a late cretaceous turonian ichthyofauna from lac des bois northwest territories canada with paleobiogeographic comparisons with turonian ichthyofaunas of the western interior seaway a fish fauna from a turonian sequence of the great bear basin at lac des bois is described the fauna includes examples of ichthyodectes cf osmeroides a euteleost and several aulopiforrn fishes such as enchodus cimolichthys and a juvenile that cannot be further identified the fauna of lac des bois most closely resembles other arctic fish assemblages of the western interior seaway based on a upgma unweighted pair group method with arithmetic averages cluster analysis of various north american turonian localities there are also slight differences between eastern and western localities along the seaway the north south differences of the ichthyofauna can be explained by current patterns distributing the fishes in the seaway or transgressive events during the turonian the east west differences may be due to changes in water depth from east to west

three dimensional finite element modelling of earth s viscoelastic deformation effects of lateral variations in lithospheric thickness summary we have developed a 3 d spherical finite element model to study the dynamic response to surface loads of a self gravitating and incompressible earth with 3 d viscoelastic structure we have forced our model with the ice 3g deglaciation history of tushingham peltier to study the effects of laterally varying lithospheric thickness on observations of post glacial rebound pgr the laterally varying lithospheric thicknesses are derived from estimates of the thermal structure of the oceanic lithosphere and from elastic thicknesses on continents as estimated from studies of long term geological loads our calculations show that the effects of lithospheric structure on the relative sea level change rslc depend on the locations of the observation sites and on the size of loads the rslc at the centre of the north american ice sheet is significantly less sensitive to lithospheric thickness compared with the rslc at the centre of the fennoscandian ice sheet at the peripheral bulges the rslc tends to be more sensitive to lithospheric thickness the rslc is controlled by local lithospheric thickness the rslc at a given location as predicted using models with laterally varying lithospheric thickness can be reproduced using a 1 d model with a uniform lithospheric thickness equal to the local lithospheric thickness coupled with efficient parallel computing we believe that the finite element model that we present here can be used to address a variety of viscoelastic deformation problems in geodynamics

strontium isotope correlation of the basal maastrichtian stage in antarctica to the european and us biostratigraphic schemes new 87 sr 86 sr dating allows the correlation of a marker horizon within the prolific late cretaceous gunnarites antarcticus faunal assemblage of the cape lamb member snow hill island formation vega island antarctica with reference sections in europe and the usa this horizon is between 81 5 and 96 5 m above the base of the g antarcticus assemblage replicate analysis of six macrofossils from within it yielded a mean value for 87 sr 86 sr of 0 707 735 9 0 000 004 3 2 s e n 17 this ratio in turn yields a numerical age of 71 0 0 2 ma when compared to the standard 87 sr s6 sr reference curve for the latest cretaceous for which the campanian maastrichtian boundary is placed at 71 3 0 5 ma the value of 0 707 735 9 0 000 004 3 correlates to a level in the belemnella lanceolata belemnite zone of the chalk of northwestern germany that is 2 5 5 m beneath the base of the overlying b pseudobtusa zone and 7 5 m above the campanian maastrichtian belemnite boundary and to an interval within the ammonite zonation of the us western interior that spans the early maastrichtian baculites baculus and b eliasi zones but with a most likely level within the b eliasi zone an earliest maastrichtian age is thereby determined for the antarctic horizon and indeed for the entire g antarcticus assemblage gunnarites sensu lato is an important ammonite marker for the base of the maastrichtian throughout the southern high latitude regions and the associated large heteromorph ammonite diplomoceras may comprise a macrofossil link back to the maastrichtian type sections

influence of lithospheric thickness variations on 3 d crustal velocities due to glacial isostatic adjustment 1 predictions of 3 d crustal velocities driven by glacial isostatic adjustment gia have generally been based on spherically symmetric earth models we adopt a finite volume formulation to explore the impact of lateral variations in elastic plate strength including lithospheric thickness changes across the continent ocean interface and plate boundary weak zones on these predictions weak zones introduce horizontal rate perturbations with a plate scale coherency and amplitudes reaching 1 2 mm yr radial velocity perturbations can be as large but are geographically isolated to the weak zones specifically the north atlantic ridge a discontinuity in ocean continent lithospheric thickness significantly impacts rates along continental margins order 1 mm yr for radial rates and generally about half this for tangential rates we conclude that lateral variations in lithospheric strength should be included in future gia analyzes of space geodetic survey results and in assessing the impact of gia on the stability of geodetic reference frames

glacial isostatic adjustment in fennoscandia with a three dimensional viscosity structure as an inverse problem abstract glacial isostatic adjustment data are commonly used to invert for the radial viscosity structure of the mantle however the effects of lateral variations in mantle viscosity in such inversions are not yet accounted for here we analysed synthetic sea level data for the fennoscandian region which are derived from a three dimensional 3d earth model with realistic lateral and vertical viscosity variations deduced from seismological and geological information the inversion of the 3d synthetic data for a best fitting 1d viscosity profile reveals that i lateral lithospheric thickness variations can be detected with 1d model predictions if the data are grouped into regional subsets ii combined lateral variations in lithospheric thickness and asthenospheric viscosity are not properly resolved with 1d model predictions and iii the spatial and temporal distribution of observational data strongly affects the resulting 1d viscosity profile

the effects of upper mantle lateral heterogeneities on postglacial rebound we have investigated the potentially important effects arising from lateral heterogeneities on postglacial uplifts time dependent solutions for maxwell rheology with lateral variations in the upper mantle are obtained by finite element techniques in cylindrical geometry the displacements in the central portion of the ice sheet are not at all influenced by these lateral variations whereas the uplifts near the edge of the ice load are extremely sensitive to lateral heterogeneities in the upper mantle for ice sheets characteristic of the laurentide ice sheet deformations around the peripheral bulge can still be affected by an asthenosphere as far as twenty five degrees away the continental lithosphere under the former ice load would appear to be thicker with the presence of a neighboring asthenosphere recent estimates of the north american plate thickness would exceed 250 km under these circumstances

contributions of a strengthened early holocene monsoon and sediment loading to present day subsidence of the ganges brahmaputra delta the contribution of subsidence to relative sea level rise in the ganges brahmaputra delta gbd is largely unknown and may considerably enhance exposure of the bengal basin populations to sea level rise and storm surges this paper focuses on estimating the present day subsidence induced by holocene sediment in the bengal basin and by oceanic loading due to eustatic sea level rise over the past 18 kyr using a viscoelastic earth model and sediment deposition history based on in situ measurements results suggest that massive sediment influx initiated in the early holocene under a strengthened south asian monsoon may have contributed significantly to the present day subsidence of the gbd we estimate that the holocene loading generates up to 1 6 mm yr of the present day subsidence along the gbd coast depending on the rheological model of the earth this rate is close to the twentieth century global mean sea level rise 1 1 1 7 mm yr thus past climate change by way of enhanced sedimentation is impacting vulnerability of the gbd populations

solid tidal friction above a liquid water reservoir as the origin of the south pole hotspot on enceladus abstract earth jupiter s moon io and saturn s tiny moon enceladus are the only solid objects in the solar system to be sufficiently geologically active for their internal heat to be detected by remote sensing interestingly the endogenic activity on enceladus is only located on a specific region at the south pole from which jets of water vapor and ice particles have been observed spencer j r and 9 colleagues 2006 science 311 1401 1405 porco c c and 24 colleagues 2006 science 311 1393 1401 the current polar location of the thermal anomaly can possibly be explained by diapir induced reorientation of the satellite nimmo f pappalardo r t 2006 nature 441 614 616 but the thermal anomaly triggering and the heat power required to sustain it over geological timescales remain problematic using a three dimensional viscoelastic numerical model simulating the response of enceladus to tidal forcing we explore the effect of a low viscosity anomaly in the ice shell localized to the south polar region on the tidal dissipation patterns we demonstrate that only interior models with a liquid water layer at depth can explain the observed magnitude of dissipation rate and its particular location at the south pole moreover we show that tidally induced heat must be generated over a relatively broad region in the southern hemisphere and it is then transferred toward the south pole where it is episodically released during relatively short resurfacing events as large tidal dissipation and internal melting cannot be induced in the south polar region in the absence of a pre existing liquid decoupling layer we propose that liquid water must have been present in the interior for a very long period of time and possibly since the satellite formation owing to the orbital equilibrium requirement meyer j wisdom j 2007 icarus 188 535 539 sustaining some liquid water at depth is impossible if heat is continuously emitted at a rate of 4 8 gw at the south pole based on that requirement we propose that the current thermal emission is not in equilibrium with the heat production and that the thermal emission rate is abnormally high at present time alternatively continuous dissipation at a rate of 1 2 gw in the ice shell at the south pole should be sufficient to induce internal melting and it could sustain a layer of liquid water at depth over geologic timescales

effect of lateral viscosity variations in the top 300 km on the geoid and dynamic topography summary we have investigated the impact of lateral viscosity variations lvv in the top 300 km of the mantle on the long wavelength gravitational response of the earth in contrast to the previous studies we demonstrate that the lvv may play a crucial role if a model with imposed plate velocities and partial layering is considered assuming lvv in the top mantle associated with the continental roots and the oceanic asthenosphere we are able to explain a significant portion of the geoid 85 per cent and of the free air gravity data 55 per cent without invoking a complex radial viscosity profile or assuming a lithosphere with an unrealistically low uniform viscosity the best fit to the data is found for models in which mass anomalies located at the boundary between upper and lower mantles reduce the mass flux across the 660 km discontinuity by a factor of 3 these models are characterized by a low average value of viscosity in the asthenosphere below the oceans 10 19 pa s and a large viscosity contrast 100 between the young suboceanic mantle and the deep continental roots the viscosity in the deep upper mantle is found to be around 3 10 20 pa s while a value higher by at least two orders of magnitude is typical for the lower mantle the predicted dynamic surface topography is influenced by the surface plate velocities and its amplitude amounts to a few hundred metres besides investigating the viscosity structures that reflect the different thicknesses of the lithosphere in continental and oceanic regions we have searched for a large scale pattern of lateral viscosity variation in the top 300 km that yields the best fit to the geoid the pattern obtained by this inversion shows a good correlation with the ocean continent distribution and 90 per cent of the geoid and 67 per cent of the free air gravity can be explained

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

driving mechanisms of holocene coastal evolution in the bonifacio strait western mediterranean abstract we produced a new suite of sea level data which allowed assessing the holocene evolution of the bonifacio strait a key coastal sector of the mediterranean sea which experienced significant morphological changes since the last glacial maximum squeezed between corsica and sardinia islands this strait connects the two major basins of the western mediterranean due to its peculiar geographic and morphological setting the bonifacio strait is affected by extreme meteomarine conditions characterized by severe winds waves and currents the millennial sea level changes were reconstructed through multiproxy investigations made of sediment coring and underwater beachrock sampling carried out on both sides of the strait these data provided fresh insights into the timing of the progressive opening of the bonifacio strait which followed the last glacial maximum when corsica and sardinia were connected forming the largest mediterranean island major palaeogeographic changes occurred before 7 ka bp since that period the significant decrease of the northern ice sheet melting triggered a significant sea level stabilization which induced only minor modifications in the palaeogeography of the strait in the late holocene the isostatic related subsidence became the dominant factor controlling the sea level changes which rose with rates 0 35 mm a 1 in the last four millennia our data have also an important archaeological implication because they indicate that the bonifacio strait has not represented a significant geographical barrier along the early neolithic migration path which connected mainland italy to northern corsica and finally to sardinia this further confirms the ability of early neolithic communities to navigate not also across large sea stretches but also maritime areas characterized by extremely complex meteomarine conditions

optimal locations for gps measurements in north america and northern europe for constraining glacial isostatic adjustment summary we determine the optimal location in north america and fennoscandia for uplift rate or tangential velocity data that will be useful for addressing ice sheet thickness lithospheric thickness lateral viscosity variation and background viscosity profile in the lower mantle an optimal location is defined by where sensitivity lies above the current accuracy of gps measurements the approach here is different from previous studies that compute sensitivity kernels for viscosity perturbations within a small volume of the mantle the advantage of the current approach is that the total effect of 3 d lateral heterogeneity in the mantle related to seismic tomography of the whole mantle can be studied the sensitivity of ice sheet models and lateral lithospheric thickness variations are also studied our results show that in north america more permanent gps stations are needed in northern canada especially in a region west of the hudson bay until the rocky mountains in fennoscandia the gps network is almost adequate but it should be extended to the last known gia affected areas in the russian part of east europe and to central europe in addition we show locations of prospective gps sites that are sensitive to all four parameters ice sheet thickness lithospheric thickness lateral viscosity variation and background viscosity profile in the lower mantle and locations that are sensitive to only one two or three parameters thus the results are useful for the inversion of one individual parameter or for the separation of the effects of two or more parameters in inversions

effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced relative sea levels and long wavelength gravity field in a spherical self gravitating maxwell earth the effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced relative sea level rsl changes and the secular rate of change of the earth s long wavelength gravity field in a spherical self gravitating incompressible visco elastic earth are investigated using the coupled laplace finite element method the ice 4g deglaciation model is used with gravitationally self consistent sea levels in realistic oceans to describe the load lateral variations in mantle viscosity and lithospheric thickness are inferred from seismic tomography model s20a the full 3 d earth model which includes all the lateral heterogeneities in the lithosphere and mantle gives a better fit to the global rsl data than the related laterally homogeneous model however the situation is less clear for the observed secular drift of the low degree geopotential coefficients j l because of the uncertain contribution of recent melting but the full 3 d model can fit the j 2 observation if recent melting contributes about 1 0 mm a of equivalent sea level rise it predicts that the gia induced secular gravity rate of change to be detected by the grace mission in the southern part of hudson bay is about 1 2 to 1 6 gal a moreover the contributions of lateral heterogeneities from individual layers in the mantle or in the lithosphere are studied the contribution from the transition zone 420 670 km is generally opposite to that from its neighboring layers and thus can mask their effects as a consequence the effects from the deep lower mantle become dominant for rsl and secular rate of change of gravity over laurentide for the secular rates of change for degrees 2 4 geopotential coefficients the contribution is mostly from lateral heterogeneities in the deeper mantle the effects of background viscosity profiles are also investigated and are found to be significant for all these observables

glacial isostatic adjustment on 3 d earth models a finite volume formulation summary we describe and present results from a finite volume fv parallel computer code for forward modelling the maxwell viscoelastic response of a 3 d self gravitating elastically compressible earth to an arbitrary surface load we implement a conservative control volume discretization of the governing equations using a tetrahedral grid in cartesian geometry and a low order linear interpolation the basic starting grid honours all major radial discontinuities in the preliminary reference earth model prem and the models are permitted arbitrary spatial variations in viscosity and elastic parameters these variations may be either continuous or discontinuous at a set of grid nodes forming a 3 d surface within the regional or global modelling domain in the second part of the paper we adopt the fv methodology and a spherically symmetric earth model to generate a suite of predictions sampling a broad class of glacial isostatic adjustment gia data types 3 d crustal motions long wavelength gravity anomalies these calculations based on either a simple disc load history or a global late pleistocene ice load reconstruction ice 3g are benchmarked against predictions generated using the traditional normal mode approach to gia the detailed comparison provides a guide for future analyses e g what grid resolution is required to obtain a specific accuracy and it indicates that discrepancies in predictions of 3 d crustal velocities less than 0 1 mm yr 1 are generally obtainable for global grids with 3 106 nodes however grids of higher resolution are required to predict large amplitude 1 cm yr 1 radial velocities in zones of peak post glacial uplift e g james bay to the same level of absolute accuracy we conclude the paper with a first application of the new formulation to a 3 d problem specifically we consider the impact of mantle viscosity heterogeneity on predictions of present day 3 d crustal motions in north america in these tests the lateral viscosity variation is constructed with suitable scaling from tomographic images of seismic s wave heterogeneity and it is characterized by approximately 2 orders of magnitude peak to peak lateral variations within the lower mantle and 1 order of magnitude variations in the bulk of the upper mantle below the asthenosphere we find that the introduction of 3 d viscosity structure has a profound impact on horizontal velocities indeed the magnitude of the perturbation of order 1 mm yr 1 is as large as the prediction generated from the underlying 1 d radial reference model and it far exceeds observational uncertainties currently being obtained from space geodetic surveying the relative impact of lateral viscosity variations on predicted radial motions is significantly smaller

glacio isostatic adjustment in the po plain and in the northern adriatic region vertical movements in the po plain northern italy are controlled by natural and anthropogenic effects since italy is located in the far field of the former late pleistocene ice sheets isostatic deformations are primarily driven by melt water loading and represent a major component of long term natural movements across the entire mediterranean in addition to far field sources here we consider the isostatic effects of melting of the nearby wurm alpine ice sheet suggesting that it is possible to put bounds on its maximum thickness extent and chronology by holocene relative sea level observations from the northern adriatic using various plausible ice models and adopting a viscosity profile that matches holocene relative sea level observations in the mediterranean we find that melting of the alpine ice sheet is always responsible for upward movements in the po plain currently at rates of 0 5 mm yr when both far and near field sources are considered the rate of sea level change in the venetian lagoon for the most reasonable mantle rheology and melting chronology is negative i e opposite to that attributed to human activity and recent climatic variations however its amplitude fractions of mm yr is small compared to the secular signal observed by tide gauges 2 mm yr which makes glacial isostasy a second order mechanism of sea level variation in this region

effects of nonlinear rheology on degree 2 harmonic deformation in a spherical self gravitating earth 1 the effect of non linear rheology on surface displacements gravitational potential perturbation and tj2 or j2 dot for a self gravitating spherical earth is studied using a finite element code coupled to poisson s equation four earth models investigated are a model with uniform linear rheology throughout the mantle and three others containing nonlinear rheology in the whole mantle upper mantle and lower mantle respectively the effect of self gravitation is shown to be non negligible the effects of nonlinear rheology in different parts of the mantle on surface displacements and potential have also been shown to be large tj2 due to cyclic glaciation of the laurentian fennoscandian barents sea and antarctic ice sheets over realistic oceans is also computed for all four rheology models the model with nonlinear lower mantle cannot be ruled out by the observed data

postglacial rebound in a non newtonian spherical earth using finite elements we study the postglacial rebound in an axisymmetric earth with a non newtonian rheology our approach allows for the first time a self consistent study of the effect of a power law creep on the long wavelength deformations which cannot be performed using flat models we show that for a non newtonian upper mantle the time variations of the low degree stokes coefficients become largely insensitive to the viscosity of the lower mantle this is in contrast with previous evidence based on newtonian models which emphasized the importance of the low degree signatures for constraining the lower mantle viscosity

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

modelling sea level data from china and malay thailand to estimate holocene ice volume equivalent sea level change abstract this study presents a new model of holocene ice volume equivalent sea level esl extending a previously published global ice sheet model bassett et al 2005 which was unconstrained from 10 kyr bp to present this new model was developed by comparing relative sea level rsl predictions from a glacial isostatic adjustment gia model to a suite of holocene sea level index points from china and malay thailand three consistent data model misfits were found using the bassett et al 2005 model an over prediction in the height of maximum sea level the timing of this maximum and the temporal variation of sea level from the time of the highstand to present the data model misfits were examined for a large suite of esl scenarios and a range of earth model parameters to determine an optimum model of holocene esl this model is characterised by a slowdown in melting at 7 kyr bp associated with the final deglaciation of the laurentide ice sheet followed by a continued rise in esl until 1 kyr bp of 5 8 m associated with melting from the antarctic ice sheet it was not possible to identify an earth viscosity model that provided good fits for both regions with the china data preferring viscosity values in the upper mantle of less than 1 5 10 20 pa s and the malay thailand data preferring greater values we suggest that this inference of a very weak upper mantle for the china data originates from the nearby subduction zone and hainan plume the low viscosity values may also account for the lack of a well defined highstand at the china sites

mode coupling in a viscoelastic self gravitating spherical earth induced by axisymmetric loads and lateral viscosity variations the importance of mode coupling in a viscoelastic self gravitating spherical earth with lateral variations in linear or nonlinear rheology is investigated with a finite element model coupled to poisson s equation both the lateral viscosity variations and the harmonic load are axisymmetric the effects of self gravitation viscosity contrast and the location of the abrupt lateral change in viscosity in a linear mantle are studied and are found to be significant in determining the strength of mode coupling it is demonstrated that a larger number of harmonics than generally assumed is required to give accurate description of the induced deformation mode coupling is also found to be important in a nonlinear mantle especially when the harmonic degree l is large

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

present day subsidence in the ganges brahmaputra meghna delta eastern amplification of the holocene sediment loading contribution the subsidence of the ganges brahmaputra meghna delta gbmd drastically increases the adverse impacts of coastal flooding and exacerbates the vulnerability of populations from ongoing rapid sea level rise we focus here on estimating the present day subsidence rates induced by the loading of sediments continuously deposited within the gbmd over the past 11 000 years by constructing a realistic gbmd 3 d numerical model with laterally variable mantle and lithospheric structure we demonstrate for the first time that the presence of the strong indian craton and the weakened indo burma margin results in significant amplification of subsidence driven by sediment loading in the eastern part of the delta where the population density is the highest 1 000 habitants per km 2 although uncertainties remain regarding the amplitude of subsidence the rate estimates 2 3 mm year are found to be comparable to the present day global mean sea level rise

decontaminating tide gauge records for the influence of glacial isostatic adjustment the potential impact of 3 d earth structure 1 we investigate the potential impact of lateral variations in mantle viscosity and lithospheric thickness on predictions of present day relative sea level change due to glacial isostatic adjustment gia we consider three viscoelastic earth models the first is a 1 d model with a lithospheric thickness of 120 km and upper and lower mantle viscosities of 5 1020 pa s and 5 1021 pa s respectively the second model includes global lithospheric thickness variations and lateral heterogeneities in upper mantle viscosity ranging over three orders of magnitude while the third model includes lateral variations in lower mantle viscosity alone we find that the impact of 3 d structure is significant indeed the difference between the 3 d and 1 d model predictions at 300 sites with tide gauge records longer than 40 years duration is greater than 0 2 mm yr and 0 5 mm yr for 50 and 25 of the sites respectively the maximum difference exceeds several mm yr we conclude that efforts to decontaminate tide gauge records for ongoing gia to determine the rate and origin of global sea level rise should incorporate 3 d mantle structure into the gia modelling

continental rift to back arc basin jurassic cretaceous stratigraphical and structural evolution of the larsen basin antarctic peninsula the larsen basin developed in jurassic times as a result of continental rifting during the early stages of gondwana break up lower upper jurassic non marine sedimentary and volcanic rocks constitute a syn rift megasequence recording initial largely amagmatic extension and subsequent widespread extension related silicic volcanism a succeeding kimmeridgian early berriasian transgressive megasequence consisting largely of anoxic dysoxic hemipelagic mudstones is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak jurassic eustatic sea levels served to maximize sediment starvation the fragmentary record for late berriasian barremian times suggests that a regressive megasequence may have developed in the earlier part of this period recording increased sediment yield to the larsen basin from the increasingly emergent antarctic peninsula arc subsequently strata in the southern but not the northern part of the basin underwent relatively intense eastward verging deformation possibly during the formation of a retro arc fold thrust belt where exposed the lower part of the succeeding aptian eocene megasequence consists of a deep marine clastic wedge deposited along the fault bounded western basin margin during a phase of arc uplift and related differential subsidence following partial basin inversion in late cretaceous times regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward

present day trends of vertical ground motion along the coast lines vertical ground motion vgm rates stand as crucial information either for predicting the impact of the actual sea level rise along low lying coasts or refining geodynamic problems because present day vgm rates have a magnitude smaller than 10 mm yr they remain challenging to quantify and often elusive we focus on the quantification of global scale vgm rates in order to identify global or regional trends we computed vgm rates by combining tide gauges records and local satellite altimetry which yield a new dataset of 634 vgm rates we further compare this database to previous studies that use geodetic techniques and tide gauges records in order to evaluate the consistency of both our results and previous ones the magnitudes differ by less than 5 mm yr and similar subsidence and uplift general tendencies appear even if the asset of our database stands in the greater number of sites the combination of all studies each with different pros and cons yields a hybrid dataset that makes our attempt to extract vgm trends more robust than any other independent study fennoscandia the west coast of north america and the eastern coast of australia are uplifting while the eastern coast of north america the british isles and western europe the eastern mediterranean sea japan and the western coast of australia are subsiding glacial isostatic adjustment gia is expected to provide a major contribution to the present day signal aside from fennoscandia observed vgm often depart from the gia model predictions of peltier 2004 this either results from an underestimate of the model predictions or from the influence of other processes indeed the influence of the geodynamic setting appears in particular along the coasts of western north america or japan where the alternation of transform faults and subduction zones makes it possible to assign contrasted behaviours to the local geodynamic context local mechanisms like anthropogenic processes or sediment compaction also contribute to vgm this remains true for the critical cases of venice the gulf of mexico the ganges delta and the maldives which are particularly exposed to the current sea level rise

glacial isostatic adjustment in fennoscandia for a laterally heterogeneous earth glaciation and deglaciation in fennoscandia during the last glacial cycles has significantly perturbed the earth s equilibrium figure changes in the earth s solid and geoidal surfaces due to external and internal mass redistributions are recorded in sequences of ancient coastlines now either submerged or uplifted and are still visible in observations of present day motions of the surface and glacially induced anomalies in the earth s gravitational field these observations become increasingly sophisticated with the availability of gps measurements and new satellite gravity missions observational evidence of the mass changes is widely used to constrain the radial viscosity structure of the earth s mantle however lateral changes in earth model properties are usually not taken into account as most global models of glacial isostatic adjustment assume radial symmetry for the earth model this simplifying assumption contrasts with seismological evidence of significant lateral variations in the earth s crust and upper mantle throughout the fennoscandian region we compare predictions of glacial isostatic adjustment based on an ice model over the fennoscandian region for the last glacial cycle for both radially symmetric and fully 3 d earth models our results clearly reveal the importance of lateral variations in lithospheric thickness and asthenospheric viscosity for glacially induced model predictions relative sea level predictions can differ by up to 10 20 m uplift rate predictions by 1 3 mm yr 1 and free air gravity anomaly predictions by 2 4 mgal when a realistic 3 d earth structure as proposed by seismic modelling is taken into account

stratigraphy and vertebrate paleoecology of upper cretaceous lowest paleogene strata on vega island antarctica the upper cretaceous maastrichtian sandwich bluff member of the lopez de bertodano formation is well exposed on vega island in the james ross basin off the northeastern coast of the antarctic peninsula although this unit is one of the richest sources of end cretaceous vertebrate fossils in antarctica it is also one of the least sedimentologically and stratigraphically characterized units in the basin new facies and stratigraphic analyses of the sandwich bluff member and the underlying cape lamb member of the snow hill island formation were performed in tandem with intensive prospecting for fossil vertebrates and stratigraphic assessment of historic paleontological localities on vega island this effort has led to a revised stratigraphy for the sandwich bluff member and the precise stratigraphic placement of important terrestrial and marine vertebrate fossil localities facies analysis reveals a fining and shallowing upward trend through the section that culminates in a newly recognized sequence boundary near the top of the sandwich bluff member followed by the deposition of a previously unrecognized 6 m thick matrix supported pebble cobble conglomerate of probable alluvial origin immediately overlying this unit well developed thalassinoides burrow networks in fine grained transgressive sandstones and siltstones indicate a rapid return to marine conditions a similar stratigraphic pattern is well documented at the top of the lopez de bertodano formation and the base of the overlying paleocene sobral formation on seymour island in the southern part of the basin although no fossils were recovered to constrain the age of the upper 10 15 m of the succession on vega island that preserves the newly recognized upper sequence boundary strata below this level can be confidently placed within the manumiella bertodano interval zone which extends to a short distance below the k pg boundary on seymour island hence based on sequence stratigraphic and lithostratigraphic evidence the uppermost 10 15 m of the succession on vega island may encompass the cretaceous paleogene boundary together with a few meters of the paleocene sobral formation

on postglacial geoid subsidence over the equatorial oceans we develop two new spectral formalisms for the gravitationally self consistent solution of the sea level equation which governs the redistribution of glacial meltwater on a visco elastic earth the first is a purely spectral technique based on an extension of theory outlined by dahlen 1976 for determining the equilibrium oceanic tide on an elastic planet using this technique with a feasible spherical harmonic truncation level l 30 we can obtain convergence in the computed sea level variations within the degree range l 10 we also develop a second pseudospectral technique however which permits the construction of gravitationally self consistent solutions to much higher degree and order l 100 the pseudospectral formalism is employed here to develop a comprehensive physical explanation for the global pattern of present day sea level variations due to ongoing glacial isostatic adjustment in particular we focus upon a mechanism which we term equatorial ocean syphoning that acts to draw water toward the oceanic portion of the collapsing peripheral bulge that encircles previously glaciated regions the collapse of the forebulge induces a flow of water which is required to maintain hydrostatic equilibrium the syphoning mechanism dominates the relative sea level rsl variation in oceans in the far field of the ice sheets that is beyond the peripheral bulge during periods such as the interglacial of the past 4000 years during which the volume of the ice sheets has not apparently changed appreciably while at the same time isostatic adjustment persists the rsl change in the near field is in contrast dominated by the local vertical displacement of the solid surface finally comparison of gravitationally self consistent predictions of rsl change in the far field with the observational data at small pacific island sites has provided an upper bound of 1 to 2 m for the eustatic sea level rise produced by any recent last 3000 years melting of the antarctic ice sheet

using commercial finite element packages for the study of earth deformations sea levels and the state of stress summary modifications to commercial finite element fe packages must be applied before they can be used for geophysical studies involving long wavelength deformation or viscoelasticity this paper provides in detail how and why the commercial codes have to be modified when incompressibility is assumed both the non self gravitating flat earth and self gravitating spherical earth will be considered the latter involves an iterative procedure which converges within 5 iterations this is demonstrated both analytically and numerically in addition implementation of the gravitationally self consistent sea level equation on a self gravitating spherical earth is also described good agreement between numerical results obtained with this coupled finiteelement method and the conventional spectral method is also demonstrated in all cases the interpretation of the outputs of fe models are particularly important in modelling the state of stress

late cretaceous antarctic fish diversity new material from the santa marta formation late coniacian early maastrichtian of james ross island contributes significantly to the current knowledge of late cretaceous antarctic fish diversity the taxon list for the santa marta formation is extended and new records of neoselachians and teleosts are reported the stratigraphic ranges of some previously known taxa are enlarged and the palaeobiogeography and palaeoecology of late cretaceous antarctic fishes are discussed top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the santa marta and lopez de bertodano formations the only fish adapted to crushing hard shelled invertebrates were the chimeroids rays an important component of marine fish associations as well as fish from lower trophic levels remain unknown from the late cretaceous of antarctica

stromatolite assemblages of the late precambrian in china abstract the late precambrian as used in this paper is represented by the sections in the jixian chihsien and yangtze gorges these rocks correspond to the middle late proterozoic of some authors and range in age from c 1900 to 600 ma the succession can be subdivided into four systems the changcheng jixian qingbaikou and sinian systems all of which yield abundant stromatolites based on the latest studies we suggest a new sixfold classification scheme supertype type subtype family genus and species and refer the stromatolites to 13 families and 50 genera including some material published already in china the stromatolites of the late precambrian of china may be represented by elements from yanshan southern liaodong peninsula and kaiyang of guizhou etc they are subdivided into eight stromatolite assemblages and correlated throughout most of china

uncertainties of glacial isostatic adjustment model predictions in north america associated with 3d structure we quantify gia prediction uncertainties of 250 1d and 3d glacial isostatic adjustment gia models through comparisons with deglacial relative sea level rsl data from north america and rate of vertical land motion urn x wiley 00948276 media grl60497 grl60497 math 0001 and gravity rate of change urn x wiley 00948276 media grl60497 grl60497 math 0002 from gnss and grace data respectively spatially the size of the rsl uncertainties varies across north america with the largest from hudson bay and near previous ice margins along the northern atlantic and pacific coasts which suggests 3d viscosity structure in the lower mantle and laterally varying lithospheric thickness temporally rsl uncertainties decrease from the last glacial maximum to present except for west of hudson bay and the northeastern pacific coast the uncertainties of both these regions increase from 30 to 45 m between 15 and 11 ka bp which may be due to the rapid decrease of surface loading at that time present day urn x wiley 00948276 media grl60497 grl60497 math 0003 and urn x wiley 00948276 media grl60497 grl60497 math 0004 uncertainties are largest in southwestern hudson bay with magnitudes of 2 4 mm year and 0 4 gal year mainly due to the 3d viscosity structure in the lower mantle

blue green algal mats of the salinas in san ya hai nan island china structure taxonomic composition and implications for the interpretation of precambrian stromatolites abstract the study of the algal mats in salinas used for salt production on hai nan island china revealed the presence of five morphological types which are dominated by different blue green algae 1 orange high pinnacle mats dominated by phormidium hypersalinum and p hypolimneticum 2 pale green low pinnacle mats dominated by p hypolimneticum p hypersalinum and aphanothece sp 3 pale green spongy mats dominated by the unicellular blue green algae aphanothece sp chroococcus minutus aphanocapsa concharum 4 yellow green gelatinous mats dominated by p hypolimneticum and microcoleus tenerrimus 5 blue green flat mats with finger like projections dominated by m tenerrimus and m chthonoplastes the distribution of these different mats is correlated to the main ecological parameters monitored salinity temperature and water depth the role of the constituent blue green algae and of the ecological parameters in the control of the composition and morphology of algal mats as well as the implications of these findings for the interpretation of precambrian stromatolites are discussed

walvis ridge barrier its influence on palaeoenvironments and source rock generation deduced from ostracod distributions in the early south atlantic ocean the early south atlantic was subdivided latitudinally by the proto walvis ridge which separated early cretaceous open marine conditions in the south from non marine environments to the north changes in the palaeogeography which can be monitored by the distribution of ostracod assemblages determined the establishment of a wide variety of depositional environments including evaporitic and total organic carbon rich facies limited northward marine influxes across the barrier are postulated for mid aptian time while largescale southward migrations of marine ostracods from the northern sector occurred in early cenomanian and or turonian times the latter established cosmopolitan faunas in the southern atlantic and effectively marked the breakdown of the walvis ridge as a physical barrier to north south migrations although possible oceanographic factors militated against longitudinal faunal movements variations in the composition of ostracod assemblages during so called oceanic anoxic events and the production of potential source rocks is briefly reviewed

a data driven model for constraint of present day glacial isostatic adjustment in north america abstract geodetic measurements of vertical land motion and gravity change are incorporated into an a priori model of present day glacial isostatic adjustment gia in north america via least squares adjustment the result is an updated gia model wherein the final predicted signal is informed by both observational data and prior knowledge or intuition of gia inferred from models the data driven method allows calculation of the uncertainties of predicted gia fields and thus offers a significant advantage over predictions from purely forward gia models in order to assess the influence each dataset has on the final gia prediction the vertical land motion and grace measured gravity data are incorporated into the model first independently i e one dataset only then simultaneously the relative weighting of the datasets and the prior input is iteratively determined by variance component estimation in order to achieve the most statistically appropriate fit to the data the best fit model is obtained when both datasets are inverted and gives respective rms misfits to the gps and grace data of 1 3 mm yr and 0 8 mm yr equivalent water layer change non gia signals e g hydrology are removed from the datasets prior to inversion the post fit residuals between the model predictions and the vertical motion and gravity datasets however suggest particular regions where significant non gia signals may still be present in the data including unmodeled hydrological changes in the central prairies west of lake winnipeg outside of these regions of misfit the posterior uncertainty of the predicted model provides a measure of the formal uncertainty associated with the gia process results indicate that this quantity is sensitive to the uncertainty and spatial distribution of the input data as well as that of the prior model information in the study area the predicted uncertainty of the present day gia signal ranges from 0 2 1 2 mm yr for rates of vertical land motion and from 3 4 mm yr of equivalent water layer change for gravity variations

additions to the diversity of elasmosaurid plesiosaurs from the upper cretaceous of antarctica abstract three specimens of elasmosaurid plesiosaurs sauropterygia plesiosauria from upper cretaceous beds of antarctica are described here these include postcranial remains of a single adult individual recovered from late maastrichtian beds of marambio seymour island possessing a distinctive combination of features cervical vertebrae having centra with a triangular outline in transverse section a vertical groove on the rostral and caudal edge of the neural spines and a deep articulation over the neural arch for the following postzygapophysis while the scapula shows an unusually large and anteriorly recurved dorsal process this combination of features is unknown in any adult postcranial elasmosaurid genus recovered to date in the upper cretaceous of the weddellian biogeographic province and could represent a new form additional specimens from james ross island comprise the first record of an aristonectinae plesiosauria elasmosauridae in late campanian beds being the oldest known record of this sub family finally a third specimen from the same age and locality reveals the presence of very long necked elasmosaurids with affinities to typical representatives from the upper cretaceous of the northern hemisphere these findings add to the known diversity of upper cretaceous elasmosaurids in high latitudes of the southern hemisphere

late quaternary relative sea level in southern california and monterey bay abstract few records of late quaternary relative sea level rsl are available for the pacific coast of north america south of san francisco bay a region where rsl data would be particularly useful for constraining vertical rates of tectonic motion this paper provides the first regional uplift corrected late quaternary rsl history for southern california derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore estuarine and freshwater deposits in sediment cores from coastal southern california we also provide a local uplift corrected rsl history for monterey bay central california generated from 48 radiocarbon ages from elkhorn slough and surrounding environments our resulting compilations show rapid sea level rise from 15 ka which begins to decelerate to present mean sea level pmsl between 6 and 8 ka late holocene

some effects of lateral heterogeneities in the upper mantle on postglacial land uplift close to continental margins summary we investigate the effects of lateral heterogeneities in the upper mantle on the calculation of postglacial land uplift for the model calculations we use a commercial finiteelement code which enables us to solve the equations governing a layered isotropic incompressible maxwell viscoelastic half space with laterally varying layer thicknesses and physical properties following previous investigations performed by sabadini yuen portney 1986 and gasperini sabadini 1989 we extend their results using a more realistic loading history and different earth models we then focus our attention on the question whether lateral heterogeneities in the upper mantle can be modelled correctly using a set of homogeneous earth models to this end a comparison of model calculations using both laterally homogeneous and heterogeneous earth models is performed we find that lateral heterogeneities in the upper mantle significantly influence the calculated postglacial land uplift the resolving power of relative sea level observations for the prescribed lateral heterogeneities used in this study is mainly focused on observations around the load margin and outside the glaciated areas where differences in predicted land uplift between individual models are large enough to be resolved by observations we can qualitatively determine lateral heterogeneities in the upper mantle using a set of laterally homogeneous earth models if the geological structure for example a continental margin is known however in order to infer the correct values of lithospheric thickness and asthenospheric viscosity we need to use laterally heterogeneous models

bounds on the time history and holocene mass budget of antarctica from sea level records in se tunisia solving the sea level equation for a maxwell earth we analyze the sensitivity of holocene sea level records in se tunisia to the time history of remote ice sheets assuming that mantle viscosity increases moderately with depth we find that in this region the sea level variations driven by the northern hemisphere ice sheets cancel so that the late holocene sea level high stand suggested by the geological record merely reflects the melting history of antarctica new insight into the history of this ice sheet is obtained analyzing the information contained in a revised set of relative sea level observations for sites across the mediterranean covering the last 8 kyrs from a trial and error misfit analysis it holds true that in this region the match between model predictions and observations improves when the volume of water released from antarctica is well below the value imposed by the ice3g chronology and when a sudden meltwater pulse is allowed between 8 and 7 kyrs before present corresponding to the epoch of the catastrophic rise event known as cre3

constraining mid to late holocene relative sea level change in the southern equatorial pacific ocean relative to the society islands french polynesia precisely quantifying the current climate related sea level change requires accurate knowledge of long term geological processes known as glacial isostatic adjustments gia although the major postglacial melting phase is likely to have ended 6 4 ka bp before present gia is still significantly affecting the present day vertical position of the mean sea surface and the sea bottom here we present empirical rsl relative sea level data based on u th dated fossil corals from reef platforms of the society islands french polynesia together with the corresponding gia modeling fossil coral data constrain the timing and amplitude of rsl variations after the holocene sea level maximum hslm upon correction for isostatic island subsidence we find that local rsl was at least 1 5 0 4 m higher than present at 5 4 ka later minor amplitude variations occurred until 2 ka when the rsl started dropping to its present position with a rate of 0 4 mm yr the data match with predicted rsl curves based on global ice sheet chronologies confirming the role of gia induced ocean siphoning effect throughout the mid to late holocene a long lasting late holocene highstand superimposed with second order amplitudinal fluctuations as seen from our data suggest that the theoretical predicted timing of rsl change can still be refined pending future calibration

late cretaceous extinction patterns in antarctica new correlations of marine clastic sedimentary rocks exposed within the james ross basin antarctica have shown that the mid to late cretaceous succession is in excess of 5 km thick plotting the ranges of the principal molluscan macrofossils against the revised stratigaphy indicates that inoceramid bivalves are totally absent and dimitobelid belemnites extremely rare throughout an extensive 1400 m thick maastrichtian succession these early extinction patterns are interpreted to be due to both a regional shallowing event and a pronounced phase of high latitude campanian maastrichtian cooling cool polar bottom waters may have been forming by as early as mid to late campanian times

lateral heterogeneities in mantle viscosity and post glacial rebound summary seismic tomographic results and convection calculations support the evidence of horizontal temperature variations in the mantle on the basis of commonly accepted rheological laws we thus expect lateral variations in the viscosity of several orders of magnitude this paper is concerned with the effects of lateral viscosity variations on vertical displacement induced by pleistocenic deglaciation a finite element scheme in axial symmetry mimics the relaxation process of a flat earth model characterized by a linear maxwell rheology we follow a spectral approach to analyse the impact of lateral viscosity variations with different amplitudes and wavelengths the potential impact of lithospheric thickening and viscosity increase in stable continental regions on the interpretation of sea level data is also analysed lateral viscosity heterogeneities are found to have strong influence on ground deformations induced in deglaciated areas from the analysis of sea level data near the centre of the former fennoscandian ice sheet and the theoretical predictions of radially and laterally stratified earth models we explore the extent to which lateral viscosity contrasts may have influenced the inference of long term mantle viscosity while radially stratified models predict a rather uniform mantle viscosity we show that lateral viscosity contrasts of 1 or 2 orders of magnitude are consistent with sea level data if the wavelength of the heterogeneity is comparable with the dimension of a convecting cell in this case the average viscosity can deviate by around an order of magnitude from the canonical value of 1021 pa s predicted by rebound models in the past viscosity values close to 1021 pa s are found to be appropriate for the mantle region underlying the load long wavelength viscosity variations of 3 or 4 orders of magnitude degrade our ability to reproduce the observed uplift in the centre of the ice sheet and must be ruled out for wavelengths comparable with the horizontal extension of the surface load and viscosity contrasts of 1 or 2 orders of magnitude model results are found to be inconsistent with sea level data these findings suggest that rebound modelling can become a useful tool to constrain the magnitude and wavelength of viscosity contrasts comparison between horizontally and vertically varying models indicates that lateral viscosity heterogeneities could have been interpreted as radial variations in previous rebound studies

shallow upper mantle rheology and secular ice sheet fluctuations on time scales from decades to centuries continental cryospheric forcing in response to climate change constitutes a major source of isostatic disequilibrium that may influence future regional sea level variations current vertical displacements and gravity field variations are often estimated neglecting rheological effects and thus assuming a fully elastic response of the earth in this study we adopt a more general point of view aiming at describing ongoing surface movements resulting from recent glacial instabilities also taking into account the effects associated with shallow upper mantle and crustal rheologies our computations are based on the post widder laplace inversion formula which permits the straightforward computation of load deformation coefficients for steady state and transient rheologies up to very high harmonic degrees using a surface load with a simple geometry and time history we compare the classical elastic solutions to those obtained considering the rheological response of the shallow upper mantle while at the center of the ice sheet rheology only magnifies the elastic response the pattern and time history of vertical displacement at the ice sheet margins show a greater complexity mainly due to the development of lateral forebulges whose shape and amplitude are particularly sensitive to the rheology of the shallow upper mantle in this region assuming an elastic rheology is generally appropriate on a century time scale but significant deviations from a purely elastic response both sign and amplitude are observed at longer time scales or when a low viscosity zone with maxwell rheology is taken into account

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

holocene relative sea level change isostatic subsidence and the radial viscosity structure of the mantle of northwest europe belgium the netherlands germany southern north sea abstract a comprehensive observational database of holocene relative sea level rsl index points from northwest europe belgium the netherlands northwest germany southern north sea has been compiled in order to compare and reassess the data collected from the different countries regions and by different workers on a common time depth scale rsl rise varies in magnitude and form between these regions revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity it clearly contains a non linear glacio and or hydro isostatic subsidence component which is only small on the belgian coastal plain but increases significantly to a value of ca 7 5 m relative to belgium since 8 cal ka bp along the northwest german coast the subsidence is at least in part related to the post glacial collapse of the so called peripheral forebulge which developed around the fennoscandian centre of ice loading during the last glacial maximum the rsl data have been compared to geodynamic earth models in order to infer the radial viscosity structure of the earth s mantle underneath nw europe lithosphere thickness upper and lower mantle viscosity and conversely to predict rsl in regions where we have only few observational data e g in the southern north sea a very broad range of earth parameters fit the belgian rsl data suggesting that glacial isostatic adjustment gia only had a minor effect on belgian crustal dynamics during and after the last ice age in contrast a narrow range of earth parameters define the southern north sea region reflecting the greater influence of gia on these deeper older samples modelled rsl data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow wnw ese trending band connecting the german federal state of lower saxony with the dogger bank area in the southern north sea identification of the effects of local scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea level index points based on model data comparisons is possible but is still complicated by the relatively large range of earth model parameters fitting each rsl curve emphasising the need for more high quality observational data

modelling of mantle postglacial relaxation in axisymmetric geometry with a composite rheology and a glacial load interpolated by adjusted spherical harmonics analysis summary although studies on glacial isostatic adjustment usually assume a purely linear rheology we have previously shown that mantle relaxation after the melting of laurentide ice sheet is better described by a composite rheology including a non linear term this modelling is however based on axially symmetric geometry and glacial forcing derived from ice 3g and suffers from a certain amount of arbitrariness in the definition of the ice load in this work we apply adjusted spherical harmonics analysis to interpolate the ice thicknesses of ice 3g and ice 1 glaciological models this filters out the non axisymmetric components of the ice load by considering only the zonal terms in the spherical harmonics expansion the resulting load function is used in finite element simulation of postglacial rebound to compare composite versus purely linear rheology our results confirm that composite rheology can explain relative sea level rsl data in north america significantly better than a purely linear rheology the performance of composite rheology suggests that in future investigations it may be better to use this more physically realistic creep law for modelling mantle deformation induced by glacial forcing

new estimates of secular sea level rise from tide gauge data and gia modelling summary during the last three decades at least 30 independent estimates of the secular global mean sea level rise gmslr have been published based on sufficiently long tide gauge tg records despite its apparent simplicity the problem of gmslr is fraught with a number of difficulties which make it one of the most challenging questions of climate change science not surprisingly published estimates show considerable scatter with rates ranging between 1 and 2 mm yr 1 for observations on the century timescale in previous work the importance of glacial isostatic adjustment gia upon the assessment of the gmslr has been clearly demonstrated in particular starting from the 1980s gia models have been routinely employed to decontaminate tg observations from the effects of melting of the late pleistocene ice sheets to fully highlight the sea level variations driven by climate change however uncertainties associated with the earth s rheological profile and the time history of the past continental ice sheets can propagate into the gia corrections after revisiting previous work and estimates we suggest a significant modification of the criteria for the selection of the tgs which are most suitable for the robust assessment of the secular gmslr in particular we seek a set of tgs for which gia corrections are essentially independent of the parametrization of the rheological profile of the earth s mantle and of the detailed time chronology of surface loading this insensitivity is established by considering predictions based upon three gia models widely employed in the recent literature namely ice 3g ice 5g and the one developed at the research school of earth sciences of the national australian university applying this approach and selection criteria previously proposed in the literature we identify a set of 22 sufficiently evenly distributed tgs by simple statistical methods these records yield a preferred gia independent gmslr estimate since 1880 namely 1 5 0 1 mm yr 1 rms 0 4 mm yr 1 wrms 0 3 mm yr 1 this value is consistent with various previous estimates based on secular tg observations and with that proposed for the 20th century by the intergovernmental panel on climate change ipcc fourth assessment report 1 7 0 5 mm yr 1

postglacial sealevels on a spherical self gravitating viscoelastic earth effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle abstract previous studies of lateral viscosity variations on postglacial rebound often neglect the spherical shape of the earth and the self gravity of the solid earth and oceans in this paper the consistent sealevel equation is solved by the coupled laplace finite element method for a spherical self gravitating incompressible maxwell earth it confirms the importance of self gravity in the oceans on sealevel computation near the ice margin where the data are most sensitive to the existence of lateral variations in lithospheric thickness and asthenospheric viscosity the effects of lateral variations in lower mantle viscosity asthenospheric viscosity and lithospheric thickness are investigated this paper confirms the finding of earlier investigations the combined effect of lateral viscosity variations in the lower mantle with reverse viscosity contrasts in the upper mantle is also investigated for sealevel data near the center of rebound the effect of lateral viscosity contrast in the lower mantle can be masked by the existence of a reverse lateral viscosity contrasts in the upper mantle however this is not the case for sealevel data just outside the ice margin

late pleistocene and holocene sea level change in greece and south western turkey a separation of eustatic isostatic and tectonic contributions summary sea level change during late pleistocene and holocene times is a combination of eustatic isostatic and tectonic contributions in the central mediterranean sea region of greece and western turkey the isostatic components are important due to the changing gravitational potential of the earth the readjustment of the crust upon the removal of the large ice sheets and the addition of the meltwater into the oceans including the mediterranean changes in relative sea level due to these glacio hydro isostatic adjustments have reached amplitudes of 1 mm yr 1 during the last few thousand years a model for the isostatic contribution to sea level change including the movement of shorelines due to the combined eustatic isostatic changes is developed based on earth model and ice sheet parameters estimated from sea level observations from other areas comparisons of this model with observations of sea level change permit rates of vertical movement to be estimated for late holocene time allowance for the isostatic factors makes a significant difference to these rates the plains of argolis lakonia messinia and navarine in the southern peloponnese for example appear to be tectonically stable on time scales of a few thousand years and longer consistent with the position of the last interglacial shoreline close to the present day sea level the observations here of a rising sea level are largely the consequence of the glacio hydro isostasy and not of a long term tectonic process crete as a whole is subject to tectonic uplift but at variable rates and forms part of an arcuate zone of uplift extending from rhodes and karpathos in the east to kithera in the west at rates that locally exceed 4 mm yr 1 the southern shore of the gulf of corinthos is also subject to uplift at rates approaching 1 5 mm yr 1 these isostatically corrected estimates for the past few thousand years are in agreement with longer term estimates based on the position of the last interglacial shoreline only on the perachora peninsula do the tectonic rates over these two time intervals appear to be in disagreement with the late holocene rates being much higher than the long term rates

fossil marine actinopterygian fishes from the kaskapau formation upper cretaceous turonian near watino alberta turonian fossil marine fishes occur at several localities near watino alberta in sandstones and in shale concretions of the vimy member kaskapau formation the actinopterygian fossils in the san

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

a new holocene relative sea level curve for western brittany france insights on isostatic dynamics along the atlantic coasts of north western europe abstract this study presents new relative sea level rsl data that were obtained in the finistere region western tip of brittany france and the implications those data have for the understanding of the isostatic dynamics across north western europe and more specifically along the atlantic and channel coasts new stratigraphic sequences were obtained and analyzed to derive 24 new sea level index points in which 6 are basal these new data considerably increase the knowledge we have of the rsl evolution along the coasts of western brittany since the last 8 kyr b p from this new dataset rsl was estimated to rise continuously over the last 8 kyr with a major inflection at ca 6 kyr cal bp our results show large vertical discrepancies between the rsl records of brittany and south western uk with the latter plotting several meters below the new data from this comparison we suggest that the two regions underwent a very different pattern and or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the european ice sheets we compared our data against predictions from glacio isostatic adjustment models gia models there are large misfits between rsl observations and the predictions of the global ice 5g vm2a peltier 2004 glac1 b tarasov and peltier 2002 tarasov et al 2012 briggs et al 2014 and regional uk models biis bradley et al 2009 bradley et al 2011 kuchar kuchar et al 2012 which can t be resolved through significant changes to the deglaciation history and size of the british irish ice sheet paleo tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data model misfits hence we propose that the misfits are due to some combination of i unaccounted mass loss of far field ice sheets antarctic ice sheet or laurentide ice sheet ii unresolved differences in the deglaciation history and size of the fennoscandian ice sheet or more likely iii significant lateral variations in the earth s structure across the english channel

sensitivity of crustal velocities in fennoscandia to radial and lateral viscosity variations in the mantle abstract we investigate the sensitivity kernels of the present day velocities in fennoscandia induced by the retreat of the late pleistocene ice sheets with a 3d finite element model having compressible viscoelastic material properties and a realistic ice load history of the fennoscandian ice sheet the model is subdivided into blocks of variable size which results in a large number of kernels to interpret thus we introduce a simple approach to calculate the averaged kernel of a block by averaging the perturbed predictions of all surface nodes of this block to one value for this block our results show that the present day uplift velocity is mostly sensitive to upper mantle layers between 220 and 540 km depth independent of the block size velocities in blocks located inside the former ice sheet area are more sensitive to viscosity variations than velocities in blocks located outside the former ice sheet the largest effects are found for blocks located below the former ice maximum on the surface the uplift velocity in the smaller blocks is more sensitive to viscosity changes than in larger blocks for the present day horizontal velocity the sensitivity depends on the block size and the location of this block in relation to the former ice sheet in general lateral viscosity variations in the transition zone of the mantle have a strong influence on the tangential motion a comparison of the results of smaller and larger blocks also indicates higher sensitivities for the horizontal velocities of larger blocks

campanian maastrichtian cretaceous stratigraphy of the james ross island area antarctica one of the most important outcrops of uppermost cretaceous campanian maastrichtian sedimentary rocks in the southern high latitudes occurs within the james ross island group northeastern antarctic peninsula these rocks comprise a 1500 2000 m thick sequence of predominantly shallow marine clastic sediments that were deposited within a retro arc basin they are virtually undeformed and have yielded prolific invertebrate and vertebrate faunas and a wide range of plant taxa campanian maastrichtian strata are contained within two component formations of the upper cretaceous lower tertiary marambio group the lower santa marta formation is approximately 1100m thick and has three constituent members ammonites within the santa marta formation indicate an early to late campanian age assignment dinoflagellates suggest that the lower levels of the formation may range into the santonian stage in the northern james ross island to vega island region there is a conformable transition into the overlying lopez de bertodano formation here the basal cape lamb member is unconformably overlain by the sandwich bluff member although there are some lithological and fauna1 discrepancies which are attributed to marked lateral facies changes across the basin it is believed that the cape lamb member can be correlated with the lower to middle regions of the 1200 m thick sequence of undifferentiated lopez de bertodano formation lithologies exposed on seymour island molluscan data indicate a late campanian palaeocene age range for this upper formation dinoflagellates again suggest that the lowest beds may be slightly older the correlation presented provides the basis for a formal subdivision of the campanian and maastrichtian stages in the southern high latitudes it has also revealed two major basin shallowing events in the late campanian early maastrichtian and latest maastrichtian respectively and the existence of a major fault fault zone across southeastern james ross island the improved temporal framework will aid late cretaceous palaeoclimatic and palaeobiological studies in antarctica

influence of glacial isostatic adjustment upon current sea level variations in the mediterranean abstract present day sea level variations in the mediterranean depend on various factors including recent climatic forcing tectonic activity anthropogenic effects and glacio isostatic adjustment the latter is governed by mantle rheology and the spatio temporal distribution of the late pleistocene ice sheets and it is expected to produce a long wavelength pattern of sea level variations across the mediterranean mostly determined by the response of the solid earth and of the geoid to loading effects of melt water since the end of deglaciation modeling glacio isostatic effects in this region is necessary for a correct interpretation of tide gauge and gps time series and thereby to constrain both the present day climate related sea level rise and regional or local geological tectonic and human driven displacements by an exhaustive exploration of the parameter space of mantle rheology and ice sheet chronologies in this work we outline upper and lower bounds on the current rate of sea level variation associated with glacial isostatic adjustment in the mediterranean this may contribute to a full assessment of coastal vulnerability by sea level rise on a regional and local scale

constraints on mantle viscosity based upon the inversion of post glacial uplift data from the hudson bay region summary we outline two parametrizations for post glacial relative sea level rsl histories associated with previously glaciated regions the first parametrization is based on a site dependent normalization of the rsl history while the second involves the estimate of a site dependent logarithm of the inverse decay time for the exponential like form which characterizes these histories both parametrizations are shown to yield data sets which are relatively insensitive to the details of the late pleistocene surface load history and therefore inferences of mantle viscosity based upon them will be particularly robust we apply the two parametrizations to consider the rsl record at a number of sites across the hudson bay region in this regard our inferences which are derived from both forward and inverse calculations are based upon the actual rsl age height pairs obtained by survey rather than the highly subjective set of rsl trends adopted in previous studies one of the main goals of the analysis is to assess the validity of a set of previously published and highly contradictory inferences of the radial profile of mantle viscosity based on the hudson bay rsl record forward analyses using models with isoviscous upper and lower mantle regions as adopted in the vast majority of previous analyses indicate that the parametrized versions of the rsl record in hudson bay excluding data from the cape henrietta maria site are best fitted by a lower mantle viscosity near 1021 pa s the same conclusion holds when data from only northern hudson bay are considered the rsl record in southern hudson bay is not self consistent if the error bars adopted herein are reasonable however the parametrized versions of the rsl curves from each site in this region can be reconciled by a model with a lower mantle viscosity somewhere in the rather moderate range 0 5 3 0 1021 pa s the value of 3 1021 pa s represents a lower bound on the lower mantle viscosity required to fit the rsl records at cape henrietta maria this record is characterized by a longer decay time than those associated with other sites in the data base this lower bound is in contrast with previous suggestions that the rsl record at cape henrietta maria requires a lower mantle viscosity of 30 1021 pa s inverse analyses described herein indicate that the rsl record from the entire hudson bay constrains the average viscosity in the radial region extending from the lower reaches of the upper mantle to mid lower mantle depths the inferences listed above are therefore more properly ascribed to this region rather than the entire lower mantle we have found that the data are sensitive to moderately deeper variations in the radial viscosity profile as one considers sites situated further north in hudson bay this provides one means for a spherically symmetric model to yield decay times which vary across the hudson bay however the data do not provide an unambiguous requirement for such a variation

mantle viscosity beneath the hudson bay an inversion based on the metropolis algorithm 1 we revisit the problem of inferring mantle viscosity from postglacial relative sea level rsl data across the hudson bay we invert a recently revised data set using the metropolis algorithm together with an annealing schedule this method which is well established in geophysics is applied here for the first time to the glacial isostatic adjustment problem the metropolis algorithm performs a search which is not limited to downhill moves in the model space and thus is less influenced by local minima of the misfit than traditional inverse approaches furthermore its cpu requirements are far superior to monte carlo methods the major drawbacks include slow convergence and the need for careful tuning of crucial variables such as the temperature schedule and the increment in the model space when all the hudson bay rsl data are considered and the viscosity of the upper mantle above the 670 km discontinuity is inverted the best fitting solution is characterized by a viscosity close to 2 1020 pa s however when the shallow upper mantle and transition zone viscosity are separately inverted other less traditional solutions with a more complex viscosity structure are found to be equally possible a stable feature is the lower mantle viscosity which is generally found to be close to the value of 1021 pa s in all of the stochastic inversions we have performed the solutions agree with previous findings concerning both postglacial rebound observables and global geodynamics signatures

a new hesperornithiform aves specimen from the late cretaceous canadian high arctic with comments on high latitude hesperornithiform diet here we describe a new hesperornithiform specimen from the upper cretaceous kanguk formation of devon island nunavut canada this specimen nuvf 286 is referred to cf hesperornis sp based on size and shape of femora and teeth preserved with other skeletal elements previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death this new cf hesperornis specimen includes the first teeth associated with a high latitude hesperornithiform allowing for comments on the trophic behavior of these birds paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high latitude hesperornithiform birds may have had more varied diets than previously assumed

lateral viscosity variations and post glacial rebound effects on present day vlbi baseline deformations by means of a finite element algorithm we investigate the effects of lateral viscosity variations upon the horizontal motions currently detected by vlbi techniques in europe our axisymmetric flat models appropriate to describe the rebound due to the melting of the fennoscandia ice sheet are characterized by a layered compressible mantle with linear maxwell rheology we have first computed the time evolution of theoretical baselines characterized by a simple geometry in agreement with previous results the rates of horizontal deformation have been found to be greatly sensitive to both lateral viscosity variations and deep mantle stratification especially for baselines located in the vicinity of the ice sheet margin to complete our study we have compared our numerical results with the observed time evolutions of relevant european baselines onsala wettzell and onsala eflsberg are fitted by a laterally varying asthenosphere and sharp viscosity increase in the lower mantle longer baselines connecting these sites to medicina northern italy indicate that post glacial rebound is responsible only for a fraction of the vlbi observations the residual being thus attributable to continental collision in the mediterranean sea

new relative sea level insights into the isostatic history of the western mediterranean abstract a recent suite of relative sea level rsl data for the past 12 ka bp has provided new insights into the sea level histories of the western mediterranean region our analysis of the chronostratigraphic context of sea level indicators from spain catalonia the balearic islands and the gulf of valencia france corsica island and italy sardinia island has yielded 162 new sea level index and limiting points these data have considerably enhanced previous rsl compilations in addition to improving the quality of spatio temporal sea level reconstructions and our capacity to estimate isostatic related vertical motions in the western mediterranean basin the glacial and hydro isostatic adjustment gia pattern elucidated by the new database shows discrepancy with respect to those predicted by the available gia models in particular the new results underscore a non coherent isostatic response of the central portion of the western mediterranean with the balearic islands manifesting significant departures from the sea level histories of corsica sardinia and more generally along most of the western mediterranean coast our results are a crucial contribution to defining both the pattern and the magnitude of the isostatic signal along the western mediterranean coast in fact vertical isostatic motions represent a key to better assess any possible post industrial acceleration in sea level rise and to define future scenarios of coastal inundation in the context of global change

definition of late cretaceous stage boundaries in antarctica using strontium isotope stratigraphy abstract new 87sr 86sr analyses of macrofossils from 13 key marker horizons on james ross and vega islands antarctica allow the integration of the antarctic late cretaceous succession into the standard biostratigraphic zonation schemes of the northern hemisphere the 87sr 86sr data enable late cretaceous stage boundaries to be physically located with accuracy for the first time in a composite southern hemisphere reference section and so make the area one of global importance for documenting late cretaceous biotic evolution particularly radiation and extinction events the 87sr 86sr values allow the stage boundaries of the turonian coniacian coniacian santonian santonian campanian and campanian maastrichtian as well as other levels to be correlated with both the united kingdom and united states these correlations show that current stratigraphic ages in antarctica are too young by as much as a stage immediate implications of our new ages include the fact that inoceramus madagascariensis a useful

glacial isostatic adjustment and relative sea level changes the role of lithospheric and upper mantle heterogeneities in a 3 d spherical earth summary the response of the earth to the melting of the late pleistocene ice sheets is commonly studied by spherically layered models based on well established analytical methods in parallel a few models have been recently proposed to circumvent the limitations imposed by spherical symmetry and to reproduce the actual structure of the lithosphere and of the upper mantle their main outcome is that laterally varying rheological structures may significantly affect various geophysical quantities related to glacial isostatic adjustment gia and particularly post glacial relative sea level rsl variations and 3 d crustal velocities in formerly ice covered regions in this paper we contribute to the ongoing debate about the role of lithospheric and mantle heterogeneities by new 3 d spherical newtonian finite elements models and we directly compare their outcomes with publicly available global rsl data this differs from previous investigations in that have mainly focused on extensive sensitivity analyses or have considered a limited number of rsl observations from formerly glaciated regions and their periphery in our study the lithospheric thickness mimics the global structure of the cratons based on geological evidence and the upper mantle includes a low viscosity zone beneath the oceanic lithosphere we use two distinct global surface loads based upon the ice1 and ice3g deglaciation chronologies respectively our main finding is that using all of the available rsl observations in the last 6000 years it is not possible to discern between homogeneous and heterogeneous gia models this result which holds for both ice1 and ice3g suggests that the cumulative effects of laterally varying structures on the synthetic rsl curves cancel out globally yielding signals that do not significantly differ from those based on the 1 d models we have also considered specific subsets of the global rsl database sharing similar geographical settings and distances from the main centres of deglaciation when we consider the data from the margins of the baltic region a laterally varying lithospheric thickness improves significantly the agreement with the observations this is not observed in other relevant situations including the hudson bay region in the regions where the disagreement between predictions and observations is particularly evident further investigations are needed to improve the geometry of the heterogeneous structures and of the surface ice sheets distribution

greenland uplift and regional sea level changes from icesat observations and gia modelling we study the implications of a recently published mass balance of the greenland ice sheet gris derived from repeated surface elevation measurements from nasa s ice cloud and land elevation satellite icesat for the time period between 2003 and 2008 to characterize the effects of this new high resolution gris mass balance we study the time variations of various geophysical quantities in response to the current mass loss they include vertical uplift and subsidence geoid height variations global patterns of sea level change or fingerprints and regional sea level variations along the coasts of greenland long wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation which accounts for both the elastic and the viscoelastic components of deformation to capture the short wavelength components of vertical uplift in response to current ice mass loss which is not resolved by satellite gravity observations we have specifically developed a high resolution regional elastic rebound er model the elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial isostatic adjustment gia according to a set of published ice chronologies and associated mantle rheological profiles we compare the sensitivity of global positioning system gps observations along the coasts of greenland to the ongoing er and gia in notable contrast with past reports we show that vertical velocities obtained by gps data from five stations with sufficiently long records and from one tide gauge at the gris margins can be reconciled with model predictions based on the ice 5g deglaciation model and the er associated with the new icesat derived mass balance

relative sea level fall since the last interglacial stage are coasts uplifting worldwide the growing interest in quantification of vertical ground motion stems from the need to understand in detail how the earth s crust behaves for both scientific and social reasons however only recently has the refinement of dating techniques made possible the use of paleoshorelines as reliable tools for tectonic studies although there are many local studies of quaternary vertical motions of coastlines we know of no comprehensive worldwide synthesis here we provide a compilation of 890 records of paleoshoreline sequences with particular emphasis on the last interglacial stage marine isotopic stage mis 5e 122 ka the quality of dating mis 5e makes it a reliable marker to evaluate vertical ground motion rates during the late quaternary on a global scale the results show that most coastal segments have risen relative to sea level with a mean uplift rate higher than 0 2 mm yr i e more than four times faster than the estimated eustatic drop in sea level the results also reveal that the uplift rate is faster on average for active margins than for passive margins neither dynamic topography nor glacio hydro isostasy may explain sustained uplift of all continental margins as revealed by the wide distribution of uplifted sequences of paleoshorelines instead we suggest that only plate tectonic processes reconcile all observations of quaternary coastal uplift we propose that long term continental accretion has led to compression of continental plates and uplift of their margins therefore this study concludes that plate tectonics processes impact all margins and emphasizes the fact that the notion of a stable platform is unrealistic these results therefore seriously challenge the evaluation of past sea levels from the fossil shoreline record

decoding last interglacial sea level variations in the western mediterranean using speleothem encrustations from coastal caves in mallorca and sardinia a field data model comparison u th ages of phreatic overgrowths on speleothems in coastal caves of the western mediterranean record high sea level positions during marine isotope stage mis 5e of the last interglacial while relative sea level rsl on the southeastern coast of mallorca stood 2 6 m above present sea level apsl during mis 5e it stood 4 3 m apsl at this time in northwestern sardinia the difference between the two sites during mis 5e and the deviation from the eustatic sea level trend during the holocene was investigated using the numerical code selen the offset between the eustatic curve and those pertaining to the two sites principally reflect the vertical deformations and geoidal variations in response to meltwater loading as sardinia is closer to the center of the mediterranean basin the hydro isostatic component of rsl is enhanced here compared to mallorca which results in a modeled offset of 60 cm between the two sites this result is qualitatively useful as it provides a partial reconciliation for the site differences however the need for refinement in the model is also recognized as it does not match the observation based on u th dating of speleothem overgrowths in mallorca that sea level there has remained stable for the past 2800 years overall the results of the study first suggest that both sites largely track the eustatic sea level curve and second suggest that glacial isostatic adjustment is a viable mechanism to reconcile some if not most of the relatively small elevation difference of mis 5e sea level observed at mallorca and sardinia although minor tectonic adjustments cannot be ruled out in explaining some low amplitude local variations

recent stromatolites in landlocked pools on aldabra western indian ocean abstract stromatolites occurring in three areas of landlocked pools on aldabra show distinctive morphologies petrography and biological characteristics related both to water chemistry and the physical characteristics of sites they are formed apparently by indirect precipitation of high magnesium calcite in association with growths of cyanobacteria and cladophora the three contrasted areas are dominated respectively by phormidium lyngbya and pleurocapsa by entophysalis lyngbya and pleurocapsa and by pleurocapsa dichothrix gypsophila and schizothrix reflecting an increasing concentration and increasing dissolved carbonate activity of pool waters centimeters to decimeters of carbonate encrustations are made up of irregular laminate columns porous layered coatings of planar or cerebroid form including oncolites and finely laminate branching columns laminae are typically alternations of dense and porous micrite with in one locality radiating fibrous sparry crystal growths although exclusively associated with cyanobacteria calcification typically begins several millimeters beneath living cells with few examples of carbonate coated unicells or filaments micrite consists of randomly arranged particles of varying size products of sparse homogeneous nucleation followed by both overgrowth and dissolution coarse cements of contrasted morphologies develop within internal cavities resembling the endostromatolites described by others chemical data indicate that waters in all three pools are supersaturated with respect to caco 3 calcite this is adequate but is not in itself sufficient to bring about precipitation of carbonate which is site specific cyanobacteria are not directly calcified but metabolic activities may promote precipitation through mechanisms such as extraction of co 2 or by the generation of specific organic molecules which promote nucleation or colonies may provide a closed passive environment in which other bacteria or inorganic processes bring about crystallization the precise path is not known but the reduction of possibilities carries implications both for the accretion of other stromatolites and the crystallization of carbonate in deposits such as tufas

effects of lateral viscosity variations on postglacial rebound an analytical approach summary so far interpretations of postglacial rebound have usually been based on the assumption of laterally homogeneous earth models however in view of the increasing evidence of the 3 d structure of the earth s mantle several studies on the effects of lateral variations of the viscosity on postglacial rebound have been completed during the last decade in the present study we consider load induced viscoelastic and viscous perturbations of incompressible and vertically homogeneous flat earth models with lateral variations of the shear modulus and viscosity the solution is obtained using a perturbation method and given in analytical form our results show that sinusoidal variations of the parameters of less than one order of magnitude can modify the vertical surface displacement associated with a model of the fennoscandian ice sheet by several tens of metres the modifications increase approximately in proportion to the amplitude of the lateral variations the overall increase of the modifications with increasing wavelength is complicated in detail and also results in changes of the spatial and temporal distributions of the vertical surface displacement