millennial scale fluctuations of the european ice sheet at the end of the last glacial and their potential impact on global climate abstract reconstructing northern hemisphere ice sheet oscillations and meltwater routing to the ocean is important to better understand the mechanisms behind abrupt climate changes to date research efforts have mainly focused on the north american laurentide ice sheets lis leaving the potential role of the european ice sheet eis and of the scandinavian ice sheet sis in particular largely unexplored using neodymium isotopes in detrital sediments deposited off the channel river we provide a continuous and well dated record for the evolution of the eis southern margin through the end of the last glacial period and during the deglaciation our results reveal that the evolution of eis margins was accompanied with substantial ice recession especially of the sis and simultaneous release of meltwater to the north atlantic these events occurred both in the course of the eis to its lgm position i e during heinrich stadial hs 3 and hs2 31 29 ka and 26 23 ka respectively and during the deglaciation i e at 22 ka 20 19 ka and from 18 2 0 2 to 16 7 0 2 ka that corresponds to the first part of hs1 the deglaciation was discontinuous in character and similar in timing to that of the southern lis margin with moderate ice sheet retreat from 22 5 0 2 ka in the baltic lowlands as soon as the northern summer insolation increase from 23 ka and an acceleration of the margin retreat thereafter from 20 ka importantly our results show that eis retreat events and release of meltwater to the north atlantic during the deglaciation coincide with amoc destabilisation and interhemispheric climate changes they thus suggest that the eis together with the lis could have played a critical role in the climatic reorganization that accompanied the last deglaciation finally our data suggest that meltwater discharges to the north atlantic produced by large scale recession of continental parts of northern hemisphere ice sheets during hs could have been a possible source for the oceanic perturbations i e amoc shutdown responsible for the marine based ice stream purge cycle or so called he s that punctuate the last glacial period

all age depth models are wrong but are getting better the construction of accurate age depth relationships and a realistic assessment of their uncertainties is one of the fundamental prerequisites for comparing and correlating late quaternary stratigraphical proxy records four widely used age depth modelling routines clam oxcal bacon and bchron were tested using radiocarbon dates simulated from varved sediment stratigraphies all methods produce mean age depth models that are close to the true varve age but the uncertainty estimation differs considerably among models age uncertainties are usually underestimated by clam whereas age uncertainties produced by bchron are often too large with oxcal and bacon the setting of model specific parameters influences the estimated uncertainties which vary from too large to too small the variability of sediment accumulation rates is underestimated by clam but overestimated by bacon and bchron bayesian age depth models mainly improve the assessment of uncertainties of age depth models

upper pleistocene loess palaeosol records from northern france in the european context environmental background and dating of the middle palaeolithic abstract in northern france the loess cover from the last glacial weichselian is represented by a semi continuous mantle up to 8 m in thickness in the best localities such as leeward slopes e ne exposures in this large area pedostratigraphic sequences from the last interglacial glacial cycle eemian weichselian have been intensively studied especially under the auspices of active rescue archaeological programmes that have provided hundreds of individual sequences from test pits or excavations in spite of variations in the thickness of the different stratigraphic units driven by differences in geomorphological contexts the pedostratigraphic sequences from the last interglacial glacial cycle exhibit a particularly constant pedosedimentary pattern including well identified pedological and periglacial marker horizons that can be followed towards the east in belgium in germany and even in central europe according to the newest data it is shown that northern france loess palaeosol sequences are well suited to record the response of western european environments to rapid climatic changes dansgaard oeschger cycles the main objective of this paper is to present a summary of the pedostratigraphic sequence from northern france supplemented by the data from the new reference sequence of havrincourt and a global correlation scheme with surrounding areas in northern france the synthesis of the observations carried out on ca 100 sequences during the last 20 years allows the establishment of a highly detailed pedostratigraphic and chronostratigraphic scheme that represents a unique database for the discussion of the relations between palaeolithic occupation and environment in this context a strong relationship between the intensity of human occupation and the climatic and environmental context is demonstrated this relationship appears to be conditioned by the relative abundance of large mammal fauna itself linked to vegetation density as indicated by the extremely sparse biomass and the hiatus in human occupation that characterise upper pleniglacial loess

the evolution of periglacial patterned ground in east anglia uk during the late pleistocene east anglia experienced multiple cycles of periglacial activity this research investigates whether chalkland patterned ground infilled with coversand developed during one or more glacial cycles or only during the last period of intensive periglacial activity to affect lowland britain single grain luminescence ages from polygons and stripes at six sites in east anglia suggest that the patterns experienced multiple phases of activity during the last 90 10 ka but do not date back to earlier glacial cycles this activity is attributed to four main phases 1 55 60 ka 2 31 35 ka 3 20 22 ka and 4 11 12 ka most sites show some activity around the greenland stadial 2a and the younger dryas stadial but polygons show a longer more temporally and spatially varied record than stripes interpreted phases of activity mostly coincide with stadials within the last glacial interglacial cycle possibly at the end of climatic cold phases

the physics of wind blown loess implications for grain size proxy interpretations in quaternary paleoclimate studies abstract loess deposits are recorders of aeolian activity during past glaciations since the size distribution of loess deposits depends on distance to the dust source and environmental conditions at the source during transport and at deposition loess particle size distributions and derived statistical measures are widely used proxies in quaternary paleoenvironmental studies however the interpretation of these proxies often only considers dust transport processes to move beyond such overly simplistic proxy interpretations and toward proxy interpretations that consider the range of environmental processes that determine loess particle size distribution variations we provide a comprehensive review on the physics of dust particle mobilization and deposition furthermore using high resolution bulk loess and quartz grain size datasets from a last glacial interglacial sequence we show that because grain size distributions are affected by multiple often stochastic processes changes in these distributions over time allow multiple interpretations for the driving processes consequently simplistic interpretations of proxy variations in terms of only one factor e g wind speed are likely to be inaccurate nonetheless using loess proxies to understand temporal changes in the dust cycle and environmental parameters requires i a careful site selection to minimize the effects of topography and source distance and ii the joint use of bulk and quartz grain size proxies together with high resolution mass accumulation rate calculations if possible

pottery versus sediment optically stimulated luminescence dating of the neolithic vinca culture serbia optically stimulated luminescence osl dating was applied to the neolithic vinca culture s type site vinca belo brdo to establish best protocols for routine luminescence dating of similar holoce

dust flux estimates for the last glacial period in east central europe based on terrestrial records of loess deposits a review loess paleosol sequences are significant records of the mineral dust cycle of glacial interglacial periods as dust particles give rise to direct and indirect radiative forcing obtaining a reliable picture of the global and regional patterns of mineral dust fluxes during glacial periods can lead to a better understanding of the contribution of mineral dust to past climate changes recent progress in absolute dating of loess deposits in the carpathian basin in east central europe made it possible to provide correct aeolian flux estimates for the last glacial period marine isotope stage mis 2 mass accumulation rates mars from chronological data of 33 loess sites exhibited a wide range of values from 150 to 1422 g m 2 a 1 centered around median and mean values of 338 and 417 g m 2 a 1 marpm10marpm10 and marpm2marpm2 estimates have been also calculated using grain size measurements of many loess samples and loess mars in order to facilitate comparison with models and since particles larger than 10 m have a negligible radiative effect here we show that some previous model simulations of the dust cycle at the last glacial maximum lgm significantly underestimated the real aeolian flux ranges of our estimates marpm10 34 324marpm10 34 324 and marpm2 9 3 88 2gm 2a 1 in east central europe for this reason some simulations of dust induced direct radiative forcing of the lgm climate failed to yield reliable results for this mid latitude region as they have been based on three dimensional dust field models that are not capable of estimating the real aeolian fluxes in central europe a recent global model of top of the atmosphere toa radiative forcing by mineral aerosols at the lgm that has been based on more realistic parameterization of dust sources transport and deposition revealed zonally averaged surface cooling of 2 c for the latitudes of our study area this surface cooling and toa radiative forcing 2 to 3 w m 2 are greater than recognized in other models and draws our attention to the importance of further modeling the impact of mineral dust on lgm climate in order to gain insight into the spatial pattern of radiative forcing and better understand resulting climate response in mid latitude loess regions such as east central europe

age and origin of clayey silt brickearth in west london england the loamy brickearth deposits overlying coarse cold climate kempton park lynch hill and taplow gravels of the r thames in west london are dated by thermoluminescence and mineralogical comparisons with loesses of three known ages although much of the brickearth resembles loess it often contains more sand or clay than typical loess and the mineralogical studies suggest that even the coarse silt 16 63 m fraction is rarely similar in composition to any known english loess the thermoluminescence measurements suggest that most of the brickearth on the taplow and lynch hill gravels was deposited in the late devensian whereas that on the park gravel is mainly flandrian it is suggested that the latter is mainly floodloam whereas the earlier brickearth is a mixed aeolian sediment derived from various local sources in and close to the thames valley

the loess and coversands of northern france and southern england loess and coversands are widespread on either side of the english channel in southern england loess is generally thin and discontinuous but locally reaches thickness of about 4 m in east kent coversands occur mainly in areas well north of the channel such as parts of east anglia and the southern side of the bristol channel most of the loess and coversand deposits in southern england date from the late devensian cold stage marine oxygen isotope stage mois 2 but there are also a few localised patches of older mainly mois 6 and 12 loess which are the dissected remnants of originally more extensive covers in france loess is widespread and locally very thick up to 12 m especially in northern and northeastern france in normandy and in the somme basin some long records indicate that accumulation began at the end of the lower pleistocene at about 900 ka nevertheless the main accumulations of typical calcareous loess are related to the upper weichselian and upper saalian stages mois 2 and end of mois 3 and mois 6 indeed before about 160 170 ka loess deposition was generally restricted to special sediment traps such as fluvial and marine terraces exposed to the east or northeast these older deposits are characterised by more sandy facies derived from local fluvial sources mainly by northwest to north northwest winds coversands occur locally along the coast of the mont saint michel bay and over the northern part of the seine estuary near le havre the main differences in thickness and extent of the loess deposits between southern england and northern france are linked to their location in relation to the source areas channel and north sea to ice sheets and to the main wind directions northwest to north northwest in france and western england but northeast in eastern england copyright 2003 john wiley sons ltd

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

rivers and loess the significance of long river transportation in the complex event sequence approach to loess deposit formation abstract rivers are essential for loess deposit formation river systems which relate directly to loess deposit formation include the danube and the rhine the mississippi and the missouri the thames and the medway the indus ganges and brahmaputra the dnepr don and volga the clutha mataura and rakaia new zealand rivers the yellow river rivers in south america siberian rivers flowing north the odra and the wisla between the mountains and the ice the syr darya and amu darya into the desert the contention is that rivers are not just important in major loess deposit formation they are mandatory necessary imperative obligatory essential indispensable requisite for a complete and satisfactory study of a loess deposit we need to know how the material is produced how it is transported and distributed across the landscape how intermediate deposits are formed how transportation provides the defining properties i e open structure collapsibility draping across the landscape and what may happen post deposition e g chernozemisation fragipan formation increased collapsibility etc if rivers are essential then it would appear that the british loess is probably alpine material delivered by the proto rhine and the polish loess is not derived from the ice sheet to the north but from the mountains to the south the lack of loess in canada is explained by the absence of suitable rivers the loess in russia and neighbouring countries can be classified as jefferson et al jefferson i f evstatiev d karastenev d mavlyanova n g smalley i j 2003b the engineering geology of loess and loess like deposits a commentary on the russian literature engineering geology 68 333 351 suggested on the basis of associated rivers a new deposit of glacial loess is recognised associated with the dnepr don and volga rivers the uswr loess the smalley leach smalley i j leach j a 1978 the origin and distribution of the loess in the danube basin and associated regions of east central europe a review sedimentary geology 21 1 26 available from www geo edu ro sgr mod downloads pdf smalley sedgeo 1978 pdf vision of the loess in the danube basin and east central europe is probably misconceived they assigned a great significance to glacial action and put loess in a northern band it appears that this proposed glacial influence is minimal and that the danube loess is essentially mountain loess derived from the alps the carpathians the sudeten mountains and other high regions the danube system is a classic example of a river controlling loess distribution

an evaluation of geochemical weathering indices in loess paleosol studies abstract applying geochemical proxies as measure for the weathering intensity of paleosols and sediments such as loess the quaternary scientist is confronted with various element ratios that have been proposed in literature this paper gives an overview on the principle of geochemical weathering indices different types of indices are evaluated with respect to the suitability for loess paleosol sequences regarding the special characteristics of this type of sediments and paleosols case examples in this study are key sections in southeastern and eastern europe the loess paleosol sequences batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine which represent archives of the late and mid pleistocene climate change of the region considering element behavior during weathering or diagenesis the chemical proxy of alteration cpa i e the molar ratio al2o3 al2o3 na2o 100 is proposed as the most appropriate index for silicate weathering the cpa was evaluated against commonly used weathering indices including the chemical index of alteration cia the chemical index of weathering ciw the plagioclase index of alteration pia the index b of kronberg and nesbitt and the ba sr and rb sr ratio depth profiles of sr type indices e g ba sr rb sr are likely to be influenced by the dynamics of secondary carbonate on the other hand common na type indices e g cia pia ciw may suffer from uncertainties in separating carbonate ca from silicate ca or from biases due to k fixation illitization the cpa is insensitive against such effects additionally using the cpa as with other na type indices provides the possibility to evaluate the homogeneity of the parent material regarding the relevant host minerals via the a cn k diagram

middle late pleistocene landscape evolution of the dover strait inferred from buried and submerged erosional landforms abstract prominent landforms either buried or preserved at the seafloor provide important constraints on the processes that led to the opening and present day configuration of the dover strait here we extend previous investigations on two distinct landform features the fosse dangeard and lobourg channel to better understand the poly phase history of their formation and inferences for the opening and pleistocene evolution of the dover strait the fosse dangeard consist of several interconnected palaeo depressions their morphology and spatial distribution are interpreted to be the result of plunge pool erosion generated at the base of north eastward retreating waterfalls their infills comprise internal erosional surfaces that provide evidence for the occurrence of several erosional episodes following their initial incision the lobourg channel comprises various sets of erosional features attesting to the occurrence of several phases of intense fluvial and or flood erosion the last one of these carved a prominent inner channel which truncates the uppermost infill of the fosse dangeard the morphology of the lobourg inner channel and the erosional features associated with its incision strongly resemble landforms found in megaflood eroded terrains indicating that this valley was likely eroded by one or several megafloods our study therefore corroborates the existence of waterfalls in the dover strait at least once during the pleistocene epoch it also provides evidence of the occurrence of multiple episodes of fluvial and flood erosion including megafloods finally this study allows us to establish a relative chronology of the erosional depositional episodes that resulted in the present day morphology of this region

rapid and cyclic aeolian deposition during the last glacial in european loess a high resolution record from nussloch germany abstract this paper reports the results of an investigation of the weichselian upper pleniglacial loess sequences of nussloch rhine valley germany based on stratigraphy palaeopedology sedimentology palynology malacology and geochemistry 13 c supported by radiocarbon tl and osl dating grain size and magnetic susceptibility records are taken at 5 cm intervals from the upper pleniglacial upg loess the data indicate cyclic variations in loess deposition between ca 34 and 17 ka when the sedimentation rate is especially high 1 0 1 2 m per ka for more than 10 m the grain size index gsi ratio of coarse silt versus fine silt and clay shows variations which are assumed to be an indirect measurement of wind intensity the sedimentation rate interpreted from the profiles indicates high values in loess loess events le 1 to le 7 and low or negligible values in tundra gley horizons g1 to g8 osl ages from the loess and 14 c dates from organic matter in the loess show that loess deposition was rapid but was interrupted by shorter periods of reduced aeolian sedimentation comparison between the data from nussloch and other european sequences demonstrates a progressive coarsening of the loess deposits between ca 30 and 22 ka this coarsening trend ends with a short but major grain size decrease and is followed by an increase to a new maximum at 20 2 ka w shape correlation between the loess gsi and the greenland ice core dust records suggests a global connection between north atlantic and western european global atmospheric circulation and wind regimes in addition the typical upper pleniglacial loess deposition begins at ca 30 31 ka close to heinrich event he 3 and the main period of loess sedimentation at about 25 2 ka is coeval to he 2 correlation of magnetic susceptibility and grain size records shows that the periods characterised by high gsi coincide with an increase in the amount of ferromagnetic minerals reworked from the rhine alluvial plain they suggest enhancement in the frequency of the storms from n nw these results are integrated within a palaeogeographical model of dust transport and deposition in western europe for the weichselian upper pleniglacial or late pleniglacial

influence of orbital parameters on pleistocene loess deposition in central alaska few long proxy climatic records are available from terrestrial locations the isotope records of pleistocene climate change found in marine cores reflect worldwide ice volume and temperature changes forced by variations in the earth s orbital geometry comparable terrestrial records are rare loess wind deposited silt is perhaps the closest terrestrial analogue to marine sediments in that both result from more or less continuous deposition of fine grained sediment here we examine the hypothesis that mag netic susceptibility variations through loess sections reflect climate forcing we statistically tested cross correlations between high precision orbitally tuned marine oxygen isotope curves recording the past 250 000 yr bp and magnetic susceptibility profiles through a thick loess section in central alaska highly significant p 0 0001 correlations indicate strong thick palaeosols formed in arctic loess during early parts of interglacial periods correspond ing to isotope stages 7 and 5 thinner soils formed during interstadial events corresponding to early stage 7 and stage 3 autocorrelation and time series analysis of the loess data show spectral peaks at 125 000 41 000 and 23 000 yr bp showing for the first time that terrestrial orbital periodicities influenced and are recorded in proxy climatic data from terrestrial aeolian deposits at high latitudes

grain size of fine grained windblown sediment a powerful proxy for process identification abstract dust transport by the wind is not a uniform process but may occur in different modes according to source area conditions and transport height and distance subsequently these differences are expressed in terms of grain size and fluxes of the aeolian deposits transport distances may vary from several tens of meters to thousands of kilometers while the height accordingly may vary from meters to more than thousand meters a relation with grain size distributions may be established on the base of type occurrences of different loess facies three main loess populations and several subpopulations of primary windblown origin may be defined according to their grain size dominated by fine sand to very coarse silt silt and very fine silt to clay respectively each of them reflects a specific aeolian process and transport conditions it follows that the grain size distribution of a loess deposit is an excellent proxy for the reconstruction of aeolian processes and wind circulation patterns apart from primary pure wind deposition loess may also be affected by secondary post depositional processes examples are settling of loess particles in a lacustrine setting and reworking by rivers or surface runoff although the primary loess characteristics are maintained reworking processes leave also their imprint in the grain size distribution as a useful tool for secondary process identification

comment new osl dating of uk loess indications of two phases of late glacial dust accretion in se england and climate implications michele l clarke antoni e milodowski jon e bouch melanie j leng and kevin j northmore 2007 journal of quaternary science 22 361 371

introducing an improved multi proxy approach for paleoenvironmental reconstruction of loess paleosol archives applied on the late pleistocene nussloch sequence sw germany to study paleoenvironmental and paleoclimatic changes in loess paleosol sequences lps most proxies except for screening parameters have often been applied at low sampling density typically 1 2 per stratigraphic unit this might lead to results that overlook paleovegetation effects that were not only restricted to paleosols but also affected underlying loess material here a new profile was investigated in the loess paleosol sequence lps at nussloch sw germany using a high resolution multi proxy approach to improve our understanding of the late pleistocene record which serves as a standard sequence in central europe this approach included several geophysical and geochemical parameters as well as frequencies of root related features grain size distribution and osl dating enabled correlation of the new section with the nearby standard profile p4 revealing considerable variations of the thickness of stratigraphic units due to local small scale variations in depositional conditions and paleogeomorphology of longitudinal greda structures magnetic susceptibility revealed weathering of the entire lps under more humid conditions than those described for se european and chinese lps it further enabled a rough differentiation between an interval that was influenced by pedogenic processes lower pleniglacial to lower part of the upper pleniglacial and loess that was not markedly affected by soil formation color measurements confirmed these results and enabled the identification of several paleosols in the upper pleniglacial for the uppermost part of the lps low magnetic susceptibility and inorganic geochemical parameters such as low fe ti ratios indicated only weak or no pedogenic influence in contrast considerable variations e g in carbonatic carbon contents and organic carbon nitrogen c n ratio might be related to the high frequency of calcified root remains up to 200 rhizoliths m 2 and up to 12 500 microrhizoliths m 2 in certain depth intervals of the lps entailing incorporation and degradation of organic matter frequencies of biopores which are suggested to derive largely from former root growth and to a lesser extent from insect and earthworm bioturbation were related to paleosols and thus confirmed the pedostratigraphy an improved assessment of terrestrial sedimentary archives can be achieved by high resolution multi proxy analysis and three dimensional investigation of terrestrial sediments that are prone to bioturbation c 2014 elsevier b v all rights reserved

loessification and hydroconsolidation there is a connection abstract loessification can be defined as the acquisition of loessic characteristics by ground systems hydroconsolidation in this context is the collapse of the loess ground structure under the influence of loading and wetting loess on aeolian deposition is metastable a pre requisite for eventual collapse the actual collapse mechanism is dependent on the presence of a critical amount of clay mineral material at major particle contacts this clay accumulates via post depositional processes processes which can be described as part of loessification and as a contribution to collapsibility studies at ospringe in kent england support observations made in the bohemian massif in the czech republic about the nature of the loess ground system and the role of clay minerals and calcite crystals fragipan formation another important post deposition event could depend on hydroconsolidation in loess ground

magnetic enhancement and palaeoclimate study of a loess palaeosol couplet across the loess plateau of china summary the origin of the milankovitch palaeoclimatic signal so dramatically recorded in the chinese loess remains uncertain at least five hypotheses have been put forward to explain the well documented enhancement of magnetic susceptibility in palaeosols which formed when conditions were warmer and wetter we report here a magnetic study of a prominent loess soil couplet l4 s3 at three widely separated sites where present day mean annual rainfall and temperature range from 350mm to 700mm and from 6 c to 13 c the properties determined are laboratory remanences isothermal irm anhysteretic arm viscous vrm including viscous decay room temperature susceptibility and thermomagnetic behaviour at fields beyond 100 mt the irm spectra are all essentially identical both in shape and in absolute magnitude suggesting a uniform magnetic component widespread across the plateau subtracting the signal of this component isolates a second component the amount of which varies by an order of magnitude between sites the magnetic properties of this latter material are remarkably similar to those reported for bacterial magnetite in geological sediments and modern soils viscous decay of vrm takes place in two distinct stages one of which falls to zero in 10min we attribute magnetic enhancement which is the source of the palaeoclimatic signal to in situ pedogenetic formation of magnetite which we characterize in our interpretation as two separate forms of bacterial magnetofossils the most magnetic sample requires a mass fraction of about half of one per cent of this biogenic material

coupled european and greenland last glacial dust activity driven by north atlantic climate centennial scale mineral dust peaks in last glacial greenland ice cores match the timing of lowest greenland temperatures yet little is known of equivalent changes in dust emitting regions limiti

benthonische foraminiferen aus der unterkreide des deep sea drilling project leg 1 79 in den dsdp legs 1 11 13 17 25 27 32 36 41 43 44 50 und 62 wurden die unterkreide foraminiferen biostratigraphisch taxonomisch und palaookologisch bearbeitet eine ubersicht zeigt die in leg 1 80 erbohrte unterkreide und ihre foraminiferen bearbeitungen

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

influence of atlantic meridional overturning circulation on the east asian winter monsoon east asian summer monsoon precipitation varied on millennial timescales during the last glacial period sediment records and climate modelling suggest that the winter monsoon was also affected by millenial scale variability and that the abrupt changes were driven by changes in the strength of the atlantic meridional overturning circulation

landscape instability at the end of mis 3 in western central europe evidence from a multi proxy study on a loess palaeosol sequence from the eastern lower rhine embayment germany abstract the lower rhine embayment hosts important loess palaeosol sequences lps within the western european loess belt yielding valuable information on landscape evolution and palaeoclimatic dynamics the study focusses on the palaeoenvironmental development based on a lps from the eastern shoulder of the lower rhine embayment dusseldorf grafenberg the palaeoenvironmental development within the study area is presented and discussed based on high resolution grain size analyses selected environmental magnetic parameters and geochemical analyses complemented by luminescence age estimates differences in grain size distribution gsd as well as the u ratio clearly reflect main stratigraphical units within the lps in addition the centered log ratio transformation of gsd gsd clr which is sensitive to post depositional grain size variations traces units of intensified soil formation despite no magnetic enhancement can be observed within the grafenberg lps environmental magnetic parameters combined with selected geochemical analyses sr rb provide direct information on the modification of silicates and magnetic minerals in the course of pedogenesis and diagenesis overall the grafenberg lps contributes to the understanding of environmental conditions within the lower rhine embayment particularly for the late mis 3 and the transition to mis 2 the lps reflects major shifts in the geomorphic system which are compared to palaeoenvironmental records from different archives and different geographic regions in north western europe indicating a direct relation to north atlantic climate oscillations during the last glacial period it is shown that the hesbaye unconformity at the mis 3 2 boundary is bound to an erosional event which can be traced over wide areas within the northern european loess belt

quartz osl dating of late quaternary chinese and serbian loess a cross eurasian comparison of dust mass accumulation rates abstract reconstructing dust mass accumulation rate mar from loess deposits is critical to understanding past atmospheric mineral dust activity and requires accurate independent age models from loess deposits across europe and asia previous correlations of loess in europe and china have tended to focus on multi millennial timescales with no detailed examination of dust mar at the two ends of the eurasian loess belt on shorter sub orbital scales here we present a detailed quartz optically stimulated luminescence osl chronology from the serbian titel loess plateau veliki surduk loess core and the chinese loess plateau lingtai section the luminescence ages pass internal tests and show consistent increases in age with depth with no obvious major hiatuses however as reported before it seems the quartz osl technique is only capable of accurate age determination up to accrued doses of ca 150 gy ca 30 40 ka due to approaching field saturation of the quartz osl signal two age depth models were used to reconstruct dust mars where one utilises osl data solely and the other additionally makes assumptions about sedimentation rates although short term fluctuations in mar are model dependent general mar patterns between the two sites are very similar with peak mar occurring rather late in the last glacial ca 13 25 ka this suggests that at least broad scale trends in dust activity within the last glacial period may be similar at a continental scale

paleowind directions from the magnetic fabric of loess profiles in central alaska abstract two parallel profiles of alternating loess and paleosol horizons from the halfway house site west of fairbanks in central alaska were evaluated in terms of their potential for preserving paleowind directions combined the profiles span specmap marine oxygen isotope stages 1 6 approximately the last 150 ka our analytical tools consisted of measuring the sample s anisotropy of magnetic susceptibility and characterizing the magnetic mineralogy by multiple approaches both primary eolian and secondary reworked magnetic fabrics are recognized along certain intervals of both profiles primary eolian fabrics display a horizontal magnetic foliation and a well defined magnetic lineation corresponding to the paleodirection of sediment transport and deposition a systematic change in transport direction is observed where long term prevailing winds appear to shift from a nw se to n s direction during glacial and interglacial periods respectively

new osl dating of uk loess indications of two phases of late glacial dust accretion in se england and climate implications windblown dust deposits or loess locally known in the uk as brickearth blanket many parts of southern england outside the limits of the british and irish ice sheet the best studied loess exposures occur in kent southeast england where the deposits are believed to be late glacial in age new sedimentological evidence is presented for phases of accretion with two distinct units a calcareous brickearth exhibiting periglacial cryoturbation and a non calcareous massive brickearth optically stimulated luminescence osl dating has been applied to chemically isolated modal quartz silts to derive a chronology for sediment accretion and to better understand the palaeoclimatic significance of these deposits

optical dating of abrupt shifts in the late pleistocene east asian monsoon chinese loess is regarded as one of the most detailed and complete terrestrial archives of late cenozoic climate change however high resolution optically stimulated luminescence osl dates presented here reveal that the suborbital chronological framework of chinese loess used in many previous climate reconstructions requires reassessment chronological uncertainty of as much as 10 15 k y for the late pleistocene is largely a result of the widespread use of nonradiometric dating techniques that fail to account for site specific depositional conditions associated with loess emplacement and diagenesis osl based age models that account for these processes are used to examine detailed records of past sedimentation as well as grain size and magnetic susceptibility proxies for late pleistocene east asian monsoon variation abrupt shifts in monsoon proxies occur over 10 2 10 3 yr time scales potentially forced by a variety of factors and influenced by site location and site specific changes in sedimentation

geomagnetic episodes of the last 1 2 myr recorded in chinese loess 1 the matuyama brunhes m b boundary termination of jaramillo normal subchron j m as well as three young geomagnetic excursions has been revealed in the weinan loess section zhu et al 1994 1998 1999 recently we carried out further paleomagnetic directional studies on the same section and recovered the onset of the jaramillo normal subchron m j and four geomagnetic excursions two in the brunhes and two in the late matuyama the fact that all seven excursions found in this section are in loess units and expected excursions in paleosols are not found suggests that short lived geomagnetic signals could be only recorded in loess units and may have been fully smoothed or wiped out in paleosol units by strong pedogenesis constrained by a new astronomical timescale hld00 ages of the geomagnetic excursions and reversal boundaries have been estimated we tentatively correlated these excursions with previous results indicating that a large lock in model may not be correct for the whole loess profile although some apparently big positive age discrepancies were observed for the main boundaries

imprint of north atlantic abrupt climate changes on western european loess deposits as viewed in a dust emission model abstract western european loess sequences of the last glaciation 100 000 15 000 years bp exhibit strong cyclic variations of the sedimentation rate which are coeval to the greenland stadial interstadial cycles and the heinrich events these north atlantic rapid climate changes appear thus as a potential cause for the sedimentation variations via changes in dust intensity cycle here we make a first step in testing this hypothesis by modelling the impact of the north atlantic abrupt climate variations on dust emission our dust emission calculations use meteorological fields generated by the lmdz atmospheric general circulation model at a resolution down to 60 km over western europe three numerical experiments are run representing a greenland stadial an interstadial and a heinrich event orbital parameters and ice sheet configuration correspond to conditions from marine isotope stage 3 60 000 25 000 years bp a period characterized by strong millennial scale climate variability the only differences we impose in the boundary conditions regard the north atlantic surface temperature and sea ice cover in the latitudinal band 30 63 n the changes in wind precipitation soil moisture and snow cover from one simulated state to another result in small differences in dust emission intensity in contrast when the inhibition of the aeolian erosion by vegetation is taken into account the dust fluxes for the cold climate states greenland stadial and heinrich event become generally more than twice higher than those for the relatively warmer greenland interstadial in agreement with the loess data these results support the hypothesis that the north atlantic millennial scale variability is imprinted in western european loess profiles and point to vegetation changes as the main factor responsible for millennial scale sedimentation variations an analysis for the english channel and southern north sea areas major potential dust sources shows that the seasonality of dust emission is not controlled by the wind speed as in modern large deserts but by the surface conditions consequently the dusty season lasts from late winter to early summer with maximum activity in april may and is shifted towards summer when the climate is colder

a direct link between the china loess and marine δ 18 o records aeolian flux to the north pacific most studies of quaternary climates conducted during the past 150 years have focused on glacial sequences and for the past 25 years marine sediments have provided significant further understanding of glacial and interglacial palaeoclimates an important goal of palaeoclimatology however to link the well known detailed continental records to marine records of similar resolution has yet to be realized the classic loess sequences of china provide an apparently continuous record of continental climate over the past 2 4 million years1 2 the oxygen isotope 18o timescale developed from the marine record3 gives us a global chrono stratigraphy of late pleistocene climates previously it has been suggested in studies of the aeolian component in pelagic sediments that it may be possible to link these two records directly by finding a suitable core from the north west pacific downwind from china4 5 here we report the results of such an effort for core v21 146 fig 1 and tie the last 500 000 years of the chinese loess soil sequence directly to the 18o timescale and in so doing refine the dating of regional loess and soil horizons

growth dynamics and deglaciation of the last british irish ice sheet the deep sea ice rafted detritus record the evolution and dynamics of the last british irish ice sheet biis have hitherto largely been reconstructed from onshore and shallow marine glacial geological and geomorphological data this reconstruction has been problematic because these sequences and data are spatially and temporally incomplete and fragmentary in order to enhance biis reconstruction we present a compilation of new and previously published ice rafted detritus ird flux and concentration data from high resolution sediment cores recovered from the ne atlantic deep sea continental slope adjacent to the last biis these cores are situated adjacent to the full latitudinal extent of the last biis and cover marine isotope stages mis 2 and 3 age models are based on radiocarbon dating and graphical tuning of abundances of the polar planktonic foraminifera neogloboquadrina pachyderma sinistral nps to the greenland gisp2 ice core record multiple ird fingerprinting techniques indicate that at the selected locations most ird are sourced from adjacent biis ice streams except in the centre of heinrich h layers in which ird shows a prominent laurentide ice sheet provenance ird flux data are interpreted with reference to a conceptual model explaining the relations between flux north atlantic hydrography and ice dynamics both positive and rapid negative mass balance can cause increases and prominent peaks in ird flux first order interpretation of the ird record indicates the timing of the presence of the biis with an actively calving marine margin the records show a coherent latitudinal but partly phased signal during mis 3 and 2 published data indicate that the last biis initiated during the mis 5 4 cooling transition renewed growth just before h5 46 ka was succeeded by very strong millennial scale variability apparently corresponding with dansgaard oeschger do cycles closely coupled to millennial scale climate variability in the north atlantic region involving latitudinal migration of the north atlantic polar front this indicates that the previously defined precursor events are not uniquely associated with h events but are part of the millennial scale variability major growth of the ice sheet occurred after 29 ka with the barra ice stream attaining a shelf edge position and generating turbiditic flows on the barra donegal fan at 27 ka the ice sheet reached its maximum extent at h2 24 ka earlier than interpreted in previous studies rapid retreat initially characterised by peak ird flux during greenland interstadial 2 23 ka was followed by readvance between 22 and 16 ka readvance during h1 was only characterised by biis ice streams draining central dome s of the ice sheet and was followed by rapid deglaciation and ice exhaustion the evidence for a calving margin and ird supply from the biis during greenland stadial 1 younger dryas event is equivocal the timing of the initiation maximum extent deglacial and readvance phases of the biis interpreted from the ird flux record is strongly supported by recent independent data from both the irish sea and north sea sectors of the ice sheet

variation of east asian monsoon precipitation during the past 21 k y and potential co2 forcing paleoclimatic research can provide critical insight on causes of change in the east asian monsoon which influences the lives of 1 6 billion people today in this study we use paleoclimatic indexes from chinese loess deposits which have clear climatic implications and are independently dated to reconstruct the monsoon precipitation since 21 ka our results show that monsoon precipitation persistently decreased from 21 ka to ca 8 ka and increased after ca 8 ka with a precipitation peak at 8 3 ka these changes in east asian summer monsoon precipitation are synchronous with changes in high northern latitude ice volume ice cover and atmospheric co2 these new data suggest that variation of the monsoon precipitation was probably driven by co2 forced high northern latitude temperature changes shifting the location of the intertropical convergence zone that dominates monsoon precipitation our trace 21000 modeling experiment supports this interpretation

an environmental magnetic fingerprint of periglacial loess records of late pleistocene loess palaeosol sequences from eastern germany a detailed rock magnetic analysis of the last glacial interglacial loess palaeosol sequences was carried out in the framework of a comprehensive stratigraphic study of loess in saxony eastern germany magnetic susceptibility and laboratory induced remanences have been determined to compare individual sections and to identify the specific rock magnetic characteristics of the saxonian loess province according to the model of pedogenic magnetic enhancement an increasing neoformation of ferrimagnetic minerals in the course of pedogenesis was observed only in the uppermost late weichselian lithological units consisting of pure aeolian loess and indicating dryer climatic conditions in contrast the rock magnetic characteristics of the lower middle and early weichselian units exhibit a significant destruction of primary magnetic minerals caused by such secondary processes as climatically controlled waterlogging and reworking this change in magnetic composition with stratigraphic depth was additionally proved by factor analysis in which the main observation an increasing fd with decreasing argues for a general magnetic depletion in conjunction with decreasing magnetic grain sizes caused by weathering of larger primary particles the magnetic fingerprint of the saxonian loess is characterised by prevailing magnetic depletion processes which effectively rules out the application of the wind vigour model moreover the magnetic characteristics differ significantly from that of other loess regions and support a new and independent model which explains the magnetic behaviour of strongly reworked and waterlogged gleyed loess palaeosol sequences in the relatively humid central european periglacial areas

magnetic mineralogy of chinese loess and its significance summary the topmost 16 metres of the loess section at xifeng central chinese loess plateau which cover the last 128000 years consist of two palaeosol beds interlayered by a loess horizon hysteresis parameters frequency dependent field and temperaturedependent susceptibility show very similar and stable magnetic mineral constituents in both loess and palaeosol samples the concentration and grain size of magnetite maghaemite and haematite control the magnetic properties of chinese loess susceptibility and loess thickness are closely related to geographic position and present climate across the loess plateau the loess and palaeosol magnetic properties are largely controlled by the fine grained magnetite formed in various quantities and grain sizes under the influence of pedogenesis during variable palaeoclimatic conditions therefore regional and global palaeoclimatic development during the last 2 5 myr can be reconstructed from susceptibility records in the loess plateau

british ice sheet dynamics inferred from north atlantic ice rafted debris records spanning the last 175 000 years sediment core md04 2822 from the rockall trough northeast atlantic provides lithological evidence for the expansion of the british ice sheet bis onto the hebridean margin during both the penultimate marine isotope stage mis 6 wolstonian saalian and last glaciation devensian weichselian a composite chronology is constructed using i the benthic foraminiferal oxygen isotope record matched to an orbitally tuned stacked record of global ice volume specmap ii the synchronisation of the planktonic foraminiferal neogloboquadrina pachyderma sinistral and itrax xrf ca records to the greenland ice core ngrip back to ca 123 ka and iii the synchronisation of the same n pachyderma sinistral and itrax xrf ca records to the atmospheric methane record of the antarctic ice core epica dome c beyond 123 ka the first offshore evidence for the expansion of the last bis within mis 4 is presented suggesting extensive glaciation of northwestern britain during the devensian weichselian as early as 70 ka the proximity of this long sediment core to the glaciated margin of northwestern scotland makes it ideal to capture the ice rafted debris ird signal of the bis for the last 175 ka via a continuous flux record of ird british geological survey nerc 2009 all rights reserved

early deglaciation of the british irish ice sheet on the atlantic shelf northwest of ireland driven by glacioisostatic depression and high relative sea level understanding the triggers and pace of marine based ice sheet decay is critical for constraining the future mass loss and dynamic behaviour of marine based sectors of the large polar ice sheets in greenland and antarctica numerical models which seek to predict this behaviour need to be calibrated against data from both contemporary and palaeo ice sheets and the latter requires accurate reconstruction of former ice sheet extent dynamics and timing marine geophysics sediment cores benthic foraminiferal assemblages and radiocarbon dating are used to reconstruct the extent of the last british irish ice sheet biis and the timing and style of its retreat on the atlantic shelf northwest of ireland shelf edge moraines and subglacial till recovered in cores from the outer continental shelf are dated to younger than 26 3 ka cal bp and indicate an extensive ice sheet at the last glacial maximum lgm that was grounded to the shelf edge nested arcuate moraines record the subsequent episodic retreat of the ice sheet across the shelf lithofacies and associated foraminiferal assemblages demonstrate that this retreat occurred in a glacimarine environment as a grounded tidewater margin and that high relative sea level and cold waters prevailed during retreat radiocarbon dates indicate that the timing of initial ice sheet retreat from the shelf edge occurred in the interval between 26 3 and 24 8 ka cal bp during the period of minimum global eustatic sea level and that the ice sheet had retreated to the mid shelf by 24 8 ka cal bp the donegal bay moraine a large moraine at the mouth of donegal bay records a major stillstand and readvance of the ice sheet during deglaciation between 20 2 and 17 9 ka cal bp estimated retreat rates of 5 5 35 m a 1 across the shelf demonstrate that retreat was slow it is noteworthy that retreat was initiated in the absence of ocean warming and when eustatic sea level was at a minimum the sea level rise that initiated deglaciation from the shelf edge therefore is inferred to have been a product of local glacio isostatic crustal depression rather than external forcing this demonstrates that marine based sectors of ice sheets can trigger their own demise internally through glacio isostatic adjustment and it provides an explanation for the early retreat of the biis on the atlantic shelf during the global lgm glgm

osl chronologies of paleoenvironmental dynamics recorded by loess paleosol sequences from europe case studies from the rhine meuse area and the neckar basin abstract loess paleosol sequences lps represent an important terrestrial archive for the reconstruction of the paleoenvironmental evolution during the last glacial cycle in europe in the rhine meuse area and the southwestern germany there are only few numerical ages determined with state of the art luminescence methods which limits the robustness of established chronostratigraphies this study presents a comparative dating approach using quartz and feldspar post infrared pirir 290 optically stimulated luminescence osl from fine and medium grained samples of five loess paleosol sequences paleoenvironmental dynamics are reconstructed by high resolution grain size analysis the osl ages are evaluated as being robust and consistent with other records furthermore we show that ages for hillslope deposits are sometimes overestimated due to low frequency high magnitude erosive processes the integration of osl ages stratigraphy and high resolution grain size data contributes to a temporal more complete data record from western and central europe secondly we propose a combined stratigraphic model for lps of the last glacial cycle which is developed and discussed in the context of other key sites such as havrincourt schwalbenberg ii tonchesberg nussloch and dolni v stonice comparable chronologies and patterns in proxy data between sites with a large spatial distance suggest a possible semi synchronous response to climatic changes in europe by combining our data with the eifel laminated sediment archive elsa and the ngrip ice core a relationship of loess archives and large scale climatic signals is discussed and a proxydata based event stratigraphy is developed this model refines existing chronostratigraphic models and contributes to solve open discussion concerning the timing and demarcation of sedimentary units and sequences from for western and central europe

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

the impact of last glacial climate variability in west european loess revealed by radiocarbon dating of fossil earthworm granules the characterization of last glacial millennial timescale warming phases known as interstadials or dansgaard oeschger events requires precise chronologies for the study of paleoclimate records on the european continent such chronologies are only available for several last glacial pollen and rare speleothem archives principally located in the mediterranean domain farther north in continental lowlands numerous high resolution records of loess and paleosols sequences show a consistent environmental response to stadial interstadial cycles however the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with greenland interstadials to overcome this problem a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of nussloch germany its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every greenland interstadial identified in isotope records with specific soil horizons furthermore eight additional minor soil horizons dated between 27 5 and 21 ka only correlate with minor decreases in greenland dust records this dating strategy reveals the high sensitivity of loess paleoenvironments to northern hemisphere climate changes a connection between loess sedimentation rate fennoscandian ice sheet dynamics and sea level changes is proposed the chronological improvements enabled by the radiocarbon earthworm clock thus strongly enhance our understanding of loess records to a better perception of the impact of last glacial climate changes on european paleoenvironments

millennial scale depositional cycles related to british ice sheet variability and north atlantic paleocirculation since 45 kyr b p barra fan u k margin lithology lithic petrology planktonic foraminiferal abundances and clastic grain sizes have been determined in a 30 m long core recovered from the barra fan off northwest scotland the record extends back to around 45 kyr b p with sedimentation rates ranging between 50 and 200 cm kyr the abundance of ice rafted debris indicates 16 glacimarine events including temporal equivalents to heinrich events 1 4 enhanced concentrations of basaltic material derived from the british tertiary province suggest that the glacimarine sediments record variations in a glacial source on the hebrides shelf margin glacimarine zones are separated by silty intervals with high planktonic foraminifera concentrations that reflect an interstadial circulation regime in the rockall trough the results suggest that the last british ice sheet fluctuated with a periodicity of 2000 3000 years in common with the dansgaard oeschger climate cycle

mass accumulation rate and monsoon records from xifeng chinese loess plateau based on a luminescence age model luminescence dating of loess accumulation in china has raised questions over disturbance and gaps in the record the magnitude of mass accumulation rates mars and monsoon forcing mechanisms here we present a detailed quartz optically stimulated luminescence osl chronology from the xifeng chinese loess plateau site we reconstruct mars and construct an age model for monsoon proxies at the site the luminescence ages show significant pedogenic and anthropogenic disturbance in material deposited after ca 20 22 ka analysis of other published data suggests that this disturbance may be more common than previously realized mars from undisturbed portions of xifeng vary dramatically with peaks potentially matching the timing of heinrich events the last glacial maximum peak mar 22 27 ka matches the pacific and greenland dust flux records although appears earlier than peak mars seen in many other osl dated loess plateau sites east asian monsoon grain size and magnetic susceptibility records also show several differences between independently dated loess sites this complicates our understanding of any lag between insolation forcing and monsoon response nevertheless the xifeng climate proxy changes show apparent broad agreement with the timing of heinrich events in the north atlantic supporting assertions of a climatic teleconnection between the two areas

palaeowind directions and sources of detrital material archived in the roxolany loess section southern ukraine abstract measurements of the anisotropy of whole rock magnetic susceptibility ams and u pb ages of detrital zircons have been combined to define the palaeowind directions and sources of wind blown dust in the loess palaeosol key section at roxolany southern ukraine zircon dating has also been used to determine the age and provenance of the interbedded roxolany tephra the distribution of ams axes in the loess indicates that the prevailing wind during its accumulation blew from the north west the same as the mean present day summer wind direction measured in the nerby city of odessa the u pb isotopic ages of the detrital zircons mostly range between 0 25 and 2 ga with clusters at 0 28 0 32 0 45 0 58 1 0 and 1 5 ga single neoarchean grains ca 2 7 ga were also found these ages indicate that material from carpathian and podolian sources formed the roxolany loess this material initially was transported by the dniester river then was wind blown form the dniester liman and the lower dniester valley located nw of roxolany most of the pyroclastic zircons from the roxolany tephra gave ages of 470 840 ka with a peak between 500 and 750 ka this age range is consistent with their being derived from the ciomadul volcano in romania

ice margin oscillations during deglaciation of the northern irish sea basin we present a new chronology to constrain ice margin retreat in the northern irish sea basin estimates on the timing of ice thinning derived from surface exposure ages for boulders from the summits of the isle of man and south west cumbria suggest that ice thinning was commensurate with the rapid retreat that followed the short lived advance of the irish sea ice stream isis to maximum limits in the celtic sea this ice retreat in the northern irish sea basin was fastest at 20 ka in response to a wider calving margin but slowed as ice stabilized and oscillated against the isle of man we provide the first age constraints for the scottish readvance 19 2 18 2 ka and demonstrate that it was a potentially regional event across the isle of man and cumbrian lowlands not linked with heinrich event 1 after the scottish readvance the ice front retreated northwards towards the southern uplands of scotland at the same time as climate north of 45 n warmed in response to summer insolation this sequence demonstrates the importance of internal dynamics in controlling ice retreat rates in the irish sea but also that deglaciation of the northern irish sea basin was a response to climate warming

thermoluminescence dating of late devensian loesses in southern england scattered across southern england are many isolated deposits of loess like material1 a few such as that at pegwell bay in kent are highly calcareous and unweathered but most have been reworked by fluvial or colluvial processes there is good stratigraphical evidence for a few pre devensian loesses also in kent but dating of more recent loess has so far been based on indirect evidence much work has been done on the pegwell bay loess as it is the most extensive truly aeolian loessic deposit in britain kerney2 compared the late devensian deposits in the isle of thanet and at pegwell bay with similar deposits in holland and belgium where radiocarbon dates have been obtained for interstadial deposits correlation of the east kent deposits with these in northern europe indicates that the loesses in kent were formed between 30 000 and 14 000 yr ago i report here dates for six of the more recent deposits in southern britain from the scilly isles to kent the dates have been obtained on the loess itself using a recently developed thermoluminescence tl dating technique3 4 and confirm the ages as being late devensian

multidecadal ocean variability and nw european ice sheet surges during the last deglaciation a multiproxy paleoceanographic record from the atlantic margin off the british isles reveals in unprecedented detail discharges of icebergs and meltwater in response to sea surface temperature increases across the last deglaciation we observe the earliest signal of deglaciation as a moderate elevation of sea surface temperatures that commenced with a weakly developed thermocline and the presence of highly ventilated intermediate waters in the rockall trough this warming pulse triggered a series of multidecadal ice rafted debris peaks that culminated with a major meltwater discharge at 17 500 years before present related to ice sheet disintegration across the nw european region the impact of meltwater caused a progressive reduction in deep water ventilation and a sea surface cooling phase that preceded the collapse of the laurentide ice sheet during heinrich event 1 by 500 1000 years a similar sequence of rapid ocean ice sheet interaction across the european continental margin is identified during the bolling allerod to younger dryas transition the strategic location of our sediment core suggests a sensitive and rapid response of ice sheets in nw europe to transient increases in thermohaline heat transport

enhanced ice sheet growth in eurasia owing to adjacent ice dammed lakes large proglacial lakes cool regional summer climate because of their large heat capacity and have been shown to modify precipitation through mesoscale atmospheric feedbacks as in the case of lake agassiz 1 several large ice dammed lakes with a combined area twice that of the caspian sea were formed in northern eurasia about 90 000 years ago during the last glacial period when an ice sheet centred over the barents and kara seas 2 blocked the large northbound russian rivers 3 here we present high resolution simulations with an atmospheric general circulation model that explicitly simulates the surface mass balance of the ice sheet we show that the main influence of the eurasian proglacial lakes was a significant reduction of ice sheet melting at the southern margin of the barents kara ice sheet through strong regional summer cooling over large parts of russia in our simulations the summer melt reduction clearly outweighs lake induced decreases in moisture and hence snowfall such as has been reported earlier for lake agassiz1 we conclude that the summer cooling mechanism from proglacial lakes accelerated ice sheet growth and delayed ice sheet decay in eurasia and probably also in north america

three climatic cycles recorded in a loess palaeosol sequence at semlac romania implications for dust accumulation in south eastern europe recent inve stigations of the semlac loess section in the south eastern carpathian basin which is situated at an undercut slope position on the right bank of the mures river in its lower reaches banat region western romanian are presented and discussed dating back to marine isotope stage mis 10 the more than 10 m thick loess sequence includes four fossil soil complexes developed in homogenous and relatively fine silty loess because of the good preservation of the sediment semlac is regarded as a key section for the carpathian basin which offers possibilities to a improve the understanding of the type and composition loess homogeneity and pedogenic alteration of the lowland loess sequences in the carpathian basin also beyond the last interglacial palaoesol complex b to reconstruct the temporal evolution of the local loess palaoesol successions c gain better insight into the regional paleoenvironments of the last 300ka and d to compare the loess of the region to loess sequences in adjacent areas and to dust proxy data in the northern hemisphere an integrated age model based on correlation to reference records and luminescence dating is compiled applying this age model we compare climate proxy data from semlac to both global data and to data from the very southeast of the carpathian basin vojvodina serbia the obtained results provide new insight into the dust accumulation regime for the eastern carpathian basin and offer new palaeoenvironmental information for the region and are an important step towards establishing a catena from the thin loess like sediments of the banat foothills in the east towards the thicker and seemingly more complete loess sections of the south eastern and central carpathian basin disentangling grain size data from soil formation proxies is used to investigate patterns of non local dust patterns of non pedogenetic fine material are similar to grain size proxies from china and other parts of the northern hemisphere suggesting western and eastern eurasian loess to have at least partly similar mechanistic climatic origins c 2016 elsevier ltd all rights reserved

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

palaeoclimate sedimentation and soil development during the last glacial stage devensian heathrow airport london uk abstract the langley silt complex overlying the taplow terrace of the river thames at prospect park near heathrow airport west of london is described in terms of lithology carbonate content organic carbon content particle size characteristic macrostructure micromorphology and stratigraphic position the langley silts were deposited by wind or water in cold climate conditions and include evidence for the development of periglacial structures and for devensian lateglacial and holocene soil formation the langley silts rest upon a last interglacial ipswichian ois 5e soil developed in the taplow gravel deposited during the previous cold stage ois 6 during the early devensian and the dimlington stadial and younger dryas of the late devensian wind deposited the silts and during the middle devensian wind and surface wash built up a laminated silt and sand during the middle devensian seasonal dessication formed non sorted polygonal patterns as this laminated unit aggraded but this process ceased with the return to loess deposition in the late devensian argillic soil development occurred during the windermere interstadial only to be disrupted by ground ice processes during the succeeding younger dryas cold phase the site provides one of the most complete sedimentary sequences through the last glacial stage in britain and confirms recent interpretations of soil development and evidence for aeolian deposition in britain during the lateglacial

new age constraints for the limit of the british irish ice sheet on the isles of scilly the southernmost terrestrial extent of the irish sea ice stream isis which drained a large proportion of the last british irish ice sheet impinged on to the isles of scilly during marine isotope stage 2 however the age of this ice limit has been contested and the interpretation that this occurred during the last glacial maximum lgm remains controversial this study reports new ages using optically stimulated luminescence osl dating of outwash sediments at battery tresco 25 5 1 5 ka and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on scilly rock 25 9 1 6 ka which confirm that the isis reached the isles of scilly during the lgm the ages demonstrate this ice advance on to the northern isles of scilly occurred at 26 ka around the time of increased ice rafted debris in the adjacent marine record from the continental margin which coincided with heinrich event 2 at 24 ka osl dating 19 6 1 5 ka of the post glacial hell bay gravel at battery suggests there was then an 5 ka delay between primary deposition and aeolian reworking of the glacigenic sediment during a time when the isis ice front was oscillating on and around the ll n peninsula 390 km to the north

the relationship of heinrich events and their european precursors over the past 60 ka bp a multi proxy ice rafted debris provenance study in the north east atlantic high resolution multi proxy records of ice rafted debris ird flux and provenance in the ne atlantic detail the development variability and decline of marine margins of the last glacial circum north atlantic ice sheets coupled lithological identification sr and nd isotopic composition and 40ar 39ar ages of individual hornblende grains reduce ambiguity as to ird potential source region allowing clear differentiation between laurentide lis icelandic and british bis ice sheet sources the icelandic and bis are collectively referred to as the nw european ice sheet nweis a step wise increase in the flux of ird to the core site at 26 5 ka bp documents bis advance and glaciation of ireland millennial scale variability of the bis at a 2 ka periodicity is inferred through clusters of pulsed ird fluxes throughout the late glacial 26 5 10 ka bp combination of these european ird events and the 7 ka periodicity of lis instability is thought to account for quasi synchronicity of the nweis and lis ird pulses at heinrich event h 2 and h1 previously suggested to represent the possible involvement of the nweis in the initiation of h events furthermore the lack of extensive nweis marine margin is inferred prior to h3 31 5 ka bp such that no european precursor event is associated with either h5 or h4 this suggests that precursor events were not directly implicated in the collapse of the lis and the persistent instabilities of the bis that are clustered at a 2 ka periodicity are incompatible with the concept that both h events and their precursors are independent responses to a common underlying trigger

mineral magnetic characterization of the upper pleniglacial nussloch loess sequence germany an insight into local environmental processes 1 first comprehensive environmental magnetism study of the nussloch rhine river valley germany loess palaeosol deposit 2 bulk ferrimagnetic concentration parameters are dominantly controlled by variations in coarse grained md ferrimagnetic particles of detrital aeolian origin 3 the imprint of waterlogging induced redoxomorphic processes on the magnetic record is observed by dissolution of fine grained magnetic minerals 4 the interpretation of magnetic susceptibility variations alone within loess and palaeosol deposits following the wind vigour or pedogenic enhancement models will be hindered by waterlogging induced redoxomorphic processes if present s u m m a r y presently most loess palaeosol magnetic susceptibility records are interpreted as following either the wind vigour model or the pedogenic enhancement model however redoxomorphic processes induced by waterlogging often referred to gleying in the loess literature are also known to alter loess deposits but their impact on loess palaeosol magnetic susceptibility records has received little attention the reported rock magnetic study aims to characterize the mineral magnetic response of loess to waterlogging induced redoxomorphic processes thus improving our understanding of mineral magnetic changes within loess deposits with respect to environmental and climate conditions the nussloch loess palaeosol deposit rhine valley germany was targeted because it is one of the best studied pleniglacial deposits for western europe in which numerous tundra gley intervals have been identified moreover a comprehensive high resolution environmental magnetism study has never been undertaken for this site various rock magnetism experiments were conducted at both room and low temperatures to characterise the composition concentration and relative magnetic grain size of the mineral magnetic assemblage the relative changes in magnetic parameters within the investigated loess interval are primarily controlled by 1 varying concentrations of coarse grained ferri magnetic particles of detrital aeolian origin and 2 dissolution of fine grained ferrimagnetic particles related to in situ post depositional alteration promoted by waterlogging induced re doxomorphic processes goethite is found to be ubiquitous throughout the studied interval and is argued to have both a primary aeolian and secondary in situ origin we conclude that redoxomorphic processes induced by waterlogging if present will hinder the interpretation of magnetic susceptibility variations within loess and palaeosol deposits following the expected relationships dictated by the wind vigour and the pedogenic enhancement magnetism models

lower cretaceous benthic foraminifera from dsdp site 263 micropalaeontological constraints for the early evolution of the indian ocean analysis of 66 samples from dsdp site 263 cores 263 4r 4 to 263 29r 4 reveals a unique faunal composition with a predominance of agglutinated taxa many of them previously unrecorded from any other dsdp and odp indian ocean sites a total of 66 agglutinated and 31 calcareous taxa are documented and five new species are described hippocrepina gracilis n sp textulariopsis elegans n sp aaptotoichus challengeri n sp gaudryinopsis pseudobettenstaedti n sp and gaudryina cuvierensis n sp three assemblages are recognized based on changes in the composition of dominant taxa and occurrences of stratigraphically important species 1 a high diversity valanginian to barremian bulbobaculites recurvoides assemblage cores 263 29r to 18r comprised of numerous elongate agglutinated forms rare nodosariids and variable numbers of tubes and ammodiscids 2 a moderately diverse aptian to albian rhizammina ammodiscus glomospira assemblage cores 26318r to 7r with highly fluctuating numbers of the nominate taxa and haplophragmoides trochammina verneuilinoides spp and vemeuilina howchini 3 a very low diversity albian or younger assemblage cores 263 6r to 4r containing sparse agglutinated foraminifera rare nodosariids and rotaliids we interpret the assemblages as shelf to lower slope and consider them to reflect a deepening palaeobathymetry as the cuvier margin subsided after the initial breakup of east gondwana during the valanginian our interpretation is in sharp contrast with initial palaeodepth estimates of less than 100 m as well as with original chronostratigraphic interpretations based on foraminifera and nannofossils which correlated the base of the recovered interval with the aptian the absence of many cosmoplitan forms despite high diversity suggests strong faunal differentiation in the austral realm or endemisn within the cuvier basin during the early cretaceous

ice marginal dynamics of the last british irish ice sheet in the southern north sea ice limits timing and the influence of the dogger bank the southern north sea is a particularly important area for understanding the behaviour of the british irish ice sheet biis during the last glacial cycle it preserves a record of the maximum extent of the eastern sector of the biis as well as evidence for multiple different ice flow phases and the dynamic re organisation of the biis however to date the known ice sheet history and geochronology of this region is predominantly derived from onshore geological evidence and the offshore imprint and dynamic history of the last ice sheet remain largely unknown using new data collected by the britice chrono project this paper explores the origin and age of the dogger bank re assesses the extent and age of the glaciogenic deposits across the shallow areas of the north sea between the dogger bank and the north norfolk coast and re examines the dynamic behaviour of the biis in the southern north sea between 31 6 and 21 5 ka this paper shows the core of the dogger bank to be composed glaciolacustrine sediment deposited between 31 6 and 25 8 ka following its formation the western end of the dogger lake was overridden with ice reaching 54 n where the ice margin is co incident with the southerly extent of subglacial tills previously mapped as bolders bank fm this initial ice override and retreat northwards back across the dogger lake was complete by 23 1 ka but resulted in widespread compressive glaciotectonism of the lake sediments and the formation of thrust moraine complexes along the northern edge of the bank moraines are on lapped by later phase glaciolacustrine and marine sediments but do not show evidence of subsequent ice override the shallow seafloor to the west and southwest of the dogger bank records several later phases of ice advance and retreat as the north sea lobe flowed between the dogger bank and the yorkshire lincolnshire coasts and reached north norfolk new optically stimulated luminescence osl ages from garrett hill on outwash limit the arrival of the biis on the norfolk coast to 22 8 21 5 ka multiple till sheets and chains of moraines on the seafloor north of norfolk mark dynamic oscillation of the north sea lobe margin as it retreated northwards this pattern of behaviour is broadly synchronous with the terrestrial record of deposition of subglacial glaciofluvial and glaciolacustrine sediments along the yorkshire coast which relate to post dimlington stadial ice marginal oscillations after 21 5 ka with respect to forcing mechanisms it is likely that during the early phases of the last glacial maximum 30 23ka the interaction between the southern margin of the biis and the dogger lake was critical in influencing flow instability and rapid ice advance and retreat however during the latter part of the last glacial maximum 22 21 ka late phase ice advance in the southern north sea became restricted to the western side of the dogger bank which was a substantial topographic feature by this time this topographic confinement in addition to decoupling of the biis and the fennoscandian ice sheet fis further north enabled ice to reach the north norfolk coast overprinting the seabed with late phase tills of the bolders bank fm

paleoclimatic significance of the temperature dependent susceptibility of holocene loess along a nw se transect in the chinese loess plateau we have conducted mineral magnetic investigations of samples of modern dune sand pristine loess and present day loess along a nw se transect from the northern to the central loess plateau in china the methods used include the temperature dependence of susceptibility tds before and after citrate bicarbonate dithionite cbd treatment as well as x ray diffraction xrd analysis the xrd analyses demonstrate that magnetite and hematite both exist in the chinese loess paleosol sequence and its modem source area but the tds measurements show that magnetite is the predominant contributor to magnetic susceptibility maghemite is present in the pristine loess and the present day loess due to pedogenesis the pedogenic processes that produce the maghemite are closely linked to paleoclimate and for this transect precipitation appears to be the most important climatic variable we suggest that tds can be used as a useful method for the analysis of pedogenesis and climatic change

thermoluminescence dating and geochemistry of loessic deposits in southeast england the results of a thermoluminescence tl dating and geochemical survey of loessic deposits in southeast england involving sampling at 26 localities demonstrate that the loessic deposits appear to be the product of at least three depositional phases of aeolian silt during the late pleistocene namely 10 25 ka bp 50 125 ka bp and 170 ka bp the majority of localities sampled date to the late devensian but isolated pockets of older material were found throughout the area the majority of the samples analysed were of decalcified material the results of geochemical analyses of major oxide and trace element concentrations indicate the uniformity of material and suggest a common provenance

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

a continuous high resolution dust record for the reconstruction of wind systems in central europe eifel western germany over the past 133 ka 1 the last glacial cycle in central europe is dominated by processes of aeolian dust transport and accumulation these dust deposits are preserved in soils and lake sediments and provide detailed information about the climate variability during cold and dry periods especially the transitions from warm into cold periods are characterized by turbulent climate conditions the main problems of terrestrial paleoclimate reconstructions are the completeness of the core material and a sampling resolution to detect single dust storms we use a particle detection method which allows high resolution sub annual analyses of sediment structures in undisturbed samples the elsa eifel laminated sediment archive stack is a compilation of four different lake sediment cores of the eifel region western germany and comprise the period of the last 133 ka the results of our analyses show high frequencies of dust storm events during the first cold events c24 and c23 after the last warm stage in opposition the coldest periods of the last glacial cycle ois 4 70 60 ka bp and ois 2 35 14 ka bp are characterized by stable climate conditions that provide the accumulation of homogenous dust sediments

deglaciation of the eurasian ice sheet complex the eurasian ice sheet complex eisc was the third largest ice mass during the last glacial maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea level lowering whilst recent terrestrial and marine empirical insights have improved understanding of the chronology pattern and rates of retreat of this vast ice sheet a concerted attempt to model the deglaciation of the eisc honouring these new constraints is conspicuously lacking here we apply a first order thermomechanical ice sheet model validated against a diverse suite of empirical data to investigate the retreat of the eisc after 23 ka bp directly extending the work of patton et al 2016 who modelled the build up to its maximum extent retreat of the ice sheet complex was highly asynchronous reflecting contrasting regional sensitivities to climate forcing oceanic influence and internal dynamics most rapid retreat was experienced across the barents sea sector after 17 8 ka bp when this marine based ice sheet disintegrated at a rate of 670 gigatonnes per year gt a 1 through enhanced calving and interior dynamic thinning driven by oceanic atmospheric warming and exacerbated by eustatic sea level rise from 14 9 to 12 9 ka bp the eisc lost on average 750 gt a 1 peaking at rates 3000 gt a 1 roughly equally partitioned between surface melt and dynamic losses and potentially contributing up to 2 5 m to global sea level rise during meltwater pulse 1a independent glacio isostatic modelling constrained by an extensive inventory of relative sea level change corroborates our ice sheet loading history of the barents sea sector subglacial conditions were predominately temperate during deglaciation with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network moreover the maximum eisc and its isostatic footprint had a profound impact on the proglacial hydrological network forming the fleuve manche mega catchment which had an area of 2 5 106 km2 and drained the present day vistula elbe rhine and thames rivers through the seine estuary during the bolling allerod oscillation after c 14 6 ka bp two major proglacial lakes formed in the baltic and white seas buffering meltwater pulses from eastern fennoscandia through to the younger dryas when these massive proglacial freshwater lakes flooded into the north atlantic ocean deglaciation temporarily abated during the younger dryas stadial at 12 9 ka bp when remnant ice across svalbard franz josef land novaya zemlya fennoscandia and scotland experienced a short lived but dynamic re advance the final stage of deglaciation converged on present day ice cover around the scandes mountains and the barents sea by 8 7 ka bp although the phase lagged isostatic recovery still continues today

palaeoclimatic records of the loess palaeosol sequences of the chinese loess plateau whether during past climate stages or into a progressively warming world changes in precipitation constitute a key component of climatic change quantitative proxies for palaeo precipitation are relatively rare the magnetic properties of the windblown loess units and interbedded palaeosols of the famous chinese loess plateau provide key palaeo precipitation data for this populous monsoon dominated region the loess palaeosol sediments record rainfall totals directly complementing the oxygen isotope records of chinese speleothems these isotopic records predominantly reflect moisture source and hence large scale atmospheric circulation changes the two major asian monsoon systems appear to display antiphase behaviour dominance of the indian summer monsoon system seems associated with minimum precession maximum northern hemisphere summer heating dominance of the east asian summer monsoons with maximum precession at 2 8 ma more intense development of the east asian winter monsoon initiated major increases in dust deposition rates and formation of relatively unweathered loess layers glacial stage loess units then interleaved with interglacial interstadial stage palaeosols throughout the quaternary period decoupling of the loess palaeosol rainfall records from the chinese cave records of moisture source shows that the indian and east asian monsoon winds were continuously driven by precessional forcing while summer monsoonal rainfall was greatly suppressed during cool glacial stages the timing of these east asian climatic transitions the subsequent intensification of northern hemisphere glaciations and the association between monsoon circulation changes and north atlantic temperatures indicates a possibly leading global role for these monsoonal changes via alterations in the poleward distribution of heat and moisture

high resolution evidence for linkages between nw european ice sheet instability and atlantic meridional overturning circulation published studies show that ice rafted debris ird deposition preceding heinrich h events h1 and h2 in the ne atlantic was derived from the nw european ice sheets nweis possibly offering clues about ice sheet sensitivity and stability and the mechanisms that caused periodic collapse of the laurentide ice sheet lis we present detailed lithological and geochemical records including radiogenic isotope fingerprinting of ird deposits from core md01 2461 proximal to the last glacial british ice sheet bis demonstrating persistent instability of the bis with significant destabilisation occurring 1 5 1 9 kyr prior to both h1 and h2 dated at 16 9 and 24 1 kyr bp respectively in the ne atlantic paired mg ca and 18o data from the surface dwelling globigerina bulloides and subsurface dwelling neogloboquadrina pachyderma sinistral are used to determine late glacial variability of temperature salinity and stratification of the upper water column a picture emerges that the bis was in a continuing state of readjustment and never fully reached steady state increased sea surface temperatures appear to have triggered the episode of nweis instability preceding h1 it seems most probable that the so called precursor events were not linked to the h events however if response to a common thermal forcing is considered an increased response time of the lis up to 2 kyr longer than the nweis may be inferred negative salinity excursions of up to 2 6 indicate significant incursions of melt water associated with peaks in nweis instability decreased surface density led to a more stable stratification of the upper water column and is associated with reduced ventilation of intermediate waters recorded in depleted epibenthic 13c cibicidoides wuellerstorfi we suggest that instability and meltwater forcing of the nweis temporarily weakened atlantic meridional overturning circulation allowing transient advance of southern sourced waters to this site prior to h events 1 and 2

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

millennial scale climate oscillations recorded in the lower danube loess over the last glacial period abstract in this study we provide a correlative age model for last glacial loess at the rasova valea cu pietre site in the lower danube region based on the correlation of palaeoenvironmental proxies to independently dated palaeoclimate archives luminescence dating and independent age control provided by the geochemically confirmed presence of the campanian ignimbrite ci tephra the ci tephra originating in the phlegrean fields of southern italy has been dated elsewhere by 40ar 39ar to 39 40 ka bp and is frequently found in the lower danube loess as such the ci tephra represents a valuable temporal and stratigraphic maker across loess deposits in the region our age model facilitates high resolution correlation of palaeoenvironmental features observed at rasova to palaeoclimate archives in greenland and the black sea mediterranean area we observe semi cyclic behaviour of the frequency dependent magnetic susceptibility throughout the profile which we ascribe to millennial scale climate variability also observed elsewhere in the black sea region this is the first study to clearly identify millennial scale climate variability over the holocene and last glacial in the lower danube loess proxy variability in the holocene indicates continuous aeolian sedimentation through this epoch

abrupt last glacial dust fall over southeast england associated with dynamics of the british irish ice sheet loess deposits in southern britain contain a record of dust climate and landscape dynamics over the last glacial yet their age and accumulation rate remain poorly known furthermore the environm

diagenesis of eolian and fluvial feldspathic sandstones norphlet formation upper jurassic rankin county mississippi and mobile county alabama norphlet sandstones in seven cores from mississippi and alabama are arkoses and subarkoses deposited in eolian dune interdune and fluvial environments similar to the deeply buried 5 km tertiary feldspathic sandstones of the gulf basin all detrital plagioclase that survived dissolution has been albitized however some k feldspar instead of dissolving was stabilized by k rich brines derived from adjacent evaporites this k feldspar then developed extensive overgrowths fluvial red sandstone lost all initial porosity by the introduction of preburial pedogenic calcite and compaction initial porosity of eolian sands was reduced by compaction to an average of 29 and later by cementation by quartz carbonates anhydrite halite k feldspar and illite quartz and anhydrite cements precipitated between 90 and 100 c approximately 2 3 km deep carbonates and halite cements formed below 120 c 3 km and late stage illite cement formed between 130 and 150 c 4 5 km deep cements are patchy and some especially quartz and anhydrite are texture selective being more abundant in coarser laminae secondary porosity which makes up approximately half the porosity in thin sections formed by dissolution of detrital grains f ldspar rock fragments and cements anhydrite carbonate halite reservoir bitumen records an early phase of oil entrapment reservoir quality is influenced by the abundance of reservoir bitumen and thread like illite both of which bridge pores the radiometric age of illite approximately 55 ma probably reflects its cementation age but may also record a later recrystallization event depleted oxygen and carbon isotopic values for ferroan dolomite reflect the progressive replacement of earlier more enriched carbonate phases by higher temperature phases isotopic data suggest that during the first 30 to 40 m y of burial subsurface diagenesis of the norphlet formation was dominated by deep circulating hot meteoric water this phenomenon may be characteristic of the early diagene ic history of rifted basins

dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle

glacial interglacial changes in dust deposition on the chinese loess plateau the chinese loess plateau clp contains an extensive record of aeolian deposition through multiple glacial interglacial cycles independent chronologies based on pedostratigraphy magnetic susceptibility radiocarbon and luminescence dating were developed for 79 sites and used to estimate aeolian mass accumulation rates mars for marine isotope stages 1 5 the regional median value of mar for stage 2 is 310 g m2 yr compared to an estimate of 65 g m2 yr for stage 5 estimated mars from individual sites for stage 2 are approximately 4 3 times greater than mars for stage 5 and 2 1 times greater than for stage 1 mar values at individual sites are consistently highest in the northwest and lowest in the southwest of the clp during all marine isotope stages mars estimated on sections through loess terraces are consistently higher than mar estimates at other sites indicating that local recycling of loess material from exposed river valley deposits has been significant throughout the last 130 kyr although the spatial and temporal patterns in mar are robust there are uncertainties about the magnitude of these changes due to a lack of bulk density measurements and uncertainties in the chronologies for individual sites b site and chronological biases in the sampling used to derive regional estimates and c the unquantified nature of human impact on accumulation rates during the late holocene nevertheless the records from the clp pose a number of challenges which could be addressed by numerical models of the palaeo dust cycle

benthonische schelf foraminiferen aus dem valanginium hauterivium unterkreide des indischen ozeans sudwestlich madagaskar deep sea drilling project leg 25 site 249 aus 12 radiolarien reichen tonstein proben aus site 249 dsdp leg 25 im westlichen indischen ozean sudwestlich madagaskar werden 4 arten agglutinierter und 38 arten benthonischer foraminiferen beschrieben davon 13 in offener nomenklatur durch das vorkommen zahlreicher valanginium arten und vongavelinella barremiana werden die faunen hier als valanginium hauterivium datiert sie enthalten leitformen der norddeutschen unterkreide und ebenso arten aus dem benachbarten madagaskar die nodosariiden dominieren mit 36 arten vor allem die gattungenastacolus citharina lenticulina lingulina marginulinopsis nodosaria saracenaria undvaginulina wichtige neokomium arten die in anderen dsdp sites vorkommen namentlichpraedorothia ouachensis sigal und planktonische foraminiferen fehlen die faunen aus site 249 werden dem schelfbereich zugeordnet

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints