vegetation and environmental changes in northern anatolia between 134 and 119 ka recorded in black sea sediments this multiproxy study on se black sea sediments provides the first detailed reconstruction of vegetation and environmental history of northern anatolia between 134 and 119 ka here the glacial interglacial transition is characterized by several short lived alternating cold and warm events preceding a meltwater pulse 130 4 131 7 ka the latter is reconstructed as a cold arid period correlated to heinrich event 11 the initial warming is evidenced at 130 4 ka by increased primary productivity in the black sea disappearance of ice rafted detritus and spreading of oaks in anatolia a younger dryas type event is not identifiable the eemian vegetation succession corresponds to the main climatic phases in europe i the quercus juniperus phase 128 7 126 4 ka indicates a dry continental climate ii the ostrya corylus quercus carpinus phase 126 4 122 9 ka suggests warm summers mild winters and high year round precipitation iii the fagus carpinus phase 122 9 119 5 ka indicates cooling and high precipitation and iv increasing pinus at 121 ka marks the onset of cooler drier conditions generally pollen reconstructions suggest altitudinal latitudinal migrations of vegetation belts in northern anatolia during the eemian caused by increased transport of moisture the evidence for the wide distribution of fagus around the black sea contrasts with the european records and is likely related to climatic and genetic factors

paravani a puzzling lake in the south caucasus abstract sediments of lake paravani the largest natural lake in the south caucasus were analysed to reconstruct the millennial history of the environment pollen analysis previously undertaken on the first core retrieved in the middle of the lake revealed a vegetation history for the last 12 millennia as part of the present study a new core was taken from the north western part of the lake pollen analysis was performed on this new core with the same methodology as for the previous one a sedimentological and geochemical analysis was also conducted on both cores in order to gain an understanding of the dynamics of erosion in the catchment area in response to landscape modifications the results show that the sediment deposits within lake paravani yield rather complex and puzzle like palaeoecological records despite the differences between the two records correlations have been made that are supported by the 14c dates by combining all of the data from both cores it was finally possible to reconstruct the puzzle of the environmental history recounted by the lake paravani sediments this reconstructed history is composed of four main phases 1 a steppic environment marked by pronounced erosion processes from 12 000 to 10 000 cal bp 2 a transition phase characterized by the expansion of grasses poaceae from 10 000 to 9 8 000 cal bp 3 a more forested phase from 9 8 000 to 2 000 cal bp during which the erosion fluxes decreased and 4 a decline in tree cover probably due to human activities over the last 2 millennia

quantifying climatic change through the last glacial interglacial transition based on lake isotope palaeohydrology from central turkey questions remain as to the nature of climatic change through the last glacial interglacial transition in the eastern mediterranean region particularly the relative contribution of evaporation and precipitation to regional water balance here changes in oxygen isotope values through this time period from eski acigol a crater lake in central turkey are investigated using hydrological and isotope mass balance models these allow changes in evaporation and precipitation to be quantified and their relative importance evaluated we show that it is the volumetric flux rate of water passing through the lake system and not the precipitation to evaporation ratio per se which controlled the stable isotope record in eski acigol early holocene precipitation is shown to be much greater than that during both the latter part of the last glaciation and the present day we test these calculated values against other records in the same region firstly with other lake records in anatolia the konya basin and lake van and secondly with isotope inferred palaeo precipitation data from soreq cave in israel this reveals a contrast between pre and post lgm precipitation values in turkey wetter and drier respectively and also suggests that during the last glacial interglacial transition there was a more marked precipitation gradient than at present between northern interior and southern coastal parts of the eastern mediterranean region

the tertiary structural and thermal evolution of the central alps compressional and extensional structures in an orogenic belt the western alpine arc has been created during the cretaceous and the tertiary orogenies the interference patterns of the tertiary structures suggest their formation during continental collision of the european and the adriatic plates with an accompanying anticlockwise rotation of the adriatic indenter extensional structures are mainly related to ductile deformation by simple shear these structures developed at a deep tectonic level in granitic crustal rocks at depths in excess of 10 km in the early palaeogene period of the tertiary orogeny the main tertiary nappe emplacement resulted from a nw thrusting of the austroalpine penninic and helvetic nappes heating of the deep zone of the upper cretaceous and tertiary nappe stack by geothermal heat flow is responsible for the tertiary regional metamorphism reaching amphibolite facies conditions in the lepontine gneiss dome geothermal gradient 25 c km the tertiary thrusting occurred mainly during prograde metamorphic conditions with creation of a penetrative nw se oriented stretching lineation xi finite extension parallel to the direction of simple shear earliest cooling after the culmination of the tertiary metamorphism some 38 ma ago is recorded by the cooling curves of the monte rosa and mischabel nappes to the west and the suretta nappe to the east of the lepontine gneiss dome the onset of dextral transpression with a strong extension parallel to the mountain belt and the oldest s vergent backfolding took place some 35 to 30 ma ago during retrograde amphibolite facies conditions and before the intrusion of the oligocene dikes north of the periadriatic line the main updoming of the lepontine gneiss dome started some 32 30 ma ago with the intrusion of the bergell tonalites and granodiorites concomitant with s vergent backfolding and backthrusting and dextral strike slip movements along the tonale and canavese lines argand s insubric phase subsequently the center of main updoming migrated slowly to the west reaching the simplon region some 20 ma ago this was contemporaneous with the westward migration of the adriatic indenter between 20 ma and the present the western aar massif toce culmination was the center of strong uplift the youngest s vergent backfolds the glishorn anticline and the berisal syncline fold the 12 ma rb sr biotite isochron and are cut by the 11 ma old rhone simplon line the discrete rhone simplon line represents a late retrograde manifestation in the preexisting ductile simplon shear zone this fault zone is still active today the oligocene neogene dextral transpression and extension in the simplon area were concurrent with thrusting to the northwest of the helvetic nappes the prealpes 35 15 ma and with the jura thin skinned thrust 11 3 ma it was also contemporaneous with thrusting to the south of the bergamasc 35 5 ma and milan thrusts 16 5 ma the oligocene neogene dextral transpression in the central alps is of the same age as the thrusting to the west and southwest in the external french part and to the east in the internal italian part of the alpine arc of the western alps

seasonality of holocene hydroclimate in the eastern mediterranean reconstructed using the oxygen isotope composition of carbonates and diatoms from lake nar central turkey a positive shift in the oxygen isotope composition 18o of lake carbonates in the eastern mediterranean from the early to late holocene is usually interpreted as a change to drier reduced p e conditions however it has also been suggested that changes in the seasonality of precipitation could explain these trends here holocene records of 18o from both carbonates and diatom silica from lake nar in central turkey provide insights into palaeoseasonality we show how 18olakewater the difference between spring and summer reconstructed 18olakewater was minimal in the early holocene and for most of the last millennium but was greater at other times for example between 4 100 1 600 years bp we suggest that increased 18olakewater could have been the result of relatively more spring summer evaporation amplified by a decline in lake level in terms of change in annual mean 18o isotope mass balance modelling shows that this can be influenced by changes in seasonal p e as well as inter annual p e but lake level falls inferred from other proxies confirm there was a mid holocene transition to drier climatic conditions in central turkey

stable isotope records of late quaternary climate and hydrology from mediterranean lakes the isomed synthesis lake isotope records can be used to assess the spatial coherency of late quaternary climate change across the circum mediterranean region we place modern and palaeo data within a simple conceptual lake response model to show that the isotope hydrology of most mediterranean lakes has been influenced strongly by water balance even in those systems that are chemically dilute i e freshwater 18o data on biogenic and endogenic carbonates from 24 lake basins are used to reconstruct multi millennial scale trends since the lgm while it is difficult to make direct comparisons between lake records in terms of single climatic parameters coherent regional isotopic trends can be identified during glacial times mediterranean lakes deposited carbonates isotopically heavier in 18o compared to the holocene partly due to source area effects isotopic enrichment was most marked during intervals corresponding to the h1 and younger dryas events confirming that late pleistocene cold stages in the north atlantic region were marked by aridity around much of the mediterranean almost all mediterranean lake records shifted to more depleted isotopic values during the last glacial interglacial transition lgit this shift is the reverse of the trend which characterised the same transition in lakes from northern and central europe and suggests that temperature changes were not an important direct driver of mediterranean lake isotopic records over glacial interglacial timescales in the early holocene many lakes in the eastern part of the region were more depleted isotopically than in recent millennia this corresponds with marine sapropel formation both chronologically and geographically and implies that increases in local rainfall contributed significantly to the creation of a freshwater lid and anoxia in the east mediterranean sea in contrast no such pattern is currently apparent from lake isotope records from the west mediterranean suggesting a possible nw se contrast in climate history during the holocene

surface deformation induced by present day ice melting in svalbard summary the vertical movement of the earth s surface is the result of a number of internal processes in the solid earth tidal forces and mass redistribution in the atmosphere oceans terrestrial hydrosphere and cryosphere close to ice sheets and glaciers the changes in the ice loads can induce large vertical motions at intraseasonal to secular timescales the global positioning system gps and very long baseline interferometry vlbi antennas in ny a u lesund svalbard that started observations in 1991 and 1995 respectively observe vertical uplift rates on the order of 8 2m m yr 1 which are considerably larger than those predicted by postglacial rebound pgr models order 2 mm yr 1 the observations also indicate increased uplift rates starting some time in 2000 a local gps campaign network that has been reoccupied annually since 1998 reveals a tilting away from the neighbouring glaciers the svalbard glaciers have been undergoing melting and retreat during the last century with increased melting since about 2000 we compared the observed vertical motion to the motion predicted by loading models using a detailed ice model with annual time resolution as forcing the model predictions correlate well with the observations both with respect to the interannual variations and the spatial pattern of long term trends the regression coefficients for predicted and observed interannual variations in height is 1 08 0 38 whereas the regression coefficient for the predicted and observed spatial pattern turns out to be 1 26 0 42 estimates of the predicted secular trend in height due to pgr and present day melting are on the order of 4 8 0 3 mm yr 1 and thus smaller than the observed secular trend in height this discrepancy between predictions and observations is likely caused by the sum of errors in the secular rates determined from observations due to technique dependent large scale offsets and incomplete or erroneous models unaccounted tectonic vertical motion errors in the ice load history scale errors in the viscoelastic pgr models and the elastic models for present day melting

thermal and structural evolution of the external western alps insights from u th sm he thermochronology and rscm thermometry in the aiguilles rouges mont blanc massifs in the western alps the external crystalline massifs ecm are key places to investigate the kinematics and thermal structure of a collisional crustal wedge as their paleo brittle ductile transition is now exhumed at the surface new u th sm he data on zircon and new raman spectroscopy on carbonaceous material rscm data from the aiguilles rouges and the mont blanc massifs coupled to hefty thermal modeling constrain the thermal evolution and exhumation of the massifs in the cover of the aiguilles rouges massif we found that the maximal temperature was about 320 c 25 c close to the maximal temperature reached in the cover of the mont blanc massif 350 c 25 c we show that after a fast heating period the thermal peak lasted 10 15 myrs in the mont blanc massif and probably 5 10 myrs in the aiguilles rouges massif this thermal peak is synchronous with crustal shortening documented in the basement u th sm he data and thermal modeling point toward a coeval cooling of both massifs like other ecm at around 18 ma 1 ma this cooling was related to an exhumation due to the initiation of frontal crustal ramps below the ecm quite synchronously along the western alps arc

determining the timing of formation of the rawil depression in the helvetic alps by palaeomagnetic and structural methods determining the timing of formation of the rawil depression in the helvetic alps with the use of paleomagnetic and structural methods

evidence of lateglacial and holocene climatic change and human impact in eastern anatolia high resolution pollen charcoal isotopic and geochemical records from the laminated sediments of lake van turkey annually laminated sediments from lake van spanning about 13000 varve years were sampled for stable isotopic geochemical pollen and charcoal analyses in order to find evidence of past regional climatic changes and human impact in the semi arid region of eastern anatolia turkey the lateglacial period was cold and dry with steppe vegetation and saline lake water during the younger dryas the lake level dropped dramatically and the vegetation turned to a semi desert geochemical and isotopic records indicate a strong increase in moisture at the onset of the holocene and artemisia chenopod steppes were partly replaced by grass steppe and pistachio scrub a delay of about 3000 years in the expansion of deciduous oak woodlands and high steppe fire frequencies suggest dry spring and summer weather during the early holocene at 8200 yr bp a shift in the regional climate regime facilitated the transport of more moisture into the interior areas of the taurus mountains and caused a change in the seasonal distribution of precipitation the steppe forests dominated by quercus advanced and reached their maximum extention at about 6200 yr bp all the proxy data indicate optimum climatic conditions low water salinity and high lake level between 6200 and 4000 yr bp after 4000 yr bp aridity increased again and the modern climatic situation was established human impact in the catchment of lake van started at 3800 yr bp and was intensified during the last 600 years

climatic and human controls on the late holocene fire history of northern israel article i nfo article history received 5 april 2013 available online 27 august 2013 long term fire histories provide insight into the effects of climate ecology and humans on fire activity they can be generated using accumulation rates of charcoal and soot black carbon inlacustrine sediments this study uses both charcoal and black carbon and other paleoclimate indicators from lake kinneret sea of galilee israel to reconstruct late holocene variations in biomass burning and aridity we compare the fire history data with a re gional biomass burning reconstruction from 18 different charcoal records and with pollen climate and popula tion data to decipher therelativeimpacts of regional climate vegetation changes and human activity on fire we showalong termdecline in fireactivityoverthepast3070 years fromhighbiomassburning 3070 1750 cal yr bp to significantly lower levels after 1750 cal yr bp human modification of the landscape e g forest clearing agriculture settlement expansion and early industry in periods of low to moderate precipitation appears to have been the greatest cause of high biomass burning during the late holocene in southern levant while wetter climate apparently reduced fire activity during periods of both low and high human activity

nappe geometry in the western swiss alps abstract detailed geological mapping during the last 20 years in the western swiss alps has shown clearly that most of the lower basement nappes are fold nappes possessing normal and inverted limbs moreover their cores are made of strongly deformed gneisses indicating that important ductile strain took place during the formation of the fold nappes it is therefore probably wrong to imagine deep basement nappes as rigid slices as often actually claimed especially when interpreting seismic profiles true brittle type thrust nappes involving basement rocks only occur in the internal and upper parts of the belt cover nappes on the contrary are in most parts of the alpine belt thrust sheets following more or less the rules of thin skinned tectonics many basement fold nappes lost part of their sedimentary cover during or just before their formation by decollement along ductile horizons the result is that many cover thrust nappes in the external part of the alps are directly related to their original basement fold nappes

geochronological evidence for continuous exhumation through the ductile brittle transition along a crustal scale low angle normal fault simplon fault zone central alps 1 major low angle normal faults juxtapose different structural levels of the crust that record both brittle and ductile deformation field relationships alone cannot establish whether these different responses to deformation represent 1 parts of a single process of exhumation along the detachment or 2 two separate events with the later more discrete brittle detachment exhuming a fossil ductile shear zone from depth these two general models are critically assessed for the low angle normal simplon fault zone sfz in the central alps the sfz shows a spatial transition from a broad ductile mylonitic shear zone to a discrete brittle detachment with identical kinematics the age of the ductile shear zone and ductile brittle transition is controversial we present a detailed geochronological study based on fission track 40ar 39ar and rb sr microsampling dating coupled with structural petrological and chemical analyses that provides tight constraints on sfz timing discontinuous mineral cooling ages over a broad range of temperatures across the fault zone argue for fault activity between 20 and 3 ma on the basis of synkinematic white mica in low temperature shear zones and necks of foliation boudinage the brittle ductile transition in the footwall could be dated at 14 5 10 ma overall the data presented here are consistent with a continuous transition from ductile shearing to a more localized zone of brittle deformation within the same geological framework over a period of 15 ma the sfz is therefore an example of a telescoped crustal section within a single major low angle fault involving a continuous period of exhumation rather than a two stage structure

late quaternary paleoclimate in the eastern mediterranean region from stable isotope analysis of speleothems at soreq cave israel abstract the eastern mediterranean continental paleoclimate during the past 25 000 years was determined by a high resolution petrographic stable isotopic and age study of speleothems from soreq cave israel 18o 13c trends indicate that all speleothems older than 7000 yr formed under conditions that differ from those of today the period from 25 000 to 17 000 yr b p was characterized by the highest 18o and 13c values which indicate deposition at temperatures of 12 16 c annual rainfall of 300 450 mm and vegetation typical of a mixed c3 c4type from 17 000 to 10 000 yr b p deglaciation in northern europe 18o values dropped progressively correlative with warming 2 3 c and a gradual increase in precipitation a simultaneous decrease in 13c gives a range expected for c3 type vegetation this period also shows significant 18o and 13c spikes which are correlatable with global events e g heinrich events and the younger dryas stade the speleothems that grew between 10 000 and 7000 yr b p have a unique petrography showing irregular thin laminae of various colors and much detritus they have the lowest 18o corresponding to 1000 mm rain coupled with the highest 13c caused by flooding events which stripped the soil cover from 7000 to 1000 yr b p conditions became closer to those of today this study demonstrates that global events which were recognized in northern europe and north africa are also evident in the eastern mediterranean and are reflected principally by large changes in the rainfall rate

dating of deformation phases using k ar and 40ar 39ar techniques results from the northern apennines abstract paleozoic to oligocene metasedimentary rocks present in the alpi apuane region of the northern apennines italy have been sequentially deformed during a tertiary progressive deformation in an attempt to date the individual deformation episodes over 50 conventional k ar and 1140 ar 39ar incremental gas release analyses have been carried out on fine grained white micas separated from samples whose structural settings were well known mineralogy x ray diffractometry and thin section analyses indicate that the constituent muscovite and phengite formed under metamorphic conditions of 3 4 kbars and 300 400 c during all deformational phases pre existing micas were variably crenulated during each subsequent deformational phase both k ar and 40ar 39ar analyses were carried out on 0 6 2 m 2 6 m and 6 20 m size separates of the phengitic white mica although the k ar apparent ages range from 11 to 27 ma and are consistent with available stratigraphic constraints the 40ar 39ar age spectra display variable internal discordancy these isotopic data indicate that 1 both the k ar and 40ar 39ar total gas ages decrease as the degree of crenulation increases 2 the k ar and 40ar 39ar total gas ages decrease as grain size decreases 3 for each sample characteristics of the 40ar 39ar age spectra depend upon grain size with fine sizes yielding discordant patterns which systematically increase in apparent age from low to high temperature and 4 phengitic micas associated with earliest structures yield generally older ages than micas associated with later structures the isotopic results are interpreted to indicate that the major deformation phase d1 occurred at approximately 27 ma with subsequent pulses ending by c 10 ma these results may be combined with finite strain data to suggest that the region was deformed at strain rates between 10 15 and 10 14 s 1 a 27 ma age indicates mid oligocene initiation of plate tectonic activity in the western mediterranean and concomitant deformation in the northern apennines

dating mylonitic deformation by the 40ar 39ar method an example from the norumbega fault zone maine strongly mylonitic rocks associated with the regionally extensive norumbega fault zone in south central maine provide an excellent opportunity for testing the effects of mylonitization on argon isotopic systems in muscovite 40ar 39ar muscovite age spectra from samples outside the zone of mylonitization are relatively undisturbed and have well defined early carboniferous plateau ages in contrast to these nonmylonitized samples all age spectra for muscovite from the mylonites are highly discordant they are characterized by young ages at low extraction temperatures which systematically increase to ages that equal the plateau ages for muscovite collected outside the mylonite zone detailed petrographic observations suggest that these systematic discordances reflect a mixing of argon components from older relict muscovite porphyroclasts and fine grained white mica aggregates that recrystallized during mylonitic deformation total gas ages of five different grain size fractions separated from the same mylonite sample become progressively younger with decreasing grain size indicating a larger component of the recrystallized grains in the finer grain size fractions although the three finest grain size fractions give different total gas ages and do not overlap in age for most of their release spectra their initial increments do coincide at approximately 290 ma this indicates a minimal older age contribution from the relict porphyroclasts in the initial increments and suggests the 290 ma age provides a good estimate for the time of mineral growth associated with mylonitic deformation these data combined with kinematic analysis reveal that the segment of the norumbega fault zone studied the sandhill corner fault is a late carboniferous early permian dextral strike slip fault a lack of significant offset in regional early carboniferous mineral age patterns across the fault suggests that displacement was probably less than 30 km this study demonstrates that 40ar 39ar dating methods can be used to date deformational events effectively as long as several important criteria are met first and foremost samples must be well characterized prior to analysis dynamic recrystallization must have occurred at or below the closure temperature of the mineral to be analyzed regional cooling patterns must also be established through detailed thermochronology so that mineral ages and age spectra from the deformed rocks can be compared to regional cooling ages of the same mineral finally the effects of excess argon must be negligible

neocrystallization or cooling 40ar 39ar ages of white micas from low grade mylonites abstract 40 ar 39 ar data for white micas from quartzite mylonites from a thrust system are evaluated with respect to whether the minerals record cooling ages or alternatively ages of deformation induced neocrystallization to address these interpretations three types of information are needed 1 the effective diffusion length scale controlling volume diffusion of argon in white micas 2 an estimate of the diffusion parameters for volume diffusion of argon and 3 the thermal history completely recrystallized quartzites exhibit smooth grain size distributions for white micas with good exponential or power law fits suggesting that the grains grew under similar conditions the microstructures indicate that the grains grew over a narrow range in time near the end of the deformation history measured grain size distributions provide a maximum limit for the diffusion length scale thermal histories are estimated by 40 ar 39 ar diffusion experiments on k feldspars using the multi diffusion domain method of lovera lovera o m richter f m harrison t m 1989 the 40 ar 39 ar thermochronometry for slowly cooled samples having a distribution of diffusion domain sizes j geophys res 94 17917 17935 these results are consistent with the expected temperature time path for the thrusting environment and predict maximum temperatures of 250 350 c during the time span recorded by the white micas experimentally and empirically calibrated diffusion parameters for white micas are applied to a cylindrical diffusion geometry to explore the question of cooling ages versus neocrystallization ages forward modeling of the passage of the white micas through the closure window for argon diffusion using the thermal histories derived from the k feldspars indicates that the white micas record neocrystallization rather than cooling and supports the idea that the white micas record the timing of when ductile deformation ceased

oxygen isotope analyses of fine grained minerals and rocks using the laser extraction technique abstract the 18o values of fine grained materials made with the laser extraction technique are often lower than those obtained conventionally we propose a simple method to overcome this problem that involves the mixing of samples with a lif binder and pressing the powder into pellets prior to evacuation and analysis the presence of the lif allows for rapid fluorination of all minerals or whole rock samples to be made thus eliminating potential problems related to loss of partially reacted ejecta slow laser heating and incidental fluorination accurate isotope determinations of fine grained materials can be made with this method

constraining deformation stages in brittle ductile shear zones from combined field mapping and 40ar 39ar dating the structural evolution of the grimsel pass area aar massif swiss alps abstract 40 ar 39 ar dating of syn kinematic white mica phengite and biotite is used to constrain the age of shear zones within the granodiorites of the grimsel pass area aar massif central alps three sets of steeply dipping shear zones have been mapped stage 1 shear zones are very broad 200 m wide zones of biotite bearing rocks with a progressive increase in intensity of ductile deformation from rim to core and have dip slip kinematics subsequent stage 2 shear zones are narrower contain phengite rich mylonites and show a gradual change from dextral strike slip to dip slip kinematics across strike strain localisation during the formation of stage 2 shear zones is interpreted to have been aided by reaction weakening during extensive fluid rock interaction brittle precursors of stage 2 shear zones are marked by biotite rich cataclasites preserved along the northern contact of the overprinting main stage 2 shear zone biotite from a stage 1 shear zone yields an age of 21 1 0 2 ma phengites in stage 2 mylonites in the grimsel pass area have a very narrow age range 13 8 12 2 ma which is interpreted to bracket the duration of ductile deformation during stage 2 deformation at mid crustal levels however the biotite rich cataclasites at the margin of a stage 2 shear zone may have localised fluid flow up to 2 ma prior to the onset of main stage 2 ductile deformation stage 3 shear zones are brittle strike slip faults containing cataclasites breccias and clay fault gouges earlier studies have established that these late faults formed at

ages of deformation from k ar and 40ar 39ar dating of white micas a structural and isotopic dating study of white micas from mylonites in the ruby gap duplex off central australia shows that mylonitic deformation occurred during the paleozoic alice springs orogeny deformation of the white micas took place under greenschist facies conditions in the approximate temperature range 250 350 c two distinct populations of white mica have been found 1 porphyroclasts of original muscovite and 2 neocrystallized phengites that define the fabric associated with deformation 40ar 39ar age spectra of neocrystallized phengites yield plateau like spectra of paleozoic age in contrast 40ar 39ar age spectra of muscovite porphyroclasts exhibit proterozoic apparent ages indicating that white micas were not open to significant argon diffusion during formation of the ruby gap duplex we conclude that the ages measured on neocrystallized phengites record the cessation of ductile deformation and migration of tectonic activity toward the internal zones of the thrust system

fluid migration through thrust faults in the helvetic nappes western swiss alps the 18o 13c and 87sr 86sr values of calcite and organic matter were measured for carbonate mylonites from numerous thrusts in the helvetic alps carbonate mylonites in most of the thrusts retain essentially unaltered protolith 18o and 13c values consistent with there having been little to no advection of isotopically distinct fluid through these faults only carbonate mylonites from the basal thrusts of the largest nappes have 18o and or 13c values that differ from those of their protoliths the zone of isotopic alteration exchange is confined to c 10 to 20 meters of these fault contacts we propose the fluids that migrated through these faults contained variable amounts of organically derived carbon and radiogenic strontium and were probably derived from dewatering of the sedimentary rocks and prograde metamorphic reactions in the nappes root zones apart from the basal thrusts of the largest nappes that behaved as narrow laterally extensive conduits for fluids there is little isotopic evidence that large quantities of fluids passed through most of the carbonate hosted thrusts in the helvetic alps

a comparison of charcoal measurements for reconstruction of mediterranean paleo fire frequency in the mountains of corsica fire history reconstructions inferred from sedimentary charcoal records are based on measuring sieved charcoal fragment area estimating fragment volume or counting fragments similar fire histories are reconstructed from these three approaches for boreal lake sediment cores using locally defined thresholds here we test the same approach for a montane mediterranean lake in which taphonomical processes might differ from boreal lakes through fragmentation of charcoal particles the mediterranean charcoal series are characterized by highly variable charcoal accumulation rates results there indicate that the three proxies do not provide comparable fire histories the differences are attributable to charcoal fragmentation this could be linked to fire type crown or surface fires or taphonomical processes including charcoal transportation in the catchment area or in the sediment the lack of correlation between the concentration of charcoal and of mineral matter suggests that fragmentation is not linked to erosion reconstructions based on charcoal area are more robust and stable than those based on fragment counts area based reconstructions should therefore be used instead of the particle counting method when fragmentation may influence the fragment abundance

a review of palaeoclimates and palaeoenvironments in the levant and eastern mediterranean from 25 000 to 5000 years bp setting the environmental background for the evolution of human civilisation abstract the southern levant has a long history of human habitation and it has been previously suggested that climatic changes during the late pleistocene holocene stimulated changes in human behaviour and society in order to evaluate such linkages it is necessary to have a detailed understanding of the climate record we have conducted an extensive and up to date review of terrestrial and marine climatic conditions in the levant and eastern mediterranean during the last 25 000 years we firstly present data from general circulation models gcms simulating the climate for the last glacial maximum lgm and evaluate the output of the model by reference to geological climate proxy data we consider the types of climate data available from different environments and proxies and then present the spatial climatic picture for key climatic events this exercise suggests that the major northern hemisphere climatic fluctuations of the last 25 000 years are recorded in the eastern mediterranean and levantine region however this review also highlights problems and inadequacies with the existing data

a late pleistocene long pollen record from lake urmia nw iran abstract a palynological study based on two 100 m long cores from lake urmia in northwestern iran provides a vegetation record spanning 200 ka the longest pollen record for the continental interior of the near east during both penultimate and last glaciations a steppe of artemisia and poaceae dominated the upland vegetation with a high proportion of chenopodiaceae in both upland and lowland saline ecosystems while juniperus and deciduous quercus trees were extremely rare and restricted to some refugia hippophae rhamnoides constituted an important phanerophyte particularly during the late last glacial period a pronounced expansion in ephedra shrub steppe occurred at the end of the penultimate late glacial period but was followed by extreme aridity that favoured an artemisia steppe very high lake levels registered by both pollen and sedimentary markers occurred during the middle of the last glaciation and late part of the penultimate glaciation the late glacial to early holocene transition is represented by a succession of hippophae ephedra betula pistacia and finally juniperus and quercus the last interglacial period eemian slightly warmer and moister than the holocene was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern european pollen sequences

40ar 39ar dating of white micas from an alpine high pressure metamorphic belt on naxos greece the resetting of the argon isotopic system overprinting of white micas from high pressure low to medium temperature m1 metamorphic assemblages in pelitic schists on naxos during subsequent thermal dome m2 metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome the original m1 minerals are phengites si4 6 7 7 0 and the overprinting minerals are muscovites si4 6 0 6 45 40ar 39ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between these upward convex age spectra are shown to be caused by mixing of two generations of micas each of which has a different age spectrum and argon release pattern seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages further the upward convex age spectra have been used to trace the isotopic signature of phengites toward increasing m2 metamorphic grade and suggest that as long as phengites can be observed in the rocks upward convex age spectra occur on naxos crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas however there is also good evidence for argon loss by volume diffusion from phengites simple diffusion calculations suggest that the m2 metamorphism was caused by a shortlived heat source

eastern mediterranean hydroclimate over the late glacial and holocene reconstructed from the sediments of nar lake central turkey using stable isotopes and carbonate mineralogy there is a lack of high resolution records of hydroclimate variability in the eastern mediterranean from the late glacial and early holocene more knowledge of the speed of climate shifts and the degree to which they were synchronous with changes in the north atlantic or elsewhere is required to understand better the controls on eastern mediterranean climate using endogenic carbonate from a sediment sequence from nar golu a maar lake in central turkey dated by varve counting and uranium thorium methods we present high resolution 25 years oxygen 18o and carbon isotope records supported by carbonate mineralogy data spanning the late glacial and holocene 18ocarbonate at nar golu has been shown previously to be a strong proxy for regional water balance after a dry period i e evaporation far exceeding precipitation in the younger dryas the data show a transition into the relatively wetter early holocene in the early holocene there are two drier periods that appear to peak at 9 3 ka and 8 2 ka coincident with cooling events seen in north atlantic records after this and as seen in other records from the eastern mediterranean there is a millennial scale drying trend through the mid holocene transition the relatively dry late holocene is punctuated by centennial scale drought intervals at the times of 4 2 ka event and late bronze age societal collapse overall we show that central turkey is drier when the north atlantic is cooler throughout this record and at multiple timescales thought to be due to a weakening of the westerly storm track resulting from reduced cyclogenesis in the north atlantic however some features such as the mid holocene transition and the fact the early holocene dry episodes at nar golu are of a longer duration than the more discrete events seen in north atlantic records imply there are additional controls on eastern mediterranean hydroclimate

initiation and development of the pennine basal thrust swiss alps a structural and geochronological study of an exhumed megathrust abstract the pennine basal thrust pbt is an exhumed megathrust developed during continental collision from late eocene to miocene to trace its evolution five samples with indications for up to three microstructurally diachronous white mica generations were investigated by laser in situ and step heating 40 ar 39 ar dating three deformation related crystallization ages can be distinguished 1 d 1 characterized in the pbt hanging wall by an s 1 foliation defined by white mica chloritoid began at or before 38 0 ma 2 d 2 formed a pervasive s 2 cleavage and synchronous white mica rich veins dated at 27 ma 3 d 3 produced an s 3 crenulation cleavage and chlorite white mica veins dated at 23 ma older ages of 96 ma footwall and 115 ma hanging wall are interpreted as minimum ages for the detrital component finally discrete faulting produced fault gouge with an illite k ar age of 19 ma a simplified back restored reconstruction provides a tectonic context for the dated structures in this framework d 1 occurred during middle to late eocene tectonic accretion after late eocene initiation of continental collision d 2 reflects oligocene top to nw shearing with both in and out of sequence thrusting d 3 then developed from 23 to 19 ma during the progressive deactivation of the pbt

mineralogical kar stable and sr isotope systematics of k white micas during very low grade metamorphism of limestones helvetic nappes western switzerland abstract mineralogical k ar rb sr and stable isotope analyses have been carried out on k white micas from helvetic malm limestones in order to examine their evolution during very low to low grade alpine metamorphism associated with intense ductile deformation metamorphic temperatures were estimated at 300 c from stable isotopes quartz calcite thermometry occurrence of chloritoid and epizonal illite crystallinity index k white micas consist of variable mixtures of 2m 1 phengite and muscovite as revealed by detailed x ray diffraction analyses using peak decomposition of the 060 331 spectra k ar apparent ages display a strong grain size dependence in which mainly fine grained size fractions m record alpine ages 37 15 ma however these ages provide a relative rather than an absolute chronology of the diachronous alpine metamorphic evolution of the helvetic nappes the resetting of the k ar isotopic system of k white micas to alpine metamorphic conditions reflects an apparent combination of crystallization recrystallization and radiogenic 40 ar diffusion loss the oxygen isotope compositions of micas 15 to 22 are intermediate between detrital and 18 o enriched values expected for micas neoformed within an abundant marine carbonate matrix no isotopic equilibrium has been reached between calcite and micas the variable depletion of hydrogen isotope compositions 126 to 82 is influenced by the interaction with organic matter under closed system conditions organic matter if not removed may also represent a serious source of error in k ar age determination by introducing radiogenic 40 ar contamination 87 sr 86 sr isotope ratios of micas range from 0 70879 to 0 70902 with one outlier at 0 71794 the low values reflect sr exchange with calcite occurring during crystallization recrystallization of micas under closed system conditions

dating incipient metamorphism using 40 ar 39 ar geochronology and xrd modeling a case study from the swiss alps six samples of a single carbonate rich unit of the swiss prealpes progressively metamorphosed from diagenesis to deep anchizone yield 40ar 39ar spectra with variably developed staircase patterns consistent with mixtures of detrital mica and neocrystallized mixed layer illite smectite the lowest temperature heating steps for different size fractions 2 6 m and 6 20 m converge to 40 ma providing an imprecise maximum age of regional metamorphism a method is described for distinguishing and quantifying the amount of pre existing detrital mica versus neoformed illite layer in the illite smectite formed during tertiary alpine metamorphism by comparison of x ray diffraction patterns with newmod simulations in the least metamorphosed samples the illite smectite contains 65 neoformed illite and this illite accounts for approximately 17 of all dioctahedral phyllosilicate minerals in the rock e g detrital mica and illite smectite in contrast the illite smectite from the more strongly metamorphosed samples contains 97 neoformed illite which accounts for 70 to 90 of all dioctahedral phyllosilicate minerals phyllosilicate morphologies viewed by scanning electron microscopy are consistent with these estimates a process of dissolution reprecipitation is inferred as a mechanism for the growth of the neoformed phyllosilicates a plot of neoformed illite content versus 40ar 39ar total fusion age yields a near linear curve with an extrapolated age of 27 ma for 100 neoformed dioctahedral phyllosilicates this age is interpreted as the time of incipient metamorphism and is consistent with independent biostratigraphic constraints model 40ar 39ar age spectra constructed with the xrd simulation results correspond well to the experimental data and illustrate the changes in degassing properties of progressively metamorphosed mixtures of detrital mica and neoformed illite

modifying the marsh evaluating early epipaleolithic hunter gatherer impacts in the azraq wetland jordan the ecological impacts of human activities have infiltrated the whole of the natural world and precipitated calls for a newly defined geological epoch the anthropocene while scholars discuss tipping points and scale viewed over the longue duree it is becoming clear that we have inherited the compounding consequences of a constructed environment with a long history of human landscape modification by linking phytolith and micro charcoal evidence from sediments in the azraq basin jordan we discuss potential early epipaleolithic 23 000 17 400 cal bp human environment interactions in this wetland our analyses reveal that during the last glacial maximum levantine hunter gatherers could have had a noticeable and increasing impact on their environment however further work needs to be undertaken to assess the range frequency intensity and intentionality of marsh disturbance events we suggest that the origin of persistent places and larger aggregation settlements in the azraq basin may have b

jurassic cooling ages in paleozoic to early mesozoic granitoids of northeastern patagonia 40ar 39ar 40k 40ar mica and u pb zircon evidence u pb shrimp zircon crystallization ages and ar ar and k ar mica cooling ages for basement rocks of the yaminue and nahuel niyeu areas in northeastern patagonia are presented granitoids that cover the time span from ordovician to early triassic constitute the main outcrops of the western sector of the yaminue block the southern yaminue metaigneous complex comprises highly deformed ordovician and permian granitoids crosscut by undeformed leucogranite dikes u pb shrimp zircon age of 254 2 ma mica separates from highly deformed granitoids from the southern sector yielded an ar ar muscovite age of 182 3 ma and a k ar biotite age of 186 2 ma moderately to highly deformed permian to early triassic granitoids made up the northern yaminue complex the late permian to early triassic u pb shrimp zircon age of 252 6 ma cabeza de vaca granite of the yaminue block yielded jurassic mica k ar cooling ages 198 2 191 1 and 190 2 ma at the boundary between the yaminue and nahuel niyeu blocks k ar muscovite ages of 188 3 and 193 5 ma were calculated for the flores granite whereas the early permian navarrete granodiorite located in the nahuel niyeu block yielded a k ar biotite age of 274 4 ma the jurassic thermal history is not regionally uniform in the supracrustal exposures of the nahuel niyeu block the early permian granitoids of its western sector as well as other permian plutons and ordovician leucogranites located further east show no evidence of cooling age reset since mica ages suggest cooling in the wake of crystallization of these intrusive rocks in contrast deeper crustal levels are inferred for permian early triassic granitoids in the yaminue block since cooling ages for these rocks are of jurassic age 198 182 ma jurassic resetting is contemporaneous with the massive lower jurassic flores granite and the marifil and chon aike volcanic provinces this intraplate deformational pulse that affected northeastern patagonia during the early jurassic sinemurian pliensbachian was responsible for the partial re exhumation of the mid crustal paleozoic basement along reactivated discrete ne sw to ene wsw lineaments and the resetting of isotopic systems these new thermochronological data indicate that early permian magmatic rocks of the nahuel niyeu block were below 300 c for ca 20 ma prior to the onset of the main magmatic episode of the late permian to triassic igneous and metaigneous rocks of the yaminue block

vegetation and environmental changes during the last interglacial in eastern anatolia turkey a new high resolution pollen record from lake van a high resolution multi proxy record from lake van eastern anatolia derived from a lacustrine sequence cored at the 357 m deep ahlat ridge ar allows a comprehensive view of paleoclimate and environmental history in the continental near east during the last interglacial li we combined paleovegetation pollen stable oxygen isotope delta o 18 bulk and xrf data from the same sedimentary sequence showing distinct variations during the period from 135 to 110 ka ago leading into and out of full interglacial conditions the last interglacial plateau as defined by the presence of thermophilous steppe forest communities lasted ca 13 5 ka from similar to 129 1 115 6 ka bp the detailed palynological sequence at lake van documents a vegetation succession with several climatic phases i the pistacia zone ca 131 2 129 1 ka bp indicates summer dryness and mild winter conditions during the initial warming ii the quercus ulmus zone ca 129 1 1272 ka bp occurred during warm and humid climate conditions with enhanced evaporation iii the carpinus zone ca 1272 124 1 ka bp suggest increasingly cooler and wetter conditions and iv the expansion of pinus at similar to 124 1 ka bp marks the onset of a colder drier environment that extended into the interval of global ice growth pollen data suggest migration of thermophilous trees from refugial areas at the beginning of the last interglacial analogous to the current interglacial the migration documents a time lag between the onset of climatic amelioration and the establishment of an oak steppe forest spanning 2 1 ka hence the major difference between the last interglacial compared to the current interglacial holocene is the abundance of pinus as well as the decrease of deciduous broad leaved trees indicating higher continentality during the last interglacial finally our results demonstrate intra interglacial variability in the low mid latitudes and suggest a close connection with the high frequency climate variability recorded in greenland ice cores c 2015 elsevier b v all rights reserved

a new dead sea pollen record reveals the last glacial paleoenvironment of the southern levant abstract the southern levant is a key region for studying vegetation developments in relation to climate dynamics and hominin migration processes in the past due to the sensitivity of the vegetation to climate variations and the long history of different anthropogenic occupation phases however paleoenvironmental conditions in the southern levant during the late pleistocene were still insufficiently understood therefore we investigated the vegetation and fire history of the dead sea region during the last glacial period we present a new palynological study conducted on sediments of lake lisan the last glacial precursor of the dead sea the sediments were recovered from the center of the modern dead sea within an icdp campaign the palynological results suggest that irano turanian steppe and saharo arabian desert vegetation prevailed in the dead sea region during the investigated period ca 88 000 14 000 years bp nevertheless mediterranean woodland elements significantly contributed to the vegetation composition suggesting moderate amounts of available water for plants the early last glacial was characterized by dynamic climate conditions with pronounced dry phases and high but unstable fire activity anatomically modern humans entered the southern levant during a climatically stable phase late mis 4 mis 3 with diverse habitats constant moisture availability and low fire activity mis 2 was the coldest phase of the investigated timeframe causing changes in woodland composition and a widespread occurrence of steppe we used a biome modeling approach to assess regional vegetation patterns under changing climate conditions and to evaluate different climate scenarios for the last glacial levant the study provides new insights into the environmental responses of the dead sea region to climate variations through time it contributes towards our understanding of the paleoenvironmental conditions in the southern levant which functioned as an important corridor for human migration processes

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

continual fire making by hominins at gesher benot ya aqov israel this paper presents the culmination of an extensive study of fire use at the early and early middle pleistocene site of gesher benot ya aqov using software available in the gis package we have examined the spatial distribution of burned and unburned flint microartifacts from eight acheulian archaeological horizons the results of this study demonstrate that the burned microartifacts are never evenly distributed and dense concentrations are observed the circumstances that introduced these burned flint artifacts to the archaeological layers are examined suggesting that anthropogenic rather than natural fires are responsible for the observed patterns as the evidence for the use of fire is recorded throughout the long stratigraphic sequence it seems that fire was continually used by the acheulian hominins of the site this repetitive use of fire indicates that the hominins of gesher benot ya aqov had a profound knowledge of fire making enabling them to make fire at will

mid holocene vegetation reconstruction from vanevan peat south eastern shore of lake sevan armenia a sediment core has been retrieved from vanevan peat south eastern shore of lake sevan armenia which is today disconnected from lake sevan thanks to an artificial shallowing of the lake based on 5 radiocarbon dates vanevan record covers the mid holocene from ca 7800 to ca 5100 cal bp the late holocene is today absent in the peat stratigraphy due to modern peat exploitation by surface mining this study focuses on a multi proxy approach including pollen charcoals and pollen inferred climate reconstruction an open land steppic vegetation is recorded up to ca 7700 cal bp followed by a more forested landscape during the mid holocene up to ca 5700 cal bp and ending again with an open land vegetation to the end of record 5100 cal bp this vegetation dynamics responds to general climate changes documented in the near east whether human activities are documented since ca 7500 cal bp late neolithic in vanevan they remain marginal and probably did not affect the area early holocene dry climate which caused the steppic environment to be widespread through the near east is strongly related to low late spring precipitation pmay jun 180 mm mid holocene forested landscape and increasing lake level seem related to late spring precipitation 28 which is the main change in estimated climate parameters this has to be linked with reinforcement of the westerlies and less active siberian high which are inversely involved in the following dry phase starting at ca 5700 cal bp

radiometric age constraints on mineral growth metamorphism and tectonism of the gummfluh klippe brianconnais domain of the prealpes switzerland a combined 40ar 39ar k ar rb sr and stable isotope study has been made of white micas from the gummfluh klippe brianconnais domain of the prealpes switzerland the klippe consists mainly of mesozoic to early tertiary carbonate rocks metamorphosed from anchizonal to epizonal conditions at the base of the klippe is a 10 50 m thick ductilely deformed marble mylonite containing deformed authigenic quartz segregations stable isotope measurements of the coexisting calcite 18osmow 24 5 and quartz 18osmow 28 4 from the mylonite indicate relatively low temperatures 300 c during mylonitization analyses of white mica separates of varying size fractions from the mylonitic rocks by k ar and rb sr techniques yield ages between 57 and 103 ma this variation is correlated with two parameters the size of the mineral fraction and the proportion of 2m1 more phengitic to 1m more muscovitic polytype in the sample the k ar and rb sr ages are generally younger in the smaller size fractions which also containless 2m1 phengite high precision 40ar 39ar age spectra from different size fractions of these micas record three distinct components a small hercynian component ca 200 300 ma a significant eoalpine component 64 80 ma forming 40ar 39ar age plateaus and a very minor tertiary component ca 20 40 ma characterization of the samples by sem indicates the presence of two white mica populations a coarser grained deformed detrital mica that probably corresponds to the 2m1 phengite and a finer grained neoformed 1m mica collectively these observations suggest that the gummfluh samples contain a mixture of detrital phengites of hercynian age together with neocrystallized muscovites grown during the late eoalpine metamorphic event followed by minor argon loss during the tertiary the main geologic episode recorded in the 40ar 39ar age spectra of white micas in the mylonite is of late cretaceous early tertiary age 64 80 ma representing the first reliable eoalpine ages ever to be reported from the prealpes contrary to tectonic models the marble mylonite at the base of the gummfluh klippe appears to be a cretaceous thrust plane and not the thrust surface formed during transport of the klippe into its present position from the penninic alps during the tertiary the late cretaceous thrust developed during marine sedimentation at a depth of 800 m below the seafloor at temperatures of 280 c facilitated by warm fluids along the tectonic discontinuity

the structure of the helvetic nappes and its relation to the mechanical stratigraphy abstract this paper discusses structure and variations in structural style due to changes in mechanical stratigraphy of the helvetic nappes based on five cross sections the ratio n of the thickness of mechanically weak to the thickness of adjacent mechanically strong layers is of particular importance a low value of n favours imbricate thrusting and harmonic folding a high value favours detachment and disharmonic folding the transition at around n 0 5 is characterized by polyharmonic folding stratigraphic thickness variations due to local basin subsidence resulted in arcuate fold hinges and important plunges upon basin inversion lateral variations in the overall structure of the helvetic nappes is largely controlled by the initial irregular arrangements of the various small basins one more or less coherent thrust sheet the cretaceous stockwerk of the wildhorn drusberg santis nappe can be traced along the entire fold and thrust belt

new pollen evidence from nariani georgia for delayed postglacial forest expansion in the south caucasus the nature and timing of environmental changes throughout the last glacial interglacial transition in the south caucasus and more widely in eastern europe are still not fully understood according to certain pollen records forest expansion occurred in many areas several millennia after what is considered worldwide as the onset of the holocene the current problem we face is that the time lag in forest expansion varies from one sequence to another sometimes with no delay at all moreover the potential forcing controlling factors behind this complex pattern contrary to the almost synchronous global holocene warming are still a matter for debate accordingly we revisit the issue of forest expansion through vegetation history obtained in the south caucasus using a new pollen record retrieved from the nariani paleolake south georgia these data attest to a steppic phase initially dominated by amaranthaceae chenopodiaceae 12 700 10 500 cal yr bp then by poaceae 10 500 9000 cal yr bp culminating with a more forested phase 9000 5000 calyrbp although some palaeoclimatic regional reconstructions show a wet early holocene we interpret the delay in forest expansion recorded in nariani 2500 years as the result of reduced spring precipitation which would have limited forest development at that time

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

a multi proxy shallow marine record for mid to late holocene climate variability thera eruptions and cultural change in the eastern mediterranean abstract the river nile catchment is considered the major source of nutrient rich freshwater and sediment draining into the eastern mediterranean sea thus exceptional high resolution record from the nile littoral cell likely traces changes in the nile outflows related to climatic changes driven by the monsoonal system this study used multi proxy analyses combining sedimentological geochemical and organic stable isotope data along with foraminiferal data in a southeastern levantine inner shelf sedimentary sequence to understand mid to late holocene northeast african climate variability the palynological record is used to reconstruct local scale changes in the regional vegetation related to the mediterranean climate system the analyzed records reveal multi decadal to centennial pacing of paleoceanographic and paleoclimatic changes with most prominent events recorded at 4 28 3 6 and at 2 9 kyr bp these transitional periods characterized by simultaneous high 15n values and low total organic carbon toc suggest drier climatic conditions decrease in nile discharge leading to lower nutrient supply a stable and arid climate during mid late holocene 4 5 3 6 cal kyr bp associated with a weaker monsoon system as well as with a weaker mediterranean climate system is indicated based on high and constant sedimentation rates 400 cm kyr 1 along with relatively stable values and only occasional weak fluctuations documented in all of the proxies this climatic pattern is punctuated by a peak in maximum aridity at 4 28 kyr bp evidenced by low toc value and low arboreal pollen ap and artemisia chenopodiaceae a c pollen ratios and the sharp decline in the abundance of benthic foraminifera cribroelphidium poeyanum and valvulineria bradyana this change corresponds with the well studied 4 2 kyr bp drought event in the middle east mesopotamia and south asia during the late holocene 3 6 2 8 cal kyr bp the climate became unstable characterized by shifts between relatively wetter and drier conditions as evident in considerable fluctuations in all proxies maximum positive excursions of toc values c n ratio along with high dominance of opportunistic foraminiferal species e g ammonia tepida indicate northeast african wetter conditions and increased nile discharge at 3 5 3 3 3 2 and 3 0 kyr bp the distinct and abrupt transition from a stable to an unstable climate regime around 3 6 kyr bp may have been influenced by the thera volcanic eruption thus the sedimentary record investigated in this study may provide evidence for the impacts of this well known volcanic eruption not just on the climate regime in the levant but also on the ancient near east and egypt

circum mediterranean fire activity and climate changes during the mid holocene environmental transition 8500 2500 cal bp a mid to late holocene synthesis of fire activity from the mediterranean basin explores the linkages among fire climate variability and seasonality through several climatic and ecological transitions regional fire histories were created from 36 radiocarbon dated sedimentary charcoal records available from the global charcoal database during the mid holocene thermal maximum around 7500 4500 cal bp charcoal records from the northern mediterranean suggest an increase in fire while records from the southern mediterranean indicate a decrease associated with wetter than present summers a north south partition between 40 and 43 n latitude is apparent in the central and western mediterranean relatively abrupt changes in fire activity are observed c 5500 5000 cal bp records of holocene fire activity appear sensitive to both orbitally forced climate changes and shorter lived excursions which may be related to north atlantic cold events possibly modulated by an nao like climate mechanism in cases wh

constraints from 40ar 39ar geochronology on the timing of alpine shear zones in the mont blanc aiguilles rouges region of the european alps the mont blanc and aiguilles rouges massifs which form part of the external crystalline massifs of the western european alps record a young and fast exhumation history as established by an extensive low temperature thermochronology and geochronology data set various kinematic and dynamic models for oligocene to neogene deformation and exhumation of the aiguilles rouges mont blanc system have been proposed however the timing of deformation along major shear zones in and around the massifs which is crucial to these models is still controversial our new 40ar 39ar data from key deformation zones in the mont blanc area show that nw directed thrusting lasted from oligocene to mid miocene times in the mont blanc massif before a nw ward jump of the deformation front to below the aiguilles rouges massif which led to updoming of the aiguilles rouges and mont blanc massifs this deactivated the main nw verging shear zones and caused back folding and back thrusting east of the mont blanc as well as upward extrusion of the aiguilles rouges massif subsequently there was a switch to more coaxial shortening between the aiguilles rouges and mont blanc massifs associated with strain partitioning and related dextral strike slip deformation on the eastern side of the mont blanc massif

dead sea pollen provides new insights into the paleoenvironment of the southern levant during mis 6 5 abstract the paleoclimate of the southern levant especially during the last interglacial lig is still under debate reliable paleovegetation information for this period as independent evidence to the paleoenvironment was still missing in this study we present a high resolution pollen record encompassing 147 89 ka from the dead sea deep drilling core 5017 1a the sediment profile is marked by alternations of laminated marl deposits and thick massive halite indicating lake level fluctuations the pollen record suggests that steppe and desert components predominated in the dead sea surroundings during the whole investigated interval the late penultimate glacial 147 3 130 9 ka and early last glacial 115 5 89 1 ka were cool and relatively dry with sub humid conditions confined to the mountains that sustained moderate amounts of deciduous oaks prior to the lig optimum a prevalence of desert components and a concomitant increase in frost sensitive pistachio trees demonstrate the occurrence of an arid initial warming phase 130 9 124 2 ka the lig optimum 124 2 ka 115 5 ka was initiated by an abrupt grass expansion that was followed by a rapid spread of woodlands in the mountains due to increased moisture availability the remarkable sclerophyllous expansion points to a strong seasonal moisture deficit these results contradict previous dead sea lake level investigations that suggested pluvial glacials and a warm dry lig in the southern levant prominent discrepancies between vegetation and dead sea lake stands are also registered at 128 115 ka and the potential causes are discussed in particular while the pollen spectra mirror increased effective moisture during the lig optimum the massive halite deposition is indicative of an extremely low lake level given that the climate amelioration triggered the migration of early modern humans to the southern levant we speculate that the diverse ecosystems in the region provided great potential for their residence across the eastern mediterranean region an analogous vegetation succession pattern is observed

vegetation fire and climate history of the lesser caucasus a new holocene record from zarishat fen armenia vegetation fire and climate history are investigated in the 10 000 year record of zarishat fen located today in the steppe grasslands of armenia near east pollen based climate quantification provides a reconstruction of seasonal parameters the development of in situ water dependant plants and of forests at lower altitude at 8200 cal a bp echoes the shift from an arid and cold annual precipitation pann 452mm mean temperature of the coldest month mtco 11 1uc early holocene to a more humid and warmer pann 721mm mtco 6 8uc mid late holocene this marks the onset of lower seasonality in particular more effective precipitation brought during late spring by the westerlies paralleling the mediterranean precipitation pattern precipitation in the near east and central asia decreased during the mid late holocene in favour of higher seasonality controlled in winter spring by the siberian high fire history and sedge based fen development record drier phases at approximately 6400 5300 4900 3000 2200 1500 and 400 cal a bp which resemble the precipitation pattern of the south western mediterranean and contrast with the holocene pattern in the south central and south eastern mediterranean regions arid phases in armenia are believed to be related to multi centennial scale variation of westerly activity north atlantic oscillation like copyright 2013 john wiley sons ltd

oxygen isotope thermometry of quartz calcite veins unraveling the thermal tectonic history of the subgreenschist facies morcles nappe swiss alps combined structural analysis and oxygen isotope thermometry of syntectonic quartz calcite fibrous veins can be used to correlate the thermal history of deformed rocks with specific structural and tectonic events results are presented for the morcles nappe in the western helvetic alps switzerland where mineral parageneses illite crystallinity and fluid inclusion chemistry record an apparent peak metamorphic temperature gradient that increased across the morcles nappe from anchizonal conditions in the foreland to epizonal conditions in its hinterland root zone twenty seven quartz calcite veins were analyzed in this study in order to determine the temperatures of veining during formation and deformation of the nappe peak metamorphic temperatures ranged from 260 to 290 c in the shallower foreland localities and to 330 to 350 c in the deeper more hinterland localities at the end of s1 foliation formation related to large scale folding temperatures gradually decreased throughout the nappe during subsequent development of the s2 foliation and s3 crenulation cleavage uplift and erosion of the overlying nappe pile resulted in slow cooling of the morcles nappe during the waning stages of the alpine orogeny the dominant foliation forming deformation of the morcles nappe occurred at elevated temperatures over the course of 10 to 15 ma combined structure oxygen isotope analyses of quartz calcite veins yield better temperature and temporal constraints on the thermal histories of subgreenschist vein bearing tectonites than do other geothermometers

timing and thermal evolution of fold and thrust belt formation in the ultima esperanza district 51 s chile constraints from k ar dating and illite characterization k ar dating on llite in upper cretaceous low grade metamorphic pelites in the torres del paine area was used to set new time constraints on the development of the patagonian retroarc fold and thrust belt ftb caused by the subduction of the antarctic plate beneath the south american plate the combined use of illite crystallinity kubler index polytype quantification and k ar dating of illite fractions 0 2 2 and 2 6 m allowed to distinguish four distinct periods of illite growth based on their k ar ages and degree of regional metamorphism 1 early cenomanian 98 ma illite crystallization 2 widespread early campanian ca 80 ma diagenetic illite growth under anchizonal metamorphic conditions 3 a significant period of illite formation in the early paleocene ca 60 ma and 4 a late stage of illite growth in the early eocene 55 46 ma under epizonal conditions the earliest indication for the emergent ftb formation in the hinterland is documented in a metapelitic clast 14 9 2 m within the upper cretaceous cerro toro conglomerate which yields a k ar cooling age of 98 3 1 2 ma and an epizonal ki value of 0 24 2 after a certain period of geological quietness an interval of major thrusting and uplift occurred between ca 60 and 46 ma the east dipping rio nutria and rio rincon thrusts record the onset of thrust and fold activity which can be placed close to 60 ma they also mark the frontal thrust towards the less deformed magallanes foreland basin in the western part of the internal domain widespread fault and thrust activity of the frontal wedge and associated thermal overprint continued and is recorded until 46 ma by k ar illite cooling ages the flexural subsidence that is driven by the thrust sheet loading in the internal domain was responsible for the eastward migration of the foreland depocenter and the rapid increase of sedimentation rate along the monoclinal belt no miocene thrusting nor uplift event has been recorded by k ar illite dating in the study area

historical landscape change in cappadocia central turkey a palaeoecological investigation of annually laminated sediments from nar lake coupled multiproxy indicators pollen stable isotopes and charcoal reconstructed from annually laminated lake sediments from nar ga la in cappadocia central turkey complemented by documentary and archaeological evidence provide a detailed record of environmental changes and their causes from late antiquity ad 300 to the present day stable isotope data indicate marked shifts in the variability in summer drought intensity and winter spring rainfall but these did not coincide in time with changes in vegetation and land use shown by pollen data rather human impacts appear to have been the main driver of landscape ecological changes in cappadocia over the last two millennia pollen and charcoal data indicate four principal land use phases i an early byzantine agrarian landscape characterized by cereals and tree crops and marking the later part of the so called beya ehir occupation phase ii a period of landscape abandonment and the establishment of secondary woodland from ad 670 to 950 coinc

palaeoecology of lake zeribar iran in the pleniglacial lateglacial and holocene reconstructed from plant macrofossils changes inaquatic andmarshvegetation atlakezeribar inthezagros mountains iran during thelast 40000years werereconstructed onthebasis ofplant macrofossils several episodes oflowwater level andincreased salinity wereevidenced bypeaks ofchenopodium rubrum seeds andtheoccurrence of obligate salicornia sp ruppia maritima andsuaeda sp andfacultative zannichellia palustris halophytic macrophytes aswell asbrackish water andmarine diatoms someofthese events canbecorrelated withan increase indiatoms indicative ofhigher conductivity andwithchanges inoxygen isotope data theyare interpreted astheexpression ofgeneral climatic dryness although water level changes might alsohave resulted fromepisodes ofdeposition onthealluvial fans that damthelake a fewsuchwater level changes occurred inthepleniglacial themostpronounced lowering corresponds totheyounger dryas interval of high climatic aridity macrofossil indicators ofwater level changes appeared also intheholocene section oftheprofiles atthesametime asquercus expanded onthesurrounding uplands culminating about 6000 500014cyrbp giving support tothehypothesis that thedelay offorest expansion inthis partofthezagros mountains wascaused byclimatic dryness

early deformation of ultrahelvetic melanges in the helvetic nappes western swiss alps abstract the ultrahelvetic melanges represent an important clue for understanding the tertiary alpine orogeny particularly in the external alps of western switzerland the remarkable architecture of the upper and lower ultrahelvetic units is classically explained by an important phase of gravity sliding and orogenic sliding accompanied by the formation of chaotic complexes and olistostromes wildflysch a phenomenon called diverticulation a structural analysis reveals evidence for early phases of deformation despite strong overprinting by late alpine deformation these early fabrics are observed in foliated pebbly mudstone a tectonic breccia part of the melange matrix in disrupted flysch sequences and in dark shales they attest to brecciation related to a complex pattern of veining with several generations of calcite cement and several stages of failure during lithification and they show the important role of fluids during the deformation they present numerous analogies with the fabrics described in association with thrusts in accretionary prisms considering the tectonic fabrics and the relations among the infra prealpine melanges a tectonic model to explain the emplacement of the ultrahelvetic units is proposed in which the decollements developed in three weak levels the early fabrics evolved within a basal thrust formed in a final stage of the valaisan subduction

the younger dryas episode and the radiocarbon chronologies of the lake huleh and ghab valley pollen diagrams israel and syria pollen diagrams from the former lake huleh in israel and the ghab valley in syria are the most important records of vegetation change in the levant during the lateglacial and early holocene environmentally deterministic explanations of the development of agriculture in this region therefore rely on the accuracy of the diagrams radiocarbon chronologies radiocarbon results at both sites are subject to large reservoir effects however the 14c content of modern water from the huleh basin implies that the huleh radiocarbon results require corrections of up to 5500 14c years a revised chronology of the latest huleh pollen diagram is proposed this is consistent with the regional vegetation sequence recorded in eastern mediterranean marine sediments the regional sequence also provides the most plausible chronology for the ghab pollen diagrams

alpine deformation and 40ar 39ar geochronology of synkinematic white mica in the siviez mischabel nappe western pennine alps switzerland we explore the timing of deformation and exhumation of the siviez mischabel nappe western swiss alps which has been considered a classic example of a midcrustal crystalline nappe since the studies of argand 1916 this study presents 40ar 39ar ages obtained on both synkinematic white mica from permo triassic cover sediments and more complex white mica populations from basement gneisses of the siviez mischabel and middle pennine nappes primary foliation developed in cover units by nucleation growth and rigid rotation of mica grains during noncoaxial alpine deformation although some samples show a crenulation of this primary foliation mica growth appears to have occurred only during the development of primary foliation the main phase of greenschist facies deformation related to imbrication of the siviez mischabel nappe and other middle pennine nappes good agreement exists between independent estimates of the timing of deformation and reported 40ar 39ar white mica ages from cover units of the central and southern siviez mischabel nappe in cover units from the central and southern siviez mischabel regions of the study area 40ar 39ar ages appear to date synkinematic white mica growth results suggest that the siviez mischabel nappe was emplaced and developed foliation during a 5 m y period from 41 to 36 ma in cover units from the eastern siviez mischabel however 40ar 39ar white mica ages appear to date postkinematic thermal events these thermal events may be related to oligocene magmatic activity in the lower pennine nappes or to miocene development of the simplon fault zone variations in the relation between alpine age and grain size for cover samples from the central eastern and southern siviez mischabel correlate well with the regional variations in temperature inferred from quartz microfabrics and the pattern of regional metamorphism when considered in concert with other recent isotopic studies on the timing of major tectonic and thermal events in the western swiss alps these data support arguments that the relative timing of events such as thrusting and back thrusting of crystalline nappes in hinterland units and exhumation of high pressure units in the suture zone of the western alps are intimately related and synchronous on the scale of a few million years

neogene kinematics of the central and western alps evidence from fission track dating zircon and apatite fission track analysis has established the continuation of a zone of rapid change in mineral ages extending from the simplon fault zone in the simplon alps through the rhone valley and along the southeastern side of the mont blanc and belledonne massifs apatite fission track ages to the northwest of this zone generally range from 1 4 to 6 ma whereas those to the southeast range from 6 to 13 ma corresponding values for zircon are 11 13 and 16 26 ma respectively the zone corresponds to the position of the frontal pennine thrust in the mont blanc belledonne region this structure a prominent feature on recent deep seismic profiles may have been reactivated in the neogene with an important normal fault component this is suggested by apatite and zircon fission track ages in the footwall that are younger than those in the hanging wall and by the observed elimination of the lower pennine or simplon nappes along this fault zone in the rhone valley mont blanc belledonne region resulting in the juxtaposition of north penninic and helvetic ultra helvetic nappes at the current erosion level the distribution of fission track ages reflects this movement and the related neogene exhumation of the mont blanc and belledonne external massifs which has continued until less than 1 4 m y ago i e it is almost certainly still active and has tilted the overlying nappe sequence

fire climate and the origins of agriculture micro charcoal records of biomass burning during the last glacial interglacial transition in southwest asia this study investigates changes in climate vegetation wildfire and human activity in southwest asia during the transition to neolithic agriculture between ca 16 and ca 9 ka in order to trace the fire history of this region we use microscopic charcoal from lake sediment sequences and present two new records one from south central turkey akgol and the other from the southern levant hula these are interpreted primarily as the result of regional scale fire events with the exception of a single large event ca 13 ka at akgol which phytolith analysis shows was the result of burning of the local marsh vegetation comparison between these and other regional micro charcoal stable isotope and pollen records shows that wildfires were least frequent when the climate was cold and dry glacial lateglacial stadial and the vegetation dominated by chenopod artemisia steppe and that they became more frequent and or bigger at times of warmer wetter but seasonally dry climate lateglacial interstadial early holocene warmer and wetter climates caused an increase in biomass availability with woody matter appearing to provide the main fuel source in sites from the levant while grass fires predominated in the interior uplands of anatolia southwest asia s grasslands reached their greatest extent during the early holocene and they were maintained by dry season burning that helped to delay the spread of woodland by up to 3 ka at the same time as neolithic settlement became established across this grass parkland landscape although climatic changes appear to have acted as the principal pacemaker for fire activity through the last glacial interglacial climatic transition lgit human actions may have amplified shifts in biomass burning fire regimes therefore changed markedly during this time period and both influenced and were influenced by the cultural economic transition from hunter foraging to agriculture and village life copyright 2009 john wiley sons ltd

effects of progressive mylonitization on ar retention in biotites from the santa rosa mylonite zone california and thermochronologic implications the santa rosa mylonite zone developed predominantly from a granodiorite protolith in the eastern margin of the peninsular ranges batholith a wide variation in k ar biotite dates within the zone is shown to reflect the times of cooling through closure temperatures whose variability is chiefly a result of deformation induced reduction in grain size we suggest that such variation generally may be exploited to place constraints on the timing of deformation episodes previous workers have shown that deformation in the santa rosa mylonite zone involved the formation of mylonites and an imbricate series of low angle faults which divide the area into structural units field work petrographic studies and tem analysis of deformation mechanisms in biotite show that the granodiorite mylonite the lowermost structural unit formed below the granodiorite solidus the granodiorite mylonite varies from protomylonite to ultramylonite with regions of high strain distributed heterogeneously within the zone previously reported biotite and hornblende k ar dates from the granodiorite protolith below 82 89 ma and the asbestos mountain granodiorite above 61 68 ma the mylonite zone indicate dramatically dissimilar thermal histories for the lowermost and uppermost structural units other workers fission track dates on sphene zircon and apatite from the granodiorite mylonite and the asbestos mountain granodiorite suggest thermal homogenization and rapid cooling to 100 c by ca 60 ma within and adjacent to the mylonite zone k ar dates on 5 samples of biotite from variably deformed granodiorite range from 62 76 ma dates are not correlated with structural depth but clearly decrease with degree of deformation and concomitant grain size reduction 40ar 39ar incremental heating analyses of biotite from the granodiorite protolith reveals no evidence of excess argon and produces a relatively flat age spectrum 40ar 39ar incremental heating analysis of biotite from the granodiorite mylonite discloses discordance consistent with 39ar recoil loss k analysis of samples allowing k ar dates to be calculated is therefore recommended as an adjunct to 40ar 39ar step heating analysis in rocks that have experienced similar deformation during mylonitization biotite grain size reduction through intracrystalline cataclasis results in estimated grain dimensions as small as 0 05 m locally within porphyroclasts as large as 1 mm because biotite compositions are relatively uniform fe fe mg mn ti alvi 0 47 0 52 and show no systematic variation with grain size compositional dependence of activation energy and diffusivity can be eliminated as sources of variation in ar retention ar closure temperatures calculated with appropriate diffusion parameters for the observed grain sizes are in the range 220 280 c and define a cooling curve consistent with a thermal history intermediate between those of the granodiorite protolith below and the asbestos mountain granodiorite above the mylonite zone changes in the slope of the cooling curve indicate that the main deformation episode initiated at or above ca 330 c 80 ma above the closure temperature for thermally activated diffusion of argon in biotite and continued to a minimum of ca 220 260 c 62 ma

the evolution of illite to muscovite mineralogical and isotopic data from the glarus alps switzerland thirty five illite and muscovite concentrates were extracted from triassic and permian claystones shales slates and phyllites along a cross section from the diagenetic alpine foreland tabular jura and borehole samples beneath the molasse basin to the anchi and epimetamorphic helvetic zone of the central alps concentrates and thin sections were investigated by microscopic x ray infrared mossbauer thermal dta and tg wet chemical electron microprobe k ar rb sr 40ar 39ar and stable isotope methods with increasing metamorphic grade based on illite crystallinity data xrd and ir the following continuous changes are observed i the 1md 2m1 polymorph transformation is completed in the higher grade anchizone ii k2o increases from 6 8 wt diagenetic zone to 8 5 10 anchizone to 10 11 5 epizone reflecting an increase in the total negative layer charge from 1 2 to 2 0 iii a decrease of the chemical variation of the mica population with detrital muscovite surviving up to the anchizone epizone boundary iv a shift of an endothermic peak in differential thermal curves from 500 to 750 c v k ar and rb sr apparent ages of the fraction 2 m decrease from the diagenetic zone to the epizone k ar ages being generally lower than rb sr ages the critical temperature for total ar resetting is estimated to be 260 30 c k ar and rb sr ages become concordant when the anchizone epizone boundary is approached the stable isotope data on the other hand show no change with metamorphic grade but are dependent on stratigraphic age these results suggest that the prograde evolution from 1 md illite to 2m1 muscovite involves a continuous lattice restructuration without rupture of the tetrahedral and octahedral bonds and change of the hydroxyl radicals however this is not a recrystallization process this restructuration is completed approximately at the anchizone epizone boundary the isotopic data indicate significant diffusive loss of 40ar and 87sr prior to any observable lattice reorganization the restructuration progressively introduces a consistent repartition of ar and k in the mineral lattices and is outlined by the 40ar 39ar age spectra concordant k ar and rb sr ages of around 35 30 ma with concomitant concordant 40ar 39ar release spectra are representative for the main phase of alpine metamorphism calanda phase in the glarus alps a second age group between 25 and 20 ma can probably be attributed to movements along the glarus thrust ruchi phase while values down to 9 ma in regions with higher metamorphic conditions suggest thermal conditions persisting at least until the middle tortonian

interpretation of the anomalous growth of austfonna svalbard a large arctic ice cap as previously reported repeat pass airborne laser altimetry measurements made in may 1996 and may 2002 show a large positive ice surface elevation change rate over parts of the accumulation area of austfonna eastern svalbard the maximum growth rate is estimated to be equivalent to a 35 40 increase in snowfall over the area of thickening thinning is observed at lower elevations here we discuss in detail the possible causes of these elevation changes including ice cap dynamics and or firn density changes and conclude that sea ice loss producing a localized increase in precipitation over austfonna remains the most convincing explanation this study highlights the problems of interpreting relatively short term altimetry measurements where auxiliary data are limited in both spatial and temporal extent

chronology and stratigraphy of late quaternary sediments in the konya basin turkey results from the kopal project abstract the late quaternary environmental history of the konya plain in south central turkey is used to examine sediment facies changes in a shallow non outlet basin which has experienced major climatically driven changes in lake extent two principal types of sedimentary archive are used to reconstruct a palaeoenvironmental record namely alluvial sequences on the carsamba alluvial fan and sediments from residual lakes the latter have been used to investigate broader climatic and vegetational histories via palaeolimnological techniques including pollen diatom and stable isotope analysis these changes are dated here by radiometric techniques including radiocarbon ams and conventional osl and u th chronological agreement is generally good between the different dating techniques although typically there is greatly reduced precision beyond ca 25 ka lake sediment cores investigated have basal ages beyond the range of 14c dating but contain hiatuses as a result of subsequent alternation between phases of lacustrine sedimentation and aeolian deflation in contrast to most deepwater non outlet lake systems the konya basin may have been occupied by a single extensive lake for as little as 10 of late quaternary time mainly around the time of the lgm this lake highstand was followed by an important arid interval in the absence of unbroken chronostratigraphic sequences palaeohydrological investigation of shallow non outlet lakes may require analysis of basin wide changes in sedimentation rather than reliance on single core records stratigraphic continuity in such sedimentary environments cannot be assumed and requires independent chronological control through radiometric dating

isotope systematics in minerals biotite rejuvenation and exchange during alpine metamorphism abstract the hercynian schists and granites of the helvetic basement aar massif in the central swiss alps are overprinted by low grade alpine metamorphism and associated deformation rb sr and k ar ages of biotites are systematically reset by the later greenschist facies event this rejuvenation is apparently controlled by temperature mineral chemistry and grain size and independent of deformation and exsolution thermally activated volume diffusion best explains this behaviour with ar and sr having similar activation energies and diffusion rates for sr showing a greater dependence on biotite composition feldspars and apatite also show increasing equilibration to the alpine event and together with alpine equilibria in the micas reveal important changes in the isotopic compositions of exchanging reservoirs these spatial and temporal variations must be assessed before true mineral ages can be calculated generally the higher grade equilibria show less radiogenic exchange reflecting increased dilution by external fluids of radiogenic components released at the main front of isotopic resetting rb sr ages of alpine muscovites in the granites suggest a maximum possible age of metamorphism of 25 ma in this low grade area this implies significant diachroneity in the timing of peak metamorphism in the central alps with the relatively delayed metamorphism in this area a reflection of the later initial thickening and delayed uplift of the helvetic basement

identification and dating of tephra layers from quaternary sedimentary sequences of inner anatolia turkey abstract results presented here are part of a research programme to investigate the environmental evolution in central anatolia during the pleistocene in this study tephra are used as chronostratigraphical markers between lacustrine sequences studied in cores or in sections surrounding eruptive centres of the central anatolian province at different locations in the konya plain and cappadocia tephra have been identified characterized and linked to eruptions of the nearby volcanoes seven different tephra have been clearly identified in lacustrine sequences of the konya plain 14 c dates on shells or organic matter as well as 230 th 234 u ages on gypsum give a chronological framework to the tephra layers in addition the study of the sediment fill of the eski acigol maar near nevsehir has allowed the recognition of several eruptions during late glacial and holocene in the vicinity of acigol the results show the first tephra to be identified in lacustrine sequences of anatolia they also show the cappadocian volcanism to be very young 35 ka this young volcanism is often of a basaltic type and does not include thick differenciated pyroclastic deposits

an 40 ar 39 ar rb sr and stable isotope study of micas in low grade fold and thrust belt an example from the swiss helvetic alps white micas in carbonate rich tectonites and a few other rock types of large thrusts in the swiss helvetic fold and thrust belt have been analyzed by 40ar 39ar and rb sr techniques to better constrain the timing of alpine deformation for this region incremental 40ar 39ar heating experiments of 25 weakly metamorphosed anchizone to low greenschist samples yield plateau and staircase spectra we interpret most of the staircase release spectra result from variable mixtures of syntectonic neoformed and detrital micas the range in dates obtained within individual spectra depends primarily on the duration of mica nucleation and growth and relative proportions of neoformed and detrital mica rb sr analyses of 12 samples yield dates of ca 10 39 ma excluding one anomalously young sample these dates are slightly younger than the 40ar 39ar total gas dates obtained for the same samples the rb sr dates were calculated using initial 87sr 86sr ratios obtained from the carbonate dominated host rocks which are higher than normal mesozoic carbonate values due to exchange with fluids of higher 87sr 86sr ratios and lower 18o 16o ratios model dates calculated using 87sr 86sr values typical of mesozoic marine carbonates more closely approximate the 40ar 39ar total gas dates for most of the samples the similarities of rb sr and 40ar 39ar total gas dates are consistent with limited amounts of detrital mica in the samples the 18o values range from 24 15 vsmow for 2 6 m micas and 27 16 for the carbonate host rocks the carbonate values are significantly lower than their protolith values due to localized fluid rock interaction and fluid flow along most thrust surfaces although most calcite mica pairs are not in oxygen isotope equilibrium at temperatures of ca 200 400 c their isotopic fractionations are indicative of either 1 partial exchange between the minerals and a common external fluid or 2 growth or isotopic exchange of the mica with the carbonate after the carbonate had isotopically exchanged with an external fluid the geological significance of these results is not easily or uniquely determined and exemplifies the difficulties inherent in dating very fine grained micas of highly deformed tectonites in low grade metamorphic terranes two generalizations can be made regarding the dates obtained from the helvetic thrusts 1 samples from the two highest thrusts mt gond and sublage have all of their 40ar 39ar steps above 20 ma and 2 most samples from the deepest helvetic thrusts have steps often accounting for more than 80 of 39ar release between 15 and 25 ma these dates are consistent with the order of thrusting in the foreland imbricating system and increase proportions of neoformed to detrital mica in the more metamorphosed hinterland and deeply buried portions of the nappe pile individual thrusts accommodated the majority of their displacement during their initial incorporation into the foreland imbricating system and some thrusts remained active or were reactivated down to 15 ma

a palynological contribution to the environmental archaeology of a mediterranean mountain wetland north west apennines italy within the framework of a regional research project on wetlands as cultural heritage sites an attempt was made to examine the natural and anthropogenic causes driving the vegetation dynamics and exploitation of a small mountain wetland to assess its potential use as an archive of the landscape history an environmental archaeology approach was used palaeoenvironmental data from traditional pollen sampling by coring were matched with stratigraphic information from an excavation area of several square metres and plant micro and macroremain analyses e g pollen assemblages micro and macrocharcoal morphological and dendrochronological features of waterlogged tree trunks were compared in order to evaluate them as effects of different environmental factors and to pinpoint these factors in this paper the focus is set mainly on the results originating from pollen analyses of a core drilled in the peat bog a few metres from the stratigraphic excavation the start of peat deposition sometimes coincidi

late pleistocene piedmont glaciations in the eastern mediterranean insights from cosmogenic 36cl dating of hummocky moraines in southern turkey abstract we report the presence of late pleistocene piedmont glaciers represented by the largest hummocky moraine field observed in the eastern mediterranean the piedmont glaciers originated from the geyikdag ice cap 40 km 2 situated between 2350 and 2650 m above sea level a s l central tauride mountains of turkey and deeply carved the north facing hillslopes before reaching the namaras valley 2000 2050 m a s l the hummocky moraines resulted from in situ deposition of stagnant glacier ice where debris cover was heterogeneously distributed on the glacier surface thirty four boulders from hummocky disintegration lateral and terminal moraines from the namaras valley and the tributary susam valley 2100 2200 m a s l were dated by cosmogenic 36 cl surface exposure dating the moraine ages indicate three phases of deglaciation during the late pleistocene the oldest deglaciation occurred in the namaras valley at 18 0 1 1 ka ka thousand years ago towards the end of the last glacial maximum lgm and is recorded entirely by hummocky moraines we speculate that hummocky moraine forming processes with cycles of relief inversion gave rise to boulder apparent ages up to a few thousand years younger in our study area therefore 18 0 1 1 ka should be regarded as a minimum age with a probable true age much closer to the local lgm values 20 ka as observed in the surrounding mountains paleo piedmont glaciers also deposited several lateral moraines that are 50 m higher than the hummocky moraines although the lateral moraines probably represent the build up and the hummocky moraines the final phase of the same local lgm pulse both lateral moraines started to retreat from the late glacial 14 0 2 7 ka and gradually disappeared by mid holocene 5 2 1 0 ka encompassing the younger dryas yd stadial in the susam valley the late glacial is represented by a terminal moraine 13 4 1 5 ka the glacier retreat was very fast as indicated by an almost instantaneous disappearance of 5 km long susam valley glacier represented by disintegration and hummocky moraines 14 0 1 3 ka alternatively in case the oldest boulder age is taken into account the susam valley glacier can be also attributed to the late lgm 17 ka to late glacial 14 ka transition near the exit of the susam valley a right lateral moraine was deposited 11 6 1 3 ka ago confirming the presence of the yd in geyikdag comparable glacial chronologies were obtained from other turkish and mediterranean mountains

sea land correlation of pollen records in the eastern mediterranean for the glacial interglacial transition biostratigraphy versus radiometric time scale abstract pollen diagrams based on marine cores from the eastern mediterranean and arabian seas and land cores from greece turkey the levant and western iran during the last deglaciation reveal a similar succession of conspicuous pollen abundance maxima an early phase with chenopodiaceae signaling the highest aridity a late phase with pistacia and gramineae in the mediterranean domain and tropical humid taxa in the arabian sea domain indicating conditions of mildest winter and wettest summer between these two phases the record for deciduous oak in the mediterranean and near east shows a continuous increase that points to rising moisture the chronology of this succession and its exact relationship with the marine isotopic record of global climate are established using marine cores the marine records dated by the ams 14 c method show that the chenopodiaceae phase correlates with the younger dryas chronozone globally dated 11 000 to 10 000 bp during which the climate reversed to quasi glacial conditions at least in the northern hemisphere they also show that the pistacia phase during which the mediterranean climate reached its seasonal optimum occurred from 9000 to 6000 14 c years bp boreal and early atlantic chronozones defined in nw europe in the first half of the holocene the oak pollen abundance increases rapidly from 10 000 to 9000 bp preboreal chronozone thus in terms of climate the younger dryas chronozone is regionally expressed by wide spread desert conditions as a cold and arid period during the pistacia phase the climate was most favourable both for plants that require frost free winters such as the mediterranean pistacia and those that need spring summer moisture such as gramineae at low annual moisture level seasonally 300 mm and deciduous oak at higher levels 600 mm all year without summer drought during the brief intermediary phase the climate changed drastically through an increase of winter temperature and of spring summer moisture the chronologies of the land cores however based on few 14 c dates show significant discrepancies with the marine based time frame these discrepancies imply a lack of coherence in the climate history of this mediterranean irano turanian region we propose using the chronology derived from the marine records for the entire region the local 14 c dates generally appear too old perhaps because of geological contamination of the material by older carbon

when the desert was green grassland expansion during the early holocene in northwestern arabia abstract an early to mid holocene lake in the north of the oasis of tayma northwestern saudi arabia proved to be an excellent palynological archive a shallow probably brackish water body formed at about 9200 cal bp with the dominance of goosefoot throughout the sequence indicating the persistence of desert vegetation however distinct vegetation changes are recorded during the early holocene grasslands spread soon after 9000 cal bp and reached their maximal expansion ca 8600 8000 cal bp at about 8000 cal bp these grasslands retreated abruptly and were replaced by more drought resistant dwarf shrublands similar to the present day ecosystems the recorded early holocene grassland expansion furnishes for the first time evidence of an additional and more favourable grazing resource and thereby improved conditions for herders hunters during the early holocene in northwestern arabia which retreated abruptly due to aridification at about 8000 cal bp

staircase 40 ar39ar spectra of fine grained white mica timing and duration of deformation and empirical constraints on argon diffusion staircase 40 ar 39 ar spectra of 2 to 6 m white micas in ductile carbonate mylonites morcles doldenhorn nappe switzerland record ages between 32 and 13 ma these ages are within independent geochronologic and biostratigraphic time limits for the beginning and ending of deformation of this fold thrust nappe we interpret these data to record protracted white mica neocrystallization and growth during low temperature ductile deformation such that the differences between the maximum and minimum ages in the 40 ar 39 ar spectra record the time span over which mica formed and grew we have modeled the argon concentrations in these micas taking into account the thermal history of the nappe mica growth and diffusional loss of argon our results indicate that available experimental data underestimate the activation energy for argon diffusion in muscovite and that the retentivity of argon in white mica is greater than generally thought

40ar 39ar dating of synkinematic white mica insights from fluid rock reaction in low grade shear zones mont blanc massif and constraints on timing of deformation in the nw external alps this paper highlights the use of synkinematic white mica biotite and phlogopite for the dating of deformation in ductile shear zones within crystalline rocks under low grade metamorphic conditions the mont blanc shear zones range from 1 mm to 50 m in width and have localized intense fluid flow resulting in substantial differences in mineralogy and whole rock geochemistry on the basis of their synkinematic alteration assemblages and geographic distribution within the mont blanc massif three main metamorphic zones are distinguished within the network of shear zones these are i epidote white mica bearing assemblages ii chlorite phlogopite bearing assemblages and iii white mica biotite calcite actinolite epidote bearing assemblages 40ar 39ar age spectra of biotite and phlogopite are complex and reflect significant variations in chemical composition in biotite this is partly due to inheritance from precursor variscan magmatic biotite in contrast new white mica grew at the expense of feldspar during alpine deformation and its ar spectra do not show any excess 40ar on the se side of mont blanc ages of shear zone phengites have a narrow range of 15 8 16 0 0 2 ma which is in the same age range as 40ar 39ar ages of minerals from kinematically related veins the top to se sense of shear is consistent with initiation of a mont blanc flower structure within a dextral transpressional system by 16 ma on the nw side mini plateaux ages of 14 5 0 3 and 23 4 0 4 ma are preserved in the same sample suggesting the possibility of two phases of deformation this is also supported by partly preserved ages of 18 36 6 ma in biotites and phlogopites ages between 36 and 18 ma might reflect ongoing top to nw thrusting following penninic front activation in a context of nappe stacking and crustal thickening nw directed thrusting on the nw side of mont blanc continued after 18 ma synchronous with se directed thrusting on the se side of the massif these divergent movements produced the overall pop up geometry of the mont blanc massif which may correspond to a positive flower structure developed within a zone of regional dextral transpression extending sw from the rhone valley into the mont blanc area

what the past can say about the present and future of fire wildfires are an integral part of most terrestrial ecosystems paleofire records composed of charcoal soot and other combustion products deposited in lake and marine sediments soils and ice provide a record of the varying importance of fire over time on every continent this study reviews paleofire research to identify lessons about the nature of fire on earth and how its past variability is relevant to modern environmental challenges four lessons are identified first fire is highly sensitive to climate change and specifically to temperature changes as long as there is abundant dry fuel we can expect that in a warming climate fires will continue to grow unusually large severe and uncontrollable in fire prone environments second a better understanding of slow interannual to multidecadal socioecological processes is essential for predicting future wildfire and carbon emissions third current patterns of burning which are very low in some areas and very high in others are often unprecedented in the context of the holocene taken together these insights point to a fourth lesson that current changes in wildfire dynamics provide an opportunity for paleoecologists to engage the public and help them understand the potential consequences of anthropogenic climate change

paleovan international continental scientific drilling program icdp site survey results and perspectives lake van is the fourth largest terminal lake in the world volume 607 km 3 area 3570 km 2 maximum depth 460 m extending for 130 km wsw ene on the eastern anatolian high plateau turkey the sedimentary record of lake van partly laminated has the potential to obtain a long and continuous continental sequence that covers several glacial interglacial cycles ca 500 kyr therefore lake van is a key site within the international continental scientific drilling program icdp for the investigation of the quaternary climate evolution in the near east paleovan as preparation for an icdp drilling campaign a site survey was carried out during the past years we collected 50 seismic profiles with a total length of similar to 850 km to identify continuous undisturbed sedimentary sequences for potential icdp locations based on the seismic results we cored 10 different locations to water depths of up to 420 m multidisciplinary scientific work at positions of a proposed icdp drill site included measurements of magnetic susceptibility physical properties stable isotopes xrf scans and pollen and spores this core extends back to the last glacial maximum lgm a more extended record than all the other lake van cores obtained to date both coring and seismic data do not show any indication that the deepest part of the lake tatvan basin ahlat ridge was dry or almost dry during past times these results show potential for obtaining a continuous undisturbed long continental palaeoclimate record in addition this paper discusses the potential of paleovan to establish new results on the dynamics of lake level fluctuations noble gas concentration in pore water of the lake sediment history of volcanism and volcanic activities based on tephrostratigraphy and paleoseismic and earthquake activities c 2009 elsevier ltd all rights reserved