fan shaped staurolite in the bolton syncline eastern connecticut evidence for porphyroblast rotation during growth fan shaped polycrystalline staurolite porphyroblasts 3 4 cm in length and 0 5 cm in width occur together with centimetre sized euhedral prismatic staurolite porphyroblasts in pelitic schists of the littleton formation on the western overturned limb of the bolton syncline in eastern connecticut the fans consist of intergrown planar splays of 001 elongated prisms which are crudely radial from a single apex the apical angles of the radial groupings range up to 70 the orientations of the individual staurolite prisms are related by a rigid rotation about an axis perpendicular to the fan plane the zone axes 001 always lie in the plane of the fan although the angle between the 100 zone axes of the individual prisms is uniform in each fan it ranges from 30 to 30 in different fans internally the fans display i remnants of a passively captured si foliation defined by disc shaped quartz blebs type 1 inclusions and layers of very fine carbonaceous material and tabular ilmenite platelets ii bent staurolite blades and undulose extinction along low angle 010 subgrain boundaries near the apex of the fans iii wedge shaped dilatational zones containing equigranular inclusion free quartz mica and staurolite and iv growth related quartz inclusion trails roughly perpendicular to a crystal face type 2 inclusions the si inclusion trails are typically perpendicular to the fan surface radiate parallel to the blades and show little to no curvature except at the very edge of the fans where they abruptly curve through nearly 90 into parallelism with an external se foliation careful examination of the three dimensional geometry of fans based on u stage measurements serial sections and two circle optical goniometric measurements permits a detailed reconstruction of their sequential development the origin of a fan involves limited intracrystalline deformation and brittle crack dilation spalling rotation and growth of small marginal fragments and of new staurolite along wedge shaped zones along the si inclusion surfaces fans preferentially develop in porphyroblasts in which si is subparallel to the 010 cleavage these internal features reflect the rotation and deformation of a brittle porphyroblast relative to syn growth shear stresses

third millennium b c climate change in syria highlighted by carbon stable isotope analysis of 14c ams dated plant remains from ebla abstract we use ams accelerator mass spectrometry techniques for the simultaneous analysis of carbon stable isotopic values and 14c dating on charred plant remains found in the archaeological site in ebla syria and propose the diachronic variation in 13c plant values as a possible palaeoclimatic tool both anthracological and carpological remains usually employed in palaeoenvironmental palaeoagricultural palaeonutritional and palaeoeconomical reconstructions are used to study stable carbon isotopic variations in a chronological framework defined through radiocarbon ams measurements the results obtained from the samples of the ebla archaeological site show a chronological correspondence with other climatic reconstructions based on various proxy data available for the near east and shed new light on the aridity crisis of the iii millennium b c

a physical theory of snow gliding snow glide slip of the entire snowpack over the ground is not observed unless water reaches the ground interface in this paper snow gliding is approached from the point of view that a perfect s

stable and clumped isotopes in shell carbonates of land snails cathaica sp and bradybaena sp in north china and implications for ecophysiological characteristics and paleoclimate studies knowledge of ecophysiological characteristics of different land snail species is crucial for defining climatic significance of snail faunal assemblages however little work has been done in this aspect hindering our obtaining unambiguous paleoclimatic information using these proxy indicators here we document for the first time the different ecophysiological characteristics of cathaica sp and bradybaena sp land snails using the stable isotopes and clumped isotope 47 of the shell carbonates the 47 derived temperatures for both species revealed a robust correlation with environmental temperatures moreover the temperatures for cathaica sp are 3 5 c higher than those for bradybaena sp land snails indicating different ecophysiological adaptations or growing seasons of the two species specifically cathaica sp snails prefer living in a warm humid summer whereas bradybaena sp snails are active in the relatively cool arid spring and or autumn the result testifies to the 47 in snail shell carbonates as a promising paleothermometer in monsoonal region and presents new insight into paleoclimatic explanation of these land snail species this finding highlights the importance of climatic seasonality in the changes of the faunal assemblages of land snails

paleoclimate and location of the border between mediterranean climate region and the saharo arabian desert as revealed by speleothems from the northern negev desert israel speleothem bearing karstic caves of the northern negev desert southern israel provides an ideal site for reconstructing the paleoclimate and paleo location of the border between mediterranean climate region and the saharo arabian desert major periods of speleothem deposition representing humid periods were determined by high resolution 230 th u dating and corresponding studies of stableisotopecompositionwereusedtoidentifythesourceofrainfallduringhumidperiodsandthevegetationtype majorhumidintervals

oxygen isotope signatures from land snail helix melanostoma shells and body fluid proxies for reconstructing mediterranean and north african rainfall abstract in this paper we show that oxygen isotope ratios from the shell carbonate of the land snail helix melanostoma reflect local rainfall parameters stable oxygen isotopes were measured in the body fluid 18 o body and shells 18 o shell of live collected h melanostoma along a north south transect across the gebel akhdar in northeast libya 18 o body ranged between 8 1 and 13 0 whilst 18 o shell ranged between 1 0 and 2 8 to investigate the relationship between snail oxygen isotope composition and climate these measurements were correlated with ambient air temperature relative humidity rainfall amount and the 18 o composition of rainwater 18 o rain strong and significant correlations were found between 18 o shell and 18 o rain and between 18 o shell and rainfall amount r 2 0 79 and 0 85 respectively suggesting that h melanostoma shells can be used as a proxy for past rainfall conditions when combined in multiple linear regressions 18 o rain and rainfall amount explained 90 of the variance in 18 o shell r 2 0 90 simple and multiple linear regressions were used to develop predictive models for these climate parameters as h melanostoma shells are commonly found in mediterranean and north african archaeological and geological deposits the predictive equations developed in this study hold great potential for reconstructing pleistocene to holocene rainfall and aridity patterns in the gebel akhdar and for assessing the relationship between environmental changes and human behavioural changes

coupled micromorphological and stable isotope analysis of quaternary calcrete development pedogenic calcretes are widespread in arid and semi arid regions using calcrete profiles from four river terraces of the rio alias in southeast spain this study explores the potential of using detailed micromorphological and stable isotopic analysis to more fully understand the impacts of quaternary environmental change on calcrete development the four profiles increase in carbonate complexity with progressive age reflecting calcretisation over multiple glacial interglacial cycles since mis 9 c 300 ka calcrete profiles contain a mixture of alpha non biogenic and beta biogenic microfabrics alpha fabrics have higher 13c and 18o values the profiles contain a range of crystal textures but there is little difference between the 13c and 18o values of spar microspar and micrite cements strong positive covariance between 13c and 18o suggests that both isotopes are responding to the same environmental parameter which is inferred to be relative aridity the study reveals that the detailed co analysis of calcrete micromorphology and stable isotope signatures can allow patterns of calcrete formation to be placed into a wider palaeoclimatic context this demonstrates the potential of this technique to more reliably constrain the palaeoenvironmental significance of secondary carbonates in dryland settings where other proxy records may be poorly preserved

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

quaternary interglacial environmental stability in san salvador island bahamas a land snail isotopic approach abstract the 13c 12c and 18o 16o ratios of modern and fossil shells of two ecologically distinct land snail taxa cerionidae and annularidae from san salvador island were analyzed to estimate the interglacial pleistocene and holocene paleoenvironmental conditions in the bahamas the average 13c value of cerion was 5 0 1 8 for modern 0 0 1 ka specimens 4 3 0 7 for late holocene 2 4 6 ka individuals 3 4 1 6 for middle holocene 5 6 3 ka shells 4 0 1 5 for 85 or 110 ka specimens and 3 6 0 4 for individuals that grew during ois 5e 125 ka annularidae specimens displayed average 13c values of 6 3 2 5 6 1 1 0 2 4 1 0 4 4 1 1 and 5 0 2 9 respectively these results suggest that snails consumed c3 and c4 plants arbitrarily through time however higher proportion of c4 plants may have been consumed in the past compared to the present cerion was 1 higher in average 13c value than annularidae specimens for some time intervals indicating greater c4 plant consumption and or higher ingestion of carbonate rich sediments the average 18o value of cerion was 0 5 0 8 for modern individuals 0 5 0 5 for late holocene specimens 0 8 0 2 for middle holocene shells 0 4 0 6 for 85 or 110 ka specimens and 0 3 0 6 for ois 5e individuals annularidae individuals exhibited average 18o values of 0 7 0 8 0 5 0 9 0 9 0 3 0 3 0 6 and 0 9 0 9 respectively these results point to similar atmospheric conditions over time intervals when shell was deposited the shell 18o values did not significantly differ between species despite the apparent differences in lifestyle calculations from a snail evaporative steady state flux balance model and proxy data suggest that modern individuals deposited shell at air temperatures of 24 25 c ambient water 18o values between 4 5 and 3 5 smow and relative humidity of 87 89 late to middle holocene and interglacial late pleistocene shells appear to have precipitated under a similar environmental setting overall atmospheric conditions during these quaternary interglacial time intervals at coastal sites of san salvador were largely comparable to the present this apparent environmental similarity is consistent with the relatively comparable snail richness and diversity observed at those same locales and time intervals

overview of the oxygen isotope systematics of land snails from north america continental paleoclimate proxies with near global coverage are rare land snail 18o is one of the few proxies abundant in quaternary sediments ranging from the tropics to the high arctic tundra however its application in paleoclimatology remains difficult attributable in part to limitations in published calibration studies here we present shell 18o of modern small 10 mm snails across north america from florida 30 n to manitoba 58 n to examine the main climatic controls on shell 18o at a coarse scale this transect is augmented by published 18o values which expand our coverage from jamaica 18 n to alaska 64 n results indicate that shell 18o primarily tracks the average annual precipitation 18o shell 18o increases 0 5 0 7 for every 1 increase in precipitation 18o and 0 3 0 7 for every 1 c increase in temperature these relationships hold true when all taxa are included regardless of body size ranging from 1 6 to 58 mm ecology herbivores omnivores and carnivores or behavior variable seasonal active periods and mobility habits future isotopic investigations should include calibration studies in tropical and high latitude settings arid environments and along altitudinal gradients to test if the near linear relationship between shell and meteoric precipitation 18o observed on a continental scale remains significant

new insight into pedogenic processes in extremely arid environments and their paleoclimatic implications the negev desert israel abstract stratigraphic studies conducted on the alluvial fill of several ephemeral stream channels in the southern arava valley dead sea rift indicate the existence of a calcic soil developed 50 100 cm beneath the channel surfaces this anomalous calcic soil does not fall within the categories of any standard soil or paleosol definition and thus has been termed fluvial pedogenic unit fpu the fpu occurs at the lower limit of the contemporary scour and fill processes in the aerated zone and it defines the maximum scour and fill during floods the fpu is also found in late pleistocene and holocene terraces termed paleo fpu indicating that the hydrological regime of past floods was similar to the present one the formation of a calcic fpu in this unique environmental setting is associated with the cumulative influence of persistent differences in water availability to various parts of the channel before and during flood events the carbonate accumulation results from low recurrence of flood events relatively limited moisture amounts and almost no involvement of vegetation in its formation the isotopic analyses of calcic crusts in the fpu and in the paleo fpu indicate that arid climatic conditions prevailed during their formation this indicates that the flood regime under arid climatic conditions characterized most of the negev desert during the late pleistocene and the holocene however a clear difference in the 18 o and the 13 c values was detected between the active channels and the terraces this difference suggests a change in the rainwater composition rather than changes of temperature or amounts of rainfall

interpretation of porphyroblast inclusion trails limitations imposed by growth kinetics and strain rates porphyroblast inclusion trails provide important information about the tectonometamorphic evolution of a metamorphic rock however there remains considerable controversy over whether porphyroblasts rotate during bulk non coaxial deformation with reference to an area of the scandinavian caledonides and utilizing existing data from theoretical and experimental modelling this study demonstrates that both straight and s shaped inclusion trails are consistent with an interpretation in terms of syndeformational porphyroblast growth in a regime approximating to newtonian simple shear at crustal strain rates of 10 14 s 1 and porphyroblast growth times of 0 1 1 0 ma it is shown that a maximum of 5d 9d angular rotation would occur during growth at faster strain rates of 10 12 s 1 e g those in a shear zone porphyroblast angular rotations of 90d are shown to occur in 0 1 0 25 ma i e times comparable with or faster than porphyroblastesis in view of this s shaped inclusion trails are to be expected in porphyroblasts growing in active shear zones or other situations of high shear strain whereas straight inclusion trails can be interpreted as static overgrowth of an existing fabric or as syndeformational porphyroblastesis at low strain rates

pressures and temperatures of metamorphism in the eastern dalradian pressures and temperatures have been determined from locations in the eastern dalradian using a number of different geothermometers and geobarometers temperatures range from 550 c in the low kyanite zone to about 800 c in the sillimanite k feldspar zone pressures range from about 5 5 kbar in glen esk to 9 10 kbar in the central highlands the barometric calibrations employed are consistent with the kyanite sillimanite equilibrium evidence from mineral zoning suggests that rocks outside the buchan area in the duchray hill gneiss glens clova and avon and in the schichallion area underwent a pressure decrease synchronous with the metamorphic peak regional temperature variations define a thermal high centred on the cromar glen muick duchray hill gneiss area to the w of this high temperatures decrease rapidly a sharp thermal break occurs between high grade sillimanite k feldspar gneisses in glen muick and kyanite staurolite schists to the w this thermal contrast is attributed to a structural break which may be analogous to a number of other thermal features in the dalradian

lineaments and basement domains an alternative view of dalradian evolution this paper examines the evidence for basement structures of predominantly non caledonoid trend which appear to have influenced the development of the dalradian belt in scotland a number of domains or blocks separated by dominantly trans caledonoid lineaments are recognized on the basis of geophysical stratigraphical and geochemical patterns these are thought to reflect fault bounded depositional basins controlled by basement lineaments during the extensional phases of the caledonian 9orogeny9 in addition the recognition of a number of these domains and lineaments in the structural metamorphic and igneous data sets for the dalradian belt shows the continuing influence of these basement controlled features throughout the compressional and uplift phases of the orogenesis a possible tectonic model is proposed which envisages the depositional basins forming in a setting dominated by caledonoid trending transcurrent faults and a major pull apart basin forming on a trans caledonoid axis

deformation partitioning during transpression in response to early devonian oblique convergence northern appalachian orogen usa abstract transpressive deformation was distributed heterogeneously within the central maine belt shear zone system which formed in response to early devonian oblique convergence during the acadian orogeny in the northern appalachians straight belts are characterized by tight folds s l fabrics and sub parallel form lines and asymmetric structures that together indicate dextral se side up kinematics in contrast intervening zones between straight belts are characterized by open folds and l s fabrics within both types of zone metasedimentary rocks have fabrics defined by the same minerals at the same metamorphic grade including a penetrative moderately to steeply ne plunging mineral lineation thus we interpret accumulation of plastic deformation and regional metamorphic re crystallization to have been synchronous across the central maine belt shear zone system discordance between inclusion trails in regionally developed porphyroblasts of garnet and staurolite and matrix fabrics in straight belt rocks records shortening by tightening of folds and greater reorientation of matrix fabrics with respect to porphyroblasts kinematic partitioning of flow was responsible for the contrasting states of finite deformation recorded in the central maine belt shear zone system perturbations in the flow were caused by serially developed thrust ramp anticlines in the stratigraphic succession immediately above the avalon like basement at which decollement of the shear zone system was initially rooted general shear deformation at the ramps involved strain softening with an enhanced component of noncoaxial flow in contrast deformation during extrusion in the intervening zones involved strain hardening with a greater component of coaxial flow part of the thickening stratigraphic succession exceeded tsolidus reflected by the occurrence of migmatites and granites the latter were partly sourced from the underlying avalon like basement that was involved in the deformation and melting

hyperconcentrated flows on a forested alluvial fan of eastern canada geomorphic characteristics return period and triggering scenarios the assessment of the dominant flow type on alluvial fans usually refers to two categories debris flow fans i e sediment gravity flows and fluvial fans i e fluid gravity flows here we report the results of combined morphometric stratigraphic and sedimentological approaches which suggest that hyperconcentrated flows a transitional process rheologically distinct from debris flows and floods and sometimes referred to as debris floods mud floods or transitional debris flows are the dominant fan building process in eastern canada these flows produce transitional facies between those of debris flows which consist of a cohesive matrix supported diamicton and those of river flows which display more distinct stratification the size of the blocks in the channels and the abrasion scars at the base of several trees attest to the high transport capacity of these flows the fan channels are routed according to various obstacles comprised primarily of woody debris that impede sediment transit however these conditions of sediment storage are combined with readily available sediment due to the friable nature of the local lithology tree ring analysis allowed the reconstruction of eight hydrogeomorphic events which are characterized by a return period of 9 25 years for the period 1934 2008 although most of the analyzed events occurred after 1970 historical weather data analysis indicates that they were related to rare hydrometeorological events at regional and local scales this evidence led to the elaboration of weather scenarios likely responsible for triggering flows on the fan according to these scenarios two distinct hydrologic regimes emerge the torrential rainfall regime and the nival regime related to snowmelt processes hydrogeomorphic processes occurring in a cold temperate climate and particularly on small forested alluvial fans of north eastern north america should receive more attention from land managers given the hazard they represent as well as because of their sensitivity to various meteorological parameters copyright 2014 john wiley sons ltd

stable carbon isotope record of middle to late holocene climate changes from land snail shells at hinds cave texas abstract stable carbon isotope ratios of shell carbonate and shell organic matter from land snails rabdotus alternatus from hinds cave texas are used to reconstruct the climate history of the drier western part of the southern great plains present mean annual rainfall of 400 mm over the last ca 5000 yr ams radiocarbon analyses of four individual shells from each of two strata indicate that there are no problems of reworking or age mixtures within strata however burning is evident in many shells amino acid composition and racemization were used to identify shells that had been significantly heated and these were rejected for isotopic analysis because of possible alteration of the isotopic signal fourteen samples of snails from hinds cave each consisting of 2 6 individual shells from the same provenience were radiocarbon dated by ams and analyzed for stable carbon isotopes in addition a sample collected alive ca ad 1890 from a nearby site was analyzed to represent modern conditions the shells show no decrease in organic content with age indicating good preservation of shell organic matter both the organic and carbonate isotope values show similar temporal trends the oldest samples 4100 4600 cal yr bp are relatively depleted in 13 c maximum 13 c values are reached at ca 3500 cal yr bp thereafter there is a regular depletion in 13 c with the recent sample showing the lowest 13 c value the change in the isotopic values over time is quite large range of 4 5 for organic matter and indicates substantial climatic changes the variations in isotopic values are interpreted as resulting primarily from changes in moisture conditions affecting the abundance of drought adapted cam crassulacean acid metabolism plant species enriched in 13 c thus relatively moist mid holocene conditions are indicated with increasingly dry conditions reaching a maximum at ca 3500 cal yr bp followed by progressively moister conditions through the late holocene

glide avalanche response to an extreme rain on snow event snoqualmie pass washington usa rain on snow events trigger immediate and delayed avalanches as liquid water penetrates the snowpack we present results from an extreme rain on snow event that triggered a glide avalanche near snoqualmie pass washington usa snoqualmie pass recorded 463 cm of snowfall from 13 december 2008 to 6 january 2009 this period of snowfall was followed by a strong southwesterly tropical flow that resulted in an extreme rain on snow event sensors at snoqualmie pass recorded 285 mm of precipitation over a 52 hour period flooding slush flows landslides and avalanches resulted from the influx of precipitation snow heights decreased rapidly over the period with settlement rates approaching 80 mm h 1 liquid water infiltrated and flowed through the snowpack within a few hours of the arrival of rain yet many of the major avalanches occurred 12 30 or more hours after the onset of rain and water outflow a glide avalanche occurred 30 hours after the onset of rain and the establishment of drainage through the snowpack increasing glide rates correlate with periods of rapid snow settlement here glide rates approached 670 mm h 1 although glide and settlement rates increased during periods of intense precipitation glide failure occurred 8 hours after peak precipitation and outflow

stable isotope δ18o δ13c and δd signatures of recent terrestrial communities from a low latitude oceanic setting endemic land snails plants rain and carbonate sediments from the eastern canary islands abstract stable isotopes of oxygen and carbon extracted from fossil land snail shells have been used increasingly to interpret past environments to evaluate the utility of this approach for low latitude oceanic islands populations of the modern helicid land snail theba geminata a species also abundant in the quaternary fossil record of the region were sampled at ten low altitude d and 2 v smow for 18 o ranging from 11 to 2 v smow and from 2 6 to 0 7 v smow respectively the local vegetation is heterogeneous including c 3 c 4 and cam plants 13 c values vary from 13 0 to 29 0 v pdb across plant species of the 24 species five are c 4 15 are c 3 and four are cam plants the 18 o values for shells represent a narrow range of values from 0 3 to 2 5 v pdb which is consistent with the low climate seasonality typifying low latitude oceanic settings hypothetical model of the expected 18 o value for shell aragonite precipitated in equilibrium suggests that the most negative 18 o shell represent the closest estimate for 18 o rain water the 13 c values of shells range from 9 4 to 1 7 v pdb the most positive 13 c values are attributed to a diet based on c 4 plants the comparison of 13 c values of soft tissues and shells suggests that snails ingested notable amounts from 20 up to 40 of foreign carbonates consequently fossil shells with the most negative 13 c values should be selected for radiocarbon dating in future geochronological studies of the region the 13 c values of body tissues vary from 12 0 to 27 2 v pdb indicating that land snails consumed c 3 and c 4 plants indiscriminately the mean carbon isotopic composition averaged across multiple fossil specimens may thus provide a useful tool for reconstructing paleoclimates and paleoenvironments throughout the quaternary history of the canary islands and other comparable low latitude oceanic settings

late glacial to holocene transition in northern spain deduced from land snail shelly accumulations abstract shells of the helicid cepaea nemoralis were studied using taphonomic isotopic and morphometric measurements to estimate late glacial holocene 12 1 6 3 cal ka bp environmental conditions in northern spain higher taphonomic alteration among holocene shells suggests lower sedimentation rates or higher shell destruction rates than during glacial conditions shells preserved the aragonitic composition despite differing degree of skeleton damage shell 13 c values were 10 3 1 1 8 2 2 3 and 7 3 1 6 for modern holocene and late glacial individuals respectively higher 13 c values during the late glacial and some holocene periods imply higher water stress of c 3 plants and or higher limestone contribution than today intrashell 13 c values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth shell 18 o values were 1 1 0 7 0 9 0 8 and 0 1 0 7 for modern holocene and late glacial specimens respectively a snail flux balance model suggests that during 12 1 10 9 cal ka bp conditions were drier and became wetter at 8 4 6 3 cal ka bp and today intrashell 18 o profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells despite possible larger hibernation periods shell size correlated positively with 18 o values suggesting that growth rates and ultimate adult size of c nemoralis may respond to climate fluctuation in northern spain

dissolution solution transfer diffusion versus fluid flow and volume loss during deformation metamorphism dissolution and solution transfer during deformation metamorphism are controlled by the partitioning of deformation into progressive shearing and shortening components progressive shearing is readily accommodated by slip on the planar crystal structure of phyllosilicates and graphite without accumulating dislocation density gradients across grain boundaries progressive shortening is accommodated by the cores of most other minerals including sulphides these minerals develop strain and hence dislocation density gradients on their rims due to progressive shearing along grain boundaries these gradients are particularly large when the mineral abuts phyllosilicate or graphite the resulting chemical potential gradients between the core and rim drive dissolution causing removal of the highly strained grain margins removal of dissolved material by solution transfer is aided by the geometry of shearing of phyllosilicates and graphite around other grains in an active anastomosing foliation interlayers and interfaces on boundaries lying at a low angle to the direction of shearing and oriented relative to the sense of shear such that they can open gape by small amounts water present in these interlayer spaces becomes destructured considerably enhancing diffusion rates along the foliation penetrative volume loss especially in deforming metamorphosing pelitic rocks is large at all metamorphic grades increasing and becoming more penetrative with depth to at least the transition into granulite and eclogite facies transference of material by fluid flow from deep to high levels in the earth s crust is precluded because thousands to tens of thousands of rock volumes of fluid are required necessitating continual recirculation of fluid from shallow to deep crustal levels in one large or several small sets of cells unless some extremely large scale form of fluid channelling is possible reassessment of diffusion mechanisms and hence rates during deformation and pervasive foliation generation in large volumes of rock where fluid channeling cannot provide enough fluid indicates that diffusion can proceed with sufficient rapidity that massive recirculation of fluid is no longer required the amount of fluid can be reduced sufficiently to allow large volume losses by a one way flow of fluid to the earth s surface in deforming metamorphosing environments where the fluid pressure equals or exceeds the hydrostatic pressure deformation partitioning controlled dissolution progressively changes the bulk chemistry of a rock containing phyllosilicates or graphite during deformation metamorphism because matrix minerals other than phyllosilicates and graphite are preferentially removed the large size of porphyroblasts if present tends to preserve them from dissolution hence the bulk chemistry operative during subsequent porphyroblast growth can have changed considerably from that operative when the first porphyroblasts grew in rocks in which bedding is still well preserved

holocene climate change in the eastern mediterranean region a comparison of stable isotope and pollen data from lake golhisar southwest turkey stable isotope and pollen data from golhisar golu a small intramontane lake located in southwest turkey provide complementary records of holocene climate change modern oxygen and hydrogen isotope water data are used as a means of comparing present day isotope composition of the lake water to the past oxygen isotope composition of the lake water as calculated from 18o 16o ratios in calcite precipitated in the summer months despite the lake system being chemically dilute the modern isotope data clearly establish that the lake water is evaporated in relation to its spring input suggesting that the palaeo data can be interpreted primarily in terms of changing precipitation evaporation ratios 18o and 13c values from authigenic calcite through the holocene show predominantly negative values indicating climatic conditions wetter than today particularly notable are low depleted isotope values during the earliest holocene ca 10 600 8800 cal yr bp a period for which pollen data imply drier conditions than at present this divergence between pollen inferred and stable isotope palaeoclimate data is found in other east mediterranean lake sediment records and suggests that vegetation may have taken several millennia to reach climatic equilibrium at the start of the holocene isotopic fluctuations during the early to mid holocene 8800 5100 cal yr bp suggest oscillations between aridity and humidity higher 18o and 13c values for the second half of the holocene indicate generally drier conditions than during the period before ca 5100 cal yr bp although there is some evidence for increased humidity coinciding with pollen evidence for increasing human impact and intensification of agriculture notably during the so called beyehir occupation phase classical and early byzantine periods the modern trend towards aridity started about 1300 yr ago

microstructural controls and the role of graphite in matrix porphyroblast exchange during synkinematic andalusite growth in a granitoid aureole in the contact metamorphic aureole of the tinaroo batholith north queensland australia mylonitic rocks were metamorphosed during a regional folding crenulation event d2 synchronous with the emplacement of muscovite bearing granitoids prismatic and skeletal andalusite porphyoblasts grew in carbonaceous schists mainly from the dissolution of staurolite muscovite quartz and biotite played a dual role in this reaction acting in a catalytic capacity as well as reactants or products staurolite was replaced by coarse grained muscovite biotite whereas andalusite locally replaced quartz muscovite biotite with diffusion of h al si mg fe and k ionic species linking sites of dissolution and growth graphite contributed to the reaction mechanism in a number of ways accumulations of graphite in front of advancing andalusite crystal faces led to skeletal growth and the formation of chiastolite structure where incremental growth occurred on adjacent 110 faces with subsequent filling in and inclusion of graphite along the diagonal zones the presence of graphite in some layers in the schist matrix prevented recrystallization of strained muscovite grains the muscovite grains in these layers in contrast to adjacent thin non graphitic layers were preferentially replaced by quartz this resulted in muscovite depletion haloes in graphitic layers around andalusite porphyroblasts somewhat arcuate zones of graphite concentrated during dissolution of quartz along a crenulation cleavage occur on some andalusite faces reactivation of the mylonitic foliation during the formation of d2 crenulations led to a preferential dissolution of quartz in zones of progressive shearing localized near andalusite porphyroblasts and hence the accumulation of graphite lack of deflection of the pre existing mylonitic foliation and anastomosing of the axial planes of d2 crenulations around andalusite porphyroblasts demonstrate not only the timing of growth but also that growing porphyroblasts do not push aside existing foliations

late pleistocene holocene environmental conditions in lanzarote canary islands inferred from calcitic and aragonitic land snail shells and bird bones aragonitic and calcitic land snails from carbonate rich paleosols in northwestern lanzarote canary islands were analyzed for 13c 12c and 18o 16o ratios to deduce the pleistocene holocene transition in the westernmost sahara zone modern mid late holocene 2 1 5 5 cal ka bp and late pleistocene 23 3 24 0 cal ka bp aragonitic shells exhibited respective values of 9 5 1 6 7 7 1 5 and 2 3 2 8 for 13c and 0 3 0 3 0 1 0 7 and 2 5 0 4 for 18o holocene and pleistocene calcitic shells of the endemic slug cryptella canariensis showed respective values of 0 7 2 6 and 8 5 2 5 for 13c and 0 8 1 5 and 3 6 0 4 for 18o both aragonitic and calcitic shells showed equivalent temporal isotopic trends higher 13c values during 23 3 24 0 cal ka bp suggest higher abundance of c4 and or cam plants likely associated with drier conditions and or lower atmospheric co2 concentration maximum shell 18o values during 23 3 24 0 cal ka bp opposes minimal values of greenland ice cores and probably reflect the combined effects of 1 higher rain 18o values linked to higher glacial seawater 18o values and or larger snail activity during summer seasons 2 relative humidity values similar or slightly lower than at present 3 higher evaporation rates and 4 cooler temperatures bone remains of the extinct dune shearwater puffinus holeae were only recovered from the holocene bed collagen 13c and 15n values 13 5 0 2 pdb and 13 7 1 0 air respectively match with the signature of a low trophic level macaronesian seabird that fed upon local fish bone carbonate 13c 7 4 1 0 pdb and phosphate 18o 18 2 0 4 smow values exhibited pristine signals denoting their potential value in future paleoenvironmental studies in the region the age of p holeae 2 1 2 7 cal ka bp supports that the aboriginal population possibly caused its extinction in contrast the extinction of the endemic helicid theba sp 23 3 24 0 cal ka bp was likely caused by environmental change

thrust tectonics thin skinned or thick skinned and the continuation of thrusts to deep in the crust abstract the paper analyses the geometry of thin skinned thrust zones where the thrusts shallow out at depth and of thicker skinned fault zones where much of the crust is involved and where the thrusts are frequently observed to become steeper downwards in the interiors of many orogenic belts the steep dip of faults is not original but due to the folding above lower decoupling zones the energy involved in the internal deformation of hanging wall rocks may prohibit many faults becoming more shallow upwards such shallowing upwards faults may occur in more ductile rocks to maintain compatibility between zones which have experienced different deformation intensities but displacements on the faults are unlikely to be large another mechanism for producing faults which steepen downwards is proposed for the major thrusts which form the southern margin to the himalayas these carry large thicknesses 30 to 100 km of crustal and upper mantle rocks to the south causing flexuring and isostatic depression of the indian plate the steeply dipping thrusts are not footwall ramps these may be some distance behind the steepened zone this thrust induced isostatic bending of the crust has important implications when considering regional seismic interpretations as well as thrust mechanics and kinematics

growth of mica porphyroblasts under low grade metamorphism a taiwanese case using in situ 40ar 39ar laser microprobe dating abstract mica porphyroblasts a common metamorphic microstructure are analyzed in the slate belt of northern taiwan where large fish like growths are found within a meta pyroclastics with constraints on the time temperature history from deposition through peak metamorphic state to exhumation in situ 40ar 39ar laser microprobe dating was carried out on muscovite and corrensite fibers of mm scale mica porphyroblasts grown on a pressure solution seam because the peak metamorphic temperature and the porphyroblast formation condition 250 c remained far below the closure temperature of the k ar radioisotope system in muscovite and the absence of muscovite in the mafic protolith the dating results likely document the growth of the mica porphyroblast fabrics the syn kinematic nature of the analyzed porphyroblasts is confirmed by the 6 to 2 5 ma growth ages suggesting that the host rock was continuously deformed during the earlier two thirds of the taiwan orogeny the pattern of fiber growth in contrast to outward decreasing ages normally observed in peripheral recrystallization appears random and resembles void fills in boudin openings we postulate that syntaxial crack seal following tensile micro boudinage along with slips on sub grain boundaries as a viable mechanism for the development of mica porphyroblasts and fish especially in lower grade metamorphic rocks

stable isotope data from loess malacofauna evidence for climate changes in the pannonian basin during the late pleistocene abstract loess is terrestrial clastic sediment composed dominantly of silt sized particles formed by the accumulation of wind blown dust it is usually inter bedded with palaeosol horizons forming loess palaeosol successions lps due to its characteristics loess represents a high quality record of climate changes in the late pleistocene the thickest and best studied loess sections in the republic of croatia are located in the eastern croatian province of baranja near the danube river this area is a southern part of the pannonian basin zmajevas lps was selected in this study grain size distribution indicates that the loess from zmajevac lps in baranja is typical loess comparable with other loess profiles in the pannonian basin the faunal assemblages in the loess samples prove the dominance of transitional palaeoecological assemblage types whereas uniformly defined types are rare helicopsis striata assemblage is dominant while columella columella and chondrula tridens assemblages are present in smaller proportion for additional information about palaeoclimate and palaeoecology in pannonian basin stable oxygen and carbon isotope ratios were measured in mollusc shells stable oxygen values range from 5 76 to 2 45 stable carbon isotope values range from 8 83 to 6 84 stable oxygen values show significant palaeotemperature changes during the late pleistocene with the average growing season ags temperature range of 13 24 c or 9 457 c depending on which formula is applied the overall climate was much cooler then present stable carbon isotope values point to dominance of c3 vegetation type during the late pleistocene in southern part of the pannonian basin

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

carbon isotope signatures from land snail shells implications for palaeovegetation reconstruction in the eastern mediterranean in this study we compare carbon isotope values in modern helix melanostoma shell carbonate 13cshell from the gebel al akhdar region of libya with carbon isotope values in h melanostoma body tissue 13cbody local vegetation 13cplant and soil 13csoil all vegetation in the study area followed the c3 photosynthetic pathway however the 13cplant values of different species formed two distinct isotopic groups this can be best explained by different water use efficiencies with arid adapted species having significantly more positive 13cplant values than less water efficient species the ranges and means of 13cbody and 13cplant were statistically indistinguishable from one another suggesting that 13cbody was primarily a function of local vegetation composition h melanostoma 13cshell reflected the 13cplant of local vegetation with a positive offset between body diet and shell of 14 5 1 4 therefore in the gebel al akhdar where only c3 plants are present higher mean 13cshell values likely reflect greater abundances of water efficient c3 plants in the snails diet and therefore in the landscape whilst lower mean 13cshell values likely reflect the consumption of less water efficient c3 plants the distribution of these plants is in turn affected by environmental factors such as rainfall these findings can be applied to archaeological and geological shell deposits to reconstruct late pleistocene to holocene vegetation change in the southeast mediterranean

a late pleistocene holocene multi proxy record of climate variability in the jazmurian playa southeastern iran abstract we present a multi proxy record from a 5 m long sediment core from the jazmurian playa in southeastern iran to provide insights into globally recognized major climatic events since the last glacial maximum lgm in particular we examined how variability in the indian ocean summer monsoon iosm and mid latitude westerlies mlw contribute to distinct environmental changes in this arid to hyper arid region in the interior of west asia while interior west asia showed cold windy conditions during the lgm and post lgm southeast iran experienced quiescent conditions similar to south asia the presence of fine grained sediments low magnetic susceptibility and a decrease in aeolian inputs from ca 21 to 14 cal kyr bp suggests that effects of both wind and precipitation were minimal during these quiescent conditions increased fluvial inputs coupled with a low abundance of evaporite minerals in jazmurian sediments indicated a greater influence of the iosm between 14 and 13 2 cal kyr bp in contrast the jazmurian playa was dry and dusty between 13 2 and 11 4 cal kyr bp as reflected by an increase in aeolian sands and the presence of evaporite minerals this was followed by a period of strong iosm activity during the early holocene coinciding with higher fluvial input ca 11 4 cal kyr bp the early holocene in southeast iran was wetter than other analogs in south asia because of inputs from both iosm and mwl several intense dry periods with sharp increases in aeolian inputs occurred after the early holocene due to the southward migration of the intertropical convergence zone precipitation sources changed from a monsoon dominated regime to one influenced mainly by the mlw during the late holocene these results show that palaeoenvironmental changes in the jazmurian playa located at the border of iosm and mlw zones were primarily governed by global and regional paleoclimatic changes

oxygen and carbon isotopic composition of quaternary meteoric carbonates from western and southern europe their role in palaoenvironmental reconstruction abstract the relationship between environmental conditions and the 18 o and 13 c values of soil and groundwater carbonates in europe is poorly understood consequently the use of the isotopic composition of these carbonate palaeoclimatic indicators in european sedimentary sequences is restricted in this study we examine the 18 o and 13 c values of soil and groundwater carbonates from western and southern europe in western europe there is no relationship between carbonate 18 o values and carbonate 13 c values the 18 o values of soil carbonate appears to be driven by temperature whilst the 13 c value of soil and groundwater carbonate reflects the persistent dominance of c 3 vegetation in this region during the quaternary the 18 o and 13 c values of soil carbonates from spain and crete show a strong degree of co variance suggesting that they are being controlled by the same environmental factor this is suggested to be aridity 18 o values are controlled by soil moisture evaporation whilst 13 c value is controlled by soil moisture degassing vegetation abundance and possible c 3 c 4 vegetation inputs the paper concludes by highlighting the fact that although currently under utilised the 18 o and 13 c values of soil and groundwater carbonates have a huge potential for providing important palaeoenvironmental information from sites across europe

holocene aeolian morphogenetic phases in southern italy problems in 14c age determinations using terrestrial gastropods abstract radiocarbon age determination is one of the most important methods for dating holocene events in particular it has been used to reconstruct the sequence of aeolian morphogenetic phases along the apulia and basilicata coasts southern italy in these areas three main holocene morphogenetic phases have been recognized using radiocarbon data obtained from sub fossil terrestrial gastropods archaeological data and osl analyses those of the middle holocene period of the greek roman time and of the middle ages sub fossil terrestrial gastropods have been considered suitable indicators in the detecting holocene climate environmental changes however it is well known that they could show problems as chronological indicators mainly due to aging effects induced by i micro particles of calcite aragonite in the shell structure derived from the local substratum and ii a variation of co 2 content in the plants eaten in order to verify these hypotheses living terrestrial gastropods were collected from coastal areas and analysed using ams the results indicate that many living gastropods gave ages of 1500 years older than those expected thus confirming the aging effect as 14 c ages of middle and late holocene aeolian morphogenetic phases obtained from terrestrial gastropods seem to be confirmed by archaeological data and osl analyses the aim of this work is to verify if the age anomalies obtained from modern gastropods could be extended to the entire holocene period

rotation of biotite porphyroblasts in pelitic schist from the nukata area central japan abstract the detailed microstructures of biotite porphyroblasts in pelitic schist from the nukata area central japan indicate that the porphyroblasts rotated in an external reference frame during non coaxial deformation the amount of rotation and rotation axis are controlled by the 001 orientation of the biotite porphyroblast with respect to the schistosity and the lineation concurrently with rotation the biotite porphyroblasts suffered shape change by solution and deposition in the shortening and dilating fields around the porphyroblast respectively the close co occurrence of inclusion free domains newly deposited biotite domains and pressure shadows along the 001 faces suggests that continuously opening fractures along the 001 faces caused biotite deposition as well as pressure shadow aggregates the role of pressure shadow formation for porphyroblast rotation is discussed in terms of stresses applied on the porphyroblast surface it is concluded that although the formation of deformation partitioning induced pressure shadows tends to suppress porphyroblast rotation that of fracture induced pressure shadows pressure fringes promotes porphyroblast rotation the present biotite porphyroblasts would have rotated at rates depending not only on their shape and shape orientation but also on the 001 orientation

major shear zones and autochthonous dalradian in the north east scottish caledonides the buchan area within the grampian caledonides of north east scotland is a classic locality for the study of low pressure regional metamorphism using detailed geophysical surveys pits and boreholes to augment sparse outcrop data we have revealed a system of steep shear belts of grampian age when combined with a reassessment of the stratigraphy the new information leads us to the view that the banff nappe does not exist we also argue that the tay nappe is of limited extent in buchan and that the tract of uninverted southern highland group upper dalradian is autochthonous

climate dynamics in the borderlands of the aegean sea during formation of sapropel s1 deduced from a marine pollen record abstract to unravel the climatic and environmental dynamics in the borderlands of the aegean sea during the early and middle holocene and notably for the interval of sapropel s1 s1 formation we have analysed terrestrial palynomorphs from a marine core in the northern aegean sea the qualitative results were complemented by quantitative pollen based climate reconstructions a land sea correlation was established based on pollen data and sediment lightness measurements from the same core and previously published benthic foraminifer data from a nearby core the borderlands of the aegean sea underwent a transition from an open vegetation to oak dominated woodlands between 10 4 and 9 5 ka cal bp a coeval increase in winter precipitation suggests that moisture availability was the main factor controlling holocene reforestation the 50 higher winter precipitation during s1 formation relative to pre sapropelic conditions suggests a strong contribution from the borderlands of the aegean sea to the freshwater surplus during s1 formation the humid and mild winter conditions during s1 formation were repeatedly punctuated by short term climatic events that caused a partial deforestation and a reorganisation within the broad leaved arboreal vegetation in the marine realm these events are documented by improved benthic oxygenation the strongest event represents the regional expression of the 8 2 ka cold event and led to an interruption in s1 formation except for the interval of s1 formation the pollen derived winter temperatures correlate with the smoothed gisp2 k series they support the previously published marine based concept that the intensity of the siberian high strongly controlled the winter climate in the aegean region during s1 formation in the aegean sea however climate conditions in the borderlands were more strongly affected by the monsoonally influenced climate system of the lower latitudes

environmental conditions framing the first evidence of modern humans at tam pa ling laos a stable isotope record from terrestrial gastropod carbonates abstract mainland southeast asia is a key region to interpret modern human migrations however due to a scarcity of terrestrial proxies environmental conditions are not well understood this study focuses on the tam pa ling cave site in northeast laos which contains the oldest evidence for modern humans in indochina dating back to mis 4 70 8 ka snail remains of camaena massiei found throughout the stratigraphic sequence contain a valuable oxygen and carbon isotope record of past local vegetation and humidity changes our data indicate that before the last glacial maximum lgm northeast laos was characterized by a humid climate and forested environments with the onset of the lgm a major climatic shift occurred inducing a sharp decrease in precipitation and a significant decline in woodland habitats in favor of the expansion to more open landscapes only during the holocene did forests return in northeast laos resembling present conditions the first homo sapiens arriving in indochina therefore encountered landscapes dominated by woodlands with a minor proportion of open habitats

full depth avalanche occurrences caused by snow gliding coquihalla british columbia canada snow glide is the translational slip of the entire snowpack over a sloping ground surface and it is thought that rapid rates of snow glide precede full depth avalanches the nature of avalanches that release at the ground makes them difficult to predict and difficult to control using explosives on slope instrumentation comprised of stainless steel glide shoes was used to measure rates of snow glide for two winters on a bedrock slope adjacent to the coquihalla highway cascade mountains british columbia canada climate data and avalanche occurrences were recorded by the british columbia ministry oftransportation and highways our results show that the supply of free water to the snow ground interface by rain or snow melt is the most important influence on full depth avalanche release full depth avalanche release responds to rainfall and snowmelt events within 12 24 hours occasionally full depth avalanches occur unexpectedly during clear cold periods snowmelt by radiation is thought to contribute enough meltwater during these cold periods to induce higher rates of snow glide and full depth avalanche release the results also indicate that snow glide alone is not a reliable indicator for full depth avalanche release

evidence for holocene environmental changes in the northern fertile crescent provided by pedogenic carbonate coatings abstract holocene environmental changes in the northern fertile crescent remain poorly understood because of the scarcity of local proxy records in the region in this study we investigated pedogenic soil formed carbonate coatings on stones at the pre pottery neolithic site gobekli tepe as an indicator of local early mid holocene environmental changes the 14c ages and stable isotopic composition of carbon and oxygen in thin 0 2 0 3 mm thick pedogenic carbonate lamina indicate two main periods of coating formation the early holocene ca 10000 6000 cal yr bp and the mid holocene ca 6000 4000 cal yr bp during the first period there was an inverse relationship between 13c and 18o curves a decrease in 13c values coincide with an increase in 18o values for this period a trend towards higher temperatures is suggested in the mid holocene the mean rate of coating growth was 2 3 times higher than in the early holocene both 13c and 18o reached their maximum values during this time and the direction of changes of the 13c and 18o curves became similar the combination of data suggests that this period was the most humid in the holocene and on average warmer than the early holocene at ca 4000 cal yr bp secondary accumulation of carbonate ceased presumably reflecting a shift to a more arid climate

amphibolite facies metamorphism in shear zones in the buchan area of ne scotland a major system of steep caledonian shear zones of regional extent has been identified in ne scotland the shear zones affect a wide range of lithologies including argyll and southern highland group dalradian younger basic intrusives and their hornfelses and also the earlier of the more acid intrusions the observed fabrics and parageneses are consistent with low pressure amphibolite facies metamorphism these shear zones represent a phase of movement which occurred in the 490 465 ma interval when ambient temperatures were still high and it is concluded that this is the principal control on the metamorphic grade achieved within the shear zones although local anomalies may exist

sediments soils and the expansion of farmers into a forager s world a geoarchaeological study of the mid to late holocene in hwange national park zimbabwe abstract the transition from foraging to food production in interior southern africa is still not well understood despite being central to hypothesized migration and diffusion routes connecting the earliest agropastoralist sites in central africa with the southern african subcontinent hwange national park 14 650 sq km zimbabwe is located along these proposed routes and has both late stone age and early iron age sites that can address this transition to better understand this change in lifeways and any environmental and or topographic factors that influenced it geoarchaeological investigations characterized the soils sediments and landforms in six different areas of the park forty eight stratigraphic sections varying from two to four m thick were described six of which are detailed here these stratigraphic sections include dated material that allows correlation between basins of different substrates and comparisons of carbon isotopic signatures to reveal whether conditions were locally favorable to grasses hot dry or woodlands cool wet through time examined river cuts and augered samples show that some river basins have sediment textures soil types and topographic relief that should have been attractive to farmers however radiocarbon ages reveal variable potential for finding remains of any early farmers from basin to basin with some bedrock constrained valleys having no preserved deposits of appropriate age the repeated scouring of these river basins testifies to sometimes volatile conditions that would have challenged sustained food production in fact in the study area landscape instability and variable environmental conditions were commonplace during the past three millennia drought between ca 2 8 and 2 6 ka may have lessened the risk of disease vectors for the earliest agropastoralists that arrived during more mesic conditions between 1 9 and 1 65 ka at this time basins began to accumulate fill and soil development suggests landscape stability even in headland basins changes in soil carbon isotope values imply relatively hot dry conditions prevailed around 0 73 ka and 0 41 ka and cool wet conditions around 0 53 ka but much information has been lost due to the numerous erosional events that wiped away swaths of sediments during intervening droughts the landscape in hwange national park continues to change rapidly as reflected by several meters of river downcutting in response to recent man made disturbance and or drought this downcutting both reveals and endangers the few remaining archaeological sites that are critical to understanding the first food producers in the region

overcoming the stauchwall viscoelastic stress redistribution and the start of full depth gliding snow avalanches 1 when a full depth tensile crack opens in the mountain snowcover internal forces are transferred from the fracture crown to the stauchwall the stauchwall is located at the lower limit of a gliding zone and must carry the weight of the snowcover the stauchwall can fail leading to full depth snow avalanches or it can withstand the stress redistribution the snowcover often finds a new static equilibrium despite the initial crack we present a model describing how the snowcover reacts to the sudden transfer of the forces from the crown to the stauchwall our goal is to find the conditions for failure and the start of full depth avalanches the model balances the inertial forces of the gliding snowcover with the viscoelastic response of the stauchwall we compute stresses strain rates and deformations during the stress redistribution and show that a new equilibrium state is not found directly but depends on the viscoelastic properties of the snow which are density and temperature dependent during the stress redistribution the stauchwall encounters stresses and strain rates that can be much higher than at the final equilibrium state because of the excess strain rates the stauchwall can fail in brittle compression before reaching the new equilibrium snow viscosity and the length of the gliding snow region are the two critical parameters governing the transition from stable snowpack gliding to avalanche flow the model reveals why the formation of gliding snow avalanches is height invariant and how technical measures to prevent snowpack glide can be optimized to improve avalanche mitigation

implications of the apparent 14c age of cultured achatina fulica and the spatial features of 14c ages among modern land snail shells in china abstract it has long been known that many terrestrial snail shells are subject to the so called limestone effect however the magnitude and impact of this effect on the 13c values of snail shells and soft body tissue 13cshell and 13cbody are still unknown in this study achatina fulica snails were hatched and cultured under controlled conditions and supplied with 14c free calcium carbonate and lettuce a c3 plant as a calcium source and food supply respectively the snail shells and soft body tissues were sampled monthly for 5 months and 13c and radiocarbon dating analyses were conducted to trace carbon source variations at different growth stages our results show that the apparent 14c age of the shells and the corresponding 13cshell values increased progressively from the 1st to 3rd months and subsequently decreased during the 4th and 5th months the results demonstrate for the first time that carbonate ingestion has a straightforward influence on the 14c ages and 13c values of shells and that the limestone effect changes over the lifetime of snails moreover the apparent 14c ages of snails sampled in the field are older than modern ages when taken from the northern carbonate region and relatively young or the same as modern ages when collected from ferralic soils this further supports our findings from cultured snails and suggests that snail shells are good archives for radiocarbon dating purposes in southern china although the 13c values of the soft body tissues of cultured snails vary synchronously with those of the shell this seemingly common phenomenon cannot be easily explained by carbonate ingestion as the snail bodies are of more recent origin than the shells atmospheric co2 may be another candidate explaining the synchronicity between 13cshell and 13cbody as well as the f 14c variations of snail bodies however it is still unclear how snails differentially incorporate carbon from different sources e g carbonate and atmospheric co2 at different growth stages since carbon from different sources is combined in the bicarbonate pool in the hemolymph before being used by snails

holocene cultural and climate shifts in nw africa as inferred from stable isotopes of archeological land snail shells cultural transitions or even societal collapses have often been associated with long term drought events linkages between humans and the environment are best documented in well constrained archeol

the layered character of snow covers snow studies have generally ignored the layered nature of snow covers having achieved a good understanding of the properties and processes in homogeneous snow snow scientists should develop more insight into the evolution of the layers and their effects on overall snow response many of the outstanding problems in snow studies can only be solved by dealing with snow as a layered medium the various mechanisms by which layers are generated their effects and some of the outstanding research problems are described here

grampian metamorphic conditions deduced from mafic granulites and sillimanite k feldspar gneisses in the dalradian of glen muick scotland metamorphic conditions of 8 1 5 kbar and 820 50 c are estimated for garnet clinopyroxene bearing mafic granulites and associated garnet sillimanite migmatitic gneisses from the dalradian sillimanite zone revised estimates for the kyanite zone in glens avon and ey w of the regional andalusite and sillimanite zones are c 7 kbar at 500 600 c results from rocks close to the kyanite sillimanite isograd in glen clova testify to the accuracy of the barometric calibrations textural indications are that sillimanite preceded andalusite in the glen muick area in this region the kyanite andalusite isograd has no reality in glen muick sillimanite grew synchronously with the development of the dominant steep foliation and as part of a progressive evolution in metamorphic conditions not as a separate late overprint the western segment of the kyanite andalusite isograd is thought to have developed before the attainment of the p t conditions recorded in rocks from glens avon and ey metamorphic and geochronological data are examined in the light of the banff nappe hypothesis it is suggested that the eastern high temperature zones were thrust over the present western kyanite zone and that rocks to the w of the kyanite andalusite isograd were metamorphosed by thermal relaxation beneath this thrust sheet

strain partitioning and crack seal growth of chlorite muscovite aggregates during progressive noncoaxial strain an example from the slate belt of taiwan abstract chlorite muscovite aggregates from the slate belt of southeastern taiwan have an ellipsoidal geometry k 1 on a flinn diagram with an aspect ratio a c ranging from about 7 1 to 12 1 and a crystallographic preferred orientation with the basal planes of the chlorite and muscovite at a high angle to the slaty fabric in the rock the principal axes of the aggregates are approximately coaxial with the principal finite strain directions determined from fibrous pressure shadows in cleavage parallel sections straight fibers parallel to the downdip mineral lineation record plane strain in cleavage perpendicular sections however pressure shadows have curved fibers that are consistent with w directed thrusting we propose a model in which the chlorite mica aggregates grow syntectonically by cracking of detrital chlorite grains parallel to the basal planes and precipitation of secondary chlorite and mica in the open cracks this model involves 1 rotation of preexiting detrital chlorite grains during progressive noncoaxial deformation 2 cracking of these grains parallel to the basal plane when the 001 planes rotate into the incremental shortening field with nucleation and growth of secondary chlorite and muscovite in the open microcracks as the aspect ratio increases the grains stabilize in orientation with the long axes normal to the basal planes at a small angle to the shear direction extension normal to 001 is also accompanied by some shortening parallel to 001 but with an overall increase in size of the aggregates the final grain size is controlled by the cumulative displacement associated with crack seal events microprobe analyses of both detrital and secondary chlorite grains show distinct compositional differences within individual grains perpendicular to 001 particularly in the detrital grains which we interpret as primary and secondary chlorite consistent with a primary and secondary origin for the aggregates

middle late quaternary paleoclimate of northern margins of the saharan arabian desert reconstruction from speleothems of negev desert israel abstract speleothems in arid and hyper arid areas of negev desert israel are used in paleoclimate reconstruction of northern margins of saharan arabian desert focused on the following objectives 1 precise u th dating of the timing of speleothem growth as an indicator of periods of humid climate i e positive effective precipitation 2 the origin of rainfall using the speleothem 18 o and changes in spatial pattern of speleothem deposition and speleothem thickness along a north south transect 3 changes of vegetation cover based on speleothem 13 c variations during the last 350 ka major humid periods referred to herein as negev humid periods nhp occurred in the central and southern negev desert at 350 310 ka nhp 4 310 290 ka nhp 3 220 190 ka nhp 2 and 142 109 ka nhp 1 nhp 4 nhp 2 and nhp 1 are interglacial events whereas nhp 3 is associated with a glacial period during nhp 1 2 and 3 the thickness and volume of the speleothems decrease from the north to the south and in the most southern part of the region only a very thin flowstone layer formed during nhp 1 with no speleothem deposition occurring during nhp 2 and 3 these data imply that the eastern mediterranean sea was the major source of the rainfall in northern and central negev more negative speleothem 18 o values relative to central parts of israel soreq cave are attributed to rayleigh distillation because of the increasing distance from the mediterranean sea speleothem deposition during the nhp 4 in the southern negev was more intensive than in most of the central negev suggesting the prominence of the tropical rain source decrease in speleothem 13 c during nhp events indicates growth of the vegetation cover nevertheless the ranges of 13 c values show that the vegetation remained semi desert c4 type throughout the nhps with an additional significant carbon fraction coming from the host rock and the atmosphere these observations together with small thickness of the speleothem layers favor that nhp events consisted of clusters of very short humid episodes interspersed with long droughts nhp events were contemporaneous with climate periods with monsoon index of 51 cal cm 2 day and with the formation of sapropel layers in the mediterranean sea such simultaneous intensification of the monsoon and atlantic mediterranean cyclones is probably related to the weakening of the high pressure cell above sub tropical atlantic ocean which enabled more rainfall to penetrate into the saharan arabian desert from the north and south the contemporaneous occurrence of the nhp events and the increased monsoon rainfall could have opened migration corridors creating climatic windows of opportunity for dispersals of hominids and animals out of the african continent

stable isotope ecology of land snails from a high latitude site near fairbanks interior alaska usa abstract land snails have been investigated isotopically in tropical islands and mid latitude continental settings while high latitude locales where snails grow only during the summer have been overlooked this study presents the first isotopic baseline of live snails from fairbanks alaska 64 51 n a proxy calibration necessary prior to paleoenvironmental inferences using fossils 13c values of the shell 10 4 0 4 and the body 25 5 1 0 indicate that snails consumed fresh and decayed c3 plants and fungi a flux balance mixing model suggests that specimens differed in metabolic rates which may complicate paleovegetation inferences shell 18o values 10 8 0 4 were 4 higher than local summer rain 18o if calcification occurred during summer a flux balance mixing model suggests that snails grew at temperatures of 13 c rainwater 18o values of 15 and relative humidity of 93 results from fairbanks were compared to shells from san salvador bahamas at 24 51 n average annual 18o values of shells and rainwater samples from the bahamas were both 10 18o enriched with respect to seasonal summer alaskan samples at a coarse latitudinal scale shell 18o values overwhelmingly record the signature of the rainfall during snail active periods while tropical snails record annual average environmental information high latitude specimens only trace summer season climatic data

paleoclimate reconstruction in the levant region from the geochemistry of a holocene stalagmite from the jeita cave lebanon dated oxygen and carbon isotopic profiles from a holocene stalagmite 11 9 1 1 ka from the jeita cave lebanon are compared to variations in crystallographic habit stalagmite diameter and growth rate the profiles show generally high 18o and 13c values during the late glacial period low values during the early holocene and again high values after 5 8 ka on the basis of the good correlation between the morphological and crystallographic aspect of the stalagmite and its isotopic records as well as the isotopic response of speleothems from central and northern israel we relate high 18o and 13c values to drier conditions between 6 5 and 5 8 ka an increase in isotopic values a decrease in growth rate and stalagmite diameter suggest a transition from wet conditions in the early holocene towards drier conditions in the mid holocene the transition occurred in two steps first a progressive change to drier conditions started at 6 5 ka but was interrupted by a short 100 years return to wetter conditions followed by an equally rapid 200 years change to drier conditions

a petrogenetic grid for pelitic schists in the system sio 2 al 2 o 3 feo mgo k 2 o h 2 o a quantitative petrogenetic grid for pelitic schists in the system kfmash that includes the phases garnet chlorite biotite chloritoid cordierite staurolite talc kyanite andalusite sillimanite and pyrophyllite with quartz h2o and muscovite or k feldspar in excess is presented the grid is based on thermodynamic data of berman et al 1985 and berman 1988 for endmember kfash and kmash equilibria and natural fe mg partitioning for the kfmash system calculation of p t slopes and the change in fe fe mg along reactions in the kfmash system were made using the gibbs method in addition the effect on the grid of mno and cao is evaluated quantitatively the resulting grid is consistent with typical buchan and barrovian parageneses at medium to high grades at low grades the grid predicts an extensive stability field for the paragenesis chloritoid biotite which arises because of the unusual facing of the reaction chloritoid biotite quartz h2o garnet chlorite muscovite which proceeds to the right with increasing t in the kfmash system however the reaction proceeds to the left with increasing t in the mnkfash system so the assemblage chloritoid biotite is restricted to bulk compositions with high fe fe mg mn typical metapelites will therefore contain garnet chlorite at low grades rather than chloritoid biotite

permanent quaternary hyperaridity in the negev israel resulting from regional tectonics blocking mediterranean frontal systems although various episodes of wet quaternary climates have been suggested in studies of the negev desert here we demonstrate that reg soils developed on flat alluvial surfaces and sensitive to minor changes in precipitation indicate that the southern negev has been permanently hyperarid at least since the middle pleistocene the wetter episodes were restricted to the northern negev currently mildly arid gypsic saline reg soils that de veloped on stable surfaces during 200 k y in the southern negev are cumulative and polygenetic but none exhibits even the weakest development of calcic horizons under current climate conditions in the negev calcic soils are widespread in areas with rainfall 80 mm yr 21 the fact that the hyperarid 50 mm yr 21 southern negev lacks any calcic horizons indicates that it never experienced an average rainfall of 80 mm yr 21 during the middle late pleistocene whereas the northern negev was wetter this negev dichotomy is explained by the main physical features controlling rainfall over the negev i e the southward decreasing depth of the atmospheric boundary layer with distance from the mediterranean and the altitude of the central negev highland 1000 m the interaction between these two features often prevents the passage of rain clouds into the southern negev the holocene and pleistocene gypsic salic soil distribution across the negev closely matches the current circumstances we suggest that hyperaridity has prevailed over the southern negev since the last stages of the uplift of the central negev highland in the late pliocene early pleistocene

crack fill porphyroblastesis garnet mica schists from the scottish highlands provide new insight into an important mechanism of phyllosilicate growth termed crack fill porphyroblastesis it is shown that grain boundary dilatancy microcracking and porphyroblast matrix decoupling all play a significant role in facilitating growth in regimes of noncoaxial shear with respect to chlorite porphyroblasts there are three growth stages following nucleation the initial phase of growth is by progressive matrix replacement to preserve inclusion trails of fine carbonaceous material the second growth stage produced new optically continuous inclusion free chlorite on the 001 margins of those crystals at a high angle to the schistosity this growth results from decoupling at the porphyroblast matrix contact on those margins at a high angle to the principal axis of extension the development of dilatant cracks at porphyroblast margins provides a sink for material migrating down pf and chemical potential gradients this causes precipitation of new optically continuous clear chlorite on the pre existing heavily included core the porphyroblast matrix boundary continues to dilate after porphyroblast growth had terminated producing plano convex quartz rich strain shadows similar growth behaviour is recognised in biotite porphyroblasts indicating that crack fill porphyroblastesis is an important growth mechanism for phyllosilicates in actively deforming metamorphic rocks it also indicates that decoupling and crack fill development at porphyroblast margins could be important in controlling the pattern of material transfer and may have significant implications for matrix permeability and fluid flow characteristics

microstructural evidence of rotation and non rotation of mica porphyroblasts abstract mica porphyroblasts in schists from several regions show nearly planar inclusion trails that are parallel over areas much larger than the wavelengths of later folds this indicates that the porphyroblasts have not rotated with respect to geographical co ordinates during deformation instead the matrix has rotated as suggested by ramsay 1962 even in zones of marked shortening in the matrix adjacent to large rigid porphyroblasts e g of cordierite or staurolite small biotite porphyroblasts have not rotated but have become thinned by solution as indicated by parallelism of inclusion trails in separate biotite grains and by evidence of truncation of inclusion trails by the matrix foliation less common are biotite porphyroblasts that have single asymmetrical microfolds in the matrix adjacent to the porphyroblasts and so appear to have rotated these porphyroblasts are characterized by kinking

a sensitive vorticity gauge using rotated porphyroblasts and its application to rocks adjacent to the alpine fault new zealand variable aspect ratio porphyroblasts deformed in non coaxial flow and internally containing rotated relicts of an external foliation can be used to characterise plane strain flow regimes the distribution obtained by plotting the orientation of the long axis of such grains classified by aspect ratio against the orientation of the internal foliation is potentially a sensitive gauge of both the bulk shear strain as previously suggested and kinematic vorticity number we illustrate the method using rotated biotite porphyroblasts in the alpine schist a sequence of mid crustal rocks that have been ramped to the surface along the alpine fault a major transpressional plate boundary results indicate that at distances greater than or equal to similar to1 km from the fault the rocks have undergone a combination of irrotational fattening and dextral oblique normal sense shear with a bulk shear strain of similar to0 6 and kinematic vorticity number of similar to0 2 the vorticity analysis is compatible with estimates of strongly oblate bulk strain of similar to 75 maximum shortening dextral reverse transpressional flow characterises higher strain s tectonite mylonite within similar to1 km of the alpine fault these relationships provide insight into the kinematics of flow and distribution of strain in the hangingwall of the alpine fault and place constraints on numerical mechanical models for the exhumation of these mid crustal rocks c 2001 elsevier science ltd all rights reserved

oxygen and carbon stable isotopes of modern land snail shells as environmental indicators from a low latitude oceanic island abstract land snails provide a unique opportunity to study terrestrial paleoenvironments because their shells which are generally highly abundant and well preserved in the fossil record contain a temporal record of environmental change in the form of isotope codes to evaluate the utility of this approach for a low latitude oceanic setting 207 modern shells of 18 species of land snail were analyzed for their oxygen and carbon isotope composition along a north and south facing altitudinal gradient 10 2160 m a s l in tenerife island 28 n of the canary archipelago shells collected at each locality showed a relatively large range in isotope composition which was greater along the south facing transect drier and hotter suggesting that the variance in shell isotope values may be related to water stress although pooled isotope values did not generally show strong relationships with environmental variables i e altitude temperature and precipitation mean isotope values were strongly associated with some climatic factors when grouped by site the mean 18o value of the shell 18oshell by site displayed a negative correlation with elevation which is consistent with the positive relationship observed between temperature and the 18o value of rain 18orain calculated 18o values of the snail body water 18obody derived from observed temperatures and 18oshell values using the equation of grossman and ku grossman e l and ku t l 1986 oxygen and carbon isotope fractionation in biogenic aragonite chem geol isotope geosci sec 59 59 74 displayed a trend with respect to altitude that was similar to measured and hypothetical 18o values for local rain water the calculated 18obody values from the shell declined 0 17 vsmow per 100 m which is consistent with the altitude effect observed for tropical rains in western africa and it correlated negatively with rainfall amount accordingly lower 18oshell values indicate lower temperatures lower 18orain values and possibly higher rainfall totals a positive correlation between the mean 13c values of shells 13cshell and plants by site suggests that shells potentially record information about the surrounding vegetation the 13cshell values varied between 15 7 and 0 6 vpdb indicating that snails consumed c3 and c4 cam plants where more negative 13cshell values probably reflects the preferential consumption of c3 plants which are favored under wetter conditions individuals with more positive 13cshell values consumed a larger percentage of c4 plants other potential factors such as carbonate ingestion or atmospheric co2 contribution were unlikely that were more common at lower elevations of the hotter and drier south facing transect the relatively wide range of shell isotope values within a single site requires the analysis of numerous shells for meaningful paleoclimatic studies although small differences were observed in isotope composition among snail species collected at a single sampling site they were not significant suggesting that isotope signatures extracted from multi taxa snail data sets may be used to infer environmental conditions over a broad range of habitats

variation in carbon isotopic composition over the past ca 46 000 yr in the loess paleosol sequence in central kazakhstan and paleoclimatic significance abstract we present a high resolution record of 13 c org variation from two loess sequences in central kazakhstan the variation shows that the vegetation was persistently dominated by c 3 plants over the past ca 46 000 yr the 13 c org signature was most likely an indicator of moisture and the moisture variation in central kazakhstan was associated with the precipitation in western europe the 13 c org indicated that moisture variation exhibited five stages decreasing during stage 1 ca 46 000 ca 31 500 yr bp increasing during stage 2 ca 31 500 ca 25 500 yr bp again decreasing during stage 3 ca 25 500 ca 19 000 yr bp fluctuating along a constant line during stage 4 ca 19 000 ca 5000 yr bp and increasing during stage 5 last ca 5000 yr our comparison demonstrated a general similarity between the 13 c org indicated moisture variation in central kazakhstan and the reconstructed precipitation variation in western europe the similarity implies that the moisture of the past ca 46 000 yr in central kazakhstan has been controlled or modulated by westerlies that brought water vapor from the north atlantic not only to western europe but also to central kazakhstan

porphyroblast inclusion trail orientation data eppure non son girate extensive examination of large numbers of spatially orientated thin sections of orientated samples from orogens of all ages around the world has demonstrated that porphyroblasts do not rotate relative to geographical coordinates during highly non coaxial ductile deformation of the matrix subsequent to their growth this has been demonstrated for all tectonic environments so far investigated the work also has provided new insights and data on metamorphic structural and tectonic processes including 1 the intimate control of deformation partitioning on metamorphic reactions 2 solutions to the lack of correlation between lineations that indicate the direction of movement within thrusts and shear zones and relative plate motion and 3 a possible technique for determining the direction of relative plate motion that caused orogenesis in ancient orogens

terrestrial stable isotope records of late quaternary paleoclimates in the eastern mediterranean region abstract terrestrial stable isotope records 13 c 12 c 18 o 16 o and d h ratios of late quaternary paleoclimates in the eastern mediterranean region are reviewed significant paleoclimatic reconstructions come from a variety of isotopic studies paleogroundwaters although they cannot be accurately dated show oxygen and hydrogen isotopic compositions highly depleted in heavier isotopes compared to modern meteoric waters in arid regions of southern israel sinai and northeastern africa and attest to a major difference in climatic regime some time in the pleistocene th u dating of land snails showing a similar 18 o depletion indicates ages of 100 000 yr and 300 000 yr for this climatic regime in the negev desert of southern israel carbon isotope records of organic matter have not been studied extensively in the region except for the record of holocene land snails in the negev these document a southward shift in pure c 3 plant communities in the middle and early holocene relative to their present distribution and indicate wetter conditions at those times an oxygen isotope curve for the holocene reflecting changes in the isotopic composition of precipitation has been established from analysis of carbonate materials land snail shells and speleothems the curve indicates a depletion of ca 2 in 18 o centered around 7000 cal yr bp with modern levels being reached by 5000 cal yr bp carbon isotope analysis of soil carbonates in paleosols developed in loess in the negev show the existence of dramatic north south climatic gradients at the times of formation of the soils ca 13 000 28 000 and 37 000 14 c yr bp as occur also today due to the waning influence of mediterranean to the south some isotopic methods widely used in other regions have received little or no attention in the eastern mediterranean region these include oxygen and hydrogen isotopes in wood phosphate oxygen and organic carbon in bones and teeth and carbon in soil organic matter

multiply deformed terrains problems of correlation abstract the best tools available for carrying out a structural analysis in a complex area are overprinting style and patterns of orientation unfortunately all have limitations which are reviewed briefly and discussed in areas of continuous unfaulted outcrop the deformational history can be established purely on the basis of overprinting but even in such areas there can be problems since not all overprinting relationships are unambiguous most fold interference patterns are reliable overprinting relationships based on foliations however are commonly unreliable and various examples are cited and discussed even in areas where the sequence of deformational events can be established their temporal significance is unclear since the methods applied only determine local relative timing and absolute relationships must vary in space and time across an orogen

metamorphic conditions and uplift history in central perthshire evidence from mineral equilibria in the foss celsian barite sulphide deposit aberfeldy interlayered lithologies of diverse mineralogy enclosing the middle dalradian syngenetic ba zn pb deposit at foss s of loch tummel in perthshire allow estimates of the p t conditions of metamorphism using several new geothermometers and geobarometers temperatures of 500 560 c are derived from calcite dolomite geothermometry and from data on mg fe partitioning within garnet hornblende and garnet biotite pairs plagioclase biotite garnet muscovite and biotite muscovite chlorite equilibria indicate peak metamorphic pressures of 8 10 kbar which are in agreement with the results of sphalerite geobarometry textural evidence indicates that the rare platy mineral cymrite baa1 2 si 2 o 8 h 2 o was widespread in mineralized lithologies during penetrative deformation and has since largely been replaced by celsian the p t location of the experimentally determined reaction line cymrite ss celsian ss h 2 o places further constraints on the peak metamorphic conditions and suggests that the final episode of penetrative deformation d 3 was followed by a period of near isothermal uplift during which celsian became stable the cymrite field appears to have been re entered during late brittle deformation peak metamorphic conditions recorded by mineral equilibria at foss differ from those of areas 10 km to the n and s

models for the tectonothermal evolution of the eastern dalradian of scotland the preserved array of pressures in the eastern dalradian indicates that considerable syn to post metamorphic differential uplift has occurred this inferred differential uplift suggests that buchan sillimanite zone rocks originally lay at higher structural levels than presently adjacent cooler kyanite zone rocks to the west a number of features are believed to coincide with the western margin of the sillimanite zone these are a maximum in temperature sharp thermal features a high strain zone and a train of metabasites these features are explained by invoking syn metamorphic movement between the buchan sillimanite zone and the kyanite zone to its west involving some horizontal component of movement it is suggested that the lateral now eroded equivalents of the buchan area once provided part of the required tectonic thickening for other parts of the dalradian areas surrounding the buchan area suffered tectonic burial followed by metamorphism during uplift relative to the buchan area

a late pleistocene refugium in mediterranean north africa palaeoenvironmental reconstruction from stable isotope analyses of land snail shells haua fteah libya abstract the late pleistocene to holocene archaeological record of north africa is key to understanding the emergence of anatomically modern humans into west asia and europe and the broadening of subsistence strategies in the shift from hunter gatherer to pastoral agricultural lifeways some contend that these developments were modulated by major shifts in climate and environment evaluation of this hypothesis requires the pairing of local and regional climate records with well dated archaeological sequences the haua fteah archaeological site in the gebel akhdar region of libya provides a key site to test this hypothesis as the cave contains one of the longest and most complete sequences of human occupation in north africa as well as abundant material for palaeoenvironmental reconstruction this study uses stable isotope analyses 18o and 13c of the terrestrial mollusc helix melanostoma to construct a palaeoenvironmental framework for interpreting north african human environment interactions from the upper palaeolithic to the neolithic 30 000 to 5000 years ago the land snail stable isotope records from haua fteah suggests that cool arid conditions in the cave peaked during marine isotope stage mis 2 this stage was however only marginally drier than previous and subsequent stages and coincided with an increase in occupation density in the cave this suggests that the gebel akhdar may have served as an environmental refugium from the more extreme aridity in the surrounding sahara and arid coastal plains for late stone age lsa populations in north africa conditions became progressively wetter towards the holocene however generally wetter conditions were interrupted by two arid episodes at c 8 0 ka and 7 3 ka that appear to coincide with regional changes reflected elsewhere in the mediterranean basin

holocene climate variability and cultural evolution in the near east from the dead sea sedimentary record abstract a comprehensive record of lake level changes in the dead sea has been reconstructed using multiple well dated sediment cores recovered from the dead sea shore interpreting the lake level changes as monitors of precipitation in the dead sea drainage area and the regional eastern mediterranean palaeoclimate we document the presence of two major wet phases 10 8 6 and 5 6 3 5 cal kyr bp and multiple abrupt arid events during the holocene the arid events in the holocene dead sea appear to coincide with major breaks in the near east cultural evolution at 8 6 8 2 4 2 3 5 cal kyr bp wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions suggesting a parallelism between climate and near east cultural development

porphyroblast rotation eppur si muove in a number of recent papers the theory has been postulated that porphyroblasts as a rule do not rotate with respect to geographical coordinates and can be used to determine the original orientation of older foliations complex inclusion patterns in spiral garnets have even been used to advocate a new model of orogenesis involving several alternating phases of horizontal shortening and extension critical assessment of the assumptions and data used to support the theory of irrotational porphyroblasts reveals numerous flaws millipede structures used as proof for flow partitioning can also form by other flow geometries evidence quoted to support irrotational behaviour of porphyroblasts is unsound porphyrobl asts do occur in sets with a preferred orientation of the internal foliation trace but these cannot be shown to represent original orientations microstructures which resemble truncation planes in spiral garnets are used as evidence that these structures developed by several phases of deformation and as proof for periodic extension and horizontal shortening in orogenesis they can however also be explained by intermittent growth of a rotating porphyroblast during a single phase of deformation finally porphyroblast sets in which orientation is a function of aspect ratio indicate that porphyroblast rotation with respect to kinematic axes does occur in at least some situations

quaternary shoreline development the northwestern coast of egypt abstract new age estimates for samples representing different sedimentary units of the coastal ridges along el omayid burg el arab northwestern coast of egypt reveal that the coastal first ridge is related to holocene high sea level aminozone a with evidence of recent 0 6 0 1 ka ooid contributions the el max abu sir second ridge appears to be associated with the last interglacial and related to oxygen isotope substages ois 5c 5a beach boulders at the bottom of the gebel maryut third ridge are related to the last interglacial high stand ois 5e while the molluscan and cardium limestones are related to a cardium beach of lagoonal to shallow marine environment this beach represents a coastal barrier which existed between 208 59 to 292 48 ka and is related to aminozones f g and ois 7 9 complex paleosols are developed on the northern flanks of both the second and the third ridges with an estimate age of 67 31 ka and aminozone c these appear related to interstadial conditions at the early last glacial stage the paleosols pink limestone at the top of the khashm el ish fourth ridge show a wide range of ages giving age estimates between 360 140 and 584 317 ka indicating a middle pleistocene age

change in snow strength caused by rain rain on snow events can cause wet snow avalanches laboratory experiments were carried out to investigate the change in snow strength with increasing water content through rainwater percolation snowpack was artificially prepared consisting of a thin ice layer and fine compacted snow and rainfall 2mmh 1 was artificially applied 22 25 5 and 49 52 hours after the snowpack was formed snow hardness was measured with a push pull force gauge to indicate the snow strength before and after each rain on snow event after the first rainfall the upper half of the snowpack became wet and a rapid decrease in snow hardness was observed after the second rainfall the rainwater penetrated the ice layer high water content was observed above the ice layer but the hardness exceeded that estimated from an empirical relationship between hardness and water content micrographs of the snow particles suggest that the delay in grain coarsening observed near the wetting front induces the harder than estimated snow condition

soil chronosequences on quaternary marine terraces along the northwestern coast of calabria southern italy abstract two soil chronosequences representative of four orders of marine terraces from early to late pleistocene have been studied along the tyrrhenian coast of northern calabria in southern italy all soil profiles show a high degree of weathering although the degree of soil evolution varies according to the age of each terrace the soils are characterized by reddish to reddish brown colors clayey textures abundant clay coatings slickensides fe mn features or calcium carbonate concretions the dominance of kaolinite and illite among phyllosilicate clay minerals in all soil horizons the intense depletion in caco 3 na and k and the severe etching of quartz crystals in the older soils all record a highly leached pedogenic environment that is progressively more intense from younger to older soils despite the carbonate bedrock quartz feldspar and mica minerals also occur suggesting a partly allochthonous eolian origin of the parent material the major pedogenic features and their formative processes occurred polycyclically on the different orders of marine terraces and we interpret the soils to have mainly developed during repeated quaternary interglacials some surface a and bw horizons show quite different features suggesting a clear change in pedogenetic processes and possibly in climate and duration of soil formation these horizons have the typical field appearance of volcanic soils with andic properties brown colors loamy textures high porosity low bulk density high water retention thixotropy the occurrence of very small volcanic glass fragments and the possible presence of short range order aluminosilicate minerals confirmed some pyroclastic supply during soil formation

stable carbon and oxygen isotopic variations in modern rabdotus land snail shells in the southern great plains usa and their relation to environment abstract variations of stable isotopic ratios of carbon 13c 12c and oxygen 18o 16o were investigated in modern shells of two species of rabdotus land snails r dealbatus and r alternatus in the southern great plains geographic variation in relation to climate and vegetation microgeographic variation variability among individuals and detailed records of seasonal variations within individual shells were studied stable carbon isotopic ratios in shell carbonate are primarily a function of the isotopic composition of the diet of the snails as represented by the isotopic composition of shell organic matter this in turn reflects the presence or absence of cam crassulacean acid metabolism or c4 plants vegetation density may have a small effect on the carbon isotope ratios microgeographic variation samples within 25 to 300 m is greater than that seen across different climatic regions and points to very local control of isotopic variations predominantly related to vegetation seasonal variations as assessed through serial analysis of individual shells up to 35 samples per shell may provide a means for distinguishing between isotopic influences of perennial cam vs annual c4 plants carbon isotopic variations in time series of shells from a site provide a means of reconstructing temporal changes in environment and climate oxygen isotopic values of shell carbonate are uniform across the region and also show no significant microgeographic variation the oxygen isotopic composition appears to be mainly a function of the rainwater isotopic composition with no direct influence of rainfall amount or evaporative effects the 18o values are only 2 enriched relative to estimated equilibrium with rainwater variability is low sd of 0 8 among sites so the isotopic composition of fossil rabdotus shells can provide a precise record of changes in the isotopic composition of rain over time

paleoclimate reconstruction based on the timing of speleothem growth and oxygen and carbon isotope composition in a cave located in the rain shadow in israel high resolution th 230 u 234 ages and delta 18 o and delta 13 c compositions of speleothems in ma ale efrayirn cave located to the east of the central mountain ridge of israel enable us to examine the nature of the rain shadow aridity during glacial and interglacial intervals speleothem growth occurred during marine glacial isotopic periods with no growth during the two last marine isotope interglacial intervals and during the peak of the last glacial maximum this contrasts with speleothem growth in caves located on the western flank of the central mountain ridge in the eastern mediterranean semiarid climatic zone which continued throughout the last 240 000 yr thus during glacial periods water reached both sides of the central mountain ridge a comparison of the present day rain and cave water isotopic compositions and amounts at the ma ale efrayim cave site with those on the western flank shows that evaporation and higher temperatures on the eastern flank are major influences on isotopic composition and the lack of rainfall the delta 18 o and delta 13 c profiles of the speleothems deposited between 67 000 and 25 000 yr b p match the general trends of the isotopic profiles of soreq cave speleothems suggesting a similar source eastern mediterranean sea and similar climatic conditions thus during glacial periods the desert boundary effectively migrated further south or east from its present day location on the eastern flank whereas interglacial periods appear to have been similar to the present with the desert boundary at the same position the decrease in overall temperature and a consequent reduction in the evaporation to precipitation ratios on the eastern flank are viewed as the major factors controlling the decay of the rain shadow effect during glacial periods c 2003 elsevier science usa all rights reserved

stable carbon and oxygen isotopic composition of modern land snails along a precipitation gradient in the mid latitude east asian monsoon region of china abstract the stable oxygen and carbon isotope composition 18oshell and 13cshell of land snail shells preserved in chinese eolian loess deposits have the potential to reconstruct past changes in the east asian summer monsoon easm since the late oligocene to assess the potential of 18oshell and 13cshell for the semi quantitative reconstruction of past variations of the easm we studied modern snails and the corresponding vegetation composition of three distinct ecosystems woodland grassland and mountains spanning a large rainfall gradient 178 1403 mm in the mid latitude east asian monsoon region the results show that different snail species in the three ecosystems have significantly different values of 18oshell and 13cshell the snails in woodland from the eastern plain area have significantly lower 18oshell and 13cshell values than those of snails in grassland from the chinese loess plateau and the snails from the qinba mountains region have values intermediate between the two systematic variations of the 13c of snail shells body tissues and local plants are evident along the rainfall gradient indicating that 13cshell is mainly influenced by the 13c of ingested plants which is controlled by the easm we confirm that 13cshell is a reliable precipitation proxy and we obtained a new empirical equation 13cshell 0 0030 0 0003 map 8 80 0 32 r 0 76 n 74 p

uplift patterns and orogenic evolution in the scottish dalradian rb sr and k ar mineral ages from the dalradian rocks of angus and perthshire indicate considerable diachronism of cooling following the caledonian regional metamorphism the oldest mineral ages 515 ma are similar to the independent estimates of peak metamorphic age and hence indicate very rapid cooling they occur in the highest grade samples of the angus region and are associated with localized uplift regional rapid uplift events at 460 440 ma and 410 390 ma may also be recognized and correlated with structural and igneous activity and metamorphic age dates within the scottish highlands thermal models show the importance of localized and discontinuous uplift in determining both the timing of metamorphism and the shape of the p t paths they suggest that the major diachronous metamorphism and granite production in the scottish highlands is depth controlled rather than representing major lateral diachronism of thickening or heat sources localized uplift may exercise considerable control on mineral facies variation within orogenic belts the local uplift in angus introduces hot high pressure tarfside nappe rocks into higher level tay nappe rocks thus the uniform block uplift models frequently used in the interpretation of metamorphic and structural phenomena in orogenic belts are an oversimplification of the real events

characteristics of snow gliding on rock summary discussion our data from gliding on steep rock show the following characteristics i highly fluctuating values of glide speed are found particularly in early winter and late spring those characteristics are however consistent with gliding theory 2 data for two winters showed that glide rates tend to be similar at the same location for winters of similar character 3 our studies of spatial variation show that glide speed is higher below the step in the rock where snow has separated from the rock in the snow cover than above it there are probably two contributing effects i the presence of the free surface at the uphill surface of the snow allows easier downslope motion of the gliding slab and 2 the open crack can help to concentrate melt water at the glide interface by serving as an open reservoir for surface melt water to concentrate 4 we cannot conclusively say whether glide rates are on average faster during the day than at night better scrutiny of meteorological parameters is needed to understand gliding on a diurnal time scale two winters gliding data do not yield a clear answer 5 we have presented simple analytical expressions for the longitudinal force on restraining barriers in deep snow covers mcclung and larsen 1989 and on roofs when gliding is present the character of the problem on a warm smooth roof is obviously of a different character than that of a deep snow cover bu t it may be approached from a similar mechanics formalism in the zero friction limit equation 3b constants from the glide constitutive equation do not appear mcclung and others snow gliding on rocks one aspect of gliding which is not included in our simple analytical formulae for barrier forces is time dependence even though gliding shows highly fluctuat ing time dependence our equations are based on quasi static formulations a complete time dependent solution is not available yet and its implications for engineering problems have not been fully considered our simple analysis of the fluctuations eq uation 8 and physics of snow gliding shows consistency with the proposed gliding constitutive equation

climatic dependency of soil organic carbon isotopic composition along the s n transect from 34 n to 52 n in central east asia abstract we explored the relationships between surface soil 1 20 cm organic carbon isotopic signatures and associated climatic factors in central east asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian paleosol sequences within the area our analysis shows that the negative correlation between the surface soil organic 13c values and the mean annual precipitation is robust r2 0 453 n 196 p

step wise growth of biotite porphyroblasts in pelitic schists of the western lys caillaouas massif pyrenees abstract detailed optical and electron microscope sem and tem examination of biotite blasts from pelitic schists of the western lys caillaouas massif in the pyrenees reveals a variety of microstructures suggesting growth of the blasts before and after a thermal peak during the d2 deformation in the early stages of growth the biotites had 001 at high angles to s1 and they appear to have existed as thin 001 parallel plates in many cases blastesis is suggested to have involved growth of the biotites into their own continuously dilating pressure shadows inclusions with dentate grain boundaries banded structures and radiator fin intergrowths suggest a mechanism analogous to the ramsay crack seal model for vein formation but here involving step wise dilation of a pressure shadow cavity into which the adjacent blast itself was growing