structural evolution of the latakia ridge and cyprus basin at the front of the cyprus arc eastern mediterranean sea abstract the active deformation front between the african and anatolian plates in the eastern mediterranean is delineated by the cyprus arc present plate kinematic vectors and earthquake data suggest that the movement along the eastern extent of the cyprus arc is largely sinistral strike slip it is however widely accepted that subduction took place beneath cyprus until the early miocene subduction has since thought to have become impeded by the collision of the eratosthenes seamount with the island of cyprus the deformation front of the cyprus arc is dominated by the latakia ridge a steep narrow high which merges gradually with the lower slope of the broad hecataeus rise in the west and extends to the northern levantine coast in the east where the expression of the ridge changes to a number of narrow northeast trending ridges and basins the latakia ridge has previously been interpreted as either a thrust culmination or a positive flower structure this study uses high resolution marine seismic reflection profiles to delineate the stratigraphic and structural architecture of the deformation front from seismic profiles four stratigraphic units bounded by major basin wide unconformities can be identified these units are eocene lower miocene miocene uppermost miocene messinian and pliocene quaternary the timing of deformation determined from growth stratal architectures on the flanks of the major structures show that two main phases of deformation characterize the structural history of the deformation front each of these phases represents a different kinematic regime a compressional regime dominated during the miocene whereas a strike slip regime dominated in the pliocene quaternary

holocene climate changes in the monsoon arid transition reflected by carbon concentration in daihai lake of inner mongolia two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for total inorganic and organic carbon tic and toc concentrations the tic concentration is inferred to reflect temperatures over the lake region and an increase in the tic concentration implies an increase in the temperature toc concentration is considered to reflect the precipitation in the lake basin and higher toc concentrations denote more precipitations thus ams 14c time series of the tic and toc records of daihai lake sediments uncovers a detailed history of changes in temperature and precipitation in north central china during the last c 12 000 yr the holocene an epoch of postglacial warmth started c 11 500 cal yr bp and can be subdivided into three stages the early c 11 500 8100 cal yr bp middle c 8100 3300 cal yr bp and the late holocene c 3300 0 cal yr bp the climate was warm and dry during the early holocene warm and wet during the middle holoce

deep air convection in the firn at a zero accumulation site central antarctica abstract ice cores provide unique archives of past atmospheres and climate but interpretation of trapped gas records and their climatic significance has been hampered by a poor knowledge of the prevalence of air convection in the firn layer on top of polar ice sheets in particular the phasing of greenhouse gases and climate from ice cores has been obscured by a discrepancy between empirical and model based estimates of the age difference between trapped gases and enclosing ice which may be due to air convection here we show that deep air convection 23 m occurs at a windy near zero accumulation rate site in central antarctica known informally as the megadunes site 80 77914 s 124 48796 e deep convection is evident in depth profiles of air withdrawn from the firn layer in the observed pattern of the nitrogen isotope ratio 15 n 14 n the argon isotope ratio 40 ar 36 ar and in the mixing ratios of the anthropogenic halocarbons methyl chloroform ch 3 ccl 3 and hfc 134a ch 2 fcf 3 transport parameters diffusivities were inferred and air was dated using measured carbon dioxide co 2 and methane ch 4 mixing ratios by comparing with the law dome atmospheric record which shows that these are the oldest firn air samples ever recovered co 2 mean age 1863 ad the low accumulation rate and the consequent intense metamorphism of the firn due to prolonged exposure to seasonal temperature cycling likely contribute to deep air convection via large grain size and vertical cracks that act as conduits for vigorous air motion the megadunes site provides a possible modern analog for the glacial conditions in the vostok dome fuji and dome c ice core records and a possible explanation for lower than expected 15 n 14 n ratios in trapped air bubbles at these times a general conclusion is that very low accumulation rate causes deep air convection via its effect on firn structural characteristics

density log of a 181 m long ice core from berkner island antarctica a 181 m long ice core was drilled at 79 36 51 s 45 43 28 w near the summit of berkner island antarctica 886 m a s l berkner island is located between the filchner and ronne ice shelves and the ice near the summit shows little lateral flow the density of the ice core was measured every 3 mm along its length using attenuation of a gamma ray beam which gave an absolute accuracy of 2 as expected there is a general density increase with depth the maximum densities of 900 kg m 3 being reached just above 100 m depth comparison with the electrical conductivity method ecm shows density variations with the same wavelength as the annual signals which can be seen in the ecm log higher acidity during summer in the shallowest part of the core the density of winter layers is higher than that of summer layers a relationship which is reversed at greater depth we assume that the densification rates for the two types of firn are different similar density phenomena were observed on ice cores from greenland showing that such phenomena are not a local effect

continuous methane measurements from a late holocene greenland ice core atmospheric and in situ signals abstract ancient air trapped inside bubbles in ice cores can now be analysed for methane concentration utilising a laser spectrometer coupled to a continuous melter system we present a new ultra high resolution record of atmospheric methane variability over the last 1800 yr obtained from continuous analysis of a shallow ice core from the north greenland eemian project neem 2011 s1 during a 4 week laboratory based measurement campaign our record faithfully replicates the form and amplitudes of multi decadal oscillations previously observed in other ice cores and demonstrates the detailed depth resolution 5 3 cm rapid acquisition time 30 m day 1 and good long term reproducibility 2 6 2 of the continuous measurement technique in addition we report the detection of high frequency ice core methane signals of non atmospheric origin firstly measurements of air from the firn ice transition region and an interval of ice core dating from 1546 1560 ad gas age resolve apparently quasi annual scale methane oscillations traditional gas chromatography measurements on discrete ice samples confirm these signals and indicate peak to peak amplitudes of ca 22 parts per billion ppb we hypothesise that these oscillations result from staggered bubble close off between seasonal layers of contrasting density during time periods of sustained multi year atmospheric methane change secondly we report the detection of abrupt 20 100 cm depth interval high amplitude 35 80 ppb excess methane spikes in the neem ice that are reproduced by discrete measurements we show for the first time that methane spikes present in thin and infrequent layers in polar glacial ice are accompanied by elevated concentrations of carbon and nitrogen based chemical impurities and suggest that biological in situ production may be responsible

itcz and enso pacing on east asian winter monsoon variation during the holocene sedimentological evidence from the okinawa trough deep sea fan sediments provide an excellent geological archive for paleoenvironment reconstruction grain size clay mineral and elemental ti fe ca compositions were measured for a core retrieved from a submarine fan in the okinawa trough varimax rotated principal component analysis v pca on time evolution of grain size spectrum reveals that since the holocene sediment was transported mainly by the benthic nepheloid layer 33 and upper layers 33 which is driven by the east asian winter monsoon eawm the intensification of the kuroshio current during the holocene masks the fluvial signal of the summer monsoon and obstructs clay minerals derived from the yellow river a major contributor prior to 12 ka bp a new grain size index gsi which represents the eawm well exhibits a negative correlation with the delta o 18 record in dongge cave china during the holocene when sea level was relatively steady this anti correlation suggests the southward migration of the intertropical convergence zone itcz the consistency among our records and rainfall records in peru ti counts in the cariaco basin monsoon records in oman and the averaged summer insolation pattern at 30 degrees n further support the itcz s impact on monsoon systems globally cross correlation analyses for gsi and log ti ca against delta o 18 record in dongge cave reveal a decoupling between the east asian winter and summer monsoon during 5500 2500 cal yr bp with greater complexity in the last 2500 years this can be attributed to exacerbated enso mode fluctuations and possibly anthropogenic interference superimposed on insolation and itcz forcing

reconstructing atmospheric histories from measurements of air composition in firn 1 this paper investigates the use of a numerical model of firn diffusion and bubble trapping in the reconstruction of atmospheric records from firn measurements we describe the concept of mean age and effective age of tracers in firn air and how the growth rate of a tracer in the atmosphere can alter the effective age we discuss an iterative method to assign effective ages to firn measurements for tracers with fairly simple atmospheric histories taking into account atmospheric growth rate variations we then develop a bayesian synthesis inversion calculation for inverting firn concentration measurements this calculation gives estimates of the atmospheric concentration record with uncertainties the dating and inversion techniques are demonstrated here with carbon tetrachloride measurements from a long firn record from law dome antarctica the techniques are then applied to measurements of a range of halocarbons in a companion paper by sturrock et al 2002

δ15n of n2 in air trapped in polar ice a tracer of gas transport in the firn and a possible constraint on ice age gas age differences with respect to gas transport the fim near the surface of an ice sheet can be divided into three zones the uppermost is a convective zone located just below the surface of the ice sheet in which the air is rapidly flushed by convective exchange with the overlying atmosphere below the convective zone there is a diffusive air column in which diffusion is rapid but there is no convection between the bottom of the diffusive air column and the bubble close off region there may be a nondiffusive zone in which diffusion is so slow that negligible gas transport occurs the diffusive air column is characterized by progressive enrichment with depth of 15n in n2 and heavy isotopes of gases in general as predicted using the barometric equation in this paper we present data on the 15n of n2 in recently trapped air samples from 12 ice cores along with numerous downcore samples from byrd vostok and dome c bubble close off depths for these cores calculated from a densification model ranged from 51 to 114 meters below the surface mbs we used these data and the barometric equation to calculate the thickness of the diffusive air column and found that it comprised 46 to 93 of the total firn thickness at our study sites paleo close off depths calculated from the densification model for glacial sections of byrd vostok and dome c are 15 25 m deeper than close off depths today diffusive column heights calculated from 15n varied in a more complex manner the diffusive column height at byrd appears to have decreased from 74 m during the last glacial period to 50 m during the holocene at vostok and dome c the diffusive column height calculated from 15n increase from about 65 m during the last glacial period to about 80 m in the holocene we use records of surface temperature and co2 at byrd and vostok along with their respective chronologies to constrain the ice age gas age difference age throughout the section of the vostok ice core corresponding to the last glacial termination in principle age values calculated from these data can be used to discriminate whether gas in the fim mixes to the bubble close off depth or to a depth equivalent to the diffusive column height in practice however uncertainties in the chronology of byrd and vostok are too great to allow us to distinguish between these two possibilities one can only say that at the time of the last termination age for vostok was between 3 and 10 5 kyr previous estimates fall within this range

impact and implications of the afro eurasian collision south of cyprus from reflection seismic data abstract the cyprus arc in the eastern mediterranean represents the active collision front between the african and eurasian anatolian plates along the cyprus arc the eratosthenes seamount is believed to have been blocking the northward motion of the african plate since the late pliocene early pleistocene based on a dense grid of 2d reflection seismic profiles covering the eratosthenes seamount and western levant basin offshore cyprus new observations regarding the cyprus arc collision front at the triple transition zone eratosthenes seamount levant basin hecataeus rise are presented the data show that the levant basin is filled with 10 km of sediments of early mesozoic probably jurassic to plio quaternary age with only a localized deformation affecting the miocene oligocene rock units the sediments onlap directly against the steep eastern flank of the eratosthenes seamount to the west and the southern flank of the hecataeus rise to the north the sediments show no deformation that could be associated with collision and are undeformed even very close to the two prominent structures pinching out of the base miocene reflector in the levant basin due to onlapping of the middle miocene reflector indicates uplift of the eratosthenes seamount and the hecataeus rise in contrast to the messinian evaporites north of the eratosthenes seamount the salt in the levant basin even close to the hecataeus rise is tectonically undeformed it is proposed that the eratosthenes seamount the western levant basin and the hecataeus rise act as one tectonic unit this implies that the collision front is located north of this unit and that the hecataeus rise shields the sediments south of it from deformation associated with collision of the african and anatolian plates

moisture variations in lacustrine eolian sequence from the hunshandake sandy land associated with the east asian summer monsoon changes since the late pleistocene abstract paleoclimate records currently lack sufficient geographic detail to understand the spatiotemporal evolution of east asian summer monsoon easm rain belt since the late pleistocene in particular there is no consensus on whether the easm rain belt reached its modern northern limit by the early holocene here we present inferred moisture variations from a multi parameter absolute dated lacustrine eolian sequence from northern china that date back to the late pleistocene 14 ka bp or thousand years ago we observed a sharp transition towards wet conditions at the onset of the holocene epoch maximum wet climate occurred here during 11 3 8 5 ka the climate remained predominantly wet until 4 2 ka then it became progressively drier we observed alternating organic rich fine grained lake deposits and organic depleted coarse grained eolian sand layers during 14 7 ka these layers correspond to sedimentation associated with the allerod younger dryas yd post yd warming pre boreal oscillation pbo early holocene and 8 2 ka event we interpreted the orbital scale moisture variation at our study site to the changes in insolation assigning these abrupt and short lived changes during the late pleistocene holocene transition to a persistent teleconnection between the north atlantic and east asian climate zones

a 15 ka ph record from an alpine lake in north china derived from the cyclization ratio index of aquatic brgdgts and its paleoclimatic significance abstract a well dated sediment core from an alpine lake in north china gonghai lake was used for analysis of branched glycerol dialkyl glycerol tetraether lipids brgdgts based on the cyclization ratio index cbt of the brgdgts and using different terrestrial and lacustrine cbt ph empirical relationships the reconstructed ph records over the past ca 15 ka exhibited similar trends of variation although the absolute ph values were different in order to better understand the reconstructed ph record samples of surface soils from the dust source area and the catchment of gonghai lake as well as surface sediments from the lake were collected for instrumental ph measurements and modern brgdgt analysis the instrumental ph results demonstrated that the surface soils from the dust source area were alkaline while those from the catchment of gonghai lake were acidic in addition the instrumental ph results for the surface sediments from the lake were slightly alkaline and the corresponding ph values were intermediate between those of the two surface soil source groups this may reflect the effect of the input of material from different sources on the sedimentary ph record however the results from modern brgdgts in some of the surface soils and surface sediment samples demonstrate that brgdgts in the core sediments from gonghai lake are predominantly of aquatic origin therefore the cbt derived ph record over the past ca 15 ka from the lake can be interpreted as a record of the lake water ph history which is consistent with the carbonate content record from a parallel core from the same lake in addition using the modern lacustrine calibration the cbt derived ph values for surface sediments of gonghai lake are consistent with instrumental modern lake water ph values for the lake further comparison indicates that the lake water ph is controlled mainly by the degree of humidity of the local climate which is closely related to the intensity of the east asian summer monsoon easm therefore the ph record can be used as an indicator of easm intensity our results demonstrate that on the basis of careful analysis of its origins the cbt index of aquatic brgdgts can be used for lake water ph reconstruction and subsequent paleoclimate reconstruction and that in north china the lake water ph is controlled mainly by the degree of humidity of the local climate

a 14 7 ka record of earth surface processes from the arid monsoon transitional zone of china the stability of earth s critical zone is intimately linked with erosion weathering and vegetation type and density therefore it affects global biogeochemical processes which in turn affect the global climate by absorbing and reflecting solar radiation and by altering fluxes of heat water vapour carbon dioxide and other trace gases through various feedback mechanisms however there is a lack of knowledge about how earth s critical zone processes have changed over time and their link with past monsoon variability especially in asia the study of lake sediments which contain a suite of inorganic elemental and isotopic proxies may facilitate the understanding of the earth s critical zone processes on millennial timescales here we reconstruct the history of erosion weathering vegetation interactions since similar to 14 7 ka using geochemical records from a radiocarbon dated sediment core from lake gonghai in the monsoon arid transitional zone of north china detrital al ti k rb and authigenic ca sr elemental records reveal distinct millennial scale late deglacial holocene erosion and weathering patterns and transitions with the former latter elements showing higher lower values in warm intervals and vice versa chemical index of alteration cia molar a humidity proxy suggests low humidity during the late deglacial similar to 11 5 14 7 ka high humidity during the early mid holocene similar to 11 5 3 2 ka and intermediate humidity during the late holocene interval since similar to 3 2 ka the results of cross spectral analysis and comparison of our records with other climate reconstructions also suggest a pattern of orbitally phased humidity changes in north china overall our results provide evidence for the solar forcing of earth s surface processes in mid latitude china under natural climatic conditions copyright c 2017 john wiley sons ltd

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

the southernmost margin of the tethys realm during the mesozoic and cenozoic initial geometry and timing of the inversion processes 1 along the northern border of africa pangea breakup has been diachronic during the jurassic the alpine tethys propagated northeastward from the atlantic to the alps during the permian the neo tethys propagated westward from oman to northwestern arabia then a secondary and late branch of neo tethys gave birth to the east mediterranean basin finally the two oceans connected at end of jurassic times achieving the development of africa northern plate boundary by the late cretaceous convergence between africa and eurasia led to the progressive closure of the tethys realm the continental collision is not completely achieved and the different segments of the confrontation zone maghreb central and east mediterranean zagros and oman expose different stages of the process however we emphasize the existence of synchronous geodynamic events from one end of the system to the other although they do not have the same meaning two of them are particularly important the campanian santonian c s event corresponds to 1 obduction and exhumation of high pressure low temperature metamorphic rocks around the arabian promontory 2 inversion along the margins of the east mediterranean basins and 3 lithosphere buckling in the atlas system maghreb and adjacent sahara platform the middle late eocene mle event corresponds to 1 the onset of collision at the northern corner of arabia 2 the onset of slab retreat in the mediterranean and 3 inversion along the margin of the east mediterranean as well as in the atlas the c s event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity the mle event coincides with a period of strong coupling between the africa and eurasia plates and an abrupt decrease of convergence velocity in the middle of the system the central mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the triassic

response of atmospheric co2 to the abrupt cooling event 8200 years ago atmospheric co2 records for the centennial scale cooling event 8200 years ago 8 2 ka event may help us understand climate carbon cycle feedbacks under interglacial conditions which are important for understanding future climate but existing records do not provide enough detail here we present a new co2 record from the siple dome ice core antarctica that covers 7 4 9 0 ka with 8 to 16 year resolution we observe a small about 1 2 ppm increase of atmospheric co2 during the 8 2 ka event the increase is not significant when compared to other centennial variations in the holocene that are not linked to large temperature changes our results do not agree with leaf stomata records that suggest a co2 decrease of up to 25 ppm and imply that the sensitivity of atmospheric co2 to the primarily northern hemisphere cooling of the 8 2 ka event was limited

little ice age cold interval in west antarctica evidence from borehole temperature at the west antarctic ice sheet wais divide 1 the largest climate anomaly of the last 1000 years in the northern hemisphere was the little ice age lia from 1400 1850 c e but little is known about the signature of this event in the southern hemisphere especially in antarctica we present temperature data from a 300 m borehole at the west antarctic ice sheet wais divide results show that wais divide was colder than the last 1000 year average from 1300 to 1800 c e the temperature in the time period 1400 1800 c e was on average 0 52 0 28 c colder than the last 100 year average this amplitude is about half of that seen at greenland summit grip this result is consistent with the idea that the lia was a global event probably caused by a change in solar and volcanic forcing and was not simply a seesaw type redistribution of heat between the hemispheres as would be predicted by some ocean circulation hypotheses the difference in the magnitude of the lia between greenland and west antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions

convective mixing of air in firn at four polar sites air withdrawn from the firn at four polar sites dome fuji h72 and ym85 antarctica and north grip greenland was measured for 15 no f n2 and 18 oo f o2 to test for the presence of convective air mixing in the top part of the firn known as the convective zone understanding the convective zone and its possible relationship to surface conditions is important for constructing accurate ice core greenhouse gas chronologies and their phasing with respect to climate change the thickness of the convective zone was inferred from a regression line with barometric slope of the data in the deep firn it is less than a few meters at h72 and ngrip whereas a substantial convective zone is found at dome fuji 8 6 2 6 m and ym85 14 0 1 8 m by matching the outputs of a diffusion model to the data effective eddy diffusivities required to mix the firn air are found at the surface of dome fuji and ym85 these are found to be several times greater than the molecular diffusivity in free air the crossover from dominance of convection to molecular diffusion takes place at 7 2 11 2 and 0 5 0 5 m at dome fuji ym85 and ngrip respectively these depths can be used as an alternative definition of the convective zone thickness the firn permeability at dome fuji is expected to be high because of intense firn metamorphism due to the low accumulation rate and large seasonal air temperature variation at the site the firn layers in the top several meters are exposed to strong temperature gradients for several decades leading to large firn grains and depth hoar that enhance permeability the thick convective zone at ym85 is unexpected because the temperature accumulation rate and near surface density are comparable to ngrip the strong katabatic wind at ym85 is probably responsible for creating the deep convection the largest convective zone found in this study is still only half of the current inconsistency implied from the deep ice core gas isotopes and firn densification models 2006 elsevier b v all rights reserved

the local insolation signature of air content in antarctic ice a new step toward an absolute dating of ice records an accurate chronology of ice cores is still needed for interpreting the paleoclimatic record and to understand the relation between insolation and climate a new domain of research in this area has been stimulated by the work of m bender linking the record of n2 o2 ratio in the air trapped in the ice with the local insolation here we investigate the potential of the air content of polar ice v as another and complementary ice proxy of local insolation we propose that the long term changes in air content recorded in ice from the high antarctic plateau is dominantly imprinted by the local summer insolation the v measurements covering the last 440 000 yr and obtained along the epica dc edc ice core are presented 86 of the variance observed in the v record can be explained neither by air pressure nor by temperature changes and then should reflect properties influencing the porosity at close off other than temperature a wavelet analysis indicates a dominant obliquity period around 41 ka over the last 440 ka we propose a mechanism which can account for the observed anti correlation between local insolation and v and explain how the local insolation via the integrated summer insolation can affect the near surface snow structure and consequently the porosity at close off the v and the integrated summer insolation changes show high coherency over all the record and a variable phase relationship with a maximum phase difference of about 4000 yr around 200 ka ago the phase difference may reflect the difference between the edc2 chronology based on an inverse dating method and an accurately dated insolation curve our work by proposing a new and complementary ice proxy for local insolation should eventually contribute to the establishment of an absolute dating of the ice paleo record

the attenuation of fast atmospheric ch4 variations recorded in polar ice cores 1 to reconstruct fast atmospheric trace gas variations from polar ice cores it has to be considered that their amplitudes are attenuated during the enclosure process in the ice relevant processes for the attenuation are the molecular diffusion in the open pores of the firn column and the gradual bubble close off in the depth of the transition from firn to ice these processes depend mainly on temperature and accumulation rate and lead e g to a strong attenuation for cold sites with low accumulation rates with a diffusion and enclosure model it is possible to calculate the attenuation for a single event and to compare ice core records from different sites we investigate the atmospheric methane ch4 variation during the cold event 8200 years ago and calculate that its amplitude as recorded in the epica dome c ice core is attenuated to a magnitude between 34 and 59

the age of the air in the firn and the ice at summit greenland in the framework of the eurocore drilling project 1989 at summit central greenland air samples were collected from a drill hole in the firn at several depth levels the samples have been analyzed for 85kr co2 ch4 cfc s f 11 and f 12 contents and for the isotopic composition of nitrogen and oxygen the measured data are compared with the results of a diffusion model co2 for example takes 12 years with a standard deviation of 7 5 years to diffuse from the surface to the firn ice transition under the present climatic conditions at summit the difference between the age of the ice and the mean age of the occluded air is approximately 210 years an enrichment of the heavier isotopes due to separation by gravity has been observed molecular diffusion alone suffices to explain the observed concentration trends in the firn column we can however not exclude the existence of a convective zone below the surface we have also measured the density and closed porosity along the firn core that has been retrieved when drilling the hole the porosity data reveal that the air is occluded into bubbles mainly between 65 and 80 m corresponding to densities of 790 and 830 kg m3 respectively

gas records from the west greenland ice margin covering the last glacial termination a horizontal ice core abstract certain sites along ice sheet margins provide an easily accessible and almost unlimited supply of ancient ice at the surface measurements of gases in trapped air from ice outcropping at pakitsoq west greenland demonstrate that ancient air is mostly well preserved no alterations in 18 o atm and 15 n of n 2 are apparent and alterations in methane are found in only a few ice sections using measurements of these gases we have unambiguously identified a stratigraphic section containing ice from the end of last glacial period as well as bolling allerod younger dryas and preboreal intervals extensive sections of ice from the holocene and most ages within the last glacial period are probably also present very accurate dating has been possible in the ice section containing the younger dryas preboreal abrupt climate transition signal the ice at pakitsoq is folded and non uniformly thinned with many cross cutting bands of bubble free ice and dust the cross cutting features are associated with anomalies in both the gas and the ice records with careful sampling to avoid these the ice at pakitsoq is suitable for recovery of large volume samples of the ancient atmosphere for analysis of trace constituents such as 14 ch 4

palaeosol development in the chinese loess plateau as an indicator of the strength of the east asian summer monsoon evidence for a mid holocene maximum the interpretation of the stalagmite delta o 18 record from southern china as an indicator of east asian summer monsoon easm rainfall amount or intensity is strongly debated soil development in the chinese loess plateau clp situated in the modern summer monsoon domain has long been treated as a direct and reliable easm proxy in this study we compiled 81 loess and 229 palaeosol dates from 77 profiles across the clp and synthesized the data statistically in order to investigate the easm history during the holocene the resulting history of holocene loess deposition and palaeosol development demonstrates that 1 loess deposition decreased and palaeosol formation increased across the clp after 11 5 ka 1 ka 1000 cal yr bp revealing a gradually intensified easm during the early holocene 2 numerous palaeosols developed in the clp between 8 8 ka and 3 4 ka indicating a generally strong easm during the mid holocene 3 the number of palaeosol dates decreased rapidly at around 3 ka suggesting a sudden retreat of the easm in the late holocene these trends of easm evolution are broadly consistent with variations in aeolian sand activity in the four main sandlands the mu us otindag horqin and hulun buir sandlands along the modern monsoon fringe in northern china and are supported by a wide range of independent evidence in addition we also found that high loess deposition and stronger aeolian activity occurred at similar to 5 ka representing a weak easm event within the context of an overall strong mid holocene easm the strong mid holocene easm revealed by palaeosol development in the clp and aeolian sand activity in the sandlands in northern china contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china our results are compatible with the proposal that the stalagmite delta o 18 variations in china do not result from changes in easm rainfall amount or intensity but instead reflect changes in moisture source driven by variations in atmospheric oceanic circulation c 2014 elsevier ltd and inqua all rights reserved

enclosure of air during metamorphosis of dry firn to ice if cold firn has reached a density of about 0 55 mg m 3 further densificaron occurs by a sintering process which increases the contact surface between the firn grains the pore volume is decreasing continuously but the firn remains permeable to air up to a density of 0 82 mg m 3 at about this density the remaining air in the pore volume is closed off in isolated bubbles we are interested in the age and the age distribution of the air enclosed in bubbles relative to the age of the surrounding ice and are investigating the development of the pore volume in firn a newly constructed measuring device allows the field measurement of the amount of air which is already enclosed in bubbles of firn samples measurements have been made during summer 1983 in greenland and during winter 1983 84 at the south pole the results are discussed and compared with results obtained with a simplified statistical sintering model using some results of percolation theory

a new device for the measurement of air content in polar ice a new device for measuring air content in polar ice has been designed built and tested with 22 samples of antarctic ice the new technique is based on the barometric method which implies 1 air extraction under vacuum by melting refreezing of the ice sample placed in a calibrated cell and 2 accurate air pressure and temperature measurements the new apparatus simplifies the experimental procedures decreases the duration of measurement and can eventually be used in the field it provides results with an accuracy equivalent to or better than other methods previously used

millennial scale dynamics of the winter cold tongue in the southern south china sea over the past 26 ka and the east asian winter monsoon millennial scale variations of the east asian winter monsoon eawm remain elusive due to sparse and controversial reconstructions by compiling a variety of alkenone based sea surface temperature sst estimates we find that the west east sst gradient in the southern south china sea scs well documents the temporal dynamics of the winter cold tongue off the southern vietnam and by inference variations in the eawm intensity over the past 26 ka our results reveal that the winter cold tongue ssts were significantly colder during heinrich event 1 and the younger dryas event resulting in an increased west east sst gradient in the southern scs due to a strengthened eawm within dating uncertainties an intensified eawm during cold stadials was coeval with the shutdown or a reduction in strength of the atlantic meridional overturning circulation amoc exhibiting a strong linkage between the amoc and the eawm system the west east sst gradient also indicates an enhanced eawm during the early holocene which may be induced by postglacial ice sheet dynamics and a strong seasonal contrast in solar insolation our findings suggest that the eawm was probably modulated by a complex interplay between the amoc solar insolation and ice sheet dynamics on sub orbital time scales

vegetation succession and east asian summer monsoon changes since the last deglaciation inferred from high resolution pollen record in gonghai lake shanxi province china a cal 20 year resolution pollen record from gonghai lake presented the detailed process of mountain vegetation succession and east asian summer monsoon easm changes since the last deglaciation i

microstructure dependent densification of polar firn derived from x ray microtomography the densification of dry polar snow and firn results in a continuous increase of density with depth accompanied by significant density fluctuations within seasonal layers density measurements of high spatial resolution reveal a persistent minimum of density fluctuations in the vicinity of the snow firn transition 0 55 0 65 g cm 3 in firn core records in this study we give an explanation for the fluctuation minimum by applying a new method of x ray microtomography to obtain three dimensional 3 d structural data of a greenland firn core at 13 different depths between 10 and 78 m a set of 16 samples of 40 cm total length for each depth interval was measured a reconstructed firn segment of 40 cm covers 1 2 years of snow accumulation using digital image analysis techniques different structural parameters are estimated including 3 d pore and particle sizes and specific surface areas it is shown that the densification rates of snow and firn layers consisting of coarse particles are much higher than those consisting of fine particles within the same depth interval this causes a density crossing of fine and coarse grained layers with a minimum of density variations at the crossover point this crossing over implies that formerly dense layers in the seasonal density signal are not of the same origin as dense layers in the deeper part of the firn column and that the seasonal density signal will totally change shape with depth it is speculated that in coarse and fine grained firn the dominant mechanism of densification acts over different regimes of density

observing and modeling the influence of layering on bubble trapping in polar firn interpretation of ice core trace gas records depends on an accurate understanding of the processes that smooth the atmospheric signal in the firn much work has been done to understand the processes affecting air transport in the open pores of the firn but a paucity of data from air trapped in bubbles in the firn ice transition region has limited the ability to constrain the effect of bubble closure processes here we present high resolution measurements of firn density methane concentrations nitrogen isotopes and total air content that show layering in the firn ice transition region at the west antarctic ice sheet wais divide ice core site using the notion that bubble trapping is a stochastic process we derive a new parameterization for closed porosity that incorporates the effects of layering in a steady state firn modeling approach we include the process of bubble trapping into an open porosity firn air transport model and obtain a good fit to the firn core data we find that layering broadens the depth range over which bubbles are trapped widens the modeled gas age distribution of air in closed bubbles reduces the mean gas age of air in closed bubbles and introduces stratigraphic irregularities in the gas age scale that have a peak to peak variability of 10 years at wais divide for a more complete understanding of gas occlusion and its impact on ice core records we suggest that this experiment be repeated at sites climatically different from wais divide for example on the east antarctic plateau

asynchronous evolution of the isotopic composition and amount of precipitation in north china during the holocene revealed by a record of compound specific carbon and hydrogen isotopes of long chain n alkanes from an alpine lake both the timing of the maximum east asian summer monsoon easm intensity in monsoonal china and the environmental significance of the chinese stalagmite oxygen isotopic record delta o 18 have been debated here we present a ca 120 year resolution compound specific carbon delta c 13 and hydrogen sd isotopes of terrestrial long chain n alkanes extracted from a well dated sediment core from an alpine lake in north china our delta c 13 data together with previously reported pollen data from a parallel core demonstrate a humid mid holocene from ca 8 5 ka bp assuming that the climatic humidity of north china is an indicator of the easm intensity then the maximum easm intensity occurred in the mid holocene our sd data reveal a similar long term trend to the delta o 18 record from nearby lianhua cave indicating that the synchronous sd and delta o 18 records faithfully record the sd and delta o 18 of precipitation respectively the most negative sd and delta o 18 values occur in t he early mid holocene from ca 11 5 ka bp this contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount or easm intensity further comparisons indicate a possible linkage between the precipitation amount in north china and the west east thermal gradient in the equatorial pacific in addition the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal china c 2016 elsevier b v all rights reserved

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

assessment of diffusive isotopic fractionation in polar firn and application to ice core trace gas records abstract during rapid variations of the atmospheric mixing ratio of a trace gas diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere records of past atmospheric trace gas isotopic composition from ice cores and firn need to be corrected for this diffusive fractionation artifact we present a novel semi empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record our method 1 consists of a relatively simple analytical calculation 2 requires only commonly available ice core data 3 is not subject to the uncertainties inherent to estimating the accumulation rate temperature close off depth and depth diffusivity relationship back in time 4 does not require knowledge of the true atmospheric variations but uses the smoothed records obtained from ice cores 5 arguably gives more accurate results than a combined firn densification firn air transport modeling study would we apply the method to records of ch4 co2 and n2o mixing ratios and we find that the correction is particularly important for 13 c ch 4 we apply the correction to 13 c ch 4 records over the last glacial termination and the 8 2 ka event in both cases the diffusive signal exceeds the analytical precision of the data and has a significant impact on the observed isotopic trends for the 8 2 ka event the corrected data show an isotopic enrichment in 13 c ch 4 for the duration of the event consistent with reduced wetland emissions

age difference between polar ice and the air trapped in its bubbles air entrapped in bubbles formed in cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation the analysis of dated ice samples therefore enables the history of atmospheric composition to be investigated 1 3 the age of the entrapped air is however not the same as that of the surrounding ice because air bubbles only become isolated from the atmosphere during the transition from firn to ice typically the age of the ice at this transition is between 100 and 3 000 yr depending mainly on firn temperature and snow accumulation rate the mean age difference between ice and enclosed air as well as the age distribution width for a given sample are especially important for the investigation of the anthropogenic increase of co2 and trace gases in the atmosphere over the last centuries and for the comparison of climatic parameters recorded in the ice with parameters recorded in the bubbles for siple station antarctica this age difference and age distribution width were deduced from the bubble volume measured as a function of depth the values are 95 yr and 22 yr respectively

tectono stratigraphic evolution of the northern levant basin offshore lebanon abstract seismic interpretation constrained by a detailed assessment of the levant paleogeography allowed subdividing the sedimentary infill of the northern levant basin offshore lebanon in eight major seismic packages fifteen seismic facies have been identified with distinctive characteristics the levant basin architecture is pre determined by a late paleozoic early mesozoic rift that led to the formation of a passive margin dominant aggrading carbonate platforms are observed along the levant margin and deepwater mixed settings i e carbonates and siliciclastics are suggested to prevail in the basin the collision of afro arabia with eurasia led to the development of a flexural basin in the northernmost offshore lebanon since the late cretaceous a southward migration of this flexural depocenter in the miocene is hindered by the change in the stress field along the latakia ridge and by the westward escape of the anatolian plate in late miocene and pliocene times interplay between major geodynamic events as well as sea level fluctuations in the mesozoic and cenozoic induced important marginal uplifts and emersion sediments sourced from the erosion of nubian siliciclastic material and from the exposed granitic red sea rift shoulders and arabian shield were driven into the levant basin the sediment sources diversity the mechanisms of sediment transport through varied pathways i e the levant margin canyons the latakia region and the nile delta deep sea cone are expected to strongly impact the reservoir characteristics and prospectivity of the northern levant basin

seismic images at the convergence zone from south of cyprus to the syrian coast eastern mediterranean abstract multichannel seismic profiles from cruise 5 of the r v akademik nikolaj strakhov provide the first deep seismic reflection images and extensive coverage south and east of cyprus five nw se trending seismic lines cross an area of active continental collision main tectonic structures are the eratosthenes seamount collision zone the hecateaus rise and the latakia larnaca ridge systems the levantine basin extends to the south all over the area the data required careful processing due to the low fold coverage the reverberatory character of the signal and the strong multiple energy the seismic results clearly image the thick sedimentary sequence of the levantine basin this basin is observed to terminate abruptly at the junction with the hecateaus rise south of cyprus to the east and north the deformation appears to be partitioned along two separated structures next to the latakia and larnaca ridges they correspond to major oblique fault systems

episode of strengthened summer monsoon climate of younger dryas age on the loess plateau of central china abstract the baxie loess section just east of the tibetan plateau contains evidence showing that the asian monsoon climate experienced an abrupt reversal near the end of the last glacial age rapid deposition of dust under cool dry full glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm moist summer monsoon a subsequent abrupt increase in dust deposition a response to a weakening of the summer monsoon was later followed by renewed soil formation as summer monsoon circulation again intensified during the early holocene by one interpretation the thin upper loess is a manifestation of the european younger dryas oscillation however in this case the available 14c ages require either that 1 onset of loess deposition lagged the beginning of the younger dryas event in europe by as much as 2000 calibrated 14c years or 2 all the 14c ages are too young possibly due to contamination alternatively the late glacial paleosol the top of which is synchronous with the abrupt end of the late glacial 18o anomaly in the dye 3 greenland ice core records the younger dryas event such an interpretation is consistent with general circulation model simulations of younger dryas climate that show strong seasonality and a strengthened summer monsoon and with marine cores from the western pacific ocean that contain evidence of pronounced cooling of surface waters during younger dryas time

spatial and temporal variability in snow accumulation at the west antarctic ice sheet divide over recent centuries mean annual accumulation rates of 0 200 0 204 and 0 221 mweq a 1 respectively small scale spatial variability ssv was determined using an analysis of variance of accumulation in the ice core array thereby quantifying the uncertainty in individual accumulation records results indicate that the spatial variability was 0 030 mweq a 1 o r approximately 15 of the average annual accumulation an accumulation record representative of the wais divide local area over recent centuries was developed using a principal component analysis to identify the coherent accumulation signal the wais divide local record exhibited 14 interannual variability 1 standard deviation of the mean with the ssv reduced to 0 017 mweq a 1 correlations of the wais divide local accumulation record with atmospheric indices e g antarctic oscillation exhibited periods when the records oscillate in and out of phase thus reconstructing local and global atmospheric indices from wais divide accumulation records over recent centuries may prove problematic

evolution of integrated lake status since the last deglaciation a high resolution sedimentary record from lake gonghai shanxi china abstract alpine lakes not only provide internationally important habitats for endangered species they also play a crucial role in the regional water balance unfortunately a rapid loss of alpine lakes in china has occurred in recent decades however intensive human activities together with regional differences in the responses of lakes to climate change has impeded our understanding of the contribution of climate change to the loss of these lakes to better understand how alpine lakes will evolve with continuing global warming we used the analysis of new sedimentary proxies from lake gonghai an undisturbed alpine lake together with a review of published records to reconstruct variations in integrated lake status since the last deglaciation from 14 660 11 890 cal yr bp the lake was in the most unstable state indicated by the highest amplitude fluctuations in lake level and the within lake environment the lake status experienced clear millennial scale changes during the early and middle holocene 11 890 3200 cal yr bp the most stable lake status occurred consistent with the highest precipitation levels owing to the highest level of freshwater influx in the middle holocene 8 5 ka the lake water was the deepest and most acidic at this time the dense vegetation cover resulted in maximum catchment stability and the lowest level of soil erosion and hence the lowest sediment accumulation rate from 3200 cal yr bp decreasing mean annual precipitation resulted in a moderately stable lake status a shallow water depth and more alkaline lake water the sparse vegetation cover caused a dramatic increase in the erosion rate and hence in the sediment accumulation rate we infer that variations in local humidity were the major control on the integrated lake status during the last 14 600 cal yr bp with the anticipated progression of global warming the status of the alpine lakes in the region may continue to deteriorate and appropriate mitigation strategies are imperative

modeling the densification of polar firn including heat diffusion application to close off characteristics and gas isotopic fractionation for antarctica and greenland sites 1 modeling the densification of polar firn is essential to estimate variations of close off characteristics density close off depth delta age in relation with past climate parameters temperature and accumulation rates furthermore the air composition in the firn is modified by gravitational and thermal fractionation and stable isotope measurements of permanent gases like nitrogen or argon can provide information on the amplitude of these fractionations in this work we propose a new model coupling firn densification and heat diffusion in addition to the determination of the firn thickness and gas ice age differences the model allows a reconstruction of the time evolution of the temperature for different sites in antarctica vostok and greenland gisp2 and therefore the evolution of gravitational and thermal isotopic fractionations in firn under present day conditions the modeled profiles are in good agreement with the available temperature measurements in firn for sites with low accumulation rates such as vostok the results show the existence of temperature gradients in the firn column even when no rapid climatic changes occur the comparison of the modeled 15n results to measurements allows to better constrain the 18o temperature relationship used to infer the surface temperature history and for gisp2 the model validates the long term borehole based temperature

design optimization and calibration of an automated density gauge for firn and ice cores a gamma ray density gauge can provide high resolution and high precision density measurements of firn and ice cores this study describes the design gamma ray energy optimization and mass attenuation coefficient calibration of the maine automated density gauge experiment madge a portable field operable gamma ray density gauge used on overland traverses in east antarctica the madge instrument uses a 241 am gamma ray source a pulse mode counting system and electronic core diameter calipers to collect high precision 0 004 g cm 3 density data from 3 8 cm diameter firn and ice cores the data are collected at a 3 3 mm spatial resolution and an average throughput of 1 5 m h 1 for 5 cm diameter cores

layering of surface snow and firn at kohnen station antarctica noise or seasonal signal the density of firn is an important property for monitoring and modeling the ice sheet as well as to model the pore close off and thus to interpret ice core based greenhouse gas records one feature which is still in debate is the potential existence of an annual cycle of firn density in low accumulation regions several studies describe or assume seasonally successive density layers horizontally evenly distributed as seen in radar data on the other hand high resolution density measurements on firn cores in antarctica and greenland showed no clear seasonal cycle in the top few meters a major caveat of most existing snow pit and firn core based studies is that they represent one vertical profile from a laterally heterogeneous density field to overcome this we created an extensive dataset of horizontal and vertical density data at kohnen station dronning maud land on the east antarctic plateau we drilled and analyzed three 90 m long firn cores as well as 160 one meter long vertical profiles from two elongated snow trenches to obtain a two dimensional view of the density variations the analysis of the 45 m wide and 1 m deep density fields reveals a seasonal cycle in density however the seasonality is overprinted by strong stratigraphic noise making it invisible when analyzing single firn cores our density dataset extends the view from the local ice core perspective to a hundred meter scale and thus supports linking spatially integrating methods such as radar and seismic studies to ice and firn cores

glacial interglacial indian summer monsoon dynamics the modern indian summer monsoon ism is characterized by exceptionally strong interhemispheric transport indicating the importance of both northern and southern hemisphere processes driving monsoon variability here we present a high resolution continental record from southwestern china that demonstrates the importance of interhemispheric forcing in driving ism variability at the glacial interglacial time scale as well interglacial ism maxima are dominated by an enhanced indian low associated with global ice volume minima in contrast the glacial ism reaches a minimum and actually begins to increase before global ice volume reaches a maximum we attribute this early strengthening to an increased cross equatorial pressure gradient derived from southern hemisphere high latitude cooling this mechanism explains much of the nonorbital scale variance in the pleistocene ism record

the layered evolution of fabric and microstructure of snow at point barnola central east antarctica snow fabric defined as the distribution of the c axis orientations of the ice crystals in snow is poorly known so far only one study exits that measured snow fabric based on a statistically representative technique this recent study has revealed the impact of temperature gradient metamorphism on the evolution of fabric in natural snow based on cold laboratory experiments on polar ice sheets snow properties are currently investigated regarding their strong variability in time and space notably because of their potential influence on firn processes and consequently on ice core analysis here we present measurements of fabric and microstructure of snow from point barnola east antarctica close to dome c we analyzed a snow profile from 0 to 3 m depth where temperature gradients occur the main contributions of the paper are 1 a detailed characterization of snow in the upper meters of the ice sheet especially by providing data on snow fabric and 2 the study of a fundamental snow process never observed up to now in a natural snowpack namely the role of temperature gradient metamorphism on the evolution of the snow fabric snow samples were scanned by micro tomography to measure continuous profiles of microstructural properties density specific surface area and pore thickness fabric analysis was performed using an automatic ice texture analyzer on 77 representative thin sections cut out from the samples different types of snow fabric could be identified and persist at depth snow fabric is significantly correlated with snow microstructure pointing to the simultaneous influence of temperature gradient metamorphism on both properties we propose a mechanism based on preferential grain growth to explain the fabric evolution under temperature gradients our work opens the question of how such a layered profile of fabric and microstructure evolves at depth and further influences the physical and mechanical properties of snow and firn more generally it opens the way to further studies on the influence of the snow fabric in snow processes related to anisotropic properties of ice such as grain growth mechanical response electromagnetic behavior

on the impact of impurities on the densification of polar firn abstract understanding polar firn densification is crucial for reconstructing the age of greenhouse gas concentrations extracted from ice cores and for the interpretation of air in ice as a dating tool or as a climate proxy firn densification is generally modeled as a steady burial and sintering process of defined layers where the structure of the layering is maintained along the whole firn and ice column however available high resolution density data as well as firn air samples question this picture and point to a lack of understanding of firn densification based on analysis of high resolution density and calcium concentration records from antarctic and greenland ice cores we show for the first time that also impurities may have a significant impact on the densification analysis of firn cores shows a correlation between density and the calcium ion ca concentration and this correlation increases with depth the existence of this relationship is independent of the local climatic conditions at the core sites analyzed the strong positive correlation between the density and the logarithm of ca concentration indicates that impurities induce softening and lead to faster densification over a wide range of concentrations in one core the impurity effect manifests itself so strongly that the density develops a seasonal cycle closely following the seasonal cycle of ca our results clearly show that the structure of the firn layering changes with depth and suggest that the increased variability in density observed in deep firn recently described as a universal feature of polar firn may arise from the influence of ca and or other impurities the impurity effect is likely to have direct implications on our understanding of glacial firn densification and on glacial gas age estimates

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

climatic and glaciological information inferred from air content measurements of a law dome east antarctica ice core the total air content v of ice has been measured along the dome summit south dss core from law dome east antarctica the main features of this record are the very well preserved sub annual fluctuations of v down to at least 900 m depth and the significant increase of the v values during the last deglaciation the sub annual variations reflect changes in close off porosity and we interpret the v seasonal peaks as tracers of depth hoar layers for the longer time scale the large v fluctuations observed are interpreted in terms of elevation and or close off porosity changes under different assumptions we analyze the possible influence of a different global pressure field and or a change in seasonal temperature and precipitation cycles during the last glacial period our estimates of surface elevation changes derived from the v data are then compared with independent reconstructions of past elevations

the hecataeus rise easternmost mediterranean a structural record of miocene quaternary convergence and incipient continent continent collision at the african anatolian plate boundary abstract the hecataeus rise represents a plateau like structure adjacent to the southern cyprus margin and directly next to the cyprus eratosthenes seamount convergence zone where incipient continent continent collision is believed to occur based on newly acquired seismic reflection and bathymetric data we report on the miocene to quaternary structural evolution of this yet underexplored sector along the african anatolian plate boundary a period of pre messinian compression has significantly deformed the western and southern part of the plateau area offshore continuation of onshore cyprus lineaments attests the existence of a pre messinian structural link between cyprus and the hecataeus rise owing to its relatively elevated position during the messinian salinity crisis the hecataeus rise experienced wide spread messinian erosion and only local deposition of evaporites which were precipitated within small isolated sub basins post messinian convergence was accommodated along the southeastern flank of the hecataeus rise where ne sw trending anticlinal structures experienced reactivation and significant growth a prominent intra pliocene quaternary unconformity in the northwestern part of the plateau area may correlate with the pliocene pleistocene transition and indicates the near synchronous occurrence of several tectonostratigraphic events we suggest that these events represent a chain of structural and depositional changes initiated by incipient collision of eratosthenes seamount with cyprus and the northwestern corner of the hecataeus rise collision derived uplift of cyprus resulted in vertical separation between cyprus and the hecataeus rise and the development of a prominent unconformity in the northwestern part of the plateau area increasing the slopes adjacent to cyprus facilitated more energetic downslope sediment transport expressed by the development of sediment waves and the evolution of a prominent canyon structure at the northeastern limit of the plateau area

crustal structure of the levant basin eastern mediterranean abstract a seismic refraction wide angle reflection experiment was undertaken in the levant basin eastern mediterranean two roughly east west profiles extend from the continental shelf of israel toward the levant basin the northern profile crosses the eratosthenes seamount and the southern profile crosses several distinct magnetic anomalies the marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources the results of this study strongly suggest the existence of oceanic crust under portions of the levant basin and continental crust under the eratosthenes seamount the seismic refraction data also indicate a large sedimentary sequence 10 14 km thick in the levant basin and below the levant continental margin assuming the crust is of cretaceous age this gives a fairly high sedimentation rate the sequence can be divided into several units a prominent unit is the 4 2 km s layer which is probably composed of the messinian evaporites overlying the evaporitic layer are layers composed of plio pleistocene sediments whose velocity is 2 0 km s the refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single layer oceanic crust takes place along the levant margin the transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual the northern profile north of the carmel structure presents a different structure the continental crust is much thinner there and the transition in the crustal structure is more rapid the crustal thinning begins under western galilee and terminates at the continental slope the results of the present study indicate that the levant basin is composed of distinct crustal units and that the levant continental margin is divided into at least two provinces of different crustal structure

physical and climatic parameters which influence the air content in polar ice abstract under present day climatic conditions the air content of polar ice v generally shows a high sensitivity to the atmospheric pressure and hence to the surface elevation of the ice sheet wherethe ice is formed the results presented here are from sixteen different sites fourteen in antartica one in greenland and one in the yukon territories canada and they allow a better understanding of the parameters which influence the air content in ice it is demonstrated the v can be expressed very simply as a function of the atmospheric pressure p i the temperature t i and the porous volume of ice v i at which the air in the firn becomes isolated in terms of pressure from the atmosphere during the process of pore close off our results confirm a v i increase with temperature and show no clear v i dependence on snow accumulation rate the possible non linearity of the v i t i relation we obtain could be due to a wind influence on v i and or to a second order effect of the accumulation rate our v i results are compared to measurements of the volume of closed pores versus depth in the firn to close we discuss the parameterization that we can obtain to interpret the air content variations observed in deep ice cores over periods covering glacial interglacial transitions in terms of paleoclimatic conditions prevailing at the surface of the ice sheet

the link between grain size components and depositional processes in a modern clastic lake it is widely recognized that lake sediment grain size distributions tend to be polymodal and consist of two or more grain size components however for specific cases the genesis of each component usually is poorly understood in this study the grain size components of the surface sediments of hulun lake inner mongolia were partitioned using the log normal distribution function method and the relationship between the identity of each grain size component and the hydraulic condition of the lake was investigated in order to relate the constituent components to specific depositional processes in the lake the data indicate that the modern clastic sediments of hulun lake contain six distinct unimodal grain size distributions representing six grainsize components each of the components retains its identity including modal size manner of transportation and environment of deposition although the relative percentage varies with the hydraulic conditions throughout the lake these components are specified from fine to coarse modes as long term suspension clay offshore suspension fine silt and medium to coarse silt and nearshore suspension fine sand saltation medium sand and traction coarse sand the percentage contribution of several grain size components interpreted as being indicative of nearshore environments is shown to be correlated negatively with water depth across the modern lake bed this suggests that the proportion of these components in core data might be useful as a proxy for water depth this possibility was tested using a sediment core from hulun lake where high percentages of the nearshore grain size components were found to be correlated with low regional precipitation reconstructed from the pollen profile of the same core the coincidence of two independent proxies does not only demonstrate the validity of log normal distribution function in partitioning polymodal sediments but reveals the potential of lake sediment grain size components for the research of lake level fluctuations during the geological past

impurity controlled densification a new model for stratified polar firn a new densification model which simulates the effect of impurities on the densification of polar firn is presented the classical densification models of herron and langway 1980 and pimienta and barnola barnola and others 1991 are modified by assuming that the activation energy for deformation is reduced by the impurities motivated by recent observations the impurity effect is formulated on an empirical basis using the seasonally varying ca2 ion concentration excellent agreement between simulated and measured high resolution density profiles confirms the new approach the same parameterization applies for greenland and antarctica despite the one order of magnitude difference in impurity concentration the new models allow us for the first time to simulate the density layering in firn down to the firn ice transition our results emphasize the importance of impurities and density layering for the air entrapment and for dating gas records of deep ice cores in particular for glacial climate conditions where the impurity concentrations are 10 100 fold higher than in modern firn

fractionation of gases in polar ice during bubble close off new constraints from firn air ne kr and xe observations gas ratios in air withdrawn from polar firn snowpack show systematic enrichments of ne n2 o 2 n2 and ar n2 in the firn ice transition region where bubbles are closing off air from the bubbles in polar ice is correspondingly depleted in these ratios after accounting for gravitational effects gas in the bubbles becomes fractionated during the process of bubble close off and fractionation may continue as ice cores are stored prior to analysis we present results from firn air studies at south pole and siple dome antarctica which add ne kr and xe measurements to the suite of observations ne o2 and ar appear to be preferentially excluded from the shrinking and occluding bubbles and these gases therefore accumulate in the residual firn air creating a progressive enrichment with time and depth in firn air early sealing of gases by thin horizontal impermeable layers into a nondiffusive zone or lock in zone greatly enhances this enrichment a simple model of the bubble close off fractionation and lock in zone enrichment fits the data adequately the model presumes that fractionation is caused by selective permeation of gas through the ice lattice from slightly overpressured bubbles the effect appears to be size dependent because ne o2 and ar have smaller effective molecular diameters than n2 and fractionation increases strongly with decreasing size ne is fractionated 34 2 times more than o2 in south pole firn air and reaches an enrichment of 90 in the deepest sample the large atoms kr and xe do not appear to be fractionated by this process despite the large size difference between the two gases suggesting a threshold atomic diameter of 3 6a above which the probability becomes very small that the gas will escape from the bubble these findings have implications for ice core and firn air studies that use gas ratios to infer paleotemperature chronology and past atmospheric composition

multidecadal variability of atmospheric methane 1000 1800 c e 1 we present a new high precision high resolution record of atmospheric methane from the west antarctic ice sheet wais divide ice core covering 1000 1800 c e a time period known as the late preindustrial holocene lpih the results are consistent with previous measurements from the law dome ice core the only other high resolution record of methane for this time period and confirm most of the observed variability multidecadal variability in methane concentrations throughout the lpih is weakly correlated or uncorrelated with reconstructions of temperature and precipitation from a variety of geographic regions correlations with temperature are dominated by changes in northern hemisphere high latitude temperatures between 1400 and 1600 c e during the onset of the little ice age times of war and plague when large population losses could have reduced anthropogenic emissions are coincident with short periods of decreasing global methane concentrations

holocene environmental change in southwest turkey a palaeoecological record of lake and catchment related changes percentage concentration and accumulation pollen data together with diatom and non siliceous microfossil data are presented for the site of go lhisar go l u 37i8 n 29i36 e elevation 930 m a small intramontane lake in burdur province southwest turkey microfossil assemblages from the longest sediment core gha 813 cm record changes in local and regional vegetation and lake productivity over the last 9500 years pollen spectra indicate that vegetation progressed from an open landscape with an increase in arboreal pollen occurring 8500 bp to mixed forest comprising oak pine and juniper until around 3000 bp cal 1240 bc when a human occupation phase becomes discernible from the pollen spectra this occurs shortly after the deposition of a volcanic tephra layer which originated from the minoan eruption of santorini thera and radiocarbon dated to 3330 70 yr bp cal 1600 bc this human occupation phase is comparable to the beys ehir occupation phase recorded at other sites in southwest turkey and involved forest clearance and the cultivation of fruit trees such as olea juglans castanea and itis together with arable cereal growing and pastoralism the presence of pollen types associated with the beys ehir occupation phase in deposits above the santorini tephra layer confirms a late bronze age early anatolian dark age date for its commencement since 3000 bp notable changes in aquatic ecology associated with tephra deposition and subsequent nutrient and sediment flux from the lake catchment are recorded the beys ehir occupation phase at go lhisar go l u came to an end around 1300 bp cla ad 700 when pine appears to have become the dominant forest tree 1999 elsevier science ltd all rights reserved

timing of uplift of the troodos massif cyprus constrained by sedimentary and magnetic polarity evidence abstract plio pleistocene sediments exposed around the ophiolitic troodos massif document spectacular uplift from below sea level to a maximum height of c 2000 m sedimentation reflects a dominant control of focused tectonic uplift modified by the effects of glacio eustatic sea level change and climatic change understanding the uplift and controls on deposition has been hindered by an inadequate age model here we present a preliminary investigation of the polarity of remanent magnetizations recorded within the upper part of the pliocene succession in the pissouri and mesaoria basins and from the pleistocene marine terrace deposits that border the troodos massif when integrated with available lithostatigraphic and biostratigraphic data the main results are as follows focused uplift of the troodos massif began during the late pliocene either between 2 14 and 1 95 ma or immediately prior to 1 77 ma shallow marine ophiolite derived clastic and bioclastic sediments accumulated in both the mesaoria and pissouri basins implying that the troodos massif was uplifted as a single tectonic entity non marine deltaic and fluvial facies prograded into both of the basins during the pleistocene 1 77 ma recent marine terraces in sw and south cyprus were cut and covered by littoral sediments from

structures and kinematics in the northeastern mediterranean a study of an irregular plate boundary abstract extensional structures are prominent in the northeastern mediterranean a unique sector of the africa eurasia plate convergence zone to explain this paradoxical situation we analyse here the young tectonics of this region by examining its structural elements and plate kinematics offshore multichannel seismic reflection profiles and onland geology show that the stuctural settings are different on the two sides of the northeastern mediterranean triple junction afr arb ana on the east stuctures controlled by strike slip and by compression coexist whereas on the west compression is not very conspicuous here deep basins separated by a partly submerged ridge are prominent we interpret the ridge which comprises the kyrenia misis andirin unit at its core as a large flower structure which extends from southeastern turkey to cyprus the adana cilicia and the iskenderun latakia mesaoria basins on its flanks are interpreted as due to extension this interpretation agrees with the relative motions between the africa arabia eurasia and anatolia plates in this region analysis of the local plate kinematics reveals that strike slip predominates along the southern boundary of the anatolia plate in this region as a result of anatolia s westward escape east of the triple junction this motion is associated with comparable shortening transverse to the plate boundary whereas west of the triple junction the motion transverse to the plate boundary varies between slight compression to extension depending mainly on the local strike of the plate boundaries these variations calculated from regional data correlate well with the observed structural changes along the northeastern mediterranean sector of the plate convergence zone the structural kinematic analysis explains both the lateral changes in the deformation style and the existence of local extension in the northeastern mediterranean

response of chironomid assemblages to east asian summer monsoon precipitation variability in northern china since the last deglaciation we investigate chironomid assemblages in a sediment core from gonghai lake which is located on the east asian summer monsoon easm boundary in northern china to quantify easm variability during the past 13 5 ka bp six significantly different chironomid assemblage zones indicate that maximum precipitation and water depth occurred in the mid holocene 8270 2700 cal a bp and the minimum period was the past 1250 years a modern dataset of 44 lakes near gonghai lake was sampled to calibrate the response of chironomid assemblages to precipitation our results demonstrate that mean annual precipitation is the most significant environmental variable influencing modern chironomid assemblages in this monsoonal region maximum easm precipitation in the mid holocene indicated by chironomid assemblages in the monsoon fringe contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china but is consistent with other evidence our findings are compatible with the proposal that the stalagmite delta o 18 variations in southern china may not reliably reflect the evolution of easm since the last deglaciation copyright c 2016 john wiley sons ltd

miocene to recent tectonic evolution of the eastern mediterranean new pieces of the old mediterranean puzzle the mediterranean sea and its surrounding land mass fig 1 have long been recognized as an excellent bnatural laboratoryq for the study of fundamental plate tectonic processes including rifting passive margin development contraction and associated subduction ophiolite emplacement and orogenesis and as such it is one of the most extensively studied regions of the world e g hsu et al 1975 dixon and robertson 1984 kastens et al 1990 emeis et al 1996 comas et al 1996 robertson 1998 mcclusky et al 2000 the late cretaceous to holocene tectonic evolution of the eastern mediterranean region is extremely complex and controversial and several commonly conflicting hypotheses have been proposed the scope of this special issue does not permit a full discussion of these hypotheses we refer the reader to robertson 1998 for a review however there is general agreement that the eastern mediterranean evolved as a small ocean basin during the late triassic robertson and dixon 1984 robertson et al 1991 this embryonic ocean achieved its maximum

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

the oligocene recent evolution of the mesaoria basin cyprus and its western marine extension eastern mediterranean abstract the neogene stratigraphic and structural evolution of the mesaoria basin and kyrenia range is studied using multi channel seismic reflection profiles from their western marine extension the region north of the front of the troodos larnaka culmination constitutes a crustal scale s verging thick skinned linked imbricate thrust system comprising most of the forearc region north of the present day cyprus arc in the eocene thrust activity gave rise to the prominent growth of the troodos larnaka culmination and concurrent imbrication further north in the forearc region creating the root of the kyrenia fold thrust belt northward retreat of the active thrust front in the oligocene miocene led to the development of a foredeep across the root of the kyrenia fold thrust belt with a prominent depositional foredeep ramp situated at the current front of this belt crustal contraction continued in the miocene along the front of the troodos larnaka culmination leading to the progressive shoaling of the basin carried on the backlimb of this culmination in the late miocene thrust activity became widespread in the forearc region with structural contraction being focussed on the kyrenia fold thrust belt pliocene thrust activity in the forearc region is primarily focussed on the kyrenia fold thrust belt with much uplift occurring in the mid late pliocene but continuing to the present the mesaoria basin evolved in the miocene to pliocene as a piggy back basin our data negate earlier models that postulate a phase of crustal extension in the forearc region during the oligocene to mid late pliocene

air content along the greenland ice core project core a record of surface climatic parameters and elevation in central greenland we present here measurements of the air content of the ice v performed along the greenland ice core project grip ice core the main features of the long term trends are 1 a decrease of 13 between the last glacial maximum lgm and the earliest part of the holocene and 2 an increase of 8 during the holocene the results are discussed in terms of changes in atmospheric pressure surface elevation and porosity at close off the v record contains a significant signal of past changes of surface elevation in qualitative agreement with ice sheet modeling simulations it suggests a thickening of central greenland during the transition from the lgm to the early holocene and a significant thinning through the holocene period it also stresses the large influence on past v variations of changes in ice porosity which are not explained by the present day spatial relationship with temperature and may reflect changes in other surface climatic parameters like precipitation seasonality or wind stress the potential role of temporal variations of atmospheric pressure patterns is also evaluated air content results in the grip ice older than 110 ka indicate values approximately in the same range as those observed during the last 40 000 years with generally higher air content corresponding to isotopically warmer ice

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

the structure of the africa anatolia plate boundary in the eastern mediterranean new marine deep seismic reflection data from south of cyprus to the syrian coast provide images of the upper crustal structure of the cyprean arc indicating that the deformation is partitioned along strike slip fault systems distributed over a wide zone rather than forming a sharp plate boundary between african and anatolian plates three major submarine strike slip fault systems tens of kilometers in length are mapped which follow bathymetric features and merge together toward the east these structures exhibit the three dimensional characteristics typical of strike slip deformation zones throughout the seven pre stack depth migrated sections including several sets of positive flower structures forming bathymetric ridges and the intervening contemporaneous subbasins beneath the plio quaternary sediments 500 m thick that are blanketing the whole area and that reflect only the main surface traces of the fault systems the subbasins are of varied dimensions and have rapid lateral changes in the thickness of the sedimentary fill they include two major unconformities that have been correlated throughout the data marked by the m and k reflections the m reflection is well imaged above varied thickness of messinian evaporites and the k reflection commonly appears at the base of syntectonic tertiary age sediments within the eastern cyprean arc the k reflection corresponds to the basement cover contact indicating that the strike slip tectonic scenario may have been active since the uppermost cretaceous or lowermost paleogene times to present the active deformation front of the alpine belt in the eastern mediterranean corresponds to a strike slip fault system that forms a 110 arc and coincides at the southern slope of the hecateaus rise continuing along the latakia ridge to the syrian coast the mapped structures fit within a general kinematic framework of left lateral transcurrent deformation that transfers slip from the subduction zone southwest of cyprus into the dead sea transform system in the east this change in the mode of deformation at the africa anatolia plate boundary occurs toward the junction between african anatolian and arabian plates

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

air content paleo record in the vostok ice core antarctica a mixed record of climatic and glaciological parameters under present day climatic conditions the air content of ice shows a high sensitivity to the atmospheric pressure and hence to the elevation at the surface of the ice sheet this observation has been used to infer past ice sheet thickness variations of antarctica and greenland a high resolution air content profile more than 1000 measurements covering approximately the last 200 000 years was obtained along the 2546 m long vostok ice core three analytical techniques were used leading to consistent results which show large amplitude and rapid air content variations the vostok results support thicker thinner ice in the central part of east antarctica during warm cold periods

the neogene evolution of the outer latakia basin and its extension into the eastern mesaoria basin cyprus eastern mediterranean the neogene stratigraphic and structural evolution of the eastern mesaoria basin is studied using multi channel seismic reflection profiles from the eastern marine extension of the basin into the outer latakia basin the region includes three major tectonic elements troodos larnaka culmination kyrenia fold thrust belt and the intervening mesaoria and outer latakia basins the troodos larnaka culmination is a large ophiolite cored ramp anticline developed above a deep seated s verging thrust complemented by a footwall imbricate thrust fan system extending into the cyprus basin the outer latakia basin is a large piggy back basin carried on the northern flank of the troodos larnaka culmination the kyrenia fold thrust belt is developed as a s verging trailing imbricate fan system these three tectonic elements form part of a crustal scale s directed linked thrust system which has a protracted tectonic history with major pulses of contraction in the eo oligocene the late miocene and the middle plio quaternary this system extends southward well into the cyprus basin and probably links with the subduction zone between the african plate and the anatolian microplate patterns of thrust activity in this linked thrust system exclude models of s migration of the plate boundary from mid tertiary to recent instead the upper plate is viewed as a broad zone of diffuse convergence distributed across a number of active fold thrust zones

constrains on the origin and history of the eastern mediterranean basin abstract the basin formed along the northern passive margin of gondwanaland as a relict of the mesozoic neotethys in early mesozoic time though direct information from the basin itself is meagre the geology of its passive margins and the regional framework of the tethys evolution constrain the formation and history of the basin the eastern mediterranean and its passive margins are interpreted to have formed as a result of several faulting and continental breakup phases from early permian to middle jurassic times before pangaea s complete disintegration this led to the detachment of the eratosthenes and tauride blocks from the margins of the levant and herodotus basins respectively the latter merged in the northeast with the cyprus basin that extended along arabia s northern margin the main rifting probably occurred in the triassic leading to seafloor spreading in the herodotus and cyprus basins while along the levant margin important rifting also occurred in the jurassic during the initial rifting stages extension perpendicular to the levant margin was important but subsequently the tauride block drifted mainly northward the existence of the passive margins and slopes of the eastern mediterranean is documented at least from the end of the middle jurassic until then the basin was probably narrow 200 300 km but during the main phase of the africa laurasia separation it grew to twice its present width or more this scenario depends critically on the interpretation that the tauride block was originally located next to northeastern africa on the western side of the eratosthenes block plate convergence and consumption of the northern portion of the basin have taken place since mid cretaceous times but the active convergent boundary on its northern side formed only in the neogene by modification of earlier structures some intra plate deformation also took place especially in the neogene but it hardly changed the original configuration of the remaining portion of the basin

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