holocene climate variability in the levant from the dead sea pollen record abstract the dead sea located at the deepest place on continent and between the subtropical mediterranean zone and the desert reflects in its water composition and levels and sedimentary records the hydrological conditions in the southern levant region temporal variations in rainfall and temperatures of the holocene levant are reconstructed here from pollen data recovered from a sediment core drilled at the ein gedi shore applying a novel biome model based on bayesian statistics our results suggest that the region was arid and warm in the early holocene period 10 6 5 ka cal bp wetter and colder in the mid holocene 6 3 3 3 ka cal bp and drier and warmer in the late holocene 3 2 ka cal bp to present these periods comprise multi centennial climate cycles that are characterized by rapid changes in temperature and precipitation reflecting sea surface temperature sst and atmospheric conditions over the atlantic ocean the pollen record responds within a short time interval to the climate conditions and marks rapid shifts from mediterranean to desert environmental conditions and back in the southern levant region we also evaluate our results in the light of possible disturbances of the natural vegetation e g the possibility of forest decrease since the neolithic

human adaptation to mid to late holocene climate change in northeast thailand this article integrates palaeoenvironmental and archaeological sequences covering the mid to late holocene in northeast thailand the former reveal the fluctuating intensity of the asian summer mo

late quaternary vegetation dynamics and hydro climate in the drakensberg south africa abstract a multi proxy study of a sediment sequence from braamhoek wetland covering the last c 16 000 years reveals a record of regional climate and vegetation dynamics in the drakensberg region south africa including signals from both the organic sediment fraction fossil pollen charcoal n alkane abundance n alkane 13c toc and the inorganic fraction mineral magnetic properties the reconstruction supported by a robust chronology indicates two major periods of increased regional wetness during the late pleistocene to early holocene phase c 13 800 12 600 cal yr bp c 10 200 8500 cal yr bp and one during the late holocene c 2000 cal yr bp to present drier conditions are recorded during the younger dryas c 12 600 11 300 cal yr bp and mid holocene c 7000 2000 cal yr bp a major decline in fynbos vegetation during the early holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern south africa from c 8500 cal yr bp comparison with records from interior of south africa show relatively high inter site variability however the braamhoek moisture proxies do co vary with the speleothem isotope records from makapansgat suggesting a similar hydro climate evolution in eastern and interior parts of the summer rainfall region during the studied period on multi millennial time scales an inverse hydro climatological pattern is evident between these two south african records and reconstructions from tropical locations in southeast africa such a rainfall dipole between eastern tropical and southern africa has previously been identified on shorter time scales i e on inter annual to millennial scales the braamhoek study suggests that a similar dipole pattern is acting also on a multi millennial perspective these long term precipitation anomalies are tentatively coupled to teleconnections from multi millennial changes in the dynamics of the indian ocean dipole iod and el nino southern oscillation enso

comment on piezometric response in shallow bedrock at cb1 implications for runoff generation and landsliding by david r montgomery william e dietrich and john t heffner

limits on the validity of infinite length assumptions for modelling shallow landslides the infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models its assumption that shallow landslides are infinitely long in a downslope direction is usually considered valid for natural landslides on the basis that they are generally long relative to their depth however this is rarely justified because the critical length depth l h ratio below which edge effects become important is unknown we establish this critical l h ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two dimensional slopes assuming that the difference between the predictions is due to error in the infinite slope method we test the infinite slope method for six different l h ratios to find the critical ratio at which its predictions fall within 5 of those from the finite element method we repeat these tests for 5000 synthetic slopes with a range of failure plane depths pore water pressures friction angles soil cohesions soil unit weights and slope angles characteristic of natural slopes we find that 1 infinite slope stability predictions are consistently too conservative for small l h ratios 2 the predictions always converge to within 5 of the finite element benchmarks by a l h ratio of 25 i e the infinite slope assumption is reasonable for landslides 25 times longer than they are deep but 3 they can converge at much lower ratios depending on slope properties particularly for low cohesion soils the implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse e g 25 m however it may also be valid even at much finer grid resolutions e g 1 m because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have l h ratios less than 25

rifting evolution in geological history abstract rift and rift like zones global linear extensional structures of the crust have appeared during most periods of the earth s history rifting as a geological process has undergone a complex evolution with its historical roots in the early precambrian the development of the oldest linear mobile tectonic zones archean greenstone belts and granulite belts combined the features of both rift and geosynclinal processes in the following epochs early proterozoic mobile zones protogeosynclinal regions and protorift zones evolved under similar tectonic regimes of crustal destruction in the early stages and compression in the late stages of their development but different in size scale and intensity of the deformations and thermal processes experienced typical rift structures have existed since the late proterozoic in the late proterozoic and paleozoic continental intracratonic rifting in the form of aulacogen and aulacogeosynclinal zone development was a process related and subordinated to a geosynclinal process in the adjacent mobile belts in the paleozoic the first epiorogenic postorogenic rift zones appeared within the epigeosynclinal folded belts during the meso cenozoic epoch of the earth s history rifting increased considerably and became independent of geosynclinal processes it is believed to be one of the main forms of continental crust destruction and formation of the oceanic basins and probably occurred under conditions of some general expansion of the earth

deep structure and metallogeny of early proterozoic mobile belts in the light of superdeep drilling in russia abstract superdeep drilling in russia and ukraine provides new direct information about the internal structure of the continental crust its evolution and associated ore forming processes deep levels of early proterozoic mobile belts have been investigated with two superdeep boreholes in russia and ukraine 1 in the kola peninsula in the baltic shield and 2 in the krivoy rog basin in the ukrainian shield the investigations of the kola superdeep borehole invalidate previous hypotheses on the conrad discontinuity they prove intensive proterozoic tectonic and metamorphic reworking of archaean rocks and reveal mineralizations of sulphide copper nickel and gold at depth in the light of the new evidence two geotectonic models of the pechenga imandra varzuga belt are reviewed 1 an intracontinental rift subject to the later compression and 2 an ocean opening followed by development of a collisional suture zone the krivoy rog belt has traditionally been described as a deep synclinorium filled with banded iron formations and cut in the west by a steep regional fault the krivoy rog superdeep hole was predicted to intersect all members of the early proterozoic krivoy rog group and to meet tonalites of the archaean basement at 9 10 km depth contrary to expectations however the borehole reached the basement complex at a depth of 2350 m the drilling stimulated geological and geophysical studies of adjacent territories and the results are reviewed in the light of two geotectonic models for the central part of the ukranian shield 1 a plate tectonic model involving westward subduction of oceanic crust and 2 a model implying a rise of asthenolite during early proterozoic times west of the krivoy rog basin the superdeep borehole data lead to better understanding of the structures of the continental crust and its metallogeny but at the same time pose new questions to which answers have yet to be found

major stages of rifting evolution in the earth s history abstract linear extensional rift and rift like structures have been generated many times during various periods of the earth s history since early times these structures have varied with time however in scale morphology formations paragenesis of tectonic features regularity of distribution and evolution i distinguish and consider five major stages of rifting they are katarchean archean early proterozoic late proterozoic paleozoic and mesozoic cenozoic linear structures of the oldest stage combine features of development and structure similar to those typical of the rift and geosynclinal zones in the later periods of the earth s history at the second stage proto rift and proto geosynclinal structures can be distinguished for the first time though differences are not distinct paleo rift zones of the third and fourth stages differ from geosynclinal belts and zones their structural and genetic evolution however is related to the development of the latter in contrast the distribution and evolution of the rift zones and belts during the fifth stage are connected mainly with the destruction of the continents and formation of the secondary oceanic basins they are complementary to the mesozoic cenozoic geosynclinal orogenic belts periods of the greatest development of rift and rift like structures in the archean riphean and mesozoic cenozoic probably correspond to the major phases of the earth s expansion which can be distinguished in its general pulsating evolution

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

post glacial slip history of the sparta fault greece determined by 36cl cosmogenic dating evidence for non periodic earthquakes 1 using 36cl cosmic ray exposure dating we obtained continuous exposure histories for 7 12 m high limestone surfaces at two sites 10 km apart on the sparta normal fault scarp as each major earthquake adds new surface to the cumulative scarp exposing new material to cosmic ray bombardment these exposure histories allow the slip history to be constrained the results show that an earthquake occurred on this fault 2800 300 yr ago we infer that this is the seismic event that destroyed ancient sparta in 464 b c four earlier earthquakes ruptured the sparta fault in the last 13 ka with similar slip amplitudes of about 2 m and with time intervals ranging from 500 yr to 4500 yr the observations also confirm that the sparta scarp is post glacial supporting the hypothesis that similar scarps elsewhere in the mediterranean region have a comparable age the absence of any event since 464 b c could suggest a future event is imminent however the irregularity of earthquake time intervals could also be due to changes of loading with important consequences for the mechanics of continental deformation

late glacial to mid holocene palaeoclimate development of southern greece inferred from the sediment sequence of lake stymphalia ne peloponnese abstract the sedimentary sequence of lake stymphalia ne peloponnese for the first time sheds light on the palaeoclimate development of southern greece from 15 to 5 ka bp new geochemical data based on high resolution x ray fluorescence scanning provide in situ and continuous analysis of predefined element suites on split core surfaces variations of elements over time were assessed constructing correlation matrices based on the calculation of pearson correlation coefficients the element suite includes al si k ca ti mn fe zn rb sr and zr a major result includes that changes in element behaviour are related to hydrological changes in the catchment precipitation lake level status and evaporation insolation solar activity and are ultimately driven by climate major trends shifts in elemental ratios correspond to the climate development in the eastern mediterranean region based on correlation of rb sr reflecting wet dry climates with foraminiferal proxies of marine core lc21 from the southern aegean sea and the stable oxygen isotope record of soreq cave israel the bolling allerod the younger dryas and the 8 2 ka cold event were identified

development of collapse sinkholes in areas of groundwater discharge abstract collapse sinkholes are found in groundwater recharge zones throughout the world they cause substantial loss of property each year and occasional fatalities in such settings the formation of these features occurs through the downward migration of regolith into karst voids the presence of a void in the bedrock and sufficient seepage pressure or gravitative force in the regolith is required for their creation we investigated the development of cover collapse sinkholes in an unusual setting areas of groundwater discharge rather than recharge upward hydraulic gradients and the likelihood of groundwater saturated with respect to calcite are difficult to reconcile with standard models for collapse development short flowpaths or renewed groundwater aggressivity towards calcite via mischungskorrosion thermally driven circulation or deep seated gaseous sources are hypothetical mechanisms that could generate the subsurface voids that are needed to allow cover collapse development in discharge areas for the two field sites in central italy that we investigated calculated carbon dioxide partial pressures in springs ranged from 7 38 10 2 to 7 29 10 1 atm this indicates that deep seated gaseous sources are most likely the mechanism allowing the development of the sinkholes groundwater is recharged in surrounding limestone massifs the water moves through the carbonates and becomes saturated with calcite as it circulates deeply in to the adjacent valleys it mixes with deep seated waters and gaseous fluxes from major fault systems acquiring renewed aggressivity towards calcite finally the water ascends into confined aquifers in the valley fill and dissolves carbonate material present within leading to surface collapse

biomarker hydrogen isotope composition δd as proxy for holocene hydroclimatic change and seismic activity in sw peloponnese greece we present a 6000 year long record tracing hydroclimate changes in sw greece based on hydrogen isotope composition of aquatic plant derived n c 23 alkanes d c23 in a sediment core from the messe

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

modelling the probability of occurrence of shallow landslides and channelized debris flows using geotop fs this paper describes a coupled distributed hydrological geotechnical model geotop fs which simulates the probability of occurrence of shallow landslides and debris flows we use a hydrological distributed model geotop which models latent and sensible heat fluxes and surface runoff and computes soil moisture in 3 d by solving richards equation numerically together with an infinite slope geotechnical model geotop fs the combined model allows both the hydraulic and geotechnical properties of soil to be considered and realistically modelled in particular the model has been conceived to make direct use of field surveys geotechnical characteristics and soil moisture measurements in the model the depth of available sediments is also used to characterize the hydraulic properties of the area examined to account for the uncertainty related to the natural variability in the factors influencing the stability of natural slopes the safety factor is computed with a probabilistic approach in order to determine the likelihood of slope failures soil parameters are assigned distributions instead of single deterministic values the analysis presented was carried out for an alpine watershed located in the friuli region italy for which some geological and geotechnical data were available in the past this watershed experienced landslides and debris flows during intense storms following long and moderate intensity rainfall events the distributed coupled geotop fs model was calibrated by reproducing some of these events and validated in order to map future failure probabilities

plant wax δd values record changing eastern mediterranean atmospheric circulation patterns during the 8 2 kyr b p climatic event abstract throughout the holocene the climate of the mediterranean region has been strongly influenced by variability in the atmospheric circulation of the high and low latitudes a prominent example for such holocene climate perturbations is the 8 2 kyr b p climatic event reorganization of northern hemisphere atmospheric circulation patterns resulted in variations of temperature and precipitation distribution across the mediterranean the effects of changing high and low latitude atmospheric circulation on mediterranean climate in relation to the 8 2 kyr b p climatic event are however not well understood here we present a high resolution record of stable hydrogen isotope composition of plant wax n alkanes dwax across the 8 2 kyr b p climatic event from the tenaghi philippon peat deposit ne greece in order to characterize patterns of precipitation and changes in atmospheric circulation in the eastern mediterranean region our record reveals pronounced changes in dwax that correlate closely with previously published palynological data a long term decline in dwax values characterizes the lower part of the section the 8 2 kyr b p climatic event itself is connected to two distinct positive dwax excursions a minor shift in dwax around 8 2 kyr b p and a major shift in dwax between ca 8 1 and 8 0 kyr b p the upper part of the section shows a progressive trend towards higher dwax values we link shifts in dwax to changes in mediterranean air mass trajectories supplying precipitation to ne greece caused by variations in the relative contributions of northerly derived d depleted moisture and southerly derived d enriched moisture possible control mechanisms for alternating air mass trajectories include changes in the influence of the siberian high and differences in the influence of the african and asian monsoon circulation on anticyclonic conditions in the mediterranean region as well as regional inflow of moist air masses from the aegean sea

speleothem evidence for late holocene climate variability and floods in southern greece abstract we present stable isotope data 18o 13c from a detrital rich stalagmite from kapsia cave the peloponnese greece the cave is rich in archeological remains and there are reasons to believe that flooding of the cave has directly affected humans using the cave using a combination of u th and 14c dating to constrain a site specific correction factor for 232th 238u detrital molar ratio a linear age model was constructed the age model shows that the stalagmite grew during the period from ca 950 bc to ca ad 830 the stable oxygen record from kapsia indicates cyclical changes of close to 500 yr in precipitation amount with rapid shifts towards wetter conditions followed by slowly developing aridity superimposed on this signal wetter conditions are inferred around 850 700 500 and 400 100 bc and around ad 160 300 and ad 770 and driest conditions are inferred to have occurred around 450 bc ad 100 150 and ad 650 detrital horizons in the stalagmite indicate that three major floods took place in the cave at 500 bc 70 bc and ad 450 the stable carbon isotope record reflects changes in biological activity being a result of both climate and human activities

δd values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha abstract a set of lake surface sediment samples and aquatic macrophytes from the eastern and central tibetan plateau and a sediment core from koucha lake northeastern tibetan plateau were analysed for hydrogen isotope signals of aliphatic lipid biomarkers the d values of n alkanes were correlated with those of meteoric water in the summer months and showed increasing pearson correlation coefficients with increasing n alkane chain length r 0 80 for n c 31 while in samples from the most humid regions southeastern tibetan plateau the apparent enrichment factors between meteoric water and lipids are close to those reported for other humid sites e 135 for mid chain and 125 for long chain n alkanes they become smaller e 118 to 41 mean value 86 at sites with a negative moisture balance northeastern and central tibetan plateau and qaidam basin this might be caused by enrichment in deuterium of the source water used for lipid synthesis as a result of lake water evaporation and soil and leaf water evapotranspiration in the core from lake koucha decreasing d values of all n alkanes between 15 and 10 cal ka bp give evidence for an intensification of the asian summer monsoon at ca 9 cal ka bp a ca 15 shift towards higher d values of mid chain n alkanes suggests enhanced evaporation of the lake water which outweighs higher precipitation amounts because of a temperature increase during the early holocene monsoonal maximum only a few surface sediment samples show a significant offset between d values of mid chain n alkanes and n c 31 d mid n c31 and no systematic dependence between this offset and environmental parameters such as mean annual precipitation was found in the core available data for most samples also do not show a significant offset only a slight increase 15 of d mid n c31 at ca 10 0 cal ka bp and a decrease 17 at ca 6 8 cal ka bp might indicate wetter and drier conditions respectively however interpretation of d mid n c31 throughout the record is difficult because of a lack of reliable data for n c 31 in key sections of the core so more records are necessary to further test the potential applicability of d mid n c31 as a proxy for palaeo hydrological conditions

climate variability and socio environmental changes in the northern aegean ne mediterranean during the last 1500 years abstract we provide new evidence on sea surface temperature sst variations and paleoceanographic paleoenvironmental changes over the past 1500 years for the north aegean sea ne mediterranean the reconstructions are based on multiproxy analyses obtained from the high resolution decadal to multi decadal marine record m2 retrieved from the athos basin reconstructed ssts show an increase from ca 850 to 950 ad and from ca 1100 to 1300 ad a cooling phase of almost 1 5 c is observed from ca 1600 ad to 1700 ad this seems to have been the starting point of a continuous sst warming trend until the end of the reconstructed period interrupted by two prominent cooling events at 1832 15 ad and 1995 1 ad application of an adaptive kernel smoothing suggests that the current warming in the reconstructed ssts of the north aegean might be unprecedented in the context of the past 1500 years internal variability in atmospheric oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north aegean sea over the past 1500 years the marked temperature drop of approximately 2 c at 1832 15 yr ad could be related to the 1809 d unknown and the 1815 ad tambora volcanic eruptions paleoenvironmental proxy indices of the m2 record show enhanced riverine continental inputs in the northern aegean after ca 1450 ad the paleoclimatic evidence derived from the m2 record is combined with a socio environmental study of the history of the north aegean region we show that the cultivation of temperature sensitive crops i e walnut vine and olive co occurred with stable and warmer temperatures while its end coincided with a significant episode of cooler temperatures periods of agricultural growth in macedonia coincide with periods of warmer and more stable ssts but further exploration is required in order to identify the causal links behind the observed phenomena the black death likely caused major changes in agricultural activity in the north aegean region as reflected in the pollen data from land sites of macedonia and the m2 proxy reconstructions finally we conclude that the early modern peaks in mountain vegetation in the rhodope and macedonia highlands visible also in the m2 record were very likely climate driven

holocene hydro climatic variability in the mediterranean a synthetic multi proxy reconstruction here we identify and analyze proxy data interpreted to reflect hydro climatic variability over the last 10 000 years from the mediterranean region to 1 outline millennial and multi centennial sca

three dimensional model of hellenic arc deformation and origin of the cretan uplift 1 the hellenic arc of greece is the most seismically active part of europe but little is know about its mechanics we modeled deformation along the arc using a finite element model the model was intended to capture large scale 3 d structure of nubian plate subduction beneath the aegean block and its deformational consequences the shape of the interface was developed using mapped traces at the surface and earthquake hypocenters at depth model block motions were constrained by recent compilations of gps velocity vectors we simulated a 10 ka period of convergence between nubia and the aegean and calculated the strain field in the overriding plate as well as the spatial distribution and orientation of differential stress 1 3 from these calculations we derived testable quantities such as the expected seismic moment rate on the interplate contact uplift pattern and distribution of strain modes our relatively simple model broadly reproduced observed uplift patterns earthquake activity and loci of extension and contraction the model showed a localization of uplift near the island of crete where the fastest aegean uplift rates are well documented comparison of calculated expected seismic moment and observed earthquake catalogs implies a nearly fully coupled interplate contact on the basis of our modeling results we suggest that south aegean deformation is driven primarily by the fast moving 33 mm a 1 aegean upper plate overriding a nearly stalled 5 mm a 1 nubian lower plate this tectonic setting thus more closely resembles a continental thrust than it does a typical oceanic subduction zone

geological contributions extinct rift valleyson the nature of greenstone belts in the precambrian at present there is considerable speculation concerning the origin of greenstone belts they are compared with phanerozoic geosynclines fold belts modern island arcs or with the rift structures formed above subduction zones in marginal seas four stages in greenstone belt development can be determined 3 8 3 0 3 0 2 6 2 6 1 9 and 1 9 b y and younger sections of early greenstone belts contain all the essential features of the modern oceanic sequences their peculiarities are great thickness presence of jaspilites and scarce occurrence of very coarse clastics on the contrary the latter type of sediment is widespread in younger greenstone belts and in those of the last stage which are completely formed in continental environment whole rock chemistry of precambrian volcanics more than 1800 analyses all over the world confirms that alkali olivine basalts are absent till 1 9 b y and andesites are generally rare widespread type of early precambrian basalts are ol hy and q normative ones showing close similarity to typical abyssal tholeiites the presence of basaltic komatiites is not a unique petrochemical feature of volcanism in the early precambrian as one thinks now similar rocks have been found in phanerozoic rift zones there is no evidence suggesting significant shortening of initial crustal complexes and greenstone belts these data along with slight metamorphism and above features can only be explained by the formation of greenstone belts in rifting environment during the early stages 3 8 1 9 b y the thickness of the protocrust was not more than 10 20 km it allows us to understand the rare occurrence of intermediate volcanics at early stages of the earth s evolution in summary it is argued that in the early precambrian the spread of primitive oceanic lithosphere was not compensated by the consumption in subduction zones consequently plate tectonics cannot explain the formation of the crust in the early history of the earth

high resolution environmental reconstruction in sw peloponnese greece covering the last c 6000 years evidence from agios floros fen messenian plain a paleolimnological record from the central messenian plain southwestern peloponnese southern greece indicates rapid changes in the water level and chemistry of a transient lake on the flanks of the taygetos mountains during the last c 6000 years the analyses are based on diatoms as well as carbon and nitrogen isotopes from bulk sediments in a 7 5 m long sediment core retrieved from the drained fen of agios floros at the northern banks of the ancient river pamisos the sequence consists of fen peat in the uppermost section underlain by lacustrine sediments which are punctuated by two layers of clay with diatomaceous silt bands high accumulation rate is recorded in the oldest part of the section up to 23 mm yr particularly during two decadal long periods centered at c 5700 and c 5300 cal bp the diatom record reveals pronounced peaks in the planktonic taxon cyclotella distinguenda which correspond to the laminated sequences reflecting the rapid development of a deep lake with an open water

late glacial holocene climate variability at the south eastern margin of the aegean sea abstract new micropaleontological palynological and geochemical results from a relatively shallow 500 m sediment core ns 14 in the south eastern aegean sea provide a detailed picture of the regional expression of sapropel s1 formation in this sub basin of the eastern mediterranean sea specifically freshwater input during 10 6 10 0 ka bp has preceded the deposition of s1 further decrease in surface water salinity is evidenced between 10 0 and 8 5 ka bp at the lower part of s1a which in respect to s1b is featured by warmer 19 5 c and more productive surface waters associated with dysoxic bottom conditions a series of coolings detected within the s1 depositional interval may be linked to outbursts of cold northerly air masses and relevant pulses in the deep intermediate water ventilation that caused the s1 interruption between 7 9 and 7 3 ka bp and culminated during the deposition of s1b with the decline of deep chlorophyll maximum dcm at 6 5 ka bp the climate instability and the relevant absence of anoxia weakened the organic matter preservation in the shallow south eastern aegean margin during the s1 times ns 14 record provides evidence for a distinct mid holocene warm up to 25 c and wet phase associated with the deposition of the sapropel like layer smh sapropel mid holocene between 5 4 and 4 3 ka bp the smh layer could represent evidence of on going albeit weak african monsoon forcing only expressed at the south eastern edge of the aegean sea its end is associated with the 4 2 ka bp northern hemisphere mega drought event and the termination of the african humid period at 3 8 ka bp

rainfall ground water flow and seasonal movement at minor creek landslide northwestern california physical interpretation of empirical relations simple ground water flow analyses can clarify complex empirical relations between rainfall and landslide motion here we present detailed data on rainfall ground water flow and repetitive seasonal motion that occurred from 1982 to 1985 at minor creek landslide in northwestern california and we interpret these data in the context of physically based theories we find that landslide motion is closely regulated by the direction and magnitude of near surface hydraulic gradients and by waves of pore pressure caused by intermittent rainfall diffusive propagation of pore pressure waves accompanies downward ground water flow along nearly vertical hydraulic gradients that exist in most of the landslide field data combined with a pore pressure diffusion analysis show that single rainstorms typically produce short period waves that attenuate before reaching the landslide base in contrast seasonal rainfall cycles produce long period waves that modify basal pore pressures but only after time lags that range from weeks to months such tune lags can depend on antecedent moisture storage and can explain variable delays between the onset of the wet season and seasonal landslide motion limit equilibrium analysis shows that when seasonal pressure waves reach the landslide base they establish a critical distribution of effective stress that delicately triggers landslide motion the critical effective stress balance is extremely sensitive to the direction and magnitude of hydraulic gradients although pervasively downward gradients instigate seasonal motion we infer from theory and limited data that ground water also may circulate locally in near surface cells the circulation can further reduce the landslide s frictional strength particularly in areas of nearly horizontal ground water flow that occur beneath steep faces of hummocks hummocky topography that results from slope instability may therefore cause ground water flow that perpetuates instability

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

isotope hydrology study of the kalamos attikis and assopos riverplain areas in greece variations in the isotopic composition of water were used to define the mechanism of recharge of the assopos riverplain and the kalamos attikis coastal brackish karst springs the plain is mainly recharged by local rain water while the karst springs are fed by the parnis mountain system the mean recharge altitude being estimated in the order of 870 m the apparent velocity and the underground pathway of the water feeding the springs were deduced and the most convenient sites for the drilling of production wells for recovery of the spring water before salinization were sited as a result 73 000 m3 of water are now pumped per day and used as additional potable water for the athens area comprizing about one sixth of the mean daily consumption

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

changes in groundwater chemistry before two consecutive earthquakes in iceland precursor events to earthquakes are rarely reproduced measurement of groundwater chemistry in iceland between 2008 and 2013 reveals distinct changes prior to two consecutive m5 earthquakes

the socio environmental history of the peloponnese during the holocene towards an integrated understanding of the past published archaeological palaeoenvironmental and palaeoclimatic data from the peloponnese in greece are compiled discussed and evaluated in order to analyse the interactions between humans and the environment over the last 9000 years our study indicates that the number of human settlements found scattered over the peninsula have quadrupled from the prehistoric to historical periods and that this evolution occurred over periods of climate change and seismo tectonic activity we show that societal development occurs both during periods of harsh as well as favourable climatic conditions at some times some settlements develop while others decline well known climate events such as the 4 2 ka and 3 2 ka events are recognizable in some of the palaeoclimatic records and a regional decline in the number and sizes of settlements occurs roughly at the same time but their precise chronological fit with the archaeological record remains uncertain local socio political processes were probably always the key drivers behind the diverse strategies that human societies took in times of changing climate the study thus reveals considerable chronological parallels between societal development and palaeoenvironmental records but also demonstrates the ambiguities in these correspondences and in doing so highlights some of the challenges that will face future interdisciplinary projects we suggest that there can be no general association made between societal expansion phases and periods of advantageous climate we also propose that the relevance of climatic and environmental regionality as well as any potential impacts of seismo tectonics on societal development need to be part of the interpretative frameworks

chemotaxonomy in some mediterranean plants and implications for fossil biomarker records the increasing utilization of n alkanes as plant derived paleo environmental proxies calls for improved chemotaxonomic control of the modern flora in order to calibrate fossil sediment records to m