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

multi phase reactivations and inversions of paleozoic mesozoic extensional basins during the wilson cycle case studies from the north sea uk and the northern apennines italy

tethyan heritage in the development of the neogene umbria marche fold and thrust belt italy a 3d approach the umbria marche fold and thrust belt northern apennines italy provides excellent opportunities to evaluate the structural heritage of the opening of the mesozoic tethys ocean in the 3d geometry of the neogene compressional structures related to the alpine orogeny the structure and evolution of a portion of the southernmost belt between the nera river and the rieti basin are described as a field example and the kinematics along well exposed mesozoic extension structures are provided cross section restoration shows a close coincidence between these extension structures and the neogene thrust ramps thus suggesting that the geometry of the latter was controlled by the map distribution of the former sequential balancing also allows for the definition of the geometrical pattern of pre existing normal faults which were produced in response to a unidirectional or a two directional extension stress field the inferred direction of principal extension corrected for the effects of late deformation is consistent with that proposed for the northern margin of the adria promontory in global scale plate tectonic reconstructions

ancient synsedimentary structural control on thrust ramp development an example from the northern apennines italy the umbria marche sabina foreland fold and thrust belt northern apennines italy provides excellent test cases for the hypothesis of ancient syndepositional structural features controlling thrust ramp development the sedimentary cover late triassic to miocene in age is made of platform and pelagic carbonates whose deposition was controlled by significant synsedimentary extension normal faulting mainly during the jurassic and the late cretaceous palaeogene determined sensible lateral thickness variations within the relative sequences by late miocene the sedimentary cover was detached from its basement along a mainly evaporitic horizon and was deformed by means of eastward verging folds and thrusts in order to locate the points where thrust ramps branch off the basal detachment both line length and equal area techniques were used in the construction of a balanced cross section through three major fault related folds in southeastern umbria the nucleation of thrust ramps was controlled by the occurrence of jurassic and cretaceous palaeogene synsedimentary normal faults these interrupted the lateral continuity of the evaporitic unit the late triassic anidriti di burano fm at the base of the sedimentary cover and acted as obstacles to the eastward propagation of the thrust system giving rise to major folds which originated from tip line folding processes therefore the inferred relationships between ancient normal faults and late thrusts indicate that synsedimentary tectonic structures and the related lateral stratigraphic variations can be envisaged as mechanically important perturbations which effectively control the nucleation and development of thrust ramps

role of faults and layer interfaces on the spatial variation of stress regimes in basins inferences from numerical modelling abstract the spatial variation of the computed state of stress is studied in a series of numerically solved boundary value problems of basin scale deformation these numerical experiments illustrate simple situations of decollement tectonism under compression the study focuses on the local variation of the state of stress in a sedimentary overburden where major discontinuities such as large scale faults and layer interfaces are present the states of stress are computed using either the distinct element method or the finite element method classic elasto plasticity laws are used for the behaviour of the continuum and the discontinuities are modelled as coulomb contact surfaces a geologic interpretation of the numerical experiments is proposed to highlight the role played by major structural discontinuities in the local variations of the stress regime the models are two dimensional in space and assume plane strain but the full three dimensional stress strain constitutive relation is used therefore the stress regime variations can be represented by constructing the contour map of the wallace bott stress ratio this simple technique together with the construction of diagrams of principal stress magnitude across the model enables us to rapidly examine the stress field pattern and further discuss the deformation modes of faulting and fracturing which may take place at a small scale we have found that the local variations of the stress tensor are in good agreement with common geologic interpretation of brittle deformations in foreland and thrust systems we demonstrate how the presence of layer interface and the difference in mechanical properties of formation lithology may strongly affect the variation of stress in space this modelling approach has important issues when interpreting well tests to gain access to in situ stresses

upper plate deformation as marker for the northern step fault of the ionian slab tyrrhenian sea central mediterranean abstract the eastern tyrrhenian margin etm the active boundary of the tyrrhenian sea backarc basin is the key for understanding the geodynamics of the central mediterranean numerous seismic tomography studies have been carried out in this region proposing different reconstructions of the lower subducting plate and cause of the slab break off existing beneath the southern apennines however the area and mode of the recent deformation of the tyrrhenian sea are still not fully defined and understood in this study we combine the analysis of a recent seismic tomography model and geological data in order to understand the relationship between the subducting lower plate and the tectonic evolution of the sedimentary basins formed on the upper plate with this aim we interpreted a large data set of seismic reflection profiles and several well logs the results consist in 2d and 3d geological models of the basins sedimentary infill and fault networks taking into account the geological data of the etm and those of the adjacent inner flank of the apennines we observe i a system of linked sedimentary basins developed on a narrow deformation belt bounded by transform fault zones ii a polyphase rifting within the upper plate iii an abrupt change of the direction of extension 90 from ne oriented in the lower pleistocene to se oriented in the middle pleistocene since these etm features are not the typical expressions of the current backarc extensional models we propose a link between the evolution of upper plate and the onset and development of a step subduction transform edge propagator fault along the northern margin of the ionian slab

lower plate geometry controlling the development of a thrust top basin the tectonosedimentary evolution of the ofanto basin southern apennines the ofanto basin is a pliocene pleistocene thrust top basin that formed with an unusual east west orientation along the frontal part of the southern apennine allochthon during the latest stages of tectonic transport its tectonic and sedimentary evolution was studied integrating field surveys biostratigraphic analyses and the interpretation of a large seismic grid well data and seismic interpretation indicate that a large east west trending normal fault underlies the northern margin of the basin displacing the apulian carbonates that form the foreland and the footwall of the southern apennine allochthon in our reconstruction the ofanto basin formed at the rear of the bulge caused by buttressing of the southern apennine allochthon against this normal fault in a second stage of contraction the footwall of the southern apennine allochthon was involved in deformation with a different trend from the normal faulting and buttressing this caused eastward tilting of the basin and broad folding around its eastern termination good stratigraphic constraints permit the age of buttressing to be defined as early pliocene and that of the shortening in the apulian carbonates as early pleistocene this study highlights the importance of early orogenic normal faults in conditioning the evolution of the frontal parts of orogenic wedges supplementary material a 3d reconstruction of the base of the pliocene deposits of the ofanto basin based on seismic interpretation is available at www geolsoc org uk sup18559

facies development along the tide influenced shelf of the burdigalian seaway an example from the ottnangian stratotype early miocene middle burdigalian abstract herein we report quantitative micropaleontological benthic foraminifers dinoflagellate cysts calcareous nannoplankton sedimentological grain size analysis and geophysical background gamma radiation analyses from ottnang schanze the stratotype for the regional ottnangian stage central paratethys lower miocene middle burdigalian the revealed trends in bathymetry primary productivity bottom water oxygenation and water energy allow exemplary insights into the paleoenvironment of the terminal burdigalian seaway several facies of a eutrophic environment are distinguished that reflect a transition from a suboxic outer neritic to upper bathyal towards a better oxygenated middle neritic setting under the influence of storm events and currents a comparison with available data from upper austria and bavaria consistently shows the regressive trend during the late early ottnangian in upper austria the deep water facies from the lower part of the stratotype represents the most distal sediments the upper part together with localities closer to the northern coast records inner to middle neritic environments that are heavily affected by tidal currents the facies distribution results from the progradation of a tide influenced environment along the northern shelf of the north alpine foreland basin heralding the closure of the burdigalian seaway the available age estimate for the stratotype constrains the onset of the regressive phase to 18 ma

structural evolution of a foreland fold and thrust belt the umbria marche apennines italy abstract outcrop scale structures that record a progressive sequence of deformation can be used to clarify the kinematic evolution of an entire fold and thrust belt the temporal progression of the compressional deformation as reconstructed by means of a mesoscopic structural analysis provides a key for unraveling the kinematic history of the umbria marche apennines central italy overprinting relationships at outcrop scale allow for the recognition of three distinct structural stages which are in sequence a layer parallel shortening b folding c thrusting individual stages are explained in the framework of a progressive deformation model where shortening of the sedimentary cover was continuous and occurred during a single contractional episode as a consequence of tip line folding processes a comparison of this history with those reported from other fold and thrust belts shows that layer parallel shortening folding and thrusting are sequentially dominant processes in areas which have experienced compressional deformation

continental margins orogenic belts and intracratonic structures angular bends promontories and embayments in rifted and passive continental margins are interpreted to be the precursors of curves recesses and salients respectively in orogenic belts convergence at an irregularly shaped continental margin results in along strike diachroneity of closing and thus of orogeny and in a variable trajectory of stress into continental crust both timing and sense of movement of intracratonic structures apparently have complex relationships to the progress of convergence at irregular continental margins

influence of precipitation phase on the form of mountain ranges observations of precipitation fall speeds and precipitation patterns suggest that precipitation phase rain versus snow is a significant control on the relationship between precipitation patterns and topography due to the potential for increased downwind advection of snow relative to rain a coupled model of orographic precipitation and surface erosion shows that for a range of climate variables steady state precipitation patterns vary from nearly uniform and maximizing over the highest topography to highly spatially variable closely coupled to topography and reaching a maximum on low slopes precipitation patterns are a first order control on modeled range scale and ridge valley scale relief channel concavity and the position of the drainage divide an association between cool climates spatially uniform precipitation and efficient erosion of high topography is indicated the importance of precipitation phase to the evolution of precipitation patterns and topography further demonstrates the fundamental importance of the coupled climate erosion and tectonic system in the evolution of mountain topography

compressional and extensional tectonics in an arc system example of the southern apennines abstract adopting the southern apennines as a case example we determine the relationships between extensional and compressional structures within an arc system based on tectonic analysis in the field we show that in addition to the well known occurrence of inner extensional structures during frontal accretion two other types of extensional structures are present in the southern apennines we classify the three types of extensional structures depending on their chronologies with the accretion of the thrust unit and we characterize them in terms of palaeostresses some normal faults of the mountain chain are old extensional structures formed in a foreland basin in the matese mountains such faults with offsets ranging several hundred metres are sealed by a late neogene thrust sheet these foredeep structures were created by extension trending almost perpendicular to the axis of the present day foreland basin other normal faults located closer to the tyrrhenian sea developed simultaneously with the pliocene quaternary accretion of thrust sheets at the front of the belt in the salerne graben a tyrrhenian basin structure extension occurred perpendicular to the compression that prevailed at the front of the mountain belt a stress gradient existed between the outer part of the arc with 1 trending ene wsw and the inner part with 2 trending ene wsw in the southern apennines middle pleistocene holocene normal faults post date all compression and thrusting the corresponding recent stress field ne sw extension results from uplift of the previously subsiding adriatic lithosphere we conclude that a given thrust unit of this nw se trending mountain chain may have successively undergone ne sw extension in the foreland basin ne sw compression during the accretion nw se extension in the back arc region and ne sw extension during the recent evolution of the prism the succession of these tectonic regimes has induced complex structures as commonly observed in an arc system

distribution of joints in the hinge line culmination of foreland verging overturned anticlines an example from the montagna dei fiori structure in the central apennines of italym francioni et al distribution of joints in overturned anticlines the distribution of joints veins and shear fractures in the montagna dei fiori overturned anticline is here reported two joint sets longitudinal and transverse to the nnw sse anticline axial trend and a conjugate system of shear fractures are recognized the transverse and longitudinal joint sets have a pre folding development likely related to the foreland foredeep flexure the transverse joints were reopened during layer parallel shortening along with the development of the shear fractures then during syn folding outer arc extension and hinge line culmination fold axial parallel extension both the longitudinal and transverse joints were enhanced and reactivated respectively

the foreland deformation in the south western basque cantabrian belt spain abstract in the south western portion of the cenozoic basque cantabrian belt structural data collected in pre orogenic upper cretaceous limestones were combined with aerial images interpretation in flat lying areas observations about fracture strike type orientation and overprinting relationships both at the macro and mesoscales allow to constrain the pre thrusting and pre folding deformational sequence that affected the area when it was forming part of the foreland basin wnw ese striking extensional structures represent the oldest elements developed during the very late stages of the mesozoic rifting associated with the opening of the bay of biscay the onset of convergence is marked by the development of extensional structures striking roughly nnw sse and wsw ene which are associated with belt parallel stretching in the foredeep and outer arc extension in the peripheral bulge respectively and developed in a non fluid assisted environment these elements are postdated by a pre folding layer parallel shortening pattern which includes wsw ene striking pressure solution cleavages and reverse faults both of them frequently reactivating inherited early orogenic wsw ene striking extensional elements and right lateral reactivation of wnw ese striking pre orogenic extensional structures this stage was followed by a syn to post folding e w oriented belt parallel compression wnw ese striking left lateral faults being the most outstanding elements associated with this stage the presence of such elements in upper cretaceous sediments provides support to the idea that left lateral shear zones of the area related with a cenozoic intrabelt lateral extrusion tectonics our results indicate coherently with previously published works in the pyrenean orogen that most of the mesoscale deformation has been acquired before layer s tilting

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

paleogene magnetic stratigraphy in umbrian pelagic carbonate rocks the contessa sections gubbio the umbrian sequence of pelagic carbonate rocks provides an opportunity for precise correlation between paleogene biostratigraphy and geomagnetic polarity history the red to pink paleocene to middle eocene scaglia rossa limestone the varicolored upper eocene scaglia variegata limestone and the gray green oligocene scaglia cinerea marlstone form a 250 m thick continuous exposure in the contessa valley near gubbio italy magnetostratigraphic lithostratigraphic and biostratigraphic investigations in three sections covering the entire paleogene have confirmed and dated the geomagnetic reversal sequence for most of this period the ferromagnetic mineral in the scaglia cinerea is magnetite and af demagnetization to peak fields of 20 mt is sufficient to define the characteristic remanent magnetization the scaglia variegata and pink scaglia rossa samples contain an additional hematite component which is very pronounced in dark red paleocene scaglia rossa samples changes of magnetic mineralogy take place in these limestones during heating especially above 500 c however thermal demagnetization is effective in isolating the characteristic remanence vectors which form almost antipodal clusters of directions representing normal and reversed polarities the directions are rotated counterclockwise partly due to post oligocene tectonism paleontological zonations of planktic foraminifera and calcareous nannofossils were hampered by poor preservation but the major epoch and stage 29 as in the gubbio bottaccione section paleocene eocene just above anomaly 25 eocene oligocene between anomalies 13 and 15 oligocene miocene just below anomaly 6c these correlations require slight modifications to previous conclusions on paleogene sea floor spreading rates

deformation history of a synorogenic sedimentary wedge northern cilento area southern apennines thrust and fold belt italy in the northern cilento area of the southern italian apennines a deformed turbiditic succession of langhian to lower tortonian age the cilento unit unconformably overlies tectonic units liguride and sicilide derived from an oceanic accretionary complex and to the east overlies mesozoic cenozoic carbonates belonging to the apulian continental paleomargin the turbiditic succession representing the sedimentary infill of a miocene foreland basin developed over the flexured southwestern margin of the apulian plate shows a complete record of the deformation at the macroscopic and mesoscopic scales structures postdating synsedimentary slump features in the cilento unit include neptunian dikes and extensional veins perpendicular to bedding all related to high pore fluid pressures associated with burial early tectonic structures consist of minor thrust faults often conjugate and at a low angle to bedding produced by initial layer parallel shortening the main regional structure mapped in the area consists of a moderately inclined to recumbent hinterland vergent backfold this structure probably developed by shortening of the strata caught between shear surfaces that cut obliquely across bedding within the framework of a noncoaxial progressive deformation the main shear surface constituting the upper boundary to the shear zone is represented by a regional backthrust which brings mesozoic cenozoic carbonates onto the terrains of the cilento unit forming a triangle zone where backfolding of the latter occurred minor open domes and basins deform both limbs of the main regional structure probably as a result of progressive shear deformation and possibly of deformation above underlying thrust culminations it appears that high pore fluid pressures must have been important not only during the development of pretectonic i e burial related structures but also during the main tectonic deformation abnormally high fluid pressures reducing the effective stress and favoring intergranular movements suppressed cleavage formation and pervasive strain during the main folding event later in the deformation sequence a decrease in pore fluid pressure probably favored local cleavage development during refolding the deformation sequence outlined above provides a case history of the structural evolution of synorogenic clastic deposits progressively deformed and incorporated within a thrust belt this study documenting the deformation of a sedimentary wedge dominated by backfolding associated with hinterland vergent reimbrication should contribute to a better understanding of the wide range of deformation sequences and processes characterizing the tectonic evolution of thrust belt foredeep systems

pre oceanic rifting in the alps abstract a review of mesozoic mainly earliest jurassic to mid jurassic rifting in the western and central alps normal faults with throws up to a few kilometers are moderately inclined and involve rotation of crustal blocks the amount of stretching and thinning of the crust by jurassic rifting is discussed the rifting 200 165 m y pre dates the opening of the alpine oceans by spreading and transform movements 165 110 m y

from extension to contraction in syn orogenic foredeep basins the contessa section umbria marche apennines italy syn orogenic deposits that occupy foredeep basins commonly experience contraction related to the migration of fold and thrust systems toward the foreland this contraction may overprint the earlier extensional deformation that is related to the initiation of the basin although predicted by models for foredeep development evidence for extension predating contraction at different scales is not extensively recorded in syn orogenic deposits mesoscopic structures from the contessa section in the umbria marche apennines italy reveal a complex history characterized by extension soon before the contractional deformation normal faults predate the folds and thrusts that are related to the miocene age orogenic event responsible for the development of the apennines extensional deformation may have resulted from flexuring of a lithospheric plate induced by the load of a stacking thrust pile the transition from extension to contraction could play an important role in the evolution of belt foredeep foreland systems as it could reflect the migration of advancing thrust fronts toward the foreland