1,720,999 research outputs found
The complete Apennines orogenic cycle preserved in a transient single outcrop near San Fele, Lucania, Southern Italy
No full textOrogenic cycles may be viewed as comprising two extensional stages that are separated by a stage of contraction. This sequence has characterized the evolution of most mountain belts resulting from continental collision, and the structural signature of individual stages is recognized on a wide variety of scales, i.e. from microscopic to regional. Whereas the history of mountain belts is generally inferred from observations carried out at different sites, the entire sequence of deformation is very rarely recorded in single exposures. The double switch in tectonic regime that led to the development of the Lucanian Apennines in southern Italy, from pre-orogenic drifting through synorogenic thrusting to post-orogenic extension, is preserved in a superb metre-scale outcrop at Serra Manarella, in the vicinity of San Fele. A Late Jurassic, synsedimentary normal fault is sealed by strata affected by a Mid-Pliocene thrust-related fold. This composite structure, in turn, is truncated by a Mid-Pleistocene normal fault. Observation of these relationships represents a unique opportunity to unequivocally establish the relative chronology of deformations in the Lucanian Apennines, and may provide useful constraints for regional cross-section restoration
The influence of the Messinian Salinity Crisis on the tectonic evolution of the Northern Apennines
No full textThe Messinian Salinity Crisis (5.85–5.35 Ma) represents a nearly unprecedented
unloading and loading event. During the Messinian Salinity Crisis, two important
things happened in terms of surface load changes—the accumulation of thick evaporites represent a load addition, while the desiccation of the Mediterranean represents
a load subtraction. The desiccation and evaporite deposition were followed by the
rapid addition of water, refilling the Mediterranean during the Zanclean. The calculated flexural response to load changes imposed significant changes on the horizontal
stresses in the upper crust of the Northern Apennines, an active orogenic system characterized by simultaneous zones of extension and compression that migrated eastward
over time. We show that these flexural stresses (approaching ± 50 MPa), added to the
preexisting stresses across the Northern Apennines, were large enough to have caused
some areas in compressional stress regimes to flip to extensional regimes, and vice versa. Among other things, our model predicts that the Marches Apennines region, which
was beginning to undergo compression at the leading edge of the orogen, should have
experienced a brief interval of extensional deformation. Previous structural studies of
this region have shown that there was, in fact, a brief period of extensional faulting
near the onset of the Messinian Salinity Crisis, which was then followed by a return
to compressional deformation, just as our model predicts. The hypothesis presented
here provides a novel explanation for this extension occurring in an area that should
have been undergoing compression, one in which the unique events of the Messinian
Salinity Crisis generated significant flexural stresses that changed the deformational
regime during the relatively brief time of the Messinian Salinity Crisis. We further
suggest that this hypothesis may provide insight into similar unexpected tectonic episodes during this time period in other parts of the Apennines
Structural investigation of background features and normal faults affecting the Calcari con Selce Formation, Southern Apennines, Italy
No full textThe Calcari con Selce formation (CSf) is a low-porosity multilayer carbonate, partially dolomitized, formation that extensively crops out in the Lucania Apennine chain. This lithostratigraphic succession represents to depth a key formation concerning hydrocarbon exploration and a potential confined acquifer system. In this work we describe the structural features affecting the CSf related to burial and tectonic deformation with emphasis on normal faults related to post-orogenic extensional deformation. A field investigation led to recognition of background structures such as: i) strata-bounded sub-vertical fracture sets (OBj) and bedding-parallel solution seams (BPss), related to lithostatic load; and: ii) oblique-to-bedding solution seams (BOss) induced by syn-orogenic flexural slip. Furthermore, different sets of dolomitic veins extensively affect dolomitized parts of the CSf showing structural relationships with bedding interfaces. Localized low-angle normal faults (LANFs) post-dating the previous structures formed further anisotropies locally associated with sub- vertical fracture sets (SVfs). These structures, enhancing permeability within carbonate beds, promoted fluid compartmentalization. High- angle normal faults and associate fracture sets, characterized by well-connected features, mainly localized along the mature fault zones, further enhanced the permeability of the CSf allowing the development of preferential fluid-flow pathways moving parallel to the fault-zones, as inferred from the structure of calcite veins. This work provides an enhanced characterization of the fracture network affecting the CSf and represents a useful tool aimed at improving hydrological models for fluid circulation within fractured reservoirs
Il progetto CARG in Basilicata: il Foglio 489 Marsico Nuovo
No full textThe stratigraphic and structural features of the Apenninic Chain exposed in the Marsico Nuovo sheet are shortly described. The Apenninic edifice is composed of tectonic units, originated since Oligocene time. It is completely detached and resting onto a deep seated thrust system (the Apulian thrust system), deformed since Tortonian in contemporaneous with the Tyrrhenian opening. The geodynamic evolution of this latter influenced the further movements of the Apenninic Chain. Stratigraphic characters of the sequences outcropping in the studied area are here discussed. The deepest units are the Lagonegrese Mesozoic basinal sequences; these underlie the coeval carbonate platform units. A general decoupling between the Mesozoic sequences and the Tertiary flysch-type terrigenous covers occurs. Oil field traps have been dected in the ramp-anticlines of the buried thrust system and a lots of subsurface data allows to restore the whole geodynamic evolution of this area
A mesoscopic inversion duplex in SW Tuscany, Italy: implications for inferring the deep geometry of collision orogens
No full textThe advances in the field of inversion tectonics illustrate that pre-orogenic extensional deformations largely control the geometry and evolution of thrust systems. While the relationships between extensional and con- tractional structures are widely documented from restoration of thrust fans, they are significantly less documented in duplex structures. In this contribution we briefly describe a mesoscopic scale duplex developed, within the Arenarie di Poggio al Carpino Fm, across a precursor boudinage structure inherited from an episode of Mesozoic age extension. The structure crops out at «I Canaloni» localty (Farma River) along the Mid Tuscan Ridge, SW Tuscany (northern Apennines of Italy)
From extension to contraction in syn-orogenic foredeep basins: the Contessa section, Umbria-Marche Apennines, Italy
No full textSyn-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
Fault growth by segment linkage in seismically active settings: examples from the Southern Apennines, Italy, and the Coast Ranges, California
No full textMost models for fault growth and scaling are based on analysis of faults which display dip-slip (i.e. reverse, normal) and strike-slip kinematics; by contrast, little information is derived from faults displaying oblique-slip kinematics. Observations on mesoscopic transpressional faults from the Salinian Block of California and transtensional faults from the Southern Apennines of Italy reveal a complex kinematic history of fault propagation. Faults initially nucleate as isolate segments, which are later kinematically and mechanically linked via development of diuse deformation zones and/or localised oblique connecting splays. The geometry of observed mesoscopic faults is similar to that of the host, larger structures, thus suggesting that the produced fault patterns are scale independent. Moreover, the overprinting relationships among minor fault-related fabrics permit to de®ne a relative chronology within fault arrays, thus enabling a general sequence of structural stages to be correctly established. Based on minor fabrics and their overprinting relationships, a kinematic deformation model of fault growth by segment linkage is presented, which may have a wide applicability in the ®eld of seismic hazard evaluation. 5 1999 Elsevier Science Ltd. All rights reserved
3D modeling and cross-section restoration as tools for imaging geological structures
No full textDifferent modelling techniques are used for reconstruct the current (deformed) architectural geometry in tectonically complex areas. We tailored workflows for geological modelling that include the use of georeferred field data, interpreted geological maps and cross-sections; when available, subsurface data like well logs and seismic images are used for better constrain the model. Surfaces representing lithological boundary and faults have been obtained in different ways, either by interpolation of the starting data (field measurements, best constrained map traces of the structures), or starting from reference surfaces (used as a proxy for subsequent morphing by using structural thickness and attitude constraints. Subsequent balancing methods in both cross-section and 3D are used for constrain the geological model with a trial-and error procedure. Our experience demonstrates the effectiveness of the 3D modelling techniques in different tectonic settings. Here we are presenting map-scale examples of models obtained in areas of the inner and the central zones of the Apennines, respectively in areas where the post-collisional extension is prevalent, and areas where the effects of the contraction does. We stress the need of 3D geometrical coherence between geological maps and related cross-sections, and the utility of the 3D modelling and visualization techniques in achieve best results and geometrically consistent linked structures
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