readvance of the last british irish ice sheet during greenland interstade 1 gi 1 the wester ross readvance nw scotland abstract fourteen samples obtained from torridon sandstone boulders on four moraines marking the limit of the wester ross readvance wrr in nw scotland yielded tightly clustered 10 be exposure ages confirming contemporaneous or penecontemporaneous moraine deposition collectively the 14 samples yield mean ages of 13 5 1 2 ka to 14 0 1 7 ka depending on choice of geomagnetic scaling and sampling surface erosion rates all fourteen moraine ages are significantly younger than an age of ca 16 3 ka previously proposed for the wrr and also younger than most samples obtained from rock outcrops within the wrr limits the ages obtained for the wrr moraines appear to confirm that a substantial cover of glacier ice persisted over low ground in nw scotland during at least the early part of the lateglacial interstade greenland interstade 1 we infer that the wrr probably occurred in response to rapid short lived cooling during the older dryas climatic reversal greenland interstade 1d though the possibilities that the wrr represents ice margin response to a later climatic reversal during the lateglacial interstade or stabilization and readvance of the ice margin following rapid offshore calving cannot be discounted

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

glacier response to climatic change during the loch lomond stadial and early flandrian geomorphological and palynological evidence from the isle of skye scotland the deglaciation of skye at the close of the loch lomond stadial is assessed on the basis of detailed geomorphological mapping and pollen stratigraphic correlations it is concluded that deglaciation proceeded in two distinct stages the first was marked by numerous glacier stillstands and readvances while uninterrupted retreat and local glacier stagnation occurred during the second and final stage the pollen evidence indicates that the first stage was well advanced before the marked thermal improvement at the start of the flandrian and it is inferred that initial glacier retreat occurred in response to a decline in precipitation in the later part of the loch lomond stadial the first stage of glacier retreat continued into the early flandrian during which climatic amelioration was interrupted briefly final deglaciation appears to have occurred rapidly in response to sustained temperature increases the collective evidence also indicates spatial variations in the timing of deglaciation which appear to reflect differences in glacier morphology

the minch palaeo ice stream nw sector of the british irish ice sheet geophysical data from the uk continental shelf off nw scotland reveal strongly parallel subglacial bedforms on the sea bed field mapping on the adjacent landmass has identified closely spaced bedrock megagrooves and highly elongate drumlinoid forms all these mega scale glacial lineations probably formed beneath the same fast flowing zone of the last british irish ice sheet the minch palaeo ice stream this ice stream drained the nw sector of the british irish ice sheet during the late devensian glaciation marine isotope stage 2 and terminated near the edge of the continental shelf the size of the adjacent trough mouth sula sgeir fan and the presence of buried mega scale glacial lineations within the quaternary stratigraphic record imply that fast ice sheet flow in the minch has been a feature of several mid to late pleistocene glaciations

exposure dating and validation of periglacial weathering limits northwest scotland periglacial weathering limits on two mountains in northwest scotland separate zones of contrasting exposure history exposure dating of bedrock below the weathering limits gives ages consistent with late devensian deglaciation but six out of seven samples from above the weathering limits give minimum exposure ages older than late devensian ice expansion these results suggest that mountain summits stood as nunataks above the last ice sheet surface and rule out formation of weathering limits by periglacial rock breakdown since deglaciation trimming of frost debris during an ice sheet readvance or enhanced weathering prior to climatic warming during ice sheet downwastage the dating results do not preclude the possibility that weathering limits mark a former englacial boundary between passive cold based ice on mountain summits and erosive warm based ice at lower elevations although 26 al 10 be ratios for high level bedrock surfaces provide no evidence of prolonged static ice cover

integration of ice core marine and terrestrial records intimate refining the record of the last glacial interglacial transition integration of ice core marine and terrestrial records intimate is a core project of the inqua palaeoclimate commission the primary goal of which is to synchronise records of the last glacial interglacial transition lgit through a series of international workshops intimate has encouraged direct collaboration between scientists with interests and expertise in a wide range of palaeoenvironmental approaches the workshops have focused on the dissemination of good practice in the dating correlation and synthesis of diverse palaeoenvironmental records that span the lgit this special issue of quaternary science reviews presents some of the outcomes of the 8th intimate international workshop held in iceland in september 2005 and focuses on four themes considered vital to intimate s long term strategy 1 an event stratigraphy approach which uses the greenland oxygen isotope record as a stratotype sequence lies at the core of intimate s operations a revised event stratigraphy scheme for application to north atlantic lgit records is presented which is based on the new gicc05 greenland ice core chronology 2 new tree ring data from switzerland and the application of bayesian based procedures in the analysis of comprehensive radiocarbon data sets provide much potential for reducing the uncertainties in radiocarbon based age models 3 three of the contributions present new evidence that helps to refine the tephrostratigraphy of the lgit in the ne atlantic and new zealand regions 4 establishing the precise order and synchroneity of events during the lgit is vital to understand the causes and effects of abrupt climate change data are presented from the baltic region and alaska which vary in degree of compatibility with north atlantic records two final papers consider the roles of dansgaard oeschger events on thermokarst during the middle weichselian and of solar activity variations during the mid holocene both illustrate how the intimate event stratigraphy approach can apply to the study of other time intervals

methylhopanoids molecular indicators of ancient bacteria and a petroleum correlation tool abstract methylhopanoids are organic compounds synthesized by certain bacteria that when preserved in sediments act as molecular fossils or biomarkers for organic matter inputs from specific bacterial sources two series of methylhopanoids occur each mainly deriving from a distinct bacterial source cyanobacteria 2 methyl and methanotrophic bacteria 3 methyl the abundance and composition of methylhopanoids within sediments of modern depositional environments varies widely apparently due to different bacterial communities contributing to the sedimentary organic matter comparable molecular characteristics are found in oils and their source rocks consequently methylhopanoids are valuable in oil oil and oil source rock correlations distinguishing between samples related to different depositional environments in particular abundant 3 methylhopanoids from methanotrophic bacteria or an additional unknown bacterial source are characteristic of some modern alkaline saline lake environments comparable compositional features in the methylhopanes of oils allow the assignment of lacustrine oils offshore west africa to two distinct lacustrine source rock facies and to distinguish between different marine source facies thus refining oil source rock correlation

ice caps existed throughout the lateglacial interstadial in northern scotland we constrain in detail fluctuations of two former ice caps in nw scotland with multibeam seabed surveys geomorphological mapping and cosmogenic 10 be isotope analyses we map a continuous sequence of 40 recessional moraines stretching from 10 km offshore to the wester ross mountains surface exposure ages from boulders on moraine ridges in assynt and the summer isles region show that substantial dynamic ice caps existed in nw scotland between 13 and 14 ka bp we interpret this as strong evidence that large active glaciers probably survived throughout the lateglacial interstadial and that during the older dryas period ca 14 ka bp ice caps in nw scotland were thicker and considerably more extensive than in the subsequent younger dryas stadial by inference we suggest that lateglacial ice cap oscillations in scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period ca 15 11 ka bp natural environment research council nerc copyright 2008 reproduced with the permission of nerc published by john wiley sons ltd

periglacial trimlines former nunataks and the altitude of the last ice sheet in wester ross northwest scotland high level weathering limits separating ice scoured topography from frost weathered detritus were identified on 28 mountains in wester ross at altitudes of 700 960 m and a further 22 peaks support evidence of ice scouring to summit level weathering limits are defined most clearly on sandstone and gneiss which have resisted frost shattering during the late devensian lateglacial but can also be distinguished on schists and quartzite schmidt hammer measurements and analyses of clay mineral assemblages indicate significantly more advanced rock and soil weathering above the weathering limits the persistence of gibbsite above weathering limits indicates that they represent the upper limit of late devensian glacial erosion the regular decline of weathering limit altitudes along former flowlines eliminates the possibility that the weathering limits represent former thermal boundaries between protective cold based and erosive warm based ice the weathering limits are therefore interpreted as periglacial trimlines that define the maximum surface altitude of the last ice sheet calculated basal shear stresses of 50 95 kpa are consistent with this interpretation reconstruction of ice sheet configuration indicates that the former ice shed lay above 900 m along the present watershed and that the ice surface descended northwestwards with broad depressions along major troughs and localised domes around independent centres of ice dispersal extrapolation of the ice surface gradient and altitude suggests that the ice sheet did not overrun the outer hebrides but was confluent with the independent outer hebrides ice cap in the north minch basin erratics located up to 140 m above the reconstructed ice surface are inferred to have been emplaced by a pre late devensian ice sheet or ice sheets of unknown age 1997 john wiley sons ltd

climatic changes in areas adjacent to the north atlantic during the last glacial interglacial transition 14 9 ka bp a contribution to igcp 253 this paper presents a summary of the evidence for climatic changes during the last glacial interglacial transition 14 9 ka bp in land areas adjacent to the north atlantic it is a synthesis of the results of the 12 regional summaries compiled by contributors to the north atlantic seaboard programme of igcp 253 that are published separately in this issue of journal of quaternary science eighteen palaeotemperature curves are compared and arranged in three transects one from southern europe to spitsbergen a second from ireland to poland and the third from southern new england to the labrador baffin shelf area ten maps are presented that summarise the synoptic climatic conditions of the region in 500 year time periods the purpose of the exercise is to examine the extent to which any emerging patterns support the ruddiman and mclntyre model of large scale shifts in the position of the oceanic polar front during the last glacial interglacial transition some broad agreement emerges although the influence of oceanic changes is diminished in areas that lay in close proximity to the laurentide and fennoscandian ice sheets attention is drawn to limitations in the compilations and to the potential for improved models in the future

cyclical patterns in volcanic degassing revealed by so2 flux timeseries analysis an application to soufriere hills volcano montserrat abstract cyclical patterns of behaviour in timeseries of seismic and geodetic data at volcanoes are frequently observed during lava dome building eruptions and are particularly well documented from the current eruption of the soufriere hills volcano shv montserrat however the discontinuous nature of many so 2 measurements often preclude the identification and quantitative analysis of cyclical patterns in degassing data here using a long so 2 timeseries from shv with continuous measurements since 2002 we explore for the first time degassing behaviour at a resolution comparable to that possible for seismic and deformation datasets timeseries analysis of flux data spanning 2002 2011 reveals that so 2 emissions at shv exhibit complex cyclicity with dominant cycles evident on both multi year and multi week 50 day timescales these cycles persist through phases of both active extrusion and eruptive pause and show close similarities to periodic components previously identified at shv in timeseries of seismicity ground deformation and lava extrusion the strength of expression or amplitude of degassing cycles particularly on multi week timescales shows distinct temporal variation and appears to correlate with the occurrence and nature of explosive activity occurring in 2002 2009 this suggests that the amplitude of surface gas flux cycles is modulated by physical conditions within the conduit direct quantitative comparison between seismicity dome growth and degassing for eruptive phases 2 2002 2003 and 3 2005 2007 reveals that peaks in so 2 flux appear to correspond broadly to enhanced lava extrusion and elevated seismicity within cycles of 30 50 days however time lags of 2 4 and 7 days are observed between initial low frequency seismic swarms and peaks in dome growth so 2 flux and rockfall event rate respectively multi parameter correlations offer valuable insights into the controls on subsurface gas ascent but further research is required to fully explore the contributions of permeability and overpressure as well as other subsurface processes

rapid thinning of the welsh ice cap at 20 19 ka based on 10be ages abstract new 10 be ages from the summits of three mountain areas of north wales reveal a very similar exposure timing as the welsh ice cap thinned after the global last glacial maximum eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19 08 0 80 ka 4 2 1 similar exposure ages over a 320 m vertical range 824 to 581 m altitude show that ice cap thinning was very rapid and spatially uniform using the same production rate and scaling scheme we recalculated six published 10 be exposure ages from the nearby arans which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19 41 1 45 ka 7 5 1 the average exposure age of all 15 accepted deglaciation ages is 19 21 1 07 5 6 1 the complete dataset from north wales provides very strong evidence indicating that these summits became exposed as nunataks at 20 19 ka this result provides important insight to the magnitude of ice surface lowering and behavior of the welsh ice cap during the last deglaciation that can be compared to other ice masses that made up the british irish ice sheet

the impact of the north atlantic ocean on the younger dryas climate in northwestern and central europe the main results of multiproxy climate reconstructions for the younger dryas and experiments carried out with an atmospheric general circulation model are discussed quantitative temperature inferences for northwestern and central europe show that winter conditions were remarkably extreme with values of 20 30 c below that of today annual temperature ranges with a continental signature 30 34 c were reconstructed for the entire study area compared with today the greatest cooling was experienced in the seaboard area the comparison of the climate reconstructions and simulation experiments indicates that sea ice in the north atlantic ocean played a decisive role in the climate of the study area by cooling the surface air temperatures and by controlling the position of the storm track surface air circulation was westerly even during younger dryas winters a slight northward shift of the mean atlantic sea ice margin during winter may explain the proposed subdivision of the younger drays into a phase of maximum cold and humidity succeeded by a less cold and relatively dry phase 1998 john wiley sons ltd

insights into the dynamic processes of the 2007 stromboli eruption and possible meteorological influences on the magmatic system 1 the unrest of stromboli volcano leading to the february 27 april 2 2007 eruptive period and to the march 15 paroxysm is constrained by combining broad band seismic data and 1 hz gps high rate gps hereinafter hrgps measurements during the pre eruptive stage the simultaneous examination of seismic and hrgps data together with weather parameters suggests the possible influence of external perturbations on the magmatic system which evolved toward a critical state after january 2007 some days after the onset of the eruption a sudden change of the seismic and eruptive behaviour was recognized while ground deformation began to show a deflation the march 15 paroxysm was preceded about two days before by a peak of the hrgps spectral power densities a small inflation and by the occurrence of a few vt earthquakes located at depths down to 3 5 km b s l these findings constrain for the first time at stromboli volcano the deep origin of a fast rising magma batch rich in gas that led to a strong explosive event

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

the younger dryas cold interval as viewed from central greenland abstract greenland ice core records provide an exceptionally clear picture of many aspects of abrupt climate changes and particularly of those associated with the younger dryas event as reviewed here well preserved annual layers can be counted confidently with only 1 errors for the age of the end of the younger dryas 11 500 years before present ice flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty glaciochemical and particulate data record atmospheric loading changes with little uncertainty introduced by changes in snow accumulation confident paleothermometry is provided by site specific calibrations using ice isotopic ratios borehole temperatures and gas isotopic ratios near simultaneous changes in ice core paleoclimatic indicators of local regional and more widespread climate conditions demonstrate that much of the earth experienced abrupt climate changes synchronous with greenland within thirty years or less post younger dryas changes have not duplicated the size extent and rapidity of these paleoclimatic changes

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

chironomid inferred late glacial air temperatures at whitrig bog southeast scotland this paper presents the first chironomid inferred mean july air temperature reconstruction for the late glacial in britain the reconstruction suggests that the thermal maximum occurred early in the interstadial with temperatures reaching about 12 degreesc there was then a gradual downward trend to about 11 degreesc punctuated by four distinct cold oscillations of varying intensity at the beginning of the younger dryas mean july temperatures fell to about 7 5 degreesc but gradually increased to about 9 degreesc before a rapid rise at the onset of the holocene the chironomid inferred temperature curve agrees closely both in general trends and in detail with the grip ice core oxygen isotope curve the reconstructed temperatures are 2 4 degreesc lower than coleopteran inferred temperatures but are closer to those inferred from plant macrofossils and glacial equilibrium line altitudes during the younger dryas copyright c 2000 john wiley sons ltd

how extreme was northern hemisphere seasonality during the younger dryas abstract in explaining the rapid transitions associated with the younger dryas cooling a reduced meridional overturning circulation has traditionally been invoked but such a scenario has been difficult to reproduce in model studies without adding excessive amounts of freshwater to the north atlantic more recent studies challenge this view and indicate that the role of an extensive sea ice cover may have been as important in promoting abrupt climate change as reorganisations of the north atlantic ocean gildor h tziperman e 2003 sea ice switches and abrupt climate change philosophical transactions of the royal society of london series a mathematical physical and engineering sciences 361 1935 1942 based on glacier evidence from eastern greenland denton g h alley r b comer g c broecker w s 2005 the role of seasonality in abrupt climate change quaternary science reviews 24 1159 1182 suggest that the seasonal temperature amplitude increased by about 20 c during the younger dryas such a switching of seasonality lends support to the idea of a fast expanding sea ice cover because it allows for extremely cold winters that are balanced by relatively mild summers however climatic interpretations based on the geometry and length of glaciers under such conditions as in scoresby sund is not well understood and equilibrium line altitude ela estimates should therefore be regarded as tentative here we discuss the absolute seasonal amplitude during the younger dryas by taking winter precipitation into account and show that the changes in seasonality may have been limited to 10 c we propose that by reducing the seasonal response in greenland compared with western europe we better understand the hinged door modus operandi cohmap 1988 climatic changes of the last 18 000 years observations and model simulations science 241 1043 1052 of the polar front and sea ice cover where the absolute southward migration of sea ice is highest in the east atlantic region

bacteriohopanepolyols preserved in silica sinters from champagne pool new zealand indicate a declining temperature gradient over the lifetime of the vent siliceous sinters from champagne pool cp a geothermal vent in the taupo volcanic zone north island new zealand contained exceptionally well preserved bacteriohopanepolyol bhp distributions bhps were present in a range of sinters deposited over the lifetime of cp 900 yr before present the distributions correlated well with the presence of members of bhp producing bacterial orders known to inhabit cp for example acidothiobacillales burkholderiales and pseudomonadales are known sources of composite bhps with a more complex functional group at c 35 such as bacteriohopanetetrol cyclitol ether found in high relative abundance in each cp sinter analysed the bhp distributions preserved in cp sinters were different from those described previously for any other environmental setting with pentafunctionalised bhps accounting for up to 55 of the total assemblage furthermore composite bhps were the most abundant compound type in each sample and accounted for up to 80 of the total bhp distribution as the age of sinter increased a general increase in bhp abundance was observed similarly in older sinters the complexity of the bhp compounds increased the observations are consistent with a higher temperature of vent water in the past the excellent preservation of bhps in this setting over the lifetime of the vent highlights the usefulness of bhps as biomarkers for reconstructing modern and ancient geothermal vent bacterial communities 2014 published by elsevier ltd

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

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

variability in aerobic methane oxidation over the past 1 2 myrs recorded in microbial biomarker signatures from congo fan sediments methane ch4 is a strong greenhouse gas known to have perturbed global climate in the past especially when released in large quantities over short time periods from continental or marine sources it is therefore crucial to understand and if possible quantify the individual and combined response of these variable methane sources to natural climate variability however past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence here we present a record from the congo fan of a highly specific bacteriohopanepolyol bhp biomarker for aerobic methane oxidation amo 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol that identifies discrete periods of increased amo as far back as 1 2 ma fluctuations in the concentration of aminopentol and other 35 aminobhps follow a pattern that correlates with late quaternary glacial interglacial climate cycles with highest concentrations during warm periods we discuss possible sources of aminopentol and the methane consumed by the precursor methanotrophs within the context of the congo river setting including supply of methane oxidation markers from terrestrial watersheds and or marine sources gas hydrate and or deep subsurface gas reservoir compound specific carbon isotope values of 30 to 40 for bhps in odp 1075 and strong similarities between the bhp signature of the core and surface sediments from the congo estuary and floodplain wetlands from the interior of the congo river basin support a methanotrophic and likely terrigenous origin of the 35 aminobhps found in the fan sediments this new evidence supports a causal connection between marine sediment bhp records of tropical deep sea fans and wetland settings in the feeding river catchments and thus tropical continental hydrology further research is needed to better constrain the different sources and pathways of methane emission however this study identifies the large potential of aminobhps in particular aminopentol to trace and once better calibrated and understood quantify past methane sources and fluxes from terrestrial and potentially also marine sources

an ice cap landsystem for palaeoglaciological reconstructions characterizing the younger dryas in western scotland abstract this paper reviews the contrasting behaviours of ice caps and icefields defines a generic landsystem model that can effectively discriminate between them and applies the model to landform sediment assemblages in an area of western scotland such a model is necessary since many palaeoenvironmental inferences from formerly glaciated terrains are based on the geometry extent and dynamics of reconstructed ice masses the validity of these glacier reconstructions is dependent on the accurate initial interpretation of relict landforms and sediments and their inter relationships a new landsystems model is presented here in which individual geological and geomorphological elements are checked against a set of eight theoretical diagnostic criteria that characterize the style of former glaciation when applied to a 1200 km 2 area of the western scottish highlands the landsystem tool predicts 1 an extensive younger dryas ice cap with a maximum surface elevation of 900 m above sea level implying colder or wetter conditions than previously thought and 2 the survival of an independent mountain icefield in part of the area during deglaciation glaciological theory proxy palaeoenvironmental data and established glacier climate topography relationships support these predictions thereby giving credibility to the landsystem methodology as a generic tool for palaeoglaciological reconstructions

cosmogenic 10be insights into the extent and chronology of the last deglaciation in wester ross northwest scotland cosmogenic 10be surface exposure ages for bedrock sites around torridon and the applecross peninsula in wester ross northwest scotland provide new insights into the lateglacial transition accounting for postglacial weathering six statistically comparable exposure ages give a late younger dryas g 1 exposure age of 11 8 1 1 ka two further outliers are tentative pre younger dryas exposure ages of 13 4 0 5 ka in torridon and 17 5 1 2 ka in applecross the younger dryas exposure ages have compelling implications for the deglaciation of marginal loch lomond stadial ice fields in torridon and applecross firstly they conflict with predictions of restricted ice cover and rapid retreat based on modelling experiments and climate proxies instead fitting a model of vertically extensive and prolonged ice coverage in wester ross secondly they indicate that 2 m of erosion took place in the upper valleys of torridon and applecross during the younger dryas implying a dominantly warm based glacial regime finally the exposure ages have clarified that corrie cirque glaciers did not readvance in wester ross following final deglaciation copyright 2011 john wiley sons ltd

the last ice sheet in north west scotland reconstruction and implications recent models of the last scottish ice sheet suggest that nunataks remained above the ice surface in areas peripheral to the main centres of accumulation this proposition has been investigated on 140 mountains over an area of 10 000 km2 in nw scotland outside the limits of the later loch lomond readvance in this area there is evidence for a single high level weathering limit that separates glacially eroded terrain from higher areas of in situ frost debris this limit occurs at altitudes ranging from 425 to 450 m in the outer hebrides to 950 m on the mainland and is best developed on lithologies that resisted breakdown after ice sheet downwastage interpretation of this weathering limit as a periglacial trimline cut by the last ice sheet at its maximum thickness is supported by 1 joint depth and schmidt hammer measurements that indicate significantly more advanced rock breakdown above the weathering limit 2 a much greater representation of gibbsite a pre late devensian weathering product in the clay fraction of soils above the limit 3 cosmogenic isotope dating of the exposure ages of rock outcrops above and below the limit 4 the sharpness of the limit at some sites and its regular decline along former ice flowlines and 5 shear stress calculations based on the inferred altitude and gradient of the former ice surface reconstruction of the ice surface based on trimline evidence indicates that the mainland ice shed lay near or slightly east of the present watershed and descended northwards from 900 m to ca 550 m at the north coast independent dispersion centres fed broad ice streams that occupied major troughs on skye an ice dome 800 m deflected the northwestwards movement of mainland ice but the mountains of rum were over ridden by mainland ice up to an altitude of ca 700 m the outer hebrides supported an independent ice cap that was confluent with mainland ice in the minches extrapolation of the trimline evidence indicates that most reconstructions of ice extent are too conservative and suggests that low gradient ice streams extended across the hebridean shelf offshore wider implications of this research are 1 that blockfields and other periglacial weathering covers are not all of the same age or significance depending on the resistance of different lithologies to frost weathering 2 that the contrasting degree of glacial modification in the western and eastern highlands of scotland may reflect a former cover of predominantly warm based ice in the former and predominantly cold based ice in the latter and 3 that the approach and techniques developed in this study have potential application for constraining ice sheet models not only in areas peripheral to the main centres of ice accumulation in britain and ireland but also in other mountain areas where nunataks protruded through warm based late pleistocene ice masses

4 1 5 c abrupt warming 11 270 yr ago identified from trapped air in greenland ice nitrogen and argon isotopes in air trapped in a greenland ice core gisp2 show two prominent peaks in the interval 11 800 10 800 b p which indicate two large abrupt warming events the first abrupt warming 10 4 c is the widely documented event at the end of the younger dryas here we report on the second abrupt warming 4 1 5 c which occurred at the end of a short lived cooler interval known as the preboreal oscillation 11 270 30 b p a rapid snow accumulation increase suggests that the climatic transition may have occurred within a few years the character of the preboreal oscillation and the subsequent abrupt warming is similar to the dansgaard oeschger d o events in the last glacial period suggestive of a common mechanism but different from another large climate change at 8 200 b p in which cooling was abrupt but subsequent warming was gradual the large abrupt warming at 11 270 b p may be considered to be the final d o event prior to the arrival of the present stable and warm epoch

geomorphological signature and flow dynamics of the minch palaeo ice stream northwest scotland large scale streamlined glacial landforms are identified in 11 areas of northwest scotland from the isle of skye in the south to the butt of lewis in the north these ice directional features occur in bedrock and superficial deposits generally below 350 m above sea level and where best developed have elongation ratios of 20 1 sidescan sonar and multibeam echo sounding data from the minch show elongate streamlined ridges and grooves on the seabed with elongation ratios of up to 70 1 these bedforms are interpreted as mega scale glacial lineations all the features identified formed beneath the minch palaeo ice stream which was ca 200 km long up to 50 km wide and drained ca 15 000 km2 of the northwest sector of the last british irish ice sheet late devensian glaciation nine ice stream tributaries and palaeo onset zones are also identified on the basis of geomorphological evidence the spatial distribution and pattern of streamlined bedforms around the minch has enabled the catchment flow paths and basal shear stresses of the palaeo ice stream and its tributaries to be tentatively reconstructed british geological survey natural environment research council copyright 2007 reproduced with the permission of bgs nerc published by john wiley sons ltd

geochemistry of metals and metalloids in siliceous sinter deposits implications for elemental partitioning into silica phases abstract sinter deposits are formed by precipitation of silica from hydrothermal fluids that have reached the surface environment they are commonly found around hot springs and represent surface expressions of underlying geothermal systems and or low sulfidation epithermal gold silver hydrothermal deposits several studies have reported ppm to weight percent concentrations of metals e g au ag cu and metalloids e g as sb b in sinters capping geothermal systems and epithermal gold silver deposits however the relation between the maturity of the siliceous sinter and its metal enrichment remains unknown here we use geochemical and mineralogical data that link the silica crystallinity degree with trace metal and metalloid contents in sinter in this paper we provide in situ trace element data in metal rich silica sinter samples from the puchuldiza geothermal field in the altiplano of northern chile that record the complete diagenetic sequence from non crystalline opal a to microcrystalline quartz combined sem xrd and la icp ms data show that the concentration of metals and metalloids in sinters from puchuldiza display a strong correspondence with silica crystallinity while arsenic and boron are predominantly enriched in the more amorphous silica phases opal a ct gold and silver show higher concentrations in the more crystalline phases opal c quartz silica structural morphological and geochemical transformations from its initial precipitation to its final maturation after diagenesis are responsible for this differential enrichment during the initial stages gold and silver are incorporated into silica microspheres as cationic species and or metal nanoparticles or colloids while arsenic and boron incorporation is controlled by as bearing accessory minerals and fe oxyhydroxides as diagenesis progresses and the crystallinity of silica increases diffusion driven processes such as ostwald ripening may progressively enrich gold and silver in the sinter while metalloids are depleted owing to the low retention of arsenic by silica these findings indicate that the diagenetic transitions of silica defined by significant structural changes that involve generation of surface defects and the creation of reactive sites may play an important role in elemental uptake by silica in near surface environments

deglaciation of the younger dryas or loch lomond stadial ice field in the northern highlands scotland when viewed from the air scottish hummocky moraine can be resolved into a series of linear ridges that resemble those found at the margins of actively retreating glaciers today recent work has supported the interpretation of these linear ridges as ice marginal landforms and the authors believe that the majority of hummocky moraine deposits can be interpreted in this way consequently the pattern of deglaciation can be established fairly precisely from the pattern of linear ridges this approach is applied to the landforms of the northern part of the loch lomond stadial ice field in order to reconstruct the regional pattern of deglaciation this leads to important inferences about the significance of topographic control during deglaciation and more importantly it provides fresh insight into the environment of the british isles during the loch lomond stadial

sedimentology stratigraphy and glacier dynamics western scottish highlands glacial sediments of the western scottish highlands are comprehensively described and characterized here for the first time enabling the first glacial stratigraphy for the area to be proposed this classification is based on the results of extensive geological mapping and field investigation of sedimentary sequences and their structures x ray diffraction and particle size distribution analyses and comparison with deposits formed in contemporary glaciated environments these new data are subsequently appraised in terms of their implications for late pleistocene glacier evolution and dynamics together the data suggest that much of the landscape is palimpsest and can be attributed to the weichselian late devensian glaciation subsequent glacier advance during the younger dryas did little to modify the area suggesting that ice flow was dominated by sliding on a meltwater lubricated rigid bed with deformation of basal sediments playing a more limited role final deglaciation was marked by a significant increase in basal meltwater flux reflecting the warming climate and increasing precipitation these new palaeoglaciological and palaeoenvironmental insights advance our understanding of former glacier dynamics in the western scottish highlands improve our knowledge of pleistocene landscape evolution of this area and enable comparisons to be made with sedimentary sequences elsewhere

experimental studies on new zealand hot spring sinters rates of growth and textural development to study the rate of growth of sinters in new zealand hot springs field experiments were conducted in seven geothermal areas at wairakei fan shaped subaqueous deposits of amorphous silica grow rapidly 350 kg a 1 m 2 of drain wall and are composed of silicified filaments with subordinate bacillus and spirillium shaped organisms characterization of bacteria revealed isolates sharing 97 16s rrna gene sequence homologies affiliated with thermus meiothermus bacillus tepidomonas thermomonas porphyrobacter thermonema and hydrogenophilus spp as well as previously uncultured bacteria at rotokawa microstromatolites have a slow growth rate 0 004 mm day 1 that is attributed to low ph capillary rise and evaporation at champagne pool sinter growth 0 023 mm day 1 is dominated by wave action building alternating microbe rich and microbe poor layers silica sinter was not observed at waikite where slides developed a layer of calcite 0 026 mm day 1 sinter growth at ngatamariki 0 016 mm day 1 forms by capillary rise evaporation and diffusion and at tokaanu subaqueous growth is slow 0 002 mm day 1 and contains silicified microbes textures at orakei korako indicate similar mechanisms to ngatamariki except that growth is more rapid 0 023 mm day 1 due to a splash contribution silica and calcite saturation indices adequately explain the growth of the sinters and calcite indicating that microbes are not inducing precipitation where it should not occur the rate of precipitation is correlated with silica supersaturation but ph effects can alter this relationship the degree of preservation of microbial material is explained by the effect of ostwald ripening on silica spherules subaqueous growth allows coarsening of spherules and poor preservation of smaller microbes while subaerial nucleation is rapid ostwald ripening is inactive and better preservation can be expected

bacteriohopanepolyol signatures of cyanobacterial and methanotrophic bacterial populations recorded in a geothermal vent sinter the distribution of bacteriohopanepolyols bhps in a modern terrestrial geothermal silica sinter has been employed as a proxy for bacterial populations and bacterially mediated processes occurring within the geothermal ecosystem analysis of samples from opaheke pool hot spring in the taupo volcanic zone north island new zealand revealed the presence of a suite of bhps relating to cyanobacteria and type i and type ii methanotrophic bacteria

dimensions and deglacial chronology of the outer hebrides ice cap northwest scotland implications of cosmic ray exposure dating cosmic ray exposure ages of frost weathered bedrock from mountain summits in the outer hebrides exceed the age of late devensian glaciation exposure ages of most glacially abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum late devensian glaciation these results confirm that previously mapped periglacial trimlines in the outer hebrides define the upper limit of bedrock erosion by late devensian ice they are consistent with the interpretation based on geomorphological evidence that the trimlines mark the approximate upper limit of a late devensian outer hebrides ice cap a postglacial exposure age from the summit of oreval 662 m suggests that this mountain was overrun during the last glaciation indicating thicker ice cover and a lower surface gradient west of the ice cap divide than previously inferred although bedrock surfaces below the trimlines are strongly ice moulded some show evidence of prior cosmic ray exposure which we attribute to limited erosion during late devensian glaciation if this interpretation is correct the youngest apparent ages from these surfaces give the most reliable dates for deglaciation at ca 14 5 14 ka this implies that ice persisted at favourable sites through the warm opening phase of the windermere interstade comparison with radiocarbon dated evidence from offshore cores suggests net ice margin retreat of 74 km eastwards across the adjacent shelf in 2 3 1 0 ka the dating evidence is consistent with relatively rapid retreat of calving margins to the coast then slower withdrawal of ice margins to high ground copyright 2005 john wiley sons ltd

modern glacier characteristics as a basis for inferring former climates with particular reference to the loch lomond stadial abstract studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude ela is the most critical parameter in the link between glaciers and climate average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind drifting and avalanching of snow and approximates closely to accumulation at the equilibrium line ablation is most usefully predicted by mean summer temperature and there is a close non linear relationship between accumulation and mean summer temperature at the equilibrium line following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes the application of the above relationships to the loch lomond readvance glaciers of highland britain is considered and an outline of the precipitation pattern and the mean summer temperature of the loch lomond stadial is given

the greenland ice core chronology 2005 15 42 ka part 2 comparison to other records a new greenland ice core chronology gicc05 based on multi parameter counting of annual layers has been obtained for the last 42 ka here we compare the glacial part of the new time scale which is based entirely on records from the northgrip ice core to existing time scales and reference horizons covering the same period these include the grip and northgrip modelled time scales the meese sowers gisp2 counted time scale the shackleton fairbanks grip time scale sfcp04 based on 14c calibration of a marine core the hulu cave record three volcanic reference horizons and the laschamp geomagnetic excursion event occurring around greenland interstadial 10 gicc05 is generally in good long term agreement with the existing greenland ice core chronologies and with the hulu cave record but on shorter time scales there are significant discrepancies around the last glacial maximum there is a more than 1 ka age difference between gicc05 and sfcp04 and a more than 0 5 ka discrepancy in the same direction between gicc05 and the age of a recently identified tephra layer in the northgrip ice core both sfcp04 and the tephra age are based on 14c dated marine cores and fixed marine reservoir ages for the laschamp event gicc05 agrees with a recent independent dating within the uncertainties

precise cosmogenic 10be measurements in western north america support for a global younger dryas cooling event the inner titcomb lakes moraine in the wind river mountains wyoming has been dated with a precision of 5 using accelerator mass spectrometric measurements of cosmogenic 10be in surface samples from nine boulders resting on its crest the age of this moraine is 11 4 0 5 to 13 8 0 6 ka the range in age is due to the uncertainty in the 10be production rate and uncertainties in rock erosion rate and shielding of cosmic rays by snow additional exposure ages on bedrock and boulder surfaces that are stratigraphically younger and older than the inner titcomb lakes moraine conform with this age the exposure ages of the inner titcomb lakes moraine overlap the north atlantic younger dryas event 12 8 0 2 to 11 5 0 3 ka

periodic behavior of soil co2 emissions in diffuse degassing areas of the azores archipelago application to seismovolcanic monitoring time series of soil co2 efflux recorded in the azores archipelago volcanic hydrothermal areas feature daily and seasonal variations the recorded co2 efflux values were lower during summer than in the winter season the diurnal co2 efflux values were higher at dawn and lower in the early afternoon contrary to that observed in biogenic environments co2 efflux cycles correlated well with the environmental variables such as air temperature wind speed and barometric pressure which also showed low and high frequency periodicities several simulations were performed here using the transport of unsaturated groundwater and heat 2 tough2 geothermal simulator to complement the study of rinaldi et al 2012 the effects of the water table depth air temperature perturbation amplitude and soil thermal gradient contributed to an explanation of the contrasts observed in the diurnal s1 and semidiurnal s2 soil co2 efflux peaks for the different monitoring sites and seasons filtering techniques multivariate regression analysis and fast fourier transform filters were also applied to the recorded time series to remove effects of external variables on the soil co2 efflux the resulting time series the residuals correspond to the best approach to the deep seated volcanic hydrothermal co2 emissions and thus should be used in seismovolcanic monitoring programs even if no evident correlation can be established yet between the soil co2 residuals and seismicity over the monitored time a seismic swarm that occurred around the end of 2008 might have triggered some deviations from the observed daily cycles

can glacial shearing of sediment reset the signal used for luminescence dating abstract understanding the geomorphology left by waxing and waning of former glaciers and ice sheets during the late quaternary has been the focus of much research this has been hampered by the difficulty in dating such features luminescence has the potential to be applied to glacial sediments but requires signal resetting prior to burial in order to provide accurate ages this paper explores the possibility that rather than relying on light to reset the luminescence signal glacial processes underneath ice might cause resetting experiments were conducted on a ring shear machine set up to replicate subglacial conditions and simulate the shearing that can occur within subglacial sediments luminescence measurement at the single grain level indicates that a number albeit small of zero dosed grains were produced and that these increased in abundance with distance travelled within the shearing zone observed changes in grain shape characteristics with increasing shear distance indicate the presence of localised high pressure grain to grain stresses caused by grain bridges this appears to explain why some grains became zeroed whilst others retained their palaeodose based on the observed experimental trend it is thought that localised grain stress is a viable luminescence resetting mechanism as such relatively short shearing distances might be sufficient to reset a small proportion of the luminescence signal within subglacial sediments dating of previously avoided subglacial sediments may therefore be possible

a field guide to finding fossils on mars the martian surface is cold dry exposed to biologically harmful radiation and apparently barren today nevertheless there is clear geological evidence for warmer wetter intervals in the past that could have supported life at or near the surface this evidence has motivated national aeronautics and space administration and european space agency to prioritize the search for any remains or traces of organisms from early mars in forthcoming missions informed by 1 stratigraphic mineralogical and geochemical data collected by previous and current missions 2 earth s fossil record and 3 experimental studies of organic decay and preservation we here consider whether how and where fossils and isotopic biosignatures could have been preserved in the depositional environments and mineralizing media thought to have been present in habitable settings on early mars we conclude that noachian hesperian fe bearing clay rich fluvio lacustrine siliciclastic deposits especially where enriched in silica currently represent the most promising and best understood astropaleontological targets siliceous sinters would also be an excellent target but their presence on mars awaits confirmation more work is needed to improve our understanding of fossil preservation in the context of other environments specific to mars particularly within evaporative salts and pore fracture filling subsurface minerals

high resolution modeling of the advance of the younger dryas ice sheet and its climate in scotland abstract ice sheet modeling tightly constrained by empirical studies provides an effective framework to reconstruct past climatic and environmental conditions scotland was severely affected by the abrupt climate change associated with the younger dryas stade during which an extensive ice sheet formed across the west highlands after a period of ice free conditions here a quasi three dimensional time dependent ice flow mass balance model is developed and applied to scotland at 1 km resolution the flow model is based on the driving stress approximation with an additional longitudinal correction term essential at this scale of operation surface mass balance is driven by temperature and precipitation changes and further mass wastage is achieved through an empirically defined calving term the ice dynamics and mass balance components are coupled through the equation for mass continuity which is integrated through time over a finite difference grid which yields the geometric evolution of the ice sheet initial experiments reveal the model to be relatively insensitive to internal parameters but highly sensitive to mass balance furthermore these experiments indicate that scotland is readily susceptible to glaciation with large glaciers building up on the flanks of ben nevis after a temperature depression of 2 5 c under present day precipitation the younger dryas is modeled using a grip temperature series locally adjusted for amplitude and a systematic series of runs enables the isolation of the climate which best matches mapped ice limits this optimum fit configuration requires an annual temperature cooling of 8 c and the introduction of substantial west east and south north precipitation gradients of 40 and 50 respectively to the present day regime under these conditions a series of substantial independent regional ice centers develop in agreement with trimline studies and after 550 years the modeled ice sheet closely resembles the maximum limits as indicated by field mapping however modeled ice continues to expand beyond 550 yr in conflict with the mapped ice limits which suggest a prolonged period of stability this discrepancy may be explained by the onset of extreme aridity ca 400 yr into the stade associated with a southern migration of the polar front leading to a reduction in atmospheric circulation which effectively starved the ice sheet of its moisture source preventing further expansion introduction of an additional 20 reduction in precipitation to the optimum fit regime after 350 yr brings the modeled ice sheet to equilibrium substantiating this conclusion

the mode and mechanism of the last deglaciation oceanic evidence changes in ocean temperature carbonate productivity and ice rafted detritus in the north atlantic suggest that half of the northern hemisphere ice volume at the last glacial maximum had disappeared by 13 000 yr b p despite the still extensive limits of the ice sheets this early thinning of the ice sheets occurred during a time when summer insolation values were slowly rising but when pollen evidence south of the ice margins indicates cold dry air masses we infer that this rapid early ice disintegration 16 000 13 000 yr b p was caused by oceanic mechanisms 1 rising sea level causing increased calving along ice margins 2 the chilling of the sea surface by icebergs and meltwater reducing moisture extraction by the atmosphere and transport to the ice sheets and 3 winter freezing of the low salinity meltwater layer suppressing local moisture extraction and the regional influx of moisture bearing storms from lower latitudes in winter and hence starving the ice sheets these oceanic feedback mechanisms were strongest from 16 000 to 13 000 yr b p and weaker but still active from that date until the end of deglaciation at 6000 yr b p

high resolution numerical simulation of younger dryas glaciation in scotland golledge n r hubbard a sugden d e 2008 high resolution numerical simulation of younger dryas glaciation in scotland quaternary science reviews 27 9 10 888 904 sponsorship nerc

periglacial trimlines in the scottish highlands abstract two periglacial weathering limits have been identified on mountains in the highlands of scotland the lower has been interpreted as a periglacial trimline marking the upper limits of loch lomond younger dryas stade glaciers and has been employed to reconstruct the dimensions of parts of the main west highland icefield and certain smaller glaciers and icefields interpretation of the upper weathering limit has been more contentious but recent research has demonstrated 1 significant contrasts in the degree of bedrock weathering above and below this limit 2 that gibbsite a pre devensian weathering product is abundant above the limit but rare in soils farther downslope 3 that the isotopic 26al age of bedrock exposures above the limit greatly exceeds that at lower altitudes and 4 that the altitude of the weathering limit descends regularly along former ice sheet flowlines collectively these attributes suggest that the upper weathering limit is a periglacial trimline defining the maximum altitude of the last ice sheet calculated basal shear stress values are consistent with this interpretation which implies that the mainland ice shed lay at ca 900 m in wester ross and descended gently northwards whilst harris and lewis in the outer hebrides supported an independent ice cap that achieved a maximum altitude of ca 700 m wider implications of this interpretation and the future potential for ice sheet reconstruction are explored

temperature gradients in northern europe during the last glacial holocene transition 14 914c kyr bp interpreted from coleopteran assemblages late glacial and early holocene climatic conditions have been reconstructed for northern europe using the mutual climatic range mcr palaeoclimate method based on fossil coleopteran assemblages altogether beetle faunas from 77 sites have been analysed ranging from ireland in the west to poland and finland in the east and mcr estimates calculated the results are plotted on 16 maps each representative of a selected time slice covering the period from 14 5 14c kyr bp to 9 0 14c kyr bp eight of the maps show the mcr estimates of tmax mean temperature of the warmest month derived from each site for which data are available while the remainder show estimated tmax isotherms interpolated from these values it can be demonstrated that at times the thermal climate was fairly uniform throughout the study area whereas at others temperature gradients were much steeper than they are in the region today there also appears to be a distinct contrast between cold periods when contours trended nw se and warmer periods when contours trend w e or even ne sw the pattern of climatic changes that emerges is shown to be very different from the traditional view that has been used up to now as a template for classifying late glacial climatic events on a wide even global scale the suddenness and intensity of changes in the thermal climate may have been partially responsible for an apparent lack of equilibrium between the flora and fauna of the time and the physical environment in which they lived 1998 john wiley sons ltd

extent and deglacial chronology of the last british irish ice sheet implications of exposure dating using cosmogenic isotopes over 160 10be and 36cl exposure ages pertaining to the extent and chronology of the last british irish ice sheet biis are critically reviewed despite uncertainties inherent in the use of exposure ages this approach has demonstrated that at the last glacial maximum lgm ca 26 21 ka the biis extended over all low ground in scotland and all or almost all of ireland consistent with recent models depicting extension of the last biis to the atlantic shelf edge all exposure ages obtained for high level sites above trimlines on the mountains of northwestern scotland and ireland pre date the lgm this finding confirms that high plateaux in these areas escaped significant glacial erosion probably under a protective cover of cold based glacier ice that remained frozen to the underlying substrate in terms of deglaciation chronology the southern irish sea basin was probably deglaciated by 19 18 ka with extensive deglaciation of low ground in ireland and northeastern scotland prior to ca 14 5 ka ice cover on low ground in northwestern scotland apparently persisted after 14 0 ka suggesting survival of ice in favourable locations during the lateglacial interstade ca 14 5 12 9 ka attempts to date readvances have had mixed success the wester ross readvance in northwestern scotland was initially dated to ca 16 3 ka but more recent research implies a much younger age ca 14 0 13 5 ka exposure ages indicating a prolonged stillstand during ice sheet retreat in the cairngorms at ca 14 5 14 0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates which indicate deglaciation before ca 15 5 15 0 ka exposure dating has been successfully employed to confirm a loch lomond stadial ca 12 9 11 5 ka age for moraines in several mountain areas and to constrain the minimum altitude of the ice cap that extended over the western grampians at that time copyright 2009 john wiley sons ltd

climate variations in britain during the last glacial holocene transition 15 0 11 5 cal ka bp comparison with the grip ice core record stratigraphic records from four sequences in britain that span the last glacial holocene transition c 15 0 11 5 cal ka bp are summarized and compared using a calibrated timescale palaeoclimatic changes are defined using temperature estimates based on coleopteran data at two of the sites and chironomid assemblages at the other sites an attempt is made to distingish between the timing of a climate shifts and b ecosystem responses at all four sites the british data are compared with the grip ice core record recently advocated by bjorck et al as the type sequence for the last termination in the north atlantic region there is a degree of compatibility between the british and grip palaeoclimatic records the clearest climatic signals in the british lake records are a a period of warm conditions a thermal maximum between 15 0 and 14 5 cal ka bp which equates approximately with grip zone gi le b the onset of climatic cooling which appears to have commenced during grip zone gi le at c 14 5 cal ka bp c a period of marked climatic instability from 14 4 to 12 7 cal ka bp the regional effects of which are difficult to resolve using the evidence presently available d further climatic cooling which commenced at around 13 0 cal ka bp after which the lake biota catchment soils and vegetation cover at least in some parts of britain did not recover until the onset of the holocene e continued climatic cooling with the most severe impact on lake ecosystems occurring during the period c 12 6 to 11 5 cal ka bp

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

a reinterpretation of scottish hummocky moraine and its significance for the deglaciation of the scottish highlands during the younger dryas or loch lomond stadial the aim of this paper is to demonstrate that much of the hummocky moraine present within the northern part of the lochlomond readvance ice cap formerly situated in the north west scottish highlands may be interpreted as suites of ice front moraines deposited during active decay these landforms can be used to reconstruct ice cap decay whichleads to important insights into the shrinking form of the ice cap and associated environmental conditions evidence has been collected from 10803 airphotographs and from detailed field survey it is presented at three spatial scales

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

radon anomaly in the soil of taal volcano the philippines a likely precursor of the m 7 1 mindoro earthquake 1994 1 the soil gas 222rn concentration had been monitored almost continuously from june 1993 till november 1996 on taal volcano luzon island the philippines during this measurement period a singular mb 7 1 earthquake occurred on november 15 1994 between luzon and mindoro 48 km south of the volcano twenty two days before the earthquake an anomalous increase in soil gas radon peak to background ratio 6 was recorded unique in the whole time series the possible generation of this anomaly by typhoon teresa which struck luzon island a few days before was ruled out one year later when super typhoon angela the most powerful storm to hit the philippines in ten years crossed luzon island along almost the same track without triggering a similar disturbance in the radon signal consequently there is strong evidence that the taal radon anomaly originated in stress accumulation preceding the mindoro earthquake

surface exposure dating 36cl and 10be of post last glacial maximum valley moraines lake district northwest england some issues and implications surface exposure ages 36cl and 10be have been obtained from 16 boulders at the margins of and within the limits of former valley glaciers at four sites in the lake district northwest england the established view is that the lake district functioned as an independent centre of ice dispersal during the last glacial maximum lgm 26 21 ka of the dimlington stade greenland stades 2 3 and that the glacial depositional landforms at the sampled sites are products of stillstands or readvances of the ice margins following the lgm however several of the apparent 36cl surface exposure ages pre date rather than post date the lgm it is inferred that these boulders retain levels of 36cl inherited from a previous period of exposure rather than indicating moraine formation prior to the lgm and their subsequent survival beneath lgm ice an implication is that lake district glaciers achieved limited erosion of bedrock during the build up to and at the maximum of the lgm and that glacial erosion rates increased at a late stage in that period single 36cl and 10be exposure ages from two sites suggest a stillstand or readvance of valley glaciers prior to the loch lomond younger dryas stade lls greenland stade 1 and windermere lateglacial interstade greenland interstade 1 but additional ages are required in order to confirm or refute these individual ages an lls age for glacial depositional landforms at both these sites had previously been proposed 36cl surface exposure ages for boulders on moraines within the lls limit do not fully support emplacement at that time there is a possibility that these moraines are associated with a pre lls stillstand or readvance of the valley glacier copyright 2013 john wiley sons ltd

application of a degree day model to reconstruct pleistocene glacial climates there is empirical evidence of a nonlinear relation between annual precipitation or accumulation and summer mean temperature at the equilibrium line altitude ela on glaciers around the world the degree day model gives a similar relation between accumulation and summer temperature although instead of a single universal curve there is a family of curves depending upon the annual temperature range furthermore the degree day model also gives nonlinear relations between accumulation and annual mean temperature thus estimations of accumulation can be made from both summer and annual temperatures at the ela of former reconstructed glaciers such as those in greece this is particularly useful since these climatic variables have major implications for biological proxies such as vegetation history indicated in the pollen record and for periglacial proxies such as permafrost distributions indicated in the geomorphological record the close relationship between glaciers and climate provides one of the most precise methods for reconstructing former climates and offers considerable potential for resolving our understanding of pleistocene cold stage climates

landscape preservation under fennoscandian ice sheets determined from in situ produced 10be and 26al some areas within ice sheet boundaries retain pre existing landforms and thus either remained as ice free islands nunataks during glaciation or were preserved under ice differentiating between these alternatives has significant implications for paleoenvironment ice sheet surface elevation and ice volume reconstructions in the northern swedish mountains in situ cosmogenic 10be and 26al concentrations from glacial erratics on relict surfaces as well as glacially eroded bedrock adjacent to these surfaces provide consistent last deglaciation exposure ages 8 13 kyr confirming ice sheet overriding as opposed to ice free conditions however these ages contrast with exposure ages of 34 61 kyr on bedrock surfaces in these same relict areas demonstrating that relict areas were preserved with little erosion through multiple glacial cycles based on the difference in radioactive decay between 26al and 10be the measured nuclide concentration in one of these bedrock surfaces suggests that it remained largely unmodified for a minimum period of 845 418 461 kyr these results indicate that relict areas need to be accounted for as frozen bed patches in basal boundary conditions for ice sheet models and in landscape development models subglacial preservation also implies that source areas for glacial sediments in ocean cores are considerably smaller than the total area covered by ice sheets these relict areas also have significance as potential long term subglacial biologic refugia

regression coefficients of thermal gradients in northwestern europe during the last glacial holocene transition using beetle mcr data palaeotemperature estimates obtained from 74 sites in northern europe and collectively spanning approximately the last 45 000 yr radiocarbon time scale have been compiled as a major component o

bacteriohopanepolyols in hydrothermal vent biogenic silicates abstract biogenic silicates from the taupo volcanic zone north island new zealand are shown to contain a number of unusual polyfunctionalised bacteriohopanepolyols hopanoid fractions isolated from the rotokawa hot spring 80 82 c contained significant amounts of 32 35 anhydrobacteriohopanetetrol and two isomers of a related trihydroxylated compound the origin of these unusual hopanoid side chains is unclear and they may result either from novel biosynthetic or diagenetic transformation pathways of known biohopanoid precursors such as bacteriohopanetetrol via cyclisation or reductive removal of adenine from adenosylhopane

tracking paraglacial sediment with cosmogenic 10 be using an example from the northwest scottish highlands abstract beryllium 10 concentrations in samples of sediment and bedrock from five study sites across the scottish highlands trace paraglacial sediment sources and define the nature of glacial erosion for the late quaternary exposure ages derived from 10 be concentrations in ridge and lower elevation bedrock range from 10 to 33 ka which suggest that polythermal ice and warm based ice were primarily responsible for producing glacial sediment comparisons of 10 be concentrations between catchment wide sediment 2 06 0 34 10 4 to 11 24 1 54 10 4 atoms g 1 sio 2 n 33 near surface deposits 2 71 0 33 10 4 to 3 48 0 49 10 4 atoms g 1 sio 2 n 6 4 m thick deep till 0 68 10 4 10 be atoms g 1 sio 2 n 1 ridge bedrock 8 93 0 47 10 4 to 34 05 1 66 10 4 atoms g 1 sio 2 n 20 and lower elevation polished bedrock 6 74 0 67 10 4 to 12 65 0 7 10 4 atoms g 1 sio 2 n 5 indicate that most sand fluxing through catchments in the scottish highlands is sourced from the remobilization and vertical mixing of near surface deposits these findings indicate that glaciogenic material continues to dominate paraglacial sediment budgets more than 11 ka after deglaciation

glaciation of scotland during the younger dryas stadial a review considerable research effort in recent years has refined our knowledge of the landforms and sedimentary sequences generated by glaciers of the last cold episode in scotland the younger dryas and the chronology of their formation these recent advances have benefited from new technologies such as high resolution digital terrain models numerical ice sheet simulations and cosmic ray surface exposure dating this review presents a summary of recent younger dryas research in scotland particularly focusing on studies from the last two decades the findings of these investigations are compared with those of earlier workers and critically are appraised in terms of their relevance to five key aspects of younger dryas glaciation growth of the ice cap its geometry dynamics mode of decay and likely stadial climate minor differences aside the consensus view appears to favour a relatively thick but areally restricted central ice cap surrounded by satellite ice fields at its centre the ice cap was probably thickest during the first 500 years of the stadial after which it most likely thinned as the climate became increasingly arid outlet glaciers were dynamic only in marginal areas where they produced abundant moraine sequences during deglaciation but throughout much of the stadial central areas of the ice cap effected only minimal landscape modification deglaciation took place by active retreat under a rapidly warming climate overall the stadial was dominated by much colder and drier conditions than present and probably experi enced greater intra annual temperature ranges copyright 2009 john wiley sons ltd