Mario Tramontana

Structural and sedimentary features in the Tyrrhenian margin off Campania, Southern Italy

Abstract The utilization of multichannel seismic reflection profiles permits the identification of the generally E-W trending Miocene orogenic and Plio-Quaternary post-orogenic features of Apennine (NW-SE) and anti-Apennine (NE-SW) trends in the Campanian margin. The former features are constituted by carbonate and/or allochthonous sheets which were thrust mainly towards the north and northeast during the Miocene tectogenetic phases. The latter are represented by extensional structures which affected the orogenic features during Plio-Quaternary times. The anti-Apennine tectonic trend is responsible for the recent (Late Pliocene—Quaternary) and remarkable block-faulting differential subsidence of the southern margin, as well as for its present morphology. The ragged and disconnected pattern of the allochthonous units over the present-day slope and their accumulation underneath the shelf area suggest that they are the result of gravitational gliding tectonics. Gravity cores and 3.5-kHz subbottom profiles indicate that the Salerno Trough and Capri Basin areas are characterized by a particular neotectonic mobility; this is proved by the thick and coarse-grained sediment accumulation from steep relief produced by block faulting. This faulting created uplift belts serving as sediment source.

The age of the oceanic accretionary wedge and onset of continental collision in the Sicilian Maghrebian Chain

New biostratigraphic data from the formations unconformably lying above the tectonic units resulting from the Flysch Basin Domain (FBD) in the Sicilian Maghrebids are here reported. The FBD constituted a southern branch of the western Tethys, separating during the Jurassic to Paleogene a Mesomediterranean Microplate from the African Plate. The age of the youngest sediments involved in the nappes and that of the unconformable terrains deposited in thrust-top basins on these tectonic units, allow to define both the age of deformation of the oceanic realm and the onset of the continental collision. The deformation migrated from internal to external areas of FBD starting from the latest Burdigalian-Langhian to Serravallian. Therefore, the previously proposed Eocene-Oligocene mesoalpine deformation of the Maghrebian FBD cannot be supported. The continental collision started during the Serravallian and it was accomplished in the late Tortonian, when clastic deposits sealed the boundaries of the tectonic units originated from all the paleogeographic domains of the Maghrebian Chain. The steps of the tectonic evolution in the Sicilian Maghrebids are now very well constrained and the proposed tectonic evolution may be extended to the whole Maghrebian Chain, as far as to the western Betic Cordilleras and to the southern Apennines, where most of the tectonic events show highly similar features and ages.

Active deformation in the frontal part of the Northern Apennines: insights from the lower Metauro River basin area (northern Marche, Italy) and adjacent Adriatic off-shore

Abstract An integration of seismological data with geological and geomorphological information aided by seismic interpretation was performed to characterise the Quaternary tectonic evolution of the Metauro River basin area (northern Marche) and adjacent off-shore sector of the external Northern Apennines. On-shore, along the Adriatic coast, the youngest age of thrusting and folding post-dates the Early-Middle Pliocene, while Pleistocene deposits appear to be, at least in part, not involved in the deformation. Recent (i.e. post-thrusting) tectonic structures have been recognised both in pre-Quaternary substratum rocks and in Upper Quaternary continental deposits (Upper Pleistocene terrace alluvium, Upper Pleistocene–Holocene slope deposits). These faults are all compatible with a WSW–ENE oriented extension. In the Metauro River basin area, preserved flights of stream terraces have been categorised according to the presence or absence of alluvial suites in relationship to each terrace level. Here, based on both the heights above the valley floor and the areal distribution of stream terraces, a generalised vertical tectonic uplift can be inferred, particularly during the Middle–Late Pleistocene. Moreover, the along-valley distribution of stream terraces provides further constraints on the age of thrusting and folding. In fact, the reconstructed terrace-levels are substantially parallel, and no evidence for any significant deformation by fold activity has been recognised. Local deformation displayed by both terrace surfaces and alluvial/slope-waste deposits suggests, instead, the intervening of some minor differential movements associated with the generalised uplift and/or to Middle–Late Pleistocene normal faulting. Their occurrence appears anyhow to be unrelated with the pattern of folds and associated thrusts. The present-day seismic activity of the study area was considered by analysing 83 seismic events that occurred from 1987 to 2000. The epicentre distribution is very scattered, and depths are generally comprised within the first 20 km of the crust, clustering between 0 and 15 km. Most of the events have magnitude

High-Mg Tertiary basalts in Southern Sardinia (Italy)

Abstract High-Mg basaltic pillow lavas, important for an understanding of the petrogenetic evolution of the Tertiary volcanism of Sardinia, have recently been recognized in the lower part of the Early-Burdigalian volcano-sedimentary succession of the Villanovaforru (VF) area (Southern Sardinian Trough). Their textures vary from porphyritic to highly phyric types (doleritic) and the paragenesis is represented by Pl+Ol+Cpx±Opx±Opq. These basalts are sub-alkaline with a tholeiitic tendency; they display high MgO (mg-number 64–68), high Ni and Cr contents and their geochemical features are related to subduction-related magmas, with large-ion lithophile element enrichment and negative Nb, Zr and Ce spikes in mantle-normalized diagrams. The mineralogical and geochemical characteristics indicate that the VF basalts crystallized from primitive magmas within an extension-dominated tectonic setting. The presence of primitive basalts suggests crustal thinning in association with the Burdigalian extensional tectonics affecting the Sardinian Trough.

The Lower Miocene volcaniclastic sedimentation in the Sicilian sector of the Maghrebian Flysch Basin: geodynamic implications

Abstract Volcaniclastic debris-rich formations, characterising the Troina–Tusa Unit in the Sicilian Maghrebian Chain, are examined. The Troina–Tusa Unit terrains sedimented in the Maghrebian Flysch Basin, which, from Jurassic to Early Miocene, constituted the southernmost branch of the Western Tethys, located between Africa and the Mesomediterranean Terrane margins. New field, biostratigraphic and petrographic data enable a reconstruction of the palaeogeographic and structural evolution of the Flysch Basin immediately before its deformation. All the studied formations transpired to be Burdigalian in age. The sandstone compositions, showing different source areas (magmatic arc, recycled orogen and continental block), indicate a provenance for the clastic material from a crystalline basement with an active volcanic arc, replaced by a remnant volcanic arc, which was rapidly completely eroded. The source area that has been considered is Sardinia, where Upper Oligocene–Aquitanian calc-alkaline volcanites are widespread, but the sedimentological characteristics and the Burdigalian age do not fit with this provenance. The Burdigalian calc-alkaline arc should be located on the internal side of the Troina–Tusa Basin, above the already stacked Peloritanian units. A migration of the volcanic activity, connected with the subduction plain roll-back, can be envisaged from the Sardinia Block to the Peloritanian Chain, this latter still docked to the Sardinia–Corsica massif.

New biostratigraphic and petrographic data from the Poggio Carnaio Sandstone Fm (Val Marecchia Nappe): insights into the tectonic evolution of the Northern Apennines

In the Northern Apennines, the Poggio Carnaio Sandstone Formation consists of sandy-clayey turbidites, cropping out in the northernmost corner of the Val Marecchia Nappe.The formation has been considered Oligocene in age and is commonly interpreted as an Epiligurian unit, unconformably deposited above the Val Marecchia Nappe during its transport towards the Adriatic foreland.The Poggio Carnaio Sandstone Fm rests on the Argille Varicolori Fm of the Val Marecchia Nappe, but field data do not allow it to be recognized wherever it abruptly replaces the pelagic sediments of the Argille Varicolori Fm, thus testifying to the foredeep evolution of the basin, or where it unconformably overlies this latter formation.Nannofossil assemblages are characterized by abundant reworked Cretaceous and Paleogene taxa and by some taxa, whose first occurrence is reported in the upper part of the NN4 Zone = upper part of the CN3 Zone. Therefore the formation must be considered not older than Langhian.Detrital modes of arenites revealed a quartz-feldspathic composition and the lithic component includes mainly metamorphic fragments and minor plutonic, sedimentary, ophiolithic and volcanic clasts. The presence of clasts of garnet, sillimanite, hornblende and glaucophane is significant. Biostratigraphic as well as petrographic data agree with the interpretation of the Poggio Carnaio Sandstone Fm as an Epiligurian succession.Rock fragments indicate source areas characterized by Ligurian-, Pennidic- and Australpine-type units. Sedimentary facies and textural features of arenites, revealing a rapid erosion and deposition of clasts in a basin close to the source area of the clastic supply, indicate that the Alps cannot be considered as the source area of these arenites, as frequently argued for many North-Apennine clastic formations. Ligurian-, Pennidic- and Australpine-type units were located close to the Poggio Carnaio Sandstone basin, probably representing the geometrically highest units of the Palaeo-Apennine Chain.

Platform-to-basin facies transition and tectono-sedimentary processes in the Jurassic deposits of the Furlo area (Umbria-Marche Apennines, Italy)

The Jurassic successions of the Furlo area (Northern Marche, Italy) are characterized by complex tectono-stratigraphic relationships related to the extreme differentiation of depositional environments occurring from the early Jurassic. In the area of the future Umbria-Marche Apennines, including the Furlo sector, the Sinemurian tectonic event dismembered the wide peritidal carbonate platform of the Calcare Massiccio Fm. into a series of uplifted and downthrown platform blocks bounded by extensional faults. The subsequent drowning of these blocks led to the development of two main environments: pelagic carbonate platforms and basins. The present paper focuses on an analysis of facies that characterize some paleogeographic sectors connecting these two different environments in order to understand the role of tectonics as a control on sedimentary processes. In these sectors, different types of facies have been identified and interpreted. Relationships between facies types, their stacking pattern, and sedimentary structures enabled the identification of different depositional processes directly or indirectly controlled by the tectonic evolution of the study area. The data compiled, compared with those from the literature, were used to relate the Furlo area to a general pelagic carbonate ramp environment constituted by two tilted and drowned carbonate platform blocks; these originated as a result of early Jurassic tectonic activity characterized by some approximately perpendicular faults showing a prevailing rotational character.

Jurassic carbonate depositional systems of the Mt. Catria-Mt. Acuto area (Umbria-Marche Apennines, Italy)

A geologic survey, integrated with sedimentalogic observations nd macrofacies analysis, has been carried out for the Jurassic eposits outcropping in the Mt. Catria-Mt. Acuto area. he study area is located within the northern Umbria-Marche pennines and is characterized by the presence of Jurassic different type sucessions that reflect depositional environment variability. te aim of this paper is to reconstruct the Jurassic paleographic structural etting and the paleotectonic evolution of the area. Parti - cular attention was given to the characterization of the relationships between deposits formed during and after the drowning of the Calcare Massiccio peritidal carbonate platform. In addition, the depo - sitional trend of this carbonate platform was determined by the charac terization of tidal environment sedimentary structures and facies associations. The data obtained allowed for the identification of two isolated, uplifted blocks of the carbonate platform (Corno di Catria and Mt. Acuto), reduced in size, bounded by escarpments of tectonic origin and separated by a narrow Jurassic basinal area (Mt. Catria). Along paleoslopes of structural highs, drowning Calcare Massiccio “B”-type deposits have been identified that differ from Calcare Massiccio “B” deposited on the tops of paleohighs in their mainly lithoclastic facies. The drowning phase, at the tops as well as along the flanks of the blocks, is also marked by unconformity surfaces (drowning unconformities). The different paleostructural sectors have been differentiated during the Lias by a phase of strong extensional tectonics that was responsible for the formation of the tectonic escarpments, subsequently affected by submarine erosion. In the early stages of the Middle Jurassic, tectonic reactivation resulted in formation of some marginal, down-dropped portions of the structural highs, which were subsequently filled by the same cherty sediments that deposited in the Mt. Catria basinal area. In the study area, the depositional environment has remained differentiated throughout the Jurassic as evidenced by the presence of conformable and unconformable boundaries between the Tithonian calpionellid pelagites of the Maiolica Formation and underlying deposits

First record of ammonites in the Bonarelli Level (uppermost Cenomanian) of the Umbria-Marche Succession

The presence of ammonites in the Bonarelli Level (uppermost Cenomanian) of the Umbria-Marche Succession is reported here for the first time. The horizon studied has been recognised near Serra S. Abbondio, on the external limb of the Mt. Catria anticline, where the upper part of the Scaglia Bianca Formation and the interbedded Bonarelli Level crop out. An ammonite, preserved as a bidimensional trace, has been found within one black shale bed which characterizes the level. The lack of diagnostic elements does not allow a precise taxonomic identification. However, based on the morphologic features, this form can be tentatively ascribed to the suborder Lytoceratina.

The Agost Basin (Betic Cordillera, Alicante province, Spain): a pull-apart basin involving salt tectonics

The Agost Basin is characterized by a Miocene–Quaternary shallow marine and continental infilling controlled by the evolution of several curvilinear faults involving salt tectonics derived from Triassic rocks. From the Serravallian on, the area experienced a horizontal maximum compression with a rotation of the maximum stress axis from E–W to N–S. The resulting deformation gave rise to a strike-slip fault whose evolution is characterized progressively by three stages: (1) stepover/releasing bend with a dextral motion of blocks; (2) very close to pure horizontal compression; and (3) restraining bend with a sinistral movement of blocks. In particular, after an incipient fracturing stage, faults generated a pull-apart basin with terraced sidewall fault and graben subzones developed in the context of a dextral stepover during the lower part of late Miocene p.p. The occurrence of Triassic shales and evaporites played a fundamental role in the tectonic evolution of the study area. The salty material flowed along faults during this stage generating salt walls in root zones and salt push-up structures at the surface. During the purely compressive stage (middle part of late Miocene p.p.) the salt walls were squeezed to form extrusive mushroom-like structures. The large amount of clayish and salty material that surfaced was rapidly eroded and deposited into the basin, generating prograding fan clinoforms. The occurrence of shales and evaporites (both in the margins of the basin and in the proper infilling) favored folding of basin deposits, faulting, and the formation of rising blocks. Later, in the last stage (upper part of late Miocene p.p.), the area was affected by sinistral restraining conditions and faults must have bent to their current shape. The progressive folding of the basin and deformation of margins changed the supply points and finally caused the end of deposition and the beginning of the current erosive systems. On the basis of the interdisciplinary results, the Agost Basin can be considered a key case of the interference between salt tectonics and the evolution of strike-slip fault zones. The reconstructed model has been compared with several scaled sandbox analogical models and with some natural pull-apart basins.