magma ascent at floor fractured craters diagnoses the lithospheric stress state on the moon abstract on the moon floor fractured craters ffcs present evidence of horizontal crater centred magmatic intrusions crater floor uplift and moat formation indicate that these sill intrusions occur at shallow depths

micropaleontological documentation for early holocene fall of relative sea level on the atlantic coast of nova scotia the presence of a marsh sequence between two shallow water marine deposits in an offshore core from lunenburg nova scotia indicates fall of relative sea level followed by rise of relative sea level the marsh sequence is now 27 m below datum level with a c 14 date of 7 070 yr b p this sequence suggests that the glacial forebulge migrated through this area 7 000 yr ago that 27 m of submergence has occurred since then and that prior to 7 000 yr b p the site was characterized by low amplitude emergence this is at present the only sequence where the entire regression transgression record is preserved along this coast the accuracy required to demonstrate this can be obtained only by using established marsh foraminiferal zonations

gravitational signatures of lunar floor fractured craters lunar floor fractured craters are impact craters characterized by distinctive shallow floors crossed by important networks of fractures different scenarios have been proposed to explain their formations but recent studies showed that the intrusion of magma at depth below the crater floor is the most plausible explanation the intrusion of dense magma within the light upper most part of the lunar crust should have left a positive signature in the gravity field this study takes advantage of the unprecedented resolution of the lunar gravity field obtained from the nasa s gravity recovery and interior laboratory grail mission in combination with topographic data obtained from the lunar orbiter laser altimeter lola instrument to investigate the gravitational signatures of both normal and floor fractured craters despite the large variability in their gravitational signatures the floor fractured and normal craters in the highlands show significant differences the gravitational anomalies are significantly larger at floor fractured craters the anomaly amplitudes for floor fractured craters are in agreement with synthetic gravity anomalies based on the predicted intrusion shapes from a theoretical flow model our results are consistent with magmatic intrusions intruding a crust characterized by a 12 porosity and where the intrusion has no porosity similar studies have been carried out in the lunar maria and south pole aikten basin although the average gravitational signature of floor fractured craters is larger than at normal craters in these regions they cannot be distinguished statistically due to the small number of craters and the large variability of the anomalies in general a better characterization of the signal due solely to the initial impact crater is needed to isolate the magmatic intrusion signal and characterize the density contrast between the magma and crust

individual lava flow thicknesses in oceanus procellarum and mare serenitatis determined from clementine multispectral data abstract we use multispectral reflectance data from the lunar clementine mission to investigate the impact ejecta deposits of simple craters in two separate lunar mare basalt regions one in oceanus procellarum and one in mare serenitatis over 100 impact craters are studied and for a number of these we observe differences between the tio 2 and feo contents of their ejecta deposits and the lava flow units in which they are located we demonstrate that in the majority of cases these differences cannot plausibly be attributed to uncorrected maturity effects these observations coupled with morphometric crater relationships that provide maximum crater excavation depths allow the investigation of sub surface lava flow stratigraphy we provide estimated average thicknesses for a number of lava flow units in the two study regions ranging from 80 m to 600 m in the case of the serenitatis study area our results are consistent with the presence of sub surface horizons inferred from recent radar sounding measurements from the jaxa kaguya spacecraft the average lava flow thicknesses we obtain are used to make estimates of the average flux of volcanic material in these regions these are in broad agreement with previous studies suggesting that the variation in mare basalt types we observe with depth is similar to the lateral variations identified at the surface

scale considerations in using diatoms as indicators of sea level change lessons from alaska this paper assesses variations in quantitative reconstructions of late holocene relative sea level rsl change arising from using modern diatom datasets from different spatial scales applied to case studies from alaska we investigate the implications of model choice in transfer functions using local sub regional and regional scale modern training sets and produce recommendations on the creation and selection of modern datasets for reconstructing rsl change over holocene timescales in tidal marsh environments comparable with those in alaska we show that regional modern training sets perform best in terms of providing fossil samples with good modern analogues and in producing reconstructions that most closely match observations where these are available local training sets are frequently insufficient to provide fossil samples with good modern analogues and may over estimate the precision of rsl reconstructions this is particularly apparent when reconstructing rsl change for periods beyond the last century for reconstructing rsl change we recommend using regional modern training sets enhanced by local samples

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

elevated mercury accumulation in a peat bog of the magellanic moorlands chile 53 s an anthropogenic signal from the southern hemisphere increasing mercury deposition rates in the northern hemisphere recorded in natural archives such as peat bogs or lake sediments have been documented in numerous studies however data on atmospheric hg deposition in the southern hemisphere dating back to pre industrial times are rare here we provide a continuous record of atmospheric hg deposition in the southern hemisphere recorded by an ombrotrophic peat bog of the magellanic moorlands chile 53 s extending back 3000 yr pre industrial mercury accumulation rates range between 2 5 and 3 9 wg m 2 yr in the past 100 yr hg accumulation rates increased 18 fold from about 3 wg m 2 yr to a maximum of 62 5 wg m 2 yr if hg accumulation rates were normalized to peat accumulation rates maximum rates were 7 9 wg m 2 yr which is only 2 5 times the pre industrial rates thus hg accumulation rates normalized to peat accumulation rates are more comparable to the three fold net increase in atmospheric hg concentrations estimated for the same period we suggest that the increase in hg accumulation rates in the magellanic moorlands within the past 100 yr is at least partly attributed to global dispersion of hg derived from anthropogenic sources in the northern hemisphere the finding that no increase of atmospheric deposition of pb could be observed in the bog indicates the extraordinary long range transport and ubiquitous dispersion of anthropogenic derived gaseous hg compared to other metals 2002 elsevier science b v all rights reserved

asymmetric thermal evolution of the moon 1 the moon possesses a clear dichotomy in geological processes between the nearside and farside hemispheres the most pronounced expressions of this dichotomy are the strong concentration of radioactive heat sources on the nearside in a region known as the procellarum kreep terrane pkt and the mare basaltic lava flows that erupted in or adjacent to this terrane we model the thermochemical evolution of the moon using a 3 d spherical thermochemical convection code in order to assess the consequences of a layer enriched in heat sources below the pkt on the moon s global evolution we find that in addition to localizing most of the melt production on the nearside such an enriched concentration of heat sources in the pkt crust has an influence down to the core mantle boundary and leaves a present day temperature anomaly within the nearside mantle moderate gravitational and topographic anomalies that are predicted in the pkt but not observed may be masked either by crustal thinning or gravitational anomalies from dense material in the underlying mantle our models also predict crystallization of an inner core for sulfur concentrations less than 6 wt

magma transport through the crust via interconnected sill complexes three dimensional seismic data from the volcanic margin offshore norway have been used to map the complex three dimensional geometry of two major sill complexes these data show that the complexes consist of bowl shaped or inclined sheetlike discordant sills that intersect with one another over a vertical distance of 8 12 km and transect basement and sedimentary rocks of the middle to upper crust using a simple graphical technique we demonstrate the interconnectedness of the sill complex and hence the maximum time for sill emplacement we show that sills are interconnected by junctions occurring systematically at the lowest points of the overlying sills and hence that the sill complex could have acted as a single throughgoing magmatic plumbing system transporting mafic melts from mid lower crustal depths to near surface based on this imaging of the magmatic plumbing system we conclude that sills can form viable and efficient conduits for crustal magma transport in volcanic margins and may play a role in feeding large extrusive complexes

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

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

calculation of dike trajectories from volcanic centers 1 patterns of dike swarms around volcanic centers or above mantle plumes are interpreted by a mechanical analysis of regional and dike induced stresses in which dike emplacement is controlled and guided by the stress state comparisons of dike patterns with patterns of principal stress trajectories caused by a source and a regional stress system are commonly used to infer paleostresses however dike trajectories are determined by a complex interaction between dike induced stresses and the source regional stress system we present numerical calculations based on a novel boundary integral formulation which examines the simultaneous effects of regional stresses magma pressure and dike injection on the local stress state around a continuously curving dike dike paths are calculated from the condition that dikes propagate by mode i failure our results suggest that the magnitude of the regional stresses would be 2 5 times higher than previous estimates based on principal stress trajectory analysis

lunar floor fractured craters as magmatic intrusions geometry modes of emplacement associated tectonic and volcanic features and implications for gravity anomalies lunar floor fractured craters are a class of 170 lunar craters with anomalously shallow fractured floors two end member processes have been proposed for the floor formation viscous relaxation and subcrater magmatic intrusion and sill formation recent morphometric analysis with new lunar reconnaissance orbiter laser altimeter lola and image lroc data supports an origin related to shallow magmatic intrusion and uplift we find that the distribution and characteristics of the ffc population correlates strongly with crustal thickness and the predicted frequency distribution of overpressurization values of magmatic dikes for a typical nearside lunar crustal thickness dikes with high overpressurization values favor surface effusive eruptions medium values favor intrusion and sill formation and low values favor formation of solidified dikes concentrated lower in the crust we develop a model for this process make predictions for the morphologic morphometric volcanic and geophysical consequences of the process and then compare these predictions with the population of observed floor fractured craters in our model the process of magmatic intrusion and sill formation begins when a dike propagates vertically towards the surface as the dike encounters the underdense brecciated region beneath the crater the magmatic driving pressure is insufficient to continue vertical propagation but pressure in the stalled dike exceeds the local lithostatic pressure the dike then begins to propagate laterally forming a sill which does not propagate past the crater floor region because increased overburden pressure from the crater wall and rim crest pinch off the dike at this boundary the sill then continues to inflate further raising and fracturing the brittle crater floor when the intrusion diameter to intrusion depth ratio is smaller than a critical value the intrusion assumes a laccolith shape with a domed central region when the ratio exceeds a critical value the intrusion concentrates bending primarily at the periphery resulting in a flat tabular intrusion we predict that this process will result in concentric fractures over the region of greatest bending this location is close to the crater wall in large flat floored craters as observed in the crater humboldt and interior to the crater over the domed floor in smaller craters as observed in the crater vitello a variety of volcanic features are predicted to be associated with the solidification and degassing of the intrusion these include 1 surface lava flows associated with concentric fractures e g in the crater humboldt 2 vents with no associated pyroclastic material from the deflation of under pressurized magmatic foam e g the crater damoiseau and 3 vents with associated pyroclastic deposits from vulcanian eruptions of highly pressurized magmatic foam e g the crater alphonsus the intrusion of basaltic magma beneath the crater is predicted to contribute a positive component to the bouguer gravity anomaly we assess the predicted bouguer anomalies associated with ffcs and outline a process for their future interpretation we conclude that our proposed mechanism serves as a viable formation process for ffcs and accurately predicts numerous morphologic morphometric and geophysical features associated with ffcs these predictions can be further tested using grail gravity recovery and interior laboratory data

relative sea level change in west greenland during the last millennium relative sea level rsl data provide important long term century to millennial scale constraints on ice load history in greenland in this paper we present the results of a litho bio and chronostratigraphic study designed to reconstruct rsl during the last millennium from salt marsh deposits recovered from a field site near to the town of sisimiut west greenland the stratigraphy at three marshes typically records an upwards transition from freshwater to salt marsh deposits we use a quantitative transfer function and subjective model to reconstruct palaeomarsh elevation and changes in mean tide level mtl from 16 sediment profiles from these marshes these palaeomarsh elevations are placed in a chronological framework established by 18 radiocarbon dated index points both models yield similar results and show mtl rose from 0 60 0 20 m at c 600 cal a bp to reach 0 10 0 20 m at c 400 cal a bp after this time mtl remained close to present 0 20 m until the present day although low sedimentation rates limit the resolution of our reconstructions during this interval the initial rise in rsl can be explained by the dominance of non greenland processes notably the collapse of the laurentide forebulge over local greenland solid earth uplift caused by postglacial ice unloading this is despite some reloading of the crust that occurred during the neoglacial expansion of the greenland ice sheet in this part of west greenland the slow down in rsl at 400 cal a bp does not record either a change in the rate of laurentide forebulge collapse or a change in eustatic sea level we argue instead that this slow down records the effects of a sustained reduction in local greenland ice mass that persists over most of the past 400 years the latter interval is widely acknowledged as a period of generally cooler than present conditions associated with the later stages of the little ice age during this period field evidence suggests that in many areas the ice sheet had reached its maximum late holocene extent it is not obvious at this stage how to reconcile an expanding ice sheet with a reduction in ice load during this interval although we hypothesise it could reflect one or more of i a change in ice sheet dynamics ii reduced mass accumulation caused by cold and dry conditions and iii a lagged response to earlier periods of climate warming

tests of glacial rebound models for fennoscandinavia based on instrumented sea and lake level records summary evidence for changing sea levels in northwestern europe related to glacial rebound is found in both the geological record of the past millennia and in the instrumental records of the past two centuries the latter records are of two types records of sealevel change primarily from the baltic and the gulfs of finland and bothnia and records of the tilting of some of the larger lakes in both finland and sweden the sealevel records are particularly important because of their long duration and high quality their large number and good spatial distribution and the spatially coherent background noise the two instrumental data types are complementary and provide constraints on the upper mantle rheology and on the distribution of ice during the late glacial stage comparisons of the observed rates of change of the water levels with models for glacial rebound yield earth models with a lithospheric thickness of 80 100 km and an uppermantle viscosity of 4 5 1020 pa s evective parameters that are consistent with those obtained from the analysis of the geological evidence for the same region the mareograph results support ice sheet models in which the late weichselian ice thickness over the eastern and southern parts of fennoscandia is relatively thinner than that for the western region also consistent with the interpretation of the geological evidence for sea level change in addition the instrumental records provide constraints on the eustatic sea level change for about the past 100 years a satisfactory separation of the earth rheology parameters from this rate of change can be achieved by estimating the latter only from those records for which the predicted isostatic evects are small a check on these results is possible by using the lake level records to establish constraints on the earth model parameters and the sea level records to constrain also the eustatic change all approaches lead to an average eustatic sea level rise for the past century of about 1 1 0 2 mm yr 1

postglacial uplift and relative sea level changes in finnmark northern norway abstract the outer coast of finnmark in northern norway is where the former fennoscandian and barents sea ice sheets coalesced this key area for isostatic modelling and deglaciation history of the ice sheets has abundant raised shorelines but only a few existing radiocarbon dates constrain their chronology here we present three holocene sea level curves based on radiocarbon dated deposits from isolation basins at the outermost coast of finnmark located at the islands soroya and rolvsoya and at the nordkinn peninsula we analysed animal and plant remains in the basin deposits to identify the transitions between marine and lacustrine sediments terrestrial plant fragments from these transitions were then radiocarbon dated radiocarbon dated mollusk shells and marine macroalgae from the lowermost deposits in several basins suggest that the first land at the outer coast became ice free around 14 600 cal yr bp we find that the gradients of the shorelines are much lower than elsewhere along the norwegian coast because of substantial uplift of the barents sea also the anomalously high elevation of the marine limit in the region can be attributed to uplift of the adjacent seafloor after the younger dryas the coast emerged 1 6 1 0 cm per year until about 9500 9000 cal yr bp between 9000 and 7000 cal yr bp relative sea level rose 2 4 m and several of the studied lakes became submerged at the outermost locality rolvsoya relative sea level was stable at the transgression highstand for more than 3000 years between ca 8000 and 5000 cal yr bp deposits in five of the studied lakes were disturbed by the storegga tsunami ca 8200 8100 cal yr bp

contrasting records of sea level change in the eastern and western north atlantic during the last 300 years we present a new 300 year sea level reconstruction from a salt marsh on the isle of wight central english channel uk that we compare to other salt marsh and long tide gauge records to examine spatial and temporal variability in sea level change in the north atlantic our new reconstruction identifies an overall rise in relative sea level rsl of c 0 30 m since the start of the eighteenth century at a rate of 0 9 0 3 mmyr 1 error in variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset the reconstruction is broadly comparable to other tide gauge and salt marsh records from the european atlantic demonstrating coherence in sea level in this region over the last 150 300 years in contrast we identify significant differences in the rate and timing of rsl with records from the east coast of north america the absence of a strong late 19th early 20th century rsl acceleration contrasts with that recorded in salt marsh sediments along the eastern usa coastline in particular in a well dated and precise sea level reconstruction from north carolina this suggests that this part of the north carolina sea level record represents a regionally specific sea level acceleration this is significant because the north carolina record has been used as if it were globally representative within semi empirical parameterisations of past and future sea level change we conclude that regional scale differences of sea level change highlight the value of using several regionally representative rsl records when calibrating and testing semi empirical models of sea level against palaeo records this is because by using records that potentially over estimate sea level rise in the past such models risk over estimating sea level rise in the future

late holocene sea level changes in eastern quebec and potential drivers abstract late holocene sea level changes can be reconstructed from salt marsh sediments with decimetre scale precision and decadal scale resolution these records of relative sea level changes comprise the net sea level contributions from mechanisms that act across local regional and global scales recent efforts help to constrain the relative significance of these mechanisms that include sediment dynamics and isostasy which cause relative sea level changes via vertical land motion ocean atmosphere processes that influence regional scale ocean mass redistribution and ocean cryosphere and steric interactions that drive global scale ocean volume changes there remains a paucity of high resolution late holocene sea level data from eastern canada this precludes an interrogation of the mechanisms that define sea level changes over recent centuries and millennia in a region sensitive to oceanic atlantic multidecadal variability atlantic meridional overturning circulation atmospheric north atlantic oscillation arctic oscillation and cryospheric ice mass balance changes we present new relative sea level data that span the past three millennia from baie des chaleurs in the gulf of st lawrence generated using salt marsh foraminifera supported with plant macrofossil analyses the accompanying chronology is based on radiocarbon and radionuclide analyses which are independently verified using trace metal and microcharcoal records relative sea level has risen at a mean rate of 0 93 1 25 mm yr 1 over the past 1500 years residual structure within the reconstruction internal variability has contributed up to an additional 0 61 0 46 mm yr 1 of short lived rsl rise prior to 1800 ce following a sea level low stand during the little ice age acceleration in relative sea level rise is identified between 1800 and 1900 ce within the estimates of internal variability and from 1950 ce to present in both the secular and residual trends phases of relative sea level changes in the gulf of st lawrence are concomitant with periods of glacier mass loss following the little ice age phase periods of the north atlantic oscillation and the atlantic meridional overturning circulation and northern hemisphere warming quantifying the individual effects of these different mechanisms is important for understanding how ocean atmosphere processes redistribute ocean mass upon larger scale background ocean volume changes

salt marshes as archives of recent relative sea level change in west greenland abstract temperate latitude salt marshes are a proven environment from which high precision 0 10 0 20 m relative sea level rsl records can be developed over recent decades and centuries such records provide an important link between millennial histories of rsl change and instrumental records the high latitude salt marshes in greenland have not previously been explored as potential archives of recent rsl change here we develop four diatom based transfer functions using contemporary diatom data collected from three salt marshes located 40 km south of the coastal town of sisimiut west greenland our preferred model has a good fit between observed and predicted elevations r 2 0 94 and a root mean square error prediction of 0 19 m we apply the four models to a short sediment profile collected from one of the marshes that formed between c 600 cal year bp and the present three of the four models predict the same trend in which rsl rose from 0 55 0 19 m mean tide level mtl to 0 05 0 19 m mtl between c 600 and 400 cal year bp at a rate of c 2 7 mm year 1 after 400 cal year bp rsl slowed and remained stable until the present day the results of this study demonstrate that greenland salt marshes are potentially valuable archives of data for developing quantitative estimates of rsl change during the last few centuries thereby bridging the gap between existing millennial scale approaches and more recent direct observations of ice sheet behaviour and associated vertical land motions

late holocene sea level change in arctic norway abstract relative sea level data from the pre industrial era are required for validating geophysical models of glacio isostatic adjustment as well as for testing models used to make sea level predictions based on future climate change scenarios we present the first late holocene past 3300 years relative sea level reconstruction for northwestern norway based on investigations in south hinnoya in the vesteralen lofoton archipelago sea level changes are reconstructed from analyses of salt marsh and estuarine sediments and the micro organisms foraminifera and testate amoebae preserved within the indicative meaning of the microfauna is established from their modern distributions records are dated by radiocarbon 201pb 137cs and chemostratigraphical analyses our results show a continuous relative sea level decline of 0 7 0 9 mm yr 1 for south hinnoya during the late holocene the reconstruction extends the relative sea level trend recorded by local tide gauge data which is only available for the past 25 years our reconstruction demonstrates that existing models of shoreline elevations and gia overpredict sea level positions during the late holocene we suggest that models might be adjusted in order to reconcile modelled and reconstructed sea level changes and ultimately improve understanding of gia in fennoscandia

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

isotopic trends and background fluxes of atmospheric lead in northern europe analyses of three ombrotrophic bogs from south sweden isotopic trends and background fluxes of atmospheric lead in northern europe analyses of three ombrotrophic bogs from south sweden

the application of δ13c toc and c n geochemistry of mangrove sediments to reconstruct holocene paleoenvironments and relative sea levels puerto rico abstract we assessed the use of 13c toc and c n values of bulk sedimentary organic matter om to reconstruct paleoenvironmental and relative sea level change from mangrove environments in puerto rico the modern distribution of 13c toc and c n values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands and was compared to microfossil foraminiferal and thecamoebian assemblages four vertically zoned environments were identified tidal flat 13c 18 6 2 8 toc 10 2 5 7 c n 12 7 3 1 mangrove 13c 26 4 1 0 toc 33 9 13 4 c n 24 3 6 2 brackish transition 13c 28 8 0 7 toc 40 8 11 7 c n 21 7 3 7 and freshwater swamp 13c 28 4 0 4 toc 42 8 4 8 c n 17 0 1 1 these environments had distinct 13c toc and c n values with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone the foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water mhhw likely resulting from washover or transport by storms however the ratio of foraminifera to thecamoebians f t along with 13c toc and c n values refines the distinction between brackish and freshwater environments using linear discriminant analysis we applied the 13c toc c n and f t distributions to a 1 7 m core containing a continuous sequence of rhizophora mangle peat which began accumulating at 1650 1930 ce together microfossils 13c toc and c n values and the core chronology from 137cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery making it unsuitable for relative sea level reconstruction we caution that in the absence of detailed litho bio chemo or chrono stratigraphic analyses as presented here care should be taken in interpreting sea level histories derived from single dates on mangrove peats

estimates of twenty first century sea level changes for norway in this work we establish a framework for estimating future regional sea level changes for norway following recently published works we consider how different physical processes drive non uniform sea level changes by accounting for spatial variations in 1 ocean density and circulation 2 ice and ocean mass changes and associated gravitational effects on sea level and 3 vertical land motion arising from past surface loading change and associated gravitational effects on sea level an important component of past and present sea level change in norway is glacial isostatic adjustment central to our study therefore is a reassessment of vertical land motion using a far larger set of new observations from a permanent gnss network our twenty first century sea level estimates are split into two parts firstly we show regional projections largely based on findings from the fourth assessment report of the intergovernmental panel on climate change ipcc ar4 and dependent on the emission scenarios a2 a1b and b1 these indicate that twenty first century relative sea level changes in norway will vary between 0 2 to 0 3 m 1 sigma 0 13 m secondly we explore a high end scenario in which a global atmospheric temperature rise of up to 6 c and emerging collapse for some areas of the antarctic ice sheets are assumed using this approach twenty first century relative sea level changes in norway are found to vary between 0 25 and 0 85 m min max 0 45 m we attach no likelihood to any of our projections owing to the lack of understanding of some of the processes that cause sea level change

radial dike formation on venus insights from models of uplift flexure and magmatism abstract giant radiating dike swarms on venus are geomorphic manifestations of deep seated volcano tectonic processes through an initial series of experiments we assess if these features can be explained as a product of the relationship between magmatism and the flexural stress state caused by lithospheric uplift due to a rising mantle diapir plume or underplating processes using gravitationally loaded axisymmetric elastic finite element models magma chambers situated in the upper extensional lithosphere fail at or near the crest redirecting magma vertically into radially aligned dikes but these are expected to feed surface eruptions conditions promoting lateral propagation of dikes do not occur magma chambers located in the lower compressional lithosphere are predicted to generate horizontal intrusions sills upon midsection failure when both uplift from basal loading and magmatic surface loading from edifice growth are introduced in sequence at discrete times however conditions that promote shallow lateral propagation of magma within radial dikes are created 1 as magma from shallow reservoirs ascends and erupts surface loading volcanic edifices can form 2 as the vertical loads increase flexing the lithosphere downward high compressional stresses produced within the edifice create a shallow stress barrier that makes it increasingly difficult for magma to complete the process of ascent and eruption and then 3 stresses acting on dikes ascending from a reservoir toward the surface will thus increasingly favor fracture along their lateral margins redirecting magma through radial dikes toward distal regions at shallow depth our results are consistent with observed patterns of laterally extensive dike systems at volcanic centers such as mbokomu mons and becuma mons the models thus provide a robust mechanical explanation that for the first time links lithosphere flexure and reservoir pressurization to the ascent and lateral spreading of magma through radial dike systems on venus thereby providing key new spatial and temporal insights into an important magmatic process operating on multiple terrestrial planets

saltmarsh foraminifera in the subarctic white sea thrive in summer endure in winter abstract abundance and diversity of intertidal benthic foraminifera decreases towards the poles well studied in the temperate zone saltmarsh foraminiferal assemblages have only recently received attention at higher latitudes we report modern foraminifera including the taxonomy abundance and zonation from a pristine saltmarsh in the subarctic white sea northern europe we sampled 10 stations surface sediment two replicates from two high tide flats covered with lush halophytic plants nine foraminiferal species found exhibited distinct vertical zonation confined to certain elevation levels the high marsh assemblage comprised arenaceous balticammina pseudomacrescens trochammina inflata jadammina macrescens and monothalamous ovammina opaca this is the northernmost location where the first two species have been encountered alive the low marsh assemblage was dominated by miliammina fusca and elphidium williamsoni summer abundances of live foraminifera were surprisingly higher than on other subarctic saltmarshes studied mostly 100 500 and up to 3000 per 10 cm in winter under a 40 cm of ice the abundances were only 15 20 ind 10 cm but the species richness was the same unlike summer specimens of calcareous foraminifera which are always brightly colored winter elphidium williamsoni all had bleak colorless cytoplasm suggesting they discard kleptoplasts and abandon algal diet we conclude that the insulating blanket of fast ice which hardly moves on saltmarshes prevents elimination of foraminifera in the harshness of winter whereas the intense continental heating in summer lets them thrive on white sea saltmarshes the composition of foraminiferal assemblages under local climatic conditions may thus deviate substantially from the latitudinal trend

utility of salt marsh foraminifera testate amoebae and bulk sediment δ13c values as sea level indicators in newfoundland canada abstract we investigated the utility of foraminifera testate amoebae and bulk sediment 13 c measurements for reconstructing holocene relative sea level from sequences of salt marsh sediment in newfoundland canada modern surface sediment was collected along transects from low to supra tidal elevations in eastern at placentia and western at hynes brook and big river newfoundland consistent with previous work low diversity assemblages of foraminifera display an almost binary division into a higher salt marsh assemblage dominated by jadammina macrescens and balticammina pseudomacrescens and a lower salt marsh assemblage comprised of miliammina fusca this pattern and composition resembles those identified at other high latitude sites with cool climates and confirms that foraminifera are sea level indicators the lowest occurrence of testate amoebae was at approximately mean higher high water the composition of high salt marsh testate amoebae assemblages centropyxis cassis type trinema spp tracheleuglypha dentata type and euglypha spp in newfoundland was similar to elsewhere in the north atlantic but preservation bias favors removal of species with idiosomic tests over those with xenosomic tests the mixed high salt marsh plant community in newfoundland results in bulk surface sediment 13 c values that are typical of c 3 plants making them indistinguishable from freshwater sediment therefore we propose that the utility of this proxy for reconstructing rsl in eastern north america is restricted to the coastline between chesapeake bay and southern nova scotia using a simple multi proxy approach to establish that samples in three radiocarbon dated sediment cores formed between the lowest occurrence of testate amoebae and the highest occurrence of foraminifera we generated three example late holocene sea level index points at hynes brook

marginal marine environments of the skagerrak and kattegat a baseline study of living stained benthic foraminiferal ecology this is the first detailed investigation of the distribution and ecology of living stained shallow water 0 6 m foraminifera along the skagerrak kattegat coast eastern north sea a total of 25 species 13 agglutinated 12 calcareous are common in the 169 sediment surface samples which were collected from 27 geographic areas the sediment grain size and total organic carbon toc content are strongly variable and the salinity and temperature ranges were 10 31 and 9 30 c respectively at the time of sampling july to october but temperatures down to freezing occur during the winter the species are divided into six environmental categories of which the first five comprise euryhaline and the sixth essentially stenohaline taxa 1 species associated only with marsh plants 2 species basically but not entirely associated with marsh plants 3 species basically but not entirely restricted to non marsh areas 4 species solely recorded in non marsh intertidal to subtidal environments 5 species restricted to subtidal areas 6 species basically living in the most open marine areas in this region marshes have a patchy distribution and they are small and compressed due to low tidal ranges 80 mud ammoscalaria runiana is common only in coarse grained sediments 20 mud with low toc 0 7 there are no marked biogeographic boundaries within the skagerrak kattegat area but 10 of the 25 commonly occurring species have not been reported from the adjacent baltic sea probably partly due to the brackish character of the water there the southern limits of distribution of the northern species elphidium albiumbilicatum ammotium cassis and ophthalmina kilianensis are in the kattegat baltic sea

floor fractured craters in mare smythii and west of oceanus procellarum implications of crater modification by viscous relaxation and igneous intrusion models endogenic modification in lunar floor fractured craters can constrain spatial variations in early lunar conditions the nature of these constraints however depends on the assumed mecha nism of crater modification for viscous relaxation the extent of crater modification depends on the surrounding crustal viscosity and thus provides loose constraints on the history of crustal heat ing within a region for igneous intrusion models the extent of crater modification reflects mag matically driven deformation and can be inverted to estimate both local magma pressure and intru sion depth both models indicate clear differences between regional conditions at mare smythii and in the highlands west of oceanus procelm the uniformly shallow crater depths in mare smythii probably indicate a long lived period of extreme crater relaxation whereas the wide range of modified crater depths in the western highlands suggest a much shorter period of partial crater relaxation for comparable relaxation times the average viscosity derived for mare smythii is over 10 times lower than the average viscosity inferred for the western highlands alternatively if modification reflects deformation over crater centered laccolithlike intrusions the derived magma pressures indicate a broad uniform magma source beneath mare smythii whereas the spatial vari ation of estimated magma pressures in the western highlands suggests the presence of several smaller magma sources the derived intrusion depths are partly a function of crater size but range from 1 to 10 km in depth for both regions and may be slightly greater on average in the western highlands while both viscous relaxation and igneous intrusions can explain the modification of individual craters the regional variations in these derived modification conditions also allow fur ther testing of each modification model in particular the correlation of the lowest viscosities or the longest relaxation times with the smallest craters in both mare smythii and the western high lands seems inconsistent with crater modification by the relaxation mechanism the onset of total relaxation at progressively smaller topographic wavelengths over time might produce such a trend in mare smythii but total relaxation cannot be invoked for the western highlands where many large craters still preserve significant fractions of their initial relief in addition the relaxation of the smallest craters in both regions suggests the presence of exceptionally high near surface ther mal gradients 150 200 k km since the observed regional variations in crater modification can be easily attributed to variations in magma pressure as a function of mantle topography we con clude that crater floor fracturing in both regions is more consistent with the igneous intrusion mechanism than with viscous relaxation during a crustal heating event

a model for the dynamics of crater centered intrusion application to lunar floor fractured craters lunar floor fractured craters are a class of craters modified by post impact mechanisms they are defined by distinctive shallow floors that are convex or plate like sometimes with a wide floor moat bordering the wall region radial concentric and polygonal floor fractures suggest an endogenous process of modification two mechanisms have been proposed to account for such deformations viscous relaxation and spreading of a magma intrusion at depth below the crater to test the second assumption and bring more constraints on the intrusion process we develop a model for the dynamics of magma spreading below an elastic overlying layer with a crater like topography as predicted in earlier more qualitative studies the increase in lithostatic pressure at the crater wall zone prevents the intrusion from spreading laterally leading to the thickening of the intrusion additionally our model shows that the final crater floor appearance after the uplift which can be convex or flat with or without a circular moat bordering the wall zone depends on the elastic thickness of the layer overlying the intrusion and on the crater size our model provides a simple formula to derive the elastic thickness of the overlying layer hence a minimum estimate for the intrusion depth finally our model suggests that crust redistribution by cratering must have controlled magma ascent below most of these craters

behavior of mg isotopes during dedolomitization in the madison aquifer south dakota abstract to constrain how mg isotopes behave during chemical interactions and physical transport in carbonate rich settings we measured 26 mg values of surface water groundwater and dolomite samples from the madison aquifer south dakota groundwater in the madison aquifer chemically evolves by dedolomitization during transport along a 236 km flow path surface streams recharging the aquifer have 26 mg values of 1 08 and 1 18 following recharge groundwater 26 mg values vary between 1 10 and 1 63 up to a distance of 20 km between 20 and 189 km 26 mg values remain nearly constant at 1 40 and a final sample at 236 km shows an increase to 1 09 dolomite exhibits a wide range of 26 mg values between 2 21 and 1 27 reactive transport modeling and isotope mixing calculations employing previously published major ion mass balances 87 sr 86 sr ratios and 44 ca values were used to determine whether dedolomitization reactions namely dolomite dissolution calcite precipitation and mg for na ion exchange fractionate mg isotopes we tentatively attribute the final 26 mg value to preferential uptake of 24 mg during mg for na ion exchange otherwise we find little evidence of isotopic fractionation and observe instead that 26 mg conservatively traces lithologic and hydrologic sources either isotope exchange between dolomite and water with a fractionation factor of 0 or mixing between different water sources establishes the 26 mg value of 1 40 at 20 km this value remains unchanged for the next 169 km of water transport because dolomite adds mg with an average 26 mg value near 1 40 and no other processes cause fractionation calcite precipitation is unimportant either because calcite is not a significant sink for mg or because mg uptake during calcite precipitation under conditions of chemical equilibrium does not fractionate mg isotopes this study suggests mg isotopes undergo conservative transport in carbonate rich settings where waters are in chemical equilibrium with respect to major sources and sinks of mg

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

a multi proxy approach to assessing isolation basin stratigraphy from the lofoten islands norway article i nfo article history received 14 november 2009 available online 24 september 2010 this study takes a comprehensive approach to characterizing the isolation sequence of heimerdalsvatnet a coastal lake in the lofoten islands northern norway we use established methods and explore new techniques to assess changes in marine influence bathymetric and sub bottom profiles were acquired to examine basin wide sedimentation and a 5 8 m sediment core spanning the last 7800 cal yr bp was analyzed we measured magnetic susceptibility bulk organic matter properties molecular biomarkers diatom assemblages and elemental profiles acquired by scanning x ray fluorescence these characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively isolated three distinct litho chemo stratigraphic units represent a restricted marine phase 7800 6500 cal yr bp a transitional phase characterized by intermittent marine influence 6500 4900 cal yr bp and complete isolation and freshwater sedimentation 4900 cal yr bp to present although there are uncertainties in the estimate of the threshold elevation of the lake the timing of these phases generally corresponds with previous interpretations of the local relative sea level history this record captures sea level regression following the tapes transgression and supports the interpretation of a subsequent sea level stillstand dated in heimerdalsvatnet from 6500 to 4900 cal yr bp

nineteenth and twentieth century sea level changes in tasmania and new zealand positive deviations from linear sea level trends represent important climate signals if they are persistent and geographically widespread this paper documents rapid sea level rise reconstructed from sedimentary records obtained from salt marshes in the southwest pacific region tasmania and new zealand a new late holocene relative sea level record from eastern tasmania was dated by ams14c conventional high precision and bomb spike 137cs 210pb stable pb isotopic ratios trace metals pollen and charcoal analyses palaeosea level positions were determined by foraminiferal analyses relative sea level in tasmania was within half a metre of present sea level for much of the last 6000 yr between 1900 and 1950 relative sea level rose at an average rate of 4 2 0 1 mm yr during the latter half of the 20th century the reconstructed rate of relative sea level rise was 0 7 0 6 mm yr our study is consistent with a similar pattern of relative sea level change recently reconstructed for southern new zealand the change in the rate of sea level rise in the sw pacific during the early 20th century was larger than in the north atlantic and could suggest that northern hemisphere land based ice was the most significant melt source for global sea level rise

reconstructing holocene sea level using salt marsh foraminifera and transfer functions lessons from new jersey usa we present an expanded training set of salt marsh foraminifera for reconstructing holocene relative sea level change from 12 sites in new jersey that represent varied physiographic environments seven groups of foraminifera are recognized including four high or transitional marsh assemblages and a low salinity assemblage a weighted averaging transfer function trained on this dataset was applied to a dated core from barnegat bay to reconstruct sea level with uncertainties of 14 of tidal range we evaluate the transfer function using seven tests 1 leave one site out cross validation suggests that training sets of salt marsh foraminifera are robust to spatial autocorrelation caused by sampling along transects 2 segment wise analysis shows that the transfer function performs best at densely sampled elevations and overall estimates of model performance are over optimistic 3 dissimilarity and 4 non metric multi dimensional scaling evaluated the analogy between modern and core samples the closest modern analogues for core samples were drawn from six sites demonstrating the necessity of a multi site training set 5 goodness of fit statistics assessed the validity of reconstructions 6 the transfer function failed a test of significance because of the unusual properties of some cores selected for sea level reconstruction 7 agreement between reconstructed sea level and tide gauge measurements demonstrates the transfer function s utility copyright 2013 john wiley sons ltd

paleo sea level changes and relative sea level indicators precise measurements indicative meaning and glacial isostatic adjustment perspectives from mallorca western mediterranean abstract paleo relative sea level rsl indicators formed during the marine isotope stage mis 5e have been reported by a large number of studies worldwide despite this three main aspects are seldom reported 1 use of high precision survey techniques applied to mis 5e rsl indicators 2 application of modern analogs to understand the indicative meaning of mis 5e rsl indicators 3 estimates of the effects of glacial isostatic adjustment gia on the mis 5e records in this study we show how the three points above have been addressed in a focused study on last interglacial outcrops on the island of mallorca we measured the elevation of several rsl indicators with high accuracy differential gps vertical accuracies down to 0 1 m and we established the relationship between each rsl indicator and the paleo sea level through calculation of the indicative meaning for each rsl indicator in particular we present a novel technique to calculate the indicative meaning of fossil beach deposits with a phase averaged morphodynamic model cshore we show how this approach helps overcoming difficulties with the survey of the modern analogs for these indicators our results show that two paleo rsls are imprinted in mallorca at 2 9 0 8 m and 11 3 1 0 m we then compare our field based results with modelled paleo rsl calculated from the predictions of the ice earth coupled anice selen model using few different ice sheet melting scenarios during mis 5e we conclude that indicative ranges can be derived from relatively simple morphodynamic models and that the comparison of field derived and modelled rsl values is a good method to validate possible scenarios of mis 5e sea level variability especially in absence of precise dating

explosive volcanism in complex impact craters on mercury and the moon influence of tectonic regime on depth of magmatic intrusion vents and deposits attributed to explosive volcanism occur within numerous impact craters on both the moon and mercury given the similarities between the two bodies it is probable that similar processes control this spatial association on both however the precise morphology and localization of the activity differs on the two bodies indicating that the nature of structures beneath impact craters and or volcanic activity may also be different to explore this we analyze sites of explosive volcanism within complex impact craters on the moon and mercury comparing the scale and localization of volcanic activity and evidence for post formation modification of the host crater we show that the scale of vents and deposits is consistently greater on mercury than on the moon indicating greater eruption energy powered by a higher concentration of volatiles additionally while the floors of lunar craters hosting explosive volcanism are commonly fractured those on mercury are not the most probable explanation for these differences is that the state of regional compression acting on mercury s crust through most of the planet s history results in deeper magma storage beneath craters on mercury than on the moon the probable role of the regional stress regime in dictating the depth of intrusion on mercury suggests that it may also play a role in the depth of sub crater intrusion on the moon and on other planetary bodies examples on the moon and also on mars commonly occur at locations where flexural extension may facilitate shallower intrusion than would be driven by the buoyancy of the magma alone

a consistent map of the postglacial uplift of fennoscandia a consistent map of the recent postglacial rebound of fennoscandia is constructed on the basis of sea level records lake level records and repeated high precision levellings the uplift rates calculated from the sea level series form a consistent framework of the map the sea level stations used are 56 reliable stations in the baltic sea and adjacent waters with series spanning 60 years or more many of them about 100 years using a reference station in the baltic sea and another one outside the baltic all results are reduced to a common time span the 100 year period 1892 1991 in order to eliminate oceanographic changes inland uplift differences are obtained from the repeated national levellings and in four of the large lakes from long water level series in pairs the levellings however yield less accurate land uplift values than the sea level and lake level data the resultant map shows a fairly smooth phenomenon with a maximum apparent uplift in the gulf of bothnia of 9 0 mm yr 1 the standard error is typically 0 2 mm yr i close to the sea level stations larger inland finally the pattern of the present uplift as determined here is observed to be very similar to that of the past uplift as determined from ancient shore lines of the litorina sea however the ratio between the past uplift and the present uplift rate tends to increase somewhat towards the uplift centre this might reflect a non uniform mantle viscosity also the uplift maximum seems to have migrated towards nne

physical controls and depth of emplacement of igneous bodies a review the formation and growth of magma bodies are now recognised as involving the amalgamation of successive discrete pulses such as sills sills would thus represent the building blocks of larger plutons sensu lato mechanical and thermal considerations on the incremental development of these plutons raise the issue of the crustal levels at which magma can stall and accumulate as sills reviewing the mechanisms that could a priori explain sill formation it is shown that principal physical controls include rigidity contrast where sills form at the interface between soft strata overlaid by comparatively stiffer strata rheology anisotropy where sills form within the weakest ductile zones and rotation of deviatoric stress where sills form when the minimum compressive stress becomes vertical comparatively the concept of neutral buoyancy is unlikely to play a leading control in the emplacement of sills although it could assist their formation these different controls on sill formation however do not necessarily operate on the same length scale the length scale associated with the presence of interfaces separating upper stiffer layers from lower softer ones determines the depth at which rigiditycontrolled sills will form on another hand the emplacement depths for rheology controlled sills is likely to be determined by the distribution of the weakest ductile zones whereas the emplacement depth of stress controlled sills is determined by a balance between the horizontal maximum compressive stress which favours sill formation and the buoyancy of their feeder dykes which drives magma vertically ultimately the depth at which a sill forms depends on whether crustal anisotropy or stress rotation is the dominant control i e which of these processes operates at the smallest length scale using dimensional analysis it is shown that sill formation controlled by remote stress rotation would occur on length scales of hundreds of meters or greater this therefore suggests that crustal heterogeneities and their associated anisotropy are likely to play a larger role than remote stress rotation in controlling sill emplacement unless these heterogeneities are several hundred meters or more apart this also reinforces the role of local stress barriers owing to interactions between deviatoric stress and crustal heterogeneities in the formation of sills

distributions of salt marsh foraminifera along the coast of sw california usa implications for sea level reconstructions abstract salt marsh foraminifera are frequently used around the world as proxies in paleoenvironmental studies of sea level change quantitative reconstructions of sea level change use transfer functions which are based on the vertical zonation of salt marsh foraminifera with respect to the tidal frame this paper explores for the first time the environmental factors that control the foraminiferal assemblages in southern california marshes using modern surface samples 1 cm thick from two marshes seal beach and tijuana estuary the dead foraminiferal assemblages demonstrate distinct zonation across the salt marsh surfaces which is primarily related to elevation other variables less important than elevation such as o2 temperature salinity and ph additionally control the distribution pattern of these assemblages the tidal flat and low marshes are characterized by high abundances of miliammina fusca and calcareous species the middle marsh is dominated by jadammina macrescens and trochammina inflata while the high marsh zone is dominated by trochamminita irregularis miliammina petila j macrescens and t inflata regression modelling was used for the development of a sea level transfer function based on a combined training set of surface samples from the two study sites the performance of the weighted average partial least squares wa pls transfer function suggests a robust relationship between the observed and estimated elevations r2jack 0 72 and is capable of predicting former sea levels to a precision of 0 09 m our results can be used for future paleoenvironmental reconstructions along the southern california coast an area that has experienced changes in sea level in the past and will be affected by future sea level rise coupled with climate and anthropogenic changes resulting in wide impacts on the natural coastal habitats in this region

tectonics of mascon loading resolution of the strike slip faulting paradox subsidence of lunar mascon maria impact basins partly filled with mare basalt and sites of prominent positive gravity anomalies typically led to the formation of concentric graben arcuate rilles around the flanks of the basin while compressive features mare ridges formed in interior regions although previous numerical models of the response of the lunar lithosphere to mascon loading predict that an annulus of strike slip faulting should also have formed around mascon maria no such faults have been observed this strike slip faulting paradox however arises from an oversimplification of the earlier models viscoelastic finite element models of lunar mascon basins that include the effects of lunar curvature heterogeneous crustal strength initial stress conditions and multistage load histories show that the width of a predicted annulus of strike slip faulting may be small the use of anderson s criterion for predicting fault styles may also overpredict the width of strike slip faulting a faulting style criterion that takes into account transitional faulting in which both strike slip and dip slip components are present predicts zones of pure strike slip faulting that are about half of the width predicted by the anderson criterion furthermore strike slip faulting should be observed only in regions in which flexural stresses are sufficient to induce rock failure however since stress patterns consistent with strike slip faulting around mascon loads represent a transition between compressional and extensional provinces differential stresses tend to be low in these regions and for at least part of this region are not sufficient to induce rock failure a mix of concentric and radial thrust faulting is observed in some mascon maria at odds with previous models that predict only radial orientations away from the basin center this apparent discrepancy may be partly explained by the multistage emplacement of mare basalt units a scenario that leads to a stress pattern where concentric and radial orientations of thrust faults are equally preferred detailed models of the serenitatis basin indicate a 25 km thick lunar lithosphere at the time of rille formation and a 75 km thick lithosphere at the time of late stage mare ridge formation the extent of observed mare ridges and the inferred cessation of rille formation around serenitatis prior to the time of emplacement of the youngest mare basalt units is consistent with the superposition of a global horizontal compressive stress field generated by the cooling and contraction of the lunar interior with the local stresses associated with lithospheric loading

lunar floor fractured craters classification distribution origin and implications for magmatism and shallow crustal structure 1 floor fractured craters ffcs are a class of lunar craters characterized by anomalously shallow floors cut by radial concentric and or polygonal fractures additional interior features are moats ridges and patches of mare material two formation mechanisms have been hypothesized floor uplift in response to shallow magmatic intrusion and sill formation and floor shallowing in response to thermally driven viscous relaxation this study combines new lunar orbiter laser altimeter lola and lunar reconnaissance orbiter camera lroc data to characterize and categorize the population of ffcs and map their distribution on the moon and uses variations in floor fractured crater morphology and regional distribution to investigate the proposed formation mechanisms the population of ffcs was categorized according to the classes outlined by schultz 1976 the distribution of these ffc categories shows an evolution of crater morphology from areas adjacent to lunar impact basins to areas in the lunar highlands we propose that this trend is supportive of formation by shallow magmatic intrusion and sill formation crustal thickness determines the magnitude of magmatic driving pressure and thus either piston like floor uplift for high magnitude or a convex floor profile for low magnitude predictions from previous studies modeling viscous relaxation are inconsistent with the observed altimetric profiles of ffcs hence our analysis favors ffc formation by shallow magmatic intrusion with the variety of ffc morphologies being intimately linked with location and crustal thickness and the driving pressure of the intrusion data from the grail gravity recovery and interior laboratory mission will help to test these conclusions

off rift volcanism in rift zones determined by crustal unloading when continents are stretched over a long period of time deep elongated rift valleys form at earth s surface and zones of ponded magma centred beneath the rift form at the crust mantle boundary1 2 ascending magma sometimes erupts within the rift valley3 4 or counterintuitively at volcanic fields away from the rift valley that are offset by tens of kilometres from the source of magma at depth5 6 7 8 the controls on the distribution of this off rift volcanism are unclear here we use a numerical model of magmatic dyke propagation during rifting to investigate why some dykes reach the surface outside the rift valley whereas others are confined to the valley we find that the location of magmatism is governed by the competition between tectonic stretching and gravitational unloading pressure caused by crustal thinning and faulting along the rift borders when gravitational unloading dominates over tectonic stretching forces dykes ascending from the ponded magma are steered towards the rift sides eventually causing off rift eruptions our model also predicts the formation of stacked magma sills in the lower crust above the magma ponding zone as well as the along rift propagation of shallow dykes during rifting events consistent with observations of magmatism and volcanism in rift zones globally we conclude that rift topography induced stress changes provide a fundamental control on the transfer of magma from depth to the surface

the origin of lunar concentric craters abstract lunar concentric craters are a unique class of impact craters because the interior of the craters contains a concentric ridge but their formation mechanism is unknown in order to determine the origin of concentric craters we examined multiple working hypotheses which include eight impact related and endogenic processes we analyzed data sets that originated from instruments onboard clementine kaguya and the lunar reconnaissance orbiter to characterize the morphology spatial distribution composition and absolute model ages of 114 concentric craters concentric craters contain five key properties 1 a concentric ridge 2 anomalously shallow floors 3 their occurrence is concentrated near mare margins and in mare pond regions 4 the concentric ridge composition is similar to the surrounding area and 5 concentric crater ages are eratosthenian and older these five key properties served as constraints for testing impact related and endogenic mechanisms of formation we find that most impact related hypotheses cannot explain the spatial and age distribution of concentric craters as for endogenic hypotheses we deduce that igneous intrusions are the likely mechanism that formed concentric craters because of the close relationship between concentric craters and floor fractured craters and the concentration of both features near mare highland boundaries and in mare ponds furthermore we observe that floor fractured craters are common at crater diameters 15 km whereas concentric craters are common at crater diameters 15 km produce floor fractured craters

mid to late holocene aeolian activity recorded in a coastal dunefield and lacustrine sediments on andoya northern norway in an effort to reconstruct past aeolian activity a foredune stratigraphy and a continuous lake sediment record from the largest dunefield on andoya northern norway have been investigated the dunefield extends landwards in a north eastward direction and consists of several parabolic dunes foredunes and blowouts the sediment record 169 cm from the nearby lake latjonna and the foredune stratigraphy 10 m covers the last 6200 and 3700 cal yr bp respectively both sites possess sediments deposited after the tapes transgression maximum 6800 cal yr bp which reached a level of 7 8 m a s l at the study site the lake sediment record consists of several units dominated by sand grains interspersed by more organic rich beds the core has been examined by x ray fluorescence xrf magnetic susceptibility ms and loss on ignition loi mineral grains were detected by wet sieving of the ignition residue ir and the influx of sand grains to latjonna was calculated based on the weight of sand grains