a new indicator of movement direction during orogenesis measurement technique and application to the alps the orientation of axes of sigmoidal staircase or spiral inclusion trails within porphyroblasts provides an indicator of the direction of movement during deformation that is synchronous with metamorphism a simple technique is presented in detail to find this axis in 3d by radially sectioning a horizontal slab cut from an oriented sample when viewed from one direction the switch in asymmetry of the porphyroblast inclusion trails in these sections defines the trend of the axis further radial sectioning of a vertical slab cut parallel to this trend determines the plunge of this axis this technique is independent of the model adopted for the formation of sigmoidal or spiral shaped inclusion trails and can be used to evaluate the mechanism by which they form it can also be used to evaluate theories of folding and orogenesis measurements of spiral and sigmoid axes in garnet porphyroblasts from the european alps show that they reflect the movement of the african plate relative to europe better than linear indicators preserved within the same rocks

simulation of groundwater exchange between an unconfined aquifer and a discrete fracture network with laminar and turbulent flows abstract in this study a new approach is developed to simulate groundwater flow through both an overlying unconfined aquifer and an underlying discrete fracture network the groundwater exchange between the aquifer and the fracture network including magnitude and direction is explicitly simulated based on the mass conservation which depends on a variety of parameters related to flow and network characteristics in the overlying unconfined aquifer we approximate the flow using the dupuit assumptions in the underlying fracture network we use the cubic law and forchheimer s law to iteratively simulate laminar or turbulent flow in individual fractures depending on the reynolds number explicitly separating laminar and turbulent flows in the fractures results in a system of nonlinear equations which is iteratively solved while the flow from the overlying unconfined aquifer is a small portion of the overall flow in the underlying fracture network incorrect use of the laminar or turbulent flow equation in the fractures can lead to significant errors in simulating the flow exchange as apertures increase both the portion of the total flowrate in the aquifer and the portion of the flow in the fractures coming from the aquifer decrease as the overall hydraulic gradient increases both the portion of the total flow in the aquifer and the portion of the fracture flow that comes from the aquifer increase the portion of the total flow in the aquifer increases with the aquifer thickness while the portion of fracture flow coming from the overlying aquifer decreases

influence of th rich mineral phases on u th radioactive disequilibrium ages of sulfide deposits from the okinawa trough abstract many samples of hydrothermal sulfide minerals from the okinawa trough yield 234u 230th radioactive disequilibrium ages that are inconsistent with the ages of coexistent barite obtained using electron spin resonance esr method these results contrast strongly against results obtained for the southern mariana trough for which the u th radioactive disequilibrium ages are roughly consistent with the esr ages sulfide minerals from the okinawa trough show large variation in u and th abundances suggesting open system behavior we infer that the interaction of hydrothermal fluids with thick terrigenous sediment caused large scale migration of u and th in the okinawa trough the 234u 230th 232th 230th plots for the sulfide samples from the hatoma knoll and the izena hole show two mixing trends for each site the presence of th rich phase with high 230th 234u ratio seems to cause incorrect age estimates of the sulfide deposits

kinematics of orocline and arc formation in thin skinned orogens the regional traces of folds faults and foliations found in many fold thrust belts are bent in plan view it proves valuable to distinguish between two types of bent orogens based on their kinematic evolution oroclines or rotational arcs are bent orogens in which segments of the orogen change strike during the evolution of the bend and nonrotational arcs are bent orogens in which segments of the orogen do not change strike during development of the bend the kinematic evolution of a bend that forms in a thin skinned orogen can be described in terms of three parameters the displacement path trajectories followed by points along the strike of the orogen the magnitude and distribution of tangential extension along the strike of the orogen and the change in position of the endpoints of the orogen with respect to a reference line only slight differences in the displacement path trajectory pattern determine whether an orogen evolves as a nonrotational arc or as an orocline thus the distinction between these two types of bends is not always of major tectonic significance compressional deformation along irregular continental margins or the impact of indentors on continental margins during collisional orogenies more likely leads to formation of nonrotational arcs as can be simulated with a sand wedge model interaction between a fold thrust wedge with obstacles in the foreland or with a wrench fault more likely leads to orocline formation orocline formation is also associated with noncoaxial reactivation of thrust faults tangential extension is a necessary consequence of certain displacement path trajectory patterns and can accompany development of either nonrotational arcs or oroclines two examples one from the umbrian apennines and one from the makran range demonstrate how movement on cross strike fault arrays can accommodate tangential extension in thin skinned bends

actinide series disequilibrium as a tool to establish the chronology of deep sea hydrothermal activity this paper describes the different radiochronological methods used to date geologically recent i e 400 000 years deep sea hydrothermal deposits as well as the basic conditions necessary to obtain reliable dates the limitations of the different techniques also are described using measurements of 210pbpb 228th228ra 230th234u 231pa235u and 228ra226ra the authors have undertaken an exhaustive chronological study of the hydrothermal deposits along the east pacific rise the mid atlantic ridge and in some back arc basins the objectives of this study were to obtain regional chronologies and to establish a general synthesis on the evolution of the hydrothermal processes at the scale of the mid oceanic ridge system some results obtained by other authors are included in this synthesis the dependence of the general trends of temporal development of the hydrothermal chimneys edifices and fields on their tectonic settings is discussed this study demonstrates that hydrothermal activity does not represent a regular input of matter to the ocean and that its pulsed character must be taken into account in all modeling attempts chemical biological and tectonic affected by hydrothermal processes in areas of rapid spreading like the east pacific rise recent and fossil deposits are spatially separated by contrast at the slow spreading mid atlantic ridge fossil and present activity are found in the same location

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

recharge of aquifers by flood events in an arid region the process of aquifer recharge by flood events in an arid region was investigated as applied to the hazeva formation the karkom graben the wadi paran watershed israel the hydrological model was established as a complex system with due regard for groundwater and transmission losses of surface runoff it was based on a previously outlined hydrogeological model of the karkom graben and a model of transmission losses in arid watercourses under conditions of data deficiency proceeding from calculation of groundwater balances the contribution of surface runoff as a decisive balance component was confirmed the main characteristics of aquifer regimes such as changes in storage volume and groundwater level as well as lateral flow were all found to be dependent upon the net extraction rate i e pumpage discounting replenishment by flood events analysis and physical interpretation of model parameters enabled assessment of the influence of groundwater extraction on aquifer recharge this became apparent as increasing absorption capacity and recharge availability of the aquifer as a result of the groundwater abstraction copyright 2002 john wiley sons ltd

field experiments and numerical simulations of confined aquifer response to multi cycle recharge recovery process through a well summary shanghai is one of the cities suffering from land subsidence in china land subsidence has caused serious financial losses thus artificial recharge measures have been adopted to compensate the drawdown in shallow confined aquifers and thereby control land subsidence in this study a multi cycle recharge recovery field experiment was performed to investigate the response of a shallow confined aquifer to artificial recharge through a well in the experiment a series of recharge recovery cycles with different recharge volumes and durations with and without artificial pressure were performed the water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi cycle recharge recovery process meanwhile a finite difference method fdm numerical model was established and its parameters were obtained via a reversed numerical analysis on the experimental data the responses of the shallow confined aquifer to the multi cycle recharge recovery process were simulated in detail using the model the calculation results showed that the water level dropped significantly when the recharge ended moreover the efficiency of a multi cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time the relationship between recharge frequency and efficiency expressed as h 0 29498 f 0 40163 and r 2 0 97264 respectively was obtained through the fdm numerical simulation in the recharge intervals the optimal recharge efficiency was achieved when the water level rose to 40 of the peak

whole rock and sulfide lead isotope data from the hydrothermal jade field in the okinawa back arc trough the mineralization of the active hydrothermal jade field resembles in many aspects the kuroko type mineralization the jade field is located in a back arc graben and is associated with a bimodal volcanism lead isotope data from igneous rocks sediments and ores further emphasize the similarities with the kuroko ores and suggest that both sediments and volcanic rocks contributed comparable amounts of lead to the deposit when compared to the sediments a much larger volume of volcanic rocks must have contributed lead to the deposit because of the considerably lower lead concentration of volcanic rocks in contrast to the crustal type lead of the jade field and the kuroko type sulfide deposits the lead isotope signatures of vms type deposits at mid ocean ridges is distinctly different in the absence of a sedimentary cover it reflects the composition of the mantle source whereas in the presence of a sedimentary cover it is either a mixture of mantle and sedimentary lead or it may even be completely dominated by the latter

crystallographic orientation chemical composition and three dimensional geometry of sigmoidal garnet evidence for rotation studies of the microstructure crystallographic orientation chemical composition and three dimensional shape of sigmoidal garnet reveal a number of features that can be used to discuss its origin and in particular to distinguish between rotational versus non rotational models crystallographic orientation mapping of sigmoidal garnet shows no evidence of subgrain formation or of being polycrystalline suggesting that neither ductile nor brittle deformation is significant chemical mapping shows that the garnet grew during a single metamorphic event arguing against ideas that sigmoidal garnet forms as the result of a series of independent growth events the chemical mapping also reveals anisotropic growth of garnet with the long axis of the ellipsoidal grain rotating in the same direction but to a lesser degree than the inclusion trails this is best explained as the result of syn growth rotation of the garnet with respect to the foliation and maximum growth direction high resolution x ray ct scanning shows that the inclusion trails have a complex three dimensional spiral geometry this type of geometry is predicted by rotational models of sigmoidal garnet formation

permo triassic changes in bulk crustal shortening direction during deformation and metamorphism of the taebaeksan basin south korea using foliation intersection inflection axes implications for tectonic movement at the eastern margin of eurasia during the songrim indosinian orogeny abstract the permo triassic songrim indosinian orogeny in south korea was a major tectonic event involving complicated continental collisions at the eastern margin of eurasia previous studies have examined the structural and metamorphic features of the songrim orogeny in each of the paleozoic terranes of the orogenic belt i e the taebaeksan basin the okcheon basin and the imjingang belt but correlations of these features among the terranes remain uncertain the aim of this paper is to reveal deformation history including bulk crustal shortening directions in the taebaeksan basin and to correlate the tectono metamorphic evolution of the taebaeksan basin with other phanerozoic mobile belts in eastern asia based on a combined analysis of foliation intersection inflection axes fia trends and metamorphic p t and t t time paths the orientations and relative timing of fia preserved as inclusion trails within porphyroblasts of andalusite chloritoid garnet and staurolite reveal two age groups of inclusion trails in the pyeongan supergroup at the northeastern margin of the taebaeksan basin these microstructures indicate the development of early nnw nne trending structures and fabrics followed by later e w trending ones these observations suggest a change in the orientation of bulk crustal shortening from e w to n s during the songrim orogeny based on the similar microstructures and temperature time paths of the three paleozoic terranes we interpret that the e w bulk crustal shortening influenced the eastern part of the korean peninsula during the early stages of the songrim orogeny presumably related to amalgamation between the proto japan terrane and the eastern margin of eurasia whereas the n s bulk crustal shortening was stronger in the western part of the peninsula during the later stages of the orogeny related to collision between the south and north china blocks

structure of the southernmost okinawa trough from reflection and wide angle seismic data abstract during a passive seismic experiment in the okinawa trough the shots of two reflection profiles were recorded by ocean bottom seismometers obs both profiles include 3 ocean bottom instruments are about 65 km in length and located in the axial portion of the southwestern okinawa trough processing of the reflection seismic data images recent deformation of the sedimentary units forward modelling of the wide angle data on both profiles reveals a 1 2 km thick sedimentary infill overlying an acoustic basement characterised by seismic velocities between 3 2 and 3 5 km s crustal thickness could only be modelled on one profile and was determined to be around 10 km thickening towards the ryukyu arc in the south gravity modelling was used to additionally constrain both profiles especially the deep structure of profile 1

distinguishing and correlating multiple phases of metamorphism across a multiply deformed region using the axes of spiral staircase and sigmoidal inclusion trails in garnet schists from the appalachian orogen in south east vermont have undergone multiple phases of garnet growth these phases can be distinguished by the trend and relative timing of foliation inflexion or intersection axes fias of foliations preserved as inclusion trails in garnet porphyroblasts the relative timing of different generations of fias is determined from samples containing porphyroblasts with two or three differently trending fias developed outwards from core to rim multi fia porphyroblasts schists from south east vermont show a consistent pattern of relative clockwise rotation of fia trends from oldest to youngest four populations or sets of fias can be distinguished on the basis of their relative timings and trends from oldest to youngest the four sets have modal peaks trending sw ne w e nnw sse and ssw nne these peaks show that each of the four fia sets has a statistically consistent trend at all scales across a 35 125 km area containing numerous mesoscopic and macroscopic folds the fias of set 4 are defined by inclusion trails that are continuous with matrix foliations have trends subparallel to most folds and are inferred to have developed contemporaneously with these structures conversely sets 1 to 3 are oblique to and pre date most matrix foliations and folds all four fia sets occur in siluro devonian rocks and must have formed in the acadian orogeny the lack of statistically significant differences in the distribution of fia trends across the study area and their consistent relative timings in multi fia porphyroblasts despite a complex regional deformation history involving numerous phases of folding at all scales suggest the porphyroblasts have not rotated relative to one another the change in fia trend with time resulted from rotation of the kinematic reference frame of bulk flow possibly as a consequence of the reorganization of lithospheric plates responsible for acadian orogenesis recognition of distinct generations of fias provides a means of distinguishing different phases of porphyroblast growth four periods of garnet porphyroblast growth occurred in the schists of south east vermont this growth was heterogeneously distributed on the cm2 m2 scale no single porphyroblast records all stages of growth and adjacent samples from the same or dissimilar rock types commonly contain porphyroblasts that preserve different sequences of growth factors that may have been responsible for switching porphyroblast growth on and off at this scale include i subtle differences in bulk chemical composition ii oscillating levels of heat owing to the buffering effect of endothermic garnet forming reactions iii channelized infiltration of fluids with localized fluid buffering of bulk composition and iv cyclic controls on the rates of diffusion and material transport of reactants either by channelized fluid flow or by a changing pattern of microfracturing during foliation development consistency in fia trend and relative timing provide a new method for potentially distinguishing and correlating successive metamorphic events or even phases of metamorphism within a progressive tectonothermal event along and across orogens using a consistent pattern of core to rim changes in fia trend multiple phases of growth of a single porphyroblastic mineral can be quantitatively distinguished allowing correlation of different phases of growth around and across macroscopic folds the relative timing of growth of different porphyroblastic minerals can also be quantitatively determined using fia data and correlated around and across macroscopic folds conceptually the paragenetic history preserved in each generation of porphyroblast growth in the form of chemical zoning and the minerals in inclusion trails could be combined to produce a more detailed p t t deformation path than previously determined

transient head development due to flood induced seepage under levees the purpose of this study was to predict the uplift force during floods on confining layers that overlay extensive horizontal confined aquifers that intersect a large river in response to the water level changes that occur with time in a flooding river transient flow of water through the confined aquifer was described by a diffusion type of equation with a boundary condition at the river in which the river head varied with time the transient head distribution developed from the unsteady flow model applied to the aquifer was compared with the hydraulic head distributions obtained from u s army corps of engineers steady state flow model and a finite element seepage model this study concluded that the transient flow model has the potential to analyze time lag in head development and to predict the seepage condition and heaving potential at various times and distances landside of a levee during a flood cycle but additional case histories are needed to justify widespread use of the model

back arc extension in the okinawa trough the okinawa trough lying to the east of china is a back arc basin formed by extension within continental lithosphere behind the ryukyu trench arc system middle to late miocene uplift associated with normal faulting of the initially adjacent ryukyu nonvolcanic arc and the taiwan sinzi folded belt corresponds to the first rifting phase the timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern okinawa trough the rifting occurred after a major early miocene change in the motion of the philippine plate with respect to eurasia and ceased during the pliocene a second rifting phase started about 2 m y ago at the plio pleistocene boundary and has continued until the present time it has proceeded to a more advanced stage in the middle and southern okinawa trough than it has farther north detailed bathymetric sea beam seismic reflection and magnetics data collected during the pop 1 cruise of the r v jean charcot reveal the principal features of the extensional processes the back arc spreading phase started very recently in the southern and middle okinawa trough as exemplified by several en echelon and in some cases overlapping active central graben oriented n70 e n80 e some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies transform faults between these en echelon active rifts are not obvious we suggest that the major part of the southern okinawa trough is underlain by a thinned continental crust and that except for the system of en echelon rifts of the southern okinawa trough the back arc basin oceanic domain is limited to a width of a few tens of kilometers or less in the axial portion of the trough the system of axial back arc volcanic ridges that occur in the rifts ends at the latitude of okinawa island whereas active volcanoes in the ryukyu arc occur only north of okinawa island we refer to this transition between active arc and back arc volcanism as the volcanic arc rift migration phenomenon vamp globally back arc volcanism propagated from the southern okinawa trough to the okinawa vamp area rifting continues to occur in the northern okinawa trough but is not yet accompanied by associated volcanism the okinawa vamp area is characterized by a series of parallel basaltic ridges oriented n75 e with associated linear magnetic anomalies characteristic of dyke intrusions we suggest that the formation of the back arc oceanic domain took place along the axial back arc extensional zone trending n75 e and that this zone presently ends at the southern extremity of the active volcanic chain the initial phase of formation of back arc basin oceanic crust is non steady state and is characterized by the lack of a developed fracture zone pattern the termination of the vamp area in the direction of the volcanic zone of the arc is consistent with the suggestion of molnar and atwater that the volcanic arc is a fundamental line of weakness which determines where initial back arc spreading occurs apparently back arc extension initially occurred within the continental lithosphere located westward of the ryukyu arc along its whole length but the subsequent back arc volcanism was initiated in the southernmost portion of the region and then moved northward this migration was accompanied by the shutting down of volcanic activity along the abandoned portions of the arc it is this transfer of volcanism that we call the vamp process thus arc and back arc basin volcanism seem to be associated in such a manner that spreading tends to migrate simultaneously with a cessation in volcanic activity along the arc this interplay of arc and back arc activity is probably linked to changes in the parameters of plate convergence since the plate motion in the phillippine sea is oblique to the trench at least in the southern part of the okinawa trough we suggest that the oblique resisting force applied to the edge of the overriding plate engenders the development of en echelon extensional features within and behind the arc the motion of the ryukyu platelet with respect to eurasia is consequently an extensional strike slip motion trending roughly parallel to the okinawa trough

dating iron skarn mineralization using hydrothermal allanite la u th pb isotopes by laser ablation icp ms abstract trace elements and u th pb isotopes of hydrothermal allanite from the beiminghe iron skarn deposit eastern north china craton were simultaneously analyzed using laser ablation inductively coupled plasma mass spectrometry la icpms to demonstrate the suitability and robustness of the u th pb system in this phase as a geochronometer of ore forming processes allanite grains from the beiminghe deposit typically exhibit optical and chemical zoning and are intergrown or texturally equilibrated with prograde and or retrograde skarn assemblages mainly consisting of tremolite diopside magnetite and garnet in addition they contain abundant aqueous two phase or daughter mineral bearing three phase aqueous fluid inclusions confirming their hydrothermal origin most grains have high la ce ratios 1 19 1 74 and thus are classified as allanite la a notable feature of the hydrothermal allanite la is the lack of common pb with values comparable with those of the zircon standards 91500 and gj 1 used in this study la icpms spot analyses reveal remarkable variation in ca rees rare earth elements fe al and mg within a single grain consistent with the substitution of ree3 mg fe2 for ca al fe3 in the mineral structure traverses of zoned grains show that the rims have th u ratios ranging from 0 73 to 11 55 significantly higher than the core areas 0 07 1 81 fifty nine spot analyses beam size of 32 m or 60 m on 5 allanite la grains yield reproducible 206pb 238u ages of 134 7 to 139 6 ma with a weighted mean 206pb 238u age 206pbexcess corrected 206pb 238u age of 136 1 ma 2 of these 34 analyses on allanite rims have a weighted mean 208pb 232th age of 139 2 ma 2 that is within error of the 206pb 238u age the dating results showed that an increase of beam size from 32 to 60 m significantly reduces the analytical uncertainties 2 petrographic and textural data have demonstrated that the allanite la grains formed during skarn alteration and notably have close paragenetic relationships with retrograde skarn assemblages and iron oxide minerals their u th pb ages therefore are interpreted as the timing of iron skarn mineralization at beiminghe thirteen zircon grains from the ore related diorite intrusion have a weighted mean 206pb 238u age of 136 2 ma 2 consistent with and thus confirming the reliability of the allanite la u th pb ages when interpreted as the formation age of the beiminghe iron deposit our results suggest that hydrothermal allanite with low th and u is a promising u th pb geochronometer and can provide reliable constraints on the timing of hydrothermal mineralization without requiring a matrix matched external standard the present dating results also indicate that the u pb rather than th pb isotope system is preferable for u th pb dating of low th u allanite

transient flow to a large diameter well in an aquifer with storative semiconfining layers the hantush theory of leaky aquifers with storge in the semiconfining layers is combined with large diameter well theory to produce equations that can be used in the analysis of pumped well and observation well data for stratified formations included in the equations are storage in the pumped well and a linear resistance to flow at the sand face or well bore skin three cases proposed by hantush are considered these depend upon whether the upper boundary of the overlying semiconfining layer or the lower boundary of the underlying semiconfining layer are constant head or no flow boundaries laplace transform solutions valid for the complete time domain are given for each of the three cases for the hydraulic head in the pumped well the aquifer and each of the semiconfining layers type cures obtained by numerical inversion are selected to illustrate the effects of well bore storage well bore skin and leakage although several dimensionless parameters are involved these parameters tend to influence the character of different portions of the type curves suggesting that unique matches are possible the type curves show that well bore storage in a large diameter well may completely obliterate effects of leakage derived from compressible storage in semiconfining layers for the purposes of aquifer testing it may be possible to reduce the magnitude of well bore storage in a large diameter well and thus reveal the presence of leaky semiconfining layers this may help to prevent erroneous interpretation of the well test data and incorrect evaluation of the aquifer parameters

exact analytical expressions for the piezometric profile and water exchange between stream and groundwater during and after a uniform rise of the stream level 1 we consider an archetypical problem relevant to a confined aquifer in contact with a stream the model problem consists of an idealized one dimensional region 0 x l where the left boundary at x 0 is held at a fixed piezometric head h0 and the right boundary s piezometric head at x l is increased from hl to h0 at a constant rate exact solutions for all times all points in the aquifer and for any possible constant rate of change of the right boundary piezometric head are presented for the piezometric head and the instantaneous flow rate an exact expression for the exchange volume at the groundwater stream interface for an arbitrary time is also provided this expression shows that there is a specific critical rising rate of the stream level above which the net exchange volume is into the aquifer and below which it is out of the aquifer the solution shows that regardless of the rise rate a certain water volume inversely proportional to the rise rate enters the aquifer

modification of canal flow due to stream aquifer interaction unsteady canal flow in an integrated canal flow groundwater flow system is analyzed by solving the coupled equations governing canal flow groundwater flow and the seepage between them analytical solu tions are obtained for the coupled system for small water level disturbances using fourier analysis methods and complex variables dimensionless parameter groups characterizing the aquifer the canal and the sediment layer are identified using the governing equations and the solution the influence in the aquifer and the semipermeable bottom sediment layer due to disturbances in canal flow is studied the analytical solutions are compared to numerical solutions obtained using the modflow model and the hydrologic simulation engine of the south florida regional simulation model results of the analysis are useful in determining the range of aquifer sediment and canal characteristics for which stream aquifer interaction is important the results can be used to determine the conditions for which the canal is hydraulically disconnected from the aquifer because of the sediment layer the analytical solution is useful to understand the propagation characteristics of small amplitude water level disturbances in the canal and the aquifer the characteristics studied include the amplitude decay constant and the speed the solution can be used to design benchmark problems that can be used to evaluate integrated canal flow groundwater flow models the results of the study can be used to estimate the space and time steps needed in the canal and the aquifer when simulating stream aquifer interaction as part of the overall effort to restore the everglades eco system in south florida and to meet its regional water man agement responsibilities the south florida water management district sfwmd sfwmd 1999 and other organizations have developed a number of mathematical models to simulate the water management system one important requirement of these models is the capability to simulate stream aquifer in teraction or stream wetland interaction a significant part of the south florida landscape is covered with a network of ca nals that extends for thousands of miles through wetlands ag ricultural areas and urban areas the behavior of water levels in the canals when areas adjacent to canals are subjected to water level changes is not completely understood the influ ences of the highly conductive surface aquifer and the less conductive bottom sediment layer of the canal on the overall hydrology are also not completely known these behaviors influence a significant part of south florida hydrology the current study provides a method to understand the basic pa rameters that govern the problem and to obtain an analytical solution stream aquifer and stream wetland interactions have previ ously been studied by a number of researchers the study by pinder and sauer 1971 was conducted by using a coupled numerical model for canal flow and 2d groundwater flow the objective was to study the influence of bank storage on the modification of flood waves the example used by pinder and sauer 1971 served as a benchmark test for integrated mod els such as modbranch swain and wexler 1996 and modnet walton et al 1999 these models consist of a modflow model mcdonald and harbaugh 1988 coupled with either the branch model schaffranek 1987 or the unet model hec 1996 the comparison between the so lution obtained by pinder and sauer 1971 and the solutions obtained using modbranch or modnet was not perfect 1

porphyroblast rotation versus nonrotation conflict resolution data on foliation intersection and or inflection axes preserved in porphyroblasts fias indicate that no porphyroblast rotation occurs during ductile deformation relative to spatial coordinates this contrasts with 99 of investigations of rigid objects in non coaxially deforming media where the objects rotate when anastomosing shear zone formation around relatively strong objects in a weaker matrix is modeled no porphyroblast rotation occurs formation of these anastomosing zones controls the development of this phenomenon called gyrostasis if such zones are absent porphyroblasts rotate in weak materials the gyrostatic situation arises because the superposition of simple shearing deformation normal to initial coaxial shortening results in only small rotations of principal axes of stress since shear zones are controlled by the orientations of principal axes of stress initial anastomosing zones retain their orientations and positions during subsequent non coaxial deformation the porphyroblast is isolated from the embedding non coaxially deforming matrix but this material close to the porphyroblast continues to deform coaxially no local rotation occurs this has major tectonic significance because allowing for the effects of rotation due to brittle deformation porphyroblasts can now be routinely used to access lengthy structural and or metamorphic histories destroyed in the matrix by reactivation such as movement directions shear senses and extended pressure temperature time paths

buffer effect on identifying transient streambed hydraulic conductivity with inversion of flood wave responses abstract determination of streambed hydraulic conductivity ksb and its variations over time are critical for quantifying exchange fluxes between surface water and groundwater previous studies have used flood wave response techniques frt to determine ksb or its transience excluding the streambed storage effect thus the estimated ksb may not be reliable in this study after improving a previous frt by substituting the gradient descent algorithm with an advanced and robust optimization method trust region reflective algorithm we have analyzed the influence of streambed storage effect on the estimation of time dependent ksb through successive inversion of flood wave responses the study shows that the streambed storage effect is not important for identifying the transience in the hydraulic properties of a relatively thin streambed e g several or dozens of centimeters but significant under estimation 1 2 orders of magnitude can be seen because of neglecting the streambed storage effect it is particularly true for a stream confined aquifer system if the streambed is composed of fine deposits e g silt clay with a thicker thickness greater than 1 m corresponding to low permeability but high storativity and the aquifer is characterized by relatively low permeability e g roughly 0 1 10 m d 1 and relatively low storativity roughly 1e 5 m 1 e g dense fine sands the new method in which streambed storage effect is incorporated can provide more reliable estimations of time dependent ksb for a stream confined aquifer system and it has been successfully applied to estimate the time dependent ksb of a reach of the arkansas river kansas usa

correlating deformation in variscan nw iberia using porphyroblasts implications for the ibero armorican arc abstract 3 d microstructural analysis of 30 porphyroblastic samples from the variscan orogen in nw iberia has revealed four sets of inclusion trails with distinctive geographic trends and relative timing the chronological and orientational consistency of these microstructures provides a reference frame for the correlation of macroscopic structural successions the two younger inclusion trail sets correlate with the main map scale structures of middle to upper carboniferous age whereas the two older sets correspond to mesoscopic structures preserved locally in low strain pods and dating back as far as 365 ma upper devonian inclusion trail orientations appear uninfluenced by a major orocline in the study area ibero armorican arc outlined by late stage folds and thrusts with variable trends it is proposed that the orocline developed by wnw ese trending transpression superposed on originally n s to ne sw trending structures during a late stage of the orogeny upper carboniferous domains of low or zero strain e g porphyroblasts are inferred to have maintained relatively constant orientations in the zone of transpression presumably due to deformation partitioning effects consequently they preserve a succession of pre orocline structural trends the collected microstructural data also indicate moderate preferred vertical and horizontal orientations of inclusion trails in the analysed samples as reported earlier in other variscan regions this probably witnesses a dynamic equilibrium between tectonic forces and gravity during four periods of differently oriented crustal shortening that generated the four recognised sets of inclusion trails

an open system model for u series age determinations of fossil corals the source of excess 234u in fossil corals and its relationship to u series age determinations has been an outstanding problem in geochronology for more than 20 years with increasing numbers of u series isotope measurements in corals and significant improvements in analytical precision through mass spectrometry it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably explained by closed system decay moreover observations of a positive correlation between 234u 238u and 230th 238u ratios in corals from the same terrace are difficult to explain however the decay of dissolved uranium and recoil mobilization of uranium daughters produce particle reactive 234th and 230th and the coupled addition of these th isotopes could simultaneously increase coral 234u 238u and 230th 238u here we present a quantitative model based on decay dependent redistribution of 234th and 230th permitting calculation of open system coral ages these equations provide a general solution to the recoil redistribution problem applicable to any alpha decay series while measured isotope ratios of corals from the three youngest stratigraphically defined barbados terraces are inconsistent with closed system decay they fall in broadly linear arrays agreeing with model predictions isotopic arrays of older barbados corals and corals from terraces around the world are also consistent with model predictions suggesting the open system model is generally applicable corals with extreme isotopic compositions that are impossible to produce by closed system decay are consistent with the limited range of isotopic compositions predicted by the model at ages older than 600 ka for corals from a single terrace 234th and 230th redistribution appears to be a source of systematic conventional age error even for corals with slightly elevated 234u however open system ages are consistent even for corals with extremely elevated 234u for the youngest three barbados terraces mean open system terrace ages are consistent with mean conventional terrace ages calculated from pristine samples if the most accurate conventional ages are from corals with an initial 234u 238u identical to modern seawater then the open system model will improve the accuracy of coral u series age determinations and dramatically increase the number of reliable ages

geochronology of early to middle proterozoic fold belts in northern australia a review abstract this geochronological review integrates geologically relevant isotopic data from the several early to middle proterozoic fold belts of northern australia a number of firm chronological benchmarks largely established by means of u pb zircon studies now provide a time framework within which to better quantify the tectonostratigraphic history of many of these terranes the apparent worldwide dearth of crustal events in the earliest proterozoic between 2500 and 2000 ma was broken in northern australia with the advent of a major crust forming episode between 1880 and 1850 ma ago these rocks may have evolved from an initial mantle or lower crustal melting and fractionation process about 400 300 ma earlier that is evidenced from sm nd model ages the extent involvement and or degree of assimilation of any pre existing archaean crust is small but whether or not it is negligible or zero is not satisfactorily known the 1880 1850 ma event the barramundi orogeny is well represented in northern australia both lithologically and analytically and the rocks that pre and post date it have a similar tectonic setting over very wide areas of the continent two consistent and widespread elements of this tectonism are regional metamorphism and deformation of the first cycle of supracrustals barramundi orogeny and crystallization of i type k rich felsic magmas closely following and in some cases overlapping with deformational processes in the halls creek inlier the ages of this rapid deep crustal to supracrustal tectonic transition cannot be distinguished within the range 1860 1850 ma this major yet short lived tectonism is mirrored in other fold belts such as pine creek tennant creek and mount isa in which u pb zircon ages give slightly older constraints of 1885 1870 ma 1920 1870 ma and 1885 10 ma respectively the ensuing felsic magmatism in these latter terranes continued for a few tens of millions of years with the crystallization and emplacement of comagmatic volcanic plutonic pairs throughout in the interval 1870 1860 ma in the georgetown and arunta inliers direct evidence of this otherwise ubiquitous event if present is masked by younger high grade metamorphism in the latter however metamorphic crustal components having approximate protolith ages of this order can be inferred from their evolved isotopic signatures the geochronological and geochemical coherency of the extensive early proterozoic 1870 ma magmatism contrasts with that of post 1800 ma magmatism which is less extensive generally anorogenic commonly bimodal in character and varies in age from one terrane to another several major sedimentary basins were being filled at this time major igneous events at 1790 1740 ma 1670 ma and 1500 ma are recognized elongate sublinear volcanic and plutonic belts 1790 1740 ma old are present at mount isa in high grade granitic gneisses of the arunta inlier a few u pb zircon ages and extrapolated rb sr protolith ages are coincident at about 1760 1750 ma indicating that this event may be important in the development of the division 2 sequences of that fold belt the platformal hart dolerite and oenpelli dolerite two of the largest mafic intrusions in the world were emplaced at 1762 25 ma and 1688 13 ma younger felsic plutonism and volcanism gave rise to rapakivi type granites in the mount isa tennant creek and the granites tanami inliers at 1670 ma a time close to that of the aileron deformational metamorphic event in central australia further at 1650 ma there is growing evidence of an unexpectedly coherent hydrothermal episode that reset or disturbed many rb sr ages gave rise to pegmatites and was possibly associated with mineralization in the davenport and eastern arunta inliers discrete middle proterozoic deformational events between 1610 and 1470 ma punctuate the tectonostratigraphic history in the arunta mount isa and georgetown fold belts where they are best documented

radioisotopic studies of submarine hydrothermal vents the importance of mid ocean ridge hydrothermal systems has been recognized for their role in the regulation of ocean and sediment chemistry as well as for providing a chemosynthetic source of carbon which drives a unique population of animals found at hydrothermal vents despite the importance of these systems the rates length and depth scale of submarine hydrothermal processes are not precisely known because they are for the most part inaccessible to observational tools we must therefore rely on indirect methods to quantify these processes one way of investigating the rates or timescales of processes in a hydrothermal or any natural system is through the study and modeling of naturally occurring radioisotopes disequilibria among the naturally occurring radioactive decay series in vent fluids associated mineral deposits and overlying effluent plume have provided geochemical tools to investigate the rates of various processes occurring in submarine hydrothermal systems because the half lives of the radioisotopes vary from days to many years processes which encompass a wide range of spatial and temporal scales can be studied this paper presents a review of methods that estimate the residence time of hydrothermal fluids in the ocean crust establish the geochronology of seafloor sulfide deposits investigate the rates of chemical reactions within hydrothermal effluent plumes and derive the heat and mass flux from seafloor hydrothermal areas

extensional v contractional origin for the southern menderes shear zone sw turkey tectonic and metamorphic implications the southern menderes massif in southwest turkey consists mainly of orthogneisses and overlying palaeozoic middle paleocene schists and marbles the contact between the two distinct rock types is almost everywhere structural herein named the southern menderes shear zone a s facing high angle ductile shear zone that separates metamorphic rocks of differing grade although there is a consensus that the shear zone was associated with top to the s ssw shearing and is of tertiary age its origin and nature have been highly debated over the last decade some claim the contact is a thrust fault while others have argued for an extensional shear zone integration of field and microstructural data the identification of different fabrics associated kinematics and overprinting relationships with fission track thermochronology and the p t paths of the rocks above and below the shear zone supports the conclusion that the southern menderes shear zone is an extensional shear zone and not a thrust the data are consistent with a model that the exhumation and cooling of the southern menderes massif occurred after a period of extensional deformation pervasive top to the n nne high temperature medium pressure ductile shear structures d 2 deformation overprint an early hp event d 1 deformation the subsequent top to the s ssw greenschist shear band foliation d 3 deformation developed mostly around the orthogniess schist contact and forms the most characteristic features of the massif the top to the n nne structures are attributed to the main alpine constructional deformation that developed during back thrusting of the lycian nappes during the latest palaeogene collision between the sakarya continent and the anatolide tauride platform across the neotethyan ocean the top to the s ssw structures are interpreted to be the result of the exhumation of the massif during the activity of the southern menderes shear zone the presence of these two distinct fabrics with differing kinematics suggests that the southern menderes shear zone operated as a top to the n nne thrust fault during early alpine contractional deformation but was later reactivated with an opposite sense of movement top to the s ssw during subsequent oligocene miocene extensional collapse

permian bulk shortening in the narragansett basin of southeastern new england usa pennsylvanian age sediments within the narragansett basin allow the effects of alleghanian deformation to be distinguished from the taconic and acadian orogenies that affected the rocks to the west three dimensional microstructural analyses of both matrix foliations and structures preserved in porphyroblasts define two extended periods of deformation and metamorphism about two differently trending foliation intersection inflection axes in porphyroblasts fias ssw nne trending fias set 1 formed first followed by wsw ene trending fias set 2 the ssw nne fia trends from the south central zone lie parallel to regional folds in the entire southern graben the changes in fia trends reveal that the direction of maximum bulk shortening changed from wnw ese to nnw sse during amphibolite facies metamorphism within the central zone of the basin they reveal a more varied history than the simple kinematic framework of solely w e directed bulk shortening that was previously suggested

aquifer response to stream stage and recharge variations i analytical step response functions abstract laplace transform step response functions are presented for various homogeneous confined and leaky aquifer types and for anisotropic homogeneous unconfined aquifers interacting with perennial streams flow is one dimensional perpendicular to the stream in the confined and leaky aquifers and two dimensional in a plane perpendicular to the stream in the water table aquifers the stream is assumed to penetrate the full thickness of the aquifer the aquifers may be semi infinite or finite in width and may or may not be bounded at the stream by a semipervious streambank the solutions are presented in a unified manner so that mathematical relations among the various aquifer configurations are clearly demonstrated the laplace transform solutions are inverted numerically to obtain the real time step response functions for use in the convolution or superposition integral to maintain linearity in the case of unconfined aquifers fluctuations in the elevation of the water table are assumed to be small relative to the saturated thickness and vertical flow into or out of the zone above the water table is assumed to occur instantaneously effects of hysteresis in the moisture distribution above the water table are therefore neglected graphical comparisons of the new solutions are made with known closed form solutions

from adria to africa driven orogenesis evidence from porphyroblasts in the betic cordillera spain abstract in order to unravel the kinematic evolution of the betic rif orogen we investigated the geometry of porphyroblast inclusion trails in the nevado filabride complex a high pressure unit situated at the base of the betic nappe stack a large number of quantitative orientation data for these microstructures and their mutual overprinting relationships reveal two age groups of inclusion trails in the study area with distinctive geographic trends coupled to a comprehensive compilation of field data in the study area these microstructures are shown to coherently witness the development of early ne sw trending structures and fabrics followed by younger nw se trending ones whereby the former experienced clockwise reorientations a major change in the direction of bulk crustal shortening from nw se to ne sw is inferred from these data and tentatively linked to the plate tectonic history of the mediterranean region paleomagnetic data indicate that prior to about 35 ma nw se convergence between adria eurasia and iberia produced orogenesis along a belt bordering greater iberia including sardinian and corsica and probably continuous in the alps brianconnais domain the roughly ne sw trend of this precursor appears to be preserved within porphyroblasts that grew during this period presumably due to the partitioning of deformation around them africa iberia relative motion had been mainly transcurrent until 35 ma azores transform but then rapidly changed to head on nne ssw convergence this gave rise to a second set of nw se trending structures which accompanied deformation of the precursor orogen into several oroclines western alps gibraltar and calabria arcs orogenic collapse and crustal extension initiated shortly after this transition in tectonic regime suggesting a causal relationship we propose that the waning of compressive stresses transmitted by adria and their substitution by a near perpendicular maximum stress direction resulting from africa eurasia convergence could have enhanced the sinking of a thick lithospheric root or roll back of a subducted slab which in turn would have provoked crustal extension and basin formation

submarine hydrothermal mineralization in the okinawa trough sw of japan an overview abstract the okinawa trough is a heavily sedimented rifted back arc basin formed in an intracontinental rift zone submarine hydrothermal activity is located within the six back arc rifts located in the middle and southern okinawa trough and its distribution is controlled principally by tectonic factors subduction of the daito and gagua ridges beneath the ryukyu arc has resulted in fracturing of the brittle lithosphere beneath the okinawa trough hydrothermal activity is strongest in the volcanic arc rift migration phenomenon vamp area plus the jade site and southernmost part of the okinawa trough spot area which form the prolongation of these two ridges these areas are characterized by extremely high heat flow locally submarine hydrothermal fluids from the okinawa trough tend to be strongly influenced by interaction of the hydrothermal fluids with organic matter in the sediment resulting in high alkalinity and nh 4 concentrations of the fluids the fluids also contain high concentrations of co 2 of magmatic origin submarine hydrothermal mineralization in the trough is diverse the clam site consists principally of carbonate chimneys interaction of the hydrothermal fluid with organic matter in the sediment is particularly strong at this site this is most probably a sediment hosted deposit in which sulphide minerals have deposited within the sediment column leaving spent ore fluids to emerge at the seafloor the jade site consists of active and inactive sulphide sulphate chimneys and mounds the zn pb rich sulphides at this site contain the highest concentrations of pb ag and au so far recorded in submarine hydrothermal sulphide deposits at minami ensei knoll and hatoma knoll active and inactive chimneys consist principally of anhydrite and barite as a result of phase separation of the hydrothermal fluids beneath the seafloor an intense black smoker has recently been discovered at yonaguni knoll in the spot area if it is confirmed that sulphide mineralization is dominant at this site this could be a highly prospective area the most prospective areas for economic grade minerals in the okinawa trough appear to be the jade site and the spot area

water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams summary karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes matrix and fractures for more than a century various approaches have used flood recession curves which integrate all hydrodynamic processes in a karst aquifer to infer physical properties of the movement and storage of groundwater these investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves we present analyses of simultaneous discharge and water level time series of two distinctly different karst systems one with low porosity and permeability matrix rocks in southern france and one with high porosity and permeability matrix rocks in north central florida usa we apply simple mathematical models of flood recession using time series representations of recharge storage and discharge processes in the karst aquifer we show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer conduit and matrix porosity which induce two distinct responses at the spring water exchange between conduits and matrix porosity successively control the flow regime at the spring this exchange is governed by hydraulic head differences between conduits and matrix head gradients within conduits and the contrast of permeability between conduits and matrix these observations have consequences for physical interpretations of recession curves and modeling of karst spring flows particularly for the relative magnitudes of base flow and quick flow from karst springs finally these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data but information must be known about the hydrodynamics and physical properties of the aquifer before the results can be correctly interpreted

porphyroblast nucleation growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development in regional metamorphic rocks the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain rate gradients across the boundaries between the partitioned zones these generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain because of their uniquely layered crystal structure however most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients and hence are susceptible to dissolution and solution transfer as a consequence zones of progressive shearing become zones of dissolution of most minerals and of concentration of phyllosilicates and graphite exceptions are mylonites where strain rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing as they would be dissolved by the effects of shearing strain on their boundaries however they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation this includes a build up of stored strain energy relative to zones of progressive shearing in which dissolution is occuring porphyroblast growth is generally syndeformational and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account porphyroblasts in a contact aureole do not grow statically either as microfracturing associated with emplacement allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening the criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning reactivation of deforming foliations and a general lack of rotation of porphyroblasts with the spectacular exception of genuinely spiralling garnet porphyroblasts

electrical and hydraulic vertical variability in channel sediments and its effects on streamflow depletion due to groundwater extraction summary the stratification of channel sediments and their vertical hydraulic conductivity kv are important hydrologic information in the analysis of stream aquifer interactions this paper describes the use of direct push technology to generate electrical conductivity ec logs and collect continuous sediment cores beneath river channels the techniques were applied to nine study sites along a 130 km reach of the platte river in southeast nebraska ec logs for the channel surface down to as much as 24 m below the channel surface indicate that the channel sediments in the western part of the reach consist predominantly of sand and gravel low kv silt clay layers occur in the rest of the reach these silt clay layers are either interbedded with sand and gravel or occur as a major unit within the channel sediments as a result the values of kv determined from the sediment cores can vary by four to five orders of magnitude in the same vertical profile of channel sediments at a number of sites the river channel is not lined by a low kv layer at the surface instead the kv values for the top part of channel sediments were consistently greater than kv values for sediments in deeper parts they show a decreasing tendency with the depth this paper also analyzes the effect of low kv layers within channel sediments on streamflow depletion induced by groundwater pumping simulation results suggest that the effectiveness of low kv layers on the calculation of streamflow depletion depends on their depth thickness vertical permeability the length along the channel and the width within the channel as well as the extension into the aquifer on both sides of the river a low kv layer present at the channel surface seems to be the most effective hydrologic feature in reducing the hydrologic connection of stream aquifer a 2008 elsevier b v all rights reserved

controls on uranium and thorium behaviour in ocean floor hydrothermal systems examples from the pindos ophiolite greece abstract a suite of hydrothermally altered basaltic rocks from the jurassic pindos ophiolite of greece was analysed for its u and th content samples taken from different levels within the ophiolite display variable degrees of hydrothermal alteration ranging from low water rock ratio recharge zone alteration to high water rock ratio discharge zone alteration most samples analysed exhibit constant u th ratios regardless of the degree of alteration however neither of these two elements correlate with any other immobile element zr y ti ree these results suggest that both u and th have been mobile during high temperature ocean floor hydrothermal alteration and indicate a common probably mineralogical control for both elements the chemical composition of hydrothermal fluids from modern tectonic settings equivalent to that of the pindos ophiolite east pacific rise guaymas basin was used to predict theoretical aqueous speciation and solubility of u and th during water rock interaction in these environments the results of this treatment agree with the above conclusions drawn from rock studies and indicate that oxide mineral phases uraninite thorianite control u and th solubility during hydrothermal alteration at oceanic spreading environments

a deformation partitioning approach to resolving the sequence of fold events and the orientations in which they formed across multiply deformed large scale regions abstract regional distributions of axial plane trends retain information on the orientation in which successive generations formed because multi scale partitioning results in most orogenic belts preserving subsequently undeformed portions of all large scale folds at depths greater than 10 km within orogens successions of regional folds are accompanied by the sequential development of crenulation hinges in pelites which are commonly overgrown early during their development by successive generations of porphyroblasts consequently the original trends of the axial planes of these folds are preserved within the distribution of foliation inflection intersection axes within porphyroblasts fias peaks in the distribution of fia trends in western maine predominantly coincide with peaks in the distribution of trends of the axial planes of macroscopic and regional folds the wnw ese 420 ma n s 408 10 ma w e 388 9 ma wsw ene 372 5 ma sw ne 353 4 ma succession of fia peaks defines the sequence of folds and accords with map scale overprinting relationships this quantitative approach to interpreting fold successions in multiply deformed terrains resolves timing where overprinting criteria are rare uncertain or obliterated by younger events in portions of the orogen significantly lengthy detailed histories of structural development can be extracted from a small area containing porphyroblastic rocks and applied to very large scale regions

distribution of pre folding linear indicators of movement direction around the spring hill synform vermont significance for mechanism of folding in this portion of the appalachians abstract three distinctly oriented sets of pre folding and one set of syn folding axes of curved inclusion trails are preserved in garnet porphyroblasts in 50 samples around the doubly plunging spring hill synform in southeast vermont over one third of the samples contain consistent changes in the trend of these axes from the core to rim since the core grew before the rim this enabled the relative timing of each set of axes to be determined from the oldest to the youngest as ne sw e w nnw sse and nne ssw the youngest trend is parallel to the axial plane of the regional folds only those samples with the latter trend have their inclusion trails connected continuously to the matrix foliation the three pre folding sets of axes have the same orientation on both limbs this consistency in orientation has significant implications for the processes operating during folding and three mechanisms are presented that could potentially explain it these involve the classic card deck model of shear folding de sitter s model of clay bricks shortening as they shear past one another and the progressive bulk inhomogeneous shortening model the relative merits of each of these models are discussed

episodic porphyroblast growth in the fleur de lys supergroup newfoundland timing relative to the sequential development of multiple crenulation cleavages inclusion trails in garnet and albite porphyroblasts in the fleur de lys supergroup preserve successive generations of microstructures some of which correlate with equivalent microstructures in the matrix microstructure porphyroblast relationships provide timing constraints on a succession of seven crenulation cleavages s1 s7 and five stages of porphyroblast growth significant destruction and alteration of early fabrics has occurred during the microstructural development of the rock mass garnet porphyroblasts grew episodically through four growth stages g1 g4 and preserve a succession of five fabrics s1 s5 as inclusion trails garnet growth during each of the four growth phases did not occur on all pre existing porphyroblasts resulting in contrasting growth histories between individual garnet porphyroblasts from the same outcrop albite porphyroblasts grew during a single stage of growth and have overgrown microstructures continuous with the matrix the garnet and albite porphyroblast inclusion trails record a succession of crenulation cleavages without any rotation of the porphyroblasts relative to other porphyroblasts in the population complex microstructural histories are best resolved by preparing multiple oriented thin sections from a large number of samples of different rock types within the area of study the succession of matrix foliations must be understood as it provides the most useful time frame against which to measure the relative timing of phases of porphyroblast growth comparable microstructures must be identified in different porphyroblasts and in the rock matrix

significance of dextral reactivation of an e w transfer fault in the formation of the pennsylvania orocline central appalachians 1 three hypotheses for orocline development including 1 primary plate boundary shape 2 arc rotation and 3 arc overprinting were evaluated for the formation of the pennsylvania orocline maryland usa using foliation intersection inflection axes preserved within porphyroblasts fia the distribution and the timing of sequences of fia data measured from garnet porphyroblasts within the loch raven formation are statistically the same across the pennsylvania orocline suggesting that all subregions of the arc have experienced the same deformation history this may suggest that the geometry of the paleocontinental margin controlled the basic shape of this orocline however if the orocline is treated as three separate regions defined by the sw we ne trending portions of its slightly staircase shaped outline a much higher proportion of the nne ssw trending fias set ii are preserved in the w e trending region than those to either side this geometric relationship could have resulted from wnw ese directed bulk stress causing a zone of dextral shear along what is now the w e trending portion of this orogen it appears that what could have been an early formed w e trending sinistral transform shear zone was preferentially dextrally reactivated during the taconian orogeny

a long lived metamorphic history in the contact aureole of the mooselookmeguntic pluton revealed by in situ dating of monazite grains preserved as inclusions in staurolite porphyroblasts emplacement of the mooselookmeguntic pluton located in the western maine region of the northern appalachians was thought to have occurred towards the end of the acadian deformation at around 370 ma crystallization ages from different parts of the pluton suggest a more sequential emplacement history over a period of c 20 myr foliation inflection intersection axes fias within porphyroblasts from its aureole reveal at least five periods of garnet and staurolite growth the orientation of fias in both garnet and staurolite porphyroblasts trend successively from ese wnw nnw sse e w ene wsw to ne sw electron probe microanalysis dating of monazite grains included in staurolite porphyroblasts containing one of these five periods of fia development reveals a succession of apparent ages from 410 ma to 345 ma a similar spread of crystallization ages can be observed for plutons from maine and adjacent regions this succession indicates that deformation and metamorphism began well before and continued long after what is classically regarded as the acadian orogeny the thermal structure of the orogen progressively evolved to enable pluton emplacement and it continued to develop afterwards with magmatic fluids still forming at depth

deformation partitioning foliation successions and their significance for orogenesis hiding lengthy deformation histories in mylonites although orogenesis commonly lasts 100 million years a maximum of three foliations are usually preserved within any outcrop they record little of the total history due to the effects of preferential partitioning of progressive shearing along s0 such reactivation eventually destroys or rotates multiple successive foliations into parallelism with any layering that is present plate motion subjects a collisional orogen to spatially partitioned episodic but non stop deformation the bulk forces operating are horizontal and intermittently vertical associated with gravitational load due to crustal thickening forming sub vertical and sub horizontal foliations these orientations are preserved in the strain shadows of anything competent that hinders reactivation of the compositional layering deformation partitioning results in portions of rock remaining unaffected for many events gravitational collapse of over thickened orogen cores leads to significant extrusion in orogen rims and a dominance of sub horizontal foliations in the latter and episodically continues throughout orogenesis reactivation causes decrenulation and or rotation of foliations into parallelism with s0 destroying evidence that multiple sub vertical and sub horizontal foliations have developed except where preserved as inclusion trails in porphyroblasts and multiply truncated foliations in mylonites however the same processes operate in both the cores of orogens and ductile portions of their margins

episodic metamorphic reactions during orogenesis the control of deformation partitioning on reaction sites and reaction duration textural unconformities or truncations are common in porphyroblasts with complex inclusion trails they reflect cycles of successive foliations that develop against competent porphyroblasts during orogenesis and are preserved by successive growth increments their truncational character results from shear and dissolution along a particular foliation generating a differentiated crenulation cleavage the increment of porphyroblast growth that follows a textural unconformity may or may not mark a significant compositional change depending on the amount of movement of the rock through p t space between cleavage forming events although historically interpreted to result from a significant metamorphic hiatus most textural unconformities indicate that the reactions involved in the formation of these minerals are episodic during continuous prograde metamorphism starting and stopping as a function of the stage of crenulation of the matrix foliation and the pattern of deformation partitioning such episodic reaction behaviour can only occur for multivariant reactions or successive but different univariant reactions the reason why garnet is the most common porphyroblast to exhibit evidence for episodic reactions is probably the fact that it grows by multivariant reactions over a much wider p t range than most other common porphyroblast phases porphyroblast growth is micrometasomatic it is episodic because a significant reduction of strain occurs within domains of progressive shortening each time continuous progressive shearing domains form on their margins this stops microfracture development across the progressive shortening domains thereby preventing rapid access and interaction of fluid ions and complexes with porphyroblast boundaries shifting patterns of deformation partitioning and resulting small scale juxtaposition of different compositional layers spreads the duration and location of multivariant reactions and causes differential timing of porphyroblast growth along a particular stratigraphic horizon it may also locally preserve metastable metamorphic assemblages in regionally metamorphosing deforming pelites near simultaneous cessation of porphyroblast growth on all rims once continuous differentiated progressive shearing domains have formed nearby precludes fluid recirculation as a significant process for removal of material during cleavage development alternatively diffusion of simple molecules and dissociated ions along actively shearing and micro gaped phyllosilicates with recomplexing in fluid filled microfractures readily explains the control of deformation partitioning on reaction site and reaction duration

groundwater flow in sloping aquifer under localized transient recharge analytical study abstractthis paper analyzes the groundwater flow system in an unconfined downward sloping aquifer of semi infinite extent in response to localized transient recharge the aquifer is in contact with a water body of constant water level at one end and receives localized transient recharge from a recharge basin of finite width the mathematical model is based on the boussinesq equation with dupuit forchheimer assumption in which the spatial coordinate of the recharge basin is treated as an additional parameter analytical solutions of the linearized boussinesq equation are obtained using the laplace transform technique by dividing the aquifer in a three zone system containing both dirichlet and neumann boundary conditions at the hypothetical interfaces upward and zero sloping cases are deduced from the main results by appropriately adjusting the slope parameter to assess the validity and efficiency of the linearization method the nonlinear boussinesq equation is also solved using a fully explicit predic

groundwater dynamics due to general stream fluctuations in an unconfined single or dual porosity aquifer subjected to general areal recharge abstract analytical solutions of groundwater dynamics in an elongated aquifer subjected to general time dependent recharge are presented the lateral boundaries are specified heads with the head variations governed by general time dependent functions general recharge function was not considered in previous works of this kind both single and double porosity aquifers are considered the solution is obtained using fourier sine and laplace transformations followed by an inverse fourier laplace transform involving residue theorem and convolutional integral for the unconfined single porosity aquifer case the exact time domain solution is obtained using the residue theorem for the unconfined double porosity aquifer case the time domain head is calculated using the de hoog inverse laplace algorithm the presented solution can be used to estimate the hydraulic parameters of 1 groundwater head variation of a river basin aquifer subjected to general lateral head variation and recharge 2 groundwater head variation in a double porosity elongated fractured anticline 3 groundwater depletion of an elongated fractured anticline subjected to recharge due to rainfall or snowmelt to its adjacent alluvial aquifer in addition the presented solution can be utilized to optimize the irrigation pattern in a cropland between two trench drains to control the groundwater mound

multi stage mountain building vs relative plate motions in the betic cordillera deduced from integrated microstructural and petrological analysis of porphyroblast inclusion trails abstract the tectonic evolution of the betic cordillera has been investigated through integrated microstructural and petrological analysis of 93 samples of garnetiferous grt cld plg ky st phengite schists from its lowermost allochthon the nevado filabride domain porphyroblast inclusion trails in these samples exhibit well developed preferred vertical and horizontal orientations and truncational relationships these features indicate a complex history of multiple crenulation cleavage development during alternating contractional and gravity induced deformations associated foliation intersection axes preserved in porphyroblasts fia were determined separately for 2 groups of samples using the asymmetry technique bell et al 1995 and the fitpitch method aerden 2003 respectively broadly consistent results establish a succession of 4 fia sets with specific trends which from the oldest to the youngest fia set are ne sw fia set 1 nw se fia set 2 w e fia set 3 and nnw sse fia set 4 this trend sequence is also reflected in the orientations of successive fold generations and associated lineations more remarkably the fia trend sequence mimics known changes in the plate motions of africa and adria relative to iberia in the 50 10 ma interval this is also the time span indicated by published radiometric ages garnet isopleth thermobarometry applied to selected samples and compositional zoning of garnets indicate that the earliest 3 fia sets formed along a prograde metamorphic path from ca 5 kb 500 c to 10 kb 550 c whereas the latest stages of fia set 3 and fia set 4 developed during exhumation exhumation involved a period of heterogeneous reheating that was spatially and temporally linked to emplacement of the overlying alpujarride complex

kinematics of the alpine arc and the motion history of adria the alps have been interpreted traditionally in terms of north or northwest directed convergence between africa and europe1 with adria the continental underpinnings of the adriatic sea and northern italy acting as a promontory of the african continent2 this has been supported by recent analyses of africa europe relative plate motions3 5 which indicate dominantly north south directed convergence during the tertiary phase of intracontinental shortening we show here however that kinematic indicators from alpine tectonites are difficult to reconcile with this motion history figs 1 and 2 and are explained best by roughly west northwest directed adria europe motion since about 70 million years ago combined with an arc normal pattern of motion driven by local body forces this implies that adria has moved independently of both africa and europe since at least the late cretaceous

flow kinematics in the deeper part of a subduction channel as inferred from inclusion trails in plagioclase porphyroblasts from the sambagawa metamorphic rocks south west japan the subduction and exhumation of accretionary prism metasedimentary rocks are accompanied by large strain ductile deformations which may be recorded in microstructures porphyroblast microstruc tures have been a key to unravel the kinematics in such deformed belts shape preferred orientation spo of epidote and amphibole inclusions that define s shaped trails in prograde cores of plagioclase porphyroblasts were analysed from the high p t sambagawa metamorphic rocks inclusions are found to be elongate parallel to the 010 and 001 directions respectively and their long axis orientations define an internal foliation si best fit great circle and lineation li maximum on the si s shaped inclusion trails in the orthogonal sections do not exhibit the same geometries but rather are grouped into two types where the foliation intersection axes fias are nearly perpendicular and parallel to li respectively these two types of s shaped inclusion trails are seen in the sections inclined at low and high angles to the li respectively however the latter type commonly consists of composite trails where the si is first rotated about an fia perpendicular to the li i e unique axis and then about an fia parallel to the li the s shaped inclusion trails are interpreted to have formed by the successive overgrowth of matrix minerals and rotation of the plagioclase porphyroblast cores about a unique axis in non coaxial deformation the rotation of si about an fia nearly parallel to the li is perhaps an apparent rotation caused by the deflection of foliation around the growing prismatic plagioclase grain prior to inclusion into the porphyroblast this study has for the first time documented the 3 d geometry of s shaped inclusion trails in porphyroblasts from accretionary prism metasedimentary rocks and identified their origin which helps to understand the flow kinematics in the deeper part of a subduction channel

sulfide geochronology along the endeavour segment of the juan de fuca ridge 1 forty nine hydrothermal sulfide sulfate rock samples from the endeavour segment of the juan de fuca ridge northeastern pacific ocean were dated by measuring the decay of 226ra half life of 1600 years in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years this dating method is effective for samples ranging in age from 200 to 20 000 years old and effectively bridges an age gap between shorter and longer lived u series dating techniques for hydrothermal deposits results show that hydrothermal venting at the active high rise sasquatch and main endeavour fields began at least 850 1450 and 2300 years ago respectively barite ages of other inactive deposits on the axial valley floor are between 1200 and 2200 years old indicating past widespread hydrothermal venting outside of the currently active vent fields samples from the half graben on the eastern slope of the axial valley range in age from 1700 to 2925 years and a single sample from outside the axial valley near the westernmost valley fault scarp is 5850 205 years old the spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift these relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

aquifer response to stream stage and recharge variations ii convolution method and applications abstract in this second of two papers analytical step response functions developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined leaky or water table aquifer are used in the convolution integral to calculate aquifer heads streambank seepage rates and bank storage that occur in response to stream stage fluctuations and basinwide recharge or evapotranspiration two computer programs developed on the basis of these step response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream aquifer systems in the northeastern and central united states these applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties recharge rates streambank seepage rates and bank storage analysis of the water table aquifer adjacent to the blackstone river in massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer negligible specific yield this finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe where sediment pores are saturated by tension extends to land surface under this condition the aquifer s response is determined by elastic storage only estimates of horizontal and vertical hydraulic conductivity specific yield specific storage and recharge for a water table aquifer adjacent to the cedar river in eastern iowa determined by the use of analytical methods are in close agreement with those estimated by use of a more complex multilayer numerical model of the aquifer streambank leakance of the semipervious streambank materials also was estimated for the site the streambank leakance parameter may be considered to be a general or lumped parameter that accounts not only for the resistance of flow at the river aquifer boundary but also for the effects of partial penetration of the river and other near stream flow phenomena not included in the theoretical development of the step response functions

preferred orientation of planar microstructures determined via statistical best fit of measured intersection lines the fitpitch computer program the fitpitch computer program allows characterisation of preferred orientation of planar microstructures in a rock from the orientations of their intersection lines on different sections measured pitch or strike angles of such intersection lines are fitted to the theoretical intersection lines of a single model plane or a combination of two or three model planes the degree of fit is quantified in terms of the deviation between natural and theoretical intersection lines normalised by uniform data a first application is described concerning porphyroblast inclusion trails whose orientation in 28 samples from the variscan iberian massif was measured analysis of these data illustrates how the method can be used to quantify preferred orientation of relict foliations contained in a group of porphyroblasts and how this complements existing techniques for determining foliation intersection axes fia in porphyroblasts a second described application deals with previously published orientation data for microfracture trace lines in quartz grains of a variscan granite in the rhine graben qualitatively established best fit planes derived originally from this data are compared with the numerically established planes using the fitpitch program and discussed in terms of the advantages and potential limitations of the method q 2002 published by elsevier science ltd

provenance weathering and erosion records in southern okinawa trough sediments since 28ka geochemical and sr nd pb isotopic evidences abstract geochemical and sr nd pb isotopic compositions of the detrital sediments from odp hole 1202b and taiwan rivers were measured in this study aiming to reveal changes in sediment provenance in the southern okinawa trough sot since 28 ka and to examine the weathering and sediment transport processes in response to monsoon climate variability large variations in sr nd pb isotopic ratios at 11 9 ka suggest changes in detrital sediment provenance in the sot from a dominance of the paleo changjiang yangtze river and or continental shelf sediment during the late deglaciation and to west taiwan rivers since 9 5 ka volcanic rocks and eastern taiwan sediments have not significantly contributed to the sot the large shift in sediment provenance during the early holocene marks a major change in oceanic circulation mainly caused by the intrusion of the kuroshio current into the trough clay mineral and geochemical proxies suggest that the taiwan derived sediments accumulated during the early mid holocene climate optimum ca 9 5 4 ka might be tightly related to the reworking of older altered sediments from terraces and floodplains rather than having experienced more intense silicate weathering than in the late holocene 4 0 ka overall silicate weathering in taiwan was greatly inhibited by accelerating sediment production and transfer from land to ocean caused by monsoon intensification in holocene our study illustrates that the radiogenic isotopic and geochemical compositions of fine grained detrital sediments are sensitive tools for fingerprinting sediment sources and for reconstructing changes in oceanic currents and monsoon climate in river dominated east asian continental margin

strontium lead and zinc isotopes in marine cores as tracers of sedimentary provenance a case study around taiwan orogen abstract the active collision zone around taiwan orogen receives a variety of sedimentary inputs including terrigenous flux from taiwan and chinese rivers oceanic currents and atmospheric dust in order to determine the present day respective contributions of these different sources we analysed the pb and sr isotopic compositions of late quaternary sediments accumulated offshore east taiwan samples from the taiwan coastal range andesites sandstones conglomerate and peinan river terraces and suspended loads have also been analysed to constrain the mean taiwan isotopic signature mixing lines between the different sources of material indicate that the core located in the okinawa trough represents a mixture of about 60 of taiwan 30 of chinese loess and 10 of yangtze river contributions the southernmost core located close to luzon arc is influenced by taiwan 60 and volcanic material 40 the sr and pb isotopic compositions of samples cored in the manila trench and in the huatung basin are strongly influenced by the taiwan signature while the ryukyu trench core samples point to significant but variable contributions of chinese loess and yangtze river this work also reports zn isotopic variations in the silicate fraction of these marine core samples the overall variation in zn isotopic compositions expressed as 66zn is greater than 0 3 per mil for an analytical precision of 0 05 the zn isotopic signal for most of the marine core samples is similar to the literature data measured on sedimentary material except for the manila trench core samples and the older sample from the huatung basin they present values heavier by 0 2 0 3 close to those obtained on all taiwan rocks and peinan river particulates these results show 1 the particular characteristics of taiwan zn isotopic compositions on a large scale and 2 the possible use of zn isotopes as a tracer of material sources

transient solution for stream unconfined aquifer interaction due to time varying stream head and in the presence of leakage summary this paper presents new analytical solutions of a linearized boussinesq equation characterizing groundwater flow in a stream unconfined aquifer system due to transient seepage the aquifer is underlain by a horizontal leaky bed and interacts with an adjoining stream of varying water level through a semipervious vertical stream bank close form analytical expressions are derived to predict water head distribution flow rate and volumetric exchange of water in response to time dependent rise or drop in the stream water level comparison between analytical and numerical results shows satisfactory agreement the effects of the finite and semi infinite lengths of the domain are considered in detail certain asymptotic situations such as sudden rise or drop in the stream water level no flow condition at the aquifer s base and absence of vertical stream bank can be dealt with as limiting cases of main results an illustration of the new analytical approach is used to quantify the accretion recession of the bank storage due to variation in various aquifer parameters

mediterranean flash flood transfer through karstic area karstic aquifers influence flash floods propagation in mediterranean countries near montpellier southern france discharge data are recorded on the coulazou river upstream and downstream of the aumelas causse two gauging stations are used to describe the hydrodynamics of this binary karstic system the first station characterizes the non karstic catchment area the second one is representative of the karstic part of the watershed records since april 2004 are used to understand how the river interacts with a karstic aquifer hydrograph analysis of three flash flood events is described corresponding discharge time series recorded at the two gauging stations are used to describe the modification of the hydrographs by auto and crosscorrelations analyses finally linear system analyses are used to provide the transfer functions of this binary karstic system according to the three flood events characteristics initial conditions volume spatial distribution of rainfall etc theses functions summarize the hydrodynamic behaviour of the system their shapes are indicative of the dynamics of the storage the release and the contribution to surface waters

sequential porphyroblast growth and crenulation cleavage development during progressive deformation abstract six stages of crenulation cleavage development during a single deformation event d2 can be recognised in both matrix and porphyroblast inclusion trails in the robertson river formation n e australia these stages progress from undeformed to crenulation and differentiated crenulation of s1 through development of differentiated crenulation cleavage s2 and differentiated schistosity s2 to homogeneous foliation s2 these rocks underwent prograde metamorphism during d2 and chloritoid garnet staurolite andalusite and sillimanite isograds have been mapped most rocks are rich in porphyroblasts which commonly contain well defined inclusion trails the geometry of these trails varies from one mineral type to the next depending on the timing of porphyroblast growth relative to the stage of crenulation cleavage development in the schistose matrix the deformation history involved progressive bulk inhomogeneous shortening and the strain is very heterogeneous on all scales partly as a consequence of this hence each of the six stages of crenulation cleavage development formed locally at various times during d2 therefore if a porphyroblast grew late in the deformation it could overgrow all stages of crenulation cleavage development including the very early ones the temperature increased during metamorphism in any one locality and consequently some porphyroblasts overgrew others that were unstable in the new conditions preserving them from destruction hence the precise timing of mineralogical reactions deduced from isograds and mineral chemistry relative to the stages in schistosity development can also be determined in the andalusite zone the sequence of porphyroblasts in decreasing order of age is biotite garnet biotite staurolite andalusite dissolution of garnet occurred during growth of staurolite and especially andalusite and dissolution of staurolite accompanied andalusite growth

correlating deformation and metamorphism around orogenic arcs the timing of metamorphism and the p t t path the rocks have undergone commonly varies around orogenic arcs hindering correlation along orogens isotopic dating enables broad correlations to be made but detailed correlations can be difficult using this approach where several phases of metamorphism are present this is compounded by the large size of oroclines which hinders correlation of deformation and metamorphism using a succession of structures and associated metamorphism however foliation inflexion intersection axes fias preserved in porphyroblasts provide a tool for correlation around oroclinal arcs consistent successions of fias that remain constantly oriented around folds and across large tracts of multiply ductilely deformed country rock allow correlation of periods of metamorphism taking place during the one direction of horizontal bulk shortening rather than correlation of inferred growth events consequently rocks that have undergone different p t t paths can be correlated measurement of fias around the spectacular kimberley arc in northwest australia reveals that the first formed set maintain a consistent average trend of 127 degrees and a subhorizontal plunge this fia trend is parallel to the western arm of the arc but lies at a very high angle to the eastern arm foliations preserved as inclusion trails in porphyroblasts are continuous with foliations in the matrix on the western arm where the fias and structural grain are sub parallel however inclusion trails in porphyroblasts defining fias with these same trends on the eastern arm are truncated by the matrix foliation this indicates that foliations in the matrix on the eastern arm postdate all foliations in the matrix on the western arm two late sets of locally developed small kinks of the matrix foliation on the western arm which have axial planes parallel to foliations on the eastern arm are weak expressions of the overprinting events that controlled the geometry of the latter arm a second group of fias has been found in some samples on the eastern arm that lie sub parallel to the northeast trend of this arm they are defined by inclusion trails that are continuous with the matrix foliation and that occur in the rims of porphyroblasts such porphyroblasts generally contain a core with inclusion trails defining the first formed fia that lies sub parallel to the western arm the inclusion trails in porphyroblast cores are truncated completely by those in the rims in the same manner that those without this rim set of inclusion trails are truncated by the matrix foliation this second set of fias has not been found in any samples from the western arm fias thus provide a simple tool for correlating metamorphism around orogenic arcs the porphyroblasts with consistently oriented fias around the arc can be readily correlated and grew during the same period of metamorphism that affected both arms those with northeast trending fia record a younger period of metamorphism that affected only the eastern arm indeed until techniques and standards for dating porphyroblasts and their inclusions by both the microprobe and ion microprobe improve fias may provide the only quantitative tool that integrates metamorphic and structural phenomena and thus allows detailed correlation of these events along an orogen

porphyroblast rotation versus nonrotation conflict resolution comment fay et al 2008 1 present a few numerical simulations with unspecified code or boundary conditions as evidence for nonrotation of porphyroblasts during non coaxial flow however the large body of work on the behavior of porphyroblasts in deforming ductile rocks is significantly undervalued

an x ray computed tomography study of inclusion trail orientations in multiple porphyroblasts from a single sample inclusion trails in 58 garnet porphyroblasts in a single sample from the cram hill formation in southeast vermont were imaged using high resolution x ray computed tomography texturally the porphyroblasts have a large core with a sub vertical foliation that has a well defined geometry with a mean orientation of 113 72e for a 95 confidence cone semi angle of 5 3 this steep foliation curves into a sub horizontal foliation the foliation intersection inflection axes fias defined by hinge lines for this curvature are tightly clustered with a mean plunge of 11 towards 201 with a 95 confidence cone semi angle of 4 1 eigenvalue analysis indicates that the clustered distribution of the foliation and fia data are unlikely to be the result of a random event there is evidence in the specimen for multiple foliation forming events subsequent to garnet nucleation and the preservation of these clustered distributions in their wake strongly suggests that the porphyroblasts have not rotated with respect to a geographic reference frame fias represent a measurable structural element that can provide information on tectonic events at the time the porphyroblasts grew a comparison of fia data collected using high resolution x ray computed tomography with data collected using the asymmetry method demonstrates that the asymmetry method is a valid technique for defining the mean fia orientations in a sample

resolving complexities associated with the timing of macroscopic folds in multiply deformed terrains the spring hill synform vermont determining the timing of macroscopic folds of bedding in multiply deformed terrains is difficult especially for rocks that have undergone a succession of overprinting near orthogonal deformations the spring hill synform in southeast vermont is an example of such a fold the origin and timing of this structure has been the subject of several previous studies understanding its development is crucial to unraveling orogenesis in the vermont appalachians the fold formed during a deformation path that involved a succession of overprinting near orthogonal deformations that produced matrix fabrics s3 s4 and s5 these foliations developed with subvertical subhorizontal and subvertical orientations respectively before being rotated by the effects of younger deformations the spring hill synform is generally thought to have formed as a recumbent structure during regional nappe development s4 developing as an axial planar foliation however we demonstrate that the spring hill synform developed as a fold with a steeply dipping axial plane that was overprinted by s4 and s5 although this geometry and overprinting history are consistent with a d3 time of formation we can find no change in the asymmetry of pre s3 foliations across the fold we suggest that the synform may have formed at a much earlier stage in the orogen s history and was subsequently modified and rotated to its present geometry by the long history of west to east shortening that dominated the later stages of acadian orogenesis in southeast vermont

evolution of an active sea floor massive sulphide deposit hydrothermal circulation at oceanic spreading ridges causes sea water to penetrate to depths of 2 to 3 km in the oceanic crust where it is heated to 400 c before venting at spectacular black smokers these hydrothermal systems exert a strong influence on ocean chemistry1 yet their structure longevity and magnitude remain largely unresolved2 the active transatlantic geotraverse tag deposit at 26 n on the mid atlantic ridge is one of the largest oldest and most intensively studied of the massive sulphide mounds that accumulate beneath black smoker fields here we report ages of sulphides and anhydrites from the recently drilled3 tag substrate structures determined from 234u 230th systematics analysed by thermal ionization mass spectrometry the new precise ages combined with existing data4 5 show that the oldest material 11 000 to 37 000 years old forms a layer across the centre of the deposit with younger material 2 300 7 800 years old both above and below this stratigraphy confirms that much of the sulphide and anhydrite are precipitated within the mound by mixing of entrained sea water with hydrothermal fluid6 the age distribution is consistent with episodic activity of the hydrothermal system recurring at intervals of up to 2 000 years

spiral and staircase inclusion trail axes within garnet and staurolite porphyroblasts from schists of the bolton syncline connecticut timing of porphyroblast growth and the effects of fold development in the littleton formation garnet porphyroblasts preserve three generations of growth that occurred before formation of the bolton syncline inclusion trails of foliations overgrown by these porphyroblasts are always truncated by the matrix foliation suggesting that garnet growth predated the matrix foliation in contrast many staurolite porphyroblasts grew synchronously with formation of the bolton syncline however local rim overgrowths of the matrix foliation suggest that some staurolite porphyroblasts continued to grow after development of the fold during younger crenulation producing deformations the axes of curvature or intersection of foliations defined by inclusion trails inside the garnet porphyroblasts lie oblique to the axial plane of the bolton syncline but do not change orientation across it this suggests the garnets were not rotated during the subsequent deformation associated with fold development or during even younger crenulation events three samples also contain a different set of axes defined by curvature of inclusion trails in the cores of garnet porphyroblasts suggesting a protracted history of garnet growth foliation intersection axes in staurolite porphyroblasts are consistently orientated close to the trend of the axial plane of the bolton syncline on both limbs of the fold in contrast axes defined by curvature or intersection of foliations in the rims of staurolite porphyroblasts in two samples exhibit a different trend this phase of staurolite growth is associated with a crenulation producing deformation that postdated formation of the bolton syncline measurement of foliation intersection axes defined by inclusion trails in both garnet and staurolite porphyroblasts has enabled the timing of growth relative to one another and to the development of the bolton syncline to be distinguished in rocks where other approaches have not been successful consistent orientation of foliation intersection axes across a range of younger structures suggests that the porphyroblasts did not rotate relative to geographical coordinates during subsequent ductile deformation foliation intersection axes in porphyroblasts are thus useful for correlating phases of porphyroblastic growth in this region

time series analyses for karst river interactions assessment case of the coulazou river southern france summary in many karst systems throughout the world numerous karst features facilitate the exchange of water between the surface the vadose zone and the saturated zone of the aquifer these interactions play actually a prominent role in the ground and surface waters circulation this study aims at assessing karst river interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research as in many others binary karst system the captured waters of the coulazou river travel through conduits and preferential flow paths in the vadose zone and join the saturated zone of the aquifer this river is an ephemeral river in a mediterranean context where rapid and intense floods occur each year this hydrologic behaviour is appropriate to study the transfer of a flood through a karst area the water level in caves the rainfall all over the karst aquifer catchment area the piezometric level within the karst aquifer and the discharge in the river upstream and downstream of the karst aquifer are measured in order to understand the karst river exchanges during a flood the modification of the surface flows in the river is treated as a linear time invariant system lti system correlation and spectral analyses are used to understand how the lti system dissipates or enhances the flood wave energy for several floods the frequency response function estimations are interpreted in term of flood wave modification through the karst area in this way according to the initial state of the karst river system the autogenic and or allogenic recharge of the aquifer may induce surge flows and a significant karst contribution to surface flows

behaviour of rigid objects during deformation and metamorphism a test using schists from the bolton syncline connecticut usa the behaviour of spherical versus highly ellipsoidal rigid objects in folded rocks relative to one another or the earth s surface is of particular significance for metamorphic and structural geologists two common porphyroblastic minerals garnet and staurolite approximate spherical and highly ellipsoidal shapes respectively the motion of both phases is analysed using the axes of inflexion or intersection of one or more foliations preserved as inclusion trails within them we call these axes fias for foliation inflexion intersection axes for staurolite this motion can also be compared with the distribution of the long axes of the crystals schists from the regionally shallowly plunging bolton syncline commonly contain garnet and staurolite porphyroblasts whose fias have been measured in the same sample garnet porphyroblasts pre date this fold as they have inclusion trails truncated by all matrix foliations that trend parallel to the strike of the axial plane however they have remarkably consistent fia trends from limb to limb the fias trend 175 and lie 25 nnw from the 020 strike of the axial trace of the bolton syncline the plunge of these fias was determined for six samples and all lie within 30 of the horizontal eleven of these samples also contain staurolite porphyroblasts which grew before during and after formation of the bolton syncline as they contain inclusion trails continuous with matrix foliations that strike parallel to the axial trace of this fold the staurolite fias have an average trend of 035 15 ne from the 020 strike of the axial plane of this fold the total amount of inclusion trail curvature in staurolite porphyroblasts about the axis of relative rotation between staurolite and the matrix i e the fia is greater than the angular spread of garnet fias although staurolite porphyroblasts have ellipsoidal shapes their long axes exhibit no tendency to be preferentially aligned with respect to the main matrix foliation or to the trend of their fia this indicates that the axis of relative rotation between porphyroblast and matrix the fia was not parallel to the long axis of the crystals it also suggests that the porphyroblasts were not preferentially rotated towards a single stretch direction during progressive deformation five overprinting crenulation cleavages are preserved in the matrix of rocks from the bolton syncline and many of these result from deformation events that post date development of this fold staurolite porphyroblast growth occurred during the development of all of these deformations most of which produced foliations staurolite has overgrown and preserved as helicitic inclusions crenulated and crenulation cleavages i e some inclusion trail curvature pre dates porphyroblast growth the deformations accompanying staurolite growth involved reversals in shear sense and changing kinematic reference frames these relationships cannot all be explained by current models of rotation of either or both the garnet and staurolite porphyroblasts in contrast we suggest that the relationships are consistent with models of deformation paths that involve non rotation of porphyroblasts relative to some external reference frame further we suggest there is no difference in the behaviour of spherical or ellipsoidal rigid objects during ductile deformation and that neither garnet nor staurolite have rotated in schists from the bolton syncline during the multiple deformation events that include and post date the development of this fold

hydrogeology of a complex champlain sea deposit quebec canada implications for slope stability the thick sequences of marine clayey deposits which blanket the st lawrence lowlands in south eastern canada are highly susceptible to landslides with 89 of the population of the province of que