quantitative reconstruction of mid to late holocene climate in ne china from peat cellulose stable oxygen and carbon isotope records and mechanistic models there has been an increasing need to reconstruct past climate from proxy records quantitatively and mechanistically the inverse proxy modeling method stands out as a novel approach to quantitative palaeoclimate reconstructions through integrating process based models and proxy records representing a major progress in quantitative palaeoclimatology it has been proposed to incorporate multiple proxy records to produce a more robust constraint on the climate parameters sought for estimation and most of the work has been conducted using pollen records in conjunction with vegetation models here i show a worked example of using paired stable oxygen and carbon isotope records of peat cellulose from one single core to infer the climate history in ne china for the last 6000 years through solving a well posed inverse problem using bayesian statistics the quantitative palaeoclimate data obtained in this study may deepen our insight into the dynamics of the east asian summer monsoon mean growing season temper

spatial fingerprint and magnitude of changes in the atlantic meridional overturning circulation during marine isotope stage 3 pronounced millennial scale climate variability during marine isotope stage 3 mis3 is considered to be linked to changes in the state of the atlantic meridional overturning circulation amoc i e a warm interstadial cold stadial state corresponds to a strong weak amoc based on a series of freshwater hosing extraction experiments with the state of the art community climate system model version 3 we construct a global spatial fingerprint of oceanic temperature anomalies in response to amoc changes under mis3 boundary conditions highest sensitivity to amoc changes especially in summer is found in northeastern north atlantic sea surface temperature but a characteristic temperature fingerprint is also found at subsurface levels after testing significance of the linear sea surface temperature sst amoc regressions the model results are combined with paleo sst records to estimate the magnitude of millennial scale dansgaard oeschger amoc variations during mis3 the results suggest a mean difference in amoc strength between interstadial and non heinrich stadial states of 9 2 1 2 sv 1

asymmetrical valleys created by the geomorphic response of rivers to strike slip fault abstract offset fluvial valleys including rivers beheaded and deflected by strike slip faults have long been used to estimate horizontal displacements on the faults larger rivers crossing such faults however sometimes show either no offset or only a small amount of offset compared to smaller rivers crossing the same faults the larger rivers with higher erosional rates may widen their valleys asymmetrically downstream of strike slip faults rather than being beheaded or deflected examples are described from the yellow river near the ne margin of the tibetan plateau river beheading and asymmetrical widening are two end members of a fluvial valley s response to strike slip faulting whereas deflection is a combination of both recognition of the formation of such asymmetrical valleys related to strike slip faulting will help to understand fault activity better over longer time spans and enable a re evaluation of many fault histories worldwide

ocean margin densities and paleoestimates of the atlantic meridional overturning circulation a model study an eddy permitting numerical ocean model is used to test to what extent the atlantic meridional overturning circulation moc can be reconstructed from sea water densities at the ocean margins by gradually reducing the number of locations where the densities are known and by adding systematic and random errors comparable to those expected in paleoreconstructions of sea water densities we test if a reliable picture of the moc can still be obtained our results show that even with only 0 07 of the boundary densities the mean state of the moc as well as its variability can be reconstructed the addition of a systematic error results in an overestimation or underestimation of the meridional transport with a random error similar to the one expected for paleoestimates of the density the mean state of the moc can still be reproduced especially north of 40 n however the random noise largely masks the relatively modest moc variability observed in the model run for both systematic and random noise in the density field there is a larger sensitivity for moc reconstructions the closer a location is from the equator for a measuring campaign that aims to infer past states of the atlantic moc on the basis of boundary densities the present study suggests that the best strategy is to collect data that allow estimation of the basin wide vertical density structure between 40 n and 50 n information from only a few latitudes is sufficient for a reasonable representation of the mean moc state

application of an inverse method to interpret 231pa 230th observations from marine sediments constraints then sediment 231 pa 230 th data for each time interval are combined with an advection scavenging model in order to determine their in consistency with the modern circulation estimate we find that the majority of sediment 231 pa 230 th data for the holocene lgm or h1 can be brought into consistency with the modern circulation if plausible assumptions are made about the large scale distribution of 231 pa and about model uncertainties moreover the adjustments in the data needed to reach compatibility with a hypothetical state of no flow no advection are positively biased for each time interval suggesting that the 231 pa 230 th data including that for h1 are more consistent with a persistence of some circulation than with no circulation our study does not imply that earlier claims of a circulation change during the lgm or h1 are inaccurate but that these claims cannot be given a rigorous basis given the current uncertainties involved in the analysis of the 231 pa 230 th data

meridional circulation during the last glacial maximum explored through a combination of south atlantic δ18o observations and a geostrophic inverse model 1 the vertical profile of meridional transport in the south atlantic is examined by combining paleoceanographic observations with a geostrophic circulation model using an inverse method 18ocalcite observations along the margins of the south atlantic show that upper ocean cross basin differences were weaker during the last glacial maximum lgm than the holocene the 18ocalcite observations can be explained by a shift of water mass properties without any change in the overturning circulation alternatively they may indicate a reduced lgm cross basin density difference and via the thermal wind relation a reduced vertical shear model inversions of 18ocalcite are found to require meridional transports different from the modern only after three assumptions are made temperature and salinity distributions are spatially smooth the relationship between salinity and 18owater is linear and spatially invariant and lgm temperatures are known to within 1 c along the margins the last assumption is necessary because an independent constraint on temperature or salinity is required to determine density from 18ocalcite observations 18ocalcite observations are clearly useful but before any firm constraints can be placed on lgm meridional transport it appears necessary to better determine the relationship between 18ocalcite and density

unravelling changing sediment sources in a mediterranean mountain catchment a bayesian fingerprinting approach to determine the provenance of holocene floodplain deposits of the bugduz catchment in southwest turkey a bayesian fingerprinting approach was used an important requirement for any provenance study is that the potential sediment sources show sufficient spatial and compositional heterogeneity the spatial distribution of potential sources in this case the various lithologies present within the catchment was mapped using field observations and aster and quickbird satellite images to distinguish the source lithologies a set of geochemical tracers was identified using linear discriminant analysis this optimum fingerprint was then used in the mixing model to determine the sediment provenance the bayesian mixing model uses markov chain monte carlo random walks to determine the most probable source composition and mixing proportions the uncertainty associated with the input data can be incorporated into the model through prior probability distributions the spread of the posterior probability distributions represents the uncertainty associated with the mixing proportion calculation the main contrasts in the provenance of the floodplain deposits reflect the spatial distribution of potential sediment sources throughout the catchment there are however also important temporal variations in sediment provenance and lateral differences due to the nature of floodplain build up the observed spatial and temporal variability of sediment provenance gives a first indication that hill slope channel and within channel coupling relations are not uniform through the catchment and that different locations showed a distinct response to disturbances copyright 2012 john wiley sons ltd

open system coral ages reveal persistent suborbital sea level cycles sea level is a sensitive index of global climate that has been linked to earth s orbital variations with a minimum periodicity of about 21 000 years although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing suborbital frequency sea level change has been difficult to resolve primarily because of problems with uranium thorium coral dating here we use a new approach that corrects coral ages for the frequently observed open system behavior of uranium series nuclides substantially improving the resolution of sea level reconstruction this curve reveals persistent sea level oscillations that are too frequent to be explained exclusively by orbital forcing

the salinity temperature and δ18o of the glacial deep ocean we use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from ocean drilling program cores to reconstruct salinity and temperature of the deep ocean during the last glacial maximum lgm our data show that the temperatures of the deep pacific southern and atlantic oceans during the lgm were relatively homogeneous and within error of the freezing point of seawater at the ocean s surface our chloride data show that the glacial stratification was dominated by salinity variations in contrast with the modern ocean for which temperature plays a primary role during the lgm the southern ocean contained the saltiest water in the deep ocean this reversal of the modern salinity contrast between the north and south atlantic implies that the freshwater budget at the poles must have been quite different a strict conversion of mean salinity at the lgm to equivalent sea level change yields a value in excess of 140 meters however the storage of fresh water in ice shelves and or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level

oceanic salt switch salinity and temperature the two determinants of the density of ocean waters play an important role in ocean circulation in today s ocean the saltiest deep waters derive from the northern north atlantic but as boyle 1 explains in his perspective the situation was very different during the last glaciation he highlights the report by adkins 2 et al who show that the saltiest waters then formed in the southern ocean the ocean circulation must thus differ substantially between glacial and interglacial periods 1 http www sciencemag org cgi content full 298 5599 1724 2 http www sciencemag org cgi content short 298 5599 1769

inferring surface water equilibrium calcite δ18o during the last deglacial period from benthic foraminiferal records implications for ocean circulation the ocean circulation modifies mixed layer ml tracer signals as they are communicated to the deep ocean by advection and mixing we develop and apply a procedure for using tracer signals observed upstream by planktonic foraminifera and downstream by benthic foraminifera to constrain how tracer signals are modified by the intervening circulation and by extension to constrain properties of that circulation a history of ml equilibrium calcite 18o 18oc spanning the last deglaciation is inferred from a least squares fit of eight benthic foraminiferal 18oc records to green s function estimated for the modern ocean circulation disagreements between this history and the ml history implied by planktonic records would indicate deglacial circulation changes no deviations from the modern circulation are diagnosed because the two estimates of ml 18oc agree within their uncertainties over the deglaciation but diagnostics suggest data collection and modeling procedures useful for inferring circulation changes uncertainties of benthic derived ml 18oc are lowest in the high latitude regions chiefly responsible for ventilating the deep ocean additional high resolution planktonic records constraining these regions are of particular utility benthic records from the southern ocean where data are sparse appear to have the most power to reduce uncertainties in benthic derived ml 18oc understanding the spatiotemporal covariance of deglacial ml 18oc will also improve abilities of 18oc records to constrain deglacial circulation

quantifying provenance of reservoir sediment using multiple composite fingerprints in an arid region experiencing both wind and water erosion abstract quantitative information on sediment sources is useful for developing targeted protection measures that effectively control soil erosion in a watershed in this study a multiple composite fingerprints method was tested and used for quantifying the sediment provenance of the danghe river and for providing effective sediment control strategies for the watershed in an arid region experiencing both wind and water erosion surface samples were taken from three geomorphic source areas of dunes gobi and upstream mountains and sediment samples from the watercourses near the reservoir to accommodate the wide range of sediment size distributions resulting from the fluvial and aeolian processes sediment contributions from each source were estimated for each of six particle size groups the results showed that the proportional contributions from each source to the reservoir sediments were 56 73 from upstream mountains 26 36 from gobi and 16 91 from dunes with the relative contributions in each size group following a similar trend the largest fraction of the sediment was from the 0 063 0 1 mm particle size group accounting for about 37 09 of the total in which 4 7 59 and 25 50 were from dunes gobi and upstream mountains our results also indicated that selective erosion existed in both erosion processes especially in wind erosion process and multiple particle size tracking should be used in the cases of severe selective erosion to improve the accuracy of estimation also the sediment contribution rate per unit area was the largest from dunes thus controlling wind blown sand to the river by stabilizing the dunes is recommended to reduce the reservoir siltation

is there evidence for magmatic underplating beneath the oslo rift we challenge some of the long standing beliefs related to the permian oslo rift structure often referred to as a case example type locality for continental rifting the crustal structure of the oslo rift was long presumed to be thinned proterozoic crust overlying a permian high density layer interpreted as magmatic underplating new data support an alternative view of the crustal structure in the oslo rift region the bouguer gravity high in the region shows a strong asymmetry a steep westward facing gradient to the west of the rift and a much gentler eastern gradient we present a 3d density model based on petrophysical and seismic information which accounts for the bouguer gravity high using an eastward extension of old precambrian structures without invoking a prominent magmatic underplated structure reactivation of old pre rift structures appears to be an important feature affecting the evolution and location of the permo carboniferous oslo rift

trends and controls of holocene floodplain sedimentation in the rhine catchment article i nfo holocene floodplain sedimentation in the rhine catchment is controlled by human and climate impacts intricate river behaviour modifies the fluvial response to the external impacts making cause effect analysis difficult especially on large spatial scales to better understand the relative importance and interdependencies of external and internal controls temporally resolved floodplain sedimentation rates are established using three different methods i floodplain storage studies on the trunk stream ii depth age analysis of overbank deposits from different parts of the catchment and iii cumulative frequency distributions of 14 c ages from floodplain deposits from various parts of the catchment the applied methodology strongly differs with the available temporal resolution and the size of the corresponding catchment all three methods show a strong increase in sedimentation rate for more recent periods that can be linked to increasing human impact evidences for climate impacts and intricate river behaviour are less clear and hindered by insufficient temporal resolution of the currently available data

k ar illite age constraints on the proterozoic formation and reactivation history of a brittle fault in fennoscandia k ar ages of authigenic illite from two drill core gouge samples of a fault in the palaeoproterozoic basement of finland record two distinct faulting events the older sample yields apparent ages from 1240 26 to 1006 21 ma for four grain size fractions between 6 and 0 1 m the second sample is structurally younger and yields statistically distinct ages ranging from 978 20 to 886 18 ma we interpret the ages of the 0 1 m fractions which are the youngest as representing the actual time of faulting xrd analysis and age modelling exclude significant age contamination of the finest dated fractions with inherited host rock components these results provide therefore an example of meaningful isotopic dating of illite type clay material formed during precambrian faulting demonstrate and constrain fault reactivation and give evidence for brittle sveconorwegian mesoproterozoic shortening and neoproterozoic extension in fennoscandia

can we use ice sheet reconstructions to constrain meltwater for deglacial simulations 1 freshwater pulses from melting ice sheets are thought to be important for driving deglacial climate variability this study investigates challenges in simulating and understanding deglacial climate evolution within this framework with emphasis on uncertainties in the ocean overturning sensitivity to meltwater inputs the response of an intermediate complexity model to a single northern hemisphere meltwater pulse is familiar a weakening of the ocean overturning circulation in conjunction with an expansion of sea ice cover and a meridional temperature seesaw nonlinear processes are vital in shaping this response and are found to have a decisive influence when more complex scenarios with a history of pulses are involved a meltwater history for the last deglaciation 21 9 ka was computed from the ice 5g ice sheet reconstruction and the meltwater was routed into the ocean through idealized ice sheet drainages forced with this meltwater history model configurations with altered freshwater sensitivity produce a range of outcomes for the deglaciation from those in which there is a complete collapse of the overturning circulation to those in which the overturning circulation weakens slightly the different outcomes are interpreted in terms of the changing hysteresis behavior of the overturning circulation i e non stationary freshwater sensitivity as the background climate warms through the course of the deglaciation the study illustrates that current uncertainties in model sensitivity are limiting in efforts to forward model deglacial climate variability furthermore ice sheet reconstructions are shown to provide poor constraints on meltwater forcing for simulating the deglaciation

why estimates of deglacial ice loss should be biased low abstract sea level rose by about 130 m over the last deglaciation but the last glacial maximum lgm 24 000 to 18 000 yr before present is estimated to have had only enough grounded ice to raise sea level by about 115 m these estimates of the mass of grounded ice are typically expressed as an equivalent sea level rise by normalizing with the oceanic surface area and seawater density here we diagnose the deglacial freshwater budget by comparing the freshwater content of the modern ocean to four reconstructions of the last glacial maximum constrained by data from porewaters benthic foraminifera and faunal assemblages a deglacial ice loss of 127 4 to 128 0 m of sea level equivalent is necessary to balance the freshwater budget suggesting a bias of 2 0 to 2 6 m less than the assumed true sea level rise oceanic thermal expansion explains 0 8 to 1 4 m of the bias independent of deglacial warming an additional 1 2 m of bias is intrinsic to the formulation of the equivalent sea level metric thus estimates of deglacial ice loss should underestimate the true sea level rise leading to a reduction in the amount of glacial land ice that needs to be found

inclined k ar illite age spectra in brittle fault gouges effects of fault reactivation and wall rock contamination k ar clay fraction ages of brittle faults often vary with grain size decreasing in the finer size fractions producing an inclined age grain size spectrum k ar ages and mineralogical characterization of gouges from two normal faults in the kongsberg silver mines southern norway suggest that inclined spectra derived from brittle fault rocks reflect the mixing of inherited components with authigenic mineral phases the ages of the coarsest and finest fractions constrain faulting at c 260 270 ma and reactivation around 200 210 ma respectively this study demonstrates how wall rock contamination influences the k ar age of the coarsest size fractions and that authigenic illite and k feldspar can crystallize synkinematically under equivalent conditions and thus yield the same k ar ages

on the abyssal circulation in the glacial atlantic an inverse method is used to evaluate the information contained in sediment data for the atlantic basin during the last glacial maximum defined here as the time interval 18 21 kyr before present the data being considered are an updated compilation of the isotopic ratios 18 o 16 o 18 o and 13 c 12 c 13 c of fossil shells of benthic foraminifera bottom dwelling organisms first an estimate of the abyssal circulation in the modern atlantic is obtained which is consistent with i climatologies of temperature and salinity of the world ocean circulation experiment ii observational estimates of volume transport at specific locations and iii the statements of a finite difference geostrophic model second estimates of water properties 18 o of equilibrium calcite or 18 oc and 13 c of dissolved inorganic carbon or 13 cdic derived from sediment data are combined with this circulation estimate to test their consistency with the modern flow it is found that more than approximately 80 of water property estimates 18 oc or 13 cdic are compatible with the modern flow given their uncertainties the consistency of glacial 13 cdic estimates with the modern flow could be rejected after two assumptions are made i the uncertainty in these estimates is 0 1 this uncertainty includes errors in sediment core chronology and oceanic representativity of benthic 13 c which alone appears better than this value on average and ii 13 cdic in the glacial deep atlantic was dominated by a balance between water advection and organic c remineralization measurements of 13 c on benthic foraminifera are clearly useful but the current uncertainties in the distribution and budget of 13 cdic in the glacial atlantic must be reduced to increase the power of the test

a temporarily changing holocene sediment budget for a loess covered catchment central belgium abstract this study presents a holocene sediment budget for the nethen catchment a typical river catchment 55 km 2 in the belgian loess belt soil erosion and hillslope sediment storage are quantified by extrapolating detailed data obtained from soil profile truncation studies in three representative zero order sub catchments floodplain sediment storage is estimated by augerings along several transects across the main river and some of its tributaries the sediment budget shows that ca 38 of the soil eroded during the holocene is redeposited as colluvium on hillslopes and in dry valley bottoms another 23 of the eroded sediment is now stored as alluvium in the floodplain the remaining 39 or 21 10 6 mg is exported from the catchment dating of both colluvial and alluvial sediment deposits reveals that sediment dynamics between the hillslopes the dry valley bottoms and the floodplain behave highly non linearly before 500 bc sediment delivery from the hillslopes to the river channels was near maximum however since the onset of significant agriculture in the late bronze age early iron age increased rates of soil erosion are only reflected in the colluvium but not in the floodplain resulting in very low hillslope sediment delivery ratios from the medieval period onwards soil erosion increased even further mainly as a result of a further increase in agricultural land use but now also accelerated floodplain sedimentation took place due to an improved slope channel coupling and the management of floodplains

a global glacial ocean state estimate constrained by upper ocean temperature proxies abstractwe use the method of least squares with lagrange multipliers to fit an ocean general circulation model to the multiproxy approach for the reconstruction of the glacial ocean surface margo

numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum 1 a hydrodynamic model incorporating a self consistent treatment of ocean self attraction and loading sal and a physically based parameterization of internal tide it drag is used to assess how accurately barotropic tides can be modeled without benefit of data and to explore tidal energetics in the last glacial maximum lgm m2 solutions computed at high resolution with present day bathymetry agree with estimates of elevations from satellite altimetry within 5 cm rms in the open ocean this accuracy and agreement with atlimetric estimates of energy dissipation are achieved only when sal and it drag are included in the model solutions are sensitive to perturbations to bathymetry and inaccuracies in available global databases probably account for much of the remaining error in modeled elevations the 100 m drop in sea level during the lgm results in significant changes in modeled m2 tides with some amplitudes in the north atlantic increasing by factors of 2 or more dissipation is also significantly changed by the drop in sea level if it drag estimated for the modern ocean is assumed dissipation increases by about 50 globally and almost triples in the deep ocean however it drag depends on ocean stratification which is poorly known for the lgm tests with modified it drag suggest that the tendency to a global increase in dissipation is a robust result but details are sensitive to stratification significant uncertainties about paleotides thus remain even in this comparatively simple case where bathymetry is well constrained

holocene environmental change and its impact on sediment dynamics in the eastern mediterranean abstract investigators have studied past environmental change in the eastern mediterranean region from a number of perspectives while climate reconstructions and palynological research have focused on forces that drive the geomorphologic system many researchers have attempted to use sediment archive studies to identify periods of change in sediment dynamics due to the large variability in environmental parameters and the variety of landscapes present in the eastern mediterranean region research has focused on sediment archives ranging from small colluvial sites to deltas of large rivers on the mediterranean coast as the cultural record for the region is extremely rich the main goal of palaeo environmental research in the eastern mediterranean has been to identify the relative importance of human impact on the landscape nevertheless sediment archives have significant limitations chronological control for many palaeo environmental records is highly uncertain and rates of landscape change are oftentimes difficult to assess most palaeo environmental research has been conducted on or near archeological sites where direct human impact may obscure the indirect impact on sediment dynamics through land use changes quantification and modeling of sediment dynamics in the eastern mediterranean environment offer one solution when erosion and sediment transport rate analyses are incorporated periods of relatively important change can be identified using multiple approaches the relative importance of the main driving forces climate and land use become distinguishable since field based data from the actual sediment archives remain vital an overview of numerous studies in the eastern mediterranean is provided in order to draw a general picture for different time periods and the relative scale of regional landscape development during the holocene a comparison of sediment dynamics with the record of driving forces indicates that while climate was the main driver of the geomorphic system during the early holocene at some point human impact became widespread and began to dictate sediment dynamics to a large extent from the byzantine period onward soil properties seem to play an increasingly important role as the hillslope soil reservoir in the eastern mediterranean was progressively depleted during the late holocene

meridional overturning circulation in the south atlantic at the last glacial maximum the geostrophic shear associated with the meridional overturning circulation is reflected in the difference in density between the eastern and western margins of the ocean basin here we examine how the density difference across 30 s in the upper 2 km of the atlantic ocean and thus the magnitude of the shear associated with the overturning circulation has changed between the last glacial maximum and the present we use oxygen isotope measurements on benthic foraminifera to reconstruct density today the density in upper and intermediate waters along the eastern margin in the south atlantic is greater than along the western margin reflecting the vertical shear associated with the northward flow of surface and intermediate waters and the southward flowing north atlantic deep waters below the greater density along the eastern margin is reflected in the higher 18o values for surface sediment benthic foraminifera than those found on the western margin for the upper 2 km for the last glacial maximum the available data indicate that the eastern margin foraminifera had similar 18o to those on the western margin between 1 and 2 km and that the gradient was reversed relative to today with the higher 18o values in the western margin benthic foraminifera above 1 km if this reversal in benthic foraminifera 18o gradient reflects a reversal in seawater density gradient these data are not consistent with a vigorous but shallower overturning cell in which surface waters entering the atlantic basin are balanced by the southward export of glacial north atlantic intermediate water

how well would modern day oceanic property distributions be known with paleoceanographic like observations author s gebbie g streletz gj spero hj abstract 2016 american geophysical union all rights reserved compilations of paleoceanographic observations for the deep sea now contain a few hundred points along the oceanic margins mid ocean ridges and bathymetric highs where seawater conditions are indirectly recorded in the chemistry of buried benthic foraminiferal shells here we design an idealized experiment to test our predictive ability to reconstruct modern day seawater properties by considering paleoceanographic like data we attempt to reconstruct the known modern day global distributions by using a state estimation method that combines a kinematic tracer transport model with observations that have paleoceanographic characteristics when a modern like suite of observations practical salinity seawater 18o 13cdic po4 no3 and o2 is used from the sparse paleolocations the state estimate is consistent with the withheld data at all depths below 1500 m suggesting that the observational sparsity can be overcome physical features such as the interbasin gradients in deep 13cdic and the vertical structure of atlantic 13cdic are accurately reconstructed the state estimation method extracts useful information from the pointwise observations to infer distributions at the largest oceanic scales at least 10 000 km horizontally and 1500 m vertically and outperforms a standard optimal interpolation technique even though neither dynamical constraints nor constraints from surface boundary fluxes are used when the sparse observations are more realistically restricted to the paleoceanographic proxy observations of 13c 18o and cd ca however the large scale property distributions are no longer recovered coherently at least three more water mass tracers are likely needed at the core sites in order to accurately reconstruct the large scale property distributions of the last glacial maximum

multiproxy approach for the reconstruction of the glacial ocean surface margo michal kucera antoni rosell mele ralph schneider claire waelbroeck mara weinelt department of geology royal holloway university of london egham tw20 0ex uk icrea and institute of environmental science and technology universitat autonoma de barcelona 08193 bellaterra catalonia spain departement de geologie et oceanographie umr5805 epoc cnrs universite de bordeaux1 33405 talence cedex france laboratoire des sciences du climat et de l environnement laboratoire mixte cnrs cea f 91198 gif sur yvette france institute for geosciences university of kiel olshausen strasse 40 d 24098 kiel germany

dynamical reconstruction of upper ocean conditions in the last glacial maximum atlantic abstractproxies indicate that the last glacial maximum lgm atlantic ocean was marked by increased meridional and zonal near sea surface temperature gradients relative to today using a least squares fit of a full general circulation and sea ice model to upper ocean proxy data with specified error estimates a seasonally varying reconstruction is sought of the atlantic ocean state that is consistent with both the known dynamics and the data with reasonable uncertainty assumptions for the observations and the adjustable control variables a consistent lgm ocean state is found one not radically different from the modern one inferred changes include a strengthening of the easterly and westerly winds leading to strengthened subtropical and subpolar gyres and increased upwelling favorable winds off the coast of africa leading to particularly cold ssts in those regions

illite and hydrocarbon exploration illite is a general term for the dioctahedral mica like clay mineral common in sedimentary rocks especially shales illite is of interest to the petroleum industry because it can provide a k ar isotope date that constrains the timing of basin heating events it is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap anticline etc that is to hold the oil illite also may precipitate in the pores of sandstone reservoirs impeding fluid flow illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial k ar ages are apparent ages of mixtures of detrital and diagenetic end members and what we need are the ages of the end members themselves this paper describes a methodology based on mineralogy and crystallography for interpreting the k ar ages from illites in sedimentary rocks and for estimating the ages of the end members

sediment tracing and environmental history for two small catchments karoo uplands south africa abstract as part of an investigation of land degradation in the south african karoo three types of fine sediment signatures radionuclides mineral magnetism and sediment geochemistry were used to trace the origins of fine particulate sediment accumulating in two reservoirs that were constructed around the mid 1930s both reservoirs are fed by gullies that are known to have been in existence before their construction robust chronologies were derived from the 137 cs profiles in the reservoir sediments from aerial photographic records and from an analysis of extreme storm events that have left stratigraphic markers in the reservoir sediments extreme daily rainfalls have become more frequent in the last 30 years but sediment accumulation rates in the two reservoirs differ significantly one reservoir has high sediment accumulation rates between 1958 and 1964 that correlates with an expansion in the area of cereal cultivation the second catchment has no cultivated land but sedimentation rates in the reservoir declined after 1941 when livestock grazing densities decreased by a factor of around three despite the increase in the frequency of high magnitude daily rainfalls after 1970 sediment availability as controlled by land use appears to be the most important limit on changes in sedimentation rates differences in lithology and land use provided an opportunity to evaluate the number of sources that could successfully be discriminated in each catchment at different timescales 137 cs and unsupported 210 pb can be used to trace sources of actively transported or very recently deposited sediment and to discriminate sources of reservoir sediments between topsoils cultivated and uncultivated and subsoils or gully sidewalls lack of current 137 cs inputs means that it will become less useful as a future discriminator of topsoil subsoil sources because it only has a half life of ca 30 years and will eventually be undetectable the potential for unsupported 210 pb to provide an alternative method for discriminating these sources is demonstrated using principal component and discriminant function analysis and the three groups of sediment fingerprint signatures it was possible to discriminate doleritic soils from other potential sources in the catchments including valley fill and soils underlying vegetation that had been recently burned as part of the rangeland management system results suggest that fire was an important contributor to destabilising soil which was subsequently delivered to the reservoir during high magnitude rainfalls it is concluded that 1 changes in the extent of cereal cultivation and livestock grazing density are most closely related to temporal changes in sedimentation rates in each of the two reservoirs 2 temporal changes in the magnitude and frequency of extreme daily rainfalls do not correlate with reconstructed patterns of sediment accumulation through time 3 the gully systems provide connectivity between the dominant hillslope sources and the reservoirs but have not contributed significantly to the sediment deposited in either reservoir and 4 there is no evidence to suggest that sources of sediment accumulating in the reservoirs have changed significantly over the last ca 70 years

dynamical reconstruction of the global ocean state during the last glacial maximum the global ocean state for the modern age and for the last glacial maximum lgm was dynamically reconstructed with a sophisticated data assimilation technique a substantial amount of data including global seawater temperature salinity only for the modern estimate and the isotopic composition of oxygen and carbon only in the atlantic for the lgm were integrated into an ocean general circulation model with the help of the adjoint method thereby the model was optimized to reconstruct plausible continuous fields of tracers overturning circulation and water mass distribution the adjoint based lgm state estimation of this study represents the state of the art in terms of the length of forward model runs the number of observations assimilated and the model domain compared to the modern state the reconstructed continuous sea surface temperature field for the lgm shows a global mean cooling of 2 2 k and the reconstructed lgm ocean has a more vigorous atlantic meridional overturning circulation shallower north atlantic deep water nadw equivalent stronger stratification and more saline deep water

use of composite fingerprints to determine the provenance of the contemporary suspended sediment load transported by rivers sediment fingerprinting appears to offer a valuable alternative to direct monitoring for elucidating the provenance of suspended sediment and the relative importance of spatial zones or subcatchments comprising larger 500 km 2 drainage basins against this background a quantitative composite fingerprinting technique incorporating both statistically verified multicomponent signatures and a multivariate sediment mixing model has been employed to determine the spatial origin of contemporary suspended sediment transported from the upper and middle reaches of the river exe 601km 2 and river severn 4325 km 2 basins uk spatial origin is addressed in terms of the relative contribution from three distinct geological subareas constituting each study basin the consistency of the composite fingerprinting approach is examined using the estimates for mean and seasonal variations in source area contributions and also a comparison between the results obtained for individual flood events and alternative lines of evidence provided by flood travel times and the spatial distribution of precipitation it is argued that fingerprinting estimates for sediment provenance are consistent with existing information on suspended sediment yields from different subcatchments within the study basins although in the severn the role of storage and remobilization in producing signature averaging may complicate comparison of the fingerprinting data with typical floodwater routing times validation represents the greatest problem for the cost benefit of fingerprinting and scope still exists for further refinement of the procedures involved 1998 john wiley sons ltd

the k ar and 40ar 39ar methods revisited for dating fine grained k bearing clay minerals abstract the strengths and weaknesses of the two ar isotopic methods k ar and 40ar 39ar were evaluated on the basis of respective recent applications mainly on low temperature k bearing illite type clay minerals this review includes a presentation of basic analytical and technical aspects for both methods as well as a discussion of varied claims on the two methods and of requests about sample preparation and characterization whenever possible the advantages and weaknesses of each method were compared on coeval results obtained by both methods on the same mineral separates the comparative review examines stratigraphic dating of glauconites indirect dating of low temperature ore deposits dating of burial related illitization and dating of polyphased tectono thermal activity more specifically of fault gouges some pending questions such as the necessary encapsulation due to 39ar recoil and its restoration into step heating patterns are also raised together with the new potential of ar dating of nanometric illite crystals weakness of the k ar method is in its pioneering status that makes many believe that it is no longer accurate because of its traditional analytical aspects and of the k determinations leading to somewhat large uncertainties however precise evaluation of varied applications points to a k ar method having probably larger applicability in sedimentary to diagenetic environments than the 40ar 39ar method the drawbacks become less important if the method is applied to nanometer sized clay minerals in diagenetic to low grade metamorphic environments in this instance the extracted size fractions are generally homogeneous and the relative uncertainty given by the age calculations if mathematically justified can be reduced by duplicate analyses weakness of the 40ar 39ar method is in its basics such as the 39ar recoil the necessary encapsulation the reintegration of the 39ar into the step heating patterns and the meaning of the step heating patterns that are more suggestive of variable 39ar reservoirs created among the clay particles by irradiation than of meaningful geologic ages if the k ar method is the preferred method for dating diagenetic clay processes such as glauconitization illite crystal nucleation and growth or low temperature hydrothermal activities then the 40ar 39ar method has more potential in dating low temperature tectono thermal activities and in detailing mixtures of multi generation illite

hydrothermal and unexpected diagenetic alteration in permian shales of the lodeve epigenetic u deposit of southern france traced by k ar illite and k feldspar dating abstract mineralogical and chemical analyses combined with k ar dating of illite and k feldspars were carried out on bulk samples and different fractions from permian shales around the lodeve u deposit to identify diagenetic and hydrothermal alteration episodes and their timing authigenic 2m1 and 1m illite with k ar ages between 270 and 245 ma are the predominant mineral types in the shales they are of early diagenetic origin relative to deposition and formed apparently directly from pyroclastic materials in a lagoonal to deltaic environment under semi arid conditions albite and a first generation of k feldspar developed by a replacement of analcime the k feldspar growing only in the former lagoonal environment that favored also early diagenetic dolomitization at the expense of calcite the hydrothermally altered shales next to the u deposit contain authigenic quartz fe chlorite neoformed illite and a second generation k feldspar with k ar ages beginning at about 220 ma triassic although jurassic and cretaceous ages were also obtained this younger age spectrum jurassic cretaceous is close to previous u pb isotope data from the u deposit probably reflecting several episodes of u mobilization therefore the hydrothermal activity extended episodically from triassic to cretaceous time within the u deposit the hydrothermal temperatures attained locally 220 c as the k ar system of illite from early permian diagenesis is partially reset triassic hot fluids ascended along faults into the northern area of the lodeve basin during an initial rifting of the nearby western tethys ocean further fluid pulses were recorded at lodeve during the opening of the north atlantic and separation of europe from africa jurassic cretaceous which also caused the peak hydrothermal activities in central and western europe as the lodeve area is located between two independently developing oceans it could have been supplied with hot fluids for a long period of time

timing of alpine fault gouges k ar ages from clay rich fault gouges in the european alps are consistent internally with established field constraints and with fission track ages demonstrating the applicability of this method for direct dating of brittle deformation illite grown by retrograde hydration of granitic and or high grade metamorphic protoliths is the major k bearing mineral in the fractions that have been separated 0 1 to 6 10 m the ages obtained are bracketed by apatite and zircon fission ages from adjacent localities this together with the interpreted cooling curve for one well constrained sample from the simplon fault indicates that illite grew or the k ar isotopic system in illite closed at temperatures in the range 120 150 c consistent with the stability of illite alone rather than illite smectite average ages obtained for fractions finer than 2 m were 1 5 2 2 6 ma 2 for 11 analyses from the detachment and footwall of the simplon fault 2 8 8 0 6 ma for four analyses from the centovalli fault at trontano 3 19 9 2 6 ma for two analyses from a major riedel fault related to the periadriatic fault offsetting the tertiary bergell tonalite at gesero 4 21 5 5 5 ma for two analyses from a zone parallel to the periadriatic fault in the adjacent southern alps in val morobbia and 5 14 5 3 9 ma for two analyses from a gouge zone on the northern rim of the tertiary mauls tonalite in the eastern alps the ages from the simplon centovalli and periadriatic faults are not identical and do not lend support to models linking these three faults as a single coeval structure

excess argon in k ar and ar ar geochronology the k ar and ar ar dating techniques occasionally produce anomalously old ages attributed to excess argon and such data is often rejected as not offering any insight into the age thermal history or geochemistry of the rock however improvements in the quantification of argon geochemistry now provide a framework to model excess argon in both open and closed systems solubility data for argon in hydrous fluids melts and emerging data for minerals can be used to understand the behaviour of excess argon and provide valuable insights into the environment in which the samples cooled to their argon retention or closure temperature treating excess argon as a trace element also throws light on its behaviour in minerals above the closure temperature in deeply buried dry systems such as eclogites blueschists granulites and even in the lithospheric mantle extremely low partition coefficients between k feldspar and hydrous fluid phases predict lower excess argon susceptibility than micas and this is observed in fluid poor systems variation of partition coefficients can lead to excess argon in fluids being introduced into minerals or removed from minerals as grain boundary fluids change during flow through a rock however excess argon can also be introduced or removed from minerals by varying temperature without the need for fluid flow high mineral melt and mineral fluid partition coefficients are also the reason why excess argon is often concentrated in inclusions within minerals partition coefficients between minerals and hydrous fluids as low as 10 6 lead fluid inclusions to dominate the radiogenic argon budget particularly in low potassium minerals melt inclusions are less dominant but become critical in dating younger samples

exhumation and uplift of the sierras pampeanas preliminary implications from k ar fault gouge dating and low t thermochronology in the sierra de comechingones argentina the sierras pampeanas in central and north western argentina constitute a distinct morphotectonic feature between 27 s and 33 s the last stage of uplift and deformation in this area are interpreted to be closely related to the andean flat slab subduction of the nazca plate beneath the south american plate k ar fault gouge dating and low temperature thermochronology along two transects within the sierra de comechingones reveal a minimum age for the onset of brittle deformation about 340 ma very low exhumation rates since late paleozoic time as well as a total exhumation of about 2 3 km since the late cretaceous new ar ar ages 7 54 1 91 ma of volcanic rocks from the san luis volcanic belt support the eastward propagation of the flat slab magmatic front confirming the onset of flat slab related deformation in this region at 11 2 ma although low temperature thermochronology does not clearly constrain the signal of the andean uplift it is understood that the current structural relief related to the comechingones range has been achieved after the exhumation of both fault walls circa 80 70 ma

a geostrophic transport estimate for the florida current from the oxygen isotope composition of benthic foraminifera we present a new method for the quantitative reconstruction of upper ocean flows for during times in the past for the warm t 5 c surface ocean density can be accurately reconstructed from calcite precipitated in equilibrium with seawater as both of these properties increase with decreasing temperature and increasing salinity vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera the net volume transport between two vertical density profiles can be calculated using the geostrophic method using benthic foraminifera from surface sediment samples from either side of the florida straits florida keys and little bahama bank we reconstruct two vertical density profiles and calculate a volume transport of 32 sv using this method this agrees well with estimates from physical oceanographic methods of 30 32 sv for the mean annual volume transport we explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater

k ar dating of synkinematic clay gouges from neoalpine faults of the central western and eastern alps abstract with ongoing alpine convergence and deformation during exhumation there is a general progression from ductile to brittle behaviour on the periadriatic fault and kinematically related faults farther north e g the simplon rhone fault and a diffuse discontinuous zone of generally dextral strike slip movement on the southern boundary of the aar massif k ar dating of fine grained illite from clay fault gouges provides a reliable method for establishing the maximum age of this transition to brittle faulting and for short lived faults the approximate time of faulting itself the new results establish that brittle faulting on the northeastern segment of the canavese fault i e the part of the periadriatic fault southwest of lago maggiore occurred around 20 ma with south side up kinematics a k ar age of ca 17 ma for the crosscutting giudicarie fault in the eastern alps is effectively identical with an already published pseudotachylyte age and places a lower limit on major and continuous strike slip movements of the periadriatic fault the age of brittle faulting farther north on the southern border of the aar massif is from 13 6 0 3 to 8 3 1 1 ma consistent with the younger cooling and exhumation in this area the dominantly dextral brittle faulting becoming younger to the north reflects the continued indentation and anticlockwise rotation of adria as alpine units become exhumed and progressively welded to the southern block in contrast to the eastern alps there is no field evidence for westward lateral extrusion of alpine units relative to adria and the european foreland

can paleoceanographic tracers constrain meridional circulation rates abstract the ability of paleoceanographic tracers to constrain rates of transport is examined using an inverse method to combine idealized observations with a geostrophic model considered are the spatial distribution accuracy and types of tracers required to constrain changes in meridional transport within an idealized single hemisphere basin measurements of density and radioactive tracers each act to constrain rates of transport conservative tracers while not of themselves able to inform regarding rates of transport improve constraints when coupled with density or radioactive observations it is found that the tracer data would require an accuracy one order of magnitude better than is presently available for paleo observations to conclusively rule out factor of 2 changes in meridional transport even when assumed available over the entire model domain when data are available only at the margins and bottom of the model radiocarbon is unable to constrain transport while density remains effective o

construction of the adjoint mit ocean general circulation model and application to atlantic heat transport sensitivity we first describe the principles and practical considerations behind the computer generation of the adjoint to the massachusetts institute of technology ocean general circulation model gcm using r giering s software tool tangent linear and adjoint model compiler tamc the tamc s recipe for fortran line by line generation of adjoint code is explained by interpreting an adjoint model strictly as the operator that gives the sensitivity of the output of a model to its input then the sensitivity of 1993 annual mean heat transport across 29on in the atlantic to the hydrography on january 1 1993 is calculated from a global solution of the gcm the kinematic sensitivity to initial temperature variations is isolated showing how the latter would influence heat transport if they did not affect the density and hence the flow over 1 year the heat transport at 29on is influenced kinematically from regions up to 20 o upstream in the western boundary current and up to 5 o upstream in the interior in contrast the dynamical influences of initial temperature and salinity perturbations spread from as far as the rim of the labrador sea to the 29on section along the western boundary the sensitivities calculated with the adjoint compare excellently to those from a perturbation calculation with the dynamical model perturbations in initial interior salinity influence meridional overturning and heat transport when they have propagated to the western boundary and can thus influence the integrated east west density difference our results support the notion that boundary monitoring of meridional mass and heat transports is feasible

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

fault gouge analyses k ar illite dating clay mineralogy and tectonic significance a study from the sierras pampeanas argentina we introduce a method for the detailed interpretation of k ar illite fine fraction ages of fault gouges from non sedimentary host rocks ages are cross evaluated with several independent parameters e g illite crystallinity illite polytype quantification grain size mineralogical observations k ar muscovite and biotite host rock cooling ages as well as low temperature thermochronological data aft ahe zhe this interpretation approach is applied to a regional study in order to constrain the deformation path of the eastern sierras pampeanas in nw argentina in the course of this study a large number of gouge bearing fault zones were systematically sampled and analysed obtained k ar illite fine fraction ages range from devonian to cretaceous times documenting a long lasting brittle fault activity in this region ages 320 ma are synchronous with a period of intra carboniferous compressional tectonism whereas permo triassic ages are contemporaneous to a flat slab subduction episode of the farallon plate beneath the south american plate middle to late permian and early triassic ages as well as early jurassic to middle cretaceous ages correlate with extensional tectonics in this region additionally k ar illite ages reveal a propagation of brittle deformation from north to south in the sierras de cordoba and san luis data integrity and consistency with other chronometers and geological evidence show that the here suggested interpretation is valid and can provide a powerful tool to evaluate cooling and deformation histories despite of that we could show that the reliability of fault gouge data strongly depends on the regional cooling

use of floodplain sediment cores to investigate recent historical changes in overbank sedimentation rates and sediment sources in the catchment of the river ouse yorkshire uk abstract floodplain sediment cores collected from seven sites in the catchment of the river ouse in yorkshire uk have been used to provide information on recent historical changes in both rates of overbank sedimentation and sediment sources the environmental radionuclides 137 cs and unsupported 210 pb have been used to establish chronologies for each core and to estimate average sediment accumulation rates for the last ca 30 and 100 years respectively average sedimentation rates for the individual cores ranged from 0 11 to 1 04 g cm 2 yr 1 in all but one case the estimates of average sedimentation rate during the last ca 30 years for the individual cores are broadly similar to those for the last ca 100 years suggesting that overbank sedimentation rates have been essentially uniform over the longer time period composite fingerprints based on a combination of geochemical and mineral magnetic properties and a numerical mixing model have been used to investigate downcore changes in sediment source in the case of source type most of the cores reflect a primarily topsoil source although there have been periods with increased contributions from subsoil channel bank sources within the ouse basin in general the period commencing in the late 19th and early 20th century and extending through to the 1960s was characterised by increased contributions from topsoil sources however contributions from subsoil channel bank sources have increased over the last few decades the source tracing results relating to sediment contributions from the three main geological topographic zones are in broad agreement with the proportion of the area of the catchment underlain by each rock type temporal variations in the contributions from the three geological topographic zones vary from site to site but for the lower reaches of the river ouse contributions from areas underlain by permian and triassic rocks which mainly outcrop in the vale of york have increased since the turn of the century the changes in sediment source identified are probably a reflection of changes in land use and management and possibly changes in climate these results enable estimates of contemporary suspended sediment fluxes and sources to be placed into a historical context and provide a means of considering the likely impact of potential future changes in land use and climate in the study basin

multi element soil prospection aiding geophysical and archaeological survey on an archaeological site in suburban sagalassos sw turkey in order to take full advantage of the archaeological information contained within buried archaeological sites it is important to apply an integrative approach combining complementary prospection methods in this study geochemical prospection data are combined with archaeological and geophysical survey results on an unexcavated site in suburban sagalassos sw turkey with the aim of obtaining better insights into the structural shapes and past functionalities of the area spatial and multivariate statistical analyses of the chemical data reveal anomalies of k p and zn on a location where archaeological and geophysical results suggest the presence of ceramic producing kilns these elemental enrichments are thought to result from burning wood or dung as fuel for the detected kilns in addition local anomalies of co cr fe mg mn and ni were found to reflect the working and storage of ophiolitic clays employed as a raw material for ceramic production radiocarbon dating of charcoal in a 2 5 m deep drill core in this zone provides ages between ad 120 and 350 at depths of 50 and 60 cm al as ba ca na sr ti and pb are considered geogenic elements in this study the present study supports the theory that geochemical prospection holds potential as a surveying technique as it was found that chemical data facilitate the interpretation of structures detected by geophysical and archaeological methods thereby creating an extra dimension to the interpretation of survey data the results further argue in favour of using strong acid extractions and the consideration of a large suite of elements when applying chemical soil survey as an archaeological prospection technique and highlight the importance of considering site lithology multivariate statistics proved to be invaluable in distinguishing anthropogenic from lithological soil patterns

glacial interglacial circulation changes inferred from 231pa 230th sedimentary record in the north atlantic region 1 studies from the subtropical western and eastern atlantic ocean using the 231pa 230th ratio as a kinematic proxy for deep water circulation provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation moc over the last deglaciation in this study we present a compilation of existing and new sedimentary 231pa 230th records from north atlantic cores between 1710 and 4550 m water depth comparing sedimentary 231pa 230th from different depths provides new insights into the evolution of the geometry and rate of deep water formation in the north atlantic during the last 20 000 years the 231pa 230th ratio measured in upper holocene sediments indicates slow water renewal above 2500 m and rapid flushing below consistent with our understanding of modern circulation in contrast during the last glacial maximum lgm glacial north atlantic intermediate water gnaiw drove a rapid overturning circulation to a depth of at least 3000 m depth below 4000 m water renewal was much slower than today at the onset of heinrich event 1 transport by the overturning circulation declined at all depths gnaiw shoaled above 3000 m and significantly weakened but did not totally shut down during the bolling allerod ba that followed water renewal rates further decreased above 2000 m but increased below our results suggest for the first time that ocean circulation during that period was quite distinct from the modern circulation mode with a comparatively higher renewal rate above 3000 m and a lower renewal rate below in a pattern similar to the lgm but less accentuated moc during the younger dryas appears very similar to ba down to 2000 m and slightly slower below

sensitivity of the eastern mediterranean geomorphic system towards environmental change during the late holocene a chronological perspective alluvial and colluvial sediment deposition provide a vital record of environmental change during the holocene firm chronological control on these archives is necessary to enable us to relate sediment dynamics to human activity and climate variability in the eastern mediterranean such relationships are hard to establish due to the lack of spatially well distributed sediment archives with good chronological control this scarcity is problematic with respect to regional scale reconstructions of the temporal variation of sediment dynamics here we present a radiocarbon database n 178 of geomorphological activity collected from multiple distinct sediment archives within the territory of sagalassos in south western turkey the data were grouped according to their sedimentary facies for analysis using cumulative probability distributions cpds and sedimentation rate sr modelling two small scale colluvial valleys where chronological information was abundant were investigated in more detail results show that sedimentation chronology differs between individual nearby cores as it depends strongly on the local geomorphic situation a generalizing approach combining multiple core results yields more widely valid conclusions high sedimentation rates coincided with the initial major anthropogenic disturbance of the landscape and decreased afterwards probably due to hillslope soil depletion cpd and sr analysis indicates that in general colluvial sedimentation rates did not change much from 2000 bc onwards river floodplain sedimentation in contrast increased markedly during the first millennium bc and during recent times and a significant time lag in enhanced sediment deposition between the upper and lower reaches of the river valleys was observed copyright 2012 john wiley sons ltd

alluvial responses to the changing earth system alluvial systems are complex self organizing and hierarchical in structure they represent stored and transitory sediment bodies transported by rivers that have eroded their catchments and created multiscalar landforms and sedimentary architectures over a range of time scales the central question we address in this paper is how environmental signals are autogenically processed and recorded by the fluvial sediment system we compare databases of alluvial units that are well constrained in terms of dating control with direct or proxy records of environmental change river system responses to environmental change are evaluated over three nested time periods spanning the past 200 000 years first focusing on mediterranean european and african catchments river responses to relatively abrupt and short term late pleistocene dansgaard oeschger and heinrich climate events are examined second the effects of rapid and globally significant episodes of holocene climate change on european rivers together with anthropogenic land use impacts are assessed last little ice age flooding and alluvial responses to modern climate warming are reviewed with particular reference to upland britain these studies are shown to have significant implications for modelling local regional and global scale alluvial responses to future environmental change they highlight the necessity for numerical simulation models to be fully informed by field based knowledge and understanding of the memory effects of whole fluvial sediment systems particularly those that have experienced repeated phases of environmental change copyright 2008 john wiley sons ltd

changes in the fine sediment dynamics of the ouse and tweed basins in the uk over the last 100 150 years sediment cores collected from nine headwater lakes and reservoirs in their catchments and adjacent areas and from ten floodplain sites in the middle and lower reaches of the two river systems have been used to reconstruct changes in suspended sediment yields rates of sedimentation and suspended sediment sources for the ouse and tweed catchments in the uk over the last ca 100 150 years in response to recent environmental change for the small lake reservoir catchments in or adjacent to the ouse basin average sediment yields for the recent period 1963 95 were generally found to exceed those for the period prior to 1963 by up to 94 suggesting that sediment yields have increased over time for the equivalent lake reservoir catchments in and adjacent to the tweed basin sediment yields were generally lower in the period since 1963 in both basins sediment yields over the past 100 150 years were characterized by considerable temporal variability which was seen to reflect at least in part the significant changes in land use and land management that occurred within their catchments no clear links between the variability of sediment yields and changes in climate were apparent changes in sediment source reconstructed for one of the lakes appeared primarily to reflect catchment disturbance during afforestation in the 1940s average rates of overbank sedimentation for the ten floodplain sites varied considerably between sites for those cores collected from the ouse basin there was no consistent temporal trend and average sedimentation rates for the period extending from ca 1895 to 1963 were broadly similar to those for the period since 1963 for the tweed basin sedimentation rates for all three cores were higher prior to 1963 reflecting the increased soil erosion and sediment yields associated with the conversion of pasture to arable land in the immediate post world war ii period and the ditching and planting operations associated with afforestation in the 1940s substantial downcore variability in the source of the overbank sediment considered in terms of both source type and spatial location was found in both river basins this was seen to reflect land use change including land drainage the conversion of pasture to arable land afforestation and increased cereal production the evidence provided by the floodplain cores again showed little indication of any influence linked to climate change although the detailed patterns of temporal variation of sediment yield overbank sedimentation rate and sediment source reconstructed from the sediment cores collected from the lake reservoirs and floodplain locations are site specific there is a general consistency between the changes in sediment dynamics reconstructed for the headwater catchments based on the cores collected from the lakes and reservoirs and the equivalent evidence for the middle and lowland reaches of the catchments provided by overbank floodplain deposits despite significant changes in climate and more particularly land use over this time period the general lack of evidence of substantial changes in downstream sediment yield and rates of overbank sedimentation over the last ca 100 150 years in the ouse and tweed basins suggests that their sediment dynamics have been generally insensitive to recent environmental change this finding has important implications when considering the likely response of these and similar uk river basins to future environmental change

constraints from paleotracer data on the north atlantic circulation during the last glacial maximum we investigate the extent to which the paleotracers 13c and 18o constrain the north atlantic ocean general circulation during the last glacial maximum lgm the distinction is made in this work between the depiction of water mass distributions and the inference of the oceanic circulation the 13c data indicate that water masses formed in the north atlantic and in the southern ocean were distributed differently during the lgm but the extent of the differences cannot be quantified because of uncertainties in the end member composition reasonable choices of values for the end members produce volumes of lower north atlantic deep water nadw significantly smaller than in the modern atlantic in agreement with previous studies to explore the range of circulations consistent with this water mass distribution a coarse resolution inverse model of the north atlantic is constrained with 13c and 18o paleodata the model shows that the glacial period tracer distribution is fully consistent with the circulation rates estimated for the modern ocean however the paleodata are also consistent with a circulation rate of one half the modern flux of nadw and indeed there are an infinite number of rates of deep water movement that are possible to remove this ambiguity the central need is for a data type capable of setting the overall rates of water movement i e a clock such as that provided by geostrophy or a well sampled radioactive tracer

skagerrak graben the offshore continuation of the oslo graben abstract new seismic mapping of skagerrak reveals eight structural provinces in particular the skagerrak graben appears to be the continuation of the oslo graben the skagerrak graben is defined by two major late paleozoic faults trending northeast southwest connecting with the faults bounding the oslo graben extensive rotated block faulting is observed within the graben and a thickness of more than 2 s twt of lower paleozoic sediments has been preserved along the boundary faults sediments of probable late paleozoic age have been deposited as erosional products from the fault scarps and a central uplifted area a substantial part of these sediments may have a volcaniclastic origin the skagerrak graben continues to the north as a province of igneous rocks exposed at the sea floor with precambrian basement on either side the skagerrak graben is flanked by small half grabens containing probable early paleozoic sediments indicating that a wider area was involved in the rift process the formation of the skagerrak graben is related to the dextral strike slip movements along the sorgenfrei tornquist zone in late paleozoic time the kimmerian extensional movements along this zone indicate however a decoupling of the skagerrak graben at this time only minor inversion in the southwestern part of the skagerrak graben reflects the major inversion tectonism along the sorgenfrei tornquist zone in late cretaceous early tertiary times

the baltica laurentia connection sveconorwegian grenvillian metamorphism cooling and unroofing in the bamble sector norway the sveconorwegian bamble sector of south norway is a segment of the high grade metamorphic basement of the baltic shield generally considered an integral piece of the global grenvillian orogenic belt in particular the bamble sector is generally directly linked to the grenville province of north america in middle proterozoic tectonic reconstructions however few high precision data exist on the metamorphic chronology of the bamble sector to test such models in this paper high precision u pb data for monazite allanite and titanite indicate that rocks from the bamble sector near arendal underwent granulite facies metamorphism at 1140 ma a second phase of metamorphism may be indicated by u pb titanite ages of 1105 ma or alternatively these may simply record delayed cooling or growth of titanite below temperatures for significant lead diffusion hornblende 40ar 39ar ages indicate cooling of the same rocks below 550 c between 1090 and 1080 ma metamorphic cooling rates of 3 8 c ma between 725 an

ar ar dating of authigenic k feldspar quantitative modelling of radiogenic argon loss through subgrain boundary networks we have analysed two distinct generations of authigenic k feldspar in fucoid bed sandstones from an t sron and skiag bridge nw highlands scotland which have experienced post growth heating to levels in excess of the predicted ar closure temperature authigenic k feldspars show microtextural similarities to patch perthites that is subgrains separated by dislocation rich boundary networks that potentially act as fast diffusion pathways for radiogenic argon the two generations of authigenic k feldspar in the fucoid bed sandstones can be distinguished by different microtextural zones bulk mineral compositions fluid inclusion populations and inferred temperatures and chemistries of parent fluids ar ar age data obtained using high resolution ultraviolet laser ablation show that the first cementing generation is ordovician and the second cementing generation is silurian modelling of ar diffusion using subgrain size as the effective diffusion dimension and a simplified tectono thermal thrust model assuming transient heating of the fucoid beds is inconsistent with observed data removal of heat from the thrust zone through rapid flushing of heated fluids rather than transient heating can be invoked to explain the observed ar ar ages for both generations of cement alternatively ar diffusion modelling using overgrowth thickness as the effective diffusion dimension instead of subgrain size also yields models that are consistent with both the fucoid bed palaeothermal maxima and determined ar ar age ages for the two generations of k feldspar cement based on this alternate explanation we propose a theoretical microtextural model that highlights fundamental differences between the microtextures of deuterically formed patch perthites and authigenic k feldspars explaining the apparent robustness of authigenic k feldspar with respect to ar retention

true to milankovitch glacial inception in the new community climate system model the equilibrium solution of a fully coupled general circulation model with present day orbital forcing is compared to the solution of the same model with the orbital forcing from 115 000 years ago the difference in snow accumulation between these two simulations has a pattern and a magnitude comparable to the ones inferred from reconstructions for the last glacial inception this is a major improvement over previous similar studies and the increased realism is attributed to the higher spatial resolution in the atmospheric model which allows for a more accurate representation of the orography of northern canada and siberia the analysis of the atmospheric heat budget reveals that as postulated by milankovitch s hypothesis the only necessary positive feedback is the snow albedo feedback which is initiated by reduced melting of snow and sea ice in the summer however this positive feedback is almost fully compensated by an increased meridionalheat transportin theatmosphereandareducedconcentrationoflow arcticclouds in contrasttosimilar previous studies the ocean heat transport remains largely unchanged this stability of the northern north atlanticcirculation is explainedby the regulatingeffect of thefreshwaterimportthroughthe naresstrait and northwest passage and the spiciness import by the north atlantic current

quantitative palaeoclimate reconstruction as an inverse problem a bayesian inference of late holocene climate on the eastern tibetan plateau from a peat cellulose δ18o record there has been a sustained need to quantify past climate changes from proxy records to better understand the driving mechanisms and thus to improve the prediction of the future transfer function is an intuitive and frequently used method in this regard however this method is unable to provide interpretive and predictive results from proxy records because physical processes are not included the inverse proxy modelling method opened up a new avenue for quantitative palaeoclimate reconstructions through the integration of proxy records with deterministic models it is fundamentally different from the statistical approach representing a conceptual advance in quantitative palaeoclimatology here we demonstrate the potential of this method by placing a mechanistic model and a 6000 year long peat cellulose 18o record obtained from the high cold and monsoonal eastern tibetan plateau c 3500 m a s l in a bayesian paradigm in this worked example the marginal posterior probability distributions of palaeo

a high resolution late holocene landscape ecological history inferred from an intramontane basin in the western taurus mountains turkey abstract late holocene vegetation and geomorphological history is reconstructed from a 800 cm long high resolution palynological and sedimentological record sampled from bereket a 6 3 km 2 semi arid to sub humid intramontane basin in the western taurus mountains southwest turkey the well dated bereket record provides from cal 360 bc to cal ad 400 a unique record of biennial to decadal landscape changes caused primarily by intensive human impacts against a background of global climate variations during this period land clearance with multiple fire episodes intensive agricultural practices and grazing pressure profoundly altered the pre existing warm mixed forest increasing moisture availability since cal 280 bc has acted as a trigger to crop cultivation and mountain adapted arboriculture starting with juglans regia during the beysehir occupation phase pollen from olive groves have been recorded above 1400 m a s l only at cal 23 bc and have disappeared definitively at cal ad 294 during this phase the sediment accumulation rate was extremely high reflecting landscape instability from cal ad 450 to recent times the area has mainly recorded pasture and minor cultivation activities reflected in stable soils and thin colluvial depths

a sediment fingerprinting approach to understand the geomorphic coupling in an eastern mediterranean mountainous river catchment article i nfo article history to understand the response of a river to anthropogenic disturbance knowledge of the links between erosion sed iment deposition and sediment export iscrucial therefore starting from field observations and connectivity prox ies a sediment fingerprinting approach using geochemical tracers was used to elucidate the subrecent sediment dynamics in the 264 km 2 bugduz river catchment in sw turkey a topography based connectivity index was used as a proxy for hillslope channel coupling and stream power estimations as a proxy for the within channel connectivity quantitative provenance information providesa link between potential sediment sources and the de rived sediment currently stored within the fluvial system provenance signals from both contemporary river bed sediments n 144 and subrecent floodplain deposits n 2 8 provide more insight into the coupling of the hillslopes to the river channel and the coupling within the river channel itself furthermore comparing the prov enance signal with the areal extent of potential sediment sources upstream in the form of enrichment ratios sheds light upon the variation of the erodibility of the sources andthe connectivity within the catchment results indicate that the valleygradient exerts an important control on the spatial variability of geomorphic coupling in the bugduz catchment furthermore different sediment sources lithologies show distinct sediment production rates in ad dition to the observed spatial variability coupling relations are characterized by an important seasonal variation indicated by variable contributions of local and more distant sediment sources

absolute dating of brittle fault movements late permian and late jurassic extensional fault breccias in western norway 40ar 39ar geochronological and palaeomagnetic dating methods applied to fault breccias in western norway have isolated two brittle reactivation episodes of the syn post caledonian extensional nordfjord sogn detachment these events of latest permian and latest jurassic early cretaceous ages demonstrate temporal relationships between development of chemical remanent magnetism and partial resetting of ar isotopic systems during distinct breccia forming episodes a third event of carboniferous age was also identified in the breccias with the 40ar 39ar technique and is a relict unroofing signature inherited from the fault wall rocks these brittle faults are significant time markers and become relevant to interpretations of offshore seismic data which attempt to place ages on faults that have undergone multiple reactivation episodes

global deepwater circulation between 2 4 and 1 7 ma and its connection to the onset of northern hemisphere glaciation we have generated an early pleistocene benthic isotopic record for the ocean drilling program odp site 807 2804 m from the western equatorial pacific between 2 4 and 1 7 ma the benthic 13c of this site and a few other deep pacific sites was consistently higher than the southern ocean site mv0502 4jc 4286 m pointing to a reversal relative to the current gradient and hence implying a different circulation regime we reconstructed the deep water mass distribution of this interval using a collection of benthic isotope records from 15 pacific and 10 atlantic sites and a 13c 18o mixing model a two end member mixing regime between the north atlantic deep water nadw and the antarctic bottom water aabw with properties very different from today was identified the southern ocean showed strong signs of stratification and aabw with low benthic 13c but high 18o values reached out to other basins only below 4000 m in contrast nadw ventilated most of the ocean interior contributing 70 to the pacific deep water pdw volumetrically our model results also reveal a strong remineralization effect at the bottom sites of the pacific and the atlantic suggesting significant accumulation of respired carbon in the bottom water between 2 4 and 1 7 ma we propose that such a circulation pattern was initiated by the reversal of salinity gradient between aabw and nadw from 3 0 to 2 4 ma possibly linked to antarctic sea ice expansion and reduced southward heat transport during the onset of northern hemisphere glaciation nhg

sediment yield and sources in dam controlled watersheds on the northern loess plateau abstract an improved understanding of the temporal variations in soil erosion rates and sediment sources is necessary to identify the main areas prone to soil erosion and to effectively implement soil and water conservation measures in this study we selected two dam controlled watersheds xiaoshilata and yangjiagou on the northern loess plateau china and determined the temporal variations in the sediment yield the sedimentation upstream of the dams showed that there were 31 and 9 flood couplets in the xiaoshilata 1958 1972 and yangjiagou watersheds 2007 2011 respectively which have trapped 16 5 104 t and 3 38 104 t of sediment respectively the estimated specific sediment yield was approximately 173 6 t ha a and 106 1 t ha a in the xiaoshilata and yangjiagou watersheds respectively a multivariate mixed model was applied to identify the different sediment sources the results indicated that weathered sandstone contributed approximately 61 52 of the total sediment and the remaining sediment loss was from bare loess soil 32 54 and grassland 5 94 in the xiaoshilata watershed in the yangjiagou watershed approximately 66 8 of the sediment originated from weathered sandstone whereas bare loess and grassland accounted for 17 5 and 15 7 of the sediment yield respectively based on these findings we recommend that comprehensive soil conservation measures are needed to soil erosion control for the permanent steep gullies due to high sediment contribution the sedimentation behind the check dams provides an indirect method for estimating the sediment yield in ungauged basins

effect of sea ice on the salinity of antarctic bottom waters abstract brine rejection during the formation of antarctic sea ice is known to enhance the salinity of dense shelf waters in the weddell and ross seas as these shelf waters flow off the shelves and descend to the bottom they entrain ambient deep water to create new bottom water it is not uncommon for ocean modelers to modify salinity boundary conditions around antarctica in an attempt to include a sea ice effect in their models however the degree to which antarctic salinities are enhanced is usually not quantified or defended in this paper studies of shelf hydrography and 18o are reviewed to assess the level of salinity enhancement appropriate for ocean general circulation models the relevant quantities are 1 the salinity difference between the water masses modified on the shelves and the final offshelf flow and 2 the flux of salt or freshwater that gives rise to this salinity difference onshelf offshelf salinity changes in the weddell and ross seas appear to be fairly small 0 15 0 20 sa

a re examination of the influence of composition on argon retentivity in metamorphic calcic amphiboles abstract the effect of composition on argon retention in metamorphic hornblende has been re evaluated by the 40 ar 39 ar step heating method utilizing the same samples from a k ar study in which a relationship between hornblende composition and argon retention was inferred incremental heating of the hornblendes yields 40 ar 39 ar age plateaus or near plateaus between 1081 3 and 1112 3 ma these data support a simple cooling history through argon closure following high grade metamorphism consistent with recent geochronological studies of the bamble sector of norway no clear evidence of extraneous argon is preserved in the 40 ar 39 ar data nor is there any sign of a thermal disturbance following argon closure contrary to the k ar results the 40 ar 39 ar data show no relationship between hornblende cooling age and composition the results of this investigation together with those from other studies suggest that the composition of metamorphic hornblende is not an important factor in controlling its argon closure temperature published studies inferring a compositional dependence on the argon closure temperature in metamorphic hornblende are commonly based on analytical data from impure retrogressed altered recrystallized or microstructurally complex hornblendes which are not representative of the diffusive properties of a pure hornblende such mineralogical and structural complexities may form both above and below the closure temperature of hornblende which may give rise to variable hornblende ages from rocks that have experienced the same geologic history such complexities forming at high temperature may contribute to a modified or variable characteristic grain size s of diffusion resulting in a modified complex hornblende closure temperature these complexities may contribute to low apparent hornblende ages if formed below its true closure temperature in addition variable hornblende ages may be obtained if fine grained mineral intergrowths are present and undergo recoil related phenomena during irradiation geologically meaningful hornblende ages are possible only when proper care is taken in sample selection and characterization

fault block rotations at the edge of a zone of continental extension southwest turkey the ne sw trending burdur acigol and baklan basins of southwest turkey are bounded by normal faults which became active in quaternary times prior to this a more widely spaced system of pliocene basins had existed each of the quaternary basins has a half graben geometry with a major nw dipping fault on its southeast side previous studies of the 1971 burdur earthquake caused by movement on the fault bounding the burdur basin have shown this fault to flatten slightly at depth deformation in the hangingwall of the fault controlling the pliocene basin in the burdur region suggests a planar fault geometry it is suggested that the pliocene fault rotated to its present shallow orientation then became inactive and acted as a detachment at depth for the more recent quaternary fault quaternary faults bounding the burdur acigol and baklan basins have a sinistral strike slip component with slip vectors indicating extension in an nw se direction this is at variance with regional n s extension in western turkey a solution for this contrast is found by invoking block rotations about vertical axes in a deforming zone between the rapidly extending aegean region to the west and the stable unstretched anatolian plateau to the east

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

abyssal atlantic circulation during the last glacial maximum constraining the ratio between transport and vertical mixing transport to vertical diffusivity in the deep atlantic our calculations suggest that the ratio was at least twice as large at the lgm we speculate that the primary cause was reduced mixing between northern and southern component waters associated with movement of this water mass boundary away from the zone of intense mixing near the seafloor the shallower water mass boundary yields an order of magnitude increase in the volume of southern component water suggesting its residence time may have increased substantially our analysis supports the idea that an expanded volume of antarctic bottom water and limited vertical mixing enhanced the abyssal ocean s ability to trap carbon during glacial times

tracer transport timescales and the observed atlantic pacific lag in the timing of the last termination 1 the midpoint of the last termination occurred 4 000 years earlier in the deep atlantic than the deep pacific according to a pair of benthic foraminiferal 18o records seemingly implying an internal circulation shift because the lag is much longer than the deep radiocarbon age here a scenario where the lag is instead caused by regional surface boundary condition changes delays due to oceanic transit timescales and the interplay between temperature and seawater 18o 18ow is quantified with a tracer transport model of the modern day ocean circulation using an inverse method with individual green functions for 2 806 surface sources a time history of surface temperature and 18owis reconstructed for the last 30 000 years that is consistent with the foraminiferal oxygen isotope data mg ca derived deep temperature and glacial pore water records thus in the case that the ocean circulation was relatively unchanged between glacial and modern times the interbasin lag could be explained by the relatively late local glacial maximum around antarctica where surface 18ow continues to rise even after the north atlantic 18owfalls the arrival of the signal of the termination is delayed at the pacific core site due to the destructive interference of the still rising antarctic signal and the falling north atlantic signal this scenario is only possible because the ocean is not a single conveyor belt where all waters at the pacific core site previously passed the atlantic core site but instead the pacific core site is bathed more prominently by waters with a direct antarctic source

man and environment in the territory of sagalassos a classical city in sw turkey abstract since 1990 archaeological research by the catholic university of leuven belgium has been carried out at the ancient site of sagalassos a lasun burdur province southwestern turkey at first research focused on the excavation of the city and the study of the immediate vicinity which provided it with raw materials the main objective was to obtain a clear picture of the history and development of the city since 1993 research has also incorporated a study of the territory of the roman city from prehistoric to modern times in order to understand why the site was selected for settlement why it developed into a middle sized town its economy and subsistence how it affected and exploited the environment its decline and what changes have taken place in the district subsequently the focus has now shifted towards obtaining a better understanding of the linkages between human and environment systems so that inter relations between the two can be more readily understood as a result a number of environmental topics concerning the territory of the roman city are presently being studied this territory extended from lake burdur in the west to the aksu canyon in the east from the a lasun da lari in the north to mt kestel in the south interdisciplinary research revealed that for the early neolithic and the roman period there was a slightly warmer climate a richer vegetation and more fertile soils for agricultural practice

use of the geochemical record preserved in floodplain deposits to reconstruct recent changes in river basin sediment sources abstract the geochemical record preserved in overbank floodplain deposits is used in combination with a composite fingerprinting technique and the chronology provided by 137 cs dateable horizons to reconstruct recent changes in sediment sources in the exe and severn basins uk composite fingerprints for discriminating potential source materials are identified from a suite of properties including heavy metals trace metals and cation bases these fingerprints are then compared with those of historical floodplain deposits using a numerical sediment mixing model relative contributions from distinct spatial sources characterised in terms of the devonian carboniferous and permian geological sub areas of the exe and the ordovician silurian devonian carboniferous permian and triassic jurassic sub areas of the severn are shown to fluctuate over the recent past in response to intrinsic e g the occurrence of extreme hydrologic events and extrinsic e g anthropogenic disturbance associated with land use change controls the potential for fingerprint property transformation in association with floodplain storage is assessed and the scope for further research using fingerprinting to reconstruct longer term sediment sources is discussed

radiocarbon variability in the western north atlantic during the last deglaciation we present a detailed history of glacial to holocene radiocarbon in the deep western north atlantic from deep sea corals and paired benthic planktonic foraminifera the deglaciation is marked by switches between radiocarbon enriched and depleted waters leading to large radiocarbon gradients in the water column these changes played an important role in modulating atmospheric radiocarbon the deep ocean record supports the notion of a bipolar seesaw with increased northern source deep water formation linked to northern hemisphere warming and the reverse in contrast the more frequent radiocarbon variations in the intermediate deep ocean are associated with roughly synchronous changes at the poles

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

cretaceous reactivation of the deokpori thrust taebaeksan basin south korea constrained by k ar dating of clayey fault gouge 1 the deokpori thrust juxtaposing the early paleozoic yeongwol type joseon supergroup yeongwol group against the duwibong type joseon supergroup taebaek group in the okcheon belt is an important regional structure in the phanerozoic tectonic evolution of korea although the initiation of the thrust has recently been conjectured to occur during the middle jurassic daebo tectonic event in a continental magmatic arc setting its movement history has never been studied we report timing of brittle reactivation of the thrust obtained from k ar dating of fault gouges in the core of the deokpori thrust zone k ar illite age data of fault gouges suggest reactivation of the thrust at ca 72 ma after a contact metamorphism around 94 ma our result is the first documentation of the reactivation of a major jurassic daebo structure and the reactivation may represent a significant contractional tectonic event during the late cretaceous in the korean peninsula

late holocene fire impact and post fire regeneration from the bereket basin taurus mountains southwest turkey abstract the 800 cm long sequence from the bereket provides the first detailed fire history in the western taurus mountains for the last three millennia the main disturbances occurred during the beysehir occupation phase bo phase a period of intensive polyculture and dated at bereket from ca 2230 to 1550 cal yr bp four phases of local and extra local fire periods have been recorded at 2320 2240 1985 1970 1865 1820 cal yr bp and post ad 1950 the fire history established for the bo phase is complex with fire periods alternating with periods without local fires as is the case for the late bo phase from 1820 until 1550 cal yr bp it is suggested that the past agricultural practices including fires cause a higher soil erodibility than agricultural practices without fires a climatic shift towards aridity during roman times may have triggered the observed change in fire regime but local processes mainly human disturbances appear to be the proximal cause of all recorded changes in the bereket surroundings fires led to a simplification of the vegetation structure favouring soil erosion pastures and intensive cultivation