Tyrrhenian Sea Basin Research Articles

Marsili and Cefalù basins: The evolution of a rift system in the southern Tyrrhenian Sea (Central Mediterranean)

Abstract The Marsili Basin (in the southern Tyrrhenian Sea), whose mode of extension is still a controversial issue, is the youngest bathyal basin of the Central Mediterranean. A thin sedimentary cover in the basin permits to image basement fabric and structure by swath mapping and seismic reflection data. We investigate the crustal structure of the southern Tyrrhenian Sea, extending from the bathyal Marsili Basin to the adjacent Sicily continental margin. Interpretation of seismic reflection profiles (calibrated by well and dredge data) and crustal cross-sections were used to identify the stratigraphic infill, structural pattern and large-scale crustal features of the region. We recognized three basins in the southern Tyrrhenian Sea: (1) the Termini basin that is an overfilled sedimentary basin on the continental shelf area; (2) the Cefalu basin, located on the continental slope area and filled by thick deep water turbidite deposits; (3) the distal Marsili basin, filled by hemipelagic and thin distal turbidite deposits. The sequence stratigraphy interpretation permitted us to recognize fourth-order depositional sequences and the stratigraphic signature of the rift stages. An important increase in the sedimentary supply from the continental shelf to the bathyal basin occurred approximately over the last 0.5 Ma and is related to the uplift of the coastal area. The stratigraphic constrains indicate a Lower Pleistocene age for the opening of the southern Tyrrhenian Sea basin. The structural map reveals a complex fault pattern, in which coeval normal faults disclose a triangular basin from the Marsili bathyal basin to the Sicily continental margin, associated to an Euler pole in the northern Sicily. Tacking in account the faults pattern that developed in the whole Southern Tyrrhenian Sea during the Lower Pleistocene, we reconstructed two opposite triangular basins separated by a perpendicular rift. For analogy with the contiguous Vavilov basin, we propose that the extension in the Marsili basin reached the mantle exhumation stage.

Early‐stage rifting of the northern Tyrrhenian Sea Basin: Results from a combined wide‐angle and multichannel seismic study

Extension of the continental lithosphere leads to the formation of rift basins and ultimately may create passive continental margins. The mechanisms that operate during the early stage of crustal extension are still intensely debated. We present the results from coincident multichannel seismic and wide‐angle seismic profiles that transect across the northern Tyrrhenian Sea Basin. The profiles cross the Corsica Basin (France) to the Latium Margin (Italy) where the early‐rift stage of the basin is well preserved. We found two domains, each with a distinct tectonic style, heat flow and crustal thickness. One domain is the Corsica Basin in the west that formed before the main rift phase of the northern Tyrrhenian Sea opening (∼8–4 Ma). The second domain is rifted continental crust characterized by tilted blocks and half‐graben structures in the central region and at the Latium Margin. These two domains are separated by a deep (∼10 km) sedimentary complex of the eastern portion of the Corsica Basin. Travel‐time tomography of wide‐angle seismic data reveals the crustal architecture and a subhorizontal 15–17 ± 1 km deep Moho discontinuity under the basin. To estimate the amount of horizontal extension we have identified the pre‐, syn‐, and post‐tectonic sedimentary units and calculated the relative displacement of faults. We found that major faults initiated at angles of 45°–50° and that the rifted domain is horizontally stretched by a factor of β ∼ 1.3 (∼8–10 mm/a). The crust has been thinned from ∼24 to ∼17 km indicating a similar amount of extension (∼30%). The transect represents one of the best imaged early rifts and implies that the formation of crustal‐scale detachments, or long‐lived low‐angle normal faults, is not a general feature that controls the rift initiation of continental crust. Other young rift basins, like the Gulf of Corinth, the Suez Rift or Lake Baikal, display features resembling the northern Tyrrhenian Basin, suggesting that half‐graben formations and distributed homogeneous crustal thinning are a common feature during rift initiation.

Lagrangian models of dispersion in marine environment

Turbulent dispersion can be studied successfully by using Lagrangian particle models. In general, the prediction of correct concentration fields is a complex issue when the turbulent field is inhomogeneous and non-stationary. Two classes of Lagrangian dispersion models have been considered in this work, which are based on the Wiener process and the so called “well-mixed” criterion. In order to test the performances of these models and shed light on the underlying physical processes and modeling assumptions, four different numerical models have been compared and tested by means of their long time behavior by considering several study cases concerning idealized marine environment. Furthermore, the coupling of the community model Princeton Ocean Model (POM) with the Lagrangian model LASEMOD (LAgrangian SEa MODel) is used to investigate the temporal and spatial evolution of a passive pollutant released in the vicinity of the coast in the Tyrrhenian Sea basin. The simulation shows with reasonable accuracy the time evolution of both the hydrodynamic and the concentration fields and provides a useful insight into the evaluation of the environmental impact of pollutant releases along the coast.

Geophysical and petrological modelling of the structure and composition of the crust and upper mantle in complex geodynamic settings: The Tyrrhenian Sea and surroundings

Information on the physical and chemical properties of the lithosphere–asthenosphere system (LAS) can be obtained by geophysical investigation and by studies of petrology–geochemistry of magmatic rocks and entrained xenoliths. Integration of petrological and geophysical studies is particularly useful in geodynamically complex areas characterised by abundant and compositionally variable young magmatism, such as in the Tyrrhenian Sea and surroundings. A thin crust, less than 10 km, overlying a soft mantle (where partial melting can reach about 10%) is observed for Magnaghi, Vavilov and Marsili, which belong to the Central Tyrrhenian Sea backarc volcanism where subalkaline rocks dominate. Similar characteristics are seen for the uppermost crust of Ischia. A crust about 20 km thick is observed for the majority of the continental volcanoes, including Amiata–Vulsini, Roccamonfina, Phlegraean Fields–Vesuvius, Vulture, Stromboli, Vulcano–Lipari, Etna and Ustica. A thicker crust is present at Albani – about 25 km – and at Cimino–Vico–Sabatini — about 30 km. The structure of the upper mantle, in contrast, shows striking differences among various volcanic provinces. Volcanoes of the Roman region (Vulsini–Sabatini–Alban Hills) sit over an upper mantle characterised by V s mostly ranging from about 4.2 to 4.4 km/s. At the Alban Hills, however, slightly lower V s values of about 4.1 km/s are detected between 60 and 120 km of depth. This parallels the similar and rather homogeneous compositional features of the Roman volcanoes, whereas the lower V s values detected at the Alban Hills may reflect the occurrence of small amounts of melts within the mantle, in agreement with the younger age of this volcano. The axial zone of the Apennines, where ultrapotassic kamafugitic volcanoes are present, has a mantle structure with high-velocity lid ( V s ∼ 4.5 km/s) occurring at the base of a 40-km-thick crust. Beneath the Campanian volcanoes of Vesuvius and Phlegraean Fields, the mantle structure shows a rigid body dipping westward, a feature that continues southward, up to the eastern Aeolian arc. In contrast, at Ischia the upper mantle contains a shallow low-velocity layer ( V s = 3.5–4.0 km/s) just beneath a thin but complex crust. The western Aeolian arc and Ustica sit over an upper mantle with V s ∼ 4.2–4.4 km/s, although a rigid layer ( V s = 4.55 km/s) from about 80 to 150 km occurs beneath the western Aeolian arc. In Sardinia, no significant differences in the LAS structure are detected from north to south. The petrological–geochemical signatures of Italian volcanoes show strong variations that allow us to distinguish several magmatic provinces. These often coincide with mantle sectors identified by V s tomography. For instance, the Roman volcanoes show remarkable similar petrological and geochemical characteristics, mirroring similar structure of the LAS. The structure and geochemical-isotopic composition of the upper mantle change significantly when we move to the Stromboli–Campanian volcanoes. The geochemical signatures of Ischia and Procida volcanoes are similar to other Campanian centres, but Sr–Pb isotopic ratios are lower marking a transition to the backarc mantle of the Central Tyrrhenian Sea. The structural variations from Stromboli to the central (Vulcano and Lipari) and western Aeolian arc are accompanied by strong variations of geochemical signatures, such as a decrease of Sr-isotope ratios and an increase of Nd-, Pb-isotope and LILE/HFSE ratios. The dominance of mafic subalkaline magmatism in the Tyrrhenian Sea basin denotes large degrees of partial melting, well in agreement with the soft characteristics of the uppermost mantle in this area. In contrast, striking isotopic differences of Plio-Quaternary volcanic rocks from southern to northern Sardinia does not find a match in the LAS geophysical characteristics. The combination of petrological and geophysical constraints allows us to propose a 3D schematic geodynamic model of the Tyrrhenian basin and bordering volcanic areas, including the subduction of the Ionian–Adria lithosphere in the southern Tyrrhenian Sea, and to place constraints on the geodynamic evolution of the whole region.

The structure and evolution of the Northern Tyrrhenian Sea

AbstractField studies on the island of Elba and seismic lines from the Northern Tyrrhenian Sea, Italy, indicate that major extensional displacements were accommodated along east-dipping low-angle detachment faults. The rifting and subsidence in the Northern Tyrrhenian Sea basin have followed convergence and collision of the Corso-Sardinian block and the Apulian microplate. This collisional episode produced the Northern Apennines fold-and-thrust belt. Major extensional faults cut down-section through the stratigraphy and pre-existing west-dipping thrust faults. West-dipping thrusts can also be reactivated and form antithetic faults to the east-dipping detachments. Brittle deformation conditions predominated during the extensional phase. The geometry, internal structure and the fabrics (brittle and penetrative) associated with a well-exposed low-angle extensional detachment in Elba are presented in this paper. A geometrical model for the brittle extensional faulting is presented in which regional extension was accommodated on a system consisting of two sets of simultaneously active antithetic faults. The east-dipping detachment faults appear to have started at steeper angles, based on field and seismic observations, and rotated counter-clockwise to lower dips. Due to this rotation, and for space accommodation, antithetic west-dipping faults formed and rotated clockwise. A tectonic model is proposed whereby slowing of the convergence between Apulia and Corsica, as well as Tethys oceanic crust and Apulian crust subduction, led to the delamination of the Apulian litho-spheric mantle away from the crust. Accompanying asthenospheric upwelling and intrusion at the crust—mantle interface beneath the Tyrrhenian Sea caused late orogenic crustal stretching in the Northern Apennines internal zone.

Correction [to “Tectonics of the Punta Bianca promontory: Insights for the evolution of the Northern Appennines‐Northern Tyrrhenian Sea basin” by Fabrizio Storti

TectonicsVolume 14, Issue 5 p. 1234-1234 Free Access Correction [to “Tectonics of the Punta Bianca promontory: Insights for the evolution of the Northern Appennines-Northern Tyrrhenian Sea basin” by Fabrizio Storti] Fabrizio Storti, Fabrizio StortiSearch for more papers by this author Fabrizio Storti, Fabrizio StortiSearch for more papers by this author First published: October 1995 https://doi.org/10.1029/95TC02747AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume14, Issue5October 1995Pages 1234-1234 RelatedInformation

Tectonics of the Punta Bianca promontory: Insights for the evolution of the Northern Apennines‐Northern Tyrrhenian Sea basin

The structural setting of the eastern headland of the La Spezia Gulf (Punta Bianca promontory) provides some constraints on the contractional and extensional framework of the Northern Apennines‐Northern Tyrrhenian Sea basin geodynamic system and allows a detailed reconstruction of a complex evolutionary path. Out‐of‐sequence thrusting is supposed in the inner side of the chain. Two different extensional events are identified; the older (early‐middle Miocene) may be related to the imbrication of the deeper metamorphic units of the Apenninic thrust wedge. Younger extension fits very well into an eastward asymmetrical faulting framework, related to the opening of the Northern Tyrrhenian Sea basin, from the late Miocene to the Pliocene‐Pleistocene (?). Well‐exposed low‐angle normal faults developed during this event. Extensional structures were then overprinted and reactivated by a mainly strike‐slip regime in the Quaternary.

Analysis of backscattering data in the Tyrrhenian Sea

Research has been conducted in the Tyrrhenian Sea basin to measure low-frequency basin reverberation and relate the measurements to backscattered strength. The receivers were a towed horizontal array and a suspended vertical array. Standard Italian Navy depth (74 kg) and SUS (0.818 kg) charges were used as sources. The unique factor in this broadband basin reverberation experiment was that data were collected simultaneously from the horizontal and vertical array. Towed-array data were taken on multiple headings; combining different headings permitted removal of the ambiguous directionality information from the towed array. Frequency-domain beamformed data are presented and reveal that, in the area examined, basin features are the strongest backscatterers. Receiver beam level data are presented primarily for 300 Hz, but some data are given for 100, 450, and 730 Hz as well. Estimates of backscattering strengths of different features are provided and are in the range quoted in other publications. A comparison of the horizontal and vertical array scattering strengths estimated for some selected basin features is also included. Statistics for the dominant backscatterers are given, and the results from one basin feature are presented showing detailed backscatter structure.

On the mechanism of formation of the tyrrhenian sea

We investigated some of the existing hypotheses on the formation of the Tyrrhenian Sea basin, and we found that none of them appears satisfactory. By quantitative considerations we show that proposed mechanisms, such as those based on oceanization or back-arc spreading, cannot explain the origin of this basin. We suggest an alternative mechanism, consisting on the gabbro-eclogite transition, which occurs in the basaltic layer of the continental crust when anomalous mantle contacts the crustal basement. This leads to the formation of eclogite, which tears off the crust, sinks into the astenosphere, and accumulates at its base. As a consequence of the destruction of the basaltic layer the crust is strongly reduced and a deep basin is formed. We also suggest that the processes of crustal thinning and subsidence developed as proposed here at different times in different regions.

Alkalibasalts from the tyrrhenian sea basin: magmatic and geodynamic significance

Alkalibasalts from the tyrrhenian sea basin: magmatic and geodynamic significance

Alkalibasalts from the Tyrrhenian sea Basin: Magmatic and geodynamic significance

Petrological characteristics of basaltic rocks from the Tyrrhenian deep-sea are discussed and related to the geotectonic situation. For the first time, distinctly alkaline basalts (hawaiites) have been found in the Tyrrhenian deep-sea. These are typical within-plate basalts related to the tensional fracturing of the Tyrrhenian area. A suggested age of 100,000 years is among the youngest indications for the Tyrrhenian Sea volcanism. Since the Miocene, magmatic activity in the inner Tyrrhenian sea basin evolved from ocean-floor basalts to ocean island tholeiites and transitional basalts, with alkaline basalts as the most recent products. Seamounts in the southern part of the Tyrrhenian deep-sea (Palinuro, Marsili) add shoshonitic and calcalkaline lavas (some with high Mgvalue) to the complexity of the Tyrrhenian magmatic evolution.