constant elevation of southern tibet over the past 15 million years the uplift of the tibetan plateau an area that is 2 000 km wide to an altitude of about 5 000 m has been shown to modify global climate and to influence monsoon intensity mechanical and thermal models for homogeneous thickening of the lithosphere make specific predictions about uplift rates of the tibetan plateau but the precise history of the uplift of the plateau has yet to be confirmed by observations here we present well preserved fossil leaf assemblages from the namling basin southern tibet dated to approximately 15 myr ago which allow us to reconstruct the temperatures within the basin at that time using a numerical general circulation model to estimate moist static energy at the location of the fossil leaves we reconstruct the elevation of the namling basin 15 myr ago to be 4 689 895 m or 4 638 847 m depending on the reference data used this is comparable to the present day altitude of 4 600 m we conclude that the elevation of the southern tibetan plateau probably has remained unchanged for the past 15 myr

episodic graben formation and extensional neotectonic regime in west central anatolia and the isparta angle a case study in the aksehir afyon graben turkey

plant community ecology and climate on an upland volcanic landscape during the early eocene climatic optimum mcabee fossil beds british columbia canada abstract the mcabee fossil beds in south central british columbia canada provide a record of forest ecosystems within a volcanically active upland landscape during the early eocene climatic optimum eeco to assess plant community ecology and climate within this environment palynology and census style macrofossil collections were investigated from two shale horizons separated in time by likely 103 104 years an ensemble of leaf physiognomic estimates indicates a persistent warm mean annual temperature mat 10 12 c and mesic mean annual precipitation 1000 mm yr 1 climate between the horizons the plant community was similar in both horizons comprising angiosperms e g ulmus fagus alnus betula and carya and gymnosperms e g metasequoia pinus picea and larix plant diversity and the distribution of dicot leaf mass per area ma values were consistent between the two horizons despite intervals of varying tuff thickness and frequency between the horizons differences in macrofossil abundances of ulmus fagus and pinus and a lack of such differences in their respective pollen abundances might be explained by local patch dynamics influenced by spatial heterogeneity resulting from topographic diversity and disturbance ma estimates suggest dicots were predominately deciduous and the distribution of ma is similar to a modern forest in panama influenced by seasonal precipitation the diversity of dicots at mcabee despite relatively lower mean annual temperatures is comparable to fossil plant quarries of similar volume from early eocene sites in patagonia e g laguna del hunco and the denver basin with relatively warmer mats 17 25 c this is best explained by a combination of predominately frost free winters high productivity and an abiotic environment characterized by spatial heterogeneity and high rates of change the sampled paleofloras of this study showcase an eeco plant community likely representing an ecological solution to volcanic disturbance over millennial time scales

low vp vs ratios in the crust and upper mantle beneath the sea of okhotsk inferred from teleseismic pmp smp and sms underside reflections from the moho 1 teleseismic ground motion recordings of deep earthquakes often contain clear seismic wave reflections from the free surface above the source pp sp ss with isolated precursors pmp smp and sms produced by underside reflections from the moho the crust mantle boundary below the free surface reflection points the waveforms of the depth phases and their precursors are readily modeled providing constraints for steep angles of incidence on integrated two way crustal travel times and moho shear and compressional impedance contrasts above deep earthquake source regions we model surface reflection waveforms in stacks of three component long period wwssn and digital broadband seismograms for signals traversing the crust and upper mantle beneath the sea of okhotsk which overlies deep earthquakes in the subducted kurile slab the crust beneath most of the sea of okhotsk is 19 25 km thick indicating a submerged continental margin with minor crustal thinning toward the kuril back arc basin where thin oceanic crust is found modeling pmp and sms phases that sample the same subregion provides tight constraints on the vp vs ratio in the crust and uppermost mantle assuming common density structure and consistent crustal thickness for p and s waves the absolute velocities are not constrained by the data we find unusually low vp vs ratios in the range 1 6 1 7 for the uppermost mantle under the sea of okhotsk and comparably low average vp vs ratios for the crust in several regions the presence of fluids and extensive silica enrichment possibly involving low temperature veining are viable explanations for the anomalous vp vs ratios this may represent an important process of continentalization taking place landward from the volcanic arc in subduction zones

taphonomy of a mass death layer of fishes in the paleocene paskapoo formation at joffre bridge alberta canada a layer of silty mudstone only a few centimetres thick in the lower part of the mainly fluvial paskapoo formation contains thousands of complete skeletons of fossil fish and is tiffanian late paleocene ti3 in age the diversity represented in the layer is low with thousands of specimens of a species in the trout perch family percopsidae tens of specimens of a species in the smelt family osmeridae and just two specimens of a species of osteoglossomorph in the family osteoglossidae recovered to date although the fishes occur without other kinds of fossils in the fish layer other layers in the same outcrop have yielded abundant remains of plants insects mollusks and mammals taphonomic features of the fish layer are used to test the hypothesis that it represents a mass death event and to evaluate mechanisms of formation there is little disarticulation and no sign of scavenging fish occur in distinct size classes individuals of the smelt species demonstrate breeding tubercles fish tend

estimating paleoatmospheric pco2 during the early eocene climatic optimum from stomatal frequency of ginkgo okanagan highlands british columbia canada abstract estimates of p co 2 for the early paleogene vary widely from near modern day levels to an order of magnitude greater based on various proxy measures resolving the relationship between climate and p co 2 during this globally warm period is a key task in understanding climate dynamics in a warmer world here we use the stomatal frequency of fossil ginkgo adiantoides from the okanagan highlands of british columbia canada to estimate p co 2 during the early eocene climatic optimum eeco the interval of peak warmth in the cenozoic we also examine a dataset of modern ginkgo biloba leaves to critically assess the accuracy and precision of stomatal frequency as a proxy indicator of p co 2 early eocene fossil g adiantoides has significantly lower stomatal frequency than modern g biloba suggesting p co 2 levels 2 modern pre industrial values this result is in contrast to earlier studies using stomatal frequency of ginkgo that indicated near modern day levels of p co 2 in the early paleogene though not including samples from the eeco we also find that levels of p co 2 as indicated by stomatal frequency are correlated with trends in climate mean annual temperature over time at the falkland fossil locality suggesting that climate and p co 2 were coupled during the eeco hyperthermal

eocene paleo physiography and drainage directions southern interior plateau british columbia a map of reconstructed eocene physiography and drainage directions is presented for the southern interior plateau region british columbia south of 53 n eocene landforms are inferred from the distribution and depositional paleoenvironment of eocene rocks and from crosscutting relationships between regional scale geomorphology and bedrock geology of known age eocene drainage directions are inferred from physiography relief and base level elevations of the sub eocene unconformity and the documented distribution provenance and paleocurrents of early cenozoic fluvial sediments the eocene landscape of the southern interior plateau resembled its modern counterpart with highlands plains and deeply incised drainages except regional drainage was to the north an anabranching valley system trending west and northwest from quesnel and shuswap highlands across the cariboo plateau to the fraser river valley contained north flowing streams from eocene to early quaternary time other valleys dating back at least to middle eocene time include the north thompson valley south of clearwater thompson valley from kamloops to spences bridge the valley containing nicola lake bridge river valley and okanagan lake valley during the early cenozoic highlands existed where the coast mountains are today southward drainage along the modern fraser chilcotin and thompson river valleys was established after the late miocene

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

geochemical features of collision related volcanic rocks in central and eastern anatolia turkey in central and eastern anatolia volcanism related to continental collision occurred in neogene to quaternary times major and trace element compositions 87sr86 sr and k ar ages were determined for volcanic rocks from selected volcanoes in this region 87sr86 sr for basalts from erciyes volcano in the eastern part of central anatolia as well as ararat nemrut and karacadag volcanoes in eastern anatolia are in the range 0 7035 0 7040 these ratios are higher than those of n type morb but overlap arc volcanic rock values this suggests that the mantle source which was possibly contaminated by fluids and melts with higher87sr86 sr during the pre collisional events has similar sr isotopic compositions in wide areas of the eastern part of central anatolia and eastern anatolia even across the collision plate boundary in addition chemical compositions of the mantle source are not homogeneous with respect to hfs element contents indicating that the slab derived components resulting from past subductions are not homogeneously distributed the mantle source beneath the western part of central anatolia which corresponds to the transitional region from collision tectonics in the east to subduction tectonics in the west has different chemical and sr isotopic signatures from other parts of anatolia in the western part of central anatolia the87sr86 sr of basaltic rocks from three regions characterized by monogenetic volcanoes are in the range 0 70427 to 0 70581 and differ from region to region in spite of indistinguishable chemical compositions this indicates either source heterogeneity on a small scale or different contributions of local crustal contaminants calc alkaline lavas from ararat and kars in eastern anatolia have chemical compositions with subduction signatures inherited from pre collision subduction events in contrast the chemical and sr isotopic features of volcanic rocks from erciyes volcano in central anatolia indicate that the combined process of fractional crystallization of basaltic magma and crustal assimilation without injection of slab derived components is the dominant process generating calc alkaline andesite under the collision tectonics regime operating in this region

depositional setting fossil flora and paleoenvironment of the early eocene falkland site okanagan highlands british columbia the fossil flora and depositional setting of the early eocene falkland site in the southern interior of british columbia canada is reported in detail for the first time using a census sampling approach the falkland site is part of the series of okanagan highlands fossil localities in british columbia and washington state that represent relatively cool upland environments within the context of the greenhouse world of the early eocene providing microthermal mean annual temperature mat 13 c climatic conditions for the establishment of cool adapted plants geographically adjacent to subtropical elements from lowland floras plant community composition of the falkland flora is most similar to the republic washington and mcabee british columbia floras based on high sorenson similarity coefficients together forming a southern cluster of okanagan highlands sites the site is a lacustrine deposit that formed in a volcanically active landscape paleoclimate reconstructions based on leaf physiognomy

the crustal structure of the eastern marmara region turkey by teleseismic receiver functions summary we study the crustal structure of eastern marmara region by applying the receiver function method to the data obtained from the 11 broad band stations that have been in operation since the 1999 earthquake the stacked single event receiver functions were modelled by an inversion algorithm based on a five layered crustal velocity model to reveal the firstorder shear velocity discontinuities with a minimum degree of trade off we observe crustal thickening from west 29 32 km to east 34 35 km along the north anatolian fault zone nafz but we observe no obvious crustal thickness variation from north to south while crossing the nafz the crust is thinnest beneath station ter 29 km located near the black sea coast in the west and thickest beneath station tar 35 km located inland in the southeast the average crustal thickness and s wave velocity for the whole regions are 31 2 km and 3 64 0 15 km s 1 respectively the eastern marmara region with its average crustal thickness high heat flow value 101 11 mw m 2 and with its remarkable extensional features seems to have a basin and range type characteristics but the higher average shear velocities 3 64 km s 1 and crustal thickening from 29 to 35 km towards the easternmost stations indicate that the crustal structure shows a transitional tectonic regime therefore we conclude that the eastern marmara region seems to be a transition zone between the marmara sea extensional domain and the continental anatolian inland region

variations in the crustal structure beneath western turkey summary we use teleseismic receiver functions to investigate the crustal structure at two locations in westernturkey using seismic data recorded on small arrays of temporary broad band seismographs the results from these analyses are compared with receiver function results from the gdsn station anto on the anatolian plateau in central turkey the crust is 30 km thick in the region of western turkey where active normal faulting reveals present day extension in the upper crust and alkali basaltic volcanism reveals recent extension within the subcrustal lithosphere the crust is 34 km thick further east where crustal extension is still evident but less pronounced in the anatolian plateau which is not currently extending the crust is 38 km thick the level of extension estimated from these measurements of crustal thickness implies a b factor of 1 2 this value agrees with the amount of extension estimated in the upper crust from the integrated seismic strain rate b factor of 1 3 from surface faulting b factor of 1 25 and from the amount of extension in the subcrustal lithosphere estimated from the volcanism b factor 2 all indicating that the extension is approximately uniformly distributed vertically throughout the lithosphere the moho transition in this region appears to thin slightly as the degree of extension increases westwards

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

a review of paleotemperature lapse rate methods for estimating paleoelevation from fossil floras one widely applied method for estimating paleoelevation from fossil floras uses the relation between vegetation and temperature to estimate mean annual temperature from two isochronous fossil assemblages one at elevation and one at or near sea level and the difference between these temperatures is multiplied by the reciprocal of a temperature lapse rate to estimate paleoelevation three fundamentally different approaches have been developed and these vary both in the method by which paleotemperatures are estimated and in the way by which modern lapse rates can be measured paleotemperature methodologies include the use of plant physiognomy or the use of nearest living relatives lapse rate methodologies use either a global terrestrial lapse rate as the world mean a regional terrestrial lapse rate that represents a large portion of a continent or a local terrestrial lapse rate for areas narrowly confined by latitude and longitude other variables and or corrective factors that should be considered in these applications include the thermal effects of continentality and elevated land surfaces in the continental interior and standardization to compensate for fluctuations or variability in sea level global climate change and paleolatitude these different methodologies can be contrasted by their common application to the late eocene florissant flora of colorado with results ranging from 455 to 4133 meters

magma generation by slab steepening and breakoff beneath a subduction accretion complex an alternative model for collision related volcanism in eastern anatolia turkey 1 eastern anatolia is regarded as one of the best examples of continental collision represented by a 2 km high plateau it displays shallow and diffuse seismicity indicating that the crust is still being actively deformed perhaps the most striking aspect of eastern anatolia is the volume and compositional variability of collision related volcanic products erupted during the neogene and quaternary time a number of models have been proposed for the genesis of this volcanism in the region however recent geophysical studies have revealed that a mantle lithosphere is almost completely absent beneath a greater portion of the region which makes us question the validity of the previous models in this paper we propose a new model for magma genesis slab steepening and breakoff beneath a large subduction accretion complex this model holds that a northward subducting oceanic lithosphere beneath the eastern anatolia accretionary prism gets steepened and eventually detached from the continental lithosphere of the bitlis poturge massif following the continent accretionary complex collision this brings the asthenospheric mantle in contact with the accretionary complex at shallow depths e g around 50 km resulting in rapid regional uplift and extensive melting which leads to collisional volcanism

regional stratigraphy and structural setting of the kamloops group south central british columbia the kamloops group is redefined as an assemblage of lower to middle eocene volcanic and sedimentary rocks widespread in south central british columbia in the type area west of kamloops the basal

a paleocene lowland macroflora from patagonia reveals significantly greater richness than north american analogs few south american macrofloras of paleocene age are known and this limits our knowledge of diversity and composition between the end cretaceous event and the eocene appearance of high floral diversity we report new unbiased collections of 2516 compression specimens from the paleocene salamanca formation ca 61 7 ma from two localities in the palacio de los loros exposures in southern chubut patagonia argentina our samples reveal considerably greater richness than was previously known from the paleocene of patagonia including 36 species of angiosperm leaves as well as angiosperm fruits flowers and seeds ferns and conifer leaves cones and seeds the floras which are from siltstone and sandstone channel fills deposited on low relief floodplain landscapes in a humid warm temperate climate are climatically and paleoenvironmentally comparable to many quantitatively collected paleocene floras from the western interior of north america adjusted for sample size there are 50 more species at each palacio de los loros quarry than in any comparable u s paleocene sample these results indicate more vibrant terrestrial ecosystems in patagonian than in north american floodplain environments 4 m y after the end cretaceous extinction and they push back the time line 10 m y for the evolution of high floral diversity in south america the cause of the dis parity is unknown but could involve reduced impact effects because of greater distance from the chicxulub site higher latest cretaceous diversity or faster recovery or immigration rates

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range

fossil biotas from the okanagan highlands southern british columbia and northeastern washington state climates and ecosystems across an eocene landscape the late early to early middle eocene okanagan highlands fossil sites spanning 1000 km north south northeastern washington state southern british columbia provide an opportunity to reconstruct biotic communities across a broad upland landscape during the warmest part of the cenozoic plant taxa from these fossil sites are characteristic of the modern eastern north american deciduous forest zone principally the mixed mesophytic forest but also include extinct taxa taxa known only from eastern asian mesothermal forests and a small number of taxa restricted to the present day north american west coast coniferous biome in this preliminary report paleoclimates and forest types are reconstructed using collections from republic in washington state usa and princeton quilchena falkland mcabee hat creek horsefly and driftwood canyon in british columbia canada both leaf margin analysis lma and quantitative bioclimatic analysis of identified nearest living relatives of megaflora indicated uppe

the okanagan highlands eocene biota environments and geological setting southern british columbia canada and northeastern washington usa climate change is a matter of concern to society decision makers and scientists as part of the debate about the science of climate change and in particular the extent to which current climate change is due to human activity or part of the natural variability of the global climate system earth scientists try to understand how climates have changed in the past and how past warming and cooling episodes affected the landscape and the plants and animals that occupied that landscape it is also clear from the fossil record that past climate change has played a role in the evolution of animal and plant lineages as well as plant and animal communities preserved in a series of lake deposits across northeastern washington state usa to smithers in north central british columbia canada the okanagan highlands fossil deposits preserve a record of a time when the world was much warmer than now because of a naturally enhanced greenhouse effect and the poles were ice free and supported great forests these s

paleoclimate and precipitation seasonality of the early eocene mcabee megaflora kamloops group british columbia early eocene fossil floras from british columbia are a rich resource for reconstructing western north american early cenozoic climate the best known of these floras reflect cooler mat 15 c upland forest communities in contrast to coeval mat 18 c forests in lowland western north american sites of particular interest is whether early eocene climates were monsoonal highly seasonal precipitation the mcabee site is a 52 9 0 83 ma 0 5 km outcrop of bedded lacustrine shale interbedded with volcanic ash in this report two historical megaflora collections that were collected independently from different stratigraphic levels and or laterally separated by 100 200 m in the 1980s university of saskatchewan and 2000s brandon university are investigated to i assess whether they represent the same leaf population ii assess whether a combined collection yields more precise climate estimates and iii reconstruct paleoclimate to assess the character of regional early eocene precipitation seas

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

systematics and phytogeography of selected eocene okanagan highlands plants the diverse early to middle eocene okanagan highlands floras of south central british columbia and northeastern washington reflect a time of rapid evolution and the early radiation of many dicot families that are currently significant elements of temperate floras recent studies of the republic washington flora klondike mountain formation and related okanagan floras in british columbia have documented both the earliest and sometimes the only known fossil occurrences of genera today many once more widespread taxa are restricted particularly to asian and or eastern north american refugia examples include members of the families betulaceae birch hazelnut rosaceae rose hamamelidaceae witch hazel and the endemic asian family trochodendraceae earliest occurrences are noted for neviusia rosaceae trochodendron trochodendraceae corylus and carpinus both betulaceae the first unequivocal leaf records of corylopsis and fothergilla both hamamelidaceae and two new eocene species of the extinct fruit palaeocarpinus betulaceae are also recognized today trochodendron and corylopsis are restricted to asia whereas neviusia and fothergilla genera with close asian relatives occur only in north america corylus johnsonii from republic is most similar to the extant asian species c heterophylla c wangii and c ferox neviusia leaves from one mile creek near princeton british columbia are more similar to n cliftonii an endemic from mount shasta california than to n alabamensis of southeastern north america a better documentation of the okanagan highlands floras is essential to our understanding of the evolution of north american temperate floras and the nature of asian north american disjunct taxa

eocene continental climates and latitudinal temperature gradients global climate during the mesozoic and early cenozoic is thought to have been warmer than at present but there is debate about winter temperatures paleontological data indicate mild temperatures even at high latitudes and in mid latitude continental interiors whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels foliar physiognomy and floristic composition of 23 eocene floras from the interior of north america and australia indicate cold month means generally 2 c even where the mean annual temperature mat was

shear wave anisotropy beneath the aegean inferred from sks splitting observations 1 sks splitting parameters are measured in the aegean region using events recorded at a dense temporary network in the south aegean and the operating permanent networks especially focusing in the back arc and the near trench areas of the hellenic arc in general fast anisotropy directions are trench perpendicular in the back arc area and trench parallel near the trench anisotropy measurements near the volcanic arc mark the transition between these two regions in the back arc a gradual increase is observed in delay times from south to north with a prevailing ne sw direction in cyclades this pattern is correlated with gps velocities and stretching lineations of metamorphic core complexes our preferred source of anisotropy in the back arc region is the mantle wedge flow induced by the retreating descending slab the westernmost termination of the trench reveals directions parallel with the kefalonia transform fault and perpendicular to the convergence boundary beneath peloponnese the trench parallel flow is probably located beneath the shallow dipping slab although scattered measurements may also reflect fossil anisotropy from a past nw se strike of the trench in western crete which may be entering a stage of continental collision the anisotropy pattern changes to trench perpendicular with a possible subslab source good nulls in central east crete indicate a change in the anisotropy origin toward the east at the easternmost side of the trench fast directions are trench parallel this reflects a similar subslab flow that may become toroidal around the slab edge beneath western turkey this may also produce a trench parallel flow within the mantle wedge

early eocene ypresian birds from the okanagan highlands british columbia canada and washington state usa we survey the known avian fossils from ypresian early eocene fossil sites of the north american okanagan highlands mainly in british columbia canada all specimens represent taxa that were pre

paleobotanical evidence of eocene and oligocene paleoaltitudes in midlatitude western north america comparisons of the physiognomy of leaves from modern vegetation of known climates with that of eocene and oligocene fossil leaf assemblages from middle latitudes of western north america indicate paleoaltitudes comparable or higher than those at present using canonical correspondence analysis a multivariate statistical approach that includes nonlinear relationships between characters and environmental parameters we relate leaf physiognomy of fossil samples to modern vegetation of known environmental parameters including moist enthalpy of the atmosphere a thermodynamically conserved quantity of the atmosphere that varies with altitude by estimating enthalpy values for both lowland leaf assemblages and coeval interior leaf assemblages altitudes for the interior assemblages can be estimated to 890 m in northeastern washington and southern british columbia the high eocene altitudes indicate subsidence or collapse of an area undergoing crustal extension and may reflect an immediately preceding period of uplift that triggered the extension similarly other areas that have undergone cenozoic crustal extension appear to have been at least as high as they are at present three sites from the rocky mountains also indicate elevations at least as high as at present and therefore suggest subsidence either resulting from cooling of a hot upper mantle or erosion and isostatic compensation of surrounding terrain high altitudes during eocene and oligocene time in western north america appear to have been normal even in areas such as the green river basin and therefore cast doubt on the commonly inferred late cenozoic uplift of that region

anisotropy beneath california shear wave splitting measurements using a dense broadband array we have determined the shear wave splitting parameters for a dense network of broad band stations in the western united states using high quality sks and skks waveforms with particularly high spatial resolution in the southern california region covered by the trinet seismic network the alignment of most fast polarization directions can be explained by plate tectonic extensional and compressional events we find that the overall pattern of fast directions agrees well with the pn anisotropy model by hearn that images the uppermost mantle furthermore the measured fast directions are generally orthogonal to the maximum horizontal compressive stress directions as determined from shallow crustal stress indicators world stress map this suggests that the pattern of anisotropy in the western us is predominantly uniform throughout the crust and upper mantle and that a 100 150 km thick layer as estimated from the sks delay time assuming 4 per cent anisotropy of anisotropic material has experienced coherent strain conditions and has undergone a similar deformation history a more detailed investigation reveals small scale lateral variations in anisotropy that are manifested by minor differences in splitting parameters between closely located stations as well as between sks and skks for the same station event pairs we also identify a contrast in splitting parameters between central the greater bay area and southern california in central california our measurements show evidence for variation of splitting parameters with backazimuth while in southern california the pattern of measurements can be fit adequately with a single layer anisotropy model this contrast dominates any consistent effect of the san andreas fault saf we can fit the variation of splitting parameters as a function of polarization azimuth for some stations in the vicinity of the saf better with a two layer anisotropy model than a single layer model with one thin layer having a fast direction parallel to the saf however many alternative models which could incorporate dipping axes of anisotropy lateral variation of anisotropy or a more continuous variation of fast direction with depth would be able to produce a similar fit

on the relation between seismic anisotropy and finite strain because seismic anisotropy in the upper mantle is due primarily to lattice preferred orientation lpo of olivine crystals induced by deformation observations of anisotropy can provide constraints on mantle deformation and flow in this paper we use a previously published theory for deformation induced lpo ribe and yu 1991 to quantify the relation between seismic anisotropy and deformation for two model compositions a pure olivine dunite aggregate and a harzburgite comprising 70 olivine and 30 enstatite analytical and numerical solutions of the governing equations show that the predicted lpo and hence also the seismic anisotropy depends only on the finite strain and not on the deformation path by which that strain is produced the magnitude of the anisotropy depends only on the ratios c1 c2 and c2 c3 where c1 c2 c3 are the lengths of the principle axes of the finite strain ellipsoid and the directions of maximum and minimum compressional wave velocity vp coincide with the axes c1 and c3 respectively we calculate the percent anisotropies for compresional and shear waves propagating along the three principle axes of the finite strain ellipsoid as functions of the axial ratios c1 c2 and c2 c3 for our two model compositions however inferences of the magnitude of finite strain obtained using these results are likely to be minimum estimates because our theory neglects the effects of dynamic recrystallization finally we present as a byproduct of this study a new direct method for calculating the finite strain produced by an arbitiary deformation history

effects of water and melt on seismic velocities and their application to characterization of seismic reflectors the effects of a silicate melt and water on seismic velocities are compared at relatively small fluid fraction less than 20 vol on the basis of a theoretical model of composite materials to show that the two fluids are clearly characterized by the velocity ratio vp vs for a silicate melt vp vs increases with increasing fluid fraction when a significant reflection is expected vp vs becomes much larger than 2 for water vp vs decreases as the fluid fraction increases to 10 vol then it increases but it remains similar to a solid state value about 1 8 unless the amount of water exceeds 15 vol this will be a good measure to distinguish between two candidates for seismic reflectors partially molten rocks and rocks containing free water if a reflector can be treated as a thin low velocity layer the velocity ratio in it can be estimated from the frequency dependence of reflection coefficient

uppermost mantle velocities and anisotropy beneath europe pn data collected within southern europe and the mediterranean are used to tomographically image variations in both seismic velocity and seismic anisotropy seismic anisotropy is an essential part of the inversion and without it several low velocity features within the uppermost mantle could not be properly imaged the technically active mantle of southern europe has much lower seismic velocities 7 6 8 1 km s than the more stable mantle of the sub african plate of the adriatic sea 8 3 km s however the most dramatic features within europe s uppermost mantle relate to the apennine dinaride and hellenide arcs these arcs all have extremely low 5 amounts of arc parallel anisotropy the tyrrhenian and aegean back arc regions also show low velocities 7 7 7 9 km s but less anisotropy the same may be true for the pannonian basin but the tomography has poorer resolution there a model explaining these observations focuses on subducted water metasomatizing the mantle wedge the addition of water causes melting creates arc volcanism lowers the seismic velocity and enhances the formation of anisotropy due to preferential olivine orientation for collisional arcs of the northern mediterranean arc parallel anisotropy has formed in response to compression across them and extension along them within back arc regions water is no longer a major factor instead convection associated with subduction and back arc extension controls the anisotropy

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

shear wave anisotropy in the upper mantle beneath the aegean related to internal deformation seismic anisotropy deduced from sks splitting measured at 25 stations installed in the aegean does not show a homogeneous pattern it is not restricted to the north anatolian fault but is distributed over a region several hundreds kilometers wide little anisotropy is observed in continental greece or along the hellenic arc however significant anisotropy is observed in the north aegean sea large values of delay times suggest that anisotropy is due to a long path within the upper mantle and to strong intrinsic anisotropy our results both in fast polarization directions and in values of delay time do not support the idea that anisotropy is associated with inherited tectonic fabric nor are they consistent with the present day aegean motion relative to an absolute frame in contrast the direction of fast polarization and the magnitude of delay times correlate well with the present day strain rate observed at the surface deduced from both geodetic measurements and seismicity this anisotropy is not horizontally restricted to major surface faults but is spread over a wide region

the geodynamics of the aegean and anatolia introduction the complexity of the plate interactions and associated crustal deformation in the eastern mediterranean region is reflected in many destructive earthquakes that have occurred throughout its recorded history many of which are well documented and intensively studied the eastern mediterranean region including the surrounding areas of western turkey and greece is indeed one of the most seismically active and rapidly deforming regions within the continents fig 1 thus the region provides a unique opportunity to improve our understanding of the complexities of continental tectonics in an actively collisional orogen the major scientific observations from this natural laboratory have clearly been helping us to better understand the tectonic processes in active collision zones the mode and nature of continental growth and the causes and distribution of seismic volcanic and geomorphological events e g tsunamis and their impact on societal life and civilization the tectonic evolution of the eastern mediterranean region is dominated by the effects of subduction along the hellenic aegean arc and of continental collision in eastern turkey anatolia and the caucasus northward subduction of the african plate beneath western turkey and the aegean region is causing extension of the continental crust and volcanism in the overlying aegean extensional province eastern turkey has been experiencing crustal shortening and thickening as a result of northward motion of the arabian plate relative to eurasia and the attendant postcollisional magmatism taymaz et al 1990 1991a b mcclusky et al 2000 2003 dilek pavlides 2006 and references therein fig 2 the resulting combination of forces the pull from the subduction zone to the west and push from the convergent zone to the east is causing the turkish plate to move southwestward bounded by strike slip fault zones the north anatolian fault zone nafz to the north and the east anatolian fault zone eafz to the south interplay between dynamic effects of the relative motions of adjoining plates thus controls large scale crustal deformation and the associated seismicity and volcanism in anatolia and the aegean region taymaz et al 2004

tertiary climatic changes at middle latitudes of western north america abstract a new multivariate analysis of leaf physiognomy provides the basis for estimating various climatic parameters for angiosperm leaf assemblages estimates from this climate leaf analysis multivariate program clamp are both accurate valid and precise repeatable application of clamp to fossil leaf assemblages from western north america confirms that eocene mean annual temperature mat was generally high early eocene mat 19 c at paleolat 70 n and 27 c at paleolat 45 n significant fluctuations 5 8 in mat occurred during the eocene each successive warm period was cooler than the preceding warm period mean annual range of temperature mart was generally low during the eocene especially at middle latitudes but then markedly increased by 12 13 c at 33 ma as mat decreased by 7 8 c these changes at 33 ma largely involved a decrease in cold month mean temperature which continued to decline into the early miocene but then increased significantly into the mid miocene thermal optimum warm month mean temperature changed little from the eocene through the early miocene this parameter however markedly decreased at 13 ma which coincides with the growth of the east antarctic ice sheet clamp also indicates that the coastal region of western north america had significantly higher mat than interior regions such as the great basin and rocky mountains these differences in mat appeared by or during the eocene and indicate that much of the interior had high altitudes in the paleogene these inferences have a significant bearing on global circulation models proposed for tertiary climates

the crustal structure of the east anatolian plateau turkey from receiver functions an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl018192 shtml http atlas geo cornell edu turkey publications zor et al 2003 htm

lithospheric structure of the aegean obtained from p and s receiver functions combined p and s receiver functions from seismograms of teleseismic events recorded at 65 temporary and permanent stations in the aegean region are used to map the geometry of the subducted african and the overriding aegean plates we image the moho of the subducting african plate at depths ranging from 40 km beneath southern crete and the western peloponnesus to 160 km beneath the volcanic arc and 220 km beneath northern greece however the dip of the moho of the subducting african plate is shallower beneath the peloponnesus than beneath crete and rhodes and flattens out beneath the northern aegean observed p to s conversions at stations located in the forearc indicate a reversed velocity contrast at the moho boundary of the aegean plate whereas this boundary is observed as a normal velocity contrast by the s to p conversions our modeling suggests that the presence of a large amount of serpentinite more than 30 in the forearc mantle wedge which generally occurs in the subduction zones may be the reason for the reverse sign of the p to s conversion coefficient moho depths for the aegean plate show that the southern part of the aegean crustal thickness of 20 22 km has been strongly influenced by extension while the northern aegean sea which at present undergoes the highest crustal deformation shows a relatively thicker crust 25 28 km this may imply a recent initiation of the present kinematics in the aegean western greece crustal thickness of 32 40 km is unaffected by the recent extension but underwent crustal thickening during the hellenides mountains building event the depths of the aegean moho beneath the margin of the peloponnesus and crete 25 28 and 25 33 km respectively show that these areas are also likely to be affected by the aegean extension even though the cyclades crustal thickness of 26 30 km were not significantly involved in this episode the aegean lithosphere asthenosphere boundary lab mapped with s receiver functions is about 150 km deep beneath mainland greece whereas the lab of the subducted african plate dips from 100 km beneath crete and the southern aegean sea to about 225 km under the volcanic arc this implies a thickness of 60 65 km for the subducted african lithosphere suggesting that the aegean lithosphere was not significantly affected by the extensional process associated with the exhumation of metamorphic core complexes in the cyclades

anisotropic pn tomography of turkey and adjacent regions summary this study presents an analysis of pn traveltimes to determine lateral variations of velocity anisotropy of uppermost mantle and crustal thickness beneath turkey and adjacent regions from 1999 to 2010 more than 50 000 pn arrivals are compiled from 700 regional earthquakes and 832 stations of permanent and temporary networks operated in the study area we used a regularized least squares inversion to estimate the uppermost mantle parameters the results reveal features that correlate well with the geology and the active tectonics of the region overall thepnvelocitiesshowveryfast 8 4kms 1 andveryslow 8 3 km s 1 western black sea basin 8 3 km s 1 adriatic sea 8 3 km s 1 and zagros suture 8 3 km s 1 pn anisotropy has maximum amplitude of 0 6 km s 1 in the study area the largest and coherent anisotropic anomalies are observed in the western anatolia aegean sea and cyprian arc pn anisotropy in western anatolia aegean sea and greece correlate well with the present deformation of n s regional extension no clear correlation between anisotropy and the shear deformation along the north anatolian fault was observed the majority of the stations in central anatolia show small station residuals indicating the average crustal thickness of 35 2 km western anatolia and the aegean sea have crustal thicknesses between 28 2 and 33 2 km in greece the crustal thicknesses are increasing from 33 3 km from the western coast to a maximum of 48 3k m beneath dinarides hellenides the large crustal thicknesses are also observed along southern coast of anatolia 40 48 km

crustal thickness variations in the aegean region and implications for the extension of continental crust 1 we installed 5 broadband and 45 short period temporary seismic stations distributed partly as a dense 100 km long n s linear array and partly as a regional network throughout the menderes massif of western turkey in order to study crust upper mantle structure and seismicity in this study we have combined teleseismic waveform data from these stations with data from several permanent seismic stations to determine crustal thickness variations in the aegean region receiver function studies at seven broadband stations using the h stacking method have yielded crustal thicknesses and vp vs ratios over a broad region of the aegean a more detailed crustal image was obtained in the central menderes massif where we applied common conversion point stacking to receiver functions obtained from the n s linear array the results show a general trend of westward crustal thinning from 36 km in central anatolia to 28 30 km in the central menderes massif to 25 km beneath the aegean sea the results also indicate that crustal thinning in the aegean is not uniform in the n s extensional direction the crust is thinner in the central menderes massif 28 30 km of crustal thicknesses and the cycladic massif 25 26 km than in surrounding regions where crustal thicknesses are 32 34 km the long lived elevated moho under the metamorphic core complexes suggests that the lower crust in the aegean region is at least 3 times more viscous than that in the basin and range province where the moho is much flatter

eocene paleontology and geology of western north america western north america preserves a rich record of eocene life and environments under globally warm climates and represents an interval where significant coal and other minerals were deposited the eocene is of interest to biologists and paleontologists for its record of the appearance and rise to dominance of many plant insect and mammal groups now typical of the temperate forests of north america admixed with groups now well represented in tropical areas or restricted to eastern asia this record is also of interest for its potential contribution to our understanding of interactions between climate the biota and the ecosystems they occupied under atmospheric carbon dioxide levels much higher than today documentation of the eocene in western north america offers insights into the effects of future greenhouse climates a special symposium held at the 2014 annual meeting of the geological society of america in vancouver british columbia brought together geologists paleontologists and biologists w

love wave group velocity maps of turkey and surrounding regions summary we present the analysis of a love wave dispersion study performed across turkey and the surroundings group velocity dispersion curves were obtained from the local and regional earthquakes recorded at both permanent and temporary stations operated in the region lovewave group velocity maps in the period range of 10 50 s were computed using a tomographic inversion method the study shows the existence of significantly different crustal types in the area the group velocity anomalies are associated with the major geological structures in the region low group velocities at shorter periods 10 20 s are observed in the local sedimentary basins the eastern mediterranean and the black sea the eastern anatolia region is also characterized by low group velocities while pontides and bitlis p ot urge massif display higher group velocities the central anatolia exhibits uniform velocity distribution indicating more homogenous crust the isparta angle is marked by a wedge shaped low group velocity anomaly the low velocities observed in the isparta angle are related to crustal thickening and subduction related complex high velocities observed on the maps are associated with metamorphics magmatic arcs along the orogenic belts of pontides p

fossil palm beetles refine upland winter temperatures in the early eocene climatic optimum eocene climate and associated biotic patterns provide an analog system to understand their modern interactions the relationship between mean annual temperatures and winter temperatures temperature seasonality may be an important factor in this dynamic fossils of frost intolerant palms imply low eocene temperature seasonality into high latitudes constraining average winter temperatures there to 8 c however their presence in a paleocommunity may be obscured by taphonomic and identification factors for macrofossils and pollen we circumvented these problems by establishing the presence of obligate palm feeding beetles chrysomelidae pachymerina at three localities a fourth tentatively in microthermal to lower mesothermal early eocene upland communities in washington and british columbia this provides support for warmer winter eocene climates extending northward into cooler canadian uplands

deformation of western turkey from a combination of permanent and campaign gps data limits to block like behavior 1 we present a new geodetic velocity field covering western turkey south of the north anatolian fault our velocity field is derived from a combination of continuously recording gps stations operating since 2003 survey type gps measurements carried out in the period 1997 2005 and velocities from reilinger et al 2006 the velocity field indicates that western turkey currently undergoes extension whose rate increases from the anatolia plateau to the aegean coast the overall extension in westernmost turkey is about 20 mm yr making it one of the fastest areas of continental extension in the world we test whether the observed deformation is better represented by the rotation of crustal blocks or by more distributed deformation while no deformation is detected in the central anatolian plateau we observe a deformation field west of the plateau that cannot be explained by block models unless the blocks are so small as to be essentially indistinguishable from a continuum although concentration of strain rates up to 140 nstrain yr are found across the major grabens strain rates above 50 nstrain yr are found throughout western turkey the distributions of topography and crustal thickness in western turkey agree with the distributions expected if the crust there had a constant thickness at 5 ma equal to that of the present central anatolian plateau and had subsequently been thinned at the present day distribution of strain rates our results therefore suggest that extensional strain affects the whole continental lithosphere of western turkey rather than being restricted to a small number of block boundaries

anisotropic pn tomography in the western united states pn travel times are affected not only by lateral variations in crust and mantle velocity but also by significant amounts of laterally varying anisotropy to investigate uppermost mantle anisotropy a tomography algorithm was reformulated to include lateral variations in both velocity and horizontal anisotropy and it was applied to pn travel time data from the western united states results show that anisotropy is as important in explaining the travel time residuals as are the velocity variations a detailed resolution study examined the trade off between the velocity variations and the anisotropy variations and showed that both could be resolved for regions with good ray path coverage pn anisotropy beneath the western united states has maximum amplitudes of 0 3 km s 7 5 when resolved on a length scales of around 3 the orientations of pn anisotropy often correlate well with those inferred from shear wave splitting results this correlation suggests that orientation of mantle anisotropy does not change significantly with depth for many regions the orientation of the pn anisotropy can be correlated with some of the tectonic processes which occur within the western united states for example the fast direction of pn anisotropy parallels the northeast direction of subduction of the juan de fuca plate beneath the northwest pacific coast suggesting that there the anisotropy is related to subduction driven deformation the fast direction of pn anisotropy also parallels the strike of the san andreas fault system in central california indicating that shear strains along the plate boundary may be responsible for the anisotropy there within the great basin the pn anisotropy varies substantially and both partial melting and small scale convection within the uppermost mantle could be responsible for these anisotropy variations

the significance of paleotopography topographic change is one of the most informative measures of continental deformation yet precise records of past elevation are scarce to non existent in most orogenic belts recent advancement and new development of techniques to measure paleoelevation promise significant progress in understanding continental tectonic processes and how erosion acts on rising topography to shape the earth s surface outstanding issues in continental tectonics include understanding driving forces to deformation how strain is vertically partitioned in the lithosphere and how mass is redistributed or conserved in the lithosphere during deformation geodynamic and mechanical models that explore these topics make testable predictions of topographic evolution this review explores key examples of how paleotopography relates to outstanding issues in continental tectonics that motivate development of robust quantitative measures of paleoelevation

a first deep seismic survey in the sea of marmara deep basins and whole crust architecture and evolution abstract increased source strength streamer length and dense spatial coverage of seismic reflection profiles of the seismarmara leg 1 allow to image the deep structure of the marine north marmara trough nmt on the strike slip north anatolian fault naf west of the destructive izmit 1999 earthquake a reflective lower crust and the moho boundary are detected they appear upwarped on an e w profile from the southern central basin eastwards towards more internal parts of the deformed region thinning of the upper crust could use a detachment suggested from an imaged dipping intracrustal reflector that would allow upper crustal material to be dragged from beneath it and above the lower crust accounting for the extensional component but also southwest motion of the southern margin of the nmt sections across the eastern half of the nmt crossing the cinarcik and imrali basins reveal several faults that are active reaching into the basement and have varying strike and proportions of normal and strike slip displacement they might be viewed as petals of a large scale negative flower structure that spreads over a width of 30 km at surface and is rooted deeper in the lithosphere under the central basin a very thick sediment infill is revealed and its extensional bounding faults are active and imaged as much as 8 km apart down to 6 km depth we interpret them as two deep rooted faults encompassing a foundering basement block rather than being merely pulled apart from a jog in a strike slip above a decollement the deep basin lengthening would account for only a modest part of the proposed 60 km finite motion since 4 myr along the same direction oblique to the nmt that sidesteps the shear motion from its two ends thus differential motion occurred much beyond the deep basins like subsidence involving the nmt bounding faults and the intracrustal detachments the complex partitioned motion localized on active faults with diverse natures and orientations is suggested to represent the overburden deformation induced from horizontal plane simple shear occurring in depth at lithospheric scale and in front of the north anatolian fault when it propagated through the region

unusual mantle poisson s ratio subduction and crustal structure in central alaska 1 subduction zones alter the upper plate in a variety of ways including metasomatism via slab derived fluids and accretion of exotic terranes these processes should produce distinctive seismic signatures as seismic velocities are sensitive to compositional variations a new method is developed to estimates depths to interfaces and poisson s ratio vp vs ratio for dipping layered structures by stacking teleseismic receiver functions it also estimates crustal vp vs and thickness using this method we analyze a broadband data set from the central alaska subduction zone to seek evidence for mantle wedge composition crustal thickness varies from 27 to 45 km and crustal vp vs indicates an intermediate to mafic composition expected for these accreted island arc terranes inversions for mantle structure confirm the presence of a 15 20 km thick low velocity zone atop of the downgoing plate to 130 km depth perhaps subducted crust of an exotic terrane vp vs in the mantle wedge allows for 15 15 serpentinization where the slab is 80 km deep and the wedge is cold where the slab is deeper vp vs for the mantle wedge is unusually low 1 7 this value is lower than predicted for any common mantle mineral and may indicate significant quantities of quartz provided that past physical properties measurements are not grossly in error these results suggest that the mantle wedge in subduction zones can occasionally differ substantially in bulk composition from normal subcrustal mantle perhaps because collisions of exotic terranes cause tectonic mixing of crustal material into the mantle

a laboratory model of subduction zone anisotropy abstract measurements of split seismic shear waves near pacific subduction zones show that fast polarization directions are primarily trench parallel in the seaward side mantle beneath a subducting slab and variable in the mantle wedge beneath back arc basins it is generally accepted that the azimuth of the fast polarization direction defines the average orientation of the crystallographic a axis in olivine here we use laboratory experiments to determine the orientation of the olivine a axis in the upper mantle in the vicinity of a subducting slab a laboratory analog for olivine a axis motion during creep deformation is developed using small cylinders whiskers suspended in a viscous fluid subduction beneath a stationary overriding plate variable dip angles and realistic rollback and down dip plate kinematics are examined plate rollback produces strong plate parallel whisker alignments for all dip angles examined alignment in the wedge occurs in three layers a layer of dip parallel alignment above the downgoing plate a layer of subhorizontal alignment beneath the overriding plate and a core of intermediate orientations the amount of alignment beneath the overriding plate and the wedge core decreases with increasing dip angle our results indicate that olivine a axis orientation in the seaward side mantle is controlled by the amount of slab rollback and that orientations in the mantle wedge depend upon slab dip angle

a window into mid latitudinal early eocene environmental variability a high resolution palynological analysis of the falkland site okanagan highlands british columbia canada a series of eocene lake shale deposits from british columbia coined the okanagan highlands are dated from associated volcanic ash as mostly from the early eocene climatic optimum eeco the longest persisting of the early paleogene hyperthermals in this report we focus on high resolution palynological sampling of short sequences for the falkland site to determine if they record centennial or millennial scale vegetation change during the eeco the falkland shales consist of alternating dark and light coloured irregular laminae along with interleaved tephras from volcanic eruptions at this site it is apparent that deposition occurred over several millennia pollen grains were counted under light microscopy using a standard transect method with clustering analysis determining whether the data show any long term trends in plant representation and abundance our data show that regional vegetation was impacted by millennial to centennial scale climatic variability as well as the effects of volcanic e

using fossil leaves as paleoprecipitation indicators an eocene example estimates of past precipitation are of broad interest for many areas of inquiry including reconstructions of past environments and topography climate modeling and ocean circulation studies the shapes and sizes of living leaves are highly sensitive to moisture conditions and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations however when tested on extant forests this method has consistently overestimated precipitation we present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set the significant relationship that results in addition to having value for paleoclimatic reconstruction refines understanding of the long observed positive relationship between leaf area and precipitation seven precipitation estimates for the eocene of the western united states are revised as lower than previously published but remain far wetter than the same areas today abundant moisture may have been an important factor in maintaining warm frost free conditions in the eocene because of the major role of water vapor in retaining and transporting atmospheric heat

new dinopanorpidae insecta mecoptera from the eocene okanagan highlands british columbia canada and washington state usa six new species of the extinct family dinopanorpidae mecoptera are described in the new genus dinokanaga gen nov from five early and early middle eocene okanagan highlands localities in british columbia and washington state these are dinokanaga hillsi sp nov d wilsoni sp nov d dowsonae sp nov d andersoni sp nov d sternbergi sp nov and d webbi sp nov the family dinopanorpidae is previously known only from a hind wing of dinopanorpa megarche cockerell and an undescribed species of dinopanorpa both from the paleogene of primorye maritime province in pacific coastal far eastern russia the family includes mostly large species with forewings up to 43 mm in length dinopanorpidae is particularly distinguished by a long r1 vein in both the fore and hind wings extending almost to the wing apex and bending posteriad distally their wings are mostly dark with light bands and spots have many to extremely dense crossveins and an expanded costal space in the basal quarter of the forewing which is more developed in larger species the rostrum is extended the medigynium is without tongue shaped structures

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

the strain rate field in the eastern mediterranean region estimated by repeated gps measurements we use the combined gps velocity field of the eastern mediterranean for the period 1988 to 1996 to determine crustal deformation strain rates in a region comprising the hellenic arc the aegean sea and western anatolia we interpret the velocity field and determine the strain rate tensor by the spatial derivatives of the collocated motion vectors the region following the line marmara sea north aegean trough northern central greece and the central ionian islands is associated with strong right lateral shear motion with maximum shear strain rates of 180 nano strain a 180 10 9 a in the central aegean sea n s oriented extensional processes prevail reaching 100 nano strain a the southern aegean is characterized by relatively small strain rates maximum extensional components of the strain rate tensor reaching 150 nano strain a in a n s direction are found in central greece the hellenic arc is associated with moderate arc parallel extension and strong compression perpendicular to it projections of the strain rates parallel to the major fault zones reveal that the northern aegean is governed by the westward continuation of the north anatolian fault zone which is associated with strong dextral shearing maximum 220 nano strain a accompanied by numerous large earthquakes in this century

stratigraphic classification of ancient lakes balancing tectonic and climatic controls lakes and lake deposits present two fundamental paradoxes 1 modern lakes are vastly complicated but the rock records of lakes are relatively simple extensive observations reveal three distinct facies associations of common and widespread occurrence these are referred to here as fluvial lacustrine fluctuating profundal and evaporative facies associations 2 most explanations of modern and ancient lakes attribute their nature to climate but neither modern lake parameters lake size depth and salinity nor the character of ancient lake strata thickness extent lithology correlate with measured or inferred climatic humidity we propose that it is the relative balance of rates of potential accommodation mostly tectonic with sediment water fill mostly a function of climate that controls lake occurrence distribution and character lake basins may be termed overfilled balanced fill or underfilled depending on the balance between these rates we conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales 1 m to hundreds of meters and macroscales hundreds to thousands of meters

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

lapse rates and other variables applied to estimating paleoaltitudes from fossil floras abstract a previous method for determining paleoaltitude from fossil floras has used the difference between sea level and upland paleotemperatures which is then multiplied by the reciprocal of a normal lapse rate the present study examines other variables that can significantly influence such results terrestrial lapse rates have been calculated for 39 areas of the world based upon mean annual temperature mat mean warm month temperature mat and mean cold month ttemperature cmt these show regional and seasonal variability that is explained by factors including continentality elevation of large massifs or high base levels cold air drainage fog mountain barrier effects and the location of the subtropical high pressure zone lapse rates and projected sea level temperatures based on data from the western united states show distinct regional patterns these indicate that within this region the highest lapse rate and temperature values are correlated with 1 continental climates in the subtropical high pressure zone and 2 areas having relief where the lowest elevation land surfaces base levels occur at high altitude the data are applied to evaluate and revise the methodology for estimating paleoaltitudes variables of climatic change sea level fluctuation and paleogeography are also considered limitations in application of the method are emphasized the method is exemplified by application to the latest eocene florissant flora of colorado u s a although the results are conjectural they strongly suggest that the late eocene erosion surface in the southern rocky mountains occurred at a much higher paleoaltitude than previously thought this high elevation may have resulted from earlier laramide crustal thickening

volcaniclastic lithostratigraphy and paleoenvironment of the lower eocene mcabee fossil beds kamloops group british columbia canada the lower eocene mcabee fossil beds 53 ma in south central british columbia canada represent a lacustrine sequence deposited during a time of pervasive regional volcanism previous studies on

regional and local vegetation community dynamics of the eocene okanagan highlands british columbia washington state from palynology palynofloras from the middle early to early middle eocene okanagan highlands northern washington state and southern british columbia are used to reconstruct vegetation across a broad upland eocene landscape in this preliminary report forest floristic composition is reconstructed using palynological analysis of sediments from republic washington localities of the allenby formation in the princeton region hospital hill one mile creek and summers creek road hat creek mcabee falkland horsefly and driftwood canyon british columbia wind dispersed taxa were dominant in all samples consistent with floras preserved in lacustrine and paludal depositional environments pseudolarix was dominant in five of the floras but abies falkland or ulmus republic corner lot site were dominant in individual samples for some floras betulaceae were dominant for mcabee alnus and allenby formation betula matching megafloral data for these sites some taxa common to most sites suggest cool conditions e g

a search for shocked quartz grains in the allerod younger dryas boundary layer the younger dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the allerod interstadial resulted in the younger dryas cold period so far no reproducible diagnostic evidence has however been reported quartz grains containing planar deformation features known as shocked quartz grains are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting although alleged shocked quartz grains have been reported at a possible allerod younger dryas boundary layer in venezuela the identification of shocked quartz in this layer is ambiguous to test whether shocked quartz is indeed present in the proposed impact layer we investigated the quartz fraction of multiple allerod younger dryas boundary layers from europe and north america where proposed impact markers have been reported grains were analyzed using a combination of light and electron microscopy techniques all samples contained a variable amount of quartz grains with sub planar microstructures often tectonic deformation lamellae a total of one quartz grain containing planar deformation features was found in our samples this shocked quartz grain comes from the usselo palaeosol at geldrop aalsterhut the netherlands scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging however show that the planar deformation features in this grain are healed and thus likely to be older than the allerod younger dryas boundary we suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the european sandbelt the single shocked quartz grain at this moment thus cannot be used to support the younger dryas impact hypothesis