quantitative constraints on the sea level fall that terminated the littorina sea stage southern scandinavia abstract the island of anholt in the kattegat sea southern scandinavia is made up largely of an extensive beach ridge plain as a result of post glacial uplift the earliest beach ridge and swale deposits are now raised 8 9 m above present mean sea level it appears that growth of the plain has been almost uninterrupted over the past 7500 years here we constrain the evolution of this plain between 6300 and 1300 years ago using optically stimulated luminescence dates the topography and internal architecture of the fossil shoreline deposits were measured on high resolution maps and in ground penetrating radar gpr reflection data with a vertical resolution of 0 25 m shoreline topography shows significant changes with time and it appears that one of the most striking changes took place between 4300 and 3600 years ago in the shoreline deposits corresponding to this time interval the surface drops by around 3 5 m suggesting a marked fall in relative sea level assuming a constant uplift rate of 1 2 mm yr the corresponding drop in absolute sea level is estimated to be around 2 6 m this marked sea level fall in 700 years took place at the transition from the middle holocene thermal maximum to the late holocene thermal decline or at the end of the littorina sea stage in the baltic sea region

late holocene record of lagoon evolution climate change and hurricane activity from southeastern cuba a sediment core from a lagoon in southeastern cuba was the focus of a multi proxy paleoenvironmental study to investigate lagoon response to sea level change and climate change and also to infer changes in the frequency of past hurricane strikes the proxy data examined included benthic foraminifera fossil pollen particle size analysis and macrocharcoal influx values the core was dated using 137cs and accelerator mass spectrometry ams radiocarbon methods the results show that lagoon formation began approximately 4000 years ago and that the lagoon environment evolved through four phases 1 from 4000 to 2800 cal yr bp the lagoon was a shallow polyhaline to euryhaline system with limited mangrove coverage 2 from 2800 to 2000 cal yr bp there was a decrease in salinity which facilitated the expansion of red mangrove 3 from 2000 to 1000 cal yr bp sea level rise resulted in an increase in water depth and possibly salinity and 4 from 1000 cal yr bp to the present water level continue

reconstructing mid late holocene cyclone variability in the central pacific using sedimentary records from tahaa french polynesia abstract we lack an understanding of the geographic and temporal controls on south pacific cyclone activity overwash records from backbarrier salt marshes and coastal ponds have been used to reconstruct tropical cyclone strikes in the north atlantic basin however these specific backbarrier environments are scarce in the south pacific with cyclone records limited primarily to the period of modern observation this instrumental record suggests a correlation with the el nino southern oscillation enso but longer records are necessary to test this relationship over geologic timescales and explore other potential climate drivers of tropical cyclone variability deep lagoons behind coral reefs are widespread in the pacific and provide an alternative setting for developing long term sedimentary reconstructions of tropical cyclone occurrence coarse grained event deposits within the sediments of a back reef lagoon surrounding tahaa reveal a 5000 year record of cyclone occurrences timing of recent high energy deposits matches well with observed tropical cyclone strikes and indicates coarse deposits are storm derived longer records show tropical cyclone activity was higher from 5000 to 3800 and 2900 to 500 yrs bp comparison to records from the north pacific out of phase and north atlantic in phase suggests a coordinated pattern of storm activity across tropical cyclone basins over the mid late holocene the changes in tropical cyclone activity we observe in the south pacific and across other basins may be related to enso as well as precession driven changes in ocean atmosphere thermal gradients

surface microtextures of ice rafted quartz grains revealing glacial ice in the cenozoic arctic abstract ice rafted grains of the central arctic ocean sediments provide a reliable proxy for arctic palaeoenvironments and climatic conditions that prevailed at the time of their deposition to understand ice involvement and implications for environmental advancement it has proven necessary to ascertain whether these detrital grains were rafted on glacial ice or sea ice surface microtexture identification allows grain differentiation based on the processes and conditions in its environmental provenance here quartz sand grain surface microtextures are used to detect glacially crushed and reworked grains from the lomonosov ridge sediments obtained by the integrated ocean drilling program expedition 302 arctic coring expedition the data show that the most frequent distributions of glacial grains were deposited at the middle late miocene and during the pliocene and early pleistocene especially the middle miocene climatic cooling and the presence of glacial ice are well indicated at 13 5 ma sediment grains earliest finding of the high frequency occurrence of glacigenic microtextures represents the age of 56 ma this first sedimentological evidence for the late palaeocene glacial ice supports the existing hypothesis of ephemeral polar glaciations during times of marked global warmth however due to lack of uninterrupted sediment recovery and non continuous nature of sampling the glacially influenced samples recovered here should be treated as an estimate of the minimum frequency of glacier appearance in the arctic

holocene sedimentary evolution of a mid ocean atoll lagoon maldives indian ocean based on detailed analyses of cores covering the lagoon of rasdhoo atoll maldives six carbonate facies one soil and one peat facies have been identified the abundance of carbonate and rare opaque grains was quantified with a point counter x ray diffractometry was used to measure mineralogical composition of samples the statistical delineation of facies using cluster analysis was based on point count mineralogical and textural analyses in decreasing abundance the six carbonate facies are classified as mollusk coral algal floatstone to rudstone 30 mollusk coral red algae rudstone 23 mollusk coral algal wackestone to floatstone 23 mollusk coral wackestone 13 mollusk coral mudstone to wackestone 9 and mollusk mudstone 2 the carbonate facies represent lagoonal background sedimentation mostly consisting of fine sediments and event sedimentation depositing transported coarse grained reefal components fifty seven carbonate samples and one peat sample were dated radiometrically covering the holocene transgression from 10 kyrs bp until today comparing the sediment accumulation data of the lagoon with two local sea level curves three systems tracts can be identified 1 a lowstand systems tract characterized by karst and soil deposition 10 kyrs bp 2 a transgressive systems tract with peat and carbonate separated by hiatus 10 6 5 kyrs bp and 3 a highstand systems tract dominated by carbonate sedimentation 6 5 0 kyrs bp and further divided into three stages 6 5 3 3 1 and 1 0 kyrs bp during the holocene transgression sedimentation rates increased continuously to a maximum of 1 4 m kyr during 3 1 kyrs bp modern 1 0 kyrs bp mean sedimentation rates average 0 6 m kyr a simple calculation suggests that two processes background sedimentation and sand apron progradation will probably fill up the accommodation space of the lagoon during the holocene highstand but these processes will not suffice to fill the larger atoll lagoons of the archipelago

quartz grains reveal sedimentary palaeoenvironment and past storm events a case study from eastern baltic abstract sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess in this study we use several proxies from sediment of the holocene thermal maximum at coastal lake lilaste latvia we focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments we then use this as a proxy for potential storm transport and combine with information on granulometry diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone grains representing very energetic subaqueous environment similar to storm events are also present terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains during drier and colder conditions an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr bp marine and terrestrial conditions alternated between 7800 and 6000 cal yr bp storm induced grains were likely deposited three times at 7300 cal yr bp 6600 6400 cal yr bp and 6200 6000 cal yr bp overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr bp except of the last portion of terrestrial induced sediment at 4100 cal yr bp

the storegga slide tsunami comparing field observations with numerical simulations abstract deposits from the storegga tsunami have been found in coastal areas around the norwegian sea and north sea from the northeast coast of england to beyond the arctic circle in northern norway the tsunami deposits reach onshore elevations of 10 12 m above sea level of their time in western norway 3 6 m in northeast scotland and above 20 m on the shetland islands these elevations are compared with surface wave elevations derived from a numerical simulation of the storegga slide a good agreement is obtained for a retrogressive slide that descends at 25 30 m s and that has short time lags of 15 20 s between each individual slide block

major storm periods and climate forcing in the western mediterranean during the late holocene abstract big storm events represent a major risk for populations and infrastructures settled on coastal lowlands in the western mediterranean where human societies colonized and occupied the coastal areas since the ancient times the variability of storm activity for the past three millennia was investigated with a multi proxy sedimentological and geochemical study from a lagoonal sequence mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal marine origin of sediments deposited into the lagoon the multi proxy analysis shows that coarser material low magnetic susceptibility and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence a comparison with north atlantic and western mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods suggesting a climatically controlled mechanism for the occurrence of these storm periods besides an in phase storm activity pattern is found between the western mediterranean and northern europe spectral analyses performed on the sr content revealed a new 270 year solar driven pattern of storm cyclicity for the last 3000 years this 270 year cycle defines a succession of ten major storm periods sp with a mean duration of 96 54 yr periods of higher storm activity are recorded from 680 to 560 cal yr bc sp10 end of the iron age cold period from 140 to 820 cal yr ad sp7 to sp5 with a climax of storminess between 400 and 800 cal yr ad dark ages cold period and from 1230 to 1800 cal yr ad sp3 to sp1 little ice age periods of low storm activity occurred from 560 cal yr bc to 140 cal yr ad sp9 and sp8 roman warm period and from 820 to 1230 cal yr ad sp4 medieval warm period

sand invasion along the portuguese coast forced by westerly shifts during cold climate events phases of higher aeolian activity are responsible for the formation and movement of large transgressive dunefields well reported phases of aeolian activity in northwest europe are coincident with global cooling events and were related to enhanced westerly winds and storminess however the extent to which these climatic episodes influenced dunefield dynamics in southwest europe remains an open question ground penetrating radar gpr was used to image the stratigraphy of a cliff top coastal transgressive dunefield in portugal and reconstruct former windfield regimes using optically stimulated luminescence osl five major phases of aeolian activity were dated at 12 6 5 6 1 2 0 4 and 0 3 ka and related to coastal instability and enhanced westerlies these phases were later reconciled to favorable patterns of atmospheric circulation simulated by global and regional climate models at both synoptic and local scales respectively the results prove that major phases of aeolian activity in southwest europe are associated with the onset of cold climate events of global distribution coinciding with aeolian accumulation in northwest europe this implies the dominance of zonal westerlies along the western coast of europe from denmark to portugal during the onset of cold climate events model simulations suggest that the pattern of atmospheric circulation during periods of enhanced aeolian activity is compatible with prolonged negative phases of the north atlantic oscillation nao

hybrid inventory gravimetry and altimetry higa mass balance product for greenland and the canadian arctic abstract we present a novel inversion algorithm that generates a mass balance field that is simultaneously consistent with independent observations of glacier inventory derived from optical imagery cryosphere attributed mass trends derived from satellite gravimetry and ice surface elevation trends derived from airborne and satellite altimetry we use this algorithm to assess mass balance across greenland and the canadian arctic over the sep 2003 to oct 2009 period at 26 km resolution we evaluate local algorithm inferred mass balance against forty in situ point observations this evaluation yields an rmse of 0 15 mwe a and highlights a paucity of in situ observations from regions of high dynamic mass loss and peripheral glaciers we assess mass losses of 212 67 gt a to the greenland ice sheet proper 38 11 gt a to peripheral glaciers in greenland and 42 11 gt a to glaciers in the canadian arctic these magnitudes of mass loss are dependent on the gravimetry derived spherical harmonic mass trend we invert we spatially partition the transient glacier continuity equation by differencing algorithm inferred mass balance from modeled surface mass balance in order to solve the horizontal divergence of ice flux as a residual this residual ice dynamic field infers flux divergence or submergent flow in the ice sheet accumulation area and at tidewater margins and flux convergence or emergent flow in land terminating ablation areas which is consistent with continuum mechanics theory

a high resolution record of climate variability and landscape response from kettle lake northern great plains north america abstract a decadal scale multiproxy record of minerals pollen and charcoal from kettle lake north dakota provides a high resolution record of climate and vegetation change spanning the entire holocene from the northern great plains ngp in north america the chronology is established by over 50 ams radiocarbon dates this record exhibits millennial scale trends evident in other lower resolution studies but with much more detail on short term climate variability and on the rapidity and timing of major climatic shifts as a proxy for precipitation we utilize the rate of endogenic carbonate sedimentation which depends on groundwater inflow which in turn depends on precipitation independent cluster analyses of mineral and pollen data reveal major holocene mode shifts at 10 73 ka ka cal yr bp 9 25 ka and 4 44 ka the early holocene 11 7 9 25 ka was generally wet with perhaps a trend to higher evaporation associated with warming temperatures a switch from calcite to aragonite deposition associated with a severe but brief drought occurred at 10 73 ka from 10 73 ka to 9 25 ka climate was generally humid but punctuated at 100 300 yr intervals by brief droughts including the most severe drought of the entire holocene at 9 25 ka this event was coeval with the 9 3 9 2 ka event in the greenland ice cores and observed at a number of sites worldwide in contrast the prominent 8 2 ka event in greenland is not remarkable at kettle lake the prominence of the 9 25 event locally in the ngp may be due to a major drawdown and northward retreat of lake agassiz at this time reducing its mesoclimatic effect on the ngp and thrusting the region into an insolation controlled regime the mid holocene 9 25 4 44 ka was characterized by great variability in moisture on a multi decadal scale with severe droughts alternating with more humid periods the high abundance of the weedy but drought intolerant ambrosia generally during the mid holocene and specifically during the multi decadal drought periods is seemingly paradoxical but can be explained by high interannual variability of moisture overlaid on the multi decadal variability the late holocene 4 44 ka present was also characterized by multi decadal variability in moisture but was generally wetter than the mid holocene and the magnitude of variability was less the trends in wet dry mineral pollen and charcoal proxies were similar to the mid holocene but late holocene mineral pollen assemblages are distinct from mid holocene the shift to wetter climate in the late holocene was more gradual than the abrupt shift to arid conditions 9 25 ka which may explain the asymmetric retreat and readvance of forest along the eastern margin of the ngp precipitation variations in the ngp have been linked with pacific and atlantic sea surface temperatures and mid holocene drought in the ngp has been linked with sustained la nina like conditions in the pacific these linkages may explain the decadal and millennial scale variations seen in the ngp but cause of the prominent century scale variations remains elusive

aeolian sediment in raised bog deposits halland sw sweden a new proxy record of holocene winter storminess variation in southern scandinavia cores of peat taken from two raised bogs in the near coastal part of halland sw sweden were examined for their content of wind transported clastic material the boarps mosse core has a length of 262 cm and covers the last 2850 years age model based on three radiocarbon dates while the hyltemossen core has a length of 347 cm and records the last 7000 years age model based on eight radiocarbon dates the peat contains aeolian quartz silt and sand from trace amount to more than 10 weight of the dry peat sample and the grain size composition of the minerogenic sediment indicates that the material is composed of both far travelled dust and local wind eroded silt and sand grains larger than 0 2mm are present in many intervals and probably record niveo aeolian transport in connection with severe snowstorms a systematic count of quartz grains between 0 2 0 35mm and larger than 0 35mm was carried out to determine variations in aeolian sand influx asi and winter wind climate with time the boarps m

quartz microtextures and microstructures owing to deformation of glaciolacustrine sediments in the northern venezuelan andes glaciolacustrine sediments ranging in age from early to late merida wisconsinan in sections in the northern venezuelan andes near pedregal were studied to assess the effect of small scale folding and faulting on the surface microtextures of individual grains at site ped5 faulting of sediments beneath 35 m of middle to late merida glaciolacustrine glaciofluvial and probable till deposits has resulted in a maximum displacement of 1 m and many crushed sand grains are found along the shear zone these dominantly quartz particles are typically smoothed and or faceted with surface skins split from parent grains to produce adhering blade or wafer shaped coarse silts faulting with displacement of 40 cm occurs in late merida glaciolacustrine beds at sites ped13 and ped11 beneath ca 1 5 m of sediment and is thought to result from the removal of lateral support during valley erosion and possibly seismic disturbance associated sediments exhibit a greater incidence of small scale fold structures and convoluted bedding but with similar numbers and types of crushed grains all of the fault traces examined exhibit microstructural modifications including microfaulting folding and multiple domains associated with fluidisation and liquefaction the microtextures described are distinct from those produced by glacial or glaciofluvial transport processes and potentially may be used to infer glaciotectonic or other post depositional disturbance of sediments rare euhedral quartz grains with distorted crystallographic axes may derive from the shear zone of the regional trans form boconofault although many of these grains appear to be overprinted by glacial and or recent deformation processes copyright 2004 john wiley sons ltd

cold event at 8200 yr b p recorded in annually laminated lake sediments in eastern europe a quantitative annual mean temperature reconstruction from an annually laminated lake sediment sequence in estonia eastern europe shows a distinct cold period at 8400 8080 yr b p before a d 2000 the timing is consistent with that seen in the greenland ice core data and various high resolution records from western europe during maximal cooling at 8250 8150 yr b p the annual mean temperature in estonia was 2 0 c colder than prior to and 3 0 c colder than after the cooling the pollen stratigraphic and sedimentological data suggest especially cold and snowy winter conditions the duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the north atlantic surface water and subsequent perturbation of the thermohaline circulation provided that the cold event was caused by a pulse of freshwater from the melting laurentide ice sheet to the north atlantic the results indicate a strong teleconnection between the north atlantic oceanic forcing and the east european climate at least up to long 26 e mediated probably by the changing intensity of the zonal atmospheric circulation

recognition of diagnostic criteria for recent and paleo tsunami sediments from sri lanka uncontaminated sediment from the december 26 2004 tsunami in southern sri lanka was collected from a previously empty arrack bottle stacked in a plastic case at an elevation of about 5 m above mean sea level and from several other localities the sediments were analysed for grain size distribution sediment petrography and microfossil assemblages and were compared with storm surge sediment and nearshore sediment the undiluted tsunami sediment is a brownish silty fine sand it is characterized by a particular grain size distribution and an assemblage of planktonic benthic microfossils consisting of foraminifera radiolarians and spicules storm surge and nearshore sediments are better sorted have fewer microfossils more rounded quartz grains and a higher proportion of heavy minerals influenced by references in sri lankan ancient texts to past tsunamis we searched for paleo tsunami sediments in potential locations such as the coastal depressions in borehole samples and well cuttings from soil profiles in the coastal village of peraliya we were able to recognize two paleo tsunami horizons at 30 and 75 cm below the present ground surface each consisting of brownish silty fine sand that remarkably resembled the recently deposited undiluted tsunami sediment

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

the ad 1755 tsunami deposits onshore and offshore of algarve south portugal sediment transport interpretations based on the study of foraminifera assemblages abstract tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events the accurate establishment of return periods can also be derived using sedimentological data onshore tsunami deposits have been extensively described over recent years through the application of a wide range of sedimentological proxies including micropalaeontological analysis in this work the identification of palaeotsunami evidence in both the onshore and offshore sedimentary record of south portugal was performed relying mostly on the study of foraminifera assemblages three onshore trenches and one offshore core were analyzed and imprints of the ad 1755 tsunami were observed based in the identification of allochthonous foraminiferal species increase in the number of broken abraded tests and its correlation with coarser mean grain size this was possible after micropalaeontological environmental characterization of both low energy onshore and offshore present day sedimentation regimes in the onshore record three distinct sediment transport phases were differentiated within the tsunamigenic unit the basal phase portraying the initial inundation represented by the dominance of marine foraminifera species in a highly diverse assemblage the higher energetic character of this phase was also reflected in the identification of the highest number of broken abraded tests the intermediate phase reflects an unspecified number of inundation and backwash pulses that were recognized based in the well balanced presence of estuarine brackish and marine species the sharp decrease in the diversity index and in the number of broken abraded tests the final phase recorded in the tsunamigenic unit registers the imprint of the last relevant backwash which was identified based on the dominance of estuarine brackish fauna the overlying unit is dominated by tidal marsh species demonstrating the start of the coastal system recovery phase in the offshore record it was possible to identify 2 distinct historical tsunami events ad 1755 and ad 1969 this was achieved through the identification of significant increases in coastal foraminifera species coupled with the presence of coarser layers this interpretation was sustained by indirect age estimation methods radiocarbon and 210 pb that ascribed compatible ages to the historical tsunami events the results obtained in this study stress the relevance and innovative character of this onshore and offshore multiproxy approach in the recognition and understanding of tsunami events

a convective vorticity vector associated with tropical convection a two dimensional cloud resolving modeling study 1 although dry moist potential vorticity e is a useful physical quantity for meteorological analysis it cannot be applied to the analysis of two dimensional 2 d simulations a new vorticity vector e convective vorticity vector cvv is introduced in this study to analyze 2 d cloud resolving simulation data associated with 2 d tropical convection the cloud model is forced by the vertical velocity zonal wind horizontal advection and sea surface temperature obtained from the tropical ocean global atmosphere toga coupled ocean atmosphere response experiment coare and is integrated for a selected 10 day period the cvv has zonal and vertical components in the 2 d x z frame analysis of zonally averaged and mass integrated quantities shows that the correlation coefficient between the vertical component of the cvv and the sum of the cloud hydrometeor mixing ratios is 0 81 whereas the correlation coefficient between the zonal component and the sum of the mixing ratios is only 0 18 this indicates that the vertical component of the cvv is closely associated with tropical convection the tendency equation for the vertical component of the cvv is derived and the zonally averaged and mass integrated tendency budgets are analyzed the tendency of the vertical component of the cvv is determined by the interaction between the vorticity and the zonal gradient of cloud heating the results demonstrate that the vertical component of the cvv is a cloud linked parameter and can be used to study tropical convection

reconstructed centennial variability of late holocene storminess from cors fochno wales uk future anthropogenic climate forcing is forecast to increase storm intensity and frequency over northern europe due to a northward shift of the storm tracks and a positive north atlantic oscillation however understanding the significance of such a change is difficult because the natural variability of storminess beyond the range of instrumental data is poorly known here we present a decadal resolution record of storminess covering the late holocene based on a 4 m long core taken from the peat bog of cors fochno in mid wales uk storminess is indicated by variations in the minerogenic content as well as bromine deposited from sea spray twelve episodes of enhanced storm activity are identified during the last 4 5 cal ka bp although the age model gives some uncertainty in the timings it appears that storminess increased at the onset and close of north atlantic cold events associated with oceanic changes with reduced storm activity at their peak cors fochno is strongly influenced by westerly moving storms so it is suggested that the patterns were due to variations in the intensity of westerly airflow and atmospheric circulation during times when the latitudinal temperature gradient was steepened

provenance of multicycle quartz arenites of pliocene age at arcos southwestern spain abstract a typical deposit of multicycle quartz arenites of considerable economic significance located in arcos sw spain has been studied to establish the provenance of the grains and their stages of sedimentary evolution the quartz grains were studied by sem and the composition of the sand determined by modal analysis of the heavy and light minerals the sources of the silica sands were the numidic sandstones known as aljibe in the betic cordilleras and the late miocene calcarenites of the guadalquivir basin four phases in the evolution of the arcos quartzose sands are a the initial surface features upturned plates b mechanical features an association of conchoidal fractures and arcuate steps formed in littoral environments inherited from the late miocene calcarenites c fluviatile features such as mechanical v s and grooves and d a final stage of chemical features oriented etch pits solution pits and hollows and silica globules developed in a hot humid climate the most important process producing the enrichment of the quartzose sands takes place during erosion depositional cycles

environmental discrimination based on quartz grain surface textures a statistical investigation the relative abundance of thirty two surface features identified on the surfaces of quartz sand grains from eight coded samples was noted independently by five scanning electron microscopists these data reduced to binary form were the subject of canonical variate analyses which discriminated clearly between all samples thirteen variables were important in distinguishing between the eight samples this indicates that there are no single key surface features which on their own would allow rapid environmental discrimination the contention that a multiplicity of surface features should be recorded for the purpose of environmental discrimination is therefore upheld operator variance although considerable in the recognition of individual surface features is negligible in discrimination of samples based on binary data the sem technique of analysis of quartz grain surface textures is a reliable and statistically valid means of discriminating between samples from different environments

hurricane signatures and landforms toward improved interpretations and global storm climate chronology abstract the correct understanding of the geological and geomorphic evolution of paralic basins and coastal barriers is a prerequisite for establishing holocene hurricane archives worldwide detection and documentation of hurricane signatures in coastal deposits are becoming instrumental in attempts to reconstruct mid and late holocene storm climate history subsurface exploration and field studies on the ne gulf coast and data gleaned from the literature suggest the need for a complex approach that provides well documented details of coastal landscape evolution until recently prehistoric hurricanes and their intensity levels have been automatically interpreted from the frequency and thickness of sand layers in muddy paralic deposits however in addition to wind velocity several hydro aerodynamic and other factors a wide range of stratigraphic conditions topographic setting and sand sources also determine variations in the extent and intensity of storm flooding erosion transfer and deposition of sand layers in small paralic basins inherent limitations in these sedimentary records and their interpretation must be overcome in order to improve local hurricane chronologies and establish interregional correlations before sedimentary and chemical signatures are accepted as diagnostic indicators of overwash especially by catastrophic hurricanes alternative causes must also be considered a parallel scale of storm flood level stages should supplement the saffir simpson hurricane categories the relationship between storm intensities and flooding elevations is highly complex changes in sea level shore positions formation and extinction of preexisting incised valley networks the impact of transgression and regression processes on estuaries and their deposits play determining roles in setting the stage for overwash processes strandplain progradation followed by erosive shore retreat played a key role in framing certain paralic lakes without overwash sand layers and marine microfossils may be also emplaced by storm driven currents that enter unobstructed estuaries inlets and storm breaches bioturbation also distorts the storm record significant lateral variations in the number and thickness of intercalated sand layers at closely adjacent sites suggest the importance of local differences in sources transport and preservation processes in the dimensions relative positions and accessibility of sand resources inside and adjacent to coastal basins variations in the number thickness and ages of sand laminae may not be related to the number of storms and their intensities this may impair correlations between regionally interpreted calm and intensive phases in partial overlap with an assumed quiescent storm phase stable isotope ratios in lacustrine muds impacted by salt water influx reveal frequent hurricane activity during the last 1 5 ka as well by mimicking effects of reduced storminess the fewer and thinner sand laminae deposited between 7 0 and 3 4 ka b p may be attributed to greater distances of estuarine landward transport by storm tidal currents at times of lower sea levels

living with sand a record of landscape change and storminess during the bronze and iron ages orkney scotland abstract palaeoenvironmental analyses of an exposed sequence of interbedded sand and peat overlying glacial till on stronsay orkney has revealed evidence of dynamic landscape change during the holocene ams radiocarbon and osl dating are used to identify periods of minerogenic and organic sediment accumulation a lengthy period of stability during the early holocene is inferred from the development of a deeply weathered till surface with pollen and soil micromorphological evidence suggesting prolonged woodland cover during the mid to late holocene phases of wind blown sand that inundated the landscape are defined from the sedimentary record and are interpreted as periods of increased storminess between c 3400 3100 cal bp and c 2800 2260 cal bp the palaeoecological evidence points to continuity of human exploitation despite the phases of increased storminess during the bronze age and into the iron age rising sea levels and a severe storm event at c 650 years bp inundated the site with massive sands and truncated the record these storm events recorded on stronsay are part of a regionally synchronous record for periods of increased storminess across the north atlantic region during the holocene

a tsunami record in the sedimentary archive of the central algarve coast portugal characterizing sediment reconstructing sources and inundation paths this study describes sedimentation associated with the tsunami generated by the lisbon earthquake of ad 1755 it is argued here that the tsunami deposited a sand sheet across the lagoa dos salgados

changes in holocene relative sea level and coastal morphology a study of a raised beach ridge system on samso southwest scandinavia changes in relative sea level rsl during the holocene are reconstructed based on ground penetrating radar gpr data collected across a raised beach ridge system on the island of samso denmark the internal architecture of the beach ridge and swale deposits is divided into characteristic radar facies we identify downlap points interpreted to mark the transition from the beachface to the upper shoreface and thus sea level at the time of deposition this new data set shows that beach steps can be preserved and resolved in gpr reflection data this is important as downlap points identified at the base of the beach steps should be corrected for beach step height in order to be used as a marker of sea level identification of beach steps in combination with observed changes in dips of the interpreted beachface reflections can give information about changes in the morphodynamic conditions of beach ridge progradation through time the vertical levels of identified downlap points are combined with an age m

early holocene coastal settlements and palaeoenvironment on the shore of the baltic sea at parnu southwestern estonia abstract studies were conducted on 16 sections of buried organic matter pre ancylus lake and pre litorina sea and associated stone age cultural layers in the parnu area southwestern estonia buried organic beds are each part of a sedimentary sequence which is repeated forming two overlying sets of an orderly succession of five layers the organic sedimentation of the lower set set 1 occurred about 10 800 10 200 years bp and that of the upper set set 2 about 9450 7800 years bp associated with set 1 is the early mesolithic settlement of pulli and with set 2 are the stone age cultural layers at sindi lodja the early and middle mesolithic sites in estonia are concentrated on shores of rivers and lakes to utilise of a variability of resources the hunters and fishermen followed the ancient parnu river downstream to the receding shoreline of the yoldia sea after about 10 700 years bp they were forced to retreat inland in front of the transgressive ancylus lake shore which first inundated the paikuse area about 10 400 years bp and pulli and higher sites about 10 200 years bp the total amplitude of the transgression preceded 11 m and reached up to 14 m a s l in the area the litorina sea transgression reached 7 m a s l after 8000 7800 years bp the mesolithic neolithic and modern sites on top of each other in the parnu area may suggest that although years apart they were inhabited by the same group of people who stayed in the area and moved back and forth together with the shifting shoreline of the baltic sea

storminess variation during the last 6500 years as reconstructed from an ombrotrophic peat bog in halland southwest sweden cores taken from an ombrotrophic peat bog in the coastal zone of halland southwest sweden were examined for wind transported mineral grains pollen and humidity indicators the core covers the period from 6500 cal yr bp to present ombrotrophic conditions existed from ca 4200 cal yr bp onwards bog surface wetness fluctuated strongly until ca 3700 cal yr bp with an apparent dominance of dry summer conditions from 4800 4500 cal yr bp local wet shifts occurred around 4300 2800 2400 and 1500 cal yr bp whereas the most recent 600 years of the record show increasingly dry conditions mineral grain content interpreted as aeolian sand influx asi was used as a proxy for winter storm frequency and intensity until ca 1500 cal yr bp after which increasing human impact as reconstructed by pollen analysis became a second important potential cause for increased sand drift strongly increased storminess occurred at 4800 4200 2800 2200 1500 1100 and 400 50 cal yr bp indicating a dominance of cold and stormy winters during these periods many of these storm periods apparently coincide with storm events in other sites in southwestern scandinavia suggesting that our asi record reflects a regional scale climatic signal furthermore these stormy periods correlate to well known cold phases in the north atlantic region suggesting a link to large scale fluctuations in atmospheric circulation patterns less

palaeohurricane reconstructions from sedimentary archives along the gulf of mexico caribbean sea and western north atlantic ocean margins hurricanes annually threaten the atlantic ocean margins historical hurricane records are relatively short and palaeohurricane sedimentary archives provide a geological and climatic context that sheds light on future hurricane activity here we review palaeo trends in hurricane activity elucidated from sedimentary archives we discuss dating methods site selection and stat istics associated with previously published records these archives have been useful for under standing the long term evolution of coastal systems and the response of intense hurricane activity to climatic changes regional shifts in hurricane overwash on centennial to millennial timescales have been linked to various climatic modes of variability including el nino southern oscillation and the north atlantic oscillation but could also reflect regional scale controls on hurricane activity

distinguishing tsunami and storm deposits an example from martinhal sw portugal abstract geological identification of past tsunamis is important for risk assessment studies especially in areas where the historical record is limited or absent the main problem when using the geological evidence is to distinguish between tsunami and storm deposits both are high energy events that may leave marine traces in coastal stratigraphic sequences at martinhal sw portugal both storm surge and tsunami deposits are present at the same site within a single stratigraphic sequence which makes it suitable to study the differences between them excluding variations caused by local factors the tsunami associated with the lisbon earthquake of november 1st 1755 ad had a major impact on the geomorphology and sedimentology of martinhal it breached the barrier and laid down an extensive sheet of sand as described in eyewitness reports besides the tsunami deposit the stratigraphy of martinhal also displays evidence for storm surges that have breached and overtopped the barrier flooding the lowland and leaving sand layers both marine derived flood deposits show similar grain size characteristics and distinctive marine foraminifera the most important differences are the rip up clasts and boulders exclusively found in the tsunami deposit and the landward extent of the tsunami deposit that everywhere exceeds that of the storm deposits identification of both depositional units was only possible using a collection of different data and extensive stratigraphical information from cores as well as trenches

multicycle sediments on the continental shelf of cadiz sw spain abstract the study of recent sedimentation in the gulf of cadiz continental shelf sw europe is of interest due to its proximity to the strait of gibraltar where the atlantic and mediterranean waters are interchanged and the western mediterranean alpidic orogen closes through the gibraltar arch the existence of relict materials hinders the distinction of the past and present hydrodynamic regimes in present day sediments an adequate combination of techniques has allowed the establishment of the multicyclic character of the sediments as well as the stages undergone by the terrigenous grains different stages were identified eolian and energetic fluvial provenance chemical alterations acquired in a pedological environment and a marine coastal origin to verify the source areas textural and mineralogical features of marine sediments were compared with those found in geological units from fluvial basins three zones were differentiated a a sandy littoral which receives local sediment supplies b a clayey zone between the guadalquivir river and cadiz controlled by contributions from this river provenant of the iberian massif and betic mountain range and c a sandy continental shelf between cadiz and the cape of trafalgar with a low rate of supplies coming from the guadalete and barbate rivers which include materials from the occidental betic mountain range and neogene units

7000 years of paleostorm activity in the nw mediterranean sea in response to holocene climate events abstract a high resolution record of paleostorm events along the french mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the gulf of lions integrating grain size faunal analysis clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating we recorded seven periods of increased storm activity at 6300 6100 5650 5400 4400 4050 3650 3200 2800 2600 1950 1400 and 400 50 cal yr bp in the little ice age in contrast our results show that the medieval climate anomaly 1150 650 cal yr bp was characterised by low storm activity the evidence for high storm activity in the nw mediterranean sea is in agreement with the changes in coastal hydrodynamics observed over the eastern north atlantic and seems to correspond to holocene cooling in the north atlantic periods of low ssts there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies we hypothesise that the increase in storm activity during holocene cold events over the north atlantic and mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large central atlantic european domain

investigation of impact spherules a new promising method for the correlation of quaternary deposits abstract during the course of the last hundred years microscopic magnetite and glassy spherules of different genesis extraterrestrial volcanic industrial biogenic diagenic explosive etc have often been found in various geological formations alongside classical geological methods research into extraterrestrial and explosive spherules can provide valuable information and facilitates stratigraphical correlations over large areas during the history of the earth there seem to have been several peaks in the global occurrence of spherules the best known being recorded on the k t boundary several tens of impact craters ranging from neoproterozoic to holocene in age and from less than 100 m to more than 50 km in diameter occur both in the crystalline basement and in the sedimentary cover of the old east european craton in the fennoscandian baltic region in the baltic states alone at least 18 impact craters and a large number of meteorite falls have been recorded the oldest palaeometeorite matter known in the baltic states to date is enclosed in lower cambrian sandstone this paper presents some promising results of spherule studies which were carried out surrounding holocene meteorite craters in estonia on the basis of spherule studies impact events can be precisely dated the spherule bearing layers serve as excellent stratigraphical markers for the correlation of sedimentary sequences

distinction between the storegga tsunami and the holocene marine transgression in coastal basin deposits of western norway many coastal lakes were inundated by both the storegga tsunami 7000 14 cy r bp and the mid holocene sea level rise the tapes transgression in western norway the tsunami eroded lake bottoms and deposited graded and or massive beds of sand rip up clasts and coarse plant material by contrast when the rising sea entered the lakes it deposited only gyttja silt and fine sand without causing much erosion of the underlying lake sediments storegga tsunami deposits in some coastal lakes were interpreted previously as ordinary marine sediments from the tapes transgression our reinterpretation of these deposits shows that the transgression maximum phase was reached after 6500 yr bp more than 1000 yr later than previously inferred for the coast of sunnmore the new data cannot be combined in a shoreline diagram without showing the 6000 yr bp and 7000 yr bp shorelines as slightly warped 1998 john wiley sons ltd

aeolian sand movement and relative sea level rise in ho bugt western denmark during the little ice age this study documents an extensive aeolian sand sheet buried in the salt marshes of the ho bugt embayment in western denmark the extent of the sand sheet was mapped from c 60 cores and sections which were also used to reconstruct late holocene changes in relative sea level based on diatom analyses chronology was provided by optically stimulated luminescence osl and radiocarbon dating our study shows that since 2000 cal yr bp relative sea level in ho bugt has risen by approximately 1 5 m the overall rise was punctuated by two periods with higher than average rates of sea level rise the first between 2000 and 1400 cal yr bp and the second commencing c 500 cal yr bp around 700 cal yr bp the evolution of the skallingen spit may have been responsible for a reduction in the local tidal range and the formation of an extensive black layer in the western part of the embayment osl analyses date the sand sheet to between ad 1460 40 and ad 1550 30 490 40 and 400 30 cal yr bp consistent wi

late holocene storm imprint in a coastal sedimentary sequence northwest iberian coast a combination of sedimentological geomorphological and pedological methods has been used to study a late holocene sedimentary sequence in a rock coast sector from nw spain with the aim of relating it to storm events and their morphodynamic effects the sequence contains two coarse beach layers at an elevation of 2 8 3 5 m above the present highest astronomical tide hat radiocarbon dating revealed that their deposition had begun during 1735 1590 cal yr bp and has continued until the present the entire beach system experienced considerable morphological change after 1320 1230 cal yr bp with a westward displacement of the beach and a retreat of the sedimentary cliff in the eastern section the two beach layers seem to have been formed by vertical aggradation of clasts and sand during high energy storm events highlighting the role of these events in the formation of sedimentary sequences on the rocky coasts of mid atlantic europe the effects of a recent storm event recorded in march 2008 and the

surface microtextures of quartz grains from vistulian loesses from selected profiles of poland and some other countries abstract the vistula glaciation loesses have been investigated in comparison to some profiles from central europe on the basis of quartz grains examination in sem and referring to lithological features a reconstruction of the sedimentary environment and transport type is made analysis of frequency of quartz grains with definite features shows important variations in terms of type and quantity amongst the features the most varied microtextures are observed on 1 0 0 5 mm grains and smaller 0 5 0 25 mm completely different microtextures have been recognized on 0 1 0 5 mm grains on which encrusted smooth surface formed due to precipitation of silica at deflation sites can be observed the 0 1 0 05 mm quartz grains from the polish loesses indicate one source area with an arid climate the grains were probably transported by high winds from a distant area located in the east in contrast the coarser sand sized quartz grains indicate a variable provenance they usually originated from an adjacent area and underwent limited transport a distinct difference in microtextures of quartz grains occurs at the boundary of the younger middle loess lms and younger upper loess lmg lmg is best defined by more aeolian and fewer corrosional post sedimentary features

rapid hydrological changes during the holocene revealed by stable isotope records of lacustrine carbonates from lake igelsjon southern sweden a holocene sediment sequence from lake igelsjon south central sweden was studied by stable oxygen and carbon isotope analyses of different carbonate components the deposit which covers the time span from ca 11 500 cal bp to the present was laid down in a small kettle hole lake the hydrological balance of which is presently dominated by groundwater flow isotopic records obtained on bulk carbonates originating mainly from summer produced calcitic algal encrustations exhibit several rapid shifts of more than 2parts per thousand likely reflecting pronounced hydrological variations corresponding isotopic data obtained on calcitic gastropod opercula from parts of the profile show subdued responses to major climatic shifts probably related to an extended calcification season the isotopic records were complemented by studies of modern isotope hydrology and our interpretations are based on a simplistic climate hydrology model in which variations in groundwater generation within the lake catchment produce changes in groundwater level and related adjustments of lake level and surface volume ratio of the basin during the ice free season assumed periods of decreased lake volume in a relatively dry climate low lake level are characterised by enrichment in o 18 and c 13 resulting from increased evaporation inflow ratio and atmospheric equilibration respectively in clear contrast to this situation intervals of more humid climatic conditions give rise to increased lake volume high lake level possibly surface over flow and relatively depleted isotopic ratios relatively humid conditions which may correlate to a wide spread cooling event recorded by various proxies across the north atlantic region are indicated by distinct isotopic shifts at ca 8300 and 8000 cal bp bracketing a period of o 18 depletion the period between ca 8000 and 4000 cal bp was characterised by relatively dry and stable climatic conditions whereas the subsequent part of the holocene experienced a more humid and variable climate following marked and coherent depletions in o 18 and c 13 at ca 4000 cal bp c 2002 elsevier science ltd all rights reserved less

persistent non solar forcing of holocene storm dynamics in coastal sedimentary archives considerable climatic variability on decadal to millennial timescales has been documented for the past 11 500 years of interglacial climate1 2 3 this variability has been particularly pronounced at a frequency of about 1 500 years with repeated cold intervals in the north atlantic1 3 however there is growing evidence that these oscillations originate from a cluster of different spectral signatures4 ranging from a 2 500 year cycle throughout the period to a 1 000 year cycle during the earliest millennia here we present a reappraisal of high energy estuarine and coastal sedimentary records from the southern coast of the english channel and report evidence for five distinct periods during the holocene when storminess was enhanced during the past 6 500 years we find that high storm activity occurred periodically with a frequency of about 1 500 years closely related to cold and windy periods diagnosed earlier1 2 3 we show that millennial scale storm extremes in northern europe are phase locked with the period of internal ocean variability in the north atlantic of about 1 500 years4 however no consistent correlation emerges between spectral maxima in records of storminess and solar irradiation we conclude that solar activity changes are unlikely to be a primary forcing mechanism of millennial scale variability in storminess

liquefaction and varve deformation as evidence of paleoseismic events and tsunamis the autumn 10 430 bp case in sweden coastal seismic events generate instantaneous changes in relative sea level i e land level vs sea level tsunamis may cause disastrous damage to coasts and coastal habitation liquefaction and deformations of annually varved sediments provide information on paleoseismic events the evidence for a major earthquake and associated tsunami waves in sweden are explored thanks to the varve chronology liquefaction structures and varve deformations caused by this event can be dated at the autumn 10 430 varve years bp the magnitude is estimated at 8 or more on the richter scale the tsunami washed the previously blocked outlet of the baltic free of icebergs and pack ice so that marine water could suddenly invade the entire baltic forming the yoldia sea

clay minerals and geochemistry record from northwest mediterranean coastal lagoon sequence implications for paleostorm reconstruction abstract the paleostorm history of coastal lagoon environments pierre blanche lagoon central part of the gulf of lions has been established by integrating clay mineralogy and geochemical analysis clay mineralogy combined with bulk major and trace elements concentrations allow for the definition of four different end members the mosson drainage basin the sandy barrier the biogenic and the anthropic components the two main sedimentary sources of the lagoonal system are the mosson drainage basin which has a high concentration of smectite and al 2 o 3 and the sandy barrier characterized by high contents of illite chlorite sio 2 and zr smectite illite chlorite sio 2 al 2 o 3 and zr al 2 o 3 ratios can be used to reconstruct the past storm history of the pierre blanche lagoon our results indicate that the sensitivities of the clay mineralogy and geochemistry proxies are different these sensitivities could be related 1 first to the comparison between different grain size for geochemistry and for clay mineralogy 2 second to the complexity of the mix four end members for the geochemistry and two end members for the clay minerals and 3 third by the storm s ability to transport sediment of different sizes

microfeatures of modern sea ice rafted sediment and implications for paleo sea ice reconstructions distinguishing sea ice rafted debris sird from iceberg rafted debris is crucial to an interpretation of ice rafting history however there are few paleo sea ice proxies this study characterizes quartz grain microfeatures of modern sird from the arctic ocean and compares these results with microfeatures from representative glacial deposits to potentially differentiate sird from ice rafted sediments which have been recently subjected to glacial processes this allows us to evaluate the use of grain microfeatures as a paleo sea ice proxy sird grains were largely subrounded with medium relief pervasive silica dissolution and a high abundance of breakage blocks and microlayering the glacial grains were more angular with lower relief and higher abundances of fractures and striations gouges discriminate analysis shows a distinct difference between sird and glacial grains with 7 of the sird grains containing typical glacial microtextures suggesting this method is a useful means of inferring paleo sea ice presence in the marine record we propose that differences in microfeatures of sird and glacial ice rafted debris reflect differences in sediment transport and weathering histories sediment transported to a coastal setting and later rafted by sea ice would be subject to increased chemical weathering whereas glaciers that calve icebergs would bypass the coastal marine environment thus preserving their glacial signature

the evolution of holocene coastal dunefields jutland denmark a record of climate change over the past 5000 years coastal dunefields have developed on the west coast of jutland in denmark over the past 5000 years the dunefields are situated in a temperate climate zone with frequent high energy wind events dunefield development was characterized by repeated periods of transgressive dune formation punctuated by periods of dune stabilization and soil formation the chronology of dunefield evolution is based on accelerator mass spectrometry ams radiocarbon dating of peaty palaeosols 24 samples and optically stimulated luminescence osl dating of aeolian sand deposits 19 samples these dates indicate that the completeness of the stratigraphic record varies considerably but that the timing of aeolian activity events was identical in the dunefields examined here initiation of aeolian activity occurred around 2200 bc 800 bc ad 100 ad 1050 1200 and between ad 1550 and 1650 proxy climate data from bogs in southwestern sweden suggest that these periods of dunefield activity were initiated during wet cool summers most likely these climatic situations were associated with a more frequent passage of cyclones across denmark in the summer seasons increased storminess causing aeolian sand movement and dune formation the continued removal of vegetation in jutland between 4000 bc and ad 1850 allowed the aeolian sand when first activated to move more and more easily across the coastal plains the final phase of aeolian sand movement between ad 1550 1650 and 1900 had catastrophic implications for many coastal inhabitants in the region c 2008 elsevier b v all rights reserved less

reconstruction of paleostorms and paleoenvironment using geochemical proxies archived in the sediments of two coastal lakes in northwest florida abstract late holocene paleoclimate records from coastal regions are important for understanding long term variability of hurricane activity here we present a nearly 4000 year record of severe storm landfalls and environmental changes based on organic geochemical proxies ogps preserved in sediment cores from two coastal lakes in northwest florida our analysis shows that there are significant variations in 13c 15n c n and c n with depth reflecting changes in lake environment which in turn affected the processes delivering water and sediment to the lake as well as biological productivity within the lake isotopic signatures of modern organic materials in the lakes and their surrounding areas show that the major sources of sedimentary organic matters in the lakes are aquatic and terrestrial c3 vegetation c4 grasses do not contribute significantly to the sedimentary organic matters in the lake although they can be found in the mostly forested watershed thus the positive c and n isotopic shifts concurrent with negative shifts in c n ratios most likely indicate shifts to a marine like environment in coastal lakes following the influx of marine water and nutrients and marine biota associated with major storm events some of these isotopic shifts observed in the sediment cores correspond to visible sand layers presumably representing overwash deposits associated with severe storm events radiocarbon dating of bulk sediment organic matters wood fragments and shells indicates that the sediment in these cores was deposited over the last 3000 4000 years based on our age model and ogp interpretation eastern lake data suggest that the recurrence interval of severe storms i e large enough to cause seawater flooding of the lakes is approximately 84 years over the last 2900 years whereas western lake data suggest an average recurrence interval of 86 years in the past 3900 years

global characterization of the holocene thermal maximum we analyze the global variations in the timing and magnitude of the holocene thermal maximum htm and their dependence on various forcings in transient simulations covering the last 9000 years 9 ka performed with a global atmosphere ocean vegetation model in these experiments we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early holocene deglaciation of the laurentide ice sheet lis considering the lis deglaciation we quantify separately the impacts of the background melt water fluxes and the changes in topography and surface albedo in the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level its timing in the holocene and the seasonal expression in the model the warmest htm conditions are found at high latitudes in both hemispheres reaching 5 c above the preindustrial level while the smallest htm signal is seen over tropical oceans less than 0 5 c this latitudinal contrast is mostly related to the nature of the orbitally forced insolation forcing which is also largest at high latitudes and further enhanced by the polar amplification the holocene timing of the htm is earliest before 8 ka bp in regions not affected by the remnant lis particularly nw north america e asia n africa n south america the middle east ne siberia and australia compared to the early holocene insolation maximum the htm was delayed by 2 3 ka over ne north america and regions directly downwind from the lis a similar delay is simulated over the southern ocean while an intermediate lag of about 1 ka is found over most other continents and oceans the seasonal timing of the htm over continents generally occurs in the same month as the maximum insolation anomaly whereas over oceans the htm is delayed by 2 3 months exceptions are the oceans covered by sea ice and north africa were additional feedbacks results in a different seasonal timing the simulated timing and magnitude of the htm are generally consistent with global proxy evidence with some notable exceptions in the mediterranean region sw north america and eastern eurasia 2012 elsevier ltd

a decadally resolved paleohurricane record archived in the late holocene sediments of a florida sinkhole article i nfo a 4500 year record of hurricane induced storm surges is developed from sediment cores collected from a coastal sinkhole near apalachee bay florida recent deposition of sand layers in the upper sediments of the pond was found to be contemporaneous with significant historic storm surges at the site modeled using slosh and the best track post 1851 a d dataset using the historic portion of the record for calibration paleohurricane deposits were identified by sand content and dated using radiocarbon based age models marine indicative foraminifera some originating at least 5 km offshore were present in several modern and ancient storm deposits the presence and long term preservation of offshore foraminifera suggest that this site and others like it may yield promising microfossil based paleohurricane reconstructions in the future due to the sub decadal 7 years resolution of the record and the site s high susceptibility to hurricane generated storm surges the average local frequency of recorded events approximately 3 9 storms per century is greater than that of previously published paleohurricane records from the region the high incidence of recorded events permitted a time series of local hurricane frequency during the last five millennia to be constructed variability in the frequency of the largest storm layers was found to be greater than what would likely occur by chance alone with intervals of both anomalously high and low storm frequency identified however the rate at which smaller layers were deposited was relatively constant over the last five millennia this may suggest that significant variability in hurricane frequency has occurred only in the highest magnitude events the frequency of high magnitude events peaked near 6 storms per century between 2800 and 2300 years ago high magnitude events were relatively rare with about 0 3 storms per century occurring between 1900 and 1600 years ago and between 400 and 150 years ago a marked decline in the number of large storm deposits which began around 600 years ago has persisted through present with below average frequency over the last 150 years when compared to the preceding five millennia

the degree of aeolization of quaternary deposits in poland as a tool for stratigraphic interpretation abstract the aim of the study was to test if it is possible to distinguish quaternary sediments bearing evidence of the impact of aeolian processes during their accumulation it was also important to verify if distinguishing of these series would be useful in the accurate determination of stratigraphic position determined previously using lithological petrographic and palynological methods the sediments were sampled from five boreholes reaching the tertiary and from six exposures all from central east and north poland the following features were taken to indicate a significant role of aeolian processes during sediment accumulation high percentage of quartz grains 0 8 1 0 mm in the sand fraction characterized by distinct rounding and frosting high quartz content and low feldspar content 0 8 1 0 mm and the composition of the heavy minerals fraction 0 1 0 2 mm garnets are particularly resistant to mechanical abrasion whereas micaeous minerals are susceptible to winnowing this spectrum of textural features that indicates the effects of intensive aeolian processes was termed deposit aeolization sediment aeolization may be observed in sediments of various origin aeolian fluvial or lacustrine the study proved that the highest degree of aeolization occurred in alluvial fluvioperiglacial sediments accumulated before the first riss odra glaciation and in aeolian and fluvial sediments during the decline of weichselian glaciation sediment aeolization is a valuable supplement to previous methods to indicate the stratigraphic position the degree of aeolization allows the delimitation of the boundary between the quaternary and tertiary it identifies glacitectonic and tectonic deformations and it distinguishes fluvial and fluvioperiglacial sheets from fluvioglacial sheets it is useful in estimating the length and intensity of aeolian processes it adds to the interpretation of climatic conditions at the time of deposition and defines the limits of interglacial sheets within sandy sediments 30 to about 100 m thick separating boulder clay units

evidence for an extreme climatic event on achill island co mayo ireland around 5200 5100 cal yr bp a range of detailed palaeoenvironmental analyses carried out on a series of three peat profiles from achill island co mayo western ireland reveal evidence for an extreme climatic event probably a storm or series of storms around 5200 5100 cal yr bp that caused the deposition of an extensive layer of silt across blanket peat this event followed a period of relatively dry climate during which neolithic communities expanded in the region there was a subsequent period of continuing dry conditions allowing extensive colonisation of the peat by pinus before a shift to wetter conditions characteristic of the later holocene the extreme climatic event is possibly linked to human abandonment of the area comparable to that observed from the work on the internationally significant ceide fields in the same region

the cretaceous continental intercalaire in central algeria subsurface evidence for a fluvial to aeolian transition and implications for the onset of aridity on the saharan platform abstract the lower cretaceous continental intercalaire of north africa is a terrestrial to shallow marine continental wedge deposited along the southern shoreline of the neotethys ocean today it has a wide distribution across the northern sahara where it has enormous socio economic importance as a major freshwater aquifer during the early cretaceous major north south trending basement structures were reactivated in response to renewed atlantic rifting and in algeria faults along the el biod hassi messaourd ridge appear to have been particularly important in controlling thickness patterns of the lower cretaceous continental intercalaire subsurface data from the krechba gas field in central algeria shows that the lower cretaceous stratigraphy is subdivided into two clear parts the lower part here termed the in salah formation is a 200 m thick succession of alluvial deposits with large meandering channels clearly shown in 3d seismic and waterlogged flood basins indicated by lignites and gleyed pedogenic mudstones the overlying krechba formation is a 500 m thick succession of quartz dominated sands and sandstones whose microstructure indicates an aeolian origin confirming earlier observations from outcrop these interbed with brick red highly oxidised mudstones representing deposition in temporary lakes or lagoons under an arid climate the switch from fluvial to aeolian sedimentation at krechba on the saharan platform occurred in the late aptian and albian and is thus synchronous to a comparable change observed by previous authors in lower cretaceous non marine deposits of ne spain this was probably driven by a combination of sea level fall and the northward shift of global arid belts into western neotethys caused by oceanic rifting between africa and south america

millennial scale storminess variability in the northeastern united states during the holocene epoch for the purpose of detecting the effects of human activities on climate change it is important to document natural change in past climate1 in this context it has proved particularly difficult to study the variability in the occurrence of extreme climate events such as storms with exceptional rainfall1 previous investigations have established storm chronologies using sediment cores from single lakes2 3 4 5 6 7 8 but such studies can be susceptible to local environmental bias here we date terrigenous inwash layers in cores from 13 lakes which show that the frequency of storm related floods in the northeastern united states has varied in regular cycles during the past 13 000 years 13 kyr with a characteristic period of about 3 kyr our data show four peaks in storminess during the past 14 kyr approximately 2 6 5 8 9 1 and 11 9 kyr ago this pattern is consistent with long term changes in the average sign of the arctic oscillation9 suggesting that modulation of this dominant atmospheric mode may account for a significant fraction of holocene climate variability in north america and europe

imprint of late pleistocene continental processes visible in ice rafted grains from the central arctic ocean abstract ice rafted quartz sand grains of sediment samples representing marine isotope stages mis 3 and 4 from the lomonosov ridge arctic ocean are here analysed with a scanning electron microscope sem to characterise processes in the sediment source area the microtextural characteristics of the grains were observed and their microtexture frequencies calculated specific sets of microtextures were identified and classified group i iii using principal component analysis pca and cluster analysis the statistically analysed microtextural data were used to identify signals of continental processes that operated during the late pleistocene mis 4 to mis 3 in the eurasian arctic the microtextures of group i generally formed as a result of prolonged fluvial alluvial or aeolian transport the glacial microtextures of groups ii and iii indicate subglacial conditions and transport based on the data two principal components seem to characterise late pleistocene continental environmental conditions glacial and non glacial there is a signal of non glacial continental processes in the ice rafted grains at around 62 64 and 67 ka ago a signal of subglacial processes was observed in the grains at around 26 34 42 and 45 ka and concurrent with non glacial at around 62 and 64 ka ago we suggest that these signals in mis 4 sediments are related to deglaciation with an increased supply of glacial sediment to the arctic ocean whereas during mis 3 they were probably related more to iceberg calving from the oscillating barents kara ice sheet

the 2011 japanese 9 0 magnitude earthquake test of a kinetic energy wave model using coastal configuration and offshore gradient of earth and beyond abstract based on geological investigations of coastal geometry and stratigraphy offshore gradient variation wave velocity energy and quartz grain microtexture analysis of key sites inundated by tsunamis during the holocene we have developed a postulated model that could be used to assess modern and ancient onshore environmental conditions during tsunami emplacement given that tsunami waves can travel up to 900 km h the kinetic energy of the wave is determined by frictional release on the offshore slope to seabed nearshore sand and sediment supply and coastal geomorphology specifically coast linearity or embayments that constrict wave energy with gentle offshore gradients and relatively linear coastlines the kinetic energy of the tsunami is decreased by friction with the seabed and radiated outward along the coast thus producing reduced flooding of the affected coast and fewer collisions of entrained grains in contrast steep offshore gradients reduce friction to mere milliseconds of wave impact and embayments specifically narrow coastal constrictions increase wave energy both of which increase on land run up heights and importantly to our proposed model grain collision effects damage to quartz grains deposited by tsunamis along coastal extents ranges from slight on linear coasts with gentle offshore gradients to highly resurfaced mineral surfaces on coasts with steep offshore gradients and narrow embayments our model can be further tested through collection analyses and comparison of quartz grains in relatively low and high energy environments of the recently tsunami impacted northeastern coast of japan for example the location of the fukushima nuclear plant along a linear coastline with a less steep offshore gradient may have attenuated the energy of the incoming wave and thus yielding less resurfaced grains when compared to the coastline located to the north of sendai city where coastal embayments of variable size coupled with steep offshore gradients would produce higher energy waves of greater magnitude as attested by greater penetration inland with considerable loss of life and property damage and resulting highly deformed grain surfaces the model could be applicable for assessing modern and ancient coastal environmental conditions on earth and postulated ancient marine conditions on the red planet

surface textural analysis of quartz grains by scanning electron microscopy sem from sample preparation to environmental interpretation abstract surface microtextures on quartz grains provide an insight into the sedimentary history of clastic sediments not only information on the depositional environment is provided but also in some cases successive sedimentary cycles can be recognised sample preparation and sem imaging are the initial and therefore crucial steps in the study of microtextures a sample preparation procedure using 15 hydrochloric acid and 50 g l tetrasodium pyrophosphate solutions removes most of the grain coatings and adhering particles the study of microtextures on 1300 quartz grains from a wide variety of environments was complemented with the reference works and atlases krinsley and doornkamp 1973 le ribault 1977 higgs 1979 mahaney 2002 to construct an interpretation scheme allowing to differentiate between fluvial marine eolian glacial and diagenetic alteration environments based on microtextures in a case study the known littoral setting of two samples was confirmed by using the interpretation scheme for quartz microtextures furthermore successive reworking of the grains in eolian and intertidal environments was recognised by presenting the research of microtextures from starting point to interpretation new researchers may find this review a useful and practical introduction into the technique

intense storm activity during the little ice age on the french mediterranean coast understanding long term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution understanding this variability is also important for predicting present and future community vulnerability and economic loss our ability to make these assessments has been limited by the short less than 50 years instrument record of storm activity storm induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales in this study we present a record of these extreme climatic events that have occurred in the french mediterrannean coast over the past 1500 years the identification of these extreme events is based on the analysis of sediment cores from gulf of aigues mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century a d the apparent increase in intense storms around 250 years ago occurs during the latter half of the little ice age a time of lower continental surface temperatures comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics the apparent increase of the superstorm activity during the latter half of the little ice age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large central atlantic european domain and leading to a modification of the occurrence of extreme wind events along the french mediterranean coast a complete understanding of the relationship between climate fluctuations storm activity and the coastal response will be crucial to predicting the impacts of future climate change

sem analysis of quartz sand grain surface textures indicates alluvial colluvial origin of the quaternary glacial boulder clays at huangshan yellow mountain east central china abstract geomorphic features and pleistocene deposits on huangshan have been attributed to glaciation recent reassessment questions this interpretation as part of the reassessment quartz sand grains from deposits identified as glacial boulder clays till composed of boulders in a clay or silt matrix were analyzed by scanning electron microscope for evidence of their sedimentary history surface textures found on the boulder clay grains were compared with those on grains with known sedimentary histories including glacial grus colluvial and alluvial grains the analysis shows that the grains lack typical glacial textures the surface textures present indicate a complex history nonuniformly weathered grain surfaces point to chemical weathering of the source rock this is supported by the deep weathering of the nonquartz clasts in the sand sized fraction as well as in boulders at the outcrops the close correspondence in surface texture frequencies with those of the alluvial grains indicates an alluvial component to the grains history the similarity with the colluvial grains and the outcrops structures suggest an alluvial colluvial origin for the deposits the history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east central china for at least part of the pleistocene