The petroleum industry has always been pursuing highly exploitable gas fields, which are often hosted in carbonate rocks. However, carbonates are highly heterogeneous and show different fabrics and structures as the result of sedimentation in various environments, and subsequent diagenesis and deformation. In this study, a multi-scale and multidisciplinary approach has been performed on classical reservoir rocks from the subsurface of the Hyblean Plateau (Sicily, Italy). We aim at unravelling the important and debated role of tectonic and diagenetic structures (mainly fractures as well as stylolites) in enhancing or reducing the porosity. Black shales, limestones, and laminites of intertidal environment represent the main lithologies. Structure cross-cutting relationships record different stages of the basin geological history, which are related to the tectonic evolution of the area. Our results show that porosity is uncommonly lightly affected by fractures and faults, because of their mineralization, whereas stylolites, which are often considered as barriers to fluid flow, show a certain porosity. Therefore, we want to highlight the importance of a multi-scale and multidisciplinary approach in the analysis of heterogeneously porous, fractured- and stylolite-rich carbonate rocks, and our study aspires to boost other similar gas reservoir studies in energy transition times.
The assessment of the vulnerability of a site to tsunami events should take into consideration the geomorphological setting, which is strongly determined by the stratigraphic framework of the area. Lampedusa island is located in the central portion of the Sicilian Channel (Mediterranean Sea, Italy), where a significant incidence of tsunamis (with wave runup above 15 m) caused by earthquakes and submarine landslides has been historically documented. This work shows the geomorphological and stratigraphic differences between the western and south-eastern sectors of Lampedusa island. This update to the geological characterization of the island was used to create 3D flooding maps according to runup steps of 5 m, 10 m, and 15 m, thus showing a homogeneous involvement of the south-eastern sector of Lampedusa. Furthermore, our study aims to provide a geomorphological-stratigraphic base for a mathematical-statistical model to create coastal flooding maps due to tsunami waves. As such, this tool is useful for evaluation of strategic infrastructure for the security of the island and the improvement of risk management in civil protection.
Surge channels on wave-swept rocky shores are characterized by the violent hydrodynamic mixing that accompanies broken waves. It has been suggested that this mixing rapidly dilutes gametes shed into the surf zone, thereby severely reducing the fraction of eggs that can be fertilized externally. Although surge channels are well mixed within themselves, field experiments show that the exchange of water between these small embayments and the adjacent mainstream is surprisingly slow. Thus, surge channels may act as "containment vessels," limiting the rate at which gametes are diluted, and thereby enhancing the efficacy of external fertilization. Indeed, a mathematical model of fertilization in surge channels suggests that given a sufficient population of adult males within a surge channel, 80-100% of eggs may be fertilized. This result must be tempered, however, by the possibility that the small-scale shears induced by turbulence interfere with fertilization.
Through the seismo-stratigraphic analysis of new high- resolution seismic data acquired along the southwestern offshore of the Hyblean Plateau, this work aims to improve the knowledge about the stratigraphic and structural setting in the marine area connecting the Hyblean Plateau Foreland to the Gela-Catania Foredeep.Two main goals have motivated the acquisition of new seismic profiles along the southern coastline of Sicily, in the Marina di Ragusa offshore:(i) to obtain a better comprehension of the Cenozoic stratigraphic and structural setting of the area, with a particular attention to the characterization of the Pliocene-Holocene sedimentary deposits and their areal distribution;(ii) to identify, in the offshore area, the possible prolongation of the main structural lineaments outcropping in the hinterland (Scicli-Ragusa-Irminio Line), and verify the presence of structures, responsible for the tectonic activity affecting the area.Our model shows that an extensional fault system, characterized by a main NE-SW orientation, affects the highly deformed Oligo-Miocene, or older, substratum, originating structural highs and down-faulted sectors. These faults are inferred to record the early history of the Scicli Line and of the polyphase kinematic evolution of the N50° oriented regional fault systems.The Gessoso-Solfifera deposits (Messinian, Late Miocene) have been recognized in several sectors of the study area, showing a very peculiar seismic facies, and occupying deep erosional channels probably resting within down-faulted sectors. This feature is in good agreement with isolated onshore areas of the Hyblean Plateau (Licodia Eubea and south Vittoria villages) where the Gessoso-Solfifera deposits are associated to normal faults, thus documenting that Messinian evaporites are not restricted to compressive tectonic setting, such as the marginal sub-basins and the thrust top mini-basins of the Appennine-Maghrebian belt.A peculiar seismic facies has been associated to the Trubi Fm., unconformably lying upon the older succession.The undeformed seismic units, onlapping the older substratum, has been associated to the post-Trubi-Holocene deposits, arranged into seven seismic units that reflect the youngest depositional evolution of the nearby Catania-Gela Foredeep. These deposits, generally represented by plane-parallel seismic facies, are in turn separated by an unconformity highlighted by an onlap termination of the yougermost terms upon the older. In some cases they are interrupted by gas rising from the deeper succession that reaches, at times, also the seafloor.
The quantitative analysis of the calcareous nannofossil content yield in the 600 m thick succession drilled at ODP Site 1123 (offshore New Zealand), considered as a reference section for the Southern Ocean region, allowed the recognition of 43 bioevents distributed along the last 20 Myr. The correlation with the excellent magnetostratigraphic record resulted in the attribution of numerical ages for the position of the detected horizons. Many of the marker species used in previous zonation were detected also at ODP Site 1123, but others revealed to be absent or of scarce applicability. On the other hand, the good applicability of additional events was verified and proved to be useful for the biostratigraphic subdivision and correlation. The obtained average bio- and chronostratigraphic resolution is about 0.6 Myr along the whole section, which increases to about 0.3 in the Pliocene–Holocene time interval. The final result is a detailed southern mid-to-high latitude nannofossil biochronology for the last 20 Myr, which confirms that the ODP Site 1123 succession represents a reference section for the Southern Ocean.
Understanding of complex sedimentary records formed by transgressive systems is critical because they provide information on sea level changes which control the evolution of the coastal environment. This paper discusses the preservation of the Transgressive System Tracts (TST) in the south-eastern Sicilian Tyrrhenian margin during the last Holocene eustatic cycle. The available dataset consists of high-resolution bathymetry (multibeam), whose description and interpretation through a Digital Elevation Model (DEM) has been integrated with six seismic profiles (CHIRP). Within the whole study area, four bathymetric contours (−120 m, −100 m, −80 m and −70 m) were identified and assumed as the markers of the main locations of the paleo-coastlines, corresponding with the steps of the main changes in the sea level. The transgressive deposits are preferentially preserved in the 70–100 m bathymetric range, bounded at the top by the maximum flooding surface and consisting of the relict geomorphic elements that represent past landscapes (coastal barrier lagoons, transgressive sheet areas, cuspate beaches, transgressive dune-field systems). Furthermore, with the support of 3D bathymetric maps, a reconstruction of the geomorphological evolution of the past coastal systems during the last transgressive stage is also provided.
