the kinematics of movements along the insubric line and the emplacement of the ivrea zone schmid sm zingg a and handy m 1987 the kinematics of movements along the insubric line and the emplacement of the ivrea zone in h j zwart m martens i van der molen c w passchier c spiers and r l m vissers editors tectonic and structural processes on a macro meso and micro scale tecta a hys 135 47 66 the insubric line west of locamo is characterized by a 1 km thick greenschist facies mylonite belt east of locamo these mylonites are overprinted by a discrete brittle fault the mylonites are derived from basement units of the central alps sesia zone and the southern alps ivrea zone as well as from the permo mesozoic cover of the southern alps canavese sense of shear criteria indicate that the mylonites accomm ated backt s g followed by dextral strike slip motion mylonitization during backtbrusting was synchronous with backfolding of the central alpine nappes under higher metamorphic conditions a horizontal temperature gradient resulted from the rapid juxtaposition of the warm central alpine block against the cold southern alpine block mylonites formed during the later dextral strike slip event are related to large transcurrent displacements in the central alps deduced from regional kinematic considerations thus both mylo t ation events are contempor eous with deformation to the north and south of the insubric line insubric phase extensively modifying the pre insubric crustal configuration of the alps the insubric phase post dates the bergell intrusion 30 m y the emplacement of the geophysical ivrea body is a combined effect of vertical uplift due to e w directed crustal thinning during the early jurassic and underplating by continental crust associated with late cretaceous compression a deep crustal normal fault pogallo line subsequently rotated during tertiary alpine orogenesis separates deeper parts of the southern alpine crust ivrea zone from intermediate crustal levels strona ceneri zone the rigid ivrea body localir ed large strains within the insubric mylonite belt and is responsible for the present curvature of the insubric line in uetion

river stage tomography a new approach for characterizing groundwater basins received 19 june 2008 revised 16 february 2009 accepted 12 march 2009 published 9 may 2009 1 data from tomographic surveys make an inverse problem better posed in comparison to the data from a single excitation source a tomographic survey provides different coverages and perspectives of subsurface heterogeneity nonfully redundant information of the subsurface fusion of these pieces of information expands and enhances the capability of a conventional survey provides cross validation of inverse solutions and constrains inherently ill posed field scale inverse problems basin scale tomography requires energy sources of great strengths spatially and temporally varying natural stimuli are ideal energy sources for this purpose in this study we explore the possibility of using river stage variations for basin scale subsurface tomographic surveys specifically we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of the river stage in a hypothetical groundwater basin we then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image subsurface heterogeneity of the basin results of the numerical exercises are encouraging and provide insights into the proposed river stage tomography using naturally recurrent stimuli such as river stage variations for characterizing groundwater basins could be the future of geohydrology however it calls for implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface

sediment discharges during storm flow from proximal urban and rural karst springs central kentucky usa summary since the mid 1990s various studies have addressed the timing of sediment transport to karst springs during storm flow or the composition and provenance of sediment discharged from springs however relatively few studies have focused on the flow thresholds at which sediment is mobilized or total sediment yields across various time scales we examined each of these topics for a mainly urban spring blue hole and a rural spring sp 2 in the inner bluegrass region of central kentucky usa suspended sediment consisted mostly of quartz silt and sand with lesser amounts of calcite and organic matter total suspended sediment tss values measured during storm flow were greater at sp 2 than at blue hole by aggregating data from four storms during 2 years we found that median suspended sediment size jumped as q exceeded 0 5 m 3 s for both springs at blue hole tss tended to vary with q and capacity approached 1 g l but no systematic relationship between tss and q was evident at sp 2 sediment fluxes from the blue hole basin were 2 orders of magnitude greater for storms in march 2002 and 2004 than september 2002 and 2003 in contrast sediment fluxes from the sp 2 basin were of similar magnitude in september 2003 and march 2004 the overall range of area normalized fluxes for both springs 9 16 10 3 4 45 10 2 kg ha h overlaps values reported for farm plots and a stream in the inner bluegrass region and for other spring basins in the eastern usa and western europe sediment compositions sizes and responses to storms in the basins may differ because of land use e g the extent of impervious cover in the blue hole basin basin size larger for blue hole conduit architecture which appears to be more complex in the blue hole basin and the impoundment of sp 2 which may have promoted decadal scale storage of sediment upgradient

reaction enhanced ductility the role of solid solid univariant reactions in deformation of the crust and mantle abstract in collision belts and subduction zones penetrative deformation of thrust sheets may be catalyzed by metamorphic reactions if the reactions have a significant effect on the mechanical properties of rocks reaction enhanced ductility may result if a reaction produces a significant decrease in grain size thus allowing the rock to deform superplastically the product grain size of a reaction is a function of the ratio of nucleation and growth rates this ratio varies along any pressure temperature time ptt path and only attains a significant value at a certain distance from an equilibrium boundary a comparison of rates of change of p and t along typical segments of ptt paths for crustal rocks leads to the conclusion that a high nucleation rate a small grain size and resulting superplastic deformation are more likely to be achieved when reaction boundaries are crossed during underthrusting rather than during the thermal readjustments of a perturbed geotherm following crustal thickening or during uplift an example of reaction enhanced ductility occurs in eclogite facies metagranitoids in the sesia lanzo zone western alps where medium grained plagioclase reacted to fine grained jadeite quartz during early alpine underthrusting microstructural evidence from shear zones shows that the jadeite quartz aggregates were highly ductile and it is inferred that the small grain size allowed superplastic deformation further evidence suggests that this process operated during regional deformation of metagranitoids rubie 1982 the reaction of olivine to spinel or the beta phase by metastable overstepping of the two phase stability fields in a subducting plate ringwood 1975 may result in fine grained products and thus may be analogous to the albite jadeite quartz reaction the consequent decrease in effective viscosity is likely to have important consequences for plate dynamics at and below the depths of major phase transitions

some geophysical implications of the deformation and metamorphism of the ivrea zone northern italy abstract the ivrea zone is commonly cited as an upthrust and steepened section through the lower continental crust being contiguous via the geophysical ivrea body with the present day lower crust beneath the po basin the rocks presently exposed were buried to lower crustal depths through the variscan orogeny and were gradually exhumed to mid crustal depths through permian and early mesozoic times as a result of crustal extension they were emplaced into their present position during the alpine orogeny an important time marker in the deep crustal evolution of the rocks was the development of a coarse grained equigranular texture following the attainment of the amphibolite and granulite facies metamorphic peak this effectively separates earlier pervasive synmetamorphic deformation from later highly localized plastic deformation associated with crustal extension and progressive cooling the geophysical properties of the section would have been markedly different during each of these two stages of development in the later stage the granulite facies rocks remained relatively dry and when buried would have been characterized by the high seismic velocities that they display under pressure in the laboratory during the prograde orogenic part of the history seismic velocities would have been substantially depressed through the effects of elevated pore water pressure particularly at high temperatures

chemical and isotopic evidence for hydrogeochemical processes occurring in the lincolnshire limestone over 150 groundwater samples from the lincolnshire limestone have been analysed for ph major ions and 13c ratios where possible field eh and iodide concentrations were measured and methane concentrations were determined for 12 samples stable isotope ratios were determined for soil and rock carbonate samples a system of zonation allows the division of hydrogeochemical processes occurring in the aquifer the use of hydrochemical and isotope data in modelling exercises enables the re evaluation and possible enhancement of the understanding of hydrogeochemical processes the carbonate chemistry of outcrop groundwaters is explained by calcite saturation being achieved under open system conditions in the soil zone 13c ratios in the range 15 99 to 10 57 may be generated from a stoichiometric reaction with possible additional partial and or simultaneous exchange with soil co2 or carbonate the isotopic composition of soil carbonate shows the effects of precipitation from soil waters the incongruent dissolution of primary depositional limestone carbonate results in increasing magnesium and strontium concentrations and increasing 13c ratios for the groundwaters with flow down the hydraulic gradient as a result of incongruent dissolution secondary calcite may be precipitated onto fissure surfaces significant nitrate and sulphate reduction in non saline groundwaters is not supported by the results of hydrochemical and isotope modelling exercises however sulphate reduction and methane fermentation may be affecting the isotopic and chemical compositions of saline groundwaters sodium calcium ion exchange leads to limited calcite dissolution deep in the aquifer but the evolution of these groundwaters is confused by the uncertain effects of oxidation of organic carbon and mixing with a saline end member solution

mechanisms of shear localization in the continental lithosphere inference from the deformation microstructures of peridotites from the ivrea zone northwestern italy the ultramafic massif of balmuccia northwestern italy shows a variety of deformation fabrics including some localized shear zones that resulted in nearly complete melting pseudotachylyte a series of peridotite specimens were collected near one of the pseudotachylyte fault veins to investigate the mechanisms of shear localization the microstructural analyses show at least three deformation stages the first stage i is nearly homogeneous deformation at low stress 3 mpa and high temperature 1300 1500 k followed by localized deformation stage ii at a higher stress 60 mpa and moderate temperature 1000 1150 k and finally semi brittle deformation stage iii at a very high stress 400 mpa that resulted in the formation of pseudotachylyte the stage ii deformation resulted in relatively small strains in most areas but significant localized deformation leading to dynamic recrystallization occurred the degree of which increases systematically toward the fault zone based on this observation together with the observation that the brittle deformation post dated dynamic recrystallization we conclude that the shear localization in this locality occurred as a result of ductile deformation rather than brittle deformation various mechanisms of shear localization in the ductile regime are examined and we conclude that the grain size reduction due to dynamic recrystallization at relatively high stresses and moderate temperatures is a probable mechanism of shear localization the intermediate regime between dislocation and diffusion creep where rheology is grain size sensitive yet continuous recrystallization occurs due to dislocation creep is suggested to play an important role in shear localization in the upper mantle the conditions of shear localization due to this mechanism are examined based on the laboratory data on creep and dynamic recrystallization it is shown that shear localization occurs at relatively low temperatures and or high stresses localized deformation in the continental lithosphere will occur well below the brittle ductile transition 10 km depth down to 40 80 km depth depending upon the geothermal gradient and water fugacity

geochemistry of surface and ground water in guiyang china water rock interaction and pollution in a karst hydrological system the chemical compositions of the surface ground water of guiyang the capital city of guizhou province china are dominated by ca2 mg2 hco3 andso42 which have been derived largely from chemical weathering of carbonate rocks limestone and dolomite the production of so42 has multiple origins mainly from dissolution of sulfate evaporites oxidation of sulfide minerals and organic s in the strata and anthropogenic sources most ground water is exposed to soil co2 and therefore the h2co3 which attacks minerals contains much soil c in addition the h2so4 produced as a result of the oxidation of sulfides in s rich coal seams and or organic s is believed to be associated with the chemical weathering of rocks the major anthropogenic components in the surface and ground water include k na cl so42 andno3 with cl and no3 being the main contributors to ground water pollution in guiyang and its adjacent areas the seasonal variations in concentrations of anthropogenic components demonstrate that the karst ground water system is liable to pollution by human activities the higher content of no3 in ground water compared to surface water during the summer and winter seasons indicates that the karstic ground water system is not capable of denitrification and therefore does not easily recover once contaminated with nitrates

deformation mechanisms and phase distribution in mafic high temperature mylonites from the jotun nappe southern norway abstract shear zones and mylonites in anorthositic to gabbroic rocks from the jotun nappe in southern norway have been studied as an example of high temperature deformation in polyphase rocks the deformation has taken place at approximately 700 c and maximum confining pressures of 900 mpa the constituent phases amphibole pyroxene and plagioclase have recrystallized synkinematically reducing the grain size of the rock to about 20 to 70 m two different microstructures develop depending on the recrystallization mechanism dynamic recrystallization of plagioclase hornblende and pyroxenes produces monophase layers which extend from porphyroclasts heterogeneous nucleation of phases due to chemical disequilibrium produces phase mixtures of hornblende and plagioclase or clinopyroxene and plagioclase these phase mixtures extend from hornblende or clinopyroxene porphyroclasts the product of the deformation and simultaneous recrystallization is a well laminated microstructure of some monophase hornblende pyroxene and plagioclase layers which alternate with abundant layers of phase mixtures different deformation mechanisms operate in the different types of microstructures dislocation substructures dynamic recrystallization microstructures and a crystallographic preferred orientation measured by ji and mainprice 1988 on samples of the same shear zone indicate crystal plastic deformation in monophase plagioclase layers dynamic recrystallization in monophase hornblende layers indicates also crystal plastic deformation the phase distribution of plagioclase and hornblende grain shapes and lower dislocation densities in the phase mixtures suggest that the deformation mechanism is not crystal plasticity but rather a granular flow grain boundary sliding probably accommodated by diffusional mass transfer in the plagioclase hornblende mixtures the phases show an anticlustered non random distribution grain boundary sliding may contribute to phase mixing but cannot be the main reason for the anticlustering of phases and the complete phase mixing directly at the boundaries of the porphyroclasts the reason for the anticlustered distribution is not clear but could be explained by preferential heterogeneous nucleation of hornblende at plagioclase grain boundaries

isotope hydrology and residence times of the unimpounded meramec river basin missouri abstract strong isotopic forcing of hydrologic systems in eastern missouri caused by the large seasonal variations in the 18 o values of meteoric precipitation can be used to determine numerous characteristics of hydrologic systems including the residence time of the water the normal annual average 18 o value of meteoric precipitation in this region is about 6 9 but during the period june 1997 may 1998 which incorporates an el nino event the average 18 o of precipitation was 9 4 monthly averages are highly variable ranging from 2 8 in august 1996 to 15 1 in january 1998 and define a cycloid like annual pattern this meteoric forcing gives rise to similar patterns of isotopic variation in springs and rivers but with greatly reduced amplitudes thus the 18 o variations for the precipitation have an amplitude exceeding 10 yet the annual amplitudes of the variations in the unimpounded meramec and big rivers are only about 3 and the amplitudes of several karst springs including the first magnitude maramec spring are even smaller at about 1 most of the isotopic variation in streamflow can be explained by a simple exponential weighting of the preexisting rainfall events such that the most recent precipitation more greatly influences the flow than earlier precipitation events according to our formulation 18 o flow i p i e t i p i e t i where i and pi are the 18 o value and amount for a given rain event ti is the time interval between the storm and the stream or spring sample and is the residence time for the meramec and big rivers takes on a value of close to 100 days whereas it is 1 2 years for several springs smaller contributions with on the order of 1 10 days are superimposed representing the latest storm events this method has a significant advantage over the standard mixing arguments for overland flow and baseflow contributions to hydrologic systems in that it not only demonstrates the dominant contributions of pre event water in the systems but it implicitly accounts for the variability of baseflow and also provides the approximate time scale for subsurface mixing

the role of transiently fine grained reaction products in syntectonic metamorphism natural and experimental examples it is proposed that one of the most important mechanisms of interrelationship between deformation and metamorphism is the facilitation of one of several grain size sensitive deformation mechanisms resulting from the formation of fine grained products of a metamorphic reaction during prograde metamorphism such effects are likely to be transient because grain coarsening and textural equilibration are likely in response to rising temperature conditions thus deformation mechanisms are often difficult to infer from such naturally deformed rocks in localized shear zones exhibiting retrogressive metamorphism evidence of enhanced deformability by such mechanisms is most likely to be preserved because cooling conditions inhibit grain growth and both deformed and undeformed rocks are likely to be preserved an experimental study has been made of the effects of deformation on serpentinite under conditions of progressive dehydration but with controlled pore pressure a marked weakening near linear viscous rheol

study of the crystalline crust from a two ship normal incidence and wide angle experiment abstract in 1992 british institutions reflection profiling syndicate conducted a two ship coincident near vertical and wide angle experiment to determine the detailed velocity structure of the continental crust in the central north sea the results show a near surface high velocity gradient layer p wave velocity reaches 6 0 km s at 5 km depth a high velocity zone 6 5 km s at 10 15 km depth a 19 km thick upper crust and the moho at a depth of 32 34 km along the 135 km profile the travel time and amplitude of wide angle data require the presence of a dipping reflector originating at the moho 32 km depth and continuing down to 38 km in the mantle the velocity between 19 and 24 km depth is slightly lower 6 1 km s than that in the upper crust the waveform modelling of the combined normal incidence and wide angle data requires a number of alternating high and low velocity layers in the lower crust 19 33 km the velocity contrast in the lower part of the lower crust 29 33 km is large of the order of 1 km s 6 5 7 5 km s there are a few alternating high 8 2 km s and low velocity 7 5 km s layers in the upper part of the mantle 33 36 km the high velocity 6 5 km s in the upper crust may be due to a high grade of metamorphism and it may have been formed during the subduction process the low velocity 6 1 km s in the upper part of the lower crust might be caused by the presence of meta sediments the large velocity variations 6 5 7 5 km s in the lower part of the lower crust suggest the presence of mafic materials and may result from under plating of mafic materials from the mantle the fractionation of melt can also produce the layering in the upper part of the mantle that is observed from seismic analyses

ivrea seismic array a study of continental crust and upper mantle summary a seismic array study of the continental crust and upper mantle in the ivrea yerbano and strona ceneri zones northwestern italy is presented a short period network is used to define crustal p and s wave velocity models from earthquakes the analysis of the seismic refraction profile lond of the crop ecors project provided independent information and control on the array data interpretation apparent velocity measurements from both local and regional earthquakes and time term analysis are used to estimate the velocity in the lower crust and in the upper mantle the geometry of the upper lower crust and moho boundaries is determined from the station delay times we have obtained a three layer crustal seismic model the p wave velocity in the upper crust lower crust and upper mantle is 6 1 0 2 km s 1 6 5 0 3 km s 1 and 7 8 0 3 km s 1 respectively pronounced low velocity zones in the upper and lower crust are not observed a clear change in the velocity structure between the upper and lower crust is documented constraining the petrological interpretation of the ivrea type reflective lower continental crust derived from small scale petrophysical data moreover we found a vp vs ratio of 1 69 0 04 for the upper crust and 1 82 0 08 for the lower crust and upper mantle this is consistent with the structural and petrophysical differences between a compositionally uniform and seismically transparent upper crust and a layered and reflective lower crust the thickness of the lower crust ranges from about 8 km in front of the ivrea body arvo arvonio station in the northern part of the array to a maximum of about 15 km in the southern part of the array the lower crust reaches a minimum depth of 5 km below the prov provola station

regional scale transport in a karst aquifer 1 component separation of spring flow hydrographs large fluctuations in ca and mg concentrations occur in the discharge of karst springs in southeastern missouri after major storm events rapid flow of relatively dilute storm derived water through solution conduits in the aquifer causes the fluctuations in chemistry a cation balance for the discharge of one spring indicates that about 25 of the total spring flow is storm derived water these storm derived contributions reach a maximum during the recession of storm responses in the spring flow hydrograph at the peak of the responses spring flow is composed primarily of prestorm water that has been displaced in the conduit system by the storm derived water the observed chemical fluctuations and hydrograph components differ from those observed in streamflow where the time of the maximum dilution usually coincides with the time of peak discharge

the seismic reflection character of the continental mohorovicic discontinuity the continental mohorovicic discontinuity is most often interpreted as a step function velocity boundary however on deep crustal seismic reflection profiles reflections at depths where refraction data places the moho have laminated character and are laterally discontinuous these observations on continental reflection data point to a model of the moho that has thin layered rather than block structure previous workers who have synthetically generated seismic responses from various crust mantle boundary models have shown that thin layered models of alternating high and low velocity generate responses that best emulate observed moho arrivals geologic interpretations of the thin layering include relatively undeformed metasediments cumulate layering tectonic banding and lenses of partial melt to obtain more direct geologic evidence a synthetic seismogram is generated from geologic cross sections of the ivrea verbano zone an exposed section through the lower crust and upper mantle the synthetic shows laminations similar to those observed on reflection data without more direct evidence no single geologic interpretation of the moho is reasonable indeed the moho may be a laterally variable boundary its composition and structure dependent upon the geologic history of the overlying crust

the effect of pre tectonic reaction and annealing extent on behaviour during subsequent deformation insights from paired shear zones in the lower crust of fiordland new zealand granulite facies pargasite orthogneiss is partially to completely reacted to garnet granulite either side of narrow 20 mm felsic dykes in fiordland new zealand forming 10 80 mm wide garnet reaction zones the metamorphic reaction changed the abundance of minerals and their shape and grain size distribution the extent of reaction and annealing temperature related coarsening and nucleation is greatest close to the dykes whereas further away the reaction is incomplete as a consequence grain size and the abundance of garnet decreases away from the felsic dykes over a few centimetres the aspect ratios of clusters of s1 pyroxene and pargasite in the orthogneiss which are variably reacted to post s1 garnet decrease from high in the host to near equidimensional close to the dyke post reaction deformation localized in the fine grained partially reacted areas this produced a pattern of paired shear zones located at the outer parts of the garnet reaction zone our study shows that grain size sensitive deformation occurs where the grain size is sufficiently reduced by metamorphic reaction the weakening of the rock due to the change in grain size distribution outweighs the addition of nominally stronger garnet to the assemblage

coincident seismic reflection refraction studies of the continental lithosphere a global review nearly 50 coincident seismic reflection refraction studies to depths of at least the moho provide an improved understanding of the continental lithosphere some conclusions include the following 1 a transparent upper crust a common observation on vertical reflection profiles cannot generally be correlated with velocity gradients or low velocity zones rather a commonly transparent upper crust may be explained by short wavelength steeply dipping features in the brittle upper crust and to a lesser degree by signal contamination from source generated noise 2 the reflective lower crust in extensional terranes appears to be characterized by a high average seismic velocity 6 6 7 3 km s and to consist of laminated high and low velocity layers with typical thicknesses of 100 200 m 3 landward dipping reflectors observed in the middle to lower crusts of convergent zones have been identified as paired high and low velocity slabs which represent oceanic crust and mantle accreted via underplating to the continental margin 4 the crust mantle boundary may differ sufficiently when imaged with vertical incidence and wide angle data to justify the retention for the present of the concept of separate reflection and refraction mohos while there is good evidence that these features are coincident within measurement uncertainties in most regions recently recorded data from the basin and range admit the possibility for noncoincidence in that area 5 upper mantle reflections which cannot be migrated into the lower crust remain rare despite isolated unequivocal examples thus the upper mantle appears to be relatively homogeneous at seismic reflection wavelengths and to lack the laminations inferred for the lower crust the wide angle method will likely provide the most reliable information on the velocity structure and physical state of this portion of the lithosphere for some years to come 6 there appear to be clear and consistent basic differences between convergent and extensional terranes which have been identified from coincident experiments these differences may be sufficiently universal to infer the tectonic history of poorly exposed terranes 7 no truly three dimensional coincident experiment i e including three dimensional migration has been conducted but some three dimensional data have been collected using both methods measurements of attenuation poisson s ratio and anisotropy within the crust using coincident data sets remain frontiers

a model of velocity structure beneath calabria southern italy based on laboratory data abstract laboratory velocity measurements of representative rock samples from across a nearly complete crustal section from the serre mountains of southern calabria have been carried out as an aid to interpreting in situ seismic velocity data the section is composed of interlayered acidic mafic and pelitic rocks metamorphosed to granulite and amphibolite facies conditions in addition a suite of post tectonic granitoids intrudes the section the experimental data include the measurement of compressional wave vp and shear wave vs velocities at confining pressure in conjunction with structural and stratigraphic field data the experimentally determined data are used to construct a seismic velocity model for the crust beneath calabria in the upper crustal levels vp and vs vary in different manners below the uppermost amphibolite facies gneisses a weak velocity inversion of vp is associated with the post tectonic granites at the granite granodiorite and the tonalite dioritic gneiss boundary vp increases in steps of about 200 and 300 m s respectively in contrast vs remains constant or even decreases slightly through this same sequence of rocks this contrasting behaviour is primarily related to the quartz feldspar ratio in the rocks the most pronounced velocity jump occurs at the top of the granulite facies metapelite unit here both vp and vs increase markedly due to mineralogic changes that accompany increasing metamorphic grade and the greater abundance of mafic and garnet bearing restites of partially melted pelite the mafic rocks of the lowermost crustal layer have p and s wave velocities that are significantly lower than those in the overlying metapelites the variation of poisson s ratio with depth suggests that this parameter which is a combination of vp and vs is more sensitive to lithology than the p and s wave velocities alone in rock units of upper and mid crustal levels with average p wave velocities

chemical similarities among physically distinct spring types in a karst terrain abstract in karst regions where correlations between physical characteristics of springs and temporal variations in spring water chemistry have been found spring water chemistry has been used to infer physical attributes of karst systems possible correlations between chemical and physical characteristics of springs were tested in the inner bluegrass karst region of central kentucky where previous dye tracing studies have identified two physically distinct spring types local high level springs discharging from shallow flow paths and major low level springs discharging from a deep integrated conduit system representative high level and major springs were sampled over a 16 month period and analyzed for major dissolved components both spring types showed similar variations in temperature calcium magnesium bicarbonate and hardness no systematic differences in ionic concentrations or in saturation indices with respect to calcite and dolomite were apparent between the two spring types chemical similarities between high level and major springs during low flow are attributed to recharge of major springs by percolation and by high level springs and to the occurrence of most chemical reactions near the recharge zone rather than in the deep conduit system during high discharge however most recharge to the major springs is surface runoff which produces low ionic concentrations similarly low ionic concentrations in the high level springs are thought to result from rapid flow through the soil rock zone and short flow distances these relationships indicate that spring water chemistry is not only a function of conduit size but also an indicator of recharge type and amount and flow path length differing flow path lengths to major and high level springs counteract the effect of varying conduit size between the two spring types and result in similar ionic concentrations these data indicate that spring water chemistry cannot be used to predict physical characteristics of karst aquifers in the inner bluegrass region the physical and chemical attributes of springs in the inner bluegrass were compared to those of springs in the nittany valley of pennsylvania a reported high correlation between physical and chemical characteristics of springs in the pennsylvania karst system reflects geological and structural controls not present in the inner bluegrass region

structural geometry lower crustal magmatic underplating and lithospheric stretching in the ivrea verbano zone northern italy abstract the ivrea verbano zone is believed to represent an up ended cross section through the lower continental crust as it existed at the end of the hercynian orogeny in the southern alps structurally oriented geological mapping has been carried out in the central and northern parts of the ivrea verbano zone a region some 30 km along strike the geology of the southern half of the zone is dominated by a large basic ultrabasic complex the mafic formation which is in contact with a strongly banded metasedimentary metabasic sequence to the north particular attention was paid to a the structural relationship between the rocks of the mafic formation and their envelope of high grade metasedimentary and metabasic rocks b the geometrical configuration throughout the ivrea verbano zone of high temperature shear zones which accommodated post hercynian crustal extension and c the geometry of late low temperature faulting the effects of which have been removed in order to produce a restoration of the structure as it existed during the post hercynian extensional phase the intrusion of large volumes of basic magma ca 50 of the outcrop area to form the rocks of the mafic formation appears to be coeval with the onset of extension ca 280 ma the main basic body has a laccolithic form which was originally more than 10 km thick overfolding developed at the northern margin of the laccolith and is interpreted in terms of the gravitational collapse of the hot immediately subsolidus or partially molten body incorporating its envelope of hot metasediments into a large originally recumbent fold a geometrical association with a high temperature low angle fault zone suggests that faulting was subsequently localized by the several km of uplift associated with the laccolithic intrusion the ivrea verbano zone may therefore demonstrate at least one particular geometry of lower crustal magmatic underplating which may aid in the interpretation of present day deep seismic profiles it also demonstrates the geometry of a network of conjugate high temperature low angle shear zones in a well layered lower crustal section

changes in sources and storage in a karst aquifer during a transition from drought to wet conditions summary understanding the sources and processes that control groundwater compositions and the timing and magnitude of groundwater vulnerability to potential surface water contamination under varying meteorologic conditions is critical to informing groundwater protection policies and practices this is especially true in karst terrains where infiltrating surface water can rapidly affect groundwater quality we analyzed the evolution of groundwater compositions major ions and sr isotopes during the transition from extreme drought to wet conditions and used inverse geochemical modeling phreeqc to constrain controls on groundwater compositions during this evolution spring water and groundwater from two wells dominantly receiving diffuse and conduit flow termed diffuse site and conduit site respectively in the barton springs segment of the edwards aquifer central texas usa and surface water from losing streams that recharge the aquifer were sampled every 3 4 weeks during november 2008 march 2010 during this period water compositions at the spring and conduit sites changed rapidly but there was no change at the diffuse site illustrating the dual nature i e diffuse vs conduit of flow in this karst system geochemical modeling demonstrated that within a month of the onset of wet conditions the majority of spring water and groundwater at the conduit site was composed of surface water providing quantitative information on the timing and magnitude of the vulnerability of groundwater to potential surface water contamination the temporal pattern of increasing spring discharge and changing pattern of covariation between spring discharge and surface water steam recharge indicates that that there were two modes of aquifer response one with a small amount of storage and a second that accommodates more storage

rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock mechanics based yield criteria for the inelastic deformations at the top and base at mid plate depths stresses are likely to be supported elastically because bending strains and elastic stresses are low the collisional tectonic regime however is far more complex because very large permanent strains are sustained at mid plate depths and this requires us to include the broad transition between brittle and ductile flow moreover important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid plate depths two specific contributions of laboratory rock rheology research are considered in this paper first the high temperature steady state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere the thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm tc above which at geologic strain rates the high temperature ductile strength falls below some arbitrary strength isobar e g 100 mpa for olivine tc is about 700 800 c but for other crustal silicates tc may be as low as 400 600 c suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the moho as suggested by a number of workers on independent grounds put another way the moho is a rheological discontinuity a second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant strain rate tests or as an accelerating creep rate stage at constant differential stress a number of physical mechanisms have been identified that may be responsible for ductile faulting including the onset of dynamic recrystallization phase changes hydrothermal alteration and hydrolytic weakening microscopic evidence for these processes as well as larger scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere

climate influence on geochemistry parameters of waters from santana perolas cave system brazil abstract a four year study of water geochemistry and hydrology was performed in a relatively deep cave system overlying bedrock thickness varies from 100 to 300 m as part of two monitoring programs from june 1990 to february 1992 and from march 2000 to march 2002 the ph saturation index for calcite ca and so 4 concentrations and elemental ratios of mg ca and sr ca were measured in surface well and drip waters throughout the system despite local hydrological and geological differences among sampling sites the monitoring revealed significant synchronous intersite variations in these parameters that are related to seasonal changes in rainfall recharge suggesting that element ratios of speleothems formed in deep caves are capable of recording short term climate variations groundwater residence time appears to be the main factor affecting the water composition in the epikarst epikarstic waters are always undersaturated with respect to calcite but both saturation index s i and dissolved solids content increase substantially during drier periods because of longer residence times and longer interaction between meteoric water and limestone by contrast results from cave drips and rimstone pools indicate constant supersaturation for calcite and demonstrate that a major control on trace element ratios of waters in the deep vadose zone is the degree of prior calcite precipitation this mechanism is more effective during drier periods when higher mg ca and sr ca values are observed in all drip and pool sites however variations do occur independently of the general trend of drip discharge which suggest non linear features in cave seepage water geochemistry in addition synchronous variations in so 4 and cl concentration indicate high connectivity between different water flow pathways characterized by similar response to interseasonal changes in vadose water level fluctuations in trace element ratios of cave streams appear to reflect increased contribution of waters flushed from the vadose fissure aquifer during very wet periods by a piston flow mechanism flushing episodes are also responsible for maintaining more positive saturation indices in streams even during periods of high river discharge our results suggest that trace elements are a potential proxy for past rainfall changes but they also reveal different scenarios for interpreting trace elements ratios of speleothems and freshwater tufa deposited in a deep cave systems located in tropical humid areas

petrogenesis and tectonic significance of amphibolites interlayered with metasedimentary gneisses in the ivrea zone southern alps northwest italy abstract amphibolites occurring as elongate lenses and boudins within the metasedimentary kinzigite formation of the ivrea zone are all of igneous parentage a detailed study of their trace element characteristics shows that they can be divided into two groups type 1 amphibolites occur as layers up to 100 m thick and have trace element distributions showing depletion in incompatible elements typical of normal n type mid ocean ridge basalts type 2 amphibolites occur as thinner layers and boudins and have higher levels of the more incompatible elements similar to transitional or enriched e type ocean basalts although metamorphism appears to have resulted in loss of sio 2 and variable enrichment in na k rb ba sr and locally ca the less mobile elements including the rare earth elements have preserved the primary basaltic geochemical characteristics the tectonic model which best explains the assemblage of slivers of morb like amphibolites within extremely highly deformed semi pelitic metasediments is that of an accretionary sedimentary wedge formed at a palaeozoic subduction zone

variation in amphibole and plagioclase composition with deformation investigation of the mineral chemistry of a shear zone in an amphibolite facies metagabbro has shown that the composition of the amphibole and plagioclase varies with deformation chemical analyses of the rocks indicate that the shear zone approximates an isochemical system the amphibole varies progressively from an initial magnesio hornblende to a ferroan pargasitic hornblende in the shear zone alkalies ti and fe2 fe2 mg increasing while the plagioclase becomes more anorthitic varying from labradorite to bytownite these changes in composition of amphibole and plagioclase from metabasic rocks are normally associated with increasing temperature in prograde regional metamorphic terrains such chemical variations observed in localized shear zones would suggest that shearing stress in regional metamorphism may play an important role in producing the documented discrepancies in amphibole chemistry between different metamorphic belts

a view toward the future of subsurface characterization cat scanning groundwater basins 1 in this opinion paper we contend that high resolution characterization monitoring and prediction are the key elements to advancing and reducing uncertainty in our understanding and prediction of subsurface processes at basin scales first we advocate that recently developed tomographic surveying is an effective and high resolution approach for characterizing the field scale subsurface fusion of different types of tomographic surveys further enhances the characterization a basin is an appropriate scale for many water resources management purposes we thereby propose the expansion of the tomographic surveying and data fusion concept to basin scale characterization in order to facilitate basin scale tomographic surveys different types of passive basin scale cat scan technologies are suggested that exploit recurrent natural stimuli e g lightning earthquakes storm events barometric variations river stage variations etc as sources of excitations along with implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface this vision for basin scale subsurface characterization faces many significant technological challenges and requires interdisciplinary collaborations e g surface and subsurface hydrology geophysics geology geochemistry information and sensor technology applied mathematics atmospheric science etc we nevertheless contend that this should be a future direction for subsurface science research

pogallo line south alps northern italy an intermediate crystal level low angle normal fault the pogallo line is a major crustal shear zone in the crystalline south alps of northern italy which separates middle amphibolite granulite facies rocks of the ivrea zone from lower middle amphibolite facies rocks of the strona ceneri zone u pb rb sr and k ar whole rock and mineral ages for samples from this region indicate that the two zones pursued different time temperature paths after caledonian peak metamorphism cooling curves for the two terrains finally converge in the late triassic early jurassic a time of large scale crustal extension in the south alps that anticipated the opening of the western tethys we suggest that the pogallo line may represent a low angle normal fault that developed at intermediate crustal levels during this period of extension and attained its present subvertical orientation during alpine deformation

experimental sytectonic dehydration of serpentinite under conditions of controlled pore water pressure we have studied the mechanical behavior of serpentinite under conditions favouring dehydration to olivine talc water at temperatures ranging between 300 and 600 and at total pressures from 100 to 300 mpa constant stress stress relaxation and constant displacement rate testing techniques permitted a wide range of deformation rates and paths to be accessed effective confining pressure was held constant during the dehydration process by means of a controlled pore water pressure system stress supported by the samples was almost independent of deformation rate at temperatures below those required for the onset of the breakdown reaction at 500 and 600 c however the strength was linearly dependent on the inverse of the deformation rate and independent of effective confining pressure over the range investigated microstructural studies revealed that the weakening was associated with sliding in narrow shear zones containing ultrafine grained 0 1 m olivine produced in the breakdown reaction the enhanced deformability is interpreted in terms of flow of the olivine in these shear zones by diffusion accommodated grain boundary sliding these experimental results suggest that metamorphic transformations affect the deformability of rocks and demonstrate enhancement of deformability through the transient existence of fine grained reaction products the results may also be applicable to the mechanics of deformation processes in oceanic transform faults and give some indication of the degree of weakening that might be expected from grain size reduction by dynamic recrystallization in plastically deforming rocks

deep crustal extensional faulting in the ivrea zone of northern italy abstract the ivrea zone in northern italy consists of amphibolite and granulite facies metasedimentary metabasic and ultrabasic rocks and is thought to represent a section through the deep continental crust detailed mapping of the high grade part of this zone has revealed a series of high temperature shear zones which after the effects of later low temperature faulting and folding have been removed appears to accommodate extension of the sequence the shear zones formed at temperatures similar to those at which thermal equilibration occurred in the host rocks and locally show evidence for development under prograde conditions these observations fit well with thermal effects calculated from a simple heat flow model for extensional faulting in this model the effects of shear heating and displacement of cool hanging wall rocks against hotter footwall rocks are calculated these observations indicate that faulting as a mode of failure may be important during extension of the lower continental crust especially when basic rocks are the dominant components of the rock pile a restored section through the extended lower crust as observed in the ivrea zone is presented and the extent to which the features observed are able to explain seismic reflectivity of the lower crust is discussed

eclogite as a seismic marker in subduction channels seismic velocities anisotropy and petrofabric of cabo ortegal eclogite tectonites spain high pressure sheath like fold nappes made of normal mid ocean ridge basalt n morb eclogites high pressure volcanic arc granulites arc root lithospheric mantle peridotites and shallow crustal volcanosedimentary gneisses were amalgamated at deep realms of an eohercynian orogenic channel and currently crop out in the cabo ortegal complex compressional seismic wave velocity measurements determined in eclogite at confining pressures of 600 mpa range from 8 4 to 7 3 km s whereas anisotropy varies between 0 7 and 3 2 shear wave velocities range from 4 8 to 4 2 km s and the respective anisotropies vary between 0 1 and 3 4 the poisson9s ratios are low 0 25 0 265 independent of the degree of retrogression or deformation seismic velocities and anisotropy are related to the fabric of omphacite and calculated eclogite anisotropy is not symmetrical with respect to the tectonic fabrics calculated seismic reflection coefficients induced by lithological structural and rock petrofabric variations of eclogites show that these can be identified as reflectors imprinting a particular penetrative and dipping fabric to discrete seismic profile segments of paleosubduction settings

hydrodynamical changes and their consequences on groundwater hydrochemistry induced by three decades of intense exploitation in a mediterranean karst system the lez karst spring located in the mediterranean basin southern france supplies drinking water to the metropolitan area of montpellier france since the nineteenth century since 1981 an intense pumping is being performed directly in the main conduit with a maximum exploitation flow rate of about 1 700 l s to improve the understanding of groundwater origins and circulation dynamic in this karst system as well as the impact of three decades of intense water exploitation groundwater samples have been collected during various hydrologic conditions since march 2006 a previous hydrochemical study on the lez karst system had been carried out before the installation of the pumping plant this dataset was compared to the present one to identify possible changes on groundwater hydrochemistry the results of this analysis indicate the existence of historical changes in water hydrogeochemistry and evidence a decrease of the deep compartment participation to the lez spring outflow this change in spring water hydrogeochemistry may be attributed to the intense pumping of the karst system and in the absence of noticeable climatic changes expresses the direct consequences of anthropogenic forcing on the overall functioning of the aquifer this study aims to analyze the differences to understand the water chemistry changes and to better foresee the aquifer evolution for the future

exposed cross sections through the continental crust implications for crustal structure petrology and evolution abstract the continental crust is exposed in cross section at numerous sites on the earth s surface these exposures which appear to have formed by obduction along great faults during continental collision may be recognized by exposures of deep crustal rocks exhibiting asymmetric patterns of metamorphic grade and age across the faults and by distinctive bouguer anomaly patterns reflecting dipping basement structure and an anomalously deep mantle from an examination of five complexes which meet these criteria it is concluded that the most prominent layering in the crust is not compositional but metamorphic the lower crust consists of granulite facies rocks of mafic to intermediate composition while the intermediate and shallow levels consist predominantly of amphibolite facies gneisses and greenschist facies supracrustal rocks respectively post metamorphic granitic intrusions are common at intermediate to shallow levels position of discontinuities in refraction velocity where present commonly correspond to changes in composition or metamorphic grade with depth the continental crust is characterized by lateral and vertical heterogeneities of varying scale which are the apparent cause of the complex seismic reflections recorded by cocorp field observations coupled with geochemical data indicate a complex evolution of the lower crust which can include anatexis multiple deformation polymetamorphism and reworking of older crustal material the complexity of the crust is thus the result of continuous evolution by recycling and metamorphism through time in a variety of tectonic environments

effects of partial and full pipe flow on hydrochemographs of logsdon river mammoth cave kentucky usa summary logsdon river within kentucky s mammoth cave system drains the 25 km2 cave city groundwater basin temperature specific conductance stage and velocity were measured at the river s downstream end within the cave with 2 min resolution for one year beginning on may 5 1995 new interpretation of these data show relationships to the conduit s geometry and fluid transport behavior the 37 observed storm hydrographs chemographs are classified into two groups open channel flow and pipe flow conduit filled in the 16 pipe flow events logsdon river exceeded the capacity of its conduit raising the water table above the conduit ceiling with some storm water thus temporarily stored within the aquifer adjacent to the conduit pipe flow events were characterized by depression of specific conductance spc before peak discharge a peak in spc at peak discharge and a second depression in spc after peak discharge the first spc minimum represents the maximum concentration of passing storm water and the second is interpreted as the result of recent storm water draining back into the conduit having been temporarily stored in the aquifer adjacent to the conduit mean velocity decreases in the transition from partial to full pipe flow due to increased head loss at full pipe flow compared to nearly full pipe flow each of the open channel flow cases shows a depression in spc either coincident with or after peak discharge while the hydrochemographs of pipe flow are mainly controlled by the aquifer conduit network geometry in open channel cases they are mainly controlled by external recharge conditions including behavior of sinking streams

inferring source waters from measurements of carbonate spring response to storms abstract we infer information about the nature of groundwater flow within a karst aquifer from the physical and chemical response of a spring to storm events the spring discharges from the maynardville limestone in bear creek valley tennessee initially spring discharge peaks approximately 1 2 h from the midpoint of summer storms the initial peak is likely due to surface loading which pressurizes the aquifer and results in water moving out of storage all of the storms monitored exhibited recessions that follow a master recession curve very closely indicating that storm response is fairly consistent and repeatable independent of the time between storms and the configuration of the rain event itself electrical conductivity initially increases for 0 5 2 9 days longer for smaller storms the result of moving older water out of storage this is followed by a 2 1 2 5 day decrease in conductivity resulting from an increasing portion of low conductivity recharge water entering the spring stable carbon isotope data and the calcite saturation index of the spring water also support this conceptual model spring flow is likely controlled by displaced water from the aquifer rather than by direct recharge through the soil zone

dynamic recrystallization of feldspar a mechanism for ductile shear zone formation feldspar aggregates experimentally deformed in the dislocation creep regime undergo dynamic recrystallization because recovery is difficult due to the limited climb of dislocations recrystallizing aggregates have a lower strength because of the cyclic production of small strain free grains and they develop a strong preferred orientation consistent with that observed in mylonites thus recrystallization accommodated dislocation creep may be responsible for the grain size reduction and strain softening that lead to the formation of many mylonites and ductile shear zones

pore pressure and oceanic crustal seismic structure summary marine refraction studies during the past decade have found considerable lateral variability in the seismic properties of the upper basaltic regions of the oceanic crust in many localities compressional and shear wave velocities are quite low at the top of the basalt section and velocities increase rapidly with depth it is concluded that pore pressure may be at least in part responsible for the low upper crustal velocities and contribute significantly to the lateral variability this is supported by compressional and shear wave velocity measurements as functions of confining pressure and pore pressure for basalt from the juan de fuca ridge and dolerite from the samail ophiolite oman within the oceanic crust regions of overpressure and underpressure will possess anomalous velocities the magnitude of which will depend upon the porosity and the deviation of the pore pressure from hydrostatic the influence of pore pressure on velocities is expected to diminish with depth and is unlikely to be significant at lower crustal depths where porosity is extremely low of significance poisson s ratio is shown to be dependent on pore pressure as well as confining pressure at constant confining pressure poisson s ratio increases with increasing pore pressure thus overpressured regions within the upper oceanic crust are likely to have relatively high poisson s ratios as well as low compressional and shear wave velocities

the role of tectonic grain size reduction in the rheological stratification of the lithosphere with the aid of published constitutive flow laws for common crustal and upper mantle rock types it is possible to construct curves showing variation of rock strength with depth in the continental lithosphere assuming a particular crustal stratification of rock types and a particular geothermal gradient such exercises lead to the conclusion that marked changes in strength can occur at major petrological interfaces such as the moho discontinuity which are therefore likely to be associated with a tendency for major sub horizontal detachments to form constitutive flow laws used for such purposes are usually assumed to represent steady state flow at constant rock microstructure

syndeformational recrystallization dynamic or compositionally induced dynamic recrystallization in the strict sense of the term is the reconstitution of crystalline material without a change in chemical composition driven by strain energy in the form of dislocations driving potentials additional to internal strain energy may contribute to the recrystallization of naturally deformed minerals which form solid solutions such as feldspar amphiboles and pyroxenes if they change their composition during recrystallization to estimate the relative importance of these driving potentials the chemical composition of porphyroclasts and recrystallized grains of plagioclase clinopyroxene and hornblende have been investigated in samples from a high grade shear zone of the ivrea zone italy the plagioclases show two different recrystallization microstructures bulging recrystallization at grain boundaries and discrete zones of recrystallized grains across porphyroclasts probably involving fracturing deformation took place under amphibolite facies conditions on a retrograde p t path porphyroclast and recrystallized compositions from bulging recrystallization microstructures differ only in their or content and yield a g between mean host grain and mean recrystallized grain composition at fixed p t conditions of approximately 5 joules 10 4 m3 extreme compositional variations yield approximately 60 j 10 4 m3 the increase of free energy due to dislocations calculated for common glide systems in plagioclase are on the order of 100 joules 10 4 m3 for high values of dislocation densities of 1014 m 2 thus the effect of chemically induced driving energies on grain boundary velocity appears small for mean compositions but may be as great as that of deformational energies for larger chemical differences in the other type of microstructure porphyroclasts and recrystallized grains in discrete zones differ in their anorthite content the maximum g induced by the compositional disequilibrium is on the order of 100 j 10 4 m3 this maximum value is of the same magnitude as the g derived from high dislocation densities of 1014 m 2 the resulting combined g is approximately twice as high as for deformational g alone and heterogeneous nucleation may become a feasible recrystallization mechanism which is evident from the microstructures the recrystallization mechanism depends on the nature of the driving potential grain boundary migration gbm and heterogeneous nucleation can release gibbs free energy induced by compositional disequilibrium whereas this is not likely for subgrain rotation therefore only gbm and heterogeneous nucleation may link metamorphism and deformation so that syndeformational recrystallization may represent a transitional process ranging from dynamic recrystallization to metamorphic reaction

storm response of the karstic carbonate aquifer of southcentral kentucky abstract temperature and specific conductance were continuously measured in the downstream drainage of the turnhole spring subbasin in the southcentral kentucky karst precipitation was monitored with a rain gage network in the catchment area so that the storm response of specific conductance and temperature could be examined the aquifer feeding the turnhole spring is highly karstic with much of the discharge through integrated open conduits some of which carry water from surface sinking stream catchments both temperature and specific conductance fluctuate rapidly in response to storm events the conductivity curves and to a lesser extent the temperature curves show a sharp dip that lags some hours behind the storm pulse at the onset of the dip is a complicated sequence of fine structures that is interpreted to be the inputs from conduit tributaries to the master trunk drainage system the recovery curves have an exponential form that can be fitted to produce a characteristic response time for the conduit system

importance of suspended sediments and dissolved organic carbon to carbon exports in karst the vadu crisului karst basin in the pădurea craiului mountains romania abstract exports of dissolved inorganic carbon dic from karst aquifers are a significant contribution to the global carbon cycle contributions of particulate inorganic carbon pic and dissolved organic carbon doc in karst groundwater are often unaccounted for in carbon budgets this investigation considers field chemistry discrete samples and continuous monitoring data collected between october 2016 and december 2016 to quantitatively evaluate the net export of dissolved solutes total suspended sediments tss and doc within the vadu crisului karst basin in the p durea craiului mountains of northwest romania measurements of carbon isotopes 13c in dic and in bedrock specific ultraviolet absorption suva and carbon to nitrogen c n ratios were used to evaluate the relative contribution of different sources of carbon to the aqueous system 13cdic at the aquifer input trend toward an atmospheric signal in winter with lower doc concentrations and suva values and c n ratios corresponding to degraded carbon sources illustrating the reduction in microbial respiration in soil with cold temperatures at the spring 13cdic values trend more toward a soil based signal after storm events that bring increased doc concentrations with suva values corresponding to significantly degraded carbon dissolution in this karst basin is principally driven by the carbonate equilibrium reactions and direct meteoric recharge only accounts for 4 to 13 of observed discharge most recharge enters the karst basin through infiltration into dolines and epikarst on the zece hotare karst plateau and this results in a broadly stable chemical signature of spring water storm events do have a significant impact on mechanical erosion and chemical processes operating in the karst basin the addition of pic and tss flux increase landscape erosion rates by 1 1 to 1 2 and 7 9 to 8 3 respectively above the denudation rate computed by dissolved solutes 36 5 56 9 mm ka the modeled annual flux of dic from this karst basin 1 37 105 to 1 64 105 kg yr scales to a global co2 flux of 7 08 1011 to 1 06 1012 kg yr adding a modeled flux of doc increases the estimates of co2 flux by 12 to 22 a significant addition to the global carbon cycle

shape of pinch and swell structures as a viscosity indicator application to lower crustal polyphase rocks abstract pinch and swell structures occur where a more competent layer in a weaker matrix is subjected to layer parallel extension in this contribution we use numerical models to explore the use of pinch and swell structure shape symmetry and asymmetry as a determinant of relative viscosity between layers maximum asymmetry is attained when the matrix viscosity on one side is subtly weaker than the competent layer while the other side is significantly weaker our numerical results are directly applied to asymmetrically developed pinch and swell structures in exposed lower continental crust here shape geometries observed in a shear zone comprised of plagioclase dominated garnet dominated and mixed amphibole plagioclase dominated bands reveals that the plagioclase dominated band is the most competent band and is marginally stronger 2 and significantly stronger 10 40 than the fine grained garnet dominated and mixed amphibole plagioclase dominated band respectively based on the experimentally determined viscosity of a plagioclase dominated material and quantitative microstructural analysis the viscosity range of the natural rock bands is 2 8 1015 to 1 1 1017 pa s consequently the assumption that the experimentally derived plagioclase flow law is an appropriate proxy for the middle to lower continental crust may lead to a viscosity over estimation by up to forty times