micro seismic measurements of cliff motion under wave impact and implications for the development of near horizontal shore platforms abstract few high resolution measurements of process form interactions have been taken on rock coasts but recent studies in california have shown that portable seismometers enable useful proxy measurements of wave energy delivery to cliffs here we describe measurements over 20 days of high frequency ground motion of cliffs formed in sedimentary flysch rocks at okakari point north of auckland new zealand three sensors were located in a shore normal array inland from the cliff top and a fourth sensor was bolted to a ledge 2 m above the cliff toe the nearshore wave field in front of the cliff and shore platform was monitored using a shore normal array of 5 wave gauges the instrumentation provided measurements of wave energy delivery and consequent ground motion including the first observations of motion at the top and bottom of cliffs results showed that horizontal ground motion is dominant at the cliff top whereas vertical motion is dominant at the cliff toe power spectra show that several high frequency peaks occur in data from the cliff toe whereas a single broader peak frequency occurs at the cliff top resulting from signal modification as seismic waves pass through tens of metres of cliff rock a 100 m wide shore platform at the cliff toe fundamentally controls the patterns of observed energy delivery the shore platform is nearly horizontal elevated close to high water level and abruptly plunges into water 10 m deep at its seaward edge as expected the magnitude of ground motion at all sensors is greatest during larger waves measurements further show that ground motion both at the bottom and top of the cliff is strongest at low tide and weakest at high tide this observation is opposite to that noted at santa cruz where ground motion was greatest at high tide at okakari point the most significant high frequency ground motions occur at low tide when waves are forced to break sometimes violently against the seaward edge of the shore platform four distinctive frequency peaks between 1 and 50 hz increase in magnitude as tidal stage drops implying that wave breaking against the outside edge of the shore platform represents an important source of vibration a detailed understanding of the energy source e g short duration shock pressures and rock resonance is not provided by this study however quantifying the spatial and temporal patterns of energy delivery places strong emphasis on the important role of shore platform geometry in filtering wave energy delivery to the cliff during the 20 day experiment most wave energy was delivered to the outside edge of the shore platform not the cliff toe the geomorphic role of high frequency shaking from wave impacts remains to be clearly demonstrated but if wave impacts are capable of eroding rock then the data from this study imply that under present conditions the outside edge of the shore platform may be subject to higher erosion rates than the cliff toe it is possible that the shore platform is currently being destroyed rather than created but a longer programme of measurements is required to test this notion

aeolian dune migration along the ceara coast north eastern brazil aeolian dune dimensions and migration rates are analysed along the ceara coast north east brazil dunes that are currently mobile along the ceara coast are composed of barchans and sand sheets the results show that barchans maintain an equilibrium form which can be characterized by values of dimensionless shape parameters h w and w l where h is the dune height w is the wing to wing width and l is the dune length dunes are highly mobile with average migration rates of 17 5 m year 1 for barchans and 10 m year 1 for sand sheets the calculated migration rates were found to depend strongly on dune dimensions for both barchans and sand sheets i e the larger the dune is the lower the migration rate will be this size dependence was associated with the existence of a representative common transport rate along the dune fields which induces a different dune migration rate dependent on dune size finally from the observed dune evolution an aggregated scale aeolian sediment transport was inferred this bulk transport rate of the order of 90 100 m3 m 1 year 1 is only valid for a timescale of years to decades which is the timescale used in dune evolution analysis

construction and evolution of submerged deltaic bodies on the high energy se african coastline the interplay between relative sea level and antecedent controls abstract this paper investigates the interplay between allocyclic controls and antecedent topography in the evolution of submerged coastal landforms including a back stepped delta using high resolution tools we examine the wave dominated thukela shelf and define the major seismic units key features identified comprise incised valleys scoured into bedrock that have overspilled to form lagoons at depths of 50 m these are in turn overlain by two prograding and backstepped sandy delta systems at 40 m and 32 m depth respectively the deltas interfinger with muddy prodelta deposits and are truncated by the holocene ravinement overlain by the contemporary prodelta of the thukela river system a bedrock high separates two physically separate strato morphological zones landward a sediment stripped steep and shallow nearshore zone and seaward a gentle zone downdip where the deltaic accumulations are sited delta development was favoured during sea level stillstands at 40 m and 32 m respectively the step back of the deltas corresponds to sharp increases in the rate of sea level rise associated with meltwater pulses the overall gentle palaeo bathymetric gradient has moderated erosion associated with rising sea level preserving a sandy back stepping delta and a draping mud clinoform submerged delta positioning relates to underlying incised valleys suggesting a synchronous transgressive evolution of the drainage and the delta incised valley network positioning is further governed by late pliocene aged growth faults in the basement rocks the geological framework has acted as a recurring primary control to the geomorphic evolution of the area partitioning accommodation for sediment accumulation and moderating the efficiency of ravinement

volume loss from antarctic ice shelves is accelerating the floating ice shelves surrounding the antarctic ice sheet restrain the grounded ice sheet flow thinning of an ice shelf reduces this effect leading to an increase in ice discharge to the ocean using 18 years of continuous satellite radar altimeter observations we have computed decadal scale changes in ice shelf thickness around the antarctic continent overall average ice shelf volume change accelerated from negligible loss at 25 64 cubic kilometers per year for 1994 2003 to rapid loss of 310 74 cubic kilometers per year for 2003 2012 west antarctic losses increased by 70 in the past decade and earlier volume gain by east antarctic ice shelves ceased in the amundsen and bellingshausen regions some ice shelves have lost up to 18 of their thickness in less than two decades

sustained increase in ice discharge from the amundsen sea embayment west antarctica from 1973 to 2013 we combine measurements of ice velocity from landsat feature tracking and satellite radar interferometry and ice thickness from existing compilations to document 41 years of mass flux from the amundsen sea embayment ase of west antarctica the total ice discharge has increased by 77 since 1973 half of the increase occurred between 2003 and 2009 grounding line ice speeds of pine island glacier stabilized between 2009 and 2013 following a decade of rapid acceleration but that acceleration reached far inland and occurred at a rate faster than predicted by advective processes flow speeds across thwaites glacier increased rapidly after 2006 following a decade of near stability leading to a 33 increase in flux between 2006 and 2013 haynes smith pope and kohler glaciers all accelerated during the entire study period the sustained increase in ice discharge is a possible indicator of the development of a marine ice sheet instability in this part of antarctica key points sustained ase mass flux increase 77 since 1973 thwaites accelerated by 33 during the last 6 years speed changes are pervasive and rapid major implications for ice flow modeling 2014 american geophysical union all rights reserved

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

geomorphology and preservation potential of coastal and submerged aeolianite examples from kwazulu natal south africa abstract the distribution and geomorphology of aeolianite outcrop on the coast of kwazulu natal south africa are described in the context of its preservation potential in the geological record aeolianite on the contemporary coast comprises discontinuous widely spaced outcrops less than 100 m in longshore extent and typically 50 60 m wide that reflects the combined action of subaerial weathering and physical abrasion in the coastal zone since the mid holocene approximately 7000 yrs the dominant morphological component is an intertidal erosional platform that slopes gently landward it is fronted by a notch in the mid intertidal zone 0 m msl and contains active erosional potholes on its seaward margin the platform surface is encrusted by a variety of marine organisms landward of and contiguous with the intertidal surface are small elevated outcrops of aeolianite in the supratidal zone these comprise a 3 m high seaward scarp with a basal notch in the high intertidal zone 1 m msl gullies in the scarp trap coarse clasts of eroded aeolianite as well as bedrock the upper surface of the supratidal aeolianite is planar with large potholes within which accumulations of coarse clasts and oyster shells have been cemented the upper surface is interpreted as a remnant of an intertidal platform formed at a higher mid holocene sea level the supratidal outcrop is subject to weathering and disintegration major joints divide the outcrop into cuboid blocks with axes of 3 4 m eroded blocks on the seaward face that exceed 1 m diameter remain in situ and become locked in place by repeated shaking smaller blocks that collapse from the seaward face accumulate in small gullies or are dispersed the facet most likely to be preserved in the geological record is the planar intertidal platform the morphology of aeolianite on the contemporary coast is markedly different from submerged aeolianite ridges on the adjacent shelf which are of higher relief wider and more laterally extensive preservation potential of aeolianite under subaerial conditions is low and the widespread high relief aeolianite on the shelf is attributed to rapid inundation or burial during transgression

potential sea level rise from antarctic ice sheet instability constrained by observations large parts of the antarctic ice sheet lying on bedrock below sea level may be vulnerable to marine ice sheet instability misi a self sustaining retreat of the grounding line triggered by oceanic or atmospheric changes there is growing evidence that misi may be underway throughout the amundsen sea embayment ase which contains ice equivalent to more than a metre of global sea level rise if triggered in other regions the centennial to millennial contribution could be several metres physically plausible projections are challenging numerical models with sufficient spatial resolution to simulate grounding line processes have been too computationally expensive to generate large ensembles for uncertainty assessment and lower resolution model projections rely on parameterizations that are only loosely constrained by present day changes here we project that the antarctic ice sheet will contribute up to 30 cm sea level equivalent by 2100 and 72 cm by 2200 95 quantiles where the ase dominates our process based statistical approach gives skewed and complex probability distributions single mode 10 cm at 2100 two modes 49 cm and 6 cm at 2200 the dependence of sliding on basal friction is a key unknown nonlinear relationships favour higher contributions results are conditional on assessments of misi risk on the basis of projected triggers under the climate scenario a1b ref 9 although sensitivity to these is limited by theoretical and topographical constraints on the rate and extent of ice loss we find that contributions are restricted by a combination of these constraints calibration with success in simulating observed ase losses and low assessed risk in some basins our assessment suggests that upper bound estimates from low resolution models and physical arguments up to a metre by 2100 and around one and a half by 2200 are implausible under current understanding of physical mechanisms and potential triggers

shoreline deposits and diagenesis resulting from two late pleistocene highstands near 5 and 6 metres durban south africa in exposures of pleistocene rocks on the east coast of south africa eight sedimentary facies were distinguished on the basis of petrology grain size internal structures and field relationships these are interpreted as deposits of surf zone breaker zone swash zone backbeach boulder beach and dune environments three phases of deposition and diagenesis are recognized as a result of the stabilising effect of pre existing coastal facies the deposits from successive sea level stands are stacked vertically in a narrow coast normal strip early cementation prevented erosion of the deposits during subsequent transgressions deposition of subsequent facies took place on an existing coastal dune facies 1 a terrace was cut into this dune at a sea level 4 5 to 5 m above present at this sea level clastic shoreline sediments were deposited which make up the main sedimentary sequence exposed facies 2 7 the steep swash zone coarse grain size and comparison with modern conditions in the study area indicate clastic deposition on a high energy wave dominated microtidal coastline vertical stacking of progressively shallower water facies indicates progradation associated with slightly regressive conditions prior to stranding of the succession above sea level during a subsequent transgression to 5 5 or 6 m above present sea level a second terrace was cut across the existing facies which by then were partly lithified a boulder beach facies 8 deposited on this terrace is indicative of high wave energy and a rocky coastline formed by existing cemented coastal facies comparison with dated deposits from other parts of the south african coast suggest a late pleistocene age for facies 2 8 deposition was terminated by subsequent regression and continuing low sea levels during the remainder of the pleistocene cementation of the facies took place almost entirely by carbonate precipitation the presence of isopachous fibrous cements suggests early cementation of facies 1 2 3 and 4 under marine conditions initially as aragonite which has since inverted to calcite facies 5 6 and 7 are cemented only by equant calcite spar evidence of cementation in the meteoric phreatic and vadose zones lowering of the water table during regression caused the remaining pore space in facies 1 2 3 and 4 to be filled with equant calcite spar decementation in a 130 cm wide zone is attributed to water table shifts associated with the later transgression which deposited facies 8 the vertical stacking of the two depositional sequences may be attributed to rapid cementation of facies 2 3 4 5 6 and 7 under humid subtropical conditions this lithified sequence then acted as a focus for deposition of coarse grained shoreline facies facies 8 during the subsequent transgression

the geomorphologic evolution of the wilderness dune cordons south africa abstract the wilderness dune cordons consist of steep sided ridges up to 207 m high separated by coastal lakes they probably formed during the sea level highstands of the pleistocene interglacials three major dune cordons are developed there is an additional huge coalesced mass of older fossil dunes landward of these cordons forming hills up to 340 m high in places lying on the coastal platform 150 260 m generally locally 210 260 m the dunesand reaches thicknesses in excess of 300 m the cordons form by accretion of transgressive dunefields and large compound imbricate parabolic dunes an individual cordon can result from numerous phases of dune formation during periods of sea level highstand the dunes of the present interglacial are mostly accreting on top of the seaward cordon which was initiated during the last interglacial during the complex sea level history there have been numerous phases of dune building followed by coastal erosion that formed seacliffs in the dune cordons in some areas almost all the cordon was subsequently eroded away these fossil seacliffs form large steep seaward facing slopes parallel to the present coastline and form a major element in the morphology of the cordons trailing arms of parabolic dunes form another major topographic element oriented at 15 30 to the shoreline river erosion has altered the cordon morphology in places the geomorphology of the cordons is thus a function primarily of dune cordon construction accentuated by coastal erosion in the form of cliff cutting secondarily of dune morphology and thirdly of fluvial erosion the evolution of the cordons can be dated tentatively using palaeontologic stratigraphic and sediment dynamic data the seaward cordon formed during the eem and holocene a fairly reliable dating the middle cordon probably formed between 200 500 ka and the landward cordon probably formed between 600 900 ka the coalesced dune deposits lie inland of the cordons and are thus older this would place the minimum age of the younger coalesced dune deposits in the middle pleistocene about 1000 ka early miocene fossil plant remains in the knysna lignites which underlie the older coalesced dunes indicate their maximum possible age westerly winds dominated in the area for the past few million years

evidence from luminescence for late pleistocene formation of calcareous aeolianite kurkar and paleosol hamra in the carmel coast israel abstract calcareous aeolianite kurkar and red loamy paleosol hamra units form ridges in the northern coastal plain of israel the kurkar ridges with hamra units have been thought to be indicators of past sea levels and of palaeoclimate though there has been no clear chronology that could correlate units from one ridge to another or to global palaeoclimate and sea level change we obtained detailed stratigraphy and luminescence ages for the kurkar and hamra units that range from 35 to 101 ka indicating coeval formation of these units during the late pleistocene independent dating suggests that hamra and similar loamy soils formed at 45 to 130 ka in the habonim quarry site at the eastern ridge when kurkar that has been dated by us to 50 67 ka was deposited in the coastal trough showing facies changes from west to east the youngest ages for exposed kurkar in the dor islet at the coastal ridge 35 and 38 ka are close to the 35 ka age obtained independently for the upper kurkar near atlit at the eastern ridge at that time when kurkar was deposited and cemented on the top of both ridges a hamra dated by us to 37 ka formed in the coastal trough our results indicate that kurkar accumulated along the coastal plain at different time intervals throughout the late pleistocene and that its deposition was not necessarily associated with high sea levels moreover our data as well as previous research suggest that hamra also formed at different periods sometimes synchronous with kurkar and its formation is therefore not related to any particular climatic events

late pleistocene carbonate aeolianites on mallorca western mediterranean a luminescence chronology abstract coastal outcrops of upper pleistocene deposits in north eastern mallorca balearic islands spain have been examined and a chronological framework established using optically stimulated luminescence osl dating the outcrops record a complex interaction between aeolian colluvial and alluvial fan deposition that result in a variable stratigraphical architecture dating and facies analysis make it possible to identify four aeolian activity episodes during mis 5c b 4 and 3 and also add to the understanding of the environmental history of north eastern mallorca over the last 100 ka the new data suggest enhanced aeolian transport and dune formation during cold climatic intervals when sea level was low sediment supply exposed marine carbonate sediment was high winter windiness was high and vegetation on coastal plains at a minimum

climate and surface mass balance of coastal west antarctica resolved by regional climate modelling west antarctic climate and surface mass balance smb records are sparse to fill this gap regional atmospheric climate modelling is useful providing that such models are employed at sufficiently high horizontal resolution and coupled with a snow model here we present the results of a high resolution 5 5 km regional atmospheric climate model racmo2 simulation of coastal west antarctica for the period 1979 2015 we evaluate the results with available in situ weather observations remote sensing estimates of surface melt and smb estimates derived from radar and firn cores moreover results are compared with those from a lower resolution version to assess the added value of the resolution the high resolution model resolves small scale climate variability invoked by topography such as the relatively warm conditions over ice shelf grounding zones and local wind speed accelerations surface melt and smb are well reproduced by racmo2 this dataset will prove useful for picking ice core locations converting elevation changes to mass changes for driving ocean ice sheet and coupled models and for attributing changes in the west antarctic ice sheet and shelves to changes in atmospheric forcing

late quaternary stratigraphic evolution of the inner continental shelf in response to sea level change santa catarina brazil abstract the inner continental shelf 0 50 m water depth off santa catarina southern brazil was investigated using seismic stratigraphic methods to identify and interpret the major seismic stratigraphic units and to reconstruct the late quaternary evolution of the inner shelf and coast the stratigraphy comprises a bedrock basement overlain by a thick 30 m unit that comprises in the distal portion laminated muds and sands and in the coast proximal zone offlapping deltaic deposits whose upper surface has been reworked to form alongshore prograding barrier spits deposition of this unit is tentatively attributed to sea levels 20 m msl during the late pleistocene mis 5a or 5c a normal fault in the muddy units with a vertical offset of 3 5 m indicates episodic tectonic activity cut into this unit is a profusion of incised valleys associated with sea level fall ultimately to 120 m at the last glacial maximum lgm the associated subaerial unconformity is only preserved close to shore where it has escaped subsequent wave ravinement this coupled with the well preserved incised valleys implies the underlying substrate to be weakly cohesive material mud the incised valleys display a variety of infilling sediments interpreted variously as basal fluvial sediments estuarine basin infill muds and marginal bar or barrier associated sands deposited during the postglacial marine transgression during a sea level stillstand at ca 50 m a 3 5 km wide planar surface was cut into the unconsolidated coastal plain sediments forming a terrace on which a thick sequence of sands accumulated this unit is regionally developed and the acoustic signature implies it to comprise littoral sand including a large aeolianite component the accumulation of sand on this mainland beach dune system is attributed to establishment of a mature littoral system with strong longshore drift the fact that it rests on an erosional surface that truncates incised valleys suggests the unit to be holocene in age it is interpreted to have been deposited during a still stand in the holocene and to have undergone aggradation and cementation until it was overstepped by sea level rise its surface and the coastal plain to landward were then subject to wave ravinement and a thin ca 5 6 m layer of modern marine sands was deposited on the eroded surface sea level rise continued to the regional glacio isostatic highstand of ca 5 5 m after which regressive strandplains developed in response to a renewed mature longshore drift system similar to that prevailing during the 50 m stillstand of sea level in the intervening period rapid shoreline translation over the low gradient surface inhibited the development of the longshore transport system the three shoreline systems identified show marked differences that relate to sea level change and the influence of the underlying topography shoreline 1 pleistocene highstand developed by localised wave reworking of delta deposits and involved a series of alongshore prograding barrier spits on a shoreline of alternating high relief bedrock and littoral sands in coastal re entrants shoreline 2 50 m was a major accumulation of beach and dune sand deposited as a mainland attached beach dune system on a low lying coastal plain environment shoreline 3 the modern coast comprises a series of headland embayment beaches strandplains and transgressive dunes with a strong bedrock control and a well developed longshore drift system delivering sediment northward

the influence of the amundsen sea low on the winds in the ross sea and surroundings insights from a synoptic climatology the amundsen sea low asl is an area of climatologically low atmospheric pressure situated over the southern ocean the depth and location of this feature have significant effects on winds temperature moisture transport and sea ice in its vicinity in this article we quantify the modulating effect of this feature on winds over the ross sea and ross ice shelf we examine composites of surface winds sampled according to extrema in asl depth longitude and latitude we employ the output of a previously developed synoptic climatology to identify the explanatory synoptic scale forcings in autumn winter and spring aws we find that the impact of the depth of the asl is smaller than that of its location the asl moves eastward when it is deep thereby reducing its influence on ross sea winds when the asl is northward we find strongly enhanced southerly flows over the ross sea and ice shelf forced by greater cyclonic activity in the north of the ross sea in summer we find increased cyclonic flow coinciding with a deeper asl despite the asl being located in the bellingshausen sea at this time the responses to the asl longitude and latitude are profoundly different to those in aws suggesting that relationships are strongly dependent on the varying seasonal location of the low we examine two metrics of the asl depth and identify that the absolute mean sea level pressure mslp has a more widespread response than that of the relative mslp

mass balance reassessment of glaciers draining into the abbot and getz ice shelves of west antarctica we present a reassessment of input output method ice mass budget estimates for the abbot and getz regions of west antarctica using cryosat 2 derived ice thickness estimates the mass budget is 8 6 gt yr 1 and 5 17 gt yr 1 for the abbot and getz sectors respectively for the period 2006 2008 over the abbot region our results resolve a previous discrepancy with elevation rates from altimetry due to a previous 30 overestimation of ice thickness for the getz sector our results are at the more positive bound of estimates from other techniques grounding line velocity increases up to 20 between 2007 and 2014 alongside mean elevation rates of 0 67 0 13 m yr 1 between 2010 and 2013 indicate the onset of a dynamic thinning signal mean snowfall trends of 0 33 m yr 1 water equivalent since 2006 indicate recent mass trends are driven by both ice dynamics and surface processes

modelling circumpolar deep water intrusions on the amundsen sea continental shelf antarctica results are presented from an isopycnic coordinate model of ocean circulation in the amundsen sea focusing on the delivery of circumpolar deep water cdw to the inner continental shelf around pine island bay the warmest waters to reach this region are channeled through a submarine trough accessed via bathymetric irregularities along the shelf break temporal variability in the influx of cdw is related to regional wind forcing easterly winds over the shelf edge change to westerlies when the amundsen sea low migrates west and south in winter spring this drives seasonal on shelf flow while inter annual changes in the wind forcing lead to inflow variability on a decadal timescale a modelled period of warming following low cdw influx in the late 1980 s and early 1990 s coincides with a period of observed thinning and acceleration of pine island glacier

large scale forcing of the amundsen sea low and its influence on sea ice and west antarctic temperature abstractusing empirical orthogonal function eof analysis and atmospheric reanalyses the principal patterns of seasonal west antarctic surface air temperature sat and their connection to sea ice and the amundsen sea low asl are examined during austral summer the leading eof eof1 explains 35 of west antarctic sat variability and consists of a widespread sat anomaly over the continent linked to persistent sea ice concentration anomalies over the ross and amundsen seas from the previous spring outside of summer eof1 explaining 40 50 of the variability consists of an east west dipole over the continent with sat anomalies over the antarctic peninsula opposite those over western west antarctica the dipole is tied to variability in the southern annular mode sam and in phase el nino southern oscillation enso sam combinations that influence the depth of the asl over the central amundsen sea near 105 w the second eof eof2 during autumn winter and spring explaining 15 20 of the vari

outer to inner shelf response to stepped sea level rise insights from incised valleys and submerged shorelines abstract shorelines respond to rising sea level through processes such as erosion landward migration and in situ drowning i e overstepping submerged and preserved shorelines on the continental shelf play a key role in examining coastal response to rising sea levels as they provide important information on how modern shorelines may evolve in time and space within the context of changing climate and post glacial sea level rise this study identifies and assesses the response of a continental shelf to stepped rises in sea level with particular focus on the stepwise evolution of incised valleys and shorelines from the shelf edge to the inner shelf multibeam bathymetry from the mid outer allows for the analysis of seafloor morphology including the protea banks reef a palaeo shoreline complex and the adjacent incised sediment starved continental shelf six seismic units and intervening surfaces are identified using interpretations from sub bottom profiles these include the incised acoustic basement variable incised valley fill successions aeolianite ridges and post transgressive shoreface and associated sediments that withstood wave ravinement processes the incised valleys of the outer shelf are manifested as distinctive seafloor depressions filled at their bases by fluvial deposits overlain in the unfilled valley by deposits derived from cascading subaqueous dunes which comprise the upper most post transgressive sediments a core intersecting the dune material yields a maximum age of deposition of 1191 1263 cal yr bp 68 range synchronous with a period of higher than present sea levels in the region suggesting reworking and redistribution of coastal sediment as shelf sediment post transgression during the stepped rises in sea level the shoreface has disconnected from the contemporary shoreline and is preserved by means of topographic barriers formed by antecedent topography as relict shoreface deposits we provide a new perspective of shoreline response to stepped rises in sea level by integrating the seismic architecture of incised valley fills and shorelines across the continental shelf thus allowing for the assessment of variation in rates of relative sea level rise since the last glacial maximum

a pragmatic method for estimating seepage losses for small reservoirs with application in rural india summary the informal construction of small dams to capture runoff and artificially recharge ground water is a widespread strategy for dealing with water scarcity a lack of technical capacity for the formal characterization of these systems however is often an impediment to the implementation of effective watershed management practices monitoring changes in reservoir storage provides a conceptually simple approach to quantify seepage but does not account for the losses occurring when seepage is balanced by inflows to the reservoir and the stage remains approximately constant to overcome this problem we evaluate whether a physically based volume balance model that explicitly represents watershed processes including reservoir inflows can be constrained by a limited set of data readily collected by non experts specifically records of reservoir stage rainfall and evaporation to assess the impact of parameter non uniqueness associated with the calibration of the non linear model we perform a monte carlo analysis to quantify uncertainty in the total volume of water contributed to the subsurface by the 2007 monsoon for a dam located in the deccan basalts near the village of salri in madhya pradesh india the monte carlo analysis demonstrated that subsurface losses from the reservoir could be constrained with the available data but additional measurements are required to constrain reservoir inflows our estimate of seepage from the reservoir 7 0 0 6 10 4 m 3 is 3 5 times greater than the recharge volume estimated by considering reservoir volume changes alone this result suggests that artificial recharge could be significantly underestimated when reservoir inflows are not explicitly included in models our seepage estimate also accounts for about 11 of rainfall occurring upstream of the dam and is comparable in magnitude to natural ground water recharge thereby indicating that the reservoir plays a significant role in the hydrology of this small watershed

groundwater modelling to quantify the effect of water harvesting structures in wagarwadi watershed parbhani district maharashtra india marathwada agricultural university pharbani has developed about 560 hectares of wagarwadi watershed in pharbani district since 1987 groundwater monitoring on 16 observations wells at weekly intervals commenced in january 1992 and rainfall and pan evaporation has been measured daily at a hydrometeorological station situated in the nearby university campus aquifer parameters namely transmissivity and specific yield have been estimated by carrying out a pumping test on a large diameter well groundwater recharge resulting from rainfall has been estimated using a water balance model of the soil moisture zone considering soil zone thickness and crops grown the scs soil conservation service curve number method was used for surface runoff estimation the groundwater flow model has been constructed using the nested squares finite difference method nested square meshes of sizes 160 m 160 m and 80 m 80 m have been used and the steady state condition of aquifer system was simulated in the model assuming the june 1992 water level configuration under equilibrium conditions the model has been calibrated for transient conditions incorporating additional seepage from the water harvesting structures and their contribution to the groundwater regime has been assessed 1998 john wiley sons ltd

a conceptual hydrodynamic model of a geological discontinuity in hard rock aquifers example of a quartz reef in granitic terrain in south india summary the structure and hydrodynamic properties of geological discontinuities and of a deeply weathered granite aquifer near these structures are described on the basis of geological geophysical and hydrodynamic investigations in two sites of south india located along a 20 40 m wide quartz reef intruding a weathered archean biotite granite one of the two sites also comprises a metre wide dolerite dyke weathering processes appear to be at the origin of fissures development and of a related enhanced local hydraulic conductivity both in the quartz reef and in the surrounding granite the weathering profile in the granite saprolite and fissured layer is characterized by an abrupt deepening of the weathered layers in the granite near the contact and in the quartz reef itself therefore the weathering profile shows a u shape geometry with among others the verticalization of the granite s fissured layer the hydraulic conductivity of this verticalized layer is on average 5 10 6 m s and storativity about 10 3 the hydraulic conductivity of the fissured quartz is 4 6 10 6 m s and its storativity about 3 5 10 4 both media are also characterized by a matrix hydraulic conductivity 10 7 10 9 m s and by a significant heterogeneity in hydrodynamic properties that generates preferential flow paths along the sub vertical fissures parallel to the reef axis a special attention has been paid for characterizing this heterogeneity the weathering of the dolerite dyke however results in a local low hydraulic conductivity which consequently does not enhance either the thickness of weathered granite layers or its hydraulic conductivity the obtained results complete the conceptual hydrogeological model developed for weathered granite aquifers in characterizing the relationships between weathering processes and hydrodynamic properties near geological discontinuities

water balance modelling in a tropical watershed under deciduous forest mule hole india regolith matric storage buffers the groundwater recharge process accurate estimations of water balance are needed in semi arid and sub humid tropical regions where water resources are scarce compared to water demand evapotranspiration plays a major role in this context and the difficulty to quantify it precisely leads to major uncertainties in the groundwater recharge assessment especially in forested catchments in this paper we propose to assess the importance of deep unsaturated regolith and water uptake by deep tree roots on the groundwater recharge process by using a lumped conceptual model comfort the model is calibrated using a 5 year hydrological monitoring of an experimental watershed under dry deciduous forest in south india mule hole watershed the model was able to simulate the stream discharge as well as the contrasted behaviour of groundwater table along the hillslope water balance simulated for a 32 year climatic time series displayed a large year to year variability with alternance of dry and wet phases with a time period of approximately 14 years on an average input by the rainfall was 1090 mm year 1 and the evapotranspiration was about 900 mm year 1 out of which 100 mm year 1 was uptake from the deep saprolite horizons the stream flow was 100 mm year 1 while the groundwater underflow was 80 mm year 1 the simulation results suggest that i deciduous trees can uptake a significant amount of water from the deep regolith ii this uptake combined with the spatial variability of regolith depth can account for the variable lag time between drainage events and groundwater rise observed for the different piezometers and iii water table response to recharge is buffered due to the long vertical travel time through the deep vadose zone which constitutes a major water reservoir this study stresses the importance of long term observations for the understanding of hydrological processes in tropical forested ecosystems c 2009 elsevier b v all rights reserved

beachrock formation in low latitudes implications for coastal evolutionary models abstract beachrock is present in many parts of the world particularly on low latitude coastlines its formation during stillstands or minor regressions in subtropical areas involves cementation of clastic grains and thus prevents grain transport in the littoral zone during later transgression or regression existing short and medium term conceptual and numerical models of coastal evolution fail to take into account this effective reduction of littoral sand supply and the effects of the beachrock itself on shoreline development in the short term reduction of sediment supply through beachrock formation during transgression should enhance landward translation of the shoreline conversely the beachrock itself may afford a degree of protection from erosion in the medium to long term beach rock formation during multiple pleistocene transgressions and regressions in areas which lack significant sediment input from land drainage systems may have caused a long term reduction in sediment volume during the course of the pleistocene this assumes that beachrock formation is not matched by its destruction through physical and bioerosion and chemical weathering preservation of coastal facies is greatly enhanced by beachrock formation which may promote overstepping and drowning of strandline facies during transgression or preferential preservation during regression precise records of sea level fluctuations may be preserved by beachrock formation a situation rendered almost impossible in other areas due to littoral transport of mobile sediment in the widespread areas in low latitudes where it occurs beachrock formation may be an important element in models of horizontal shoreline displacement and coastal evolution

beach cement incipient caco 3 cemented beachrock development in the upper intertidal zone north uist scotland abstract beachrock has only rarely been observed previously along high latitude coasts on several beaches on north uist nw scotland at over 57 n there is evidence of small scale beach cementation an area of beach cement at the back of traigh ear as well as unconsolidated sands from the beach and the adjacent traigh hornais have been studied using sem xrd and petrographical thin sections to throw light on the nature and causes of cementation unconsolidated sands from both beaches are similar in grain sizes shape and mineralogy but traigh ear grains commonly possess abundant cover of high mg calcite the beach cement on traigh ear exhibits low porosity with abundant micritic and aragonitic cements showing no evidence of vadose cementation along with traces of microorganisms these findings contrast with the vadose low mg calcite cements commonly reported from temperate zone beachrocks

late quaternary sea level change in south africa abstract a late quaternary sea level curve for south africa is presented on the basis of new and published data from a range of sea level indicators and a variety of locations available evidence suggests that sea level in south africa broadly follows that described from the caribbean but that deviations occur during sea level highstands during the last interglaciation oxygen isotope stage 5 and the late holocene coastal emergence produced higher sea levels in south africa than those identified in the caribbean during the same time intervals this is tentatively ascribed to predicted lithospheric deformation in continental margin settings

9000 years of sea level change along the southern african coastline abstract beachrocks are good indicators of sea level stillstands on microtidal coastlines and data for this sea level curve is mainly based on dating a series of holocene beachrocks and planation episodes on the southeast african coastline sea level reached its present level along the southern african coastline at ca 6500 bp sea level then rose depositing a series of beachrocks at an elevation of 2 75 m this mid holocene sea level highstand persisted for a period of 2500 years with a 3 5 m stillstand dated at 4480 bp being the highest sea level reached during the holocene in post holocene sea level optimum times a regression occurred lowering sea level to its present level at 3880 bp and down to 2 m at approximately 3000 bp subsequently sea level rose to 1 5 m at 1610 bp and attained its present level at about 900 bp the mid holocene sea level highstand appears to have resulted from a combination of isostatic emergence and the steric expansion of seawater relating to warmer ocean temperatures associated with the holocene hypsithermal event on the eastern agulhas bank

submerged shoreline preservation and ravinement during rapid postglacial sea level rise and subsequent slowstand submerged shorelines hold much potential for examining the interplay between the rate of sea level rise and geomorphic setting and informing the development of models of contemporary shoreline behavior this paper describes the sedimentary architecture of a submerged barrier shoreline complex off durban south africa the complex consists of several barriers that have survived the postglacial transgression and associated erosive ravinement processes the main shoreline sequence 60 m dates to 11 690 90 calibrated cal yr b p and rests on a pleistocene lagoonal deposit 35 395 592 cal yr b p the entire barrier shoreline complex is truncated by a strongly diachronous wave ravinement surface the ravinement surface seaward of the main 60 m shoreline is steep but the gradient declines across and landward of the subordinate landward shoreline complexes the steep ravinement surface is attributed to fast sea level rise possibly associated with meltwater pulse 1b while the gentle ravinement surface is associated with a subsequent slowing of the rate of sea level rise to 0 15 mm yr 1 preservation of the main barrier and back barrier deposits through overstepping is associated namely with rapid transgression and increased back barrier accommodation the smaller barriers landward of the main barrier were preserved through overstepping related to gentle antecedent gradients despite more intense ravinement during a very slow rise in sea level slowstand this process was assisted by a sediment deficit the resulting post transgressive drape is also influenced by antecedent topography created by the barriers themselves damming along the landward sides of overstepped barriers thickens the drape and creates a temporal disconnect between the migration of the shoreface and more landward elements of the littoral system in examining the rates of shoreline migration associated with the overstepped barrier system these are far greater than those calculated for the predicted rates of shoreline change on similarly steep coastal profiles future rates of shoreline migration appear to be insufficient to cause overstepping and rollover or erosional responses are more likely

divergent trajectories of antarctic surface melt under two twenty first century climate scenarios ice shelves modulate antarctica s contributions to sea level rise regional climate model simulations and observations suggest historical ice melt intensification before collapse of antarctic peninsula shelves and project future melt evolution

development of shore platforms on kaikoura peninsula south island new zealand ii the role of subaerial weathering the role of subaerial weathering in the development of shore platforms on kaikoura peninsula is investigated evidence for weathering came from a number of distinctive surface morphologies on platforms salt crystal growth water layer weathering and slaking schmidt hammer test data showed that weathering had occurred and that rock strength was reduced through weathering by as much as 50 weathering processes on shore platforms rely on repeated wetting and drying and for this reason the number of wetting and drying cycles was estimated it was found that the number of wetting and drying cycles depend not only on the pattern of tidal water levels but also on algae growth and desiccation the number of cycles ranged from 104 to 379 per year at elevations low in the tide range fewer cycles occurred the greatest number occurring between the peaks of spring and neap tides and where rainfall adds to the number the zone of most cycles was estimated to occur between 0 6 and 0 9 m above mean sea level on the more landward margins of platforms it is at these elevations that the highest rates of erosion occur based on these results it is argued that the development of shore platforms at kaikoura results from subaerial weathering caused by repeated wetting and drying this is contrary to the view that shore platforms result from marine erosion

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

the distribution of carbonate eolianite abstract carbonate eolianite forms distinctive coastal landforms on many mid latitude continents and islands numerous studies of extensive continental and smaller island deposits in both hemispheres have shown the eolianites are predominantly pleistocene in age the coorong coastal plain of south australia contains the world s longest record of eolianite deposition revealing that major phases of carbonate accumulation occurred during interglacial and some interstadial sea level highstands throughout the quaternary similarly the well studied eolianite islands of bermuda and the bahamas record a close match between dune accretion and sea level highstands since the middle pleistocene several other eolianite deposits appear to have formed at least partially during glacial periods the glacial age deposits are eolian reworked relict shelf or coastal sediments or remnants of former highly mobile coastal dunes sourced from low sea level shorelines the distribution and bioclastic composition of large scale eolianite deposits suggests carbonate production on shallow shelves and banks is the ultimate control on the formation of eolianite the bulk of the carbonate comprising those eolianites is heterozoan being produced where there is low terrigenous sediment input in dominantly temperate cool water and subtropical carbonate provinces quaternary cyclical movements of sea level have also controlled the form and rate of coastal carbonate deposition with repeated pulses of sedimentation during highstands forming laterally coalesced vertically stacked or composite dune successions major unconformities within the deposits are marked by paleosols which record hiatuses in coastal sedimentation in several regions major eolianite units overlie coastal deposits of terrigenous sediment those successions suggest that the trend towards aridity and reduction in the supply of terrigenous sediment to shelves during the quaternary has enhanced the production of carbonate and the deposition of eolianite

marine geology of the sodwana bay shelf southeast africa abstract the geostrophic current controlled northern zululand shelf displays a unique assemblage of interesting physical sedimentological and biological phenomena the shelf in this area is extremely narrow 3 km and is characterised by submarine canyons coral reefs and steep gradients on the continental slope three submarine canyons occur in the study area and are classified as mature or youthful phase canyons depending on the degree to which they breach the shelf these canyons originated as mass wasting features which were exploited by palaeo drainage during sea level regressions shelf lithology is dominated by a series of coast parallel patch coral reefs which have colonised beachrock and aeolianite sequences that extend semi continuously from 5 to 95 m and delineate late pleistocene palaeocoastline events the unconsolidated sediment on the shelf is either shelf sand mainly terrigenous quartz grains or bioclastic sediment large scale subaqueous dunes commonly form in the unconsolidated sediment on the outer shelf due to the agulhas current flow these dunes occur as two distinct fields at depths of 35 to 70 m the major sediment transport direction is towards the south but occasional bedload parting zones exist where the bedform migration direction changes from south to north

solute recycling an emerging threat to groundwater quality in southern india summary groundwater from crystalline aquifers is abstracted at large rates for paddy irrigation in southern india resulting in widespread over exploitation of the resource detailed field studies at watershed scale have shown that basin closure is happening i e groundwater contribution to base flow has stopped and irrigation return flow can contribute to as much as half of the aquifer recharge studies in other semi arid regions have shown that irrigation return flow through a process known as solute recycling can contribute significantly to aquifer salinisation to evaluate the impact of this process in the southern india context a lumped reservoir model has been designed in order to simulate long term trends of piezometric levels and solute concentrations at watershed scale the model is applied to the well studied watershed of maheshwaram 53 km2 located 40 km south of hyderabad it can reproduce qualitatively watershed average groundwater levels and chloride concentrations inferred since 2001 that shows a progressive buildup simulation of the period 2010 2044 indicates that forecasted reservoir concentrations are very sensitive to aquifer mixing efficiency in the case of complete mixing base flow that activates after rainy years may export significant solute mass and level off aquifer concentration to acceptable levels in the more realistic case of incomplete mixing diluted base flow will export less solute and progressive solute mass buildup continues throughout the simulation period to end up with concentrations close to the ones that makes water no longer suitable for irrigation final aquifer concentrations may become even higher with scenarios that accelerate the lowering of the water table such as higher pumping rates decrease in daily rainfall or increase in daily evaporation these simulations show that solute recycling may have a significant negative impact on groundwater quality in southern india especially in aquifers located in semi arid hard rock areas where the main source of irrigation is provided by groundwater

tidal notches a sea level indicator of uncertain archival trustworthiness abstract in this paper after a short summary on the processes and rates of bioerosion that contribute to the deepening of a tidal notch profile some mediterranean case studies are presented where a tidal notch is prevented either from forming or from being preserved furthermore as shown also in a complementary paper the recent global sea level rise is preventing the development of new tidal notches in the present mid littoral zone this very useful sea level indicator of past temporary standstills of the relative sea level in carbonate rock areas is of great value in assisting interpretations of relative sea level change in locations where it is preserved the possibilities of absence of formation or of preservation however imply that it should be interpreted carefully before reconstructing local relative sea level histories in particular the lack of fossil tidal notches cannot be relied upon to interpret the absence of past periods of relative sea level stabilization

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

summer drivers of atmospheric variability affecting ice shelf thinning in the amundsen sea embayment west antarctica satellite data and a 35 year hindcast of the amundsen sea embayment summer climate using the weather research and forecasting model are used to understand how regional and large scale atmospheric variability affects thinning of ice shelves in this sector of west antarctica by melting from above and below linked to intrusions of warm water caused by anomalous westerlies over the continental shelf edge el nino episodes are associated with an increase in surface melt but do not have a statistically significant impact on westerly winds over the continental shelf edge the location of the amundsen sea low and the polarity of the southern annular mode sam have negligible impact on surface melting although a positive sam and eastward shift of the amundsen sea low cause anomalous westerlies over the continental shelf edge the projected future increase in el nino episodes and positive sam could therefore increase the risk of disintegration of west antarctic ice shelves

sedimentology and petrography of dredged carbonate sands from stocking island bahamas implications for meteoric diagenesis and aeolianite formation abstract piles of carbonate sand dredged onto stocking island exuma chain bahamas during world war ii are now relatively well lithified down to a depth of about 80 cm and may contain up to 8 of interstitial calcite cement a volume comparable to that measured from 1000 yr old beach ridges elsewhere in the bahamas rates of meteoric diagenetic changes are thus more rapid than previously assessed in this area 600 cm3 of calcite cement produced by m3 of rock per year preservation of hydrodynamic sedimentary structures footprints and the lack of aeolian bedforms e g dunes ripples on the surface of these sediments further show they have not been reworked by the wind at all therefore the carbonate aeolianites of holocene and pleistocene ages forming the bulk of the islands of bermuda and the bahamas were likely deposited during relatively dry periods when the effects of meteoric diagenesis were limited reduced moisture along with sediment availability and wind energy appears as a key player in carbonate aeolianite genesis

morphology mineralogy and magnetic susceptibility of epikarst terra rossa developed in late quaternary aeolianite deposits of southeastern saurashtra india the nature and development of epikarst and soil development in aeolianites under a monsoonal climatic regime has not yet been described late quaternary aeolianites of the southeastern coast of saurashtra in western india show a wide array of epikarst and red soil formation and serve to typify the character of aeolianite weathering under a monsoonal climate three varieties of epikarst are identified that represent down profile increase in groundwater flow five types of terra rossae represent a transition from the karstified limestone to soil development terra rossae differ in the content of residual aeolianite and show both simple and complex profiles the latter at places shows ped development the results show that an ontogenetic growth sequence exists from incipient epikarst to complex palaeosols this ontogenetic sequence represents an incremental increase in the groundwater budget of the region in response to changing intensification of the indian monsoon rainfall magnetic properties of the terra rossae formed under a monsoonal climate are described for the first time the magnetic susceptibility together with its frequency dependent and anhysteretic remanent magnetization arm represents both the concentration of single domain and ultrafine superparamagnetic sp magnetite the formation of single domain and superparamagnetic magnetite and hematite are linked genetically to weathering of the aeolianite that leads to the formation of terra rossa

holocene coastal dune development and environmental changes in apulia southern italy abstract the coastal area of southern apulia is characterised by marine deposits of pleistocene and holocene ages it shows the effects of different phases of coastal morphology evolution during the middle and upper pleistocene a number of marine terraces were shaped in some places they are characterised by thin beach deposits along with a dune belt and relative back dune deposits two important morphogenetic phases occurred during the holocene the former was characterised by deposition of beach deposits placed slightly above present mean sea level and by formation of dune belts which were radiometrically aged about 6000 years bp this event marks the end of the rapid postglacial transgression that occurred during the holocene climatic optimum during the younger phase dated at about 2500 years bp deposition of aeolian sands occurred archaeological and morphological evidences suggest that this phase should be related to a low sea level stand followed by a slow sea level rise up to the present position and by humid temperate climatic conditions the collected data about the holocene dune belts occurring along the apulian coastline suggest that main phases of dune development could be related to the effects of sea level changes climatic conditions and in a subordinate way to human activity

morphology and origin of coastal karst landforms in miocene and quaternary carbonate rocks along the central western coast of sardinia italy in the area of punta funtanas arbus central west sardinia some small surfaces of miocene limestones crop out partially covered with quaternary calcarenites and plio quaternary basalts the biggest of these outcrops forms a fossil wave cut shore platform of up to 50 m wide with an altitude above sea level of approximately 4 5 m on this platform a wide variety of dissolution landforms can be observed these morphologies are related to the influence of the seawater zone of wave action marine splash and spray zone up to progressively more continental environments and to biokarst processes erosional action of marine organisms algae and micro organisms and are arranged in bands parallel to the coast corresponding to different morphological zones this paper describes all the karst landforms observed in this coastal area from a morphological and genetic point of view

quaternary sea level changes and aeolianites in the fernando de noronha archipelago northeastern brazil abstract finite and directional sea level indicators were found in the fernando de noronha archipelago brazil showing that in the mid to late holocene the sea level was similar to present and had been stable for at least the preceding 500 years this sea level behaviour is different from that observed in the nearest continental coast of northeastern brazil suggesting a slight sinking of the archipelago relative to the mainland the caracas formation that corresponds to the conspicuous aeolianites found on the archipelago was subdivided into two chronological units i and ii unit i is pleistocene formed before 50 000 bp and could correspond to an interglacial stage unit ii was formed during the holocene and was built up over the period from 10 700 to 5700 bp meaning that the sand dunes were transgressive and formed during the postglacial sea level rise prior to a mid holocene maximum at 7000 5000 bp

late quaternary aeolianites palaeosols and depositional environments on the nepean peninsula victoria australia abstract the nepean peninsula is a bay mouth bar near melbourne it is comprised of late quaternary aeolianites palaeosols and calcretes tl dates show that most of the sands from which the aeolianites developed as mobile sand dunes were deposited during times of low sea level towards 47 and 23 ka bp and others during times of relatively high sea level towards 118 ka bp aeolian dust mantles were laid down during brief intervals when aeolianite formation had ceased incipient soil formation and minor organic staining of the upper 0 3 0 5 m of the dust mantles points to a lull in dune formation and the temporary development of a widespread plant cover the dust mantles have tl ages of 118 57 54 51 and 47 ka bp indicating that apart from the 118 ka mantle most of the deposition was when sea level was low and the regional climate was drier windier colder and under a more continental climatic regime during times of glacially lower sea level the coastal climate in this region was not invariably cold dry and windy but was punctuated by brief intervals of milder moister and less windy conditions during which dunes and dust mantles became vegetated and soils began to form rapid climatic fluctuations were coeval with aeolianite deposition during times of very low sea level

relict and contemporary influences on the postglacial geomorphology and evolution of a current swept shelf the eastern cape coast south africa abstract few stratigraphic models of continental shelves incorporate the process of geostrophic current sweeping consequently its role in the stratigraphic record is often overlooked we examine the narrow current swept eastern cape shelf of south africa using a combination of geophysical techniques seafloor sampling and video observations and interpret the role of current action on the transgressive stratigraphy of this steep subtropical shelf during the last glacial maximum fluvial valleys incised the acoustic basement rocks during the subsequent transgression two distinct shorelines were formed and preserved at 105 m and 60 m their development and preservation is linked to i high sediment supply from adjacent fluvial sources ii early diagenesis and iii alternating sea level stillstands and periods of rapid sea level rise during melt water pulses 1a and 1b respectively the deeper shoreline formed in a sandy wide coastal plain setting with limited bedrock influence whereas the shallower shoreline comprised alternating rock headlands and embayments like the contemporary coast differences in antecedent topography and geology are responsible for the temporal variability in shoreline type coastal squeeze is exacerbated with increasing bedrock control as the shoreline migrates landward between the two shoreline complexes in the mid shelf the transgressive stratigraphy records initial valley infill by progradation of coast parallel sandy spits these are capped by a stiff lagoonal mud deposited as ongoing sea level rise overspilled the valley interfluves onlapping the adjacent aeolianites the uppermost stratigraphy comprises mounds of rhodoliths which interfinger with a sandy inner to middle shelf highstand wedge after sea level reached its present position ca 7 4 ka yr bp the shelf became subject to reworking by the high energy geostrophic agulhas current this has had the following major effects on the shelf stratigraphy 1 the topographic relief of the cemented palaeo shorelines has been emphasised by removal of the post transgressive cover and 2 the shelf no longer acts as a depocenter instead the seabed consists of rhodoliths gravel streamers bedrock or gravel hash of the wave ravinement surface given the necessary antecedent conditions such as accommodation sediment supply and favourable diagenetic climate prominent shorelines can form and be preserved on the shelf strong current sweeping emphasises these morphological features on subtropical shelves

recent dramatic thinning of largest west antarctic ice stream triggered by oceans a growing body of observational data suggests that pine island glacier pig is changing on decadal or shorter timescales these changes may have far reaching consequences for the future of the west antarctic ice sheet wais and global sea levels because of pig s role as the ice sheet s primary drainage portal we test the hypothesis that these changes are triggered by the adjoining ocean specifically we employ an advanced numerical ice flow model to simulate the effects of perturbations at the grounding line on pig s dynamics the speed at which these changes are propagated upstream implies a tight coupling between ice sheet interior and surrounding ocean

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

submerged barrier shoreline sequences on a high energy steep and narrow shelf abstract late pleistocene holocene shoreline sequences and associated shelf stratigraphy are described from a high gradient high wave energy shelf although shoreline preservation by overstepping is considered unlikely in such an environment as a result of intense ravinement during shoreline translation the development and preservation of two distinct shorelines at 100 m and 60 m are evident and attributed to century to millennial scale periods of stillstand during these periods shoreline equilibrium forms developed characterised by early diagenesis of beachrock and aeolianite between these features the shelf is dominated by erosional surfaces reflecting ravinement during periods of slowly rising sea level where shorelines are not preserved areas of scarping in the ravinement surface at similar depths to the adjoining shorelines represent rocky headlands separating the sandy coastal compartments where the depositional shorelines formed shoreline preservation by overstepping was facilitated by rapid relative sea level rise associated with meltwater pulses 1a and 1b although the features preserved are likely to represent only the cemented cores of the coastal dunes and linear beachrock outcrops formed the steep antecedent shelf gradient fostered the erosion of significant portions of the shorelines by ravinement with loose sediment re organised into a thick post ravinement drape the removal of shorelines during ravinement was countered by the rapid rate of sea level rise and early sub tropical diagenesis it is clear that due to the combined effects of subtropical diagenesis long periods of stillstand and drowning by meltwater pulses the governing controls on shoreline preservation can be over ridden by combinations of local climatic and global eustatic factors

geomorphic and stratigraphic signals of postglacial meltwater pulses on continental shelves selective development and preservation of major shoreline complexes on the continental shelf provide geomorphic evidence in support of alternating periods of holocene sea level stillstand and rapid rise during meltwater pulses on a tectonically stable far fi eld setting the southeast african shelf regionally developed well preserved shoreline complexes occur at 100 m and 60 m within an overall shelf sequence dominated by transgressive ravinement non preservation of shorelines the development of geomorphically mature submerged shorelines with equilibrium forms is attributed to extended periods of sea level stability and their preservation is the result of early cementation followed by very rapid sea level rise several centimeters per year that caused overstepping meltwater pulses 1a and 1b are recorded in the shelf stratigraphy and geomorphology setting aside local infl uences of topography and sediment supply we hypothesize that shelf stratigraphies should preferentially preserve shorelines at water depths associated with the stillstands or slowstands immediately preceding meltwater pulses a reappraisal of shelf stratigraphy and geomorphology in particular the preservation potential of former shorelines is required in the light of contemporary understanding of postglacial sea level history

a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering summary the weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas these weathering profiles generally develop under both stable geodynamic conditions weathering rate erosion rate and a hydrolysing climate they are composed of thick stratiform layers that follow the paleo landscape paleotopography and thus present a gently dipping sequence at a regional scale the structure and the hydrodynamic properties of the weathering profile of a granitic area 53 km 2 maheshwaram catchment state of andhra pradesh india were characterized in detail and mapped from observations on outcrops 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones the structure of the weathering profile results from a multiphase process an ancient weathering profile was partly eroded down to its fissured layer it was later re weathered more or less parallel to the current topographic surface this peculiar structure is linked to the geodynamic history of the indian peninsula that underwent alternate weathering and erosion dominated phases the profile is thus composed from top to bottom up to a total depth of 35 m of sandy regolith saprolite 1 3 m 10 15 m of laminated saprolite containing unusual preserved fissures and a 15 20 m thick fissured layer by comparing various case studies in similar terrain a generalized 3 d geological and hydrogeological conceptual model of granite type aquifers granites gneisses etc is proposed in granite type rocks single weathering or multiphase weathering and erosion processes induce similar geological structures a few main geological differences arise from the comparison of single phase and multiphase weathering profiles i in the later the respective thicknesses of the various layers can be deeply modified ii the ancient fissured layer can be re weathered and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures and iii the upper part of the fissured layer is more densely fissured as a result of the same weathering processes the fissures from the fissured layer of single phase or multi phase profiles exhibit very similar hydraulic conductivities and show both a higher density of conductive fissures at the top of the layer the preserved ancient fissures within the laminated layer of a multiphase profile are partly obliterated by the recent weathering their hydraulic conductivity is thus significantly reduced nevertheless they do significantly contribute to borewell yield these weathering induced fissures provide most of the aquifer permeability the use of such a conceptual model for the precise geological mapping of the weathering structure appears to be a prerequisite for groundwater development and management in hard rock areas as it answers to several key issues

widespread rapid grounding line retreat of pine island thwaites smith and kohler glaciers west antarctica from 1992 to 2011 we measure the grounding line retreat of glaciers draining the amundsen sea sector of west antarctica using earth remote sensing ers 1 2 satellite radar interferometry from 1992 to 2011 pine island glacier retreated 31 km at its center with most retreat in 2005 2009 when the glacier ungrounded from its ice plain thwaites glacier retreated 14 km along its fast flow core and 1 to 9 km along the sides haynes glacier retreated 10 km along its flanks smith kohler glaciers retreated the most 35 km along its ice plain and its ice shelf pinning points are vanishing these rapid retreats proceed along regions of retrograde bed elevation mapped at a high spatial resolution using a mass conservation technique that removes residual ambiguities from prior mappings upstream of the 2011 grounding line positions we find no major bed obstacle that would prevent the glaciers from further retreat and draw down the entire basin 2014 american geophysical union all rights reserved

combined estimation of specific yield and natural recharge in a semi arid groundwater basin with irrigated agriculture a water budget approach is developed to jointly estimate specific yield and natural recharge in an unconfined aquifer with significant seasonal water table fluctuations water table fluctuations are due to distinct seasonality in groundwater recharge the separation of the hydrologic year into two or more extended seasons of recharge wet season and no recharge dry season with accompanying changes in water table allows for a split use of the water table fluctuation wtf method first to estimate specific yield from the water table drop during the dry season no recharge and second to estimate recharge from the water table rise during the wet season after considering all other water budget components explicitly the latter includes explicit computation of groundwater storage with the wtf method the application of the wtf method requires a large number of water level measurements throughout the unconfined aquifer before and after each season the advantage of the method is that specific yield and recharge are estimated at the scale of interest to basin hydrologic studies and that the method requires no extensive in situ instrumentation network here the method is demonstrated through a case study in a fractured hard rock aquifer subject to intensive groundwater pumping for irrigation purposes

upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale in deeply weathered crystalline aquifers two innovative approaches for upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale are proposed they are based on the concept that large scale variations in hydraulic head may characterize large scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering located in south india maheshwaram watershed 53 km2 both methods are based on field data such as water levels discharge rates of irrigation wells geological observations and the results of small scale hydraulic tests the resulting hydraulic conductivity map uses the statistical empirical relationship between log normal distributions of hydraulic conductivity from small scale tests and linear discharge rates from exploited wells i e the ratio between discharge rate and the saturated aquifer thickness the empirical relationship agrees with thiem dupuit s assumption for unconfined aquifers the performance of the method was compared to the values of local hydraulic conductivity estimates deduced from small scale tests not used for drawing the map about 90 of simulated values varies less than 20 from local measurements logk 0 4 on average which is reasonable considering the complexity of the studied fractured aquifer the regionalization of the effective porosity was based on a method that combines both water table fluctuation and groundwater budget techniques in the absence of recharge from rainfall however the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells which here is unknown to avoid this difficulty a coarse graining method was used assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell our results show that cell sizes over 520 520 m achieve a negligible balance in addition porosity maps provide average values of around 1 5 that are almost identical to the ones previously found at watershed scale the proposed methods for regionalizing hydraulic conductivity and porosity fields provide access not only to the average large scale values but also to their spatial distribution which is of prime interest in terms of flux and contaminant transport in a hard rock environment the uncertainty introduced by field data the choice of the computation scale as the impact of cell size on the calculated effective porosity value and the possible meaning of their spatial variations are also discussed

a low level explanation for the recent large warming trend over the western antarctic peninsula involving blocked winds and changes in zonal circulation 1 we demonstrate a mechanism whereby the impact of stronger circumpolar westerly winds on the mountains of the antarctic peninsula contributes significantly to the enhanced warming trend observed over its western side in the last 50 years numerical and laboratory meteorological modelling demonstrate how when westerly winds impinge on this side warm air below the height 1 5 2 0 km of the peninsula is advected in a southerly direction the strength of the annual mean westerly winds has increased by about 15 20 since the 1960s while the modelling results indicate that contemporaneously the air advected to its western side originates from an increasingly northerly and warmer location this gives rise to increased northerlies and a greater transport of warm air into this region consequently there is a reduction in the sea ice extent further amplifying the local warming this low level orographic mechanism for the local climate trend is supported by observational evidence

atmosphere ocean ice interactions in the amundsen sea embayment west antarctica over recent decades outlet glaciers of the amundsen sea embayment ase west antarctica have accelerated thinned and retreated and are now contributing approximately 10 to global sea level rise all the ase glaciers flow into ice shelves and it is the thinning of these since the 1970s and their ungrounding from pinning points that is widely held to be responsible for triggering the glaciers decline these changes have been linked to the inflow of warm circumpolar deep water cdw onto the ase s continental shelf cdw delivery is highly variable and is closely related to the regional atmospheric circulation the ase is south of the amundsen sea low asl which has a large variability and which has deepened in recent decades the asl is influenced by the phase of the southern annular mode along with tropical climate variability it is not currently possible to simulate such complex atmosphere ocean ice interactions in models hampering prediction of future change the current retreat could mark the beginning of an unstable phase of the ase glaciers that if continued will result in collapse of the west antarctic ice sheet but numerical ice sheet models currently lack the predictive power to answer this question it is equally possible that the recent retreat will be short lived and that the ase will find a new stable state progress is hindered by incomplete knowledge of bed topography in the vicinity of the grounding line furthermore a number of key processes are still missing or poorly represented in models of ice flow

assessment and development of snowmelt retrieval algorithms over antarctica from k band spaceborne brightness temperature 1979 2008 abstract results from several previously published algorithms for wet snow detection in antarctica from k band spaceborne brightness temperature are compared and evaluated vs estimates of wet snow conditions from ground measurements in addition a new physically driven algorithm in which the detectable liquid water content is assumed constant is proposed and assessed all algorithms are also evaluated by analyzing their results during collapses of ice shelves two algorithms are selected for deriving updated trends of melting index mi the number of melting days times the area subject to melting between 1979 and 2008 over the whole antarctica and at sub continental scales in the first algorithm wet snow is identified when brightness temperature exceeds the mean of winter brightness temperature plus 30 k and the second is the new model based approach described here both negative and positive mi trends are obtained depending on the algorithm used a high number of melting days up to 100 days are detected over the wilkins ice shelf the peninsula and the george vi ice shelf over east antarctica the west and amery ice shelves are subject to melting for a maximum of approximately 50 days positive trends of number of melting days are detected over most of the west antarctica with peak values up to 1 2 days year over the larsen c ice shelf 1 8 days year over the george vi ice shelf and 0 55 days year over the wilkins ice shelf area the correlation between mi values and december january dj averaged air surface temperature over selected locations show values ranging between 0 8 and 0 4 results suggest that a 1 c increase in the monthly averaged dj air surface temperature corresponds to an average mi increase of approximately 2 106 km2 day

formation and preservation of an overstepped segmented lagoon complex on a high energy continental shelf the duration of shoreline occupation at a given sea level coastal response to sea level change and the controls on preservation of various shoreline elements can be recognized by detailed examination of submerged shorelines on the continental shelf using bathymetric and seismic observations this article documents the evolution and preservation of an incised valley and lithified barrier complex between 65 m and 50 m mean sea level on a wave dominated continental shelf the barrier complex is preserved as a series of aeolianite or beachrock ridges backed by laterally extensive back barrier sediments the ridges include prograded cuspate lagoonal shoreline features similar to those found in contemporary lagoons the incised valley trends shore parallel behind the barrier complex and records an early phase of valley filling followed by a phase of extensive lagoonal sedimentation beyond the margins of the incised bedrock valley sea level stability at the outer barrier position ca 65 m enabled accumulation of a substantial coastal barrier that remained intact during a phase of subsequent slow sea level rise to 58 m when the lagoon formed these lagoonal sediments are stripped seawards by bay ravinement processes which caused the formation of several prograded marginal cuspate features an abrupt rise in sea level to 40 m correlated with melt water pulse 1b enabled the preservation of thick lagoonal sediments at the top of the incised valley fill and preservation on the sea bed of the cemented core of the barriers this situation is unique to subtropical coastlines where early diagenesis is possible the overlying sandy sediment from the uncemented upper portion of the barriers is dispersed by ravinement partly burying the ridges and protecting the underlying sediments the high degree of barrier or shoreline preservation is attributed to rapid overstepping of the shoreline early cementation in favourable climatic conditions and the protection of the barrier cores by sand sheet draping

antarctic ice sheet loss driven by basal melting of ice shelves accurate prediction of global sea level rise requires that we understand the cause of recent widespread and intensifying glacier acceleration along antarctic ice sheet coastal margins atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves potentially limiting their ability to buttress the flow of grounded tributary glaciers indeed recent ice shelf collapse led to retreat and acceleration of several glaciers on the antarctic peninsula but the extent and magnitude of ice shelf thickness change the underlying causes of such change and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum antarctic pattern of ice shelf thinning through increased basal melt we deduce that this increased melt is the primary control of antarctic ice sheet loss through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow the highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of antarctic ice shelves through ocean upwelling in the amundsen and bellingshausen seas and atmospheric warming on the antarctic peninsula this implies that climate forcing through changing winds influences antarctic ice sheet mass balance and hence global sea level on annual to decadal timescales

managed aquifer recharge in south india what to expect from small percolation tanks in hard rock summary many states in india are currently facing general overuse of their groundwater resources mainly due to growing demand for irrigated agriculture groundwater levels are declining despite water harvesting measures to enhance aquifer recharge which are supported on a massive scale by watershed development programmes new programmes are being implemented to improve artificial percolation i e managed aquifer recharge mar although the impact of former measures on aquifer recharge has not yet been assessed it is therefore crucial to increase our understanding of mar to successfully overcome the threat of groundwater scarcity in the near future this paper scrutinizes the ability of a typical percolation tank to recharge the aquifer using a comprehensive approach combining water accounting geochemistry and hydrodynamic modelling over 2 years of observation the percolation efficiency percolated fraction of stored water of the tank ranged from 57 to 63 the rest being evaporated modelling showed that the percolated water was mostly 80 pumped straight back by the neighbouring boreholes limiting the area of mar influence but increasing percolation efficiency

the luminescence chronology of dune development on the maputaland coastal plain southeast africa abstract geomorphological and lithostratigraphic mapping of dune systems on the maputaland coastal plain of northeastern kwazulu natal province south africa has defined the relative age relationships between the complex pattern of quaternary parabolic and hummocky dunes sand megaridges and the composite coastal barrier dune cordon here infra red stimulated luminescence irsl ages are presented in the context of regional stratigraphic relationships and serve to bracket the period of accumulation of the main dune systems the luminescence ages challenge the widely held belief that the north south aligned dune pattern reflects a coastward younging sequence the framework of ages highlights the spatial variations in dune mobilization and long accretion history on some dune forms weathered dune and interdune wetland sediments spanning from prior to marine isotope stages mis 11 and up to mis 7 underlie the coastal plain at least two generations of decalcified aeolianite of mis 5 and 4 form the core of the complex coastal barrier dune on the coastal plain frequent sand mobilization events during mis 3 2 resulted in the development of discrete complexes of highly extended northward directed parabolic dune systems and reworking of the crest of the central sand megaridge the luminescence dated dune mobilization history brackets the period of formation of interdune and lacustrine peat and diatomite deposits during the holocene marine transgression at least four laterally extensive complex transverse ridges of coalesced ascending parabolic dunes accreted against the aeolianite core of the coastal barrier polyphase dune formation and remobilization is discussed in the context of the regional groundwater and vegetation responses to global climatic changes wind regimes and glacio eustatic sea level fluctuations

contrasting styles of swell driven coastal erosion examples from kwazulu natal south africa during 2006 2007 the kwazulu natal coast of south africa was exposed to several large swell events ho 3 m near the peak of the lunar nodal cycle causing shoreline recession the largest swell hs 8 5 m struck the coast on the march equinox 18th 20th and generated a strong storm return flow observations made before during and after record dramatic coastal erosion shoreline recession of up to 40 m and substantial property damage this swell event removed the semi continuous nearshore bar system and conditioned the coast such that lesser subsequent swell events accomplished much greater amounts of coastal erosion than expected up to 100 m at certain erosion hotspots because waves reached the coast without significant energy dissipation subsequent bar generation rebuilt the inshore bars within six months the styles of erosion during the march 07 event and other 2007 swells were markedly different lesser swells are focused by headlands and result in megarip development and activation of erosion hotspots the march 07 event still water level was raised equinoctial spring high tide and a storm surge of 0 33 0 45 m to a level that rendered most headlands and erosion hotspots ineffective and resulted in laterally extensive erosion of soft shorelines results record cumulative effects of successive swell events on coastal behaviour that proved to be critical in enabling erosion to proceed at rapid rates after the coast had been initially destabilized unlike hurricanes and tsunamis surges associated with swell events are relatively minor and therefore extensive erosion is linked with high lunar tides there is circumstantial evidence that swell induced erosion follows the broad 18 6 yr lunar nodal tidal cycle when the chances of large swells coinciding with high water levels are increased

the late cretaceous to holocene sequence stratigraphy of a sheared passive upper continental margin northern kwazulu natal south africa abstract high resolution single channel seismic data reveal seven seismic units a g from the narrow and steep upper portions of the sheared passive continental margin of northern kwazulu natal several characteristic internal geometries are evident onlapping sheet like unit c aggradational progradational unit a and facies d3 and progradational unit b facies d1 2 and facies g1 on the basis of internal geometry and bounding unconformities lowstand units b facies d3 and lowermost unit g possible transgressive unit c highstand upper unit g and falling stage facies d1 and d2 systems tracts are delineated units e and f are not reconcilable due to acoustic opacity overall five incompletely preserved sequences are observed sequence one comprises unit a of suspected middle maastrichtian age separated from the overlying sequence by a subaerial unconformity surface sb1 units b and c form sequence two and span the late cretaceous late maastrichtian to mid late palaeocene two major hiatuses ensued angus and jimmy until mid pliocene times when unit d was deposited during shelf margin advance linked to hinterland uplift these falling stage systems tract deposits are separated from latest pliocene early pleistocene lowstand shelf edge deltaic deposits by a subaerial unconformity marking the deposition of sequence four facies d3 the age of unit e is uncertain unit f represents a series of shorelines formed during oxygen isotope stage ois 5a to 2 on the regressive and transgressive limbs preceding and following the last glacial maximum lgm the final partial sequence preserved is comprised of unit g formed during the ois 2 transgression to present mean sea level and subsequent development of the contemporary highstand wedge in terms of stratigraphic architecture this study shows an evolution from a ramp style margin with a poorly defined shelf break to that of a shelf break profile with a narrow and steep shelf in this respect the narrowness of this shelf cannot be accounted for by the inheritance of shearing effects rather the stratigraphic architecture reflects a period of slow and protracted subsidence with strong sediment dispersal later punctuated by hinterland uplift this formed the late pliocene shelf margin clinoforms of unit d and established the shelf break position at the offlap break of this wedge the resulting narrow shelf may play a significant role in the preservation of later sequences particularly in light of the continued uplift of the margin causing off shelf sediment bypass where tst and hst sequences may not be preserved this is reflected in the isolated preservation of shoreline and shallow marine deposits of the pleistocene units e and f

comparison of surface and groundwater balance approaches in the evaluation of managed aquifer recharge structures case of a percolation tank in a crystalline aquifer in india summary to face the problem of groundwater depletion the indian government relies on large projects of managed aquifer recharge mar numerous recharge structures such as percolation tanks exist but the impact of these structures on groundwater resources remains poorly understood although the evaporation infiltration ratio of percolation tanks was determined in several studies in semi arid contexts using surface water balance methods few studies evaluated the impact on the aquifer recharge however knowledge on recharge dynamics over time and space is essential for 1 the quantitative evaluation of stored water volumes 2 the identification of beneficiaries farmers and 3 the estimation of percolation tanks recharge zone to the extent that is required to define proper management regulations at basin scale these three points are of prime importance in the case of semi arid regions where a limited number of rain events determine the water stored over the entire year assessment of the stored groundwater is even more difficult in crystalline aquifers due to the heterogeneous structure of flow paths to date no methodological guidelines exist for local assessment of percolation tanks in crystalline aquifers in this paper we develop a method for calculating a local groundwater budget and we compare it with a computed surface balance the method is applied to a case study in semi arid crystalline context from the groundwater balance we draw conclusions on 1 the limited amount of stored water in the aquifer 2 the delayed recharge of the aquifer highlighting temporary storage slow groundwater movement in the unsaturated zone and 3 the limited number of beneficiaries in years of medium monsoon rainfall these results complement the understanding of the hydrodynamic functioning of percolation tanks and their impact on the local groundwater balance

early marine isotope stage 5 sea levels coastal dune palaeoenvironments and human occupation on the southeast coast of south africa abstract quaternary age human and animal footprints have been reported from coastal deposits along the south african coast these footprints and their sedimentary contexts can inform on quaternary palaeoenvironments and processes stratigraphically associated with the palaeoanthropological record of past human occupation in the coastal zone and exploitation of its resources this study examines the palaeoenvironmental context and sedimentology of marine isotope stage 5 aeolianite at nahoon point southeastern coast of south africa where preserved human footprints have been previously recorded this study identifies seven sedimentary facies from 20 logged profiles through the coastal aeolianite in order to develop a landscape scale stratigraphic framework for coastal palaeoenvironmental reconstruction during the period of the mis 5 highstand two phases of aeolianite deposition are identified which bracket a single stepped sea level transgression phase up to 7 82 0 82 m asl evidenced by intraformational beachrock facies and marine benches this correlates with the second known global mis 5e highstand no evidence for the first highstand reported from the literature was found in the study area aeolianite bed geometries and sedimentary structures indicate that wind regimes and rainfall seasonality were similar to present newly discovered faunal tracks in aeolianites of the first depositional phase suggest the presence of unidentified bovids of varying sizes evidence for human activity is preserved in all three recorded depositional phases suggesting people were present throughout the early mis 5 sequence despite changing environmental conditions this evidence suggests that human occupation of coastal areas and the exploitation of marine food resources was more widespread than generally thought in southern africa during early mis 5

holocene sea level fluctuations inferred from the evolution of depositional environments of the southern langebaan lagoon salt marsh south africa a holocene sea level curve is constructed from the facies distribution and radiocarbon ages of sediment recovered from the distal southern salt marsh of langebaan lagoon on the southwest coast of south africa calibrated radiocarbon analyses of an oyster rich bioclastic gravel indicate that the flandrian transgression flooded the lagoon to 0 3 m above present day levels by 6750 years ago 6 8 ka organic matter and shell material dated in distal lagoonal sediments indicate that sea level returned to present day levels by 4 9 ka and have since remained within 61 m of present day levels bleached shell and a hiatus in sedimentation suggest an approximate 1 m sea level lowstand between 2 5 and 1 8 ka changes in the macrobenthos assemblage since 1 5 ka that include the loss of the oysterostrea atherstonei razor clamsolen capensis brown musselarcuatula capensis and periwinkleoxystele variegata reflect loss of hard substrate decreased tidal flow velocities as reworked sands prograded into the southern la

hydrologic issues in arid unsaturated systems and implications for contaminant transport analysis of unsaturated flow and transport in arid regions is important not only in water resource evaluation but in contaminant transport as well partic ularly in siting waste disposal facilities and in remediat ing contaminated sites the water fluxes under consid eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow the purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings because individual techniques for estimating water fluxes in the unsaturated zone have limitations a variety of physical measurements and environmental tracers should be used to provide multiple independent lines of evidence to quantify flow and transport in arid regions the direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients the similarity of water fluxes in a variety of settings in the southwestern united states indicates that vegetative cover may be one of the pri mary controls on the magnitude of water flow in the unsaturated zone however our understanding of the role of plants is limited most unsaturated flow in arid systems is focused beneath topographic depressions and diffuse flow is limited thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib rium with current climate whereas water movement along preferred pathways is common in humid sites field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions results of field studies of preferential flow in humid sites generally restricted to the upper 1 2 m because of shallow water tables cannot be applied readily to thick vadose zones in arid regions

calcareous dunes of the united arab emirates and noah s flood the postglacial reflooding of the persian arabian gulf abstract aeolian dunes cover most of the united arab emirates and a large part of the eastern arabian peninsula although these sands as well as older aeolianites are largely composed of quartz there is a high percentage of detrital carbonate in them south of the persian arabian gulf for more than 40 km this percentage decreases inland these carbonate grains consist mainly of marine bioclastic fragments and calcareous ooids and were derived from the floor of the persian gulf which was exposed during low sea level of the last glacial period the postglacial rise in sea level rapidly reflooded the floor of the persian gulf cutting off the source for these aeolian sediments between 12 and 6 ka the sea transgressed more than 1000 km inundating the extended route of the tigris euphrates river and forcing people living on the exposed floor of the gulf to abandon their settlements because of the varying rate of eustatic sea level rise these waters at times flooded across the flat floor of the persian gulf at more than a kilometer per year we proposed that the stories of a great flood recorded in the bible as noah s flood and in babylonian history on clay tablets excavated in the tigris euphrates delta as the epic of gilgamesh are a record of this rapid postglacial flooding of the floor of the persian gulf

use of hydraulic tests at different scales to characterize fracture network properties in the weathered fractured layer of a hard rock aquifer the hydrodynamic properties of the weathered fractured layer of a hard rock pilot watershed in a granitic terrain are characterized using hydraulic tests at different scales the interpretation of numerous slug tests leads to characterize the statistical distribution of local permeabilities in the wells the application of flowmeter profiles during injection tests determines the vertical distribution of conductive fracture zones and their permeabilities it appears that the extension of the most conductive part of the weathered fractured layer is limited down to 35 meters depth the partition of drainage porosity between blocks 90 and fractures 10 is determined thanks to the interpretation of pumping tests using a double porosity model the application of anisotropic and single fracture analytical solutions on pumping test data allows to determine respectively the degree of anisotropy of permeability and the radius 4 to 16 meters of the horizontal conductive fractures crossed by the wells two different scales of fractures networks are identified the primary fracture network pfn which affects the matrix on a decimeter scale by contributing to an increase in the permeability and storage capacity of the blocks and the secondary fracture network sfn which affects the blocks at the borehole scale sfn is composed of two sets of fractures the main set of horizontal fractures is responsible for the sub horizontal permeability of the weathered fractured layer a second set of less permeable sub vertical fractures insures the connectivity of the aquifer at the borehole scale the good connectivity of fractures networks is shown by fractional dimension flow solutions the absence of scale effect in the study area suggests that the hydraulic conductivity at the borehole scale is laterally homogeneous finally the analysis and synthesis of the hydrodynamic properties allow to propose a comprehensive hydrodynamic model of the fractured weathered layer many geological and hydrogeological indicators suggest that a continuous and laterally homogeneous weathering process is responsible for the origin of the fractures and permeability encountered in the aquifer these results confirm the major role played by weathering in the origin of fractures and on resulting hydrodynamic parameters in the shallow part of hard rock aquifers

geomorphology and clast assemblages of intertidal beachrock implications for submerged shoreline preservation abstract beachrock may be considered a reliable indicator of sea level in addition to a reliable and recognizable source for onshore movement of beachrock clasts by overwash processes associated with extreme events key to this is its geomorphology and preservation potential both of which are poorly understood here we examine the processes and deposits associated with beachrock breakdown from camurupim ne brazil and compare its preservation to beachrocks found on continental shelves in south africa we study a prominent and continuous 50 60 m wide beachrock complex that crops out along a 10 km stretch of coastline and which mostly comprises 1 5 to 2 m thick trough crossbedded sandstones these have generated large joint bounded blocks that have been transported landwards under extreme energy conditions based on numerical modelling and comparisons to the contemporary wave climate tabular clasts have accumulated as isolated very coarse boulders on the seaward margin small clasts in various topographic traps boulder ridges with large landward and seaward dipping clasts on the uppermost part of the outcrop and subaqueous and subaerial washover fans isolated fine meso boulders emplaced during extreme waves hs ca 12 m exhibit fitted textures and pressure solution contacts pointing to subsequent rocking and shaking smaller clasts in boulder ridges and overwash settings are initially liberated and transported by waves within the annual decadal frequency spectrum deposited on the high points of the outcrop subsequent movement during less extreme wave action progressively transports the clasts across the surface where they are often trapped in the fitted fabric on top of the platform our breakdown model and overall beachrock preservation scheme is consistent with reported seismic signatures of submerged holocene beachrock shorelines beachrock preservation during transgression is strongly influenced by the original sedimentary facies thick trough crossbedded joint bound clasts preserve the former shoreline clasts from the planar units accumulate as washover fans to landwards of the ridge

contribution of antarctica to past and future sea level rise polar temperatures over the last several million years have at times been slightly warmer than today yet global mean sea level has been 6 9 metres higher as recently as the last interglacial 130 000 to 115 000 years ago and possibly higher during the pliocene epoch about three million years ago in both cases the antarctic ice sheet has been implicated as the primary contributor hinting at its future vulnerability here we use a model coupling ice sheet and climate dynamics including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine terminating ice cliffs that is calibrated against pliocene and last interglacial sea level estimates and applied to future greenhouse gas emission scenarios antarctica has the potential to contribute more than a metre of sea level rise by 2100 and more than 15 metres by 2500 if emissions continue unabated in this case atmospheric warming will soon become the dominant driver of ice loss but prolonged ocean warming will delay its recovery for thousands of years