4,217 research outputs found
Fluid-Related Features in the Offshore Sector of the Sciacca Geothermal Field (SW Sicily): The Role of the Lithospheric Sciacca Fault System
No full textThe Sciacca basin extends in the southwestern part of Sicily and hosts an important
geothermal field (the Sciacca Geothermal Field) characterized by hot springs containing mantle
gasses. Newly acquired high-resolution seismic profiles (Boomer data) integrated with a multichannel
seismic reflection profile in close proximity to the Sciacca Geothermal Field have documented the
presence of numerous active and shallow fluid-related features (pipes, bright spots, buried and
outcropping mud volcanoes, zones of acoustic blanking, and seafloor fluid seeps) in the nearshore
sector between Capo San Marco and Sciacca (NW Sicilian Channel) and revealed its deep tectonic
structure. The Sciacca Geothermal Field and the diffuse submarine fluid-related features probably
form a single onshore–offshore field covering an area of at least 70 km2. This field has developed
in a tectonically active zone dominated by a left-lateral transpressive regime associated with the
lithospheric, NNE-striking Sciacca Fault System. This structure probably favored the rising of magma
and fluids from the mantle in the offshore area, leading to the formation of a geothermal resource
hosted in the Triassic carbonate succession that outcrops onshore at Monte San Calogero. This field
has been active since the lower Pleistocene, when fluid emissions were likely greater than today and
were associated with greater tectonic activity along the Sciacca Fault Syste
The paleo‐community of the Sciacca red coral
No full textThe sub-fossil red coral deposits of Sciacca (Sicily Channel) have attracted scientific attention for nearly 150 years. Their
origin and formation have been long questioned and investigated, given the fact that they represent one of the most intriguing
geobiological events ever to occur in the Mediterranean basin. Less attention was given to the paleo-community associated
with the sub-fossil coral. Radiocarbon age determinations, in particular, were provided only for red coral, neglecting the
possibility of understanding which species were simultaneously present in the coralline paleo-community and which was
their role. The study of cemented coral rubble pieces revealed that Corallium rubrum covered the largest time interval (more
than 3000 years) and was contemporary to many secondary epibionts over two millennia and to Madrepora oculata for about
500 years; this last finding suggested that an uncommon co-dominance between the two structuring species occurred in the
nearby living communities. The lack of Fe–Mg deposits on the cemented coral rubbles coupled with the low bioerosion
rate of the red coral skeletons by the demosponge Siphonodictyon coralliirubri (assessed through the analysis of the erosive
paleo-scars) suggested that the deposits met with a rapid sediment cover-up. Moreover, for the first time, the analysis of a
piece of cemented coral rubble of sub-fossil red coral coming from Sardinian waters confirmed that, albeit to a lesser extent,
the conditions favouring the preservation of dead corals can occur also in different localities far from Sciacca
The paleo-community of the Sciacca red coral
No full textThe sub-fossil red coral deposits of Sciacca (Sicily Channel) have attracted scientific attention for nearly 150 years. Their origin and formation have been long questioned and investigated, given the fact that they represent one of the most intriguing geobiological events ever to occur in the Mediterranean basin. Less attention was given to the paleo-community associated with the sub-fossil coral. Radiocarbon age determinations, in particular, were provided only for red coral, neglecting the possibility of understanding which species were simultaneously present in the coralline paleo-community and which was their role. The study of cemented coral rubble pieces revealed that Corallium rubrum covered the largest time interval (more than 3000 years) and was contemporary to many secondary epibionts over two millennia and to Madrepora oculata for about 500 years; this last finding suggested that an uncommon co-dominance between the two structuring species occurred in the nearby living communities. The lack of Fe-Mg deposits on the cemented coral rubbles coupled with the low bioerosion rate of the red coral skeletons by the demosponge Siphonodictyon coralliirubri (assessed through the analysis of the erosive paleo-scars) suggested that the deposits met with a rapid sediment cover-up. Moreover, for the first time, the analysis of a piece of cemented coral rubble of sub-fossil red coral coming from Sardinian waters confirmed that, albeit to a lesser extent, the conditions favouring the preservation of dead corals can occur also in different localities far from Sciacca
Offshore 3D geological model of the 628 Sheet “Sciacca” (Progetto CARG)
No full textThe offshore sector of southwestern Sicily, as represented in the Sheet 628 “Sciacca”, is part of the external
segment of the Sicilian Fold-and-Thrust Belt (SFTB) and has recorded a complex geological evolution. The
integration of marine geophysical data, seismic stratigraphy, and well-log interpretations has allowed for a
detailed reconstruction of the 3D geological model down to a depth of 5 km, correlating tectonic structures
between offshore and onshore sectors.
The main stratigraphic setting of this sector consists of Meso-Cenozoic carbonate successions (Saccense
domain) overlain by Neogene-Quaternary syntectonic deposits, with the Pleistocene terrigenous sediments
recording the most recent tectonic deformation.
The regional Neogene to Quaternary tectonic evolution of this sector of the SFTB is defined by a multistage
deformation history: i) Messinian to Early Pliocene compressional event resulted in south-east vergent
folds in the post-early Jurassic portion of the sedimentary succession with local decollement surfaces at
different stratigraphic intervals, ii) the Late Pliocene–Early Pleistocene compressional stage generated highangle
thrusts responsible for the exhumation of main carbonate reliefs and the development of the a new
forward thrust system named Gela Thrust Wedge; this last was also responsible for the occurrence of structures
generated by gravity processes; iii) a post-Early Pleistocene compressional-transpressional event activated
major tectonic structures, including a conjugate NNE-SSW-oriented left-lateral transpressive fault (pop-up
structure). This structure is recognizable in the western offshore sector (Capo San Marco).
The integration of seismic-stratigraphic and structural data has provided insights into the linkage between
deep and shallow geological structures. The gravimetric anomaly map reveals a NE-SW-trending positive
Bouguer anomaly, consistent with subsurface tectonic features. Heat flux data confirm the relationship between
deep aquifer systems within fractured Mesozoic carbonates and offshore fluid escape structures, linking the
Sciacca Geothermal Field to offshore thermal anomalies.
Analysis of high-resolution single channel seismic profiles provided for a detailed assessment of most
recent tectonic activity, that is responsible for NNE-SSW trending high angle faults affecting the seabed, as
well as pockmarks, chimneys, and gas flares, concentrated in the western and central offshore sector (Capo
San Marco and Verdura River mouth, and indicating active fluid migration. These morphological features are
strongly correlated with the most recent buried tectonic structures here reconstructed, providing evidence of
active tectonics. Finally, the 3D geological model has delineated the extent, thickness, and fault boundaries
of buried tectonic units, refining our understanding of the region’s tectonic evolution and the relationships
between deep geological structures and seabed morphological features
A computational method for the Helmholtz equation in unbounded domains based on the minimization of an integral functional
No full textWe study a new approach to the problem of transparent boundary conditions for the Helmholtz equation in unbounded domains. Our approach is based on the minimization of an integral functional arising from a volume integral formulation of the radiation condition. The index of refraction does not need to be constant at infinity and may have some angular dependency as well as perturbations. We prove analytical results on the convergence of the approximate solution. Numerical examples for different shapes of the artificial boundary and for non-constant indexes of refraction will be presented
A spectral approach to a constrained optimization problem for the Helmholtz equation in unbounded domains
No full textWe study some convergence issues for a recent approach to the problem of transparent boundary conditions for the Helmholtz equation in unbounded domains (Ciraolo et al. in J Comput Phys 246:78–95, 2013) where the index of refraction is not required to be constant at infinity. The approach is based on the minimization of an integral functional, which arises from an integral formulation of the radiation condition at infinity. In this paper, we implement a Fourier–Chebyshev collocation method to study some convergence properties of the numerical algorithm; in particular, we give numerical evidence of some convergence estimates available in the literature (Ciraolo in Helmholtz equation in unbounded domains: some convergence results for a constrained optimization problem, 2013) and study numerically the minimization problem at low and mid-high frequencies. Numerical examples in some relevant cases are also shown
Multi-temporal tectonic evolution of Capo Granitola and Sciacca foreland transcurrent faults (Sicily channel)
No full textJoint analysis of high-penetration multi-channel and high-resolution single-channel seismic reflection profiles, calibrated by deep well boreholes, allowed a detailed reconstruction of the Late Miocene to Recent tectonic history of the Capo Granitola and Sciacca fault systems offshore southwestern Sicily. These two fault arrays are part of a regional system of transcurrent faults that dissect the foreland block in front of the Neogene Sicilian fold and thrust belt. The Capo Granitola and Sciacca faults are thought to reactivate inherited Mesozoic to Miocene normal faults developed on the northern continental margin of Africa. During Latest Miocene-Pliocene, the two ~NNE-SSW striking faults were active in left transpression, which inverted Late Miocene extensional half-grabens and created push-up ridges along both systems. Tectonic activity decreased during the Pleistocene, but transpressional folds deform Middle-Late Pleistocene sediments as well, suggesting that the two fault systems are active. The ~40 km long longitudinal amplitude profile of 1st order folds (Capo Granitola and Sciacca anticlines) shows ~15–20 km bell-shaped undulations that represents 2nd order folds. The length of these undulations together with the map pattern of faults allowed to divide the CGFS and SFS into two segments, northern and southern, respectively. Total uplift of the Sciacca Anticline is twice than the uplift of the Capo Granitola Anticline. Incremental fold growth rates decreased during time from 0.22 mm/yr (Capo Granitola Anticline) and 0.44 mm/yr (Sciacca Anticline) in the Pliocene, to 0.07 and 0.22 mm/yr, respectively, during the last ~1.8 Ma
Route to chaos in the weakly stratified Kolmogorov flow
No full textWe consider a two-dimensional fluid exposed to Kolmogorov’s forcing cos(ny) and heated from above. The stabilizing effects of temperature are taken into account using the Boussinesq approximation. The fluid with no temperature stratification has been widely studied and, although relying on strong simplifications, it is considered an important tool for the theoretical and experimental study of transition to turbulence. In this paper, we are interested in the set of transitions leading the temperature stratified fluid from the laminar solution [U∝cos(ny),0, T ∝ y] to more complex states until the onset of chaotic states. We will consider Reynolds numbers 0 < Re ≤ 30, while the Richardson numbers shall be kept in the regime of weak stratifications (Ri ≤ 5 × 10 −3 ). We shall first review the non-stratified Kolmogorov flow and find a new period-tripling bifurcation as the precursor of chaotic states. Introducing the stabilizing temperature gradient, we shall observe that higher Re are required to trigger instabilities. More importantly, we shall see new states and phenomena: the newly discovered period-tripling bifurcation is supercritical or subcritical according to Ri; more period-tripling and doubling bifurcations may depart from this new state; strong enough stratifications trigger new regions of chaotic solutions and, on the drifting solution branch, non-chaotic bursting solutions
Characteristics of silver iodide ice nuclei originating from anhydrous ammonia-silver iodide complexes
No full textIncludes bibliographical references (page [12]).Part I. [untitled] -- Part II. Thermal systems / R. L Steele and F. W. Sciacca
* CMS technical design report, volume II: Physics performance. Published in J.Phys.G34:995-1579,2007.
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