dactyl galileo observations of ida s satellite abstract galileo s flyby of 243 ida in august 1993 led to the discovery of a small satellite dactyl some 85 km from the asteroid s center from earth at mean opposition the satellite is a v 20 3 mag object some 6 7 magnitudes fainter than ida forty seven images of the satellite at 18 different observing times were played back including one multicolor sequence in which the satellite is resolved adequately to distinguish surface markings 105 m pxl and three higher resolution single color views 89 39 and 24 m pxl the satellite mean radius 0 7 km is an elongated but not angular body with principal diameters of 1 6 1 4 1 2 km in the highest resolution view the longest axis points approximately in the direction of ida and its shortest axis is perpendicular to the orbital plane the spin period is slow 8 hr and may be synchronous the satellite shows no conspicuous sharp edges and is much less irregular in shape than ida limb profiles are remarkably smooth over distances of 200 300 m the geometric albedos of the two objects are similar 0 20 vs 0 21 as are the 0 4 1 0 m colors like ida dactyl is an s asteroid but has a slightly deeper 1 m band than ida by 5 8 while no identical regions in color are seen on ida the color difference is consistent with color variations reported within the koronis family and may be due to a slightly higher pyroxene olivine ratio on the satellite more than a dozen craters ranging from 90 to 280 m diameter are visible in the best image 39 m pxl at 47 phase the largest contains an off centered positive relief feature some 75 m across the image includes an intriguing crater chain but no grooves ridges or sharp edges are evident in terms of limb roughness dactyl is much smoother than ida but comparable to the two satellites of mars phobos and deimos while the satellite s origin is uncertain a likely scenario would have the satellite date from the breakup of the koronis family it is interesting that crater densities on the satellite are similar to those on ida itself

recent estuarine sedimentation rates from shallow inter tidal environments in western scotland implications for future sea level trends and coastal wetland development during the mid late holocene large sections of the scottish coastline have been characterized by falling relative sea levels resulting from differential glacio isostatic uplift of this region of northern britain the complex interplay between crustal and sea level movements continues to influence the morphological development of the scottish coast a number of geophysical models predict ongoing uplift of the scottish landmass however a number of recent studies based upon the analysis of satellite altimetry data indicate a late 20th century acceleration in the rate of eustatic sea level rise detailed geochemistry radiometric dating and diatom analysis on selected sediment cores from four mature coastal marsh environments in argyll western scotland provides an opportunity to investigate the linkages between twentieth century crustal movements eustatic sea level rise and recent rates of sedimentation recorded within marsh sediments across the proposed scottish glacio isostatic uplift dome solid phase major and trace element geochemistry has been used to examine the extent to which post depositional physical disturbance and or chemical reactions may have influenced the reliability of the radiometric dating methods geochemical data indicate that the evolution of these marsh environments has not been significantly influenced by physical disturbance and overall the supply of minerogenic material to the marshes has been quite uniform vertical distributions of 210pbexcess and 137cs activity have been measured and used to develop models of recent marsh vertical accretion dating of the cores reveals subtle variations in the rates of sediment accumulation over the last c 70 years between sites for much of the last hundred years or so sedimentation rates have been in good overall agreement with various estimations for sea level rise although at the more easterly sites these estimates are generally exceeded however quasi equilibrium between marsh sedimentation and sea level rise for much of the twentieth century is indicated from the diatom analysis over the most recent period of marsh development 10 years a significant increase in the rate of surface sedimentation is recorded at all sites across the study area diatom analysis of these surface layers reveals an increase in the relative abundance of marine polyhalobous taxa in the near surface sediments this signifies a very recent increase in the rate of regional relative sea level rise indicating that a regional threshold in coastal forcing has now been exceeded these findings provide clear evidence that recent relative sea level rise is now outpacing estimated rates of glacio isostatic adjustment gia across the proposed scottish uplift dome

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

high strain deformation of conglomerates numerical modelling strain analysis and an example from the wutai mountains north china craton abstract conglomerates have been widely used to investigate deformation history and rheology strain vorticity and viscosity previous studies reveal that several factors such as pebble shapes and concentrations as well as material properties affect conglomerate deformation however how pebble concentration and interaction between pebbles affect deformation is not understood very well we use the 2d numerical modelling platform elle coupled to the full field crystal visco plasticity code vpfft to simulate the deformation of conglomerates with various viscosity contrasts between pebbles and matrix and different pebble concentrations with both linear stress exponent n 1 and power law n 3 viscous rheologies under simple shear conditions up to a shear strain of ten pebbles can behave as effectively passive deformable or effectively rigid an increase in pebble concentrations viscosity contrasts enhances pebble deformation but reduces their rotation a mean aspect ratio rf orientation plot is proposed to gain an estimate of pebble deformation behaviour and the amount of bulk strain closely spaced rigid or deformable pebbles can form clusters that mechanically act as single inclusions rigid clusters rotate and survive for only short strain increments whereas the more stable deformable ones keep on elongating with minor rotation we provide a natural example of deformed conglomerates from the wutai mountains north china craton these consist of banded iron formation bif pebbles embedded in a schistose matrix using the mean rf plot a finite strain of 6 under simple shear could be determined the viscosity of the pebbles is estimated at about 5 8 times that of the matrix for a linear rheology n 1 or 2 to 5 times if a power law rheology with n 3 is assumed

holocene relative sea level changes on the margin of a glacio isostatically uplifted area an example from northern caithness scotland evidence is presented for holocene relative sea level changes on the margin of a glacio isostatically uplifted area the lower wick river valley northern caithness scotland lithostratigraphic b

lateglacial and holocene relative sea level changes and first evidence for the storegga tsunami in sutherland scotland we reconstruct one of the longest relative sea level rsl records in northwest europe from the north coast of mainland scotland using data collected from three sites in loch eriboll sutherland that we combine with other studies from the region following deglaciation rsl fell from a late glacial highstand of 6 8 m od ordnance datum c mean sea level at c 15 k cal a bp to below present then rose to an early holocene highstand and remained at c 1 m od between c 7 and 3 k cal a bp before falling to present we find no evidence for significant differential holocene glacio isostatic adjustment between sites on the northwest lochinver loch laxford north loch eriboll and northeast wick coast of mainland scotland this suggests that the region was rapidly deglaciated and there was little difference in ice loads across the region from one site at the head of loch eriboll we report the most westerly sedimentary evidence for the early holocene storegga tsunami on the scottish mainland the presence of the storegga tsunami in loch eriboll is predicted by a tsunami wave model which suggests that the tsunami impacted the entire north coast of scotland and likely also the atlantic coastline of northwest scotland

holocene relative sea level changes in harris outer hebrides scotland uk evidence for relative sea level changes during the middle and late holocene is examined from two locations on the atlantic coast of harris outer hebrides scotland using morphological mapping and survey stratigraphical grain size and diatom analysis and radiocarbon dating the earliest event identified is a marine flood which occurred after 7982 8348 cal a 7370 80 14c a bp when the sea crossed a threshold lying at 0 08 m ordnance datum newlyn od 2 17 m mean high water springs mhws before withdrawing this could have been due to a storm or to the holocene storegga slide tsunami by 6407 6122 cal a 5500 60 14c a bp relative sea levels had begun to fall from a sandflat surface with an indicated mhws level of between 0 08 and 1 96 m 2 01 to 4 05 m this fall reached between 0 30 and 2 35 m 2 39 to 4 44 m after 5841 5050 cal a 4760 130 14c a bp but was succeeded by a relative sea level rise which reached between 0 54 and 1 57 m 1 55 to 3 66 m by 5450 4861 cal a 4500 100 14c a bp this rise continued possibly with an interruption until a second sandflat surface was reached between 2 34 and 0 26 m 0 25 to 2 35 m between 2952 3375 cal a 3000 80 14c a and 1948 2325 cal a 2130 70 14c a bp before present levels were reached the regressive episode from the earliest sandflat is correlated with the abandonment of the main postglacial shoreline it is maintained that the fluctuations in relative sea level recorded can be correlated with similar events elsewhere on the periphery of the glacio isostatic centre and may therefore reflect secular changes in nearshore sea surface levels despite published evidence from trim lines of differential ice sheet loading across the area no evidence of variations in uplift between the locations concerned could be found copyright 2009 john wiley sons ltd

patterns of isostatic land uplift during the holocene evidence from mainland scotland preliminary results of a lengthy and detailed investigation into middle and late holocene raised shorelines in mainland scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate the shorelines are the storegga tsunami shoreline reached at c 7100 14c years bp at the culmination of the main postglacial transgression and the blairdrummond shoreline reached after the main postglacial shoreline at c 2000 4200 14c years bp at the time of a tsunami believed to have been caused by the second storegga submarine slide the main postglacial shoreline reached at c 5800 6850 14c years bp the main postglacial shoreline previously believed to be the highest holocene raised shoreline in scotland is now believed to be overlapped around the periphery of the uplifted area by the later blairdrummond shoreline isobase models based upon quadratic trend surface analysis of available comparable height dat

mid holocene environmental changes in the bay of skaill mainland orkney scotland an integrated geomorphological sedimentological and stratigraphical study a detailed multidisciplinary investigation of intertidal freshwater sediments exposed in the north of the bay of skaill mainland orkney scotland have revealed a complex sedimentary sequence this provided evidence for dynamic coastal environmental changes in the area since the mid holocene freshwater ponds developed on glacial sediments ca 6550 80 yr bp cal bc 5590 5305 from ca 6120 70 yr bp cal bc 5040 4855 these were infilled by blown sand from the distal edge of a dune ridge located to the west thereafter a series of sand blow events alternating with periods of quiescence occurred until ca 4410 60 yr bp cal bc 3325 2900 between ca 5240 160 and 4660 80 yr bp cal bc 4370 3115 pollen and charcoal records show evidence of anthropogenic activities associated with the nearby neolithic settlement of skara brae agriculture was probably affected by recurrent sand movement and widespread deposition of calcium carbonate in the hinterland of the bay machair development between ca 6100 and 5000 yr bp cal bc 5235 3540 corresponds to a mid holocene phase of dune formation recorded elsewhere in northwest europe the more recent and progressive formation of the bay has probably been related to increasing external forcing via storminess long term relative sea level change and sediment starvation within this exposed environment copyright 2000 john wiley sons ltd

boulder size and shape distributions on asteroid ryugu abstract in 2018 the japanese spacecraft hayabusa2 arrived at the small asteroid ryugu the surface of this c type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study using a few hundred optical navigation camera onc images with a pixel scale of approximately 0 65 m we focus on boulders greater than 5 m in diameter smaller boulders are also considered using five arbitrarily chosen onc close up images with pixel scales ranging from 0 7 to 6 cm across the entire surface area 2 7 km2 of ryugu nearly 4400 boulders larger than 5 m were identified boulders appear to be uniformly distributed across the entire surface with some slight differences in latitude and longitude at 50 km 2 the number density of boulders larger than 20 m is twice as large as on asteroid itokawa or bennu the apparent shapes of ryugu s boulders resemble laboratory impact fragments with larger boulders being more elongated the ratio of the total volume of boulders larger than 5 m to the total excavated volume of craters larger than 20 m on ryugu can be estimated to be 94 which is comparatively high these observations strongly support the hypothesis that most boulders found on ryugu resulted from the catastrophic disruption of ryugu s larger parent body as described in previous papers watanabe et al 2019 sugita et al 2019 the cumulative size distribution of boulders larger than 5 m has a power index of 2 65 0 05 which is comparatively shallow compared with other asteroids visited by spacecraft for boulders smaller than 4 m the power index is even shallower and ranges from 1 65 0 05 to 2 01 0 06 this particularly shallow power index implies that some boulders are buried in ryugu s regolith based on our observations we suggest that boulders near the equator might have been buried by the migration of finer material and as a result the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes

late devensian and holocene relative sealevel changes at loch nan eala near arisaig northwest scotland pollen diatom radiocarbon and lithostratigraphical data from isolation basins in northwest scotland are used to quantify the reference water tide level indicative range and age of differenty types of isolation and connection contacts tendencies of sea level movement and relative sea level changes from the mid lateglacial interstadial 11 8 ka bp to the late holocene are constructed from these data relative sea level fell continuously from 17 8 m od at 11 8 ka bp to ca 5 2 m od at 10 1 ka bp from an unkown minimum between 10 ka and 9 ka bp relative sea level then rose to 6 3 m od at 8 3 ka bp the maximum holocene sea level occurred within the range 6 6 m od to 9 3 m od between 6 6 ka bp and 4 0 ka bp before falling to present isobase age altitude and quantitative rebound models for northwest scotland are tested using these sealevel data but none of the published models shows close agreement with the new results

geology of 243 ida abstract the surface of 243 ida is dominated by the effects of impacts no complex crater morphologies are observed a complete range of crater degradation states is present which also reveals optical maturation of the surface darkening and reddening of materials with increasing exposure age regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely bound surface materials diameter depth ratios for fresh craters on ida are 1 6 5 similar to gaspra results but greater than the 1 5 ratios common on other rocky bodies contributing causes include rim degradation by whole body ringing relatively thin ejecta blankets around crater rims or an extended strength gradient in near surface materials due to low gravitational self packing grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts evidence for the presence of debris on the surface includes resolved ejecta blocks mass wasting scars contrasts in color and albedo of fresh crater materials and albedo streaks oriented down local slopes color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene olivine ratio a large relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from azzurra rather than representing internal compositional heterogeneity a small number of bluer brighter craters are randomly distributed across the surface unlike on gaspra where these features are concentrated along ridges this implies that debris on ida is less mobile and or consistently thicker than on gaspra estimates of the average depth of mobile materials derived from chute depths 20 60 m grooves 30 m and shallowing of the largest degraded craters 20 50 m minimum 100 m maximum suggest a thickness of potentially mobile materials of 50 m and a typical thickness for the debris layer of 50 100 m

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

patterns of holocene relative sea level change in the north of britain and ireland temporal and spatial patterns of relative sea level rsl change in the north of britain and ireland during the holocene are examined four episodes each defined by marked changes in the rsl trend are identified each episode is marked by a rise to a culminating shoreline followed by a fall episode hrsl 1 dates from the younger dryas to early in the holocene hrsl 2 to hrsl 4 occurred later in the holocene there is extensive evidence for each episode and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the holocene storegga slide tsunami ca 8110 100 cal bp is analysed ordinary kriging is used to determine the general pattern following which gaussian trend surface analysis is employed recognising that empirical measurements of rsl change can be unevenly distributed spatially a new approach is introduced which enables the developing pattern to be identified the patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines the analyses described provide models of the spatial pattern of holocene rsl change in the area between ca 8100 cal bp and ca 1000 cal bp based on 2262 high resolution shoreline altitude measurements these models fit the data closely no shoreline altitude measurement lying more than 1 70 m or 1 82 m from the predicted value the models disclose a similar pattern to a recently published glacial isostatic adjustment model for present rsl change across the area indicating that the overall spatial pattern of rsl change may not have varied greatly during the last ca 8000 years

a 7600 year sedimentary record of climatic instability in dunnet bay north scotland abstract we present a partial reconstruction of ne atlantic climatic variability the first based on stratigraphic evidence obtained from a vegetated dune system of the northern scottish coast the dune system at dunnet bay is fringed by prominent submerged peat deposits exposed only at low tide which record stable climatic periods when lower energy wind regimes prevailed allowing the formation of organic soils by contrast periods of sand influx are associated with high energy conditions the majority of sand material tested had a narrow range of particle sizes and major element composition supporting the interpretation of a common aeolian origin sand layers were dated with optically stimulated luminescence osl and peat layers were 14 c dated in four cores c1 c4 and seven sample sections s1 s7 the results from the two master sections s1 and s2 1 km apart indicate synchronous episodes of climatic stability 7650 6310 4340 4000 2690 2290 100 0 cal a bp and instability 6310 4340 4000 2690 2290 2000 170 100 cal a bp in spite of very different mean accumulation rates at the two sites 1 mm a 1 at s1 and 0 2 mm a 1 at s2 phases of sand deposition i e aeolian activity at dunnet tend to be associated with high average levels of chloride in the greenland ice sheet project 2 ice core gisp2 phases of peat development show a fairly good correspondence with low ice rafting activity in the ne atlantic and with indicators of wetness measured from a peat bog in sw sweden by contrast comparison of the dunnet depositional timeline with other regional studies e g hebrides and orkney shows little synchronicity this suggests that a local scale variables have a strong effect on regional patterns of dune instability and b the geological and geographic settings of dunnet bay mean that only large climatic regime shifts in the ne atlantic are capable of triggering instability and being preserved in the depositional record

erratum holocene coastal environmental changes on the periphery of an area of glacio isostatic uplift an example from scapa bay orkney uk the first detailed investigation of a deep coastal sedimentary basin in orkney reveals a complex holocene history of back barrier morphodynamics at scapa bay the sea flooded a freshwater marsh after ca 9400 yr bp at ca 5 4 m od before ca 7800 bp abundant sediment from nearby cliffs was mobilised inland into a series of gravel barriers across the valley mouth by ca 7500 bp direct marine influence was restricted in the back barrier area although saltmarsh persisted until ca 5900 bp by then at least four gravel ridges had enclosed the backing lagoon where freshwater inputs became dominant as terrestrial sediments filled the basin another freshwater marsh developed the multiple barrier complex demonstrates progradation resulting from continuous sediment supply in a sheltered embayment the progressively rising height of the barrier crests seawards probably resulted from a combination of factors such as barrier morphodynamics increased storminess and long term rising relative sea levels the dominant vegetation surrounding scapa bay changed from open grassland to scrub ca 9400 bp then to deciduous woodland ca 7800 bp and to dwarf shrub heath ca 2600 bp the latter probably a response to a combination of climate change and human activity copyright 2007 john wiley sons ltd

evaluation of holocene crustal movement in the ako plain western japan holocene sea level observations have been obtained from the ako plain in western japan in this coastal area the holocene crustal movements have been evaluated except the crustal response due to the last deglaciation by comparing observations and theoretical predictions of relative sea level rsl variations analyses of diatom assemblages and sedimentary sulphur in core sediments were used along with radiocarbon dates to derive the rsl variations a crustal movement rate between 0 2 mm and 0 2 mm per year corrected for the prediction fits well with the observed rsl index points owing to the constraint of the reconstructed palaeo mean sea level pmsl at 7300 cal bp the coast of the ako plain may have the best estimate of a tectonic subsidence rate of 0 0 2 mm yr the tectonic uplift rates along the tectonically active coast of western kobe were derived to be 0 3 0 7 mm yr and 0 11 0 45 mm yr for tarumi and tamatsu respectively relative to ako over the period concerned the relative uplift along the traverse from ako to western kobe is primarily the result of the crustal movement resulting from the active faulting of the rokko awaji fault system rfs

late devensian and holocene records of relative sea level changes in northwest scotland and their implications for glacio hydro isostatic modelling raised tidal marshes and isolation basins lakes that were once connected to the sea in northwest scotland record changes in relative sea level following deglaciation during the late devensian to the present the kentra to arisaig area which was covered by relatively thick ice c 900 m at the last glacial maximum lgm shows a regression from a marine limit between 36 5 m od and 40 m od at c 15 9 kyr cal bp range 15 6 16 3 kyr cal bp through to an early holocene minimum a range of sites in the same area record a mid holocene maximum indicative of mean sea level c 6 5 m above present the maximum is not a well developed and short duration highstand as predicted by a number of models but is an extended period 8 0 5 0 kyr cal bp with sea level within c 1 m of the maximum sites to the north in kintail show no late devensian record because much of the area lies within the younger dryas ice limit the altitude of the mid holocene maximum in kintail is not well constrained but occurred 7 9 8 1 kyr cal bp further north sites on the applecross peninsula record a late devensian fall in sea level and a holocene maximum for mean sea level no higher than c 3 0 m above present in coigach the furthest north of the new sites and well outside the younger dryas ice limit there is no evidence recorded of late devensian sea levels above present the holocene maximum here was around c 2 5 m above present these observations of sea level change all standardised to change in mean sea level relative to present constrain the glacio hydroisostatic rebound model parameters earth models comprising three mantle layers with lateral viscosity and elastic parameters give a satisfactory description of rebound the parameters h lithosphere thickness 65 km g 6 upper mantle viscosity 4 1020 pa 14c seconds and g lower mantle viscosity 1022 pa 14c seconds give the best overall agreement but discrepancies between observations and predictions remain an increase of 10 in ice thickness north of the great glen compared to the previous optimum ice model provides good agreement for many sites but important discrepancies remain for the northern sites and indicate inadequacies in the model of the british ice sheet several alternative ice models are examined but the various combinations of earth and ice model illustrate the non uniqueness of the solution a combination of more extensive ice limits especially onto the hebridean shelf and west shetland shelf and some changes to ice thicknesses over the mainland should produce a better agreement but the spatial coverage of observations remains a limitation to producing a unique solution the characteristics of the holocene highstand age duration and amplitude at the di erent sites refutes the assumption that globally deglaciation ceased abruptly 7000 yr ago the observations are consistent with an ice model that includes c 3 m of melting over the last 7000 yr 2000 elsevier science ltd all rights reserved

detecting crater ejecta blanket boundaries and constraining source crater regions for boulder tracks and elongated secondary craters on eros abstract we present results of a numerical model of the dynamics of ejecta emplacement on asteroid 433 eros ejecta blocks represent the coarsest fraction of eros regolith and are important readily visible tracer particles for crater ejecta blanket units that may be linked back to specific source craters model results show that the combination of irregular shape and rapid rotation of an asteroid can result in markedly asymmetric ejecta blankets and it follows ejecta block spatial distribution with locally very sharp distinct boundaries we mapped boulder number densities in near shoemaker msi images across a portion of a predicted sharp ejecta blanket boundary associated with the crater valentine and confirm a distinct and real ejecta blanket boundary significant at least at the 3 sigma level using our dynamical model we back track the landing trajectories of three ejecta blocks with associated landing tracks in an effort to constrain potential source regions where those blocks were ejected from eros surface in impact events the observed skip distances of the blocks upon landing on eros surface and the landing speeds and elevation angles derived from our model allow us to estimate the coefficient of restitution e of eros surface for impacts of 10 m scale blocks at approximately 5 m s 1 impact speeds we find mean values of e of approximately 0 09 0 18

late devensian and holocene relative sea level changes on the isle of skye scotland uk detailed litho and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the isle of skye scotland uk reveal evidence for several changes in relative sea level during the late devensian and holocene at the start of the record relative sea level in the area was high at ca 12 500 14c ca 14 800 cal yr bp but then fell reaching a low point during the younger dryas at ca 11 000 10 000 14c ca 13 000 11 600 cal yr bp when a rock platform correlated with the main rock platform was formed in the early middle holocene relative sea level was rising by ca 8000 14c ca 8800 cal yr bp and in northeast skye a lagoonal surface correlated with the main postglacial shoreline was formed at ca 6600 14c ca 7500 cal yr bp by the late holocene relative sea level was again falling but a rise registered at at least two sites began probably before ca 4000 14c ca 4500 cal yr bp and a second lagoonal surface in northeast skye correlated with the blairdrummond shoreline was formed although by ca 3000 14c ca 3200 cal yr bp relative sea level in the area had resumed its downward trend the pattern of relative sea level changes disclosed is compared with evidence elsewhere in scotland

glacial rebound and sea level change in the british isles observations of sea levels around the coastline of the british isles for the past 10 000 15 000 years exhibit a major regional variation and provide an important data base for testing models of glacial rebound as well as models of the late devensian ice sheet a high resolution rebound model has been developed which is consistent with both the spatial and temporal patterns of sea level change and which demonstrates that the observations are the result of i the glacio isostatic crustal rebound in response to the unloading of the ice sheet over britain and to a lesser degree of the ice sheet over fennoscandia and ii the rise in sea level from the melting late pleistocene ice sheets including the response of the crust to the water loading the hydro isostatic effect the agreement between model and observations is such that there is no need to invoke vertical crustal movements for great britain and ireland of other than glacio hydro isostatic origin the rebound contributions are important throughout the region and nowhere is it sufficiently small for the sea level change to approximate the eustatic sea level rise the observational data distribution around the periphery as well as from sites near the centre of the former ice sheet is sufficient to permit constraints to be established on both earth model parameters specifying the mantle viscosity and lithospheric thickness and the extent and volume of the ice sheet at the time of the last glaciation preliminary solutions are presented which indicate an upper mantle viscosity of 3 5 1020 pas a lithospheric thickness of about 100 km or less and an ice model that was not confluent with the scandinavian ice sheet during the last glaciation and whose maximum thickness over scotland is unlikely to have exceeded about 1500 m

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

the sedimentology of middle holocene tsunami facies in northern sutherland scotland uk abstract lagoonal sediments attributed to the main holocene marine transgression in strath halladale northern sutherland contain a complex coarser layer believed to have been deposited during the tsunami associated with the second storegga slide off south west norway the coarser sequence is dated at between 7590 50 and 7290 50 radiocarbon years bp 6507 6260 cal bc and 6228 6029 cal bc detailed stratigraphical analysis has determined a distinctive suite of sedimentary sub units within the coarser layer in marked contrast to the sediments which occur above and below a pronounced erosional unconformity with the underlying sediments is recorded with the base of the tsunami layer characterised by eroded material from the underlying peat the presence of a mixed diatom assemblage although fragmentary indicates a chaotic accumulation of the deposit with all habitats represented variations in particle size within the sequence disclose striking similarities with those from contemporary tsunami deposits the run up of the tsunami sediments is calculated at a minimum of 4 6 m this is the first occasion on which a deposit of the second storegga slide tsunami has been found outside the north sea basin and indicates that the area affected by the tsunami may have been larger than has been previously described

ejecta blocks on 243 ida and on other asteroids abstract seventeen positive relief features 45 150 m across are identified as probable blocks in galileo high resolution images of ida their presence provides direct evidence for regolith retention on asteroids the spatial distribution maximum size and integrated volume of the blocks are consistent with those of blocks associated with craters on the earth the moon phobos and deimos the concordance suggests that the features are impact ejecta fragments and that cratering mechanics on ida an object of average diameter 32 km are similar to those applying on previously studied rocky bodies the blocks that lie within or near the rims of craters lascaux and mammoth were likely mobilized in the low velocity tail portion of the excavation flow that formed those craters a few blocks located near smaller craters may have migrated some distance away from their source possibly by impact induced spallation hopping rolling and or sliding some blocks on ida could be surviving fragments from the koronis parent body accreted after its breakup the lifetime of 102 m sized boulders against collisional disruption is estimated to be in the 108 109year range consistent with ages considered for the largest and oldest craters on ida extrapolation of successful ejecta scaling laws to other asteroids suggests that blocks 15 and 70 m across could be present on dactyl and gaspra respectively in both cases too small to be identified in available galileo images blocks 100 m in size could be present on 433 eros and km sized megablocks on 4 vesta

holocene uplift derived from relative sea level records along the coast of western kobe japan abstract mid to late holocene sea level observations have been obtained from tamatsu and tarumi in western kobe japan in this tectonically active area we evaluate the local tectonic effect during the holocene by comparison between observations and predictions of sea level variations for the purpose of this study we analysed the diatom assemblages and carried out sulphur analysis of sediments these were used along with radiocarbon dates to derive relative sea level variations for the sites a rate of tectonic uplift of between 0 1 and 0 3 mm per year corrected for the prediction fits well with relative sea level rsl index points of tamatsu at 6415 5320 cal bp depending on the altitude of the rsl index point at about 5700 cal bp the best estimate of the rate of tectonic uplift for tamatsu is calculated as 0 11 0 25 mm yr over the period concerned a rate of tectonic uplift between 0 3 and 0 5 mm per year is derived for tarumi at about 7300 and 3835 3365 cal bp these values may explain the height distributions of the late pleistocene marine terraces along the coast of the western kobe providing a first approximation for rates of local crustal movements during the late quarternary

holocene coastal evolution and uplift mechanisms of the northeastern raukumara peninsula north island new zealand abstract the coastal geomorphology of the northeastern raukumara peninsula new zealand is examined with the aim of determining the mechanisms of holocene coastal uplift elevation and coverbed stratigraphic data from previously interpreted coseismic marine terraces at horoera and waipapa indicate that despite the surface morphology there is no evidence that these terraces are of marine or coseismic origin early holocene transgressive marine deposits at hicks bay indicate significant differences between the thickness of preserved intertidal infill sediments and the amount of space created by eustatic sea level rise therefore uplift did occur during early holocene evolution of the estuary the palaeoecology and stratigraphy of the sequence shows no evidence of sudden land elevation changes beach ridge sequences at te araroa slope gradually toward the present day coast with no evidence of coseismic steps the evolution of the beach ridges was probably controlled by sediment supply in the context of a background continuous uplift rate no individual dataset uniquely resolves the uplift mechanism however from the integration of all evidence we conclude that holocene coastal uplift of this region has been driven by a gradual aseismic mechanism an important implication of this is that tectonic uplift mechanisms do vary along the east coast of the north island this contrasts with conclusions of previous studies which have inferred holocene coastal uplift along the length of the margin was achieved by coseismic events this is the first global example of aseismic processes accommodating uplift at rates of 1 mm yr 1 adjacent to a subduction zone and it provides a valuable comparison to subduction zones dominated by great earthquakes

ejection of rock fragments from planetary bodies the recent discovery of alha81005 a small meteorite that undoubtedly came from the moon has raised questions about how an intact rock fragment could survive acceleration to planetary escape velocities this acceleration could only have been produced by a large impact on the lunar surface a small amount of material 0 005 to 0 02 projectile volume may be ejected from an impact crater at speeds exceeding lunar escape velocity without suffering petrographically detectable shock damage the ejected material is protected by stress wave interference close to the free surface the existence and size of this zone depend upon parameters such as the rise time of the stress pulse produced by an impact the fragment size is a function of ejection velocity the lunar meteorite was ejected during an impact event that produced a crater at least 3 6 km in diameter other meteorites may have originated in a similar way

distribution geomorphology and lithofacies of cliff top storm deposits examples from the high energy coasts of scotland and ireland abstract cliff top storm deposits ctsds occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles this study examines the distribution geomorphology and lithofacies of ctsds at sites from shetland orkney caithness and the outer hebrides in scotland and from the aran islands in galway bay in ireland ctsds are generated largely by the quarrying of blocks from the cliff top and transported by green water bores across cliff top platforms and ramps to be deposited in backing ridges or as debris spreads maximum boulder sizes reach 48 m 3 but it is likely that much larger blocks can be quarried prior to disintegration during transport eye witness accounts and field mapping demonstrate that formation and modification of ctsds has continued during major storms over recent decades recent ctsds bury a range of man made debris but older deposits lack this and instead show weathering effects that indicate a longer residence time in shetland osl dates on intercalated sands suggest that the oldest ctsds date from 800 ad radiocarbon dates on shell buried inside ctsd ridges relate to major storms between 1700 and 1900 ctsds represent an overlooked archive of storm sedimentation that has great potential for the elucidation of local storm chronologies ctsds also provide evidence of wave impacts on any part of the cliff face or top in fundamental contrast to the concentration of wave action at the cliff foot implicit in traditional models of the erosion of rock coasts

bulk density of asteroid 243 ida from the orbit of its satellite dactyl during its reconnaissance of the asteroid 243 ida the galileo spacecraft returned images of a second object 1993 243 1 dactyl1 the first confirmed satellite of an asteroid sufficient data were obtained on the motion of dactyl to determine its orbit as a function of ida s mass here we apply statistical and dynamical arguments to constrain the range of possible orbits and hence the mass of ida combined with the volume of ida2 this yields a bulk density of 2 6 0 5 g cm 3 allowing for the uncertainty in the porosity of ida this density range is consistent with a bulk chon dritic composition and argues against some but not all classes of meteoritic igneous rock types that have been suggested as compositionally representative of s type asteroids like ida

towards improved empirical isobase models of holocene land uplift for mainland scotland uk a new approach to modelling patterns of glacio isostatic land uplift during the holocene in mainland scotland uk is described the approach is based upon altitude measurements at the inner margin or locally highest point of raised estuarine surfaces dated by radiocarbon assay supported by microfossil analyses 2241 altitudes have been analysed by a technique new to studies of former sea levels gaussian trend surface analysis and isobase models for four holocene shorelines the holocene storegga slide tsunami shoreline abandoned rapidly circa 7900 sidereal years bp the main postglacial shoreline abandoned during circa 6400 7700 sidereal years bp the blairdrummond shoreline abandoned during circa 4500 5800 sidereal years bp and a speculative fourth shoreline the wigtown shoreline abandoned during circa 1520 3700 sidereal years bp are shown in a series of maps the implications of the shoreline patterns for glaicio isostasy in the area are discussed it is maintained that the statistical technique used enables broad estimates to be made of nearshore sea surface change

flandrian relative sea level changes in the ythan valley northeast scotland relict flandrian estuarine deposits in the ythan valley are confined to an area in the lower valley around the present estuary they rest upon a discontinuous layer of peat over an irregular surface of sand and gravel and consist for the most part of a grey silty clay or carse deposit which forms terraces or small areas of carseland at the seaward end of the estuary the grey silty clay contains a layer of grey micaceous silty fine sand which tapers into the basal peat whilst in places the surface of the grey silty clay is covered by peat and or blown sand the vegetational context and age of these deposits have been determined at waterside near the mouth of the present estuary here the grey silty clay accumulated as the result of a marine transgression which began in the early flandrian and culminated between about 6189 95 and some time prior to 4000 80 radiocarbon years b p the carseland surface produced by this phase of accumulation is the highest flandrian estuarine surface in the valley at about 4 5 m o d and is correlated with the main postglacial shoreline elsewhere in eastern scotland withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached though this is far from certain the grey micaceous silty fine sand layer is dated at approximately 6850 140 radiocarbon years b p and is correlated with similar layers that may have been deposited following a storm surge the paper concludes with some considerations on the age and distribution of the main postglacial shoreline in eastern scotland

on the postglacial isostatic adjustment of the british isles and the shallow viscoelastic structure of the earth summary observations of postglacial relative sea level rsl history at sites beyond the margins of the main accumulations of wu rm wisconsin devensian ice may be invoked to test the accuracy of global models of the glacial isostatic adjustment process the existing database of rsl time series for the british isles forms a continuous network of sites that sample the coasts of scotland england and wales fairly uniformly and which may be especially important in this regard not only are these 14c data for the holocene epoch of very high quality in terms of our knowledge of the coastal environment and relationship to palaeo sea level of each age measurement but they are especially numerous and relate to an island that was itself partly glaciated in the north essentially ice free in the south and located well outboard of the massive ice sheet that covered fennoscandia at the last glacial maximum lgm taken together the time series from 55 distinct locations allow us to perform a fairly stringent test of the recently formulated ice 4g vm2 global model of the isostatic adjustment process even without modification this model has been shown to fit most of the time series in the uk data set rather well in order to satisfy very recently published a priori constraints on the maximum thickness of the scottish ice sheet however we find that the lithospheric thickness the feature of the radial viscoelastic structure to which the rebound data from scotland are most sensitive must be somewhat reduced whereas the assumed thickness of the lithosphere in ice 4g vm2 was near to 120 km best fits to the scottish data require a lithospheric thickness near to 90 km this reduced value for lithospheric thickness agrees exceedingly well with the latest estimates of this earth property based on the inversion of oceanic geoid and topography data as the asymptotic thickness characteristic of the oldest ocean floor this would appear to be the best possible a priori estimate for the thickness of the cratonic lithospheres upon which the largest ice sheets of the late pleistocene are known to have rested we also demonstrate explicitly that inferences of the shallow viscoelastic structure beneath the british isles are strongly influenced by the details of the history of deglaciation at remote locations at antarctica in particular

archaeology of the continental shelf marine resources submerged landscapes and underwater archaeology we provide a critical review of the evidence for the long term use of marine resources and coastal environments in human evolution and later development we emphasise the importance of the coastal archaeological record in understanding patterns of human settlement and dispersal and draw attention to the large potential biases introduced by the destructive or obscuring effects of pleistocene sea level change we note that lowered sea levels have been the norm for most of the pleistocene and that periods of high sea level have been too short lived to provide other than a fragmentary coastal record and one that is beset with ambiguities and uncertainties we examine the geological processes of coastal uplift and underwater preservation that may help to mitigate these biases coastlines elevated by isostatic and tectonic processes or with very steep offshore drop offs at plate boundaries are important in providing a potential window into coastal landscapes and archaeology formed during periods of lowered sea level however we conclude that the opportunities afforded by these geological factors are too limited to obviate the need for underwater exploration we review the evidence now available from submerged landscapes across the africa eurasia interface from the atlantic coastlines of northwest europe to the southern red sea we show that geomorphological conditions for the preservation of archaeological and palaeoenvironmental data are commonly present that much material has already been discovered and that new techniques technologies and projects are providing the momentum for a rapidly expanding field of investigation the results do not simply add to what we already know from sites on land but are likely to produce qualitatively different evidence for coastal adaptations and landscapes that have no analogue on present day coastlines we note the strong probability that many coastal landscapes exposed at lowered sea level provided relatively fertile and productive refugia for plants land mammals and humans at a time when increased aridity would have reduced or deterred hinterland occupation we conclude that underwater investigation is essential if hypotheses of early human adaptation and dispersal are to be fully tested

rapid holocene relative sea level changes in gruinart isle of islay scottish inner hebrides litho and biostratigraphic analyses undertaken in the gruinart estuary central islay reveal a detailed sedimentary record of holocene relative sea level changes and high energy flood events during the last 10 000 years during the lateglacial holocene transition relative sea level had fallen to below c 0 5 m od and remained at this depth until c 8830 14c years bp thus the early holocene minimum sea level is here relatively well constrained altitudinally a sustained and largely uninterrupted rise in relative sea level took place after c 8500 14c years bp reaching a maximum altitude of c 4 5 m od and remained at an elevation of c 4 m od until c 2000 14c years bp both the recorded maximum altitude of the main holocene transgression and the late age of the relative marine regression are incompatible with published shoreline uplift isobase models for this area

the storegga slides evidence from eastern scotland for a possible tsunami abstract the second storegga slide on the continental slope off western norway has been dated at between 8000 and 5000 yrs b p a prominent sand layer in flandrian holocene deposits along the coast of eastern scotland and dated at approximately 7000 yrs b p may have been deposited by a tsunami generated by the slide the altitude and stratigraphy of the layer allow estimates to be made of the magnitude of the earthquake which initiated the slide

holocene relative sea level changes in a glacio isostatic area new data from south west scotland united kingdom abstract this paper contributes to knowledge of holocene relative sea level change along the mainland ayrshire coast and offshore isle of bute sw scotland uk where few such studies have previously been undertaken morphological studies mapping and altitude survey together with stratigraphical and biostratigraphical studies pollen and diatom analyses and radiocarbon dating disclose evidence for mid and late holocene relative sea level changes the main postglacial and blairdrummond displaced shorelines previously identified widely in mainland scotland are dated in the area at c 6800 calibrated years c 6000 14c years and c 4200 calibrated years c 3800 14c years bp respectively this information is compared with previously published information for scotland against the classical theoretical model of relative sea level change in areas of glacio isostasy for the mid and late holocene in conformity with the model a falling sequence of relative sea level changes near the centre of uplift is replaced by a rising sequence towards the periphery in which later shorelines overlap earlier ones in particular the blairdrummond shoreline which overlaps the earlier main postglacial shoreline is identified as the highest holocene shoreline over much of the coastline of scotland

relative sea level change and evidence for the holocene storegga slide tsunami from a high energy coastal environment cocklemill burn fife scotland uk a site in the cocklemill burn valley on the north shore of the firth of forth scotland provides evidence of relative sea level changes during the holocene from ca 7970 to ca 5090 radiocarbon years bp and of the holocene storegga slide tsunami dated here as having taken place after ca 7215 radiocarbon years bp marine sediments associated with two shorelines widely present in mainland scotland the main postglacial shoreline and the blairdrummond shoreline are recorded the holocene storegga slide tsunami deposits are unique here in the record of such sediments in eastern scotland in that they occur within marine sands of which the upper horizons are intertidal sandflat deposits the tsunami deposits probably accumulated shortly after a period of accelerated relative sea level rise the pattern and timing of which could have played a role in triggering the holocene storegga slide

late devensian and holocene relative sea level changes in northwestern scotland new data to test existing models abstract pollen diatom lithostratigraphic and radiocarbon data from five sites in northwestern scotland provide new data from an area previously devoid of reliable and precise information on late devensian and holocene sea level changes the sites cover a range of palaeoenvironments indicative of diversity in coastal evolution since deglaciation for each site and palaeoenvironment the reference water tide level indicative range age and tendency of sea level movement of all sea level index points are quantified to enable correlation of the diverse coastal environments the data record patterns of relative sea level change and tendencies of sea level movement from 12 ka bp to 1 ka bp this is the longest and most comprehensive published record of relative sea level change from the area the information is used to test the accuracy of existing models of relative sea level change the results are only broadly consistent with a quantitative rebound model and there is significant disagreement with empirical models during the late devensian and the early holocene

the altitude and age of the main postglacial shoreline in eastern scotland abstract this paper discusses the patterns of altitude and age variation of the main postglacial shoreline in eastern scotland from the firth of forth to the dornoch firth for reasons of comparability attention is confined to the carseland areas the mean altitude of the shoreline declines eastwards from 14 8 m to 6 1 m od in the forth area from 11 2 m to 8 1 m in the earn tay area and northwards up the coast from the tay area to ca 6 4 m in the montrose basin area ca 3 9 m around the ythan estuary and ca 2 0 m near fraserburgh in the beauly firth inner moray firth area it declines northeastwards from ca 9 m to 7 1 7 9 m and declines to 5 7 m in the dornoch firth the isobase pattern for eastern scotland as represented by a quadratic trend surface conceals a significant regional variation in the tay area the age of the shoreline has been investigated at 14 sites grouped in 8 locations at varying distances from the centre of uplift the ages range from ca 6800 14c years bp in the upper forth carselands to 6095 75 5700 90 bp near fraserburgh with the exception of one site the data are consistent with the hypothesis that the shoreline is measurably diachronous having been abandoned progressively later with increasing distance from the centre of uplift the implications of these findings for understanding isostatic eustatic relationships are discussed

linking tsunami deposits submarine slides and offshore earthquakes abstract the recognition that many tsunamis are associated with coastal sedimentation has been of great value in the study of tsunamis prehistorically geological investigation of such sediments has resulted in the identification of a series of palaeotsunamis that appear to have taken place in different areas of the world in most cases however it has proved difficult to link former tsunamis to specific source mechanisms studies of modern tsunamis have also faced difficulties in the recognition of the specific source mechanisms for example offshore earthquakes may trigger submarine slides that combine to produce complex patterns of tsunami flooding at the coast

a tsunami ca 6300 years bp and other holocene environmental changes northern hawke s bay new zealand abstract sediment cores collected in a coastal lagoon a few kilometres east of wairoa northern hawke s bay new zealand were examined using sedimentological geochemical palynological and micropaleontological analyses a distinct short lived catastrophic saltwater inundation csi about 6300 years bp and possibly other minor marine incursions are preserved in the coastal estuarine to lagoonal freshwater sedimentary sequences which have been deposited in the last 6500 years the csi is characterised by a gravel unit that thins landward and decreases in particle size to sand within a sequence consisting mainly of brackish estuarine muds diatom assemblages indicate a marked change from the shallow brackish estuarine muds to marine gravels and sands to brackish estuarine muds the marine influence in the gravel and sand is also shown by the presence of marine dinoflagellates and a peak in na rb sedimentological chemical and paleontological in particular diatoms evidence indicates it is a csi we conclude that this was a tsunami and propose the most likely propagating mechanisms marine influence decreases upcore and totally freshwater conditions are evident in the upper section of the cores the geochemistry of the sediments mainly reflects the change in stratigraphy with distinct signatures for tephra na fe cr organic rich and peat units as br and the coarse gravel sand csi unit na rb cr fe but it is also indicative of changes in depositional environment the change in chemistry na rb in the csi event is indicative of a saltwater influence whereas a marked change in s content suggests a sudden change from brackish to freshwater conditions shortly after 4800 years bp another peak in s and br content about 3200 years bp may indicate another temporary change to brackish conditions

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

holocene relative sea level changes in the inner solway firth abstract bio and lithostratigraphic data from four sites from the inner solway firth allow an accurate reconstruction of holocene rsl changes in the estuary radiocarbon assays give eleven new sea level index points providing a total of 24 reliable index points for the inner solway firth these data show a consistent pattern of rapid rsl rise during the early holocene culminating in a mid holocene sea level maximum then a gradual fall to the present day level detailed analysis of this dataset quantifies for the first time differential crustal movement between the north and south shores of the solway firth these data are used to test the accuracy of quantitative isostatic rebound models of lambeck and peltier and show there is good general agreement between the data and the models especially during the early holocene the models predict the mid holocene sea level peak slightly later than shown by the data c 500 and c 2000 yr this may be partly due to lack of resolution in the models and for the south solway the maximum altitude at this peak is 1 and 2 5 m too high in the two models the data are also compared to the isobase models of the main postglacial shoreline showing slight diachroneity between the north and south shore but otherwise general agreement with the postulated age and indicating that the altitude of this feature is 1 3 m higher than suggested by the models

first images of asteroid 243 ida the first images of the asteroid 243 ida from galileo show an irregular object measuring 56 kilometers by 24 kilometers by 21 kilometers its surface is rich in geologic features including systems of grooves blocks chutes albedo features crater chains and a full range of crater morphologies the largest blocks may be distributed nonuniformly across the surface lineaments and dark floored craters also have preferential locations ida is interpreted to have a substantial regolith the high crater density and size frequency distribution 3 differential power law index indicate a surface in equilibrium with saturated cratering a minimum model crater age for ida and therefore for the koronis family to which ida belongs is estimated at 1 billion years older than expected

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd