effects of fault slip distribution on the geometry and kinematics of the southern junggar fold and thrust belt northern tian shan abstract at the foreland edge of fold and thrust belts ftbs tectonic shortening could either be accommodated by thick skinned faulting and or structural wedges developed near range fronts or be transferred along detachment layers further into basins forming thin skinned structures although the geometry and kinematics of each structure have been well investigated studies that characterize slip distribution along a specific fault as well as the effects of variations in magnitude of fault displacement on the development of fault related folds are still lacking in this study we present a case study of the southern junggar thrust sjt a seismically active fault developed in the southern junggar ftb northern tian shan with an overall vergence to the north the results of structural interpretations of seismic reflection profiles combined with the age constraints provided by previous magnetostratigraphic studies demonstrate that 1 the kinematics of the sjt vary along strike from purely structural wedging to classical fault bend folding besides these end member models intermediate cases exist between them in which fault slip is partitioned by two stage structural deformation i e fault bend folding subsequent to structural wedging at the range front as a result part of the displacement is transferred northward forming the tugulu anticline 2 along strike variations in displacement along the tugulu fault frontal fault of the sjt also affect the geometry and kinematics of the tugulu anticline varying from detachment folding trishear fault propagation folding with a pure shear fault bend folding back limb and classical trishear fault propagation folding to fault bend folding with increasing displacement 3 the sjt has an average quaternary slip rate of 3 9 0 4 mm yr serving as a principal structure accommodating tectonic shortening in the southern junggar ftb the results of this study are helpful for seismic hazard assessments of the study area which may also shed light on structural evolution of fault related folds in other ftbs

thrusting evolution in the southern cordillera oriental northern argentine andes constraints from growth strata abstract growth strata and unconformities in the cenozoic synorogenic sediments in the southern cordillera oriental of the northern argentine andes provide new evidence for the eastward migration of the andean deformation from the puna to the santa barbara system the growth sequences and unconformities allow us to constrain the age of the structures with greater precision and to determine the distribution of this deformation in the thrust and fold wedge over time thrust evolution was mainly controlled by the reactivation of earlier extensional faults of the cretaceous salta rift basin the geometry of the inverted structures together with the general forward migration of the deformation gave rise to different thrust sequences the foreland dipping imbricate stack of the western cordillera oriental developed forwards during middle late miocene resulting in a break back thrusting sequence thrust propagation rate increased in late miocene early pliocene times when the eastern part of the cordillera oriental developed at that time a widespread deformation and synchronous thrusting occurred in the cordillera oriental subsequently deformation was mainly confined to the eastern part of the cordillera oriental finally during the pleistocene holocene deformation affected a wider zone including the cordillera oriental and the santa barbara system giving rise to the reactivation of previously developed thrusts

the fracture patterns of the tin tin anticline fracturing process during the foreland evolution in the calchaqui valley northwestern argentina abstract we present a field based work which illustrates the fracture patterns of the carbonate silicoclastic yacoraite formation in the tin tin anticline a basement fault related fold located in southern part of the eastern cordillera northwestern argentina the fracture patterns include small scale strike slip faults vertical shear fractures and en echelon arrays thrust faults extension fractures joints veins and normal faults and stylolites extensional mesostructures were formed by along foreland stretching prior to the contractional ones that were formed by the layer parallel shortening mechanism furthermore all fractures are interpreted to be formed before or at the early stages of folding and thrusting during the andean contraction all of them belonging to the eocene thrust belt foreland system at the calchaqui valley of northwestern argentina

numerical modelling of inversion tectonics in fold and thrust belts abstract this work presents numerical experiments of inversion of rift basins and consequent sub thrust imbrication in tectonic wedges half graben basins initially develop and then are covered with a post rift sequence bearing a decollement prone horizon i e the upper decollement a total of twelve models of tectonic inversion have been conducted varying i the strength of inherited extensional fault arrays and ii applying different fluid pressure ratios i e strength within syn rift strata combinations of those were simulated using different internal angles of friction for the inherited faults different strengths for the syn rift infill and for the upper decollement results show that changes in relative strength between inherited faults syn rift deposits and the upper crustal decollement leads to important variations in structural styles weak faults systematically favour the compressional reactivation of inherited extensional faults weak syn rift sediments favour hanging wall by pass structures instead of fault reactivation and less internal deformation of the syn rift deposits weak upper decollements supports the accretion of basement in a hinterland antiformal stack decoupling of basement and cover and forward tectonic transport of rift basins strong upper crustal decollements favours basement and cover coupling can lead to fault reactivation in the absence of weak faults and syn rift sediments however combinations of weak faults and strong upper decollement shows fault reactivation weak syn rift sediments and strong upper decollement form hanging wall by pass structures modelling results are compared to natural case studies

formation of the vysoka zlatno cu au skarn porphyry deposit slovakia the central zone of the miocene stiavnica stratovolcano hosts several occurrences of cu au skarn porphyry mineralisation related to granodiorite quartz diorite porphyry dyke clusters and stocks vysoka zlatno is the largest deposit 13 4 mt at 0 52 cu with mineralised mg ca exo and endoskarns developed at the prevolcanic basement level the alteration pattern includes an internal k and na ca silicate zone surrounded by phyllic and argillic zones laterally grading into a propylitic zone fluid inclusions in quartz veinlets in the internal zone contain mostly saline brines with 31 70 wt nacl eq and temperatures of liquid vapour homogenization th of 186 575 c indicating fluid heterogenisation garnet contains inclusions of variable salinity with 1 31 wt nacl eq and th of 320 360 c quartz chalcopyrite veinlets host mostly low salinity fluid inclusions with 0 3 wt nacl eq and th of 323 364 c data from sphalerite from the margin of the system indicate mixing with dilute and cooler fluids the isotopic composition of fluids in equilibrium with k alteration and most skarn minerals both prograde and retrograde indicates predominantly a magmatic origin 18ofluid 2 5 12 3 with a minor meteoric component corresponding low dfluid values are probably related to isotopic fractionation during exsolution of the fluid from crystallising magma in an open system the data suggest the general pattern of a distant source of magmatic fluids that ascended above a zone of hydraulic fracturing below the temperature of ductile brittle transition the magma chamber at 5 6 km depth exsolved single phase fluids whose properties were controlled by changing pt conditions along their fluid paths during early stages ascending fluids display liquid vapour immiscibility followed by physical separation of both phases low salinity liquid associated with ore veinlets probably represents a single phase magmatic fluid magmatic vapour which contracted into liquid upon its ascent

style and history of andean deformation puna plateau northwestern argentina topographically the puna plateau of northwestern argentina is the southern continuation of the bolivian altiplano its thickening and consecutive uplift result from the andean orogeny to better constrain the structural style and its progressive development we have studied field data topographic and satellite imagery balanced cross sections seismic reflection data kinematic analysis of fault slip data anisotropy of magnetic susceptibility ams paleomagnetic data and apatite fission track aft data across the puna plateau precambrian and paleozoic basement ranges bounded by high angle reverse faults dips 60 alternate with cenozoic intermontane basins major thrusts trend nne ssw and do not show a preferred vergence intermontane basins have various degrees of symmetry depending on the geometries and attitudes of associated thrusts as well as on the magnitudes of their offsets there is a close correlation between the surface expression of a basin and the amount of internal deformation a line balanced cross section of the puna at 25 s has yielded a cenozoic shortening of 10 15 in a direction subperpendicular to the orogen by kinematic analysis of cenozoic fault slip data we have obtained principal directions of strain rate across the puna shortening axes are subhorizontal and trend on average wnw ese n110 stretching axes are subvertical and intermediate axes are subhorizontal and trend on average nne ssw strain ellipsoids are dominantly of plane strain type and they represent dip slip thrusting from paleomagnetic and ams data shortening axes form a radial pattern around the eastern edge of the central andes the pattern is attributed to an inhomogeneous stress field reflecting the eastward convex shape of the central andean thrust front from the history of burial and uplift andean shortening reached the northeastern part of the puna in the late eocene and the adjacent eastern cordillera in the late eocene or early oligocene this shortening was presumably due to the incaic phase of the andean orogeny in the eastern part of the orogen the onset of shortening was probably guided by preexisting paleozoic and mesozoic structures so that andean deformation propagated unevenly eastward

styles of positive inversion tectonics in the central apennines and in the adriatic foreland implications for the evolution of the apennine chain italy abstract integration of new field structural and geophysical data with existing information from the apennines chain in italy and its adjacent adriatic foreland indicates that the styles of positive inversion tectonics and the modes of interaction between the extensional and the subsequent compressive structures vary starting from the cretaceous the contractional deformation induced by the mainly north directed convergence of africa adria with respect to the european plate promoted the closure of various arms of the atlantic and the neo tethys oceans which opened in different times and with distinct orientations the mosaic of continental blocks carbonate platforms rift basins and oceanic domains with several geometries and orientations with respect to the axis of the subsequent compression and the resulting heterogeneities within the shallow sedimentary cover and the overall lithosphere strongly influenced both the structural evolution of the apennine orogenic belt and the intra continental deformation within the adriatic foreland field observations reveal that the steeply e and w dipping mesozoic cenozoic normal faults are systematically decapitated by sub horizontal or gently west dipping thrusts propagating with short cut trajectories pre thrusting normal faults were commonly deformed by later thrusts but little evidence seems to support their entire reactivation as high angle reverse faults this suggests that these shallow and steeply dipping discontinuities were not suitable to be reutilized by the superficial thin skinned thrust faults propagating within the sedimentary cover in contrast presumably late paleozoic and mesozoic w dipping normal faults appear moderately reactivated in the adriatic foreland and strong positive inversion tectonics affect the deeper and buried structural levels of the apennine chain within the latter the syn rift sediments in the hangingwall blocks of the fault bounded basins were totally extruded and generated the strong uplift of the thinned adria continental crust finally the contrasting styles of interactions of the pre existing normal faults with later thrusts i e passive truncation or positive reactivation strictly result from the different evolution of the apennine chain and the combined thin and thick skinned modes of deformation of the stretched lithosphere of the adria plate

analogue modelling of orthogonal and oblique rifting abstract the three dimensional progressive development of orthogonal and oblique rift systems has been simulated using scaled analogue sandbox models the orientation of the zone of rifting where angle between the rift axis and the extension direction was varied systematically from 90 orthogonal rifting to 75 60 and 45 oblique rifting completed models were impregnated and sectioned both vertically and horizontally orthogonal rift models are characterized by long straight rift border faults and intra rift faults perpendicular to the extension direction oblique rift models are characterized by shorter segmented rift border faults and intrarift faults in the oblique models the rift border faults formed en echelon arrays parallel to the inderlying zone of basement stretching whereas the intra rift faults formed at a high angle to the extension vector increased extension in the moderately oblique and oblique rift systems 60 and 45 caused the intra rift faults to rotate towards parallelism with the rift border faults no strike slip or oblique slip transfer faults were found in any experiments rift border faults and intra rift faults in the models are segmented along strike with relay ramp structures formed between overlapping fault tips along the strike of the rift variations in half graben polarities and offsets of depocentres are accomplished by accommodation zones formed by interlocking conjugate fault arrays the experimental fault patterns compare well with the fault architectures found in those modern or relatively young rift systems where well defined basement controlled strike slip or oblique slip transfer faults are absent an accommodation zone model consisting of interlocking conjugate extension faults is proposed for the along strike switching of half graben asymmetries and offsetting of depocentres in rift systems the fault geometries in the analogue models can be used as templates for recognition of fault styles in both orthogonal and in oblique rift environments

tectonic inversion in the santa barbara system of the central andean foreland thrust belt northwestern argentina 1 the santa barbara system sbs of northern argentina is a 400 km long segment of the subandean foreland thrust belt it is characterized by predominantly west verging relatively high angle thrust faults many of these faults are reactivated normal faults from one branch of a complex cretaceous to paleogene rift system heteroaxial folding in parts of the sbs is probably due to a slight component of range parallel dextral strike slip motion acting on preexisting faults striking north and ne during inversion regional balanced cross sections along two transects across the northern sbs indicate that the major faults flatten into a detachment in the basement at about 10 km depth neogene e w contraction in the sbs is of the order of 21 26 km rift extension is not very well constrained but was probably less than 10 km the structural style of the sbs differs from the thin skinned subandean thrust belt to the north and from the large wavelength sierras pampeanas basement uplifts to the south the changes between the different styles are sharp and coincide with the northern and southern boundaries of the rift in the foreland suggesting that crustal or lithospheric heterogeneities exert an overriding control on foreland structural style

the role of inherited tectono sedimentary architecture in the development of the central andean mountain belt insights from the cordillera de domeyko abstract the structure of the cordillera de domeyko is dominated by a number of elongated n s trending basement ridges these ridges were uplifted by steep reverse n s faults that deformed the mesozoic cenozoic cover the vergence of the fault system varies along strike conferring an apparent doubly vergent pop up geometry to the axial zone two mesozoic pre compressional extensional events were recorded in the area new structural data presented in this paper indicate that most of the generated n s trending thrusts and related folds were controlled by the inversion of the pre existing mesozoic extensional faults thin skin structures in the mesozoic cenozoic cover are genetically linked to major basement upthrusts which could be interpreted as basement short cuts formed during inversion rather than as uplifted blocks associated with major cenozoic strike slip faults growth strata geometries date the beginning of the andean compressional event which generates the chilean precordillera as far back as 90 ma ago the resulting structural architecture is strongly controlled by inherited pre andean extensional structures the association of porphyry intrusives with major reverse faults suggests that the emplacement of the eocene oligocene porphyry cu mo deposits in northern chile can be explained by an oblique inversion tectonics model the upper eocene lower oligocene giant porphyry copper bodies chuquicamata la escondida el salvador located in the cordillera de domeyko show an adakitic affinity this magma affinity together with structural evidence presented in this work indicates that porphyry emplacement occurred at the end of the basement involved contractional stage that generates the anomalous thickened crust needed to generate these magmas this tectonic evolution is coherent with the existence of a flat slab subducting beneath the central andes 22 26 s during early cenozoic that will also produce the eastward migrating of the compressional regime in the upper plate since late cretaceous

the role of inherited structures in a foreland basin evolution the metan basin in nw argentina the foreland basin of the central andes in nw argentina is formed by partially unconnected basins limited by uneven high ranges the metan basin is located in the foothills of the central andes in nw argentina between the eastern cordillera the sierras pampeanas and the santa barbara system this basin resulted from a cretaceous to paleogene rifting event and from two neogene to quaternary foreland basin stages for this study field data log well seismic reflection and satellite images have been interpreted the propagation of deformation in this sector of the andes is influenced by inherited structures e g cretaceous extensional faults which have been reactivated during andean compression as high angle and oblique reverse faults deformation does not advance regularly throughout the foreland in a normal forward sequence but jumps across inherited faults fault reactivation has resulted in uplift of basement cored ranges and hanging wall anticlines that divided the foreland into small basins e g the metan basin

seismic and field evidence for selective inversion of cretaceous normal faults salta rift northwest argentina abstract northwestern argentina was the site of the continental salta rift in cretaceous to paleogene time the salta rift had a complex geometry with several subbasins of different trends and subsidence patterns surrounding a central high fault trends in the rift were extremely variable there is evidence of normal and or transfer faults trending n ne e and se it is not clear if all these faults were active at the same time indicating a poorly defined extension direction or if they formed in different non coaxial extension phases in either case their trends were very likely influenced by preexisting fault systems beginning in early eocene time the rift basins were superseded by andean foreland basins and later became caught in the andean thrust deformation propagating eastward resulting in the inversion of rift faults due to their different orientations not all faults were equally prone to reactivation as thrusts n to nne trending faults were apparently most strongly inverted probably often to a degree where the traces of their normal fault origin have become obliterated we present seismic evidence of moderately inverted n trending faults in the tres cruces basin and field examples of preserved e trending normal faults however reactivation sometimes also affects faults trending approximately parallel to the main neogene shortening direction indicating short term deviations from the general pattern of neogene thrust deformation these pulses of orogen parallel contraction may be linked to the intermittent activity of oblique transfer zones

neogene to quaternary broken foreland formation and sedimentation dynamics in the andes of nw argentina 25 s 1 the northwest argentine andes constitute a premier natural laboratory to assess the complex interactions between isolated uplifts orographic precipitation gradients and related erosion and sedimentation patterns here we present new stratigraphic observations and age information from intermontane basin sediments to elucidate the neogene to quaternary shortening history and associated sediment dynamics of the broken salta foreland this part of the andean orogen which comprises an array of basement cored range uplifts is located at 25 s and lies to the east of the arid intraorogenic altiplano puna plateau in the salta foreland spatially and temporally disparate range uplift along steeply dipping inherited faults has resulted in foreland compartmentalization with steep basin to basin precipitation gradients sediment architecture and facies associations record a three phase 10 5 and 2 ma east directed yet unsystematic evolution of shortening foreland fragmentation and ensuing changes in precipitation and sediment transport the provenance signatures of these deposits reflect the trapping of sediments in the intermontane basins of the andean hinterland as well as the evolution of a severed fluvial network present day moisture supply to the hinterland is determined by range relief and basin elevation the conspiring effects of range uplift and low rainfall help the entrapment and long term storage of sediments ultimately raising basin elevation in the hinterland which may amplify aridification in the orogen interior

development of the southern eastern cordillera nw argentina constrained by apatite fission track thermochronology from early cretaceous extension to middle miocene shortening 1 for the puna plateau and eastern cordillera of nw argentina the temporal and spatial pattern of deformation and surface uplift remain poorly constrained analysis of completely and partially reset apatite fission track samples collected from vertical profiles along an ese trending transect extending from the plateau interior across the southern eastern cordillera at 25 s reveals important constraints on the deformation and exhumation history of this part of the andes the data constrain the neogene andean development of the eastern cordillera as well as rift related exhumation for some of the sampled locations in the late jurassic early cretaceous an intervening eocene oligocene exhumation episode in the southern eastern cordillera was probably related to crustal shortening subsequent reburial of the area by andean foreland basin strata commenced between 30 and 25 myr magnitude and duration of sedimentation revealed by thermal modeling differ between the sample locations pointing to an eastward propagating basin system in the southern eastern cordillera andean deformation commenced at 22 5 21 myr predating both the inferred formation of significant topography by 5 7 5 myr and preservation of sediments in the adjacent cenozoic basins by 6 5 8 myr comparing the calculated structural depth of partially reset samples suggests that newly formed west dipping reverse faults along the former salta rift margin accommodated most of the neogene tectonic movement late cenozoic deformation at the southern eastern cordillera began earlier in the west and subsequently propagated eastward the lateral growth of the orogen is coupled with a foreland basin system developing in front of the range and then becomes subsequently compartmentalized by later emergent topography

seismic imaging of a convergent continental margin and plateau in the central andes andean continental research project 1996 ancorp 96 1 a 400 km long seismic reflection profile andean continental research project 1996 ancorp 96 and integrated geophysical experiments wide angle seismology passive seismology gravity and magnetotelluric depth sounding across the central andes 21 s observed subduction of the nazca plate under the south american continent an east dipping reflector nazca reflector is linked to the down going oceanic crust and shows increasing downdip intensity before gradual breakdown below 80 km we interpret parts of the nazca reflector as a fluid trap located at the front of recent hydration and shearing of the mantle the fluids being supplied by dehydration of the oceanic plate patches of bright quebrada blanca bright spot to more diffuse reflectivity underlie the plateau domain at 15 30 km depth this reflectivity is associated with a low velocity zone p to s wave conversions the upper limits of high conductivity and high vp vs ratios and to the occurrence of neogene volcanic rocks at surface we interpret this feature as evidence of widespread partial melting of the plateau crust causing decoupling of the upper and lower crust during neogene shortening and plateau growth the imaging properties of the continental moho beneath the andes indicate a broad transitional character of the crust mantle boundary owing to active processes like hydration of mantle rocks in the cooler parts of the plate margin system magmatic underplating and intraplating under and into the lowermost crust mechanical instability at moho etc hence all first order features appear to be related to fluid assisted processes in a subduction setting

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

the role of inversion tectonics in the structure of the cordillera oriental nw argentinean andes the salta basin of cretaceous age in the andes of nw argentina was inverted during the development of the cordillera oriental between the neogene and recent the different orientations of the extensional faults of the salta rift system and the subsequent w e shortening resulted in a great variety of inversion structures extensional faults dipping ne to ese were preferentially reactivated as contractional faults the initial stepped geometry of these faults gave rise to a distinctive sigmoidal pattern of basement involved thrusts and related folds these contractional structures tended to run parallel to the extensional faults and acquired a n s trend across the previous accommodation zones resulting in folding interference patterns other interference patterns are attributed to the superposition of contractional folds on previous rollovers and to the constrictional deformation imposed by the reactivation of adjacent extensional faults with different orientations the nnw to wsw dipping extensional faults show no evidence of reactivation despite the fact that some of them are folded the inversion at crustal scale is limited owing to the presence of the cretaceous salta rift across the different andean structural units and foreland

thick skinned tectonics and basement involved fold thrust belts insights from selected cenozoic orogens defining the structural style of fold thrust belts and understanding the controlling factors are necessary steps towards prediction of their long term and short term dynamics including seismic hazard and to assess their potential in terms of hydrocarbon exploration while the thin skinned structural style has long been a fashionable view for outer parts of orogens worldwide a wealth of new geological and geophysical studies has pointed out that a description in terms of thick skinned deformation is in many cases more appropriate this paper aims at providing a review of what we know about basement involved shortening in foreland fold thrust belts on the basis of the examination of selected cenozoic orogens after describing how structural interpretations of fold thrust belts have evolved through time this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics and emphasizes the key control exerted by lithosphere rheology including structural and thermal inheritance and local regional boundary conditions on the occurrence of thick skinned tectonics in the outer parts of orogens

the structure of the precambrian and lower paleozoic basement of the central andes between 22 and 32 s lat three major diastrophic cycles defined by their structural style and their spatial distribution are recognized in the andean basement of this region the oldest structures are related to the panamerican orogeny 500 to 700 m a which produced in the central craton multiply deformed complexes of schists gneisses and granites that are covered discordantly by unmetamorphosed cambrian and ordovician beds west of the central craton ordovician sedimentary beds are folded with a simple structural style and intruded by granites both the sedimentry beds and the granites are covered discordantly by undeformed devonian sequences the folding of the ordovician is attributed to the ocloyic phase of the caledonian movements west of the ocloyic belt is another foldbelt consisting of strongly folded devonian beds attributed to the chanic phase hercynian the chanic belt is intruded by carboniferous and permian granites and covered discordantly by carboniferous and permian sequences

patterns and timing of exhumation and deformation in the eastern cordillera of nw argentina revealed by u th he thermochronology 1 the eastern cordillera ec and related ranges of bolivia and argentina exhibit a wide variety of structural features both thick and thin skinned that make this region a prime area to study the evolution of these two contrasting styles using a combination of structural geochronological and thermochronological techniques this study investigates how and in what order the various structures of the argentinean ec from 25 to 26 s have developed during the cenozoic new mapping in the angastaco area preserves one of the thickest cenozoic stratigraphic sections and records a complex structural evolution during the neogene characterized by inversion of cretaceous salta rift structures detrital zircon u pb geochronology combined with stratigraphic and structural features typical of synsedimentary deformation constrains the age of orgenic growth in the area to 14 ma detrital apatite u th he thermochronology on samples collected across the width of the southernmost ec at this latitude document an eastward younging of ages interpreted as the result of sequential eastward propagation of exhumation and inferred deformation from 14 to 3 ma at a rate of 8 3 mm a our data when compared with existing data show that the puna plateau of nw argentina was exhuming and deforming at the same time as the ec and inter andean regions of bolivia suggesting that the deformation front connects along strike despite of the differences in structural style whereas the deformation front reached the sub andes of bolivia by 10 ma deformation localized in the ec of nw argentina until 4 ma rates of propagation through the whole region seem to be quasi uniform regardless of different structural styles

one dimensional airflow in unsaturated zone induced by periodic water table fluctuation the amplitude of p0 t increases with the frequency of the head fluctuation the upper layer s thickness and the unconfined aquifer s air filled porosity and decreases with the upper layer s permeability the phase shift of p0 t ranges from 0 to p 2 indicating a time advance particularly p0 t is approximately proportional to the temporal derivative of the head for sufficiently thin or permeable upper layer and to the head itself for sufficiently thick or less permeable one the fluctuation amplitude of the water table is always less than that of the head and can be only one tenth of the latter if the upper layer is sufficiently thick or less permeable which may slow significantly the landward attenuation speed of the tide induced head fluctuation in a coastal air confined aquifer the analytical solution was used to estimate the value range of the air permeability of the marine sand fill at a coastal reclamation area of hong kong

sedimentary aspects and paleoenvironmental evolution of a rift basin salta group cretaceous paleogene northwestern argentina the rift history of the salta basin is related to the evolution of the central andes and to the activity of the pacific margin owing to its geographic location sedimentation occurred from the neocomian to the paleogene with deposits reaching up to 5 000 m in thickness paleoenvironmental analysis reveals an evolutionary history controlled by tectonic and climatic changes isolated grabens characterized the early synrift stage differential subsidence provoked distinct environments in the southern and northern subbasins in the southern subbasins alluvial fan fluvial fan and lacustrine deposits prevail whilst in the northern subbasins eolian and fluvial environments dominate during the maastrichtian two major factors controlled the basin fill the decrease in tectonic subsidence and a relative sea level rise as recorded in south america an extensive and shallow atlantic marine ingression installed a carbonate system coincident with mainly humid conditions until the danian until the middle eocene the fluvial and lacustrine environmental evolution of the sag basin was controlled especially by the alternation of temperate with dry and humid periods paleontological records reflect these climatic changes and show their relationship to the sedimentation regime

neogene to recent contraction and basin inversion along the nubia iberia boundary in sw iberia the sw of iberia is currently undergoing compression related to the convergence between nubia and iberia multiple compressive structures and their related seismic activity have been documented along the diffuse nubia iberia plate boundary including the gorringe bank west of the gulf of cadiz and the betic rif orogen to the east despite seismic activity indicating a dominant compressive stress along the algarve margin in the gulf of cadiz the structures at the origin of this seismicity remain elusive this paper documents the contractional structures that provide linkage across the gulf of cadiz and play a major role in defining the present day seismicity and bathymetry of this area the structures described in this paper caused the neogene inversion of the jurassic oblique passive margin that formed between the central atlantic and the ligurian tethys this example of a partially inverted margin provides insights into the factors that condition the inversion of passive margins

oligocene to present shallow subduction beneath the southern puna plateau abstract the southern puna plateau is a conspicuous example of a high elevation orogenic plateau in a non collisional setting this orogenic sector is currently located above an anomalously shallow subduction segment in which timing and relation to upper plate tectonics have been widely overlooked this subduction segment here referred to as the southern puna shallow subduction spss is characterized by a 200 km wide shallow area located at 300 km from the trench at a depth of 100 120 km and dipping 10 12 to the east to determine the onset of the spss and its link to the tectonic and magmatic activity in this region we analyzed the tectonomagmatic record of the southern puna plateau from preexisting datasets also we present a new approach based on global subduction data that provides a straightforward methodology to extract potential paleo slab angles from the bedrock arc record this analysis reveals that a pronounced eastward arc front migration and magmatic broadening took place at 26 ma and was preceded by 4 ma of reduced magmatic activity which we link to the inception of the spss as expected in shallow subduction settings a change to basement cored distributed deformation south of 25 s in the southern puna plateau coincides with the beginning of shallow subduction also the spss is coincident with the enigmatic post eocene intraplate deformation of the otumpa hills located at 950 km from the trench we suggest that this succession of events is not fortuitous and that the development of the spss impacted directly the overriding plate since the oligocene contributing to the building of one of the largest topographies 3 km and thickest orogenic crusts 70 60 km on earth the shallow subduction would have acted jointly with cenozoic changes in plate kinematics and climate enhancing andean orogenesis at studied latitudes

episodic out of sequence deformation promoted by cenozoic fault reactivation in nw argentina abstract the central andes are the product of contractional deformation related to subduction of the nazca plate beneath the south american continent in this geodynamic setting thrust belt propagation in the central andean retroarc in nw argentina and southern bolivia has been linked with the critical wedge model implying progressive eastward migration of the deformation front during the cenozoic however eocene unconformities and growth strata within the orogenic hinterland of the eastern cordillera and puna plateau suggest selective reactivation of pre andean and andean faults revealing a pattern of diachronous and spatially disparate range uplifts the calchaqui valley in nw argentina is characterized by basin and range morphology which is intimately linked with the heterogeneous neoproterozoic basement cretaceous rift structures and the cenozoic foreland in this study we analyze this complex deformation by reconstructing cenozoic fault reactivation and sedimentation patterns in the eastern cordillera detailed structural mapping along the eastern calchaqui border tonco area reveals five cenozoic unconformities in the former foreland deposits related to multiple episodes of fault reactivation during the eocene to pleistocene a refined chronostratigraphy u pb zircon new ahe thermochronological data apatite u th sm he and existing evidence for deformation indicate episodic out of sequence deformation and increased eo oligocene puna plateau to miocene eastern cordillera fault displacement apparently controlled by pre cenozoic heterogeneities the coeval eastward propagation of deformation and continuing deformation in the west generally challenge the applicability of the critical wedge model