shell mounds as environmental proxies on the southern coast of brazil despite the multiple constraints of using shell mounds for building relative sea level rsl curves one of the premises behind this use is still valid in modern archaeological research this refers to the sites being continuously built near bodies of water rich in fish species and mollusk beds studies that combine the evolution of settlement patterns with the geological evolution of coastal areas in brazil reach analogous results the distribution of shell mounds in time and space follows the landscape transformations induced by rsl variations through the holocene although shell mounds are not precise indicators of rsl they provide evidences of the paleo geographical changes during the holocene of which rsl is one of the many control variables by collecting and transporting mollusks to the shell mounds humans inevitably carry sediments from the substrate where mollusks live for example the beaches and lagoons near the sites in this work the geoarchaeological study of three shell mounds located in the southern coast of santa catarina state combined with mollusk taxa identification show the direct association of shell mound content with the changing landscape the predominance of ostrea sp versus anomalocardia brasiliana the presence of colluvial versus lagoonal sediments and the occurrence of echinoid spines versus muddy aggregates with diatoms gastropods and glauconitic clay characterize the distinction between sites built before and after the maximum holocene transgression respectively this attests the potential of geoarchaeological analyses in shell mounds as a complementary proxy for paleo environmental reconstructions

alexander the great s tombolos at tyre and alexandria eastern mediterranean tyre and alexandria s coastlines are today characterised by wave dominated tombolos peculiar sand isthmuses that link former islands to the adjacent continent paradoxically despite a long history of inquiry into spit and barrier formation understanding of the dynamics and sedimentary history of tombolos over the holocene timescale is poor at tyre and alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts in 332 bc following a protracted seven month siege of the city alexander the great s engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress tyre s causeway served as a prototype for alexandria s heptastadium built a few months later we report stratigraphic and geomorphological data from the two sand spits proposing a chronostratigraphic model of tombolo evolution

state of strain in a quartzite mylonite central australia abstract the finite strain due to mylonitization of a quartzite has been determined using measurements of deformed quartz grains and ribbons developed from quartz grains equant before the deformation the mylonites are developed in long narrow steeply dipping mylonite zones within the chewings range quartzite of central australia this quartzite is very pure 98 quartz the quartzite surrounding the mylonite zones appears unstrained the samples examined exhibit severe flattening strains k values of between 0 01 and 0 12 and r values of between 5 and 30 have been determined application of formulae to calculate volume change assuming the model of an ideal ductile deformation band structure indicate significant apparent volume losses with values between 0 69 and 0 95 such values seem unreasonably high as no geological evidence for large volume loss is seen the band structure model is considered inapplicable for these mylonite zones the observed structural features can best be explained by a deformation history involving severe bulk shortening normal to the zones

shell concentration dynamics driven by wave motion in flume experiments insights for coquina facies from lake margin settings abstract coquinas are important carbonate oil reservoirs in the sin rift sequence of the brazilian marginal basins mainly in campos and santos basins they are generated from shell accumulations in lake margin environments in which waves and bottom currents at storm conditions were the main hydrodynamic agents of transport and reworking in order to investigate the role of wave transformation processes in shallow waters swash breaking and wave shoaling in shell concentrations a physical modelling of the coastal environment was performed in laboratory the experimental setup consisted of a 2d flume a wave generator and a sedimentary bottom composed by quartz sand and shells bivalves gastropods and fragments an underwater camera wave gauges and an adv were used to record the sedimentary processes and to perform a quantitative analysis of the hydrodynamics the experimental scenario reproduced a rift lake margin a coastal sector of lake tanganyika tanzania africa was used to set the model boundary conditions in a 1 20 scale as well as the coastal gradient and wave conditions from 54 h of wave experiments which alternated from fair weather to storm wave conditions three shell concentration dynamics were observed reworking winnowing and dynamic bypassing the reworking erosion was characterized by traction rolling and saltation of bioclasts together with the traction and suspension of sand the occurrence of the latter was restricted to the breaking and swash zone in both fair weather and storm conditions the winnowing erosion was featured by sand suspension and the gentle traction and rotation of the bioclasts on the bottom the winnowing occurred at the proximal area of the shoaling zone just behind the first wave breaking point in storm wave conditions the dynamic bypassing omission was identified by the ripples migration over static shells on the bottom of the distal shoaling zone which produced alternated burial and exhumation of bioclasts the quantitative analysis of the oscillatory flow indicated higher velocities at the breaking zone reworking domain than at the shoaling zone winnowing domain mainly during storm conditions this study provided new and more accurate insights to depositional models of lake margin coquinas suggesting that each wave transformation process control a specific dynamic of shell concentration also the limit between the breaking zone and the shoaling zone in storm conditions 1st wave breaking point was identified as a better criterion to bound the reworking domain where fragmented coquinas are produced from the winnowing and dynamic bypassing domains where non fragmented coquinas occur in contrast to the fair weather wave base criterion

radarfacies and sedimentological analysis study of sedimentary substrate from an archaeological site shell mound southern brazil integrated results of gpr ground penetrating radar and sedimentological analysis are presented for the jabuticabeira ii archaeological site shell mound santa catarina brazil by means of rada

deglacial climate and relative sea level changes forced the shift from eolian sandsheets to dunefields in southern brazilian coast abstract quaternary sea level and climate changes can promote spatio temporal shifts in the morphology of coastal eolian depositional systems a shift of depositional features such as from sandsheets to dunefields occurs as response to a disequilibrium condition in the system promoted by changes in accumulation space and sediment supply balance on the other hand the eolian system migration with maintenance of morphological patterns points to an equilibrium conservation under minor variations in the external controlling factors of the system the santa catarina coast in southern brazil hosts widespread active and stabilized eolian depositional systems with varied morphology in this study geomorphologic and stratigraphic changes of eolian deposits of the southern coast of santa catarina were constrained by optically stimulated luminescence osl dating this allowed to assess how coastal eolian systems responded to late quaternary climate and sea level changes eolian sandsheets initiated around 22 ka ago during the last glacial maximum lgm and persisted during most of the deglacial period under conditions characterized by sea level lowstand wider exposition of shelf sediments more continental and drier climate and scarcer vegetation cover in the study setting the shift from eolian sandsheets to dunefields occurred approximately at 6 ka ago and marks the establishment of coastal conditions in the study setting the development of dunefields since the middle holocene would result from eolian system disequilibrium in response to a condition characterized by sea level highstand wetter climate and denser vegetation cover the maintenance of a dunefield morphology since 6 ka ago despite its onshore migration indicates a new equilibrium between accumulation space and sediment supply sandsheets evolved to dunefields around 6 ka ago when the coastline stabilized and the accumulation space was limited by onshore vegetation growth favoring eolian sediment aggradation the precipitation ridge in the inner margin of the dunefield has been successively stabilized abandoned and repositioned seaward accompanying the coastal progradation since 4 ka ago the decreasing migration rate of dunefields since 4 ka ago is attributed to rainfall reduction which deplete fluvial sediment supply to coastal systems and therefore slow down the coastal progradation rate

the holocene infill of lake conjola a narrow incised valley system on the southeast coast of australia a detailed holocene sedimentological and geomorphological history of the sedimentary infill of lake conjola a barrier estuary on the southeast coast of australia is presented results show that a remnant last interglacial barrier system is preserved in the mouth of a narrow incised valley during the early stage of holocene sedimentary infill a laterally extensive transgressive sand facies was deposited as rising post glacial sea level breached remnants of the last interglacial barrier ca 7500 cal bp from 7500 to 4000 cal bp sediment continued to accumulate within the mouth of the incised valley forming an extensive flood tide delta within the drowned river estuary marine influences were restricted by further sediment accumulation at the mouth of the estuary leading to the development of mid holocene barrier and back barrier depositional environments this research adds detail to stratigraphic models of the sedimentary infill and geomorphological evolution of barrier estuaries formed in narrow incised valley systems on the southeast coast of australia and provides a global model for estuarine deposition in regions that have been tectonically stable over the late quaternary

eolian depositional episodes controlled by late quaternary relative sea level changes on the imbituba laguna coast southern brazil the late quaternary coastal eolian deposits of the imbituba laguna region santa catarina state southern brazil comprise two eolian depositional sequences separated by an unconformity the older eolian sequence a is correlated to the relative sea level rise of the last interglacial period the eolian sequence b was initiated during the relative sea level rise in the post glacial period and extends up to active dunefields the correspondence between the two eolian depositional episodes represented by these sequences and the relative sea level highstand phases is confirmed by thermoluminescence and optically stimulated luminescence dating this correspondence is explained by a conceptual model that links the availability of coastal sediments for eolian transport with relative sea level changes the link between relative sea level changes and coastal eolian sedimentation can be used to integrate coastal eolian systems to the sequence stratigraphy model

low energy sandy beaches in marine and estuarine environments a review this review was undertaken to identify locations where low energy beaches may occur and their diagnostic forms and process controls including waves tides and water levels examples are drawn from the sheltered coastline of western australia near perth and fetch limited estuarine environments on the northeast coast of the united states we suggest that the term low energy be used in locations where 1 non storm significant wave heights are minimal e g 0 25 m 2 significant wave heights during strong onshore winds are low e g 0 50 m 3 beachface widths are narrow e g 20 m in microtidal environments and 4 morphologic features include those inherited from higher energy events micro topographic features can persist in the swash zone of low energy beaches under non storm wave conditions there is little evidence of cyclic cross shore sediment exchange bars excepting transverse forms located seaward of low still water level do not appear to be part of the sediment exchange system with the foreshore developing a better definition of the term low energy requires understanding the occurrence and duration of morphological characteristics and the type magnitude and frequency of hydrodynamic controls that are responsible for these characteristics efforts also should be directed toward 1 discriminating between processes generated within basins in true fetch limited environments and processes generated outside basins that affect sheltered environments 2 identifying the relative contributions of tide and surge related water level fluctuations on low energy beach shape and 3 estimating thresholds for beach change

evidence of late holocene shoreline progradation in the coast of kerala south india obtained from osl dating of palaeo beach ridges abstract the luminescence chronology of beach ridges in the central part of kerala along the west coast of india has been made for the first time in order to reconstruct past sea level highstands and coastline progradation transitional boundaries between shoreface to foreshore and foreshore to dune aeolian environments were used as marker horizons for determining the palaeo shoreline as well as sea level indicators the study presents the results of optically stimulated luminescence osl dating of sand samples collected from wave and wind built horizons derived from quartz using single aliquot regenerative dose sar protocol the osl ages from most of the sites are consistent with each other indicating a stage of coastline progradation between 3 and 5 ka and widespread beach ridge formation all along the west coast of kerala during this period the osl ages of transition levels together with the elevation measured using differential global positioning system dgps indicates that the sea level was between 3 5 and 4 5 m above present msl during the late holocene period it may also imply the emergence of the coast due to neo tectonic activity as the sea level curve for the east coast from reported ages indicates a mean elevation between 1 5 and 2 5 m the ages are discussed in the light of reported events such as sea level changes coastal geomorphology hydrological variations and neo tectonics

a critical review of mid to late holocene sea level fluctuations on the eastern brazilian coastline abstract the eastern coast of brazil is 7000 km long and has been the subject of systematic paleo sea level investigations for more than 35 years more than 1000 samples have been radiocarbon dated and paleo sea level trends have been determined for 14 coastal sectors these trends have in common a mid holocene sea level maximum pmt above present sea level and a subsequent fall to the present time the time and elevation of the pmt the time when relative sea level rose above present mean sea level and the nature of late holocene sea level fall can however differ significantly discrepancies are observed not only between neighboring coastal sectors but also between different studies in a same coastal sector this paper discusses all the key radiocarbon dated samples used to establish regional trends in relative sea level on the eastern coast of brazil it is concluded that although many of the key sea level indicators are imprecise in time and space there is widespread evidence 30 of the data set for a progressive decline possibly with uneven rates of relative sea level since the end of the pmt

the geomorphological evolution of a wave dominated barrier estuary burrill lake new south wales australia abstract the geomorphological evolution of the holocene wave dominated barrier estuary at burrill lake on the new south wales coast australia has been investigated using a combination of seismic stratigraphy and lithostratigraphic analysis of vibracores collected from the back barrier estuarine environment a combination of radiocarbon and aspartic acid racemisation derived ages obtained on holocene fossil molluscs and the thermoluminescent signal in remnant the last interglacial barrier provides the chronological framework for this investigation results from this paper show that the barrier estuary occupies a relatively narrow

geological characteristics and spatial distribution of paleo inlet channels beneath the outer banks barrier islands north carolina usa abstract nearly 200 km of high resolution ground penetrating radar gpr data were acquired along the outer banks barrier island system of north carolina usa gpr data combined with lithofacies and biofacies data reveal multiple depositional facies including inlet channel flood tide delta overwash peat and inner shelf previously undocumented paleo inlet channels constitute a significant portion of the shallow geologic framework between oregon inlet and cape hatteras gpr data reveal the complex stratigraphy associated with multiple sequences of cut and fill within inlet channels two types of paleochannels non migrating and migrating were classified based on geometry and fill patterns sediments and foraminifera collected from vibracores were correlated to gpr data to define the regional shallow stratigraphic framework channel fill facies are characterized by clinoform packages sometimes bounded by erosional surfaces indicating variable sediment transport directions from the ocean and sound sides channels are incised into older flood tide delta deposits corresponding to older inlet activity when barriers existed further seaward flood tide delta deposits are capped with marsh peat and overwash units migrating inlet facies occur under the widest portions of the island whereas narrow portions of the island are underlain by the non migrating inlet facies or flood tide delta overwash facies this geologic geomorphic relationship is attributed to the successional stage of island evolution during transgression and sediment transport processes associated with the different inlet types the radar facies lithofacies and biofacies provide a comprehensive dataset that will permit more precise identification of barrier island facies in the geologic record

crustal heterogeneity as inferred from seismic coda wave decomposition by small aperture array observation abstract seismic coda waves have complex waveforms and are considered to be caused by 3 dimensional structural heterogeneities we carried out 3 component small aperture array observations of seismic coda waves from natural earthquakes in tsukuba central japan to decompose complex coda waveforms and to clarify the nature of crustal heterogeneity epicentral distances in the present study are less than 200 km the observational results are summarized as follows 1 the remarkable feature of the coda from natural earthquakes is the difference between the p coda and the s coda especially in the vertical component the p coda consists mainly of coherent p wave phases which have almost the same slowness vector as the initial p wave motion whereas the s coda is decomposed into incoherent phases with random propagation directions 2 coherency of waveforms among the array sensors of the vertical component rapidly becomes low from the high value of coherency of the direct s wave 3 in the two horizontal components radial and transverse ones both the p and s coda are decomposed into incoherent random phases 4 coherency in the early s coda of the horizontal components gradually becomes low compared to the vertical component these features indicate that s to p converted waves at horizontal boundaries of the structure are dominant in the p coda of the vertical component while the p coda of the horizontal components and the s coda consist of scattered waves from the lateral heterogeneity this interpretation leads to a model of crustal heterogeneity in which the degree of the lateral heterogeneity is smaller than the degree of vertical heterogeneity of layered structures

an evolutionary categorisation model for backbarrier environments abstract shorelines occurring along restricted fetch environments such as the backsides of barrier islands are extremely diverse with respect to their morphologic characteristics and evolution in order to better understand the morphodynamic evolution of backbarriers and the associated implications for entire barrier systems this study proposes a backbarrier evolutionary categorisation model based on the development of two types of index backbarrier evolution tendency and backbarrier maturation condition the proposed characterisation system is applied to the ria formosa backbarrier located in southern portugal for the period 1947 to 2001 cross shore and longshore backbarrier trends in ria formosa suggest a shrinking of the lagoon system as a consequence of a decrease in the coastal length of the backbarrier coastline and a landward displacement of it even though some of the backbarriers examined were found to be in an immature state the results obtained illustrate a maturing trend for the system overall barriers in ria formosa fall into two main evolutionary categories backbarrier reduction and backbarrier growth this means that neither smoothing nor branching has been significant and therefore that backbarrier recent evolution is closely related to barrier coast length application of the proposed characterisation to the ria formosa case study has helped reveal backbarrier evolutionary trends and therefore should be of use in the management of backbarrier systems

shell sclerochronology and stable isotopes of the bivalve anomalocardia flexuosa linnaeus 1767 from southern brazil implications for environmental and archaeological studies abstract this study presents the first stable isotopic and sclerochronological calibration of the bivalve anomalocardia flexuosa linnaeus 1767 in relation to environmental variables in a subtropical coastal area of southern brazil we investigate incremental shell growth patterns and 18o and 13c values of modern specimens collected alive from the laguna lagoonal system lls shells of anomalocardia flexuosa are also one of the main biological components of pre columbian archaeological shell mounds and middens distributed along the brazilian coastline we therefore selected archaeological specimens from a local late holocene shell mound cabecuda to compare their stable carbon and oxygen isotope values with those of modern specimens shell growth increments 18o and 13c values respond to a complex of environmental conditions involving for example the effects of temperature and salinity the isotopic information extracted from archaeological specimens from cabecuda shell midden in the lls indirectly indicates that environmental conditions during the late holocene were different from present day in particular intra shell 18o and 13c values of archaeological shells reveal a stronger marine influence at 3 ka cal bp which is in contrast to the seasonal freshwater seawater balance that currently prevails at the lls

tectonic controls on the stratigraphic development of the rifted taipei basin a late quaternary marine influenced inland half graben abstract we establish the three dimensional stratigraphic architecture of the taipei basin and its spatiotemporal palaeoenvironmental development during the past 50 kyr by analysing 36 borehole cores and 177 age dates we calculate the rates of basin subsidence from the borehole data at depths where radiocarbon age dates are available our results indicate that during the eustatic sea level falling period 35 20 ka low rates of sediment supply and or rapid basin subsidence controlled sedimentation leading to a change in the depositional environment from gravelly braided rivers through sandy braided rivers to meandering rivers with falling eustatic sea level during the early stage of eustatic sea level rise 20 10 2 ka balanced rates of sediment supply eustasy and basin subsidence maintained the meandering river environment rapid sea level rise led to the initial appearance of estuarine facies at 10 2 ka and widened the distribution of the estuarine environment after 8 5 ka however the coeval phases of rapid basin subsidence 10 6 10 2 ka and 9 8 5 ka promoted the first appearance and widening of the estuary respectively after 7 ka when the eustatic sea level and rate of basin subsidence remained relatively stable sufficient sediment supply gradually infilled the estuary the established stratigraphy improves our understanding of the factors controlling stratigraphic development in marine influenced inland half grabens specifically in the taipei basin with high rates of sediment supply accommodation space in the taipei basin was governed by eustatic fluctuations with modulations by basin subsidence and sediment supply since the last glacial period

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

coastal response to late stage transgression and sea level highstand coastal morphologic features associated with past shoreline transgressions and sealevel highstands can provide insight into the rates and processes associated with coastal response to the modern global rise in sea level along the eastern and southern brazilian coasts of south america 6000 years of sea level fall have preserved late stage transgressive and sea level highstand features 1 4 m above present mean sea level and several kilome ters landward of modern shorelines gps with real time kinematics data ground penetrating radar stratigraphy and radiocarbon dating within a 2 3 km wide river associated strandplain in central santa catarina southern brazil uncovered a diverse set of late stage transgressive and highstand deposits here the highstand took the forms of 1 an exposed bedrock coast in areas of high wave energy and low sediment supply 2 a 3 8 m high transgressive barrier ridge where landward barrier migration was prohibited by the presence of shallow bedrock and 3 a complete barrier island complex containing a 5 2 m high barrier ridge washover deposits a paleo inlet and a backbarrier lowland formed in a protected cove with ample sediment supply from small local streams and the erosion of upland sediments similar signatures of the mid holocene highstand can be traced across all coastal brazilian states this study presents the fi rst complete compilation of the diversity of these sedimentary sequences they are broadly classifi ed here as exposed bedrock coasts type a back barrier deposits type b transgressive barrier ridges type c and barrier island complexes type d according to localized conditions of upland migration potential wave exposure and sediment supply these brazilian systems present a paradigm for understanding future coastal response to climate change and accelerated sea level rise the recognition of a minimum threshold sea level rise rate of 2 mm yr 1 above which transgression proceeded too rapidly for the formation of these stable accretionary shoreline features demonstrates the nonlinearity of coastal response to sea level change and the site specifi city of conditions associated with the formation of each highstand deposit type even within a single small embayment demonstrates the non uniformity of that response

high resolution q 1 estimation based on extension of coda normalization method and its application to p wave attenuation structure in the aftershock area of the 2005 west off fukuoka prefecture earthquake m7 0 summary we developed a method for estimating the seismic wave attenuation 1 q in a seismically active region such as an aftershock area to estimate the attenuation factor between two adjacent hypocentres we employed two seismograms recorded at a station and calculate the ratio between two power spectra of direct waves normalized by those in the coda for both the events the coda normalization of the spectrum and the ratio between the two events minimize the possible influences of sources sites instruments and attenuation from the station to the hypocentral area the 1 q value can be estimated from the variation of the ratios of event pairs calculated at many stations for various traveltime differences between the even pairs this method involves double difference dd estimation from the logarithmic power spectra for estimating the 1 q structure employing a concept similar to the recently developed dd tomography for velocity structures we applied this method to the aftershock area of the 2005 west off fukuoka prefecture earthquake m7 0 in order to investigate the 1 q structure of p waves by using the spectra of the seismograms of 1781 events recorded at a dense seismic network deployed around the aftershock area we obtained the spatial variation of the 1 q value in this region the 1 q distribution thereby obtained suggests that there exists a high attenuation region around the edge of the main shock fault which could correspond to the segment boundary between the earthquake fault and the adjacent faults in addition we found that the initiation points of the main shock and aftershocks were located in a low attenuation region

barrier dynamics and landward migration with holocene sea level rise barrier beaches islands and spits have become the subject of mounting interest1 2 due to human development on these land forms it is commonly thought that barrier beaches continuously migrate landward in response to sea level rise often by over wash processes maintain mass through time and that these processes are occurring at a rate commensurate with human 100 yr time frames while some barriers are naturally migrating quite rapidly3 4 other barriers decidedly are not here i present data which illustrate that many us atlantic coast barriers are not evolving over the short term in accordance with generally accepted hypotheses and argue that the presumed norm may actually be the exception

three dimensional attenuation structure beneath the northeastern japan arc estimated from spectra of small earthquakes abstract a fine scale three dimensional attenuation structure beneath the northeastern japan arc has been obtained using a joint inversion for source parameters site response and q values data used for this study are p wave spectra of microearthquakes occurring in the subducting pacific plate the subducting plate is found to have higher q values than the overlying mantle there is an along arc variation in the distribution of low q zones in the crust and the mantle wedge within the study area for the southern part of the study area low q zones are distributed in the crust beneath the volcanic front they extend into the mantle wedge and become deep toward the west that is toward the backarc region on the other hand the northern part of the study area has low q zones at two depth ranges at shallower depths just beneath the volcanic front and at the deeper part of the mantle wedge beneath the backarc region the region without active volcanoes along the volcanic front has relatively high mantle q values seismic activity in the lower plane of the double planed deep seismic zone is high beneath this relatively high q region of the mantle wedge spatial distribution of low q zones found in the present study is nearly consistent with that of the low velocity zones estimated from studies of travel times tomography partial melting zones in the mantle wedge whose existence has been suggested from the study of seismic velocity structure and laboratory experiments are located in the low q zones obtained in the present study these results suggest that spatial distribution of q values is closely related to heterogeneous distribution of temperature in the mantle wedge

barrier evolution and placer formation at bujuru southern brazil abstract this paper demonstrates the link between the evolution of a coastal barrier in southern brazil during the late holocene and the formation of a large volume of eolian disseminated heavy mineral deposits our data set is based on an earlier heavy mineral prospecting campaign 1991 and on 10 new shallow vibrocores 2 5 m long the model presented has three main steps of barrier evolution the first step is the recycling of coastal plain deposits during the postglacial marine transgression which ended at 5 6 ka when heavy minerals were incorporated into beach and washover facies of a transgressive barrier the second step is the shoreward retreat of the barrier under a slow and small sea level fall during the last 5 6 ka this second step eroded and recycled sediments from the pleistocene substrate which acted as an extra source of heavy minerals heavy minerals were concentrated in backshore deposits by wave action during barrier recession the third step is the erosion and transport of backshore sands by onshore winds into an inter barrier depression in the form of transgressive dune deposits these deposits contain an average of 4 66 1 02 disseminated heavy minerals 1494 samples this eolian placer deposit has started to form 1 ka ago and is still under formation

a 3000 yr paleostorm record from st catherines island georgia abstract tropical cyclones hurricanes in the northern hemisphere are amongst the most devastating of the world s natural disasters and cause billions of dollars in damage every year data on the likelihood of a coastal site being struck by a major hurricane strike can potentially aid in planning and mitigation efforts that could save money and lives however forecasting requires data that are currently insufficient for the georgia bight this study provides information to enhance the paleohurricane record by analysis of a 467 cm thick vibracore raised from st catherines island ga sediment geochemistry and foraminiferal assemblages indicate deposits attributable to seven paleohurricane events five of which were likely major hurricanes when they made landfall on st catherines magnitudes were estimated by comparison to the overwash deposit left by the sea islands hurricane of 1893 a major hurricane recorded by the recent sediment of st catherines island the st catherines record also shows a change in the activity levels on the georgia coast with two distinct activity regimes over the past 3000 years

temporal changes in p wave attenuation in the loma prieta rupture zone 1 clusters of recurring nearly identical microearthquakes have been recorded near loma prieta california such events make possible direct measurement of temporal changes in the attenuation operator t along fixed paths under what are tantamount to laboratory conditions analysis of almost 10 years of p wave data following the 18 october 1989 loma prieta california main shock m 7 0 reveals a large amplitude t increase within the first 3 weeks of the main shock a gradual t recovery toward its level prior to the main shock is seen in the years ensuing the results point to changes in porosity and fluid saturation taking place in parts of the main shock source volume stemming from coseismic crack opening and postseismic relaxation processes such as postseismic fluid flow into the cracks crack healing and rock compaction

beach morphodynamics in a strong wind bay a low energy environment abstract the morphodynamic behaviour of a multibarred beach in a fetch limited strong wind bay seaford beach se australia was examined during both high and low energy conditions and considered in the context of a definition of low energy provided in the literature measurements of nearshore waves currents and morphology revealed a bimodal behaviour under initial low energy conditions the beach exhibited a low tide terrace state and waves and currents were of very low magnitude during subsequent high energy conditions the beach demonstrated dynamic behaviour through the formation of a transitional transverse bar and rip rhythmic bar and beach and migration of the middle bar with the morphology remaining in an arrested high energy state during intervening low energy periods although broadly conforming to the morphodynamic model the beach did exhibit some distinct characteristics attributable to its fetch limited location limited progression through the morphodynamic model and the importance of wind direction and magnitude in governing morphodynamic behaviour furthermore rip currents were not significant in driving beach change through intermediate states the presence of infragravity energy in the storm wave spectra a dissipative multibarred surf zone dynamic inner and middle bars and the attainment of a transitional transverse bar and rip rhythmic bar and beach state during rising wave conditions underline seaford beach as bimodal exhibiting process and morphologic features of both higher and lower energy beaches as an example of a beach in a strong wind bay seaford illustrates that not all fetch limited beaches are low energy furthermore the presence of infragravity energy in a highly fetch limited environment indicates that infragravity energy may occur commonly in fetch limited environments that are subject to periodic strong winds a process that has remained largely unrecognised

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

transition of a regressive to a transgressive barrier island due to back barrier erosion increased storminess and low sediment supply bogue banks north carolina usa abstract although back barrier erosion is a prevalent process of island narrowing it is often overlooked in conceptual models of barrier island evolution in many wave dominated barrier island settings the absence of overwash precludes landward movement of the back barrier shoreline and hence the island as a whole from sustaining its width typically regressive barriers are wide and exhibit high elevations with the most seaward dune ridge possessing the highest elevation this morphology may prevent overwash and inlets from breaching the barrier and therefore the associated sediment from reaching the back barrier shoreline for millennia back barrier shoreline erosion from sea level rise and storms can be permanent in the absence of sediment supply from rivers overwash and inlet processes with continued narrowing and lowering of the island regressive barriers may reach a critical state making overwash and inlet formation imminent and transitioning the island to a transgressive barrier the modern day morphologic variability along the 40 km long island of bogue banks north carolina includes both regressive and transgressive segments making this setting ideal for examining whether the transition between these barrier island types is gradual or threshold driven bogue banks consists of two discrete segments characterized by high elevation beach ridges large island widths and stratigraphy consistent with regressive barrier islands these regressive island segments are separated by a broad narrow section of the island devoid of any washover fans flood tide deltas or other transgressive elements analyses of seismic data from the inner continental shelf reveal paleochannels intersecting the wide sections of the island while the narrow central part of the island occupies an inter fluvial area reworking of fluvial sediment from paleochannels was an important sediment source for the barrier during regression optically stimulated luminescence osl dates from the most landward beach ridges constrained initiation of island regression at 3000 cal yr bp close to when there was a significant decrease in the rate of relative sea level rise from 5 mm yr to 0 8 mm yr transects of cores seismic data ground penetrating radar data and radiocarbon and osl dates show that prior to 1500 cal yr bp the central narrow section of the island was wide and progradational similar to adjacent areas back barrier erosion of the central part of the barrier primarily caused island narrowing as a result of increased storminess which occurred around the medieval climate anomaly 1100 cal yr bp this part of the island was more vulnerable to erosion than adjacent areas due to increased bay ravinement bogue sound is widest there and its lower elevation farther away from paleochannel sediment source relict inlet channels exist along the central portion of the island formed within the last 250 yr and likely closed shortly after formation the presence of historical inlets along the narrow central section of the island indicates bogue banks may be nearing a critical width threshold and will subsequently transition to a transgressive barrier because the change in barrier morphology associated with back barrier erosion occurred over a period of time when the rate of sea level rise was relatively low low sediment supply and increased storm frequency are shown to be the main forcing mechanisms of island narrowing these impacts in addition to a predicted increase in sea level rise rates and human modifications e g maintenance of a high elevation foredune closing of inlets prevention of island overwash and associated sediment delivery to the back barrier shoreline will likely promote rapid transition of regressive barrier islands to those dominated by transgressive processes

holocene stratigraphy in the paranagua bay estuary southern brazil abstract the paranagua bay estuary is a 50 km long microtidal barrier estuary that is still far from infilled even after 3 5 m of continuous sea level fall during the last 5000 years data derived from several independent studies including surface sediment samples jet probe cores vibracores and seismic records were compiled in order to provide an assessment of the quaternary stratigraphy of the estuary the estuary displays the longitudinal tripartite zonation of surface sedimentary facies marine sand estuarine mud fluvial sand that is characteristic of many coastal plain estuaries five sedimentary facies were identified overlying the bedrock pre holocene fluvial and continental deposits within the paleo valley form the substrate for the more recent sedimentation a transgressive mud facies marks the initial stages of estuary inundation this deposit is observed only in the lower half of the estuary where greater accommodation space existed and less intensive tidal scouring associated with the subsequent deposition of the transgressive sand facies occurred the onset of the regressive stage is marked by the deposition of the regressive mud facies which is presently the most extensive sedimentary deposit within the estuary the regressive sand facies which is composed of fluvially derived sediments and is restricted to the head of the estuary is the least developed sedimentary facies the vertical succession of the sedimentary facies shows an almost complete stratigraphic sequence and the presence of several bounding surfaces a transgressive surface a maximum flooding surface a tidal ravinement surface and a tidal diastem a comparison of the paranagua bay gironde and james estuaries all of similar size illustrates various stages of sequence development in modern incised valley systems

holocene sea level fluctuation in the southern hemisphere abstract if rising sea levels dominate in the northern hemisphere nh falling or fluctuating sea levels predominate in the southern hemisphere sh endogenic processes tectonics isostasy or geoidal changes could explain local or regional mean sea level msl fluctuations but not an hemispherical one evidence from south america africa antarctica australia and the pacific and indian oceans suggest that the holocene transgression rose above the present msl in higher latitudes before the tropics by plotting latitude against the age of msl arrival at present coasts good correlation is observed oceanic salinity mixing has been already proposed to explain this mid holocene sea level fluctuation climate could be the only factor responsible for this hemisphere wide behavior of msl it has been suggested previously that the climate of the sh precedes that of the nh by 3000 years the climatic optimum or maximum warmth occurred predominantly about 6000 bp in the nh but about 10 9000 bp in the sh short term climatic effects on the sea level monsoons southern oscillation el nino phenomena should have significant occurrences during the past in the windiest oceanic hemisphere this latitudinal trend in former msl should be considered when using shorelines as reference points for measuring vertical crustal movements

source parameters and three dimensional attenuation structure from the inversion of microearthquake pulse width data qp imaging and inferences on the thermal state of the campi flegrei caldera southern italy the three dimensional p wave attenuation structure of the campi flegrei caldera and the estimate of source parameters for 87 local microearthquakes is obtained by the nonlinear inversion of pulse width and rise time measurements by using the method described by zollo and de lorenzo this issue source radii represent the better resolved parameters with values ranging from 70 m to 230 m the dip and strike angles defining fault orientations are usually affected by larger uncertainties and are well constrained only for 11 events the dip fault is usually confined in the range 30 60 with an average uncertainty of 12 the fault strikes mainly range between 60 and 60 and seem to define preferential directions oriented radially from the symmetry axis of the ground deformation stress drop estimates indicate rather low values 0 01 1 mpa which suggest low strength properties of the incoherent and brittle materials filling the caldera primarily yellow tuffs the three dimensional qp images obtained from the inversion of p pulse durations show two significant low qp anomalies between 0 and 1 km of depth in the north eastern sector and at 2 3 km of depth in the central eastern sector of the caldera the high degree of spatial correlation of the low qp zone and low vs as inferred by aster and meyer 1988 at 0 1 km in depth and other geophysical and geochemical observations suggest that this anomaly can be related to the presence of densely fractured porous and fluid filled rocks in the ne sector of the caldera the deeper low qp anomaly is interpreted as being related to a dominant thermal effect we used the surface and deep borehole temperature measurements available in the area to obtain a local calibration curve to convert qp in temperature at campi flegrei the retrieved t qp map shows a high thermal deep disturbance 450 500 c at depths between 2 and 3 km in the eastern sector of the caldera where the most recent eruptive activity is concentrated the present day temperature field retrieved by qp images has been interpreted by using a three dimensional thermal conduction model assuming an extended heat source initial temperature of 800 c located underneath the attenuation anomalous region the results indicate that the qp inferred temperature field can be related to the heat conduction effect of one or more molten bodies whose top should be at about 4 km depth consistent with recent seismic estimates of the magma chamber top at campi flegrei ferrucci et al 1992 this study suggests that the present thermal state and rock rheology of the inner caldera could be controlled by the cooling of molten bodies that originally intruded at depths of 1 4 1 6 km during one or more recent time of 10 kyr eruptive events

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

facies associations and controls on the evolution from a coastal bay to a lagoon system santa catarina coast brazil abstract the diverse holocene morphological features along the south coast of the state of santa catarina include lagoons and residual lakes a barrier a delta constructed by the tubarao river and pre existing incised valleys that have flooded and filled this scenario contains the sedimentary record of the transition from a bay to a lagoon system which occurred during the rise and subsequent semi stabilisation of the relative sea level during the holocene the geomorphological evolution of this area was investigated using a combination of morphology stratigraphic analysis of rotary push cores vibracores and trenches with radiocarbon dating taxonomic determination and taphonomic characterisation of holocene fossil molluscs palaeogeographic maps were constructed to illustrate how the bay evolved over the last 8000 years the relative sea level rise and local sedimentary processes were the prime forcing factors determining the depositional history and palaeogeographic changes the holocene sedimentary succession began between 8000 and 5700 cal bp with the deposits of transgressive sandsheets these deposits correspond to the initial marine flooding surface that was formed while the relative sea level rose at a higher rate than the input of sediments prior to the formation of the coastal barrier the change from a bay to a lagoon system occurred around 5700 and 2500 cal bp during the mid holocene highstand with the formation of the barrier and with the achievement of a balance between sea level rise and sedimentary supply until 2500 cal bp the presence of this barrier the following gentle decline in sea level and the initial emergence of back barrier features restricted the hydro dynamic circulation inside the bay and favoured an increase in the tubarao river delta progradation rate the final stage during the last 2500 years was marked by the increasing back barrier width with the establishment of salt marshes the arrival of the delta in the back barrier and the advance of aeolian dunes along the outer lagoon margins this study shed light on the mechanisms of coastal bay evolution in a setting existed prior to the beginning of barrier lagoon sedimentation

paleoenvironmental reconstruction of a late quaternary lagoon system in southern brazil jaguaruna region santa catarina state based on multi proxy analysis this paper provides a paleoenvironmental reconstruction of a late quaternary lagoon system in the jaguaruna region of santa catarina state southern brazil integrated results of bulk sedimentary organic matter characterization d 13 c d 15 n and c n microfossil pollen and diatom and grain size analysis from three shallow cores 2 5 m depth allowed us to propose an evolving paleogeographic scenario in this coastal region for the last ca 5500 cal a bp the lagoonal system in this area was more extensive during the mid holocene than today with a gradual and continuous lagoon sea disconnection until the present we add to the debate regarding relative sea level rsl variations for the brazilian coast during the holocene and discuss the importance of sedimentary dynamics for interpreting changes in coastal ecosystems the multi proxy analysis suggests that changes in coastal ecosystems could be directly related to local sedimentary processes which are not necessarily linked to rsl fluctuations and or to climatic variations copyright 2011 john wiley sons ltd

relative sea level changes in the last 5500 years in southern brazil laguna imbituba region santa catarina state based on vermetid ages abstract twenty six new radiocarbon dates from vermetid shells collected in the southernmost sector of the brazilian rocky coast presented dates ranging from 5410 80 to 190 65 years b p with associated paleosea levels varying from 2 10 m to 0 20 m above present sea level the overall suggested trend of the relative sea level rsl declining until at least 190 years b p is somewhat contradictory to a proposed rsl rise in the last 1000 years in southern brazil the data also seem to undermine a more widely accepted rsl trend that suggests that at least two negative rsl oscillations occurred between 4100 and 3800 years b p and between 3000 and 2700 years b p the maximum elevation of the rsl in the holocene in southern brazil was possibly lower than that observed in most of the brazilian eastern coast discrepancies between ancient sea levels of similar ages are attributed to coincidental methodological problems to imprecisions in determining past relative sea levels and to possible changes in the geomorphology and wave climate close to shore during the last 5000 years a general trend of increasing 18 o with a reduction in age in the studied samples may suggest a gradual reduction of water temperature in the region during the same period

regional body wave attenuation using a coda source normalization method application to mednet records of earthquakes in italy we develop a new methodology to determine apparent attenuation for the regional seismic phases pn pg sn and lg using coda derived source spectra the local to regional coda methodology mayeda 1993 mayeda and walter 1996 mayeda et al 2003 is a very stable way to obtain source spectra from sparse networks using as few as one station even if direct waves are clipped we develop a two step process to isolate the frequency dependent q first we correct the observed direct wave amplitudes for an assumed geometrical spreading next an apparent q combining path and site attenuation is determined from the difference between the spreading corrected amplitude and the independently determined source spectra derived from the coda methodology we apply the technique to 50 earthquakes with magnitudes greater than 4 0 in central italy as recorded by mednet broadband stations around the mediterranean at local to regional distances this is an ideal test region due to its high attenuation complex propagation and availability of many moderate sized earthquakes we find that a power law attenuation of the form q f q sub 0 f sup y fit all the phases quite well over the 0 5 to 8 hz band at most stations the measured apparent q values are quite repeatable frommore event to event finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques this is important if coda and direct wave amplitudes are to produce consistent seismic results less

the importance of sea level and climate change including changing wind energy on the evolution of a coastal estuary copano bay texas abstract 123 km of high resolution 2 d seismic lines and 6 sediment cores up to 16 m in length were collected from copano bay texas these data were used to examine the role of climate and sea level changes in the evolution of the bay paleogeographic maps of the bay were constructed to show how the bay evolved through time the overall transgression was punctuated by five environmental changes within copano bay over the past 9 6 ky the largest environmental change occurred at 8 2 ka when the bay head delta back stepped approximately 7 5 km as a result of a 0 4 1 2 m rapid rise in sea level with a well constrained model of how the bay changed through time textural data from the most continuous record of middle bay deposits was used to produce a proxy for wind strength over the last 8 2 ky our wind strength proxy reveals that copano bay experienced relatively tranquil winds during the early holocene followed by its windiest conditions from 5 2 to 4 1 ka and a return to more tranquil winds during the late holocene the wind strength proxy was compared with other published paleo climatic records for the region and a reasonable correlation was found between periods of higher wind energy and drier climate this study illustrates that despite their complex depositional systems and many sediment and water sources a system wide approach to studying an estuary can still be used to extract paleoclimate archives from estuarine deposits

stratigraphy and holocene evolution of a regressive barrier in south brazil abstract the paranagua coastal plain is a 600 km 2 barrier system located in south brazil 25 30 s and is largely made up of pleistocene and holocene beach ridges sea level history in the area is characterized by a gradual 3 5 m sea level fall in the last 5000 years several reverse circulation drill logs from the pleistocene and holocene sectors allowed for the definition of a general morphostratigraphic model of the coastal plain which proposes the staking of at least two generations of marine deposits upon continental and paleo estuarine sediments analysis of shallow vibro cores and exposures along back barrier creeks indicates the existence of four transgressive estuarine estuarine channel overwash and flood tidal delta and three regressive beachface nearshore and upper shoreface sedimentary facies in the holocene section of the coastal plain the morphostratigraphy suggests that barrier emplacement took place at the last stages of the post glacial marine transgression when the back barrier estuary was squeezed in between the pleistocene and holocene barriers holocene barrier progradation was significant in both the shore normal and longshore direction and was apparently very swift in the last thousand years corresponding to a period when sea level fell by 1 5 m and when about half of the present barrier volume was accumulated higher progradation rates are ascribed to the arrival of sediment yielded by an active littoral drift system which appears to have eroded large extents of several holocene barriers along 100 km of coastline

bedrock controls on barrier island development west central florida coast abstract fifty vibracores and 130 km of high resolution seismic profiles were taken in the lagoons and nearshore area of northern pinellas county florida to determine the role of antecedent topography upon barrier island location origin and development east west seismic profiles show a terrace with 1 1 5 m of relief located along the seaward trend of the barrier islands between 4 and 6 m msl this antecedent topography is composed of a relatively erosion resistant miocene limestone and the terrace is usually present as an increase in slope a contour map of the pre holocene surface shows that this subsurface feature is continuous along the entire study area and is mimicked by the opposing orientations of honeymoon and caladesi islands the correspondence of the modern barrier system to the antecedent topography indicates that 1 the islands formed on the terrace or that 2 landward migration of the barriers was stopped by grounding on this feature stratigraphic analyses of lagoonal and nearshore environments were conducted in order to establish the overall response of the northern pinellas coastal system to the late holocene sea level rise this analysis indicates a basically transgressive holocene sequence with lagoonal sediments occurring seaward of the islands underlying the lagoonal deposits in all areas is a 1 m thick relict pleistocene unit that has been flooded reworked and vegetated by intertidal to subtidal organisms a model of development for these barriers is proposed which incorporates an early transgressive history followed by a recent progradational phase the progradational phase was probably initiated by the late holocene slowdown in sea level rise and an increased sediment supply as the barrier islands migrated over a relict sediment source the antecedent topography thus served as a stabilization point for landward barrier migration and seaward progradation the antecedent topographic control of barrier island location described by this model is dependent upon the coincident decline in the rate of sea level rise and an increased sediment supply

complex patterns of fluid and melt transport in the central andean subduction zone revealed by attenuation tomography abstract we present a high resolution 3 d model of p wave attenuation q p 1 for the central andean subduction zone data from 1500 mostly intermediate depth 60 250 km earthquakes recorded at three temporary seismic networks covering the forearc arc and backarc around 23 s were used for tomographic inversion the forearc is characterised by uniformly high q p values indicating low temperature rocks in accordance with low surface heat flow values prominent low q p anomalies are found beneath the magmatic arc and the backarc in the crust and mantle continuous regions of low q p connect earthquake clusters at 100 km and 200 km depth with zones of active volcanism in the arc and backarc fluids fluxed from the subducted oceanic lithosphere into the overlying mantle wedge where they induce melting explain our observations we propose that low q p regions indicate source and ascent pathways of metamorphic fluids and partial melts ascent of fluids and melts as imaged by seismic q p are not vertical as is often implicitely assumed instead sources of fluids are located at different depth levels and ascent paths are complex and exhibit significant variation within the study area the largest quaternary backarc volcano cerro tuzgle is fed by mantle melts which are imaged as a plume of low q p material that reaches to the strong earthquake cluster at 200 km depth