Vincenzo Tripodi

Link between thrust tectonics and sedimentation processes of stratigraphic sequences from the southern Apennines foreland basin system, Italy

We discuss here tectonics and sedimentation processes occurring during continent-continent collision and relationships between accretionary processes on overplate, flexural lithosphere on underplate and related controls on clastic sedimentation in developing foreland basin systems. This paper focuses on and clastic sedimentation developed during the sequential history of the southern Italy orogenic system. These clastic trends, covering a large time span from pre-collisional Early Mesozoic to the present, may contribute: (1) to the paleogeographic and paleotectonic reconstructions of the southern Italy portions of the western Mediterranean orogen, and (2) to the general models of complex relationships between clastic sedimentation and paleotectonic history of other major orogens. The evolutionary record of Earth’s processes preserved in the form of sedimentary rocks has been pivotal in paleogeographical and paleotectonic reconstructions of source/basin systems. Compositional trends of clastic strata through space and time are used to infer the structural history of adjacent mountain belts and to monitor the key geodynamic changes during orogenic processes (e.g. Dickinson, 1985, 1988; Critelli & Ingersoll, 1994; Critelli, 1999). The controls on the composition and dispersal pathways of clastic strata along the convergent plate margins have long been debated (e.g. Dickinson, 1988; Ingersoll et alii, 1995). Clastic infilling of sedimentary basins in orogenic systems have been used as important indicators of tectonic activity and climatic changes. In the orogenic systems, clastic sedimentation may record the accretionary processes, the accomodation of the thrust units, and the flexural features of the foreland plate. The development of an orogenic wedge during continental collision results in thickening of the crust. The excess mass of this thickened crust acts as a load on the underthrust plate, causing it to be flexed downwards close to the load, so developing a foreland basin (e.g. Beaumont, 1981; Sinclair and Allen, 1992). During plate convergence, the vertically acting load of the mountain belt migrates over the foreland plate, thus resulting in the migration of the associated foreland basin. The foreland is the region between the front of a thrust belt and the adjacent craton (e.g. Dickinson, 1974; Bally and Snelson, 1980; Allen et alii, 1986; Miall, 1995). Large volumes of clastic sediment are derived from erosion of the thrust belt and deposited in the foreland basin. The foreland basin generally is defined as an elongate trough that forms between a linear contractional orogenic belt and the stable craton, mainly in response to flexural subsidence caused by thrust-sheet loading in the orogen.Foreland basin stratigraphy records tectonic, eustatic, and climatic changes at convergent plate margins (e.g. Miall, 1995). The formation of unconformities is the results of the interplay of temporal variations in the erosion and lateral progradation rates of the orogenic wedge, as well as tectonic and eustatic sea-level changes (e.g. Beaumont, 1981; Jordan, 1981; Schedl & Wiltsc hko, 1984; Peper et alii, 1995).

Structural style and tectono-stratigraphic evolution of the Neogene–Quaternary Siderno Basin, southern Calabrian Arc, Italy

The Neogene–Quaternary Siderno Basin is located in the southern Calabrian Arc, along an E–W transect including the Ionian side and part of the Tyrrhenian margin. The orogenic belt was generated by ongoing northward subduction of Ionian oceanic lithosphere beginning in the Early Cretaceous. Since the Oligocene, the area has experienced complex tectonics, including NW–SE-oriented pull-apart basins. The forearc region contains >2000 m of Oligocene-to-Quaternary strata that cover pre-Tertiary rocks. The succession forms an E-dipping monocline, with tectonic growth structures increasing upward. Erosional truncations and thickness variations suggest a different evolution for the Siderno Basin, which in comparison with northern and southern parts of the Ionian accretionary wedge, evolved differently during the Serravallian–Tortonian stages. NW–SE and NE–SW fault systems are dominant, the first exhibiting strike–slip and normal kinematics in the Nicotera–Gioiosa and Molochio–Antonimina fault zones. These structures were active during infilling of the Neogene basin, and represent a complex transfer zone. The NE–SW system shows two types of tectonic kinematics: (1) a compressive stage, with NW–SE-orientated shortening, responsible for inversion tectonics documented by east-verging folds, thrusts, and back-thrusts, and (2) emplacement of the variegated clay during the Langhian, which is related to back-thrust propagation. The strike–slip accommodated stress generated in the accretionary prism in response to subduction of Ionian lithosphere and progradation of the accretionary front of the Calabrian forearc.

Neogene tectonostratigraphic evolution of allochthonous terranes in the eastern Calabrian foreland (southern Italy)

Along the Ionian side of the Calabrian Arc, Neogene-Quaternary successions overlie the Hercynian basement made up of crystalline-metamorphic tectonic units and their Mesozoic-Tertiary cover. The Neogene successions rest unconformably along the eastern border of the Sila Massif and form the Neogene basin fills. In the external portion of basins, Oligocene-Lower to Middle Miocene clastic successions, overling the variegated clay of the Sicilide Complex, outcrop. The Miocene-Quaternary evolution of the northern Calabria was mainly associated with the accrectionary processes creating Miocene wedge-top depozones onto the growing orogenic belt and flexed Adria passive margin. Middle Miocene deposits accumulated in longitudinal wedge-top depozones of the Calabrian foreland-basin system, partitioned into three depocentres: the Rossano, Ciro, and Crotone basins. The surface, subsurface and aerial-photo analyses has provided new geological data, which better define the architecture and development of the allochthonous terranes outcropping in the northeastern wedge-top basins of the Calabrian Arc. The main onland outcrop of allochthonous units is represented by the so-called Cariati Nappe. Structural investigations allowed to characterize the surface and subsurface tectonic structures detailing the style and timing of the Cariati Nappe emplacement. This structure consists of a complex NW-SE oriented back-thrust (top to the west) propagated starting from the late Tortonian time. During Messinian-Pleistocene the allochthonous terranes were involved and reworked by left-lateral NW-SE oriented transpressive fault zones. Progressive propagation of these transpressive structures compartmentalised pre-Messinian formerly continuous basin, creating distinct asymmetric depocentres during the Messinian and Pliocene. The entire Ionian Calabrian margin experienced accretion during the Neogene in consequence of which portion of Varicoulered Clays, overlain by Oligocene-Miocene successions, were extruded and emplaced into the wedge-top basins.

Petro-structural geology of the Eastern Aspromonte Massif crystalline basement (southern Italy-Calabria): an example of interoperable geo-data management from thin section – to field scale

The presented maps provide an example of the synoptic display of multi-scale geological features characterizing the tectono-metamorphic evolution of the crystalline basement terranes in a poly-orogenic-multistadial evolutionary scenario. The petro-structural map of the eastern Aspromonte Massif (southern Calabrian Peloritani Orogen) is characterized by a nappe-like edifice composed by the superimposition of three crystalline basement tectonic units which, sharing the same Alpine-Apennine reworking, underwent a different metamorphic evolution, mostly derived from the Hercynian orogenic cycle. This geological framework is completed by the suture deposition of a Oligocene-Miocene syn-orogenic clastic formation, partly roofed by the back-thrusting of a clay-rich mélange. In order to understand the potential relationships within the complex dataset deriving from the geological investigations of this crystalline basement area, a geo-database, capable of handling multi-scale information from field-derived structural data (i.e. foliation, lineation, fold- and fault-related structures) to micro-scale derived ones (i.e. thin-section analysis, electron microscope and microprobe investigations, thermodynamic modeling outputs) has been constructed, according to the international standards using the Geo-Scientific Markup Language developed by the Commission for the Management and Application of Geo-science Information. Proposed outputs will show the relationships between field-related geological features, showing collected samples and the subsequent laboratory investigations. These are fundamental to achieving reliable results in geological contexts, such as those for reconstructing the tectono-metamorphic evolution of crystalline basement terrains.

Tectono-stratigraphic architecture of the Ionian piedmont between the Arso Stream and Nicà River catchments (Calabria, Southern Italy)

ABSTRACT Along the northern Ionian margin of Calabria, three Neogene basins comprise wedge-top depozones containing syntectonic deposits which cover the frontal part of the fold-thrust belt. One of the best exposed onshore allochthonous siliciclastic successions is represented by the Cariati Nappe, cropping out in the Cirò Basin. Field geological mapping and aerial interpretations were used to characterize the stratigraphy and tectonics of the area between the Arso Stream and Nicà River catchments (about 170 km2), including a Paleozoic metamorphic basement complex unconformably overlain by Upper Oligocene to Quaternary siliciclastic deposits and minor carbonates. This paper presents a 1:25,000 scale map of the Ionian study area, providing lithological and structural data towards reconstructing its tectono-sedimentary evolution.

Transition from strike-slip to extensional tectonics in the Plio-Pleistocene Catanzaro Trough (Calabria, south Italy)

The Catanzaro Trough (South Italy) is a Neogene-Quaternary sedimentary basin developed between the Serre and the Sila Massif, located in the central Calabrian Arc. Since Miocene, the study area experienced different tectonic phases, resulting confined by both longitudinal and transversal faults systems.Combining of land geo-structural with marine geophysical data was performed a detailed analysis of processes that during last 5 My have controlled the evolution of western portion of the Catanzaro Trough.Sedimentary basin hosted by the Catanzaro Trough is controlled, mainly, by NW–SE and NE–SW oriented fault systems. The data analysis allowed us to state the activity of NW-SE oriented faults with strike slip and oblique kinematics related to the opening of a WNW–ESE-oriented paleo-strait connecting the Tyrrhenian area to the Ionian Sea. The NW-SE trending faults have acted since Miocene as edges of a transfer zone, and represent elements of tectonic accommodation between northern and southern Calabrian Arc.The structural framework is further complicated by the activation of the NE-SW striking normal faults, arranged as a graben-type system, which since Middle Pleistocene segment the western Catanzaro Trough.Thanks to this multidisciplinary approach we are able to provide a more reliable and detailed structural frame of the central Calabria segment, providing new elements about recent activity of faults, and giving a further contribution for the seismogenetic potential assessment of an area historically considered with the highest earthquake and tsunami risk throughout Italy.

Tectono-stratigraphic evolution of southern margin of the Crotone Basin (Calabria, south Italy)

The Crotone Basins (CB) (Zecchin et al., 2013 and references therein) is located in the eastern sectors of the Sila Massif. The CB depicts the Neogene-Quaternary foreland basin of central Mediterranean region. The study area is influenced by different set of NW-SE major transcurrent faults and their antithetic lineaments which show alternating episodes of transtensional and transpressional faulting. Southwestern sector of the basin was characterized by three main fault patterns: 1) Active since Serravallian, NW-SE oriented faults bordering the CB to the west and with a left-lateral strike slip kinematics at the first stage. This transtensional phase has produced the basin opening, filled by coarse-grained, sand, clay and evaporitic deposits. 2) To the central part of the study area, Miocene deposits was displaced by NNW-SSE and NE-SW oriented faults, this pattern displays a dextral transpressional kinematic which seems to replace extensional kinematic giving rise to local inversion of former basins.3) The CB experienced a new extensional phase along N-S or NNW- SSE oriented normal faults, starting from the Middle Pleistocene period.