static bay beach concept for scientists and engineers a review abstract headland bay beach hbb is one of the most prominent physiographic features on the oceanic margin of many countries in the world under the influence of a predominant swell its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and or a riverain source within its own embayment coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s as the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management nowadays many useful applications have emerged since the publication of the parabolic bay shape equation pbse developed for static equilibrium planform sep in late 1980s the advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept sbbc this paper reviews the progress on the research in hbb made by geographers and geologists since the 1940s together with the involvement of coastal engineers working on shore protection and management from the 1960s aided by software mepbay developed in 2003 for the pbse several practical examples are demonstrated in this paper for the stability verification of natural and man made bay beaches shore protection mitigating downdrift erosion of a harbour design of recreational bay beach as well as for environmental impact assessment limitations on and clarifications for engineering applications based on the sbbc are also discussed in this paper

morphometric classification of swell dominated embayed beaches abstract globally embayed beaches are common to hilly and mountainous coastlines they are typically characterised by two headlands that are a primary control on incident wave exposure and beach morphodynamics embayed beaches exist under a range of headland morphologies and degree of embaymentisation here we present a generalised embayment morphometric parameter e which classifies the geomorphological setting of embayed beaches based on the embayment indentation and area we apply this to 168 swell dominated embayed beaches from 6 regions using open access imagery the embayment morphometric parameter e was subjected to k means cluster analysis to identify 4 classes of embayed beaches with increasing e indicating greater headland influence and impact on incident wave exposure the classes range from 1 to 4 with increasing degree of embayment the most common is class 2 43 n 73 which represents embayed beaches that have moderate embayment indentation and headland influence there are clear trends in embayment geometry regardless of location wave climate or tidal regimes within the embayments there were 6 possible headland orientations types h1 h6 the most common 58 n 97 is when both headlands are orientated outwards from the beach h6 and may result in greater morphological beach response from less headland shadowing compared with headlands orientated inwards onto the beach h1 in summary we have developed a simple classification scheme for embayed beaches based on degree of indentation and headland orientation that can be applied to any embayed beach globally

stratigraphic record of basin development within the san andreas fault system late cenozoic fish creek vallecito basin southern california the fish creek vallecito basin contains a 5 5 km thick section of late miocene to early pleistocene sedimentary rocks exposed in the hanging wall of the west salton detachment fault these deposits preserve a high fidelity record of late cenozoic subsidence and basin filling that resulted from deformation in the san andreas fault system of southern california existing and new paleomagnetic data combined with new u pb zircon ages of two tuffs high in the section show that the section ranges in age from ca 8 0 0 4 ma at the base to ca 0 95 ma at the top geohistory analysis reveals 1 moderate subsidence 0 46 mm yr from ca 8 0 to 4 5 ma 2 rapid subsidence 2 1 mm yr from 4 5 to 3 1 ma 3 moderate subsidence 0 40 mm yr from 3 1 to 0 95 ma and 4 rapid uplift and erosion that has exhumed the section since ca 1 ma onset of sedimentation at ca 8 0 0 4 ma records earliest extension or transtension in the area possibly related to localization of the pacific north america plate boundary in the salton trough and gulf of california alternatively marine incursion at 6 3 ma may be the earliest record of plate boundary deformation in the gulf of california salton trough region a thick interval higher in the section records progradation of the colorado river delta into and across the basin starting ca 4 9 ma progradation continued during an abrupt increase in subsidence rate at 4 5 ma and fluvial deltaic conditions persisted for 1 4 m y during the rapid subsidence phase indicating that delta progradation was driven by a large increase in rate of sediment input from the colorado river uplift and inversion of the basin starting ca 1 0 ma record initiation of strike slip faults that define the modern phase of dextral wrench tectonics in the western salton trough

crustal evolution of northern alaska inferred from sedimentology and structural relations of the kandik area one of the most complete stratigraphic sections in north america crops out in east central alaska and western yukon territory north of the tintina fault these uppermost precambrian to uppermost mesozoic strata record in ascending order a late precambrian and paleozoic continental rifting and margin subsidence history a late devonian orogenic pulse possibly coinciding with a eustatic low stand continental margin uplift of at least 3 km in the carboniferous renewed subsidence in permian and triassic time uplift of the ancestral brooks range in the early cretaceous opening of the canada basin in mid cretaceous to late cretaceous time resulting in counterclockwise rotation of all of northern alaska and parts of western yukon territory including the kandik area and a crustal sag that evolved into the yukon flats the latter resulted from transtensional slip along the tintina fault reflecting plate motions dictated by kinematics of the pacific realm the rotation of northern alaska was about a pole located near mackenzie delta and transpired between barremian and campanian time circa 120 to 80 ma

alternative methods for calculating compaction in sedimentary basins abstract subsidence analysis is an important technique in the study of sedimentary basins but the effects of compaction must be backstripped the compaction of sediments is also of importance for petroleum and water reservoir research with very important economic derivations most methods for calculating compaction are based on empirically derived porosity depth relationships from a variety of known sediment types the challenge of this paper is to apply alternative methods for calculating compaction in sedimentary basins based on physical calculation with elastic by steinbrenner oedometric and change of the specific weight of the sediment methods and use of loadcap software the triassic to lower miocene 3025 m thick succession of sierra espuna se spain is used as case study for the calculations in this succession former mineralogical studies and apatite fission track suggested an original thickness between 4 and 6 km the validity of each one of the proposed methods is discussed as well as compared for the whole succession compaction but also separately for hard vs soft sediments and for thick vs thin beds the compaction values obtained with the alternative methods are similar to those resulting with the lower limit curves of the porosity depth change method the new methods have provided values slightly higher than 4 km for the whole original thickness using the geotechnical software and the change of the sediments specific weigh methods meanwhile values below 4 km for other methods so in our opinion the geotechnical software and the change of the specific weight of the sediment methods are compatible with mineralogical constraints and also the input data are usually better known and easier to determinate otherwise the elastic method seems only accurate for soft sediments meanwhile the oedometric method is highly influenced by the thickness of the considered beds

wave driven sediment transport and beach dune dynamics in a headland bay beach abstract this paper presents a comprehensive study of wave refraction wave and wind driven sediment transport foredune development and holocene barrier evolution over a variety of time scales at mocambique beach santa catarina state southern brazil the motivation for this study was to examine the relationships between estimated wave driven sediment transport medium and long term aeolian transport foredune development and holocene barrier volumes and morphology an analysis of 2 years of wave rider data for the region shows two well defined peaks of frequencies one of swell waves from the south with a period of 12 s and another peak of sea waves from east northeast with a period of 7 s longshore sediment transport rates were calculated using high resolution hindcast wave data for the south atlantic ocean which was calibrated by the measured buoy data the dominant southerly waves drive a longshore gradient in wave energy from south to north and nearshore surf zone sediment transport increases from south to north beach grain size is fine in both the south and north and medium in the center the combination of grain size and wave energy variations creates a marked alongshore variation in surf zone beach types ranging from low energy dissipative in the south moderate energy intermediate in the central area to moderate to high energy dissipative in the north estimates of aeolian sediment transport volumetric changes in foredune deposition and total holocene dunefield volumes were also calculated results indicate that the morphological behavior of the foredune profiles reflects the gradients of longshore sediment transport and the exposure to wind energy and aeolian sediment delivery with a maximum of sediment volume and transport towards and in the central part and northern end of the barrier holocene 0 7000 years barrier volumes vary along the embayment mimicking the trends in both calculated wave and wind driven sediment transport the short and hesp 1982 model was more suitable in predicting the long term holocene barrier evolution than the size and volume of the foredune the combination of wide beach high energy dissipation maximum sediment supply and high exposure to strong onshore winds is found in the northern end of the embayment where holocene subaerial barrier volumes are at a maximum overall this study proves that foredune development is closely related to wind exposure wave energy and gradients of longshore sediment transport and that dunefield development reflects the increase downdrift in potential sediment supply from the southern to the northern end of the beach and the change alongshore from low energy dissipative through intermediate to high energy dissipative beach surf zone environments this paper significantly extends previous models of beach and dune interactions in that it i actually determines wave driven sediment transport for various sections of a long embayment ii relates those transport patterns to surf zone beach morphodynamic types and variations in alongshore sediment patterns and iii correlates foredune volumes and holocene barrier volumes which reflect proxy holocene onshore transport rates with wave driven sediment transport rates

active synsedimentary tectonism on a mixed carbonate siliciclastic continental margin third order sequence stratigraphy of a ramp to basin transition lower sekwi formation selwyn basin northwest territories canada the lower part of the early cambrian sekwi formation in the selwyn basin of the northwest territories canada is composed of two regional unconformity bounded sequences s0 and s1 which record the first widespread carbonate deposition during the initial palaeozoic transgression onto the western margin of laurentia these early cambrian sequences are unique to the western north american cordillera representing the only record of primarily deep water deposition on a tectonically active mixed carbonate siliciclastic ramp during this period more specifically the geometry of the sekwi ramp changed during deposition of s0 and s1 from a shallowly dipping homoclinal ramp during the s0 transgressive systems tract to a steeply dipping tectonically modified ramp during the early highstand systems tract of s0 the steeply dipping ramp profile of s0 was preserved into the early transgressive systems tract of s1 the sekwi ramp returned to a gently sloping ramp during the late highstand systems tract of s1 and remained so throughout the remainder of sekwi deposition the evolving shape of the sekwi ramp is attributed to syndepositional down to the basin faulting during deposition of both s0 and s1 and is recorded by i the westward thickening irregular geometries of s0 and s1 ii geographical restriction of deep water facies including sediment gravity flow deposits iii the presence of large allochthonous blocks and iv the clast composition of sediment gravity flow deposits sediment gravity flow deposits play an unusually important role in the sequence stratigraphic interpretation of the lower sekwi formation as they delineate depositional packages including the maximum flooding zone the transitions between portions of systems tracts and the inferred locations of syntectonic extensional faults syntectonic faults increased accommodation basinward of an extensive ooid shoal complex that developed along the sekwi ramp crest greatly influencing sequence geometry and initiating the downslope motion of sediment gravity flows the syndepositional faulting probably was a continuation of extension that began during the latest neoproterozoic rifting of western laurentia the composition of sediment gravity flow deposits track changing accommodation space on the lower sekwi ramp and can be used to differentiate systems tracts that probably were related more to tectonism than eustasy

paleotectonic and stratigraphic implications of the kingston peak noonday contact in the panamint range eastern california geologic mapping in parts of the southern panamint range eastern california has documented critical stratigraphic relationships at the upper proterozoic contact between the kingston peak formation and noonday dolomite these relations bear significantly upon the timing and style of development of the latest proterozoic and paleozoic continental margin of western north america they include 1 an unconformity below wildrose diamictite interpreted as glaciogenic the uppermost kingston peak unit 2 diamictite similar to wildrose diamictite interbedded within carbonate strata of the overlying basal noonday dolomite and 3 interfingering between rocks of the kingston peak and noonday formations the kingston peak noonday contact is thus complex and variable in character and does not represent a regional unconformity instead it marks a transition from rift to post rift sedimentation without any hiatus and shows there was no regional doming during rifting the stratigraphic relations also demonstrate

in situ measurement of electrical resistivity of marine sediments results from cascadia basin off vancouver island abstract electrical properties of sediments encompass information about other linked physical properties such as porosity and thermal conductivity in situ measurements of electrical resistivity offer a cost and time effective method for obtaining a comprehensive overview of near surface sediment physical properties they also provide a quality check for in situ measurements of related sediment properties or for data obtained from sediment core analysis we present results from the deployment of a sediment penetrating in situ probe which logs electrical resistivity of marine or limnic sediments up to 4 mbsf additionally acceleration and pressure are recorded during sediment penetration as the integration of acceleration delivers penetration depth with respect to time a resistivity depth profile can be derived the measurements presented were performed during cruise so 149 in the cascadia basin and at the eastern flank of the juan de fuca ridge the in situ probe is attached to a lister type heat flow instrument therefore simultaneous measurements of thermal and electrical resistivities are possible strongly influenced by porosity both data sets show good correlation continuous recordings of electrical resistivity can be used to validate and supplement the thermal data which is only measured in depth intervals of 30 cm comparison with other independent measurements such as porosity measured on sediment cores also confirm the correct operation of the probe

tidal littoral offshore shelf deposits lower cambrian gog group southern rocky mountains canada abstract nearly 600 m of shallow marine fine to coarse grained quartzites interbedded with shales of the lower cambrian gog group are exposed at the spiral tunnels section kicking horse pass yoho national park facies are defined and interpreted on the basis of sedimentary structures as follows 1 interbedded shale and sandstone pelagic sediments with interbedded coarse grained bottom current deposits 2 massive to laminated shale pelagic sediments 3 conglomerate storm deposits 4 linsen bedded sandstone in shale bedload deposits with pelagic or suspended sediments 5 planar tabular cross bedded sandstone small scale bedload deposits from two dimensional megaripples large scale sand wave or sand ridge deposits 6 trough cross bedded sandstone three dimensional ripple and megaripple deposits 7 low angle to horizontally stratified standstone shoaling wave deposits and 8 massive sandstone well sorted deposits large scale 1 5 m thick lateral accretion epsilon deposits also occur facies trends are interpreted as reflecting the migration and aggradation of offshore sand ridges larger sand ridge complexes are comprised of amalgamated individual sand ridge accumulations progradation of sand ridge complexes yield coarsening upward sequences whereas retreat of sand ridge complexes yield fining upward trends overall the sequences are poorly defined mainly a consequence of the interaction of sand ridge and inter ridge swales theoretical considerations of the early cambrian configuration of continents earth moon separation and paleoceanographic conditions suggest that storms were not that important in the emplacement of the sand ridge complexes major offshore current systems are interpreted as being tidally driven with perhaps a secondary littoral or geostrophic current influence the thick sequence of the section 500 m along with a consistent trace fossil signature suggests that the gog group was deposited under shallow marine offshore shelf settings of a rapidly subsiding passive continental margin this is consistent with the geophysical model for the proto pacific margin which during the early cambrian was characterized by very rapid thermal subsidence

nd evidence for proterozoic crustal development in the belt purcell supergroup a knowledge of the chemical and isotopic characteristics of the continents as they existed in the past is essential to an understanding of their evolution1 7 vestiges of these characteristics remain in the sedimentary record for example the character and crustal residence age4 of ancient continental crust has been deduced from the sm nd isotopic patterns of clastic sediments that have survived to the present day4 6 8 we report here sm nd isotopic measurements from the belt purcell supergroup of western north america which form the first detailed isotopic investigation of a major proterozoic sedimentary succession the belt purcell has many features also seen in the detrital load of the world s major contemporary rivers including exceptionally homogeneous 147sm 144nd and 143nd 144nd ratios and a small range of crustal residence ages mantle additions to the continental crust seem to have been relatively minor since the middle proterozoic

southwestward weakening of wyoming lithosphere during the laramide orogeny the mechanism of laramide deformation in the central rocky mountains remains enigmatic it is generally agreed that the deformation resulted from low angle subduction of the farallon plate beneath the north american plate during the latest cretaceous early eocene however recent studies have suggested the importance of slab removal or slab rollback in causing this deformation here we infer wyoming lithosphere structure and surface deformation pattern by conducting 2 d flexural subsidence modeling in order to provide constraints on the mechanism of laramide deformation we assume that wyoming lithosphere behaved as an infinite elastic plate subject to tectonic loading of mountain ranges and conduct 2 d flexural subsidence modeling to major laramide basins to document lithospheric stiffness and mountain load height our results show that the stiffness of wyoming lithosphere varied slightly in each basin during the 30 myr duration of the laramide deformation and decreased from northeastern wyoming te 32 46 km to southwestern wyoming te 6 9 km our results also imply that the increase of equivalent load height of major laramide ranges accelerated during the early eocene we propose that the bending stresses induced by the topographic load of the sevier fold and thrust belt combined with crust mantle decoupling initiated by the overthickened sevier hinterland and the end loads due to the low angle subduction at the western edge of the thick wyoming craton have caused the southwestward decrease of lithospheric stiffness in wyoming moreover we attribute the accelerated load height gain during the early eocene to both dynamic and isostatic effects associated with slab rollback

intraplate stresses and the subsidence history of the sirte basin libya abstract results of quantitative analysis of subsidence data from 20 wells covering six major basement blocks from the sirte basin libya are presented following the late cretaceous onset of extension and associated collapse of the sirte arch the tectonic history post dating this event can be separated into four distinct phases 1 1 minor subsidence during the late cretaceous 2 2 differential fault tectonics and reactivation of basement faults during latest cretaceous to paleocene 3 3 regional uplift and subsidence during the eocene 4 4 minor subsidence during the early oligocene and early miocene a late cretaceous paleocene stretching phase of finite duration can explain the overall patterns of observed tectonic subsidence during the syn and post rift evolution of the sirte basin strong short term deviations from thermally induced long term subsidence observed during the eocene can be explained by intraplate compression and subsequent stress release related to changes in atlantic flowline geometry modelling of the observed tectonic subsidence for the sirte basin yields estimates of extension in excess of estimates inferred from displacements along high angle normal faults the effect of late stage intraplate compression on tectonic subsidence may cause part of the observed discrepancy between estimates of crustal extension

pliocene quaternary tectonic sedimentary evolution of the ne alboran sea sw mediterranean sea abstract the pliocene quaternary tectonic sedimentary evolution of the ne alboran sea is established using high resolution seismic profiles the pliocene quaternary deposits resting upon an acoustic basement with a complex morphostructure are stratigraphically made up of three seismic sequences whose facies stratal patterns and nature of boundaries result from the interaction between sea level changes tectonics and physiographic configuration during the early pliocene a generalized synsedimentary transgression with extensive tectonic activity resulted in a homogeneous sedimentation deformed by extensional tectonic activity along two main fault systems ne sw and nw se the sediment distribution was controlled by the pre existing palaeotopography during the late pliocene a generalized synsedimentary regression with a n s compressive tectonic activity favoured the development of a great variety of seismic facies related to the initiation of the almeria turbidite system and the triggering of gravity mass flow deposits the deformation of these seismic facies was mainly controlled by the transcurrent ne sw and nw se structures and their distribution was related to the point source represented by the almeria canyon during the quaternary the high frequency sea level oscillations coeval to nnw sse compressive tectonic activity resulted in the progradation of the margin the occurrence of instability phenomena and the sedimentary displacements of the almeria turbidite system an analysis of subsidence evolution shows an attenuation during the pliocene quaternary from a maximum of 342 m m y to 160 m m y for the total subsidence and from a maximum of 196 to 116 m m y for the tectonic subsidence

numerical modeling of crenulate bay shapes a numerical model is developed to compute the shoreline planform in a crenulate bay beach the new model combines polar and cartesian coordinates and can be used effectively to compute a hooked zone shoreline in the lee of upcoast headland the model is calibrated using laboratory data with an incident wave angle ranging from 25 to 60 the results of calibration and verification suggest that the ratio of the sediment transport parameters by wave and longshore current in this model is close to unity and the computed shoreline planforms for the hooked and unhooked zones are in good agreement with the ones measured especially when a bay is close to static equilibrium in addition the bay shape calculated by the present model is similar to that given by the well known empirical parabolic equation for a bay in static equilibrium the process of bay shape development from a straight beach to a static equilibrium bay is studied using laboratory experiments and the present numerical model the temporal variations in the computed longshore sediment transport at different locations within a bay beach are analyzed from this the decrease in the sediment transport becomes apparent while a bay beach changes its shape from straight toward a state of equilibrium based on this experience it may be concluded that the present numerical model can produce a temporal change in the shoreline planform of a crenulate bay beach from a transition state to static equilibrium subject to seasonal wave action

modelling of embayed beach equilibrium planform and rotation signal abstract embayed beaches are highly attractive sandy beaches bounded laterally by rigid boundaries which deeply affect equilibrium beach planform and shoreline dynamics we use lx shore a state of the art shoreline change model coupled with a spectral wave model to address embayed beach shoreline dynamics driven by longshore sediment transport processes the model is applied to different idealized embayed beach configurations including variations in headland lengths the model simulates a large range of equilibrium embayed beach planforms and associated spatial and temporal modes of shoreline variability for short headlands enabling occasional headland sand bypassing both embayed beach curvature and maximum erosion at the upwave side of the embayment increases with increasing headland length beach curvature also increases with increasing headland length for headlands long enough to prevent any headland sand bypassing in contrast at the same time embayed beach becomes increasingly curved and symmetric with maximum localised erosion within the embayment decreasing in intensity when there is no headland sand bypassing rotation signal decreases in amplitude and becomes increasingly symmetric with increasing headland length the modal time invariant directional spreading of incident waves is critical to embayed beach behaviour with the envelope and variance of cross shore shoreline change and time averaged shoreline curvature all increasing with decreasing modal directional spreading embayed beach rotation characteristic timescale increases with increasing embayed beach length while the narrower the embayment the smaller the cross shore amplitude of shoreline variability our simulations provide new insight into the influence of embayment characteristics and incident wave conditions on equilibrium planform and shoreline dynamics of embayed beaches this work also implies that the degree of potential headland sand bypassing should be taken into account for modelling of beach rotational dynamics and embayed beach dynamic planform configuration

chemostratigraphy of predominantly siliciclastic neoproterozoic successions a case study of the pocatello formation and lower brigham group idaho usa abstract isotopic chemostratigraphy has proven successful in the correlation of carbonate rich neoproterozoic successions in successions dominated by siliciclastic rocks chemostratigraphy can be problematic but if thin carbonates punctuate siliciclastic strata useful isotopic data may be obtained the upper pocatello formation and lower brigham group of southeastern idaho provide an opportunity to assess the potential and limitations of isotopic chemostratigraphy in overwhelmingly siliciclastic successions the 5000 m thick succession consists predominantly of siliciclastic lithologies with only three intervals that contain thin intercalated carbonates its depositional age is only broadly constrained by existing biostratigraphic sequence stratigraphic and geochronometric data the lowermost carbonates include a cap dolomite atop diamictites and volcanic rocks of the pocatello formation the delta 13c values of these carbonates are distintly negative 5 to 3 similar to carbonates that overlie neoproterozoic glaciogenic rocks worldwide stratigraphically higher carbonates record a major positive delta 13c excursion to values as high as 8 8 within the carbonate member of the caddy canyon quartzite the magnitude of this excusion is consistent with post sturtian secular variation recorded elsewhere in the north american cordillera australia svalbard brazil and nambia and exceeds the magnitude of any post varanger delta 13c excursion documented to date in most samples sr isotopic abundances have been altered by diagenesis and greenschist facies metamorphism but a least altered value of approximately 0 7076 supports a post sturtian and pre marinoan varanger age for upper pocatello and lower brigham rocks that lie above the pocatello diamictite thus even though available chemostratigraphic data are limited they corroborate correlations of pocatello formation diamictites and overlying units with sturtian glaciogenic rocks and immediately post sturtian successions in western north america and elsewhere

thermal subsidence and eustasy in the lower palaeozoic miogeocline of western north america we have recently developed a procedure for calculating tectonic subsidence in fully lithified basin sequences and applied it to cambrian and ordovician strata of tbe cordilleran miogeocline exposed in the southern canadian rocky mountains1 the cumulative tectonic subsidence curves were found to be mainly thermal in form as predicted by the passive margin model for the miogeocline2 in this paper we extend the analysis to cambrian and ordovician strata in a much larger segment of the miogeocline extending from the yukon territory to central nevada the results indicate that thermal contraction was the dominant subsidence mechanism for more than 2 000 km along the eastern or inner part of the miogeocline in addition we find a slight but persistent deviation in the subsidence curves from a purely thermal form that is consistent with a global sea level change proposed by vail and others3 for cambrian to middle ordovician time

beaches downcoast of harbours in bays abstract in spite of beach berms being removed during each storm sequence the waterline may be retained constant either by a constant supply of littoral drift or static equilibrium bays being formed between headlands the construction of salients behind offshore breakwaters may be at the expense of the adjoining coast which resembles the ubiquitous bay shapes formed between headlands that can be either in dynamic or static equilibrium this is the same silting situation in the lee of breakwaters extending from the coast where beach erosion results downcoast ports constructed upcoast of a bay in dynamic equilibrium can have their breakwaters so located that the bay can become statically stable in the case of the bay being already in static equilibrium breakwater extension often causes massive accretion in its lee and concomitant erosion further downcoast thus demanding prodigious expense for beach protection installations appropriate procedures are now suggested to minimise this undesirable effect of beach erosion associated with the construction and extension of breakwaters to ports upcoast of a bay

high resolution downscaled ocean waves dow reanalysis in coastal areas abstract large scale wave reanalysis databases 0 1 1 spatial resolution provide valuable information for wave climate research and ocean applications which require long term time series 20 years of hourly sea state parameters however coastal studies need a more detailed spatial resolution 50 500 m including wave transformation processes in shallow waters this specific problem called downscaling is usually solved applying a dynamical approach by means of numerical wave propagation models requiring a high computational time effort besides the use of atmospheric reanalysis and wave generation and propagation numerical models introduce some uncertainties and errors that must be dealt with in this work we present a global framework to downscale wave reanalysis to coastal areas taking into account the correction of open sea significant wave height directional calibration and drastically reducing the cpu time effort about 1000 by using a hybrid methodology which combines numerical models dynamical downscaling and mathematical tools statistical downscaling the spatial wave variability along the boundaries of the propagation domain and the simultaneous wind fields are taking into account in the numerical propagations to performance similarly to the dynamical downscaling approach the principal component analysis is applied to the model forcings to reduce the data dimension simplifying the selection of a subset of numerical simulations and the definition of the wave transfer function which incorporates the dependency of the wave spatial variability and the non uniform wind forcings the methodology has been tested in a case study on the northern coast of spain and validated using shallow water buoys confirming a good reproduction of the hourly time series structure and the different statistical parameters

an assessment of the age and tectonic setting of volcanics near the base of the windermere supergroup in northeastern washington implications for latest proterozoic earliest cambrian continental separation mafic metavolcanics of the huckleberry formation in northeastern washington occur near the base of the windermere supergroup a sequence of immature clastic rocks thought to have been deposited dur

on the application of static equilibrium bay formulations to natural and man made beaches crenulate shaped bays are common features found all around the world the most widely used formulation for representing this kind of bay is the parabolic approach proposed by hsu and evans institution of civil engineers proc london england 87 1989 556 who suggested a methodology to test and predict the stability of static equilibrium shapes in natural and man made bays based on an analytical model of null drift current and using an empirical approach a modified methodology is proposed the new procedure is able to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of hsu and evans is valid this methodology is applied with good results to different natural and man made beaches along the atlantic and mediterranean coasts of spain including tombolo shaped beaches

tectonic subsidence flexure and global changes of sea level tectonic models for the evolution of passive continental margins predict that following rifting sediments should progressively onlap basement at the edge of a margin as the lithosphere cools and increases its flexural rigidity with age the pattern of modelled onlap is strikingly similar to that used by vail and colleagues to estimate sea level rise through geological time this similarity suggests that major portions of stratigraphical sequences at margins may have a tectonic rather than eustatic control the patterns of onlap used by vail and colleagues may be widespread however because several widely separated passive margins rifted at similar times but they are unlikely to be worldwide

dynamic equilibrium planform of embayed beaches part 2 design procedure and engineering applications abstract the design of equilibrium beach systems employing beach nourishment techniques in conjunction with coastal support structures has received increased interest from coastal engineers in recent years one such solution to remedy coastal erosion problems is to design an equilibrium pocket beach in order to stabilize the shoreline such coastal landforms may exist in nature in static or dynamic equilibrium states the concept of the static equilibrium planform sep has received much more attention from coastal engineers than that paid to the dynamic equilibrium planform dep this paper presents a design procedure for embayed beaches in dynamic equilibrium which have a specific net littoral drift rate the proposed methodology employs the net sediment transport rate passing through the bay together with the time series of the wave climate impinging on the beach in order to compute the angle d this angle represents the difference in degrees between the direction of the mean wave energy flux at the diffraction point ef and the orientation of the dynamic equilibrium beach db to be utilized in a newly derived dep formula to predict the shoreline shape in the long term the procedure was applied and validated using prototype bays in dynamic equilibrium with different net sediment transport rates along the brazilian coast producing good results furthermore it was employed as a tool to investigate the influence of changes in the net annual littoral drift rate on the dep shape in a case study along the spanish coast taken together these confirm its utility as a valuable tool for coastal management and engineering practice

a new model for predicting three dimensional beach changes by expanding hsu and evans equation the empirical bay shape model proposed by hsu and evans in 1989 for predicting the static planform of a pocket beach is expanded to enable the calculation of three dimensional beach changes on a pocket beach with a seawall the original formulation was developed on the basis of a second order regression analysis unlike the one line model of shoreline changes the model of hsu and evans does not require repeated calculations of the wave field and shoreline position because it was derived on the assumption of null sediment movement within a pocket beach in static equilibrium hence without the need of applying the continuity condition of total sand volume in the calculation the expanded model proposed by the present authors satisfies the total sand budget on a pocket beach by taking into account the concept of depth change due to longshore sand transport model tests were carried out and the new model was further applied to the beach changes at kemigawa on the northeast of tokyo bay in chiba prefecture as well as at oarai in ibaraki prefecture japan on both locations seawall has been installed as countermeasures against beach erosion where wave sheltering effect of the main breakwater and beach changes in front of the seawall has also been observed with this expansion the present model can be applied to predict the three dimensional beach changes on a coast with seawall on a pocket beach

kinematic and mechanic evolution of the andes buried front at the boomerang hills hydrocarbon province bolivia control exerted by the pre andean history abstract the boomerang hills are a hydrocarbon rich region located in front of the bolivian andes central south america where the andean chain bends forming the bolivian orocline the geological interpretation of seismic 2d profiles and 3d volumes and well data allowed us to generate a complete stratigraphic section cross sections maps and a 3d model and to obtain the parameters to carry out a depth conversion and decompaction a cross section and a 3d model were kinematically and mechanically restored as well as decompacted to decipher the evolution of this region through time the southern boomerang hills are the buried frontal part of the andes where thin skinned contractional structures of andean age late cenozoic predominate whereas the northern boomerang hills belong to the beni chaco plain where contractional structures are almost absent and thick skinned extensional tectonics of pre andean age paleozoic mesozoic and early cenozoic dominate the buried frontal thrust of the andes resulted from transpressional reactivation of a gravity driven extensional detachment developed along the slope of a basement high tilted during paleozoic times thus the thrust orientation position dimensions and type of structural termination were controlled by the extensional fault geometry the paleozoic mechanical stratigraphy and the structural relationships between the paleozoic cover and the basement

calculating the long term displacement rates of a normal fault from the high resolution stratigraphic record early tethyan rifting french alps displacement rates of normal faults deduced from stratigraphic data are often unreliable here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a highresolution time frame established by biostratigraphy and physical stratigraphy our example is the ornon normal fault bounding the early jurassic bourg d oisans basin formed during tethyan rifting we show that motion on the fault was discontinuous when examined at high resolution and over a long time interval during a first interval hettangian to sinemurian arietites bucklandi zone a low rate of displacement 202 423 m myr 1 coeval with diffused extensional deformation throughout the sedimentary basin is observed a second interval of localized deformation early sinemurian caenisites turneri zone is characterized by higher rates of displacement on the fault 1846 m myr 1 our results concur with recent numerical models identifying the main stages of extensional deformation

morphodynamics of structurally controlled headland bay beaches in southeastern brazil a review abstract this paper presents a comprehensive review on the interaction between hydrodynamic processes beach morphology and sedimentology at large scale coastal behaviour along the coastline of santa catarina between laguna and sao francisco island a microtidal east coast swell environment with headland and bay geomorphologies the parabolic bay shape equation has proven to be a convenient and practical tool for studying the stability of the headland bay beaches tombolos and salients in santa catarina the beaches exhibit different patterns of sediment removal as a function of the degree of beach curvature in highly curved beaches there is a well developed shadow zone and a range of morphodynamic conditions from a sheltered low energy beach adjacent to the downdrift headland to a high energy exposed beach on the straight end of the headland bay beach the less curved beaches instead tend to show more uniform behaviour since they are directly exposed to incident waves there is no obvious relationship between average wave height and mean grain size showing the importance of sediment source to characterize the sedimentary distribution patterns in the study area the analysis of beaches showed that beach morphodynamics and sequence profiles for a bay headland coast in a microtidal east coast environment is a function of geological inheritance e g distance between headlands and orientation nearshore and inner shelf morphology coastal plain morphology and sediment source and hydrodynamic factors wave conditions oceanic wave exposure and relative tidal range

sea level cycles during the growth of atlantic type oceans abstract first order changes in global sea level are commonly thought to be the result of short term fluctuations in oceanic spreading rate however eustatic high stands have occurred only twice in phanerozoic time and in both cases have followed supercontinent break up by a lag period of 50 100 ma therefore if pulses in spreading rate were the primary control of eustasy then for some reason rate increases would have had to have occurred with predictable periodicity with respect to major rifting events alternatively we propose that the major control on first order sea level cycles is the formation of atlantic type oceans with its attendant changes in the area age distribution of the global ocean floor and the formation of extensional passive margins our calculations indicate that both the approximate magnitude and relative timing of sea level highstands relative to supercontinent break up are predicted by this mechanism thus the importance of short term spreading rate variations in eustatic cycles becomes secondary

dynamic equilibrium planform of embayed beaches part 1 a new model and its verification abstract equilibrium beach formulations are useful tools for diagnosing and managing coastal engineering problems providing solutions for beach erosion problems headland bay beaches hbbs can be used as equilibrium coastal systems for stabilizing coastlines and mitigating erosion problems these embayed beaches may exist in a state of static or dynamic equilibrium throughout the literature several equations can be found for obtaining the static equilibrium planform sep of headland bay beaches hbbs with almost negligible net littoral drift rates however the formulations used to define the dynamic equilibrium planform dep of embayed beaches with specific net sediment transport rates are scarce and based on a limited number of studies this paper proposes a new derived formula for obtaining the planform shape of hbbs in dynamic equilibrium conditions the formula represents a general form of the parabolic bay shape equation pbse with modified coefficients as a function of both the wave obliquity and the net littoral drift rate passing through the bay q the angular difference d between the direction of the mean wave energy flux at the diffraction point of the headland and the beach orientation down coast is also incorporated in the proposed formula the model was verified against natural hbbs in dynamic equilibrium with different net littoral drift rates along the brazilian coast producing good results

new isotopic data and a preliminary age for volcanics near the base of the windermere supergroup northeastern washington u s a new sm nd and rb sr data are presented from the volcanic member of the huckleberry formation a unit near the base of the upper proterozoic windermere supergroup in northeastern washington the isotopic data are compatible with a rift setting during deposition of windermere strata a best fit line through all the data yields an age of 795 ma with a large error of 115 ma 2 however a preliminary sm nd mineral whole rock age of 762 44 ma 2 obtained from a least altered basalt is within error of other age information from the canadian cordillera that broadly constrains the initiation of windermere deposition to 750 30 ma a synthesis of isotopic data of the results of tectonic subsidence analyses and of geologic relations within the windermere supergroup and the immediately overlying uppermost proterozoic lower cambrian strata leads to the conclusion that the windermere supergroup does not represent the rift deposits that led directly to the initiation of the early paleozoic miogeocline in

tectonic subsidence of the early paleozoic passive continental margin in eastern california and southern nevada quantitative analysis of tectonic subsidence in cambrian and ordovician platform carbonates and associated strata exposed in the spring mountains nevada and the nopah funeral and inyo ranges california indicates that subsidence associated with this segment of the early paleozoic passive continental margin is exponential in form consistent with thermal contraction of the lithosphere following extension as in other parts of the north american cordillera continental separation in the southern great basin appears to have taken place between 590 and 545 ma these results are not sensitive to uncertainties in stratigraphic thickness biostratigraphic age control or paleobathymetry uncertainties in the cambrian time scale lead to predictable variations in the inferred time of onset of thermal subsidence but they have no effect on the inferred stratigraphic position of the rift to post rift transition a younger age for the base of the middle cambrian results in a younger inferred age of onset of thermal subsidence accompanied by greater rates of subsidence during the cambrian whereas a significantly older estimate of the onset of thermal subsidence can be obtained only if the base of the middle cambrian is substantially older than 540 ma a possibility that is inconsistent with available data results of the subsidence analysis are particularly significant because this is one of the few regions along the length of the north american cordillera where they can be compared directly to the geologic evidence for syn rift and post rift deposition basement involved faulting associated with the amargosa basin aulacogen ceased during deposition of the noonday dolomite which is thought to be older than 700 680 ma on the basis of stromatolites of late riphean affinity the overlying johnnie formation contains supposed vendian stromatolites younger than 700 680 ma if it is assumed that our results indicate the timing of the final rift to post rift transition then either the ages inferred from stromatolites are incorrect or the lithosphere was thinned regionally after deposition of the noonday the latter possibility is supported by limited geologic evidence for extension in latest proterozoic and early cambrian time the lack of appreciable physical evidence for crustal extension after deposition of the noonday however may imply that 1 a uniform extension model for lithospheric thinning is inappropriate for this part of the margin or that 2 some or all of the localities studied are continentward of the hinge zone and that the observed subsidence is exaggerated by flexural loading in a deeper basin to the west

an early cambrian rift to post rift transition in the cordillera of western north america the upper proterozoic and lower palaeozoic wedge of miogeoclinal strata in the north american cordillera is widely regarded as evidence for a proto pacific passive margin1 3 the rifting history of this margin appears to have been protracted possibly spanning 200 myr in a tectonic setting that is not well understood3 quantitative subsidence analyses of lower palaeozoic strata between british columbia and utah however provide indirect evidence that the transition from rifting to post rift cooling occurred within a relatively short interval of time although probably not synchronously between 600 and 555 myr refs 4 6 this age is significantly younger than that implied in previous studies1 2 we describe here new field data which together with published geological data provide direct evidence of a latest proterozoic or early cambrian age for the rift to post rift transition the data support recent arguments for widespread initiation of passive margins around the edge of the north american craton close to the cambrian precambrian boundary7