implications for caledonian plate tectonic models of chemical data from volcanic rocks of the british old red sandstone volcanic rocks associated with the continental sediments known as the old red sandstone outcrop widely in northern britain and form a dominantly calc alkaline suite comparable to those developed on modern continental margins rocks rich in ni and cr are unusually abundant and are thought to have incompatible element concentrations little different from those of primary magmas such rocks show pronounced spatial chemical variation with concentrations of sr ba k light rare earth elements and p 2 o 5 and the ratio la y showing up to a six fold increase in a northwestward traverse across scotland in more evolved rocks a similar increase is shown by sr ba and la y but regional comparisons are made difficult by the varying effects of fractional crystallization the chemistry of all old red sandstone volcanic rocks n of the southern uplands fault is consistent with the former existence of a subduction zone that changed in strike from ene in ireland and southern scotland to n in the north sea this orientation in conjunction with almost e w plate motion may explain the great contrast in end silurian deformation styles between britain and scandinavia old red sandstone volcanic and plutonic rocks s of the southern uplands fault are thought to be younger and are perhaps unrelated to subduction activity

dolomitic breccia veins as evidence for extension and fluid flow in the dalradian of argyll veins of red dolomite occur extensively in the dalradian rocks of argyll scotland and adjacent areas the veins represent brittle extensional deformation preferentially reactivating caledonian quartz veins the dolomite is associated with reddening of the adjacent dalradian country rock which it partially replaced dolomite was also precipitated in overlying old red sandstone and probably dates to late carboniferous early permian fluid inclusion studies show that the veining involved moderate temperature 75 to 115 c fluids stable isotope data suggest that these fluids were basinal brines traces of chalcopyrite paragenetically late in the veins may reflect the mineralization which occurs more widely in the dalradian rocks of argyll the red colour of the dolomite is due to abundant haematite crystallites that grew in the dolomite crystal fabric palaeomagnetic analysis yields a consistent late permian early triassic age for the haematite growth in the dolomite veins and the reddened dalradian country rocks this age represents the time of haematite precipitation from iron rich dolomite that may have been related to deep oxidizing weathering gold anomalies associated with reddened basement rock must be of this age or younger

sea level changes in the tectonically stable malay thai peninsula abstract the malay thai peninsula is part of sundaland a geological region of relative crustal stability therefore the positions of old shorelines of the past 20 000 years or so can be considered to indicate positions of actual past sea levels over 200 shoreline indicators at positions below as well as above present sea level have been radiocarbon dated these dated positions indicate that prior to 6 ka the sea rose from at least 90 m below present sea level at rates that initially amounted to 15 mm year and later became 6 mm year at ca 6 ka the rising sea surpassed its current position and at ca 5 ka it reached 5 m during this maximum marine inundation the peninsula was narrower since the low coastal plains did not yet exist in the period following this maximum transgression the available shoreline data indicate that regional sea level subsided through a series of fluctuations that were characterized by amplitudes of 2 m and periods of about 2000 years the peaks and troughs of the fluctuations became progressively lower the latest peak was at about 1 7 m or 0 7 m above present high tide a few hundred years ago the cause of these fluctuations is not yet known but the trend suggests that in the near future regional sea level may subside at annual rates between 1 5 mm and 2 mm this rate of descent is 25 to 30 of the estimated rate of sea level rise that may result from global warming in other words for the malay thai peninsula the effect of sea level rise on account of manmade greenhouse gases will be partly compensated by actual subsidence of regional sea level

modelling a paleo valley glacier network using a hybrid model an assessment with a stokes ice flow model modelling paleo glacier networks in mountain ranges on the millennial timescales requires ice flow approximations hybrid models calculating ice flow by combining vertical shearing shallow ice approximation and longitudinal stretching shallow shelf approximation have been applied to model paleo glacier networks on steep terrain yet their validity has not yet been assessed quantitatively moreover hybrid models consistently yield higher ice thicknesses than last glacial maximum geomorphological reconstructions in the european alps here we compare results based on the hybrid parallel ice sheet model pism and the stokes model elmer ice on the rhine glacier a catchment of the former european alpine icefield for pism we also test two magnitudes of flux limitation in a scheme that reduces shearing velocities we find that the flux limitation typically used in pism yields significantly reduced shearing speeds and increases ice thicknesses by up to 500 m partly explaining previous overestimations however reducing the ice flux limitation allows the hybrid model to minimize this mismatch and captures sliding speeds ice thicknesses ice extent and basal temperatures in close agreement with those obtained with the stokes model

magnetic polarity stratigraphy of the tertiary igneous rocks of skye scotland summary palaeomagnetic results are given for 115 sites mainly from the central igneous intrusive complex and also radiometric dates by the 40ar 39ar step heating method these are combined with published dates and palaeomagnetic results for the lavas and regional dyke swarms with the aim of establishing the magnetic polarity stratigraphy igneous activity spanned at least the approximate interval 61 54 ma and a polarity sequence of at last r n r n r but could span seven polarity intervals r n r n r n r depending on the age of the loch ainort epigranite however these polarities cannot be identified with specific chrons of either the harland et al 1982 or berggren et al 1985 polarity time scales the skye igneous activity therefore spans more polarity intervals than in mull ardnamurchan or rhum and this is consistent with the radiometric ages interpretations of the results for the coire uaigneich and related granites and for the loch ainort epigranite present problems and partial solutions are offered

shore platform downwearing in eastern canada the mega tidal bay of fundy abstract laboratory and field work was conducted to determine rates of surface downwearing on shore platforms at two sites in the bay of fundy canada these data are needed to assess and model the effect of downwearing mechanisms on platform evolution sandstone and basalt samples 900 were exposed to semidiurnal tidal cycles over 3 years using de ionized water or artificial sea water they were immersed for 1 6 or 11 h over each 12 h tidal cycle representing the lowest high lht mid and highest low hlt tidal levels respectively a further 600 samples were immersed in de ionized water or artificial sea water for 90 min every 1 2 or 3 weeks representing increasingly higher elevations above the lht level or exposed for 90 min every 1 2 or 3 weeks representing increasingly lower elevations below the hlt level these experiments ran for 12 months in the field surface downwearing was measured at 108 transverse micro erosion meter tmem stations over 2 to 6 year periods in the laboratory mean downwearing rates between the lht and hlt levels were 0 61 1 80 mm yr 1 in sandstones and 0 01 0 18 mm yr 1 in basalts rates were highest at the lht level rates decreased with elevation above the lht level and were uniformly low below the hlt level salt weathering was dominant above the lht level salt weathering and wetting and drying were important in sandstones between the lht and hlt levels but salts inhibited rock breakdown in basalts in the field the mean downwearing rate was 1 254 mm yr 1 in sandstones which was similar to the experimental data and 0 722 mm yr 1 in basalts which was much higher than in the experiments with artificial sea water but similar to the experiments with de ionized water there was no relationship in the field between downwearing rate and rock hardness or tmem station elevation

shallow shelf approximation as a sliding law in a thermomechanically coupled ice sheet model 1 the shallow shelf approximation a balance of membrane stresses for ice flow is an effective sliding law for ice sheet modeling our use of it as a sliding law becomes a standard model for ice stream flow when the sliding velocity is large 100 m a 1 and faster following schoof 2006a we describe the basal resistance as plastic till for which the yield stress is given by a mohr coulomb formula pore water pressure is related to basal melt rate the velocity field used in the mass continuity and conservation of energy equations is an average of velocities from the shallow shelf approximation and the nonsliding shallow ice approximation using this scheme our model has realistic time dependent ice streams which exhibit the range of surface velocities seen in actual ice streams we demonstrate the model at high spatial resolution 5 km grid over multiple millenia using its implementation in the parallel ice sheet model numerical experiments show that the entire scheme is stable with respect to many parameter changes some experiments reveal significant ice stream variability in a hypothetical steady climate with characteristic cycles on the order of 1000 years we believe this is the first practical whole ice sheet model with a unified treatment of vertical shear stresses and membrane stresses it is capable of high resolution thermomechanically coupled multimillenia simulations of ice sheets containing ice streams

palaeozoic palaeomagnetic results from scotland and their bearing on the british apparent polar wander path abstract palaeomagnetic studies of the lower and upper old red sandstone ors western midland valley indicate the presence of two principal remanence components ib and hb both components can be demonstrated to be of secondary post upper ors origin component ib compares with palaeomagnetic results from upper carboniferous permian dykes and sills in the midland valley whereas hb conforms to palaeomagnetic results from the overlying lower carboniferous lavas a combination of hb components from the lower upper ors and lower carboniferous lavas western midland valley yields a relative pole position near s14 and e322 which compares well with lower carboniferous data from the kinghorn and burntisland lavas eastern midland valley s14 and e332 from kinghorn the palaeomagnetic data can be demonstrated to be of primary lower carboniferous origin seen in conjunction with the british polar wander path the lower carboniferous poles reported here seemingly dissociate middle upper devonian and upper silurian lower devonian poles owing to the lack of magnetic age control in the middle upper devonian data base it is argued that the majority of middle upper devonian data from the british isles should be reconsidered as carboniferous magnetic overprints this carries the implication that any tectonic models based on middle upper devonian palaeomagnetic results should be considered highly suspicious

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

application of a polythermal three dimensional ice sheet model to the greenland ice sheet response to steady state and transient climate scenarios abstract steady state and transient climate change computations are performed with the author s three dimensional polythermal ice sheet model simulation code for polythermal ice sheets for the greenland ice sheet the distinctive feature of this model is the detailed consideration of the basal temperate ice layer in which the water content and its impact on the ice viscosity are computed its transition surface to the cold ice region is accounted for by continuum mechanical jump conditions on this interface the simulations presented include steady states subject to a range of physical parameters and two different climates present and glacial conditions as well as three types of transient scenarios namely i sinusoidal milankovic period forcing ii paleoclimatic forcing from the greenland ice core project core reconstruction and iii future greenhouse warming forcing

current variability on a narrow shelf with large ambient vorticity signals respectively and with corresponding phase speeds of 0 85 and 1 7 m s 1 the phase trend in east west direction of the 10 hour signal is consistent with unstable growing waves the 10 and 27 hour signals appear dominantly barotropic near the coast out to depths of at least 50 m but the 10 hour signal displayed a 180 phase change between surface and bottom farther away from the shelf break at 160 m depth the two dominant signals cannot be attributed to barotropic instability index terms 4219 oceanography general continental shelf processes 4520 oceanography physical eddies and mesoscale processes 4572 oceanography physical upper ocean processes keywords shelf circulation florida current vorticity flow instability surface doppler radar

syn orogenic alkaline magmatism and its relationship to the moine thrust zone and the thermal state of the lithosphere in nw scotland the alkaline complexes of nw scotland lie in a zone sub parallel to the moine thrust and represent the nw edge of the otherwise overwhelmingly calc alkaline late orogenic magmatism of the caledonian fold belt the emplacement of intrusives in assynt overlapped the thrust movements and new u pb zircon ages for the loch ailsh intrusion 439 4 ma provide are liable bracket when combined with existing age data for the loch borralan intrusion 430 4 ma for the main movements on the ben more thrust plane a detailed history of the main tectonic and igneous events in the moine thrust zone is tabulated zircons from the undeformed cnoc nan cuilean syenite emplaced in moine rocks near loch loyal give an age of 426 9 ma in contrast to the deformed glen dessary syenite for which earlier work gave 456 5 ma the linear distribution of the alkaline complexes to the west of the calc alkaline plutons and the ultra potassic character of the loch borralan complex the most westerly are consistent with but do not prove generation related to a w dipping subduction zone the persistence of the magmatism over 30 ma in a belt being shortened by thrusting suggests a source in the mantle lithosphere the absence of magmatism further to the nw and the production of calc alkaline magmas to the se of this zone is compatible with a model in which the thermal state of the lithosphere exercises the most important control on the nature of late caledonian magmatism

tidal notches in mediterranean sea a comprehensive analysis abstract recent works evelpidou et al 2012 suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century in order to assess this hypothesis we measured modern tidal notches in several of sites along the mediterranean coasts we report observations on tidal notches cut along carbonate coasts from 73 sites from italy france croatia montenegro greece malta and spain plus additional observations carried outside the mediterranean at each site we measured notch width and depth and we described the characteristics of the biological rim at the base of the notch we correlated these parameters with wave energy tide gauge datasets and rock lithology our results suggest that considering the development of tidal notches the consequence of midlittoral bioerosion as done in evelpidou et al 2012 is a simplification that can lead to misleading results such as stating that notches are disappearing important roles in notch formation can be also played by wave action rate of karst dissolution salt weathering and wetting and drying cycles of course notch formation can be augmented and favoured also by bioerosion which can in particular cases be the main process of notch formation and development our dataset shows that notches are carved by an ensemble rather than by a single process both today and in the past and that it is difficult if not impossible to disentangle them and establish which one is prevailing we therefore show that tidal notches are still forming challenging the hypothesis that sea level rise has drowned them

multiphase magnetic overprints in the moine thrust zone palaeomagnetic studies from the southern part of the moine thrust zone mtz indicate a complex pattern of four major secondary remanence components a d their relative ages appear to vary from mid ordovician to recent tertiary the oldest remanence a is tentatively interpreted as associated with the formation of the lochalsh syncline dl and or d2 however the consistency between component a and the regional southeast plunging lineation makes it uncertain to what extent component a reflects the structural grain rather than a true palaeofield record component b appears to be associated with early devonian uplift along the mtz relating to localized shearing high level brittle thrusting and is almost synchronous with the emplacement of lamprophyre and felsic dykes in the inverted limb of the lochalsh syncline and beneath the balmacara thrust possible permian component c and recent tertiary magnetic overprints are recognized component c is partly of high magnetic stability and may indicate localized shears in the inverted limb usually considered as caledonian shearing it is uncertain to what extent the youngest component d essentially recorded in rocks close to the balmacara thrust in mylonites and fault breccias reflects important tectonic reactivation and magnetic resetting this component is governed by low stability magnetic phases with blocking temperatures below 200 c

holocene tectonic uplift patterns in northeastern sicily evidence from marine notches in coastal outcrops abstract marine notches are groove like features formed in rocky coastal outcrops in relation to past sea levels and are widely used as indicators of rates and patterns of tectonic activity examination of uplifted notches in the complex plate boundary setting of northeast sicily reveals the need for considerable care in their interpretation present notch forming processes are dominated by carbonate dissolution aided by microbial activity as waves surge and recede at the base of the cliffs and produce notches approximately 0 5 m above present biological mean sea level i e above an organic constructional rim of coralline algae used to define sea level at sea level dissolution is restricted through saturation and the bedrock protected by the outbuilding algal rim this assemblage varies in response to fetch exposure and uplift rate typically producing a complex band of uplifted notch features exposed above sea level correlations based on height of the shallow and discontinuous notch indentations within this band are unreliable however the upper margin of the band marked by the roof of the uppermost notch is a prominent and laterally persistent feature easily recognised as the boundary between subaerial and marine processes we propose that this is an approximately coeval datum formed when post glacial sea level rise decelerated in the mid holocene to match the rate of tectonic uplift a notion strengthened by the available dates of about 5 ka for this feature subsequent uplift outpaced later sea level rise taking the notches above sea level this proposed datum varies in height from about 2 m at capo milazzo on the north coast to about 5 m on the east coast bordered by the messina fault system the height differential is consistent with the respective elevations of nearby marine terraces dating from the last interglacial at about 125 ka but also exhibits shorter term variations suggesting holocene increases in activity rates on more localised structures affecting the localities involved regionally northeast sicily is characterised by long term differential uplift rather than behaving as a coherent block the highest uplift rate probably exceeding 2 mm a 1 calculated using the sea level curve from fairbanks r g 1989 a 17000 year glacio eustatic sea level record influence of glacial melting rates on the younger dryas event and deep ocean circulation nature 342 637 642 is suggested for a notch locality on the upthrown side of the malta escarpment rates of about 2 mm a 1 are indicated by the 5 m notch at localities bordered by the messina fault system and a rate close to 1 mm a 1 is suggested for the undated 2 m notch at capo milazzo

preservation of mesoproterozoic age deep burial fluid signatures nw scotland abstract bedding parallel fibrous calcite is a widely developed feature of mudrock successions reflecting conditions of fluid overpressure stoneley 1983 parnell et al 2000 cobbold et al 2013 the calcite preserves signatures of fluids developed during deep burial including hydrocarbons most studied examples are of phanerozoic

on estimating length fluctuations of glaciers caused by changes in climatic forcing the reaction of alpine glaciers to shifts in the equilibrium line altitude ela is calculated by using a two dimensional numerical model to solve the full equations for the velocity and stress fields full system model in the absence of basal motion rates of advance and retreat of the snout of typically sized alpine glaciers are found to be insensitive to the details of the flow at the snout even when the glaciers are far from steady state a comparison of results obtained with a full system model and a shallow ice approximation sia model yields no significant differences in advance or retreat rates this assumption has been implicitly made in numerous previous climatic studies and is here shown to be well justified using a realistic mass balance altitude feedback only slight model dependent changes in steady state lengths are found the relative importance of mass balance and glacier dynamics for the transient response of alpine glaciers to changes in the ela is given a precise meaning by determining the model dependent additional shifts in ela needed for the sia and the full system models to produce identical changes in length for alpine glaciers these additional shifts in ela are on the order of 10 m which is within the error range of ela estimates it follows that at least in the absence of significant basal motion there is no need to include the effects of horizontal stresses when calculating the reaction of alpine glaciers to climatic changes attention should focus on accurate determination of the mass balance distribution and model tuning to give realistic ice thickness distributions

thermal effects and timing of thrusting in the moine thrust zone illite crystallinity studies in the foreland to the moine thrust belt show a widespread heating event which is interpreted as a thermal response to thrust sheet emplacement temperatures reached 275 c approximately 24 ma after the main thrusting events based on the relationships between syn thrusting intrusions and the thrust planes combined with radiometric dates from the moine sheet it is argued that movement on the moine thrust started between 440 and 430 ma ago contractional slip in the moine thrust belt ceased at about 425 ma ago and it is proposed that illite metamorphism attained temperatures of 275 c at about 408 ma ago

short term rock surface expansion and contraction in the intertidal zone transverse micro erosion meter tmem stations were installed in rock slabs from shore platforms in eastern canada the slabs were put into artificial sea water for 1 6 or 11 hours representing high mid and low tidal areas respectively the tmems were used to record changes in surface elevation as the rocks dried during the remainder of the 12 h of a semi diurnal tidal cycle a similar technique was used on the same rock types at intertidal tmem stations in the field as the rocks dried during low tide argillite and basalt surface contraction was from 0 to 0 04 mm there was little surface expansion sandstones contracted by up to 0 03 mm in the field but there was almost no contraction in the laboratory argillite and basalt contraction tended to be greatest in the upper intertidal zone and to increase with rates of longer term surface downwearing but there was little relationship with rock hardness or air temperature and humidity changes in elevation at the same points at tmem stations in the laboratory and field were quite consistent from one tidal cycle to the next but there were considerable variations within single tidal cycles between different points within each station the data suggest that contraction within the elevational zone that is normally submerged twice a day by the tides is by alternate wetting and drying short term changes in elevation are generally low compared with annual rates of downwearing owing to erosion but they may generate stresses that contribute to rock breakdown copyright 2007 john wiley sons ltd

improvement of a 2 d sia ice flow model application to glacier de saint sorlin france a number of improvements have been made to an existing two dimensional ice flow model applied to an alpine glacier analysis of the results of the existing model revealed several shortcomings the first concerns the lack of mass conservation of the applied alternating direction implicit adi scheme a semi implicit si scheme is therefore proposed and the effects on mass conservation assessed by a comparison with the adi scheme the comparison is first carried out with a simple theoretical glacier for which the improvement is significant concerning the real case of glacier de saint sorlin france the initial deviation in mass conservation was much less pronounced such that the new scheme although improving mass conservation does not significantly change the modelled dynamics however other shortcomings that have a more profound impact on the modelling of glacier behaviour have been identified the ice thickness may become negative over some gridpoints leading to an inconsistency the problem is partly resolved by incorporating extra checks on critical gridpoints at the glacier border finally with the help of ice particle tracking unrealistic ice settlement above the bergschrund has been identified as the main reason for spurious dynamic effects and has been corrected

restraining bend tectonics in the santa cruz mountains california imaged using 10be concentrations in river sands reverse faults frequently generate large and destructive earthquakes yet their seismic hazard remains diffi cult to assess with traditional paleoseismic tools because their surface expressions are often complex and subtle this contribution assesses the utility of millennial scale denudation rates derived from in situ cosmogenic 10be for revealing the spatial patterns and magnitudes of rock uplift produced by slip along reverse faults we present seventeen basin averaged denudation rates from rivers draining the santa cruz mountains along the san andreas fault california usa which closely reproduce known uplift rate patterns associated with a restraining bend along the fault an additional component of vertical deformation appears to be superposed on the uplift due to the restraining bend this may result from regional transpression further irregularities in the fault trace or interactions with neighboring faults our results indicate that 10be derived denudation rates can reveal patterns of rock uplift adjacent to reverse faults over length scales relevant for characterizing their seismic hazard potential

last interglacial sea level high stand deduced from well preserved abrasive notches exposed on the galilee coast of northern israel abstract this study investigates the morphometry and structure of abrasive notches exposed along the tectonically stable micro tidal galilee coast israel south eastern mediterranean since they can serve as past sea level indicators the characteristics of the notches height h vertex d distance of maximum retreat point from cliff face height of retreat point from the floor and roof h f and h r respectively etc were surveyed using lidar and a digital laser rangefinder and elevations were measured using dgps rock resistance was measured by schmidt hammer tests which show that the most developed and best preserved notches were formed within the more resistant host rocks of the cenomanian chalk and the pleistocene aeolianite sandstone the elevations of the abrasive floors of the exposed notches indicated a sea level slightly higher than at present at the beginning of mis5e with an upper limit between 0 5 and 0 75 m the morphometry of the mis5e notches which are larger than modern notches in the study area suggests mechanical erosion by broken waves where an energetic wave dominant sea batters a sheltered coastal cliff two sub units of mis5e the yasaf mb were deposited within the notches a a conglomerate containing the diagnostic fossil strombus bubonius which was found on the notch floor and b a younger bioclastic sandstone sub unit which fills and covers parts of the notches these unique field relationships link the formation of the notches to the beginning of mis5e indicating an erosive phase which parallels large scale mis5e sea level evidence suggesting relatively long stand stills at an elevation of about 1 m the early mis5e erosive phase was followed by a depositional phase during the later stage of mis5e

anomolous multi origin marine notch sites three case studies in the central mediterranean sea abstract we present and discuss the genesis age and evolution of indented landforms carved at sea level in correspondence of carbonatic headlands in three sites of the central mediterranean coasts between marseille france and balzi rossi italy the island of tavolara sardinia italy and the promontory of tindari sicily italy the shape of these anomalous notches landforms can be referred to is very similar to tidal notches despite their genesis and morphometric parameters are different from those suggested by other authors for the central mediterranean area two of these sites are located in tectonically stable areas while the third falls is located in an uplifting area those the notches we investigated along the coast of southern france are submerged notch type landforms located in the vicinities surroundings of current modern tidal notches at tavolara island these anomalous notches are placed at about 25 m b s l these landforms and have the shape of mushroom like notches finally those investigated along the metamorphic carbonatic promontory of tindari are marine and abrasional notches that have been uplifted likely during the holocene

multiple fluid migration events along the moine thrust zone scotland a palaeomagnetic study of different lithologies exposed along the moine thrust zone from skye to durness scotland has identified three chemical remanent magnetizations crms a potential fourth crm and one possible primary component that all reside in hematite local and regional fold tests suggest that the crms are post folding and post thrusting a contact test in the torridon group sandstone indicates that a permian crm is localized in and near the fault zone the permian crm which is also found in the durness group and associated alteration are direct evidence for post orogenic activity in which the thrusts vented excess heat during regional crustal extension on the isle of skye sandstones sleat torridon and eriboll groups in and around the fault zone contain a tertiary crm interpreted to be related to hydrothermal fluids associated with tertiary intrusions a possible mesozoic crm is also present but it could represent the vector addition of the permian and tertiary crms a devonian crm is interpreted to be related to hydrothermal fluids associated with devonian volcanic rocks or to fluids triggered by late stages of the caledonian orogeny geochemical and petrographical studies provide supporting evidence for multiple fluid flow events along the moine thrust zone these results show that palaeomagnetism can be used to date multiple fluid migration events and that dormant fault zones can act as conduits for flow

evolution and opening of closed depressions developed in a quartz kaolinitic sedimentary substratum at taubate basin sao paulo brazil and analogy to the slope evolution abstract the occurrence of dated peat 17 000 12 500 yr b p in the soil in a closed depression in quartz kaolinitic rocks of the taubate basin brazil allowed 1 reconstruction of the evolution of this depression and 2 estimation of the rate of sinking the analogy with the soil cover of a slope in the same area has shown that this valley developed by the same mechanisms as those of the depression chemical erosion is the main agent for the generation of landforms in this region

uplift of oahu hawaii during the past 500 k y as recorded by elevated reef deposits studies of paleo sea level and past climate have focused upon proxy methods in ice and deep sea cores and more direct information provided by past shorelines in some cases preserved as raised or submerged reef deposits in tropical areas paleo shorelines need to be constrained by accurate tectonic history because these environments and their marine deposits can be confused with past tsunami deposits and vice versa a maximum 21 m high extensive emerged reef on oahu hawaii u series dated to 334 17 ka together with a mean u series age of 335 22 ka n 5 for slightly higher energetic shoreline deposits nearby suggest a marine isotope stage 9 mis 9 highstand and extend the earlier work indicating a linear uplift for oahu of 0 060 0 001 mm yr over the past 500 k y five of the past six major emerged interglacial highstand reefs on oahu have been identified and these data provide little evidence for past maximum sea levels significantly greater than 2 m above the sea level datum at that time there is currently no evidence for a mis 11 highstand on oahu

new structural and re os geochronological evidence constraining the age of faulting and associated mineralization in the devonian orcadian basin scotland the devonian orcadian basin in northern scotland belongs to a regionally linked system of post caledonian continental basins extending northwards to western norway and eastern greenland extensional fault systems that cut the orcadian basin sequences are commonly assumed to be devonian with some limited inversion and reactivation proposed during the carboniferous and later times we present a detailed structural study of the regionally recognized fault systems exposed in the dounreay area of caithness which host significant amounts of authigenic mineralization carbonate base metal sulphides bitumen structural and microstructural analyses combined with re os geochronology have been used to date syndeformational fault infills pyrite suggesting that faulting brecciation and fluid flow events are likely to have occurred during the permian 267 5 3 4 3 5 ma stress inversion of fault slickenline data associated with mineralization suggest nw se regional rifting an episode also recognized farther west in sutherland thus a dominant set of permian age brittle faults is now recognized along the entire north coast of scotland forming part of the regional scale north coast transfer zone located on the southern margin of the offshore west orkney basin supplementary material onshore and offshore fault and fracture lineament data are available at https doi org 10 6084 m9 figshare c 2182433

assessing subsidence rates and paleo water depths for tahiti reefs using u th chronology of altered corals we present uranium thorium chronology fora 102 m core through a pleistocene reef at tahiti french polynesia sampled during iodp expedition 310 tahiti sea level we employ total and partial dissolution procedures on the older coral samples to investigate the diagenetic overprint of the uranium thorium system although alteration of the u th system cannot be robustly corrected diagenetic trends in the u th data combined with sea level and subsidence constraints for the growth of the corals enables the age of critical samples to be constrained to marine isotope stage 9 we use the ages of the corals together with o based sea level histories to provide maximum constraints on possible paleo water depths these depth constraints are then compared to independent depth estimates based on algal and foraminiferal assemblages microbioerosion patterns and sedimentary facies confirming the accuracy of these paleo water depth estimates we also use the fact that corals could not have grown above sea level to place a maximum constraint on the subsidence rate of tahiti to be 0 39 m ka with the most likely rate being close to the existing minimum estimate of 0 25 m ka

tidal and storm influenced sedimentation from a cambrian transgressive passive margin sequence the basal cambrian clastic sediments in northwest scotland record a transgressive sequence of barrier island to tidal shelf quartz arenites eriboll sandstone lower member and pipe rock overlain by a storm dominated interval of mixed clastic carbonate sediments fucoid beds two shallowing events interrupt this sequence the lower near the middle of the pipe rock and the upper at the top of the fucoid beds which led to the deposition of the quartz arenites of the salterella grit variations in the proportion of storm deposited facies and in the thickness of tidally generated structures suggests that tidal currents progressively increased during deposition of the quartz arenites and then decreased until deposition of the mixed clastic carbonate deposits these features suggest amplification of tides as the shelf approached a resonant width during transgression further transgression produced a wide non resonant shelf where tides were frictionally damped and storm processes were dominant similar sequences of the same age in western newfoundland eastern greenland and spitsbergen may also have been produced by the shelf bordering the north american craton responding to tidal amplification followed by frictional damping

weathering rates on a caribbean reef limestone results and implications abstract weathering of presently raised reef islands provides an analogue for the behaviour of pleistocene reefs made emergent by glacio eustatic falls in sea level micro erosion meter measurements on grand cayman island west indies have shown that high mean weathering rates 1 00 mm yr 1 are restricted to the marine environment large scale landform development is unlikely to have been the product of the last period of exposure but rather the result of successive phases of weathering and reef growth increasing the differential relief of the reef base throughout the pleistocene

petroleum generation and migration in the cambro ordovician laurentian margin succession of nw scotland fluid inclusion and organic biomarker data show that there was formerly a hydrocarbon system in the cambro ordovician laurentian margin rocks of nw scotland oil fluid inclusions occur in stylolitized eriboll formation sandstone in k feldspar cements with an 40 ar 39 ar age of 415 5 5 5 8 ma 2 analytical precision full external precision organic extracts from durness group black limestones yield biomarker ratios characteristic of high thermal maturity organic maturation to yield oil probably occurred during orogenic deformation along the moine thrust zone the recognition of a hydrocarbon system in scotland adds to a huge hydrocarbon province in laurentian rocks including north america and greenland supplementary material technical data for ar ar dating are available at https doi org 10 6084 m9 figshare c 3879616

surface swelling of coastal bedrock on inter tidal shore platforms kaikoura peninsula south island new zealand this paper reports the occurrence of swelling of coastal bedrock measured with a traversing micro erosion meter tmem on inter tidal mudstone and limestone shore platforms while numerous micro erosion meter mem studies have been made only a small number have reported surface swelling during this study 24 055 measurements were made with a tmem of those 4047 indicated swelling or 17 of the total number of measurements vertical swelling of up to 8 9 mm was measured and values of 3 and 4 mm were common swelling displayed a complex pattern with minor swelling being superimposed on longer period episodes duration of swelling events in excess of 697 days were recorded while other events were commonly in the order of 3 to 4 months there is a distinct seasonal variation with greater and more frequent swelling occurring during summer months compared with winter explanation for swelling includes the growth of salt crystals in rock lattices and expansion from wetting and drying warm summer temperatures provide the best conditions for both processes swelling appears to be an important precursor to erosion of material from shore platform surfaces the conclusion drawn is that subaerial weathering makes an important contribution to the lowering of the shore platforms on the kaikoura peninsula

devonian extensional tectonics versus carboniferous inversion in the northern orcadian basin the old red sandstone middle devonian orcadian basin was formed as a consequence of extensional collapse of the caledonian orogen onshore study of these collapse basins in orkney and shetland provides directions of extension during basin development the origin of folding of old red sandstone sediments that has generally been related to a carboniferous inversion phase is discussed syndepositional deformation supports a devonian age and consequently some of the folds are related to basin formation large scale folding of devonian strata results from extensional and left lateral transcurrent faulting of the underlying basement spatial variation of extension direction and distribution of extensional and transcurrent tectonics fit with a model of regional releasing overstep within a left lateral megashear in nw europe during late caledonian extensional collapse later inversion probably during the upper carboniferous is characterized by e w to ne sw contraction it induced reactivation of extensional faults as thrusts development of small scale folds and thrusts and right lateral transcurrent movement of the major faults such as the great glen and walls boundary faults

shore platform downwearing in eastern canada micro tidal gaspe quebec abstract work has been conducted in the laboratory and field on a micro tidal subhorizontal shore platform in argillaceous rocks at mont louis in gaspe quebec surface downwearing rates for 450 rock samples were measured over 3 years in the laboratory at the neap low mid and high tidal levels under semi diurnal tidal conditions de ionized water was used to determine the role of wetting and drying and artificial sea water for the additional effect of salt and possibly chemical weathering another 300 samples were immersed in de ionized water or artificial sea water for 90 min every 1 2 or 3 weeks representing conditions between the neap and spring high tidal levels and exposed in air for 90 min every 1 2 or 3 weeks to represent conditions between the neap and spring low tidal levels surface downwearing was recorded in the field at 34 transverse micro erosion meter tmem stations most of which were installed along 4 shore normal profiles in 2004 and 2005 mean downwearing rates in the laboratory ranged from 1 25 mm yr 1 at the neap high tidal level to 0 63 mm yr 1 at the neap low tidal level downwearing was much slower between the neap and spring tidal levels and it was uniformly slow below the neap low tidal level the presence of salts inhibited downwearing within the neap tidal range where wetting and drying was dominant and promoted it between the neap and spring high and low tidal levels surface swelling was fairly common in the field and the mean downwearing rate 0 242 mm yr 1 was much lower than in the laboratory possibly because the tmem stations were installed in harder rocks modeling supports the contention that the mont louis platform was cut initially by waves at a higher elevation and then lowered by weathering in the last few thousand years as relative sea level fell to its present elevation

an enthalpy formulation for glaciers and ice sheets polythermal conditions are ubiquitous among glaciers from small valley glaciers to ice sheets conventional temperature based cold ice models of such ice masses cannot account for that portion of the internal energy which is latent heat of liquid water within temperate ice so such schemes are not energy conserving when temperate ice is present temperature and liquid water fraction are however functions of a single enthalpy variable a small enthalpy change in cold ice is a change in temperature while a small enthalpy change in temperate ice is a change in liquid water fraction the unified enthalpy formulation described here models the mass and energy balance for the three dimensional ice fluid for the surface runoff layer and for the subglacial hydrology layer together in a single energy conserving theoretical framework it is implemented in the parallel ice sheet model results for the greenland ice sheet are compared with those from a cold ice scheme this paper is intended to be an accessible foundation for enthalpy formulations in glaciology

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

geological constraints structural evolution and deep geology of the northwest scottish caledonides the front of the caledonian orogenic belt in nw scotland is marked by a zone of foreland thrusting which contains imbricates of lewisian basement proterozoic cover and cambrian shelf sediments faults within this moine thrust belt in most localities propagated in a foreland directed sequence therefore the earliest of these thrusts was the moine thrust which carried a basement assemblage of moine and lewisian rocks over the cambrian shelf the development of large duplex and imbricate structures in the footwall postadted movement on this thrust hence a restoration of these imbricates provides a minimum estimate of the eastern extent of the cambrian shelf no synsedimentary or prethrust extensional features are recognised within the cambrian succession which displays a remarkable stratigraphic and thickness consistency this implies a corresponding consistency in crustal structure beneath these cover rocks immediately prior to caledonian thrusting a balanced cross section constructed across the northern part of the moine thrust belt has given a restored width for the cambrian shelf of 54 km geophysical data suggest that the present foreland crustal thickness is 28 km if this is taken to be the crustal thickness beneath the cambrian shelf during caledonian thrusting a minimum cross sectional area of 1512 km of lewisian rocks must remain beneath the present outcrop of the moine thrust sheet this foreland basement wedge may have been imbricated subsequent to the development of the cambrian imbricates caledonian structures within the moine thrust sheet are interpreted as forming an imbricate stack with the moine thrust acting as a floor thrust the ductile imbricate thrusts possibly roofed into the naver slide late open folds which warp foliation slides and metamorphic isograds within the moine sheet may represent culminations in the foreland lewisian imbricates beneath the moine thrust these postulated culminations may have been sufficient to initiate gravity driven structures this may explain late movements on high level faults within the moine thrust belt

late holocene shorelines in east attica greece abstract a coastal and submarine geomorphological investigation took place in the coasts of eastern attica aiming to identify palaeoshorelines former sea level positions were deduced from emerged and submerged tidal notches eight fossil shorelines were deduced in the study area two emerged ones at about 24 30 and 40 30 cm and six submerged ones at about 22 30 modern 40 30 60 30 80 30 130 30 and 460 30 cm it is worth mentioning that a rather different tectonic behavior may be distinguished between the south at1 at5 and the north at10 at28 part of the study area

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

use of a new 10be and 26al inventory method to date marine terraces santa cruz california usa marine terraces along active continental margins reflect the interplay between sea level oscillations and rock uplift well dated marine terraces record the timing of sea level highstands and delimit both uplift and geomorphic rates cosmogenic radionuclides provide a new tool for dating previously undatable terraces because the five marine terraces north of santa cruz california are capped by well developed soils formed in regressive marine sands both predepositional cosmogenic radionuclide inheritance and bioturbation of the profile must be accounted for we present a new cosmogenic radionuclide inventory method that uses the depth integrated cosmogenic radionuclide concentration to determine the terrace age this method yields terrace ages that correlate well with sea level highstands of marine oxygen isotope stages 3 5a 5c 5e and 7 the implied uplift rate is steady at 1 1 mm yr and is two to three times higher than rates suggested by earlier studies

morphometry and elevation of the last interglacial tidal notches in tectonically stable coasts of the mediterranean sea abstract we report detailed morphometric observations on several mis 5 5 and a few older mis 11 21 25 fossil tidal notches shaped along carbonate coasts at 80 sites in the central mediterranean sea and at an additional six sites in the eastern and western mediterranean at each site we performed precise measurements of the fossil tidal notch ftn width and depth and of the elevation of its base relative to the base of the present tidal notch ptn the age of the fossil notches is obtained by correlation with biologic material associated with the notches at or very close to the site this material was previously dated either through radiometric analysis or by its fossiliferous content the width i e the difference in elevation between base and top of the notches ranges from 1 20 to 0 38 m with a mean of 0 74 m although the ftn is always a few centimetres wider than the ptn probably because of the lack of the biological reef coupled with a small erosional enlargement in the ftn the broadly comparable width suggests that tide amplitude has not changed since mis 5 5 times this result can be extended to the mis 11 features because of a comparable notch width but not to the mis 21 and 25 epochs although observational control of these older notches is limited we regard this result as suggesting that changes in tide amplitude broadly occurred at the early middle pleistocene transition the investigated mis 5 5 notches are located in tectonically stable coasts compared to other sectors of the central mediterranean sea where they are uplifted or subsided to 100 m and over in these stable areas the elevation of the base of the mis 5 5 notch ranges from 2 09 to 12 48 m with a mean of 5 7 m such variability although limited indicates that small land movements deriving from slow crustal processes may have occurred in stable areas we defined a number of sectors characterized by different geologic histories where a careful evaluation of local vertical land motion allowed the selection of the best representative elevation of the mis 5 5 peak highstand for each sector this elevation has been compared against glacial isostatic adjustment gia predictions drawn from a suite of ice sheet models ice g5 ice g6 and anice selen that are used in combination with the same solid earth model and mantle viscosity parameters results indicate that the gia signal is not the main cause of the observed highstand variability and that other mechanisms are needed the gia simulations show that even within the mediterranean basin the maximum highstand is reached at different times according to the geographical location our work shows that besides gia even in areas considered tectonically stable additional vertical tectonic movements may occur with a magnitude that is significantly larger than the gia

last glacial maximum climate in new zealand inferred from a modelled southern alps icefield abstract we present a simulation of the new zealand southern alps icefield at the last glacial maximum lgm c 30 000 20 000 calendar years ago ka in an attempt to constrain the climate of that period we use a 500 m resolution ice sheet model parameterised using empirical glaciological climatological and geological data specific to the model domain to simulate the entire southern alps icefield we find that an lgm cooling of at least 6 6 5 c is necessary to bring about valley glaciers that extend beyond the mountains however climate topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain and in order to remain within geologically reconstructed lgm limits we find that the lgm cooling was most likely associated with a precipitation regime up to 25 drier than today wetter than present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence these results perhaps indicate that either the westerly air masses affecting new zealand during the lgm were drier than today or that they were weaker or zonally displaced with respect to present

remagnetization and chemical alteration of sedimentary rocks remagnetization is a common phenomenon in rocks and developing a greater understanding of its mechanisms has several benefits acquisition of a secondary magnetization is usually tangible evidence of a diagenetic or thermal event which can be dated using palaeomagnetic techniques this is important because the timing of diagenetic and thermal events is commonly difficult to determine remagnetization can also obscure primary magnetizations and a better understanding of remagnetization could improve our ability to uncover primary magnetizations many chemical remagnetization mechanisms have been proposed including those associated with chemical alteration by a number of different fluids e g orogenic weathering mineralizing hydrocarbons and burial diagenetic processes e g clay diagenesis maturation of organic matter this book contains case studies and review articles that focus on remagnetization chemical remagnetization mechanisms and magnetic changes associated with chemical alteration by hydrocarbons

paleomagnetic dating of fracturing using breccia veins in durness group carbonates nw scotland abstract a paleomagnetic study of red fault related breccia veins in the cambro ordovician durness group in nw scotland was conducted to determine the time of brecciation the origin of the veins and the nature and timing of associated fluid related diagenetic alteration the veins contain brecciated fragments of the host durness group and strike either east west or north south clasts of breccia cemented by calcite suggest multiple brecciation events the host durness limestone is a gray dolomite and contains a devonian chemical remanent magnetization crm that resides in magnetite the veins contain magnetizations that reside in hematite and are interpreted as crms the breccias in north south veins contain a triassic crm whereas the veins with east west strikes contain a jurassic crm authigenic hematite is common in the breccias along growth planes in the calcite cements the two crms within the veins are interpreted as dating two separate brecciation and fluid flow events that precipitated authigenic hematite the brecciation and fluid flow events are interpreted to be related to extension in the mesozoic which is consistent with the extensional history of the northern atlantic margins

palaeomagnetism of the torridonian of rhum scotland evidence for limited uplift of the central intrusive complex abstract the tertiary central intrusive of rhum was emplaced into the torridonian sandstone causing a heat influx into the sediment detailed progressive demagnetisation of sandstones from the thermal aureole of the intrusion show that they reached maximum temperatures which decrease systematically with distance in a manner indicative of conduction dominated cooling temperatures reached near to the intrusion are higher than would be predicted theoretically probably as a result of the presence of smaller plugs of magma at depth which are only rarely exposed at the surface the shape and magnitude of the thermal aureole suggest that upward movement of the central intrusive along the bounding fault was limited primary remanence in torridonian sandstones unaffected by the intrusion is carried by both magnetite and haematite often with both occurring in the same specimen it is suspected that only magnetite carries a truly primary detrital remanence the haematite probably formed diagenetically largely by oxidation of detrital magnetite at some time shortly after deposition

laurentian palaeostress trajectories and ephemeral fracture permeability cambrian eriboll formation sandstones west of the moine thrust zone nw scotland abstract cambrian eriboll formation sandstones of the ardvreck group that crop out west of the moine thrust zone contain joints and quartz filled or quartz lined fractures that resemble cemented joints of the fractures containing quartz five sets strike north nw to wnw ne west and north according to crosscutting relations this is a progression from the oldest to the youngest set sets include opening mode microfractures partly visible in transmitted light as fluid inclusion planes and sharply defined as microveins using sem based cathodoluminescence cl dating the oldest north striking set using inferred quartz accumulation rates fluid inclusions and burial history suggests that these fractures mark a palaeozoic east west least horizontal stress trajectory in laurentia the youngest two sets of porous fractures are associated with faults that cut and postdate the moine thrust zone data indicate that at depth in basins pervasive fracture systems arising from discrete loading events are ephemeral owing to fracture porosity destruction by cementation

modeling the evolution of the juneau icefield between 1971 and 2100 using the parallel ice sheet model pism we study the evolution of the juneau icefield one of the largest icefields in north america 3700 km 2 using the parallel ice sheet model pism we test two climate datasets 20 km weather research and forecasting model wrf output and data from the scenarios network for alaska planning snap derived from spatial interpolation of observations good agreement between simulated and observed surface mass balance was achieved only after substantially adjusting wrf precipitation to account for unresolved orographic effects while snap s climate pattern is incompatible with observations of surface mass balance using the wrf data forced with the rcp6 0 emission scenario the model projects a decrease in ice volume by 58 68 and a 57 63 area loss by 2099 compared with 2010 if the modeled 2070 99 climate is held constant beyond 2099 the icefield is eliminated by 2200 with constant 1971 2010 climate the icefield stabilizes at 86 of its present day volume experiments started from an ice free state indicate that steady state volumes are largely independent of the initial ice volume when forced by identical scenarios of climate stabilization despite large projected volume losses the complex high mountain topography makes the juneau icefield less susceptible to climate warming than low lying alaskan icefields

paleomagnetic dating of the smectite to illite conversion testing the hypothesis in jurassic sedimentary rocks skye scotland 1 a hypothesized connection between clay diagenesis and magnetite authigenesis is supported by the results of paleomagnetic rock magnetic geochemical and petrographic studies on jurassic sedimentary rock of skye scotland the results have implications for understanding remagnetization mechanisms and for the development of a paleomagnetic method to date clay diagenesis previous diagenetic studies indicate that rock in north skye contains abundant detrital smectite whereas the clays in the same age rock in south skye have altered to illite because of tertiary igneous activity geochemical 87sr 86sr 13c 18o studies confirm that sedimentary rocks in south skye are altered the magnetization in the rocks in north skye is weak and unstable in contrast the rocks in south skye contain a multicomponent magnetization at intermediate temperatures 225 450 c a magnetization with southerly declinations and negative inclinations or its antipodal equivalent is present at higher temperatures 450 580 c a magnetization with northerly declinations and positive inclinations or its antipodal equivalent is removed both magnetizations have directions similar to tertiary igneous rocks on skye rock magnetic studies indicate the presence of pyrrhotite and magnetite the intermediate temperature component resides in pyrrhotite and or magnetite and is interpreted as a thermoviscous remanent magnetization or a thermochemical remanent magnetization related to the heat and or hydrothermal activity associated with the igneous activity the high temperature component resides in magnetite and is a chemical remanent magnetization crm the presence absence test and the timing of acquisition for this crm suggest that magnetite authigenesis is related to the smectite to illite conversion and that clay diagenesis is a viable remagnetization mechanism

coastal notches their morphology formation and function deep coastal notches develop through undercutting of steep coastal slopes consisting of rocks that are strong enough to support the weight of the overburden notches are found from the tropics to the poles and in a wide range of rock types virtually tideless to megatidal seas and high to low wave energy environments the emphasis in the literature has been on notches in calcareous rocks in warm microtidal seas and with the general assumption that they have been produced by bioerosion or chemical dissolution few scientifically rigorous attempts have been made to determine the processes responsible for notch formation in different environments and rock types however or to determine whether different processes produce distinct notch morphologies within the same tidal and wave environments the use of notches as palaeo sea level markers and to determine rates of tectonic uplift has been particularly important in the mediterranean notches are more difficult to employ for this purpose in the middle latitudes where higher waves and tides amplify the range of elevations over which the erosional mechanisms are effective as well as increasing the exposure and effect of rocks of variable resistance to erosion to maximize the utility of notches as sea level markers and to better understand and model their development in a wide range of environments we need to understand and be able to quantify the relationship between notch shape and size and the elevational efficacy of the various erosional processes

the occurrence and origin of late paleozoic remagnetization in the sedimentary rocks of north america although it has been known for 25 years that some paleozoic sedimentary rock units in europe and north america were remagnetized during pennsylvanian or permian time it is only very recently that the complex and widespread nature of the late paleozoic remagnetization phenomenon has been generally acknowledged it is now recognized that many paleozoic paleomagnetic poles for north america that were once considered reliable are in fact the result of remagnetization and as a consequence the paleomagnetic data base for the paleozoic is undergoing rapid and drastic revision the causes of late paleozoic remagnetization in north america are currently the focus of much interest and active research the remagnetization can reside in either hematite or magnetite and different remagnetization mechanisms have been important in different settings chemical remagnetization processes some related to specific diagenetic events are dominant in hematite bearing sandstones and carbonates in magnetite bearing carbonates both chemical and thermoviscous remagnetization processes appear to have been important but it is difficult to determine which process is the dominant one in some settings some of the observed remagnetizations can be linked to the migration of chemically active and perhaps hot fluids during the mountain building events that affected much of the continent during the late paleozoic paleomagnetic studies promise to be important in assessing the role of orogeny in driving fluid migrations within sedimentary basins and in constraining the age of the migrations and the nature of the fluids

resolution of regional fluid flow related to successive orogenic events on the laurentian margin seven localities distributed along a 180 km long outcrop within the uk sector of the laurentian margin were sampled and all showed two phases of authigenic k feldspar the first phase was precipitated from a cool fluid of moderate salinity and the second phase was precipitated from a hotter more saline fluid ar ar ages for the two episodes of authigenesis are ca 470 ma and ca 432 ma the data can be interpreted to represent two phases of regional scale fluid migration related to ordovician arc accretion and silurian continent continent convergence corresponding to the grampian and scandian episodes of the caledonian orogeny respectively

late quaternary sea level and tectonic changes in northeast fiji the islands of northeast fiji studied are all the emergent parts of the northern end of the lau colville ridge a remnant island arc which has been rising for most of the quaternary within the study area investigations of coastal landforms primarily emerged notches and shore platforms and emerged coral reefs allow rates of tectonic movements to be calculated the vanuabalavu island group is shown to have subsided during the late quaternary while the area around is shown to have risen over the same time period this disparity may be a result of tensional rifting associated with the continuing rotation of the fiji platform

climatic patterns over the european alps during the lgm derived from inversion of the paleo ice extent abstract quaternary climate has been dominated by alternating glacial and interglacial periods while the timing and extent of past ice caps are well documented local variations in temperature and precipitation as a response to cyclic glaciations are not resolved resolving these issues is necessary for understanding regional and global climate circulation in particular the impact of the cold high pressure zone above the fennoscandian ice cap on the position of the jet stream in europe and a possible change in the direction and the source of moisture flow are still debated here we reconstruct climate conditions that led to the observed ice extent in the european alps during the last glacial maximum lgm using a new inverse method to reconstruct the spatially variable position of the equilibrium line altitude ela we investigate whether the alpine lgm ice cap dominantly received precipitation in the south due to a strong southward shift of the westerlies in midlatitudes we report inversion results that enable us to estimate the role of climate inversion method parameters ice dynamics flexure and topography in modulating the inferred equilibrium line altitude our main finding is the increase of the position of the ela from west to east and from north to south of the mountain range which suggest dominant moisture delivery over the alps during the lgm relatively similar to today

long term growth and subsidence of ascension island constraints on the rheology of young oceanic lithosphere the dating of material from deep boreholes drilled in volcanic ocean islands allows constraints to be placed on their growth and long term subsidence rates we dated lavas from a 3 km geothermal borehole at ascension island by the laser heating 40ar 39ar technique the samples yield ages of up to 3 4 ma and volcanic growth rates of 0 4 km myr the transition from submarine to subaerial eruption occurs at 710 m below present sea level and 2 5 ma since 2 5 ma there has been 430 500 m of subsidence over and above the expected 190 260 m due to lithospheric cooling plausible elastic thicknesses and growth histories would generate a maximum elastic subsidence since 2 5 ma of 200 m we infer that the subsidence includes a component of viscous relaxation resulting from rapid loading prior to 2 5 ma and place constraints on the timescale of this relaxation and hence the viscosity of the underlying lithosphere

coastal morphology and late quaternary history cayman islands west indies abstract instrumental surveys of coastal profiles in the cayman islands western caribbean reveal the presence of a horizontal erosional bench at 1 9 m on grand cayman and a deep horizontal notch at 6 4 m on cayman brac but no raised erosional features on little cayman each island is surrounded by a horizontal constructional raised reef usually below 2 m here dated by u series methods as 124 000 8000 yr old and hence broadly contemporary with other western atlantic raised reefs of similar elevations the different raised erosional features indicate independent vertical tectonic movement of the three islands predating the formation of the raised reef the accordance and horizontality of the raised reef indicates stability of the islands since the last interglacial times an erosional notch at present sea level has formed since the sea reached its present level less than 2100 b p and algal benches on exposed coasts are also in equilibrium with present conditions

a palaeomagnetic study of recumbently folded and thermally metamorphosed torridon group sediments eishort anticline skye scotland two geologically significant palaeomagnetic components have been isolated in samples of torridon group sandstones from the kishorn nappe of nw scotland the samples were collected from the eishort anticline a large recumbent fold of caledonian age the softer component which is demagnetized by low temperatures and weak magnetic fields when in situ displays a steep upward direction typical of reversed tertiary magnetizations both polarities of the harder component which is demagnetized by high temperatures only are present and when dip corrected display either northwesterly upward or southeasterly downward directions characteristic of torridonian remanences it is suggested that the tertiary component is of chemical origin and the result of alteration of magnetite titanomagnetite grains the geographical distribution of these grains is irregular and as a result the distribution of the tertiary overprint is irregular the torridonian palaeomagnetic components from both limbs of the fold can be restored by rotation about the fold axis to internally consistent directions which lie close to previously published data from the caledonian foreland no correction is necessary for finite strain which suggests that the eishort anticline formed by a flexural slip mechanism however an anticlockwise rotation of 26 is required to reconcile the torridonian directions from the kishorn nappe with those of the caledonian foreland which suggests that during emplacement the thrust sheet rotated on the underlying fault surface

tidal wetting and drying on shore platforms an experimental study of surface expansion and contraction laboratory experiments have been conducted to measure rock expansion and contraction induced by wetting and drying on intertidal shore platforms in eastern canada almost 800 rock cores and cubes were subjected to between 800 and 1000 tidal cycles the rocks were put into tidal simulators and inundated in de ionized water for 1 6 or 11 h of each 12 h cycle replicating conditions at the high mid and low tidal levels respectively micro erosion meter mem stations were also installed in slabs of argillite sandstone and basalt the slabs were subjected to conditions at the high mid and low tidal levels and a traversing mem was used to measure rock expansion and contraction as the slabs dried in air with variable temperature and humidity during low tide the slabs were also exposed for long periods to air with variable humidity cores and cubes often gained in weight when they absorbed or adsorbed water and retained it for periods ranging from 1 month to 1 year or more although this did not appear to be a prelude to rock breakdown tidal wetting and drying and exposure to humid air caused the argillite and basalt slabs to expand and contract by up to 0 14 and 0 04 mm respectively wetting and drying did not induce expansion or contraction of the sandstone but the sandstone did respond slightly to changes in air humidity the greatest amount of expansion and contraction was at the high tidal level in the argillite and at the mid tidal level in the basalt which is consistent with previously measured rates of downwearing

shore platform erosion and evolution implications for cosmogenic nuclide analysis abstract determining rates and modes of shore platform development and the age of associated elements are among the greatest challenges facing rock coast researchers today these coasts generally lack dateable deposits but cosmogenic nuclide analysis cna can be applied directly to bare rock surfaces to estimate erosion rates or the time that a surface has been exposed over millennial timescales therefore this technique has the potential to revolutionize current theories on rock coast evolution and modes of development because environmental and geomorphological factors affect rates of nuclide accumulation and retention however the results of cna analysis are dependent on the validity of the theoretical models that have to be employed according to the particular application among the important assumptions that may be made are those concerned with shading tidal immersion beach sediment covers and other factors that influence rates of nuclide accumulation and with possible spatial and temporal patterns in shore platform erosion primarily by wave generated backwearing and weathering induced downwearing that reduce nuclide concentrations our lack of understanding of the factors that control these variables and in particular shore platform erosion which is the subject of this review has important implications for modelling rock coast evolution assessing the possible contribution of inheritance and dating especially by cna the occurrence of important formative events

numerical modeling of tidal notch sequences on rocky coasts of the mediterranean basin publisher s version pdf must be used in institutional repository 6 months after publication

secondary magnetizations in shear and fault zones in southern finland abstract studies on remanent magnetization of shear and fault zones of crystalline rocks in southern finland have been carried out to test juvenile fluid activity that can be dated paleomagnetically locating in the central part of baltica the area has been tectonically relatively quiet since the precambrian however tectonism at the margins of the craton during the caledonian hercynian and uralian orogenies probably reactivated faults and resulted in low temperature hydrothermal activity also within the craton we identified two consistent remanent magnetization components in four out of five studied localities one remanence component has an intermediate to high coercivity nnw directed magnetization d 334 7 i 35 2 k 92 1 95 9 6 and unblocking temperatures suggest that it resides in titano magnetite the direction is similar to the remanence that is commonly observed in svecofennian age ca 1 9 ga rocks all over the precambrian fennoscandian shield and probably represents the primary svecofennian magnetization preserved in the host rocks another common component is directed ne i 30 8 d 35 3 k 264 5 95 5 7 and is carried by hematite and maghemite its resulting paleomagnetic pole compares well with phanerozoic paleopoles of baltica and is suggested to represent a permian remagnetization we interpret that this remanence reflects the reactivation of the svecofennian crust in the late paleozoic due to tectonic events related to the formation of the supercontinent pangea in addition remagnetizations due to mesoproterozoic rapakivi magmatism and younger mesozoic to present events were identified

late proterozoic reconstructions of north west scotland and central canada magnetic fabrics paleomagnetism and tectonics red beds dominate the stoer group and the unconformably overlying torridon group having accumulated between 1400 and 1000 ma in a rift of the hebridean foreland the sequences were weakly strained and shortened e w and each underwent successive diagenetic changes which altered their magnetic properties and caused their different characteristic post depositional magnetizations anisotropy of magnetic susceptibility ams reveals an n s vertical tectonic foliation superimposed on the bedding planar ams sub fabric the tectonic ams sub fabric was isolated by comparing normalized and non normalized mean tensors of multiple specimens the n s vertical ams tectonic foliation postdates warps of bedding thus the high susceptibility minerals including those carrying palaeomagnetic signals re oriented or recrystallized after deposition and diagenesis thus characteristic remanence vectors chrm were acquired long after deposition first in the stoer group then in the torridon chrms were isolated for 143 stoer specimens and 94 torridon specimens using two cycles of low temperature demagnetization followed by at least 12 steps of thermal demagnetization for the stoer group two structurally integral groups of sites yield mean magnetizations of 317 0 43 1 95 11 3 n 49 and 309 9 52 1 95 10 6 n 23 some stoer specimens bear a torridon age overprint 133 3 525 95 9 6 n 19 the younger torridon group yields 138 4 52 2 95 7 4 n 42 134 9 45 5 95 16 0 n 15 and 134 4 55 1 95 11 3 n 19 from three structurally integral clusters of sites these late chemical magnetizations postdate bedding warps faults and tectonic ams fabrics they do not warrant local rigid body tilt corrections however we restored the chrm directions for the regional post cambrian eastwards tilt which affected the entire foreland from the lewisian basement to the overlying proterozoic strata paleopoles calculated from the strata s restored vectors were rotated into laurentian coordinates for comparison with canadian proterozoic palaeopoles the stoer group was magnetized in a normal polarity geomagnetic field whereas the torridon group was magnetized in a reversed polarity epoch however both sequences include at least one polarity transition indicating long duration chemical magnetizations successfully averaging secular variation at a minimum red bed magnetization processes exceeded 0 1 ma and may have encompassed several million years during stoer group magnetization the hebridean craton was at paleolatitudes of 26 44 n when the torridon group magnetized it was at 23 27 s accepting published ages this defines a minimum southward latitudinal displacement rate of 27 40 km ma restored stoer group paleopoles lie in the present day north central pacific ocean 190e 25n corresponding to the laurentian apwp dated at between 1090 and 1109 ma torridon group paleopoles lie in the south central pacific 210e 25s near the poorly documented 900 ma southernmost part of the laurentian apwp

frost weathering and the saturation of coastal rocks measurements were made of the water content in coastal rocks by simulating tidal oscillations in the laboratory and by field measurement in eastern canada if rapid freezing takes place upon exposure to the air saturation levels may be high enough to permit frost weathering in fine grained rocks in the lower portions of the intertidal zone near the high tidal level however it may be dependent upon a supply of water from the ice foot and from melting snow if freezing is slow frost action may be inhibited by desorption of the rocks while they are exposed by the ebb tide there was no evidence of a level of permanent sea water saturation within the intertidal zone ambient temperature and humidity may affect the rate of rock desorption

palaeomagnetic dating of sub torridon group weathering profiles nw scotland verification of neoproterozoic palaeosols a palaeoplain that cuts across lewisian gneiss in the cape wrath area northwest scotland is weathered to depths of 1 6 m beneath fluvial red conglomerates and sandstones of the applecross formation of the early neoproterozoic torridon group weathered lewisian rocks are enriched in k 2 o and fe 2 o 3 and contain hematite as an alteration product of biotite and magnetite palaeomagnetic analysis of the weathering profiles has been carried out to constrain the age of alteration thermal step demagnetization of 87 oriented core specimens of biotite gneiss and amphibolite spanning four profiles at poll a mhurain and sheigra reveal a stable high temperature component with a mean direction of remanence of d 149 1 i 57 2 95 5 0 corrected for dip of the overlying applecross strata that gives a pole at 9 8 s 199 2 e dp 5 3 dm 7 3 this direction differs significantly from that for little weathered lewisian at those two localities and also from directions for the late mesoproterozoic stoer group the remanence direction for the weathered rocks is however near the dip corrected high temperature remanence direction d 122 3 i 50 5 95 10 8 obtained by us from the thermal step demagnetization of 39 sandstone specimens of the applecross formation in the cape wrath area furthermore the direction for the weathered rocks agrees closely with other dip corrected results for the torridon group such as the detrital remanent magnetization drm mean direction d 148 3 i 59 9 95 13 8 for the applecross formation on rum and that for the main outcrop of the aultbea formation d 139 7 i 52 6 95 14 5 the concordance of palaeomagnetic results for the sediments and weathered rocks implies that the weathering profiles in the cape wrath area acquired their remanence penecontemporaneously with deposition of the applecross and aultbea formations the palaeomagnetic results therefore argue strongly that the weathering profiles are palaeosols of applecross age c 980 ma that formed at a palaeolatitude of 38 and constitute the oldest known palaeosols in the british isles views that the weathering is substantially older or younger than applecross deposition cannot be sustained our findings carry implications for applecross palaeoclimate and source and strengthen the conclusion that atmospheric oxygen was a substantial fraction of its present abundance by early neoproterozoic time

tidal wetting and drying on shore platforms an experimental assessment abstract rocks were subjected to wetting and drying cycles with de ionized water under real time conditions using tidal simulators one third of the samples experienced 11 h of exposure and 1 h of inundation over a 12 h tidal cycle representing high tidal conditions one third experienced 6 h of exposure and 6 h of inundation representing mid tidal conditions and one third experienced 1 h of exposure and 11 h of inundation representing low tidal conditions we obtained 324 cores from igneous metamorphic and sedimentary rocks from ontario which were exposed to more than 930 wetting and drying cycles over 16 months we obtained 675 cores and cubes from basalts sandstones and argillites from shore platforms in eastern canada which were exposed to about 700 cycles over 12 months many of the cores and cubes experienced very little to no breakdown particularly those from the igneous and metamorphic rocks of ontario sandstones from a sloping platform in the macrotidal bay of fundy and argillites from a horizontal mesotidal platform in gaspe quebec were the most susceptible rock types with equivalent surface downwearing rates ranging from 0 to 4 mm year 1 the results suggest that downwearing rates decrease with elevation within the intertidal zone probably because rocks require much longer to desorb than to absorb water the experiments demonstrated that wetting and drying can be an important process on shore platforms in some types of rock helping to lower the height and reduce the gradient of sloping macrotidal platforms and to reduce the height of horizontal micro and mesotidal platforms

bioconstruction bioerosion and disturbance on tropical coasts coral reefs and rocky limestone shores the ecology of tropical carbonate coasts including coral reefs and rocky limestone shores is susceptible to disturbance that may have linked effects on geomorphology biogeomorphology which considers the interrelations between biological and geomorphological processes is particularly well suited toward the understanding of such carbonate systems field observations and experimentation on tropical and temperate coasts by both biologists and geomorphologists and the development of ecological theory have come to stress the importance not of stable successional littoral communities but rather of nonequilibrial multistate systems these ideas now need to be incorporated into improved models of coastal dynamics case studies from the central pacific the caribbean and the western indian ocean illustrate the interactions between external environmental variability and internal biological processes these studies show how changing the balance between bioconstructional and bioerosional processes can interrupt a system s development and in some cases shift carbonate based systems between healthy and degradational states a better understanding of the spatial and temporal complexities present in carbonate coastal and shallow marine environments is an important precursor to effective coastal zone management on these prevalent tropical shorelines

modelling tidal notch formation by wetting and drying and salt weathering abstract the formation and morphology of marine notches formed by tidal wetting and drying and salt weathering was modelled for 6 micro to megatidal environments the model used published tidal elevation dependent weathering and erosional data from 1 to 3 year experiments conducted on more than 2000 sandstone argillite and basalt samples from eastern canada the model analysed annual tidal predictions to convert the weathering data into slope recessional units realistic model profiles with notches at the high tidal level were produced within the 3000 6000 year period since the sea attained its present level there were up to 4 cycles of notch formation and collapse during this time in the rapidly eroding sandstones and a smaller number in the argillites notch morphology was affected by the tidal range the rock type and the initial slope gradient but the maximum depth of the notch before collapse controlled only the number and frequency of the collapse events continuous positive and negative changes in rsl extended the notches in the vertical plane according to the rate and direction upwards or downwards of these changes a distinct series of notches can develop from episodic changes in rsl but the survival of older notches and consequently their utility as palaeosea level indicators depends upon such factors as their elevation with respect to the present tidal range

coastal evolution on volcanic oceanic islands a complex interplay between volcanism erosion sedimentation sea level change and biogenic production abstract the growth and decay of oceanic hotspot volcanoes are intrinsically related to a competition between volcanic construction and erosive destruction and coastlines are at the forefront of such confrontation in this paper we review the several mechanisms that interact and contribute to the development of coastlines on oceanic island volcanoes and how these processes evolve throughout the islands lifetime volcanic constructional processes dominate during the emergent island and subaerial shield building stages during the emergent island stage surtseyan activity prevails and hydroclastic and pyroclastic structures form these structures are generally ephemeral because they can be rapidly obliterated by marine erosion with the onset of the subaerial shield building stage coastal evolution is essentially characterized by rapid but intermittent lateral growth through the formation of lava deltas largely expanding the coastlines until they typically reach their maximum extension with the post shield quiescence in volcanic activity destructive processes gradually take over and coastlines retreat adopting a more prominent profile mass wasting and marine and fluvial erosion reshape the landscape and if conditions are favorable biogenic processes assume a prominent role post erosional volcanic activity may temporarily reverse the balance by renewing coastline expansion but islands inexorably enter in a long battle for survival above sea level reef growth and or uplift may also prolong the island s lifetime above the waves the ultimate fate of most islands however is to be drowned through subsidence and or truncation by marine erosion

origin of orogenic remagnetizations in mississippian carbonates sawtooth range montana 1 paleomagnetic results are presented from mississippian madison group carbonates in the sawtooth range northwestern montana samples were collected from sites along two east west trending transects perpendicular to the thrust faults in the sun river canyon and in the north and south forks of the teton river and from three folds the madison group contains a widespread characteristic remanent magnetization chrm that resides in magnetite with southerly declinations and moderately steep up inclinations tilt test results suggest that the chrm is pretilting in the thrust sheets and teton anticline but syntilting in the clary coulee and swift dam folds the chrms all have the same characteristics and were probably caused by the same remagnetization event yet the tilt test results are different one explanation involves the difference in fold types between the teton anticline fault bend fold geometry and the clary coulee and swift dam folds fault propagation fold geometries the deformation that produced the two geometries could have caused variations in strain stress which may have altered an original pretilting into a syntilting chrm a mean paleopole for the three pretilting tilt test results 67 2 n 177 9 e a95 13 1 suggests remanence acquisition in the late jurassic early tertiary the chrm is interpreted as a chemical remanent magnetization crm geochemical studies indicate that the mississippian carbonates were altered by evolved fluids with radiogenic 87sr 86sr values and petrographic analysis indicates that hydrocarbons migrated through the carbonates the crm is interpreted to be related to alteration by one of these fluids

patterns of surface downwearing on shore platforms in eastern canada downwearing rates were measured on shore platforms at about 200 transverse micro erosion meter tmem stations over periods ranging from 2 to 6 years there were seven study areas in eastern canada the platforms were surveyed and a schmidt rock test hammer was used to measure rock hardness more than 1200 rock samples from three of the study areas were also subjected each day over a 3 year period to two tidal cycles of immersion and exposure which simulated the central intertidal zone a further 840 samples were subjected to longer periods of exposure and immersion over a 1 year period which represented different elevations within the upper and lower intertidal zone respectively these experiments suggested that tidally generated weathering and debris removal is an effective erosional mechanism particularly at the elevation of the lowest high tides in the field mean rates of downwearing for each study area ranged from 0 24 mm yr 1 to more than 1 5 mm yr 1 rates tended to increase with elevation in the field with maxima in the upper intertidal zone this trend in the field cannot be attributed entirely to the tidally induced weathering processes that were simulated in the laboratory and must reflect in part the effect of waves frost ice and other mechanisms it is concluded that there are no strong spatial downwearing patterns on shore platforms and that downwearing rates in the intertidal zone are the result of a number of erosional mechanisms with different elevation efficacy characteristics furthermore even if only one or two mechanisms were dominant in an area any resulting relationship between downwearing rates and elevation would be obscured or eliminated by the effect of variations in the chemical and physical characteristics of the rocks copyright 2010 john wiley sons ltd

estimation of the intertidal bioerosion rate from a well dated fossil tidal notch in greece abstract in this paper a re analysis of previous research concerning an uplifted tidal notch developed near the modern harbor of poros eastern cephalonia island ionian sea greece is undertaken according to radiocarbon dating this notch was active between the 4th 6th century ad and 1953 ad i e for at least 1450 years recent measurements have shown that the inward depth of the notch profile at well preserved sites is 93 cm this permits an estimate of the average rate of intertidal bioerosion to 0 64 mm a for this time period

short term patterns and processes of coastal cliff erosion in santa barbara california abstract sequential terrestrial lidar scans and 3d volumetric change were used to document coastal cliff erosion at several sites along the coast of santa barbara california retreat rates along the base middle and cliff top were calculated for six different scans throughout the el nino of 2015 16 to quantitatively link wave action to cliff base erosion and two seasonal scans were taken during 2017 to investigate patterns in erosion and retreat rates retreat rates along the cliff base middle and top converged over the course of the study period and observations and patterns in erosion help characterize the fundamental mechanisms that govern the retreat of soft shale cliffs the base and middle of the cliff preferentially eroded during high energy swell events and are strongly coupled whereas cliff top erosion is temporally variable and retreat rates increased with higher seasonal rainfall totals we observe that the cliff base experiences erosion from both abrasion and mechanical wave action but the dominant processes is segregated by elevation above the cliff toe abrasion was found to be the dominant processes at elevations up to 0 8 m above the cliff toe whereas block removal from mechanical wave action was dominant at elevations above 0 8 m threshold behavior was observed for cliff base retreat rates and spearman correlation coefficients suggest strong relationships with the sum of the wave energy flux imparted to the cliff base r2 0 84 the sum of the wave energy flux 35 000 w m r2 0 82 and the average total water level above the cliff toe r2 0 85 threshold behavior and maximum retreat rates occurred when average total water levels were 0 8 m above the cliff toe seasonal schmidt hammer measurements suggest that energy thresholds are modulated by weathering rates which remain poorly understood these thresholds when exceeded produced the highest cliff base retreat rates during the study period and reinforce the expectation that coastal cliff retreat rates will increase with rising sea levels

the tornquist sea and baltica avalonia docking early ordovician late arenig limestones from the sw margin of baltica scania bomholm have multicomponent magnetic signatures but high unblocking components predating folding and the corresponding palaeomagnetic pole latitude 19degreesn longitude 051degreese compares well with arenig reference poles from baltica collectively the arenig poles demonstrate a midsoutherly latitudinal position for baltica then separated from avalonia by the tomquist sea tornquist sea closure and the baltica avalonia convergence history are evidenced from faunal mixing and increased resemblance in palaeomagnetically determined palaeolatitudes for avalonia and baltica during the mid late ordovician by the caradoc avalonia had drifted to palaeolatitudes compatible with those of sw baltica and subduction beneath eastern avalonia was taking place we propose that explosive vents associated with this subduction and related to andean type magmatism in avalonia were the source for the gigantic mid caradoc c 455 ma ash fall in baltica i e the kinnekulle bentonite avalonia was located south of the subtropical high during most of the ordovician and this would have provided an optimum palaeoposition to supply baltica with large ash falls governed by westerly winds in scama we observe a persistent palaeomagnetic overprint of late ordovician ashgill age pole latitude 4degreess longitude 012degreese the remagnetisation was probably spurred by tectonic derived fluids since burial alone is inadequate to explain this remagnetisation event this is the first record of a late ordovician event in scania but it is comparable with the shelveian event in avalonia low grade metamorphism in the north sea basement of ne germany 440 450 ma and sheds new light on the baltica avalonia docking c 2002 elsevier science b v all rights reserved less