the effect of floodplain grass on the flow characteristics of meandering compound channels abstract laboratory experiments were conducted in a large scale meandering compound channel to investigate the effect of floodplain grass on the main flow field in the channel three dimensional velocity fields turbulences and reynolds shear stresses were measured along half a meander the experiments revealed that flexible artificial grass planted on a floodplain can significantly reduce the conveyance capability of the entire channel two parallel stage discharge curves increased with increasing flow depth the additional resistance of the floodplain grass increased the streamwise velocity and conveyance in the main channel along a meander an analysis of the generation mechanism of secondary flows in the main channel indicated that the secondary current consisted of an enhanced original secondary cell that was strengthened by the centrifugal force and a component of the upstream floodplain flow the relative dominance of these two components in the secondary flows was primarily determined by the angle between the floodplain flow and the main channel ridge and also the floodplain roughness at the same flow depth the secondary flow in cases with grass on the floodplain was generally stronger than that in the case of a smooth meander bend although it was weaker near the middle cross over section floodplain grass enhanced the intensity of the lateral turbulence above the bankfull level and significantly modified the turbulence structure although it had a negligible effect on the vertical turbulence except at the bend entrance floodplain grass also affected the reynolds shear stresses in the main channel generating stronger lateral shear stresses at a low flow depth in contrast at a high flow depth the distribution of the interface shear stresses changed entirely while its magnitude remained the same when the floodplains were grassed the vertical shear stress that was induced by secondary flows was greater at the apexes but reduced at the cross over sections these observations highlight the important effects of floodplain grass on the main channel flow

rethinking conditions necessary for pseudotachylyte formation observations from the otago schists south island new zealand abstract pseudotachylytes and two distinct types of cataclasite in the otago schist at tucker hill south island new zealand provide evidence for both seismic slip and aseismic creep on a normal fault zone during regional crustal extension in late cretaceous time regional geologic evidence suggests that the fault had its present low angle dip ca 10 at the time it was active type a cataclasites presumably aseismic can be recognized by bi fractal grain size distributions monomict composition angular clasts of uniform textural maturity and a crude fabric defined by oriented grains and transgranular fractures type b cataclasites possibly cosesimic have characteristics consistent with fluidized grain flow including heterogeneous clast shapes and types a bimodal grain size distribution intrusive relationships with other rocks and the absence of any fabric or transecting fractures pseudotachylyte which occurs as fault veins injection veins and more complex types of intrusive structures consistently cuts across and invades type a cataclasites but is both intrusive into and included as clasts in type b cataclasites these relationships are consistent with a fault evolution model in which the development of a damage zone through aseismic cataclasis type a facilitates the formation of pseudotachylyte in a subsequent seismic event by providing a permeable matrix through which fluids can drain in the early stages of slip thereby maintaining frictional contact between rock surfaces the formation of pseudotachylyte in turn may seal the fault zone and lead to thermal pressurization in a later seismic cycle forming fluidized type b cataclasites seismic slip on the low angle normal fault zone at tucker hill may have occurred by two distinct modes of dynamic weakening melt lubrication and thermal pressurization in successive seismic events although there is a perception among geologists that pseudotachylyte is most likely to form in intact crystalline rocks geophysical models of fault zones clearly demonstrate that pseudotachylyte formation is actually suppressed in low permeability rock because any fluids present would be unable to escape the fault zone and thermal pressurization would rapidly reduce frictional resistance the paradigmatic occurrences of pseudotachylyte in otherwise pristine crystalline rocks probably represent somewhat exceptional circumstances single rupture events at very high effective stress in dry rock coseismic frictional melts may actually be more common in hydrated rocks like the schist at tucker hill but harder to recognize and also vulnerable to overprinting as a fault zone matures in such rocks pseudotachylyte may represent an intermediate stage in the evolution of a fault zone the period between the formation of a high permeability damage zone and the development of a low permeability fault core

storage change in a flat lying fracture during well tests 1 the volume of water released from storage per unit head drop per volume of an rev is a basic quantity in groundwater hydrology but the details of the process of storage change in the vicinity of a well are commonly overlooked we characterize storage change in a flat lying fracture or thin sedimentary bed through the apparent hydraulic compliance cf the change in aperture of the fracture or thickness of the layer per unit change in pressure the results of theoretical analyses and field measurements show that cf increases with time near the well during pumping but it drops suddenly and may become negative at the beginning of recovery during a well test profiles of cfincrease with radial distance from a well but they are marked by a sharp increase and a sharp decrease at the edge of the region affected by the wellbore pressure transient the conventional view in groundwater hydrology is that storage change at a point is proportional to the local change in pressure which requires that the hydraulic compliance is uniform and constant it appears that this conventional view is a simplification of a process that varies in both space and time and can even take on negative values this simplification may be a source of uncertainty when interpreting well tests and extensometer records or predicting long term well performance

flood plain and main channel flow interaction experimental results are presented concerning the discharge characteristics the boundary shear stress and boundary shear force distributions in a compound section comprising of one rectangular main channel and two symmetrically disposed flood plains equations are presented giving the shear force on the flood plains as a percentage of the total shear force in terms of two dimensionless parameters the experimental shear force results are used to derive ancillary equations for the lateral and vertical transfer of momentum within the cross section the apparent shear force acting on the vertical interface between one flood plain and the main channel is shown to increase rapidly for low relative depths and high flood plain widths equations are also presented giving the proportion of the total flow which occurs in the various sub areas the division of flow based on linear proportion of the areas is shown to be inadequate on account of the interaction between the flood plain and main channel flows

rotation of ductile fabrics across the alpine fault and cenozoic bending of the new zealand orocline this study examines the role and kinematic mechanism of vertical axis rotations and folding during early development phases of a transform plate boundary in continental crust near the alpine fault in new zealand this involved an initial period of widely distributed shear including wrench folding together with vertical axis rotations and orocline development followed by a focusing of slip onto a single fault in the south island the haast schist has been displaced horizontally in the neogene by c 480 km of dextral slip on the alpine fault ls tectonites on either side of the fault lie on different limbs of a profound z shaped orocline rotation of these limbs took place about a vertical axis resulting in 25 30 of clockwise rotation of fabrics to the nw of the alpine fault relative to those to the south foliation anisotropy caused bending to take place locally by folding about an inclined hinge in the limbs of a pre existing synform which tightened during the deformation on both sides of the fault involvement of post oligocene age structures in wrench folding and bending suggests that the bending took place entirely in the cenozoic before or during miocene development of the alpine fault as a through going structure during this early phase of plate boundary deformation shear was distributed across a zone 100 km wide vertical axis rotation affected fault bounded basement slivers that shortened perpendicular to their strike a style of deformation like that in the transverse ranges in california today

estimation of flow direction in meandering compound channels abstract the flow in the main channel of a meandering compound channel does not occur in the ridge direction because of the effect of the upstream floodplain flows this study proposes a model for estimating the flow direction in the depth averaged two dimensional domain depth averaged flow angles between the entrance and the apex sections detailed velocity measurements were performed in the region between the meander entrance section and apex section in a large scale meandering compound channel the vertical size of the secondary current cell is highly related to the depth averaged flow angle thus the means of the local flow angles above the secondary current cell and within the cell are separately discussed the experimental measurements indicate that the mean local flow angle above the cell is equal to the section angle whereas the mean local flow angle within the cell is equal to zero the proposed model is validated using published data from five sources good agreement is obtained between the predictions and measurements indicating that the proposed model can accurately estimate the depth averaged flow direction in the meandering compound channels finally the limitations and application ranges of the model are discussed

flow patterns in compound channels with vegetated floodplains understanding the hydraulics of flow in a compound channel with vegetated floodplains is very important for determining the stage discharge curve and for supporting the management of fluvial processes in this paper the flow patterns over different types of vegetation such as tree shrub and grass are described based on an experimental study for vegetation on the floodplain the authors choose plastic grass duck feathers and plastic straws as model grass shrubs and trees respectively a 3d acoustic doppler velocimeter was used to measure the local flow velocities for different types of vegetation on the floodplain and the total discharge and flume slope were measured independently in the cases of nonvegetated floodplains all measured streamwise velocity distributions followed the logarithmic distribution but for vegetated floodplains they followed an s shaped profile exhibiting three zones for all cases the fluctuating velocity followed a normal distribution the influence of different types of vegetation on the distributions of the secondary currents turbulence intensities and reynolds shear stresses were also analyzed

hydrodynamic behavior of partly vegetated open channels the hydrodynamic response of turbulent flow in a compound wide rectangular open channel with a vegetated domain at the channel bank in a channel corner and in a floodplain to the vegetation density and diameter is discussed to this end a phenomenological model was imbedded in an algebraic stress model with the vegetation modeled as an internal resistance that exerts drag force produces energy of turbulence and interferes with its anisotropy and length scale simple suggestions for some modeling problems associated with the presence of wide vegetated domains are used to yield the three dimensional flow vorticity sources relaxation was implemented to smooth periodic behavior and dissipation correction was introduced as a coordinate invariant damping with these the results represent fully developed flow

fractal vein distributions within a fault fracture mesh in an exhumed accretionary melange chrystalls beach complex new zealand a well developed fault fracture mesh is observed in the chrystalls beach complex an accretionary melange within the otago schist on the south island of new zealand in this study an analysis of vein thicknesses and clustering of veins is presented both shear and extension veins have a power law thickness distribution measures of vein spacing best fit a power law distribution but a small data set limits this interpretation to a small fractal range vein clustering varies from random to moderately clustered between outcrops and is the greatest where a large proportion of relatively competent blocks occurs within the melange fractures are distributed within the melange matrix and this localized deformation requires heterogeneity in rheology and or fluid pressure distribution whereas pervasive distributed deformation occurs in relatively homogeneous rock the overall trend of this deformation being mainly accommodated by thin veins required that new fractures formed preferentially over refracturing existing veins which highlights the distributed nature of deformation within a fault fracture mesh the predominance of new fractures may result from vein material being stronger than the cleaved wall rock such that wall rock failure occurred instead of reopening of pre existing shear and extension veins

flow and velocity distribution in meandering compound channels an investigation of flow and velocity distribution in meandering compound channels with over bank flow is described equations concerning the three dimensional variation of longitudinal transverse and vertical velocity in the main channel and floodplain of compound section in terms of channel parameters are presented the flow and velocity distributions in meandering compound channels are strongly governed by interaction between flow in the main channel and that in the floodplain the proposed equations take adequate care of the interaction affect results from the formulations simulating the three dimensional velocity field in the main channel and in the floodplain of meandering compound channels are compared with their respective experimental channel data obtained from a series of symmetrical and unsymmetrical test channels with smooth and rough sections the aspect ratio of the test channels varies from two to five the equations are found to be in good agreement with the experimental data the formulations are verified against the natural river and other meandering compound channel data the power laws used for simulating the three dimensional velocity structure are found to be quite adequate

field testing of fiber optic distributed acoustic sensing das for subsurface seismic monitoring distributed acoustic sensing das is a relatively recent development in the use of fiber optic cable for measurement of ground motion discrete fiber optic sensors typically using a bragg diffraction grating have been in research and development and field testing for more than 15 years with geophysical applications at least 12 years old bostick 2000 and summary in keul et al 2005 however developments in recent years have sought to remove the need for point sensors by using the fiber cable itself as a sensor mestayer et al 2011 miller et al 2012

prediction of the depth averaged two dimensional flow direction along a meander in compound channels abstract for overbank flows in meandering channels the flow direction along a meander varies and is affected by floodplain vegetation this study proposes a model for predicting the depth averaged two dimensional flow direction depth averaged flow angle along a meander in smooth and vegetated meandering compound channels laboratory experiments were performed in smooth and vegetated channels measurements show that the height of the secondary current cell in the main channel is increased by dense floodplain vegetation comparing with that in a non vegetated channel a method of determining the height of the cell is proposed at the middle section between the apex and exit sections where the secondary current cell is absent the depth averaged flow angle is independent of the height of the cell beyond the middle section a new secondary current cell is formed and the flow angle is highly dependent on the height of the cell the proposed model is thoroughly verified using the flume experimental and field observed data good agreement is obtained between predictions and measurements indicating that the proposed model is capable of accurately predicting the depth averaged flow angle along a meander in smooth and vegetated meandering compound channels

interpreting tracer breakthrough tailing from different forced gradient tracer experiment configurations in fractured bedrock 1 conceptual and mathematical models are presented that explain tracer breakthrough tailing in the absence of significant matrix diffusion model predictions are compared to field results from radially convergent weak dipole and push pull tracer experiments conducted in a saturated crystalline bedrock the models are based upon the assumption that flow is highly channelized that the mass of tracer in a channel is proportional to the cube of the mean channel aperture and the mean transport time in the channel is related to the square of the mean channel aperture these models predict the consistent 2 straight line power law slope observed in breakthrough from radially convergent and weak dipole tracer experiments and the variable straight line power law slope observed in push pull tracer experiments with varying injection volumes the power law breakthrough slope is predicted in the absence of matrix diffusion a comparison of tracer experiments in which the flow field was reversed to those in which it was not indicates that the apparent dispersion in the breakthrough curve is partially reversible we hypothesize that the observed breakthrough tailing is due to a combination of local hydrodynamic dispersion which always increases in the direction of fluid velocity and heterogeneous advection which is partially reversed when the flow field is reversed in spite of our attempt to account for heterogeneous advection using a multipath approach a much smaller estimate of hydrodynamic dispersivity was obtained from push pull experiments than from radially convergent or weak dipole experiments these results suggest that although we can explain breakthrough tailing as an advective phenomenon we cannot ignore the relationship between hydrodynamic dispersion and flow field geometry at this site the design of the tracer experiment can severely impact the estimation of hydrodynamic dispersion and matrix diffusion in highly heterogeneous geologic media

fault growth and landscape development rates in otago new zealand using in situ cosmogenic 10be abstract we use in situ cosmogenic 10 be measurements in quartzites to examine the growth and propagation rates of a late quaternary anticline forming above a blind reverse fault in central otago new zealand we obtain average uplift and propagation rates of 0 10 0 15 mm yr 1 and 1 0 2 0 mm yr 1 respectively over the last 450 000 yr though it is probable that growth occurred episodically with more rapid development in the periods 600 400 kyr and 200 100 kyr and relative quiescence between about 400 and 200 kyr ago these results quantify and confirm a qualitative analysis of the fault evolution based on geomorphology and drainage patterns we obtain minimum 10 be exposure ages of up to 750 000 yr for the quartzites some of the oldest ages obtained by this method outside antarctica which are made possible by the extremely low erosion rates of less than 0 6 mm kyr 1 in the resistant quartzites these rocks consequently provide an opportunity to study geomorphic and tectonic processes in this region over unusually long time periods

hydraulic fracture geometry characterization using low frequency das signal abstract monitoring and diagnosing completion during hydraulic fracturing operations provides insight into the fracture geometry interwell frac hits and connectivity conventional monitoring methods microseismic pressure gauges tracers etc can provide a range of information about the stimulated rock volume but may often be limited in detail or clouded by uncertainty utilization of distributed acoustic sensing das as a fracture monitoring tool is growing however most of the applications have been limited to acoustic frequency bands of the das recorded signal in this paper we demonstrate some examples of using the low frequency band of das signal to constrain hydraulic fracture geometry das data were acquired in both offset horizontal and vertical monitor wells in horizontal wells das data record formation strain perturbation due to fracture propagation events like fracture opening and closing stress shadow creation and relaxation ball seat and plug isolation can be clearly identified

effective matrix diffusion in kilometer scale transport in fractured crystalline rock concentrations of tritium 3h and dichlorodifluoromethane cfc 12 in water samples taken from glacial drift and fractured crystalline rock over 4 km2 in central new hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient dispersion and mass transfer to and from fractures has affected the 3h concentration to the extent that the peak 3h concentration of the 1960s is no longer distinguishable because of heterogeneity in the bedrock the sparsely distributed chemical data do not warrant a three dimensional transport model instead a one dimensional model of cfc 12 and 3h migration along flow lines in the glacial drift and bedrock is used to place bounds on the processes affecting kilometer scale transport arid model parameters are varied to reproduce the measured relation between 3h and cfc 12 rather than their spatial distributions a model of mass exchange to and from fractures that is dependent on the time varying concentration gradient at fracture surfaces qualitatively reproduces the measured relation between 3h and cfc 12 with an upper bound for the fracture dispersivity approximately equal to 250 m and a lower bound for the effective matrix diffusion coefficient equal to 1 m2 yr 1 the diffusion coefficient at the kilometer scale is at least 3 orders of magnitude greater than laboratory estimates of diffusion in crystalline rock the large diffusion coefficient indicates that diffusion into an immobile fluid phase rock matrix is masked at the kilometer scale by advective mass exchange between fractures with large contrasts in trarismissivity the measured transmissivity of fractures in the study area varies over more than 6 orders of magnitude advective mass exchange from high permeability fractures to low permeability fractures results in short migration distances of a chemical constituent in low permeability fractures over an extended period of time before reentering high permeability fractures viewed at the kilometer scale this process is analogous to the chemical constituent diffusing into and out of an immobile fluid phase

unstable patterns in partly vegetated channels unstable patterns are identified in the results of numerical simulations of two cases of partly vegetated open channels at the free unobstructed flow side of the shear layer that separates the unobstructed channel from the vegetated zones a time dependent pattern was identified in a rectangular open channel compound with a vegetated bank and cellular structure was found in a wide ractangular open channel spanning over a vegetated thin layer at the channel bed distinction between three modes of algebraic stress models a prompt algebraic stress model a delayed algebraic stress model and an algebraic stress model with longitudinal vorticity sources relaxation and the modeling of time dependent turbulence is made and discussed in the present context

field testing of modular borehole monitoring with simultaneous distributed acoustic sensing and geophone vertical seismic profiles at citronelle alabama a modular borehole monitoring concept has been implemented to provide a suite of well based monitoring tools that can be deployed cost effectively in a flexible and robust package the initial modular borehole monitoring system was deployed as part of a co2 injection test operated by the southeast regional carbon sequestration partnership near citronelle alabama the citronelle modular monitoring system transmits electrical power and signals fibre optic light pulses and fluids between the surface and a reservoir additionally a separate multi conductor tubing encapsulated line was used for borehole geophones including a specialized clamp for casing clamping with tubing deployment the deployment of geophones and fibre optic cables allowed comparison testing of distributed acoustic sensing we designed a large source effort 64 sweeps per source point to test fibre optic vertical seismic profile and acquired data in 2013 the native measurement in the specific distributed acoustic sensing unit used an idas from silixa ltd is described as a localized strain rate following a processing flow of adaptive noise reduction and rebalancing the signal to dimensionless strain improvement from repeated stacking of the source was observed conversion of the rebalanced strain signal to equivalent velocity units via a scaling by local apparent velocity allows quantitative comparison of distributed acoustic sensing and geophone data in units of velocity we see a very good match of uncorrelated time series in both amplitude and phase demonstrating that velocityconverted distributed acoustic sensing data can be analyzed equivalent to vertical geophones we show that distributed acoustic sensing data when averaged over an interval comparable to typical geophone spacing can obtain signal to noise ratios of 18 db to 24 db below clamped geophones a result that is variable with noise spectral amplitude because the noise characteristics are not identical with vertical seismic profile processing we demonstrate the effectiveness of downgoing deconvolution from the large spatial sampling of distributed acoustic sensing data along with improved upgoing reflection quality we conclude that the extra source effort currently needed for tubing deployed distributed acoustic sensing vertical seismic profile as part of a modular monitoring system is well compensated by the extra spatial sampling and lower deployment cost as compared with conventional borehole geophones

nd and sr isotopic signatures of metasedimentary rocks around the south pacific margin and implications for their provenance an nd sr isotope database including c 200 new analyses is presented for palaeozoic and mesozoic metasedimentary successions extending through southeastern australia new zealand west antarctica and the antarctic peninsula to southern south america combining with u pb detrital zircon age data this enables characterization of new zealand terranes especially within the eastern province where there is a progression from westernmost terranes of both volcanic volcaniclastic and accretionary origin with primitive sediment sources to easternmost terranes with mature continental sediment inputs in southern south america west antarctica and the antarctica peninsula similar accretionary complexes have nd model ages principally reflecting mixing of sedimentary material from multiple sources both mature and juvenile a mature gondwana continental provenance dominates in sedimentary basins inboard of the active margin especially in the palaeozoic western province new zealand interior west antarctica and nw argentina and contributes significantly to pre mesozoic sedimentary rocks of patagonia east of the andes along the gondwanaland margin nd systematics for younger late palaeozoic to early mesozoic accretionary complex metasediments reflect younger source inputs notably in the scotia metamorphic complex many of the accretionary complex deposits must involve significant crustal reworking there is no apparent south american equivalent of the primitive provenance of the westernmost accretionary terranes of new zealand

two dimensional solution for straight and meandering overbank flows this paper presents a practical method to predict depth averaged velocity and shear stress for straight and meandering overbank flows an analytical solution to the depth integrated turbulent form of the navier stokes equation is presented that includes lateral shear and secondary flows in addition to bed friction the novelty of the present approach is not only its inclusion of the secondary flows in the formulation but also its applicability to straight and meandering channels the analytical solution is applied to a number of channels at model and field scales and is also compared with other available methods such as that of shiono and knight and the lateral distribution method the present formulation gives much better predictions of velocity and shear stress particularly in those cases where the secondary flows are dominant

tracer transport in fractured crystalline rock evidence of nondiffusive breakthrough tailing extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media this behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels along fracture walls or within the bulk matrix we present a field example where tracer breakthrough tailing apparently results from nondiffusive transport tracer tests were conducted in a fractured crystalline rock using both a convergent and weak dipole injection and pumping scheme deuterated water bromide and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity the late time behavior of the normalized breakthrough curves were consistent for all tracers even when the pumping rate was changed the lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes this finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured rock

40ar 39ar thermochronologic constraints on deformation metamorphism and cooling exhumation of a mesozoic accretionary wedge otago schist new zealand abstract structural thickening of the torlesse accretionary wedge via juxtaposition of arc derived greywackes caples terrane and quartzo feldspathic greywackes torlesse terrane at 120 ma formed a belt of schist otago schist with distinct mica fabrics defining i schistosity ii transposition layering and iii crenulation cleavage thirty five 40ar 39ar step heating experiments on these micas and whole rock micaceous fabrics from the otago schist have shown that the main metamorphism and deformation occurred between 160 and 140 ma recorded in the low grade flanks through 120 ma shear zone deformation this was followed either by very gradual cooling or no cooling until about 110 ma with some form of extensional tectonic exhumation and cooling of the high grade metamorphic core between 109 and 100 ma major shear zones separating the low grade and high grade parts of the schist define regions of separate and distinct apparent age groupings that underwent different thermo tectonic histories apparent ages on the low grade north flank hanging wall to the hyde macraes and rise and shine shear zones range from 145 to 159 ma n 8 whereas on the low grade south flank hanging wall to the remarkables shear zone or caples terrane range from 144 to 156 ma n 5 most of these samples show complex age spectra caused by mixing between radiogenic argon released from neocrystalline metamorphic mica and lesser detrital mica several of the hanging wall samples with ages of 144 147 ma show no evidence for detrital contamination in thin section or in the form of the age spectra apparent ages from the high grade metamorphic core garnet biotite albite zone range from 131 to 106 ma n 13 with a strong grouping 113 109 ma n 7 in the immediate footwall to the major remarkables shear zone most of the age spectra from within the core of the schist belt yield complex age spectra that we interpret to be the result of prolonged residence within the argon partial retention interval for white mica 430 330 c samples with apparent ages of about 110 109 ma tend to give concordant plateaux suggesting more rapid cooling the youngest and most disturbed age spectra come from within the alpine chlorite overprint zone where samples with strong development of crenulation cleavage gave ages 85 107 and 101 ma due to partial resetting during retrogression the bounding remarkables shear zone shows resetting effects due to dynamic recrystallization with apparent ages of 127 122 ma whereas overprinting shear zones within the core of the schist show apparent ages of 112 109 and 106 ma these data when linked with extensional exhumation of high grade rocks in other parts of new zealand indicate that the east gondwana margin underwent significant extension in the 110 90 ma period

evolution of cretaceous cenozoic quartz pebble conglomerate gold placers during basin formation and inversion southern new zealand abstract numerous auriferous fluvial quartz pebble conglomerates qpcs are present within the late cretaceous recent sedimentary sequence in southern new zealand the qpcs formed in low relief settings before during and after regional marine transgression in alluvial fan and a variety of fluvial and near shore depositional settings in particular during slow thermal subsidence associated with late cretaceous early cenozoic rifting and during the early stages of orogenic uplift following mid cenozoic marine regression qpc maturity characteristics are complex and vary with sediment transport and recycling history stratigraphic proximity to the transgressive waipounamu erosion surface and the amount of first cycle detritus incorporated during recycling for pre marine qpcs the amount of first cycle detritus varies with tectonic intensity and proximity of the depositional setting to remnant cretaceous topography for post marine qpcs it varies with tectonic intensity and proximity to late cenozoic uplift of basement ranges qpcs do not form during a single bedrock erosion sediment deposition cycle non oxidised and or oxidized groundwater alteration kaolinisation of labile minerals in immature sediment and the upper part of underlying basement and repeated sedimentary recycling are fundamental processes of qpc formation regardless of the tectonic or sedimentary settings altered immature rock disaggregates easily upon erosion and alteration clays are winnowed to leave quartz rich residues containing resistant heavy minerals such as zircon and gold detrital sulfide survives recycling if deposition and burial in saturated sediments are rapid qpcs result only if sediment recycling is not accompanied by excessive erosion of fresh basement rock uplift of many parts of the otago schist belt since late miocene has raised rocks above the water table increased erosion rates and inhibited groundwater alteration and qpc formation qpc formation is still occurring in southland where the water table is high sediments are saturated and undergoing alteration and uplift and erosion rates topography and fluvial gradients are all low the qpcs accumulate as residual gravel on the valley floors of low competence streams that are slowly incising pervasively altered dominantly late miocene pliocene immature conglomerates qpcs formation essentially represents physical and chemical lagging of precursor strata accumulation of detrital gold and other heavy minerals is an inevitable consequence and most qpcs contain some gold three types of significant gold placer have developed in the qpcs type 1 placers are essentially eluvial and or colluvial in origin and form without significant fluvial transport by residual accumulation in low competence valleys during low rate uplift fluvial incision and qpc formation type 2 placers have formed during significant fluvial transport and subsequent fluvial incision mainly in higher energy proximal and medial reaches of larger pre marine eocene and post marine fluvial systems type 3 placers formed by wave base and marine current winnowing in the shallow shelf setting during low rate regional marine transgression especially in the eocene

reactions leading to the formation and breakdown of stilpnomelane in the otago schist new zealand semi pelitic rocks ranging in grade from the prehnite pumpellyite to the greenschist facies from south eastern otago new zealand have been investigated in order to evaluate the reactions leading to formation and breakdown of stilpnomelane detrital grains of mica and chlorite along with fine grained authigenic illite and chlorite occur in lower grade rocks with compactional fabric parallel to bedding at higher grades detrital grains have undergone dissolution and metamorphic phyllosilicates have crys tallized with preferred orientation sub parallel to bedding leading to slaty cleavage stilpnomelane is found in metapelites of the pumpellyite actinolite facies and the chlorite zone of the greenschist facies but only rarely in the biotite zone of the greenschist facies illite or phengite is ubiquitous whereas chlorite occurs only rarely with stilpnomelane upgrade of the pumpellyite out isograd chemical and textural relationships suggest that stilpnomelane formed from chlorite phengite quartz k feldspar and iron oxides stilpnomelane was produced by grain boundary replacement of chlorite and by precipitation from solution overprinting earlier textures some relict 14 achlorite layers are observed by tem to be in the process of transforming to 12 astilpnomelane layers the aem analyses show that fe is strongly partitioned over mg into stilpnomelane relative to chlorite k d 2 5 and into chlorite relative to phengite k d 1 9 modified aaefm diagrams projected from the measured phengite composition rather than from ideal kal 3 si 3 o 10 oh 2 are used to elucidate reactions among chlorite stilpnomelane phengite and biotite in addition to pressure temperature and bulk rock composition the stilpnomelane in isograd is controlled by variations in k fe3 fe2 o oh and h 2 o contents and the locus of the isograd is expected to vary in rocks of diverent oxidation states and permeabilities biotite quartz and less phengitic muscovite form from stilpnomelane chlorite and phengite in the biotite zone projection of bulk rock compositions from phengite naalo 2 sio 2 and h 2 o reveals that they lie close to the polyhedra defined by the aaefm minerals and albite other extended aaefm diagrams such as one projected from phengite naalo 2 caal 2 o 4 sio 2 and h 2 o may prove useful in the evaluation of other low grade assemblages

fiber optic network observations of earthquake wavefields author s lindsey nj martin er dreger ds freifeld b cole s james sr biondi bl ajo franklin jb abstract 2017 american geophysical union all rights reserved our understanding of subsurface processes suffers from a profound observation bias seismometers are sparse and clustered on continents a new seismic recording approach distributed acoustic sensing das transforms telecommunication fiber optic cables into sensor arrays enabling meter scale recording over tens of kilometers of linear fiber length we analyze cataloged earthquake observations from three das arrays with different horizontal geometries to demonstrate some possibilities using this technology in fairbanks alaska we find that stacking ground motion records along 20nm of fiber yield a waveform that shows a high degree of correlation in amplitude and phase with a colocated inertial seismometer record at 0 8 1 6nhz using an l shaped das array in northern california we record the nearly vertically incident arrival of an earthquake from the geysers geothermal field and estimate its backazimuth and slowness via beamforming for different phases of the seismic wavefield lastly we install a fiber in existing telecommunications conduits below stanford university and show that little cable to soil coupling is required for teleseismic p and s phase arrival detection

flow characteristics within different configurations of submerged flexible vegetation summary the effects of three configurations aligned staggered and columnar of submerged flexible vegetation on flow structure are investigated experimentally in the laboratory time averaged flow velocity and turbulence behavior are evaluated at different positions in each configuration by using a 3d acoustic doppler velocimeter adv according to the hydrodynamic regimes in experimental results the vertical distribution of streamwise velocity can be separated into three layers the upper non vegetated layer middle vegetation layer and lower sheath layer this three layer model which is associated with different logarithmic equations can be applied to describe the vertical distribution of streamwise velocity the local maximum velocity within vegetation occurs at the sheath section of a plant clump 0 10 0 15 vegetation height h v where the frontal width is minimal turbulent intensities in the streamwise u rms and spanwise v rms directions peak at the sheath section and at the approximate top of the canopy 0 9 1 2 h v the maximum reynolds stresses exist at roughly 0 9 1 2 h v which may be migrated vertically as the frontal width of a plant clump is increased this high frontal width also increases streamwise velocity above vegetation leading to increase variations in reynolds stresses around the canopy top on the vertical turbulent velocity scale w rms the vortices above a still canopy rotate faster than those above a waving canopy therefore the experimental results demonstrate that the flow field can vary significantly at the sheath section and at the top of a plant clump due to altered flow pass these analytical findings will likely prove useful when designing ecological habitats and preventing riverbed erosion

calculating shear stress at channel overbank interfaces in straight channels with vegetated floodplains a series of eight experiments was performed in a physical model of a compound channel to quantify the apparent shear stress at the interface between a main channel and both a vegetated and unvegetated floodplain data were analyzed using a turbulence based method for calculating the apparent shear stress as a function of the fluctuation in channel velocities a predictive expression was developed to permit the estimation of the apparent shear stress at the boundary of a main channel and floodplain as a function of the bed shear stress average velocity and depth in both the main channel and floodplain and the blockage caused by floodplain vegetation

vegetative impacts on hydraulics and sediment processes across the fluvial system summary vegetation creates a complicated system of feedbacks and linkages across the fluvial system that is realized through river planform shape interactions occur among flow hydraulics sediment deposition and erosion and plant morphology density and biomechanics interest in the interactions and feedback loops between vegetation and the fluvial system has grown extensively in the past few years this interest is partially driven by the popularity of stream restoration activities worldwide that include re vegetation of stream banks and formation of an ecosystem that is intended to encourage the growth of aquatic macrophytes we present a review of the research into the interactions and dependencies between vegetation and the fluvial system to identify hydraulic and sediment dynamics that are consistent around vegetation located in the channel on channel banks and over the floodplain we illustrate process commonalities operating across spatial locations within the fluvial system and highlight some of the current research opportunities and challenges to encourage research collaborations between those working in areas of the fluvial system traditionally viewed as disparate

turbulent open channel flows with variable depth across the channel the flow of water in straight open channels with prismatic complex cross sections is considered lateral distributions of depth mean velocity and boundary shear stress are derived theoretically for channels of any shape provided that the boundary geometry can be discretized into linear elements the analytical model includes the effects of bed generated turbulence lateral shear turbulence and secondary flows experimental data from the science and engineering research council serc flood channel facility are used to illustrate the relative importance of these three effects on internal shear stresses new experimental evidence concerning the spatial distribution of reynolds stresses yx and zx is presented for the particular case of compound or two stage channels in such channels the vertical distributions of zx are shown to be highly nonlinear in the regions of strongest lateral shear and the depth averaged values of yx are shown to be significantly different from the depth mean apparent shear stresses the importance of secondary flows in the lateral shear layer region is therefore established the influence of both reynolds stresses and secondary flows on eddy viscosity values is quantified a numerical study is undertaken of the lateral distributions of local friction factor and dimensionless eddy viscosity the results of this study are then used in the analytical model to reproduce lateral distributions of depth mean velocity and boundary shear stress in a two stage channel the work will be of interest to engineers engaged in flood channel hydraulics and overbank flow in particular

sediment deposition within and around a finite patch of model vegetation over a range of channel velocity the interaction between flow and vegetation creates feedbacks to deposition that vary with channel velocity this experimental study describes how channel velocity and stem generated turbulence influence the deposition within and around an emergent patch of model vegetation with a particular focus on deposition within the patch the reynolds number threshold for stem scale turbulence generation was determined using velocity spectra and flow visualization at high channel velocity resuspension occurred in the bare regions of the channel and a nonuniform spatial distribution of net deposition was observed around and within the patch in contrast at low channel velocity there was no or limited resuspension and a uniform distribution of net deposition was observed around and within the patch the deposition inside the patch was enhanced relative to a bare channel control only when the following two criteria were met 1 the absence of stem turbulence and 2 the presence of sediment resuspension in the bare channel comparison to previous lab and field studies further support these criteria

numerical modelling of mechanical controls on coeval steep and shallow dipping auriferous quartz vein formation in a thrust zone macraes mine new zealand the hyde macraes shear zone hmsz is a regionally continuous low angle ne dipping 15 late metamorphic thrust zone in the mesozoic otago schist the shear zone which is host to large volumes of mineralised schist consists of foliated fissile schist with some massive schist pods two sets of quartz veins are found within the hmsz thrust related shallowly dipping veins that were emplaced parallel or sub parallel to the shears and swarms of steeply dipping extensional veins which cut across the metamorphic foliation the latter are restricted to the massive schist pods mutual cross cutting relationships occur between steep extensional veins and shallow dipping veins suggesting that they formed contemporaneously the co existence of these two vein types locally implies local rotation of the principal stress axes to produce extensional veins within a regional thrust setting the steep extensional veins are spatially related to lateral and oblique ramps within the hmsz three dimensional mechanical models show that these lateral or oblique ramps can produce favourable conditions for extensional vein formation when combined with a high fluid pressure and oblique convergence mechanical requirements include a reduced differential stress a positive volumetric strain and an increase in the horizontal shear stress our models show that under certain conditions it is possible for extension related structures to form during shortening because of local changes in the stress state without the need for a regional scale switch in the imposed stress field the convergence direction across the hmsz during formation of the steep extensional veins was wnw