C. Invernizzi

Tectonic burial and 'young' (< 10 Ma) exhumation in the southern Apennines fold and thrust belt (Italy)

In the southern Apennines fold-and-thrust belt, thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km. The thrust belt is made of allochthonous sedimentary units that overlie a 6–8-km-thick, carbonate footwall succession. The latter, continuous with the foreland Apulian Platform, is deformed by reverse faults involving the underlying basement. Therefore, a switch from thin-skinned to thick-skinned thrusting occurred as the Apulian Platform carbonates—and the underlying thick continental lithosphere—were deformed during the latest shortening stages. Apatite fission track data, showing cooling ages ranging between 9.2 ± 1.0 and 1.5 ± 0.8 Ma, indicate that exhumation marks these late tectonic stages, probably initiating with the buttressing of the allochthonous wedge against the western margin of the Apulian Platform. Pliocene-Pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that, based on cross-section balancing and restoration, could be transferred to the base of the allochthon from the underlying thick-skinned structures. This suggests that emplacement of the allochthon above the western portion of the Apulian Platform carbonates was followed by gravitational readjustments within the allochthonous wedge, coeval—and partly associated with—thick-skinned shortening at depth. The related denudation processes are interpreted to have played a primary role in tectonic exhumation.

Structural signature of tectonic processes in the Calabrian Arc, southern Italy: Evidence from the oceanic‐derived Diamante‐Terranova unit

The Diamante-Terranova unit is an oceanic-derived element within the thrust and nappe structure of the northern sector of the Calabrian Arc. Its metamorphic and structural signature reveals a long history of SE dipping subduction and collision-related deformation of an oceanic lithospheric section underlying the narrow Diamante-Terranova basin. The deformation history of the Diamante-Terranova unit may be related to three main tectonic phases. The first one is characterized by a structural association which includes features that developed during a progressive deformation related to the evolution of a deep-seated shear zone. Kinematic indicators characterizing subduction-related structures clearly show a top-to-the-northwest sense of overthrust shear. The second tectonic phase that can be recognized in the area is characterized by structures that may be related to the onset of shear deformation induced by a postcollisional northeastward motion of the overriding plate. The third tectonic phase is recorded by brittle features related to the latest tectonic events affecting the Calabrian Arc during the opening of the Tyrrhenian Sea. Shear sense indicators and available radiometric and stratigraphic information, together with plate kinematic data, allowed us to infer the time evolution of this sector of the Calabrian Arc and to assess that the Diamante-Terranova unit cannot be considered as an “Eoalpine” element since its deformation, related to subduction-collision processes, occurred prior to the end of the Cretaceous.

Fault properties and fluid flow patterns from Quaternary faults in the Apennines, Italy

The study of Quaternary fault zones in the High Agri Valley (southern Italy) and in the axial zones of the central Apennines, allowed us to collect information on the permeability structure, fluid characteristics, and scaling properties of the main fault zones exposed in the area. Detailed structural mapping allowed us to derive the appropriate values of the fractal dimension characterising different active fault zone patterns and to evaluate the basic parameters needed for assessing the architecture and related permeability structure of the mapped faults. Scan line and scan area analysis helped in constraining the scaling properties of some of the attributes (i.e. fault zone thickness, fracture spacing etc.) of the main fault zones and in defining their validity range. Our results suggest that, in the Apennines, (i) extrapolation of the architectural indices of a fault zone is admissible over three orders of magnitude, and (ii) the composition of the analysed fluid inclusions and related homogenisation temperatures are associated with fault-driven fluid circulation from both superficial and deep (4–6 km) levels.

Fault zone fabrics and geofluid properties as indicators of rock deformation modes

Abstract In this paper we present the results of a geostructural study on active faults in central Italy, where seismogenic fault zones occur as part of a Quaternary network dissecting and/or inverting earlier tectonic features of the central Apennines fold and thrust belt. In our work we focus on the possibility of using structurally-oriented quantitative analysis of fault fabrics and fluid inclusion studies for assessing the hydraulic properties and scaling relations of fault zones in order to evaluate the role and effects of the interaction between rock and fluids in the brittle deformation of strained crustal rock volumes. The results of our study show that this approach is appropriate for (i) assessing the structural permeability of faulted and fractured rock volumes, (ii) defining the conduit/barrier behaviour of fault zones to fluid flow, (iii) mapping spatial variations of the fluid pressure across different fault segments, (iv) evaluating the maturity of a structural network and the degree of interaction of linked structural discontinuities, (v) assessing fluid composition and the conditions of deformation by means of microstructural and fluid inclusion data.

Thermal history of the Aragón-Béarn basin (Late Paleozoic, western Pyrenees, Spain); insights into basin tectonic evolution

Organic and inorganic thermal indicators throughout the Late Paleozoic sedimentary fill of the Aragon-Bearn Basin in the western Pyrenees, integrated with stratigraphic and structural data, point to a two-stage tectonic evolution:(i) High heat flow values and widespread magmatic intrusions driven by deeply rooted strike-slip faults characterized the first stage. This regime accompanied the rapid and localized deposition of the lower sedimentary succession and ended with uplift and erosion.(ii) The second stage was characterized by lower heat flow values, shallower strike-slip faults active during the deposition of an upper transgressive sedimentary succession and minor magmatic intrusions.The lower portion of the succession (Unidad Gris, Unidad de Transito and Unidad Roja Inferior, mainly Stephanian-Early Permian in age) records maximum temperatures between 170°C and 220°C as shown by clay mineral-based geothermometers (KI between 0.40 and 0.52°?2?, conversion of mixed layer illite-smectite to discrete illite), vitrinite reflectance (about 2.5%), and total homogenization temperatures from host-rock quartz cements between 160 and 180°C.The upper portion of the succession (Unidad Roja Superior, mainly Upper Permian in age) records maximum temperatures between 100-110° and 150°C as indicated by KI values between 0.57 and 0.94°?2?, illite content in mixed layer illite-smectite of 85-92%, and fluid inclusions in host-rock quartz-calcite cements.Local thermal maturity anomalies affected selected portions of the Late Paleozoic sedimentary succession with organic matter and clay minerals reaching respectively Ro%: 4.2-4.7% and KI up to 0.32°?2??in the lower sequence, and Ro% 2.9% in the upper sequence. These localized anomalies with respect to the basin thermal signature are the result of contact metamorphism related to the emplacement of magmatic intrusions across the sedimentary fill during two different magmatic events.

A space-time journey through the composite Conero Geosite (Marche, Italy): a tool for teaching Earth Sciences at school

This work is part of a PhD project devoted to promoting the study of Earth Sciences at schools by presenting significant geosites in the Marche Region. The Mount Conero geosite, with several outcrops and geological trails, offers teachers prime locations for showing the most interesting moments of the geological evolution of the region, from the Cretaceous to the Pleistocene, and can serve as a springboard for introducing a variety of geoscience topics related to the major themes of Earth sciences courses at schools. These outcrops also meet certain requirements for school field trips, in terms of logistics, appeal, availability of data, and they can be modulated for students of different ages. Teachers can avail themselves of general, specific, and interdisciplinary teaching material at different school levels (http://d7.unicam.it/teachingearthsciences/) for the field trips and class activities.

Thermal and Thermo-chronological Constraints to the Southern Apennines Evolution, Italy

A multidisciplinary approach for thermo-baric data acquisition is proposed along the southern Appennines, a key region of the Alpine orogen in the central Mediterranean area, including the remnants of a Cretaceous to Palaeogene accretionary complex. Ophiolite-bearing HP-LT tectonic units occur on top of the thrust pile. The underlying outcropping thrust sheets consist of Mesozoic and Cenozoic rocks derived from the sedimentary cover of the foreland plate (Apennine carbonate platform and Lagonegro pelagic units). These latter suffered, in some parts, HT-LT metamorphic conditions. We integrated independent thermal and thermo-chronological methods such as XRD analyses of clay mineral assemblages, fluid inclusion micro-thermometry, apatite fission tracks and vitrinite reflectance analyses, sampling both metamorphic and non methamorphic low-temperature successions. Our results indicate that a significant part of the sedimentary rocks exposed in the southern Apennines experienced substantial tectonic burial (locally in excess of 5 km), and confirm that, besides kinetics factors, a combination of methods allow to define thermo-cronological and, subordinately, pressure characteristics also for the HP-LT successions. Finally, in the northern sector of the area (Lucania), a break in thermal maturity from the Apennine carbonate platform and Lagonegro pelagic derived units has been documented, and along-strike variations of thermal maturity also emerged.

Structural, Morphotectonic and Thermo-chronological Constraints to the Late Miocene-quaternary Tectonic Evolution and Exhumation in the Southern Apennines, Italy

In the southern Apennines fold and thrust belt, thermal indicators record exhumation of sedimentary units from depths locally in excess of 5 km. The belt is made of allochthonous sedimentary units that overly a 6–8 km thick, carbonate footwall succession. The latter is deformed by reverse faults involving the underlying basement. Therefore, a switch from thin-skinned to thick-skinned thrusting occurred as the Apulian Platform carbonates - and the underlying continental lithosphere - were deformed during the latest shortening stages. Apatite fission track data, with cooling ages ranging between 9.2 ± 1.0 and 1.5 ± 0.8 Ma, indicate that exhumation marks these late tectonic stages, probably initiating with the buttressing of the allochthonous wedge against the western margin of the Apulian Platform. Pliocene-Pleistocene foreland advancing of the allochthonous units exceeds the total amount of slip that could be transferred to the base of the allochthon from the underlying thick-skinned structures. This suggests that emplacement of the allochthon above the western portion of the Apulian Platform carbonates was followed by gravitational readjustments within the allochthonous wedge, coeval - and partly associated with - thick-skinned shortening at depth. The related denudation processes have played a primary role in tectonic exhumation.