surface stresses associated with arrested dykes in rift zones many theoretical models predict that arrested dykes may generate major grabens at rift zone surfaces arrested dyke tips in eroded rift zones however are normally not associated with major grabens or normal faults that could be generated by dyke induced stresses ahead of the tips and normal faults and grabens tend to be less common in those parts of eroded rift zones where dykes are comparatively abundant similarly there are feeder dykes as well as dykes arrested a few metres below the surface that do not generate faults or grabens at the surface here i propose that this discrepancy between theoretical models and field observations may be explained by the mechanical layering of the crust numerical models presented here show that abrupt changes in young s moduli layers with high dyke normal compressive stresses stress barriers and weak horizontal contacts have large effects on the dyke induced stress fields for the models considered the surface tensile stresses induced by arrested dykes are normally too small to lead to significant fault or graben formation at the rift zone surface the only significant dyke induced surface tensile stresses 2 mpa in these models are for a dyke tip arrested at 1 km depth below the surface of a rift zone with a weak contact at 400 m depth and subject to extension that tensile stress however peaks above the ends of the weak horizontal contact which in the model considered occur at distances of 4 km to either side of the dyke and shows no simple relation to the depth to the dyke tip thus for a layered crust with weak contacts straightforward inversion of surface geodetic data to infer dyke geometries may result in unreliable results

an updated holocene sea level curve for the delaware coast abstract we present an updated holocene sea level curve for the delaware coast based on new calibrations of 16 previously published radiocarbon dates kraft 1976 belknap and kraft 1977 and 22 new radiocarbon dates of basal peat deposits a review of published and unpublished 137 cs and 210 pb analyses and tide gauge data provide the basis for evaluating shorter term 10 2 yr sea level trends paleosea level elevations for the new basal peat samples were determined from the present vertical zonation of marsh plants relative to mean high water along the delaware coast and the composition of plant fossils and foraminifera current trends in tidal range along the delaware coast were used to reduce elevations from different locations to a common vertical datum of mean high water at breakwater harbor delaware the updated curve is similar to belknap and kraft s j sediment petrol 47 1977 610 629 original sea level curve from 12 000 to about 2000 yr bp the updated curve documents a rate of sea level rise of 0 9 mm yr from 1250 yr bp to present based on 11 dates in good agreement with other recent sea level curves from the northern and central u s atlantic coast while the previous curve documents rates of about 1 3 mm yr based on 4 dates the precision of both estimates however is very low so the significance of these differences is uncertain a review of 210 pb and 137 cs analyses from salt marshes of delaware indicates average marsh accretion rates of 3 mm yr for the last 100 yr in good agreement with shorter term estimates of sea level rise from tide gauge records

a new late holocene sea level record from the mississippi delta evidence for a climate sea level connection abstract a detailed relative sea level rsl record was constructed for the time interval 600 1600 ad using basal peat to track sea level and containing 16 sea level index points that capture 60 cm of rsl rise the study area is in the mississippi delta where the spring tidal range is 0 47 m the impact of ocean currents on sea surface topography is limited and crustal motions are well constrained age control was obtained by ams 14 c dating and most ages represent weighted means of two subsamples sample elevations were determined by combining differential gps measurements with optical surveying all index points were plotted as error boxes using 2 confidence intervals for the ages plus all vertical errors involved in sampling and surveying as well as the indicative range of the samples a striking clustering of sea level index points between 1000 and 1200 ad suggests a possible acceleration in the rate of rsl rise removal of the long term trend 0 60 mm yr 1 allows for the possibility of a sea level oscillation with a maximum amplitude of 55 cm however given the size of the error boxes the possibility that oscillations did not occur cannot be entirely ruled out comparison of the new rsl record with various proxy climate records suggests that sea level in this area may have responded to hemispheric temperature changes including the medieval warm period and the little ice age however given the error margins associated with this reconstruction it is stressed that this causal mechanism is tentative and requires corroboration by high resolution sea level reconstructions elsewhere

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

coupling instrumental and geological records of sea level change evidence from southern new england of an increase in the rate of sea level rise in the late 19th century 1 we construct a high resolution relative sea level record for the past 700 years by dating basal salt marsh peat samples above a glacial erratic in an eastern connecticut salt marsh to test whether or not the apparent recent acceleration in the rate of sea level rise slr is coeval with climate warming the data reveal an average slr rate of 1 0 0 2 mm year from about 1300 to 1850 a d coupling of the regional tide gauge data 1856 to present with this marsh based record indicates that the nearly three fold increase in the regional rate of slr to modern levels likely occurred in the later half of the 19th century thus the timing of the observed slr rate increase is coincident with the onset of climate warming indicating a possible link between historic slr increases and recent temperature increases

salt marsh sea level indicators and transfer function development for the magdalen islands in the gulf of st lawrence canada abstract late holocene salt marsh sediments allow the reconstruction of pre industrial relative sea level changes typically reconstructions are derived by quantifying a relationship between contemporary proxies and elevation which is then applied to down core fossil assemblages via a transfer function common sea level indicating proxies are salt marsh foraminifera and diatoms however testate amoebae represent an alternative complementary proxy with current sea level research increasingly invoking multi decadal timescale processes such as ocean current strength or wind stress to explain relative sea level changes there is a need for increased vertical precision in reconstructions this paper presents new surface assemblages of salt marsh foraminifera and testate amoebae with respect to elevation from two coastal locations in the magdalen islands in the gulf of st lawrence eastern canada we analyse the suitability of each proxy for reconstructing sea level using multivariate statistics ordination and regression modelling testate amoebae are found in greater abundance and diversity than foraminifera and their assemblage variations can be better accounted for by changes in elevation the contemporary training sets from the magdalen islands were able to predict marsh surface elevations viz sea level to precisions of 0 08 m and 0 12 m for testate amoebae and foraminifera respectively there were no benefits from combining the two proxies into a unified training set it was possible to improve the performance of the foraminifera based transfer function by incorporating a second dataset from newfoundland which served to increase the range of the sampled environment and improve the correlation coefficient between sample elevations and model predictions in accordance with existing literature we find transfer function performance to be better at locations with smaller tidal ranges

identifying the causes of sea level change global mean sea level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades a review of the latest work shows that global mean sea level rise is unlikely to exceed one metre over the twenty first century but regional departures from this global mean could reach several decimetres

surface distributions of salt marsh foraminifera from connecticut usa modern analogues for high resolution sea level studies abstract salt marsh foraminifera are routinely used as sea level indicators since their vertical distribution is closely linked with elevation relative to the tidal frame the precise nature of these relationships is variable in time and space and the accuracy of sea level reconstructions depends upon the selection of appropriate modern analogues that reliably reflect past fauna environment associations the marshes of connecticut usa are sites of ongoing research seeking to produce high resolution records of sea level change yet little published data regarding their modern foraminiferal distributions exist this paper presents new surface foraminiferal data from three connecticut salt marshes and evaluates their suitability as modern analogues for past sea level changes the results indicate that significant intra and inter site variability between these marshes and those of neighbouring states exists as a consequence of this the extrapolation of fauna environment relationships developed from marshes with different hydrographic physiographic vegetative or climatic characteristics may produce erroneous reconstructions even when adjusted for variations in tidal range these errors are potentially greatest if single indicator species are used since the relative abundance of individual taxa does not vary consistently with elevation even in high marsh environments from the same site whilst cluster analysis demonstrates that foraminiferal assemblages from connecticut are vertically zoned with respect to mean high water mhw the composition elevation and height range of these zones is variable between sites this spatial heterogeneity results in reconstructions of relatively low and variable precision that restricts their utility in high resolution sea level research new studies seeking to distil decimetre scale changes in relative sea level will need to employ quantitative methods capable of combining multi site information to develop fauna environment relationships that capture this spatial variability reconstructions will be most precise when employing local foraminiferal distributions but may require the collection of additional modern analogue samples from other regions when the extant foraminiferal population of a site differs in composition from its sub fossil counterpart

relative sea level rise across the eastern border fault branford connecticut evidence against seismotectonic movements abstract basal peat age depth data from four salt marsh sites located 500 1500 m south of the eastern border fault ebf near branford connecticut document an error envelope for the lower limit of relative mean high water mhw rise during the past 3300 yr the long term rate of relative lower limit mhw rise during the past 3000 yr 1 1 mm yr 1 corresponds with late holocene rates of relative mhw rise found elsewhere in coastal connecticut 0 9 1 2 mm yr 1 this result invalidates repeated claims that multiple seismotectonic lowering of a crustal block towards the south has occurred along a segment of the ebf near branford shortly after 815 cal yr bc and during the past 1200 yr and calls for a non tectonic interpretation of biostratigraphic evidence of local short term sea level variations

reconstruction of recent sea level change using testate amoebae abstract proxy based sea level reconstructions place the instrumentally observed rates of recent sea level rise in a longer term context by providing data that extend the instrumental sea level record into past centuries this paper presents the first sea level reconstructions based on analyses of testate amoebae to test their ability to produce high precision reconstructions of past sea level we present two reconstructions for the past 100 yr from sites in maine usa and nova scotia canada based on short cores from salt marshes and modern training data from north america and the united kingdom these are compared with tide gauge records and reconstructions based on foraminifera from the same cores the reconstructions show good agreement with both the tide gauge data and the foraminifera based reconstructions the uk data perform well in predicting known elevations of north american surface samples and produce sea level reconstructions very similar to those based on the north american data suggesting the methodology is robust across large geographical areas we conclude that testate amoebae have the potential to provide robust higher precision sea level reconstructions for the past few centuries if modern transfer functions are improved and core sites are located within the main zone of testate amoebae occurrence on the salt marsh

north atlantic climate ocean variations and sea level in long island sound connecticut since 500 cal yr a d abstract a record of detrended mean high water mhw variations from hammock river marsh connecticut is extended from ca 850 to ca 500 cal yr a d and correlated with summer temperature reconstructions from northern fennoscandia and northern eurasia greenland ice sheet project 2 18 o and greenland ice core project borehole temperature variations from central greenland a sargasso sea sea surface temperature sst record and a proxy record for deep ocean flow south of iceland the records from northern fennoscandia eurasia and central greenland document century scale intervals of warming four and cooling three since ca a d 850 the mhw fluctuations lag behind these climate intervals by 0 100 yr with the two larger mhw rises corresponding to the two larger temperature increases this positive correlation suggests that surface air temperature sat is a dominant variable controlling sea level in the northwestern north atlantic since ca a d 850 the sst variations parallel the mhw fluctuations back to ca 950 cal yr a d a positive correlation is found also for sub century scale sat and mhw variations during the period a d 500 850 but this result is less firm mhw sst correlation over this time interval is not consistent

new evidence of relative sea level stability during the post 6000 holocene on the banc d arguin mauritania abstract morphological investigations on the northwest coastal plain of mauritania banc d arguin lead to a revised post 6000 yrs bp sea level curve the region is characterized by extensive sand flats occasionally surmounted by low sand barriers these barriers pick out a set of paleoshorelines attributed to the six episodes defined by dia 2013 morphological evidence of the extreme flatness of the coastal plain is provided by topographic transects based on total station surveys index points distributed throughout the second half of the holocene are defined in relation to the position of the barrier sole which is adjusted to the upper limit of the berm uprush the elevation of index points is related to the mean sea level msl through an assessment of the various errors likely to affect the results over the period since ca 7000 cal yr bp the measured elevations remain within a few decimetres of the present day sea level this implies that throughout this time interval sea level in the mauritanian region oscillated within the usual range of natural variations whereas oscillations of larger magnitude prevailed elsewhere because the study area is tectonically stable the glacio eustatic adjustment due to hydro isostatic effects is of minor importance in mauritania and the relative sea level rsl has responded solely to the eustatic component therefore we would expect to find some record of ocean syphoning through a gradual emergence of the land after the mid holocene marine transgression and the subsequent development of vertically stepped paleoshorelines the absence of such evidence raises the question of whether the drop in rsl was compensated by continuing deglaciation during the post 6000 holocene

quantifying the contribution of sediment compaction to late holocene salt marsh sea level reconstructions north carolina usa abstract salt marsh sediments provide accurate and precise reconstructions of late holocene relative sea level changes however compaction of salt marsh stratigraphies can cause post depositional lowering pdl of the samples used to reconstruct sea level creating an estimation of former sea level that is too low and a rate of rise that is too great we estimated the contribution of compaction to late holocene sea level trends reconstructed at tump point north carolina usa we used a geotechnical model that was empirically calibrated by performing tests on surface sediments from modern depositional environments analogous to those encountered in the sediment core the model generated depth specific estimates of pdl allowing samples to be returned to their depositional altitudes after removing an estimate of land level change error in variables changepoint analysis of the decompacted and original sea level reconstructions identified three trends compaction did not generate artificial sea level trends and cannot be invoked as a causal mechanism for the features in the tump point record the maximum relative contribution of compaction to reconstructed sea level change was 12 the decompacted sea level record shows 1 71 mm yr 1 of rise since ad 1845

salt marsh aggradation in response to late holocene sea level rise at amherst point nova scotia canada a radiocarbon 14c chronology determined for plant macrofossils in exposed salt marsh sediments at amherst point nova scotia canada shows that the edge of the high salt marsh aggraded 7 5 m since 900 bc equivalent to a mean rate of 25 9 cm 100 yr 1 four phases of rapid aggradation 900 600 bc 100 bc ad 200 ad 700 1100 and ad 1600 to present were interspersed with three phases of slower aggradation 600 100 bc ad 200 700 and tentatively ad 1100 1600 the stepped pattern of marsh aggradation probably resulted from eustatic sea level fluctuations superimposed on background signals of crustal subsidence and tidal range expansion because the rate of high salt marsh aggradation lagged or exceeded the rate of higher high water hhw increase at various times the high salt marsh aggradation trend only approximates the trend of hhw increase the eustatic sea level fluctuations are estimated to have a range of at least 0 8 m

mid to late holocene relative sea level change in poole harbour southern england a foraminiferal transfer function for mean tide level mtl is used in combination with ams radiocarbon dated material to construct a record of relative sea level rsl change from poole harbour southern britain these new data based on multiple cores from duplicate sites indicate four phases of change during the last 5000 cal calendar yr i rising rsl between ca 4700 cal yr bp and ca 2400 cal yr bp ii stable to falling rsl from ca 2400 cal yr bp until ca 1200 cal yr bp iii a brief rise in rsl from ca 1200 cal yr bp to ca 900 cal yr bp followed by a period of stability iv a recent increase in the rate of rsl rise from ca 400 200 cal yr bp until the present day in addition they suggest that the region has experienced long term crustal subsidence at a rate of 0 5 mm c 14 yr 1 although this can account for the overall rise in mtl observed during the past 2500 yr it fails to explain the changes in the rate of rise during this period this implies that the phases of rsl change recorded in the marshes of poole harbour reflect tidal range variations or eustatic fluctuations in sea level copyright 2001 john wiley sons ltd

holocene highstand deposits in the gulf of cadiz sw iberian peninsula a high resolution record of hierarchical environmental changes a comparison of the internal structure of holocene highstand shallow marine deposits with emerged spit bar systems in the gulf of cadiz margin sw iberian peninsula is presented in order to increase the knowledge about the patterns of environmental fluctuations of sub milankovitch periodicity during the recent highstand period a high resolution seismic database of boomer profiles was interpreted focusing on shallow marine deposits of the gulf of cadiz shelf such as the guadalquivir river prodelta the guadiana river depositional system and the faro tavira infralittoral prograding wedge the results indicate that the internal architecture of recent highstand shelf deposits is complex as the recognition of three main types of seismic unit motifs suggests the existence of a hierarchical pattern of environmental fluctuations a major scale motifs the most significant feature observed in the seismic records is the pervasive occurrence of two major scale motifs lower and upper within the holocene highstand systems tract b intermediate scale motifs each major scale motif is composed of two intermediate scale motifs defining four intermediate scale motifs h1 to h4 c minor scale motifs the internal structure of major and intermediate scale motifs reveals a high degree of environmental variability during the recent highstand probably led by climatic cyclicities of submillenial scale the lower major scale motif is characterised by alternating progradational aggradational minor scale motifs whereas the upper major scale motif presents a more uniform internal structure dominated by progradational units the influence of two distinct trends or asymmetric cycles of sea level change seems to have been significant in the generation of the major scale architecture the transition between both major phases was probably related with a major sea level rise other factors such as changes in the magnitude and or direction of storm events and climatically induced changes of sediment supply are proposed to have controlled the generation of intermediate and minor scale architectures

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

sea level variability in the northwest atlantic during the past 1500 years a delayed response to solar forcing 1 numerical experiments with a coupled oceanatmosphere model ecbilt have shown that centennial variations in sea level sl in the northwest atlantic may be associated with deep ocean salinity anomalies generated by solar forced variations in the north atlantic overturning circulation here we compare simulated sl curves for the gulf stream region with reconstructed late holocene sl records from connecticut usa simulated sl variations lag the solar forcing record by ca 120 year this lag is found to be robust over a small number of different experiments the reconstructed sl curves visually match the solar forcing optimally when lagging it by ca 125 yr a quantitative test shows that the correlation is significant while this result is not sensitive to dating uncertainties the temporal response pattern of the simulated sl curves compares reasonably well with the reconstructions index terms 4556 oceanography physical sea level variations 1650 global change solar variability 4255 oceanography general numerical modeling 4267 oceanography general paleoceanography 3030 marine geology and geophysics micropaleontology citation van de plassche o g van der schrier s l weber w r gehrels and a j wright sea level variability in the northwest atlantic during the past 1500 years a delayed response to solar forcing geophys res lett 30 18 1921 doi 10 1029 2003gl017558 2003

modern saltmarsh diatom distributions of the outer banks north carolina and the development of a transfer function for high resolution reconstructions of sea level we collected modern diatom samples from currituck barrier island oregon inlet and pea island marshes outer banks north carolina usa which have different salinity regimes due to their varying distances from a major barrier island inlet multivariate analyses separate the saltmarsh diatom assemblages into distinct elevational zones dominated by differing abundances of polyhalobous mesohalobous and oligohalobous taxa suggesting that the distribution of saltmarsh diatoms is a direct function of elevation with the most important controlling factors being the duration and frequency of subaerial exposure we developed the first diatom based transfer function for the east coast of north america to reconstruct former sea levels based upon the relationship between diatom assemblage and elevation results imply that this is possible to a precision of 0 08 m superior to most similar studies from temperate mid latitude environments the transfer function is used to construct a relative sea level curve from fossil assemblages from salvo north carolina these results suggest a sea level rise of 0 7 m over the last c 150 years at an average of c 3 7 mm year 1 this is

sea level climate correlation during the past 1400 yr we present a new mean high water curve for hammock river marsh clinton connecticut obtained by improving the age model for an existing record of relative marsh elevation based on foraminiferal analysis of a 1 8 m long peat core unlike the earlier curve the new curve confirms trend changes in mean high water rise during the past 1400 yr as noted for salt marshes 15 km farther west suggesting a regional cause these trend changes and century scale mean high water variations in the clinton record correlate positively with large scale regional variations in sea surface and summer air temperature indicating a link between sea level and the climate ocean system on the basis of the clinton mean high water curve we conclude that real sea level oscillated centimeters to decimeters on a century time scale over the past 1400 yr was 25 25 cm higher ca a d 1050 medieval warm period than ca a d 1650 little ice age and rose at a mean rate of 1 mm yr 1 over the past 350 yr there was little or no rise during the cool 1800s

late holocene sea level variability and atlantic meridional overturning circulation pre twentieth century sea level sl variability remains poorly understood due to limits of tide gauge records low temporal resolution of tidal marsh records and regional anomalies caused by dynamic ocean processes notably multidecadal changes in atlantic meridional overturning circulation amoc we examined sl and amoc variability along the eastern united states over the last 2000 years using a sl curve constructed from proxy sea surface temperature sst records from chesapeake bay and twentieth century sl sea surface temperature sst relations derived from tide gauges and instrumental sst the sl curve shows multidecadal scale variability 20 30 years during the medieval climate anomaly mca and little ice age lia as well as the twentieth century during these sl oscillations short term rates ranged from 2 to 4 mm yr 1 roughly similar to those of the last few decades these oscillations likely represent internal modes of climate variability related to amoc variability and originating at high latitudes although the exact mechanisms remain unclear results imply that dynamic ocean changes in addition to thermosteric glacio eustatic or glacio isostatic processes are an inherent part of sl variability in coastal regions even during millennial scale climate oscillations such as the mca and lia and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise

the skull of stephanorhinus kirchbergensis jager 1839 mammalia rhinocerotidae from spinadesco cremona lombardia northern italy morphological analyses and taxonomical remarks an opportunity for revising the three other skulls from the po valley abstract the exceptional discovery of a complete and extraordinary well preserved skull of stephanorhinus kirchbergensis jager 1839 on an alluvial bar of the po river near spinadesco cremona lombardia northern italy in july 2013 presented us with the opportunity for reporting on the specimen the thorough morphometric and morphological analyses carried out on the specimen dentition included revealed typical characteristics of s kirchbergensis also known as merck s rhinoceros these peculiar tracts highlighted distinctive taxonomic characteristics which are useful for reassessing the classifications of the specimens found in adjacent areas up to now in this paper the distinguishing characters are discussed privileging the morphological features rather than the metrical characteristics also if the dimensions of the skull are significative the adopted criteria employed for the first time by loose 1975 were used also for comparing the skull from spinadesco with other fossil rhinoceros skulls discovered in the po valley adjacent areas the dicerorhinus hemitoechus falconeri azzaroli 1962 from mezzana rabattone zinasco pavia the dicerorhinus hemitoechus aretinus azzaroli 1962 from san colombano al lambro milano and the dicerorhinus hemitoechus intermedius from the torrente stirone studied by cigala fulgosi 1976 up to now s kirchbergensis appears to be a rather rare species on the vast eurasian landmass as few fossils have been found in a relatively limited number of localities furthermore there are generally not available chrono or biostratigraphic data

dynamics of volcanic systems in iceland example of tectonism and volcanism at juxtaposed hot spot and mid ocean ridge systems volcanic systems are swarms of tectonic fractures and basalt volcanoes formed as a result of plate pull as the plates are pulled apart associated with the mid ocean ridges and the magma dynamics of the iceland mantle plume most systems are 40 150 km long 5 20 km wide and develop a central volcano they supply magma to all eruptions in iceland data obtained in the last few years have greatly improved our knowledge of their volcanotectonic environment as a result the geometry of the plume is better constrained and the crust previously considered thin 10 km is now modeled as thick 20 40 km depending on the location of the volcanic systems their activity either decreases or increases faulting in the two main seismic zones from this we can infer that emplacement of the feeder dike to the largest historical eruption in iceland that of laki in 1783 increased shear stress in the south iceland seismic zone and almost certainly triggered the largest m 7 1 in 1784 historical earthquake in ic

lagoon subsidence and tsunami on the west coast of new zealand abstract sediment core and trench data from a coastal lagoon on the west coast of the south island new zealand are used to investigate evidence for co seismic subsidence and associated tsunami inundation physical data are used to document a salt marsh soil buried 80 cm below the modern sediment surface that is locally covered by a gravelly sand bed the sediment record also contains geochemical and biological diatom and foram evidence for abrupt changes in salinity of lagoon waters that link to subsidence tsunami flooding and to the open versus closed state of the lagoon tidal entrance at the local scale these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon we also propose a conceptual connection between these local changes and regional drivers of landscape development most notably major earthquakes and resultant pulses in sediment supply to the coast

assessing sea level data from connecticut usa using a foraminiferal transfer function for tide level concerns surrounding possible future climate change sea level rise and their potential impacts on coastal environments have stimulated research seeking to elucidate the relationship between ocean levels and climate at the sub century scale the need for increasingly precise reconstructions of relative sea level change has in turn driven the development of new methodologies capable of resolving fine scale variability within salt marsh sedimentary sequences the use of salt marsh foraminifera as precise indicators of past tide levels has played a central role in this process and is exemplified by a number of detailed studies conducted in connecticut usa in this paper we apply the most recent methodological advance in the reconstruction of relative sea levels using salt marsh foraminifera we develop a foraminiferal transfer function for tide level derived from the modern foraminiferal distributions of four connecticut salt marshes in contrast to existing approaches that employ site specific interpolations of local vertical foraminiferal assemblage zones this transfer function can provide objective quantitative and reproducible estimates of palaeomarsh surface elevation with explicitly stated error terms for marshes throughout connecticut irrespective of differences in tidal range we demonstrate the foraminiferal transfer function approach by employing it to reconstruct changes in palaeomarsh surface elevation from three cores recovered from hammock river marsh connecticut the resulting reconstructions which are precise to f0 09 m are tested using an independent dataset from the neighbouring state of maine and are used to assess a pivotal record of mean high water mhw change from this site we conclude that the transfer function reconstructions show good general agreement with previous records of palaeomarsh surface elevation but with the advantages of quantified error terms and a transparent reproducible methodology this replicability will assist in the comparison or combination of local records of mhw change to infer large scale regional sea level variations d 2003 elsevier b v all rights reserved

punctuated environmental change along the holocene 6 ka bank margin of south west exuma sound bahamas characteristics of environmental change along the holocene 6 ka bp bank margin of south west exuma sound bahamas are defined by comparing mineral isotope and lithologic stratigraphic patterns in deep water 1081 m slope strata in odp hole 631a exuma sound with proximal 6 km shoal water and insular geology of the lee stocking island lsi region after platform submergence a bank top transition from non skeletal to skeletal dominated deposition occurred in the lsi region by 3 8 ka and is recorded in the adjacent slope sediments by a contemporaneous change in the abundance of transported allochems the transition at site 631 is punctuated by an anomalous shift in foraminiferal 13c 1 and 18o 3 which may represent a period of climate change that established a brackish coastal zone at least 6 km wide coincident 3 8 4 ka with bank top erosion and pedogenesis non skeletal allochems reappeared in hole 631a sediments as the dominant transported allochem type by 2 4 ka then again over the last several hundred years and are contemporaneous with periods of increased platform margin circulation in the lsi region such rejuvenation of platform circulation may have resulted from rapid relative rises in sea level superimposed on the net gradual post glacial rise at site 631 a prominent 25 decline in aragonite abundance occurred during the period from 2 4 ka to the last few hundred years and coincided with an increase in magnesian calcite and skeletal debris and a positive shift in foraminiferal 18o values these patterns lend support to the hypothesis that during this period the lsi margin was barred by skeletal shoals allowing bank top trapping of aragonite and hypersaline water with increased coastal salinity resulting from reflux of hypersaline waters through the shoals and or cooled coastal waters caused by reduced exchange of warmed bank derived water relative to wind generated upwelling along the exuma slope a diagenetic overprint may further enhance the recent decline in aragonite accumulation integration of holocene deep water slope and bank top stratigraphies along the bank margin of south west exuma sound reveals a pattern of punctuated environmental change superimposed on longer term development of interglacial conditions

dykes faults and palaeostresses in the teno and anaga massifs of tenerife canary islands abstract a structural field study was made of 578 sheet intrusions mostly dykes and 153 mostly normal faults dissecting the anaga and teno massifs where a complex volcanic succession of tertiary age the old basaltic series representing the shield building stage of tenerife canary islands crops out many of the intrusions mostly sub vertical mafic dykes are emplaced by multiple magma injections with cumulative thicknesses mostly less than 2 m dyke tips are exposed and preserved for 12 of the dykes three differently oriented sets of dykes exist in the anaga massif nnw sse nne ssw e w whereas there is only one main set in teno trending nnw sse dyke swarms and other structural features having similar orientations also exist in other canary islands a minimum value of the horizontal component of extension induced by dykes is computed using a step of 5 of azimuth accounting also for the dip of dykes the cumulative crustal dilation is at least 300 m 4 in anaga and 270 m 6 in teno the maximum extension peaks at n75 in anaga and n60 in teno indicating a general prevailing extension in direction ene wsw most of the measured faults are normal and strike nnw sse computation of palaeostresses from inversion of fault slip data sets suggests the existence of a polyphase brittle deformation due to an extensional stress field with the minimum compressive principal axes trending ne sw and wnw ese

rapid sea level rise abstract several global and regional factors contribute to observed sea level change along any particular coast global processes include changes in ocean mass glacio eustasy from ice melt ocean volume steric effects viscoelastic land movements glacioisostatic adjustment gia and changes in terrestrial water storage regional processes often connected to steric and glacial changes include changes in ocean circulation meridional overturning circulation moc glacial melting local gia regional subsidence and others paleoclimate instrumental and modeling studies show that combinations of these factors can cause relatively rapid rates of sea level rise exceeding 3 mm yr 1 over various timescales along particular coasts this paper discusses patterns and causes of sea level rise with emphasis on paleoclimatological records it then addresses the hypothesis of late holocene pre 20th century sea level stability in light of paleoclimatic evidence notably from reconstructions of sea surface temperature and glacial activity for significant climate and sea level variability during this time the practical difficulties of assessing regional sea level sl patterns at submillennial timescales will be discussed using an example from the eastern united states

rapid sea level rise in the gulf of maine usa since ad 1800 two sea level records from salt marshes in coastal maine are derived from foraminiferal analyses and ams 14 c 210 pb 137 cs and pollen chronology both records cover the period from ad 800 until the present and show corresponding patterns of sea level change when corrected for trends which could accommodate millennial scale isostatic adjustments the records provide a detailed sea level chronology for the last few centuries and thus link the instrumental tide gauge record with the long term geological record of sea level change results show that sea level was relatively stable between ad 800 and 1300 and reached a lowstand around ad 1800 which was preceded by an oscillation in the eighteenth century since ad 1800 sea levels in the gulf of maine have risen by 0 3 0 4 m the onset of this rise corresponds with regional climatic warming and could be interpreted as thermal expansion of the gulf of maine and north atlantic sea surface sea level rise possibly slowed temporarily during the mid nineteenth century but twentieth century rates are unprecedented in the last millennium and correspond with hemispheric warming

palaeoenvironment palaeoclimate and sea level changes in the shuaiba lagoon during the late holocene last 3 6 ka eastern red sea coast saudi arabia multi proxy investigations of sediment lithology geochemistry benthic foraminifera and 18o and 13c of elphidium striatopunctatum were carried out on a sediment core shua3 2 2 m long spanning

crustal spreading due to dikes and faults in southwest iceland abstract a 30 km long profile extending from 3 million year old pleistocene rocks to the holocene rocks of the rift zone in southwest iceland is dissected by 443 dikes and 156 normal faults nearly all the dikes are basaltic with an average strike of n26 e which is subparallel to the trend of fractures in the nearby rift zone their average dip is 69 and average thickness 1 37 m both values much lower than averages for regional tertiary dike swarms in iceland many dikes are seen to change into sills the great majority of the faults are pure dip slip with an average throw of 10 2 m their average strike n37 e is different from the average strike of the dikes in this area and the fractures in the nearby rift zone their average dip is 75 2 which is somewhat steeper than in the tertiary areas but the dips are less in the interbedded sedimentary layers than in the lava flows growth faults are very rare in the area and most of the faults appear to have completed their growth in less than 10 000 years in subsections crustal dilation due to dikes is 0 4 3 7 that due to faults is 0 6 5 3 and that due to both dikes and faults is 1 04 6 44 in these subsections average fault spacing is one fault per 170 563 m spacing decreases toward the active rift zone it is concluded that in typical fissure swarms of the rift zone the dilation at the surface is almost entirely due to extensional fractures and gaping vertical normal faults in the depth range of a couple of hundred metres to perhaps 1 km the non vertical faults contribute most to the dilation at deeper crustal levels however dilation due to dikes becomes dominant

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

relative sea level change in connecticut usa during the last 2200 yrs we produced a relative sea level rsl reconstruction from connecticut usa spanning the last 2200 yrs that is free from the influence of sediment compaction the reconstruction used a suite of vertically and laterally ordered sediment samples 2 cm above bedrock that were collected by excavating a trench along an evenly sloped bedrock surface paleomarsh elevation was reconstructed using a regional scale transfer function trained on the modern distribution of foraminifera on long island sound salt marshes and supported by bulk sediment 13c measurements the history of sediment accumulation was estimated using an age elevation model constrained by radiocarbon dates and recognition of pollution horizons of known age the rsl reconstruction was combined with regional tide gauge measurements spanning the last 150 yrs before being quantitatively analyzed using an error in variables integrated gaussian process model to identify sea level trends with formal and appropriate treatment of uncertainty and the temporal distribution of data rsl rise was stable 1 mm yr from 200 bce to 1000 ce slowed to a minimum rate of rise 0 41 mm yr at 1400 ce and then accelerated continuously to reach a current rate of 3 2 mm yr which is the fastest century scale rate of the last 2200 yrs change point analysis identified that modern rates of rise in connecticut began at 1850 1886 ce this timing is synchronous with changes recorded at other sites on the u s atlantic coast and is likely the local expression of a global sea level change earlier sea level trends show coherence north of cape hatteras that are contrasted with southern sites this pattern may represent centennial scale variability in the position and or strength of the gulf stream comparison of the new record to three existing and reanalyzed rsl reconstructions from the same site developed using sediment cores indicates that compaction is unlikely to significantly distort rsl reconstructions produced from shallow 2 3 m thick sequences of salt marsh peat

centennial scale cycles in middle holocene sea level along the southeastern swedish baltic coast submerged sea grasses and stoneworts growing in the immediate nearshore of the baltic sea are sensitive indicators of sea level the alternating changes in concentrations of sea grass and stonewort macrofossils obtained from an ancient lagoon of the baltic sea are ascribed to middle holocene sea level fluctuations along the southeastern swedish coast abundances of stonewort and sea grass macrofossils between 7500 and 6000 cal calibrated yr b p were lower and less variable indicating high and relatively stable sea level low frequency fluctuations of sea level with a 1470 yr period during this time may have been forced by tidal action in the millennial band after 6000 cal yr b p sea level was lower and exhibited strong fluctuations at centennial time scales as evident in the stonewort and sea grass macrofossil records such a high frequency oscillatory mode of sea level may have been regulated by centennial scale solar activities or tidal actions or both the modest variation in solar irradiance is unlikely to have resulted in large scale oscillations of sea level by directly changing the steric component instead it governed sea level fluctuations by changing the regional storminess through a north atlantic oscillation nao like system storms embedded in the nao induced southwesterly winds played a major role in the centennial scale fluctuations of the baltic sea level by pushing saltwater from the north sea into the baltic basin less

timing and magnitude of recent accelerated sea level rise north carolina united states we provide records of relative sea level since a d 1500 from two salt marshes in north carolina to complement existing tide gauge records and to determine when recent rates of accelerated sea level rise commenced reconstructions were developed using foraminifera based transfer functions and composite chronologies which were validated against regional twentieth century tide gauge records the measured rate of relative sea level rise in north carolina during the twentieth century was 3 0 3 3 mm a consisting of a background rate of 1 mm a plus an abrupt increase of 2 2 mm a which began between a d 1879 and 1915 this acceleration is broadly synchronous with other studies from the atlantic coast the magnitude of the acceleration at both sites is larger than at sites farther north along the u s and canadian atlantic coast and may be indicative of a latitudinal trend

emplacement of dikes sills and crustal magma chambers at divergent plate boundaries abstract a model of dike emplacement at divergent plate boundaries is developed which predicts that below the uppermost 1 3 km of the oceanic crust the number and lengths of dikes in any particular swarm should increase but that the thickness should decrease with depth in the crust these predictions are supported by field observations it is proposed that rapid injections of dikes at divergent plate boundaries may temporarily alter the normal stress field in such a way that at a certain level in the crust subsequent dikes change into sills such sills may develop into crustal magma chambers either when many nearby sills combine into a large one or when an initial sill absorbs the magma of many dikes that enter it in a rapid succession while the sill is liquid for the fastest spreading ridges the initial thickness of a sill that is to develop into a crustal chamber need only attain 20 m whereas at the slowest spreading ridges the initial thickness must exceed 170 m because thin sills are much more likely to form than thick sills the probability of sills developing into crustal chambers increases with dike intrusion frequency hence with spreading rate furthermore the model predicts first that with increasing spreading rate the length of the chamber along the ridge axis should increase and second that the most likely site for magma chambers is at depths of 2 4 km both these predictions are supported by available data

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

sea level changes since the last glacial maximum an appraisal of the ipcc fourth assessment report the ipcc fourth assessment report ar4 stated that global sea level rose by about 120 m between the last glacial maximum lgm and 3 2 ka and did not rise again until the late 19th century a review of relevant literature demonstrates that the rise may have been larger by 10 15 m that the timing of stabilisation is poorly constrained within the last 7 ka bp and that the onset of modern rates of sea level rise is not synchronous and uniform across the globe the lgm lowstand as defined in the ar4 is based on the classic barbados sea level history but the sea level curve from this island may not be an accurate eustatic approximation if glacial isostatic adjustment gia processes were significant as suggested by various authors the barbados sea level curve revealed the existence of meltwater pulse mwp 1a at around 14 000 cal a bp questions about the source and causal mechanism of mwp 1a are still being explored by field scientists and gia modellers these problems have direct relevance for contemporary measurements of ice mass changes because space geodetic measurements rely on information provided by gia models to separate land motion from ice mass changes global patterns of holocene sea level change are controlled by regional sea level variability not only through isostatic and tectonic processes but also through steric effects longer wavelength gravitational changes produced by changing ice ocean mass flux and hemispheric scale perturbations in the earth s rotation eustasy is therefore merely a concept not a measurable quantity constraining the late holocene ice melt contribution to global sea level rise and determining regional sea level rise patterns in the 18th and 19th centuries are important future tasks for sea level scientists these will establish the baseline contributions to 20th and 21st century sea level rise and will help to determine the causes of modern rates of sea level rise constraining historical sea level accelerations and short term ice mass flux will aid models of ice sheet dynamics and help to reduce current uncertainties in future sea level predictions the ar4 shows that regional sea level variability is clearly present in sea level change patterns for the past 50 a and an important challenge for the next ipcc assessment is to incorporate this variability into regional future sea level rise scenarios copyright 2009 john wiley sons ltd

middle and late holocene sea level changes in eastern maine reconstructed from foraminiferal saltmarsh stratigraphy and ams 14c dates on basal peat abstract a relative sea level history is reconstructed for machiasport maine spanning the past 6000 calendar years and combining two different methods the first method establishes the long term 10 3 yr trend of sea level rise by dating the base of the holocene saltmarsh peat overlying a pleistocene substrate the second method uses detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long term trend the indicative meaning of the peat the height at which the peat was deposited relative to mean tide level is calculated by a transfer function based on vertical distributions of modern foraminiferal assemblages the chronology is determined from ams 14 c dates on saltmarsh plant fragments embedded in the peat the combination of the two different approaches produces a high resolution replicable sea level record which takes into account the autocompaction of the peat sequence long term mean rates of sea level rise corrected for changes in tidal range are 0 75 mm yr between 6000 and 1500 cal yr b p and 0 43 mm yr during the past 1500 years the foraminiferal stratigraphy reveals several low amplitude fluctuations during a relatively stable period between 1100 and 400 cal yr b p and a sea level rise of 0 5 m during the past 300 years

marine sediments from southeastern brazilian continental shelf a 1200 year record of upwelling productivity abstract a sediment core from the cabo frio coastal shelf 23 19 s 41 8 w 117 m depth was analyzed for toc c n ratio organic petrography and planktonic foraminiferal content to evaluate variations in local productivity caused by changes in upwelling intensity and its relation to regional and global climatic variations during the last millennium the cabo frio core recorded the last 1200 years of sedimentation with rates varying from 0 11 to 0 32 mm yr 1 foraminiferal and organic geochemical analyses indicate the occurrence of three distinct periods of productivity from 850 ad until 1070 ad foraminifera fluxes consisting primarily of turborotalita quinqueloba indicate stronger south atlantic central water sacw transport onto the shelf which induced high biological productivity that was also recorded by high toc and marine palynomorphs content and a low c n atomic ratio this period coincided with a northward displacement of the atmospheric intertropical convergence zone itcz and south atlantic high sah systems driven by positive temperature anomalies in the north atlantic ocean during the medieval climate anomaly mca from 1070 until 1500 ad low toc flux and planktonic foraminifera fluxes and high c n atomic ratios suggest a reduction in marine productivity probably driven by reduced transport of sacw associated with the southward displacement of the sah and weakening of northeasterly winds the period between 1500 and 1830 ad which corresponds to the little ice age is marked by increased fluxes of planktonic foraminifera principally of globigerina bulloides and globigerinita glutinata these species mark an increase in productivity linked to sacw upwelling supported by the enhancement of northeasterly winds and southward displacement of the itcz and sah

the relative utility of foraminifera and diatoms for reconstructing late holocene sea level change in north carolina usa abstract foraminifera and diatoms preserved in salt marsh sediments have been used to produce high resolution records of holocene relative sea level rsl change to determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in north carolina usa regional scale transfer functions were developed using foraminifera diatoms and a combination of both multi proxy from three salt marshes oregon inlet currituck barrier island and pea island we evaluated each approach on the basis of transfer function performance foraminifera diatoms and multi proxy based transfer functions all demonstrated a strong relationship between observed and predicted elevations r 2 jack 0 74 and rmsep 210 pb and 14 c based chronology and we were able to reconcile this with tide gauge records

reconstructed topography of southern new england prior to isostatic rebound with implications of total isostatic depression and relative sea level abstract topographic models of the late quaternary landscape prior to isostatic rebound aid interpretation of glacial lake water levels and geomorphic features as well as ice thickness mantle viscosity and lithospheric strength the well established limit of glacial marine inundation in central and northern new england provides a test of total isostatic depression relative sea levels reflecting differing magnitudes of isostatic rebound show that published values of isostatic depression in southern new england would inundate the landscape in southern new england with marine water south of the limit of late pleistocene marine inundation this suggests that isostatic depression at the terminal margin of the laurentide ice sheet lis was 50 m a first order estimate of ice thickness based on total isostatic depression and the observed uplift profile in southern new england supports the thin ice models in new england ice thickness ranged from 100 m at the southeastern margin of the lis to 1000 m at a point 300 km north of the terminal margin this regional model places constraints on continental ice sheet and geophysical models that should be considered in the future

use of insolation as a proxy for high frequency eustasy in forward modeling of platform carbonate cyclostratigraphy a promising approach abstract eustatic oscillations driven by milankovitchian astronomical forcing have been interpreted as sea level drivers for high frequency carbonate depositional cycles in studies dating from the mid 1960s forward modeling of these oscillations with respect to their recorded effects on cyclical stacking patterns has only been attempted using generalized parameters for milankovitchian forcing the development of increasingly advanced forward modeling software coupled with the availability of formulas quantifying insolation incoming solar radiation as a function of composite orbital variations allows for the testing of milankovitchian insolation against measured stratigraphy in this case a series of milankovitchian insolation curves were calculated and used to generate proxy sea level curves for use in the carb3d forward modeling package in order to synthesize a series of stacked carbonate strata these synthetic successions are compared against that of the latemar platform middletriassic northern italy which has been interpreted to contain a record of orbital forcing within its stratigraphy while the timing and nature of periodic drivers that affected latemar stratigraphy have stirred a vigorous debate results from this study indicate that use of milankovitchian insolation as a proxy for high frequency sea level oscillations was successful in modeling latemar like stratigraphy with both pure milankovitchian and mixed milankovitchian sub milankovitchian temporal frameworks

developing detailed records of relative sea level change using a foraminiferal transfer function an example from north norfolk uk this paper provides a brief overview of the transfer function approach to sea level reconstruction using the example of two overlapping sediment cores from the north norfolk coast uk the advantages and limitations of the transfer function methodology are examined while the selected cores are taken from different sites and display contrasting patterns of sedimentation the foraminiferal transfer function distils comparable records of relative sea level change from both sequences these reconstructions are consistent with existing sea level index points from the region but produce a more detailed record of relative sea level change transfer functions can extract sea level information from a wider range of sedimentary sub environments this increases the amount of data that can be collected from coastal deposits and improves record resolution the replicability of the transfer function methodology coupled with the sequential nature of the data it produces assists in the compilation and analysis of sea level records from different sites this technique has the potential to bridge the gap between short term instrumental and long term geological or geophysical records of sea level change

relative sea level trends in new york city during the past 1500 years new york city nyc is threatened by 21st century relative sea level rsl rise because it will experience a trend that exceeds the global mean and has high concentrations of low lying infrastructure and socioeconomic activity to provide a long term context for anticipated trends we reconstructed rsl change during the past 1500 years using a core of salt marsh sediment from pelham bay in the bronx foraminifera and bulk sediment 13c values were used as sea level indicators the history of sediment accumulation was established by radiocarbon dating and recognition of pollution and land use trends of known age in down core elemental isotopic and pollen profiles the reconstruction was generated within a bayesian hierarchical model to accommodate multiple proxies and to provide a unified statistical framework for quantifying uncertainty we show that rsl in nyc rose by 1 70 m since 575 ce including 0 38 m since 1850 ce the rate of rsl rise increased markedly at 1812 1913 ce from 1 0 to 2 5 mm y

sea level change during the last 2500 years in new jersey usa relative sea level changes during the last w2500 years in new jersey usa were reconstructed to test if late holocene sea level was stable or included persistent and distinctive phases of variability foraminifera and bulk sediment d 13 c values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt marsh sediment at two sites using a multi proxy approach the additional paleoenvironmental information provided by bulk sediment d 13 c values reduced vertical uncertainty in the sea level reconstruction by about one third of that estimated from foraminifera alone using a transfer function the history of sediment deposition was constrained by a composite chronology an ageedepth model developed for each core enabled reconstruction of sea level with multi decadal resolution following correction for land level change 1 4 mm yr four successive and sustained multi centennial sea level trends were objectively identified and quantified 95 confidence interval using error in variables change point analysis to account for age and sea level uncertainties from at least 500 bc to 250 ad sea level fell at 0 11 mm yr the second period saw sea level rise at 0 62 mm yr from 250 ad to 733 ad between 733 ad and 1850 ad sea level fell at 0 12 mm yr the reconstructed rate of sea level rise since w1850 ad was 3 1 mm yr and represents the most rapid period of change for at least 2500 years this trend began between 1830 ad and 1873 ad since this change point reconstructed sea level rise is in agreement with regional tide gauge records and exceeds the global average estimate for the 20th century these positive and negative departures from background rates demonstrate that the late holocene sea level was not stable in new jersey

stratigraphy pollen history and geochronology of tidal marshes in a gulf of maine estuarine system climatic and relative sea level impacts abstract sedimentologic and stratigraphic characteristics of five tidal marshes in great bay estuary new hampshire which is located on the western boundary of the gulf of maine were assessed from 20 vibracores detailed descriptions of surficial environments pollen analyses and radiocarbon dating modern marsh sequences in great bay estuary initiated with a time transgressive basal peat that formed at the upland brackish marsh boundary the oldest basal peat deposit sampled during this study was dated at 4560 cal yr b p based on an age of 4060 40 14 c yr b p the original tidal marshes that formed in great bay estuary apparently were unable to accrete at a high enough rate to allow seaward expansion resulting in a transgressive sequence of low marsh or mudflat sediments overlying the basal peat the transgressive tidal marsh sequence is capped by high marsh sediments that corresponded to a slowing of relative sea level rsl rise in the region and regressive seaward expansion of the tidal marshes however significant variations from these transgressive regressive sequences occur in the great bay tidal marshes as a result of more recent marsh expansion and tidal channel migrations detailed pollen analyses of a vibracore taken in a tidal marsh along squamscott river with a sedimentary record spanning the last 3900 cal yr b p exhibit five well documented marker horizons including 1 an increase of tsuga hemlock 2 the appearance of picea spruce 3 tsuga and fagus beech declines 4 an increase in ambrosia ragweed coupled with a sudden decrease in quercus oak and 5 the castanea chestnut decline using published ages for these pollen horizons and a calibrated 14 c age obtained during this study for a basal peat accretion rates for this marsh system over five time intervals were calculated 1 0 4 to 0 5 mm yr 1 from 3900 to 2850 cal yr b p 2 0 6 mm yr 1 from 2850 to 1960 cal yr b p 3 0 8 mm yr 1 from 1960 to 580 cal yr b p 4 0 7 to 0 8 mm yr 1 from 580 to 210 cal yr b p and 5 0 8 to 0 9 mm yr 1 over the last 210 years the long term accretion rate for the entire sequence based on the calibrated 14 c age of the basal peat was 0 6 to 0 7 mm yr 1 this result agrees with accretion rates determined from calibrated 14 c ages from two other tidal marsh systems in great bay estuary with accretion rates between 0 6 to 0 8 mm yr 1 higher accretion rates were obtained at a nearby tidal marsh with 1 2 mm yr 1 for just the marsh and 1 3 mm yr 1 for the marsh and underlying subtidal sediment the results of this study indicate that the sedimentology and stratigraphy of moderate size tidal marshes in rocky glaciated coasts are highly variable and are strongly influenced by complex interactions among rsl climatic variations and anthropogenic influences for instance the early development of many of the marshes in the great bay estuary area were likely driven by changes in rates of rsl resulting in transgressive onlap boundaries subsequently overlain by regressive intertidal marsh sequences however more recent changes in tidal marsh sediment composition deposited during a relatively slow steady rsl rise likely result from other forcings such as changes in minerogenic and orogenic sediment inputs due to anthropogenic effects tidal channel migrations major storms causing erosion of the marsh or climatic changes causing shifts in sediment delivery or vegetation

sea level in time and space revolutions and inconvenient truths in this paper we identify four revolutions that in our view have shaped the study of sea level changes in recent decades i the search for eustasy one of the most hotly debated issues in the 1960s is still relevant as models of glacial isostatic adjustment gia require input of the amount of meltwater transferred to the world s oceans following the demise of the large pleistocene ice sheets ii resolution of sea level archives all sea level archives have limitations in their resolving power but are we willing to define these from studies of salt marsh deposits and corals it is highly likely that climate driven metre scale sea level fluctuations have not occurred during the middle and late holocene iii rapid sea level changes improved coring technology has resulted in the suggestion of meltwater pulses during the last deglaciation low frequency high magnitude events have been documented along seismically active shorelines and provide information on seismic hazards and storm impacts iv merging of empirical sea level investigations and models much sea level research in the past two decades has embraced the integration of models and field derived data providing testable hypotheses and insights into processes we conclude with some reminders about the inconvenient truths that keep the sea level scientist honest

reinterpretation of past sea level variation of the bay of fundy reports of shifts in rates of aggradation in a salt marsh deposit at amherst point nova scotia have been linked with fluctuations in eustatic sea level crustal subsidence and possibly changes in tidal amplitude however evidence for the most recent fluctuation is an artifact of early acadian land reclamation that occurred in the seventeenth century at amherst point acadian settlers had constructed dikes to prevent regular tidal flooding but probably allowed occasional flooding of the surface by tidal waters thus maintaining the salt marsh signature of the deposit statistical analysis of the pollen assemblage from the uppermost deposit inter preted as a regressive sequence aligns critical depths with pollen assemblages retrieved from modern soils of diked and drained marshes inspection of historical aerial photographs confirms that the dikes persisted on the site until at least 1939 interpretations of earlier fluctuations recorded in deposits below this regressive sequence remain valid it is possible that the bay of fundy experienced a regressive period just prior to acadian diking but future research on unexamined salt marsh deposits here or elsewhere must include an exhaustive search of historical documents to avoid misinterpretation of anthropogenic modifications

some problems in the reconstruction of mean sea level and its changes with time the ocean level is constantly changing and there are many different forcing functions today we realize that a rise in one area may in fact correspond to a fall in another area a number of prob

late holocene sea level change around newfoundland differential sea level change in formerly glaciated areas is predicted owing to variability in extent and timing of glacial coverage newfoundland is situated close to the margin of the former laurentide ice sheet and the orientation of the shoreline affords the opportunity to investigate variable rates and magnitudes of sea level change analysis of salt marsh records at four sites around the island yields late holocene sea level trends these trends indicate differential sea level change in recent millennia a north south geographic trend reflects submergence in the south very slow sea level rise in the northeast and a recent transition from falling to rising sea level at the base of the northern peninsula this variability is best explained as a continued isostatic response to deglaciation

modeling ocean heat content changes during the last millennium 1 observational studies show a significant increase in ocean heat content over the last half century herein we estimate heat content changes during the last millennium with a climate model whose forcing terms have been best fit to surface proxy data the model simulates the observed late 20th century ocean heat content increase and a comparable little ice age minimum when glacial advances are factored in these results imply a sea level fall after the middle ages that is consistent with some geologic data the present ocean heat content increase can be traced back to the mid 19th century with a near linear rate of change during the 20th century

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso