components to the water at the sulphur bank mine fracturing of otherwise impermeable franciscan rocks by faulting has created a localized zone of permeability in which thermal water boils repeatedly with limited venting to the surface boron rich fluids were apparently present at depth in the geysers geothermal field when intrusion of silicic magma occurred because the concealed intrusion of felsite is surrounded by a halo of tourmaline bearing hornfels the volume of this poorly dated early to middle quaternary intrusive body probably exceeds the 100 km 3 of erupted clear lake volcanics similar intrusions may have occurred in the eastern part of the area at wilbur springs and the mclaughlin mine where gold deposition and evidence of hydrothermal phenomena suggest more magmatic activity than is indicated by the small exposed bodies of early quaternary basaltic lava the clear lake volcanics are the present locus of volcanism in the northern coast ranges and progressively older volcanic centers occur to the south geophysical data suggest that a large silicic magma body may be centered north of the geysers steam field providing the heat for the geothermal field geothermal power production has peaked at the geysers and pressure declines indicate significant depletion of the fluid resource the vapor dominated field evolved from a preexisting hydrothermal system within fractured otherwise impermeable franciscan metamorphic rocks a deep water table of saline fluid has been postulated to be present under the steam field but no chloride rich water has been found at drillable depth we propose that recently discovered isotopically shifted steam in the northwest geysers area indicates the presence not of deep connate water but xather of boiled down boron rich franciscan evolved meteoric water this water is likely to be present in limited quantities and will not provide a significant hot water resource for geothermal power production at the geysers field or from the main clear lake volcanic field

problems in characterizing dynamics of mud shore profiles the relationship between profile shape and wave forcing at shores composed of soft mud is examined at a given still water level the modality of change in profile shape under wave action depends on the fluidization potential of mud which in turn is contingent on the wave characteristics and the dissipative properties of mud an important determinant of profile shape in areas where mud can be fluidized is the wave attenuation coefficient comparatively large values of this coefficient tend to correlate with erosional concave upward profiles and low values with accretionary convex upward shapes assuming that the rate of energy dissipation per unit area of nonbreaking normally incident waves is constant in the nearshore shallow zone an equation to simulate soft mud shore profiles has been developed this equation is shown to be applicable to profile data obtained from a variety of mud shore environments however it is noted that realistic simulations of the accretionary and erosional characteristics

south flank of the yangtze delta past present and future abstract chenier plain and mudflat development in the south flank of the yangtze delta are examined by multi disciplinary methods over different spatiotemporal scales and changing human earth interactions the study site contains a narrow belt of elongated ridge complexes that formed along the sediment deficient open coast from 6500 to 4000 yr bp since then and until the past two decades shoreline progradation has accelerated due to increasing sediment supply fueling rapid deltaic expansion superimposed on this trend are a series of discrete sand dominated ridges deposited during several stormy intervals tidal flat development is regulated by complex estuarine processes short term morphodynamic variations at the site are caused by the alternations of tides and waves while intermediate morphodynamic variations are controlled by the multi decadal shifting of river stem channel and stormy climates the ongoing rapid accretion on the tidal flats is predicted to continue into the near future because the estuarine buffer effect is expected to balance the adverse impacts of decreasing riverine sediment discharge and rising sea level technological developments during the last 2000 years are exemplified by seawall construction against sea flooding marking a transition from passive to active dike construction has been used more frequently and intensively to reclaim land since the 1970s in support of the booming socioeconomic development in the region lessons from complex morphodynamic change and human earth interactions in the southern yangtze delta admonish us to not reclaim coastal wetland by lower flat enclosures constructing new dikes near the low waterline while an optimal alternative would be to implement upper flat enclosures constructing new dikes around the high waterline on the continuously accretionary tidal flats with auxiliary biological restoration engineering to satisfy both socioeconomic development and sustainable wetland conservancy

modelling of modern mercury vapor transport in an ancient hydrothermal system environmental and geochemical implications mercury has been used in some mineralizing hydrothermal systems as a significant pathfinder of au and other elements in addition its geochemical behaviour reflects some characteristics related to the transport mechanism of metal bearing fluids in this work the authors analyse the geochemical aspects and the environmental impact of hg mobilization from the old mining area of valle del azogue va from smelting slags mining waste and the partially exploited mineralization that remains a few metres underground the main pathway of hg is the transport of vapor from different foci therefore a mathematical simulation of the process of hg vapor transport was carried out in the valle del azogue va mineral deposit this is one of the two sites in spain the other being the famous district of almaden where hg vapor emissions have been cited the results obtained by means of mathematical simulation were compared with both the real hg concentration values detected in the field upper part of the mining area and with the geochemical distribution patterns of au and other elements related to the mineralization a close relationship between the simulated hg vapor distribution and soil gas concentrations was identified it is proposed that the transport of hg emissions from this old mining area could be the cause of present contamination of marine sediments in the area

a comparison of observed and theoretical postglacial relative sea level in atlantic canada two extreme models of late wisconsinan ice cover in atlantic canada and the northeastern u s a are shown to produce postglacial relative sea level curves that bracket existing field observations at six sites throughout the region this suggests that the true late wisconsinan ice distribution is probably intermediate to the two contrasting reconstructions proposed both ice models predict the existence of four relative sea level zones an innermost zone closest to the centre of glaciation in which relative sea level falls continuously throughout postglacial time an outermost zone in which it rises continuously and two transitional zones in which it first falls and then rises in varying proportions according to the distance from the ice margin the distinctive forms of the relative sea level curves are probably representative of each of the zones and are unlikely to be significantly perturbed even by large local ice readvances they therefore establish patterns with which future field data are expected to conform the form that the geological record of relative sea level change is likely to take within each zone is discussed and promising settings for the collection of new data are proposed the common practice of separating relative sea level into an isostatic and a eustatic component is analysed and shown to be incorrect as usually applied the practice is also shown to be unnecessary because the models discussed in this paper predict changes in relative sea level that can be compared directly with the observations

barrier island evolution middle atlantic shelf u s a part ii evidence from the shelf floor where the atlantic coastal gradient is low and the substrate is unconsolidated shoreface processes lead to an equilibrium shoreface surface characterized by a straightened plan view and a concave up profile maintenance of this surface during the post glacial sea level rise may lead to barrier formation by mainland beach detachment where the outer oceanic shoreface is maintained by wave and current processes downwelling storm currents sweep sand from the shoreface of the middle atlantic bight transport it downcoast and seaward and deposit it on the adjacent inner shelf some of this sand is returned by the action of asymmetrical wave orbital currents during fair weather however there is a net loss in most areas the loss is not made good by river sand input since on the atlantic coast all river sand is trapped by estuaries as a result the shoreface in these areas is undergoing erosional retreat mean horizontal retreat rates are on the order of 1 3 m yr 1 but most movement occurs in brief episodes with recurrence rates on the order of several events per century erosional shoreface retreat coupled with aeolian overshoot storm washover and the movement of sand through inlets into the lagoons has lead to landward migration of the atlantic barriers through the holocene period of sea level rise the landward retreat of the barrier as a whole is as dependent on inlet formation as it is on erosional shoreface retreat repeated inlet breaching and the downdrift migration of inlets yields coalescing flood tidal deltas within the lagoon the resulting surface forms a platform on which the subaerial barrier deposits can advance under the impetus of storm washover and aeolian action the backbarrier deposits eventually re emerge at the shoreface where their upper beds are eroded and recycled the barrier thus migrates over a pavement of its own flood tidal deltas and washover fans sand is added to the system partly through the erosion of updrift headlands but mainly by means of scour in inlets which reaches down to the underlying pleistocene the modern shelf sand sheet is the debris blanket resulting from the retreat process the leading edge occurs as a thin veneer of rip current fallout on the shoreface this is periodically stripped off by winter storms to expose the underlying backbarrier strata further seaward shelf sands eroded from the shoreface rest disconformably on backbarrier deposits shoreface beach and dune strata are always missing every grain of sand in this shelf sand sheet has occupied a position on the beach or upper shoreface within the recent past however the sheet as a whole has been reconstituted its primary structures are those of the inner shelf floor backbarrier sand and mud deposits characterized by channeling and landward dipping reflectors can be traced for over 100 km seaward across the middle atlantic shelf beneath the modern sand sheet the backbarrier stratum together with the overlying shelf sand layer constitutes the record of barrier retreat across the atlantic shelf surface during holocene time the sheet like nature of this record indicates that viewed at the appropriate time scale barrier migration is a continuous process

mobilization of ag heavy metals and eu from the waste deposit of the las herrerias mine almeria se spain we studied the mobility of silver heavy metals and europium in waste from the las herrerias mine in almeria se spain the most abundant primary mineral phases in the mine wastes are hematite hydrohematite barite quartz muscovite anorthite calcite and phillipsite the minor phase consisted of primary minerals including ankerite cinnabar digenite magnesite stannite siderite and jamesonite and secondary minerals such as glauberite szomolnokite thenardite and uklonscovite the soils show high concentrations of ag mean 21 6 mg kg 1 ba mean 2 5 fe mean 114 000 mg kg 1 sb mean 342 5 mg kg 1 pb mean 1 229 8 mg kg 1 zn mean 493 mg kg 1 mn mean 4 321 1 mg kg 1 cd mean 1 2 mg kg 1 and eu mean 4 0 mg kg 1 the column experiments showed mobilization of ag al ba cu cd eu fe mn ni sb pb and zn and the inverse modelling showed that the dissolution of hematite hausmannite pyrolusite and anglesite can largely account for the mobilization of fe mn and pb in the leaching experiment the mobility of silver may be caused by the presence of kongsbergite and chlorargyrite in the waste while the mobility of eu seems to be determined by eu oh 3 which controls the solubility of eu in the ph eh conditions of the experiments the mineralogy ph eh and geochemical composition of the mine wastes may explain the possible mobilization of heavy metals and metalloids however the absence of contaminants in the groundwater may be caused by the carbonate rich environment of host rocks that limits their mobility

block theory and its application block theory is a geometrically based set of analyses that determine where potentially dangerous blocks can exist in a geological material intersected by variously oriented discontinuities in three

the pulpi gigantic geode almeria spain geology metal pollution microclimatology and conservation the discovery of the giant geode of pulpi almeria spain was considered as an important highlight in the geological heritage of spain projects developed for their conser vation were immediately initiated with legal figures of protection and tourist projects the geode has a tourist interest which must be tem pered by environmental restrictions limiting the public visits first results demonstrate that a continuous visit of two or three people for more than 10 min provokes the appearance of condensation and risks corrosion of the gypsum crystals in addition the electron microprobe analyses con firms 1 the hydrothermal phases of iron manganese in carbonated host rock 2 the presence of sulphides with fe zn pb ag sb cu hg as te se and 3 ba ca and sr sulphates with mercury traces the present proposal to label the geode and the mining environment as geological natural heritage is feasi ble although any tourist adaptation must not permit visits to the geode indoor and hg levels must be con trolled

seasonal interannual and mesoscale variability of the black sea upper layer circulation derived from altimeter data 1 topex poseidon and ers altimeter data comprising the period from may 1992 to may 1999 are assimilated into a shallow water model for providing a dynamically consistent interpretation of the sea surface height variations and estimation of the temporal and spatial characteristics of the upper layer circulation in the black sea these 7 year long observations offer a new capability for interpretation of major transient and quasi permanent features of the upper layer circulation the instantaneous flow fields involve a complex eddy dominated system with different types of structural organizations in which the eddies and the gyres of the interior cyclonic cell interact continuously among themselves and with meanders and filaments of the rim current the circulation possesses a distinct seasonal cycle whose major characteristic features repeat every year with some year to year variability an organized two gyre winter circulation system disintegrates gradually into a series of interconnecting eddies in the summer and autumn months which are also characterized by more pronounced and complex mesoscale activity in the peripheral flow system our analyses suggest a revised schematic circulation picture of the major quasi permanent and recurrent elements of the black sea

evolution of the barrier islands of southern long island new york three lines of evidence based on data from more than 400 boreholes and vibrocores have been used to reconstruct the evolution of the barrier islands during the holocene transgression in southern long island new york 1 the holocene transgressive stratigraphic sequence behind the present barriers 2 the stratigraphic patterns of the inner shelf and 3 the morphology of the now buried late pleistocene coastal features the extensive preservation of backbarrier sediments radiocarbon dated between 7000 and 8000 yr bp on the inner shelf of southern long island suggests that the barriers have not retreated by continuous shoreface erosion alone but have also undergone discontinuous retreat by in place drowning of barriers and stepwise retreat of the surf zone such stepwise retreat of the surf zone has prevented the backbarrier sediments from being reworked based on the presence of submerged barrier sand bodies in seismic records it is inferred that about 9000 years ago when the sea stood about 24 m below the present sea level a chain of barriers developed on the present shelf about 7 km offshore of the present barriers with continued sea level rise the 24 m barrier built upward until the sea reached about 15 m msl just prior to 7000 yr bp the barriers were then submerged by the rapidly rising sea and the surf zone shifted rapidly landward to a position about 2 km from the present shoreline the surf zone overstepped to the landward margin of the old lagoon which had become fixed at the steep seaward face of mid wisconsinan or sangamonian coastal barriers during the past 5000 or 6000 years the shoreface has retreated continuously by about 2 km evidence from southern long island and elsewhere in regions of coastal submergence indicates that rapid sea level rise and low sand supply seem to favour the stepwise retreat of barriers whereas slow rates of submergence and a greater supply of sand generally favour continuous shoreface retreat stationary upbuilding or seaward progradation of barriers may occur when supply of sand is great and or submergence is slowed or reversed morphologic highs on the pretransgression surface such as old barrier ridges tend to fix the migrating barrier shoreline during either continuous retreat or stepwise retreat of barriers

dynamic stability analysis of jointed rock slopes using the dda method king herod s palace masada israel abstract a dynamic two dimensional stability analysis of a highly discontinuous rock slope is demonstrated in this paper the studied rock slope is the upper terrace of king herod s palace in masada situated on the western margins of the seismically active dead sea rift the slope consists of sub horizontally bedded and sub vertically jointed stiff dolomite blocks the dynamic deformation of the slope is calculated using a fully dynamic version of dda in which time dependent acceleration is used as input the analytically determined failure modes of critical keyblocks in the jointed rock slope are clearly predicted by dda at the end of the dynamic calculation it is found however that for realistic displacement estimates some amount of energy dissipation must be introduced into the otherwise fully elastic un damped dda formulation comparison of predicted damage with actual slope performance over a historic time span of 2000 years allows us to conclude that introduction of 2 kinetic damping should suffice for realistic damage predictions this conclusion is in agreement with recent results of tsesarsky et al in y h hatzor ed stability of rock structures proceedings of the fifth international conference of analysis of discontinuous deformation balkema publishers lisse 2002 pp 195 203 who compared displacements of a single block on an inclined plane subjected to dynamic loading obtained by dda and by shaking table experiments using dynamic dda it is shown that introduction of a simple rock bolting pattern completely stabilizes the slope

the betic segment of the lithospheric trans alboran shear zone during the late miocene abstract the betic sinistral transcurrent shear zone betic cordilleras crosses the southeastern part of spain the study of the geodynamics of this area is approached from tectonic sedimentary magmatic and geophysical data large strike slip movements tectono sedimentary processes and magmatic events are seen at the boundary between two different lithospheric slabs they are located in a thinned compartment with a high geothermal gradient the large scale movements vertical and horizontal and the intensity of magmatic activity are the expression of the mechanical behaviour of this hot and thin crust all the geological events from the late miocene to recent are integrated in a crustal scale cross section which shows that the betic sinistral transcurrent shear zone widely affects the lithosphere it appears that subduction zones are not the only geodynamic context in which calc alkaline magmatism occurs

beach ridges definitions and significance abstract beach ridges frequent components of quaternary coastal plains and other coastal landforms have been cited as indicators of the positions of ancient seashores and associated sea levels numerous authors utilized the term beach ridge for active and relict usually wave built supratidal and or intertidal forms wind built ridges have been only occasionally included in the definition the term was applied also to submerged landward shifting eventually stranded bars a consistent redefinition of the term is highly desirable beach ridges should include all relict strandplain ridges whether dominated by wave swash built or by eolian lithosomes all active ridge like shore features regardless of dimensions morphology and origin are excluded because of the resistance of coarse clastic ridges to wave and wind erosion swash built gravel or coarse shell storm ridges may build several meters above the level of high tide swash built high berms even on pure sandy beaches exceed the highest tides during episodes of wind induced record water levels frequently but not always burying underlying low relief berm ridges of berm lithosomes sequences of relatively steep multiple foredunes are commonly named beach ridge plains the narrow subparallel relict foredunes that form these strandplains presently are designated as eolian beach ridges beach ridges thus are defined as relict semiparallel multiple wave and wind built landforms that originated in the inter and supratidal zones until separated from the shoreline by progradation sandy pebbly or shell enriched backshore berm ridges behind an active foreshore should not be considered beach ridges strandplain progradation is either continuous or with the inclusion of subtidal cat s eye ponds discontinuous contrary to claims transgressive cheniers do not represent true cheniers alone within their overall progradational context cheniers a special category of beach ridges bracketed by subtidal intertidal mudflats may be transgressive or regressive in character landward driven transgressive ridges should be designated beach ridges only after they are stabilized on intertidal flats when recognizable between clearly identifiable intertidal and overlying eolian intervals the horizontal interface between these lithosomes in beach ridges may help the reconstruction of ancient tide lake levels diagnostic sedimentary textures structures and fossils however often may be unavailable in the deposits along with various types of elevated terraces composed of raised marine deposits and certain coastal landforms of erosional origin that occur worldwide beach ridges of clearly proven wave built origin may also serve as indicators of ancient higher than present sea levels

the mississippi delta region past present and future the mississippi delta region of south louisiana houses a wealth of resources within a dynamic subsiding landscape foundations for the delta region reflect neogene evolution of the depocenter whereas details of the modern landscape reflect late pleistocene to holocene evolution of the alluvial deltaic plain the holocene delta plain was constructed by cyclical growth of deltaic headlands followed by avulsion and relocation of the fluvial sediment source abandoned headlands were then submerged and reworked while a new headland was created at the site of active fluvial sediment input historic period levees have decoupled the delta plain from its fluvial sediment source at the same time global sea level rise was accelerating which has accelerated delta plain submergence diversions of mississippi river water and sediment are necessary to achieve delta plain sustainability but upstream dams trap 50 of the total sediment load and there is not enough supply to keep pace with subsidence and accelerated

deep water deposits of the tanqua and laingsburg subbasins southwest karoo basin south africa analog for the gulf of mexico abstract the tanqua and laingsburg subbasins in south africa had near contemporaneous formation and filling and contain permian age basin floor and slope fans that display characteristics similar to deposits in the northern gulf of mexico outcrop area for each subbasin is about 650 km2 and individual fans range from 150 to 450 km2 with lateral continuity of individual fans up to 34 km with a sandstone shale ratio of 75 90 the arenaceous fans vary in thickness from 20 to 60 m with interlying shales ranging from 20 to 75m in thickness both subbasins were influenced in their formation and in the architecture of their deposits by structures and events associated with the cape fold belt having undergone little tectonic tilting the highly continuous outcrops in the tanqua subbasin expose two fans continuing from mid fan channel complexes with associated levee overbank deposits to sheet like outer fan lobes while three other fans expose outer fan depositional lobes paleocurrent directions for four of the fans are from ssw to s and a direction of w to wnw for the fifth these fans most likely had a single point source which migrated over the time of basin fill unrestricted deposition suggests an open basin depositional setting the laingsburg subbasin was strongly influenced by the tectonism associated with the cape fold belt deposition occurred in a deeper and narrower basin and the deposits except for the overlying deltaics cannot be correlated with those of the tanqua subbasin the two subbasins while associated with an active margin were likely filled at slightly different times both had a distant source area which led to deposits exhibiting characteristics of a passive margin depositional environment understanding the evolution of the subbasins and the tectonic conditions under which the submarine fans were deposited leads to the determination of the mechanisms that influenced the formation of the fans and their resulting architecture these fans permit detailed studies on their architecture necessary to 1 increase our understanding of fine grained low sandstone shale ratio fans 2 determine influences of paleostructures and tectonics on basin fill 3 carry out detailed reservoir simulation programs and 4 make predictive models of deep water sands in the northern gulf of mexico end of record last page 646

storm impact and evolution of a mangrove fringed chenier plain shoal bay darwin australia abstract storms are considered to have significant impacts on the development of chenier plains particularly through the devastation of mangrove vegetation but also in terms of winnowing sand and shell from mudflats and forming chenier ridges shoal bay in the beagle gulf northern australia contains a small chenier plain which was struck by a severe tropical cyclone cyclone tracy on christmas day 1974 as it devastated the city of darwin the morphology vegetation and stratigraphy of the plain are described the plain is underlain by lower intertidal sand with shell hash a radiocarbon age of 6130 years bp indicates mangrove colonisation of this flat at the time that sea level stabilised around its present level after the postglacial transgression subsequently progradation of mudflats has occurred especially around 2300 years ago and shells of this age are found both in growth position from within the mudflats and incorporated into the shelly chenier ridges a further phase of build out and subsequent erosion is reflected by stumps and in situ bivalves being excavated presently on the foreshore radiocarbon dating about 900 1100 years bp within this context of evolution cyclone tracy can be seen to have had severe consequences upon the patterning of mangroves with extensive windthrow of ceriops and defoliation of rhizophora at the western end of the plain recovery of the mangrove vegetation has been gradual and is still incomplete however the storm had little influence on the pattern of landform development indeed the aerial photographic sequence indicates a trend by which sand shoals are gradually reworked landwards in places moving through mangrove vegetation the study suggests that rather than pronounced regional episodes of alternative mudflat buildout and erosion both processes occur simultaneously at different points along this foreshore

coastal mudflat accretion under energetic conditions louisiana chenier plain coast usa mudflat accretion on the chenier plain coast of louisiana northern gulf of mexico is anomalous in an area that otherwise experiences widespread land loss due to rapid relative sea level rise accretion is shown to be related to energetic events winter cold fronts and occasional tropical depression storms using a 17 year record of meteorological conditions and aerial surveys the results indicate substantial differences between the behavior of sand and mud dominated coastal systems under energetic conditions comparison of the louisiana chenier plain to other mud rich coasts indicates that certain conditions are necessary for mudflat accretion to occur during energetic atmospheric activity these include an abundant supply of fine grained fluvial sediment and resuspension events that maintain an unconsolidated sea floor dominant onshore wind direction during energetic conditions particularly when onshore winds coincide with high fluvial sediment input to the coastal ocean and a low tidal range

metal mobilization from base metal smelting slag dumps in sierra almagrera almeria spain abstract smelting slags associated with base metal vein deposits of the sierra almagrera area se spain show high concentrations of ag 2 0 mg l fe 0 22 9 8 mg l mn 0 85 40 2 mg l ni 0 092 2 7 mg l pb 2 0 mg l and zn 2 5 mg l and mobilization of ag 0 2 31 g l as 5 2 31 g l cd 1 3 36 8 g l and hg 0 2 7 g l the leachates were modeled using the numerical code phreeqc the results suggested the dissolution of fayalite ferrihydrite jarosite pyrrhotite goethite anglesite goslarite chalcanthite and cotunnite the presence of secondary phases in the slag dumps and contaminated soils may indicate the mobilization of metals and metalloids and help to explain the sources of groundwater contamination

coastal geology of the king point area yukon territory canada abstract at king point on the yukon coast of the canadian beaufort sea a sand gravel barrier is migrating landward across a sequence of lacustrine muds which were deposited in a thermokarst lake the lacustrine deposits were laid down between 12 ka and the time of breaching of the thermokarst lake breaching occurred at some point after 1 7 ka probably a few hundred years ago estimates of sediment supply and barrier growth can be best reconciled if a model is assumed that involves initial erosion of a 1 km wide headland an extension of a diamict ridge which forms king point itself followed by straightening of the coast and an increased sediment supply from gravel rich cliffs north of the ridge this is compatible with historical evidence for development of the barrier comparison of sediment supply retreat rates and longshore sediment transport potential lead to the conclusion that the development of the barrier and coastal retreat are limited by the longshore transport potential the evolution of the king point barrier is similar to that of gravel barriers in temperate regions but short term increases in sediment supply through thermal erosion of adjacent bluffs and erosion of the lower shoreface by ice scouring may be important additional factors