depositional and sea level history from mis 6 termination ii to mis 3 on the southern continental shelf of south africa abstract pleistocene shoreline deposits comprised of calcified shallow marine palaeobeach and aeolian palaeodune facies found along mid latitude coastlines can be useful indicators of past sea levels here we describe a succession of such deposits that are presently exposed both above subaerial and below submerged mean sea level along the southern cape coast of south africa 18 km east of the town of mossel bay the submerged units provide a window on late pleistocene coastal processes as palaeoshoreline deposits in this study extend to water depths of up to 55 m on the mid shelf five sedimentary facies were identified in the strata and were compared to modern depositional environments of the local littoral zone which include aeolian dune upper shoreface foreshore intertidal swash and back barrier settings twenty two geological units were observed and mapped some of these units were directly dated with optically stimulated luminescence osl dating osl ages were obtained for ten samples from the subaerial and twelve samples from the submerged deposits those geological units not directly dated were interpreted based on sedimentology and field stratigraphic relationships to dated units the stratigraphy and chronology of the succession indicates a record of initial deposition during termination ii t ii meltwater events preceding and leading to marine isotope stage mis 5e indicators for multiple sea level fluctuations between mis 5d and mis 4 and sediment deposition at the end of mis 4 and start of mis 3 are also found both regressive and transgressive depositional cycles are well preserved in the succession we propose that palaeodune and palaeobeach deposits along the south coast of south africa have no clear preference for deposition during sea level transgressions or regressions sediment deposition more closely mirrors the rate of sea level change with deposition and preservation either during times of rapid sea level movement or oscillation around still stand events periods of relatively slow average rise or fall of sea level are represented by erosional planation surfaces in this record

migration of pleistocene shorelines across the palaeo agulhas plain evidence from dated sub bottom profiles and archaeological shellfish assemblages abstract intertidal zones on shorelines are geologically complex features of the coastal plain shaped by heterogeneous substrate lithologies palaeocoastlines have been heavily modified by sea level change ocean currents wind waves and swell rocks and sediments along intertidal zones create rich habitats for biogenic forms including shellfish which are highly sensitive to subtle variations in underlying lithology here we assess pleistocene shoreline migrations on the south coast of south africa in relation to fluctuating sea levels and changes in sediment supply the study area extends from still bay to mossel bay south africa with a particular focus on pinnacle point our goal is to better understand the changes to the intertidal zone along these palaeocoastlines and how this may have affected marine resources available to early humans we interpret marine geological records at select time slices along sub bottom profiled transects that run perpendicular to the coast we describe the character of specific shorelines to establish expectations of coastline character which we then compare to archaeological records at pinnacle point we base our interpretations on 1 significant events in pleistocene glacio eustatic and depositional records such as widespread deposition of coastal sand dunes at 90 74 and 50 ka mis 5e mis 4 and 2 empirical evidence from high resolution records of shellfish assemblages at the archaeological sites of pp13b and pp5 6 we demonstrate a prevalence of dissipative beaches and mixed coasts on pleistocene sea level lowstands on the coast of the palaeo agulhas plain this differs significantly from the modern coastline with its significance of rocky shorelines

sensitivity of post hurricane beach and dune recovery to event frequency the recovery of santa rosa island in northwest florida is characterized following hurricane katrina september 2005 which was preceded by hurricanes ivan 2004 and dennis 2005 beach and dune recovery were quantified to the east and west of pensacola beach through a comparison of lidar data collected immediately following hurricane katrina and in july 2006 after almost a year of recovery east of pensacola beach the santa rosa unit the shoreline retreated by an average of 64 m during the 2004 2005 hurricane season and recovered by an average of 19 m to the west of pensacola beach the fort pickens unit the shoreline retreated by an average of 30 m and while no significant shoreface recovery was observed the presence of vegetation on low profile dunes promoted backshore accretion it is found that beachface recovery in the santa rosa unit and backshore accretion in the fort pickens unit occurred at the widest sections of the island where the pre storm profile volume had been relatively large and overwash penetration was at a minimum the narrow sections of the island between cuspate headlands had a smaller profile volume before the storms leading to greater overwash penetration and in some cases island breaching in both sections which limited the volume of sediment available for shoreface recovery the alongshore variation in recovery is not only related to the island width but also the offshore bathymetry height of the pre storm dunes and the overwash penetration if sufficient time is allowed for the return of vegetation and the recovery of the dunes the variations in storm impact observed during hurricane ivan will be reinforced during subsequent storms in this respect the level of impact during subsequent storms and the ability of the island to recover will depend on the frequency of storm events copyright 2009 john wiley sons ltd

coastal dynamics under conditions of rapid sea level rise late pleistocene to early holocene evolution of barrier lagoon systems on the northern adriatic shelf italy this multidisciplinary case study of two preserved barrier systems combined the analysis of radiocarbon datings grain size distributions high resolution seismics and shelf bathymetry with reconstructions of palaeo environmental conditions tides waves sea level change and forward modelling of barrier lagoon systems to provide an integrated view of the coastal transgressive evolution of a large sector of the northern adriatic shelf between 15 and 8 ka bp palaeoenvironmental reconstructions point to increased tidal amplitude low energy wave climate and high rates of sea level rise up to 60 mm a during the formation of the oldest preserved barrier system not vert similar90 m water depth 14 3 cal ka bp a younger barrier system 42 m water depth 10 5 cal ka bp formed under conditions of lower tidal amplitude higher wave energy and a lower rate of sealevel rise 10 mm a forward modelling suggests that the probability of barrier island overstepping during transgression is inversely proportional to tidal amplitude if all other factors are assumed equal the oldest barrier lagoon system developed under conditions of large tidal amplitude which permitted rapid transgression however this system apparently failed to keep up with the anomalously high rate of sea level rise resulting from melt water pulse 1a the youngest barrier system appears to have drowned in place due to antecedent topography as the barrier system transgressed over an ancient pleistocene alluvial plain the rapid increase in backbarrier accommodation caused an abrupt disequilibrium between shoreface and backbarrier sedimentation which led to barrier overstepping although barsim modelling indicates that tidal deposition can reduce the probability of barrier overstepping there are other driving mechanisms in our case extremely rapid sea level rise and antecedent topography which are more determinative in explaining the transgressive coastal evolution of barrier lagoon systems in the northern adriatic sea grain size analysis of shoreface deposits sampled above the transgressive ravinement surface across the northern adriatic shelf indicate a distinct relation between the sediment grain size and the rate of sea level rise during deposition which implies that progressive sorting must have been highly effective

the chronological sedimentary and environmental context for the archaeological deposits at blombos cave south africa abstract the site of blombos cave bbc is well known for archaeological remains that have advanced our understanding of the development of modern human behaviour during the middle stone age msa occupation of the cave occurred against a backdrop of landscape scale environmental and sedimentary processes that provide the broader context for finer scale interpretations of the site formation history and archaeological patterns detected in the cave deposits aeolian and palaeosol sequences are abundant in the vicinity of bbc and these provide a partial view of the past landscapes available to the inhabitants of the cave an important extension to the palaeo landscape around bbc currently lies submerged on the agulhas bank as sea levels were lower than at present for the entire period of human occupation of bbc in this paper we revisit the optically stimulated luminescence osl chronology for the full sequence of sediment deposition inside bbc increasing the number of dated samples to a total of 40 and revising the period of msa occupation to between 97 7 7 6 and 71 0 5 7 ka uncertainties at 95 4 probability we describe the geological successions at four main areas around bbc estimate the time of sediment deposition using osl and describe and interpret three seismic profiles on the agulhas bank offshore of bbc by correlating these onshore and offshore geological sequences with the sedimentary deposits inside bbc we place the archaeological record within a landscape scale chrono stratigraphic framework to examine how environmental changes may have regulated the presence or absence of humans in the cave and surrounding terrain between about 100 and 70 ka

tracking the last sea level cycle seafloor morphology and shallow stratigraphy of the latest quaternary new jersey middle continental shelf seafloor geomorphology and surficial stratigraphy of the new jersey middle continental shelf provide a detailed record of sea level change during the last advance and retreat of the laurentide ice sheet 120 kyr b p to present a nw se oriented corridor on the middle shelf between water depths of 40 m the mid shelf paleo shore and 100 m the franklin paleo shore encompasses 500 line km of 2d huntec boomer profiles 500 3500 hz an embedded 4 6 km2 3d volume and a 490 km2 swath bathymetry map we use these data to develop a relative stratigraphy core samples from published studies also provide some chronological and sedimentological constraints on the upper 5 m of the stratigraphic succession the following stratigraphic units and surfaces occur from bottom to top 1 r a high amplitude reflection that separates sediment 46 5 kyr old by ams 14c dating from overlying sediment wedges 2 the outer shelf wedge a marine unit up to 50 m thick that onlaps r 3 channels a reflection sub parallel to the seafloor that incises r and appears as a dendritic system of channels in map view 4 channels fill the upper portion of which is sampled and known to represent deepening upward marine sediments 12 3 kyr in age 5 the t horizon a seismically discontinuous surface that caps channels fill 6 oblique ridge deposits coarse grained shelly units comprised of km scale shallow shelf bedforms and 7 ribbon floored swales bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits we interpret this succession of features in light of a global eustatic sea level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr the morphology of the new jersey middle shelf shows a discrete sequence of stratigraphic elements and reflects the pulsed episodicity of the last sea level cycle r is a complicated marine non marine erosional surface formed during the last regression while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum wisconsin lowstand i e marine oxygen isotope stage 3 1 channels is a widespread fluvial subarial erosion surface formed at the late wisconsin glacial maximum 22 kyr b p the shoreline migrated back across the mid shelf corridor non uniformly during the period represented by channels fill oblique ridges are relict features on the new jersey middle shelf while the ribbon floored swales represent modern shelf erosion there is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

understanding late quaternary change at the land ocean interface a synthesis of the evolution of the wilderness coastline south africa coastal barrier systems have been widely used to understand the responses of coastal margins to fluctuating pleistocene sea levels what has become apparent particularly with the development of robust chronological frameworks is that gaps in terrestrial barrier sedimentary records are not uncommon and that they most likely reflect phases of barrier construction on the now submerged continental shelf thus understanding the land ocean interface through time is critical to fully appreciate the quaternary archives contained within the barriers and their associated back barrier deposits this study uses offshore and lakefloor back barrier seismic profiling from the south african south coast at wilderness to link the sub aerially exposed barrier stratigraphy to the currently submerged geological and sedimentological record a total of eight separate submerged aeolian units are identified at water depths of up to 130 m below mean sea level their approximate ages are constrained with reference to the eustatic sea level record and the deepest units are consistent with the estimated magnitude of sea level lowering during the last glacial maximum lgm on the south african coastline as previously assumed aeolian sedimentation tracked the shoreline onto the continental shelf during the late pleistocene during sea level regressions both the incision of fluvial channels and the deposition of back barrier systems occurred across the continental shelf during late low stand early transgression periods landward shoreface migration occurred pre existing channel incisions were infilled and pre existing barriers were truncated rapid transgression however allowed the preservation of some back barrier deposits possibly aided by protection from antecedent topography as sea level neared the present day elevation erosion of the mid shelf sediments resulted in the development of a holocene sediment wedge which was augmented by holocene fluvial sediment supply the holocene sand wedge is preserved in the back barrier lakes and was deposited during the holocene highstand inundation overlying middle to late holocene terrestrial muds reflect the deposition of river borne mud onto the shelf these results clearly demonstrate that within transgressive regressive sea level cycles accommodation space for barriers is controlled by antecedent drainage systems and gradients on the adjacent inner continental shelf

hurricane induced beach change derived from airborne laser measurements near panama city florida this study used airborne laser data to investigate spatial variations in shoreline migration beach width subaerial volume and subaqueous volume change due to a hurricane event five separate airborne laser data sets of panama city fl area beaches were collected during a seven month period before and after landfall of hurricane ivan contour shorelines were extracted from digital elevation models interpolated from these laser measurements and were used to measure changes in shoreline position and beach width the shoreline migrated 16 m landward due to hurricane ivan and migrated 10 m seaward following hurricane ivan no significant spatial relationship was found between shoreline migration before and after the hurricane linear relationships between a time series of beach width and subaerial volume were found at many locations however utilization of a single coefficient to represent all relationships is problematic due to the spatial variability in the linear relationship differences in two bathymetric data sets for summer and fall show that only a small portion of sediments were transported beyond an active zone and most sediments remain within the active zone despite the occurrence of a hurricane

palaeo drainage incised valley fills and transgressive systems tract sedimentation of the northern kwazulu natal continental shelf south africa sw indian ocean abstract two sequence boundaries are recognised in seismic data collected from the narrow northern kwazulu natal continental shelf these correspond to late cretaceous and latest pleistocene last glacial maximum lgm periods of sea level fall where fluvial incision into the shelf resulted in several incised valleys having formed in both examples the ensuing transgressive valley fills document an evolution from fluvially dominant sedimentation to classic backbarrier estuarine conditions central estuary basin sedimentation is most prominent within each fill and is separated from the underlying fluvial sediments by bayline ravinement processes tidal ravinement surfaces separate the upper estuarine sequences from barrier and shoreface deposition most easily observed in the latest pleistocene holocene valley fills where a holocene unconsolidated sediment wedge overlies the estuarine fill the wedge itself is characterised by two packages of sediment separated by a regionally occurring wave shoreface transgressive ravinement surface which crops out as a semi indurated shell hash in the mid to outer shelf late cretaceous examples are capped by deposits exhibiting oblique parallel to wavy reflectors interpreted as increasingly energetic deposits analogous to flood tide deltaic sedimentation valley incision and fill are linked to two onshore coastal lake systems lake sibaya and lake st lucia and appear to be the product of barrier breaching and fluvial re adjustment to baseline shifting of these systems during forced regression lake st lucia exhibits a composite palaeo drainage channel where both sequence boundaries merge within the lake margins lake sibaya has two distinct palaeo channels for each sequence boundary episode a late cretaceous channel which fed a small incised valley within which a modern day submarine canyon is located the other an lgm channel directed in towards the head of wright canyon the subsequent input of sediment causing this canyon to breach furthest into the shelf than any other canyon in the area offshore of lake st lucia the most proximal portions of the associated leven canyon occupy the mid shelf and are underlain by lake st lucia palaeo drainage channels of lgm age where erosion along the initial lgm palaeo channel has occurred freshwater exchange between the shelf and the fringing lake system has resulted in the development of sinuous features of leven canyon which have eroded in a downslope fluvial like manner thus occupying palaeo drainage lows as erosive flows were entrained models proposed here indicate that 1 the limited accommodation space offered by a narrow continental shelf may allow for a greater preservation potential of wave dominated estuarine facies 2 the seismic expression of these fills may vary yet still satisfy similar sedimentological conditions and 3 antecedent valley topography increases the preservation potential of these valley fills by providing a preferred space in which to re incise and then fill during sea level rise

the importance of extratropical and tropical cyclones on the short term evolution of barrier islands along the northern gulf of mexico usa abstract data are presented indicating the complexity and highly variable response of beaches to cold front passages along the northern gulf of mexico in addition to the impacts of tropical cyclones and winter storms within the past decade an increase in the frequency of tropical storms and hurricanes impacting the northern gulf has dramatically altered the long term equilibrium of a large portion of this coast a time series of net sediment flux for subaerial and nearshore environments has been established for a section of this coast in florida and to a lesser extent mississippi the data incorporate the morphological signature of six tropical storms hurricanes and more than 200 frontal passages data indicate that 1 barrier islands can conserve mass during catastrophic hurricanes e g hurricane opal a strong category 4 hurricane near landfall 2 less severe hurricanes and tropical storms can promote rapid dune aggradation and can contribute sediment to the entire barrier system 3 cold fronts play a critical role in the poststorm adjustment of the barrier by deflating the subaerial portion of the overwash terrace and eroding its marginal lobe along the bayside beach through locally generated high frequency steep waves and 4 barrier systems along the northern gulf do not necessarily enter an immediate poststorm recovery phase although nested in sediment rich nearshore environments while high wave energy conditions associated with cold fronts play an integral role in the evolution and maintenance of barriers along the northern gulf these events are more effective in reworking sediment after the occurrence of extreme events such as hurricanes this relationship is even more apparent during the clustering of tropical cyclones it is anticipated that these findings will have important implications for the longer term evolution of barrier systems in midlatitude microtidal settings where the clustering of storms is apparent and winter storms are significant in intensity and frequency along the coast

seismic stratigraphy of the inner to mid agulhas bank south africa abstract the inner to mid continental shelf of the agulhas bank which forms part of the palaeo agulhas plain is scattered with pleistocene deposits their wide lateral extension is the expression of a flat underlying substrate availability of accommodation space and depositional processes in response to glacio eustatic sea level change we present seismic sub bottom profiles up to 30 m deep sediment cores up to 5 m in length and pleistocene deposits that date back to marine isotope stage mis 7 from the inner to mid shelf between the breede river in the west and plettenberg bay in the east radiocarbon and optically stimulated luminescence dates are integrated with microfossil analysis into a seismic stratigraphic model comprised of twenty quaternary facies units within two depositional sequences bounded by shelf wide unconformities sequence boundary 1 sb1 corresponds to the erosional unconformity with bedrock and sb2 to the mis 2 glacial lowstand incised palaeo river channels are associated with both sequence boundaries and cored deposits also mapped seismically from estuarine lacustrine and fluvial systems are grouped to represent the lower floodplain the most pervasive stratigraphic pattern in these shelf deposits is made up of the depositional sequence remnant of the falling stage systems tract fsst forced regression from mis 5e 2 the other dominant stratigraphic group is the transgressive systems tract tst associated with the post glacial marine transgression the tst makes up an almost equal proportion of deposits in both sequences in the sedimentological record as the fsst despite the shorter temporal span of the tst a wave ravinement surface marks the rise in sea level from the last glacial maximum in a landward direction

coupled climate and sea level changes deduced from huon peninsula coral terraces of the last ice age abstract huon peninsula papua new guinea is a tectonically unstable uplifting shoreline ringed by emergent coral terraces the terraces were formed during episodes of rapid sea level rise when corals constructed large discrete coral platforms that were subsequently uplifted uranium series ages of four prominent huon peninsula last glacial ois 3 coral terraces coincide with the timing of major north atlantic climate reversals at intervals of 6000 7000 yr between 30 000 yr and 60 000 yr ago terrace elevations when combined with uplift indicate 10 15 m high sea level excursions at these times we attribute the growth of the terraces directly to sea level rises arising from ice calving episodes from major north atlantic ice sheets and the antarctic ice sheet that precipitated extremes of cold climate called heinrich events these periods are associated with major discharges of land based ice and enhanced concentrations of ice rafted debris in deep sea cores sea levels at this time were 60 90 m lower than present

sedimentary deposits on the southern south african continental margin slumping versus non deposition or erosion by oceanic currents seismic profiles extending from the southern south african shelf into the deep sea reveal a strong erosional activity which affects large parts of the continental margin quaternary to oligocene units and in places the complete sedimentary column appear to have been removed mass movements were previously considered as the origin of this erosion however structures indicating slumping can be identified in only a few places the erosional activity is confined to specific water depths which correlate well with the activity levels of water masses observed here we thus suggest that the agulhas current antarctic intermediate water north atlantic deep water and antarctic bottom water have intensively shaped the sedimentary units over a long period this indicates a stable circulation comparable to that at present day since the neogene

coastal palaeoenvironments and hunter gatherer plant use at waterfall bluff rock shelter in mpondoland south africa from mis 3 to the early holocene abstract waterfall bluff in eastern mpondoland eastern cape province south africa is a recently excavated archaeological site with deposits spanning marine isotope stage mis 3 to the middle holocene here we present preliminary results of a multi proxy palaeoenvironmental study combining macro botanical remains charcoal phytoliths pollen and plant waxes derived from the same archaeological record we aim to understand the interactions between hunter gatherer plant foraging and climate and environmental change in coastal mpondoland from mis 3 to the early holocene at waterfall bluff the charcoal and pollen records at waterfall bluff show the gathering of a variety of woody taxa characterised by their combustion and medicinal properties e g millettia grandis and apodytes dimidiate the leaves identified in the macrobotanics and in the phytolith record might belong to some of these taxa and it is likely that they were used for medicinal purposes from a palaeoenvironmental perspective our results indicate low precipitation and low rainfall seasonality under cool conditions during mis 3 and the last glacial maximum lgm under these conditions open woodlands interspersed with dry and hygrophilous grasslands and bushveld vegetation with significant representation of fynbos elements occurred in the local landscapes probably along podocarpus afrocarpus forests the latter could have been 1 present along river valleys and scarps on the mpondoland exposed continental shelf towards the south and west of waterfall bluff supported by palaeo rivers and cool temperatures favouring low evapotranspiration or 2 present in the interior with pollen grains possibly transported to the site by intensified westerly winds these forests contracted as a result of the post glacial marine transgression or reduced westerlies following the lgm during the early holocene the palaeoenvironmental signal points to higher summer rainfall and higher summer seasonality than during mis 3 the lgm and the lgit these changes are coeval with an increase of coastal forests and c4 mesic grasslands with localized wetland vegetation around waterfall bluff these multi proxy archaeobotanical and biochemical data show that landscapes surrounding waterfall bluff changed in relation to marine transgressions regressions and changes in rainfall intensity and seasonality the people of waterfall bluff foraged the coasts during glacial periods to collect wood

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

controls on coastal dune morphology shoreline erosion and barrier island response to extreme storms abstract the response of a barrier island to an extreme storm depends in part on the surge elevation relative to the height and extent of the foredunes which can exhibit considerable variability alongshore while it is recognized that alongshore variations in dune height and width direct barrier island response to storm surge the underlying causes of the alongshore variation remain poorly understood this study examines the alongshore variation in dune morphology along a 11 km stretch of santa rosa island in northwest florida and relates the variation in morphology to the response of the island during hurricane ivan and historic and storm related rates of shoreline erosion the morphology of the foredune and backbarrier dunes was characterized before and after hurricane ivan using empirical orthogonal function eof analysis and related through canonical correlation analysis cca the height and extent of the foredune and the presence and relative location of the backbarrier dunes varied alongshore at discrete length scales of 750 1450 and 4550 m that are statistically significant at the 95 confidence level cospectral analysis suggests that the variation in dune morphology is correlated with transverse ridges on the inner shelf the backbarrier cuspate headlands and the historical and storm related trends in shoreline change sections of the coast with little to no dune development before hurricane ivan were observed in the narrowest portions of the island between headlands west of the transverse ridges overwash penetration tended to be larger in these areas and island breaching was common leaving the surface close to the watertable and covered by a lag of shell and gravel in contrast large foredunes and the backbarrier dunes were observed at the widest sections of the island the cuspate headlands and at crest of the transverse ridges due to the large dunes and the presence of the backbarrier dunes these areas experienced less overwash penetration and most of the sediment from the beachface and dunes was deposited within the upper shoreface it is argued that this sediment is returned to the beachface through nearshore bar migration following the storm and that the areas with larger foredunes and backbarrier dunes have smaller rates of historical shoreline erosion compared to areas with smaller dunes and greater transfer of sediment to the washover terrace since the recovery of the dunes will vary depending on the availability of sediment from the washover and beachface it is further argued that the alongshore pattern of dune morphology and the response of the island to the next extreme storm is forced by the transverse ridges and island width through alongshore variations in storm surge and overwash gradients respectively these findings may be particularly important for coastal managers involved in the repair and rebuilding of coastal infrastructure that was damaged or destroyed during hurricane ivan

melting ice sheets 400 000 yr ago raised sea level by 13 m past analogue for future trends abstract marine isotope stage mis 11 was possibly the longest 423 000 362 000 yr ago and warmest interglacial of the entire quaternary period this resulted from a special arrangement of earth s orbital parameters similar to the present interglacial mis 1 suggesting that mis 11 provides an analogue for future natural climate forcing and sea levels although precise documentation of mis 11 sea level history is therefore crucial especially considering additional impetus from anthropogenic warming the maximum mis 11 sea level remains highly contentious estimates from onshore indicators have ranged from below present sea level to about 20 m resulting from uncertainties in reliability of sea level indicators estimates of their subsequent displacement by vertical crustal motion and in dating we used a clear and unambiguous sea level indicator interface between subtidal and intertidal deposits in well exposed regressive raised shoreline deposits along south africa s southern coast the coast is stable in terms of tectonic setting and falls within a zone of low predicted glacio isostatic adjustment gia and low sensitivity for plausible model parameters the sea level indicators were directly dated using thermally transferred optically stimulated luminescence tt osl which gave a mean age of 390 ka corresponding with mis 11 we determined a precise maximum elevation of 14 m for the mis 11 sea level indicator which corrected for minor crustal uplift and gia yielded a eustatic sea level of 13 m 2 m the complete mis 11 transgressive regressive shoreline succession is preserved and the wave cut platform extends 950 m inland from the present shoreline indicating a prolonged highstand we have also documented sea level fluctuations during mis 11 including an earlier lower highstand close to present sea level which may explain the lower elevation range of some previous estimates at one locality mis 11 deposits form a sea cliff against which mis 5e sediments at an elevation of 6 2 m abut the 13 m mis 11 sea level tallies with total melting of the greenland and west antarctica ice sheets regarded as most susceptible to melting our data predict notably higher sea levels in the future regardless of anthropogenic influence on climate

the last interglacial sea level high stand on the southern cape coastline of south africa abstract the continental margin of southern south africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long term eustatic sea level changes we report a suite of optical luminescence ages and supplementary amino acid racemization data which provide paleosea level index points for three sites on this coastline deposits in the swartvlei and groot brak estuaries display tidal inlet facies overlain by shoreface or eolian facies contemporary facies relations suggest a probable high stand 6 0 8 5 m above modern sea level amsl at cape agulhas evidence of a past sea level high stand comprises a gravel beach ca 3 8 m amsl and an overlying sandy shoreface facies up to 7 5 m amsl osl ages between 138 7 ka and 118 7 ka confirm a last interglacial age for all marginal marine facies the high stand was followed by a sea level regression that was associated with the accumulation of eolian dunes dating to between 122 7 ka and 113 6 ka these data provide the first rigorous numerical age constraints for last interglacial sea level fluctuations in this region revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far field locations

aeolianite and barrier dune construction spanning the last two glacial interglacial cycles from the southern cape coast south africa the southern cape region of south africa has extensive coastal aeolianites and barrier dunes whilst previously reported limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea level fluctuations that have taken place during the late quaternary sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial interglacial cycles aeolianite deposition has occurred on the southern cape coast at ca 67 80 88 90 104 128 160 189 and 200 ka before the present using this and other published data coupled with a better understanding of late quaternary sea level fluctuations and palaeocoastline configurations it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea level high stands these marine transgressions and regressions allowed onshore carbonate rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions the lack of carbonates in more recent dunes oxygen isotope stages 1 2 and 4 5 is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and or changes in the balance between the warm agulhas and nutrient rich benguela ocean currents

west coast dune plumes climate driven contrasts in dunefield morphogenesis along the western and southern south african coasts abstract this study examines two major late quaternary coastal dune systems situated in the southwestern most extremity of africa the false bay and duinefontyn dune plumes formed in close proximity but under contrasting oceanographic regimes warm agulhas and cold benguela oceanic current systems respectively the false bay and duinefontyn dune plumes have hitherto lacked the objective numerical chronology required to realize their full potential in unraveling the complex palaeo oceanographic and palaeoclimatic history of the region here we present a dual amino acid racemizationn aar and optically stimulated luminescence osl chronological framework from the extensive three dimensional exposures in sea cliffs at false bay three generations of dune deposition corresponding with orbitally forced climatic sea level cycles mis 7 mis 5 and holocene were resolved whereas the duinefontyn plume is dominated by mis 5 and holocene sedimentation at false bay and duinefontyn glacial periods are marked by the development of mature palaeosols confirming the link between glacio eustacy and dune deposition determined previously on the west and southern coasts of south africa along the west coast dune plumes typify dunefield morphology whereas shoreline parallel dune cordons are commonly developed on the southern coast these regional variations in dune system morphogenesis are largely controlled by contrasting wind and rainfall patterns the attenuated dimensions of the mis 5 plumes at false bay and duinefontyn may indicate a weakening of the south atlantic anticyclone during the last interglacial at false bay stone artifacts illustrate a human presence in the region during mis 7

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

relationship between beach profiles and waves at duck north carolina determined by canonical correlation analysis abstract an 11 year long measurement time series of waves and profiles from duck north carolina was analyzed using canonical correlation analysis cca in order to determine the covariability between waves and profile response the main objectives of this analysis were 1 to detect simultaneously occurring patterns in the wave and profile data and if possible give such patterns a physical interpretation to increase the insight into the governing processes and 2 to investigate the possibility to use cca in a predictive mode with the aim to calculate the profile response from the waves the profile shape itself and the change between consecutively surveyed profiles were correlated with both the offshore deep water and nearshore wave conditions in the offshore the waves were described by composite probability density functions pdf derived based on the measured wave conditions prior to a profile survey nearshore wave conditions were calculated using a random breaker decay model and averaged local wave properties were used as input to the cca the profile response displayed significantly higher correlation with the nearshore wave properties as compared to the offshore waves and the highest correlation was found between the profile shape and the mean ratio of breaking waves for the time period preceding the profile survey the cca using nearshore wave properties indicates a potential for predicting the profile response with an acceptable degree of accuracy once a regression matrix relating the profiles to the waves has been established that represents the typical variability at the site

hydrodynamics and sediment transport within the inner surf zone of a lacustrine multiple barred nearshore abstract it has become increasingly recognized that the typically unexpected behavior of the nearshore profile over a sequence of storm events is a response to strong feedback between the antecedent morphology and the incident wave field this paper systematically examines the suspended sediment transport and morphodynamics within the surf zone of a lacustrine multiple barred upper shoreface a range of significant wave heights h s and local relative wave heights h s h 1 h water depth are considered in order to describe and identify the limits to the feedback mechanisms that can dominate the nearshore response data from collocated concentration and velocity sensors indicate that the direction and magnitude of suspended sediment transport varies with the degree of local wave energy dissipation and the cross shore variation in these relationships depends partly on the local bed slope this dependence indicates the presence of a strong self organization at the scale of the individual bar within the inner surf zone these bar scale relationships are constrained by the shoaling transformations which occur over the outermost bar for ranges of incident wave height defined locally e g intermediate waves h s 0 4 to 0 9 m storm waves 0 9 to 1 4 m the innermost and middle bars remain in a state of self organized equilibrium for intermediate range waves this equilibrium is a consequence of wave height reduction over the outer bar through breaking and the generation of secondary harmonic waves for the storm wave range the equilibrium is maintained through a resonant amplification of discrete edge wave modes with the bars forced to a position coincident with the surface elevation antinodes these upper shoreface scale feedback mechanisms are weakened particularly for intermediate wave heights following threshold storms capable of moving the outermost bar offshore and lower on the profile this allows the middle and inner bars to be forced directly by variations in the offshore incident waves thus the bars respond in a cyclic manner the bar cycle

chronology of quaternary coastal aeolianite deposition and the drowned shorelines of southwestern western australia a reappraisal abstract aeolianite successions of low gradient continental margins commonly show complex records of coastal dune deposition linked to a wide range of sea level positions and climatic periods of the middle and late pleistocene recording both regional and broader scale drivers of sediment production coastal dune development and landform preservation to better characterise the general pattern of sedimentation that occurs over quaternary glacial interglacial cycles on low gradient temperate carbonate continental shelves we examine the morphology stratigraphy and age of aeolianite deposits in the perth region western australia this includes an analysis of well defined drowned coastal landforms preserved on the adjacent shelf new and previously published optical ages provide a preliminary timeframe for the deposition of aeolianite in the perth region and on rottnest island 17 km offshore an extensive aeolianite ridge near perth representing a former barrier has optically stimulated luminesence osl ages that range from 120 12 to 103 10 ka mis 5e 5a in the context of associated age uncertainties osl ages for an exposure in the same ridge 2 5 km inland record the onlap of much older aeolianite osl age 415 70 ka by shell rich estuarine beds osl age 290 30 ka a further 5 5 km inland from the coast two thick aeolianite units separated by a well developed palaeosol have stratigraphically consistent osl ages of 310 30 and 155 20 ka in contrast aeolianite units that form the northern coast of rottnest island have osl ages of 77 12 ka and 27 5 ka the new osl ages and previously reported tl and u th ages indicate that the bulk of the island comprises dunes deposited around the end of the last interglacial sensu lato mis 5a 4 and during the last glacial mis 4 2 accumulating over a last interglacial coral reef and basal calcarenite drowned barrier and dune landforms preserved on the adjacent continental shelf reveal that barriers were formed during periods of intermediate sea level e g mis 3 and significant dune mobility occurred when the shelf was subaerially exposed the pattern of shelf sedimentation discernible in the perth region large scale coastal carbonate dune deposition during periods of high and intermediate sea level and reactivation during glacial lowstands is largely consistent with published stratigraphic and age data for large scale aeolianite deposits on other low gradient carbonate shelves based on these data a general model is proposed for the cycle of quaternary sedimentation and landform evolution that occurs on these shelves which are dynamic sedimentary environments with coastal landforms and sedimentary successions that are very sensitive to erosion and sediment reworking

geological and soil maps of the palaeo agulhas plain for the last glacial maximum abstract the south african cape south coast is bordered by one of the broadest continental shelves in africa the agulhas bank inshore shelf and presently exposed coastal plain make up the palaeo agulhas plain pap though our area of study extends beyond this limit and as far inland as the first mountain belt quaternary sea levels have been significantly lower than at present for 90 of the pleistocene exposing a terrestrial ecosystem on what is now the submerged shelf the presently drowned component makes up 94 of the total area of the pap past work has hypothesised a contrast in character of this submerged landscape when compared to the subaerial environment here we assimilate newly acquired geophysical and geological datasets to produce geological and soil maps from the last glacial maximum on a scale of 1 750 000 covering an area of 55 000 km three broad geomorphic zones are defined including the western section from cape agulhas to cape infanta the central section from cape infanta to knysna and the eastern section extending eastward of knysna we demonstrate that mesozoic sedimentary deposits crop out near the surface on this current swept shelf and soils derived from siltstone and shale bedrock are prominent when the coast is up to 64 km distant from the modern shoreline at its maximum point beyond this weathered limestone dominates the substrate sequences on the agulhas bank we show that the submerged landscape was a unique terrestrial environment and that there is no exact modern day analogue in the region other than a small 70 km2 area located at the edge of the agulhas plain near cape agulhas and map major contrasts in the geological topographic and edaphic nature of the landscape from the onshore to the offshore the expansion of this plain is coupled with exaggerated floodplains meandering shallowly incised rivers and wetlands the submerged shelf is dominated by fertile soils compared to the dissected onshore belt and extensive calcareous dunefields extending up to 10 km inland from their associated palaeoshorelines covered much of the emergent shelf sedimentary bedforms may have obstructed or slowed drainage as suggested by leached palaeosols and carbonate mixing observed in petrographic thin sections and grain mounts the data show a low relief plains landscape which contrasts strongly to the topographically complex contemporary coastal foreland

evolution of ocean temperature and ice volume through the mid pleistocene climate transition earth s climate underwent a fundamental change between 1250 and 700 thousand years ago the mid pleistocene transition mpt when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing over this time an increase occurred in the amplitude of change of deep ocean foraminiferal oxygen isotopic ratios traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep ocean temperature we have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios our results suggest that the mpt was initiated by an abrupt increase in antarctic ice volume 900 thousand years ago we see no evidence of a pattern of gradual cooling but near freezing temperatures occur at every glacial maximum

a parameterisation for the threshold shear velocity to initiate deflation of dry and wet sediment abstract a new parameterisation for the threshold shear velocity to initiate deflation of dry and wet particles is presented it is based on the balance of moments acting on particles at the instant of particle motion the model hence includes a term for the aerodynamic forces including the drag force the lift force and the aerodynamic moment force and a term for the interparticle forces the effect of gravitation is incorporated in both terms rather than using an implicit function for the effect of the aerodynamic forces as reported earlier in literature a constant aerodynamic coefficient was introduced from consideration of the van der waals force between two particles it was further shown that the effect of the interparticle cohesion force between two dry particles on the deflation threshold should be inversely proportional to the particle diameter squared the interparticle force was further extended to include wet bonding forces the latter were considered as the sum of capillary forces and adhesive forces a model that expresses the capillary force as a function of particle diameter squared and the inverse of capillary potential was deduced from consideration of the well known model of fisher and the young laplace equation the adhesive force was assumed to be equal to tensile strength and a function which is proportional to particle diameter squared and the inverse of the potential due to adhesive forces was derived by combining the capillary force model and the adhesive force model the interparticle force due to wet bonding was simplified and written as a function of particle diameter squared and the inverse of matric potential the latter was loglinearly related to the gravimetric moisture content a relationship that is valid in the low moisture content range that is important in the light of deflation of sediment by wind by introducing a correction to force the relationship to converge to zero moisture content at oven dryness the matric potential moisture content relationship contained only one unknown model parameter viz moisture content at 1 5 mpa working out the model led to a rather simple parameterisation containing only three coefficients two parameters were incorporated in the term that applies to dry sediment and were determined by using experimental data as reported by iversen and white sedimentology 29 1982 111 the third parameter for the wet sediment part of the model was determined from wind tunnel experiments on prewetted sand and sandy loam aggregates the model was validated using data from wind tunnel experiments on the same but dry sediment and on data obtained from simulations with the model of chepil soil sci soc am proc 20 1956 288 the experiments showed that soil aggregates should be treated as individual particles with a density equal to their bulk density furthermore it was shown that the surface had to dry to a moisture content of about 75 of the moisture content at 1 5 mpa before deflation became sustained the threshold shear velocities simulated with our model were found to be in good agreement with own observations and with simulations using chepil s model

a general framework for modeling sediment supply to coastal dunes including wind angle beach geometry and fetch effects a series of spatially explicit equations are derived that form the foundation of a modeling framework that provides insight into how the interaction of the fetch effect and angle of wind approach leads to tradeoffs that govern the magnitude of aeolian sediment transport across beaches of different geometry the spatial distribution of sediment transport rate per unit width at any point on the beach is shown to vary predictably as a function of wind angle critical fetch and beach geometry and this has evident implications for the total volume and distribution of sediment transport into the dunes behind the beach as well as the proportion of sediment lost from the beach dune system at the downwind margin as the wind field shifts from onshore shore perpendicular to oblique shore parallel approach angle total sediment transport rate across a dune line segment will reflect a tradeoff between transport reduction because of the cosine effect and transport enhancement because of potentially longer fetch distances traversed by the wind prior to encountering the dune line this tradeoff is most evident on long narrow beaches when beach width is less than the critical fetch for such beaches and with onshore winds the total sediment transport rate across the dune line will be less than that predicted for a wide beach because of the constraint imposed by the fetch effect however as the angle of wind approach becomes oblique the available fetch becomes progressively longer transport limitations imposed by the fetch effect are negated and transport enhancement across the dune line is to be expected with very large angles of wind approach the cosine effect dominates the interaction and transport reductions across the dune line occur until the wind is shore parallel and sediment supply to the dunes ceases altogether this sequence of adjustments and tradeoffs were only partially understood prior to this study and yet they form the foundation of coastal dune modeling the framework proposed in this paper serves to place future studies of process form interaction in beach dune systems on a robust theoretical foundation it also facilitates the testing of various alternative hypotheses regarding the uneven spatial and temporal distribution of dune height and growth rate in coastal environments

magnetic techniques applied to the study of rock varnish the authors report the successful application of magnetic techniques to the study of rock varnish a surficial coating that forms on rocks in arid environments using thin wafers of varnished and unvarnished greywacke sandstone they have detected a stable remanent magnetization that can be unambiguously attributed to the rock varnish they have also measured several rock magnetic properties of the rock varnish and have shown that the primary magnetic carrier is either magnetite or maghemite these results demonstrate the feasibility of applying magnetic techniques to the study of geomorphic surfaces subsequent rock magnetic and paleomagnetic studies of rock varnish should provide new information about the geochemical processes involved in the formation of rock varnish and about the validity of a new chronological technique known as rock varnish dating

seismic stratigraphy of the gulf of cadiz continental shelf a model for late quaternary very high resolution sequence stratigraphy and response to sea level fall

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

post break up tectonic inversion across the southwestern cape of south africa new insights from apatite and zircon fission track thermochronometry the south west african margin is regarded as an example of a passive continental margin formed by continental rifting following a phase of lithospheric extension and thinning recent attention focused on this margin has included theoretical modelling studies of rift processes plate kinematic studies of the opening geometry and timing and empirical studies focused on documenting the crustal structure and offshore sedimentary record here we examine the onshore geomorphic and tectonic response to rifting and breakup with a specific focus on the sw cape of south africa we present 75 new apatite and 8 new zircon fission track analyses from outcrop samples and onshore borehole profiles along the western margin of south africa the data are used to derive robust thermal histories that record two discrete phases of accelerated erosional cooling during the early cretaceous 150 130 ma and late cretaceous 100 80 ma respectively both periods of enhanced erosion are regional in extent involved km scale erosion and extend well inland of the current escarpment zone albeit with spatially variable intensity and style the late cretaceous episode is also expressed more locally by tectonic reactivation and inversion of major faults causing km scale differential displacement and erosion the new aft data do not exclude the possibility of modest surface uplift occurring during the cenozoic but they restrict the depth of regional cenozoic erosion on the western margin to less than c 1 km the inferred pattern and chronology of erosion onshore is consistent with the key features and sediment accumulation patterns within the offshore orange and bredasdorp basins it is suggested that the late cretaceous event was triggered by a combination of regional dynamic uplift augmented along the western margin and in the sw cape by local tectonic forces arising from dextral displacement of the falkland plateau along the falkland agulhas fracture zone

relation of sequence stratigraphy to modern sedimentary environments one method of testing the concept of sequence stratigraphy is to compare it to quaternary sediments in which chronology stratigraphic relations and facies geometry are more clearly understood than in older rocks rapid deposition rates during quaternary glacial eustatic cycles in large deltaic depocenters generate sequences comparable to those in the ancient stratigraphic record in the northern gulf of mexico the late wisconsinan holocene mississippi river has deposited a type 1 sequence that includes lowstand transgressive and high stand systems tracts characteristics of modern mississippi river sedimentary environments support the methodology used in sequence analysis but the short time taken for sequence generation here raises important questions about sequence time scales correlation and driving mechanisms

high resolution seismic study as a tool for sequence stratigraphic evidence of high frequency sea level changes latest pleistocene holocene example from the korea strait abstract sequence stratigraphic analysis of high resolution seismic reflection profiles and sediment data reveals that the latest pleistocene holocene deposits in the korea strait shelf off the southeastern korean peninsula form a high frequency sequence consisting of a set of lowstand transgressive and highstand systems tracts that corresponds to a fifth order 20 kyr sea level cycle eight depositional systems each with different seismic facies constitute the systems tracts the lowstand systems tract consisting of sandy mud forms a deltaic wedge that pinches out updip near or at the relict shelf edge the transgressive systems tract consisting mainly of sands includes six depositional systems 1 inner shelf transgressive layer 2 transgressive estuarine deltaic complex 3 transgressive sand ridge 4 mid shelf transgressive layer 5 incised channel fill and 6 beach shoreface complex although the transgressive systems tract is widely distributed it is much thinner than the lowstand and highstand systems tracts the highstand systems tract is composed of a prodelta shelf complex consisting almost exclusively of holocene muds the distribution and geometry of the systems tracts in the latest pleistocene holocene sequence in the korea strait shelf is different from that of vail s model in that 1 the lowstand systems tract consists only of the lowstand deltaic wedge which forms an elongated sediment body along the paleoshelf edge and 2 the highstand systems tract is completely confined to the inner shelf and forms a nearshore belt parallel to the coastline high frequency 20 kyr high amplitude magnitude of about 130 m sea level change together with strong currents flowing northeastward along the southeastern coast of the korean peninsula and varying sediment supply have resulted in this rather unusual stratigraphic architecture

stratigraphic and three dimensional morphological evolution of the late quaternary sequences in the western bohai sea china controls related to eustasy high sediment supplies and neotectonics abstract the bohai sea is a shallow semi closed gulf basin at the proximal position of the very wide one to several thousand kilometers eastern chinese margin and was persistently impacted by tectonic frameworks its late quaternary stratigraphy provides an excellent natural laboratory for research on the sedimentary processes and evolutionary patterns on flat proximal continental margins with high sediment inputs and how these processes respond to synsedimentary tectonic activity however due to the scarcity of comprehensive sequence stratigraphic studies our understanding of the above processes is limited here we conducted a high resolution sequence stratigraphic study using boomer seismic data with pseudo 3d coverage the seismic data revealed seven seismic units sus a g within the late quaternary stratigraphy including 1 three marine prodeltaic units sus a c g characterized by dipping oblique internal reflections and or lobate structures 2 two terrestrial fluvial lacustrine units sus b and e dominated by heterogeneous reflections 3 an erosional remnant unit sus d with semitransparent reflectors and a lenticular geometry and 4 a ravinement attributed aggradational unit su f based on the extrapolation between the seismic stratigraphy and the onshore sedimentary architecture and well established sequence stratigraphic models our preferential interpretation for the four sets of sus is that they correspond to the highstand lowstand falling stage and transgressive system tracts respectively the seismic geomorphology suggests that the bulk of the accommodation is dominated by the former two which is consistent with the alternative terrestrial and marine succession revealed by previous borehole studies at such a proximal gulf although the accumulation of thick highstand units is not surprising the two thick lowstand units that are bounded above and below by two different subaerial unconformities are exceptional our interpretation indicates that abnormally thick accumulation occurred under subaerial environments during the lowstand period which most likely corresponds to alluvial floodplain progradation aggradation given the western bohai sea is connected to the alluvial north china plain the lower subaerial unconformities of the lowstand units are associated with intensive subaerial most likely fluvial excavation erosion under su e leads to the formation of incised and eroded areas that can be tens of kilometers wide and tens of meters deep cutting into su a or even into su b which are several times greater than the last glacial maximum incised valley at the top of su e such intensive erosion appears to be a crucial contributor to the thick lowstand units as it created more accommodation the great scale of the subaerial incisions is presumably attributed to the fact that the bulk of them evolved from tectonically triggered depressions because their locations are consistent with the ne sw and nw se striking fault populations the tectonic forces also controlled the accumulation by resulting in high relief basement blocks for the pre holocene sedimentation however despite such strong tectonic controls the subsequent deposition filled and leveled the areas between the high relief steep sided basement blocks and eventually resulted in a relatively flat substratum for post lgm deposition suggesting that the geomorphic threshold for geological control at such a proximal gulf was passed because of the high supply environment

multiple sediment sources and a cellular non integrated longshore drift system northwest florida and southeast alabama coast usa abstract the morphosedimentary maintenance of a 225 km stretch of coast along the northeast gulf of mexico from grayton beach florida to morgan point alabama has been interpreted previously within the framework of a unidirectional integrated monotonic longshore drift model with a single headland source of sediment located east of grayton beach net longshore transport and the granulometry and composition of some 2000 foredune beach and step samples indicate a cellular net drift system supplied by three independent sources of sediment one source is provided by the pleistocene barrier island complex along grayton mirimar beach the second at pensacola beach on santa rosa island and the third is onshore transport across the inner shelf between pensacola florida and morgan point alabama the pleistocene headland and pensacola beach supply two cells along santa rosa island whereas onshore transport from the low gradient inner shelf supplies sediment to three cells along the largely accretional beach ridge dominated coast from pensacola pass to morgan point drift cells along this coast experience negligible net sediment exchange these findings have significant implications for both the late holocene evolution and the morphodynamic maintenance of this coast

antarctic temperature and global sea level closely coupled over the past five glacial cycles sea level has varied by over one hundred metres across glacial interglacial cycles over the past 520 000 years an extended sea level reconstruction shows a strong coupling between these sea level changes and antarctic surface temperatures over the past five glacial cycles

sedimentary response to climate and sea level changes during the past 400 ka from borehole prad1 2 adriatic margin 1 borehole prad1 2 was drilled in 186 m water depth on the upper slope of the central adriatic in the frame of profiles across mediterranean sedimentary systems promess1 european union funded project the borehole penetrated 71 2 m through a stratigraphic interval characterized by subparallel seismic reflections and uniform seismic units according to an age depth model based on several independent proxies including foraminifera and nannoplankton stratigraphy 18o curves and magnetostratigraphy the cored interval records marine isotope stages and substages mis from mis1 to the top of mis11 thus encompassing the past 370 ka prad1 2 therefore represents an unprecedented continuous record through the last four glacial interglacial cycles from a proximal continental margin setting where depositional sequences are typically composed of progradational units these progradational units record dominantly interglacial intervals mis5 mis7 and mis9 and appear composed of thicker highstand deposits hst formed during interstadials and thinner forced regression units fsst deposited during stadials above distinctive downward shift surfaces the development of thicker highstand deposits with a distinctively thicker bottomset reflects enhanced shore parallel advection any time sea level rise leads to the drowning of the adriatic shelf triggering the formation of dense water and vigorous cyclonic circulation this advection mechanism persisted in each cycle throughout the early phases of the sea level fall but progressively decreased as sea level fall proceeded approaching the maximum lowstand position when most of the shelf became exposed relative sea level falls punctuating interglacials within each 100 ka cycle were thus accompanied by a dearth in sediment flux on the outer shelf the alternation of hst and fsst progradational wedges with markedly different thickness and downlap geometry of their bottomsets is the most evident stratigraphic signature within each 100 ka depositional cycle of the impact on the shelf of higher frequency 20 ka sea level cycles and concomitant supply fluctuations

stratigraphic architecture and spatio temporal variability of high frequency milankovitch depositional cycles on modern continental margins an overview abstract this study is a review of quaternary milankovitch cycles as recorded on modern continental shelves worldwide on the background of the many existing examples we focus on selected case studies from mediterranean adriatic and tyrrhenian seas and atlantic gulfs of mexico and cadiz margins that represent general and peculiar characters of middle upper pleistocene sequences forming under the control of composite 100 and 20 ka milankovitch cycles the most pervasive stratigraphic pattern displayed by shelf deposits is referred to the 100 ka sea level cycle and consists of fairly uniform depositional sequences mostly composed by regressive deposits forming during the falling limb of the sea level curve these are generally classified as falling stage systems tract fsst and display a regressive facies architecture reflecting the dominant control of sea level on many margins fsst units may show slight though significant differences with respect to highstand systems tract hst and lowstand systems tract lst regressive units more closely reflecting environmental changes and the local variability of depositional systems in contrast with the theoretical and overall scale independent model developed to predict composite stratigraphic cycles and sequences the middle upper pleistocene stratigraphic record from numerous shelf settings shows a subdued signature of the higher frequency 20 ka milankovitch cyclicity however when detectable the 20 ka architectural pattern is characterized by a relatively greater spatial and temporal variability compared to 100 ka sequences this fact likely reflects the increasing importance of factors controlling the depositional environment e g seafloor morphology oceanographic regime sediment input and dispersal etc with respect to sea level change during the shorter intervals encompassed by 20 ka cycles on this basis two end member cases have been distinguished depending on the generation or not of high frequency sequence boundaries a prerequisite to qualify the higher frequency motifs as depositional sequences these two end members are comprehensive of the highly variable patterns displayed by middle upper pleistocene shelf sequences which in turn reflect the interplay between the geological setting the dominant sea level control and the effective response of sedimentary systems the variable stratigraphic patterns of milankovitch cycles represent conceptual and practical constraints as to the classification of high frequency quaternary sequences under the general schemes of the standard sequence stratigraphy model

pleistocene sea level fluctuations and human evolution on the southern coastal plain of south africa abstract humans evolved in africa but where and how remain unclear here it is proposed that the southern coastal plain scp of south africa may have served as a geographical point of origin through periodic expansion and contraction isolation in response to glacial interglacial changes in sea level and climate during pleistocene interglacial highstands when sea level was above 75 m human populations were isolated for periods of 360 3400 25 yr generations on the scp by the rugged mountains of the cape fold belt climate and vegetation barriers the scp expands five fold as sea level falls from 75 to 120 m during glacial maxima to form a continuous unobstructed coastal plain accessible to the interior an expanded and wet glacial scp may have served as a refuge to humans and large migratory herds and resulted in the mixing of previously isolated groups the expansive glacial scp habitat abruptly contracts by as much as one third in 300 yr during the rapid rise in sea level associated with glacial terminations rapid flooding may have increased population density and competition on the scp to select for humans who expanded their diet to include marine resources or hunted large animals successful adaptations developed on an isolated scp are predicted to widely disperse during glacial terminations when the scp rapidly contracts or during the initial opening of the scp in the transition to glacial maxima the hypothesis that periodic expansion and contraction of the scp as well as the coastal plain of north africa contributed to the stepwise origin of our species over the last 800 thousand years kyr is evaluated by comparing the archeological dna and sea level records these records generally support the hypothesis but more complete and well dated records are required to resolve the extent to which sea level fluctuations influenced the complex history of human evolution

nearshore shore oblique bars gravel outcrops and their correlation to shoreline change abstract this study demonstrates the physical concurrence of shore oblique bars and gravel outcrops in the surf zone along the northern outer banks of north carolina these subaqueous features are spatially correlated with shoreline change at a range of temporal and spatial scales previous studies have noted the existence of beach surf zone interactions but in general relationships between nearshore geological features and coastal change are poorly understood these new findings should be considered when exploring coastal zone dynamics and developing predictive engineering models the surf zone and nearshore region of the outer banks is predominantly planar and sandy but there are several discrete regions with shore oblique bars and interspersed gravel outcrops these bar fields have relief up to 3 m are several kilometers wide and were relatively stationary over a 1 5 year survey period however the shoreward component of the bar field does exhibit change during this time frame all gravel outcrops observed in the study region a 40 km longshore length were located adjacent to a shore oblique bar in a trough that had width and length similar to that of the associated bar seismic surveys show that the outcrops are part of a gravel stratum underlying the active surface sand layer cross correlation analyses demonstrate high correlation of monthly and multi decadal shoreline change rates with the adjacent surf zone bathymetry and sediment distribution regionally areas with shore oblique bars and gravel outcrops are correlated with on shore areas of high short term shoreline variability and high long term shoreline change rates the major peaks in long term shoreline erosion are onshore of shore oblique bars but not all areas with high rates of long term shoreline change are associated with shore oblique bars and troughs

a simple model for the spatially variable coastal response to hurricanes abstract the vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm induced water levels to those of the dune or berm a simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50 km stretch of the north carolina coast to the landfalls of hurricane bonnie on august 27 1998 and hurricane floyd on september 16 1999 maximum total water levels at the shoreline were calculated as the sum of modeled storm surge astronomical tide and wave runup estimated from offshore wave conditions and the local beach slope using an empirical parameterization storm surge and wave runup each accounted for 48 of the signal the remaining 4 is attributed to astronomical tides indicating that wave driven process are a significant contributor to hurricane induced water levels expected water levels and lidar derived measures of pre storm dune and berm elevation were used to predict the spatially varying storm impact regime swash collision or overwash predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall the storm averaged mean accuracy of the model in predicting the observed impact regime was 55 4 a significant improvement over the 33 3 accuracy associated with random chance model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84 2 and 89 7 for hurricanes bonnie and floyd respectively the model not only allows for prediction of the general coastal response to storms but also provides a framework for examining the longshore variable magnitudes of observed coastal change for hurricane bonnie shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore swash regime during hurricane floyd this pattern became more pronounced as magnitudes of change were four times greater within the overwash regime than in the swash regime comparisons of pre storm topography to a calm weather survey collected one year after hurricane floyd s landfall show long term beach volume loss at overwash locations here the volume of sand eroded from the beach was balanced by the volume of overwash deposits indicating that the majority of the sand removed from the beach was transported landward across the island rather than being transported offshore in overwash locations sand was removed from the nearshore system and unavailable for later beach recovery resulting in a more permanent response than observed within the other regimes these results support the predictive capabilities of the storm scaling model and illustrate that the impact regimes provide a framework for explaining the longshore variable coastal response to hurricanes

terrigenous sediment export from the western margin of south africa on glacial to interglacial cycles abstract similar to many shelves globally pleistocene terrigenous sediment deposition on the western shelf of south africa is strongly influenced by high amplitude sea level fluctuations over glacial to interglacial climate cycles here variations in the glauconitic quartzose sand and terrigenous mud content of gravity cores from the western slope of south africa are used to evaluate the dynamics of shelf sediment export over climate cycles of the last 450 kyr calcareous ooze on the slope contains a mean of 0 2 to 8 wt glauconitic quartzose sand derived from erosion of neogene outer shelf sediments and 13 to 40 wt terrigenous mud sourced from the orange river quartz sand content on the slope increases during glacial periods and is sharply reduced across glacial terminations and throughout interglacial highstands relative sea level changes on the margin estimated from the quartz sand content on the slope are consistent with the timing but not amplitude of proposed eustatic sea level records a possible mechanism of sand erosion on the outer shelf is the vertical mixing forced by internal tides which may intensify over the shelf break as sea level is lowered during glacials turbidites are rare and bottom currents are generally capable of suspending mud but not sand except locally along the margin estimated variations in the bulk sedimentation rate and terrigenous mud mass accumulation rate on the slope suggest that export of terrigenous mud off the shelf during glacial lowstands is transported beyond the slope at intermediate and deeper water depths to the southern ocean

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

factors controlling the survival of coastal dunes during multiple hurricane impacts in 2004 and 2005 santa rosa barrier island florida abstract santa rosa island is an 85 km long wave dominated low lying barrier island situated along the northwestern florida coast facing the gulf of mexico the entire island was severely impacted by ivan a strong category 3 hurricane that made landfall about 45 km to the west in september of 2004 ten months later in july of 2005 dennis another category 3 hurricane made landfall about 30 km east of the western tip of the island santa rosa island is characterized by well developed but relatively low dunefields described in this paper as incipient and established dunes based on the presence of grassy and woody types of vegetation respectively the dunes were severely eroded by the two hurricanes this paper investigates the factors controlling the regional scale destruction and survival of the dunefields dune survival is controlled by 1 hurricane characteristics including intensity duration and frequency and 2 morphological parameters including width of the barrier island height and width of the dunefields vegetation type distance of the dunes to the ocean and continuity of the dunefields three processes of dune destruction are described including from most to least severe inundation overwash and scarping the interaction of all the above factors determines the different dune responses to the storm impacts in general the extensive and densely woody vegetated dunefields near the bay side shoreline survived the storms while the discontinuous dunes with grassy vegetation near the gulf shoreline were almost completely destroyed

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