The development and behaviour of low-angle normal faults during Cenozoic asymmetric extension in the Northern Apennines, Italy

Collettini, Cristiano; Paola, N. De; Holdsworth, R. E.; Barchi, Massimiliano R.

doi:10.1016/j.jsg.2005.10.003

Cited by 125 publications

(75 citation statements)

References 51 publications

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“…Characterization of the synorogenic fabric is essential for the correct interpretation of the overprinting relationships between structures developed during the later deformation events. Nevertheless, it is fundamental to establish the role played by the surface diagenetic changes on both synorogenic fabric and late-extensional fabric [Collettini et al, 2006]. (c) Crustal scale cross section based on the Crop03 deep seismic reflection profile [Barchi et al, 1998a[Barchi et al, , 1998b.…”

Section: Tc4017mentioning

confidence: 99%

Fault zone architecture and deformation processes within evaporitic rocks in the upper crust

et al. 2008

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Recently, in the Northern Apennines, geophysical data have identified the Triassic Evaporites (TE, anhydrites and dolomites) as the source region of the major extensional earthquakes of the area (M ∼ 6). In order to characterize fault zone architecture and deformation processes within the TE, we have studied exhumed evaporite‐bearing normal faults within the upper crust. The structure of large displacement (>100 m) normal faults is given by 1) a zoned fault core with a wider portion of fault‐parallel foliated Ca‐sulphates (ductile deformation), overprinted by an inner fault core (IFC) of localized brittle deformation, and 2) wide (dolostones) to absent (Ca‐sulphates) damage zones of fault fracture patterns. Fault rock assemblage within the IFC is characterized by fault breccia, gouge, and cataclasites of different grain size. Most of the deformation within the IFC is localized along thin and fault parallel principal slip surfaces (PSS) made of dolomite‐rich fine‐grained cataclasite. SEM analyses show an evolution from Ca‐ to St‐ to gypsum‐rich mineralization, due to episodic fluid flow events channeled along the fault zones during different stages of fault exhumation. The development of the observed fault geometry can be explained by a mechanical fault evolution model where initial faulting occurs along broad and ductile shear zones within the anhydrites and causes fracturing within the dolostones. Progressive deformation within the fault core leads to the development of fault parallel dolomite‐rich cataclastic layers. Their reactivation coupled with transient fluid overpressures can produce embrittlement and localization of brittle deformation within the IFC.

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Section: Tc4017mentioning

confidence: 99%

Fault zone architecture and deformation processes within evaporitic rocks in the upper crust

et al. 2008

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“…7). In fact, in the central Apennines affected by extensional tectonics (where the maximum sustainable Pf should be less than that expected for a strike -slip regime) fluid overpressures with l up to 0.8 have been found (Collettini & Barchi 2002;Collettini et al 2006). Also, the adopted increase in strain rate is probably a lower estimate (Fig.…”

Section: Discussionmentioning

confidence: 94%

Deep-crust strike-slip earthquake faulting in southern Italy aided by high fluid pressure: insights from rheological analysis

Boncio¹

2008

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I present the results of a crustal rheological analysis of the Potenza 1990 and Molise 2002 (southern Italy) deep foci (10-25 km) strike-slip earthquake sequences (M max ¼ 5.7) located in the upper half of the middle crust. The analysis consists of geotherms and twomechanism (brittle frictional v. ductile plastic flow) strength envelopes. Strength envelopes are calculated along a sub-vertical E -W-striking inherited crustal-scale fault zone reactivated under a strike-slip tectonic regime. The effects of high pore-fluid pressure (Pf ) and strain rate increase due to afterslip processes during the co-seismic and early post-seismic phases are evaluated. The results are compared with the depth-distribution of seismicity. Under long-term strain rates, the rheology predicts a brittle layer in the upper part of the middle crust embedded by two plastic horizons: the base of the carbonates and the Verrucano layer (above) and the lower part of middle crust (below). The best rheological model for the observed seismicity is that considering high Pf in the middle crust (l ! 0.65). Brittle faulting aided by high Pf in the middle crust is in agreement with the focal depths and magnitudes of the main shocks. The upward and downward widening of the brittle layer in the middle crust, due to the increased strain rate in the co-seismic and early post-seismic phases (afterslip), agrees with the width of the aftershock zones. The weak ductile layer at the base of the carbonates (and possibly within the Verrucano) appears to have an important role in delimiting the seismogenic faulting upwards and probably played a role in defining a seal to fluid up-flow along the fault zone.

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“…Low-angle normal faults gently dipping eastward, show evidence of present-day activity along the axial part of the Apennine chain, whereas their older equivalents now outcrop along the western part of the margin. Here, exhumed normal faults have been widely recognized in the Alpine metamorphic units in the Elba and Giglio Island, offshore Tuscany (Jolivet et al, 1998;Collettini et al, 2006). Toward the south, the existence of low-angle normal faults is less evident and active extension is mainly given by high-angle normal faults, NW-SE oriented.…”

Section: Structural and Geological Features Of The Extensional Tyrrhementioning

confidence: 97%

“…N-S to NW-SE oriented extensional basins developed on the previously thickened Alpine crust in the hinterland, contemporary with flexural basins in the foreland (e.g., Kastens et al, 1988), which get younger eastward as well documented by the age of the infilling sedimentary sequences. In the westernmost Tyrrhenian sea these sedimentary sequences are Lower Miocene in age and are characterized by N-S trending east-dipping normal faults (Bartole, 1995) while they are Pleistocene in age in the Umbrian region, where extensional tectonics is presently active and most of the normal faults strike NW-SE and dip westward (Jolivet et al, 1998;Collettini et al, 2006).…”

Section: Excursion Notesmentioning

confidence: 99%

“…Crustal thickness has been recently defined in detail along a transect from Northern Corsica to the Adriatic Sea (Pialli et al, 1998;Collettini et al, 2006) using receiver functions from tele-seismic data (Piana Agostinetti et al, 2002;Di Bona et al, 2008). Results converge to show the upwelling of the Moho in the Tyrrhenian area, where Moho depth is about 22 km, and a progressive westward thickening of the continental crust as far as the Apennine chain, with a maximum crustal thickness of about 35-38 km toward the Adriatic foreland.…”

Section: Structural and Geological Features Of The Extensional Tyrrhementioning

confidence: 99%

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The development and behaviour of low-angle normal faults during Cenozoic asymmetric extension in the Northern Apennines, Italy

Cited by 125 publications

References 51 publications

Fault zone architecture and deformation processes within evaporitic rocks in the upper crust

Fault zone architecture and deformation processes within evaporitic rocks in the upper crust

Deep-crust strike-slip earthquake faulting in southern Italy aided by high fluid pressure: insights from rheological analysis

The Vesuvius and the other volcanoes of Central Italy

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