middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

striated clast pavements products of deforming subglacial sediment studies of modern glaciers have recently drawn attention to the importance of subglacial sediment deformation to glacier dynamics and processes inferences regarding the probable shear strength of this sediment imply that large clasts may in some cases sink to underlying rigid sediment where abrasion by overlying deforming sediment could occur this scenario provides a formative mechanism for striated clast pavements commonly described from the base of fine grained massive diamictons associated with the late pleistocene laurentide ice sheet such a mechanism indicates that at the time of formation of clast pavements overlying diamictons associated with pavements had a low yield strength 0 5 kpa and were deforming mechanically like a debris flow clast pavements may therefore be an important criterion for recognition of sediments deposited by subglacial deformation transport

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

response of sediment to ice sheet loading in northwestern germany effective stresses and glacier bed stability laboratory tests on sediment over ridden by the last ice sheet in northwestern germany reveal very low ice induced pre consolidation and high palaeo pore water pressures sediment consolidation at the base of the glacier was largely controlled by hydraulic properties of the substratum generally low permeabilities of the bed caused sustained high pore water pressure in over ridden sediments close to the flotation point this implies a serious possibility of hydraulic lifting of the ice sheet it is believed that the reduced basal coupling limited the transformation of glacier shear stress on to the bed sediments which is indicated by a lack of sedimentological evidence for widespread pervasive bed deformation ice motion was probably focused at the glacier sole by some combination of sliding and ploughing however isolated spots with deformation occur so that the subglacial system in the study area can be characterized as a stable deforming mosaic

multiproxy record of late pleistocene holocene climate and vegetation changes from a peat bog in patagonia abstract pollen assemblage changes and stable hydrogen isotope analysis of mosses sphagnum magellanicum and drepanocladus s l from a bog in tierra del fuego argentina provided independent proxies for reconstructing changes in effective moisture and temperature over the past 16 000 cal yr b p a deterministic model was used to reconstruct the stable hydrogen isotope composition of meteoric water from the d h ratios of bog mosses over the last 16 000 years abrupt changes in temperature as recorded in d h ratios of moss cellulose were accompanied by synchronous changes in vegetation composition during the late pleistocene and early and middle holocene when moisture levels were lower than today in contrast temperature variability during the late holocene was not accompanied by comparable vegetation changes in particular grass pollen poaceae increased during periodic cold spells between 15 000 and 11 000 cal yr b p but a cold spell of similar magnitude ca 2000 cal yr b p did not appear to affect vegetation during the late pleistocene the isotopic record from the peat core shows variations similar to the d h ratios in the antarctic taylor dome ice core however the timing of the changes in the harberton record is more in line with the timing of other southern hemisphere records

deglacial environmental changes on isla de los estados 54 4 s southeastern tierra del fuego the island of isla de los estados is situated at 54 5 degrees s 64 degrees w east of argentinian tierra del fuego and is located in a sensitive geographic position in relation to the zonal circulation between antarctica and south america its terrestrial records of the last deglaciation recording atmospheric conditions but within an oceanic setting can help to clarify changes of regional circulation patterns both atmospheric and marine here we present geochemical analyses from 16 10 ka cal bp of a peat core from lago galvarne bog at the northern coast of the island and a lake sediment core from laguna cascada 3 kin further south the data comprise tc tn loss on ignition analyses and continuous xrf scanning on both cores as well as age depth modeling based on ams c 14 dating deglaciation and onset of peat formation in the coastal areas began before 16 ka cal bp followed by a rapid glacial retreat and the start of lacustrine sedimentation further inland data suggest initially windy conditions with permafrost succeeded by gradually warmer and wetter conditions until ca 14 5 ka cal bp the warming trend slows down until ca 13 5 ka cal bp followed by arid conditions culminating around 12 8 ka cal bp our data suggest fairly warm conditions and the establishment of denser peat and forest vegetation ca 10 6 ka cal bp contemporaneous with the onset of the antarctic thermal optimum this indicates large scale shifts in the placement of zonal flow and the westerlies at the beginning of the holocene c 2008 elsevier ltd all rights reserved

palaeoenvironmental conditions during the middle holocene at isla de los estados staaten island tierra del fuego 54 s argentina and their influence on the possibilities for human exploration abstract the middle holocene is a particular time period in which there are uneven environmental dynamics all along the southern portion of the continent whereas in the puna extreme aridity and high temperatures the so called hypsithermal period have been recorded a more humid and rainy phase dominated southern tierra del fuego the present paper explores the palaeoenvironmental situation of isla de los estados staaten island 54 38 54 55 s 63 48 64 46 w and its relationship with the archaeological record left behind by ancient canoeing people the considered period is characterized by exceptionally windy conditions the palaeoenvironmental information could be used as an explanation for the absence of cultural remains and also for the scarce archaeological record for peninsula mitre at the beginning of the middle holocene the diatom record shows a large amount of aulacoseira sp that could indicate either windy conditions or higher water levels at the site core the more distinctive changes in the diatom assemblages occurred at ca 5000 cal b p suggesting a shallower water level and more acidic conditions by 3000 cal b p the diatom species are strongly linked to peat and swampy environments however during the late holocene milder conditions might have favored seasonal travelling to the outer islands of the fuegian archipelago though no definitive or permanent settlements have been found

reconstruction of far field tsunami amplitude distributions from earthquake sources the probability distribution of far field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones tsunami amplitude distributions at tide gauge stations follow a similar functional form well described by a tapered pareto distribution that is parameterized by a power law exponent and a corner amplitude distribution parameters are first established for eight tide gauge stations in the pacific using maximum likelihood estimation a procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps 1 define the distribution of seismic moment at subduction zones 2 establish a source station scaling relation from regression analysis 3 transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone and 4 mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station the tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies in comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation the reconstructed distributions consistently exhibit higher corner amplitude values implying that in most cases the empirical catalogs are too short to include the largest amplitudes because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog it is less susceptible to the effects of record breaking events and more indicative of the actual distribution of tsunami amplitudes

southern patagonian glacial chronology for the last glacial period and implications for southern ocean climate the magellan region of southern south america is in a unique setting at 50 s on the equatorial side of the antarctic frontal zone to record in detail terrestrial glacial to interglacial events a 10be chronology shows growth and millennial fluctuations of a patagonian ice sheet between 25 and 17 6 17 0 cal ka in the strait of magellan the maximum ice margin position is dated to 24 6 0 9 ka and other moraine ages are 18 5 1 8 and 17 6 0 2 ka mean 1 standard deviation in bahia inutil dated moraine ages are 20 4 1 2 and 17 3 0 8 ka the chronology of the local last glacial maximum lgm reveals a record of atmospheric cooling that was broadly in phase with changes in southern ocean conditions such as sea ice fluctuations and surface water characteristics published modeling results indicate that a decline in temperature of 6 c and slight drying over southernmost patagonia could simulate the growth and sustained presence of an ice sheet to the mapped lgm limit the terrestrial record in southern patagonia and marine records in adjacent oceans indicate mean northward movement of the antarctic frontal zone which caused the last southern south american ice age the antarctic frontal zone at present lies only 3 5 to the south some significant changes in the magellan region occurred in step with north atlantic region and the northern hemisphere for example the overall time span of the last glaciation and the timing of maximum ice extent were similar between the hemispheres despite maximum local summer insolation intensity in southern south america other characteristics of the southern patagonian glacial history differ from the north atlantic region specifically an out of phase relationship during deglaciation which is more similar to that of southern ocean and antarctic records

fabric signature of subglacial till deformation breidamerkurjokull iceland the foreland of breidamerkurjokull iceland is the only locality where tills known to have undergone subglacial deformation are exposed till on the foreland has a two tiered structure consisting of a dilatant upper horizon c 0 5 m thick and a compact lower till these horizons correspond to the ductile deforming a horizon and the brittle ductile b horizon observed below the glacier by g s boulton and co workers the relationship between known strain history and a variety of macrofabric elements is examined for these two genetic facies of deformation till the upper horizon exhibits variable a axis fabrics and abundant evidence for clast re alignment reflecting ductile flow and rapid clast response to transient strains in contrast the lower horizon has consistently well organized a axis fabrics with a narrow range of dip values recording clast rotation into parallel with strain axes during brittle or brittle ductile shear the data indicate that till strain history imparts identifiable macrofabric signatures providing important analogues to guide the interpretation of pleistocene tills

computation of tsunamis in the east japan sea using dynamically interfaced nested model a study of 1983 and 1993 tsunami events in the east japan sea using multigrid dynamically interfaced finite difference models was performed to produce detailed features of coastal inundations along the eastern coast of korea the computational domain is composed of several subregions with different grid sizes connected in parallel or inclined directions the innermost subregion represents the coastal alignment reasonably well and has a grid size of about 30 meters numerical simulations have been performed in the framework of shallow water equations linear as well as nonlinear over the plane or spherical coordinate system depending on the dimensions of the subregion results of simulations show the general agreements with the observed data of the runup height for both tsunamis the evolution of the distribution function of tsunami heights is studied numerically and it shows a tendency to the log normal curve for a long distance from the source

the last glacial maximum and deglaciation in southern south america abstract this paper models the extent of the patagonian icesheet during the last glacial maximum lgm and its subsequent deglaciation it constrains a new coupled icesheet climate numerical model with empirical evidence and simulates the icesheet at the lgm and at stages of deglaciation under lgm conditions an icesheet with a modelled volume slightly in excess of 500 000 km3 builds up along the andes there is a marked contrast between the maritime and continental flanks of the modelled icesheet with positive mass balance exceeding 2 m in the west and declining tenfold to the east modelled ice velocities commonly reach 400 m yr 1 in the western fjords the model is most sensitive to variations in temperature and good agreement between modelled ice extent and empirical evidence was achieved by applying a temperature decrease of 6 c relative to present day temperatures with constant wind fields over the model domain assuming a stepped start to deglaciation modelled ice volumes declined sharply contributing 1 2 m to global sea level 80 of it within 2000 years the empirical record suggests that such a stepped warming occurred around 17 500 17 150 cal yr ago

statistical self similarity of hotspot seamount volumes modeled as self similar criticality the processes responsible for hotspot seamount formation are complex yet the cumulative frequency volume distribution of hotspot seamounts in the easter island salas y gomez chain esc is found to be well described by an upper truncated power law we develop a model for hotspot seamount formation where uniform energy input produces events initiated on a self similar distribution of critical cells we call this model self similar criticality ssc by allowing the spatial distribution of magma migration to be self similar the ssc model recreates the observed esc seamount volume distribution the ssc model may have broad applicability to other natural systems

the mid oxfordian late jurassic positive carbon isotope excursion recognised from fossil wood in the british isles the carbon isotope ratios of fossil wood have recently been confirmed as a proxy for changes in the isotopic composition of palaeoatmospheres carbon isotope data from fossil wood samples collected from the jurassic oxfordian staffin shale formation on the isle of skye scotland boreal sub boreal ammonite zonation reveal a long term positive carbon isotope excursion of at least 3 this excursion reaches a maximum in the mid oxfordian and closely matches the carbon isotope ratios previously reported from belemnites collected from the same section and carbon isotope data from carbonates in other european sections this confirms that the mid oxfordian positive carbon isotope excursion affected the total exchangeable carbon reservoir fossilised wood samples collected at a higher stratigraphic resolution but over a shorter interval from the corallian group in dorset england antecedens parandieri and cautisnigrae subzones nw european ammonite zonation show considerable scatter in their carbon isotope ratios and no trends are discernable the combined isle of skye and dorset dataset shows that the long term oxfordian positive carbon isotope trend coincides with a long term relative sea level change and that the most positive carbon isotope ratios occur across the plicatilis transversarium biozonal boundary sub mediterranean ammonite zonation this implies that the carbon isotope excursion was not caused by the well documented rise in sea level in the transversarium zone although very low carbon isotope ratios from fossil wood samples are recorded from the nodular rubble member parandieri subzone of dorset there is not a sufficiently coherent signal to ascribe these values to the gas hydrate dissociation event previously hypothesized from the carbon isotope ratios of tethyan marine carbonates a microscopal analysis of the charcoalified debris from the staffin shale formation indicates a prevalence of the wood genus cupressinoxylon derived from a cheirolepidiaceaen conifer

high resolution organic carbon isotope stratigraphy of the middle jurassic lower cretaceous agardhfjellet formation of central spitsbergen svalbard we present the first complete organic carbon isotope curve from the agardhfjellet formation central spitsbergen svalbard samples from two drill cores dh2 and dh5r were analysed for 13corg total organic carbon toc and rock eval rock eval litho and biostratigraphy demonstrate a similar development in the two cores allowing construction of a composite 13corg curve covering the bathonian to lowermost cretaceous there are only weak correlations between rock eval parameters and 13corg suggesting the isotopic signal is not mainly controlled by type of kerogen maturation but rather reflects regional or global environmental changes the carbon isotope curves from the cores can be correlated with previously published curves from outcrops of the slottsmoya member and with more distant localities in the barents sea siberia great britain and the atlantic features in common with other published curves include a callovian oxfordian positive excursion a kimmeridgian middle volgian negative trend and a middle volgian negative excursion these correlations allow refinement chronostratigraphy of the jurassic of svalbard

extensive recession of cordillera darwin glaciers in southernmost south america during heinrich stadial 1 abstract the geographic expression and phasing of events during the last termination are important for isolating mechanisms that caused earth to emerge from the last ice age heinrich stadial 1 hs1 14 600 18 000 yr bp is a key because of the central role that its far field effects had on the last termination in the southern hemisphere here we present new data from cordillera darwin that show rapid glacier recession in southern south america during hs1 this retreat was coeval with ice recession elsewhere in south america and new zealand with increased upwelling in the southern ocean with warming of ssts offshore of chile and with a rise in atmospheric co2 together these data indicate a coherent and rapid response to the effects of hs1 in the middle and high latitudes of the southern hemisphere

modeling of the runup heights of the hokkaido nansei oki tsunami of 12 july 1993 the hokkaido nansei oki earthquake mw 7 7 of july 12 1993 is one of the largest tsunamigenic events in the sea of japan the tsunami magnitudemt is determined to be 8 1 from the maximum amplitudes of the tsunami recorded on tide gauges this value is larger thanmw by 0 4 units it is suggested that the tsunami potential of the nansei oki earthquake is large formw a number of tsunami runup data are accumulated for a total range of about 1000 km along the coast and the data are averaged to obtain the local mean heightshn for 23 segments in intervals of about 40 km each the geographic variation ofhn is approximately explained in terms of the empirical relationship proposed byabe 1989 1993 the height prediction from the available earthquake magnitudes ranges from 5 0 8 4 m which brackets the observed maximum ofhn 7 7 m at okushiri island

the last glacial holocene transition in southern chile warming at the last glacial termination in the north atlantic region was interrupted by a period of renewed glacial activity during the younger dryas chronozone ydc the underlying mechanism of this cooling remains elusive but hypotheses turn on whether it was a global or a north atlantic phenomenon chronological sedimentological and palaeoecological records from sediments of small lakes in oceanic southern chile demonstrate that there was no ydc cooling in southern chile it is therefore likely that there was little or no cooling in southern pacific surface waters and hence that ydc cooling in the north atlantic was a regional rather than global phenomenon

the interpretation and classification of subglacially deformed materials abstract a general classification of subglacially deformed materials is proposed based on sediment properties and their relationship to styles of subglacial strain deformation till is defined as homogenized usually diamictic material formed by glacially induced shear of subsole materials three types are recognized type a formed by pervasive ductile deformation type b formed by brittle shear and comminution till produced by the reduction of void space by in situ crushing and abrasion the term glacitectonite is adopted for materials that have undergone subglacial shear but retain some of the structural characteristics of the parent material original structures may be truncated by glacitectonic fabric elements type a or distorted but not truncated type b the principles of strain and material response particle orientation mechanisms fabric development and drainage conditions are reviewed examples of deformation tills and glacitectonites from breidamerkurjokull iceland slettmarkbreen norway loch lomond scotland and east yorkshire england are used to illustrate the nature of subglacially deformed materials and their relationship to former subglacial strain and drainage conditions the geologic evidence suggests a continuum of bed strengths can be recognized in deforming substrata ranging from high strength low strain type b deformation till and comminution till to low strength high strain type a deformation till

late quaternary glaciation history of isla de los estados southeasternmost south america isla de los estados is a mountainous island southeast of tierra del fuego in southernmost south america its central and eastern parts have an alpine topography transected by u shaped valleys small partly over deepened fjords and a multitude of abandoned cirques all associated with extensive former local glaciations traces of glacial erosion generally reach 400 450 m a s l and above that trimline a distinct sharp edged nunatak derived landscape is present the westernmost part of the island has a lower more subdued topography reflecting its softer geology but possibly also over running and erosion by mainland derived ice streams the present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs a combination of osl and c 14 datings show that these sediments mostly date from the latest wisconsinan weichselian glacial cycle i e from the last ca 100 ka with the oldest glaciolacustrine deposits possibly as old as 90 80 ka the upper parts of overlying tills with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island date from the last global glacial maximum lgm radiocarbon ages of peat and lake sediments indicate that deglaciation began 17 16 cal ka bp c 2010 university of washington published by elsevier inc all rights reserved

assessment of source probabilities for potential tsunamis affecting the u s atlantic coast abstract estimating the likelihood of tsunamis occurring along the u s atlantic coast critically depends on knowledge of tsunami source probability we review available information on both earthquake and landslide probabilities from potential sources that could generate local and transoceanic tsunamis estimating source probability includes defining both size and recurrence distributions for earthquakes and landslides for the former distribution source sizes are often distributed according to a truncated or tapered power law relationship for the latter distribution sources are often assumed to occur in time according to a poisson process simplifying the way tsunami probabilities from individual sources can be aggregated for the u s atlantic coast earthquake tsunami sources primarily occur at transoceanic distances along plate boundary faults probabilities for these sources are constrained from previous statistical studies of global seismicity for similar plate boundary types in contrast there is presently little information constraining landslide probabilities that may generate local tsunamis though there is significant uncertainty in tsunami source probabilities for the atlantic results from this study yield a comparative analysis of tsunami source recurrence rates that can form the basis for future probabilistic analyses

distribution of tsunami interevent times 1 the distribution of tsunami interevent times is analyzed using global and site specific hilo hawaii tsunami catalogs an empirical probability density distribution is determined by binning the observed interevent times during a period in which the observation rate is approximately constant the empirical distributions for both catalogs exhibit non poissonian behavior in which there is an abundance of short interevent times compared to an exponential distribution two types of statistical distributions are used to model this clustering behavior 1 long term clustering described by a universal scaling law and 2 omori law decay of aftershocks and triggered sources the empirical and theoretical distributions all imply an increased hazard rate after a tsunami followed by a gradual decrease with time approaching a constant hazard rate examination of tsunami sources suggests that many of the short interevent times are caused by triggered earthquakes though the triggered events are not necessarily on the same fault

comment on the mid oxfordian late jurassic positive carbon isotope excursion recognised from fossil wood in the british isles by c r pearce s p hesselbo a l coe palaeogeography palaeoclimatology palaeoecology 221 343 357

climate induced changes as registered in inorganic and organic sediment components from laguna potrok aike argentina during the past 51 ka total organic carbon total inorganic carbon biogenic silica content and total organic carbon total nitrogen ratios of the laguna potrok aike lacustrine sediment record are used to reconstruct the

isotopic signals from callovian kimmeridgian middle upper jurassic belemnites and bulk organic carbon staffin bay isle of skye scotland abstract the stable isotope data presented here significantly extend and expand upon previous isotopic investigations of the middle to late jurassic interval the belemnite samples collected from the staffin bay and staffin shale formations from the isle of skye scotland yielded oxygen isotope values consistent with callovian kimmeridgian palaeotemperatures of 6 7 20 6 c the carbon isotope data comprise one of the first moderately high resolution investigations of the relationship between terrestrial 13 c org predominantly fossil wood debris and marine 13 c carb belemnites as derived from a geologically coeval record the staffin bay data reveal a broad early to mid oxfordian positive carbon isotope excursion the excursion maximum occurs in the cordatum zone british boreal ammonite zonation although high values persist into the tenuiserratum zone the correspondence between the marine and terrestrial records indicates a strong coupling of the ocean atmosphere system and suggests that the total exchangeable carbon reservoir would have been affected at this time the mid oxfordian negative carbon isotope excursions identified in published tethyan records and commonly attributed to methane release are not recorded in the staffin bay data which may suggest that the tethyan excursions do not represent fluctuations in the global carbon reservoir and that the fidelity of the methane hypothesis should be re evaluated supplementary material isotopic and geochemical data are available at http www geolsoc org uk sup18339

paleoclimatic control of biogeographic and sedimentary events in tethyan and peri tethyan areas during the oxfordian late jurassic abstract the paleobiogeographical distribution of oxfordian ammonites and coral reefs in northern and central europe the mediterranean area north and east africa and the middle east and central asia is compared with the distribution in time and space of the most important lithofacies interest in the oxfordian is focused on changes in facies and in biogeographical patterns that can be interpreted as the results of climatic events paleotemperature trends inferred from oxygen isotopes and paleoclimatic simulations are tested against fossil and facies data a late callovian early oxfordian crisis in carbonate production is indicated by the widespread absence of lower oxfordian reefal formations there is a gap hiatus in deposition on epicontinental platforms with middle oxfordian deposits resting paraconformably on upper callovian while shales accumulated in adjacent intracratonic basins simultaneously in mediterranean tethys radiolarites accumulated in deep troughs while rosso ammonitico facies formed on pelagic swells however deposition on swells was also discontinuous with numerous gaps hiatuses and sequences that are much reduced in thickness middle callovian deposits are generally overlain by middle oxfordian limestones the dearth of carbonates is consistent with a cooling event lasting about 1 my by the middle oxfordian a warming leading to greenhouse type conditions is suggested on the basis of both biogeographical mostly coral reef distribution and geochemical data carbonates spread onto an extensive european platform while radiolarites reached a maximum development in the mediterranean tethys two distinct latitudinal belts with seemingly different accumulation regimes are therefore inferred similar latitudinal belts were also present in the late oxfordian when carbonates were widespread the distribution of reefal facies in the late oxfordian early kimmeridgian fits relatively well with gcms simulations that imply low rainfall in the tethyan mediterranean area and slightly higher precipitation in central and northern europe local salinity variations reflecting more arid or humid conditions may bias the paleotemperature signal inferred from 18o values biogeographical and facies distributions combined with 18o values unravel the ambiguity and support a late callovian early oxfordian cooling followed by warming in the later oxfordian

reflections on soft subglacial beds as a mosaic of deforming and stable spots abstract much discussion regarding subglacial processes is centred around the question of how soft beds respond to ice overriding in particular how widespread and penetrative is their deformation how does it affect the ice stability and what are the consequences for large scale sediment redistribution patterns contrasting views have been proposed which are difficult to verify and reconcile in the light of scarcity of agreed criteria to identify deforming beds here we suggest that soft beds under warm based glaciers can be envisaged as a mosaic of deforming and stable spots transient in time and space according to changes in the control parameters at the ice bed interface the subglacial mosaic model is consistent with field data showing heavily deformed beds interspersed with largely undisturbed beds it is suggested that deformation found in tills is a cumulative effect of strain within a relatively thin ephemeral deforming spots under the ice sole affecting the till as it accretes during ice overriding in accord with the coulomb plastic rheology the role of clast ploughing in bed deformation is emphasised

climatic fluctuations and seasonality during the late jurassic oxfordian early kimmeridgian inferred from δ18o of paris basin oyster shells abstract oxygen isotope data from biostratigraphically well dated oyster shells from the late jurassic of the eastern paris basin are used to reconstruct the thermal evolution of western tethyan surface waters during the early oxfordian early kimmeridgian interval seventy eight oyster shells were carefully screened for potential diagenetic alteration using cathodoluminescence microscopy isotope analyses were performed on non luminescent parts of shells n 264 intra shell 18 o variability was estimated by microsampling along a transect perpendicular to the growth lines of the largest oyster shell the sinusoidal distribution of the 18 o values along this transect and the dependence of the amplitude of variations with bathymetry suggest that intra shell variability reflects seasonal variations of temperature and or salinity average amplitudes of about 5 c in shallow water environments and of about 2 3 c in deeper offshore environments are calculated these amplitudes reflect minimum seasonal temperature variation our new data allow to constrain existing paleotemperature trends established from fish tooth and belemnite 18 o data and are in better agreement with paleontological data more specifically a warming trend of about 3 c is reconstructed for oceanic surface waters during the early to middle oxfordian transition with maximum temperatures reaching 24 c in the transversarium zone late middle oxfordian from the transversarium zone to the bimmamatum zone a cooling of about 7 c is indicated whereas from the bimmamatum zone temperatures increased again by about 7 c to reach 24 c in average during the cymodoce zone early kimmeridgian

tsunami recurrence function structure methods of creation and application for tsunami hazard estimates this paper considers a theoretical basement for a poissonian probability model for tsunami run up heights with emphasis on the tsunami recurrence function it is shown that the tsunami recurrence function of a general type contains at least two scale parameters asymptotic frequency of big tsunamis f related to the considered region and characteristic tsunami height h for the considered location in the region a method for the correct statistical evaluation of the parameters f and h and their variations using observational data from tsunami catalogues is created the paper considers some theoretical and applied problems related to the tsunami recurrence function an example of a two parameter tsunami hazard map and also the problem of probabilistic tsunami hazard estimation

multi proxy analyses of a peat bog on isla de los estados easternmost tierra del fuego a unique record of the variable southern hemisphere westerlies since the last deglaciation we have analyzed an almost 14 000 year old peat sequence on the island of isla de los estados 55 degrees s 64 degrees w east of tierra del fuego in the core of the southern hemisphere westerlies a multitude of methods have been used high resolution c 14 dating detailed lithologic descriptions including humification degree loss on ignition magnetic susceptibility bulk density pollen and spore analysis and determination of aeolian sand influx by combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the atlantic sector of the southern ocean it shows that this westerly wind belt was most intense at the onset of the record 13 600 13 200 cal bp coinciding with the mid to late part of the antarctic cold reversal followed by a gradual decline at 12 200 cal bp the westerlies seem to have shifted to a position south of tierra del fuego and this phase the calmest and driest period on the island throughout the sequence ended at 10 000 cal bp when the westerlies moved equatorward again since then the westerlies have been present but with a variable impact on the 55 degrees s latitude of the atlantic mostly conditions have been fairly similar to today but occasionally with a wider or narrower and or weaker or stronger wind belt at 7200 cal bp wind intensity began to increase and between 4500 and 3500 cal bp these southern latitudes experienced a distinct wind and precipitation maximum both in terms of perseverance and intensity our results show a both wide and strong wind belt with possible niveo aeolian activity in tierra del fuego in winter and possibly creating milder summers around the antarctic peninsula in the later part of the holocene expansion contraction phases of the wind belt especially in winter seem to have been a common phenomenon c 2012 elsevier ltd all rights reserved

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

carbon and oxygen isotope composition of oxfordian early kimmeridgian belemnite rostra palaeoenvironmental implications for late jurassic seas abstract stable isotope analyses have been undertaken on oxfordian early kimmeridgian belemnite rostra derived from three palaeogeographic provinces of europe 1 the boreal subboreal province isle of skye in scotland 2 the submediterranean province central poland and southern germany and 3 the mediterranean province pieniny klippen belt in the western carpathians the samples have been screened for possible diagenetic alteration by using cathodoluminescence and trace element analyses and have been found to be largely well preserved calculated palaeotemperatures 10 15 c and analyses of belemnite habitats suggest that the boreal subboreal belemnites were living in a relatively shallow sea not deeper than 100 150 m while the other belemnites possibly inhabited deeper neritic environments despite the influence of a vital effect the 13c values of belemnite rostra are interpreted to reflect primary variations in the oceanic carbon isotope signal the fairly uniform submediterranean 13c values indicate a similar isotope composition of dissolved inorganic carbon dic in the area of sedimentation of sponge megafacies in the deep tethyan shelves the slightly lowered 13c values of some mediterranean belemnites might occur due to upwelling providing 12c enriched bottom waters onto the area of the czorsztyn ridge in the oxfordian the discernibly more positive 1 2 5 13c values of boreal subboreal belemnites are related to a high biologic productivity and a high organic matter burial in the partly isolated boreal sea the stated differentiation in carbonate 13c values distinctly exceeds present day differences in isotope composition of seawater dic

power law scaling and probabilistic forecasting of tsunami runup heights a power law scaling relationship describes tsunami runup heights at ten locations in japan knowledge of the scaling law for tsunamis can be the basis for probabilistic forecasting of the size and number of future events and for estimating probabilities of extremely large events using tsunami runup data archived by the u s national geophysical data center we study ten locations where the tsunami record spans at least one order of magnitude in runup height and the temporal record extends back several decades a power law or upper truncated power law describes the cumulative frequency size distribution of tsunami runup heights at all ten locations where the record is sufficient to examine shorter time intervals within the record the scaling relationship for the shorter time intervals is consistent with the scaling relationship for the entire record the scaling relationship is used to determine recurrence intervals for tsunami runup heights at each location in addition to the tsunami record used to determine the scaling relationship at some of the locations a record of large events 5 m extends back several centuries we find that the recurrence intervals of these large events are consistent with the frequency predicted from the more recent record for tsunami prone locations where a scaling relationship is determined the predicted recurrence intervals may be useful for planning by coastal engineers and emergency management agencies

evaluation of tsunami potential based on conditional probability for specific zones of the pacific tsunamigenic rim abstract the pacific tsunamigenic rim is one of the most tsunamigenic regions of the world which has experienced large catastrophic tsunamis in the past resulting in huge loss of lives and properties in this study probabilities of occurrences of large tsunamis with tsunami intensity soloviev imamura intensity scale i 1 5 i 2 0 i 2 5 i 3 0 i 3 5 and i 4 0 have been calculated over the next 100 years in ten main tsunamigenic zones of the pacific rim area using a homogeneous and complete tsunami catalogue covering the time periods from 684 to 2011 in order to evaluate tsunami potential we applied the conditional probability method in each zone by considering the inter occurrence times between the successive tsunamis generated in the past that follow the lognormal distribution thus we assessed the probability of the next generation of large tsunamis in each zone by considering the time of the last tsunami occurrence the a posteriori occurrence of the last large tsunami has been also assessed assuming that the time of the last occurrence coincides with the time of the event prior to the last one the estimated a posteriori probabilities exhibit satisfactory results in most of the zones revealing a promising technique and confirming the reliability of the tsunami data used furthermore the tsunami potential in different tsunamigenic zones is also expressed in terms of spatial maps of conditional probabilities for two levels of tsunami intensities i 1 5 and i 2 5 during next 10 20 50 and 100 years estimated results reveal that the conditional probabilities in the south america and alaska aleutian zones for larger tsunami intensity i 2 5 are in the range of 92 93 much larger than the japan 69 for a time period of 100 years suggesting that those are the most vulnerable tsunamigenic zones the spatial maps provide brief atlas of tsunami potential in the pacific rim area

consolidation of sediments by glaciers relations between sediment geotechnics soft bed glacier dynamics and subglacial ground water flow a theory of subglacial consolidation is developed which shows how the meltwater flux beneath a glacier leaves a consolidation signature from which many important glacier dynamic properties can be inferred conditions under which water is discharged through channels or in a thin film at the ice bed interface or by ground water flow are discussed and it is concluded that glaciers flowing over aquifers of high transmissibility can induce deep circulation patterns quite different from non glacial circulation

theory of glacial erosion transport and deposition as a consequence of subglacial sediment deformation a theory of erosion transport and deposition of unlithified sediments by glaciers is presented it predicts the large scale areal distribution of zones and rates of erosion and deposition in time and space through a complete glacial cycle together with the resultant intensity of large scale lincations drumlins which will be incised in the landscape the theory also predicts the dispersal patterns of subglacial lithologies together with the form of dispersal trains derived from distinctive sources and the vertical and horizontal distribution of lithologies within a till it predicts major erosional discontinuities within tills and the formation of boulder pavements it suggests that the dominant proportion of the lowland tills produced by pleistocene mid latitude ice sheets was generated by subglacial deformation and explains why they are predominantly fine grained the theory is based on an analysis of glacier dynamic processes and therefore can be used to infer the dynamic behaviour of former ice sheets from the distribution of tills and their lithologic composition

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

the upper truncated power law applied to earthquake cumulative frequency magnitude distributions evidence for a time independent scaling parameter earthquake cumulative frequency magnitude cfm distributions are described by the gutenberg richter power law where the exponent is the b value although it has been reported that the b value changes before large earthquakes we find that an upper truncated power law applied to earthquake cfm distributions yields a time independent scaling parameter herein called the value we analyze earthquakes associated with subduction of the nazca plate beneath south america and find a region of isolated seismic activity at depths greater than 500 km between 20 s and 30 s for the entire record 1973 2000 the earthquake cfm distribution in this isolated region is well described by a gutenberg richter power law with b 0 58 the data set includes several large seismic events with m b 6 8 a power law applied to the cfm distributions for short time intervals between the large events yields b values greater than the b value for the entire record cfm distributions for the short time intervals are better described by an upper truncated power law than by a power law the value determined by applying an upper truncated power law to the short time intervals is equal to the b value obtained by applying the gutenberg richter power law to the entire record temporal changes in b value are due to temporal fluctuations in maximum magnitude analysis of four flinn engdahl regions two in subduction zones and two along spreading ridges demonstrates wider applicability of the results the value is an unchanging characteristic of the system that may be determined from a short term record manuscript received 2 july 2001

tsunami hazard probability in japan abstract an analysis of future tsunami hazard on the coast of the japanese islands is made in terms of probability for a coastal site being hit by a tsunami of which the wave height exceeds a certain level during a period from 2000 to 2010 tsunami wave height at a site on the pacific coast is estimated mostly based on numerical experiment in which a typical fault model of the tsunami generating earthquake is assumed meanwhile probability of the tsunami generating earthquake occurring during 2000 to 2010 is evaluated either from historical data of earthquake occurrence or from near shore crustal strain accumulation combining the wave height estimate with the probability evaluation of tsunami occurrence probabilities of a site being hit by a tsunami of which the wave height exceeds certain levels are evaluated on the pacific coast it seems that the probability for a violent tsunami of which the wave height exceeds 5 m is highest along the pacific coast in central japan reaching a value of 41 per cent on the other hand a probability value as high as 69 per cent is found for a moderately large tsunami having a wave height of 1 m or so along the shikoku and kyushu coasts a crude probability evaluation is also made for tsunamis on the japan sea coast where tsunami activity is substantially lower than that of the pacific coast the probability for a violent tsunami seems to amount to only 1 per cent or so for a 10 yr period similar probabilities for tsunamis excited by a distant source off peru chile kamchatka and aleutian alaska are also evaluated in this case probabilities of tsunami wave height exceeding 1 and 3 m are respectively evaluated as 19 and 15 per cent on the pacific coast such probabilities being not quite negligible

quaternary of tierra del fuego southernmost south america an updated review abstract the quaternary of tierra del fuego is represented by glacial glaciofluvial glaciolacustrine marine and aeolian deposits six drift units have been described the oldest dating from the late pliocene these are starting from the oldest the rio grande sierra de los frailes cabo virgenes punta delgada primera angostura and segunda angostura drifts neoglacial and little ice age events are represented in cirques and higher mountain valleys marine deposits and raised beaches were formed during middle pleistocene late pleistocene and holocene interglacial stages after the definitive ice retreat 10 ka ago vegetation changed from tundra and cold steppe to subantarctic forest environments marine deposits reflect also colder conditions than the present ones aeolian processes prevailed in northern tierra del fuego where semiarid conditions and the frequent westerlies favoured the retransportation of finer materials coming from pre existing deposits before the opening of the magellan straits earliest human colonization occurred in northern tierra del fuego ca 11 ka bp in tundra like environmental conditions pedestrian hunters of camelids and foxes co existed with pleistocene fauna that became extinct during late glacial earliest holocene times the steppe area inland and atlantic coast was successively occupied since then until recent times on the other hand the beagle channel coasts were occupied since 6 ka bp by hunter gatherer groups adapted to maritime littoral conditions finally the easternmost area of the island was inhabited at least since 1 5 ka bp the human settlements in these latter areas occurred under environmental conditions similar to the present ones when the fuegian forest was definitively established

southern hemisphere westerly wind changes during the last glacial maximum paleo data synthesis changes in the strength and position of southern hemisphere westerly winds during the last glacial cycle have been invoked to explain both millennial and glacial interglacial climate fluctuations however neither paleo models nor paleodata agree on the magnitude or even the sign of the change in wind strength and latitude during the most studied glacial period the last glacial maximum lgm compared to the recent past this paper synthesizes paleo environmental data that have been used to infer changes in lgm winds data compilations are provided for changes in terrestrial moisture dust deposition sea surface temperatures and ocean fronts and ocean productivity and existing data on southern hemisphere ocean circulation changes during the lgm are summarized we find that any hypothesis of lgm wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents cooler temperatures and higher productivity in the subantarctic zone and reductions in agulhas leakage around southern africa our comparison suggests that an overall strengthening an equatorward displacement or no change at all in winds could all be interpreted as consistent with observations if a single cause related to the southern westerlies is sought for all the evidence presented then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the observations however other processes such as weakening or poleward shifts in winds a weakened hydrological cycle extended sea ice cover and changed buoyancy fluxes cannot be ruled out as potential explanations of observed changes in moisture surface temperature and productivity we contend that resolving the position and strength of westerly winds during the lgm remains elusive based on data reconstructions alone however we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the lgm

late jurassic climate and its impact on carbon cycling abstract the climate of the late jurassic has been characterized by high atmospheric co2 levels and by a monsoonal rainfall pattern in this study we traced the evolution of the global carbon cycle through the late jurassic with the help of carbonate carbon isotope stratigraphy the oxfordian tithonian 13c curve is marked by one major positive carbon isotope excursion with an amplitude 13 c 1 0 middle to late oxfordian and a second minor positive excursion with an amplitude 13 c late kimmeridgian the early kimmeridgian and early tithonian 13c values fluctuate around 13 c 2 0 3 and contrast with the less positive 13c values of early oxfordian and late tithonian age 13 c 1 0 5 a comparison of the late jurassic carbonate carbon isotope curve with the occurrence of organic rich sediments suggests that not only fluctuations in organic carbon burial but also in carbonate carbon burial had an impact on the c isotope record the oxfordian c isotope excursion appears to correspond to a time of overall increased organic carbon burial triggered by increased nutrient transfer from continents to oceans during a time of rising global sea level however episodes of enhanced organic carbon burial during the kimmeridgian and early tithonian are not reflected by prominent spikes in the c isotope record favourable conditions for carbonate platform growth at a time of high global sealevel may have resulted in the stabilisation of the c org c carb burial ratio and hence maintained the 13c record at steady but relatively positive values the middle and late tithonian c isotope values drop below 13 c 1 5 a similar shift to less positive c isotope values was recognized in other c isotope records from the tethys and atlantic oceans and reflects a decrease in the c org c carb burial ratio possibly related to a reorganisation of the global climate system globally widespread marine black shale mature quartzose sandstone assemblages suggest that the relative efficiency of the late jurassic carbon pumps was controlled by weathering erosion and runoff causing widespread marine eutrophication eutrophication favoured the organic carbon pump but it diminished the carbonate platform growth potential the monsoonal rainfall distribution pattern may explain why late jurassic carbonate platforms experienced less severe growth crises than early cretaceous carbonate platforms

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

modelling the sedimentary signature of long waves on coasts implications for tsunami reconstruction abstract we describe a process based mathematical model of suspended and bedload sediment transport under long non breaking waves on a plane beach and we use this model to investigate the relationship between the hydrodynamics of run up and run down and the resulting erosive and depositional signature which the wave leaves in particular we compare the results of our forward model with several recently proposed methods for reconstructing tsunami hydrodynamics from their deposits we find that sediment transport both as bedload and in suspension is strongly controlled by asymmetries in the direction of maximum velocity in the latter case it is also affected by settling lag especially around the point of maximum run up the combination of these effects appears to preclude simple methods of reconstructing tsunami hydrodynamics from the large scale features of their signatures however our results suggest some promising avenues for further investigation

subglacial till formation sedimentary characteristics and classification we review the major subglacial till forming processes as presently understood by glacial researchers and define the parameters within which tills are produced and reconcile them with sedimentary end members processes of deformation flow sliding lodgement and ploughing coexist at the base of temperate glacier ice and act to mobilize and transport sediment and deposit it as various end members ranging from glacitectonically folded and faulted stratified material to texturally homogeneous diamicton the dominance of any one subglacial process varies both spatially and temporally giving rise to the possibility that a till or complex till sequence contains a superimposed signature of former transportation deposition at the ice bed interface we recommend that while glacial geologists and geomorphologists should be able to recognize the sedimentary imprints of various subglacial processes genetic fingerprinting of subglacial tills should be less process specific and till classification must reflect the range of products encompassed by the subglacial till production continuum glacial geologists can presently unequivocally identify a glacitectonite rock or sediment that has been deformed by subglacial shearing deformation but retains some of the structural characteristics of the parent material b subglacial traction till sediment deposited by a glacier sole either sliding over and or deforming its bed the sediment having been released directly from the ice by pressure melting and or liberated from the substrate and then disaggregated and completely or largely homogenised by shearing and support the theoretical case for c melt out till sediment released by the melting of stagnant or slowly moving debris rich glacier ice and directly deposited without subsequent transport or deformation because observations on contemporary glaciers reveal that their beds are most likely to be mosaics of deformation and sliding and warm based and cold based conditions the patterns of which change temporally and spatially it is extremely unlikely that subglacial till end members in the geological record will be anything but hybrids produced by the range of processes operative in the subglacial traction zone

tsunami recurrence versus tsunami height distribution along the coast the tsunami frequency of occurrence recurrence function is the main functional parameter for description of tsunami activity and one of the most serious problems is to establish its form it is the main parameter of the tsunami probability model and it is needed as the foundation for tsunami zoning and insurance strategy theoretical investigation of the tsunami frequency size function for selected coastal points together with tsunami height distribution along the coast allows one to find the relationship between these distributions some exact results regarding the structure of the tsunami frequency size function are derived

late wisconsin landform distribution and glacier bed conditions in wisconsin abstract the late wisconsin laurentide ice sheet advanced across permafrost and reached its maximum extent in wisconsin between about 18 000 and 15 000 years ago deep permafrost persisted in southern wisconsin until about 14 000 years ago and in northern wisconsin until about 13 000 years ago we suggest that during maximum glaciation a zone about 5 km wide in the south and 20 km wide in the north along the margin of the late wisconsin glacier was frozen to its bed meltwater from farther behind the margin where the bed was at least locally thawed cut a series of closely spaced tunnel channels through the frozen bed zone these channels most likely formed episodically and they were the source for much of the meltwater stream sediment deposited in broad outwash plains beyond the ice margin frozen bed conditions near the margin also likely contributed to increased upward shearing of sediment and the accumulation of thicl supraglacial sediment in northern areas up ice from the frozen bed zone the glacier bed was at least locally thawed in a zone about 75 km wide extensive drumlin fields formed in the area of the bed that was thawed by about 13 000 years ago permafrost melted in northern wisconsin and thawed bed conditions probably extended to the ice margin throughout wisconsin and adjacent areas after about 13 000 years ago in northern wisconsin the glacier was sliding on its bed and forming drumlins out to the ice margin and thick supraglacial sediment no longer accumulated

relative sea level change and carbon isotopes data from the upper jurassic oxfordian of central and southern europe studies on cretaceous pelagic limestones have shown a close correspondence between putative sea level curves and the carbon isotope profile suggesting a possible relationship between the two phenomena such a relationship could relate to shelf sea area governing the global burial rate of organic carbon which in turn controls the 13c 12c ratio of dissolved inorganic carbon in the oceanic reservoir in order to see whether or not this relationship might be of more general applicability the major mid oxfordian jurassic transgression is documented to zonal level and appropriate carbon isotope data are presented although the applicability of ammonite zonation to the mid oxfordian is problematic on a regional scale a clear 13c excursion is present in the trunsversariurn zone which is coincident with regional overstep and or evidence of shoreline retreat and or evidence of bathymetric deepening in europe and elsewhere the use of the carbon isotope curve as a proxy for shelf sea area or relative sea level is worthy of further exploration

detailed oxygen and carbon isotope stratigraphy of the oxfordian in central poland a collection of 73 belemnites and brachiopods from detailed stratigraphically documented sections in the polish jura chain of central poland representing almost the whole oxfordian stage was studied for oxygen and carbon isotopes the 18o and 13c v pdb values range from 3 6 to 0 5 and from 1 6 to 2 for belemnite rostra and from 2 5 to 0 4 and from 1 6 to 4 3 for brachiopod shells respectively the 13c temporal trends of belemnite rostra and brachiopod shells show a constant isotopic difference ca 2 5 3 which is interpreted as a vital effect of belemnites or as a result of different life environments 18o values are similar in both groups of fossils the 18o values in the lower and middle oxfordian oscillate around 0 and decrease in the upper oxfordian this decrease results mainly from diagenetic overprint as proved by the cathodoluminescence studies the lower and middle oxfordian 18o derived temperatures were constant in consequence of significant ocean depth for this reason there are no established links with distribution of ammonite faunas the 13c temporal trend displays a gentle slope through the oxfordian and reaches maximum values at the turn of the plicatilis transversarium zones of the middle oxfordian which is commonly considered as a global event it can be related to the sea level highstand and growth crisis of carbonate platforms the decrease in 13c values starting in the upper middle oxfordian is interpreted to be due to the acceleration of carbonate sedimentation rate during this time period

oxygen and carbon isotope composition of callovian lower oxfordian middle upper jurassic belemnite rostra from central poland a record of a late callovian global sea level rise abstract oxygen and carbon isotope data of well preserved and stratigraphically well dated belemnite rostra are presented from a callovian lower oxfordian succession of the polish jura chain south central poland that was deposited in a deep shelf environment palaeotemperatures calculated from belemnite 18 o values 9 to 14 c indicate relatively constant climatic conditions during studied callovian and early oxfordian intervals belemnite 13 c temporal trends which are interpreted to record primary variation in the isotope composition of dissolved inorganic carbon reservoir display a prominent positive carbon isotope shift up to around 1 7 vpdb in the upper callovian this excursion is preceded and followed by a drop in average 13 c values of belemnite rostra of around 1 the late callovian carbonate carbon isotope excursion is likely linked to the enhanced storage of organic carbon in shelf sediments during a global sea level rise the presented data are not compatible with the theory of prolonged global glaciation at the middle late jurassic transition

glacial trimlines to identify former ice margins and subglacial thermal boundaries a review and classification scheme for trimline expression abstract reconstructions of former ice sheets and glaciers provide important palaeoglaciological information about their behaviour in response to climate changes glacial trimlines record both the margin positions and palaeo ice thickness enabling the production of empirically constrained 3 dimensional reconstructions however the literature review into the characteristics interpretation and use of glacial trimlines here presented shows that these features have been under utilised and are poorly described in the existing literature with a confusing terminology currently in use a new classification scheme and terminology for trimline identification and interpretation is developed to better facilitate further research into these common features of glacierised and formerly glaciated landscapes