crystallographic fabrics of omphacite rutile and quartz in vendee eclogites armorican massif france consequences for deformation mechanisms and regimes abstract this study aims at further understanding of the mechanisms how lattice preferred orientations lpo develop during deformation in the main eclogite minerals microstructures and textures of deformed eclogites from the les essarts complex western france were investigated using optical microscopy and electron backscatter diffraction ebsd in the scanning electron microscope microfabric analyses of eclogite facies minerals are used to identify their deformation mechanisms which define the rheology at high pressure metamorphic conditions mechanisms of intracrystalline deformation by dislocation movement dislocation creep result usually in a non linear flow law typically power law while diffusive processes diffusion creep correspond to linear flow laws general microstructural observations may suggest intracrystalline deformation dislocation creep of omphacite the omphacite lpo vary between s and l type and correlate with oblate or prolate grain shape fabrics respectively until now these lpo types have not been understood by plasticity models based on dislocation glide on the known slip systems in clinopyroxene an alternative interpretation is given in terms of anisotropic growth and dissolution with grain boundary diffusion as the rate controlling process there are further indications suggesting diffusion creep with concomitant anisotropic growth and dissolution as a main deformation mechanism in omphacite in omphacite around a hollow garnet crystallographic and shape fabrics align with the c 001 axes parallel to the grain elongations defining the mineral lineation which rotates locally with the inferred flow direction in this part the grain sizes of omphacite and rutile are larger than in the surrounding matrix the geometry of both the shape and crystallographic fabrics is interpreted to represent the local stress regime directions and ratios of the principal stresses the lpo of rutile duplicate the lpo of omphacite and a similar distinction between s and l type was used rutile deformation mechanisms probably involve dislocation creep as well as diffusion creep quartz mainly occurs as an interstitial phase with weak lpo patterns interpreted as random no representative obliquity of the lpo in omphacite nor rutile with respect to foliation and lineation was observed to be used as potential shear sense criteria however the rutile lpo was slightly rotated relative to the omphacite lpo consistently in most samples the results suggest that diffusion processes are strongly involved in the deformation of eclogites a linear flow law should be taken into account in tectonic models where eclogites are incorporated

cambro ordovician anatexis and magmatic recycling at the thinned gondwana margin new constraints from the kouřim unit bohemian massif the kou im unit represents one of the largest pre variscan meta igneous complexes in the bohemian massif and a geochronological whole rock geochemical and sr nd isotopic study was conducted to better understand the magmatic evolution of the early paleozoic gondwana margin five orthogneisses yield u pb zircon ages ranging from 492 4 to 484 2 ma two leucogranites give u pb zircon ages of 500 4 and 485 2 ma interpreted to be inherited from their orthogneiss host rock two samples from the metasedimentary host rock are dominated by neoproterozoic cambrian detrital zircons the abundance of zircon inheritance in the orthogneisses and whole rock sr nd isotopic composition imply an origin from relatively mature continental crustal material the subalkaline subaluminous slightly peraluminous and high k calc alkaline arc like geochemical signature of the orthogneisses is interpreted as inherited from the recycled cadomian metasedimentary source and both the magmatic and metasedimentary rocks are correlated with similar occurrences in the adjacent moldanubicum and tepla barrandian unit the late cambrian early ordovician magmatic activity is linked to crustal anatexis which was probably initiated by thermal and gravitational relaxation of the thickened cadomian arc type crust followed by lithospheric thinning assisted by far field forces the extensional event led to the formation of a passive margin associated with the opening of the rheic ocean supplementary material analytical methods petrographic descriptions with photographs of studied samples collections of cl images of representative zircon grains results of la icp ms u pb analyses of zircons and an additional geochemical diagram are available at https doi org 10 6084 m9 figshare c 4649255

structure emplacement and tectonic setting of late devonian granitoid plutons in the tepla barrandian unit bohemian massif the st novice and cista granodiorite tonalite plutons are small 27 and 38 km2 respectively intrusions that are largely discordant to regional ductile structures in the center of the upper crustal tepla barrandian unit bohemian massif their whole rock and trace element compositions are consistent with medium k calc alkaline magma generated above a subducted slab in a continental margin arc setting the u pb zircon age of the st novice pluton newly determined at 375 2 ma using the laser ablation icp ms technique is within the error of the previously published pb pb age of 373 1 ma for the cista pluton the two plutons also share other characteristics that are typical of concentrically expanded plutons ceps such as elliptical cross section in plan view steep contacts inferred downward narrowing conical shape faint normal zoning and margin parallel magmatic foliation decoupled from the regional host rock structures we interpret the st novice and cista plutons as representing the initial late devonian stage of much more voluminous early carboniferous arc related plutonism represented most typically by the central bohemian plutonic complex in the upper crust of the central bohemian massif these two plutons are important tectonic elements in that they indicate an overall shift of the arc related plutonic activity from the nw to the se accompanied with a general compositional trend of the magmas from medium k calc alkaline to shoshonitic ultrapotassic such a pattern is compatible with se directed subduction of the saxothuringian ocean beneath the tepla barrandian overriding plate as a cause of arc related magmatism in this part of the bohemian massif

late quaternary mega lakes fed by the northern and southern river systems of central australia varying moisture sources and increased continental aridity optically stimulated and thermoluminescence ages from relict shorelines along with accelerator mass spectrometer 14c ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to lake mega frome in southern central australia during the late quaternary additional lacustrine palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka confirming that lakes mega frome and mega eyre were joined to create the largest system of palaeolakes on the australian continent as recently as 50 47 ka the palaeohydrological record indicates a progressive shift to more arid conditions with marked drying after 45 ka subsequently lake mega frome has filled independently at 33 31 ka and at the termination of the last glacial maximum to volumes some 40 times those of today further sequentially declining filling episodes to volumes 25 10 those of today occurred immediately prior to the younger dryas stadial in the mid holocene and during the medieval climatic anomaly southern hemisphere summer insolation maxima are a poor predictor of palaeolake filling episodes an examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced southern ocean circulation and strengthened tropical moisture sources

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

b type olivine fabric in the mantle wedge insights from high resolution non newtonian subduction zone models several hypotheses have been proposed to explain trench parallel shear wave splitting in the mantle wedge of subduction zones these include 3 d flow effects parallel melt filled cracks and b type olivine fabric we predict the distribution of btype and other fabrics with high resolution thermal and stress models of subduction zones a composite viscous rheology is used that incorporates wet diffusion creep wet dislocation creep and a stress limiting approximated peierls creep law rheological parameters for dislocation and diffusion creep are based on deformation experiments the effects of variable viscous coupling between the slab and mantle are explored using kinematic boundary conditions that change along the top of the slab two end member models are observed which depend on the depth of partial viscous coupling between the slab and mantle 1 deep partial coupling which gives rise to cold high stress conditions in the forearc mantle and high temperature low stress conditions in the arc and back arc mantle 2 full viscous coupling at the base of a 40 km conducting lid which is characterized by high temperature and low stress the case with deep partial coupling which produces a better match with attenuation tomography and heat flow shows a large region with suitable conditions for b type fabric in the forearc mantle and a rapid transition toward the back arc to conditions that are more suitable for a c or e type fabrics full viscous coupling gives rise to high temperature low stress conditions unsuitable for b type fabric our modeling predicts that the best candidates for regions with b type fabric are the forearc mantle and a cold 10 15 km layer above the slab d 2005 elsevier b v all rights reserved

last glacial to holocene evolution of semi arid rangelands in southeastern australia pollen sequences from playa lakes in the darling anabranch dunefields of southwestern new south wales record vegetation changes over the last glacial period and into the holocene this interval was one of marked taxonomic and structural reorganization with the plant communities that became established after the last glacial maximum lgm 24 18 ka distinct from those that had prevailed over the build up to full glacial conditions 70 24 ka the glacial period was characterized by a gradual reduction of woodland and tall shrubland cover recolonization of the dunefields involved a similar gradual succession from herbfields and low shrublands to tall shrublands and finally woodlands these changes are likely to have been driven by climatic change particularly fluctuations in temperature precipitation and atmospheric co2 as global climate systems entered and emerged from the last glaciation

vertical extrusion and horizontal channel flow of orogenic lower crust key exhumation mechanisms in large hot orogens a large database of structural geochronological and petrological data combined with a bouguer anomaly map is used to develop a two stage exhumation model of deep seated rocks in the eastern sector of the variscan belt an early sub vertical fabric developed in the orogenic lower and middle crust during intracrustal folding followed by the vertical extrusion of the lower crustal rocks these events were responsible for exhumation of the orogenic lower crust from depths equivalent to 18 20 kbar to depths equivalent to 8 10 kbar and for coeval burial of upper crustal rocks to depths equivalent to 8 9 kbar following the folding and vertical extrusion event sub horizontal fabrics developed at medium to low pressure in the orogenic lower and middle crust during vertical shortening fabrics that record the early vertical extrusion originated between 350 and 340 ma during building of an orogenic root in response to se directed saxothuringian continental subduction fabrics that record the later sub horizontal exhumation event relate to an eastern promontory of the brunia continent indenting into the rheologically weaker rocks of the orogenic root indentation initiated thrusting or flow of the orogenic crust over the brunia continent in a north directed sub horizontal channel this sub horizontal flow operated between 330 and 325 ma and was responsible for a heterogeneous mixing of blocks and boudins of lower and middle crustal rocks and for their progressive thermal re equilibration the erosion depth as well as the degree of reworking decreases from south to north pointing to an outflow of lower crustal material to the surface which was subsequently eroded and deposited in a foreland basin indentation by the brunia continental promontory was highly noncoaxial with respect to the se oriented saxothuringian continental subduction in the early visean suggesting a major switch of plate configuration during the middle to late visean

geodynamic model for the palaeozoic crustal consolidation of western and central europe abstract the crystalline basement of western and central europe consists of a mosaic of crustal elements which were consolidated during pre grenvillian the grenvillian dalslandian morarian cadomian caledonian and hercynian orogenic cycles contemporaneous with the caledonian suturing of the precambrian laurentia greenland and fennosarmatian shields a number of gondwana derived cadomian micro cratons were accreted to the southern margin of laurasia following the late caledonian paroxysm the devonian and early carboniferous evolution of europe was dominated by continued northward subduction of the proto tethys plate at an arc trench system parallelling the southern margin of laurasia the accretion of additional gondwana derived continental fragments back arc rifting and a sinistral translation of major proportions between the laurentia greenland and the fennosarmatian sub plates the acadian and bretonian orogenies were of the pacific type the visean collision of gondwana with laurasia marked the onset of the himalayan type variscan orogeny during which collision related compressive stresses overpowered the devonian early carboniferous back arc rift systems and caused the development reactivation of a subduction zones the central armorican and saxothuringian successor basins became folded and destroyed during the latest visean whilst the variscan foredeep became scooped out in part by nappes involving the basement during the late westphalian major crustal shortening during the variscan diastrophism was accompanied by the anatectic remobilisation of subducted crustal and upper mantle material and a widespread syn and late orogenic magmatism the latest carboniferous early permian reorientation of the convergence direction between gondwana and laurasia induced the development of a complex wrench fault system transecting the variscan fold belt and an extensive post orogenic volcanism the hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data and faunal analyses

contrasting tectono metamorphic evolution of orogenic lower crust in the bohemian massif a numerical model abstract the bohemian massif located at the eastern margin of the european variscan belt is characterised by an exceptional accumulation of felsic high pressure granulites the petrological structural and geochronological studies of this region revealed systematic differences between the tectonometamorphic evolution of the southern moldanubian and northern west sudetes parts of the orogen two contrasting tectonic scenarios have been proposed gravity driven vertical mass exchanges followed by continental indentation in the moldanubian domain and crustal scale folding leading to gneiss dome formation in the west sudetes we present a numerical model in order to correlate the apparent differences between these two regions with the variations in the dynamics of the modelled system we model two colliding blocks an orogenic root where a felsic lower crust is overlain by a mafic layer and a middle crust and a continental indentor we examine the role of the rate of convergence of the two blocks radiogenic heat production within the felsic lower crust and efficiency of erosion the prograde part of the metamorphic evolution is controlled by the rate of convergence and the peak temperature depends on the heat production the retrograde evolution is controlled mostly by erosional processes in the models where the material is weakened due to the heating in the felsic lower crust the gravitational instability of the mafic and felsic layers causes their complete vertical exchange followed by a flow above the indentor in colder and or faster models the thickening is dominated by the buckling of the mafic layer these two styles of deformation i e gravity dominated and fold dominated models correspond to the structures observed in the moldanubian and the west sudetes moreover the calculated pressure temperature paths of the felsic lower crust are in agreement with available data

multiple magmatic fabrics in the sazava pluton bohemian massif czech republic a result of superposition of wrench dominated regional transpression on final emplacement abstract the sazava pluton 354 ma of the central bohemian plutonic complex was emplaced syntectonically into the upper crustal neo proterozoic and lower paleozoic host rock along the se margin of the tepla barrandian zone bohemian massif czech republic the host rock is characterized by transpressional fabric dominated by steep se nw dipping foliations and subhorizontal ne sw stretching lineations associated with flattening to a plane strain ellipsoid the strain intensity degree of oblateness and temperature conditions of deformation increase in the host rock towards the pluton margin in the pluton quartz microfabric indicates progressive cooling of the syntectonically emplaced magma the ams method revealed multiple magmatic fabrics and lateral variations in the shapes of the ams ellipsoid and the magnetic fabric intensity in the pluton the central part of the pluton yields prolate shapes of the ams ellipsoid and a low degree of anisotropy with preserved steep magnetic lineations whereas along the pluton margins oblate ams ellipsoids are associated with a high degree of anisotropy we interpret the multiple fabrics and the partially decoupled fabric pattern between the host rock and the pluton as being a result of superposition of regional tectonic strain during highly oblique transpression on emplacement related intrusive strain where outer solidified and more rigid edges of the pluton enabled preservation of older steep fabrics in its interior

application of matrix analysis in delineating sinkhole risk areas along highway i 70 near frederick maryland sinkhole collapse in the area of maryland interstate 70 i 70 and nearby roadways south of frederick maryland has been posing a threat to the safety of the highway operation as well as other structures the occurrence of sinkholes is associated with intensive land development however the geological conditions that have been developing over the past 200 million years in the frederick valley control the locations of the sinkholes within an area of approximately 8 km 2 138 sinkholes are recorded and their spatial distribution is irregular but clustered the clustering indicates the existence of an interaction between the sinkholes the point pattern of sinkholes is considered to be a sample of a gibbsian point process from which the hard core strauss model is developed the radius of influence is calculated for the recorded sinkholes which are most likely to occur within 30 m of an existing sinkhole the stochastic analysis of the existing sinkholes is biased toward the areas with intensive land use this bias is adjusted by considering 1 topography 2 proximity to topographic depressions 3 interpreted rock formation 4 soil type 5 geophysical anomalies 6 proximity to geologic structures and 7 thickness of overburden based on the properties of each factor a scoring system is developed and the average relative risk score for individual 30 m segments of the study area is calculated the areas designated by higher risk levels would have greater risk of a sinkhole collapse than the areas designated by lower risk levels this risk assessment approach can be updated as more information becomes available

magmatic to solid state fabrics in syntectonic granitoids recording early carboniferous orogenic collapse in the bohemian massif abstract the 354 336 ma central bohemian plutonic complex is a variscan magmatic arc that developed in the central bohemian massif in response to subduction of the saxothuringian lithosphere beneath the tepla barrandian microplate magmatic to solid state fabrics in the most voluminous portion of this arc the 346 ma blatna pluton record two superposed orogenic events dextral transpression associated with arc parallel stretching and arc perpendicular shortening and normal shearing associated with exhumation of the high grade core of the orogen moldanubian unit this kinematic switch is an important landmark in the evolution of this segment of the variscan belt for it marks the cessation of subduction related compressive forces in the upper crust giving way to gravity driven normal movements of the tepla barrandian hanging wall block relative to the high grade moldanubian footwall we use thermal modeling to demonstrate that the emplacement of huge volumes of arc magmas and their slow cooling produced a thermally softened domain in the upper crust and that the magmatic arc granitoids may have played a major role in initiating the orogenic collapse in the bohemian massif through lubrication and reactivation of a pre existing lithospheric boundary and decreasing the overall strength of the rigid orogenic lid

tectonic evolution of a continental magmatic arc from transpression in the upper crust to exhumation of mid crustal orogenic root recorded by episodically emplaced plutons the central bohemian plutonic complex bohemian massif the central bohemian plutonic complex cbpc consists of episodically emplaced plutons the internal fabrics of which recorded tectonic evolution of a continental magmatic arc the 354 350 ma calc alkaline plutons were emplaced by multiple processes into the upper crustal tepla barrandian unit and their magmatic fabrics recorded increments of regional transpression multiple fabrics of the younger 346 ma blatna pluton recorded both regional transpression and the onset of exhumation of mid crustal orogenic root moldanubian unit continuous exhumation related deformation during pluton cooling resulted in the development of a wide zone of sub solidus deformation along the se margin of the cbpc finally syn exhumation tabular durbachitic pluton of ultrapotassic composition was emplaced atop the intrusive sequence at 343 340 ma and the ultrapotassic tabor pluton intruded after exhumation of the orogenic root 337 ma we suggest that the emplacement of plutons during regional transpression in the upper crust produced thermally softened domain which then accommodated the exhumation of the mid crustal orogenic root and that the complex nature of the tepla barrandian moldanubian boundary is a result of regional transpression in the upper crust the enhancement of regional deformation in overlapping structural aureoles the subsequent exhumation of the orogenic root domain and post emplacement brittle faulting

an olivine fabric database an overview of upper mantle fabrics and seismic anisotropy we present a unique database of 110 olivine petrofabrics and their calculated seismic properties the samples come from a variety of the upper mantle geodynamic environments ophiolites subduction zones and kimberlites with a wide range of micro structures a phenomenological relationship is established between p and s wave seismic anisotropy and the degree of crystal alignment fabric strength seismic anisotropy increases rapidly at low fabric strength before reaching a near saturation level of 15 to 20 for p waves and 10 to 15 for s waves despite a large variation in the symmetry of fabric patterns the average seismic properties of the different fabric micro structural and geodynamic settings have similar anisotropies in both magnitude and symmetry hence it would seem possible to determine some measure of fabric strength from seismic anisotropy if the dimensions of the anisotropic region are known but not geodynamic environment or details of the petrofabric pattern a simple pattern of seismic anisotropy characterises the average sample of the database which has the following features the polarisation plane of the fastest s wave is parallel or sub parallel to the foliation plane the maximum shear wave splitting is parallel to the y structural direction in foliation plane and normal to the lineation the maximum of the p wave velocity is parallel to the high concentration of 100 axes which is sub parallel to the lineation the 100 orientation distribution has the greatest influence on the p wave seismic anisotropy the 100 and 001 orientation distributions have the greatest influence on the symmetry of s wave anisotropy although the magnitude of anisotropy is influenced by the distribution of all three principal axes although the database only contains olivine petrofabrics this statistical study clearly shows that seismic anisotropy can be used to deduce the orientation of the structural frame in the upper mantle 1998 elsevier science b v all rights reserved

improving sinkhole hazard models incorporating magnitude frequency relationships and nearest neighbor analysis abstract this work presents a methodology for elaborating sinkhole hazard models that incorporate the magnitude and frequency relationships of the subsidence process the proposed approach has been tested in a sector of the ebro valley mantled evaporite karst where sinkholes largely induced by irrigation practices have a very high occurrence rate 50 sinkholes km 2 yr in this area covering 10 km 2 a total of 943 new cover collapse sinkholes were inventoried in 2005 and 2006 multiple susceptibility models have been generated analyzing the statistical relationships between the 2005 sinkholes and different sets of variables including the nearest sinkhole distance the quantitative evaluation of the prediction capability of these models using the 2006 sinkhole population has allowed the identification of the method and variables that produce the most reliable predictions the incorporation of the indirect variable nearest sinkhole distance has contributed significantly to increase the quality of the models despite simplifying the modeling process by using categorical rather than continuous variables the best susceptibility model generated with the total sinkhole population and the selected method and variables has been transformed into a hazard model that provides minimum estimates of the spatial temporal probability of each pixel to be affected by sinkholes of different diameter ranges this transformation has been carried out combining two equations derived from the more complete 2006 sinkhole population one of them expressing the expected spatial temporal probability of sinkhole occurrence and the other the empirical magnitude and frequency relationships generated for two different types of land surfaces which control the strength of the surface layer and the size of the sinkholes the presented method could be applied to predict the spatial temporal probability of events with different magnitudes related to other geomorphic processes e g landslides

european mantle lithosphere assembled from rigid microplates with inherited seismic anisotropy abstract we have modelled three dimensional seismic anisotropy of the mantle lithosphere from anisotropic parameters of teleseismic body waves we invert jointly shear wave splitting parameters and p residual spheres based on data from dense networks of temporary and permanent stations in four european regions ranging from the variscan belt to the baltic shield changes in orientation of the large scale anisotropy caused by systematic preferred orientation of olivine identify boundaries of domains of mantle lithosphere individual domains are characterized by a consistent large scale orientation of anisotropy approximated by hexagonal or orthorhombic symmetry with generally inclined symmetry axes the domains are separated by mapped tectonic boundaries sutures which cut the entire lithosphere besides the change of anisotropy orientation at domain boundaries we often observe a change of the lithosphere and or crust thicknesses we do not detect any fabric of the mantle lithosphere which could have been produced by a collision of microcontinents in a volume detectable by large scale seismic anisotropy the observations of consistent anisotropy within individual blocks of the mantle lithosphere reflect frozen in olivine preferred orientation most probably formed prior to the assembly of microcontinents that created the modern european landmass therefore our findings support a plate tectonic view of the continental lithosphere as a mosaic of rigid blocks of the mantle lithosphere with complicated but relatively sharp contact zones these contacts are blurred by the easily deformed overlying crust terranes

stick nest rat middens and a late holocene record of white range central australia stick nest ratmiddens arepreserved piles ofmacrofossils thatrecord changes inplants and animals during thelate holocene atwhiterange thebuilders lesser stick nest rats leporillus apicalis after atleast 2500years inthearea becameextinct during themodemradiocarbon period therats collection ofplant andanimal material provides anecological survey ofthesite during this period thespecies composition ofthevegetation hasapparently responded toincreased aboriginal populations fire incidence orrainfall inthelast 2500years a dramatic increase intree andshrub material between 2510 40bpand835 62bpattheexpense ofherbs ispossibly related toincreasing moisture availability themiddens record acollapse oftrees andshrubs by606 136 bpthenastrong recovery grasses have generally decreased inimportance throughout therecord bonesofthecentral rockrat zyzomys pedunculatus whichiscurrently restricted tothewestern macdonnell ranges werefoundin middens datedat433 60bp information aboutlong term changes inaustralia s aridareasis accessible usingthemiddens ofstick nest ratsandprovides a useful long term perspective for environmental management

boundaries of mantle lithosphere domains in the bohemian massif as extinct exhumation channels for high pressure rocks abstract five domains microplates have been recognized by seismic anisotropy in the mantle lithosphere of the bohemian massif the mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their variscan assembly the present day mantle fabric indicates that this process consisted of at least three oceanic subductions each followed by an underthrusting of the continental lithosphere the seismic anisotropy does not detect remnants of the oceanic subductions but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions the most robust continent continent collision was followed by westward underthrusting of the brunovistulian mantle lithosphere still detectable by seismic anisotropy more than 100 km beneath the moldanubian mantle lithosphere major occurrences of the high pressure ultra high pressure hp uhp rocks follow the ene and nne oriented sutures and boundaries of the mantle lithosphere domains mapped from three dimensional modeling of body wave anisotropy the hp uhp rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries the close relation of the mantle sutures and occurrences of the hp uhp rocks near the paleosubductions testifies for models interpreting the granulite garnet peridotite association by oceanic continental subduction underthrusting followed by the exhumation of deep seated rocks our findings support the bivergent subduction model of tectonic development of the central part of the bohemian massif the inferences from seismic anisotropy image the bohemian massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric the collisional mantle boundaries blurred by tectonometamorphic processes in easily deformed overlying crust served as major exhumation channels of the hp uhp rocks

holocene palaeoecology of the northern flinders ranges south australia based on stick nest rat leporillus spp middens a preliminary overview eight stick nest rat leporillus spp middens from three locations in the northern flinders ranges south australia provide a discontinuous palaeoecological record spanning the holocene evidence from radiocarbon dates pollen plant macrofossils and animal macrofossils is presented both pollen and plant macrofossils show that in the early to mid holocene c 8 8 5 3 ka woodlands with grassy understoreys were more widespread than present this accords with other studies suggesting wetter conditions at this time samples dating of the pleistocene holocene transition 10 9 9 ka are dominated by halophytes it is not yet clear whether this is due to the continuation of pleistocene aridity changes in rainfall seasonality or local influences on vegetation

karst collapse related to over pumping and a criterion for its stability karst collapse caused by natural or artificial abstraction of groundwater has been an environmental geological problem the origin of karst collapse has been described by the potential erosion theory and the vacuum absorption erosion theory however a mathematical prediction criterion for karst collapse cannot be established by these two theories this paper from a new perspective attempts to explain the microcosmic mechanism of karst collapse on the basis of these two theories at a certain point in the unconsolidated soil covered on karst caves when shearing stress surpasses shear strength of the soil it fails under the mechanic effects of water and gas as well as gravity pressure with an increase in damage points a break plane appears and the soil overlying the karst caves is completely damaged and thus the ground surface collapses on the basis of mohr coulomb damage theory and previous studies a prediction criterion of karst collapse is presented an example displays the calculating process of the model and proves its reliability by analyzing nine typical collapses caused by a pumping test in guizhou province china

karst database implementation in minnesota analysis of sinkhole distribution this paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the karst feature database kfd of minnesota nearest neighbor analysis nna was extended to include different orders of nna different scales of concentrated zones of sinkholes and directions to the nearest sinkholes the statistical results along with the sinkhole density distribution indicate that sinkholes tend to form in highly concentrated zones instead of scattered individuals the pattern changes from clustered to random to regular as the scale of the analysis decreases from 10 100 km2 to 5 30 km2 to 2 10 km2 hypotheses that may explain this phenomenon are 1 areas in the highly concentrated zones of sinkholes have similar geologic and topographical settings that favor sinkhole formation 2 existing sinkholes change the hydraulic gradient in the surrounding area and increase the solution and erosional processes that eventually form more new sinkholes

stress strain and b type olivine fabric in the fore arc mantle sensitivity tests using high resolution steady state subduction zone models 1 shear wave splitting observations at several subduction systems show trench parallel fast directions in the fore arc mantle the presence of b type olivine fabric in the mantle wedge may provide an explanation for this pattern of anisotropy under low temperature and hydrated conditions sensitivity tests are shown that provide insights into the distribution and magnitude of b type fabric using two dimensional high resolution kinematic dynamic subduction zone models these models include a wet olivine rheology and a simulated aseismic creep zone in the fore arc mantle with parameterized viscous coupling between the slab and mantle wedge the calculated thermal structure is in reasonable agreement with heat flow observations and q tomography for small amounts of coupling and moderate amounts of shear heating in the seismogenic and aseismic creep zones these small amounts of viscous coupling give rise to a slowly flowing fore arc mantle with thermal stress and strain conditions suitable for significant b type fabric development the minimum shear stress necessary to drive geologically significant flow in the predicted b type region is sensitive to the magnitude of shear heating along the aseismic creep zone and ranges from less than 100 to 300 mpa the minimum time required to generate sufficient finite strain for fabric development in the b type region is around 10 myr depending on the amount of coupling and shear heating the predicted distribution of olivine fabric is consistent with a pattern of shear wave anisotropy with trench parallel fast polarization directions above the fore arc and a rapid rotation to trench perpendicular in the arc and back arc

magma mixing in the genesis of hercynian calc alkaline granitoids an integrated petrographic and geochemical study of the sazava intrusion central bohemian pluton czech republic the devonian early carboniferous 354 1 3 5 ma conventional zircon u pb age sazava intrusion biotite amphibole quartz diorite tonalite and granodiorite of the central bohemian pluton cbp associated with bodies of olivine pyroxene amphibole gabbro gabbrodiorite quartz diorite and rare hornblendite gives an opportunity for a comparative study of a rather shallow calc alkaline magma mixing zone at two levels separated by a vertical difference of approximately 1 km the deeper section p ibram displays the direct evidence for the existence of a long lived periodically tapped and replenished floored magma chamber masli the contacts between the subhorizontal sheet like basic bodies and the surrounding commonly cumulus rich sazava granitoid are arcuate and cut by a series of veins and ascending pipes shallow dipping swarms of strongly elongated and flow aligned mafic microgranular enclaves mme concordant with the contacts of the basic bodies are commonplace the higher level teletin section shows relatively independent basic intrusions some of them distinctly hybrid in character and mainly of quartz dioritic composition surrounded by relatively homogeneous nearly cumulus free sazava tonalite rich in texturally variable mme larger quartz microdiorite bodies and the mme both interpreted as hybrids contain varying proportions of highly heterogeneous plagioclase megacrysts with complex zoning particularly well shown by cathodoluminescence cl most often the megacrysts have cores of labradorite anorthite partly resorbed and overgrown by andesine rims but some are strongly brecciated and fragments have been annealed by rim growth also characteristic are long prisms of apatite oikocrysts of quartz and k feldspar and zoned amphibole the latter has brown pargasite and magnesiohastingsite cores resorbed and overgrown by magnesiohornblende compositionally similar to the amphibole in the sazava tonalite the brown cores are probably relics of a higher p t stage with temperature exceeding 900 c plots of major element analyses of the teletin quartz microdiorite and the mme fall close to the line joining the compositions of the evolved sazava granodiorite tonalite and the associated gabbros the estimated minimal proportions of the acidic end member range from ca 15 to 20 for the quartz microdiorite and ca 40 to 60 for the enclaves field relationships macroscopic and mineralogical features and whole rock geochemistry are consistent with a hybrid origin of the quartz microdiorite masses and enclaves unzoned calcic plagioclase cores are interpreted as having crystallized from a basic magma prior to its injection into a high level acidic magma chamber the sudden decrease in ca activity and introduction of water due to magma mixing with tonalitic melt led to their resorption and brecciation quartz ocelli that are abundant locally in some basic bodies are most likely xenocrysts introduced from the felsic magma in the basic melt they were resorbed and became a substrate for heterogeneous nucleation of the amphibole or pyroxene coronas strong undercooling of the basic magma resulted in the growth of long prismatic apatite together with dendritic boxy cellular plagioclase both types of plagioclase cores were subsequently overgrown by more sodic mantles at the same time small unzoned plagioclase crystals nucleated in the groundmass following thermal re adjustment crystallization of the hybrid magma ended with considerably slower growth of quartz and k feldspar oikocrysts

regional risk assessment of karst collapse in tangshan china this paper discusses the reasons why the number of karst collapses has been increasing in tangshan china since 1978 it gives the main factors that influence the regional risk of karst collapse and the method for assessing it using the risk assessment method developed three zones in downtown tangshan with different risk levels were delineated based on the risk assessment results some recommendations are given on the treatment of karst collapse and related urban engineering issues

viscoplastic self consistent and equilibrium based modeling of olivine lattice preferred orientations implications for the upper mantle seismic anisotropy anisotropy of upper mantle physical properties results from lattice preferred orientation lpo of upper mantle minerals in particular olivine we use an anisotropic viscoplastic self consistent vpsc and an equilibrium based model to simulate the development of olivine lpo and hence of seismic anisotropy during deformation comparison of model predictions with olivine lpo of naturally and experimentally deformed peridotites shows that the best fit is obtained for vpsc models with relaxed strain compatibility slight differences between modeled and measured lpo may be ascribed to activation of dynamic recrystallization during experimental and natural deformation in simple shear for instance experimental results suggest that dynamic re crystallization results in further reorientation of the lpo leading to parallelism between the main 010 100 slip system and the macroscopic shear thus modeled simple shear lpos are slightly misoriented relative to lpos measured in natural and experimentally sheared peridotites this misorientation is higher for equilibrium based models yet seismic properties calculated using lpo simulated using either anisotropic vpsc or equilibrium based models are similar to those of naturally deformed peridotites errors in the prediction of the polarization direction of the fast s wave and of the fast propagation direction for p waves are usually 15 moreover overestimation of lpo intensities in equilibrium based and vpsc simulations at high strains does not affect seismic anisotropy estimates because these latter are weakly dependent on the lpo intensity once a distinct lpo pattern has been developed thus both methods yield good predictions of development of upper mantle seismic anisotropy in response to plastic flow two notes of caution have nevertheless to be observed in using these results 1 the dilution effect of other upper mantle mineral phases in particular enstatite has to be taken into account in quantitative predictions of upper mantle seismic anisotropy and 2 lpo patterns from a few naturally deformed peridotites cannot be reproduced in simulations these abnormal lpos represent a small percent of the measured natural lpos but the present sampling may not be representative of their abundance in the earth s upper mantle

evaluating and comparing methods of sinkhole susceptibility mapping in the ebro valley evaporite karst ne spain abstract multiple sinkhole susceptibility models have been generated in three study areas of the ebro valley evaporite karst ne spain applying different methods nearest neighbour distance sinkhole density heuristic scoring system and probabilistic analysis for each sinkhole type separately cover collapse sinkholes cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes the quantitative and independent evaluation of the predictive capability of the models reveals that 1 the most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density these models can be generated in a simple and rapid way from detailed geomorphological maps 2 the reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes consequently the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences 3 the predictive capability of the best models obtained in this research is significantly higher 12 5 82 5 than that of the heuristic sinkhole susceptibility model incorporated into the general urban plan for the municipality of zaragoza although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios

shear wave splitting around the northern atlantic frozen pangaean lithospheric anisotropy abstract although the number of teleseismic shear wave splitting measurements has considerably increased world wide during the last decade there is no consensus on a unique and universal interpretation of these data splitting might primarily originate in the lithospheric and or asthenospheric mantle but the technique has no vertical resolution and therefore leaves this question of anisotropy location unresolved generally the consequences of the two possibilities are used to infer which is more likely if splitting occurs in the lithosphere the splitting parameters the orientation of the fast split shear wave o and the delay time t should be related to frozen or active deformation on the other hand if the splitting occurs in the asthenosphere the observed splitting parameters should be related to the present day flow induced by the differential motion between the tectonic plates and the underlying mantle the aim of this paper is to test these hypotheses against shear wave splitting observations from western europe and the eastern u s indeed except in a few places splitting on either side of the atlantic on hercynian caledonian or grenvillian structures do not appear to have been deeply and pervasively affected by the opening of this ocean this provides us the opportunity to place these results in the pangaean reference frame of the hercynian caledonian belt before the opening of the atlantic in many places the close parallelism between lithospheric structure and the absolute plate motion apm impedes a reliable identification of the origin of the anisotropy especially an asthenospheric flow channelled around the deeply rooted north american craton may be compatible with the large scale anisotropy pattern in the eastern u s despite this ambiguity fast polarization directions o observed on or near some major lithospheric structures correlate better with the trend of the local tectonic structures than with the expected asthenospheric flow therefore we suggest that these lithospheric structures developed before the opening of the atlantic remain frozen since hercynian caledonian or grenvillian times and are responsible for the observed splitting at these places

probabilistic sinkhole modelling for hazard assessment a method for quantitatively assessing sinkhole susceptibility spatial probability and hazard spatio temporal probability has been developed and independently tested in a 50 km2 sector of the ebro valley evaporite karst three genetic types of sinkholes have been mapped in the floodplain and a terrace surface 947 small cover collapse sinkholes type 1 terrace large collapse sinkholes type 2 floodplain and large subsidence depressions type 3 floodplain the type 1 sinkhole inventory includes two temporal populations 447 sinkholes formed before 24 november 2005 and 500 between that date and 2 november 2006 sinkhole susceptibility models have been elaborated analysing the statistical relationships between the sinkholes of the 2005 inventory and a set of potential conditioning factors the independent evaluation validation of the susceptibility models by means of several strategies random sequentially excluded and temporal has allowed us to select the most significant variables for each sinkhole type and assess quantitatively the quality of models which are reasonable for the three sinkhole types validation has also provided information on the contribution of specific variables and the effect of changing their accuracy to the prediction capability of models susceptibility models for type 3 sinkholes have been validated satisfactorily with the 2006 sinkhole inventory temporal validation the best susceptibility model has been transformed into a hazard map considering the frequency of sinkholes that occurred in each susceptibility class between 2005 and 2006 as well as their average size the susceptibility and hazard models obtained could be used as an objective basis for the application of mitigation measures either of preventive or corrective nature copyright 2008 john wiley sons ltd

the influence of karst features on environmental studies in turkey the carbonate rocks of turkey which underlie about one third of the country possess major water resources with great potential for electricity generation and water supplies the ongoing development of karst features especially in the southern part of turkey demonstrates specific environmental problems that occur in many karst water supply projects karst aquifers springs sinkholes dolines poljes and other karst features are of great importance from the standpoint of karst water resources and environmental research studies in karst regions conservation and protection of groundwater resources for both qualitative and quantitative evaluations is possible only when the catchment area is determined accurately since the catchment area in karst terrains is not limited by the surface drainage boundaries and the groundwater flows through well developed coduits or fissures the equations used in non karstic areas cannot be applied to such karstic regions studies on the development of karst features and its environmental impacts in turkey are of recent origin therefore many unreliable methods are being applied in karstic areas for example the use of shallow holes or sinkholes and fault zones for septic water waste disposal or as sewage by those who are not familiar with karst sometimes causes very serious problems of extensive groundwater pollution this paper discusses the development of different karstic features in turkey and case studies on its environmental impacts

plastic deformation and development of clinopyroxene lattice preferred orientations in eclogites abstract we use an anisotropic viscoplastic self consistent vpsc model to simulate the development of omphacite lattice preferred orientations lpos in response to deformation by dislocation glide in these simulations we consider slip systems identified either in naturally deformed omphacite or in experimentally deformed diopside simulated lpos reproduce very well the characteristic omphacite lpo pattern in naturally deformed eclogites a strong concentration of 001 axes sub parallel to the lineation and of 010 poles sub perpendicular to the foliation these models reconcile the interpretation of omphacite lpos in eclogites and tem observations of naturally deformed omphacite since they show that omphacite lpos in naturally deformed eclogites may develop by dislocation glide on 1 2 110 110 001 110 and 001 100 we also investigate the effect of the strain regime on the omphacite lpo development the simulations show that changes in deformation regime lead to second order variations in omphacite lpo patterns similar to those observed in eclogites such as an asymmetry of the lpo relative to the structural frame a stronger concentration of the 001 axes relative to the 010 pole concentration or a dispersion of 001 axes in the foliation plane this suggests that omphacite lpo patterns may carry information on the deformation regime simple shear transtension active during the high pressure events

pressure sensitivity of olivine slip systems and seismic anisotropy of earth s upper mantle the mineral olivine dominates the composition of the earth s upper mantle and hence controls its mechanical behaviour and seismic anisotropy experiments at high temperature and moderate pressure and extensive data on naturally deformed mantle rocks have led to the conclusion that olivine at upper mantle conditions deforms essentially by dislocation creep with dominant 100 slip the resulting crystal preferred orientation has been used extensively to explain the strong seismic anisotropy observed down to 250 km depth the rapid decrease of anisotropy below this depth has been interpreted as marking the transition from dislocation to diffusion creep in the upper mantle but new high pressure experiments suggest that dislocation creep also dominates in the lower part of the upper mantle but with a different slip direction here we show that this high pressure dislocation creep produces crystal preferred orientations resulting in extremely low seismic anisotropy consistent with seismological observations below 250 km depth these results raise new questions about the mechanical state of the lower part of the upper mantle and its coupling with layers both above and below

new type of olivine fabric from deformation experiments at modest water content and low stress a new type of olivine fabric was found by high strain simple shear deformation experiments in the presence of trace amounts of water at 0 5 2 2 gpa and 1470 1570 k in this fabric called e type fabric the olivine 100 axis is subparallel to the shear direction and the 001 plane is parallel to the shear plane this geometry suggests that the 100 001 slip system makes the dominant contribution to total strain this fabric is dominant at a modest water content 200 coh 1000 h 10 6 si at low stresses and high temperatures some mylonites from peridotite massifs show this type of olivine fabric which suggests the presence of water during the shear localization the seismic anisotropy caused by this fabric is qualitatively similar to that by dry fabric a type but the magnitudes of anisotropy are different between the two types for horizontal flow the amplitude of vsh vsv anisotropy is weaker but the amplitude of shear wave splitting is stronger for the e type fabric than for the a type dry fabric seismic anisotropy in the oceanic upper mantle may be due to the olivine e type fabric

chronological constraints on the pre orogenic history burial and exhumation of deep seated rocks along the eastern margin of the variscan orogen bohemian massif czech republic key lithological units of the high grade eastern margin of the bohemian massif were dated using the u pb and pb pb methods on zircons in order to establish a chronological framework for the geodynamic evolution of the variscan orogenic root the protolith ages for metagranitoids orthogneisses and granulites of thickened lower and middle crust reveal the existence of magmatic activity that occurred over a 100 million year time interval from cambro ordovician to early devonian times probably related to discontinuous intracontinental rifting of neoproterozoic crust our geochronological data suggest that the eastern part of the orogenic root represents thermally softened and rifted neoproterozoic crust preserved farther to the east as the brunia microcontinent zircon ages for felsic granulites high grade gneisses of the lower crust and of a syn convergence granodioritic intrusion in the upper crust indicate that thickening and exhumation of the crust occurred during a narrow time interval between 370 and 340 ma exhumation of the lower crust to mid crustal levels was a localized process that occurred at 340 ma and was associated with crustal scale folding in the internal part of the root as well as orogenic channel flow along the eastern collisional margin both types of exhumation mechanisms were driven by deep level wedging indentation of the easterly brunia continent followed by deposition of heavy minerals and pebbles derived from high pressure rocks in the adjacent foreland basin final orogenic development was characterized by ne sw dextral transpressive shearing parallel to the brunia margin as well as dextral trans tension associated with activity along the elbe lithospheric fault these processes affected the marginal parts of the orogenic root and were accompanied by 330 to 325 ma old syntectonic granitoid intrusions along reactivated lithotectonic boundaries rotation of the assembled orogenic belt accompanied by lithospheric faulting driven by westerly subduction roll back may be the most plausible model to explain late deformation of the orogenic root

modeling doline populations with logistic growth functions initiation and evolution of a large karst depression population consisting of parent and daughter dolines were spatially and temporally modeled using logistic growth functions logistic growth models are well suited for analyzing doline population initiation and evolution because they reflect the density dependent growth mechanisms present in the evolution of karst depressions seven assumptions based upon previous studies were refined into mathematical statements and tested using more than 2000 dolines from a subpopulation of both parent and daughter karst depressions on the western highland rim and pennyroyal plain of tennessee and kentucky logistic growth models quantify the initiation and evolution of doline populations and interface well with recent models describing the evolution of three dimensional conduit systems logistic growth models should apply to modeling other doline populations in karst terranes with hydraulically efficient three dimensional conduit systems copyright 2006 john wiley sons ltd

development and validation of sinkhole susceptibility models in mantled karst settings a case study from the ebro valley evaporite karst ne spain abstract a preliminary sinkhole susceptibility analysis has been carried out in a stretch 50 km 2 in area of the ebro valley alluvial evaporite karst ne spain a spatial database consisting of a sinkhole layer and 27 thematic layers related to causal factors was constructed and implemented in a gis three types of sinkholes were differentiated on the basis of their markedly different morphometry and geomorphic distribution large subsidence depressions 24 large collapse sinkholes 23 and small cover collapse sinkholes 447 the susceptibility models were produced analysing the statistical relationships between the mapped sinkholes and a set of conditioning factors using the favourability functions approach the statistical analyses indicate that the best models are obtained with 6 conditioning factors out of the 27 available ones and that different factors and processes are involved in the generation of each type of sinkhole the validation of two models by means of a random split strategy shows that reasonably good predictions on the spatial distribution of future dolines may be produced with this approach around 75 of the sinkholes of the validation sample occur on the 10 of the pixels with the highest susceptibility and about 45 of the area can be considered as safe

palynological analysis of hyrax middens from southern africa abstract hyrax middens in relatively dry parts of africa preserve plant material which includes pollen the bottoms of two stratified hyrax dung middens from blydefontein basin in the karoo shrubland of south africa were dated by radiocarbon to ca 300 yr b p and ca 1130 yr b p comparison of midden pollen spectra with pollen from alluvial sediments near one of the hyrax middens and in modern surface samples indicates that middens contain pollen which reflects local vegetation and that diet probably does not have a major influence on pollen spectra changes in pollen composition probably reflect climatic conditions during the early history of the older midden profile grass dominated spectra suggest moist conditions existed between 1200 and 300 yr b p and an interval of slightly more shrubby karoid vegetation possibly points to a minor dry spell at 1000 yr b p a sharp increase of karoid shrub vegetation and a decrease of grass since 300 yr b p is reflected in both middens the change was apparently triggered by relatively dry conditions and later during the last 150 years it was enhanced by overgrazing from european domestic stock

evaluation of susceptibility for terrain collapse and subsidence in karst areas municipality of iraquara chapada diamantina ba brazil the morphological evolution of the karstic systems is associated with a set of physical and chemical processes triggered by the dissolution of the rocks related to percolation of groundwater and surface water which consequently open underground voids and carve out peculiar forms of relief due to environmental and geotechnical aspects this system is naturally more fragile and vulnerable than other natural systems and therefore has increasingly received the attention of the scientific community over the past decades the objective of the study was to delimit zones with varying degrees of susceptibility for collapses and subsidence of sinkholes in the municipality of iraquara chapada diamantina ba brazil and to understand their geological and morphological determinant factors geological data karst phenomenon map and visual analysis in the field were used to categorize zones with different types of susceptibilities to the nucleation of new sinkholes based on a hazard index this index was defined from the sum of geological hazard factors lineament density and sinkhole density the areas that presented the highest susceptibility for terrain collapse and subsidence corresponded to regions where carbonate rocks outcrop with high density of photolineaments and 2 62 sinkholes km2 processes associated with terrain collapse and subsidence in karst areas consisted of a combination of various factors hindering precise predictions however zones of different types of susceptibilities to terrain collapse and subsidence can be delimited when the relationships between these processes and their factors are understood the hazard index proposed does not provide quantitative values for the probability of hazard susceptibility but rather indicates areas that are more susceptible to terrain subsidence and collapse

modelling diverse processes in the petrogenesis of a composite batholith the central bohemian pluton central european hercynides the multiple intrusions making up the central bohemian pluton in the central european hercynides have petrographic and geochemical features consistent with the presence of four main granitoid suites major element trace element and sr nd isotopic compositions are used to model their petrogenesis partial melting of metabasic locks or of a chur like mantle source are interpreted to have produced melts parental to the most primitive calc alkaline sazava suite interaction of basic with more acidic magmas followed by extensive amphibole plagioclase dominated fractionation accounts for the production of trondhjemites alternatively the trondhjemites correspond to small degree melts of a metabasic source afc assimilation fractional crystallization modelling with a paragneiss as a contaminant and increasing d nd values simulates the characteristics of the blatna suite closed system fractionation of strongly enriched mantle derived magmas or their interaction with leucogranitic melts is deduced for the petrogenesis of the shoshonitic certovo bremeno suite partial melting of a metasedimentary source followed by k feldspar dominated fractionation accounts for the granites of rite ricany suite the progression from relatively primitive calc alkaline granitoids towards evolved k rich calc alkaline and shoshonitic rocks is interpreted to reflect the increasing enriched mantle input in the petrogenesis of the later suites the evidence for hercynian subduction is equivocal and the mantle enrichment could have been significantly older

changes in vegetation and seasonal climate since the last full glacial at lake frome south australia abstract results are presented from stratigraphy radiocarbon and pollen analysis from lake frome south australia close to the summer winter rainfall boundary at 30 south latitude the pollen sequence shows that tree vegetation was minor around 18 000 yr b p the landscape was dominated by chenopod low shrublands and ephemeral tubuliflorae vegetation by 17 000 yr b p callitris moved in and rose to 25 of the pollen sum values of casuarina myrtaceous shrubs acacia dodonaea and cyperaceae also rose at about the same time between 17 000 and 14 500 yr b p callitris and eucalyptus dominated the tree vegetation with callitris reaching its maximum values eucalpt woodlands were associated with undershrubs belonging to myrtaceae acacia dodonaea and gyrostemonaceae whereas callitris woodlands had probably supported only a sparse understorey chenopodiaceae today distributed mainly in the winter rainfall zone continued to show high values 25 gramineae today associated with high summer rainfall generally remained below 20 the sporadic presence of a number of taxa which now grow in temperate areas further south suggest that average annual temperatures were a little lower than at present from 14 500 to 13 000 yr b p there was a sudden decline in the values of callitris and a more gradual decline in chenopodiaceae and dodonaea the rise of ephemeral vegetation together with a fall in chenopodiaceae would indicate that winter precipitation had started to decline between 13 000 and 4500 yr b p chenopodiaceae and tubuliflorae ephemerals declined and gramineae rose to its highest values tribulus pollen a subtropical tropical taxon first appeared 13 000 yr b p overall plants from the summer rainfall zone became more prominent and taxa from the temperate south declined summer monsoon incursions apparently strengthened and temperature increased during this phase since 4500 yr b p both chenopodiaceae and tubuliflorae returned to high values whereas gramineae declined values of acacia and myrtaceous shrubs rose but those of casuarina declined and callitris remained extremely low these changes were accompanied by the onset of playa environments which have since persisted vegetation during this phase suggests that summer precipitation declined and summer monsoon incursions became rare during the late holocene

strain coupling between upper mantle and lower crust natural example from the běstvina granulite body bohemian massif strain patterns within mantle rocks and surrounding coarse grained felsic granulites from the kutna hora crystalline complex in the variscan bohemian massif have been studied in order to assess their strain coupling the studied rock association occurs within low strain domains surrounded by fine grained granulite and migmatite the doubrava peridotite contains closely spaced and steeply dipping layers of garnet clinopyroxenite which are parallel to the ne sw striking high temperature foliation in nearby granulites while the uhrov peridotite lacks such layering the spacice eclogite is not associated with peridotite and shows upright folds of alternating coarse and fine grained varieties bearing ne sw striking axial planes electron back scattered diffraction measurements revealed full strain coupling between clinopyroxenites and coarse grained granulites in the s1 fabric that is superposed on the s0 fabric preserved in peridotites the b type olivine lattice preferred orientation lpo characterizes the s0 fabric in peridotites and its reworking is strongly controlled by the presence of macroscopic clinopyroxenite layering the s1 in clinopyroxenites and coarse grained granulites is associated with the ls type clinopyroxene lpo and prism slip in quartz respectively while the s1 fabric in these rock types is accompanied invariably by a sub vertical stretching lineation the s1 fabric developed in reworked uhrov peridotite is associated with strongly planar axial 010 type of olivine lpo the peridotites with the s0 fabric are interpreted to be relicts of a fore arc mantle wedge hydrated to a various extent above the saxothuringian subduction zone the prograde metamorphism recorded in peridotites and eclogites occurred presumably during mantle wedge flow and was reaching uhp conditions strain coupling in the s1 fabric between clinopyroxenites and granulites at doubrava and upright folding of eclogites at spacice document a link between tectonic and magmatic processes during orogenic thickening coeval with intrusions of the arc related calcalkaline suites of the central bohemian plutonic complex c 360 345 ma juxtaposition of peridotites and granulites could be explained by a rheological heterogeneity connected to the development of clinopyroxenite layering in the upper mantle and a previously published model of a lithospheric scale transpressional arc system it invokes vertical shearing along ne sw trending sub vertical foliations in the upper mantle that could have led to an emplacement of mantle bodies into the granulitized orogenic root in the sub arc region clearly such a transpressional arc system could represent an important pathway for an emplacement of deep seated rocks in the orogenic lower crust

drainage and flooding in karst terranes flooding in karst terranes is a commonly occurring geo hazard it causes damage to property businesses and roadways it can lead to the formation of cover collapse sinkholes and groundwater contamination generally three types of flooding or their combinations are related to karst recharge related sinkhole flooding flow related flooding and discharge related flooding understanding of the type of flooding is essential for solving the flooding problem areas prone to karst flooding should be recognized and restrictions and laws on land use should be implemented runoff and erosion control plans should address the unique characteristics of karst features digging out clogged sinkholes creating retention basins or installing class v injection wells are possible solutions to improve drainage of storm water solutions to flooding problems in karst areas should also be coordinated with the water quality control to prevent groundwater contamination

garnet bearing ultramafic rocks from the erzgebirge and their relation to other settings in the bohemian massif garnet bearing ultramafic rocks gbu enclosed in high grade gneisses are known from several parts of the bohemian massif one of these is the high pressure hp unit 1 in the erzgebirge crystalline complex which is the subject of the present study hitherto two different models have been put forward to explain the stabilisation of garnet in mantle derived ultramafic rocks from the bohemian massif and their emplacement into the crust 1 garnetiferous assemblages were formed in the ultramafics before they came in contact with their crustal host rocks 2 garnet was formed in the ultramafics at the expense of spinel due to cooling caused by their tectonic emplacement in the crust the pt evolution revealed by the investigated gbu from the erzgebirge crystalline complex however requires a third model the reconstruction of the pt paths for the erzgebirge gbu is based on both conventional thermobarometry and phase relations thermodynamic calculations allowed the construction of a pt phase diagram for the system na2o cao mgo al2o3 sio2 h2o which is the first quantitative petrogenetic grid in this model system relevant to ultramafic hp rocks the grid shows the uni di and tri variant assemblages stable in peridotitic rocks at different pt conditions providing a tool to constrain pt paths from the succession of mineral assemblages observed in a rock the pt path obtained for the erzgebirge gbu suggests that the garnet bearing assemblages formed by hp metamorphism of spinel peridotite which was emplaced into the crust prior to or during the hp compressional stage this model is supported by peak pt conditions around 900 c and 30 35 kbar recorded by the ultramafic rocks which are very similar to those attained in the eclogites sensu stricto which occur in the same tectonic unit hp unit 1 and for which an in situ metamorphism has been inferred schmadicke et al 1992 on the other hand the other two high pressure units in the erzgebirge hp units 2 and 3 which also contain eclogites sensu stricto but lack peridotites record lower peak pt conditions of 650 750 c 24 26 kbar and 600 650 c 20 24 kbar respectively postulating an in situ hp metamorphism for the garnet peridotites as result of continental collision during the variscan orogeny a crustal thickness of 90 110 km would be required a comparison of the distribution of eclogites sensu stricto and mantle derived rocks from the bohemian massif together with their reported pt conditions reveals a correlation between peak pt conditions in eclogites sensu stricto and the prevailing assemblages in the ultramafic rocks in the same unit furthermore the erzgebirge crystalline complex and the snieznik complex on one hand as well as the granulitgebirge and the sowie gory on the other hand are thought to be genetically linked the garnet peridotites from the granulitgebirge the sowie gory and the gfohl unit seem to have experienced peak pt conditions not recorded by their country rocks with non eclogitic basic interlayers inferring a formation of hp assemblages in the ultramafics prior to their emplacement into the crust

thermobarometry diffusion modelling and cooling rates of crustal garnet peridotites two examples from the moldanubian zone of the bohemian massif abstract different origins for crustal garnet peridotites are illustrated by two variscan bodies in adjacent tectonically juxtaposed terranes in the moldanubicum of the bohemian massif eastern moravia the nove dvory garnet peridotite contains lenses of eclogite and is allochthonous and allofacial with respect to surrounding gfohl gneiss the mohelno spinel garnet peridotite is devoid of eclogite and has concordant contacts with surrounding felsic granulite the bulk of the mohelno body is spinel peridotite and garnet occurs only along its margins where it has formed at the expense of spinel thermobarometry of mineral cores from garnet bearing assemblages yields values for nove dvory from 1195 c 54 6 kbar to 970 c 41 8 kbar and for mohelno from 1265 c 27 9 kbar to 1070 c 23 4 kbar the compositional zoning profiles in garnets at both localities are matched closely by diffusion modelling in which bilinear cooling rates are utilized at nove dvory initial cooling rates of 50 200 c ma are followed by slower rates of 10 50 c ma in contrast at mohelno an extremely rapid initial cooling rate of 1 c year was followed by one of 500 c ma an idealized tectonic model is proposed for the emplacement of the mohelno peridotite to account for its cooling history the predicted garnet zoning profiles that result from conductive cooling agree closely with the observed zoning profiles both peridotites were derived from the upper mantle the nove dvory body was emplaced from a deep fault zone into the crust as garnet peridotite and the mohelno body was emplaced as a hot slab of spinel peridotite in which garnet formed only along contacts as the body cooled into the garnet stability field

on the equivocal fate of late pleistocene callitris vent cupressaceae woodlands in arid south australia fossil pollen assemblages suggest callitris cupressaceae dominated woodlands were prominent elements in landscapes near lake frome and lake eyre during latest pleistocene times callitris woodlands were present at lake eyre before 30 000 bp but became fragmented and disappeared in the lead up to the last glacial maximum callitris was again prominent from approximately 10 000 bp until about 5000 bp after which time it vanishes from the pollen record and presumably the region at lake frome callitris was abundant between 16 000 bp and 13 000 bp before declining to low modern levels from 11 000 bp at both sites the latest pleistocene or holocene decline in callitris occurrence and its eventual extinction in the vicinity of lake eyre broadly corresponds with archaeological indications of increasing human presence in the landscape in the absence of evidence of significant climatic changes at the times in question these observations lend tentative support to arguments that the composition and structure of modern zone vegetation has been significantly modified by aboriginal land management practices although the charcoal record is ambiguous fire is argued to be the principle agent of the changes wrought during human re colonisation of lands around lake frome and lake eyre

terrane character of the north east margin of the moldanubian zone the kutna hora crystalline complex bohemian massif three major allochthonous units have been distinguished on the north eastern border of the moldanubian zone which differ each from other in lithology and structural and metamorphic evolution their present day position displays significant metamorphic and structural inversion resulting from progressive nappe stacking during the variscan orogeny the uppermost gfohl unit consists of anatectic rocks containing high temperature high pressure relics i e granulites eclogites and garnet peridotites the rocks of the gfohl unit were strongly mylonized during uplift and later also extensively migmatized in the kyanite stability field the koui im nappe is built up by a sequence of fine grained leucocratic migmatites with preserved relics of a pre variscan deformation event this event was terminated by the intrusion of coarse grained porphyritic granites converted into augen orthogneisses by the variscan orogeny the lowermost micaschist zone was formed from a sequence of metapelites intercalated with diopsidic amphibolites

shear wave splitting in the appalachians and the pyrenees importance of the inherited tectonic fabric of the lithosphere splitting of teleseismic shear waves has been measured in the appalachians eastern usa and the pyrenees western europe using data recorded by permanent and portable stations from a comparison of the results it appears that an interpretation of the recorded seismic anisotropy in terms of geodynamics is not straightforward successive geodynamic events have generated structures that may have resulted in a similar pattern of mantle flow and that therefore may have contributed in the development of the recorded anisotropy combining geological and geophysical arguments it appears that the mantle anisotropy measured across the appalachians and the pyrenees may not be systematically appalachian or pyrenean in age but may be mainly due to a lithospheric structure formed during earlier major tectonic events i e the grenvillian and the hercynian orogenies respectively we suggest that during major episodes of continent assembly a pervasive tectonic fabric is developed in the lithospheric mantle in the subsequent evolution of the continent this fabric may induce a significant mechanical anisotropy that will drastically influence the mechanical behaviour of the iithosphere when submitted to new tectonic events

palaeo karst collapse pillars in northern china and their damage to the geological environments according to statistics there are a total of 39 sites of palaeo karst collapse pillars in northern china as well as 3 650 palaeo karst collapse pillars through an overall survey and analysis of the distribution regularities and formation mechanisms of palaeo karst collapse pillars in the northern coal mine regions this paper found that the rock formation structures geological structures karst characters underground hydrodynamic conditions of karst and neotectonic movement conditions are basic geological bases for the formation of karst collapse pillars and rule the distribution of them karst collapse pillars apparently have three south north regularities in terms of distribution and they have resulted in severe damages to geological resources and environment in their distribution areas mine water inrush causing and coal resources damage and influencing the impounding of reservoirs as well as the stability of dam sites based on the basic geological features of palaeo karst collapse pillars in northern china this paper also introduces the new methods of integrated prospecting of successive approximation to determine hydraulic conductivity of palaeo karst collapse pillars

eastern variscan fold belt paleomagnetic evidence for oroclinal bending the rhenohercynian zone of variscan europe trends from southern portugal around the ibero armorican arc into southern britain belgium northern germany and the moravo silesian zone of the east czech republic although the geodynamic evolution of the central and western segments of this arcuate belt is now fairly well understood the scenario for the more easterly parts remains enigmatic a paleomagnetic study of upper devonian rocks from the moravo silesian zone has been undertaken two ancient directions of magnetization have been identified the first the a magnetization is secondary in origin and relates to a remagnetization of permian carboniferous age the b magnetization passes the fold test is considered late devonian in age and agrees in terms of inclination to previously published paleomagnetic results from coeval rocks of the harz mountains and franconian forest central europe the declination however differs by about 90 restoring the moravo silesian zone to its original devonian orientation as defined by the new paleomagnetic data brings the structural trends of central and eastern europe into agreement because they were previously part of the same tectonostratigraphic unit as suggested by the stratigraphic record this implies that rotational oroclinal bending around the northern and eastern flanks of the bohemian massif occurred sometime between the late devonian and late carboniferous

upper mantle seismic anisotropy resulting from pressure induced slip transition in olivine seismic anisotropy in the oceanic lithosphere results from flow induced crystallographic preferred orientation of dry olivine during lithosphere creation recent experiments however showed that high water activity changes the flow mechanisms of olivine and hence the crystallographic preferred orientation better explaining the seismic anisotropy in the mantle wedge above subduction zones whether changes in the crystallographic preferred orientation of olivine are unique to the effects of water has become controversial and is critical to resolve here we report low stress high strain experiments on typical dry mantle rock at high pressures and temperatures showing that at 3 gpa pressure induces the same profound transition in olivine crystallographic preferred orientation that is produced by high water activity at lower pressure one important consequence for global tectonics is that alignment of fast seismic waves parallel to trenches beneath subducting slabs probably reflects entrainment of sub lithospheric mantle in the direction of subduction rather than trench parallel flow as interpreted at present from the large variety of crystallographic preferred orientations in olivine in both experiments and natural rocks we infer that in addition to the pressure induced changes in olivine slip systems implied here there are probably further changes in slip systems at higher pressure and temperature seismic anisotropy in earth s oceanic lithosphere and in the mantle wedge above subduction zones is associated with crystallographic preferred orientations of olivine experiments at high pressure and temperature suggest that a pressure of 3 gpa can induce the same changes in the crystal structure of olivine as high water activity at lower pressures

deformation induced clinopyroxene fabrics from eclogites abstract clinopyroxene omphacite microfabric studies in eclogites are useful in characterizing the deformation that has affected deeper parts of subduction zones we present the microfabrics and tem structures of four samples representative of the various deformation types known in eclogites the 001 axis tends to be parallel to the lineation while the 010 plane is close to the foliation but these general features undergo strong variations in relation to the shape fabric in strongly lineated samples 010 tends to be spread out in a great circle normal to the lineation whereas 001 is dispersed in the foliation in the case of strongly foliated samples the slip systems identified by tem are 001 100 001 110 and 1 2 110 110 operation of dislocation creep is testified by the presence of dislocations and dislocation walls but this process alone cannot explain all the observed features particularly some aspects of the crystallographic preferred orientation hence other deformation mechanisms must be involved these may be dynamic migration recrystallization by grain boundary migration as well as mass transfer processes this study illustrates that not every crystallographic mineral preferred orientation can be explained by dislocation glide and or twinning processes alone in addition it also demonstrates that eclogite microfabrics can be used to unravel deformation parameters in subduction and or collision zones

recrystallization and fabric development in plagioclase the microstructures and fabrics of naturally deformed intermediate composition plagioclase feldspars from the amphibolite granulitic gneisses from the lower crust have been studied special interest in the effects of dynamic recrystallization and deformation fabrics has been taken the plagioclase feldspars an40 50 have undergone extensive ductile deformation by intracrystalline slip and twinning they show strong crystallographic preferred orientation which was produced by dominant 010 001 slip dynamic recrystallization is indicated by fine grained new grains neoblasts interspersed with deformed relicts porphyroclasts the neoblasts have formed preferentially along grain boundaries kink band boundaries kbbs intracrystalline shear zones and around solid inclusions such as garnet and pyroxene optical microstructural evidence suggests that dynamic recrystallization occurred primarily by grain boundary migration with subsidiary subgrain rotation which appears to have occurred only at low st

does cation ordering in omphacite influence development of lattice preferred orientation three mantle eclogite xenoliths from the robert victor mine in south africa were studied the calculated pt conditions are ps4 5 gpa and t between 950 and 1145 8c the clinopyroxene has a jadeite component between 0 19 and 0 52 in situ at these compositions and temperatures clinopyroxene omphacite has the high temperature c2 c structure which has perfect cation disordering the lattice preferred orientation lpo of clinopyroxene in the samples of different microstructure and composition has been measured by ebsd the lpo for all three samples is characterized by a strong alignment of the 001 axes with the lineation typical of the l type or ls type patterns for omphacite these data disagree with a cation ordering model for dislocation slip which predicts a s type lpo pattern with the 001 axes forming a girdle in the foliation plane numerical simulation using the vpsc model has been undertaken to show the influence of the h110i 1 10 slip system on the lpo development in axially symmetric compression and extension and pure and simple shear the activity of the h110i 1 10 system should be very sensitive to changes in the cation ordering as the clinopyroxene goes towards the low temperature fully ordered p2 n structure increasing the critical resolved shear stress on this system from 1 to 10 resulted in a decrease of the slip activity of 80 but produced no significant changes to the lpo the most important slip systems for lpo development are 001 100 100 010 and 001 010 in all simulations the ls index is introduced to quantify the symmetry of omphacite lpo the index is based on the eigenvalues of the 010 and 001 pole figures and has a value of one for the end member l type zero for the end member s type and intermediate values for ls types the naturally deformed omphacite lpos have ls indexes of between 0 61 and 0 85 confirming they are ls types but closer to the l type end member in the vpsc models the s type end member develops in axially symmetric compression ls indexz0 whereas the l type end member develops in axially symmetric extension ls indexz1 in simple and pure shear the ls type fabric develops with ls index of between 0 55 and 0 60 the vpsc simulations show that the ls index is nearly constant with increasing strain for a constant macroscopic velocity gradient which prescribes the constant strain path we conclude that development of s and l type lpos in omphacite is controlled by the strain path and that the ls index is a useful quantitative indicator of fabric symmetry q 2005 elsevier ltd all rights reserved

the role of water in the deformation of dunite specimens of two natural dunites anita bay of 100 m grain size and aheirn of 900 m grain size have been deformed in experiments at temperatures between 1200 and 1400 c and constant strain rates between 10 4 and 10 6 s 1 in a gas medium deformation apparatus at 300 mpa confining pressure prior to these experiments the specimens were given a heat treatment in a controlled oxygen fugacity furnace at 1200 c for 60 hours to dehydrate the trace layer silicate minerals present and drive off adsorbed water the predried specimens are much stronger than specimens tested under wet conditions in an earlier study the predried specimens also do not show the apparent grain size dependence seen under wet conditions infrared absorption measurements on the present specimens and those of the earlier study indicate that for a given rock flow stress can be correlated with the intensity of a residual water related broad absorption the addition of water to a predried specimen results in both a mechanical reweakening and an intensifying of the broadband infrared component the weakening of the dunites under wet conditions is probably strongly influenced by the presence of small amounts of a water related species in the grain boundaries but intragranular weakening may also be contributing it is suggested that the concentration of the water related species in the grain boundaries is governed by its concentration in the small melt fraction present the amounts of water that have been found to be of importance for the strength of these dunites are of the order of 0 01 wt amounts much less than most estimates of the water content of the earth s undepleted upper mantle such water may have an important role in determining upper mantle flow behavior stress strain curves for all experiments are available with entire manuscript on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b84 008 2 50 payment must accompany order

the moldanubian zone in the french massif central vosges schwarzwald and bohemian massif revisited differences and similarities in order to portray the main differences and similarities between the northeastern variscan segments french massif central fmc vosges black forest and bohemian massif bm we review their crustal scale architectures the specific rock associations and lithotectonic sequences as well as the ages of the main magmatic and metamorphic events this review demonstrates significant differences between the moldanubian domains in thebmand the fmc on this basis we propose distinguishing between the eastern and western moldanubian zones while the vosges black forest mountains are an intermediate section between the bm and the fmc the observed differences are the result of first the presence in the french segment of an early large scale accretionary system prior to the main variscan collision and second the duration of saxothuringian armorican subduction which generated long lived magmatic arc and back arc systems in the bohemian segment while the magmatic activity in the fmc was comparably short lived

holocene climate change in arid australia from speleothem and alluvial records new high resolution mc icpms u th ages and c and o isotopic analyses from a holocene speleothem in arid south central australia provide evidence for increased effective precipitation ep relative to present at c 11 5 ka and c 8 5 ka peak moisture at 7 6 ka and onset of an arid climate similar to present by c 5 ka 18o and 13c time series data exhibit marked 1 contemporaneous excursions over base line values of 5 3 and 11 0 respectively suggesting pronounced moisture variability during the early middle holocene climatic optimum optically stimulated luminescence and 14c ages from nearby terraced aggradational alluvial deposits indicate a paucity of large floods in the late pleistocene and at least five large flood events in the last c 6 kyr interpreted to mark an increased frequency of extreme rainfall events in the middle holocene despite overall reduced ep increased ep in south central australia during the early to middle holocene resulted from 1 decreased el nino southern oscil