organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

a lateglacial and holocene organic carbon isotope record of lacustrine palaeoproductivity and climatic change derived from varved lake sediments of lake holzmaar germany abstract a composite varve dated 11 4 m long sediment sequence from lake holzmaar situated in the eifel region of western germany was investigated for total organic matter content total nitrogen content and stable organic carbon isotopes mean time resolution is 75 years for tn and 14 years for 13 c org on millennial time scales primary production of lacustrine algae strongly depends on the delivery of nutrients from the catchment the respective carbon isotope record is characterized by marked variations of 13 c org ranging from 36 0 to 27 0 and includes a number of pronounced shifts reactions of the lacustrine system and the catchment to changes of environmental parameters e g runoff solar radiation and temperature induce changes of algal associations and of lacustrine primary production which are reflected in the sediments as carbon isotope variations clear evidence of ecosystem reorganizations is detected by the carbon isotope record around 14 200 10 400 9600 5500 2700 1700 and 900 varve years bp in particular the holocene events of 9600 around 5500 and 2700 are interpreted as the expression of massive changes of the climate system the steady rise of 13 c org values during the mid holocene is interpreted as a continuous climatic amelioration reaching an optimum around 6500 varve years bp rapid and large changes of 13 c org values from 2700 varve years bp to the present indicate major disturbances in the catchment area these are most probably related to deforestation or reforestation and runoff changes presumably in conjunction with human impact carbon isotopes thus characterize the holzmaar ecosystem in time revealing lacustrine palaeoproductivity as well as providing palaeoenvironmental and palaeoclimatic information

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

post saalian transformation of dry valleys in eastern europe an example from ne poland the studies were conducted in a dry valley in ne poland they were aimed at determining the origin of this structure and tracing the processes that have shaped the dry valley in a time span of about 130 ka the research included detailed geological mapping including piercing of a number of boreholes and electrical resistivity tomography ert surveys the obtained material was pollen analysed osl dated and the grain size distribution and the morphoscopy of sand quartz grains were investigated additionally the organic matter om content was determined based on the obtained results it was concluded that the structure currently occupied by sediments of the dry valley was formed during the warta stadial of the odranian glaciation saalian mis 6 as a glacial tunnel valley small probably isolated depressions functioned in the dry valley bottom after the ice sheet retreat the sediments record a full succession of climate oscillations from the eemian interglacial mis 5e pollen zones e1 to e7 through the early vistulian mis 5a 5d to mis 4 in the early vistulian the depressions functioned as lakes or got shallower and were replaced by peat bogs depending on the climate conditions during mis 4 the bottom of the dry valley was subjected to erosion as a result of concentrated water flow this caused draining of the existing depressions and their incorporation within the flow probably during mis 3 solifluction was activated on the slopes of the dry valley during lgm permafrost aggradation occurred in the study area recorded by two generations of epigenetic sand wedges and development of aeolian processes in contrast to analogous processes within the european sand belt the latter processes acted for a short time and only locally the final record are holocene soils it seems that the analysed valley is a good example of palaeoenvironmental conditions in eastern europe

out of tune the dangers of aligning proxy archives abstract tuning is a widespread technique to combine date and interpret multiple fossil proxy archives through aligning supposedly synchronous events between the archives the approach will be reviewed by discussing a number of literature examples ranging from peat and tephra layers to orbital tuning and 18o series from marine and ice deposits potential problems will be highlighted such as the dangers of circular reasoning and unrecognised chronological uncertainties and some solutions suggested fossil proxy research could become enhanced if tuning were approached in a more quantitative reliable and objective way and especially if individual proxy archives were non tuned and kept on independent time scales

the holocene palaeoenvironmental changes reflected in the multi proxy studies of lake slone sediments se poland abstract multi proxy data from the lake slone sediments se poland yielded information on the holocene changes of lake slone in a karst region changes of limnological conditions and vegetation reconstructions correspond to high resolution multi proxy records from north central europe ostracods showed several small oscillations most significant changes occurred at 12300 cal yr bp younger dryas preboreal transition and between 11800 and 11100 cal yr bp preboreal oscillation lowering of the water table at around 11100 10800 cal yr bp was probably connected with abrupt warming at ca 11000 cal bp temperature and water depth fell at about 8400 8100 cal yr bp 8200 cal yr bp the atlantic period was generally warm and is divided into two parts an older one with comparatively stable water level and a second one between 7000 and 6300 cal yr bp with two phases of higher water level separated by lowering at 6800 cal yr bp at the transition from the atlantic to the subboreal 6200 5950 cal yr bp the dry period is more pronounced than changes in the second half of the atlantic since the beginning of the subboreal an increase in human activity in central europe was the main factor shaping the landscape and changing the limnic regimes

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

mid to late holocene paleoclimatic changes and paleoenvironmental shifts inferred from pollen and diatom assemblages at lake hamra wadi el natrun western nile delta north western desert egypt abstract four palynological and three diatom zones of mid to late holocene are identified along a 370 cm long radiocarbon dated sediment core collected in lake hamra at wadi el natrun western nile delta egypt the mid late holocene between the predynastic to old kingdom was terrestrial wetland habitat with high seasonal rainfall and or nile flood as revealed by the dominance of cyperaceae pollen therefore people gathered in and around the nile valley and the agricultural activities increased during the early stage of late holocene coincident with the old kingdom to middle kingdom the paleoclimate became more arid with low seasonal precipitation and or nile flood as reflected by the increasing abundance of poaceae pollen and the absence of diatoms in addition to low values of toc tn ts c s and high values of c n these drought conditions possibly played a role in the old kingdom collapsing the late stage of the late holocene showed terrestrial wetland habitat with brackish conditions coupled with aquatic contribution under oxic conditions as inferred by the dominance of typha sp and amaranthaceae pollens as well as the diatom assemblages the relatively high values of toc c n c s coupled with low values of ts and tn reveal terrestrial origin of organic matter the late holocene recent has turned into a terrestrial wetland habitat with more brackish conditions and increasing in the seasonal rainfall as supported by the marked increasing of cyperaceae pollen the overall increase of the diatom inferred salinity dis as well as the marked increasing of c s tn and decreasing of toc c n and ts values towards the recent point to higher saline brackish wetland paleoenvironment and a terrestrial origin of the organic matter with more aquatic contribution under oxic conditions

climate change vegetation development and lake level fluctuations in lake purwin ne poland during the last 8600 cal bp based on a high resolution plant macrofossil record and stable isotope data δ13c and δ18o abstract this paper presents a history of the vegetation in lake purwin ne poland and its catchment along with water level changes for the last 8600 cal bp the reconstructions are based on a high resolution plant macroremains analysis and the stable isotope record in authigenic carbonates a fine fraction that is precipitated within the epilimnion of the lake the stable isotope records suggest that the lake had throughflow during the holocene and that isotope data can therefore be used in palaeoclimatic reconstructions the 18o values record the thermal maximum of the holocene and the subsequent cooling of the upper holocene water level changes and the history of the lake s productivity are both recorded in the 13c values a chronology is established using radiocarbon dating of terrestrial plant macrofossils the vegetation and water levels in lake purwin reflect regional climate changes the combination of the lithology along the sedimentary sequence the results of the plant macroremains analysis and the isotope data allowed several alternating periods of high 8600 7300 6500 5200 4400 3500 and 3000 950 cal bp and low 7300 6500 5200 4400 3500 3000 and 950 to 59 cal bp water stands to be distinguished in lake purwin low water levels are indicated by sediments that are enriched in coarse plant detritus seeds of rubus ideaus fruits of uritca dioica and more macroremains of alnus glutinosa and rushes

environmental and climatic changes in the jura mountains eastern france during the lateglacial holocene transition a multi proxy record from lake lautrey this paper presents a multi proxy reconstruction of the climatic and environmental changes during the last glacial interglacial transition as recorded by a sediment sequence from lake lautrey jura eastern france this reconstruction is based on analysis of pollen chironomid organic matter oxygen isotope mineralogical magnetic susceptibility and inferred lake level data at a high temporal resolution the chronology is derived using ams radiocarbon dates the position of the laacher see tephra lst and of correlation between the lautrey and grip oxygen isotope records this data set reveals a detailed sequence of environmental changes in the jura mountains from greenland stadial 2a to the early holocene biotic and abiotic indicators allow the recognition of major abrupt changes associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions and other minor fluctuations related to the cold events gi 1d gi 1b and the preboreal oscillation pbo they also suggest additional cooling spells at ca 14 550 and 14 350 cal yr bp intra bolling cold periods at ca 13 500 and ca 12 700 cal yr bp just before the gs 1 onset and at ca 11 350 cal yr bp just before the pbo as well as an intriguing brief warming episode within gs 1 at ca 12 080 cal yr bp summer temperature increased by ca 5 c at the start of gi 1e and by 1 5 3 c at the holocene onset while it decreased by ca 3 4 c at the beginning of gs 1 major changes in local hydrology and in seasonality appear to be also associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions pollen and abiotic indicators suggest a greater sensitivity of the vegetation cover to climatic oscillations during the first part of the lateglacial interstadial than during the second part after ca 13 700 cal yr bp when a closed forest had been restored in this area by contrast the restoration of forest cover took less than 300 yr after the end of gs 1 at the beginning of gi 1e and gs 1 no lag occurs within the sampling resolution of 20 50 yr in the responses of aquatic chironomids and terrestrial pollen ecosystems while at the onset of the holocene the response of the vegetation appears slightly delayed in comparison with that of the chironomid community finally the recognition of two successive tephra layers which were deposited just before the lst at ca 12 950 cal yr bp and which originated from le puy de la nugere massif central france provides an additional tephrochronological tool for correlation between lateglacial european sequences

palaeoclimatic changes in the qinghai lake area during the last 18 000 years abstract multi proxy analysis of a sediment core from qinghai lake including pollen carbonate toc tn and 13 c of organic matter was used to document regional climatic changes during the last 18 000 years climate was very cold and dry before 16 9 cal kyr bp the warm and wet period which began at about 14 1 cal kyr bp culminated at 6 5 cal kyr bp and came to its end at about 4 5 cal kyr bp after that the climate gradually became colder and drier during the transitional period from the late glacial to the holocene the climate fluctuated frequently the short term climatic oscillations including the bolling allerod younger dryas and the cooling event at ca 8 2 cal kyr bp appear to be recorded in the qinghai lake sedimentary record the climatic evolution in the qinghai lake area during the past 18 000 years indicates that solar insolation changes on the ten thousand year scale are the likely driving force of the east asia monsoon

non linear holocene climate evolution in the north atlantic a high resolution multi proxy record of glacier activity and environmental change from hvitarvatn central iceland abstract iceland is well situated to monitor north atlantic holocene climate variability terrestrial sites there offer the potential for well dated high resolution continuous records of environmental change and or glacier activity laminated sediments from the proglacial lake hvitarvatn provide a continuous record of environmental change and the development of the adjacent langjokull ice cap for the past 10 2 ka replicate lake sediment cores collected from multiple locations in the basin are placed in a secure geochronology by splicing a varve chronology for the past 3 ka with a tephra constrained paleomagnetic secular variation derived chronology for older sediments multiple proxies including sedimentation rate bulk density ice rafted debris sediment organic matter biogenic silica and diatom abundance allow annual to multi decadal resolution and reveal a dynamic holocene terrestrial climate following regional deglaciation of the main iceland ice sheet summer temperatures were high enough that mountain ice caps had already melted or were contributing insignificant sediment to the lake pronounced increases in sedimentation rate sediment density and the influx of terrestrial organic matter between 8 7 and 7 9 ka suggest early holocene warmth was interrupted by two distinct pulses of cold summers leading to widespread landscape destabilization and possibly glacier growth the holocene thermal maximum htm 7 9 to 5 5 ka was characterized by high within lake productivity and ice free conditions in the watershed neoglaciation is recorded as a non linear transition toward cooler summers landscape destabilization and the inception and expansion of langjokull beginning ca 5 5 ka with notable increases in ice cap size and landscape instability at 4 2 and 3 0 ka the past two millennia are characterized by the abrupt onset of sustained cold periods at ca 550 and 1250 ad separated by an interval of relative warmth from ca 950 to 1150 ad the greatest holocene extent of langjokull occurred in the nineteenth century and is coincident with peak landscape instability followed by ice recession throughout the twentieth century

the preboreal oscillation around the nordic seas terrestrial and lacustrine responses the occurrence of an early preboreal climatic cooling oscillation pbo in lacustrine and glacial records from northwest europe iceland and greenland is reviewed and documented the often subtle response of the proxy records to this oscillation in combination with its short duration make it difficult to detect owing to its chronostratigraphic position between the 10 000 9900 and 9600 9500 14 c plateaux c 11 300 11 150 calendar yr bp it is also difficult to 14 c date with precision we find that the vegetation response to the pbo varies between sites and regions in contrast to the pioneer vegetation in iceland and southern sweden the expanding birch pine forest in germany denmark was more susceptible to deteriorating growing conditions the combined lacustrine tree ring and glacial records imply that the pbo was characterised by cool and humid conditions throughout northwestern and central europe this is documented by vegetation changes decreased aquatic production increased soil erosion increased 2 h and 13 c content in tree rings readvances or stillstands of the ice sheet in norway and finland and ingression of brackish water into the baltic icelandic proxy records from lake sediments and glacial moraines imply cooler conditions than during the previous preboreal period but not as extreme as during the younger dryas greenland records suggest that the early preboreal was characterised by ice readvances as an effect of cool climate and increased precipitation in relation to the younger dryas it was not until the end of the pbo that climate was warm enough to melt the land based ice sheet this preboreal oscillation found on both sides of the nordic seas is interpreted as an effect of increased freshwater forcing on the thermohaline circulation in the nordic seas which is implied by a simultaneous and distinct rise in the atmospheric 14 c 12 c ratio a slow down of the thermohaline circulation may tempor arily have pushed the polar front further south 1997 by john wiley sons ltd preboreal oscillation thermohaline circulation lacustrine records glacial records chronology

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

regional and local changes inferred from lacustrine organic matter deposited between the late glacial and mid holocene in the skaliska basin north eastern poland abstract the article presents the results of a combination of isotopic 15 n and 13 c geochemical toc tn c n and palaeobotanical investigations they were carried out on organic matter om that had been deposited from the younger dryas to the subboreal chronozone in palaolake sediments north eastern poland om from the late younger dryas consists only a small amount of toc and tn which together with the lack of aquatic macrophyte macrofossils confirm low primary production in the then reservoir the higher values of c n ratio 18 27 and 13 c ca 26 suggest that om was mainly terrestrial in origin during the preboreal chronozone 11 450 10 150 cal bp there was a probable deepening of the reservoir through the melting of dead ice this might have been intensified by an increase in precipitation and a fall in evapotranspiration during the preboreal oscillation from the early preboreal chronozone ca 11 345 cal bp a mixed source of om is indicated by c n ratio from 8 to 13 at the same time significant increase in toc and tn probably registered a rise in primary production in the palaeolake from the older part of the boreal chronozone ca 9865 cal bp algae productivity increased the c n ratio dropped to ca 8 and was then constant at the beginning of the atlantic chronozone ca 8650 cal bp a probable increase in the water level caused the partial relocation of om from the reed swamp belt and or the adjacent alder carr into deeper sections of the palaeolake an increase in toc and tn in the late atlantic chronozone ca 6965 6650 cal bp toc and tn decreased while 13 c had high values which probably reflected a more distinct stratification of the water column with anoxic bottom waters next in the late atlantic and early subboreal chronozone ca 6650 5205 cal bp the amount of om in palaeolake sediments was still rising the 13 c values dropped suggesting an intensification of processes of water mixing these processes were simultaneous with the constant shallowing of the palaeolake and the disappearance of habitats suitable for submerged macrophytes the topmost part of the profile is characteristic of a strong decomposition of peat causing a release of carbon dioxide and therefore the depletion of the carbon pool in the peat a drop in the c n ratio the concurrent upward trend of the 15 n curve is probably the effect of a greater anthropogenic impact on the palaeolake mire and its catchment and or more recent human interference in the topmost peat layers

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

mean july temperatures during the younger dryas in northwestern and central europe as inferred from climate indicator plant species abstract we estimated minimum mean july temperatures in northwestern and central europe during the younger dryas 10 950 10 15014c yr b p from distributions of climate indicator plant species which were reconstructed from 140 pollen and plant macrofossil diagrams paleobotanical records mainly from the central and eastern part of the study area show that the coldest conditions occurred early in the younger dryas before 10 55014c yr b p for this phase mean july temperatures at sea level of around 10 c are suggested for the northern part of the british isles and for ice free scandinavia we estimated a mean july temperature of 12 c for central england the netherlands and northern germany the 13 c mean july isotherm largely based on the modern distribution oftypha latifolia was most probably located in southern england belgium central germany and poland the reappearance of thermophilous elements in the records after 10 55014c yr b p suggests a summer warming at least temporarily of 1 to 2 c in the study area the reconstructed temperatures are comparable with temperature estimates based on beetle data however they appear rather high when compared with estimates based on glaciological evidence

moho offsets beneath the western ghat and the contact of archean crusts of dharwar craton india abstract we present the moho depth variation along a 600 km long profile from the west to the east coast of south india covering the passive continental margin and the western ghat escarpment created during india madagascar separation at 85 ma archean western and eastern dharwar craton and proterozoic basin the image is generated through three different approaches h vp vs stacking common conversion point ccp migration and inversion of teleseismic receiver functions at 38 locations the moho depth along the profile varies smoothly between 34 and 41 km except beneath the western ghat and at the contact of east and west dharwar craton where it is offset by up to 8 km the study suggests i the possible differential uplift of the western ghat as a consequence of india madagascar separation and the prominent role of deep crustal structure in the location of the escarpment compared to the surface process and ii presence of long lived steeply dipping fault separating the two distinct archean crustal blocks indicative of mechanically strong continental lithosphere beneath the dharwar craton

climatic and environmental changes in north western russia between 15 000 and 8000 cal yr bp a review multi proxy palaeoenvironmental studies of nine sediment sequences from four areas in north western russia reveal significant changes in climate lake productivity and vegetation during the lateglacial and early holocene that show some degree of correlation with changes reconstructed from sites throughout the north atlantic region at lake nero in the rostov jaroslavl area which is outside the maximum limit of the scandinavian ice sheet sedimentation recommenced shortly after 15 cal ka bp in response to increases in temperature and humidity during greenland interstadial 1 gi 1 bolling allerod however climatic amelioration during gi 1 was slow to increase lake organic productivity or trigger large scale changes in much of northwestern russia in general this region was characterised by long lasting lake ice cover low lake productivity soil erosion and dwarf shrub and herb tundra until the end of greenland stadial 1 gs 1 younger dryas at some sites distinct increases in lake organic productivity mean summer temperatures and humidity and the expansion of forest trees coincide with rapid warming at the beginning of the holocene and the increasing influence of warm air masses from the north atlantic at other sites particularly on the karelian isthmus but also in russian karelia the delayed response of limnic and terrestrial environments to early holocene warming is likely related to the cold surface waters of the baltic ice lake the proximity of the scandinavian ice sheet and associated strengthened easterlies and or extensive permafrost and stagnant ice these multi proxy studies underscore the importance of local conditions in modifying the response of individual lakes and their catchments while lateglacial vegetation was dominated by betula nana and salix shrubs and various herbs pollen and plant macrofossils suggest that betula pubescens trees became established as early as 14 13 cal ka bp in the rostov jaroslavl area in general our data sets suggest that trees migrated from the southeast to the west and then spread later to the northeast and northwest paralleling the direction of ice retreat with betula pubescens immigrating first followed by pinus sylvestris and picea abies however palaeoecological records from lake terebenskoye in the valdai highlands suggest that the arrival of picea abies preceded other trees in that area and that it colonised tundra communities as early as 12 cal ka bp since lateglacial vegetation change in north western russia was time transgressive independent measures of palaeoclimate e g chironomid based palaeotemperature estimates are needed for this region r 2007 elsevier ltd all rights reserved

chironomidae insecta diptera succession in żabieniec bog and its palaeo lake central poland through the late weichselian and holocene abstract subfossil chironomidae assemblages were studied in a sediment sequence from abieniec bog in central poland the climate history and habitat changes in the palaeo lake were reconstructed from these assemblages currently no chironomid based climate calibration set is available from poland and so past mean july air temperatures were inferred from chironomid climate calibration data sets from norway russia and switzerland during the late weichselian the three calibration functions from these data sets provided similar temperature inferences but there was some divergence in the reconstructions for the younger dryas and holocene in the late pleniglacial inferred summer air temperature was relatively low 8 12 c and the lake was oligotrophic at about 16 5 ka bp temperature rapidly rose to 15 c and assemblage diversity substantially increased during the interstadial temperature stayed at this level in the younger dryas july air temperature was only 1 2 c lower than in the interstadial as inferred from the norwegian calibration data set whereas the russian and swiss calibration functions did not indicate any temperature decrease from the beginning of the holocene taxa typical of meso eutrophic conditions dominated there was an increased abundance of phytophilous species and the assemblage composition was also influenced by changes in water level palaeotemperature reconstructions differed in their values from 8 0 to 8 7 ka bp inferences based on the swiss and russian data sets indicated a cold oscillation while reconstructions based on the norwegian data set did not show any temperature decrease after 2 5 ka bp assemblage diversity and head capsule concentrations decreased in the last millennium semi terrestrial taxa dominated except from late medieval to early modern times when shallow water species reappeared

the record of hydroclimatic changes in the sediments of a kettle hole in a young glacial landscape north central poland abstract multidisciplinary research on the bottom sediments of a kettle hole at the retno site the brodnica lake district north central poland provided some information about changes in hydroclimatic conditions in the late glacial and the holocene detailed analysis sedimentological palynological macroremains geochemical and radiocarbon dating helped to identify 6 stages in the development of the depression in the village of gaj near retno lake with 11 phases of hydroclimatic conditions sediments of the retno profile with a total thickness of 6 72 m reflected individual natural stages in the development of the depression from a lake to a peat bog most of the environmental changes were gradual a sequence of late glacial and early holocene lacustrine sediments mainly gyttja occurred in the floor of the profile the upper 4 10 m consisted of paludal deposits peat of transitional and raised bogs divided at a depth of 1 56 1 54 m b g l by a thin layer of clay dated late subboreal early subatlantic the presence of this layer indicates a sudden change in the environmental conditions associated with a water level rise at that time denudation processes started within the drainage basin probably induced by human activity the important effects related to contemporary anthropopressure included desiccation of the peat bog muck formation in the uppermost 10 cm layer and elevated trophic conditions resulting in a change of the vegetation cover

komatiitic sills and multigenerational peperite at dundonald beach abitibi greenstone belt ontario volcanic architecture and nickel sulfide distribution the density and the tectonic stresses in the deep crust and the physical properties of komatiitic magmas determine the level to which they will rise but once in the near surface environment the density and rheology of the near surface rocks consolidated and dense lava flows and sedimentary rocks versus unconsolidated sedimentary or volcaniclastic deposits govern whether they will be emplaced as lava flows invasive flows or sills where near surface strata are competent i e flow dominated or consolidated sedimentary and or volcaniclastic successions komatiitic magma erupts as flows that form extensive lava shields e g kambalda however where near surface strata are not competent i e unconsolidated volcaniclastic and or sediment dominated successions komatiitic magmas typically are emplaced as high level sills that increase the bulk density of the volcano sedimentary pile and eventually allow the eruption of lava and the construction of complex sub volcanic volcanic lava shields e g dundonald and shaw dome abitibi belt raglan cape smith belt pechenga kola peninsula thompson ni belt manitoba the latter environment is illustrated in the volcano sedimentary succession in dundonald township which is only weakly metamorphosed and deformed and superbly exposed in glacially polished outcrops the volcano sedimentary succession in this area comprises from base to top 1 the mcintosh formation composed of a succession of pillowed and massive intermediate volcanic flows 2 the dundonald formation composed of a lower section of komatiite sills argillites and felsic volcaniclastic deposits and an upper section of komatiite flows komatiitic sills and pillowed intermediate volcanic flows and 3 the frederick house lake formation composed of massive and pillowed mafic flows the distribution and thickness of argillites and felsic volcaniclastic rocks define a synvolcanic graben in which the dundonald south and alexo ni cu pge deposits occur within the center and the margin respectively sills and peperites in the lower komatiitic succession at dundonald beach exhibit a multigenerational emplacement history recording progressive lithification and increases in the bulk density and rheological strength of the unconsolidated argillites which ultimately permitted the eruption of lavas at alexo importantly the nature of the near surface rocks also influences the localization of ni cu pge deposits in lava shields e g kambalda the initial eruptions are typically most voluminous and if erupted at sufficient flow rates form channelized flows conducive to thermomechanical erosion of sulfur rich footwall rocks in sub volcanic volcanic lava shields however channelized units may occur within the subvolcanic plumbing system and or within overlying lavas where only sills are channelized e g thompson mineralization will occur only within the subvolcanic environment where only the flows are channelized e g damba silwane zimbabwe mineralization will occur only within the volcanic environment where both sills and lava flows are channelized e g dundonald shaw dome raglan the distribution of the mineralization is more diverse and may occur as subsea or sea floor ni cu pge deposits

preboreal climate oscillations in europe wiggle match dating and synthesis of dutch high resolution multi proxy records abstract in order to compare environmental and inferred climatic change during the preboreal in the netherlands five terrestrial records were analysed detailed multi proxy analyses including microfossils e g pollen spores algae and fungal spores macroremains e g seeds fruits wood mosses etc and loss on ignition measurements were carried out with high temporal resolution to link the five preboreal records accurate chronologies were produced by ams 14c wiggle match dating the dutch records show that following the lateglacial holocene climate warming birch woodlands expanded between 11 530 and 11 500 cal bp during the friesland phase of the preboreal after the friesland phase two distinct climatic shifts could be inferred 1 around 11 430 11 350 cal bp the expansion of birch forests was interrupted by a dry continental phase with open grassland vegetation the rammelbeek phase this phase was coeval with the coldest part of the preboreal oscillation pbo as observed in the 18o record of the greenland ice core records and has been attributed to a large meltwater flux that resulted in a temporary decrease of the thermohaline circulation in the north atlantic 2 at the start of the late preboreal between 11 270 and 11 210 cal bp a sudden shift to a more humid climate occurred and birch forests expanded again a simultaneous increase in the cosmogenic nuclides 14c and 10be suggests that these changes in climate and vegetation were forced by a sudden decline in solar activity expansion of pine occurred during the later part of the late preboreal at the onset of the boreal between 10 770 and 10 700 cal bp dense woodlands with hazel oak elm and pine started to develop in the netherlands

the kettle hole mire as archives of postglacial changes in biogenic sedimentation tuchola forest north central poland abstract kettle holes are a circular shape product of ice decay and thus are strongly linked with young glacial landscapes once glaciation terminates these holes transform either into wetland and lakes or occasionally into kettle hole mires since an entire sediment sequence preserve in the kettle holes these provide an excellent settings to exploit any sensitive paleoenvironmental changes here the kettle hole mire located onto the brda river outwash plain tuchola forest is explored towards a better understanding of local and global environmental trends in the late glacial present day time frame to fulfill this multi proxy study as geochemical palynological and macrofossils analyses along with the radiocarbon dating are used therefore this study allows to distinguish five phases of steep environmental gradients in the investigated mire as follows 1 paludification after glaciation when dead ice melted and long term permafrost was degraded 2 lake started to disappear in the late glacial followed by a rich vegetation in the first part of the holocene 3 vegetation encroachment onto the lake in the first part of the holocene which consequently turned into an peat bog 4 the late holocene peat bog with a limited human influence and finally 5 the peat bog with a major human impact along with acidification as related to sandy underlying sediments leaching of calcium carbonate recharge from precipitation and pine monoculture as additionally apparent from this small ecosystem both local character of substrate sediments morphology of the area rate of permafrost melting climate conditions and human activity and regional climate changes and human activity are detectable nevertheless the record of these changes is sometimes unclear

a 15 000 year stable isotope record from sediments of lake steisslingen southwest germany abstract stable isotope records for carbon and oxygen in bulk carbonates carbon in bulk organic matter and for total and chromium reducible sulfur in a lacustrine sediment core from lake steisslingen southwest germany show several distinct and abrupt shifts during the last 15 000 years variations in the isotopic composition of authigenic carbonates indicate two major phases in the lake history in the pre holocene the hydrological budget of the lake was apparently stable variations of 18 o values of authigenic carbonates were therefore dominantly controlled by temperature changes a decrease in the 18 o carb values of about 2 at the allerod younger dryas transition is interpreted as a drop in mean annual air temperatures of approximately 5 c an abrupt temperature increase of a similar magnitude is inferred at the younger dryas preboreal boundary throughout most of the holocene the isotopic composition of authigenic carbonates was influenced by marked changes in the hydrological budget of the lake a major positive excursion in the 13 c carb and 18 o carb values at the beginning of the atlantic and a smaller one in the preboreal were related to evaporation effects which indicate that dry climatic conditions must have prevailed at that time a simultaneous increase in 13 c values of bulk organic matter at the beginning of the atlantic suggests a high level of productivity in the lake as a consequence aqueous sulfate became limited as indicated by variations in the 34 s values of total and chromium reducible sedimentary sulfur therefore we conclude that the beginning of the atlantic was characterized not only by dry but also by warm climatic conditions which triggered a higher productivity in the lake in the subatlantic sediments large variations in carbon oxygen and sulfur isotope ratios were observed as a result of human activities causing considerable perturbations in the biogeochemical element cycling of lake steisslingen results obtained by the study of the continuous 15 ka record of lake steisslingen document clearly that isotopic proxy data from lacustrine sediments can provide useful information on environmental and climatic changes of local regional and in the case of the younger dryas event of even hemispherical significance

holocene annual mean temperature changes in estonia and their relationship to solar insolation and atmospheric circulation patterns abstract we reconstructed annual mean temperature tann trends from three radiocarbon dated holocene pollen stratigraphies from lake sediments in estonia northern europe the reconstructions were carried out using a north european pollen climate calibration model based on weighted averaging partial least squares regression the cross validated prediction error of the model is 0 89 c and the coefficient of determination between observed modern tann values and those predicted by the model is 0 88 in the reconstruction the holocene thermal maximum htm is distinguishable at 8000 4500 cal yr b p with the expansion of thermophilous tree species and tann on average 2 5 c higher than at present the pollen stratigraphical data reflect progressively warmer and drier summers during the htm analogously with the modern decadal scale climatic variability in north europe we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow post htm cooling started abruptly at around 4500 cal yr b p all three reconstructions show a transient ca 300 years cooling of 1 5 2 0 c at 8600 8000 cal yr b p we tentatively correlate this cold event with the north atlantic 8 2 ka event at 8400 8000 cal yr b p provided that the 8 2 ka event was caused by freshening of the north atlantic surface water our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the north atlantic thermohaline circulation and the zonal energy transport over europe no other cold events of comparable magnitude are indicated during the last 8000 years

very fast environmental changes at the pleistocene holocene boundary recorded in laminated sediments of lake gościz poland abstract this paper presents a reconstruction of the climatic changes at the pleistocene holocene transition recorded in the annually laminated sediments of lake go ci a z poland this reconstruction is based on pollen stable isotope mineralogical and chemical analyses of sediments made with a time resolution of 1 4 yr it reveals a sequence of abrupt climatic changes which preceded and followed the major warming around 11 500 cal bp our data show that the warming period was preceded by a 30 yr long phase of increased winter and decreased summer precipitation 11 550 11 520 cal bp about 11 520 cal bp a very brief period of wetter conditions occurred simultaneously with the beginning of the major warming however most of the first phase of the major warming 11 520 11 500 cal bp was characterised by a generally dry climate presumably due to lowered winter precipitation our records suggest that in this phase the warming concerned winter seasons mostly in the second phase 11 500 11 460 cal bp the warming also concerned summer seasons also a distinct increase of humidity is noted in this period which caused moistening of soils and despite enhanced evaporation and evapotranspiration inhibited the process of lake level drop the following 70 years 11 460 11 390 cal bp were rather dry which caused a distinct lowering of the lake and probably also of groundwater level in this period maximum biological productivity per unit area in the lake is noted the whole sequence of phases of rather different climates was completed within a time interval 160 years spanning two human lifes only one should stress that the transitions between the consecutive phases were rather abrupt lasting no longer than 10 years

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research