an 40ar 39ar thermochronology of the ofoten troms region implications for terrane amalgamation and extensional collapse of the northern scandinavian caledonides fifteen 40ar 39ar cooling ages are reported for metamorphic hornblende and muscovite from far traveled terranes constituting the ofoten nappe stack of northern norway eight cooling ages on hornblende range from 425 to 394 ma and seven muscovite ages from the same or nearby outcrops as the hornblendes range from 400 to 373 ma these data are compared with 40ar 39ar ages from over a large part of the northern caledonides to evaluate regional mineral cooling patterns results indicate that 1 scandian silurian devonian metamorphism was predominant 2 most of the nappes investigated contain some vestige of pre scandian tectonism and or metamorphism 3 hornblende and muscovite cooling ages are progressively younger to the west and south which suggests a hinged to the east mineral cooling pattern and 4 a late out of sequence thrust is the only disruption of this cooling pattern synmetamorphic amalgamation of the nappes resulted from scandian a type subduction the hinged to the east mineral cooling pattern implies isostatic adjustment and exhumation of the footwall of a west dipping crustal scale extensional fault located somewhere west of the present norwegian coast during late synorogenic gravitational collapse the late out of sequence fault formed contemporaneously with uplift in the hinterland implying a kinematic and temporal connection with east directed contractional faulting in the foreland

positive inversion tectonics in foreland fold and thrust belts a reappraisal of the umbria marche northern apennines central italy by integrating geological and geophysical data abstract unraveling the tectonic style in the outer zones of fold and thrust belts is generally puzzling because the basement cover relationships are often hidden in the subsurface as in the outer northern apennines of italy this study aims to reconstruct the deep setting of the northern apennine foreland thrust belt by integrating surface structural geological and subsurface seismic reflection profile and well data corroborated by a gravity magnetic modeling a remarkable mountain ridge the umbria marche apennine ridge umar which corresponds to a prominent area of structural and topographic elevation characterizes the morphology of the northern apennines this mountain ridge is constituted by meso cenozoic carbonates involved in neogene compressive structures and is surrounded by wide exposures of foredeep deposits the basement cover relationships are poorly constrained and both thin and thick skinned tectonic styles have been applied the interpretation of subsurface data allowed recognizing a thick pre jurassic sedimentary sequence filling a late paleozoic triassic symmetric fault bounded extensional basin lying directly below the umar this deep rooted basin underwent positive inversion during the neogene compression and thrust fold development the reconstructed thick skinned inversion tectonic model is consistent with both the modest amount of shortening and the remarkable structural elevation of the umar the outcomes of this study reveal that prominent mountain ridges occurring in foreland thrust belts are most likely related to the deep rooted basement involved positive inversion of pre existing extensional basins

geochronology and tectonic implications of magmatism and metamorphism southern kootenay arc and neighbouring regions southeastern british columbia part i jurassic to mid cretaceous k ar dates and u pb zircon dates define three periods of igneous activity in the southern kootenay arc 1 emplacement of late synkinematic to post kinematic granodioritic plutons in mid jurassic time 170 165 ma accompanying amphibolite facies regional metamorphism 2 emplacement of post kinematic granitic plutons in mid cretaceous time 100 ma and 3 emplacement of small bodies of syenite in eocene time 50 ma in the western part of the area micas from mid jurassic plutons that yield the oldest k ar dates 158 166 ma also yield plateau shaped 40ar 39ar age spectra age spectra for biotites younger than these but older than 125 ma reflect thermal overprinting in southeastern british columbia the kootenay arc marks the transition from the north american rocks of the cordilleran miogeocline to the tectonic collage of allochthonous terranes that have been accreted to it deformation metamorphism and plutonism recorded in rocks of the southern kootenay arc commenced in mid jurassic time as a co

evidence for ophiolite obduction terrane accretion and polyorogenic evolution of the north scandinavian caledonides abstract recent work on the thrust sheets of the ofoten troms region north norwegian caledonides has resulted in revision of the tectonostratigraphic correlations providing new constraints on models for terrane accretion and poly orogenic cambro ordovician and siluro devonian development previous studies on late ordovician early silurian fossils in metasediments unconformably overlying the lyngen ophiolite complex within one of the troms nappes documented a period of ophiolite obduction prior to the major siluro devonian scandian orogenic event correlation of these units and underlying and overlying thrusts sheets southward into the ofoten area 150 km to the south is demonstrated this implies that an extensive completely transported upper ordovician lower silurian basin developed on top of the obducted ophiolite composes the bedrock of much of northern norway metamorphism and deformation within these basinal rocks resulted from the scandian phase of the caledonian orogeny the relatively weak metamorphic and deformational imprint on the ophiolitic basement provides a rare opportunity to evaluate the pre scandian tectonic evolution of northern scandinavia poly orogenic evolution a controversial subject in northern norway is documented the character and relative extent of cambro ordovician and siluro devonian orogenic zones in northern norway are elucidated the balsfjord ofoten unconformity formed approximately concomitant with other post ophiolite obduction unconformities in central and southern norway implying an orogen wide late cambrian early ordovician event

geologic thermobarometry of retrograded metamorphic rocks an indication of the uplift trajectory of a portion of the northern scandinavian caledonides kyanite grade pelitic schists from the efjord area 68 15 n 16 45 e northern norway show abundant textural evidence of retrograde reequilibration during late orogenic uplift and cooling of this part of the scandinavian caledonides graphical analysis of mineral compositions in seven samples that show a range of retrograde textures indicates that they reached final chemical equilibrium under nonuniform pressure temperature conditions three element partitioning geothermometers and geobarometers yield consistent pt estimates in individual samples which together define a trend in pt space the sample showing the fewest signs of retrogression yields the highest pressure and temperature estimates whereas samples exhibiting abundant reequilibration textures give lower pt estimates we suggest that the trend indicated by these samples reflects a portion of the pt trajectory assumed by the efjord area during uplift thus the judicious use of element partitioning geothermometers and geobarometers on samples showing signs of retrograde metamorphism may yield important new information concerning the late tectonic evolution of metamorphic terrains

the arcuate shape of the umbria marche sabina apennines central italy abstract the umbria marche belt constitutes the most southern and external portion of the northern apennine arc typically convex to the northeast within this the central part the umbria marche sabina apennines is the most elevated and is characterized by a locally more pronounced curvature the umbria marche belt is a thrust belt built mainly by thrust faults affecting a multilayer sedimentary series characterized by levels with markedly different competence the main thrust the m sibillini thrust produced the tectonic superposition of the umbria marche sabina apennines over the most external units represented by the lazio abruzzi platform to the south and the marche abruzzi domain to the north farther north it joins the thrusts buried under the po plain the most important of the more internal thrusts is that of the valnerina the pronounced local curvature of the umbria marche sabina apennines may be due to accentuation of an original arcuate shape this accentuation is probably caused by differential displacement along the two main thrusts during the initial stage of the evolution of the belt late messinian early pliocene at that time this displacement was more important in the northern part where the thrust fronts show a nw se trend than in the southern portion where they are n s trending on account of the lazio abruzzi carbonate platform which perhaps represented a local obstacle to thrusting as for the initial curvature we think that this is determined by older discontinuities which controlled thrust development the final arcuate shape was not substantially changed during the subsequent compressional history of the belt early pliocene middle pliocene

sinkhole swarms from initiation to stabilisation based on in situ high resolution 3 d observations abstract we study in this paper the evolution of sinkhole fields along the dead sea coastal plains from initiation to stabilisation the prevailing hypothesis attributes their formation to the dissolution of a buried halite layer by groundwater but fails to explain their evolution in some places and their stability in others based on thirteen years of high resolution laser scanning and field surveys we trace a complete evolutionary cycle of sinkholes and show that the prevailing theory explains only the first out of a four stage cycle we show that following the formation stage an acceleration phase begins when the sinkholes interact with the drainage system a deepening and spatial localisation phase ensues then some parts of the field cease to expand leading to a fourth stage of stabilisation we further show that during their embryonic stage sinkhole development is limited due to a lack of connectivity between the surface and subsurface hydrological processes but as this connectivity evolves the development rate increases up to three orders of magnitude moreover observations show a high correlation with hydrological seasonality the most active field demonstrated a development rate of 13 540 m 3 month during the wet season in contrast to a rate of 1010 m 3 month during the dry season these measurements and observations allow us to propose a new theoretical model for sinkhole swarm development from initiation to stabilisation with linkage to seasonality and hydrology

analogue modeling of positive inversion tectonics along differently oriented pre thrusting normal faults an application to the central northern apennines of italy inversion tectonics represent a key process in many orogens worldwide the related mechanisms of fault reactivation and the effects of an articulated preshortening setting on thrust and fold development are still challenging questions modes and geometries of inversion have been the object of several analogue models in this work we analyzed the influence of an articulated high angle preexisting discontinuity in the development of thrusts using sandbox modeling the model geometry is based on the architecture of the major faults in the central northern apennines of italy where differently oriented mesozoic cenozoic inherited extensional structures are clearly detectable and display contrasting styles of positive inversion tectonics quartz sand is the analogue material adopted to model mesozoic cenozoic sedimentary successions and glass microbeads represent preexisting fault rocks the geometry of the segmented preexisting structure is composed of two segments with the same dip 60 one oblique and another orthogonal to the shortening direction our results show that different styles of positive inversion tectonics can coexist and that the obliquity angle between inherited structures and the shortening direction is a leading factor controlling the degree of inversion the oblique segment of the discontinuity exhibits a complete reactivation whereas along the orthogonal segment shortcut is the prevalent mechanism the oblique element moreover represents a cross strike discontinuity that guides the localization and curved geometry of the thrusts compartmentalizing the deformation our findings can be applied to fold and thrust belts characterized by the presence of cross strike discontinuities

conduit evolution in deep seated settings conceptual and numerical models based on field observations 1 to examine the interrelation between hydrogeological environment and conduit development in deep seated settings a conceptual model is tested by numerical modeling based on field observations simplified model settings are designed and crucial parameters are varied a coupled continuum pipe flow model is employed for simulating conduit development within the soluble unit of a multilayer aquifer system in agreement with field observations the evolving cave patterns are characterized by pronounced horizontal passages and multiple vertical conduits at the bottom of the soluble unit but only few at the top the frequency distribution of conduit diameters is found to be bimodal if the permeability of the rock formation is sufficiently high to allow competitive conduit development governed by the feedback between increasing flow and dissolution rates this feedback however is suppressed in low permeability formations as a consequence conduit development is uniform rather than competitive

long term erosion rate measurements in gypsum caves of sorbas se spain by the micro erosion meter method abstract the present work deals with the results of long term micro erosion measurements in the most important gypsum cave of spain the cueva del agua sorbas almeria se spain nineteen mem stations were positioned in 1992 in a wide range of morphological and environmental settings gypsum floors and walls carbonate speleothems dry conduits and vadose passages inside and outside the cave on gypsum and carbonate bedrocks and exposed to variable degree of humidity different air flow and hydrodynamic conditions four different sets of stations have been investigated 1 the main cave entrance las vinicas spring 2 the main river passage 3 the abandoned laboratory tunnel and 4 the external gypsum surface data over a period of about 18 years are available the average lowering rates vary from 0 014 to 0 016 mm yr 1 near the main entrance and in the laboratory tunnel to 0 022 mm 1 on gypsum floors and 0 028 mm yr 1 on carbonate flowstones the denudation data from the external gypsum stations are quite regular with a rate of 0 170 mm yr 1 the observations allowed the collecting of important information concerning the feeding of the karst aquifer not only by infiltrating rainwater but under present climate conditions also by water condensation of moist air flow this contribution to the overall karst processes in the cueva del agua basin represents over 20 of the total chemical dissolution of the karst area and more than 50 of the speleogenetically removed gypsum in the cave system thus representing all but a secondary role in speleogenesis condensation corrosion is most active along the medium walls being slower at the roof and almost absent close to the floor this creates typical corrosion morphologies such as cupola while gypsum flowers develop where evaporation dominates this approach also shows quantitatively the morphological implications of condensation corrosion processes in gypsum karst systems in arid zones responsible for an average surface lowering of 0 047 mm yr 1 while mechanical erosion produces a lowering of 0 123 mm yr 1

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

hypothesis on the hydrogeological context of wetland areas and springs related to evaporitic karst aquifers malaga cordoba and jaen provinces southern spain the northern sector of the external zone of the betic cordillera s spain is formed by an olistostrome unit known as the chaotic subbetic complexes csc this megabreccia is basically made of clays and evaporite rocks gypsum and salt of upper triassic keuper age as well as other lithologies dolostones limestones marls and calcareous sandstones belonging to different ages jurassic cretaceous and tertiary despite of low permeability has been traditionally assumed for these materials water flow and storage through them is possible due to the aquitard behavior of clays and sandstones and the presence of conduits generated by dissolution karstification processes within the evaporite rocks the lithological complexity of the csc determines its hydrogeological heterogeneity with groundwater flows of different length and various scales from recharge areas to discharge zones thus wetlands and springs placed at lower altitudes are associated with large regional groundwater flows of greater residence time within the aquifer and they normally drain high salinity waters mostly connected with ascending flow this work provides an overview of the main geological and hydrogeological aspects related to groundwater flow within the csc on the basis of several case studies conceptual models are proposed for these cases since they are the base to carry out a genetic functional classification of wetlands potentially useful for their management

complexity of the mw 6 3 2009 l aquila central italy earthquake 2 broadband strong motion modeling 1 near fault strong ground motions 0 1 10 hz recorded during the mw 6 3 2009 l aquila earthquake exhibit great spatial variability modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event we utilize a hybrid integral composite approach based on a k square kinematic rupture model combining low frequency coherent and high frequency incoherent source radiation and providing omega squared source spectral decay several source model features proven to be stable by means of an uncertainty analysis in the preceding low frequency 2 hz

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

metamorphism within the cokkul synform evidence for detachment faulting within the metamorphic infrastructure of the norwegian caledonides 67 30 n within the cokkul synform caledonian metamorphic rocks of the middle koli nappe complex mknc are in low angle fault contact with the basement mylonites derived from the precambrian tysfjord granite gneiss in the synform the mknc is composed of four fault bounded nappes each of which has a distinct tectonic stratigraphy composed of amphibolite facies metamorphosed pelitic and psammitic schists with minor lensoidal bodies of mafic and ultramafic rocks pelitic rocks from the three structurally lowest nappes contain the low variance afm mineral assemblages gar bio staur and staur ky bio with mu qtz ilm whereas staur and ky are absent from the highest nappe the kallakvare nappe afm mineral assemblages in the three lowest nappes indicate peak metamorphic temperatures of 610 660 c and peak pressures in excess of 600 mpa mineral assemblages from the kallakvare nappe are not as diagnostic of metamorphic grade however rocks from that nappe contain coexisting plagioclases from both sides of the peristerite gap suggesting lower grade peak p t conditions than those of the structurally lower nappes in addition biotite from the lower nappes is more ti rich than biotite from the kallakvare nappe however gar bio mu plag and gar bio ky plag qtz thermobarometry suggests that all four nappes equilibrated at approximately 525 25 c and 700 100 mpa gibbs method thermodynamic modelling of garnet zoning profiles suggests that the lower three nappes followed clockwise p t paths that involved heating and compression to a metamorphic peak of approximately 575 625 c 800 mpa followed by cooling and decompression to 525 c 700 mpa p t paths calculated for the kallakvare nappe show decompression and minor heating to a peak t of 500 525 c in the lower nappes staur and ky grew during the heating phase not seen by the highest nappe the outer parts of the paths from all four nappes are approximately parallel possibly recording the emplacement of the kallakvare nappe onto the already stacked lower three nappes at some time following the metamorphic peak these p t paths suggest that the sole fault of the kallakvare nappe is a normal fault garnet zonation thus appears to record a previously unrecognized phase of uplift and tectonic thinning of the mknc this event appears to be restricted to the mknc and to have occurred prior to the emplacement of the mknc onto the tysfjord granite gneiss basement of baltoscandia under greenschist facies conditions it may have been responsible for the uplift and cooling of the mknc from 25 30 km amphibolite facies conditions prior to its emplacement onto baltoscandia under 15 20 km greenschist facies conditions the deformation zone associated with this normal fault is relatively narrow generally less than 1 m thick if this is typical of other detachment faults in the metamorphic infrastructure of the scandinavian caledonides they may be relatively common but not often recognized due to the detailed study needed to document them

a technique for analyzing the thermal and uplift histories of eroding orogenic belts a scandinavian example geothermometric and geobarometric data from pelitic schists in the upper plate of the forsa thrust in the northern norwegian caledonides are interpreted as recording part of the uplift trajectory of this area during erosion and slow cooling a method developed in this paper for reconstructing the thermal history of orogenic belts from such data is based on a general mathematical description of thermal conduction in a lithospheric slab with an arbitrary initial temperature distribution and uplifted at a constant rate with certain restrictions the uplift trajectory tz path of any rock parcel can be calculated from only a few temperature depth points along that uplift trajectory by applying this method to geothermometry and geobarometry data from near the forsa thrust we can 1 extrapolate tz paths measured over a limited depth range upward to the surface 2 recover geotherms present at various times during the uplift and erosion history of the mountain belt 3 obtain tz paths for rock parcels above and below those for which pt data are available and 4 use pt data in combination with geochronological data to obtain accurate estimates of uplift rates our analysis suggests that shortly after nappe emplacement the nappe stack was hot near 800 c in the lower part of the nappe stack while the underlying autochthon was cold near thermal equilibrium prior to nappe emplacement the maximum burial depth of rocks near the forsa thrust was probably between 35 and 60 km

mantle fragments in the scandinavian caledonides abstract mantle fragments of ultramafic composition are widespread in the scandinavian caledonides sc lenses and boudins of alpine type peridotites in the scandinavian caledonides represent parts of dismembered ophiolite sequences and fragments of sub continental upper mantle metaperidotites of nappes in internal positions are generally isofacial with the metamorphic envelope usually caledonian metasediments but in places also precambrian metagranitoids forming the basement cores of the nappes caledonian metamorphism strongly modified the texture and mineralogy of the peridotites and resulted in a systematic metamorphic pattern which is consistent with the pattern observed in the envelope metaperidotites of the external massifs display at least a two stage metamorphic history an early caledonian high pressure high temperature phase related to early crustal stacking and a late caledonian regional metamorphic overprint which produced a regular barrovian type metamorphic pattern of in situ metamorphism metaperidotites from nappes in intermediate positions iapetus ocean ophiolites and ultramafic rocks from island arc environments show strongly diverging histories metaperidotites from internal ophiolites oceanic ophiolites koli lack any evidence of subduction metamorphism are serpentinized to various degrees show abundant primary mantle relic mineralogies and the caledonian metamorphic overprint is low metaperidotites from external island arc ophiolites and other associations seve often show relic high pressure metamorphism related to the finnmarkian phase of the caledonian orogeny the seve metaperidotites are occasionally associated with eclogites and show a weak overprint of late caledonian regional metamorphism alpine type peridotites are absent in the foreland of the baltic shield and in the innermost nappes lofoten the metamorphic characteristics and evolution recorded by the metaperidotites in the scandinavian caledonides allow a general reconstruction of the dynamics of collision belt formation

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

thermobarometric profile through the caledonian nappe stack of western ofoten north norway p t estimates from pelite thermobarometry along a transect through the caledonian nappe stack in ofoten north norway 68 30 n plot as a trend in p t space ranging from 443 c 6 9 kb to 688 c 10 6 kb the p t range for each nappe overlaps the others except for those from the lowest unit narvik group which has significantly higher values within the p t ranges for each nappe the position on the trend of a given sample is independent of its tectonic position results support our earlier conclusion based on structural and petrographic grounds that the regional metamorphic peak was reached during or after stacking of the nappes in the siluro devonian scandian orogeny

large earthquake triggering clustering and the synchronization of faults large earthquakes are sometimes observed to trigger other large earthquakes on nearby faults the magnitudes of the calculated coulomb stress transfers presumed to cause the triggering are 10 2 10 3 of the earthquake stress drops the earthquake stress drops and the triggering delay times are similarly small with respect to the natural recurrence time of the earthquakes this requires that both faults be simultaneously very close to the ends of their seismic cycles paleoseismological data show that for the same regions prior earthquakes have occurred in clusters of ruptures of several faults separated by long quiescent periods both observations suggest that synchronization is occurring between faults theory and observations indicate that synchronization can occur between nearby faults with positive stress coupling and intrinsic slip velocities within an entrainment threshold in the south iceland seismic zone the central nevada seismic belt and the eastern california shear zone several synchronous clusters that apparently act independently can be recognized this behavior is the 3d equivalent of the phase locking that results in the seismic cycle of individual faults being dominated by large characteristic earthquakes and for synchronization of fault segments along a given fault rupture patterns of repeated individual earthquakes or earthquake clusters are not identical in either the 2d or 3d cases the state of this system which exhibits strong indications of synchrony without exact repetition may be called fuzzy synchrony

frictional constraints on crustal faulting we consider how variations in fault frictional properties affect the phenomenology of earthquake faulting in particular we propose that lateral variations in fault friction produce the marked heterogeneity of slip observed in large earthquakes we model these variations using a rate and state dependent friction law where we differentiate velocity weakening behavior into two fields the strong seismic field is very velocity weakening and the weak seismic field is slightly velocity weakening similarly we differentiate velocity strengthening behavior into two fields the compliant field is slightly velocity strengthening and the viscous field is very velocity strengthening the strong seismic field comprises the seismic slip concentrations or asperities the two intermediate fields weak seismic and compliant have frictional velocity dependences that are close to velocity neutral these fields modulate both the tectonic loading and the dynamic rupture process during the interseismic period the weak seismic and compliant regions slip aseismically while the strong seismic regions remain locked evolving into stress concentrations that fail only in main shocks the weak seismic areas exhibit most of the interseismic activity and aftershocks but can also creep seismically this mixed frictional behavior can be obtained from a sufficiently heterogeneous distribution of the critical slip distance the model also provides a mechanism for rupture arrest dynamic rupture fronts decelerate as they penetrate into unloaded complaint or weak seismic areas producing broad areas of accelerated afterslip aftershocks occur on both the weak seismic and compliant areas around a fault but most of the stress is diffused through aseismic slip rapid afterslip on these peripheral areas can also produce aftershocks within the main shock rupture area by reloading weak fault areas that slipped in the main shock and then healed we test this frictional model by comparing the seismicity and the coseismic slip for the 1966 parkfield 1979 coyote lake and 1984 morgan hill earthquakes the interevent seismicity and aftershocks appear to occur on fault areas outside the regions of significant slip these regions are interpreted as either weak seismic or compliant depending on whether or not they manifest interevent seismicity

hydrochemistry and solution rates in gypsum karst case study from the western ukraine the gypsum karst in the western ukraine spreads through a large territory covering more than 20 000 km2 and is represented by a range of stages evolutionary types from deep seated through subjacent to entrenched correspondingly hydrogeological settings of karst development circulation patterns and chemical characteristics of groundwaters differ substantially between the respective areas based on 1 800 analyses this paper summarises hydrochemistry of the gypsum hosting miocene aquifer the majority of sampling has been performed in conjunction with a study regime of gypsum solution rates by means of standard tablets in this study which included 53 tablet stations representing varying conditions of water rock interaction 644 weight loss measurements were made over the period 1984 1992 the highest rates are characteristic of entrenched karst although active dissolution is localised along well defined sinking streams with short underground courses rare vertical percolation paths and the water table lower but still quite substantial rates are characteristic of subjacent and deep seated confined karst however the overall dissolution removal is greater due to higher flow through the gypsum and the larger area of rock solvent contact the results are generalised in order to derive the approximate solution rates characterising major situations and to be suitable for modeling purposes

hydrological and geochemical processes constraining groundwater salinity in wetland areas related to evaporitic karst systems a case study from southern spain abstract chemical and isotopic evolution of groundwater in an evaporite karst plateau including wetland areas and saline to hyper saline springs located at s spain was studied physicochemical parameters major ions and stable isotopes were analyzed in rain brine spring wetland and leakage water samples from which the most common mineral saturation indexes were computed and geochemical and isotopic modelling were performed results show an apparent relationship between the elevation of brine springs and their water mineralization indicating that drainage at higher altitude may be associated to gravity driven flows since brackish groundwater is isotopically fractionated due to evaporation on the other hand the lower altitude springs could drain deeper flows with longer residence time resulting in highly mineralized and warmer briny groundwater the dissolution of halite and gypsum has proved to be the main geochemical processes which are favored by the great ionic strength of groundwater calcite precipitation occurs in brackish waters draining wetlands being boosted by common ion effect when caso 4 waters are present and solute concentration caused by evaporation modelling results strongly support the hypothesis that most of the selected springs geochemically evolve in a common s n flowpath the methods used in this research contribute to a better understanding of the hydrogeological processes occurring in the studied evaporitic system but also in equivalent hydrological environments worldwide

valid garnet biotite gb geothermometry and garnet aluminum silicate plagioclase quartz gasp geobarometry in metapelitic rocks abstract at present there are many calibrations of both the garnet biotite gb thermometer and the garnet aluminum silicate plagioclase quartz gasp barometer that may confuse geologists in choosing a reliable thermometer and or barometer to test the accuracy of the gb thermometers we have applied the various gb thermometers to reproduce the experimental data and data from natural metapelitic rocks of various prograde sequences inverted metamorphic zones and thermal contact aureoles we have concluded that the four gb thermometers perchuk l l lavrent eva i v 1983 experimental investigation of exchange equilibria in the system cordierite garnet biotite in saxena s k ed kinetics and equilibrium in mineral reactions springer verlag new york berlin heidelberg pp 199 239 kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 holdaway m j 2000 application of new experimental and garnet margules data to the garnet biotite geothermometer american mineralogist 85 881 892 model 6av kaneko y miyano t 2004 recalibration of mutually consistent garnet biotite and garnet cordierite geothermometers lithos 73 255 269 model b are the most valid and reliable of this kind of thermometer more specifically we prefer the holdaway holdaway m j 2000 application of new experimental and garnet margules data to the garnet biotite geothermometer american mineralogist 85 881 892 and the kleemann and reinhardt kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 calibrations due to their small errors in reproducing the experimental temperatures and good accuracy in successfully discerning the systematic temperature changes of the different sequences in addition after applying the gasp barometer to 335 natural metapelitic samples containing one kind of aluminosilicate and 33 natural metapelitic samples containing two kinds of aluminosilicate as well as to rocks in limited geographic areas and thermal contact aureoles we propose that the calibrations of holdaway holdaway m j 2001 recalibration of the gasp geobarometer in light of recent garnet and plagioclase activity models and versions of the garnet biotite geothermometer american mineralogist 86 1117 1129 and newton and haselton newton r c haselton h t 1981 thermodynamics of the garnet plagioclase al2sio5 quartz geobarometer in newton r c navrotsky a wood b j eds thermodynamics of minerals and melts new york springer verlag 131 147 based on kleemann and reinhardt s kleemann u reinhardt j 1994 garnet biotite thermometry revised the effect of alvi and ti in biotite european journal of mineralogy 6 925 941 thermometer are the most valid gasp barometers other gb thermometers and gasp barometers are not recommended

empirical garnet muscovite geothermometry in metapelites abstract two empirical garnet muscovite geothermometers assuming no ferric iron model a and 50 ferric iron model b in muscovite respectively were calibrated under the physical conditions of p 3 0 14 0 kbar and t 530 700 c the input temperatures and pressures were determined by simultaneously applying the garnet biotite thermometer am mineral 85 2000 881 and the gasp geobarometer am mineral 86 2001 1117 to natural metapelites to confirm internal thermodynamic consistency holdaway s am mineral 85 2000 881 garnet mixing properties were adopted muscovite was treated as a symmetric fe mg al vi ternary solid solution and its margules parameters were derived in this work the resulting two formulae reproduced the input garnet biotite temperatures well within 50 c and gave identical results for a great body of natural samples moreover they successfully distinguished the systematic changes of temperatures of different grade rocks from a prograde sequence inverted metamorphic zone and thermal contact aureole pressure estimation has almost no effect on the two formalisms of the garnet muscovite geothermometer assuming analytical error of 5 for the relevant components of both garnet and muscovite the total random uncertainty of the two formulations will generally be within 5 c the two thermometers derived in this work may be used as practical tools to metamorphic pelites under the conditions of 480 to 700 c low to high pressure in the composition ranges xalm 0 51 0 82 xpyr 0 04 0 22 and xgros 0 03 0 24 in garnet and fe tot 0 03 0 17 and mg 0 04 0 14 atoms p f u in muscovite

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

active tectonics in the central apennines and possible implications for seismic hazard analysis in peninsular italy abstract the central apennines fault system cafs of peninsular italy overprints earlier structures of a neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a nnw sse trending zone 50 60 km wide the system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments the resulting fault structure consists of an interconnecting network of roughly n s trending left lateral strike slip segments and mostly nw se oriented transtensional to normal faults evidence for recent activity of cafs structures is provided by faulted middle pleistocene holocene deposits including 30 40 ka old pyroclastites and 40 ka old palustrine sediments fresh scarps in both bedrock and late quaternary continental deposits and decametric lateral offsets locally affecting the post wurmian drainage pattern of the area the regional stress field responsible for the development and evolution of the cafs as inferred from fault slip data is characterized by a nw se compression and by a ne sw extension the cafs pattern and its present day kinematics have been related to left lateral strike slip motion on north south trending crustal faults the existence of deep seated strike slip faults in the central apennines has implications for seismic hazard analysis motion along these structures suggests in fact that coseismic surface faulting is distributed and that cumulative displacements include normal transtensional and strike slip components the seismogenic potential of cafs structures can therefore be best described by multiple rupture models and be better analysed in terms of partial contributions of lower rank features constituting congruent structural associations within the system

reply to comment on tectonic burial thrust emplacement and extensional exhumation of the cabot nappe in the appalachian hinterland of cape breton island canada

investigating fault reactivation during multiple tectonic inversions through mechanical and numerical modeling an application to the central northern apennines of italy abstract within inversion tectonic contexts the reactivation of pre existing discontinuities depends upon many structural stratigraphic and mechanical factors among these a fundamental aspect is represented by the orientation and attitude of pre existing discontinuities with respect to the new stress field the aim of this work is to evaluate the stress regimes and the mechanical conditions that controlled the reactivation of segmented pre thrusting normal faults in the central northern apennines of italy these faults were involved both in positive and negative inversion tectonic events during tertiary quaternary times mechanical slip tendency analysis and numerical using coulomb 3 3 software models allowed us to reconstruct a 3d stress field for both inversion events and to evaluate the effect of many parameters orientation of faults fault dip angle and mechanical parameters on fault reactivation our results highlighted that the orientation of pre existing faults with respect to the stress axes represents the main factor controlling inversion tectonic phenomena where other mechanical and geometric variables exert a subordinate role the models well reproduce the neogene quaternary deformation history reconstructed from detailed geological and structural analyses for the central northern apennines of italy and could be applied to other regions that have experienced inversion tectonic processes

marble dykes emanating from marble layers in an amphibolite facies multiply deformed carbonate succession troms northern norway in one of the higher nappes of the caledonides of troms northern norway rare thin dykes of calcite marble lie subparallel to the axial surfaces of folds in multilayered marble beds the dykes emanate from pure calcite marble layers mostly in or close to the hinge zones of these flat lying tight to sub isoclinal f3 folds in many cases they appear to penetrate along the axial surfaces of these same folds and there is an up to 10 angular disparity between dyke orientation and axial surfaces the dykes are considered to have originated and been expelled from parent calcite marble layers either at or shortly after the peak of amphibolite facies metamorphism between the d2 and d3 deformation phases of the scandian orogeny the dykes display a dyke parallel dark grey to white colour banding the origin of which is uncertain at present in thin section an equigranular texture is dominated by 2 3 mm equant unstrained calcite grains with straight boundaries and low t twin lamellae denoting a late stage recrystallization a weak oblique calcite grain shape orientation fabric curves into a dyke parallel alignment along the finer grained margins reflecting the simple shear deformation imposed on the host rock regarding the initiation of these marble dykes it seems likely that a combination of p t conditions and possibly partial melting processes was conducive to generating extreme ductility superplasticity at least locally and that this led to the sudden expulsion of a partially molten carbonate aggregate which had momentarily attained a critical pressure and intruded preferentially along available transient fractures prior to the imposition of the d3 simple shear regime

pre existing cross structures and active fault segmentation in the northern central apennines italy abstract the multideformed axial zone of the apennines provides a great opportunity to explore the influence of pre existing cross structures inherited from pre quaternary tectonic phases on the segmentation of quaternary active seismogenic extensional faults detailed geological and structural data and their comparison with seismological data show that although the attitudes strike and dip of oblique pre existing faults are certainly an important factor in determining a segment boundary the size of the inherited oblique structures seems to be more crucial pre existing cross structures with lengths ranging from several kilometers to a few tens of kilometers show a twofold behavior they can act as segment barriers during the rupture of a single fault segment or they can be reactivated as transfer zones inducing the activation of two adjacent segments that belong to the same fault system regional basement crustal oblique pre existing cross structures with lengths ranging from several tens of kilometers to hundreds of kilometers commonly nne striking may act as persistent structural barriers that halt both fault segment and fault system propagation thus determining their terminations and maximum sizes in the northern central apennines the nne striking ancona anzio valnerina and ortona roccamonfina tectonic lineaments although having been repeatedly reactivated since the mesozoic represent the most important examples of these structures moreover probably due to their misorientation with respect to the present extensional stress field regional nne striking pre existing structures appear to be less likely to produce strong magnitude events no surface evidence for quaternary faulting has been found thus far and historical and instrumental seismicity shows only m m 7 event on the other hand is more likely to occur along the n nw s se trending normal fault systems lastly we propose a model that can explain the different sizes of fault segments and fault systems on the basis of their location with respect to the persistent structural barriers and their spacing in this view our results may contribute to a more reasonable assessment of the nature and size of future surface ruptures in the northern central apennines which are of critical importance to estimating seismic hazard

the role of felsic and mafic igneous rocks in deciphering the evolution of thrust stacked terranes an example from the north norwegian caledonides excellent exposure of appropriate structural levels across the trace of the regional ofoten synform north norway make this an exceptional area in which to investigate the role of felsic and mafic igneous rocks in the amalgamation and final emplacement of a stack of far traveled terranes the nappe sequence in ofoten is composed from bottom to top of the narvik ofoten and niingen nappe complexes each of these nappe complexes contains multiple internal thrust sheets or nappes that were emplaced onto precambrian cambrian rocks of the baltic shield along east directed thrusts during the caledonian orogeny distinct contrasts in rock types structural arguments and regional correlations indicate that the nappes are suspect or exotic terranes whole rock chemistry petrography and field relations of felsic and mafic igneous rocks within each allochthon are used to explore the tectonic setting of each terrane the crustal levels of their amalgamation and the relative and absolute timing of their amalgamation three different types of felsic intrusions were distinguished in each lithologic package with the exception of the evenes group ofoten nappe complex which has none caledonian plutons also are lacking in the underlying baltic basement complex the intrusions are separated temporally into early phase nappe specific plutons and late phase intrusions some of which cut across nappe boundaries most are s and i type collisional granitoidal rocks early phase granitoids in the bogen group ofoten nappe complex however have an a type chemistry and mineralogy probably indicating either second cycle melting of a granulite terrane or melting of calc alkaline rocks the lack of caledonian intrusives in both the evenes group and the basement requires that allochthons overlying these units rooted to the west discrimination of the various tectonic settings based on the geochemistry of the felsic intrusions dovetails closely with that determined from a sampling of mafic rocks each nappe originated as a laterally distinct entity that rode piggyback with the niingen nappe complex being emplaced first and the composite nappe stack thrust lastly upon the basement complex previously reported lithologic correlations with fossiliferous units and u pb and 40ar 39ar mineral cooling dates combine with new rb sr and u pb dates to place the relative nappe stacking chronology into an absolute timeframe metamorphism of the narvik nappe complex was first at 432 ma followed by metamorphism of the niingen around 430 ma which later metamorphosed the ofoten by down heating between 430 and 425 ma the stacking process took only 7 my and resulted from the silurian devonian scandian orogeny pre scandian relics occur within each of the nappe complexes and were strongly reworked and emplaced during the scandian event

late caledonian extension in the ofoten area northern norway abstract structural observations along the base of the caledonian nappe pile in the ofoten region of northern norway demonstrate a complex interaction of compressional and extensional structures top to the west extensional structures are consistently superimposed on top to the east southeast compressional structures and control the basement cover relationships across the orogen extensional shear zones offsetting the basement cover contact appear to be restricted to the area east of the ofoten synform the eastern flank of the synform is an approximately 1 km wide w dipping shear zone with more than 30 km of dip slip offset the basement culimination roll over west of the synform is most likely controlled by the listric geometry of this shear zone at depth this major shear zone and other minor extensional shear zones within the rombak window have a ductile shear fabric with post kinematic recovery fabrics developed under middle to upper greenschist facies conditions suggesting that the footwall and hanging wall rocks were still at a mid crustal level some time after the extensional event the extensional shear zone flattens upsection and splays into a network of anastomosing detachment zones eastwards cutting both upsection and downsection in the direction of westward tectonic transport development of steeply dipping extensional basement faults and subhorizontal detachment faults in the cover have resulted in a complex basement cover relationship and reworking of the nappe stratigraphy established during the preceeding compressional event these relationships make restoration of the caledonian nappe pile to a pre orogenic configuration uncertain and shortening estimates difficult the recognition of the extensional event as a distinct post contractional tectonic event suggests a link with the devonian extensional collapse in southern norway a major difference between southern and northern norway however is the lack of brittle extensional features in the often area suggesting different amounts of extension and basement uplift in the two regions

the metamorphic signature of contemporaneous extension and shortening in the central himalayan orogen data from the nyalam transect southern tibet abstract geological relationships and geochronological data suggest that in miocene time the metamorphic core of the central himalayan orogen was a wedge shaped body bounded below by the n dipping main central thrust system and above the n dipping south tibetan detachment system we infer that synchronous movement on these fault systems expelled the metamorphic core southward toward the indian foreland thereby moderating the extreme topographic gradient at the southern margin of the tibetan plateau reaction textures thermobarometric data and thermodynamic modelling of pelitic schists and gneisses from the nyalam transect in southern tibet 28 n 86 e imply that gravitational collapse of the orogen produced a complex thermal structure in the metamorphic core amphibolite facies metamorphism and anatexis at temperatures of 950 k and depths of at least 30 km accompanied the early stages of displacement on the main central thrust system our findings suggest that the late metamorphic history of these rocks was characterized by high t decompression associated with roughly 15 km of unroofing by movement on the south tibetan detachment system in the middle of the metamorphic core roughly 7 8 km below the basal detachment of the south tibetan system the decompression was essentially isothermal near the base of the metamorphic core roughly 4 6 km above the main central thrust the decompression was accompanied by about 150 k of cooling we attribute the disparity between the p t paths of these two structural levels to cooling of the lower part of the metamorphic core as a consequence of continued and probably accelerated underthrusting of cooler rocks in the footwall of the main central thrust at the same time as movement on the south tibetan detachment system

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

combining hydrodynamics hydrochemistry and environmental isotopes to understand the hydrogeological functioning of evaporite karst springs an example from southern spain abstract this work adopts a multicriteria approach combining diverse karst hydrogeology techniques to investigate the functioning of evaporite karst systems which are normally less studied due to the poor quality of their water resources the applicability of using several methods was also verified in view of previous experience at a pilot site within southern spain the natural responses of the main discharge point of the system of study lower anzur spring were controlled by continuous monitoring of the discharge rate water temperature and electrical conductivity water samples were collected for chemical analysis and for the determination of intrinsic fluorescence water stable isotopes 18o 2h and tritium 3h concentrations physico chemical data were statistically examined applying principal component analysis pca and trend analysis tests mann kendall and sen s slope the system shows a clear karstic functioning highly dependent on concentrated recharge and influenced by a limited drainage capacity of the conduit network the piston flow effects at the beginning of floods indicate a contribution to the drainage of deep ascending flows through the saturated zone subsequent drops in temperature and mineralization values in the water drained by the spring as well as a recent infiltration deduced from the signature of intrinsic fluorescence and stable isotopes point to a good hydrogeological connection from the recharge areas to the spring later restoration of the initial values of mineralization in a much shorter time than those of temperature reveals a faster geochemical evolution of the recently infiltrated groundwater which may be a distinctive trait of evaporite karst aquifers lastly the high solute content of the spring water in depletion conditions with ascending trends of mineralization and temperature observed during several dry years as a consequence of lower recharge contribution together with the tritium activity of selected samples suggest the existence of an old component partly responsible for the spring base flow thus groundwater would be linked to gravity driven regional flows but also to recent conduit flows all the results obtained led us to devise a hydrogeological conceptual model to precisely reflect the functioning of the studied system the results presented here demonstrate the advantages of using diverse techniques when investigating evaporite karst aquifers

a genetic classification of sinkholes illustrated from evaporite paleokarst exposures in spain this contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four spanish tertiary basins bedrock strata are subhorizontal evaporites and in three of the basins they include halite and glauberite in the subsurface our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed with the exception of solution dolines it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements cover bedrock or caprock and the main type of process involved collapse suffosion or sagging sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one e g bedrock sagging and collapse sinkhole the mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material such as upward stoping of cavities by roof failure development of well defined failure planes and rock brecciation suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock the paleokarsts we analysed suggest that the sagging mechanism not included in previous genetic classifications plays an important role in the generation of sinkholes in evaporites moreover collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks

empirical garnet muscovite plagioclase quartz geobarometry in medium to high grade metapelites abstract based on the net transfer reactions among garnet muscovite plagioclase and quartz for both mg and fe end member models the garnet muscovite plagioclase quartz gmpq geobarometry was empirically calibrated under the physical conditions of p 1 0 11 4 kbar and t 505 745 c for 128 natural metapelitic rock samples collected from the literature the input temperatures and pressures were simultaneously determined by the garnet biotite thermometer and the garnet aluminosilicate plagioclase quartz gasp barometer the gmpq calibrations adopted the same asymmetric quaternary solid solution model of garnet and the same al avoidance asymmetric ternary model of plagioclase as the calibrations of the garnet biotite geothermometer and the gasp geobarometer a symmetric fe mg al vi ternary solid solution model of muscovite was adopted and the margules parameters of muscovite were obtained through regression the mg and fe model reactions along with the assumption of whether the ferric iron content in muscovite is 0 or 50 resulted in four gmpq barometry formulae the gmpq barometry formulae reproduce the input gasp pressures well within 1 0 kbar mostly within 0 5 kbar for both aluminosilicate bearing and aluminosilicate absent samples the gmpq barometry formulae yield identical pressures for every sample whether the sample was included or not in calibrating the barometers for each of the mg or fe model reaction the formulae gave identical pressures within 40 bars the random error of the gmpq barometry may be expected as 1 4 kbar the d p d t slopes of these gmpq formulae are close to that of the gasp barometer in the p t space applications of the gmpq barometry to aluminosilicate absent metapelites within a limited geographic area without postmetamorphic structural discontinuity generally show no pressure difference it may be concluded that the gmpq barometry formulae derived in this work may be used as practical tools for metamorphic pelites under the conditions of 505 745 c and 1 11 4 kbar in the composition range of x gros 3 in garnet and x an 17 in plagioclase

self accelerated development of salt karst during flash floods along the dead sea coast israel we document and analyze the rapid development of a real time karst system within the subsurface salt layers of the ze elim fan dead sea israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements sinkhole mapping time lapse camera monitoring groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater the 1 m yr drop of dead sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater subsurface salt dissolution gradual land subsidence and formation of sinkholes since 2010 this process accelerated dramatically as flash floods at the ze elim fan were drained by newly formed sinkholes during and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically the overlying ground surface subsided a large number of sinkholes developed over short time periods hours to days and salt saturated water resurged downstream groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the dead sea the process is self accelerating as salt dissolution enhances subsidence and sinkhole formation which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface the rapid terrain response is predominantly due to the highly soluble salt it is enhanced by the shallow depth of the salt layer the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the ze elim fan

depth and modes of pliocene pleistocene crustal extension of the apennines italy since early pliocene times the apenninic chain has been dissected by normal faults propagating towards the adriatic foreland in the tyrrhenian sea extension involved deep crustal sections whereas in the central apennines downfaulted area it affected the shallow crust the tyrrhenian back arc domain is connected to the overall flexural retreat of the adriatic apulia plate in front of the apenninic collisional wedge in the outer apenninic belt thin skinned delamination and gravitational collapse occurred in the hanging wall of a thickened wedge overthrusting the uplifted buoyant crust of the apulia foreland differential sinking velocity of the foreland plate results from the inherited competence contrast between the rigid gargano apulia carbonate platform to the south and the low competence lithology of the pelagic sequence of the adriatic basin to the north during late messinian early pliocene times this palaeogeographical boundary acted as a lithospheric tear separating segments of the apulia plate subjected to different subduction modes

complexity of the mw 6 3 2009 l aquila central italy earthquake 1 multiple finite extent source inversion 1 strong ground motion recordings of the mw 6 3 2009 l aquila earthquake are analyzed by a newly proposed slip inversion technique the source model consists of multiple finite extent mufex subsources the slip amplitude rupture velocity rake and risetime are assumed constant within each subsource the size and location of the mufex subsources have to be inferred independently from other methods preferably those free of strong constraints such as constant rupture velocity over the whole fault etc here we use two published approaches satisfying such requirement the truncated singular value decomposition and the iterative multiple point source deconvolution each mufex subsource is characterized by an individual set of trial nucleation points rupture velocities and nucleation times which are grid searched for each combination of these parameters the subsources slip is determined by the least squares approach this procedure thus provides not only the best fitting model but also a whole range of acceptable models allowing for the uncertainty analysis the method is demonstrated on three synthetic tests when applied to the l aquila data both the best fitting model and the uncertainty analysis suggest that the event consisted of two major episodes one with the rupture propagating immediately after the nucleation in the updip direction the other being delayed by 3 4 s with dominant propagation toward the se along the deeper part of the fault the retrieved complexity of the rupture propagation warns against attempts to stabilize inversions by the use of a constant rupture velocity over the whole fault

empirical evaluation of solution models for pelitic minerals and their application to thermobarometry one of the major sources of uncertainty for thermobarometry in pelitic rocks is the inability of solution models to represent accurately the non ideal behavior of important pelitic minerals in particular garnet biotite and plagioclase in recent years a large number of different solution models have been proposed for these phases the purpose here is to test the effects on the overall uncertainty of the most commonly used solution models using the garnet muscovite annite plagioclase gmap barometer and the empirical calibration technique the gmap reaction has been empirically calibrated several times with varying results due in large part to the choice of solution models the method s dependence on the choice of solution model makes it an excellent was in which to address the quality of specific models by repeating the calibration exercise for different combinations of solution models it is possible to determine which set of solution models results in the lowest uncertainties using a sample set of 72 published electron microprobe analyses of pelitic rocks containing the assemblage garnet muscovite biotite plagioclase aluminum silicate quartz as an independent test of the suitability of solution models we compare the fit of the sample set to the kyanite sillimanite equilibrium curve obtaining thermobarometric estimates by simultaneous solution of the garnet biotite exchange thermometer and gmap calibrated from thermochemical data

pressure temperature time paths the past decade has been a time of unprecedented improvement in our ability to reconstruct the thermal evolution of orogenic belts like many instances of rapid advancement in science this achievement can be traced to the convergence of disparate research directions the new field of thermochronology the study of the time temperature evolution of rocks derived from the realization by geochronologists that many mineral iso topic systems could be used to determine the time of cooling of a terrain through a series of predictable temperatures e g armstrong 1966 wagner et ai 1977 harrison mcdougali 1980 berger york 1981 petrologists have made great progress in their ability to discern the pressure tem perature history of metamorphic rocks through the improvement of con ventional thermobarometric techniques see bohlen lindsley 1987 and essene 1989 for reviews and the development of important new approaches to relating changes in mineral chemistry to changes in environ mental parameters spear selvcrstonc 1983 st onge 1987 from a theoretical standpoint several geophysical papers in the midto late 1970s and early 1980s explored heat transfer processes in orogenic belts and the role of these in the development and preservation of metamorphic mineral assemblages oxburgh england 1974 bickle et a1 1975 bird et a1 1975 england richardson 1977 toksoz bird 1977 england thompson 1984 among others the integration of geochronologic and petrologic techniques aliows us

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

structural inheritance in mountain belts an alpine apennine perspective abstract the geological structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization and amplification of contractional structures during mountain building in the alpine apennine sector together with other sectors of the tethyan orogenic system the pre orogenic crustal template can include arrays of extensional faults other faults can form adjacent to the evolving mountain belt and subsequently become incorporated as the thrust belts migrate into their forelands while in some areas these inherited features may simply reactivate under inversion more commonly faults show complex partial reactivation structures in volumes of distributed strain faults may serve to nucleate large scale buckle folds for example along basement cover interfaces these different patterns of basement reactivation may reflect spatially varying strength depth profiles in continental lithosphere that are themselves inherited from spatially distinct geological histories even when not themselves reactivating basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally extensive detachment horizons the 3d form of thrust systems can be strongly compartmentalized by pre existing cross faults such as the oblique lineaments of the apennines on a large scale the distribution of pre existing faults and other weaknesses may affect the propensity for orogenic contraction in basement and therefore directly control larger scale tectonic processes in the central mediterranean the evolution of slab roll back and the related growth of overlying extensional basins e g tyrrhenian sea may be strongly modulated by the distribution of rift related weak zones in the adjacent continental crust the subduction of continental crust will strongly depend on the inherited structure of this crust specifically the distribution of deep crust of basic composition this develops relatively higher densities associated with eclogite metamorphism which act in turn to reduce the buoyancy of thickened continental crust that otherwise serves to inhibit further shortening investigating all these aspects from the scale of bulk crustal compositions to the geometry timing and strength of earlier fault zones preserved in orogenic belts requires the integration of substantial multidisciplinary geological data sets the extent to which continental orogenic belts represent the amplification of inherited geological heterogeneities as opposed to self ordered phenomena modulated by the syntectonic environment remains unclear

a computer model of sheath nappes formed during crustal shear in the western gneiss region central norwegian caledonides abstract the eastern western gneiss region of central norway is part of the deepest exposed norwegian caledonides where basement gneisses and an overlying thrust nappe sequence have been folded into large fold nappes structural analysis of a fold nappe within the central part of the district the grovudal area suggests that it has a strongly sheath like form and that other fold nappes of the western gneiss region may also have sheath like forms the structural history within the grovudal area is dominated by intense east directed subhorizontal shear in an overthrust sense followed by asymmetric refolding with an easterly vergence a computer generated kinematic model was developed to test whether the regional interference patterns could be explained by sheath fold development during this type of deformation the computer model shows that the major regional interference patterns could have been formed by such a kinematic history but does not rule out other possibile histories the proposed kinematic history is however compatible with the regional tectonic history of the main caledonian nappe pile suggesting that the complex nappe interference patterns typical of the region were formed in a kinematically simple but intense ductile deformation associated with caledonian continental imbrication

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

the silurian to permian history of a metamorphic core complex in lofoten northern scandinavian caledonides 1 the lofoten archipelago exposes precambrian baltic basement and caledonian allochthonous sequences within a 1000 km long chain of gravity and magnetic highs and structural culminations along the extended british and norwegian continental shelf previous regional geophysical studies indicate that post caledonian extension and development of the northern norwegian shelf occurred during broadly defined carboniferous permian cretaceous jurassic and early tertiary events structures related to these events are known to young westward we report field structural and 40ar 39ar thermochronologic data from rocks exposed in lofoten that further define the history and style of post caledonian extension the islands of southwest lofoten also represent the most outboard exposures of caledonian basement in northern norway that presumably formed the middle to deep crustal core of the orogen metasedimentary rocks and penetratively deformed basement in lofoten record high grade silurian devonian metamorphism and top to the east hereinafter tops east thrusting followed by episodes of late devonian to early carboniferous tops west ductile extension which progressed into oblique left slip movements the structural style and timing of silurian contraction in this area are remarkably similar to that determined for the more forelandward areas on the mainland 120 km to the east supporting the inference that distal parts of the baltic continental margin that were once deeply subducted are presently exposed in lofoten the timings of post devonian structural events that affected rocks in lofoten are partially constrained by the ages of unconformities and strata known to be preserved in graben flanking the lofoten culmination the radiometric age and structural data presented in this study in combination with stratigraphic constraints suggest a westward progression through time of extensional deformation over a protracted interval of silurian to permian time the latest permian extension in lofoten is largely characterized by brittle structures that formed at conditions substantially less than 300 c compared to the exhumation history of the southern western gneiss region the depth of caledonian continental a type subduction and subsequent unroofing of lofoten are of lesser magnitude and the present erosional level remained in the middle crust for a much longer interval of time the permian 40ar 39ar mineral ages documented in this study are the youngest such ages yet identified in scandinavia these ages relate to episodes of deformation and cooling in response to extensional tectonic events that occurred roughly 100 m y after comparable effects identified on the caledonian mainland our preferred explanation for the carboniferous permian radiometric ages structural evolution and stratigraphic data for lofoten is that they all developed in the context of a long lived cordilleran style metamorphic core complex

connecting seismically active normal faults with quaternary geological structures in a complex extensional environment the colfiorito 1997 case history northern apennines italy 1 the northern apennines of italy are characterized by a complex tertiary tectonic history where superposed compressional and extensional deformation occurred in such regions characterized by low active extensional strain rate the coseismic surface ruptures are rare and often a matter of much debate resulting in a difficult connection between geological faults i e faults which can be mapped at the surface and seismological faults i e faults which actually generate earthquakes the availability of detailed geological mapping and high resolution seismological data for the colfiorito area struck in 1997 by a sequence of six 5 mw 6 normal faulting earthquakes allow us to compare and verify the existence of geometric and kinematic correspondence between the mapped geological quaternary faults and the activated structures in map view the earthquakes distribution reflects the fault pattern mapped at the surface the length of activated and mapped faults is quite similar 7 10 km the coseismic subsided region imaged by interferometric synthetic aperture radar data is located in the hanging wall of the mapped normal faults that bound the quaternary basins in section view there is a geometric connection between mapped normal faults and the aftershock alignments used to image fault geometry at depth comparison of striated fault planes and aftershock focal mechanism solutions show a strong kinematic consistency this study points out that the quaternary tectonosedimentary evolution and the present day geological and geomorphologic setting of the colfiorito area can be interpreted as the result of repeated extensional earthquakes similar to the 1997 events occurring on nw se trending normal faults our data also show that the main shocks of the colfiorito sequence nucleated close to the intersections between the normal faults and the preexisting compressional transpressional structures which in 1997 acted as lateral barriers to rupture propagation and consequently constrained the fault size

structural expressions and tectonic implications of general noncoaxial flow in the midcrust of a collisional orogen the northern scandinavian caledonides mapping and strain analysis in the northern scandinavian caledonides indicate that one way in which contemporaneous upper crustal extension and deeper thrusting within collisional orogens may be linked in a kinematically compatible manner is through the ductile flow of rocks in the midcrust of these mountain belts in the ofoten efjorden region of north norway amphibolite facies metamorphism and strong penetrative strain occurred at deep levels of the caledonian nappe stack as it was thrust eastward onto the western margin of baltica kinematic analysis of deformation in the lower portion of the caledonian nappe stack indicates that the rock mass underwent heterogeneous noncoaxial flow with components of foreland directed simple shear and subvertically shortened pure shear general noncoaxial flow simultaneous simple shear pure shear can accomplish foreland directed tectonic transport subvertical thinning and transport parallel elongation at deep levels of a nappe stack this pattern of flow is significant technically for two reasons first it suggests spreading of the caledonian allochthon during thrust emplacement and second it can form a kinematic link between normal faulting at shallower structural levels and thrusting at the base of the nappes by analogy with the caledonides general noncoaxial flow of midcrustal rocks may represent an important process in other collisional and contractional orogens particularly in those that have undergone upper crustal extension while thrusting continued in the foreland

fault segmentation as constraint to the occurrence of the main shocks of the 2016 central italy seismic sequence we perform the finite extent fault inversion of the three main events of the 2016 central italy seismic sequence using near source strong motion records we demonstrate that both earthquakes nucleation and rupture propagation were controlled by segmentation of the n nw s se trending quaternary normal faults the first shock of the sequence august 24th mw 6 0 ruptured at the relay zone between the laga mts lf and the cordone del vettore cvf normal faults the second shock october 26th mw 5 9 nucleated at a minor relay zone within the mt vettore mt bove fault vbf while the third and largest one october 30th mw 6 5 initiated at the relay zone between the vbf and cvf triggering the multiple rupture of the vbf cvf and probably lf we show that this latter relay zone corresponds to the deeper high angle fault zone of the sibillini mts cross structure a thrust ramp inherited from the miocene pliocene contractional phase of the apennines this structure acted as a barrier to rupture propagation of the first two events thus defining an area of large stress concentration until it acted as the initiator of the rupture originating the largest mw 6 5 event that crossed the barrier itself we suggest that the young cvf have started to cut through the barrier acting as a soft linkage between the two long lived lf and vbf the evidence that coseismic cumulative slip shows a maximum at the cvf provided by both slip inversion and original surface rupture data suggests that the cvf is growing faster than the adjacent faults

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

nature and origin of collapse breccias in the zechstein of ne england local observations with cross border petroleum exploration and production significance across the north sea

fault growth and interactions in a multiphase rift fault network horda platform norwegian north sea abstract physical models predict that multiphase rifts that experience a change in extension direction between stretching phases will typically develop non colinear normal fault sets furthermore multiphase rifts will display a greater frequency and range of styles of fault interactions than single phase rifts although these physical models have yielded useful information on the evolution of fault networks in map view the true 3d geometry of the faults and associated interactions are poorly understood here we use an integrated 3d seismic reflection and borehole dataset to examine a range of fault interactions that occur in a natural multiphase fault network in the northern horda platform northern north sea in particular we aim to i determine the range of styles of fault interaction that occur between non colinear faults ii examine the typical geometries and throw patterns associated with each of these different styles and iii highlight the differences between single phase and multiphase rift fault networks our study focuses on a ca 350 km 2 region around the 60 km long n s striking tusse fault a normal fault system that was active in the permian triassic and again in the late jurassic to early cretaceous the tusse fault is one of a series of large 1500 m throw n s striking faults forming part of the northern horda platform fault network which includes numerous smaller 2 10 km long lower throw nd stage nw se striking faults grew interacted and linked with the n s striking tusse fault documenting a range of interaction styles including mechanical and kinematic isolation abutment retardation and reactivated relays our results demonstrate that i isolated and abutting interactions are the most common fault interaction styles in the northern horda platform ii pre existing faults can act as sites of nucleation for 2 nd stage faults or may form mechanical barriers to propagation iii the throw distribution on reactivated 1 st stage faults will be modified in a predictable manner if they are intersected or influenced by 2 nd stage faults iv sites of fault linkage and relay breaching associated with the first phase of extension can act as preferential nucleation sites for 2 nd stage faults and v the development of fault intersections is a dynamic process involving the gradual transition from one style to another

effects of the adjacent evaporitic formations on groundwater quality of alluvial sand gravel aquifers a study in the derincay basin north central turkey evaporite bearing formations extending in large areas in turkey affect quality of water resources the derincay basin is an example to the impacts of evaporites on the adjacent alluvial aquifers miocene pliocene aged evaporites cover nearly one third of the basin and mostly surround the low elevated alluvial sand gravel aquifer the higher quality of the groundwater in the upstream regions where the evaporites do not crop out or partially crop out turns into low to very low quality in the downstream areas due to the large extents of the evaporites waters from the evaporites increase tds ca so4 na and cl in the alluvium aquifer particularly in the downstream region of the basin ec values rise from 1000 1300 s cm to over 5000 s cm from upstream to downstream high salinity but low sodium hazard category for the upstream parts turns into very high salinity and medium high sodium hazard for the downstream regions on the salinity diagram groundwater in the upstream parts falls in good to permissible class however the class turns into permissible to doubtful and doubtful to unusable classes for the downstream on the wilcox diagram ca bicarbonate type in the upstream region turns into ca sulfate type in the downstream region due to the evaporite effect this study indicates three main sources affecting the quality of groundwater of the alluvium aquifer in the derincay basin extent of the evaporite formations in the catchment area recharge from the evaporite springs and dilution with relatively high quality stream waters

relationships between thrusts and normal faults in curved belts new insight in the inversion tectonics of the central northern apennines italy abstract the relationships between thrusts and normal faults represent primary constraints in the reconstruction of the modes and timing of pre syn and post orogenic deformation events in fold and thrust belts such relationships are well exposed in curved orogenic belts where the thrusts are oblique to the trend of normal faults we study the nne ssw trending olevano antrodoco sibillini oblique thrust and its crosscutting relationships with nw se trending normal faults in order to constrain the neogene quaternary deformation history of the central northern apennine italy the analysis of structural and geological data allowed us to reconstruct the geometric and kinematic constraints of two inversion events 1 during the pliocene positive inversion reactivated the nne ssw trending pre existing ancona anzio normal fault as the olevano antrodoco sibillini oblique thrust ramp and caused the shortcut of nw se oriented normal faults 2 during the quaternary negative inversion reactivated nw se trending pre thrusting normal faults the growth of the nw se quaternary normal faults causes seismicity and is responsible of the development of wide quaternary intramontane basins their distribution and the related seismicity have been controlled and compartmentalized by nne ssw trending oblique thrusts thus the crosscutting relationships between thrusts and normal faults are crucial in seismic hazard assessment

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue

palinspastic restoration and paleogeographic reconstruction of the peri tyrrhenian area during the neogene abstract this paper presents the results of research carried out on the paleogeographic and geodynamic post collisional evolution of the peri tyrrhenian area from the southern alps to sicily during this post collisional evolution a back arc area thrust belt foredeep system developed in which the following tectono sedimentary zones can be distinguished from the external to the internal ones the foreland zone connected to the foredeep through a slope generally controlled by normal faults the foredeep an assymmetric depression with strong subsidence related to the compressional activity of the thrust zone the chain whose outward migration from the late oligocene onward was discontinuus with important stages of crisis partially connected to the mechanical response of different crustal thicknesses existing in the foreland the discontinuous satellite basins developed within the thrust belt the back arc basins developed in the inner part of the chain where the superposition of the extensional tectonics over previous compressional domains causes the fragmentation of the thrust belt leading to its destruction according to this model seven palinspatic maps are discussed regarding the following time intervals late oligocene 25 24 m y burdigalian 22 20 m y langhian 17 16 m y serravallin 15 13 m y tortonian 10 9 m y late messinian 5 5 5 3 m y and early pliocene 5 3 4 6 m y during five of these time intervals significant geodynamic modifications occurred in the whole peri tyrrhenian area leading to paleogeographic changes in any case the geodynamic evolution of the whole area seems clearly controlled by the activity of important bundles of tectonic lines transversal to the chain which in the same time interval in the outermost part of the thrust belt separated areas with different values of shortening and in tthe most internal zones separated segments having different amount of extension these tectonic lines certainly have a crustal significance and have probably acted along previous formed discontinuities