Repeated surveys reveal nontectonic exposure of supposedly active normal faults in the central Apennines, Italy

In west-directed subduction zones, as the compression moves towards the foreland, the accretionary prism progressively expands to follow the hinge migration towards the east. Although late Miocene foreland propagation implies the shift of the thrust front, in the central Apennines, the effects of the Messinian compression can be observed on a much broader area, implying out-of-sequence thrusting in the rear.In order to understand the Messinian involvement of the previously formed Tortonian belt-foredeep system, a regional reinterpretation is here provided. The analysis of publicly available 2D seismic reflection lines across the upper and middle Latin Valley and 10 wells enables the identification of two main seismostratigraphic units: i) the Meso-Cenozoic neritic carbonates and ii) the upper Tortonian siliciclastic pelitic and arenaceous turbiditic associations of the Frosinone Formation.The most evident reflectors are the upper Cretaceous and upper Serravallian top paraconformities, which, due to tectonic repetition can be followed at different depths. We find that minor reflectors can be attributed to the several thrusts affecting folded Meso-Cenozoic neritic carbonates. This observation allows us, together with field and well evidences, to trace several thrust sheets characterized by a general top-to-the NE sense of shear. In a few sections from the Latin Valley (e.g. Line FR-309-80), we recognized the Meso-Cenozoic neritic carbonates being thrusted together with the Tortonian Frosinone Formation, on top of a laterally variably thick siliciclastic succession. This further syn-orogenic unit could be related to the early Messinian sandstones of the Torrice Formation, implying that out-of-sequence thrusting took place in the Latin Valley during the wedge-top sedimentation. The thin-skinned fold-and-thrust fabric is defined by en-&#233;chelon distributed thrusts, NNE- and ENE striking tear faults and minor pop-up structures often determining ideal traps for hydrocarbon and geothermal fluids. Finally, conjugated NW-striking high-angle normal faults crosscut the orogenic heritage and sets a horst and graben structure associated with continental deposition and the Volsci Volcanic Field.The limited oil exploitation over the past century has targeted only the shallower siliciclastic traps and some evidences in the shallower neritic carbornate thrust sheets. At the light of our new interpretation, the deeper carbonate units could be a new focus for hydrocarbon accumulation and may furnish targets for geothermal and/or hydrocarbon research in the area. Future work aims at quantify the Tortonian and Messinian amount of shortening by taking into consideration the adjoining Volsci Range. Finally, our findings bear implications on geodynamic reconstructions and may represent an example of the geometry and kinematic evolution of platform derived thrust sheets and similar belts worldwide associated with W-directed subduction zones.

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Comb-veins as a marker for crustal-scale fluid circulation: insight from geochronological (U-Th dating), geochemical, and field to microstructural analyses along the seismogenic Val Roveto Fault (central Apennines, Italy)

10.5194/egusphere-egu2020-660 ◽

2020 ◽

Author(s):

Luca Smeraglia ◽

Stefano M. Bernasconi ◽

Fabrizio Berra ◽

Andrea Billi ◽

Chiara Boschi ◽

...

Keyword(s):

Active Faults ◽

Shallow Groundwater ◽

Optical Microscope ◽

Maximum Temperature ◽

Normal Faults ◽

Fluid Circulation ◽

Central Apennines ◽

Study Region ◽

Fault Surface ◽

Geochemical Signature

Comb-veins are mineral-filled fractures oriented perpendicular to fault surfaces, with their intersection with the fault surface generating lineations that are perpendicular to the downdip slip direction. Despite the large occurrence along normal faults within seismogenic extensional tectonic settings (i.e. Greece, Turkey, Italy), their origin, geochemical signature, and kinematics are still poorly constrained. Here we present the first multidisciplinary study, combining field to microscale observations (optical microscope and cathodoluminescence) with geochemical-geochronological analyses (U-Th dating, stable-clumped isotopes, Strontium isotopes, whole-rock geochemistry, and fluid inclusions), on calcite-filled comb-veins cutting through the principal surface of the seismogenic Val Roveto Fault in the central Apennines, Italy. We show that comb-veins precipitated in Late Pleistocene time (between 300 ky and 140 ky) below the present-day outcrop level at a maximum depth of &#8764;350 m and temperatures between 32 and 64&#176;C from deep-seated fluids modified by reactions with crustal rocks and with a mantle contribution (up to &#8764;39%). The observed geochemical signature and temperatures are not compatible which those of cold meteoric water and/or shallow groundwater (maximum temperature of 12 &#176;C) circulating within shallow aquifers (&#8804; 500 m depth) in the study region. Therefore, we propose that deep-seated crust/mantle-derived warm fluids were squeezed upward during earthquakes and were hence responsible for calcite precipitation at shallow depths in co-seismic comb fractures. As comb-veins are rather common, particularly along seismogenic normal faults, we suggest that further studies are necessary to test whether these veins are often of co-seismic origin. If so, they may become a unique and irreplaceable tool to unravel the seismic history and crustal-scale fluid circulation of active faults.

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Defining a mid-Holocene earthquake through speleoseismological and independent data: implications for the outer Central Apennines (Italy) seismotectonic framework

Solid Earth ◽

10.5194/se-8-161-2017 ◽

2017 ◽

Vol 8 (1) ◽

pp. 161-176 ◽

Cited By ~ 6

Author(s):

Alessandra Di Domenica ◽

Alberto Pizzi

Keyword(s):

Normal Fault ◽

Transitional Zone ◽

Quantitative Modeling ◽

Normal Faults ◽

Independent Data ◽

The West ◽

Central Apennines ◽

Strong Earthquakes ◽

Surrounding Areas ◽

Karst Conduit

Abstract. A speleoseismological study has been conducted in the Cavallone Cave, located in the easternmost carbonate sector of the Central Apennines (Maiella Massif), in a seismically active region interposed between the post-orogenic extensional domain, to the west, and the contractional one, to the east. The occurrence of active silent normal faults, to the west, close to blind thrusts, to the east, raises critical questions about the seismic hazard for this transitional zone. Large collapses of cave ceilings, fractures, broken speleothems with new re-growing stalagmites on their top, preferential orientation of fallen stalagmites and the absence of thin and long concretions have been observed in many portions of the karst conduit. This may indicate that the cave suffered sudden deformation events likely linked to the occurrence of past strong earthquakes. Radiocarbon dating and, above all, the robust correspondence with other coeval on-fault and off-fault geological data collected in surrounding areas outside the cave, provide important constraints for the individuation of a mid-Holocene paleoearthquake around 4.6–4.8 kyr BP. On the basis of the available paleoseismological data, possible seismogenic sources can be identified with the Sulmona normal fault and other active normal fault segments along its southern prosecution, which recorded synchronous strong paleoevents. Although the correlation between speleotectonic observations and quantitative modeling is disputed, studies on possible effects of earthquake on karstic landforms and features, when corroborated by independent data collected outside caves, can provide a useful contribution in discovering past earthquakes.

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Contrasting transient and steady-state rivers crossing active normal faults: new field observations from the Central Apennines, Italy

Basin Research ◽

10.1111/j.1365-2117.2007.00337.x ◽

2007 ◽

Vol 19 (4) ◽

pp. 529-556 ◽

Cited By ~ 95

Author(s):

Alexander C. Whittaker ◽

Patience A. Cowie ◽

Mikaël Attal ◽

Gregory E. Tucker ◽

Gerald P. Roberts

Keyword(s):

Steady State ◽

Normal Faults ◽

Field Observations ◽

Central Apennines ◽

Transient And Steady State

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Structural characterization of fault damage zones in carbonates (Central Apennines, Italy)

10.5194/egusphere-egu21-1525 ◽

2021 ◽

Author(s):

Miriana Chinello ◽

Michele Fondriest ◽

Giulio Di Toro

Keyword(s):

Fault Zone ◽

Hanging Wall ◽

Damage Zone ◽

Normal Fault ◽

Vertical Displacement ◽

Fault System ◽

Normal Faults ◽

Central Apennines ◽

Fault Surface ◽

Fracture Intensity

The Italian Central Apennines are one of the most seismically active areas in the Mediterranean (e.g., L&#8217;Aquila 2009, Mw 6.3 earthquake). The mainshocks and the aftershocks of these earthquake sequences propagate and often nucleate in fault zones cutting km-thick limestones and dolostones formations. An impressive feature of these faults is the presence, at their footwall, of few meters to hundreds of meters thick damage zones. However, the mechanism of formation of these damage zones and their role during (1) individual seismic ruptures (e.g., rupture arrest), (2) seismic sequences (e.g., aftershock evolution) and (3) seismic cycle (e.g., long term fault zone healing) are unknown. This limitation is also due to the lack of knowledge regarding the distribution, along strike and with depth, of damage with wall rock lithology, geometrical characteristics (fault length, inherited structures, etc.) and kinematic properties (cumulative displacement, strain rate, etc.) of the associated main faults.Previous high-resolution field structural surveys were performed on the Vado di Corno Fault Zone, a segment of the ca. 20 km long Campo Imperatore normal fault system, which accommodated ~ 1500 m of vertical displacement (Fondriest et al., 2020). The damage zone was up to 400 m thick and dominated by intensely fractured (1-2 cm spaced joints) dolomitized limestones with the thickest volumes at fault oversteps and where the fault cuts through an older thrust zone. Here we describe two minor faults located in the same area (Central Apennines), but with shorter length along strike. They both strike NNW-SSE and accommodated a vertical displacement of ~300 m.The Subequana Valley Fault is about 9 km long and consists of multiple segments disposed in an en-echelon array. The fault juxtaposes pelagic limestones at the footwall and quaternary deposits at the hanging wall. The damage zone is < 25 m &#160;thick &#160;and comprises fractured (1-2 cm spaced joints) limestones beds with decreasing fracture intensity moving away from the master fault. However, the damage zone thickness increases up to &#8764;100 m in proximity of subsidiary faults striking NNE-SSW. The latter could be reactivated inherited structures.The Monte Capo di Serre Fault is about 8 km long and characterized by a sharp ultra-polished master fault surface which cuts locally dolomitized Jurassic platform limestones. The damage zone is up to 120 m thick and cut by 10-20 cm spaced joints, but it reaches an higher fracture intensity where is cut by subsidiary, possibly inherited, faults striking NNE-SSW.Based on these preliminary observations, faults with similar displacement show comparable damage zone thicknesses. The most relevant damage zone thickness variations are related to geometrical complexities rather than changes in lithology (platform vs pelagic carbonates). &#160;In particular, the largest values of damage zone thickness and fracture intensity occur at fault overstep or are associated to inherited structures. The latter, by acting as strong or weak barriers (sensu Das and Aki, 1977) during the propagation of seismic ruptures, have a key role in the formation of damage zones and the growth of normal faults.

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Foreland-dipping normal faults in the inner edges of syn-orogenic basins: a case from the Central Apennines, Italy

Tectonophysics ◽

10.1016/s0040-1951(00)00229-8 ◽

2001 ◽

Vol 330 (3-4) ◽

pp. 211-224 ◽

Cited By ~ 33

Author(s):

V. Scisciani ◽

F. Calamita ◽

E. Tavarnelli ◽

G. Rusciadelli ◽

G.G. Ori ◽

...

Keyword(s):

Normal Faults ◽

Central Apennines

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Stable isotope evidence for contrasting paleofluid circulation in thrust faults and normal faults of the central Apennines, Italy

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jb900377 ◽

2001 ◽

Vol 106 (B5) ◽

pp. 8811-8825 ◽

Cited By ~ 53

Author(s):

F. Ghisetti ◽

D. L. Kirschner ◽

L. Vezzani ◽

F. Agosta

Keyword(s):

Stable Isotope ◽

Normal Faults ◽

Thrust Faults ◽

Central Apennines ◽

Isotope Evidence

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Dinaric up-thrusts in the Pliocene evolution of the Central Apennines thrust belt of Italy: the Montagna dei Fiori structure

Geological Magazine ◽

10.1017/s0016756821000613 ◽

2021 ◽

pp. 1-16

Author(s):

Fernando Calamita ◽

Paolo Pace ◽

Vittorio Scisciani ◽

Fabiana Properzi ◽

Mirko Francioni

Keyword(s):

Large Scale ◽

Quaternary Structure ◽

Regional Scale ◽

Normal Fault ◽

Structural Data ◽

Normal Faults ◽

Seismic Reflection Profile ◽

Thrust Belt ◽

Central Apennines ◽

Orogenic Belts

Abstract Several orogenic belts exhibit regional-scale anticlines characterized by prominent faults in their crestal/forelimb zone. These faults are also a common feature in the Neogene fold-and-thrust belt of the Apennines, where they have been contrastingly interpreted as younger-on-older thrust faults, large-scale strike-slip faults, and pre- or syn-thrusting normal faults. In this study, we analysed a NW–SE-trending fault (Montagna dei Fiori Fault) that affects the hinge-zone/forelimb of the Montagna dei Fiori Anticline. This fold is the outermost exposed contractional structure within the Pliocene–Quaternary antiformal stack of the outer Central Apennines. The integration of stratigraphic and structural data collected during a field geological survey enabled us to reconstruct a multiphase reactivation and deformation along the Montagna dei Fiori Fault. From the novel field data, a different interpretation for the evolution of the Montagna dei Fiori Fault is proposed. The fault originated as a Late Cretaceous – middle Miocene, NE-dipping, Dinaric up-thrust and was later reactivated, displaced and rotated during Pliocene Apennine thrusting and related folding, until assuming a present-day SW-dipping attitude with an apparent normal fault character. This newly proposed Dinaric origin of the Montagna dei Fiori structure is compared with an analogous subsurface example of a Palaeogene–Quaternary structure imaged by seismic reflection profile in the Adriatic foreland. The outcome of this combined field and subsurface investigation provides new elements to unravel the complex evolution of the Apennine thrust belt that developed at the expense of a previously deformed foreland, ahead of the advancing Dinaric chain.

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EVIDENCE FOR FAULT-VALVE BEHAVIOR IN ULTRACATACLASITES OF CARBONATE-HOSTED NORMAL FAULTS, CENTRAL APENNINES, ITALY

10.1130/abs/2019am-339492 ◽

2019 ◽

Author(s):

Jordan W. Wang ◽

◽

Juliet G. Crider ◽

Katharine W. Huntington ◽

Fabrizio Agosta

Keyword(s):

Normal Faults ◽

Central Apennines ◽

Fault Valve

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Defining a Mid-Holocene earthquake through speleoseismological and independent data: constraints for the outer Central Apennines (Italy) seismotectonic framework

10.5194/se-2016-77 ◽

2016 ◽

Author(s):

Alessandra Di Domenica ◽

Alberto Pizzi

Keyword(s):

Normal Fault ◽

Transitional Zone ◽

Normal Faults ◽

Independent Data ◽

The West ◽

Central Apennines ◽

Blind Thrust ◽

Causative Structure ◽

Surrounding Areas ◽

Data Constraints

Abstract. A speleoseismological study has been conducted in the Cavallone Cave, located in the easternmost carbonate sector of the Central Apennines (Maiella Massif), in a seismically active region interposed between the post-orogenic extensional domain, to the west, and the compressional one, to the east. The occurrence of active ''silent normal faults'', to the west, close to blind thrust, to the east, raises critical questions about the identification of the true seismogenic sources for this transitional zone. Large ceiling collapses, fractures, broken speleothems with new re-growing stalagmites on their top, preferential orientation of fallen stalagmites and absence of thin and long concretions have been observed in many portions of the conduit and may indicate that the cave suffered of sudden and catastrophic events likely linked to the occurrence of past strong earthquakes. Although controversies exist about the correlation between speleotectonic observations and quantitative modeling, speleotectonic studies, when corroborated by independent data collected outside caves, can play a fundamental role in discovering past earthquakes. Radiocarbon dating and, above all, the surprisingly correspondence with other coeval paleoseismological and geological data collected in surrounding areas outside the cave, provide important constraints for the individuation of a Mid-Holocene paleoearthquake around 4770 ± 30 yr BP and for the identification of the Sulmona normal fault as the most likely causative structure.

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