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Seismic velocity-depth relation in a siliciclastic turbiditic foreland basin: A case study from the Central Adriatic Sea
No full textStarting from reprocessed seismic profiles and borehole data, we investigate the Central Adriatic foredeep basin by deriving velocity depth trend of the Pliocene-Quaternary (PQ) siliciclastic succession (mainly composed by shales and sands). Relying on independent approaches to map two-way time (TWT) thickness of the PQ deposits, we converge on testing linear and exponential functions to predict VP depth trend. Results suggest that for large (>1500 m) thicknesses of the PQ deposits best fit is achieved by the exponential function VP(z) = c z(1-n) while for shallower and thinner deposits, a linear function like VP(z) = V0 + k z provides the best fitting estimates. We also investigate anomalies in velocity trend with depth and suggest that velocity drops observed within the PQ succession at significant depth (2500–3500 m) may reflect overpressured deposits. This hypothesis is consistent with the Apennine compression and high sedimentation rates in Central Adriatic during the Pliocene-Quaternary. Finally, we stress the importance of considering vertical-component phenomena and their time evolution when modeling foreland basins
The interaction of extensional and contractional deformations in orogenic belts: the example of the Central Apennines, Italy
No full textThe relationships among normal faults and thrusts in the Apennines of Italy are often unclear, and the local absence of syn-tectonic stratigraphic controls have led to contrasting interpretations on the relative chronology for both classes of structures. The activity of normal faults has been variously regarded as due to pre-, syn- or post-orogenic extension, and the contrasting evidence from different sites has produced an ongoing debate on the normal fault±thrust interaction. The results of a kinematic analysis on selected composite structures of the outer zones of the Central Apennines make it possible to unequivocally establish a relative chronology of extensional and contractional deformations. Detailed mapping, outcrop-scale observations and structural overprinting relationships support a positive inversion tectonic history, where normal faults and fault-controlled escarpments formed ®rst, and were later deformed by thrusts and related folds. All normal faults control the distribution of foredeep deposits, thus indicating that the recognised episode of positive inversion is related to the incipient stages of construction of the Apennine thrust belt. The systematic collection of structural data may help to unravel the evolution of adjacent sectors of the Apennine chain, as well as of other belt-foredeep±foreland systems whose extension±contraction relationships are poorly constrained
Styles of tectonic inversion within syn-orogenic basins: examples from the Central Apennines, Italy
No full textThe geometry of several thrust-related folds in the Central Apennines of Italy results from a switch in deformation regime, from extension to contraction. This switch in tectonic regime occurred during the deposition of syn-orogenic sediments, and the emplacement and migration of the thrust belt±foredeep system towards the foreland in Neogene time. The styles of positive tectonic inversion result from normal faults that were steepened, rotated and truncated by thrusts, with local development of minor folds due to buttressing. Normal fault-controlled escarpments are also locally preserved in the forelimbs and backlimbs of thrust-related anticlines. The location and amplitudes of contractional structures across the belt re ̄ects the distribution of pre-thrusting normal faults within precursor syn-orogenic basins, a result that may improve our understanding of the evolution of Apennine, as well as other thrust belt±foredeep systems
Short cut geometry along the N-S trending Gran Sasso and Morrone Thrust front (Central Apennines)
No full text“Gravity modeling reveals a Messinian foredeep depocenter beneath the intermontane Fucino Basin (Central Apennines)”, reply to the comment from Florio et al. (2022)
No full textThis is a reply to the comment from Florio et al. (2022) about the paper by Mancinelli et al. (2021).
Both the paper and the comment concern the modeling of the gravity anomaly in the intermontane Fucino basin (Central Italy).
In contrast with literature and data, the comment supports a model without Miocene flysch beneath the Plio-Quaternary
Kinematic characterization and deformational evolution of quaternary faults displaying a Holocenic activity: Some cases in the Central Apennines (Italy)
No full textGeological and structural researches on Quaternary faults in key-areas of Umbria-Marche and Abruzzi in the Central Apennines, emphasised the occurrence of complex kinematic conditions, which are characterised by various and alternating generations of slip vectors along the same fault plane. Quantitative analyses of these structures allowed the reconstruction of a mean ellipsoid of finite extensional deformation characterised by a NE-SW stretching direction and a vertical shortening axis. The Quaternary tectonic framework is characterised by kine-matically interconnected active thrusting - in the Adriatic off-shore - and normal faulting - in the Apennines ridge -, which gave rise to a progressive deformation with mean shortening and extensional axes both trending NE-SW. Oblique ramps and transfer faults commonly developed along pre-existing N-S and E-W trending structures (such as Jurassic and Cretaceous faults). This complex kinematic situation is interpreted in terms of mechanical interactions caused by the variation of one or more tectonic stress modules, associated with the presence of oblique ramps and transfer faults
Inherited mesozoic architecture of the Adria continental paleomargin in the Neogene Central Apennines evolution
No full textStructural analysis carried out in the outer zones of the Central Apennines of Italy, integrating surface and subsurface data with seismic profiles, has made it possible to define the main modes of interaction between the architecture of the Mesozoic palaeomargin of the Adria plate and the central-Apennines orogenic system (namely the thrust-foredeep-foreland system) during the Neogene- Quaternary contractional events.
A complex architecture of the Mesozoic palaeomargin is well defined in the central Apennines by the occurrence of alternating Triassic-Miocene platforms and basins. These palaeogeographic domains were differentiated following the onset of extensional def- ormation during Upper Triassic and Middle Liassic times, and the consequent drowning of distinct parts of a formerly wider platform. Within the Apennine fold-and-thrust system, the main features rec- ognised are: a) the distribution of the Triassic-Miocene platform and basin domains, which are transverse and longitudinal with respect to the trends of younger contractional structures; b) the cor- respondance of the Neogene-Quaternary syn-orogenic depocentres with older pelagic basins; c) the occurrence, in the thrust belt, of salient geometries, as seen in map view, corresponding to the pala- leomargin architecture and to the physiography of the syn-orogenic basins.
Balanced and restored cross-section construction across the Adriatic offshore area, i.e. the present foreland of the Apennine belt, and the axial zone of the thrust system through the orogenic front, has made it possible to outline the role of the architecture of the Mesozoic palaeomargin in the evolution of the Messinian-Quater- nary syn-orogenic basins. These depressions are characterised by wide antiformal and synformal flexures with wavelength of 50-80 km, located respectively on carbonate platform and pelagic basin domains.
The reconstructed geometry suggests that crustal- and/or lithos- pheric-scale buckling was more important than foreland bending as a driving deformation process. The development of reverse/trans- pressive and normal faults further accentuated the prominent phys- iographic differences within syn-orogenic basins. Some of these nor- mal faults accommodated outer-arc extension and reactivated pre-orogenic extensional structures. During development of the thrust system, the palaeomargin architecture and pre/syn-orogenic normal faults controlled the location of thrust ramps, producing the salient geometries characteristic of the outer zones of the Apennine belt. In particular, pre-existing normal faults were truncated by thrusts that propagated upwards following «short-cut» trajectories, but also were rotated in steep fold limbs and/or partly reactivated.
Therefore, the tectonic setting of the belt results from interac- tion of the orogenic system and the architecture of the palaeomar- gin. The syn-orogenic basins were characterised by structural highs and depocentres that appear controlled by crustal-lithospheric anisotropies related to buckling and foreland flexure induced by oro- genic load. This geometry, in turn, controlled the final geometry of the thrust belt, where it is possible to document that thrust sheet culminations and depressions reflect syn-orogenic structural highsand basins, respectively. The modes of palaeomargin-foredeep-thrust belt interaction recognised provide important information on the estimate of orogenic shortening, and on the burial-exhumation path of the Central Apennines
Gravity modeling reveals a Messinian foredeep depocenter beneath the intermontane Fucino Basin (Central Apennines)
No full textResidual gravity anomalies over Central Italy clearly indicate a prominent regional minimum over the Fucino Basin. Here, we forward model this anomaly along seven cross-sections. The modeling results validate the geometries and petrophysical properties of the Plio-Quaternary units previously proposed by reflection seismic data interpretation. Moreover, we suggest that a thick wedge-shaped sequence is present beneath the Plio-Quaternary post-orogenic units. Based on the inferred density and velocity properties, as well as outcrop evidence from around the Fucino Basin, this sequence would likely represent thick (~1700 m) siliciclastic syn-orogenic Messinian foredeep deposits. The proposed model implies a long-lasting tectonic inheritance history for the Fucino area, which originally hosted primary paleogeographic Mesozoic-Miocene boundaries. In the Messinian-Recent time, the Fucino has continuously represented a first-order tectonic depocenter for siliciclastic sediments, despite differences in tectonic regime (syn-orogenic Messinian, post-orogenic Plio-Quaternary) and palaeoenvironments (Messinian marine flysch, Plio-Quaternary alluvial-lacustrine facies). The compaction-corrected sedimentation rate (~0.89 mm yr−1), suggests a foredeep activity possibly spanning the entire pre-evaporitic, evaporitic and post-evaporitic Messinian time and is comparable to the sedimentation rate observed in the larger Pliocene Apennine foredeep, ~100 km northeast of the study area, suggesting a self-similarity of the belt-foreland system across time and space
Caratterizzazione cinematica ed evoluzione deformativa delle faglie quaternarie con attività olocenica: esempi dall'Appennino centrale
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