modelling shoreface profile evolution current knowledge of hydro sediment and morpho dynamics in the shoreface environment is insufficient to undertake shoreface profile evolution modelling on the basis of first physical principles we propose a simple panel type model to map observed behaviour the internal dynamics are determined by slope dependent wave induced cross shoreface transports while the external driving factors are lateral sediment supply and sea level rise this model concept is tested with reasonable success against the observed behaviour of the central holland coast considering two hindcast periods one covering the evolution over the last century the other the subboreal subatlantic evolution a limitation of this model is that the cross shoreface dynamics are solely steered by the variations of shoaling short waves since a variety of other wave and current dynamics may be expected to be present in the coastal boundary layer it may well be that the effects of the mechanisms and conditions which are not represented are hidden in the coefficients of the sediment transport formula this limits the accuracy of the coefficients as used and our findings should be considered as an order of magnitude estimate only indeed behaviour oriented modelling implies that generalization of results to arbitrary situations and conditions is not straightforward yet we expect that some of the conclusions are more generally applicable this concerns the substantiation of the assumption that the upper shoreface responds on a much smaller time scale than the lower shoreface and the idea that the shoreface profile is not always and everywhere in equilibrium with its forcing a worthwhile observation from the holland coast application is that the bottom slope effect on the transport is only important at geological time scales the profile evolution at the engineering time scales say 10 to 100 years is effectively quasi static in that there is no feedback between the long term averaged transport and the state of the profile this implies that at these smaller scales the profile changes can be predicted on the basis of a static sediment balance this does not mean that the gravitational downslope transport is unimportant as a physical phenomenon in coastal profile evolution it is only unimportant if a highly aggregated model like this is applied at relatively short time scales

late cretaceous cenozoic exhumation of the helanshan mt range western ordos fold thrust belt china insights from structural and apatite fission track analyses abstract the western ordos fold thrust belt is an intracontinental chain predominately formed in the jurassic and subsequently reworked in the late cretaceous and cenozoic the structural deformation of the western ordos fold thrust belt was driven by the force transmitted from the plate boundary of asian collage this study presents new structural analysis apatite fission track and thermal modeling data in the helanshan mt range of the western ordos fold thrust belt the apatite fission track analysis and thermal modeling suggest that the helanshan mt range underwent two stages of cooling and exhumation since the late cretaceous the first fast cooling stage in the late cretaceous 90 70 ma led to ca 1 1 2 km exhumation and the second fast cooling was after ca 30 ma with an exhumation of ca 1 8 2 2 km structural studies indicate that the late cretaceous exhumation was related to nw se compression and the exhumation of after ca 30 ma was associated with wnw ese transtension the wnw ese transtension produced high angle normal faults by reworking the mesozoic pre existing factures comprehensive analyses of the synchronous structures around the boundaries of the asian collage suggest that the late cretaceous exhumation of the helanshan mt range might be the far field results of the convergence between the pacific and eurasian plates the varying rates of the pacific plate subduction may transmit nw sw horizontal stress across the north china plate in contrast the post oligocene

headlands and offshore islands as dominant controlling factors during late quaternary barrier formation in the forster tuncurry area new south wales australia abstract pleistocene and holocene barrier systems along the coast of southeast australia differ from those of the coastline of the eastern u s a and elsewhere there are no continuous barrier island chains along the coast of new south wales such chains developed only in eastern victoria in new south wales pleistocene and holocene barriers were built within rocky embayments along the coastline the forster tuncurry coastal zone of central new south wales is an excellent example of such embayment it is a mosaic of sedimentary environments that covers about 270 km 2 and includes late pleistocene bay barriers holocene beach ridges tide dominated channels mudflat islands peripheral tidal flats lake sediments and nine beaches of various types headlands and offshore islands played a dominant role in the sedimentary process marine sediment washed into the embayment by refracted waves formed the following type of bay barriers a bay barrier between mid bay headland and an offshore island b between two opposing mid bay headlands and c two barrier types between the outer headlands of the bay mouth and the large centrally located offshore island these barriers are seen as beach ridges in the northern half of the embayment and a lagoon barrier in the southern half the large centrally located cape hawke was an island and the most significant of these features dividing the bay into two compartments through time laterally accreting barriers were generated in the northern compartment and a lagoon barrier was created to the south

subtropical sea level history from coral microatolls in the southern cook islands since 300 ad abstract relative sea level rsl history is reconstructed for the southern cook islands since 300 ad using porites sp coral microatolls the upper surface or height of living coral of the modern microatolls on rarotonga was rigorously determined by 400 laser survey measurements to be constrained by the sea level 0 36 m below mean sea level with a standard deviation of 0 008 m that is equivalent to midway between mean low water neaps and mean low water springs tidal datums fossil microatoll history on the fringing reefs is fragmentary due to multi decadal to centennial windows of microatoll growth cyclone destruction and preservation through coastal progradation the mid late holocene highstand ceased prior to 500 bc and rsl fell from 1 3 0 1 m to 0 45 0 15 m by 1000 ad at a rate of 0 5 mm yr the rsl minimum occurred during the late 1700s to 1800s ad at 0 2 m below present before rising during the 1900s during the past 500 yr rsl fluctuated including an abrupt fall at 1750 ad following a sustained multi decadal high anomaly similarly low rsl anomalies and slow coral growth rates during the 950 to 1000 ad period are indicative of pacific basin wide climate variability and are consistent with extreme la nina like climate anomalies previously reported around the pacific basin the fall in rsl during the first millennium ad crossed over tidal thresholds for rapid coastal progradation when ambient mean high water neaps and mean high water springs fell below the low tide level of the mid late holocene high stand this coastal response is inversely analogous to the projected response to sea level rise during the latter part of the modern century

oligo miocene rift of sardinia and the early history of the western mediterranean basin the geodynamic evolution of the western mediterranean basin in spite of many studies is still uncertain there is some consensus for interpreting this basin as a kind of small oceanic marginal basin its opening has generally been related to a subduction process which was active during the oligocene miocene somewhere east of sardinia corsica1 7 as the margins of the basin are deeply buried below miocene to present sediments direct lithological and stratigraphical data which could explain the events responsible for its formation are rare8 10 or missing altogether to obtain such data detailed field studies have been undertaken in sardinia fig 1 and the first results are presented here this approach is justified by the fact that in that island oligocene and miocene sediments were deposited in a rift fossa tettonica sarda of verdabasso11 which is the easternmost arm of the complex rift system that affected the european plate during oligocene and miocene times one of these arms evolved towards a small oceanic basin the western mediterranean or algero provencal basin while others such as the gulf of valencia and the sardinia rift aborted and remained at the rift stage its exceptional exposures make it possible to examine the sardinia rift to clarify the sequence of events which created it and to establish a sedimentological model which we believe is directly applicable to the western mediterranean basin

calculation of synthetic seismograms in a laterally varying medium by the boundary element discrete wavenumber method abstract we investigate the propagation of lg waves in laterally varying crustal structures by numerical simulation the method of calculation is formulated in terms of boundary integral equations where the green9s functions are evaluated by wavenumber summation the approach is well suited to study the propagation of seismic waves in a layered medium where the interfaces are flat in some regions and irregular in others we investigate the effect of a crustal fault with vertical offset and study the case of a lateral change in crustal thickness the results show that the lg wave amplitude is only slightly affected by the presence of these heterogeneities they confirm the robustness of lg wave propagation in presence of lateral heterogeneities observed in other numerical simulations they show that large scale geometric features of the crust cannot account alone for the strong attenuation of lg waves observed in many regions the results also suggest a possible relation between the level of lg wave coda and the degree of roughness of the moho they further indicate the importance of backscattering and suggest a possible use of the backscattered wave field to map strong crustal heterogeneities

simulation of large scale coastal change using a morphological behaviour model abstract quantitative simulation of large scale coastal behaviour lscb is possible using a model based only on principles of sand mass conservation and geometric rules for shoreface and active sand body morphology dynamic processes are subsumed into a set of parameters that define the geometry of the active cross shore profile which in turn can represent an entire coastal cell the parameters together with a set of local behaviour rules governing adjustments at discrete points along the profile provide a simple formulation that is constrained by sediment mass balance to yield emergent numerical solutions for profile kinematics the emergent qualities of this shoreface translation model are exemplified in simulation experiments on changes to sand deposits on the southeastern australian coast and shelf during the post glacial marine transgression in another example the model is used to simulate lscb over engineering time scales at an idiosyncratic site both examples illustrate the over riding importance of small residual sand movements that accumulate through time to cause lscb in comparison to gross sand movements the residuals are too small to measure directly or predict on the basis of available theory exploratory inverse simulation provides a quantitative method for side stepping these limitations the shoreface translation model therefore is used as a tool to explore possible forms of coastal behaviour through an approach that incorporates available data along with theoretical considerations validation is not strictly possible for this type of inverse approach so the degree to which a simulation reproduces observed features in nature is a measure of its success

holocene sea level change on the southeast coast of australia a review a revised holocene sea level curve for the southeast coast of new south wales australia is presented based on a review of previously published geochronological results for fossil molluscs organi

last interglacial and holocene trends in sea level maxima around australia implications for modern rates this paper defines the spatial trend in sea level around australia at 3 timescales namely at the time of the maximum of the last interglacial around 125 000 yr b p during the holocene maximum between 5000 and 6000 yr b p and over the last 20 years last interglacial elevations range from 2 m around the great barrier reef to 32 m in northeast tasmania trend surface analysis shows that over 77 of the noise in these sea level elevations can be accounted for by a pattern evidencing tectonic uplift towards the southern edge of the continent assuming a eustatic sea level at this time of 4 to 6 m most of the east coast of new south wales and the west coast of western australia can be considered tectonically stable while the southern edge of the continent has risen by at least 5 m and the north northeast corner has downwarped by at least 2 m the spatial pattern of the holocene maximum tentatively supports the continuation of this tectonic deformation sea level at this time reached 1 6 and 2 4 m above present high tide limits around the northern and southeastern coastlines of australia respectively this holocene pattern is weak because much of the data is dominated by local variations reflecting differential loading of the continental shelf by water during the holocene transgression the holocene trend surface does not support geophysical modelling implying a southern latitudinal downwarping of the crust produced by the melting of the antarctic ice sheet and the loading of the ocean crust with meltwater however the spatial pattern of modern trends appears to contain a remnant holocene signal fitting this isostatic model rather than the long term pattern of tectonic flexure since the last interglacial sea level is presently rising at a rate of 1 75 mm yr 1 in northern australia compared to only 0 75 mm yr 1 in tasmania these results imply that isostatic factors as well as previously identified climatic variables may be controlling present day variations in the rate of change of sea levels around the australian continent

paleomagnetism of jurassic carbonate rocks from sardinia no indication of post jurassic internal block rotations 1 several paleomagnetic studies on carboniferous and permian sedimentary and volcanic rocks from sardinia and corsica have recently demonstrated 1 the tectonic coherence between southern corsica and northern sardinia and 2 significant rotations between individual crustal blocks within sardinia itself the geodynamic significance of these rotations however is not clearly understood mainly because of uncertainties in defining their timing and causes in order to contribute to these issues a pioneering paleomagnetic study on jurassic carbonates from the baronie supramonte region of eastern central sardinia has been extended regionally and stratigraphically a total of 280 oriented drill cores were taken from 44 sites of middle and late jurassic age in the nurra baronie supramonte barbagia sarcidano and sulcis regions despite generally weak remanent magnetization intensities on the order of less than 1 ma m thermal and alternating field demagnetizations were successfully applied to define a characteristic remanent magnetization component in about 60 of the samples site mean directions show rather good agreement after correction for bedding tilt and yield middle and late jurassic overall mean directions of d 269 7 and i 45 0 95 8 0 k 14 and n 25 sites and d 275 5 and i 50 7 95 7 2 k 45 3 and n 10 sites positive regional and local fold and reversal tests demonstrate the primary character of the natural magnetic remanence which is carried by magnetite these results indicate only insignificant amounts 10 of post jurassic rotations within the island of sardinia the resulting middle and late jurassic paleopoles latitude lat 16 5 longitude long 299 1 dp 6 4 and dm 10 1 and lat 23 4 long 301 2 dp 6 5 and dm 9 7 corrected for the opening of 1 the liguro provencal basin and 2 the bay of biscay using rotation parameters from the literature fall near the coeval segment of the european apparent polar wander path these results constrain the timing of large differential block rotations found in late carboniferous permian rocks to a pre middle jurassic age and lead us to exclude tectonics related to the alpine orogeny for such rotations

simulating the evolution of coastal morphology and stratigraphy with a new morphological behaviour model geombest abstract a new morphological behaviour model is used to simulate evolution of coastal morphology associated with cross shore translations of the shoreface barrier and estuary the model encapsulates qualitative principles drawn from established geological concepts that are parameterized to provide quantitative predictions of morphological change on geological time scales order 10 3 years as well as shorter time scales applicable for long term coastal management order 10 1 to 10 2 years changes in sea level and sediment volume within the shoreface barrier and estuary drive the model behaviour further parameters defining substrate erodibility sediment composition and time dependent shoreface response constrain the evolution of the shoreface towards an equilibrium profile results from numerical experiments are presented for the low gradient autochthonous setting of north carolina and the steep allochthonous setting of the washington shelf simulations in the currituck region of north carolina examined the influence of sediment supply substrate composition and substrate erodibility on barrier transgression results demonstrate that the presence of a lithified substrate reduces the rate of barrier transgression compared to scenarios where an erodible sand rich substrate exists simulations of the washington coast 20 km north of the columbia river confirmed that the model can reproduce complex stratigraphy involving regressive and transgressive phases of coastal evolution results suggest that the first major addition of sediment to the shelf occurred around 12 900 years ago and resulted from the rapid addition of sediment volume from the columbia river attributed to the missoula floods this was followed by a period where little or no sediment was added 12 400 9100 bp and a third period when most sediment was added to the shelf 9100 bp to present from the columbia river comparing results from each setting demonstrates an indirect control that substrate slope has on shoreface transgression rates shoreface transgression is shown to be sensitive to the rate of estuarine sedimentation with the sensitivity increasing as substrate slope decreases

late pleistocene and holocene sea level change along the australian coast abstract tectonically the australian continent is relatively stable and as such it provides a good platform for studying late pleistocene and holocene sea level change the observations indicate that present sea level was reached at about 6000 years ago and that since then level has remained constant to within a few metres considerable spatial variability in the amplitude of the emergence and in the time at which sea levels first reached their present values have been observed spatial variability has also been observed in the sea level during the last glacial maximum and during the late phase of the holocene transgression much of this variaiblity is the result of the earth s adjustment to the glacial melting in the late pleistocene early holocene time and the concomitant distribution of this meltwater into the oceans conclusions that are drawn from matching observations with this glacio hydro isostatic model include the following 1 the mantle viscosity increases with depth the average upper mantle viscosity is about 2 3 10 20 pa s and the average lower mantle defined as below 670 km depth viscosity is about 10 22 pa s the average lithospheric thickness for the coastal and offshore region is about 70 80 km lateral variations in these mantle parameters are indicated 2 the addition of melwater into the oceans did not cease 6000 years ago but continued at a reduced rate up to more recent times adding an amount of water equivalent to a 3 m sea level rise in this interval 3 the amplitude of the holocene emergence is a function inter alia of coastal geometry and significant variations occur over distances of a few hundred kilometres and more holocene highstands of 1 2 m are generally well developed at the continental margins but are less well developed or do not developed at all at offshore islands and reefs 4 variations in the time of maximum emergence also occur being earlier at upstream tidal river sites than at coastal sites at offshore reefs or islands the sea level curve lags the coastal curves by 1000 years or more 5 considerable spatial variability occurs in the sea levels at the time of the last glacial maximum with variations of up to 30 m occurring across the continental shelves 6 there is generally no need to invoke tectonic movements to explain the sea level data along the australian coast but possible exceptions occur for the perth region and for tasmania

an insight into headland sand bypassing and wave climate variability from shoreface bathymetric change at byron bay new south wales australia abstract the headland sand bypassing mechanisms in the eastern australian longshore sand transport system are investigated at cape byron in response to wave climate variability the mechanisms are interpreted from shoreface bathymetric change between surveys in 1883 2002 and 2011 ce they involve a split in the sand transport to follow a nearshore path along the inner bar and a cross embayment path connecting the up coast and down coast outer bars the relative magnitude of the net sand transported via the two pathways is controlled by a rotation in directional wave conditions two bypassing mechanisms were interpreted i a predominantly cross embayment transport during unimodal east southeast wave climate such as those interpreted for the period prior to 1883 and ii a split transport between the inner nearshore and cross embayment paths during a bimodal dominant south south easterly and sub dominant east north easterly wave climate such as in the 2000s the net sand transport bypassing cape byron was dominated by a connected outer bar system prior to 1883 and conversely a stronger inner bar system during the 1960s to 2000s this is manifest in the 10 rotation in seabed morphology and shoreline planforms these changes are in accordance with decadal climate variability described by the interdecadal pacific oscillation ipo the switching between headland sand bypassing mechanisms on interannual to decadal timescales determines the geometry of the bypass strand with the downcoast littoral zone and has important implications for understanding the shoreline rotation and the application of the headland bay beach concept to predicting planform curvature in open compartments

relative sea levels and coastal sedimentation in southeast australia in the holocene abstract in recent years australian studies of relative sea level change have shown reasonable consistency on the termination date of the postglacial marine transgression at c 6 500 14c years bp the following stillstand period has been characterized in some regions by a slight falling trend from a high stand or in other areas by a level not easily distinguished from the present the latter situation occurs on the embayed coast of new south wales here studies of depositional environments and sequences within bed rock embayments have linked the holocene sea level history to patterns of sedimentation on the inner shelf in bay barriers and in estuaries deposition of quartz rich sand in shoreface flood tidal delta and backbarrier environments occurred during the marine transgre sion and the subsequent stillstand shell fragments from these deposits have been radiocarbon dated shoreline displacement continues to the present day partly in response to changes in availability of sand in the shoreface zone and partly in response to variations in regional storminess patterns a nd the great shroud of the sea rolled on as it rolled five thousand years ago herman melville moby dick

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

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

thermochronological evidence for mesozoic tertiary tectonic evolution in the eastern sardinia apatite fission track analyses on samples from eastern sardinia document a complex tectonic history whose reconstruction is problematic because of the reactivation of faults and structures at different times from jurassic to miocene the oldest ages 150 154 ma have been detected on the southern margin of the gulf of orosei and are related to the extensional tectonics that characterize the european passive margin during early and middle jurassic times thermal modelling of these data allows reconstruction of the burial history of the mesozoic basin and estimation of a sedimentary thickness of 2000 m part of these sediments was eroded during the following uplift documented by mid cretaceous fission track ages a further exhumation episode of eocene age has been revealed by fission track data on granite samples and has been inferred to be related to the alpine orogenic phase this tectonic episode caused the exhumation of crustal blocks bound by faults that were finally reactivated during the late oligocene early miocene

extensional tectonics on sardinia italy insights into the arc back arc transitional regime although the tectonic features and stress regime typical for accretionary complexes and back arc domains have been widely documented so far few are known on the transitional zone separating these two systems here we report on structural analysis and anisotropy of magnetic susceptibility ams results from eocene pliocene sediments exposed in western sardinia from late oligocene to middle miocene the studied area was located between the alpine apennine wedge to the east which was undergoing shortening and accretion and the liguro provencal basin undergoing extension and spreading we find that prior to the formation of the liguro provencal basin the middle eocene lower oligocene sediments cropping out at the southwesternmost edge of sardinia were subjected to ne sw shortening in present day coordinates in agreement with recently reported geological information conversely the upper oligocene pliocene sedimentary sequences record a different evolutionary stage of extensional processes upper oligocene middle upper burdigalian sediments clearly show a n s oriented magnetic lineation that can be related to extensional direction along the prevalent e w oriented normal faults on the other hand no magnetic lineation has been detected in upper burdigalian serravallian sediments which mark the end of the first rifting process in sardinia which likely coincides with the rift to drift transition at the core of the liguro provencal basin finally a ne sw extension is observed in two tortonian pliocene sites at the northwestern margin of the nnw sse oriented campidano graben our study confirms that ams may represent a valuable strain trajectory proxy and significantly help to unravel the characters of temporally superimposed tectonic events

the relationship between track shortening and fission track age reduction in apatite combined influences of inherent instability annealing anisotropy length bias and system calibration abstract the relationship between reduced track density 0 and reduced mean confined track length l l 0 during annealing has been studied for both spontaneous and induced tracks in four apatite samples with different chemical composition compositional range and origin and with spontaneous tracks giving mean confined track lengths varying from 14 5 m down to 12 3 m in all four apatites induced tracks show a relationship between l l 0 and 0 composed of two regions at higher values the two appear to be equal while at lower values l l 0 is greater than 0 this can be understood qualitatively in terms of the anisotropy of annealing and the bias against revelation of short tracks data from three apatites of uniform composition show near identical relationships in a sample showing a range of apatite compositions the point of divergence from the 1 1 relationship is somewhat higher than in the uniform composition apatites because individual grains anneal at different rates and the presence of highly annealed grains affects the track density more strongly than the mean track length spontaneous tracks show similar relationships to those observed for induced tracks in each sample when the data are renormalised to allow for the natural annealing present in the spontaneous tracks previous studies which led to the idea of length reduction without density reduction for spontaneous tracks did not renormalise density data as well as length data thereby distorting the apparent relationship data for the multi compositional apatite sample where annealing has taken place in geological conditions also agrees with the laboratory annealing data for both spontaneous and induced tracks this consistency suggests that a single process is responsible in all three cases implying that a laboratory based description of annealing can be applied to geological conditions with confidence recognition that spontaneous tracks in apatite are commonly annealed suggests that in general the fission track age should be interpreted as a reflection of both the time over which tracks have been retained and the distribution of etchable track lengths since the latter is a manifestation of the thermal history the fission track age should be interpreted in similar terms

wave climate sand budget and shoreline alignment evolution of the iluka woody bay sand barrier northern new south wales australia since 3000 yr bp abstract multi centennial fluctuations in the northern new south wales nsw coastline alignment are interpreted from a detailed reconstruction of the morphological and depositional evolution of the iluka to woody bay barrier during the late holocene the regional coastline is aligned obliquely to the south east inner shelf modal wave direction and hence sediment is transported obliquely on the shoreface with a net northward movement on centennial to millennial time scales the coastline is shown to have responded to fluctuations in mean wave direction longshore gradients in sand transport and headland sand bypassing processes overall barrier progradation has been punctuated by episodes of shoreline recession and realignment throughout the late holocene a prolonged shoreline recessional phase occurred at 1500 yr bp in response to a rotation in modal wave direction from more southerly towards east south easterly subsequent to this realignment renewed shoreline progradation occurred along the east aspect coastline after 1400 yr bp whilst the north east aspect coastline remained in a receded alignment until after 1000 yr bp when renewed progradation occurred progradation rates increased throughout the past millennium driven by changes to the alongshore gradient in sand transport under an implied shift to a more southerly and energetic modal wave climate in the past 50 yrs the north east aspect shoreline has experienced a rapid recessional trend which is associated with a shift in modal wave climate to a more east southeasterly direction and a reduction in headland sand bypassing the average sand supply rate to the iluka to woody head section of the northern nsw shoreline is 4 1 m3 m yr since 3000 yr bp

inter tidal fixed indicators of former holocene sea levels in australia a summary of sites and a review of methods and models abstract the reconstruction of mid to late holocene marine environments using the calcareous remains of inter tidal fixed biological indicators as sea level proxies is reviewed useful palaeo environmental information can be obtained from the fossil evidence of successive invasions and disappearances of tropical and temperate species within the sub fossil inter tidal biological sequences examples illustrating spatially synchronous late holocene sea level fluctuations are described from 3000 km of north south coastline along eastern australia the method uses tightly constrained species such as the tubeworm galeolaria caespitosa which allows for the precise measurement of relative sea level fluctuations by using the differential between emerged sub fossil encrustations and current distributions of the same species the error range can be defined according to the extent of preservation of the relic distributions particularly the extent that diagnostic boundaries between species limited to different inter tidal zones have been preserved the rapidity of sea level fluctuations is inferred by the preservation from erosion of emerged shell layers as well as discontinuities in the relic biological sequences and the relative preservation of fragile species this apparent rapidity of sea level fluctuations as well as evidence of near uniform synchronous sea level heights along the north south span of the entire australian coast and equally consistent variations australia wide in spencer gulf and rottnest island raises questions about the predicted poleward decline of sea level curves derived from hydro isostatic rebound modelling

the barrier island system abstract barrier islands are part of a major coastal system composed of six interactive sedimentary environments the six environments are also elements needed to impose the designation barrier island on littoral sand bodies the elements are 1 mainland 2 backbarrier lagoon 3 inlet and inlet deltas 4 barrier island 5 barrier platform and 6 shoreface the morphodynamic and sedimentary evolution of each element affects adjacent environments as well as the entire system the interactive elements are defined and described by their morphologic sedimentologic and stratigraphic relationships to the barrier island and the barrier island system the stratigraphic relationships of the various elements of the system may be a valuable tool for paleogeographic reconstruction and sand body mapping

seismic motion in urban sites consisting of blocks in welded contact with a soft layer overlying a hard half space we address the problem of the response to a seismic wave of an urban site consisting of a large and infinite number n b of identical equispaced blocks overlying a soft layer underlain by a hard substratum the results of the theoretical analysis appealing to a space frequency mode matching mm technique are compared to those obtained by a space time finite element fe method the two methods are shown to give rise to much the same prediction of seismic response for n b 10 the mm technique is also applied to the case n b infty notably to reveal the structure and natural frequencies of the vibration modes of the urban site the mechanism of the interaction between blocks and the ground as well as that of the collective effects of the blocks are studied it is shown that the presence of a large number of blocks modifies the seismic disturbance in a manner which evokes and may partially account for what was observed during many earthquakes in mexico city disturbances at a much smaller level induced by a small number of blocks are studied in the companion paper

paleomagnetic data from late paleozoic dykes of sardinia evidence for block rotations and implications for the intra pangea megashear system paleomagnetic studies of dyke swarms from the variscan belt of europe can be used to reconstruct internal postorogenic rotations within the fold belt here we present paleomagnetic data from 13 late variscan dykes from sardinia ranging in age from 298 5 to 270 10 ma the dykes can be grouped on the basis of their different directions in strike in a northern a central eastern and a south eastern province paleomagnetic component directions have been obtained using thermal and alternating field demagnetization techniques which give reproducible results the paleomagnetic mean directions differ significantly between northern sardinia and south eastern and central eastern sardinia the latter two regions yielding statistically similar paleomagnetic mean directions these results indicate that sardinia fragmented into two arguably three crustal blocks after emplacement of the dykes which experienced differential relative rotations as is also indicated by the differences in overall strike directions the determination of timing sense and magnitude of these rotations has major implications for the reconstruction of the geodynamic evolution of the region in post carboniferous times we argue that the observed block rotations occurred during the permian as the result of post variscan intra pangea mobility possibly related to the transformation of an early permian pangea b to a late permian pangea a

towards more robust chronologies of coastal progradation optically stimulated luminescence ages for the coastal plain at moruya south eastern australia accurate chronologies are fundamental for detailed analysis of palaeoenvironmental conditions archaeological reconstructions and investigations of holocene coastal morphological changes chronolog

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

shoreface morphodynamics on wave dominated coasts abstract an open ocean shoreface typical of long wave dominated sandy coasts has been examined through a combination of extensive field measurements of wave and current patterns with computations of marine bedload transport and sedimentation sand transport on the upper shoreface is dominantly controlled by waves with only secondary transport by currents sand on the middle and lower shoreface as well as the inner continental shelf is entrained by storm waves and transported by a complex pattern of bottom boundary layer currents storm events have been studied and modeled for the shoreface off tiana beach long island the dominant effect of coastal frontal storms is to cause significant shore parallel bedload transport with important shore normal secondary components these storms tend to result in net offshore transport of sand removed from the beach and surf zone systems the bedload transport during a storm is convergent on the shoreface leading to accretion most accretion occurs on the upper shoreface with lesser deposits covering the middle and lower shoreface as well as the inner continental shelf longer term equilibrium can be maintained by slow return of sand up the shoreface during non storm conditions annual and geologic time scale budgets of shoreface sand transport and sedimentation yield equilibrium net accretion or net deposition the annual balance results from an integration of the event scale bedload transport patterns and morphologic responses these processes and responses have feedback mechanisms which stabilize the system over longer but not geologic time scales geologic time scale balances are controlled by relative sea level changes and relative availability of sediment supply with the event scale shoreface and transporting processes providing the mechanism to produce the changes in long term morphology and sedimentation patterns in the area of study the long term pattern is one of net shoreface erosion and the permanent loss of sand to the shelf floor

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

on postglacial geoid subsidence over the equatorial oceans we develop two new spectral formalisms for the gravitationally self consistent solution of the sea level equation which governs the redistribution of glacial meltwater on a visco elastic earth the first is a purely spectral technique based on an extension of theory outlined by dahlen 1976 for determining the equilibrium oceanic tide on an elastic planet using this technique with a feasible spherical harmonic truncation level l 30 we can obtain convergence in the computed sea level variations within the degree range l 10 we also develop a second pseudospectral technique however which permits the construction of gravitationally self consistent solutions to much higher degree and order l 100 the pseudospectral formalism is employed here to develop a comprehensive physical explanation for the global pattern of present day sea level variations due to ongoing glacial isostatic adjustment in particular we focus upon a mechanism which we term equatorial ocean syphoning that acts to draw water toward the oceanic portion of the collapsing peripheral bulge that encircles previously glaciated regions the collapse of the forebulge induces a flow of water which is required to maintain hydrostatic equilibrium the syphoning mechanism dominates the relative sea level rsl variation in oceans in the far field of the ice sheets that is beyond the peripheral bulge during periods such as the interglacial of the past 4000 years during which the volume of the ice sheets has not apparently changed appreciably while at the same time isostatic adjustment persists the rsl change in the near field is in contrast dominated by the local vertical displacement of the solid surface finally comparison of gravitationally self consistent predictions of rsl change in the far field with the observational data at small pacific island sites has provided an upper bound of 1 to 2 m for the eustatic sea level rise produced by any recent last 3000 years melting of the antarctic ice sheet

rollover drowning and discontinuous retreat distinct modes of barrier response to sea level rise arising from a simple morphodynamic model we construct a simple morphodynamic model to investigate the long term dynamic evolution of a coastal barrier system experiencing sea level rise using a simplified barrier geometry the model includes a dynamic shoreface profile that can be out of equilibrium and explicitly treats barrier sediment overwash as a flux with barrier behavior primarily controlled by the maximum potential overwash flux and the rate of shoreface response the modeled barrier system demonstrates four primary behaviors height drowning width drowning constant landward retreat and a periodic retreat height drowning occurs when overwash fluxes are insufficient to maintain the landward migration rate required to keep pace with sea level rise on the other hand width drowning occurs when the shoreface response rate is insufficient to maintain the barrier geometry during overwash driven landward migration during periodic barrier retreat the barrier experiences oscillating periods of rapid overwash followed by periods of relative stability as the shoreface resteepens this periodic retreat which occurs even with a constant sea level rise rate arises when overwash rates and shoreface response rates are large and of similar magnitude we explore the occurrence of these behaviors across a wide range of parameter values and find that in addition to the maximum overwash flux and the shoreface response rate barrier response can be particularly sensitive to the sea level rise rate and back barrier lagoon slope overall our findings contrast with previous research which has primarily associated complex barrier behavior with changes in external forcing such as sea level rise rate sediment supply or back barrier geometry

seismic response of three dimensional alluvial deposit with irregularities for incident wave motion from a point source abstract the purpose of this article is to further investigate the influence of local site conditions of surface soil layers on seismic ground motion by studying the response of a semi spherical alluvial deposit model under the more realistic type incident wave field the incident wave field is a spherical wave radiated from a point source that is situated at the near focal distance and the far focal distance a plane sh wavelet is also considered for comparison a least squares technique is applied to solve the boundary problem the surface displacements on the alluvial deposit and in the elastic half space are evaluated for various focal distances and source incidence angles the numerical results indicate that there are significant differences concerning scattering and diffraction of wave motions between the two horizontal components when the semi spherical alluvial deposit is subjected to incident wave motions from a point source in the near field and for the component involving predominantly p and sv waves the coupling of these waves induces a great variation in the spatial distributions the amplitudes and the time histories of the surface displacements compared to the tangential component which involves mostly sh waves the wave propagation characteristics of this component are very similar to those for a plane sh wavelet in the far field and for the tangential component there is not such strong coupling among waves it is also shown that the first reflected waves at the curved boundary are deeply related to scattering and to diffraction of wave motion in a surface soil layer with irregularities and play an important role in the development of later arrivals

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

complexities in barrier island response to sea level rise insights from numerical model experiments north carolina outer banks using a morphological behavior model to conduct sensitivity experiments weinvestigate the sea level rise response of a complex coastal environment to changes ina variety of factors experiments reveal that substrate composition followed in rankorder by substrate slope sea level rise rate and sediment supply rate are the mostimportant factors in determining barrier island response to sea level rise we find thatgeomorphic threshold crossing defined as a change in state e g from landward migratingto drowning that is irreversible over decadal to millennial time scales is most likely tooccur in muddy coastal systems where the combination of substrate composition depth dependent limitations on shoreface response rates and substrate erodibility mayprevent sand from being liberated rapidly enough or in sufficient quantity to maintain asubaerial barrier analyses indicate that factors affecting sediment availability such aslow substrate sand proportions and high sediment loss rates cause a barrier to migratelandward along a trajectory having a lower slope than average barrier island slope therebydefining an effective barrier island slope other factors being equal such barrierswill tend to be smaller and associated with a more deeply incised shoreface therebyrequiring less migration per sea level rise increment to liberate sufficient sand to maintainsubaerial exposure than larger less incised barriers as a result the evolution of larger lessincised barriers is more likely to be limited by shoreface erosion rates or substrateerodibility making them more prone to disintegration related to increasing sea level riserates than smaller more incised barriers thus the small deeply incised north carolinabarriers are likely to persist in the near term although their long term fate is less certainbecause of the low substrate slopes that will soon be encountered in aggregate results point to the importance of system history e g previous slopes sediment budgets etc in determining migration trajectories and therefore how a barrier island will respondto sea level rise although simple analytical calculations may predict barrier responsein simplified coastal environments e g constant slope constant sea level rise rate etc our model experiments demonstrate that morphological behavior modeling is necessary toprovide critical insights regarding changes that may occur in environments havingcomplex geometries especially when multiple parameters change simultaneously

transgressive and regressive stratigraphies of coastal sand barriers in southeast australia abstract in recent years attempts have been made in southeast australia to document the stratigraphic characteristics of coastal sand barriers two basic arrangements of facies are distinguished those associated with transgressive depositional sequences and those associated with regressive sequences transgressive sequences either are formed during the postglacial marine transgression or are related to receding or transgressive barriers at present sea level in the former case complex interfingering of nearshore washover and lagoonal facies are evident in many areas these facies underlie those associated with regressive sequences which have formed since sea level has reached its present position ca 6000 6500 yrs ago examples of regressive sequences associated with both prograded and stationary barrier types occur in southeast australia here the thickness of nearshore facies in particular is commonly greater than equivalent units beneath barriers on coasts of lower energy and for less steep inner shelf gradients in the northern hemisphere the interplay of various factors within embayments has led to the development of several barrier types such as prograded stationary receded and episodic dune with some sedimentary characteristics in common with similar types recognized in other parts of the world e g texas delaware the netherlands barriers formed as a result of migrating spits and tidal inlets are not common in southeast australia

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

variability of apatite fission track annealing kinetics ii crystallographic orientation effects a method is presented that permits the length of any horizontal confined fission track inclined at a specified angle to the crystallographic c axis in apatite to be converted to an equivalent track length parallel to the crystallographic c axis the model is based on the results of annealing experiments for six selected apatites five calcian fluorapatites and durango apatite representing a subset of the 15 total apatite specimens studied an iterative process of calculation is required to project fission track lengths onto the c axis and computer source code implementing the solution to this problem is presented this method of projecting apatite fission track lengths onto the crystallographic c axis is shown to remove effectively fission track length variation within single fission track populations due to anisotropic track length reduction for all 15 apatites studied in addition a model is developed that offers predictions that closely reproduce published experimental data concerning the relationship between fission track density etched fission tracks per unit area of apatite surface and the arithmetic mean fission track length finally it is shown that natural fission track populations exhibit fission track length anisotropy similar to that of fission track populations created and annealed in the laboratory this observation implies that the same process by which apatite fission tracks anneal in the laboratory is responsible for annealing of apatite fission tracks in the geological environment

the evolution of coastal barrier systems a case study of the middle late pleistocene wilderness barriers south africa abstract barrier systems contain lengthy but complex records of long term environmental fluctuations the wilderness embayment south africa contains a system of shore parallel barriers reaching up to 200 m above modern sea level this study reports the results of chronological topographical both on and off shore sedimentological and micromorphological analyses within the wilderness embayment sixty one new luminescence ages from sixteen sites in unconsolidated dunes and three separate barriers are presented which when combined with previously published luminescence ages from the area provide a high resolution chronological framework for the emplacement and evolution of the barrier system the preserved barriers have been constructed within at least the last two glacial interglacial cycles with notable phases between 241 221 ka 159 143 ka 130 120 ka 92 87 ka and post 6 ka multiple phases of barrier construction occurred during sea level highstands with sediment deposition on each individual barrier occurring over at least two interglacials holocene evolution of the system sheds light on earlier events with dune preservation occurring only during early regression from the mid holocene highstand tectonic stability at wilderness allowed glacio eustatically formed shorelines to occupy similar positions on multiple occasions this in conjunction with a relatively humid climate and a well vegetated landscape enabled deflated sediment from beaches to form dunes which stacked upon each other to form an extensive and complex vertical accretionary sequence repeated erosion and recycling of pre existing barriers as well as barrier construction on what is currently the off shore platform during still stands in sea level regressional cycles when sea levels dropped below ca 50 m from the present day has added to the complexity of the preserved terrestrial barrier record the wilderness barrier system contrasts with barriers developed elsewhere in the world where higher rates of crustal uplift have allowed preservation of a more complete and more widely spaced palaeorecord this research also shows the utility of integrating off shore topography as revealed by bathymetry with terrestrial topographic data for the better understanding of the evolution of palaeo coastlines and the preserved dune record found on present day coastal plains local variation in the topography of the continental shelf at wilderness has generated spatial and temporal complexity within the sedimentary records of individual barriers as well as having a significant influence on preservation

origins of holocene coastal strandplains in southeast australia shoreface sand supply driven by disequilibrium morphology abstract coastal barriers store depositional records of past environmental conditions such as sea level wave climate and sedimentary regime the embayed highstand coast of southeast australia features a diverse range of coastal sand barriers suggesting varying depositional responses to holocene environmental conditions in particular the varying chronologies of prograded barrier strandplains along a passive margin with a predominantly autochthonous sedimentary regime raises questions about relative sea level change and sediment sharing within and between compartments during the holocene here we apply detailed geological data and geochronology from the holocene prograded barrier system at tuncurry within a morphodynamic modelling approach to investigate the depositional response of the coastal system to possible drivers of strandplain growth including 1 forced regression driven by mid to late holocene relative sea level fall 2 time varying external sand supply via the alongshore transport system and 3 shoreface sand supply in response to disequilibrium morphology and stable sea level comparison between the simulated depositional response of the coastal system and the geological records suggests that progressively weakening and depth decaying shoreface sand supply in response to disequilibrium morphology was the primary driver of holocene strandplain growth alongshore sand transport into the tuncurry compartment via a headland attached shelf sand body may have provided a secondary sand source although the simulated barrier shoreface evolution precludes a dominant external sand supply mid to late holocene sea level fall from a highstand level within the range of uncertainty in available indicators 1 5 m above present could only have contributed a minor portion of strandplain growth by process of forced regression the simulations demonstrate the potential sensitivity of strandplain chronologies to the sampling location i e shoreface or dune facies which emerges from coupled barrier shoreface evolution that may support time decaying volumetric growth and steady shoreline progradation simultaneously shoreface sand supply driven by the ongoing relaxation of disequilibrium morphology may persist at subtle rates 1 2 m3 m yr today on some southeast australian beaches promoting shoreline stability and potentially moderating initial shoreline response to sea level rise

geomorphic evidence for mid late holocene higher sea level from southeastern australia an elevated sheltered pocket beach sequence at batemans bay nsw australia composed of shelly fine to medium grained sand provides geomorphic evidence of higher than present sea level during the mid late holocene the sequence is composed of a sand facies with variable amounts of shell and contains a number of well defined dipping reflectors identified in ground penetrating radar gpr profiles indicative of a small prograded beach system this beach succession is overlain by storm or tsunami deposits the beach deposit accumulated between 2500 and 5000 cal bp under relatively high energy conditions within a more open immature estuary during a period of higher sea level both deposits have been preserved by a low energy mangrove facies that accumulated after the recent fall in sea level cut off ocean wave activity from the area approximately 2000 2500 cal bp this beach sequence provides new evidence for a period of higher sea level 1 1 5 m higher than present that lasted until at least c 2000 2500 cal bp and adds complementary geomorphic evidence for the mid to late holocene sea level highstand previously identified along other parts of the southeast australian coast using other methods

comparison of linear and nonlinear seismic responses of two dimensional alluvial basins theoretical comparisons of linear and nonlinear seismic responses of two dimensional 2d alluvial basins show that in general the character of the seismic wave propagation is similar in both cases but important differences exist regarding both the time history and the response spectra the nonlinear model based on yielding elements arranged into a 2d finite difference mesh tends to distribute the total seismic energy over longer time durations resulting in lower peak accelerations and lower response spectra than those produced by the linear model on the other hand the fourier spectra in each comparison are similar particularly the peak amplitudes occur at about the same frequencies in both cases however resonant peaks obtained with both models for weak input amplitudes do not appear when the input amplitude is increased 10 fold in the nonlinear case due to greater damping determined by its assumed stress strain relationship which restricts the buildup of resonances the examples presented in this study correspond to a trapezoidal sedimentary basin embedded in an elastic half space the p and s wave velocities of the sediments are chosen to be constant in one case and linearly varying with depth in the other the input motion is obtained from the bedrock at the castaic old ridge route station during the 1971 san fernando earthquake scaled to provide a weak motion with peak acceleration 0 04 g and a strong motion with peak acceleration 0 4 g in the linear case suitable values of q are chosen to yield the same average damping as that by the nonlinear case for both inputs

sediment supply to beaches cross shore sand transport on the lower shoreface many beaches have been built by an onshore supply of sand from the shoreface and future long term coastal evolution critically depends on cross shore sediment exchange between the upper and the lower shorefaces even so cross shore sediment supply remains poorly known in quantitative terms and this reduces confidence in predictions of long term shoreline change in this paper field measurements of suspended sediment load and cross shore transport on the lower shoreface are used to derive a model for sediment supply from the lower to the upper shoreface at large spatial and temporal scales data collection took place at five different field sites that exhibit a wide range of wave conditions and sediment characteristics data analysis shows that both suspended sediment load and cross shore sediment transport scale with the grain related mobility number which ranged up to 1000 in the measurements while the effect of orbital velocity skewness is more limited a 1 year long simulation of sediment transfers between the lower and the upper shorefaces on a natural beach compares well with transport rates estimated from long term bar migration patterns and aeolian accretion on the same beach

effects of an alluvial basin on strong ground motions it has been reported that structures on loose soil sustain more damage during earthquakes than those on solid rock this phenomenon has long been ascribed to the influence of local site geology gutenberg 1956 observed stronger shaking and longer duration at sites on alluvium than at those on crystalline rock and large variations in ground shaking even at sites only 1000 feet apart during the recent michoacafi earthquake of 1985 most of the damages occurred in mexico city more than 300 km from the epicenter anderson et al 1986 the city is situated atop very soft sediments that caused dramatic amplification of strong ground motion severe damage to the structures and considerable loss of life within the area of the city located on top of the soft sediments on 20 may 1986 a magnitude m l 6 5 earthquake occurred near hualien in eastern taiwan the epicenter was located at 24 4 9 n and 121o35 49 e and the focal depth was 15 8 kin this earthquake caused some damage in the hualien and taipei areas tsai et al 1986 accelerographs at 37 sites of the strong motion accelerographs array in taiwan phase 1 smart1 array fig 1 bolt et al 1982 were triggered the lotung large scale seismic test array lsst array figs 1 and 2 wen et al 1986 is situated within the southwestern quadrant of the smart1 array surface recordings and two groups of downhole recordings of the lsst array were also obtained in this study we use the frequency wavenu mber f k analysis to study the variations in wave propagation direction and velocity the change in peak acceleration velocity and displacement with respect to depth and the frequency dependent ground motion amplification are studied by using the downhole and surface recordings of the lsst array

shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea abstract although pulses of coastal dune development in the course of the holocene have been attributed to variations in the availability of sand to modulation of sand supply by sea level change and to changes in wind conditions identifying the processes driving such pulses has been rather elusive the shore deposits bordering the tide and storm wave dominated southern north sea evince complex mid to late holocene stratigraphy and sediment heterogeneity these deposits include a unique 7 km long 0 3 0 6 km wide and up to 7 m high aeolian sand unit the ghyvelde dune occurring astride the french belgian border in an apparently anomalous inland location the dune overlies and is surrounded by tidal sandy and muddy deposits incorporating freshwater peat data from four mechanical cores and eight auger holes and three radiocarbon ages and one osl age suggest that this inland dune was part of an ancestral north sea sand flat and mudflat environment confronting the dune stratigraphy with the prevailing tide and storm controlled dynamics of shoreline progradation in this area indicates that dune formation occurred under a pulse of abundant sand supply resulting from the attachment to a mid holocene north sea tidal flat shore of a shoreface tidal bank under repeated storms this mode of onshore sand supply generates extremely rapid progradation up to 1 km over a century of the sand flat shore the surface of which serves as a large aeolian fetch zone for active backshore dune accumulation while parts of this surface trap locally significant amounts of mud that are subsequently fossilised by aeolian sand the potential influence of sea level and storminess in modulating the timing of shoreface sand supply and late holocene coastal dune development in the southern north sea reported in studies from other areas remains to be established

station site characteristics of wwssn stations in india and southern asia the continental boundary between the eurasian and indian plates is of great geophvsical significance because it is one of the rare instances of presently active continent continent collision the region has been instrumented with a relatively large number of wwssn stations the crustal structure beneath these stations has been studied by examining their crustal transfer characteristics for incident teleseismic p waves at those stations well removed from the collision boundary poo kod ndi shi and msh the crustal structure appears to be relatively flat lying so that long period body waves are regularly polarized for these cases p to s converted phases from the moho have been identified in the records and modeled with synthetic seismograms to measure crustal thickness the depth to the moho beneath these stations falls within the usual continental range but shows no systematic variation between the indian and eurasian plates those stations which lie on or near the collision boundary que kbl and nil show evidence of strongly dipping structure teleseismic p waves recorded there generally contain prominent tangential arrivals the tangential phases are strong for waves approaching from all azimuths indicating that they are due to complex three dimensional structures rather than planar layers with a single direction of dip

seismic response of a class of alluvial valleys for incident sh waves an approximate solution is presented for the surface ground motion on a class of alluvial valleys under incident sh waves it is based on the existence of a complete family of rays supported by the basin s boundaries it is approximate as diffraction is neglected this method is developed initially for rigid bases and extended to consider deformable boundary and arbitrary incidence angles comparison of results with a more rigorous solution shows very good agreement at a much lower computational effort time domain results are presented for different property contrasts and incidence angles the method is suited to study time domain resonse of a family of alluvial deposits due to its low cost and practically no upper frequency limit

smooth or oscillating late holocene sea level curve evidence from cross regional statistical regressions of fixed biological indicators abstract what if any is the pattern of change of the late holocene sea level curve if a common pattern exists can it be better discerned in the non glaciated tectonically stable regions of the southern hemisphere and is sea level data more reliable from one type of marine sample than another to begin an investigation of these questions we present a review of regressing time elevation plots from the low to mid latitudes of the southern hemisphere based upon the differential between modern and past levels of various fixed biological indicators mainly calcareous tubeworms and corals stranded up to 2 m above present relative sea levels the sample sets come from our work in southeast australia and comparable work from north east australia the pacific islands and brazil we show that using evidence obtained from fixed intertidal tubeworm species there is no statistical exclusivity between the smooth and oscillating polynomials but corals are more problematic in situ tubeworm species with their reduced error bars in comparison to corals fulfil the condition of providing more robust results for statistical analysis regression curves based on these species point to cross regional similarities in the pattern of sea level movement of the last 6000 years across the lower latitudes of the southern hemisphere these statistical exercises while not able to yield definitive conclusions can highlight statistically equally likely alternative patterns of sea level movement which can then be tested by field evidence they can also give useful indications of the quality of sea level data obtained from different biological sources as in the difficulties in the use of corals compared to common intertidal tubeworm species

wave propagation in a three dimensional circular basin abstract wave propagation in a three dimensional circular basin model is studied by using a ray technique which employs the method of principal curvature for geometric spreading calculation three components of ground motion are calculated at surface stations assuming incident plane p and sh waves with various incidence angles computed results show that seismic energy is substantially enhanced in the central region of the basin while it diverges rapidly toward the edge of the basin compared to a two dimensional basin with the same cross section amplitudes are larger for stations in the central region and smaller for stations near the edge waveforms and amplitudes can change drastically between two nearby stations due to caustics and geometric focusing for different paths it is found for the particular basin geometry and velocity contrast used that the first multiple p wave and other particular phases experience two caustics near the basin center which are associated with the principal curvatures of the wave front this results in the reversal of the polarity of the waveform as incidence angle increases later arrivals at near edge stations and the stations in the diagonal direction are more strongly developed from the curved boundary of the basin but amplitudes of ground motions generally decrease as incidence angle increases in general wave responses strongly depend on the incidence angle and station location these results have important implications for site amplification of strong ground motions since wave behavior is so complex even for this simple idealized structure

strong motion seismology strong motion seismology is concerned with earthquake ground motion in the amplitude range that poses the threat of human injury or property damage because the occurrence of strong motion cannot be predicted in advance and because the time between significant events at any one place may range from tens to thousands of years strong motion data is recorded on triggered instruments that typically must be maintained in readiness for years between periods of significant recording as a consequence the strong motion data set is sparse because of the engineering need for estimates of future ground motion the scope of the field of strong motion seismology encompasses seismic source theory and any other aspect of seismology that can provide insights helpful in making the best possible estimates given the limited data this relationship with the rest of seismology is a reciprocal one in that strong motion data gives perhaps the best information available on earthquake source processes

study of the propagation and amplification of seismic waves in caracas valley with reference to the 29 july 1967 earthquake sh waves the antiplane response of a 2 d model of the valley of caracas venezuela a ns cross section through the palos grandes district to seismic excitations such as those due to antiplane line point sources and incident plane sh waves is investigated it is found that the steeply sloped northern edge of the valley is a more efficient generator and reflector of surface waves than the midly sloped southern edge also the spectral amplification and time response characteristics of this asymmetric wedge shaped valley are a function of the direction of incidence of the excitation waves e g incidence from the north versus incidence from the south versus vertical incidence the same 2 d model of the valley is used to simulate also the antiplane response of the valley to synthetic strong motions equivalent in amplitude frequency content and duration to those that most likely were generated by the 29 july 1967 caracas earthquake this event has been found to consist of four subevents of which the second subevent located at a distance of 25 km from the valley caused the damage in caracas the source spectrum of each of the subevents used in the generation of the synthetic time histories was assumed to be a simple square model the locations relative times of occurrence seismic moments and mechanisms of the subevents were available from an inversion study of teleseismic data it is found that peak acceleration was fairly uniform across the valley varying from 0 15 to 0 21 g on the contrary peak velocities and peak rotational torsional strains varied considerably factor of 2 to 3 across the valley with the maximum values being 25 cm sec for velocity and 1 5 10 4 for rotational strain for sites in palos grandes spectral accelerations sa reached values as high as 0 4 g for periods in the range 0 4 t 1 4 sec and damping ratio 5 our estimates of the intensity of motion on rock and on the sediments are higher by a factor of 3 compared with estimates proposed by previous investigators who assumed that all the seismic energy was released from a point located at a distance of 55 km from caracas various pieces of evidence e g seismoscope response recorded on rock are presented that suggest that the intensity of motion was at least as high as estimated in this paper

wave propagation and site response in the santa clara valley forty two portable digital instruments were deployed across the santa clara valley from june until early november 1998 this array recorded 14 small and moderate local events and 7 large teleseismic events we analyze the ground motion from these events to determine station delays and relative site amplification within the valley p waves from an event at the southern edge of the valley are early t 0 35 sec at stations over an axial ridge in the basement interface in the middle of the valley but late t 0 20 sec for stations over the cupertino and evergreen basins to either side the s wave delays are approximately twice as large teleseismic p waves from an m 7 0 event beneath the bonin islands show a similar pattern in travel time delays the p waves are amplified by factors of 1 5 3 for frequencies below 2 hz at stations within either basin compared with stations on the axial ridge the p wave coda appear enhanced at 2 3 sec but coda q estimates at frequencies from 0 2 to 1 1 hz are not markedly different at stations over the basin compared with stations on the ridge with the possible exceptions of consistently high values over the northern end of the evergreen basin we invert the s wave spectra for site specific attenuation and amplification from the 14 local events by assuming a common source spectra for each event 1 r geometrical spreading and constraining the inversion using the 30 m velocity profile at four stations in the array the largest amplifications occurred in the 1 to 6 hz band at stations near the northwest edge of the evergreen basin while the highest amplifications occur at stations with the lowest s wave velocities the scatter obscures the correlation between velocity and amplification the stations in the basins are characterized by higher attenuation than the stations on the basement ridge manuscript received 2 july 2001

detrital fission track analysis and sedimentary petrofacies as keys of alpine exhumation the example of the venetian foreland european southern alps italy sedimentary petrography and detrital apatite fission track analysis of sediments from the oligo miocene venetian foreland succession ne italy reveal a multi stage evolution of the alpine source areas during the first stage of sedimentation chattian to langhian the foreland basin was filled by sediments derived from erosion of mainly crystalline austroalpine units exhumed north of the periadriatic lineament these sediments are characterized by litharenites with mean quartz content of about 61 and by a mean detrital apatite fission track peak of about 30 ma the permian paleogene sedimentary cover of the southalpine crystalline basement dolomite region was bypassed by the sediments and made only a minor input from the serravallian onwards the foreland basin was incorporated into the southalpine thrust belt the compressional events of the valsugana phase resulted in thrusting and uplift of the southalpine domain as documented by tortonian fission track ages in the hanging wall of the major regional thrust valsugana thrust fault the southalpine crystalline basement unaffected by alpine metamorphism and its sedimentary cover became the main source of sediments as revealed by the increase in extrabasinal carbonate grains and detrital apatite grains with late triassic jurassic fission track ages during this final stage of basin evolution about 3000 m of sediments were deposited these strata subsequently have been uplifted and eroded since the pliocene indicating a southward migration of the alpine deformation front

burial and exhumation of corsica france in the light of fission track data 1 the mesozoic and cenozoic exhumation and cooling history of corsica is reconstructed by fission track ft data on basement and sedimentary rocks apatite ages are 105 16 ma zircon ages are 160 145 ma the jurassic and cretaceous ages show that parts of the variscan basement escaped alpine influence the basement was thermally affected by rifting prior to jurassic opening of the ligurian piedmont ocean then it cooled to near surface temperatures in paleocene eocene times subduction buried parts of the basement and overlying flysch to greater depth in the oligocene both collapse of the nappe stack and rifting prior to opening of the ligurian provencal basin affected the apatite ft system of the basement in different partly overlapping areas causing a complex age pattern the study shows that thorough analysis of ft data and thermal modeling allow to assign age populations to distinct cooling processes even when several thermotectonic events contributed to generate an intricate age pattern

mid late holocene sea level variability in eastern australia a re analysis of sea level data from eastern australia based on 115 calibrated c 14 ages is used to constrain the origin timing and magnitude of sea level change over the last 7000 years we demonstrate that the holocene sea level highstand of 1 0 1 5 m was reached 7000 cal yr bp and fell to its present position after 2000 yr bp these findings are in contrast to most previous studies that relied on smaller datasets and did not include the now common conversion of conventional c 14 ages to calendar years during this 5000 year period of high sea level growth hiatuses in oyster beds and tubeworms and lower elevations of coral microatolls are interpreted to represent short lived oscillations in sea level of up to 1 m during two intervals beginning c 4800 and 3000 cal yr bp the rates of sea level rise and fall 1 2 mm yr 1 during these centennial scale oscillations are comparable with current rates of sea level rise the origin of the oscillations is enigmatic but most likely the result of oceanographic and climatic changes including wind strengths ice ablation and melt water contributions of both greenland and antarctic ice sheets

cenozoic denudation of corsica in response to ligurian and tyrrhenian extension results from apatite fission track thermochronology 1 the island of corsica france occupies a unique position in the western mediterranean since it has recorded both the cenozoic alpine orogenic history of the area as well as subsequent extensional collapse and oceanic basin formation we present 41 new apatite fission track aft ages and 23 measurements of track length distributions from corsica in order to elucidate its cenozoic thermal and morphological evolution aft ages vary from 10 5 0 8 ma to 53 8 4 1 ma and form a clear spatial pattern oldest ages are encountered in the southwest of the island with a broad band of ages between 20 and 30 ma running across the mountainous central area and ages 20 ma confined to the eastern half of the island samples along the western and northwestern coasts record kilometer scale erosional denudation linked to rifting in the ligurian provencal basin whereas samples from close to the extensionally inverted alpine deformation front record a later cooling phase related to tyrrhenian extension the eastward younging pattern of aft ages suggests the migration of a wave of erosional denudation from west to east across the island apparently controlled by the migrating locus of extension our aft data therefore support models of mediterranean extension controlled by slab roll back

holocene evolution of the coast of holland abstract the holocene evolution of the coast of holland was controlled by the complex interaction of such diverse parameters as wave and tidal climate the rate of sea level rise and the morphology of the pre transgressional surface the latter in combination with the rate of sea level rise mainly determines the location of sediments sources and sinks while the hydrodynamic parameters mainly determine the rate and direction of sediment transport in the early holocene the low sea level in the shallow southern north sea strongly affected wave climate and tidal regime however the barrier and back barrier sedimentary record since 5000 14c yrs b p gives us no reason to assume major changes in these parameters since then so we conclude that breaks in barrier development are due to variations in rate of sea level rise inl combination with the morphology of the pre transgressional surface the transformation from an open tide dominated to a closed wave dominated coast which occurred in the subboreal period and the concomitant change in barrier movement from transgressive to regressive around 5000 yrs b p are the main events in the development of the coast of holland up to the middle ages the morphology of the pre transgressional surface gives a shoreline in the late atlantic which consists of two protruding headlands separated by a large tidal basin the southern headland is the alluvial plain of the rhine and the meuse the northern headland constitutes the moraines of the texel high the tidal basin in between is connected to the north sea by a large number of inlets the rate of sea level rise at that time 1 m century outran the supply of sediment to the tidal basin after 6000 yrs b p the rate of sea level rise decreased gradually whereas the rate of sediment supply remained constant this led to a gradual decrease in the tidal prisms of the inlets as the tidal basin was filled in with sediment shortly before 5000 yrs b p the first channels silted up and closed the last tidal channel disappeared around 3300 yrs b p leaving two inlets along the coast which were both connected to the river rhine the closure of the first inlets occurred at the same time as the barrier began prograding because 1 the rate of sea level rise diminished considerably 2 not all the sand supplied by longshore and cross shore transport disappeared into the tidal basin but instead could be used for barrier progradation and 3 ebb tidal deltas of the closed inlets provided major sand sources the prograding barrier sequence enclosed between the two headlands roughly forms a closed system using the relationships between tidal prism cross sectional area of inlets and volume of the ebb tidal delta and the results of modelling of longshore transport along the subboreal coast under present day wave conditions a simple sand budget for the coast of holland is given which shows that a large part of the sand now stored in the barrier sequence was obtained by cross shore transport from the north sea

effect of structure geometry on strong ground motions the duwamish river valley seattle washington abstract a three dimensional ray tracing algorithm is used to compute the high frequency response of an sh plane wave incident under several models of the sediment filled with duwamish river valley of central seattle models are based on valley geometry previously determined using borehole logs the sh wave response is considered in an effort to simulate the s wave radiation from the 1965 magnitude 6 5 puget sound earthquake although the structure models considered are two dimensional three dimensional ray tracing is needed to treat incident sh waves of various incidence angles and azimuths of approach appropriate for the uscgs and isc hypocenters of the 1965 event generally amplification of the direct sh wave due to the curved basin geometry is comparable to an equivalent elastic layer over a half space model however for points near the center of the valley multiple s rays become focused after undergoing several reflections from the curved lower boundary of the valley fill this produces an order of magnitude increase in effective amplification a detailed study of these rays shows that significant amplitudes occur over narrow distance ranges 200 m at the surface and that they are sensitive to moderate changes in incident wave direction focusing effects of this type were probably an important factor in damage caused by the 1965 earthquake especially over the thicker portions of the duwamish river valley effects of randomly focused rays also give an explanation for the apparently capricious nature of strong ground shaking in the puget sound area

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

a statistical model for ground motion produced by earthquakes at local and regional distances to adapt random process theory techniques for statistical estimation of peak ground motion to more realistic earth models we constrain the parameters of duration geometrical spreading and spectral shape by modeling the main ground motion as being the result of major contributions by the direct s wave and supercritically reflected s waves the results of our modeling are constrained to be consistent with values from full wave synthetics for the test models the combination of estimation theory and theoretical amplitude spectrum of the main ground motion within the ergodic window successfully predicts the mean peak vertical ground displacements velocities and accelerations of the 1982 miramichi earthquakes in new brunswick canada in addition upon considering the effects of source depth and crustal structure for the november 25 1988 saguenay earthquake m 5 8 in quebec canada the predicted mean peak horizontal ground accelerations match the observed data very well the effects of source depth and crustal structure on the peak ground motion are complicated for different source sizes and at different epicentral distance ranges

further evidence from relic shellcrust sequences for a late holocene higher sea level for eastern australia abstract new evidence from dating the fossil residue of intertidal organisms on the central new south wales coast extends the findings of an earlier use of this method and supports the case for a regional highstand between 1 and 2 m above present relative sea level for much of the middle to late holocene evidence demonstrating a vertical shift over time by in situ intertidal organisms provides a more precise record of holocene sea level fluctuation than the more ambiguous evidence from estuarine and dunal depositional features by extrapolating back from dated hard evidence of this kind secondary evidence such as remnant rock platforms may be used to reconstruct the age and duration of coastal geomorphic features

offshore transport and sand body formation evidence from a steep high energy shoreface southeastern australia abstract elongate shore parallel sand bodies lie on the lower shoreface of the embayed and cliffed coast of central new south wales australia these sand bodies are 10 to 30 m thick extend almost continuously for 40 km parallel to the coast and display a pronounced convexity on the sea floor in profile sediment sampling and detailed seismic reflection and side scan sonar profiling provide evidence that the upper part of these large lobate sand bodies consists chiefly of sand transported downslope from the upper shoreface and surf zone the sand bodies consist entirely of marine sand probably derived locally from retreating embayed beaches and in part from sandstone cliffs channels and sediment lobes oriented normal to the shoreline and internal structure indicate growth by seaward progradation and surface morphology indicates coalescing of lobes and damming of bed load sediment against bed rock ridges in water depths of 70 to 80 m the precise mechanism or mechanisms of seaward transport on the shoreface is unresolved we surmise that during storm events disturbance by large waves and seaward transport by downwelling bottom currents result in sand movement onto and across the sand body surface at depths of 40 to 80 m concurrent modification of the sand bodies by shore parallel processes is suggested by textural trends bed forms and the overall alongshore continuity of the sand bodies

behaviour of beach profiles during accretion and erosion dominated periods beach profiles have been surveyed at monthly intervals between 1972 and 1988 at moruya on the south coast of new south wales australia four profile sites have been used as a data set to provide an understanding of changes to beach volume width and shape moruya beach represents a moderately high energy microtidal environment which responds in a dramatic way to major storm events such as those experienced in the mid 1970s this study distinguishes between profile characteristics associated with such a period erosion dominated or edp compared with periods when accretion dominated adp accompanied by foredune expansion in both height and width