horizontal wells in shallow aquifers field experiment and numerical model this paper is concerned with horizontal wells in shallow aquifers information about a field test is presented and the development of appropriate conceptual and computational models is discussed particular attention is paid to the processes of flow from the aquifer into the horizontal well and the hydraulic conditions within the well a combined computational model representing the aquifer and the horizontal well is developed this methodology is used to study a horizontal well in a shallow coastal aquifer a detailed pumping test is analysed using the combined model the combined model is then used to predict the consequences of increasing the abstraction lengthening the well or using the horizontal well for an extended period when there is no recharge the results from the combined model indicate that the commonly adopted assumptions of either a uniform flux into the well or a constant head along the well are not suitable for this field problem

crustal versus mantle core complexes deep crustal and mantle rocks are exhumed in core complex mode of extension in three types of structures metamorphic core complexes oceanic core complexes and magma poor passive margins using available analogue and numerical models and their comparison with natural examples the present paper reviews the mechanical processes involved in these different types of extensional setting three main aspects are considered i the primary role of lithosphere rheology ii the lithosphere scale patterns of progressive deformation that lead to the exhumation of deep metamorphic or mantle rocks and iii the initiation and development of detachment zones crustal core complexes develop in continental lithospheres whose moho temperature is higher than 750 c with upper crust dominated strength profiles contrary to what is commonly believed it is argued from analogue and numerical models that detachments that accommodate exhumation of core complexes do not initiate at the onset of extension but in the course of progressive extension when the exhuming ductile crust reaches the surface in models convex upward detachments result from a rolling hinge process mantle core complexes develop in either the oceanic lithosphere at slow and ultra slow spreading ridges or in continental lithospheres whose initial moho temperature is lower than 750 c with sub moho mantle dominated strength profiles it is argued that the mechanism of mantle exhumation at passive margins is a nearly symmetrical necking process at lithosphere scale without major and permanent detachment except if strong strain localization could occur in the lithosphere mantle distributed crustal extension by upper crust faulting above a decollement along the ductile crust increases toward the rift axis up to crustal breakup mantle rocks exhume in the zone of crustal breakup accommodated by conjugate mantle shear zones that migrate with the rift axis during increasing extension

extension crustal structure and magmatism at the outer voring basin norwegian margin regional analysis of new 2d and 3d multichannel seismic data has improved interpretation of the crustal configuration and structural style along the norwegian margin five domains with different structural styles and evolutions are defined along the outer voring basin 1 the nyk high naglfar dome 2 the north gjallar ridge 3 the gleipne saddle 4 the south gjallar ridge 5 the ran ridge early campanian early paleocene and early to mid cretaceous extensional events are evidenced timing of deformation and structural styles observed along each segment reflect a lateral variation of the rifted system probably affected by magma tectonic processes correlation with the deep structures of the outer voring basin shows that the shallow structure in that basin is directly controlled by a deep seated strong high amplitude reflection the t reflection marking the top of a high velocity body v p 7 km s 1 the relation between the lower crustal architecture and the subsurface basin structures has implications for the margin evolution and for the nature of the high velocity body

onshore offshore potential field analysis of the more trondelag fault complex and adjacent structures of mid norway abstract the more trondelag fault complex mtfc is one of the most prominent fault complexes of scandinavia it exerted a strong control on the development of offshore basins of mid norway and onshore topography however the relationships between the faults observed in the field onshore and those identified by means of seismic profiling offshore remain obscure regional gravity and aeromagnetic data are used to map regional scale faults and in particular to delineate the main geophysical features related to the mtfc the advantage of potential field data is to provide an almost continuous coverage and to tie bedrock mapping onshore to seismic interpretation offshore in this paper we apply potential field transformations to focus on the regional and deep seated structures in order to extract new geological information also the tilt derivative technique tdr is applied to gravity and magnetic data with the aim of enhancing linear trends the results indicate the possible onshore offshore links of large scale structural elements like the mtfc and late caledonian detachments e g kollstraumen detachment the locations of different segments of the mtfc are detected and possible new faults lineaments are depicted correlating petrophysical data with gravity and magnetic maps explains the influence of the mtfc on the deformation and mineralisation of bedrock along its strike in addition the structural pattern seen in the enhanced lineaments is diagnostic for the sinistral strike slip movements that are known to have occurred in devonian time along the mtfc this confirms the important role of the mtfc in the tectonic setting and geological evolution of mid norway

flow to horizontal drains in isotropic unconfined aquifers the laplace transform solution for the problem of flow to horizontal drains in an anisotropic unconfined aquifer is derived the solution for the constant flux horizontal well by zhan and zlotnik zhan h zlotnik v a 2002 groundwater flow to a horizontal and slanted well in an unconfined aquifer water resour res 38 7 13 1 13 11 is modified to obtain the solution for a constant head horizontal drain the laplace transform solution is converted to the real time domain and type curves for the drawdown around and the discharge to a horizontal drain are computed the solution is verified by a numerical simulation the type curves and derivative type curves of the drains are compared with type curves for horizontal wells the sensitivity of type curves on piezometer location specific storage horizontal drain elevation aquifer delay index and drain length is tested these type curves can be used for interpretation of drainage data

basement structure and its influence on the structural configuration of the northern north sea rift the northern north sea rift basin developed on a heterogeneous crust comprising structures inherited from the caledonian orogeny and devonian post orogenic extension integrating two dimensional regional seismic reflection data and information from basement wells we investigate the pre rift structural configuration in the northern north sea rift three seismic facies have been defined below the base rift surface 1 relatively low amplitude and low frequency reflections interpreted as pre caledonian metasediments caledonian nappes and or devonian clastic sediments 2 packages of high amplitude dipping reflections 500 ms thick interpreted as basement shear zones and 3 medium amplitude and high frequency reflections interpreted as less sheared crystalline basement of proterozoic and paleozoic caledonian origin some zones of seismic facies 2 can be linked to onshore devonian shear zones whereas others are restricted to the offshore rift area interpreted offshore shear zones dip s ese and wnw in contrast to w to nw dipping shear zones onshore w norway our results indicate that devonian strain and ductile deformation was distributed throughout the caledonian orogenic belt from central south norway to the shetland platform most of the devonian basins related to this extension are however removed by erosion during subsequent exhumation basement shear zones reactivated during the rifting and locally control the location and geometry of rift depocenters e g in the stord and east shetland basins pre rift structures with present day dips 15 were reactivated although some of the basement shear zones are displaced by rift faults regardless of their orientation relative to rift extension direction

pre existing intra basement shear zones influence growth and geometry of non colinear normal faults western utsira high heimdal terrace north sea abstract pre existing intra basement shear zones can induce mechanical and rheological heterogeneities that may influence rifting and the overall geometry of rift related normal faults however the extent to which physical and kinematic interaction between pre existing shear zones and younger rift faults control the growth of normal faults is less well understood using 3d reflection seismic data from the northern north sea and quantitative fault analysis we constrain the 3d relationship between pre existing basement shear zones and the geometry evolution and synrift depositional architecture of subsequent rift related normal faults we identify ne sw and n s striking rift faults that define a coeval middle jurassic early cretaceous non colinear fault network ne sw striking faults are parallel to underlying intra basement shear zone the faults either tip out above or physically merge with the underlying shear zone for faults that merges with the basement shear zone a change from tabular to wedge shaped geometry of the hangingwall synrift strata records a transition from non rotational to rotational extension faulting which we attribute to the time of rift fault s linkage with the shear zone following downward propagation of its lower tip n s striking faults are oblique to and offset rather than link with intra basement shear zones these observations highlight the selective influence pre existing intra basement shear zones may or may not have on evolving rift related normal faults

mountain permafrost dynamics within a recently exposed glacier forefield inferred by a combined geomorphological geophysical and photogrammetrical approach geomorphological observations geoelectrical soundings and photogrammetric measurements of surface movement on the muragl glacier forefield were used to obtain an integrative analysis of a highly complex glacial and periglacial landform consisting of a push moraine creeping permafrost and permafrost free glacial till in close proximity electrical resistivity tomography is considered as an important multifunctional geophysical method for research in periglacial permafrost related environments joint application with measurements of surface displacements offers a promising tool for investigating periglacial landforms related to ice rich permafrost for a more comprehensive characterization of permafrost characteristics and geomorphological interpretation of periglacial morphodynamics the patchy permafrost distribution pattern described in this paper is determined by several factors including the sediment characteristics the snow cover distribution and duration the aspect and the former glacier distribution and thermal regime recent and modern permafrost dynamics within the glacier forefield comprise aggradation degradation and permafrost creep copyright 2007 john wiley sons ltd

new models for evolution of magma poor rifted margins based on a review of data and concepts from west iberia and the alps direct observation and extensive sampling in ancient margins exposed in the alps combined with drill hole and geophysical data from the present day iberia margin result in new concepts for the strain evolution and near surface response to lithospheric rupturing at magma poor rifted margins this paper reviews data and tectonic concepts derived from these two margins and proposes that extension leading to thinning and final rupturing of the continental lithosphere is accommodated by three fault systems each of them characterized by a specific temporal and spatial evolution during rifting of the margin by its fault geometry and its surface response the data presented in this paper suggest that margin architecture and distribution of rift structures within the future margin are controlled first by inherited heterogeneities within the lithosphere leading to a contrasting behaviour of the future distal and proximal margins during an initial stage of rifting the place of final break up appears to be determined early in the evolution of the margin and occurs where the crust has been thinned during a first stage to less than 10 kilometres during final break up the rheology of the extending lithosphere is controlled by the thermal structure related to the rise of the asthenosphere and by serpentinization and magmatic processes

basement reactivation in the development of rift basins an example of reactivated caledonide structures in the west orkney basin the west orkney basin is a poorly studied palaeozoic and mesozoic rift basin that overlies a highly seismic reflective caledonian orogenic basement terrane this study presents a novel approach of using 2d seismic data to map single intra basement reflection packages and their relationship to overlying normal faults in the west orkney basin it is demonstrated that the rift architecture of the west orkney basin is more linear with a prominence of relay zones relative to previous interpretations and that rift structures form complex discordant and concordant relationships with pre rift caledonide basement structures restoration of basement fabrics to their pre extensional geometry indicates that the reactivation of basement structures as normal faults has occurred only where the pre extensional dip of basement structures is greater than 30 the relatively high density of relay zones mapped in the west orkney basin is proposed to be the result of the rift system forming a partially exploitative relationship with basement structure where extension has been accommodated between segments that have or have not reactivated basement fabrics

theoretical and experimental studies of coupled seepage pipe flow to a horizontal well abstract this study proposes a new approach which describes a finite diameter horizontal well and flow inside the pumping well jointly this approach utilizes a new treatment for in well hydraulics thus eliminating the flux or head based boundary condition along the horizontal well an equivalent hydraulic conductivity concept is applied for treating the horizontal wellbore this conceptual model is more general than previous models that describe the horizontal wellbore the description of in well hydraulics depends on the reynolds number a sample case of horizontal well pumping underneath a river is first used to illustrate the solution of the proposed approach a physical laboratory model was constructed and hydraulic heads and the well flow rate were carefully monitored and compared with the numerically calculated results using the proposed model the experimental data agree well with the numerical solution

crustal taper and topography at passive continental margins terra nova 23 349 361 2011 abstract the long term evolution of kilometre s high seaward facing escarpments at passive margins is linked directly to the crustal thinning gradient the development of post rift faults in the onshore parts of the margin and the associated distribution of drainage patterns landscape types and sediment dispersal patterns reflect this linkage for the seismically well imaged norwegian margin as well as for a number of passive margins worldwide we identify a scaling relationship that correlates escarpment height with the distance to the highly extended distal margin or more specifically the taper break the highest escarpments and the most asymmetric margin topography are found inboard of sharply tapering crystalline crust independent of margin age conversely escarpments are lower where the taper is gentle thus the topography of passive margins does not primarily reflect age magmatism climate or mantle convection but more probably the response to loading of the laterally variable fault controlled architecture of the crystalline crust

uplift of deep crust during orogenic extensional collapse a model based on field studies in the sogn sunnfjord region of western norway the western gneiss region wgr in norway experienced high pressure metamorphism during silurian devonian continent continent collision the eclogite bearing lower crust is separated from the middle and upper crust by major detachment zones formed during extensional collapse of the orogen formation of the devonian basins is related to the extension the footwall of the detachment zones comprises three structural and metamorphic zones the upper zone zone 1 is characterized by penetrative homogeneous down to the west simple shear developed under retrograde greenschist facies metamorphism zone 2 suffered inhomogeneous simple shear of the same polarity petrography and mineral chemistry data from the lower zone zone 3 show a record of initial eclogite facies metamorphism at 600 c and 16 kbar which was decompressed almost isothermally to amphibolite facies conditions at 550 c and 10 12 kbar both the eclogite and amphibolite facies metamorphism developed in a regime of pure shear with vertical shortening the rapid decompression records an approach of approximately 20 km to the surface related to uplift that was probably the result of the removal of a thickened thermal boundary layer in the mantle lithosphere the pure shear regime which developed initially in the lower crust was truncated by zones of simple shear as the lower crust was uplifted to middle and upper crustal levels extension by simple shear in the upper crust was rooted in the lower crust where extension occurred by pure shear the shear zones in zones 1 and 2 did not penetrate the pure shear regime of the lower crust a considerable amount of tectonic stripping of the orogenic welt predates deposition of the devonian sedimentary basins

lower crustal high velocity bodies along north atlantic passive margins and their link to caledonian suture zone eclogites and early cenozoic magmatism abstract in this study we use crustal scale ocean bottom seismic models to infer the presence of two types of lower crustal bodies at north atlantic passive margins type i primarily interpreted as early eocene magmatic intrusions and type ii interpreted as caledonian eclogites we discuss how these eclogites might be related to the main caledonian suture zone and other tectonic features in a conjugate north atlantic setting based on the first order approximation that p wave velocities can be related to rock strength the narrower continental margin at the southern more transect may be explained by stronger lower crust there compared with the northern voring transect this difference in strength possibly resulting in a steeper dip in the subducting baltica plate south of the proto jan mayen lineament may explain the asymmetry in extensional style observed across this lineament our interpretation locates the main suture off mid norway close to the more trondelag fault zone on the more margin along the western boundary of the trondelag platform on the voring margin and further northwards beneath the lofoten ridge the lower crustal body type i is about 60 thicker on the greenland side for both transects and its thickness along the northern transect is more than twice that of the southern transect these differences are consistent with sub lithospheric interaction between the icelandic hotspot and the continental rift oceanic accretion system around the time of continental break up

flow to a horizontal well in an aquitard aquifer system a horizontal well is sometime installed in an aquifer beneath a water reservoir to get significant amount of groundwater with better quality an aquitard often separates the surface water body from the underneath aquifer previous studies in vertical wells related to this subject treated leakage from the aquitard as a volumetric source term in the governing equation of flow in the main aquifer a hypothesis termed hantush s approximation for partially penetrating wells in this study flow in the aquitard and aquifer is treated as two systems which are linked through the continuity of flux and head at the aquitard aquifer boundary in particular we treat leakage as a boundary at the aquitard aquifer interface not as a volumetric source the leakage induced by the pumping horizontal well depends on several parameters such as the aquitard thickness the vertical hydraulic conductivity of the aquitard the aquitard specific storage the well location and the well length in general we find that the solution based on the hantush s approximation to some extent deviates from that obtained based on the actual scenario of leakage through the interface during the transient flow condition particularly at the early time for steady state flow the hantush s approximation works reasonably well under realistic conditions of aquitard thickness and hydraulic conductivity as long as the aquitard thickness is relatively thick aquitard aquifer ratio greater than 0 001 this approximation also works reasonably well under realistic horizontal well length and well location as long as the well is not too close to the aquitard aquifer boundary q 2005 elsevier b v all rights reserved

scandinavia s north atlantic passive margin 1 the tectonics of the eastern passive margin of the north atlantic are reexamined the scandinavian north atlantic passive margin includes not only the offshore exploration and basin domain but also large portions of the onshore domains of the scandinavian caledonides combined information from structural geology potential field data regional geology basin development and geomorphology made it possible to propose a new definition of the passive margin the rift shoulder is formed by linked faults defining the present rift flank these faults are the extensional structures located furthest to the east onshore norway sweden that can be linked to the rifting that led to the formation of the north atlantic this innermost boundary fault system ibf is formed by a set of normal west dipping crustal faults it extends over a distance exceeding 2000 km from the north sea across the caledonian mountain belt to the barents sea the passive margin width between the continent ocean boundary and the ibf ranges from 550 km in the south to over 700 km in mid norway to 165 km north of lofoten rifting and faulting on the ibf started in permo carboniferous and a succession of rift phases eventually culminated in continental breakup and the formation of the north atlantic basin development between permian and cretaceous was toward the future breakaway fault but faulting was also active on land from mesozoic to present onshore offshore crustal scale cross sections show the geometry of the passive margin the dip orientation of the major faults and the changes in crustal thickness

hydraulics of horizontal wells in fractured shallow aquifer systems abstract an analysis of groundwater hydraulic head in the vicinity of a horizontal well in fractured or porous aquifers considering confined leaky confined and water table aquifer boundary conditions is presented solutions for hydraulic heads in both leaky confined and water table aquifers are provided the fracture model used in this study is the standard double porosity model the aquitard storage is included in the formula solutions for the confined and unconfined conditions fractured and porous conditions wellbore storage and skin effect are compared several findings of this study are 1 the influence of wellbore storage and skin upon the drawdown for a fractured confined aquifer is similar to that for a porous confined aquifer 2 aquitard storage affects the intermediate time the most by delaying the drawdown and 3 there is a significant difference between the type curves of fractured and porous confined aquifers in most aquifer boundary conditions because of the contribution of matrix storage and such a difference disappears at the later time

the thickness and internal structure of fireweed rock glacier alaska u s a as determined by geophysical methods geophysical investigations on rock glaciers are often difficult because rock glaciers are covered by an unconsolidated debris mantle a few meters thick are typically 50 m thick and are composed of an ice rock mixture of unknown composition transient electromagnetics tem is a method that allows some of these difficulties to be minimized and data collection is relatively efficient tem with calibration from terminus exposure was used to determine the thickness 60 m of fireweed rock glacier alaska u s a under complex valley geometry a conductive layer beneath the rock glacier was identified and its distribution is consistent with a till like layer seismic refraction used to resolve the debris mantle thickness 2 4 m suggests the presence of a discontinuity at 18 28 m depth within the rock glacier the discontinuity is also indicated in the radio echo sounding and the tem data but to a lesser extent this discontinuity is important because the motion of the rock glacier may occur across this as a shear plane

origin of contrasting devonian supradetachment basin types in the scandinavian caledonides supradetachment basins that formed during the devonian extensional collapse of the scandinavian caledonides have been explained as hanging wall basins formed along the listric breakaway zone of a major detachment fault system this model involves significant rotation of bedding as the detachment flattens to an approximately horizontal orientation and explains the large stratigraphic thicknesses of east dipping layers overlying in tectonic contact the top to the west nordfjord sogn detachment zone nsdz however it fails to explain one of the basins the hasteinen basin where east dipping devonian strata rest unconformably on a metamorphic substrate that forms part of the upper plate of the detachment system based on detailed field mapping we present a model where the hasteinen forms as a ramp basin that develops on the upper plate above a major west facing ramp in the nsdz we test both of these models by forward modeling using 2dmove two dimensional kinematic modeling software the results show how two different types of supradetachment basins can coexist in a subhorizontal detachment zone in an area that underwent many tens of kilometers of lateral crustal extension

mismatch of geophysical datasets in distal rifted margin studies the interpretation protocols for defining offshore rifted margin architecture normally include seismic reflection analysis supplemented by refraction and or potential field modelling to help constrain sedimentary basement and moho geometries at depth and or the presence of magmatic material interpretation of modern high resolution long offset reflection profiles shows that significant mismatches may arise between the structural observations made from these data and the common translation of density magnetic or velocity values into specific rock types made by geophysical models we illustrate this problem with three examples from the mid norwegian rifted system and discuss the implications with respect to the geological interpretation

tectonically enhanced forced regressions examples from growth folds in extensional and compressional settings the miocene of the suez rift and the eocene of the pyrenees

late orogenic extension in mountain belts insights from the basin and range and the late paleozoic variscan belt from two examples of orogenic domains some general mechanisms significant of late orogenic tectonic processes in mountain belts are characterized the basin and range province and the variscan belt in the french massif central have both suffered important compressional orogenic crustal thickening and the results of late orogenic processes can be observed in the field both areas are covered by deep seismic profiling providing constraints on the geometry of a crust which has been restored to a normal thickness late orogenic features from the two domains are compared at different scales and their tectonic significance for extension mechanisms is discussed at the scale of the orogenic domains the most prominent tectonic features are the metamorphic core complexes mcc which expose deformed rocks from the middle crust generally affected by high temperature low to medium pressure metamorphism partial melting and widespread granite emplacement in these mcc large scale extensional shear zones present an intense mylonitic deformation characterized by low dipping foliations and pervasive stretching lineations they show a complete evolution from early deep seated ductile deformation generally achieved under high temperature low to medium pressure metamorphism to a late shallow brittle stage characterized by cataclastic deformation the late detachment stage generally controls the development of asymmetrical extensional sedimentary basins filled by continental deposits two main geometries of mcc are defined that are characterized by differing geometry and kinematics of low angle shear zones in the first case two low angle shear zones with opposite vergence develop along the flanks of a roughly symmetrical mcc often one system is dominant over the other the second geometry characterizes asymmetrical mcc bounded by a single normal shear zone which is upwarped during uplift and doming of the core caused by tectonic denudation detailed strain analysis performed in several extensional shear zones shows that the deformation regime is heterogeneous and results from general noncoaxial flow deformation along the shear zones evolves progressively from slight homogeneous pure shear strain to intense heterogeneous noncoaxial shear strain strain distribution within the lower crust is less well constrained by field observation however analogies between cocorp and ecors deep seismic reflection profiles give important constraints on crustal structure wide zones of highly subhorizontally layered lower crust and a flat high amplitude reflection moho characterize both evolved orogenic domains suggesting that major deformations and flow occur within the lower crust during extension a kinematic model involving heterogeneous crustal deformation and regional scale flow fits relatively well with late orogenic structures observed in continental domains a weak hot upper mantle allows large scale flow of lower crust material from zones of deep ductile extension to uplifted domains of upper crustal denudation heterogeneous strain is accommodated by low angle extensional shear zones from localized zones of extension in the brittle crust to ductile lower crust combined pure and simple shear occurs along localized shear zones whereas at the scale of the whole lithosphere deformation nearly corresponds to a vertical pure shear such deformation processes which affect a thick and hot crust seem to be common in both compared domains suggesting that late orogenic extensional processes are slightly dependent of the type of contractional tectonics thus as much in the andean type west american cordilleran belt as in the collision type variscan belt late orogenic processes produced similar extensional features

the middle devonian basins of western norway sedimentary response to large scale transtensional tectonics abstract the devonian basins of western norway were formed during late to post orogenic extension of overthickened caledonian crust the basins are situated in the hanging wall of the extensional nordfjord sogn detachment zone nsdz and display extensional half graben geometries in sections parallel to the local direction of principal extension based on overall facies configurations paleocurrent patterns and intrabasinal structures we infer an anticlockwise rotation of the syndepositional extension direction from nw se in the south solund basin to wsw ene in the north hornelen basin the axes of folds that are roughly parallel to the local extension direction are rotated correspondingly the kvamshesten basin is located between the solund and hornelen basins sedimentological and structural data show evidence of an early southeastwards tilt direction followed by a more eastwards tilt and associated e w flowing paleodrainage correspondingly nw se trending folds and reverse faults are superposed by e w trending ones at low to intermediate stratigraphic levels the variations in apparent tilt direction for the basins together with variations in intrabasinal structure is interpreted to reflect an anticlockwise rotation of the regional syndepositional strain field the above observations and inferences indicate that the devonian basins in western norway formed in a strain field dominated by regional transtension accommodated by extension along the nsdz and sinistral strike slip along orogen parallel shear zones and faults to the north of the basins alternatively nw directed extension preceded the introduction of a sinistral strike slip component the models are in accordance with recent work carried out in the footwall of the nsdz and illustrates the tectono sedimentary response to a complex interplay between extension and strike slip that appears to have been fundamental in the late stage disintegration of the caledonian orogen

unsteady flow to a partially penetrating pumping well with wellbore storage in a dual permeability confined aquifer abstract in this article a new model is presented for imparting unsteady flow to a partially penetrating pumping well with wellbore storage placed in double permeability confined aquifers to investigate the wellbore drawdown transient behavior in this model both the fracture and matrix systems are connected directly with the wellbore as flow pathways while comprehensively considering the crossflow between the matrix and the fractures the top and bottom boundaries are assumed to be impermeable and the outer side boundaries could be infinite subsequently laplace transformation and finite fourier cosine transformation are employed to obtain analytical solutions of the dual permeability flow model in the laplace domain the derived analytical solution is general and can be reduced to several other previous results the numerical inversion algorithm of stehfest is used to solve the wellbore drawdown in the real time domain subsequently the model is validated by comparing it with previous results groundwater flow characteristics are analyzed in detail and divided into five flow stages wellbore storage flow early radial flow quasi spherical flow crossflow between the matrix and the fractures and quasi radial flow the different flow stages show some special values on the drawdown and its derivative log log plots there is a hump dip feature in the semi logarithmic curve of the drawdown derivative which are inherent characteristic for dual permeability flow behavior the effects of some important parameters of the aquifer or pumping wells on drawdown and its derivative such as wellbore storage coefficient penetration ratio crossflow coefficient storativity ratio transmissivity ratio dimensionless aquifer thickness of anisotropy and skin factor are analyzed and discussed in detail

the flow of fireweed rock glacier alaska u s a fireweed rock glacier is a large rock glacier in south central alaska u s a it flows relatively fast with velocities up to 3 5 ma 1 and exhibits both seasonal and annual velocity variations some of which are related to periodic terminus calving and increased rainfall our analysis reveals that motion is likely concentrated in a pseudo rectangular channel within the larger parabolic channel with a shear plane at 27 m depth there is likely motion along the shear plane as well as internal deformation above it we estimate that the ice rock mixture is up to seven times softer than clean glacier ice with a temperature of 2 c calving at the terminus is an important component of the mass balance of this rock glacier

groundwater flow to a general well configuration in an unconfined aquifer overlying a fractured bedrock abstract unconfined aquifers sometimes overlie fractured bedrocks consisting of unconfined fractured aquifer systems pumping induced hydrodynamics in such aquifer systems has not received much attention as in other types of aquifer systems this paper aims to obtain semi analytical solutions of flow to a general well configuration in such an unconfined fractured two layer aquifer system the examples of general well configuration specifically discussed here include 1 a horizontal well 2 a vertical well 3 a vertical well with one horizontal collector and 4 a vertical well with two horizontal collectors which are perpendicular with each other the methodology is general and can be extended to other types of wells with minor modifications of solutions developed in this study the point sink source solution is first obtained using double infinite fourier and laplace transformations where sink is for pumping and source is for injection the line sink source solution is then obtained via integrating the point sink source along the desired direction and following the principle of superposition the de hoog numerical inverse laplace transform and gaussian quadrature are used to obtain time domain dimensionless drawdown solutions the instantaneous drainage of water table and the inter porosity flow of the underlying fractured aquifer are taken into account the effects of the length of horizontal well on dimensionless drawdown and dimensionless drawdown derivative and scaled sensitivity of the hydraulic parameters of the underlying fractured aquifer are explored the dimensionless drawdowns and drawdown derivatives of a vertical pumping well a vertical well with a single horizontal collector and a vertical well with two perpendicular horizontal collectors are also compared the scaled sensitivity of dimensionless drawdown to the hydraulic parameters of the underlying fractured aquifer of these different pumping well structures is explored the results of this study can be used to evaluate the hydraulic parameters using the drawdown data collected during a pumping test performed in a general well configuration in a unconfined fractured two layer aquifer system furthermore the presented solutions can be utilized to design the pumping well to minimize drawdown in low permeability or thin aquifers by eliminating the inter porosity flow term from the underlying fractured aquifer the solutions are applicable to groundwater flow to a pumping well in leaky aquifers

geometric and temporal evolution of an extensional detachment fault hohhot metamorphic core complex inner mongolia china the early cretaceous hohhot metamorphic core complex and its master hohhot detachment fault are 400 km west of beijing in the daqing shan mountains of inner mongolia the complex developed across the east trending yinshan fold and thrust belt within 4 m y following cessation of thrusting ca 125 ma see note added in proof in main text postcontractional extension was initiated within a mid crustal zone of mylonitic and ductile shear that was in part controlled by carboniferous strata sandwiched between its proterozoic and archean crystalline basement and an overlying thrust sheet of similar crystalline rocks the hohhot detachment fault appears to have rooted into deep kinematically active levels of the mid crustal shear zone higher inactive levels of the mylonitic section were transected by the fault and carried upward in its footwall geometries of the footwall mylonitic rocks indicate localized ramp flat geometries of the fault within and across them the crosscut top of the mylonitic sequence defines a mylonitic front that departs from the gently south dipping detachment fault and dips northward into its footwall early cretaceous extension was widespread elsewhere in northern china and was particularly pronounced in the yunmeng shan core complex north of beijing the gravitational collapse of orogenically thickened crust acting in concert with localized centers of deep seated plutonism appear to have led to the development of isolated metamorphic core complexes within a broad region of more distributed extensional deformation

the role of pre existing precambrian structures in rift evolution the albertine and rhino grabens uganda abstract we integrated shuttle radar topography mission srtm digital elevation models dem airborne magnetic radiometric and three dimensional full tensor gravity gradiometry 3d ftg data to investigate the role of precambrian structures in the evolution of the largely amagmatic miocene recent aged albertine and rhino grabens in uganda these grabens represent the northern segment of the western branch of the east african rift system ears the two ne trending grabens are connected by a right stepping transfer zone and they extend within the archean paleoproterozoic northeast congo block which represents the northeastern extension of the congo craton our results show the following and highlight the importance of pre existing structures in the evolution of continental rift systems 1 the ne extent of the albertine full graben is controlled by ne trending precambrian fabric and the graben terminates at its northeastern end when it encounters a multiply folded precambrian basement terrain with poorly developed nw trending structural grain additionally the northeastern termination of the albertine graben coincides with the presence of nw trending right stepping high density bodies within the precambrian terrain 2 the transfer zone between the albertine and rhino grabens is controlled by ne trending precambrian structures which might have facilitated the development of relay ramp faults 3 strain localization within the better developed southeastern border fault of the rhino half graben is facilitated by the presence of precambrian structures better aligned in a ne direction in the southeastern part of the basin compared to its northwestern part 4 further to the northeast the rhino graben is segmented and transitions into a narrower ene trending half graben with a better developed border fault on its northwestern side this segmentation coincides with the presence of n trending precambrian structures 5 the rhino graben terminates farther northeast against the nw trending precambrian aswa shear zone a prominent structure with complex but generally nw trending fabric

lower crustal composition and crustal lineaments on the voring margin ne atlantic a review abstract a prominent lower crustal high velocity layer observed in the voring basin ne atlantic has been investigated with regard to composition and spatial link to crustal scale lineaments in the southernmost part of the basin the lower crustal layer is interpreted as eclogites based on anomalously high p wave velocities 8 4 km s in the remainder of the basin the layer is preferably interpreted as mafic intrusions emplaced during the last phase of rifting but it cannot be excluded that the body consists of older caledonian mafic rocks direct link with high grade caledonian rocks to the east and westwards to east greenland cannot be made since these rocks are mainly of felsic composition the crustal scale lineaments inferred from wide angle seismic data appear to represent the oceanward extension of post caledonian detachments the spatial variation in the thickness of the layer is within the late rifting magmatic hypothesis partly interpreted in terms of pre magmatic variations in thickness of the lithosphere in addition lateral variations in extension mantle upwelling and decompressional melting during the last phase of rifting may also have contributed

terrane boundary reactivation barriers to lateral fault propagation and reactivated fabrics rifting across the median batholith zone great south basin new zealand prominent pre existing structural heterogeneities within the lithosphere may localise or partition deformation during tectonic events the ne trending great south basin offshore new zealand formed perpendicular to a series of underlying crustal terranes including the dominantly granitic median batholith zone which along with the boundaries between individual terranes exert a strong control on rift physiography and kinematics we find that the crustal to lithospheric scale southern terrane boundary of the median batholith zone is associated with a crustal scale shear zone that was reactivated during late cretaceous extension between zealandia and australia this reactivated terrane boundary is oriented at a high angle to the faults defining the great south basin we identify a large granitic laccolith along the southern margin of the median batholith expressed as sub horizontal packages of reflectivity and acoustically transparent areas on seismic reflection data the presence of this strong granitic body inhibits the lateral south westward propagation of ne trending faults which segment into a series of splays that rotate to align along the margin as they approach further we also identify two e w and ne sw oriented basement fabrics likely corresponding to prominent foliations which are exploited by small scale faults across the basin we show that different mechanisms of structural inheritance are able to operate simultaneously and somewhat independently within rift systems at different scales of observation the presence of structural heterogeneities across all scales need to be incorporated into our understanding of the structural evolution of complex rift systems

fractured basement play development on the uk and norwegian rifted margins fractured crystalline basement reservoirs basement on the uk continental shelf ukcs and the norwegian continental shelf ncs have been underexplored over the last 12 years hurricane energy has deliberately set out to explore basement potential by exploring and appraising the rona ridge west of shetland and the rona ridge lancaster field is now being progressed towards being the first uk basement field development the norwegian basement play is also recognized as a potentially material resource through serendipitous oil discoveries with the 16 1 15 well drilled in 2011 being the first successful full scale basement test on the ncs building on this success the 2018 rolvsnes appraisal well 16 1 28 s has demonstrated the significant basement potential of the extensive utsira high and confirmed the materiality of a norwegian basement play the rona ridge and utsira basement discoveries are used as a comparison with two other yet to be evaluated prospective basement plays on the ncs with the objective of establishing technical subject areas where future ukcs and ncs collaboration would aid in accelerating understanding of the ukcs ncs basement play

the moho boundary above upper mantle peridotites or lower crustal eclogites a global review and new interpretations for passive margins abstract we have performed a global study of 2d crustal scale wide angle profiles across passive margins with regard to local elevations in the moho which could possibly be interpreted as indicative of lower crustal eclogites a total of 16 candidates have been found mainly in the north atlantic and around australia these cases make up c 6 only of the total profile length studied confirming the interpretation of the moho generally representing the top of the mantle the interpreted candidates for lower crustal eclogites indicate that there may be a link between eclogite bodies and continental suture zones in the barents sea off mid norway in the newfoundland appalachians and in the yilgarn craton western australia it is also possible that there is a genetic link between the formation of caledonian eclogites and the jan mayen fracture zone which is the only major fracture zone in the north atlantic several of the inferred lower crustal eclogite bodies are located close to lines of major changes in strain such as coastlines and shelf edges indicating that lower crustal eclogite bodies may be important in guiding the evolution of basin architecture interpreting the moho beneath the bedout high on the northwest shelf of australia as the top of a body of lower crustal eclogites may imply that the northern termination of the lambert shelf represents a paleo suture zone and that the western termination of the broome platform acted as a major transfer zone the significant increase in crustal thickness implied by the eclogite model has important implications for estimates of stretching history subsidence and hydrocarbon maturation modelling

water flow from a horizontal tunnel in an unsaturated zone flow from a horizontal tunnel in an unsaturated zone is an important factor in calculation of water loss from the conveying tunnel and in predicting the amount of water table build up this study has investigated the three dimensional unsaturated flow from a tunnel by using the linearized richards equation it superposes the point source solution along the tunnel axis to yield the line source solution for treating the tunnel surface as a saturated water content boundary this study first provides an empirical function to numerically calculate the flux distribution along the tunnel axis it then provides an analytical solution to calculate flow from the tunnel we find that the recharge rate from a horizontal tunnel decreases with time and gradually approaches a steady state rate the recharge increases with increasing tunnel length and radius and also with increasing the pore size distribution parameter of the soil the vertical downward recharge beneath the tunnel becomes constant and equals the total recharge from the tunnel at late time

an integrated gis based tool for aquifer test analysis the quantification of the hydraulic parameters is important to support decision making in environmental impact assessment water resources evaluation or groundwater contamination remediation among others these kind of parameters derived from aquifer tests usually encompasses a vast amount of data spatial and non spatial for management and analysis to achieve this in a clear and understandable manner the gis environment is a useful instrument development of innovative software to analyze pumping tests in a gis platform environment to support the hydraulic parameterization of groundwater flow and transport models is presented in this paper this new platform provides three interconnected modules to improve a pumping test interpretation code through a user friendly interface b pumping test data visualization supported by a set of tools that perform spatiotemporal queries in a gis environment and c the storage and management of hydrogeological information additionally within the gis platform it is possible to process the hydraulic parameters obtained from the pumping test and to create spatial distribution maps perform geostatistical analysis and export the information to an external software platform finally a real world application in the area of barcelona spain has shown the usefulness of the tools developed in support of hydrogeological analysis

assessment of subsurface lithology in mountain environments using 2d resistivity imaging abstract the use of 2d resistivity imaging for the investigation of typical periglacial phenomena is shown on different case studies from a mid latitude high alpine and a high latitude subarctic periglacial environment important parameters that need to be determined for geomorphological studies in mountain environments are the location and extent of permafrost and its characteristics the spatial variability of the active layer as well as the internal structure of different periglacial landforms the investigations on different typical periglacial features demonstrate that 2d electrical resistivity imaging is a suitable method to detect permafrost with an appropriate accuracy delineation of active layer thickness is possible but depends on the contrast in resistivity between the active layer and the permafrost underneath the detection of small scale variability within the internal structure of some typical periglacial landforms can be limited because of the smoothing effect of the wenner array and the high ground resistances and weak signal strength which do not allow the successful application of the dipole dipole array hence limitations of application of geoelectric methods can arise from the rugged terrain conditions in periglacial mountain environments since good electrical coupling between the electrodes and the ground is a prerequisite for geoelectrical surveys nevertheless it is demonstrated that even on rough terrain conditions 2d electrical resistivity imaging could be used successfully to obtain reproducible results which are required to use changes in the apparent resistivity measurements to monitor changes in the subsurface resistivity distribution and hence permafrost aggradation and degradation

rifted margins ductile deformation boudinage continentward dipping normal faults and the role of the weak lower crust the stunningly increased resolution of the deep crustal levels in recent industrial seismic profiles acquired along most of the world s rifted margins leads to the unraveling of an unexpected variety of structures it provides unprecedented access to the processes occurring in the middle and lower continental crust we present a series of so far unreleased profiles that allows the identification of various rift related geological processes such as crustal boudinage ductile shear and low angle detachment faulting and a rifting history that differs from the classical models of oceanward dipping normal faults the lower crust in rifted margins appears much more intensely deformed than usually represented at the foot of both magma rich and magma poor margins we observe clear indications of ductile deformation of the deep continental crust along large scale shallow dipping shear zones these shear zones generally show a top to the continent sense of shear consistent with the activity of continentward dipping normal faults cdnf observed in the upper crust this pattern is responsible for a migration of the deformation and associated sedimentation and or volcanic activity toward the ocean we discuss the origin of these cdnf and investigate their implications and the effect of sediment thermal blanketing on crustal rheology in some cases low angle shear zones define an anastomosed pattern that delineates boudin like structures the maximum deformation is localized in the inter boudin areas the upper crust is intensely boudinaged and the highly deformed lower crust fills the inter boudins underneath the boudinage pattern controls the position and dip of upper crustal normal faults we present some of the most striking examples from the margins of uruguay west africa south china sea and barents sea and discuss their implications for the time temperature history of the margins

on the horizontal well pumping tests in anisotropic confined aquifers a method that directly solves the boundary problem of flow to a horizontal well in an anisotropic confined aquifer is provided this method solves the point source problem first and then integrates the point source solution along the horizontal well axis to obtain the horizontal well solution the short and long time approximations of drawdowns are discussed and are utilized in the semilog analysis of the drawdown a closed form analytical solution of geometrical skin effect at the wellbore is derived type curves and derivative type curves of horizontal pumping wells are generated using the chow program this program also calculates the drawdown at any given observation well at any given time the horizontal well type curves are different from the vertical well type curves at early time reflecting the different nature of flow to a horizontal well and to a vertical well the horizontal well type curves converge to the vertical well type curves at late time showing the similar nature of flow to a horizontal well and to a vertical well at late time the sensitivity of the type curves and derivative type curves on monitoring well location aquifer anisotropy horizontal well depth and horizontal well length is tested these type curves and derivative type curves can be used in the matching point method for interpreting the pumping test data

the growth of non colinear normal fault systems what can we learn from 3d seismic reflection data abstract many rift zones exhibit a range of fault orientations rather than simple colinear faults that strike orthogonal to the inferred least principal stress the formation of non colinear fault sets has implications for assessing rift zone kinematics as well as determining palaeo stress state in extensional basins using 3d seismic reflection data we deduce the likely mechanisms responsible for the formation of a population of non colinear faults in the maloy slope area of the northern north sea three basement displacing fault populations exist on the maloy slope i large 1 km throw n s striking faults ii smaller

quantification and restoration of extensional deformation along the western iberia and newfoundland rifted margins 1 many recent papers describe the structure of the iberia and newfoundland rifted margins however none of them propose kinematic restorations of the complete rift system to quantify the amount of extension necessary to exhume mantle and initiate seafloor spreading in our study we use two pairs of cross sections considered as conjugate lines one across the galicia bank flemish cap and the other across the southern iberia abyssal plain flemish pass both transects have been imaged by reflection and refraction seismic methods and have been drilled during ocean drilling program legs 103 149 173 and 210 drilling penetrated parts of the rift stratigraphy and the underlying basement the cross sections can therefore be considered as the best documented conjugate transects across present day hyperextended magma poor rifted margins the aim of this paper is threefold 1 provide a detailed description of the crustal architecture of the two conjugate sections 2 define the extensional structures and their ages and 3 quantify the amount of strain and strain rate accommodated along these lines this paper proposes a quantitative description of extension along the iberia newfoundland rift system and discusses the limitations and problems in quantifying extensional deformation along hyperextended rifted margins

capture zone between two streams summary we have investigated stream aquifer interaction with a single pumping well in an aquifer bounded by two parallel nearby streams this study presents steady state semi analytical solutions to calculate the fraction of water withdrawal from two streams potential theory is used to describe the capture zone between two streams when low permeability streambeds are not present steady state flow equations in the aquifer and two streambeds are solved following rigorous mass balance requirements if low permeability streambeds are present when the low permeability streambeds are not present and the regional flow exists between two streams this study finds that the maximal capture size without extracting water from the down gradient stream decreases with the normalized well location in an approximately linear fashion furthermore the normalized flux from the up gradient stream decreases with the normalized well location faster than the linear fashion when the low permeability streambeds exist and the regional flow is neglected the normalized flux across either streambed varies with the normalized well location in a linear function furthermore the magnitude of the slope of that function is nearly unity when the hydraulic conductance ratio of the two streambeds is one and is less than unity when the hydraulic conductance ratio of the two streambeds is either greater or smaller than one when the normalized well location with equal fluxes from two streams versus the hydraulic conductance ratio of the two streambeds are plotted semi logarithmically we observed a segmented curve including a steep segment at the beginning followed by a flat segment and a final steep segment

late mesozoic to early cenozoic components of vertical separation across the more trondelag fault complex norway abstract low temperature apatite fission track aft data from two horizontal transects across the more trondelag fault complex mtfc and along the coast of the fosen peninsula have defined a complicated series of structural blocks whose exhumation to temperatures cooler than the uppermost apatite partial annealing zone paz occurred during a broad mesozoic to cenozoic time span the 100 million year cooling difference between the innermost and outermost blocks indicates they were subjected to very different exhumation pathways track length histograms and inverse model results also suggest that significant differences in thermal histories are present over very short horizontal distances in conjunction with the offshore geological evidence the aft data and models strongly suggest that the innermost zones of the mtfc underwent between 2 and 4 km of structurally controlled net vertical rock column uplift subsidence following latest cretaceous time and potentially much of the tertiary as well the up to the east down to the west relative offset at the norwegian margin is interpreted in terms of a flexed nearly broken lithospheric plate architectural model for late mesozoic and tertiary scandes mountain building whose driving force was likely dominanted by erosionally induced loading unloading at the margin

origin and significance of intra basement seismic reflections offshore western norway we use 3d seismic data to image a series of enigmatic sw dipping reflection packets within pre mesozoic crystalline basement offshore western norway based on their low angle dip and complex reflection wave train our preferred interpretation is that the reflection packets are the seismic expression of mylonitic zones generated by nappe emplacement during the caledonian orogeny late jurassic faults truncate and offset these reflection packets by several hundred metres suggesting that these faults did not exploit pre existing basement weaknesses our observations suggest that older basement fabrics may not always play a significant role in determining the geometry of later fault systems supplementary materials details of the time depth relationships from wells that have been used to depth convert interpretations s1 a supplementary figure showing an uninterpreted version of the seismic profile presented in fig 2 s2 and a throw v distance plot for fault f1 at the structural levels of the basement reflection and intra basement reflection 1 are available at www geolsoc org uk sup18683

the norway basin revisited from continental breakup to spreading ridge extinction abstract we re evaluate the structure and spreading evolution of the southeastern norway basin nb based on a new high resolution aeromagnetic survey nb 07 the survey covers a complete oceanic spreading segment from the continental oceanic transition of the more margin off norway to the aborted aegir ridge the new survey documents a transform margin an orthogonally rifted segment and an oblique sheared volcanic margin formed during the onset of breakup observed from the east jan mayen fracture zone to the faroe platform the detailed fabric of the nb revealed by the new data indicates that two distinct tectonic phases have reshaped the basin before the cessation of seafloor spreading and abortion of the aegir ridge in the late oligocene after continental breakup phase i from c24 to c21r 52 to 49 ma marks the earliest phase of spreading probably initiated in the central and outer part of the more basin during this period competing oceanic segments led to the formation of overlapping systems and pseudo fault development we observe a significant change in the nb s oceanic spreading system in the late early eocene and based on observations from surrounding areas we suggest that this is a record of a major tectonic event in the norwegian greenland sea around c21r 49 47 9 ma during phase ii from c21r to c10 48 to 28 ma of nb s development spreading rates decreased spreading direction changed and the number of faulting with large displacement increased leading to the formation of unexpected n s oriented oceanic fracture zones the fan shaped development of the spreading system initiated around c21r 49 47 9 ma instead of c18 c17 40 38 ma or c24 53 3 52 3 ma as previously proposed these new observations were used to re evaluate the tectonic evolution of the norwegian greenland sea and discuss some implications on the syn and post breakup development of the surrounding continental margins and the evolution of the jan mayen microcontinent

reactivation of intrabasement structures during rifting a case study from offshore southern norway abstract pre existing structures within crystalline basement may exert a significant influence over the evolution of rifts however the exact manner in which these structures reactivate and thus their degree of influence over the overlying rift is poorly understood using borehole constrained 2d and 3d seismic reflection data from offshore southern norway we identify and constrain the three dimensional geometry of a series of enigmatic intrabasement reflections through 1d waveform modelling and 3d mapping of these reflection packages we correlate them to the onshore caledonian thrust belt and devonian shear zones based on the seismic stratigraphic architecture of the post basement succession we identify several phases of reactivation of the intrabasement structures associated with multiple tectonic events reactivation preferentially occurs along relatively thick c 1 km relatively steeply dipping c 30 structures with three main styles of interactions observed between them and overlying faults i faults exploiting intrabasement weaknesses represented by intra shear zone mylonites ii faults that initiate within the hangingwall of the shear zones inheriting their orientation and merging with said structure at depth or iii faults that initiate independently from and cross cut intrabasement structures we demonstrate that large scale discrete shear zones act as a long lived structural template for fault initiation during multiple phases of rifting

anatomy and tectono sedimentary evolution of a rift related detachment system the example of the err detachment central alps se switzerland the discovery of hyperextended crust in present day magma poor distal rifted margins has major implications for the development of rift concepts indeed the occurrence of low angle detachment faulting changes the structural style and modifies the classical architecture of rifted margins often represented by tilted blocks and bounded by high angle normal faults at present little is known about the ways in which detachment systems form in distal margins through time and space and the way in which they control the formation of supradetachment rift basins in this paper we discuss a jurassic rift related detachment system of the fossil adriatic distal rifted margin today exposed in the lower austroalpine err nappe in se switzerland a palinspastic restoration of the alpine units places the three dimensional postrift architecture of this detachment system over more than 200 km 2 and 34 km in transport direction based on the description of a preserved supradetachment basin we can show that the synrift sedimentary evolution records the formation of supradetachment extensional allochthons and the exhumation of basement rocks using this well exposed example we will show that detachment systems are intimately related to the overall tectono sedimentary evolution of the most distal parts of the adriatic rifted margin and possibly other atlantic type magma poor hyperextended rifted margins

influence of glacier advance on the development of the multipart riffeltal rock glacier central austrian alps the multipart riffeltal rock glacier located in a tributary valley of the kaunertal tyrol austria is investigated to enlarge the knowledge about spatial and temporal development of rock glaciers in and at the margins of pro glacial areas and to get a better understanding of glacier rock glacier interactions the subject of interest consists of a complex system of two adjacent rock glacier tongues and various superposed lobes with differing ages origin and root zones and therefore diverse development to determine the reasons for their diverging development the internal structure and permafrost occurrence on and in the surrounding area of the rock glacier were studied by application of geomorphological mapping geophysical methods and measurement of the basal temperature of the winter snow cover bts permafrost modelling was performed on the basis of bts data and land surface parameters derived from a high resolution airborne laser scanning als digital elevation model dem additionally the als data were used to measure vertical and horizontal changes of the rock glacier surface between 2006 and 2012 glacier rock glacier interactions during and since the little ice age lia are evident for the development of the studied rock glacier a geomorphic map gives important information about the connection between glacial advance or retreat and permafrost or ground ice occurrence the combination of all information helps in the analysis of diverse kinematic action of neighbouring rock glacier tongues copyright 2014 john wiley sons ltd

the role of structural inheritance in the development of high displacement crustal faults in the necking domain of rifted margins the klakk fault complex froya high offshore mid norway abstract the role of inherited structures during the development of normal faults in continental rifts and proximal domains of passive margins have been extensively studied few studies however have a focus on deciphering the role of inheritance in the development of high displacement 10 km low angle 25 km is present during rifting

detachment faulting and the evolution of passive continental margins major detachment faults play a key role in the lithospheric extension process in the basin and range province and may also be important in other continental extension terranes such detachment faulting leads to an inherent asymmetry of extensional structure and of uplift subsidence patterns detachment models developed for the formation of metamorphic core complexes can also be applied to the formation of passive continental margins we therefore suggest the existence of upper plate and lower plate passive margins these give rise to a complementary asymmetry of opposing margins after continental breakup transfer faults offset marginal features and allow margins to switch from upper plate to lower plate characteristics along strike

layer cake depth conversion part i in areas of uniform lithology which have not undergone tectonic inversion or severe structural deformation depth conversion can often be performed according to some simple mathematical function e g average velocity as a linear function of depth in areas where there are dramatic changes of velocity such as thick carbonate or evaporite units alternating with thick clastic units as those found in the southern north sea basin then simple functions cannot adequately cope with the inherent velocity inversions and are inadequate for depth conversion

tectono sedimentary evolution of the eastern gulf of aden conjugate passive margins narrowness and asymmetry in oblique rifting context abstract here we focus on the yet unexplored eastern gulf of aden on socotra island yemen southeastern oman and offshore conjugate passive margins between the socotra hadbeen shfz and the eastern gulf of aden fracture zones our interpretation leads to onshore offshore stratigraphic correlation between the passive margins we present a new map reflecting the boundaries between the crustal domains proximal necking hyper extended exhumed mantle proto oceanic and oceanic domains and structures using bathymetry magnetic surveys and seismic reflection data the most striking result is that the magma poor conjugate margins exhibit asymmetrical architecture since the thinning phase upper rupelian burdigalian their necking domains are sharp 40 10 km wide and their hyper extended domains are narrow and asymmetric 10 40 km wide on the socotra margin and 50 80 km wide on the omani margin we suggest that this asymmetry is related to the migration of the rift center producing significant lower crustal flow and sequential faulting in the hyper extended domain throughout the oligo miocene rifting far field forces dominate and the deformation is accommodated along ew to n110 e northward dipping low angle normal faults convection in the mantle near the shfz may be responsible of change in fault dip polarity in the omani hyper extended domain we show the existence of a northward dipping detachment fault formed at the beginning of the exhumation phase burdigalien it separates the northern upper plate oman from southern lower plate socotra island and may have generated rift induced decompression melting and volcanism affecting the upper plate we highlight multiple generations of detachment faults exhuming serpentinized subcontinental mantle in the ocean continent transition associated to significant decompression melting final detachment fault may have triggered the formation of a proto oceanic crust at 17 6 ma and induced late volcanism up to 10 ma finally the setting up of a steady state oceanic spreading center occurs at 17 ma

devonian orogen parallel opposed extension in the central norwegian caledonides late orogenic early to middle devonian extension in the scandinavian caledonides was unidirectional in western norway new data from two detachment zones hoybakken and kollstraumen north of the more trondelag fault complex show that bidirectional opposed orogen parallel extension dominated in this region at this time the fault complex acted as a transfer zone for the hoybakken detachment extension and uplift in central norway triggered significant magmatic activity in contrast to the lack of granite intrusions during exhumation of western norway

rifting and shallow dipping detachments clues from the corinth rift and the aegean the corinth rift is superimposed on the hellenic nappe stack that formed at the expense of the apulian continental crust above the subducting african slab extension started in the pliocene and the major steep normal faults that control the geometry of the present day rift were born very recently some 600 kyr ago only they root into a shallow dipping zone of microseismicity recorded near the base of the upper crust the significance of this seismogenic zone is debated considering the northward dip of the zone of microseismicity the depth of microearthquakes and their focal mechanisms we observe a strong similarity with the northern cycladic detachments in terms of expected pressure temperature conditions and kinematics we herein show 1 that the formation of the corinth rift can be considered a part of a continuum of extension that started some 30 35 ma in the aegean and that was recently localised in a more restricted area 2 that the present day structure and kinematics of the corinth rift can be explained with a series of decollements relayed by steeper ramps that altogether formed a mechanically weak crustal scale detachment and 3 that the deformation fluid behaviour and metamorphic features seen in the northern cycladic metamorphic core complexes can be good analogues of the processes at work below the corinth rift

ductile extensional shear zones in the lower crust of a passive margin we describe and interpret an unpublished set of ion geophysical seismic reflection profile showing strong organized seismic reflectors at the base of the continental crust of the uruguayan volcanic rifted margin we distinguish two main groups of reflectors in the lowermost continental crust a first group at depths ranging from 32 km below the continent to 16 km in the continent ocean transition comprises reflectors continuous over tens of kilometers peculiarly visible near the mantle crust boundary a second group of reflectors dipping toward the ese oceanward is widely distributed in the lower crust these reflectors are slightly curved and tend to merge and become sub parallel with the first group of reflectors together they draw the pattern of thick shallow dipping top to the continent shear zones affecting the lower continental crust such sense of shear is also consistent with the continentward dip of the normal faults that control the deposition of the thick syn tectonic volcanic formations sdr a major portion of the continental crust behaved in a ductile manner and recorded a component of top to the continent penetrative simple shear during rifting indicative of a lateral movement between the upper crust and the mantle

styles of extension offshore mid norway and implications for mechanisms of crustal thinning at passive margins 1 eocene magmatic breakup along the mid norway rifted margin was preceded by extreme jurassic cretaceous crustal thinning in a magma poor environment along the se borders of the rift top basement detachment faults with heaves on the order of 15 40 km evolved in at least two stages to become the boundaries between moderately thinned 20 30 km thick crust and a 100 200 km wide highly extended area with crustal thicknesses generally between 2 and 12 km under the present day more and voring basins in the footwalls of the basin flank detachments lower and middle crust was exhumed in extensional domes that became incised by a younger set of normal faults under the most highly thinned areas a more distal set of deep seated basin floor detachments incised and extended remnant crust and probably the upper mantle leaving as little as 5 km of continental crust to be preserved under thick synrift and postrift deposits we suggest that basin flank detachments such as the ones described above hold the potential to reduce the crustal thickness down to the critical value required for embrittlement of continental crust thus they prepare the ground for incision by the basin floor detachments which may become responsible for exhumation of deep crust or continental mantle if extension is allowed to proceed

how does the continental crust thin in a hyperextended rifted margin insights from the iberia margin the discovery of hyperthinned continental crust and exhumed mantle on present day deep water rifted margins leads to two fundamental questions 1 in detail how does the crust thin in extension and 2 what controls extreme crustal thinning and mantle exhumation reflection and refraction seismic lines across the iberian margin show decoupling levels in the crust cut by structures that eventually transfer deformation to mantle levels the region of decoupled extension appears to be more broadly distributed on the northern iberian margin and more localized on the southern margin based on drill hole data the transition from decoupled to coupled deformation occurred during tithonian time ca 145 ma this evolution from decoupled to coupled deformation may help explain the crustal architecture of the iberian margin an apparent delay of subsidence across the hyperextended coupled zone of the iberian margin may indicate that crustal thinning had to occur simultaneously with lithospheric necking and the advection of heat related to lithospheric mantle thinning

analytical models of slug tests in the present paper attempts are made to develop solutions to various models of slug tests that may be applicable in analyzing the results of such tests where existing solutions are inadequate various geometries that may be encountered in heterogeneous systems such as fractured rocks are considered solutions are presented for linear flow radial flow with boundaries two layer and concentric composite models with different flow geometries between the inner and outer region solutions are obtained in laplace space and inverted back to real space numerically type curves are presented for each solution analyses of the type curves and derivative response curves reveal that many curves have unique shapes only for certain combination of the flow parameters and the distance other sets of type curves are similar in shape although log log plots and derivative plots may emphasize some features that may not be apparent in semilog plots these results show that slug tests suffer problems of nonuniqueness to a greater extent than other well tests

semi analytical solutions of discharge variation of a qanat in an unconfined aquifer subjected to general areal recharge and nearby pumping well discharge abstract qanat is a type of drain that extract water from aquifers by gravity significant amount of fresh water used in middle east and other parts of the world are supplied by qanats despite their importance discharge variation of these type of wells received almost no attention the aim of this research is to obtain a laplace domain solution of discharge variation of a qanat installed in an anisotropic unconfined aquifer subjected to arbitrary areal recharge and nearby pumping well s discharge a new semi analytical solution of drawdown is obtained first to implement the effects of arbitrary areal recharge and nearby pumping well s using the principle of superposition then the discharge variation solution of the qanat is obtained from the drawdown solution to establish a constant head boundary condition at the qanat periphery the qanat is discretized into several segments the results of this study are presented in dimensionless discharge dimensionless time curves the effects of hydraulic as well as geometric parameters on the discharge variation of the qanat due to arbitrary areal recharge falling of water table from its initial position and discharge of nearby wells are explored we also investigate the influences of distance and screen depth and location of the nearby well on the discharge variation of the qanat the results of this study can be utilized for multiple purposes 1 to predict discharge of qanat in response to rainfall and nearby pumping well s 2 to estimate the aquifer parameters using hydrograph of the qanat 3 to determine optimal location and pumping pattern of the nearby wells to minimize their influences on the discharge of the qanat 4 to calculate water budget of aquifers drained by a qanat the equation presented in this work can also be used to estimate discharge of a horizontal drain installed in cropland subjected to arbitrary irrigation pattern

deep crustal flow within postorogenic metamorphic core complexes insights from the southern western gneiss region of norway 2019 the authors this is an open access article under the terms of the creative commons attribution license which permits use distribution and reproduction in any medium provided the original work is properly cited

mechanisms of inheritance of rift faulting in the western branch of the east african rift tanzania the western branch of the east african rift system is commonly cited as a result of phanerozoic reactivation of the paleoproterozoic ubendian belt in western tanzania geological evidence is provided to show that prominent mechanical anisotropies successively appeared during proterozoic evolution of the precambrian basement and that their different reactivation behavior contributed to the phanerozoic rift pattern the ubende belt 1950 1850 ma is a nw oriented amphibolite facies ductile lateral shear belt in which older 2100 2025 ma and complex granulite facies terranes are included along trend retrograde multiphase sinistral strike slip mylonites developed along the nw oriented ductile shear belt they reflect persistent proterozoic wrench fault reactivation of the latter shallow level sedimentary basins upon and along the ductile shear belt display deformational structures attributable to the proterozoic wrench fault reactivation neoproterozoic sinistral transpression produced the final geometrical pattern of the wrench fault zone which appears as an elongate and nw trending positive flower structure locally enhanced by late proterozoic contraction phanerozoic rifting is demonstrated by others to occur in three distinct episodes during which the complex rift segment formed upon the multiphase proterozoic wrench fault zone the evaluation of the relationship between multiphase rift and multiphase prerift fabrics is reconsidered the proterozoic prerift fabrics correspond with a dextral transpressional and ductile deformational pattern which became selectively reactivated by sinistral transpressional ductile brittle mylonites proterozoic mylonites constitute shallow level mechanical anisotropies and define the general trend of the rift faults according to the position of these mylonites in the center or in the external parts of their nw oriented neoproterozoic transpression they reactivate as complex and multiphase rift faults or as normal and recent faults respectively the paleoproterozoic nw oriented and ductile lateral shear belt constitutes the deep level mechanical anisotropy its reactivation in phanerozoic stress fields is likely dextral oblique transtension considered as a leading mechanism of the pluriphase and nw oriented deep rift basins

analytical study of capture time to a horizontal well we have investigated capture time through a horizontal well for several types of aquifers we have studied two scenarios in which wells are at the middle and at the bottom or the top of an aquifer we have obtained the closed form analytical solutions of capture times for these two scenarios in homogeneous confined aquifers for both isotropic and anisotropic cases we have discussed the applicability and the limitation of the analytical solutions the presence of confining boundaries in vertical direction constrains the vertical flow but enhances the horizontal flow the presence of anisotropy with a smaller vertical conductivity further limits the vertical flow and increases the horizontal flow we have conducted numerical simulations to obtain capture times and found that they were very close to the analytical solutions given the same conditions we have further analyzed the advantages and disadvantages of two different methods of simulating a horizontal well uniform flux and uniform head

rock glacier dynamics and paleoclimatic implications many rock glaciers contain massive ice that may be useful in paleoclimate studies interpreting geochemical ice core records from rock glaciers requires a thorough understanding of rock glacier structure and dynamics high precision surface velocity data were obtained for the galena creek rock glacier absaroka mountains wyoming surface velocities range from 0 to 1 00 m yr and vary across the rock glacier in a manner similar to true glaciers we used glen s flow law to calculate the thickness of the deforming ice layer the modeled ice thickness ranges from 0 to 50 m and is confirmed by direct observations this agreement shows that rock glacier movement can be entirely explained by deformation of massive ice within the rock glacier neither basal sliding nor deformation of basal debris is necessary recovered ice cores to depths of 25 m contain thin debris layers associated with summer ablation in the accumulation zone the ages of four samples of organic material removed from several debris layers inthe southern half of the rock glacier range from 200 40 to 2250 35 14c yr b p demonstrating that the rock glacier formed well before the little ice age and may contain ice dating to the middle holocene or earlier

horizontal well hydraulics in leaky aquifers abstract this paper presents a general study of horizontal well hydraulics for three aquifer types a leaky confined aquifer a leaky water table aquifer and a leaky aquifer under a water reservoir semi analytical solutions are obtained for cases that exclude and include the aquitard storage the type curves and derivative type curves for these different conditions are provided a graphically integrated matlab program named hw leak is written to facilitate numerical calculations and generation of the type curves and derivative type curves this study shows that 1 derivative type curves are more sensitive to the aquitard parameters than the type curves and that 2 drawdown is sensitive to the aquitard aquifer thickness ratio and the hydraulic conductivity ratio at the intermediate and later time both curves are less sensitive to the aquitard aquifer specific storage ratio while the degree of sensitivity of the drawdown to the aquitard parameters is high in a leaky confined aquifer moderate in a water table aquifer and low in an aquifer under a water reservoir

patterns of basement structure and reactivation along the ne atlantic margin a lineament pattern on the ne atlantic margin is discussed illustrated by gravity and magnetic images in the norwegian sea and reviewed in the context of onshore field evidence while most possible fault trends exist three major sets predominate a ne sw left stepping lineament set defines the gross geometry of the margin while interposing northerly trends impose a rhomboidal geometry at a variety of scales the margin is segmented by nw se transfer zones sometimes involving significant offsets the principal trends are primarily a function of mesozoic cenozoic plate wide extensional stress fields certain proterozoic and caledonian lineaments were however opportunistically reactivated according to the extension direction caledonian ne sw orogen oblique shears typified by the more trondelag fault zone were reactivated via jurassic strike slip or oblique slip and were further exploited during cretaceous early cenozoic extensional episodes leading to continental break up jurassic e w extension may also have reactivated n s faults existing in the basement or generated in duplex systems between the ne sw shears precambrian and caledonian basement lineaments striking at a low angle to the extension direction probably predisposed the formation of major transfer zones

structural comparison of archetypal atlantic rifted margins a review of observations and concepts abstract in this study we compare three pairs of conjugate rifted margins that are often referred to as archetypes of rift systems despite numerous differences a remarkable first order structural similarity appears between the magma poor iberia newfoundland the magma rich mid norway east greenland and the sediment rich angola brazil rifted margins typical is the seaward arrangement of distinct domains proximal necking distal and outer that each present specific comparable structural characteristics our study also suggests that magma rich systems may go through a stage of hyper extension indicating that extreme crustal thinning does not preclude a magmatic breakup in this contribution we clarify the definition of a number of terms introduced recently in rifted margin studies we review the major features constitutive of these key referenced systems discuss their similarities and differences and examine how the related deformation modes develop in the life cycle of a rift that goes to seafloor spreading we conclude that the distinct domains observed in the margin architecture represent distinct stages in the evolution of rifted margin independently of their later evolution into magma poor or magma rich environments

3d structure and evolution of folds during normal fault dip linkage understanding the 3d geometry and evolution of extension related folds is important because they may document the geometry and evolution of the associated faults influence sediment routing and accommodation development and may represent targets for hydrocarbon exploration or co 2 storage previous work on extension related folds has largely been restricted to a 2d plane of observation in this study we use 3d seismic reflection data from the gulf of suez egypt to determine the 3d geometry and evolution of fault parallel folds during dip linkage of a vertically segmented extensional fault array that is locally decoupled across a salt bearing interval the 3d geometry of individual faults in the array and adjacent hanging wall folds varies along strike rollover structures occur above listric faults whereas fault bend folds occur above faults that have a ramp flat ramp geometry quantitative analysis of fault fold attributes e g fold amplitude and the growth history of the fault array indicate that fault shape is controlled by the style of dip linkage which in turn is controlled by the lateral separation of sub and supra salt segments prior to linkage small lateral separation yields a relatively subtle change in the overall convexity of the listric fault whereas larger lateral separation results in a ramp flat ramp fault geometry with the layer parallel detachment lying within the salt this study provides a link between fault spacing style of dip linkage final fault shape and ultimately the style of hanging wall folding in mechanically layered stratigraphy our study indicates that 3d seismic reflection data have the ability to provide us with new 3d insights into the variability of and controls on the geometry and evolution of fault related folds

influence of a pre existing basement weakness on normal fault growth during oblique extension insights from discrete element modeling abstract we use discrete element modeling to investigate three dimensional fault geometry and the three dimensional evolution of a fault network that develops above a 60 dipping planar pre existing weakness striking 60 relative to the extension direction the evolution of the fault network comprises three stages i reactivation of pre existing structure and nucleation of new faults 0 10 extension ii radial propagation and interaction between reactivated structure and new faults 15 20 extension and iii linkage between reactivated structure and adjacent faults 20 25 extension during the first stage the pre existing structure mostly reactivates forming a long and under displaced fault new faults are mainly extension perpendicular and dip at 60 during the second stage saw tooth fringes grow upwards from the upper tip of the reactivated structure which becomes the major fault and influence the density and orientation of surrounding faults during the third stage the reactivated structure links laterally and vertically with adjacent faults creating non planar fault geometries following linkage the reactivated structure enhances the displacement of linked faults along branch lines our study demonstrates that pre existing weak faults can be reactivated propagating upwards in an irregular saw tooth pattern and affecting fault density orientation dip and displacement and providing the nucleation site of new faults

aquitard effect on drawdown in water table aquifers 1 the effects of an aquitard on drawdown in an overlying unconfined aquifer can be represented by a drainage type term at the aquitard aquifer interface the functional form of this boundary condition is similar to the boulton neuman boundary condition used for water table aquifers except the kernel contains an inverse square root of time instead of a negative exponential type curves using the new boundary condition were obtained in semianalytical form examples for several representative conditions show that the effect of the underlying aquitard can contribute to the type curve at early and intermediate times but the effect becomes negligible at late times

on the aquitard aquifer interface flow and the drawdown sensitivity with a partially penetrating pumping well in an anisotropic leaky confined aquifer summary a mathematical model for describing groundwater flow to a partially penetrating pumping well of a finite diameter in an anisotropic leaky confined aquifer is developed the model accounts for the jointed effects of aquitard storage aquifer anisotropy and wellbore storage by treating the aquitard leakage as a boundary condition at the aquitard aquifer interface rather than a volumetric source sink term in the governing equation which has never developed before a new semi analytical solution for the model is obtained by the laplace transform in conjunction with separation of variables specific attention was paid on the flow across the aquitard aquifer interface which is of concern if aquitard and aquifer have different pore water chemistry moreover laplace domain and steady state solutions are obtained to calculate the rate and volume of total leakage through the aquitard aquifer interface due to pump in a partially penetrating well which is also useful for engineers to manager water resources the sensitivity analyses for the drawdown illustrate that the drawdown is most sensitive to the well partial penetration it is apparently sensitive to the aquifer anisotropic ratio over the entire time of pumping it is moderately sensitive to the aquitard aquifer specific storage ratio at the intermediate times only it is moderately sensitive to the aquitard aquifer vertical hydraulic conductivity ratio and the aquitard aquifer thickness ratio with the identical influence at late times

the middle to late devonian hoybakken detachment central norway 40ar 39ar evidence for prolonged late post scandian extension and uplift the regionally significant 0 5 2 km thick hoybakken detachment in central norway bounds the southern margin of the central norway basement window and exhibits a well developed top to the wsw fabric characteristic of late scandian devonian ductile extension 40 ar 39 ar data obtained from hornblende mica and k feldspar mineral separates of rocks collected in a transect through the hoybakken detachment yield well defined plateau and isochron mineral ages early devonian exhumation and cooling of the hoybakken detachment footwall is recorded by hornblende ages of 400 ma and mica ages of 390 ma the mylonitic fabric overlying the footwall records younger middle devonian mica crystallization ages of 384 381 ma that are among the youngest extensional ductile fabrics dated in the caledonides and suggest prolonged extensional activity on the hoybakken detachment after inferred cessation of ductile extension at 381 ma the rate of uplift and cooling was reduced and the footwall records late devonian to early carboniferous k feldspar ages of 371 356 ma prolonged extensional activity at hoybakken is compatible with recent u pb ages of deformed titanite crystals and established rb sr ages of white mica in shear related pegmatites both from the southwestern part of the fosen peninsula and 40 ar 39 ar ages of syn tectonic mica overgrowth from the adjacent hitra snasa fault together these ages suggest the onset of ductile extension soon after 401 ma and with the middle devonian crystallization ages determined here suggest that ductile extension on the hoybakken detachment had a duration of 11 20 ma the youngest age of 320 ma was obtained from a k feldspar in a cataclastic granite of the hoybakken detachment s hangingwall and is considered to date a phase of post scandian brittle deformation that overprinted the mylonitic shear fabric

crustal structure and evolution of the outer more margin ne atlantic abstract five regional ocean bottom seismic profiles from the northwestern part of the more margin ne atlantic have been modeled with regard to crustal structure and the interpretations have been supported by the use of multi channel seismic and potential field data the chi squared values uncertainty for the studied profiles are generally in the range 1 3 and the uncertainty in the moho depth is estimated to 1 km the continent ocean transition is found to be relatively sharp 10 40 km wide expressing a change in physical properties corresponding to felsic continental crust along the landward part of the marginal high vp 6 2 6 5 km s and thick mafic oceanic crust further northwestwards the early eocene breakup was associated with excessive magmatism and the models document direct continuity between this magmatism and a lower crustal high velocity layer in the more basin vp 7 1 7 3 km s suggesting a genetic link the jan mayen lineament is observed across the entire study area as northeastward termination of the lower crustal body as well as structuring in the top of the crystalline basement and the moho we present a speculative model involving lower crustal bodies of eclogites vp 8 km s inferred in the easternmost part of the more basin linking the jan mayen lineament to the post caledonian nordfjord sogn detachment

kinematics of the hoybakken detachment zone and the more trondelag fault complex central norway the tectonic disintegration of the caledonian orogen through combined extension contraction and strike slip was characterized by spatial and temporal strain partitioning through a period of at least 30 ma early to mid devonian exhumation of the central norway basement window was associated with retrograde top to the sw extensional shearing in the hoybakken detachment zone sinistral shearing along the more trondelag fault complex and formation of extension parallel folds progressive exhumation led to increasing strain localization and to the transition from ductile to brittle deformation in the interval between c 370 and 320 ma the hoybakken detachment fault cut previously folded detachment mylonites capturing mylonites in its hanging wall 40 ar 39 ar mica and k feldspar ages indicate a late devonian or younger age for the uppermost parts of the adjacent old red basin gentle folding of this stratigraphic level attests to the continuation of shortening and orogen oblique extension into late devonian carboniferous time shortening was intensified along strands of the more trondelag fault complex as shown by mutually cross cutting reverse and strike slip faults flower structures may be particularly common in constrictional strain systems where strike slip faults develop parallel to the principal elongation trend but normal to the principal axis of shortening

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage