fanning of fracture zones and a three dimensional model of the mid atlantic ridge present day spreading directions as represented by the active transform fault sections of fracture zones in the central north atlantic do not fit a small circle pattern about a unique pole1 5 as recently confirmed by a gloria survey contrary to this pattern which is geometrically required if ocean floor spreading is to occur6 the active transform fault directions show a convergence towards the east3 because of the fanning of the present directions the african and american plates are caught in what might be likened to a dovetail construction to allow motion the african plate must shrink about 2 in a north south direction such a shrinkage might be accomplished by thermal contraction tension due to the horizontal component of this contraction has been proposed as the primary cause of fracture zones4 7 however horizontal thermal contraction alone cannot explain the recorded pattern of spreading segments and transform faults because it does not explain why transform faults converge to the east and diverge to the west for this an active driving mechanism is needed we show here that the gravitational drive ridge push caused by thermal contraction in the lithosphere formed along a sinusoidal mid ocean ridge delivers such a mechanism

hydrogeochemical and isotope evidence of groundwater evolution and recharge in minqin basin northwest china a hydrochemical investigation was conducted in the minqin basin to identify the groundwater evolution and recharge in the aquifer the mbr cl ratio is strongly depleted average 0 000451 compared with sea water 0 0035 indicating an evaporite origin the ionic ration plot saturation index si and chloro alkaline indices cai suggest that the dissolution of halite the glauberite gypsum dolomite and calcite determine na cl ca2 mg2 so42 and hco3 chemistry but other processes such as na exchange for ca2 and mg2 and calcite precipitation also contribute to the water composition the 6180 and 62 h in precipitation near the study area are linearly correlated similar to that for the world meteoric water line wmwl with an equation of delta h 2 7 49 delta o 18 5 11 r 2 0 97 according to radiocarbon residence time estimates the deep groundwater is approximatety 40 ka old and was recharged during a period when the climate was wetter and colder the radiocarbon content of shallow groundwater shows a clear evolution along the groundwater flow path from the beginning of the groundwater flow path to similar to 31 km the radiocarbon values are 73 6 pmc whereas beyond this point the values are 42 9 pmc based on radiocarbon content the shallow groundwater is older than 1 ka and represents pataeowaters mixed with a limited quality of modern recharge the rain fed groundwater direct recharge was estimated by chloride mass balance cmb method to range from 1 55 to 1 64 mm yr 1 with a mean value of 1 6 mm yr 1 this value represents about 1 5 of local rainfall the direct recharge volumes is about 0 666 x 10 8 m 3 yr 1 indirect recharge volumes by the surface water is about 0 945 x 10 8 m 3 yr 1 the total natural recharge in the minqin basin is 1 6 x 10 8 m 3 yr 1 whereas the groundwater abstraction has reached 11 6 x 10 8 m 3 yr 1 far exceeding the groundwater natural recharge c 2006 elsevier b v all rights reserved

geochemical evidence for possible natural migration of marcellus formation brine to shallow aquifers in pennsylvania the debate surrounding the safety of shale gas development in the appalachian basin has generated increased awareness of drinking water quality in rural communities concerns include the potential for migration of stray gas metal rich formation brines and hydraulic fracturing and or flowback fluids to drinking water aquifers a critical question common to these environmental risks is the hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers we present geochemical evidence from northeastern pennsylvania showing that pathways unrelated to recent drilling activities exist in some locations between deep underlying formations and shallow drinking water aquifers integration of chemical data br cl na ba sr and li and isotopic ratios 87sr 86sr 2h h 18o 16o and 228ra 226ra from this and previous studies in 426 shallow groundwater samples and 83 northern appalachian brine samples suggest that mixing relationships between shallow ground water and a deep formation brine causes groundwater salinization in some locations the strong geochemical fingerprint in the salinized cl 20 mg l groundwater sampled from the alluvium catskill and lock haven aquifers suggests possible migration of marcellus brine through naturally occurring pathways the occurrences of saline water do not correlate with the location of shale gas wells and are consistent with reported data before rapid shale gas development in the region however the presence of these fluids suggests conductive pathways and specific geostructural and or hydrodynamic regimes in northeastern pennsylvania that are at increased risk for contamination of shallow drinking water resources particularly by fugitive gases because of natural hydraulic connections to deeper formations

origin of lode gold deposits of the juneau gold belt southeastern alaska mesothermal gold bearing quartz veins along the juneau gold belt formed in the early tertiary from h 2 o co 2 n 2 h 2 s ch 4 rich low salinity fluids at temperatures of 200 to 325 c and pressures in excess of 1 1 5 kbar isotopically heavy ore forming fluids with 18 o values between 8 and 12 and d values of 20 to 30 indicate a deep seated fluid source the data are compatible with a model of ore fluid generation via metamorphic devolatilization within material subducted below the southern alaska continental margin prograde metamorphic fluids infiltrated up zones of mechanically enhanced permeability associated with the coast range megalineament and formed the gold bearing veins within brittle units at higher retrograding crustal levels deposition of gold was accomplished by several mechanisms including boiling fluid wall rock reactions and decreases in pressure and temperature of the hydrothermal fluids

east pacific rise from siqueiros to orozco fracture zones along strike continuity of axial neovolcanic zone and structure and evolution of overlapping spreading centers we have used the sea beam multibeam echo sounding system to survey the east pacific rise epr from 8 20 n to 18 30 n obtaining complete coverage of the epr axial neovolcanic zone and all intervening transform faults here we focus on the epr neovolcanic zone and the definition of overlapping spreading centers ocs s between the orozco and siqueiros transform faults the neovolcanic zone is narrow 0 5 2 0 km and continuous along strike and occurs within and near a strike continuous axial summit graben the neovolcanic zone and summit graben reside along the crest of a volcanic axial high which is 2 10 km wide and which continues uninterrupted along strike for 40 140 km within 20 50 km of an intersection with a transform fault the axial neovolcanic zone narrows and deepens and within only 3 6 km of the intersection the neovolcanic zone turns sharply into the transform valley at seven locations between the siqueiros and orozco transform faults the axial neovolcanic zone is discontinuous and is laterally offset a short distance 1 15 km in contrast with a classic ridge transform ridge plate boundary however offset rise terminations overlap each other by a distance approximately 3 times greater than their offset they curve toward each other and often one merges into the other along strike separating the osc s is an elliptical overlap basin up to 600 m deep whose long axis is subparallel to the adjacent spreading centers the overlap basin is characterized by volcanic constructional edifices a key difference between these offsets and small transform faults in the atlantic is that there are no transform fault structures in the overlap basin which link the offset rise axes a continuous axial depth profile reveals a long wavelength 20 60 km undulation of the rise axis which may be associated with variations in the magmatic budget along strike the lowest points in the axial depth profile occur near transform faults and at osc s suggesting that these features are associated with along strike minima in the magmatic budget we suggest that major phases of volcanic activity propagate episodically along the axis away from centers of magmatic inflation and that osc s develop where magmatic pulses fail to meet due to misalignment of fracture systems sinuous bends in the rise axis or other heterogeneities transform faults fail to develop on fast spreading centers where the lateral offsets are small 15 km because the lithosphere is too thin and weak to maintain a classic rigid plate ridge transform fault pattern the osc geometry is unstable and evolves rapidly and the overlapping rises may propagate at rates faster than the local spreading rate one of the two osc s prevails while the other is abandoned while the locations of osc s may not be fixed relative to the rise axis they may tend to recur near the same place creating scars in older lithosphere which resemble fracture zones but whose fine scale structure is quite different there is excellent agreement between the observed structure of osc s and laboratory studies of osc s using wax models photoelastic studies of overlapping cracks and boundary element modeling of overlapping cracks seismic refraction and reflection near two osc s suggests that large offset osc s have separate magma chambers beneath the offset rise axes while small offset osc s may share a single axial magma chamber three dimensional inversion of magnetic anomalies suggests that significant petrologic anomalies may occur near some osc tips waxing and waning of overlapping magma chambers may give rise to the eruption of highly fractionated feti basalts and associated magnetic anomalies

gloria investigations of oceanic fracture zones comparative study of the transform fault zone the tectonic patterns of some twenty spreading centre offsets have been determined using the long range sidescan sonar gloria and are reviewed in this paper offsets of less than about 20 km fail to produce transform faults but are accommodated by short sections of oblique spreading with overlapping spreading centres in the fast spreading case at slow slip rates such offsets can be associated with topographic fracture zones that are indistinguishable from those produced at true transform faults such features may account for a significant proportion of spreading centre offsets on slowly spreading mid ocean ridges offsets larger than about 30 km produce a true 9transform fault9 this comprises a 1 to 5 km wide band of individual faults that are parallel or subparallel to the spreading direction the band corresponds to the 9transform fault zone9 tfz of continental wrench faulting it includes the 9principal transform displacement zone9 ptdz and secondary structures such as riedel shears a narrow tfz is normally associated with a prominent ptdz which appears to be either a narrow furrow or a single scarp on the other hand wider zones often fail to show a clear ptdz on gloria both types are common on the slowly spreading mid atlantic ridge and may even occur at different points along the same large offset transform such as romanche although the narrow type appears to occur preferentially where the local ridge axis is oblique to the spreading direction narrow tfzs and prominent ptdzs appear to be more common on the fast spreading east pacific rise it is suggested that broader tfzs and less prominent ptdzs may form in response to the complicating effects of small components of compression across the transform fault perhaps as a result of departure of the transform fault trace from a true small circle such compression would be more easily supported in the thicker stronger lithosphere of slowly spreading ridges but could be relieved by tension due to the ridge push force where the ridge is oblique to the spreading direction

timing of mineralization and source of fluids in a slate belt auriferous vein system hill end goldfield nsw australia evidence from 40ar39ar dating and o and h isotopes abstract 40 ar 39 ar dating of metamorphic biotite and alteration muscovite from the auriferous veins and host rocks at the hill end goldfield n s w australia has distinguished four major geological events including the timing of gold mineralization the earliest hydrothermal event occurred during the middle devonian tabberabberan orogeny 370 380 ma and resulted in the formation of quartz veins barren of au a second and major episode of vein emplacement occurred in the early carboniferous during the principal phase of metamorphism and deformation at 359 363 ma this was followed by au accumulation in two stages 1 after the major phases of quartz deposition and 2 during and after the development of conspicuous internal vein laminations 357 ma and 343 ma respectively two sources of fluid are proposed for vein and ore formation the first is a local metamorphic fluid characterized by 18 o h 2 o values of 8 9 to 12 5 per mil and d h 2 o values of 87 to 90 per mil the second is a mixed ore fluid with 18 o and d values in the range of 18 o h 2 o 8 4 to 11 per mil and d h 2 o of 49 to 36 per mil progressive entry of this second fluid sourced from trough fill or deeper crustal rocks is linked closely to cycles of gold precipitation at hill end

fluid evolution in a slate belt gold deposit a fluid inclusion study of the hill end goldfield nsw australia auriferous quartz veins in the hill end goldfield nsw australia comprise bedding parallel vein sets and minor extension and fault controlled veins which are hosted by a multiply deformed late silurian slate metagreywacke turbidite sequence fluid inclusions in quartz either from bedding parallel veins or from narrow steeply n dipping veins leader veins indicate a similar range in homogenisation temperatures th from 350 c to 110 c within this range th data demonstrate five groupings in the temperature intervals 350 280 c 280 250 c 250 190 c 190 150 c and 150 110 c corresponding to a variety of primary and secondary inclusions developed during five periods of vein growth under a generally declining temperature regime inclusion fluids are characterised by a low salinity of around 0 1 to 3 6 wt nacl equivalent laser raman microprobe inclusion analysis indicates that gas phase compositions relate to the paragenetic stage of the host quartz h2o g and n2 dominate in the primary inclusions from barren stage i quartz ch4 and ch4 h2o g are important in inclusions related to the early gold forming events equivalent to stages ii and iii quartz but inclusions developed during the last episode of gold deposition are characterised by h2o g co2 rich and liquid co2 bearing fluids precipitation of gold was aided by sulphidation reactions or phase separation in response to periods of vein opening late in the paragenesis gold deposition may have been promoted by oxidation of the ore fluid

deep tow seismic profiles from the vema transform and ridge transform intersection a recently developed near bottom reflection profiling system has been used to obtain high resolution seismic sections across the vema transform fault at the western ridge transform intersection deep towed 3 5 khz echo sounder data show evidence of fresh lava flows at the seabed within the nodal deep over one kilometre of sediment fills the bottom of the ridge transform intersection deep many strong discontinuous reflectors within the sedimentary section caused by lava layers indicate that the intersection deep has been the site of sustained igneous activity on the eastern side of the deep is a large uplifted fault block created as the newly formed crust moved out of the spreading centre dipping strata within the fault block document back tilting as the new crust is extended by normal faulting profiles across the active transform fault reveal that the zone of deformation throughout the one kilometre thick sediment column is narrow suggesting that the location of the fault has remained stable throughout at least the last million years

the use of hydrogeochemical analyses and multivariate statistics for the characterization of groundwater resources in a complex aquifer system a case study in amyros river basin thessaly central greece the present study investigates the hydrogeochemical regime of a complex aquifer system in a highly cultivated area of thessaly central greece to do so totally forty 40 groundwater samples were collected for three aquifer units with diverse geological and hydrogeological attributes and analyzed for 77 parameters data processing was accomplished with the joint use of classic hydrogeochemical techniques including major ion molar ratios and graphical interpretation as well as multivariate statistical methods including r mode factor fa and hierarchical cluster analysis hca results showed that major ion hydrogeochemistry is characterized by the prevalence of calcium median 81 mg l and bicarbonates median 308 mg l in the following descending order of concentrations for cations ca2 mg2 na k and anions hco3 no3 so42 cl respectively nitrate values are elevated median 23 mg l especially in the porous quaternary aquifer indicating the ongoing agricultural impact from the excessive use of nitrogen fertilizers and manure the results of multivariate statistics highlighted four factors that chiefly control 81 4 of overall hydrogeochemistry related with both geogenic and anthropogenic impacts the geogenic impact is mainly attributed to the geological substrate and secondarily to the ongoing geochemical redox conditions which in turn enrich or deplete groundwater solution with different ions anthropogenic impact is mainly related with the extensive agricultural practices which favor nitrate enrichment and salinization due to irrigation water return flow

a tectonic model for ridge transform ridge plate boundaries implications for the structure of oceanic lithosphere abstract the first order geologic and morphologic relationships at along and proximal to ridge transform ridge plate boundaries are used to construct an empirical and speculative tectonic model the distinctive but variable morphotectonic fabric and crustal structure of the transform domain are the product of a tectonic continuum that ranges from very slow rates of strain associated with very thick edges of lithosphere slowly slipping ridge transfrom ridge plate boundaries to extremely high rates of strain associated with very thin edges of lithosphere fast slipping ridge transform ridge plate boundaries the geometry of a ridge transform intersection necessitates the juxtaposition of a relatively cold thick edge of lithosphere against the truncated end of an accreting plate boundary the cold face of lithosphere cools the adjacent wedge of asthenosphere rising beneath the axis of accretion and restricts the amount of partial melting thus attenuating the volume of basaltic melt segregated from the asthenosphere per unit time the shallow level manifestation of this cold edge effect is a thinner oceanic crust at depth the evolving lithosphere thickens rapidly as the cold edge is approached creating changes in the properties of the young lithosphere and forming a weld of upper mantle material against the cold edge of truncating lithosphere the ridge transform weld of upper mantle material creates a shear couple in the lithosphere underlying the intersection resulting in the progressive reorientation of the maximum tensile stress from normal to the ridge axis at some distance from the ridge transform intersection to an oblique angle near the boundary the brittle carapace of oceanic crust that overlies the mantle weld will deform accordingly with the development of oblique dip slip faults the model predicts that the geologic expressions of this cold boundary effect will become more dramatic with increasing thickness of the truncating edge at very slow rates of accretion 100 km juxtapose thick 30 50 km edges of lithosphere against the accreting plate boundary all but nullifying the processes that lead to the emplacement of normal oceanic lithosphere in this environment a relatively strong mantle weld will form at the ridge transform intersection and the thick edges of opposing lithosphere along the length of the transform will tend to confine the strike slip tectonism to a relatively narrow and temporally stable principal transform displacement zone in contrast at very fast rates of accretion large offset transforms 100 km place relatively thin edges of lithosphere

shrimp s isotope evidence for fluid mixing during gold mineralization in a slate belt gold deposit hill end new south wales australia abstract sensitive high resolution ion microprobe shrimp sulfur isotope data show that pyrrhotite pyrite galena and chalcopyrite in syntectonic auriferous quartz veins at the hill end goldfield are characterized by two populations with 34sfluid values of 7 and 0 these two populations are accounted for by fluid mixing involving two sources of sulfur during evolution of the vein systems a local sulfur source and reduced fluids derived from trough fill siluro devonian sedimentary and volcano sedimentary sequences are responsible for the first two gold bearing events whereas a more oxidized fluid and a sulfur source from turbidites and volcanics in deeper parts of the crustal sequences appear responsible for gold deposition late in the second gold forming event and are the dominant influences in the final gold forming stage for fine grained mixtures where mineral separation is difficult the shrimp analyses are particularly useful for tracing detailed 34s variations of sulfides precipitated in different paragenetic stages

temporal and spatial scaling of hydraulic response to recharge in fractured aquifers insights from a frequency domain analysis quantification of the recharge in fractured aquifers is particularly challenging because of the multiscale heterogeneity and the range of temporal scales involved here we investigate the hydraulic response to recharge of a fractured aquifer using a frequency domain approach transfer functions are calculated in a range of temporal scales from 1 day up to a few years for a fractured crystalline rock aquifer located in ploemeur s brittany france using recharge and groundwater level fluctuations as input and output respectively the spatial variability of the response to recharge characteristic response time amplitude temporal scaling is analyzed for 10 wells sampling the different compartments of the aquifer some of the transfer functions follow the linear reservoir model behavior on the contrary others display a temporal scaling at high frequency that cannot be represented by classic models large scale hydraulic parameters estimated from the low frequency response are compared with those estimated from hydraulic tests at different scales the variability of transmissivity and storage coefficient tends to decrease with scale and the average estimates converge toward the highest values at large scale the small scale variability of diffusivities which implies the existence of a range of characteristic temporal scales associated with different pathways is suggested to be at the origin of the unconventional temporal scaling of the hydraulic response to recharge at high frequency

the case for metamorphic base metal mineralization pyrite chemical cu and s isotope data from the cu zn deposit at kupferberg in bavaria germany the stratiform cu zn sulfide deposit at kupferberg in germany represents bavaria s largest historic base metal producer the deposit is hosted by early paleozoic volcano sedimentary strata at the margin of a high grade allochthonous metamorphic complex the present paper reports on the first cu and s isotope data as well as trace element analyses of pyrite from this unusual deposit the new data point to syn orogenic mineralization that was driven by metamorphic fluids during nappe emplacement primary cu ore occurs as texturally late chalcopyrite within stratiform laminated pyrite in black shale in two different tectonostratigraphic units of very low and low metamorphic grade respectively that were juxtaposed during the variscan orogeny trace element contents of different pyrite types suggest the presence of at least one hydrothermal pyrite generation mean co ni 35 with the other pyrite types being syn sedimentary early diagenetic mean co ni 3 7 copper isotope analyses yielded a narrow 65cu range of 0 26 to 0 36 for all ore types suggesting a hypogene origin for the principal chalcopyrite mineralization the ore lenses in the two different tectonostratigraphic units differ with regard to their 34s values but little difference exists between poorly and strongly mineralized domains within a given locality a genetic model is proposed in which syn sedimentary early diagenetic pyrite with subordinate chalcopyrite and sphalerite formed in black shale beds in the two different stratigraphic units followed by late tectonic strata internal hydrothermal mobilization of fe cu and zn during syn orogenic thrusting which concentrated especially cu to ore grade in agreement with this model cu distribution in stream sediments in this region shows distinct enrichments bound to the margin of the allochthonous complex thus kupferberg can be considered a rare example of a syn orogenic cu deposit with the cu probably being derived from syn sedimentary early diagenetic pyrite contained in early paleozoic shale units

hydrogeochemistry of roccamonfina volcano southern italy this is the first hydro geochemical investigation carried out on the roccamonfina volcanic complex groundwaters the chemistry of roccamonfina waters is defined by water rock and water rock gas interactions in fact interactions between rocks of the first eruptive high k formations and circulating groundwaters are recognized by high k concentrations on the other hand inverse concentration of calcium versus alkali metals is related to two different rock interactions occurring in different areas of the volcano a within the caldera where groundwaters flow within latite and pyroclastic formations releasing calcium and b similarly at the base of the volcano where groundwaters flowing from surrounding carbonates got strongly enriched in ca these geochemical processes are also associated with k se of caldera and mg ca in sites located at the ne base of the volcano decrease completely different dynamics occurs at riardo groundwaters se here waters are the result of a mix between the roccamonfina deep aquifer and the carbonate aquifer of the riardo plain rich co2 emissions make these waters strongly mineralized minor elements show a similar geochemical behavior of major ions and are crucial defining interactions processes the evolution of roccamonfina groundwaters is also evident along the simultaneous enrichment of ba sr and ca ba increase is the result of deep local carbonate alteration enhanced by co2 emissions and the lower sr ca ratio from 10 to 2 ppb ppm is also due to the same process in the light of our results the roccamonfina aquifer can be schematically divided into two main reservoirs a a superficial aquifer which basically follows the volcanic structure morphology and tectonics and b a deeper reservoir originating within the oldest roccamonfina volcano ultra potassic lavas and then flowing into the carbonate aquifers of the neighboring plain eventually the chemistry of the roccamonfina aquifer does not show any specific and visible pollution contrary to what happens in the volcano surrounding plains in fact only 14 of the samples we collected 206 show a no3 content 30 mg l these sites are all located at the base of the volcano near the plain

late tertiary quaternary tectonics of the southern apennines italy new evidences from the tyrrhenian slope this paper summarises the results of combined structural and geomorphological investigations we carried out in two key areas in order to obtain new data on the structure and evolution of the tyrrhenian slope of the southern apennines analysis by a stress inversion method angelier j 1994 fault slip analysis and paleostress reconstruction in continental deformation p l hancock ed pergamon press oxford 53 100 of fault slip data from mesozoic to quaternary formations allowed the reconstruction of states of stress at different time intervals by integrating these data with those deriving from the stratigraphic and morphotectonic records chronology and timing of the sequence of the deformation events was obtained the tectonic history of the region can be related to four deformation events structures related to the first event that was dominated by a strike slip regime with a nw se oriented 1 and was active since mid late miocene do not significantly affect the present day landscape as they were strongly displaced and overprinted by subsequent deformation events and or deleted by erosion the second and third events that may be considered as the main responsible for the morphostructural signature of the region are comparable with the stretching phases recognised offshore and considered to be responsible for the opening and widening of the tyrrhenian basin in particular the second event with an e w oriented 3 took place in the late miocene earliest pliocene and was first dominated by a strike slip regime that was also responsible for thrusting and folding since late pliocene it was dominated by an extensional regime that created large vertical offsets along n s to nw se trending faults the third event that was dominated by extension with a nw se oriented 3 started in the early pleistocene and was responsible for formation of the horst and graben structure with ne sw trend that characterises the tyrrhenian margin of the southern apennines the fourth deformation event which is characterised by an extensional regime with a ne sw trending 3 started in the late middle pleistocene and is currently active

correlating specific conductivity with total hardness in gypsum karst waters modern digital conductivity meters are readily portable robust cheap and give precisely reproducible values of specific electrical conductivity spc in s cm 1 here we investigate the accuracy of their estimates of the amounts of gypsum dissolved in waters collected in gypsum karst terrains expressed as total hardness th in mg l 1 of caso4 2h2o gyp total dissolved solid concentrations tds are also considered curves obtained with the program phreeqc for the dissolution of pure gypsum in water at 25 c are compared with 574 comprehensive water chemical analyses selected from gypsum karst studies in europe and the americas principal common and foreign ions encountered are the bnc group bicarbonates nitrates chlorides it is found that gyp 1 12 spc 62 where bnc 2400 s cm 1 gyp 0 74 spc 777 where bnc 3100 s cm 1 gyp 0 97 spc 209 where bnc 4300 s cm 1 there are similar results for the more complex waters found in gypsum karsts where much carbonate rock or salt is also present to the limit of bnc 0 8 copyright 2006 john wiley sons ltd

extensional detachment faulting on the tyrrhenian margin of the southern apennines contractional belt italy the tectonic evolution of the campania margin during the late pliocene pleistocene is characterized by extensional deformation coeval with the opening of the marsili oceanic basin the initial stages of stretching are represented in the analysed area by the development of low angle normal faults that extended the belt in the same direction as the direction of spreading recognized for the oceanic basin detachment faulting was accompanied by the onset of magmatic activity and by major uplifts that resulted in the accumulation of thick conglomerate successions in the half grabens that developed in the upper plate of the extensional detachment deformation continued during the mid pleistocene with the formation of strike slip and normal faults trending almost parallel to the spreading direction of the marsili basin these faults dissected the extensional detachment and promoted counter clockwise block rotations about vertical axes which accommodated the ese directed stretching of the marsili basin and the consequent sinistral shear imposed on the southern apennine chain the development of a regional detachment fault along the tyrrhenian margin of campania explains the complex patterns of subsidence and uplift that characterize this area during the pleistocene and fits well within the regional geodynamic framework of the southern tyrrhenian sea

the memory of the accreting plate boundary and the continuity of fracture zones a detailed aeromagnetic anomaly map of the mesozoic seafloor spreading lineations southwest of bermuda reveals the dominant magnetic grain of the oceanic crust and the character of the accreting boundary at the time of crustal formation the magnetic anomaly pattern is that of a series of elongate lobes perpendicular to the fracture zone flowline trends the linear sets of magnetic anomaly peaks and troughs have narrow regions of reduced amplitude anomalies associated with the fracture zones during the period of mesozoic geomagnetic polarity reversals when 1200 km of central north atlantic seafloor formed the atlantic accreting boundary consisted of stationary elongate spreading center cells that maintained their independence even though sometimes only minor spatial offsets existed between cells normal oceanic crustal structure was formed in the spreading center cells but structural anomalies and discontinuities characteristic of fracture zones were formed at their boundaries which parallel flowlines of mesozoic relative plate motion in the central north atlantic we suggest that the memory for a stationary pattern of independent spreading center cells resides in the young brittle lithosphere at the accreting boundary where the lithosphere is weakest here each spreading center cell independently goes through its cylce of stress buildup stress release and crustal accretion after which its memory is refreshed the temporal offset between the peaks of the accretionary activity that takes place within each cell may provide the mechanism for maintaining the independence of adjacent spreading center cells through times when no spatial offset between the cells exists

large scale longitudinal extension in the southern apennines contractional belt italy during late cenozoic thrusting the interior of the peri tyrrhenian orogenic belt in the southern apennines underwent two episodes of nearly orthogonal extension early extension was oriented subparallel to the axis of the tectonic belt and formed in response to progressive thrust belt arcuation the length of the tectonic belt increased by 50 and the longitudinal strain was accommodated by low angle normal faults concentrated in tectonic domains recording up to 150 200 extension younger extension oriented at a high angle to the orogen was accompanied by pliocene pleistocene uplift and by southeasterly migration of tyrrhenian sea rifting

a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering summary the weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas these weathering profiles generally develop under both stable geodynamic conditions weathering rate erosion rate and a hydrolysing climate they are composed of thick stratiform layers that follow the paleo landscape paleotopography and thus present a gently dipping sequence at a regional scale the structure and the hydrodynamic properties of the weathering profile of a granitic area 53 km 2 maheshwaram catchment state of andhra pradesh india were characterized in detail and mapped from observations on outcrops 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones the structure of the weathering profile results from a multiphase process an ancient weathering profile was partly eroded down to its fissured layer it was later re weathered more or less parallel to the current topographic surface this peculiar structure is linked to the geodynamic history of the indian peninsula that underwent alternate weathering and erosion dominated phases the profile is thus composed from top to bottom up to a total depth of 35 m of sandy regolith saprolite 1 3 m 10 15 m of laminated saprolite containing unusual preserved fissures and a 15 20 m thick fissured layer by comparing various case studies in similar terrain a generalized 3 d geological and hydrogeological conceptual model of granite type aquifers granites gneisses etc is proposed in granite type rocks single weathering or multiphase weathering and erosion processes induce similar geological structures a few main geological differences arise from the comparison of single phase and multiphase weathering profiles i in the later the respective thicknesses of the various layers can be deeply modified ii the ancient fissured layer can be re weathered and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures and iii the upper part of the fissured layer is more densely fissured as a result of the same weathering processes the fissures from the fissured layer of single phase or multi phase profiles exhibit very similar hydraulic conductivities and show both a higher density of conductive fissures at the top of the layer the preserved ancient fissures within the laminated layer of a multiphase profile are partly obliterated by the recent weathering their hydraulic conductivity is thus significantly reduced nevertheless they do significantly contribute to borewell yield these weathering induced fissures provide most of the aquifer permeability the use of such a conceptual model for the precise geological mapping of the weathering structure appears to be a prerequisite for groundwater development and management in hard rock areas as it answers to several key issues

multiple closely spaced transform faults in fast slipping fracture zones the 400 km long offset of the east pacific rise spreading axis between the quebrada fracture zone lat 3 5 s and the gofar fracture zone lat 4 6 s has been surveyed using the long range sidescan sonar gloria the offset is accomplished in three distinct fracture zones each of which contains up to four actively slipping transform faults separated by short spreading centers transform spacings range from 5 to 16 km each transform is associated with its own transverse valley but at quebrada fracture zone and to some extent at the other two these valleys merge into one large slightly oblique fracture zone valley the morphological trends of fracture zone valleys are therefore not necessarily reliable for estimating directions of relative plate movement multitransform fracture zones appear to be much commoner on the fast spreading east pacific rise than on slower spreading ridges the tectonic spreading fabric which comprises closely spaced normal faults formed near the spreading axes and striking subparallel to them is modified to a sigmoidal pattern between the closely spaced transforms even midway between transforms these faults remain oblique to the spreading direction the degree of obliquity increases as the transform separation decreases showing progressive rotation of the stress ellipse as transforms are approached

seismic activity in the transition zone between southern and central apennines italy evidences of longitudinal extension inside the ortona roccamonfina tectonic line abstract we analyze the 1997 2006 seismicity of the transition zone between southern and central apennines which is one of the most active seismic areas of italy our aim is to add information on the seismotectonic picture of this area seismic activity is characterized by single events with m

the structure of the charlie gibbs fracture zone this short paper summarizes the results of a major combined seismic refraction and gravity survey carried out over the charlie gibbs fracture zone crust 3 4 5 km thick and possessing an anomalously low seismic velocity structure was found beneath the fracture zone and gradual crustal thinning was detected over some 40 km to the south of the transform the most plausible explanation for the ridge to the north is that it consists of uplifted normal crust

gloria survey of the east pacific rise near 3 5 s tectonic and volcanic characteristics of a fast spreading mid ocean rise abstract a long range sidescan sonar gloria survey of an approximately 100 km square area of the east pacific rise crest between 3 s and 4 s extends results obtained in the same area by lonsdale 1977 using deep tow the axial linear volcano was found to be continuous over a distance of 75 km the presence of major inward and outward facing fault scarps was confirmed but the gloria data show several distinct differences between the two fault sets the inward dipping faults are more numerous more closely spaced and longer than the outward dipping ones and their dip slopes backscatter sound more extensively than those of the outward dipping faults moreover most of them appear to be formed within 2 km of the axis whereas the majority of the outward dipping faults begin to develop between 5 and 8 km from the axis these differences suggest that the two sets of faults have different origins the horizontal pattern of inward dipping faults is similar to those observed on other mid ocean rises at all spreading rates though the lengths and separations of the scarps are slightly and their throws considerably less than on slower spreading rises this common horizontal pattern suggests that inward dipping faults on all rises have a common mode of formation regardless of spreading rate horizontal tension is probably the dominant factor but an additional mechanism is needed to explain the polarization of fault dips that occurs in the region 2 8 km from the axis the similarity of major fault spacings on the east pacific rise to those on slower spreading rises suggests that faulting is invariant in space rather than time and that the lithosphere where these faults are formed about 2 km from the spreading axis has a similar small thickness for all spreading rates this is attributed to the regulating effect of hydrothermal circulation and plate cooling

late quaternary incision and deposition in an active volcanic setting the volturno valley fill southern italy abstract article history received 30 january 2012received in revised form 1 august 2012accepted 5 october 2012available online 17 october 2012editor g j weltjekeywords incised valleysequence stratigraphyforaminifer and ostracod analysisvolturno riverquaternary extensive illustration of depositional facies ostracod and foraminiferal assemblages and late quaternarystratigraphic architecture is offered for the rst time from beneath the modern coastal plain of volturnoriver the longest river in southern italy proximity to an active volcanic district including quiescent vesuviusvolcano provides an easily identi able stratigraphic marker campania grey tuff or cgt up to 55 m thick emplaced39 ky cal bpbyalarge volumeexplosivepyroclasticeruption identi cationoftopcgttoamaximumdepthof30 mallowstracingouttheshapeofa15 20 kmwidelatequaternarypalaeovalleyincisedbyvolturnoriver into the thick ignimbritic unit immediately after its deposition a terraced palaeotopography of the valley anksisreconstructedonthebasisofcoredata abovethebasal uvialdeposits theearlyholocenetransgressivefacies consist of asuite of estuarine freshwater to brackish deposits these are separated from overlyingtransgressive barrier sands by a distinctive wave ravinement surface upwards a distinctive shallowing upward succession of middle late holocene age is interpreted to re ect initiation and subsequent progradationof a wave dominated delta system with anking strandplains in response to reduced rate of sea level rise theturnaround from transgressive to highstand conditions is identi ed on the basis of subtle changes in themeiofauna theseenabletrackingofthemaximum oodingsurfaceintoitsupdip lagoonal estuarine counterpart thus highlighting the role of re ned palaeontological criteria as a powerf ul tool for high resolution sequence stratigraphic studies 2012 elsevier b v all rights reserved

geolithological and anthropogenic controls on the hydrochemistry of the volturno river southern italy the present work aims to study the main chemical and physical water parameters in the upper and middle volturno river catchment southern italy between the capo volturno springs and the confluence with the calore river this study makes use of morphology geolithology tectonic land use and physico chemical ph ec eh temperature major ions and 222rn data for the identification of the main sources of surface and ground waters in the volturno catchment and of their evolution and mixing both in base flow and peak flow conditions the study was also performed to assess whether the alteration due to potential anthropogenic contamination may hamper the identification of natural primitive sources of surface waters especially in the populated and farmed plains far from the river headwaters our data suggests that water chemistry of this stretch of the volturno river is dominated mainly by lithology and only marginally by the intense exogenous activities and that this trend is appreciable in both base flow and peak flow conditions the proposed simple geochemical approach based on easy to sample matrices and on cost effective standard methods is a valuable tool to address catchment functionality especially in upland areas where complex geologic and structural settings heterogeneous groundwater flow and logistical issues are the rule rather than the exception since the upper and middle volturno catchment is comparable to numerous valleys of the mediterranean area this study could be a reference for analogous applications this article is protected by copyright all rights reserved

tufa and travertines of southern italy deep seated fault related co 2 as the key control in precipitation continental carbonates of quaternary age in southern italy commonly exhibit the facies of calcareous tufa often reported as related to shallow aquifers fed by meteoric waters and to organic processes a close spatial relationship exists between the mappable tufa deposits and major quaternary extensional faults with respect to the ca mg hco3 composition of limestone aquifers springs tufa depositing springs exhibit higher salinity and alkalinity are slightly warmer have lower ph and are enriched in so4 and co2 their d 13 c values are systematically positive and compatible with a deep seated carbon source a clear input of soil derived organic carbon is indicated only for small non mappable tufas deposited by perched springs the dataset indicates that the large tufa deposits owe their origin to a supplementary source of co2 advected by degassing through active faults as a necessary prerequisite for inducing a rise of total dissolved salts and alkalinity meteoric waters that have come from a shallow aquifer are able to precipitate only limited amount of carbonates

recharge processes of matese karst massif southern italy the recharge processes have been evaluated for the matese massif a wide karst system of southern italy which feeds several major springs this massif is characterized by wide endorheic areas exploited for hydroelectrical purposes several hydraulic works have modified the natural recharge processes of the massif and the regime of karst springs recharge on massif is based on the annual means recharge estimation by gis using regression of annual mean values of different ground elevated rain gauges and thermometers a calibrated daily scale recharge model estimates the amount of effective rainfall that is retained as soil moisture the amount reaching the water table recharge s s and the amount of runoff leaving the catchment all these amounts vary through the hydrological year as so function of soil moisture deficit and daily rainfall intensity when soil moisture reaches the field capacity daily rainfall exceeding 24 3 mm develops runoff the runoff amount increases during wet year and reduces during dry years highlighting the important role of the endorheic areas mainly during wet years the ratio between the total water volume spring outlet and the effective rainfall effective recharge coefficient has been estimated for several hydrological years and varies between 0 81 dry year and 0 58 wet year

the active part of charlie gibbs fracture zone a study using sonar and other geophysical techniques a short survey with gloria side scan sonar and other geophysical instruments has revealed new information about charlie gibbs fracture zone between 29 and 36 w the traces of two transform faults have been clearly delineated they fit small circles about the pole of rotation with an rms error of only about 1 km but they do not always follow the deepest parts of the transform valleys the transforms are joined by a short spreading center at 31 45 w the median transverse ridge appears to have been produced by normal seafloor spreading at this center and bears identifiable vine matthews magnetic anomalies a transverse ridge along the eastern inactive part of the northern transform may be an intrusive feature considerable thicknesses of sediment appear to have been deposited in the northern transform valley from norwegian sea overflow water passing through the fracture zone but transverse ridges have prevented the sediment reaching the southern valley