warm and wet conditions in the arctic region during eocene thermal maximum 2 several episodes of abrupt and transient warming each lasting between 50 000 and 200 000 years punctuated the long term warming during the late palaeocene and early eocene 58 to 51 myr ago epochs1 2 these hyperthermal events such as the eocene thermal maximum 2 emt2 that took place about 53 5 myr ago2 are associated with rapid increases in atmospheric co2 content however the impacts of most events are documented only locally86 here we show on the basis of estimates from the tex 86 proxy that sea surface temperatures rose by 3 5 c in the arctic ocean during the emt2 dinoflagellate fossils demonstrate a concomitant freshening and eutrophication of surface waters which resulted in euxinia in the photic zone the presence of palm pollen implies5 that coldest month mean temperatures over the arctic land masses were no less than 8 c in contradiction of model simulations that suggest hyperthermal winter temperatures were below freezing6 in light of our reconstructed temperature and hydrologic trends we conclude that the temperature and hydrographic responses to abruptly increased atmospheric co2 concentrations were similar for the etm2 and the better described palaeocene eocene thermal maximum7 8 55 5 myr ago 2009 macmillan publishers limited all rights reserved

late oligocene miocene mid latitude aridification and wind patterns in the asian interior the asian interior has the largest mid latitude arid zone in the northern hemisphere and so has become increasingly attractive for studying the initiation and the past extent of aridification in this zone given the enormousness of the asian interior it remains unclear how old and extensive the eolian deposits might have been and what wind regimes have been responsible for the formation of the mid latitude arid zone here we report new eolian records of widespread tertiary eolian deposits in a region far from the chinese loess plateau the giant junggar inland basin of northwestern china our results demonstrate that the earliest eolian deposition initiated ca 24 ma we interpret that the tertiary eolian dust in the junggar basin was transported by westerly winds possibly from areas in kazakhstan the dust differs from the airborne dust transported by winter monsoon winds from the deserts of mongolia and northern china that accumulated on the loess plateau these results further reveal that the climate pattern similar to that of the present has prevailed at least since the latest oligocene in central asia

marked decline in atmospheric carbon dioxide concentrations during the paleogene the relation between the partial pressure of atmospheric carbon dioxide pco2 and paleogene climate is poorly resolved we used stable carbon isotopic values of di unsaturated alkenones extracted from deep sea cores to reconstruct pco2 from the middle eocene to the late oligocene approximately 45 to 25 million years ago our results demonstrate that pco2 ranged between 1000 to 1500 parts per million by volume in the middle to late eocene then decreased in several steps during the oligocene and reached modern levels by the latest oligocene the fall in pco2 likely allowed for a critical expansion of ice sheets on antarctica and promoted conditions that forced the onset of terrestrial c4 photosynthesis

global cooling during the eocene oligocene climate transition about 34 million years ago earth s climate shifted from a relatively ice free world to one with glacial conditions on antarctica characterized by substantial ice sheets how earth s temperature changed during this climate transition remains poorly understood and evidence for northern hemisphere polar ice is controversial here we report proxy records of sea surface temperatures from multiple ocean localities and show that the high latitude temperature decrease was substantial and heterogeneous high latitude 45 degrees to 70 degrees in both hemispheres temperatures before the climate transition were 20 c and cooled an average of 5 c our results combined with ocean and ice sheet model simulations and benthic oxygen isotope records indicate that northern hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time

geochemistry of thermal springs alhama de granada southern spain abstract the waters of the thermal springs at alhama de granada vary in temperature between 27 and 45 c temporal changes in the composition of the principal spring banos viejos indicate that a small degree of mixing may occur between deep thermal waters and shallow groundwater slight compositional variations also occur between the various thermal springs in the study area these spatial variations are due to the different local hydrodynamic conditions in the springs towards the north in less hydraulically transmissive rocks cooling of the rising water is more noticeable as are ion exchange and processes of so 4 reduction the chemical composition of the water is related to the dissolution of evaporites so 4 and cl salts carbonates and silicates and to the possible existence of sources of s within the rock estimates of the mean residence times have been obtained based on 14 c dic and t the state of thermodynamic equilibrium at the spring discharge was calculated using the solmineq 88 program the results indicate that all the samples are supersaturated with respect to quartz chalcedony cristobalite calcite aragonite and dolomite and undersaturated with respect to gypsum anhydrite and halite the use of different geothermometers and modelling of saturation indices for quartz albite and anhydrite indicate temperatures of about 110 c

atmospheric and oceanic impacts of antarctic glaciation across the eocene oligocene transition the glaciation of antarctica at the eocene oligocene transition approx 34 million years ago was a major shift in the earth s climate system but the mechanisms that caused the glaciation and its effects remain highly debated a number of recent studies have used coupled atmosphere ocean climate models to assess the climatic effects of antarctic glacial inception with often contrasting results here using the hadcm3l model we show that the global atmosphere and ocean response to growth of the antarctic ice sheet is sensitive to subtle variations in palaeogeography using two reconstructions representing eocene and oligocene geological stages the earlier stage eocene priabonian which has a relatively constricted tasman seaway shows a major increase in sea surface temperature over the pacific sector of the southern ocean in response to the ice sheet this response does not occur for the later stage oligocene rupelian which has a more open tasman seaway this difference in temperature response is attributed to reorganization of ocean currents between the stages following ice sheet expansion in the earlier stage the large ross sea gyre circulation decreases in size stronger zonal flow through the tasman seaway allows salinities to increase in the ross sea deep water formation initiates and multiple feedbacks then occur amplifying the temperature response this is potentially a model dependent result but it highlights the sensitive nature of model simulations to subtle variations in palaeogeography and highlights the need for coupled ice sheet climate simulations to properly represent and investigate feedback processes acting on these time scales

paleogene monsoons across india and south china drivers of biotic change monsoonal climates at low latitudes 32 n are an inevitable consequence of seasonal migrations of the inter tropical convergence zone itcz but the character of these monsoons depends on continental configuration orographic expression and the strength of hadley circulation to explore the evolution of monsoon systems across southern asia we compare climate signatures archived in ten paleogene floras from northern india tibet and southern china occupying low palaeolatitudes at a time of extreme global warmth and elevated co2 fossil leaf form reveals that under such hothouse conditions megathermal early eocene to earliest miocene forests were exposed to strong monsoonal climates typical of those experienced today arising from annual migrations of the itcz possibly enhanced by a lower equator to pole temperature gradient throughout the paleogene an elevated tibetan highland produced no discernable modification of this itcz monsoon although rainfall seasonality similar to that of the modern south asia monsoon sam is observed in northern india as early as the beginning of the eocene despite its near equatorial palaeoposition in south china rainfall seasonality increased progressively achieving modern monsoon like wet season dry season precipitation ratios by the early oligocene despite evidencing weak rainfall seasonality overall fossil leaves from south china have exhibited monsoon adapted morphologies comparable to those seen in today s indonesia australia monsoon for at least 45 million years together the indian and south china fossil leaf assemblages show that the evolution of megathermal ecosystems across southern asia has been influenced profoundly by monsoonal climates for at least the last 56 million years the paleogene itcz driven monsoon system strongly impacted india as it transited the equator likely eliminating gondwanan taxa not able to adapt to seasonal precipitation extremes furthermore powerful seasonally reversing winds and associated surface ocean currents are likely to have facilitated two way biotic transfer between india and eurasia long before closure of the tethys ocean

the heartbeat of the oligocene climate system a 13 million year continuous record of oligocene climate from the equatorial pacific reveals a pronounced heartbeat in the global carbon cycle and periodicity of glaciations this heartbeat consists of 405 000 127 000 and 96 000 year eccentricity cycles and 1 2 million year obliquity cycles in periodically recurring glacial and carbon cycle events that climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle solar forcing and glacial events box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass the pronounced 405 000 year eccentricity cycle is amplified by the long residence time of carbon in the oceans

slab rupture and delamination under the betics and rif constrained from receiver functions abstract we map the lithospheric structure under the westernmost mediterranean convergent setting interpreting p receiver functions obtained from a dense seismic network no orogenic root occurs under the eastern and great part of the central betics however the subducted south iberian continental lithosphere is found beneath the western betics where the iberian moho reaches depths of approximately 65 km dipping gently towards the se meanwhile at the rif strong crustal and lithospheric thickness contrasts occur across the nekor nw se sinistral fault that overlies the region of present slab tearing east of the nekor fault there is no orogenic root and the crust has been thinned to approximately 22 km whilst to the west the crust reaches 55 km thickness and the maghrebian continental lithosphere is attached to the lithospheric slab imaged by tomography under the alboran basin these data suggest that subduction rollback under the alboran and algerian basins together with continental slab tearing or detachment producing edge delamination under the betics and rif have been the main tectonic mechanisms driving extension magmatism and regional uplift in the westernmost mediterranean since the late miocene until present the surface expression of edge delamination and slab tearing is marked by regional uplift denudation of hp rocks in elongated core complex type domes late miocene volcanism in the eastern betics and rif and by large ne sw strike slip transfer faults like the alpujarras crevillente torcal or nekor faults that accommodate strong gradients in crustal displacements the iberian slab is still attached to the oceanic slab imaged under the alboran basin at the western betics where intermediate depth seismicity recent dextral strike slip faulting and folding could reflect slab tearing meanwhile active faulting and differential gps measured displacements would mark slab tearing beneath the rif coinciding with the trace of the sinistral nekor fault

active shallow extension in central and eastern betic cordillera from cgps data abstract the betic cordillera is an alpine belt formed in the western mediterranean by the westward displacement of the alboran domain in between the eurasian and african convergent plates new cgps data from the central and eastern betic cordillera and its foreland obtained mainly from the topo iberia project allowed us to precisely determine the rate of tectonic deformation most of the displacements of the central and eastern betics are westward with a variable southwestward component in relation to the eurasian stable plate while in the iberian foreland the displacements are extremely low some deformation related to low compressional deformation occurs in the easternmost foreland basin and eastern betic cordillera the displacement increases substantially southwards and westwards in relation to present day extensional deformation major active discontinuities correspond to the nw se normal fault zones which dip westwards they are located in almeria tabernas balanegra and western sierra de gador whereas the padul fault zone located west of sierra nevada extends northwards to the granada basin nw se extensional faults are also observed to the north in the baza basin moreover the activity of dextral faults along the sorbas tabernas alpujarras guajares band generally considered as a transfer fault zone is evidenced by the displacement data these results come to demonstrate the low activity or inactivity of the large northern e w oriented folds of the central and eastern internal zone such as the sierra de los filabres antiform they also point to the possible residual activity of the northern part of the ne sw sierra nevada antiform where the maximum relief of the cordillera is found altogether our data support a heterogeneous present day westward extension that affects the upper crust of the betic cordillera and increases towards the thinned continental crust of the alboran sea and towards the west which is compatible with roll back subduction along the gibraltar arc

atmospheric carbon dioxide through the eocene oligocene climate transition geological and geochemical evidence1 2 3 indicates that the antarctic ice sheet formed during the eocene oligocene transition4 33 5 34 0 million years ago modelling studies5 6 suggest that such ice sheet formation might have been triggered when atmospheric carbon dioxide levels fell below a critical threshold of 750 p p m v but the timing and magnitude of relative to the evolution of the ice sheet has remained unclear here we use the boron isotope ph proxy7 8 on exceptionally well preserved carbonate microfossils from a recently discovered geological section in tanzania9 10 to estimate before during and after the climate transition our data suggest that a reduction in occurred before the main phase of ice growth followed by a sharp recovery to pre transition values and then a more gradual decline during maximum ice sheet growth was between 450 and 1 500 p p m v with a central estimate of 760 p p m v the ice cap survived the period of recovery although possibly with some reduction in its volume implying as models predict11 a nonlinear response to climate forcing during melting overall our results confirm the central role of declining in the development of the antarctic ice sheet in broad agreement with carbon cycle modelling12 and help to constrain mechanisms and feedbacks associated with the earth s biggest climate switch of the past 65 myr

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

the impact of climate vegetation interactions on the onset of the antarctic ice sheet a global coupled atmosphere vegetation model and a dynamic ice sheet model were employed to study the impact of climate vegetation interactions on the onset of the antarctic ice sheet during the eocene oligocene transition we found that the co2 threshold for antarctic glaciation is highly sensitive to the prevailing vegetation in our experiments the co2 threshold is less than 280 ppm if the antarctic vegetation is dominated by forests and between 560 and 1120 ppm for tundra and bare ground conditions the large impact of vegetation on inception is attributed to the ability of canopies to shade the snow covered ground which leads to a weaker snow albedo feedback and higher summer temperatures however the overall effect of canopy shading on the antarctic climate also depends on features like local cloudiness and atmospheric meridional heat transport our results suggest that vegetation feedbacks on climate are crucial for the timing of the antarctic glaciation

oligocene plant ecological strategies in low latitude asia unraveled by leaf economics abstract the oligocene represents an important epoch in the history of the stepwise global climate evolution from a warm climate to a cooler climate the change probably introduced selective pressures influencing ecological strategies and caused the past ecosystems restructured however little is known about the paleoenvironment and adaptive plant ecological strategies in the terrestrial realm of the low latitudes here based on the plant fossils from the baigang formation of the baise basin low latitude china the paleoclimate paleovegetational type and paleoecological strategy are reconstructed using leaf physiognomic analyses integrated plant record and leaf economics spectrum respectively the results show that under a warm and wet sub tropical climate with low seasonality the oligocene baise flora was dominated by slow return maximized resource retention species but mixed with a considerable proportion of fast return rapid resource acquisition species these ecological strategies might promote the community to maximize the use of limited living resources and at the same time to better tolerate potential extreme situations these results allow us to examine which ecological strategies that fossil plants selected under a given paleoclimate condition and might potentially provide a clue to predict the direction of ecological strategy changes in a future climate change scenario

ongoing lithospheric removal in the western mediterranean evidence from ps receiver functions and thermobarometry of neogene basalts picasso project the western mediterranean tectonic system consists of the betic mountains in southern spain and the rif mountains in northern morocco curved around the back arc extensional alboran basin multiple tectonic models have been developed to explain the coeval compressional and extensional tectonic processes that have affected the western mediterranean since the oligocene in order to provide constraints on these evolutionary models we use ps teleseismic receiver functions rf thermobarometric analyses of post oligocene basalts and previous teleseismic tomography images to investigate the lithospheric structure of the region ps rfs were calculated using seismic data from 239 broadband seismic stations in southern iberia and northern morocco and thermobarometric analysis was performed on 19 volcanic samples distributed throughout the region the rf images reveal a highly variable moho depth 25 to 55 km as well as a strong positive sub moho horizon between 45 and 80 km depth beneath the central betic and rif mountains which we interpret to be the top of the previously imaged alboran sea slab thermobarometric constraints from magmas in the eastern betics and rif indicate mantle melting depths between 40 and 60 km typical of melting depths beneath mid oceanic ridges where little to no lithosphere exists together the rf and thermobarometric data suggest ongoing and recent slab detachment resulting from delamination of the continental lithosphere

cenozoic paleotemperatures and leaf physiognomy a european perspective for 21 european leaf floras with a focus on central europe which span a stratigraphic range from the late eocene to the pliocene paleoclimate estimates have been calculated using five different quantitative techniques a leaf margin analysis lma1 using a regression model based on data from east asia b the multivariate climate leaf analysis multivariate programm clamp technique based on data from east asia and n america c a recently developed multivariate technique based on modern european vegetation elpa d a provisional lma regression model based on the vegetation of several wet localities from n america lma2 and e the coexistence approach ca a technique based on comparisons with the nearest living relatives nlrs of fossil taxa according to our results there seems to be certain discrepancies where the different techniques are compared for paleotemperatures estimates depending mainly on the stratigraphic age of the floras for paleogene floras both multivariate leaf physiognomic techniques are in rather good agreement with ca although both techniques may differ considerably from each other in contrast for the neogene clamp shows a tendency to produce estimates that are considerably colder than ca whereas elpa provides generally warmer estimates and is in better agreement with ca and other independent evidence our results and interpretations add some caveats to temperature reconstructions based on leaf physiognomy especially when applied to european floras from older periods i e paleogene cretaceous possible changes of the relationship between climate and leaf physiognomy over time should be taken into account as a possible source of error whenever such techniques are used there is the possibility that the actual correlation between climate and leaf form may be modified by long time evolutionary responses or floral changes leading to erroneous paleoclimate estimates if a calibration data set is used which is not suited for the region and time interval in question however further research will be needed to test whether such changes in the relationship between climate and leaf physiognomy over time can also be detected on other continents or whether this is a problem restricted to europe

palaeobotanical evidence for a warm cretaceous arctic ocean the cretaceous period was a time of global warmth1 4 mid cretaceous equatorial temperatures were similar to today s5 but the equator to pole temperature gradient is the subject of some controversy5 7 although it is unlikely that the poles were ice free8 10 fossil evidence3 5 11 12 indicates that near polar temperatures were much higher than they are today little is known moreover about oceanic poleward heat transport and this makes it hard to model the cretaceous climate or to evaluate the extent to which it provides an analogue for a greenhouse world warmed by increased atmospheric co2 alone here we use relationships between leaf physiognomy such as shape and size and modern climate to determine cretaceous climate conditions in the arctic region from fossil leaves we find that the arctic ocean was relatively warm remaining above 0 c even during the winter months this implies that there was significant poleward heat transport during all seasons

production redistribution and loss of helium and argon isotopes in a thick sedimentary aquitard aquifer system molasse basin switzerland abstract in a rock water system an apparent residence time for he can be derived from the bulk he concentration in the rock and the porewater and the he production rate provided that 1 the system is at steady state and 2 the he flux from external sources is negligible this second condition is crucial and needs to be assessed by identifying the various he sources in a given hydrologic environment he and ar isotope abundances were investigated in whole rock samples and mineral separates of the alternating shale sandstone rock sequence of the permo carboniferous trough pct of the molasse basin in northern switzerland 4 he concentrations and 40 ar 36 ar ratios in groundwater in the bounding aquifers are lower than those in pct groundwaters thus eliminating a possible external source of radiogenic noble gases the elements producing radiogenic helium isotopes u th and li are mainly concentrated in the shales where they reside in biotite muscovite clay minerals and organic matter contents of these elements as well as chronological and chemical data allow us to calculate maximum closed system he isotope concentrations and the retention coefficients e g 3 he measured 3 he calculated ratios as deduced from the low retention coefficients almost all helium 3 that has been produced in these minerals since their deposition has been lost into the complementary reservoir i e the porewater the same conclusion is valid for 4 he this is also indicated by the similarity between the calculated 4 he 3 he production ratio of the shales and that observed in pct groundwater 1 3 10 7 moreover similar 4 he 3 he ratios are measured in quartz and plagioclase mineral grains from the sandstone layers by far exceeding the production ratios derived for these minerals also the measured concentrations of he isotopes especially 3 he are higher than the calculated production capacities of these minerals these observations suggest that some of the he produced in the shale and released from these rocks migrates via the porewater into the sandstone layers and penetrates further into some rock forming minerals such as quartz and plagioclase measurements of the migration rate of he atoms through quartz crystals showed that equilibrium between internal gas fluid vesicles and external porewater he concentrations is reached on a short time scale of 10 4 years at an in situ temperature of 70 c the equilibrium allows the he concentrations in the porewater across the pct sequence to be quantified using quartz crystals as detectors for the pct segment opened by the weiach borehole these quartz derived concentrations as well as those directly measured in pct groundwaters are rather high implying a long residence time for the he atoms in the pct rock porewater system well exceeding 10 7 years

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

upper level features associated with winter monsoon surges over south china abstract the upper level features associated with the two kinds of winter monsoon surges over south china are studied the easterly surge es and the northerly surge ns the study is similar to that used by wu and chan except that a broader region 0 60 n 70 160 e is considered the outbreak of an ns is associated with a breakdown of the siberia mongolia high the upper level features suggest that the evolution of the siberia mongolia high in an ns can be related to an eastward passage of a short wave trough and the polar jet based on the quasigeostrophic theory the intensification of the siberia mongolia high appears likely to be caused mainly by the adiabatic cooling due to rising motion associated with the trough and the polar jet passages after the passage of the trough and the jet the siberia mongolia high breaks down in response to the sinking motion upstream of the trough causing a surge of the northerly winds over the south china coast for the es the passage of an upper ridge is obse

patterns and average rates of late neogene recent uplift of the betic cordillera se spain abstract the facies distribution in the sedimentary units infilling a series of neogene basins has been used to reconstruct the relief generation and uplift across the internal zone of the betic cordillera in southern spain uplift amounts and average rates can be estimated using the current elevation of the outcrops of well dated deposits indicative of ancient sea level positions coral reefs and coastal conglomerates record the initial development of emergent betic relief during the langhian continental and marginal marine deposits indicate the existence of a large island centred on the present sierra nevada sierra de los filabres chain by the end of the middle miocene the precursor of the sierra nevada sierra de los filabres chain originally part of this large island remained emerged whilst the surrounding areas were re invaded by the sea during the early tortonian at the end of the tortonian the inland basins granada and guadix basins became continental while the sierras de la contraviesa sierra de gador and sierra alhamilla emerged separating the alboran basin from the alpujarra tabernas and sorbas basins which became narrow passages of the mediterranean sea in contrast the sierra cabrera emerged during the late messinian suggesting a progressive uplift from west to east of the sierras south of the sierra nevada sierra de los filabres chain during the pliocene only the low areas closest to the present day coast remained as marine basins and progressively emerged throughout this stage the highest average uplift rate recorded is 280 m ma for the sierra de gador although the average uplift rates of upper neogene coastal marine rocks since depositon have maximum values of approximately 200 m ma most of the uplift of the betic mountains took place before the early pliocene the recorded uplift of neogene rocks was highest at the margins of western sierra nevada where peaks higher than 3000 m occur the average rates of uplift were lower to the east of this major relief the main sierras and depressions in the present day landscape correspond respectively to the emergent land in which uplift was concentrated and to the marine basins that existed before the final emergence of the region the altitude of the sierras reflects the time at which they became emergent the highest mountains being the first to rise above sea level

effect of orogeny plate motion and land sea distribution on eurasian climate change over the past 30 million years the eurasian climates of today 10 million and 3o million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions the resulting climates compare well with various palaeoclimate records the retreat of the paratethys an epicontinental sea shifts the central asian climate from temperate to continental conditions and plays as important a role as uplift of the himalayan tibetan plateau in driving the asian monsoon changes

the coexistence approach theoretical background and practical considerations of using plant fossils for climate quantification the coexistence approach was established by mosbrugger and utescher 1997 as a plant based method to reconstruct palaeoclimate by considering recent climatic distribution ranges of the nearest living relatives of each fossil taxon during its existence for over more than 15 years its basics have been tested and reviewed in comparison with other terrestrial and marine climate reconstruction techniques and climate modelling data however some controversies remain about its underlying data or its applicability in general in view of these controversies this paper discusses the power and limitations of the coexistence approach by summarising past results and new developments we give insights into the details and problems of each step of the application from the assignment of the fossil plant to the most suitable nearest living relative the crucial consideration of the usefulness of specific taxa towards their climatic values and the correct interpretation of the software based suggested palaeoclimatic intervals furthermore we reflect on the fundamental data integrated in the coexistence approach by explaining different concepts and usages of plant distribution information and the advantages and disadvantages of modern climatic maps additionally we elaborate on the importance of continually updating the information incorporated in the database due to new findings in e g palaeo botany meteorology and computer technology finally for a transparent and appropriate use we give certain guidelines for future applications and emphasize to users how to carefully consider and discuss their results we show the coexistence approach to be an adaptive method capable of yielding palaeoclimatic and palaeoenvironmental information through rime and space c 2014 elsevier b v all rights reserved

diffusion of helium in zircon and apatite abstract diffusion of helium has been characterized in natural zircon and apatite polished slabs of zircon and apatite oriented either normal or parallel to c were implanted with 100 kev 3he at a dose of 5 1015 3 he cm2 diffusion experiments on implanted zircon and apatite were run in pt capsules in 1 atm furnaces 3he distributions following experiments were measured with nuclear reaction analysis using the reaction 3he d p 4he for diffusion in zircon we obtain the following arrhenius relations d c 2 3 10 7 exp 146 11 kj mol 1 r t m 2 s 1 d c 1 7 10 5 exp 148 17 kj mol 1 r t m 2 s 1 although activation energies for diffusion normal and parallel to c are comparable there is marked diffusional anisotropy with diffusion parallel to c nearly 2 orders of magnitude faster than transport normal to c these diffusivities bracket the range of values determined for he diffusion in zircon in bulk release experiments although the role of anisotropy could not be directly evaluated in those measurements in apatite the following arrhenius relation was obtained over the temperature range of 148 449 c for diffusion normal to c d 2 10 10 6 exp 117 6 kj mol 1 r t m 2 s 1 in contrast to zircon apatite shows little evidence of anisotropy he diffusivities obtained in this study fall about an order of magnitude lower than diffusivities measured through bulk release of he through step heating and within an order of magnitude of determinations where ion implantation was used to introduce helium and he distributions measured with elastic recoil detection since the diffusion of he in zircon exhibits such pronounced anisotropy helium diffusional loss and closure cannot be modeled with simple spherical geometries and the assumption of isotropic diffusion a finite element code cylmod has recently been created to simulate diffusion in cylindrical geometry with differing radial and axial diffusion coefficients we present some applications of the code in evaluating helium lost from zircon grains as a function of grain size and length to diameter ratios and consider the effects of shape anisotropy where diffusion is isotropic as in the case of apatite but shapes of crystal grains or fragments may depart significantly from spherical geometry

correlation of himalayan exhumation rates and asian monsoon intensity although most data suggest that the india eurasia continental collision began 45 55 myr ago the architecture of the himalayan tibetan orogen is dominated by deformational structures developed in the neogene period 23 myr ago the stratigraphic record and thermochronometric data indicate that erosion of the himalaya intensified as this constructional phase began and reached a peak around 15 myr ago it remained high until 10 5 myr ago and subsequently slowed gradually to 3 5 myr ago but then began to increase once again in the late pliocene and pleistocene epochs here we present weathering records from the south china sea bay of bengal and arabian sea that permit asian monsoon climate to be reconstructed back to the earliest neogene these indicate a correlation between the rate of himalayan exhumation as inferred from published thermochronometric data and monsoon intensity over the past 23 myr we interpret this correlation as indicating dynamic coupling between neogene climate and both erosion and deformation in the himalaya although the india eurasia collision initiated 50 myr ago major deformation and exhumation of the himalaya did not begin until the early neogene 23 myr ago this coincides with the increased intensity of the asian monsoons as indicated by weathering records from the south china sea bay of bengal and arabian sea and hints at a dynamic coupling between climate and both erosion and deformation in the himalaya

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

what triggers the transition of palaeoenvironmental patterns in china the tibetan plateau uplift or the paratethys sea retreat abstract geological research has illustrated the transition of palaeoenvironmental patterns by the earliest miocene from a planetary wind dominant type to a monsoon dominant type indicating that the east asian monsoon became markedly intensified and played a leading role in the east asian climate from a modeling point of view the pioneering research using the reduced number of scenarios had demonstrated that both the tibetan plateau uplift and the paratethys sea retreat were important for understanding the asian monsoon evolution however the sensitivity of the paratethys retreat to the east asian climate still needs further studies based on the more detailed scenarios thirty numerical experiments under the six paratethys sea and the five tibetan plateau conditions illustrate the shifts from zonal climate to the monsoon climate in east asia the results confirm again that both the paratethys retreat and the tibetan plateau uplift play important roles in the formation of the monsoon dominant environmental pattern and show that the paratethys retreat can strengthen the east asian monsoon and greatly increase humidity and aridity respectively in the monsoon areas and northwest china which is similar to the impact of the tibetan plateau uplift on the east asian climate furthermore the fact that the paratethys sea retreats to the turan plate is found to be the key criterion for the palaeoenvironmental patterns transition in china the shrinkage of paratethys sea leads to the reconstructions of the pressure system and the atmospheric circulations which result in the variations of precipitation and the transition of palaeoenvironmental patterns

increased seasonality through the eocene to oligocene transition in northern high latitudes a profound global climate shift took place at the eocene oligocene transition approximately 33 5 million years ago when cretaceous early palaeogene greenhouse conditions gave way to icehouse conditions during this interval changes in the earth s orbit and a long term drop in atmospheric carbon dioxide concentrations resulted in both the growth of antarctic ice sheets to approximately their modern size and the appearance of northern hemisphere glacial ice however palaeoclimatic studies of this interval are contradictory although some analyses indicate no major climatic changes others imply cooler temperatures increased seasonality and or aridity climatic conditions in high northern latitudes over this interval are particularly poorly known here we present northern high latitude terrestrial climate estimates for the eocene to oligocene interval based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the norwegian greenland sea our data indicate a cooling of approximately 5 degrees c in cold month winter mean temperatures to 0 2 degrees c and a concomitant increased seasonality before the oi 1 glaciation event these data indicate that a cooling component is indeed incorporated in the delta 18 o isotope shift across the eocene oligocene transition however the relatively warm summer temperatures at that time mean that continental ice on east greenland was probably restricted to alpine outlet glaciers

paleogene temperature gradient seasonal variation and climate evolution of northeast china abstract continental paleogene climates have been well studied in europe and north america but very little is known from asia because paleoclimatic results have only been reported from particular geological intervals here based on 29 plant assemblages from 8 well age controlled fossiliferous sites we quantitatively reconstruct the climates through most of the paleogene of northeast china and discuss related seasonal variations our results demonstrate that the mean annual temperature mat gradient was fairly shallow 0 27 c 1 latitude during the paleocene throughout this region in the eocene seasonality was high in the region indicated by marked differences in both temperature and precipitation between winters and summers of the sites the paleo east asian monsoon must have had intensified at least in the late mid eocene shown by apparent differences in annual precipitation distribution at all the sites regarding the paleogene climatic evolution of northeast china our quantitative results suggest that mat overall declined from warm in the paleocene and eocene to moderate in the oligocene generally consistent with the trend of marine records but with some distinctions two significant cooling events are recognized in the early and mid eocene with mat 3 4 c and 3 8 c lower and winter temperature 5 8 c and 4 7 c lower respectively in similar magnitudes to corresponding variations in europe and north america furthermore the present results show that mat rebounded in the late mid eocene and then decreased until the oligocene a similar pattern demonstrated in europe during the mid eocene to oligocene interval

large temperature drop across the eocene oligocene transition in central north america the eocene oligocene transition about 33 5 million years ago was a major global climate event the end of the eocene was unusually warm with no significant ice on antarctica but the oligocene saw the arrival of a permanent antarctic ice sheet two papers this week relate to the continental effects of this global change dupont nivet et al examined sedimentary records from the tibetan plateau and find a drop in atmospheric water which caused cooling and aridification coincident with antarctic cooling previous studies attributed this phenomenon to the rapid uplift of the tibetan plateau but this new work suggests that regional tibetan climate was influenced by global events in an unrelated paper on the same climate transition zanazzi et al explore the cooling in north america at the time using stable isotope measurements from fossil teeth and bones to create a proxy temperature record they find a large drop in mean annual temperature of 8 2 c a greater fall than seen in the oceans this continental transition may explain why many cold blooded reptiles and amphibians became extinct whereas mammals able to regulate their body temperature escaped relatively unscathed an analysis of fossil tooth enamel and fossil bones is used to derive a continental temperature record for the eocene oligocene transition and reports a large drop in mean annual temperature over roughly 400 000 years this cooling explains the decline in cold blooded terrestrial animals whereas most mammals in the region were unaffected the eocene oligocene transition towards a cool climate 33 5 million years ago was one of the most pronounced climate events during the cenozoic era1 the marine record of this transition has been extensively studied however significantly less research has focused on continental climate change at the time yielding partly inconsistent results on the magnitude and timing of the changes2 3 4 5 6 7 8 here we use a combination of in vivo stable isotope compositions of fossil tooth enamel with diagenetic stable isotope compositions of fossil bone to derive a high resolution about 40 000 years continental temperature record for the eocene oligocene transition we find a large drop in mean annual temperature of 8 2 3 1 c over about 400 000 years the possibility of a small increase in temperature seasonality and no resolvable change in aridity across the transition the large change in mean annual temperature exceeding changes in sea surface temperatures at comparable latitudes9 10 and possibly delayed in time with respect to marine changes by up to 400 000 years explains the faunal turnover for gastropods amphibians and reptiles whereas most mammals in the region were unaffected our results are in agreement with modelling studies that attribute the climate cooling at the eocene oligocene transition to a significant drop in atmospheric carbon dioxide concentrations

asian eocene monsoons as revealed by leaf architectural signatures abstract the onset and development of the asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations coupled with a diversity of definitions and metrics characterizing monsoon phenomena have generated much debate failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the inter tropical convergence zone itcz from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils leaf form adapts to the prevailing climate particularly under the extreme seasonal stresses imposed by monsoons so it is likely that fossil leaves carry a unique signature of past monsoon regimes leaf form trait spectra obtained from fossils from eocene basins in southern china were compared with those seen in modern leaves growing under known climate regimes the fossil leaf trait spectra including those derived from previously published fossil floras from northwestern india were most similar to those found in vegetation exposed to the modern indonesia australia monsoon i am which is largely a product of seasonal migrations of the itcz the presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in eocene time across southern asia the characteristics of the modern topographically enhanced south asia monsoon had yet to develop by the eocene leaves in south asia had become well adapted to an i am type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the eocene no fossil trait spectra typical of exposure to the modern east asia monsoon were seen suggesting the effects of this system in southern china were a much later development

changing atmospheric co2 concentration was the primary driver of early cenozoic climate the early eocene climate optimum eeco which occurred about 51 to 53 million years ago was the warmest interval of the past 65 million years with mean annual surface air temperature over ten degrees celsius warmer than during the pre industrial period subsequent global cooling in the middle and late eocene epoch especially at high latitudes eventually led to continental ice sheet development in antarctica in the early oligocene epoch about 33 6 million years ago however existing estimates place atmospheric carbon dioxide co2 levels during the eocene at 500 3 000 parts per million and in the absence of tighter constraints carbon climate interactions over this interval remain uncertain here we use recent analytical and methodological developments to generate a new high fidelity record of co2 concentrations using the boron isotope 11 b composition of well preserved planktonic foraminifera from the tanzania drilling project revising previous estimates although species level uncertainties make absolute values difficult to constrain co2 concentrations during the eeco were around 1 400 parts per million the relative decline in co2 concentration through the eocene is more robustly constrained at about fifty per cent with a further decline into the oligocene provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the eocene was similar to that of the late quaternary period this co2 decline was sufficient to drive the well documented high and low latitude cooling that occurred through the eocene once the change in global temperature between the pre industrial period and the eocene caused by the action of all known slow feedbacks apart from those associated with the carbon cycle is removed both the eeco and the late eocene exhibit an equilibrium climate sensitivity relative to the pre industrial period of 2 1 to 4 6 degrees celsius per co2 doubling 66 per cent confidence which is similar to the canonical range 1 5 to 4 5 degrees celsius indicating that a large fraction of the warmth of the early eocene greenhouse was driven by increased co2 concentrations and that climate sensitivity was relatively constant throughout this period

tectonic evolution of the alpujarride complex betic cordillera southern spain abstract the alpujarride complex belonging to the internal zones of the betic cordillera is an e w elongated domain of metamorphic nappes which extends over more than 400 km in southern spain the alpujarride complex suffered two shearing episodes defined by different kinematic and physical conditions the first one involved ductile thrusting from the south west towards the north east related to the regional metamorphism of the alpujarride nappes this process led to crustal thickening related to which the hot thrusting of the ronda peridotites occurred the second shearing episode directed northwards occurred after the metamorphism it corresponds to a deformation in the brittle ductile transition that led to the thinning of the crust thickened in the previous episode previous tectonic models of the betic cordillera have only considered the northwards shearing which reflect the n s convergence of europe and africa from the oligocene onwards the present work clearly points to the existence of previous episodes of ductile thrusting towards the north east that reflect an earlier process of continental collision and that in future should be considered in tectonic models of the betic orogen

miocene pollen assemblages from the zeku basin northeastern tibetan plateau and their palaeoecological and palaeoaltimetric implications abstract a comprehensive understanding of the tectonic uplift history of the tibetan plateau tp a 2000 km wide region with a mean altitude of 4000 5000 m above sea level asl is crucial for interpreting global cenozoic climate change collisional tectonics and the evolution of the asian climatic system however the timing degree and extent of the uplift of the tp remain controversial here we report new palynological data from early to mid miocene lacustrine swamp sediments in the zeku basin northeastern tp the palynoflora includes 68 palynotaxa at a family or genus level comprising gymnosperms 16 2 angiosperms 77 9 pteridophytes 2 9 and others 2 9 and is suggestive of a mixed warm temperate forests of coniferous e g picea abies and tsuga and deciduous broadleaved trees e g ulmus zelkova betula and quercus with some subtropical elements e g carya and liquidambar three periods of vegetation succession can be recognized from the caergen section indicating a stepwise warming and drying trend from bottom to top the local palaeoclimatic parameters obtained by applying the coexistence approach coa to palynologic assemblages rendered mean annual temperature mat values of 14 2 16 1 c and mean annual precipitation map values of 797 1113 mm this study departs from the traditional application of the coa relying on published determination of plant climate relationships rather than on data derived from the paleoflora database which is currently not fully open access based on the difference in temperatures between the early to mid miocene and the present day and the temperature lapse rate corrected to take account of miocene global temperature differences the estimated palaeoaltitude of the zeku basin during the early to mid miocene was 1200 1400 m asl this palaeoaltitude estimate suggests that this basin has experienced about 2200 2500 m of uplift since the early to mid miocene findings therefore do not support previous hypotheses that the northeastern tp attained its present altitude before the miocene

resolving apparent conflicts between oceanographic and antarctic climate records and evidence for a decrease in pco2 during the oligocene through early miocene 34 16 ma abstract an apparent mismatch between published oxygen isotopic data and other paleoclimate proxies for the span from 26 16 ma is resolved by calibration against global sea level estimates obtained from backstripping continental margin stratigraphy ice volume estimates from calibrated oxygen isotope data compare favorably with stratigraphic and palynological data from antarctica and with estimates of atmospheric pco2 throughout the oligocene to early miocene 34 16 ma isotopic evidence for an east antarctic ice sheet eais as much as 30 larger than its present day volume at glacial maxima during that span is consistent with seismic reflection and stratigraphic evidence for an ice sheet covering much of the antarctic continental shelf at the same glacial maxima palynological data suggest long term cooling during the oligocene with cold near tundra environments developing along the coast at glacial minima no later than the late oligocene a possible mechanism for this long term cooling is a decrease in atmospheric pco2 from the middle eocene to oligocene reaching near pre industrial levels by the latest oligocene and remaining at those depressed levels throughout the miocene

helium and argon isotopes in rocks minerals and related ground waters a case study in northern switzerland abstract to address the problems related to the transfer of helium and argon isotopes from rocks into related aquifers the concentrations of u th li and k and helium and argon isotopes were measured in a sedimentary sequence from tertiary to permo carboniferous and in crystalline rocks in northern switzerland in addition to whole rock samples mineral separates have also been investigated the observed concentrations of 3 he 4 he and 40 ar in rocks minerals and groundwaters are compared to calculated values which would result from in situ radiogenic production in a closed system this comparison shows that the rocks and minerals have almost completely lost radiogenic in situ produced helium loss of 3 he and 4 he has been controlled by different retention capacities of the rock forming and accessory minerals and fillings therefore measured 3 he 4 he ratios in these rocks can differ from the calculated production ratios the deviation is generally less than a factor of 3 however in certain chemical sediments e g anhydrites elevated ratios of 3 he 4 he up to 15 10 8 which is 20 times the production ratio were observed it is postulated that 3 h the precursor of 3 he might be chemically bound in such sediments during the 12 3 years half life of 3 h and that the beta decay energy of 3 h is too small to liberate 3 he the calculated closed system concentrations of helium in groundwater exceed the measured ones by up to three orders of magnitude implying that the water rock system has not been a closed system since the time of sedimentation and that movable waters have removed helium to a discharge area and to the atmosphere stagnant old waters however could contain high concentrations of helium and supply it to younger movable waters aquitards with low permeability permian shales appear to be a more important source of helium isotopes than water bearing rocks permian sandstones high abundances of all parent elements in the shales almost complete loss of radiogenic helium and the enhanced production ratio of 3 he 4 he 7 2 10 8 in these rocks similar to the ratio observed in the neighbour permian aquifer 9 4 10 8 suggest the shale as a major source of helium isotopes for this aquifer and diffusion as a principal process for helium transfer from the stagnant porewaters in shales into the movable waters in sandstones some sedimentary rocks e g permian sandstones and shales contain more helium than could have been produced since the time of sedimentation while permian sandstones mainly have retained this excess rare gas component they have released radiogenic helium the difference in the retention of these two components most probably demonstrates that migration of radiogenic helium from damage tracks along crystal imperfections to grain boundaries is an important process controlling its loss the abundances of excess 3 he and 4 he in rocks cannot be predicted by in situ production calculations studies of rocks and minerals are required the average ratio of 40 ar 36 ar 385 in groundwaters collected from permian sediments from the weiach borehole is much higher than that in the aquifers from the crystalline basement below the sediments radiogenic 40 ar in permian sediments is mainly liberated by diagenetic water rock interactions the low contribution of radiogenic 40 ar in deep aquifers of the crystalline basement and the fact that chlorine concentrations in groundwaters from the basement are also much lower than in the overlaying permian aquifer eliminates a hypothetical upwards fluid flux from this study we envisage intrabasin sources for helium and argon isotopes in groundwaters with mainly lateral migration of waters through sedimentary layers at different rates and diffusion of helium from slower velocity older waters in more stagnant zones shales into flow passes with highervelocity younger waters in sections with higher permeability sandstones an external source for noble gases is not required in such a model

convergent cenozoic co2 history reconstructions of atmospheric carbon dioxide concentrations over the past 65 million years are heading towards consensus it is time for systematic testing of the proxies against measurements and against each other

tibetan plateau aridification linked to global cooling at the eocene oligocene transition the eocene oligocene transition about 33 5 million years ago was a major global climate event the end of the eocene was unusually warm with no significant ice on antarctica but the oligocene saw the arrival of a permanent antarctic ice sheet two papers this week relate to the continental effects of this global change dupont nivet et al examined sedimentary records from the tibetan plateau and find a drop in atmospheric water which caused cooling and aridification coincident with antarctic cooling previous studies attributed this phenomenon to the rapid uplift of the tibetan plateau but this new work suggests that regional tibetan climate was influenced by global events in an unrelated paper on the same climate transition zanazzi et al explore the cooling in north america at the time using stable isotope measurements from fossil teeth and bones to create a proxy temperature record they find a large drop in mean annual temperature of 8 2 c a greater fall than seen in the oceans this continental transition may explain why many cold blooded reptiles and amphibians became extinct whereas mammals able to regulate their body temperature escaped relatively unscathed precisely dated evidence details that aridification on the tibetan plateau occurred at the time of the eocene oligocene transition in the marine records this suggests a direct link between the palaeontological and palaeoenvironmental changes recorded in continental asia at the time and global climate cooling continental aridification and the intensification of the monsoons in asia are generally attributed to uplift of the tibetan plateau and to the land sea redistributions associated with the continental collision of india and asia1 2 3 whereas some studies suggest that past changes in asian environments are mainly governed by global climate4 5 6 the most dramatic climate event since the onset of the collision of india and asia is the eocene oligocene transition an abrupt cooling step associated with the onset of glaciation in antarctica 34 million years ago7 8 9 however the influence of this global event on asian environments is poorly understood here we use magnetostratigraphy and cyclostratigraphy to show that aridification which is indicated by the disappearance of playa lake deposits in the northeastern tibetan plateau occurred precisely at the time of the eocene oligocene transition our findings suggest that this global transition is linked to significant aridification and cooling in continental asia recorded by palaeontological and palaeoenvironmental changes10 11 12 and thus support the idea that global cooling is associated with the eocene oligocene transition13 14 15 we show that with sufficient age control on the sedimentary records global climate can be distinguished from tectonism and recognized as a major contributor to continental asian environments

depositional controls and characteristics of subaqueous bedded volcaniclastics of the lower devonian snowy river volcanics abstract the mt johnson member represents a relatively deep quiet marine enclave within the largely subaerial lower devonian snowy river volcanics it is intersected by seven diamond drill holes allowing a detailed analysis of the constituent sediment sequences normal sedimentation is represented by a mudstone facies which consists of interbedded black mudstones and turbiditic siltstones however this fine grained deposition was periodically interrupted by the emplacement of thick amalgamated volcaniclastic mass flow sequences six mass flow sequences are defined and two types can be recognized according to their overall bedding thickness and grainsize profile upward thinning and fining sequences are characterized by thickly bedded basal deposits of juvenile magmatically fragmented pyroclastic debris emplaced as cold water supported mass flows these are interpreted to be essentially syn eruptive arising either from flow transformation as pyroclastic flows ingested water upon entering the sea or from immediately post eruptive slumping of unreworked pyroclastic debris ponded at the shoreline these juvenile deposits are overlain by intervals of thinner bedded mass flows which are of a similar provenance but are considerably depleted in fines the second type of mass flow sequence the complex bedding thickness sequences has a basal zone of bedded fines depleted mass flow deposits with juvenile deposits in the mid to upper portions these mass flow sequences are interpreted to have arisen either from volcanic eruptive events which did not initially deposit primary pyroclastic debris subaqueously or from epiclastic events which eroded previously erupted unconsolidated volcaniclastic debris the depletion of fines in much of the volcaniclastic debris within the mt johnson member indicates that it was subjected to a degree of epiclastic reworking since this cannot have occurred in the deep quiet marine host environment it indicates an external source for the parental magmatic eruptions the eruptions probably occurred in an adjacent subaerial hinterland drained by an alluvial fluvial deltaic or fan deltaic system this system would have been a natural site for ponding and storage of freshly erupted debris and would have allowed the complex interaction between eruptive and epiclastic events which appear to have been responsible for the mass flow sequences

oligocene climate signals and forcings in eurasia revealed by plant macrofossil and modelling results abstract the oligocene represents a transitional time period from a warm climate to a cooler climate that is more representative of the modern day yet a general view of continental climate pattern and forcings are still lacking different proxies and models show striking disparities especially in mid high latitudes requiring validation of oligocene climate reconstruction in order to understand the large scale processes that drive the observed climate changes here we compiled 149 macrofossil floras in the mid high latitudes of eurasia then quantitatively reconstructed the oligocene climate using coexistence approach ca and combined previously published paleoclimate data during the oligocene eurasian mid high latitudes were mainly dominated by a humid subtropical climate mean annual temperature mat ranged between 5 4 c and 25 5 c with mean annual precipitation map ranging from 338 to 2453 mm three regions europe central eurasia and eastern asia indicate different climatic regimes with a generally warmer and wetter climate in europe and a colder and drier climate in central eurasia when compared to eastern asia no significant reorganization of climate was observed between the early and late oligocene the climate anomalies between the oligocene and present indicate that geographic changes e g retreat of the paratethys sea played an important role in shaping the climate pattern of eurasia by comparing the fossil data to a range of different hadcm3l model simulations of the oligocene with differing boundary conditions e g co2 and topography we demonstrate similar large scale climate spatial patterns between models and fossil data however models simulated much higher temperature seasonality lower simulated winter temperatures and higher simulated summer temperatures in eurasia mean annual temperature analysis indicates that simulations with 560 and 1120 ppmv co2 matched better with fossil data when compared to other simulations depending on the topography these results provide some constraints that should be considered for future paleoclimate modelling

dissolved helium isotope ratios in ground waters a new technique based on gas water re equilibration and its application to stromboli volcanic system here a new technique for the determination of dissolved he isotope ratios in ground waters is presented this method is based on the extraction and subsequent equilibrium of dissolved gases in an added host gas phase ultra pure n2 is placed in glass flasks 250 cc containing water samples that were hermetically sealed after their collection after shaking in an ultrasonic bath for 10 min an aliquot of the separated gas phase was removed from the flask for ms analysis 3he 4he ratios are measured by using a modified double collector mass spectrometer vg 5400 tft helium and ne concentrations are calculated by comparing the partial pressures of masses 4 and 20 of the samples with those of the air standard measured by a quadrupole mass spectrometer qms vg quartz using he and ne equilibrium partitioning coefficients it is possible to calculate the amount of gas originally dissolved in the water the technique was tested on both air saturated waters asw and thermal waters from stromboli aeolian islands south italy the results of which confirmed good reproducibility 5 and accuracy 3 of the data the method was then applied to three thermal water samples collected from the same volcanic area and the results compared with those of a fumarolic and a soil gas the isotope ratios for dissolved he gave values of 4 06 4 23 ra which are significantly higher than those previously reported in the literature 3 0 3 5 and 2 9 ra and that measured at the fumarole 3 09 ra suggesting a newer and higher isotopic signature for the volcanic system the proposed method appears to be a useful tool in the determination of 3he 4he ratios in ground water systems especially when free gases are not available or are dangerous to collect