Francesco Muto

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).

Application and validation of bivariate GIS-based landslide susceptibility assessment for the Vitravo river catchment (Calabria, south Italy)

The Calabria (Southern Italy) region is characterized by many geological hazards among which landslides, due to the geological, geomorphological, and climatic characteristics, constitute one of the major cause of significant and widespread damage. The present work aims to exploit a bivariate statistics-based approach for drafting a landslide susceptibility map in a specific scenario of the region (the Vitravo River catchment) to provide a useful and easy tool for future land planning. Landslides have been detected through air-photo interpretation and field surveys, by identifying both the landslide detachment zones (LDZ) and landslide bodies; a geospatial database of predisposing factors has been constructed using the ESRI ArcView 3.2 GIS. The landslide susceptibility has been assessed by computing the weighting values (Wi) for each class of the predisposing factors (lithology, proximity to fault and drainage line, land use, slope angle, aspect, plan curvature), thus evaluating the distribution of the landslide detachment zones within each class. The extracted predisposing factors maps have then been re-classified on the basis of the calculated weighting values (Wi) and by means of overlay processes. Finally, the landslide susceptibility map has been considered by five classes. It has been determined that a high percentage (61%) of the study area is characterized by a high to very high degree of susceptibility; clay and marly lithologies, and slope exceeding 20° in inclination would be much prone to landsliding. Furthermore, in order to ascertain the proposed landslide susceptibility estimate, a validation procedure has been carried out, by splitting the landslide detachment zones into two groups: a training and a validation set. By means of the training set, the susceptibility map has first been produced; then, it has been compared with the validation set. As a result, a great majority of LDZ-validation set (85%) would be located in highly and very highly susceptible areas. The predictive power of the model is considered reliable, since more than 50% of the LDZ fall into 20% of the most susceptible areas. The reliability of the susceptibility map is also suggested by computing the SCAI index, true positive and false positive rates; nevertheless, the most susceptible areas are overestimated. As a whole, the results indicate that landslide susceptibility assessment based on a bivariate statistics-based method in a GIS environment may be useful for land planning policy, especially when considering its cost/benefit ratio and the need of using an easy tool.

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.

Landslide inventory map of north-eastern Calabria (South Italy)

Landslides are one of the most widespread natural hazards in many areas of Calabria region (Southern Italy), due to the combination of its peculiar geological, morphological, and climatic characteristics and very often to unsustainable land management. This study reports the reconnaissance and the characterization of landslides of north-eastern Calabria (south Italy). The landslide inventory map was obtained by combining field surveys with the analysis of topographic maps and multi-temporal air photos, taken in the period ranging from 1954 to 2006. This analysis has provided the spatial and temporal evolution of mass movements. The integration and elaboration of the data obtained in a GIS environment provided the inventory map of landslides on a scale 1:50,000. Landslides are widespread in the study area and play an important role in the present-day landscape evolution. A total of 1003 landslides were recognized, occupying a surface of 230.4 km2, about 30.5% of the whole study area. The landslides were mapped on the basis of the movement type, as follows: slides, flows, falls and complex landslides. Slide and complex type mass-movements are very common, and represent more than 87% of the landslides mapped. The pelitic lithologies show the highest density of landslides, mainly complex type. Multi-temporal air photo interpretation and field surveys provided data for distinguishing the state of activity of the landslides; therefore, 29% of the landslides mapped has been assessed active while the remaining 71% has been considered inactive. This kind of map is an useful tool for land planning policy. As all the data are digitized and stored in GIS database, this will provide the basic input needed to generate the landslide susceptibility assessments besides evaluate the landslide hazard and risk.

Facies analysis and depositional architecture of shelf-type deltas in the Crati Basin (Calabrian Arc, south Italy)

This study focuses on facies analysis and depositional architecture of the Arente shelf-type delta, located at the southernmost margin of the Pleistocene Crati Basin (northern Calabria, southern Italy). Tectonically-controlled Gilbert deltas are extensively discussed in the literature, whereas few works document shelf-type deltas and factors controlling sedimentation. This paper contributes to these issues, with a special focus on evaluating eustatic and tectonic control on depositional architecture also by considering the occurrence of coeval Gilbert-delta systems.The Arente delta complex represents part of the coarse-grained sediments presently exposed along the eastern margin of the Crati Basin. It was sourced from the rising Sila Massif to the E and shows an overall westerly progradation.Conventional sedimentological analysis allowed to distinguish seven different facies associations. Well-exposed sections, at the basin margin, generally show an overall upward transition, locally basinward, from mouth-bar conglomerates and sandstones, to deltafront sandstone, to offshore mudstones. Facies distribution and arrangement are interpreted as the record of a shoal-water fan delta.Depositional processes were clearly influenced by the high sediment input, with a dominance of hyperpycnal deposits.Based on the occurrence of a series of bounding surfaces indicating abrupt drowning stages, the Arente deltaic succession can be divided into 5 distinct transgressive-regressive sequences.The fining and the thinning upward trend of the whole succession and the stacked landward-stepping architecture of the transgressiveregressive sequences, i.e. the E-directed retrogradational behavior of the Arente delta complex indicate that.Tectonic subsidence provided the accommodation space for the deposition of the delta complex, for the marked local backstepping of the system, and for the progressive drowning of bedrock. Highfrequency sea level fluctuations led to the repeated arrangement of the facies associations; in particular, the stacking of the individual deltaic sequences separated by transgressive surfaces suggests amplitudes of eustatic sea-level changes of a few tens of metres, thus representative of a higher-order cyclicity. The differing internal architecture, if compared to the steeply-dipping foreset beds of the Gilbert-type delta cropping out to the N of the study area, is interpreted as due to a decrease in displacement toward the southern tip of the Crati system fault.

Vertical movements in the Ionian margin of the Sila Massif (Calabria, Italy)

Detailed geological-geomorphological investigations, carried out in the Ionian coastal belt between the Trionto River and the Colognati River, allowed us to set up a tectonic-sedimentary model of the northern flank of the Sila Massif during Pliocene-Pleistocene times. The study area is characterised by a distinct step-like topography displaying a well-preserved flight of coastal plain (alluvial/marine) terraces, arranged in five altimetric orders (T1 to T5). The deposition of sandy-clayey marine sediments of Middle Pliocene age ( CTSL Unit ) and beach sandstones grading upward to gray silty clays, referred to the Emilian-Sicilian ( Bisciglia Unit ) on the basis of micropaleontological analysis, has been related to a phase of subsidence, likely induced by the activity of E-W trending extensional faults. The Bisciglia Unit grades westward into conglomerates, sandstones and silty-clay sediments forming part of juxtaposed and superimposed deltaic (and subordinate alluvial/beach) deposits. A phase of subaerial landscape modelling, starting from the Middle Pleistocene, marks the end of subsidence and the onset of a rapid uplift which, interacting with eustatic sea-level changes, gave rise to the five orders of terraces. The uplift rate of the whole area, inferred by correlating the terrace surfaces with the paleoclimatic curve proposed by Bintanja et alii (2005), is 0.65 ± 0.1 mm yr −1 . However, the contemporaneous occurrence of extensional fault activity in the area induced variations in the uplift rates, which actually range between 0.52 and 0.88 mm yr _1 in relation to the distance from the fault trace. These data highlight the competing role of fault activity and regional uplift in controlling vertical movements and surface topography at the local scale.

Weathering grade and geotectonics of the western-central Mucone River basin (Calabria, Italy)

This paper illustrates the compilation of an engineering geological map based on structural architecture and weathering grade of crystalline rocks occurring in the central-western portions of the Mucone River basin (Sila Massif, Calabria, Italy). The map, drawn at 1:10,000 scale and covering an area of about 100 km2, was compiled by combining new geological and structural data with the results of a weathering-grade field survey. Five weathering classes, each characterized by comparable mechanical behaviour, have been mapped, from the class VI (residual and colluvial soils) to class II (slightly weathered rock). Both qualitative and semi-quantitative criteria (e.g. rock colour, discolouration processes, samples broken by hand and hammer, sound of the rock when it is struck by a geological hammer, Schmidt Hammer tests) were used to distinguish and map weathering-grade classes at outcrop scale. The thematic map presented in this paper aims to provide a useful tool for land planning policy, for the evaluation of geological and geotechnical hazard and for environmental and engineering perspectives of land use.

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.

Sourceland controls and dispersal pathways of Holocene muds from boreholes of the Ionian Basin, Calabria, southern Italy

Deep-marine muds were collected from two boreholes (Crati II and Neto VI) along the Ionian Calabrian Basin. The samples from the Crati II and the Neto VI boreholes show a similar mineralogical distribution; the marine muds contain mostly phyllosilicates, quartz, calcite, feldspars and dolomite. Traces of gypsum are present in a few samples. The Neto muds show higher concentrations of carbonates than the Crati muds; these contents are mainly related to recycling of the Neogene–Quaternary carbonate-rich marine deposits of the Crotone Basin, which mostly influences the composition of the Neto muds. The geochemical signatures of the muds mainly reflect a provenance characterized by felsic rocks with a minor, but not negligible, mafic supply. In particular, the hinterland composition of the Crati drainage area is on average more mafic in composition than the Neto drainage area. The higher mafic concentration of the Crati sample muds is probably related to the ophiolitiferous units that are exposed in the Crati drainage basin. The degree of source area weathering was most probably of low–moderate intensity because the Chemical Index of Alteration values for the studied muds range from 67 to 69. Furthermore, the low and constant Al/K and Rb/K ratios suggest low–moderate weathering without important fluctuations in weathering intensity. The Al 2 O 3 –TiO 2 –Zr ternary diagram and the values of the Index of Compositional Variability indicate that both the Neto and Crati muds are first-cycle, compositionally immature sediments, related to a tectonically active (collision) setting such as the Calabria–Peloritani Arc, where chemical weathering plays a minor role.

Seismotectonics and landslides of the Crati Graben (Calabrian Arc, Southern Italy)

ABSTRACT The Crati Graben is a depression of Plio-Holocene age mainly controlled by extensional N–S striking faults and WNW–ESE transcurrent faults, in its northern and southern extremity. It is characterized by high landslide susceptibility due to the particular geo-structural pattern and seismotectonic characters. Landslides involve many villages, infrastructure and food crops, bringing serious economic and social damage. The seismotectonic and landslides Main Map of the Crati Graben, described in this paper, represents an update in detail of the framework of landslide risk areas and shows the main active and recent faults of the Crati Graben. The landslides and the faults, have been identified and classified, originally at detail scale (1:5000) and, then, represented at 1:50,000 scale. The geo-structural and geomorphological data were analysed in a geographic information system. The work has revealed a correlation between the trend of faults with respect to the distribution of landslides and of the historical and instrumental seismicity. The work presents an updated knowledge framework of risk conditions of the study zone, where risk areas related to slope instability are hierarchically classified according to the destructive potential of landslides. This document may be therefore a useful reference in planning and prioritising in the design of interventions for the safety of slopes and waterways.