Bruno D'Argenio

Active fragmentation of Adria, the north African promontory, central Mediterranean orogen

Global Positioning System (GPS) velocities indicate that Adria no longer behaves as a rigid tectonic indenter into southern Europe and is divided into northwestern and southeastern velocity domains. Differential motions are recognized in a velocity field determined from the Peri-Tyrrhenian Geodetic Array (PTGA) and International GPS Service (IGS) sites in the circum-Tyrrhenian region of the central Mediterranean and published GPS velocities from the eastern Adriatic coast. In a fixed Eurasian reference frame, PTGA and IGS site velocities in Sicily and southern Italy are as much as 10 mm/yr in a northward direction, similar to GPS velocities along the eastern coast of the Adriatic Sea. In contrast, velocities in northern Italy are small or statistically insignificant and similar to velocities in Sardinia and Corsica outboard of western Adria. The tectonic boundary dividing Adria is seismically active and passes around the southern and eastern margins of the Tyrrhenian Basin, crosses central Italy, extends into the Adriatic Sea, and follows the western margin of the Dinaride tectonic belt north to the Gulf of Venice. The eastern margin of Adria is approximately located and follows the axis of the central Dinaric Alps southeast to the Hellenic arc. Southeastern Adria has a velocity related to northward motion of Africa, whereas northwestern Adria has negligible differential motion in the Eurasian frame and now is part of the Alpine collage of southern Europe.

Large-scale longitudinal extension in the southern Apennines contractional belt, Italy

During late Cenozoic thrusting, the interior of the peri-Tyrrhenian orogenic belt in the southern Apennines underwent two episodes of nearly orthogonal extension. Early extension was oriented subparallel to the axis of the tectonic belt and formed in response to progressive thrust-belt arcuation. The length of the tectonic belt increased by ∼50%, and the longitudinal strain was accommodated by low-angle normal faults concentrated in tectonic domains recording up to 150%-200% extension. Younger extension, oriented at a high angle to the orogen, was accompanied by Pliocene-Pleistocene uplift and by southeasterly migration of Tyrrhenian Sea rifting.

Tectonic history of the Lagonegro Domain and Southern Apennine thrust belt evolution

Abstract The tectonic history of the Lagonegro Domain in Southern Italy is an intriguing topic for the Mesozoic Mediterranean paleogeography and is important for reconstructions of the Tethys. Previous interpretations postulate the paleogeographic position of a deep Lagonegro-Molise-(Sicilide) basinal domain between the external Apulia carbonate platform to the east, and the internal Apenninic carbonate platform (i.e. the Alburno-Cervati-Maddalena Mountains) to the west. A second and separate deep basin more to the west was the home of the Liguride units which cover extensive areas of the Southern Apennines. Following an extensive review of previously published concepts and on the base of the structural interpretation of the Southern Apennines thrust belt using additional subsurface data and extensive field mapping, the authors now suggest that all deep basinal units of the Southern Apennines, i.e. the Ligurides, the Lagonegro units and the Molise-Sicilide units, derive from internal areas located to the west with respect to a coeval wide carbonate platform-slope-shallow-basin complex which, in its pre-Middle Miocene reconstruction, extended from Apulia well beyond the present-day Tyrrhenian coast of Southern Italy. The basinal units were first assembled as an accretionary wedge and overthrusted during the Late Miocene over the carbonate platform-slope-shallow-basin complex. The Liguride-Lagonegro-Molise-(Sicilide) accretionary wedge was later cut by an envelopment thrust which overthrust the previously underlying platform complex over the previously emplaced complex accretionary wedge. Our hypothesis in part revives an old concept proposed by Selli (1962) and requires further testing and research. We conclude that paleogeographic reconstructions of the Southern Apennines and the Mediterranean Tethys are still in a state of flux.

Eustatic cycles and tectonics in the Cretaceous shallow Tethys, Central-Southern Apennines

Carbonate platforms bordering the Tethyan margins carry a distinct periodic signal that can be related to Jurassic-Cretaceous climate and eustatism. They yield a rich archive of information, including the tectonics affecting the platforms at regional (subsidence) as well as at «local» (uplift) scale, at a time scale between 104 and 105/106 years (order of magnitude). In Central and Southern Italy, we have analyzed at centimetre scale, along well exposed sections and in bore cores, textures and early diagenetic features of Cretaceous carbonate platform deposits that evidence oscillations in which a hierarchy of cycles (elementary cycles, bundles and super bundles) has been recognized. Eustatic-climatic, high-frequency changes, linked to the Earth’s orbital perturbations, have been considered at the origin of this hierarchy, where the elementary cycles record the precession and/or the obliquity periodicities, while the bundles and super bundles record the short- and long-eccentricity, respectively. These orbital cycles are, in turn, superimposed on lower-frequency cycles (Trangressive/Regressive Facies Trends, T/RFTs). Adopting a sequence stratigraphy approach, the super bundles and the T/RFTs have been interpreted in terms of depositional sequences and used for high-resolution, long-distance (regional to supraregional) correlation, as well as for assembling orbital chronostratigraphic diagrams which quantify the minimum time required for each succession to stack up. Moreover, we have observed that a number of gaps are randomly intercalated in the various sections so that the high-precision correlation of distant intervals rises the problem of explaining their local absence. To reconcile these discrepancies, we propose a tectonic mechanism, already used to explain the stratigraphic gaps related to bauxitic horizons intercalated up section in the same stratal successions. Namely we postulate that the action of transient lithospheric bulges (few meters to tens of meters in elevation, few to several tens of kilometres across), arising from distant compressional or extensional tectonics, may give an explanation for the stratigraphic architecture characterizing the cyclic organization of the lower Cretaceous shallow-water carbonates. In conclusion, we assume that while the eustatic oscillations, driven by orbital and allied climatic variations, follow high-frequency composite rhythms of few tens to few thousand years (Milankovitch periodicities), the regularity of the subsidence is locally modified by transient lithospheric bulges, that result in increase (lows) and decrease (ups) of subsidence (and hence variation of rate of sediment deposited), up to the emersion of more or less large areas evidenced by omission of strata as well as by paleokarst and bauxites.

The Barremian-Aptian shallow-marine carbonates of Monte Faito and of Santa Maria bore cores (central-southern Apennines, Italy). Regional correlation based on cyclostratigraphy

In the last twenty years, high-resolution (cm scale) studies of several Cretaceous carbonate platform successions in centralsouthern Italy have demonstrated that they carry clear evidence ofastronomically controlled eustatic oscillations refl ected on their hierarchical stacking patterns (elementary cycles, bundles and superbundles) and exhibit a sequence-stratigraphic configuration, that is well evident in their superbundles (long eccentricity cycles) as well as in the composite mode of their aggradational pattern, laterally consistent also at more than 100 km distance. Here are presented the centimetre-scale facies analysis of the S. Maria 6 and 4 Agip bore cores (east of Maiella Mountain, Abruzzi region, Early Barremian- Late Aptian in age) and of the Monte Faito section (Monti Lattari, Campania Region, Barremian – Early Aptian in age). Taking into account the cyclic stacking patterns of the lithofacies and their grouping as well as of the early diagenetic features, the environmental oscillations have been constrained in well defi ned time intervals, typical of the Milankovitch periodicities (from ≈ 20 to ≈ 400ky).Based on cyclostratigraphy and sequence stratigraphy criteria and using appropriate biostratigraphic, isotopic and paleomagnetic markers, high-resolution physical correlations (precision 100 ky) have been traced at regional scale among S. Maria composite core, Monte Faito and the previous studied Monte Raggeto (Monte Maggiore) sections. A chronostratigraphic diagram has been assembled for each of the above sections showing that bundles may be locally missing. Moreover, a Barremian-Aptian composite orbital chronostratigraphy has been assembled suggesting the minimum time duration recorded in the considered interval, so that a regional sea-level oscillations history may be restored with a precision of ≤400 ky. On these bases, a minimum duration of 5.2 my for the Barremian interval (13 superbundles) has been estimated, close to the 5 my calculated for the whole Barremian from OGG et alii (2008). These results show as cyclostratigraphy of carbonate platform sequences, integrated with other stratigraphic methodologies and high-precision long distance correlations, is a valid tool to estimate the time duration of stratigraphic intervals and to assemble a floating orbital time scale.

Travertines of central and southern Italy

This is a short presentation of central and southern Italy travertine deposits based on several case histories analyzed in the last decades. Travertines are freshwater carbonate sediments forming in miniature depositional systems and are originated by precipitation from fluvial or spring waters. They display peculiar characteristics, like the ability to modify the morphology of their substrate, and to give rise commonly to “small” sedimentary bodies. Parent water temperature is a key factor in these deposits: high values bring on elevated carbonate precipitation rates and a decrease of abundance, size, and diversity of the eukaryotic organisms colonizing the depositional sites, while the decrease of temperature has an opposite outcome. This allows to distinguish between thermal- and ambient-water travertines (the latter often referred to as calcareous tufa), the transition between these two end-members being often gradual. The space-time evolution of the above sediments tends to modify the original substrate morphology, giving origin to different sedimentary environments (slope, shallow-lake/swamp, rapid/waterfall). Owing to their areal and vertical distribution, Italian travertines build terraced bodies whose upward growth is punctuated by recurrent erosional and/or non depositional discontinuities. The systematic (cyclic?) alternation of periods of calcium carbonate precipitation and starvation intervals suggests allocyclic regulation of climatic origin, even though autocyclic control mechanisms (sometimes including volcanism and/or tectonics) have to be also taken into account locally.

The geological map n. 465 Isola di Procida (scale 1:50.000): an example of cartographic representation of marine areas in the Campania offshore

In the last decade the Geomare Sud Institute, National Research Council of Italy, now Institute of Coastal Marine Environment has carried out a marine geological survey of the Campania Region (CARG Project) for the construction of experimental geological maps committed from the National Geological Survey of Italy, now APAT (Agency for the Protection of the Environment and the Technical Services). The start-up of the project has been dedicated to the data acquisition for the marine sector of the geological maps n. 465 Procida, n. 466 Sorrento, n. 467 Salerno and the maps n. 484 Capri and n. 485 Termini within the 200 m isobath. Several geological and geophysical surveys of the continental shelf and slope of the Naples Bay have been carried out to realize the geological map n. 465 Procida, including the most part of the gulf. A high-resolution Multibeam bathymetry of the Naples Bay coupled with Sidescan Sonar profiles allowed for the construction of a marine DEM, giving a detailed image of the morpho-structures at the sea bottom and realization of geological maps, varying in scale from 1:50.000 to 1:10.000. The stratigraphic architecture of the Naples Bay has been controlled by volcano-tectonic processes, preventing a simple application of seismic and sequence stratigraphic techniques, strongly recommended by the guidelines for the redaction of marine geologic cartography. The realized cartographic approach, however experimental, is based on the recognition of laterally coeval depositional systems, representing portions of systems tracts of the Late Quaternary Depositional Sequence (SDTQ). The marine geological map shows the distribution of several lithostratigraphic units cropping out at the sea bottom and of the main morphological lineaments, based on the CARG guidelines for the realization of marine cartography. In this way, we tried to realize an integration between classical stratigraphic approach, sequence stratigraphic approach and characterization of present-day and recent depositional systems.