palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

distribution and mechanisms of strain within rocks on the northwest ramp of pine mountain block southern appalachian foreland a field test of theory fractures faults stylolites and strain determined from an analysis of twinning in calcite in the mississippian newman limestone at the base of the pine mountain block show that deformation was accomplished primarily by a combination of bedding plane slip and layer parallel shortening poles to joints are either parallel to strike of the thrust sheet or are in the transport plane small slip surfaces with syntaxial calcite fibers lie either parallel to bedding or parallel to the strike of the pine mountain block and dip steeply movement along the former is in the direction of transport of the block whereas movement on the latter is approximately along strike tectonic stylolites are rare but appear to be controlled by subtle changes in lithology wackestones contain more stylolites than do packstones strains in calcite from closely spaced samples show the converse relationship they are highest in units without stylolites maximum shortening strain e 1 10 4 and lowest in units with stylolites or small faults e 1 2 0 the maximum principal shortening strain directions however are identical within the error and are parallel to both bedding and the transport direction a sequence of events in this portion of the pine mountain block is 1 layer parallel shortening producing tectonic stylolites and a strong preferred orientation of compression axes 2 development of fractures parallel to the strike of the block on the lower hinge of the ramp to accommodate stretching parallel to the transport direction these strike parallel fractures can also be interpreted as having occurred quite late 3 during 2 above and continuing the start of bedding plane slip marked by syntaxial calcite fibers which trend in the direction of transport and 4 complications such as shear parallel to the strike of the pine mountain fault as a result of motion of the entire block between bounding tear faults events 2 through 4 most likely overlapped in time these data suggest that the acquisition of dip of the rocks on the ramp was primarily accomplished by bedding plane slip on the slip surfaces which experienced a shear stress of

a multi proxy record of holocene climatic change in southwestern spain the laguna de medina cadiz palaeolimnological data diatoms ostracods foraminifera molluscs aquatic pollen and lithology from a radiocarbon dated sediment core from a saline lake the laguna de medina provide the first complete record of holocene lake level change for southwest spain for the last c 9000 cal years the lake has always been relatively shallow but has exhibited marked fluctuations in salinity and water depth especially in the earlier record when oscillations culminate in maximum lake levels from c 6960 6680 cal bp c 6070 5830 bp indicating enhanced early to mid holocene humidity and a mid holocene humidity maximum prolonged shallowing thereafter reflects in part increased aridity in the later holocene lake desiccation followed by a c 800 yr phase zone 2 of major limnological change commencing at c 8000 cal bp c 7200 bp and a number of other abrupt desiccation events are also noteworthy the mid holocene maximum is consistent with widespread evidence for high lake levels around 6000 bp but t

littoral landforms and pedosedimentary sequences indicating late holocene lake level changes in northern central europe a case study from northeastern germany abstract a multidisciplinary study was carried out at lake groser furstenseer see lfs in order to explore the potential of littoral sediments palaeosols and landforms as indicators of historical lake level changes this research was initiated to investigate the extent to which lakes in northern central europe responded hydrologically to climatic and land use changes in the last millennium specific landforms investigated comprise lake terraces beach ridges local basins peatlands and dunes revealing a wealth of sedimentary sub environments at the lakeshore eleven sections were recorded with subsequent sedimentological pedological geochronological osl 14c and palaeobotanical pollen macro remains analyses most of the pedosedimentary littoral sequences show a succession of basal glacial sand intermediate palaeosols and lacustrine sand on top a broader number of semi terrestrial buried palaeosols along the lakeshore were systematically identified and analysed providing evidence for changing hydrological conditions during the late holocene additional historical data from the last centuries e g maps aerial photos public records allow the lake levels reconstructed from geoarchives to be connected with modern gauging data all local data sources available enable a tracing of lake level changes of the lfs during the last millennium comprising periods of relatively low c 1200 ad 2000s ad and relatively high water levels c 1250 1450 ad c 1780 ad 1980s ad the amplitude of lake level changes during the last c 1000 years amounts to c 3 m so that the fluctuations of the last 30 years recorded by lake level monitoring only reflect a small amount of the potential variability regional climate and local land use history suggest that the medieval lake level dynamics of lfs were primarily governed by climate and secondarily influenced by human impact on the drainage system at present the lake level is additionally influenced by the impact of highly water consuming pine plantations in the catchment area the regional significance of the local development at lfs can be demonstrated by comparison with other regional and supra regional lake level data the present study underlines the potential of a closer examination of the littoral zone for lake level reconstructions with high altitudinal precision

the holocene history of lop nur and its palaeoclimate implications abstract the holocene hydrological history of lop nur in northwestern china s tarim basin and its response to climate conditions are inferred from a relatively well dated multi proxy record including grain size pollen and spores and soluble salt data a dated pit section ykd0301 with a depth of 570 cm in the center of the dry lop nur basin was investigated the sediments contain a total of twenty fining upward cycles as a result of strong discharge from the catchment to the lake during relatively wet conditions the fluvial sediments were probably widely dispersed by wind driven waves and currents in the large and shallow basin of lop nur higher runoff and dilution of lake waters are also indicated by lower contents of soluble salt in the sediments and recorded ostracod shells of brackish and oligohaline to freshwater species in contrast sediment sections with smaller mean grain size and fewer flood layers are dominated by aeolian sediments which were accumulated during drier periods ostracod shells are mostly lacking from these sections suggesting a higher salinity in the lake lop nur experienced six stages during the last 9 ka relatively wet conditions existed between 9 0 8 9 8 7 5 1 and 2 4 1 8 ka with periods of increased aridity in between and after 1 8 ka the lowest salinity was recorded between 8 7 and 5 1 ka which represents the wettest phase during the last 9 ka and probably the regional holocene optimum relatively wet climate conditions between 2 4 and 1 8 ka and dry conditions afterwards possibly first fostered and later on caused the devastation of the ancient loulan kingdom in the region the uppermost sediments of the section represent a massive salt crust formed during the final desiccation of the lake in the last century the effective moisture change pattern of the lop nur region is roughly consistent with synthesized holocene moisture records for western china dominated by the westerlies

reconstruction of lake level changes in lake xinias central greece during the last 40 000 years abstract the investigation of lake xinias greece deals with lake level changes since about 40 000 b p particular effort was made to obtain a reconstruction of lake level during the last glacial maximum at about 18 000 b p the reconstruction was based on a transect of sediment cores the cores were pollen stratigraphically correlated and the interpretation of the sediment stratigraphy was based on sediment chemical and mineral magnetic analyses the chronology was based on accelerator and conventional radiocarbon datings the most striking change was a lake level lowering at about 32 000 b p resulting in an overgrowing of the whole lake the lake level probably remained generally low until somewhat before 15 000 b p the period around the last glacial maximum must have been characterized by a low lake level which is in contrast to the hitherto common opinion additional investigations are required to demonstrate that the lake level changes reconstructed in lake xinias are regionally significant and record climatic changes however it may already be suggested that the conflict between pollen and lake level evidence which hitherto has produced controversy about the glacial climate perhaps does not exist the low lake level in lake xinias around the last glacial maximum is in accordance with the pollen evidence of steppe vegetation both recording a dry climate another distinct lowering occurred around the late wurmian holocene boundary at about 10 000 b p some minor lowerings are recorded also during the holocene e g at about 6000 5000 and 3000 b p

climatic controls on holocene lake level changes in europe sensitivity experiments with a simple water balance model were used to constrain the possible climatic causes of distinct holocene patterns of lake level variation in different regions of europe lakes in s sweden were low at 9 ka high around 6 5 ka low again around 4 ka and are high now lakes in estonia show similar but weaker trends lakes in s france were highest around 9 ka lowest around 4 ka intermediate now lakes in greece were also high around 9 ka but continued rising until 7 5 ka then fell gradually from 5 ka with a brief high phase around 3 ka and are low now the model was forced with insolation anomalies deduced from orbital variations temperature anomalies inferred from the pollen record and cloudiness anomalies derived from changes in the position of the subtropical anticyclone inferred from reconstructed changes in the equator to pole temperature gradient in order to evaluate the effects of resultant evaporation changes on catchment water balance the resulting simulated changes in runoff precipitation minus actual evapotranspiration were slight and frequently opposite to the observed trends larger changes in precipitation are plausible and are required to explain the data the required precipitation increase in n europe from 9 ka low to 6 ka high is suggested by gcm experiments to have been a consequence of interacting insolation and residual ice sheet effects on the atmospheric circulation over the north atlantic the explanation of other observed changes including the drying trend during the holocene in s europe has not been provided by gcm experiments to date explanations may lie in changes in mesoscale circulation sea surface temperature patterns and the coupling between these phenomena that may not follow orbital changes in any simple way

postglacial land uplift patterns of south sweden and the baltic sea region comparison of the land uplift pattern for the last 10 300 years shown by studies of raised shorelines of the baltic ice lake with the pattern of present day land uplift of fennoscandia shows that significant regional changes of uplift pattern have taken place some of these changes seem to be related to a halt in ice retreat during the younger dryas cold stage it is also probable that some observed anomalies in the present uplift are not of glacio isostatic origin but are possibly related to structures in the lower lithosphere and upper mantle or large scale tectonics

the holocene and upper pleistocene pollen record from padul granada spain a new study two borings were made at the site of padul granada pollen analysis of 200 spectra from two successive sequences 14 8 and 8 m deep enables a description of the vegetational and climatic history of this region the most southern one in europe from early wurmian times the chronology is supported by twenty one 14c dates original equivalents are found for the great european prewurm interstadials a markedly arid though thermically not extreme episode exactly equivalent to stage 4 of the marine isotopic stratigraphy closes this relatively temperate period the middle part of the last glacial shows climatic fluctuations that are poorly characterized as is often the case in europe for this period a long section very probably corresponding to the complete last pleniglacial does not show any climatic amelioration towards 15 000 yr b p a change in the diagram is noted that can only be interpreted as reflecting a larger expansion of a regional steppe cover this event also reported on three occasions in southeast france marks the beginning of the oldest dryas the climatic amelioration of ca 13 000 yr b p is far more pronounced here than anywhere else in europe whereas that at 10 000 yr b p is not so clearly marked this unexpected result may be accounted for by the fact that padul is the first continental site so far south and so near pleniglacial refuges to be known on the other hand this result is consistent with what is known from oceanic isotopic stratigraphy a quite new late glacial and holocene vegetational history is revealed characterized by the early appearance and dominance of quercus ilex oak forests of a southern type and the early occurrence of quercus suber and olea it is the first account of a complete history of the postglacial reafforestation in a region with a modern semi arid mediterranean climate from the palaeoclimatic point of view it shows that the hot and humid holocene optimum was attained slightly before 8000 yr b p and that the holocene climatic fluctuations were of but small amplitude

pollen based continental climate reconstructions at 6 and 21 ka a global synthesis subfossil pollen and plant macrofossil data derived from 14c dated sediment profiles can provide quantitative information on glacial and interglacial climates the data allow climate variables related to growing season warmth winter cold and plant available moisture to be reconstructed continental scale reconstructions have been made for the mid holocene mh around 6 ka and last glacial maximum lgm around 21 ka allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth assessment report ar5 of the intergovernmental panel on climate change the synthesis of the available mh and lgm climate reconstructions and their uncertainties obtained using modern analogue regression and model inversion techniques is presented for four temperature variables and two moisture variables reconstructions of the same variables based on surface pollen assemblages are shown to be accurate and unbiased reconstructed lgm and mh climate anomaly patterns are coherent consistent between variables and robust with respect to the choice of technique they support a conceptual model of the controls of late quaternary climate change whereby the first order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance

pleistocene and holocene fluvial development of the ecemis valley central anatolia turkey abstract the ecemis river developed during the pleistocene and holocene in the ecemis basin the basin developed because of tectonic movement on the ecemis fault which is west of the aladag mountains in the pleistocene glacial interglacial climate changes directly affected the regimes and discharges of rivers causing changes in river levels along the ecemis channel fluvial formations became extremely complicated when active tectonic movements accompanied the changes resulting from the climatic conditions the rivers embedded in their beds according to new local base levels in interglacials terraces formed due to interruptions in the cycle of morphological development along the ecemis river from the morphologic structure of these terraces and their positions in the ecemis valley two groups and five levels of terraces were defined in the ecemis valley modern terraces 1 5 m formed in the holocene while low terrace systems 5 10 m and 15 20 m and high terrace systems 30 40 and 70 80 m formed in the pleistocene

late glacial and holocene vegetational changes on the ulagan high mountain plateau altai mountains southern siberia three well dated pollen diagrams from 1985 m 2050 m and at the tree line at 2150 m asl show the vegetational succession in the central altai mountains since 16 cal ka bp pioneer vegetation after deglaciation was recorded first at the lowest site subsequently dense dry steppe vegetation developed coincident with the change from silt to organic sediments at the two lower sites but silt lasted longer at the highest site indicating the persistence of bare ground there forests of pinus sibirica pinus sylvestris picea obovata larix sibirica abies sibirica and betula pendula started to develop about 12 cal ka bp with the change to a warmer and wetter climate at the beginning of the holocene results indicate that the timberline did not rise above the highest site mesophilous dark coniferous forests were fully developed by 9 5 cal ka bp the role of abies and picea decreased by about 7 5 cal ka bp suggesting cooler climate after which the forests changed little until today the vegetational development in this portion of the central altai mountains is compatible with that described in neighbouring areas of the altai southern siberia mongolia and kazakhstan

paleoshoreline geomorphology of boon tsagaan nuur tsagaan nuur and orog nuur the valley of lakes mongolia abstract we conducted a preliminary study of paleoshoreline features associated with boon tsagaan nuur tsagaan nuur and orog nuur lakes located in the gobi altai transition zone of the valley of lakes dolina ozor which stretches from central to western mongolia the paleoshoreline features were first identified on radarsat satellite sar imagery we investigated the features during the 1998 field season of the joint mongolian russian american archaeological expedition to the gobi altai region we identified paleoshorelines of multiple elevations in the field which are considered to be relict beach ridges and wave cut terraces other paleolake landforms include spits and gilbert type deltas these landforms are complex large and well established implying that the paleolakes were stable for extended periods the reconstructed paleolakes cover extensive areas of the valley floor implying that hydrological and climatic conditions were very different in the past paleolake expansions may have occurred under a variety of circumstances one hypothesis is that the high lake stands occurred during the wetter period corresponding to the oxygen isotope stage 3 prior to the last glacial maximum lgm during the warmest early holocene and the late holocene or during all these periods if low evaporation rates due to lower temperatures glacier meltwater and possibly increased precipitation are important factors then the expansions may have occurred during the terminal late glacial period after the last glacial maximum the greatly expanded lakes in the gobi altai could have significantly affected the quaternary human demography and migration in the region

late quaternary lake level changes of lake el gygytgyn ne siberia abstract lake el gygytgyn is situated in a 3 6 ma old impact crater in northeastern siberia presented here is a reconstruction of the quaternary lake level history as derived from sediment cores from the southern lake shelf there a cliff like bench 10 m below the modern water level has been investigated deep water sediments on the shelf indicate high lake levels during a warm mid pleistocene period one period with low lake level prior to marine oxygen isotope stage mis 3 has been identified followed by a period of high lake level 10 m above present in the course of mis 2 the lake level dropped to 10 m at the end of mis 2 the bench was formed and coarse beach sedimentation occurred subsequently the lake level rose rapidly to the holocene level changes in water level are likely linked to climate variability during relatively temperate periods the lake becomes free of ice in summer strong wave actions transport sediment parallel to the coast and towards the outlet where the material tends to accumulate resulting in lake level rise during cold periods the perennial lake ice cover hampers any wave activity and pebble transport keeping the outlet open and causing the lake level to drop

holocene environmental changes in the ugii nuur basin mongolia in this study we investigate the holocene environmental evolution of the ugii nuur basin in the orkhon valley central mongolia in order to gain a better understanding of the climate and landscape dynamics of the steppe region in central asia we assess terrestrial and lake sediments using mineralogical geochemical and statistical techniques and provide absolute chronologies by radiocarbon datings and infra red stimulated luminescence datings including fading correction our findings and their discussion in a broader regional context show that there is a mid holocene climate optimum the shift towards warmer and wetter conditions involved changes from aeolian dynamics of sand mobilization to loess like sediment accumulation owing to the establishment of dust trapping vegetation between 4 and 2 8 ka bp we track a decline in moisture supply which is then followed by relatively humid conditions until today we infer that the region is sensitive to changes of the westerlies dynamics in addition we conclude that the late holocene was characterized by favorable climatic conditions that probably were an important prerequisite for the repetitive colonization of the orkhon valley throughout the last 3000 years

late weichselian valdaian and holocene vegetation and environmental history of the northern timan ridge european arctic russia abstract lake and peat deposits from the timan ridge arctic russia were pollen analysed reconstructing the vegetation history and paleoenvironment since the last glacial maximum lgm 20 18 000 years ago the sites studied are located inside the margins of a large paleolake of about 20 km 2 by us named lake timan this lake developed in the late weichselian more than 30 000 years after the deglaciation of this region and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment the lake was drained during the early holocene when the outlet rivers eroded the spillways a new generation of much smaller lakes formed during the holocene when the last remnants of buried glacier ice melted away causing the exposed floor of lake timan to subside since deglaciation the following regional vegetation development has been recorded 1 during the initial stage of lake timan the dominant vegetation was discontinuous steppe tundra with patches of snow bed vegetation 2 a dwarf shrub tundra established during the late weichselian interstadial allerod probably reflecting warmer and moister conditions 3 the younger dryas cooling is recognised by a reversal to steppe tundra and snowbeds on unstable mineral soils and higher palynological richness 4 soon after the transition into the holocene a birch forest established on the timan ridge 5 a cooling starting around 8200 cal years bp initiated the deforestation of the exposed hills in the most protected sites birch trees persisted until later than 4000 years ago reflecting a gradual development into the present treeless dwarf shrub tundra

evidence for high frequency cyclic fault activity from high resolution seismic reflection survey rukwa rift tanzania a high resolution seismic survey of the rukwa rift has imaged the upper 300 m of the pliocene holocene section the sediments are characterized by aggradational deposition in shallow lacustrine conditions that episodically dried out overall the reflection package expands northeastwards towards the lupa fault half graben bounding fault isopach maps for nine intervals 6 m to 65 m thick show four periods of marked expansion of the section towards the lupa fault interpreted to represent times of fault activity or infilling of fault created topography during the early stage of fault quiescence there are three periods of little or much reduced expansion interpreted to represent infilling of the accommodation space between the lake floor and the lake surface during periods of fault inactivity cyclicity of such high frequency has not been widely reported for faults which penetrate the crust the periods of activity show remarkably similar displacement patterns with no lateral migration of the main depocentre implying that seismic and aseismic slip has persistently clustered in the same parts of the fault identification of high frequency fault cyclicity has implications for sequence stratigraphy in tectonically active areas since there is a tendency to assume faults do not have cyclic effects on the scale of tens of thousands of years

co2 h2o and orbitally driven climate variability over central asia through the holocene small variations in earth s orbit have a direct impact on global climate with the greatest changes occurring over large land masses such as asia orbitally driven climate signals are therefore likely to be identifiable in climate proxy records derived from sediment sections in the continental interior proxy records derived from temperature dependent variables are also likely to display a signal due to temporal variability of atmospheric co2 and related climatic parameters such as water vapour content to determine the magnitude of climate anomalies associated with shortwave and longwave radiative forcing over asia a suite of numerical atmospheric simulations is performed that spans most of the holocene from 10 000 to 2500 years bp at 500 year intervals over central asia the amplitude of the summer winter seasonal cycle is greater than today in all simulations but exhibits two distinct maxima at 9000 and 6000 bp simulated precipitation and snow accumulation over central asia are markedly higher during the early mid holocene and are oscillatory exhibiting peaks at 8000 7500 and 4500 bp the atlantic and subboreal times respectively co2 h2o forcing and orbital forcing combine to drive temperature oscillations over central asia which in turn regulate relative humidity and changes in surface hydrology correlation between simulated results and proxy records from across asia suggest that co2 h2o and orbital forcing are dominant factors driving fluctuations of large scale central asian climate through the holocene

an early advance of glaciers on mount akdag sw turkey before the global last glacial maximum insights from cosmogenic nuclides and glacier modeling abstract for the first time in turkey we report an early advance of glaciers before the broadly defined global last glacial maximum lgm forty one moraine boulders from three glacial valleys on mount akdag 36 54 n 29 57 e 3016 m southwest coast of turkey were dated with cosmogenic 36 cl valleys on the north side of the mountain were filled with few km long glaciers that terminated at elevations of about 2000 m above sea level a s l the pre lgm glaciations reached their maximum positions 2150 m a s l by 35 1 2 5 ka ago 1 ka 1000 calendar years the glaciers readvanced during the global lgm and reached their farthest locations 2050 m a s l by around 21 7 1 2 ka ago later glaciers retreated and shortly stabilized during the lateglacial at around 15 1 0 9 ka ago using the glacier modeling and paleoclimate proxies from the eastern mediterranean we estimated that if temperatures during the lgm were 8 11 c colder than modern which is suggested by paleotemperature proxies from the region precipitation was up to two times more than that of today previous estimates on southwest coast of turkey indicate a similar precipitation value while central turkey requires drier conditions implying regional heterogeneity on lgm climates in turkey

reconciling diverse diatom based lake responses to climate change in four mountain lakes in the south carpathian mountains during the last 17 kyrs abstract climatic changes were studied using siliceous algae diatoms and chrysophyta stomatocysts analyses in four mountain lakes in the retezat mountains in the south carpathian mountains with the aim to search for synchrony in aquatic ecosystem responses according to the basal radiocarbon dating of the lake sediment cores these lakes were formed around 17 000 15 000 cal yr bp high resolution diatom analyses were carried out together with loss on ignition loi and biogenic silica bisi measurements on the lakes comparison of the proxy results suggests that despite the different slope aspect water depth and basin parameters diatom assemblage changes show clear synchrony the most remarkable changes in the aquatic ecosystems were observed around 6500 cal yr bp on the northern slope and around 6100 cal yr bp on the southern slope during the holocene evidences for sharp concomitant shifts were found between 9200 9000 and 3200 3000 cal yr bp in the siliceous algal communities on both slopes the late glacial holocene boundary was not pronounced in the shallow lakes but was significant in a deep lake the signs of a dry and bipartite younger dryas gs 1 were evident but floristic changes differed in the lakes principal component analyses explained very similar variances along the first and second axes for three lakes while the fourth lake lake bucura proved less sensitive to climate change due to the dominance of moss inhabiting diatom assemblages lake level changes have only been reconstructed on the basis of diatom life forms in one of the deep lakes lake gales high lake levels were inferred between 9300 9000 and 3000 1700 cal yr bp in addition to loi biogenic silica content bisi was measured on the sediments of the northern slope and pointed to different seasonal biological productivities increasing loi was often coupled with low bisi values

age palaeoenvironments and climatic significance of late pleistocene konya lake turkey abstract the konya basin a closed depression at the southern margin of the anatolian plateau contained a shallow but extensive lake during the late quaternary nearshore sands and gravels containing dreissena shells form prominent depositional terraces around the basin edges at elevations between 1005 and 1020 m and the highest has been dated at more than 30 000 yr b p the last major phase of limnic sedimentation occurred between 23 000 and 17 000 yr b p after which the lake fragmented into a number of subbasins or secondary depressions which evolved to become either marshes or playas a final expansion of these residual lakes has been dated to ca 11 000 yr b p in one secondary depression archaeological and other evidence indicate that only minor lake level fluctuations occurred during the holocene the dominant sedimentary process over the last 10 000 years has been alluviation at the basin margin the konya sequence confirms that the most recent period of high lake levels in the northern near east was of the last glacial age the palaeolakes of anatolia and iran were however more a product of reduced evaporation brought about by temperature depression than of changes in precipitation and thus belie their often used description as an indicator of pluvial climatic conditions

response of surface processes to climatic change in the dunefields and loess plateau of north china during the late quaternary this paper draws on recent optically stimulated luminescence osl dating to evaluate the long held assumption that dust accumulation rates in the loess plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time because both are controlled by the strength of the asian monsoons and also possibly because the dunefields are proximal loess sources the results show there is little evidence that high rates of loess accumulation coincided with well dated episodes of extensive dune activity in the mu us otindag and horqin dunefields at 11 8 ka and 1 0 ka explanations for the apparent lack of coupling include local variation in the trapping of dust and post depositional preservation of the loess and dune sediments in response to varying local environmental conditions in addition a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields the results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale the dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale but the timing of late quaternary dune activity along with a variety of other evidence indicates that moisture changes in many of the drylands of northern china may not be in phase with precipitation in core regions of the asian monsoons copyright 2011 john wiley sons ltd

high resolution sr isotopic evolution of black sea water during the holocene implications for reconnection with the global ocean abstract the 10 m thick holocene succession at core site m02 45 41 41 17 n 28 19 08 e 69 m water depth has key advantages for investigation of the sr isotopic evolution of the holocene black sea earlier studies have focussed on thinner successions and coquinas at the m02 45 site augmented by nearby core m05 03p 87sr 86sr determinations on mollusc shells extracted at mostly 10 20 cm depth increments provide a temporal resolution mostly

human influence upon sedimentation in llangorse lake wales palaeolimnological studies at llangorse lake wales constitute part of the british contribution to igcp project 158 the palaeohydrology of the temperate zone in the last 15000 years the lake has been adopted as the reference site for the south wales region under subproject 158b lake and mire environments and is located in the reference area for britain the severn basin results of biological physical and multielement chemical analyses on a 12 35 m livingstone core are presented and compared with previous analyses on short mackereth cores taken from two troughs in the lake basin human impact upon post glacial sedimentation is assessed with reference to sediment chemistry physical properties and sedimentation rates based on relative pollen 14c and 210pb dating vegetational history of the catchment is inferred from a pollen diagram for a section of the core from c 8 to 6 75 m depth in which evidence for human impact is first apparent water content loss on ignition and carbonate content are presented for the whole core density water content loss on ignition carbonates and elemental analyses of p ca mg k ti al fe and mn for the interval 6 75 and 8 25 m depth sedimentation rates were low during boreal and atlantic times c 9000 5000 bp rose significantly from the time of the elm decline estimated at 5000 bp and increased further at c 1800 bp when nekron muds were succeeded by deposition of silty clay inferred rates of erosion of soils from the catchment are discussed and related to sediment chemistry

interrelated continental sedimentary environments in the central iberian range spain facies characterization and main palaeoenvironmental changes during the holocene a complex holocene system in the central iberian range ne spain has been reconstructed on the basis of sediments recovered from cores and in situ observations small alluvial fans graded into a wide shallow lacustrine area anavieja lake that connected downstream with a carbonate fluvial system with associated vegetated zones the fluvial system was mainly characterized by the development of tufa barriers especially during the first part of the holocene that separated pools or small lakes oncolites detrital tufas calcarenites and marls were deposited in these pools adjacent vegetated areas were covered by macrophytes and were episodically reached by detrital tufa supplies indicating high flood stages high sedimentary rates existed in both the fluvial including the pools and vegetated areas suggesting that despite the common erosion of tufas a clear aggradating evolution existed by contrast very low sedimentary rates were registered in the anavieja lake all the environments but especially the vegetated areas registered the climate evolution during the holocene although the onset of the holocene was characterized by wide climate variability warm and humid conditions dominated during the first part and drier conditions during the second part a water level recovery seems to have been existed during the last millennium this is a good example of the potential of continental systems other than lakes to be useful for palaeoenvironmental and palaeoclimatic studies

holocene environmental changes in northern mongolia inferred from diatom and pollen records of peat sediment abstract the holocene paleoenvironment in nur sphagnum bog northern mongolia was reconstructed by diatom pollen analysis and measurement of chemical properties on a 3 7 m long peat boring sample development processes of peatland are well reflected in these multiproxy records showing that peat accumulation started as early as 9 ka cal bp and the present acidic peat bog was established no later than 6 ka cal bp synchronous trends in diatom and pollen assemblages revealed wetter climate in the early holocene and extensive drought in the mid late holocene centered at 5900 2800 cal bp as a result of temperature increase and low precipitation periods of shifts in proxy data were potentially correlated with other studies in not only mongolia and siberia but also the north atlantic ocean and the climatic periods at 8 4 and 2 8 ka cal bp were highly significant however responses to climate changes seem regionally varied in time and strength demonstrating that local differences in vegetation and orography greatly influence the balance of precipitation and evapotranspiration climate changes that coincided in time with the medieval climate anomaly and little ice age were observed as wetter 1200 980 cal bp and drier 370 240 cal bp conditions probably caused by meridional shifts of westerlies

geomagnetic secular variations in greece through the last 6000 years obtained from lake sediment studies summary geomagnetic declination and inclination secular variation curves have been constructed back to 6000 yr bp from palaeomagnetic measurements of sediments cored in lakes volvi trikhonis and begoritis greece they have been dated by palynological studies and by comparison with observatory and archaeomagnetic records radiocarbon ages are all affected by the old carbon factor cores from all three lakes contain a thin ash layer which we associate with the pompeii eruption of vesuvius in ad 79 averaged curves of secular variations of declination and inclination have been computed for the whole study the broader scale pattern of secular variations is basically similar to lake sediment records from the uk poland and switzerland though finer detail in the structure of some of the principal features is resolved

pollen recorded bioclimatic variations of the last 22 600 years retrieved from achit nuur core in the western mongolian plateau abstract this research focuses on the reconstructions of vegetation variations and the associated climate changes over the past 22 600 years based on pollen data of 91 samples obtained from achit nuur in the western part of the mongolian plateau the vegetation in the achit nuur area was forests in higher elevations and steppes in lower elevations from 22 600 to 13 200 cal bp the subsequent period from 13200 to 6400 cal bp was characterized by steppes in higher elevations and deserts in lower elevations followed by taiga expansion in high elevations in the following period from 6400 to 1600 cal bp the last 1600 years were characterized by high herb percentages pollen based reconstruction of the temperature showed that the achit area experienced cold conditions between 22 600 and 13 200 cal bp and mild conditions from 13 200 6400 cal bp with the past 5000 years being relatively warm the reconstructed precipitation suggests two wet periods 1 from 22 600 to 13 200 cal bp and 2 from 6400 to 1600 cal bp the two intervening dry periods are 1 from 13 200 6400 cal bp and 2 from 1600 to 0 cal bp

water depth affecting thaumarchaeol production in lake qinghai northeastern qinghai tibetan plateau implications for paleo lake levels and paleoclimate abstract archaeal glycerol dialkyl glycerol tetraethers gdgts are increasingly popular and versatile tool for palaeolimnology studies but their applications in paleohydrology are scarce especially for thaumarchaeol which is specific for the newly proposed phylum thaumarchaeota after investigating our published gdgt data of lake qinghai we found that both the concentration of thaumarchaeol and the relative abundance of thaumarchaeol to total archaeal gdgts thaum in core top sediments increased significantly with increasing water depth r 0 88 and 0 95 respectively with lower concentrations of 5 5 ng g in shallow areas water depth 10 m this is likely because that the producers of thaumarchaeol thaumarchaeota prefer living in the relative deeper zone in lacustrine systems where probably both competition of ammonium the substrate from other microbes and light intensity are low therefore we proposed that thaumarchaeol was mainly produced in situ and changes in thaum might reflect water depth variations in this closed basin lake the application of thaum as a water depth indicator in a holocene sediment sequence of core qh 2011 provided a high resolution relative lake level history of lake qinghai which resembles that inferred from the 13corg value obtained in the same core this supports the use of thaum as an indicator of lake water depth in paleohydrology studies especially for medium lakes moreover the records of the two independent proxies in core qh 2011 confirmed a shallow lake qinghai in the early holocene and a late holocene highstand highlighting the importance of local temperature and evaporation loss in controlling effective moisture in the arid semi arid region

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

influence of insolation and glaciation on atmospheric circulation in the north atlantic sector implications of general circulation model experiments for the late quaternary climatology of europe abstract atmospheric general circulation models have been used to simulate the sensitivity of regional climates to late quaternary changes in insolation ice sheets and atmospheric co 2 model results for full glacial conditions 18 ka show the atlantic westerly jet strengthened and shifted south a corresponding southward shift of the icelandic low and a strengthening and northward shift of the subtropical anticyclone sta a glacial anticyclone developed over the european ice sheet and cold dry conditions prevailed over much of europe the full glacial climate anomaly for the north atlantic sector is explained by a combination of low atmospheric co 2 reducing global surface temperatures and circulation changes caused by the ice sheets by the early holocene 9 ka the ice sheets were much reduced while the orbital anomaly was near its maximum producing mid continental summer warming and winter cooling and a reduced latitudinal temperature gradient in the northern hemisphere in both seasons the jet and the icelandic low were displaced to north of their present position producing strong onshore flow and mild wet winters in northern europe while the sta was also shifted northwards producing offshore flow and dry summers in the same region during the late glacial transition the effects of insolation and glaciation were antagonistic for some features of the circulation and synergistic for others the model results suggest palaeoclimatic hypotheses that could be directly tested by comparison with palaeoclimatic data mapped at a synoptic scale

late quaternary lake level changes and climates of australia abstract spatial and temporal patterns in lake level data from 38 sites in australia and papua new guinea provide a basis for reconstructing changes in water balance and atmospheric circulation during the past 30 000 years the reconstructions are consistent with hydrological changes inferred from pollen analysis and palaeowind directions inferred from dunes generally wetter conditions between 30 000 and 24 000 bp are consistent with a strong walker circulation with the sta near its present position general aridity at the glacial maximum until 12 000 bp with higher than present lake levels in the southeastern interior of australia implies that the southern margin of the subtropical anticyclone belt was expanded southward and the southern westerlies were correspondingly displaced this southward shift appears in all gcm simulations of the 18 000 bp climate and may be a result of the increased vigour of the northern hemisphere circulation a northward migration of the belt of high lake levels between 11 000 and 6000 bp suggests that the sta shifted back equatorward to north of its present position relaxation to modern conditions occurred after 6000 bp interrupted by an unexplained dry phase 6000 5000 bp in tasmania and queensland

climate proxies for the last 17 3 ka from lake hazar eastern anatolia extracted by independent component analysis of μ xrf data abstract the elemental composition of lake sediment cores is often the result of several independent processes in this study we attempt to extract statistically independent climate related signals from xrf multi element data of a core drilled from lake hazar in eastern anatolia using the independent component analysis ica method in addition we analysed ostracod shells for oxygen and carbon isotopes the ica method has advantages over traditional dimension reduction methods such as principal component analysis or factor analysis because it is based on maximal statistical independence rather than uncorrelatedness where independence is a stronger property the hz11 p03 core which represents the last 17 3 ka was recovered from lake hazar which at times formed the headwaters of the tigris applying the ica method we selected two out of six independent components by measuring distance correlation similarity we propose that one of the selected components can be read as a proxy for temperature and the other for precipitation in this region our results indicate that the region was relatively cold and wet during the late glacial between 17 3 and 14 8 ka bp and wet and warm during bolling allerod the lake level dropped below today s level during the younger dryas stadial 12 49 and 11 76 ka bp forming a marked hiatus in the core s stratigraphic record during the beginning of the holocene while precipitation values were high the temperature gradually increased until 8 ka bp between 8 and 5 ka bp the region was warm but extremely dry after 5 ka bp around 3 5 ka bp temperatures suddenly fell and three abrupt dry phases are observed around 3 5 ka and 2 8 ka and 1 8 ka bp

last glacial maximum climate of the former soviet union and mongolia reconstructed from pollen and plant macrofossil data an improved concept of the best analogues method was used to reconstruct the last glacial maximum lgm climate from a set of botanical records from the former soviet union and mongolia terrestrial pollen and macrofossil taxa were grouped into broad classes plant functional types pfts defined by the ecological and climatic parameters used in the biome1 model pft scores were then calibrated in terms of modern climate using 1245 surface pollen spectra from eurasia and north america in contrast to individual taxa which exhibit great variability and may not be present in the palaeoassemblages even in suitable climates pfts are more characteristic of the vegetation types the modified method thus allows climate reconstruction at time intervals with partial direct analogues of modern vegetation e g the lgm at 18 kbp mean temperatures were 20 29 degrees c colder than today in winter and 5 11 degrees c colder in summer in european russia and ukraine sites from western georgia show negative but moderate temperature anomalies compared to today 8 11 degrees c in january and 5 7 degrees c in july lgm winters were 7 15 degrees c colder and summers were 1 7 degrees c colder in siberia and mongolia annual precipitation sums were 50 750 mm lower than today across northern eurasia suggesting a weakening of the atlantic and pacific influences reconstructed drought index shows much drier lgm conditions in northern and mid latitude russia but similar to or slightly wetter than today around the black sea and in mongolia suggesting compensation of precipitation losses by lower than present evaporation

holocene glacier variability three case studies using an intermediate complexity climate model synthetic glacier length records are generated for the holocene epoch using a process based glacier model coupled to the intermediate complexity climate model ecbilt the glacier model consists of a massbalance component and an ice flow component the climate model is forced by the insolation change due to variations in the earth s orbital parameters we consider three glaciers ranging from maritime to continental at nigardsbreen southern norway the simulated long term trend in the annual mass balance is primarily determined by summer temperature with a smaller contribution from winter precipitation in the early holocene summers were warmer and winters wetter than today in the ecbilt simulation both signals seem consistent with proxy data the simulated glacier length shows a phase of rapid expansion during the mid holocene followed by more gradual growth at rhonegletscher the swiss alps ecbilt simulates warmer and wetter summers in the early holocene the temperature signal seemns realistic but proxy data and earlier modelling results are not conclusive with respect to the precipitation signal the implied glacier length shows a maximum extent at 3 5 kyr bp which seems unlikely this suggests that the simulated precipitation response is not realistic the simulated early holocene climate at abramov glacier kirghizia is characterized by high summer precipitation associated with a northward extension of the asian monsoon the precipitation signal reaches its maximum around 6 kyr bp which is consistent with the timing of the maximum in lake level data the simulated glacier length shows a pronounced postglacial maximum at the time of maximum monsoon intensity there is considerable centennial timescale variability in the simulated glacier length records these length variations are generated by internal climatic variability they are typically asynchronous among the three different glaciers ecbilt has reasonable skill in simulating the relative importance of temperature and precipitation as well as the seasonality of the forcing although the overall level of variability is underestimated length variations are shown to behave as a lagged moving average process with a glacier specific memory

paleoclimatic significance of lake level fluctuations in the lahontan basin abstract an energy flux balance model has been developed which treats evaporation as a function of air temperature surface water temperature precipitable water aloft the amount height and type of sky cover and the optical air mass the model has been used to estimate the mean historical evaporation rate for pyramid lake nevada using as input climatic data from the reno area averaged over the period 1950 1975 estimated and measured values of the mean annual evaporation rate were found to be in good agreement the model was used to simulate changes in the level the surface area and the volume of paleo lake lahontan in particular possible climatic states responsible for past high stands 1270 and 1330 m were investigated a conservative range of discharge values was used in the calculations results of the simulations indicate the fundamental importance of sky cover in the creation and destruction of large lake systems

lake levels and climate for the last 30 000 years in the fucino area abruzzo central italy a review abstract lake fucino was in a closed basin that was drained in 1875 a review of published data as well as new geological and geomorphological studies are used to define changes in lake level over the last 30 000 years the changes are summarized as follows 1 a general rise of level between 33 000 and 18 000 20 000 yr b p 2 a general lowering between 18 000 20 000 and 7500 6500 yr b p 3 a rise between 6000 5000 yr b p 4 a lowering between 5000 2800 yr b p 5 a rise between 2800 2300 yr b p 6 lower between 2300 1800 yr b p 7 very low levels in the 16th century and 8 a rise during the 1750 1861 period of the so called little ice age lake level fluctuations are attributed to climatic variations in particular there is a clear link between fluctuations and changes in seasonal insolation produced by the orbital parameters of the earth precession of the equinoxes and obliquity of the ecliptic and average annual rainfall the fluctuations of lake levels do not seem to have been influenced significantly by tectonic movements affecting the fucino plain or by karst drainage pits present along the periphery

mediterranean vegetation lake levels and palaeoclimate at the last glacial maximum the apparent conflict between pollen evidence for widespread artemisia steppe1 6 implying semi arid conditions and geomorphological evidence for high lake levels4 7 11 has produced controversy about the ice age palaeoclimate of the mediterranean region here we use a water balance model12 to predict catchment runoff and a biome model13 to predict vegetation type to reconstruct the palaeoenvironment around lake loannina a type locality for the northern mediterranean region we show that both sets of evidence are compatible with a summer dry winter wet regime with seasonal temperature anomalies similar to those predicted by atmospheric model simulations of the last glacial maximum14 18 the drying effect of the cold north atlantic ocean may have been counteracted in winter by increased storm frequency under a southward shifted jet stream as shown by several atmospheric models16 18

last glacial holocene paleoceanography of the black sea and marmara sea stable isotopic foraminiferal and coccolith evidence multi proxy data and radiocarbon dates from several key cores from the black sea and marmara sea document a complex paleoceanographic history for the last v30 000 yr the marmara sea was isolated from both the black sea and the aegean sea during glacial periods when global sea level lowering subaerially exposed the shallow sills at the straits of bosphorus and dardanelles i e lake stage and reconnected through both straits during interglacial periods when rise of global sea level breached the shallow sills i e gateway stage micropaleontological data show that during the lake stage the surface water masses in both the marmara sea and black sea became notably brackish however during the gateway stages there was a low salinity surface layer and normal marine water mass beneath two sapropel layers are identified in the marmara sea cores sapropels m2 and m1 were deposited between v29 5 and 23 5 ka and v10 5 and 6 0 ka respectively micropaleontological and stable isotopic data show that the surface water salinities were reduced considerably during the deposition of both sapropel layers m2 and m1 and calculation using planktonic foraminiferal transfer functions shows that sea surface temperatures were notably lower during these intervals the presence of fauna and flora with black sea affinities and the absence of mediterranean fauna and flora in sapropels m1 and m2 strongly suggest that communication existed with the black sea during these times a benthic foraminiferal oxygen index shows that the onset of suboxic conditions in the marmara sea rapidly followed the establishment of fully marine conditions at v11 10 5 ka and are attributed to black sea outflow into the marmara sea since 10 5 ka these suboxic conditions have persisted to the present the data discussed in this paper are completely at odds with the flood hypothesis of ryan et al 1997 and ryan and pitman 1999 crown copyright 2002 elsevier science b v all rights reserved

holocene sedimentology of hypersaline lake urmia northwestern iran abstract a limnogeological expedition examined the sedimentary record of lake urmia one of the world s largest saline lakes located in a tectonically active arid intermontane plateau in northwestern iran near the cradle of western civilization lake urmia resembles the great salt lake u s a in many respects of morphology water chemistry and sediments the present lake area is about 5000 km 2 shallow 8 12 m and a perennial sodium chloride sulfate system 22 salts high resolution 3 5 khz seismic profiles show morphological relicts from a desiccation playa phase buried below only a few meters of sediments from lacustral phases in places around the deeper areas the lake floor is not smooth but covered with mounds aligned in prevailing current directions these are erosional relicts rather than bioherms sediments comprise aragonite chemical precipitates fecal pellet sands detrital clayey muds thin aragonite crusts oolites various gypsum types and occurrences of dolomite in peripheral areas organic matter characteristic of the present shorelines is not preserved at depth in basinal areas piston cores up to 6 m long penetrated a holocene sequence of hypersaline facies with laminated aragonite fecal pellet muds and bottomed in a playa mudflat facies with central gypsiferous muds and marginal terrigenous to dolomitic muds preliminary radiocarbon and pollen analyses suggest a playa stage prior to 9000 yr b p with saline lake deposition in a cool arid climate from 9000 to 7500 yr b p higher energy facies prevailed in a shallow saline lake and since then present day saline environments have persisted with evidence of numerous second order water level fluctuations the preliminary results suggest a lake system out of phase with north african and some other middle eastern lakes

late quaternary lake level record from northern eurasia lake records from northern eurasia show regionally coherent patterns of changes during the late quaternary lakes peripheral to the scandinavian ice sheet were lower than those today but lakes in the mediterranean zone were high at the glacial maximum reflecting the dominance of glacial anticyclonic conditions in northern europe and a southward shift of the westerlies the influence of the glacial anticyclonic circulation attenuated through the late glacial period and the westerlies gradually shifted northward such that drier conditions south of the ice sheet were confined to a progressively narrower zone and the mediterranean became drier the early holocene shows a gradual shift to conditions wetter than present in central asia associated with the expanded asian monsoon and in the mediterranean in response to local monsoon type circulation there is no evidence of mid continental aridity in northern eurasia during the mid holocene in contrast the circum baltic region was drier reflecting the increased incidence of blocking anticyclones centered on scandinavia in summer there is a gradual transition to modern conditions after ca 5000 yr b p although these broad scale patterns are interrupted by shorter term fluctuations the long term trends in lake behavior show a clear response to changes in insolation and glaciation

hydrology in the sea of marmara during the last 23 ka implications for timing of black sea connections and sapropel deposition 1 sediments deposited under lacustrine and marine conditions in the sea of marmara hold a late quaternary record for water exchange between the black sea and the mediterranean sea here we report a multiproxy data set based on oxygen and strontium isotope results obtained from carbonate shells major and trace elements and specific organic biomarker measurements as well as a micropaleontological study from a 14c dated sediment core retrieved from the sea of marmara pronounced changes occurred in 18o and 87sr 86sr values at the fresh and marine water transition providing additional information in relation to micropaleontological data organic biomarker concentrations documented the marine origin of the sapropelic layer while changes in n alkane concentrations clearly indicated an enhanced contribution for organic matter of terrestrial origin before and after the event when compared with the black sea record the results suggest that the black sea was outflowing to the sea of marmara from the last glacial maximum until the warmer bolling allerod the first marine incursion in the sea of marmara occurred at 14 7 cal ka b p however salinification of the basin was gradual indicating that black sea freshwaters were still contributing to the marmara seawater budget after the younger dryas which is associated with a high input of organic matter of terrestrial origin both basins were disconnected resulting in a salinity increase in the sea of marmara the deposition of organic rich sapropel that followed was mainly related to enhanced primary productivity characterized by a reorganization of the phytoplankton population

european lakes as palaeohydrological and palaeoclimatic indicators abstract lakes in temperate regions have fluctuated in size on annual to millenial time scales changes in water level or depth can be reconstructed by applying geomorphic sedimentological and biostratigraphic methods to transects of sediment cores this systematic field based approach has been used at a number of sites in europe it is illustrated by reconstructions of water level changes in lakes from southern sweden these lakes have shown broadly synchronous changes during the holocene such synchronous changes in water levels at several sites in a region reflect climatic changes inferences about the mechanism of the climatic change depend on identifying both synchronous changes within a region and differences in the direction magnitude and timing of lake level changes between regions continental compilations of lake level data are therefore necessary detailed studies are not available from enough sites but the interpretation of already existing stratigraphic and biostratigraphic data in terms of lake level changes has greatly increased the number of sites available for a continental scale synthesis in europe this eclectic literature based approach is illustrated with examples from southern europe lakes in the mediterranean region were high around the glacial maximum and again somtime during the first half of the holocene in the western mediterranean the peak of late glacial aridity occurred at 15 000 16 000 bp and the lakes were already high again by 12 000 bp in the east maximum late glacial aridity occurred between 13 000 and 11 000 bp and there was a gradual return to wetter climates during the early holocene such that 9000 bp was more arid than 6000 bp most lakes in the mediterranean region were high at 6000 bp the transition to arid conditions after 5000 bp occurred abruptly in the west and more gradually in the east the lakes of southern sweden indicate drier climates in the early holocene ca 9000 bp more effective moisture between 8000 and 6000 bp increased aridity between 5500 and 3500 bp and increased effective moisture again during the last 3000 years the history of lake level changes in southern sweden and the mediterranean region can be partially explained in terms of changes in the direct effects of insolation and in the strength and position of the westerlies and of the subtropical high pressure cell during the late quaternary

holocene climate variations in the altai mountains and the surrounding areas a synthesis of pollen records abstract based on pollen data from 30 sequences reviewed here we reconstruct the spatial and temporal variations in temperature and in aridity that occurred during the holocene in the altai mountains and the surrounding areas i e the examined area the synthesized regionally averaged temperature index curves from low elevation regions show that the climate was consistently warming from 12 000 to 9000 cal yr bp and has experienced a gradual cooling trend since 9000 cal yr bp it means that the holocene temperature trend in low elevation regions of the examined area has sensitively responded to variations in the total solar irradiance the synthesized regionally averaged aridity index curve exhibits a persistent wetting trend during the holocene in low elevation regions the deduced holocene precipitation index variations suggest that the holocene wetting trend resulted from a combined effect of temperature decreasing and precipitation increasing the holocene precipitation increase seems to be associated with the holocene amo like i e atlantic centennial oscillations events in the north atlantic ocean however the early holocene variations of temperature and aridity in high elevation regions were significantly deviated from the variations in low elevation regions and this deviation was probably a result of permafrost thawing at higher elevations

seismic stratigraphy of late quaternary deposits from the southwestern black sea shelf evidence for non catastrophic variations in sea level during the last 10 000 yr abstract detailed interpretation of single channel seismic reflection and huntec deep tow boomer and sparker profiles demonstrates that the southwestern black sea shelf formed by a protracted shelf edge progradation since the miocene pliocene five seismic stratigraphic units are recognized unit 1 represents the last phase of the progradational history and was deposited during the last glacial lowstand and holocene it is divided into four subunits subunit 1a is interpreted as a lowstand systems tract 1b and 1c are interpreted as a transgressive systems tract and subunit 1d is interpreted as a highstand systems tract the lowstand systems tract deposits consist of overlapping and seaward prograding shelf edge wedges deposited during the lowstand and the subsequent initial rise of sea level these shelf edge wedges are best developed along the westernmost and easternmost segments of the study area off the mouths of rivers the transgressive systems tract deposits consist of a set of shingled shore parallel back stepping parasequences deposited during a phase of relatively rapid sea level rise and include a number of prograded sediment bodies including barrier islands beach deposits and thin veneers of seismically transparent muds showing onlap onto the flanks of older sedimentary features a number of radiocarbon dates from gravity cores show that the sedimentary architecture of unit 1 contain a detailed sedimentary record for the post glacial sea level rise along the southwestern black sea shelf these data do not support the catastrophic refilling of the black sea by waters from the mediterranean sea at 7 1 ka postulated by ryan pitman major shimkus maskalenko jones dimitrov gorur sakinc yuce mar geol 138 1997 119 126 ryan pitman touchstone book 1999 319 pp and ballard coleman rosenberg mar geol 170 2000 253 261

interaction of burial history and diagenesis of the upper cretaceous frontier formation moxa arch green river basin wyoming abstract low permeability sandstones of the frontier formation produce gas from reservoirs along the south plunging moxa arch in the green river basin southwestern wyoming petrographic examination of 247 frontier thin sections indicates that the main causes of low porosity and permeability in these sublitharenites and litharenites are compaction and cementation by quartz calcite and clay minerals major differences in burial history between the northern and southern ends of the arch have resulted in an average of 5 quartz cement in frontier sandstones at the north end compared with 13 at the south end burial histories of four wells along the north south trend of the moxa arch and one well off the arch in the deep green river basin were reconstructed using stratigraphic data from well logs uplift and erosion events incorporated into the burial history curves occurred during the late cretaceous at the end of the cretaceous and from the oligocene to the present modern geothermal gradients of 1 7 to 2 0 f 100ft 3 1 to 3 7 c 100 m were used to model thermal maturity second frontier sandstone on the la barge platform at the northern end of the arch t28n r113w has a calculated time temperature index tti value of 30 compared with a tti of 334 in henry field at the southern end of the arch t13n r113w second frontier sandstone in the deep basin well t22n r106w has a tti value of 3079 in the five wells for which tti was calculated an excellent correlation r 0 95 exists between thermal maturity of the sandstone log tti and average volume of quartz cement frontier sandstones at the southern end of the moxa arch and in the basin were buried to greater depths and exposed to higher temperatures than those at the northern end so they experienced more stylolitization and intergranular pressure solution of chert thereby liberating more silica for quartz cement however tti is not a good predictor of reservoir quality because porosity and permeability in frontier sandstones are controlled by many other variables in addition to quartz cement volume

holocene moisture evolution across the mongolian plateau and its surrounding areas a synthesis of climatic records abstract based on the review of 26 high standard holocene climatic reconstructions mainly pollen based from the mongolian plateau and its surrounding areas temporal and spatial patterns of the holocene moisture evolution are synthesized the regionally averaged moisture history from the summer monsoon influenced semiarid belt in china i e region a demonstrates that the moisture index curve is broadly in agreement with the synthesized east asian monsoon strength curve both following the general trend of the west tropical pacific sst that is in turn the delayed response to the northern hemispheric summer solar insolation the regionally averaged moisture indices from the winter monsoon dominated southern siberia including lake baikal area and the altai mountains i e region b exhibit a general declining trends since 10 6 9 6 cal kyr bp being largely consistent with the trends of the annual precipitation and the warm season temperature in the russian plain the consistency might be attributable to the holocene declining trend of the warm season temperature in north atlantic region the predominant feature of the regionally averaged moisture index from the westerlies affected northern xinjiang i e region c is a persistent increasing trend since 8 cal kyr bp the wetting trend of northern xinjiang during the past 8000 years might be attributable to the increasing trend of winter insolation and to the associated increasing trend of cold season temperature in northwestern europe the chronological correspondences between dry phases and warm intervals in the arid areas of the mongolian plateau i e northern mongolian plateau within mongolia and southern mongolian plateau within china region d lend a support to the proposal that the mid holocene dry phase was most likely the result of mid holocene high warm season temperature

paleoclimatic estimates from water and energy budgets of east african lakes abstract the turkana nakuru elmenteita and naivasha basins in the rift valley of east africa experienced high water levels during the period of 10 000 7000 yr b p analyses of the modern hydrologic and energy budgets for these basins along with that of lake victoria were used to infer the amount of precipitation that would have been required to maintain the enlarged paleolakes of the early holocene precipitation must have been at least 150 300 mm yr 15 to 35 above the modern average the precipitation estimates were fairly consistent among the various basins but no quantitative estimate was made for the additional precipitation required to account for overflow from the rift valley lake basins discharge from the lake victoria basin around 1880 a d was considerably above the more recent average and the increased discharge into the white nile for that period might have been similar to that of the early holocene a sensitivity analysis showed that temperature changes were probably not too important for changing the hydrologic energy budget changes of albedo bowen ratio and cloudiness were likely to have been of greater importance

comparison of modeled and reconstructed changes in forest cover through the past 8000 years eurasian perspective reproducing the tree cover changes throughout the holocene is a challenge for land surface atmosphere models here results of a transient holocene simulation of the coupled climate carbon cycle model climber2 lpj driven by changes in orbital forcing are compared with pollen data and pollen based reconstructions for several regions of eurasia in terms of changes in tree fraction the decline in tr ee fraction in the high latitudes suggested by data and model simulations is driven by a decrease in summer temperature over the holocene the cooler and drier tr end at the eastern side of the eurasian continent in mongolia and china also led to a decrease in tree cover in both model and data in contrast the holocene trend towards a cooler climate in the continental interior kazakhstan is accompanied by an increase in woody cover ther e a relatively small reduction in precipitation was likely compensated by lower evapotranspiration in comparison to the monsoon affected regions in general the model data comparison demonstrates that climate driven changes during the holocene result in a non homogeneous pattern of tree cover change across the eurasian continent for the eifel region in germany the model suggests a relatively moist and cool climate and dense tree cover the holzmaar pollen r ecord agrees with the model for the intervals 8 3 ka and 1 7 1 3 ka bp but suggests great reduction of the tree cover 3 2 ka and after 1 3 ka bp when highly developed settlements and agriculture spread in the region

late glacial and holocene vegetational history of the altai mountains southwestern tuva republic siberia two lakes of glacial origin grusha at 2413 m and akkol at 2204 m are located on a broad high mountain plateau on the dry eastern end of the russian altai mountains in the republic of tuva just north of mongolia the present vegetation of the area is an open high mountain tundra steppe mosaic with patches of larix and pinus sibirica forests on north facing slopes 30 km northwest of the lakes alpine meadows occur near streams and snow patches pollen diagrams and radiocarbon dates 16 for grusha and 12 for akkol were used to reconstruct the vegetational history since the last glaciation the core from grusha contains about 50 cm of late glacial sediment of relatively low organic content mostly correlated with the younger dryas episode because of the high percentages of artemisia gramineae and chenopodiaceae along with a diversity of non arboreal pollen types indicating tundra steppe and meadow steppe in the earliest holocene starting with increased organic matter at about 195 cm 12 000 cal yr bp the artemisia gramineae chenopodiaceae pollen assemblage continued along with an increase in shrub betula but without the diversity of minor non arboreal types the interpretation of dry and warm climate at this time is supported by the unconformity at akkol implying a dried lake then after about 1000 years the increase of pinus sibirica p sylvestris picea obovata and abies sibirica suggests that forests developed in response to increased humidity first at the higher elevation grusha and then at akkol after about 6000 cal yr bp the role of forests decreased sharply in the area the picea and abies components almost disappeared as they did also in more westerly areas of the altai mountains steppe elements increased along with alpine herbs especially after 2000 cal yr bp as a result of cooling or increased aridity as well as probable human activity correlation of the vegetation sequence for the tuva sites with those to the west in the central altai mountains indicates that the late glacial open landscapes persisted in the earliest holocene but then were invaded by coniferous forests as a result of increased moisture and temperature associated with atlantic storm systems as well as with insolation enhanced asian monsoon cooling and drying after about 6000 cal yr bp brought the decline of abies and picea and the expansion of tundra steppe

vegetation changes and associated climatic changes in the southern altai mountains within china during the holocene the location of the altai mountains at the limits of both the pacific and atlantic influences implies that this mountain range is an important climatic boundary based on pollen data of 188 samples

glaciations and paleoclimate of mount erciyes central turkey since the last glacial maximum inferred from 36cl cosmogenic dating and glacier modeling abstract forty four boulders from moraines in two glacial valleys of mount erciyes 38 53 n 35 45 e 3917 m central turkey dated with cosmogenic chlorine 36 36cl indicate four periods of glacial activity in the past 22 ka 1 ka 1000 calendar years last glacial maximum lgm glaciers were the most extensive reaching 6 km in length and descending to an altitude of 2150 m above sea level these glaciers started retreating 21 3 0 9 ka 1 ago they readvanced and retreated by 14 6 1 2 ka ago lateglacial and again by 9 3 0 5 ka ago early holocene the latest advance took place 3 8 0 4 ka ago late holocene using glacier modeling together with paleoclimate proxy data from the region we reconstructed the paleoclimate at these four discrete times the results show that lgm climate was 8 11 c colder than today and moisture levels were somewhat similar to modern values with a range between 20 more and 25 less than today the analysis of lateglacial advance suggests that the climate was colder by 4 5 6 4 c based on up to 1 5 times wetter conditions the early holocene was 2 1 4 9 c colder and up to twice as wet as today while the late holocene was 2 4 3 c colder and its precipitation amounts approached to similar conditions as today our paleoclimate reconstructions show a general trend of warming for the last 22 ka and an increase of moisture until early holocene and a decrease after that time the recent glacier terminates at 3450 m on the northwest side of the mountain it is a remnant from the last advance possibly during the little ice age repeated measurements of glacier length between 1902 and 2008 reveal a retreat rate of 4 2 m per year which corresponds to a warming rate of 0 9 1 2 c per century