Hyblean Region Research Articles

Present‐Day Surface Deformation of Sicily Derived From Sentinel‐1 InSAR Time‐Series

AbstractThe Quaternary geodynamics of the Central Mediterranean region is controlled by the migration of narrow orogenic belts within the slow Nubia‐Eurasia plate convergence. As testified by the occurrence of major volcanic and seismic events, the Eastern Sicilian Margin is presently one of the most active regions. Using a Permanent‐Scatterer approach, we process Sentinel‐1 satellite images acquired from 2015 to 2020 to provide an island‐wide quantification of surface displacements at a high spatiotemporal resolution. We then convert the calculated mean surface velocities along the ascending and descending satellite line of sight into the ITRF2014 reference frame by using GNSS velocity data derived from regional stations. The resulting pseudo‐3D velocity field mainly highlights a general uplift of about 1.5 ± 0.5 mm/yr of the Nebrodi‐Peloritani range and its differential motion with respect to mainland Sicily along the Cefalù‐Etna seismic zone. Permanent/Persistent‐Scatterer (PS) vertical velocities in the Eastern Hyblean region reveal a long wavelength eastward downbending of the margin, including the inferred epicentral area of the 1693 Noto earthquake. Compared to Quaternary coastal uplift rates, these results confirm the relative low activity of Western Sicily, a potential slow uplift of South‐Central Sicily and a significant discrepancy along the Eastern Hyblean margin were PS‐derived vertical velocities that appear 2–3 mm/yr lower than the Quaternary rates. Over the 2015–2020 timespan, transient processes are also captured, notably on Mount Etna, showing both magmatic pressurization uplift and collapse of the eastern flank, but also all over Sicily where numerous gravitational mass movements and anthropogenic ground subsidence are detected.

3D modelling of the upper Tortonian-lower Messinian shallow ramp carbonates of the Hyblean domain (Central Mediterranean, Faro Santa Croce, Sicily)

This work illustrates a combined modelling approach using digital photogrammetry and geological modelling to create a high detailed 3D facies model of the inner environment of the Monte Carrubba carbonate ramp outcropping in the South Sicily. The Monte Carrubba Formation (Tortonian-lower Messinian) is the youngest marine Miocene carbonate deposit of the Hyblean region, prior to the Messinian crisis of the Mediterranean. In particular, Faro Santa Croce outcrop, which is in vertical thickness up to 8 m, shows the most proximal sector of this ramp. The Faro Santa Croce outcrop offers the opportunity to investigate and reproduce a highly-detailed facies heterogeneity 3D model for a very narrow and limited area of few squared kilometers (0.1 Km2), developed in a tectonically stable area. Within this small areal, five facies have been recognized and modelled revealing a high level of facies heterogeneity. In this area marine ooidal shoals (ooidal grainstone to packstone) interfingered with shallow water seagrass environment (green-algal-floatstone facies and bioclastic grainstone-to-packstone facies) with abundant mollusc fauna. The distal part of this vegetated environment (fine-grained mollusc-packstone facies) passed basinward into coral mounds (coral boundstone). The combination of digital photogrammetry and 3D geological modelling software has allowed to obtain a very high-resolution model of facies heterogeneity, evidencing the complexity of facies associations and, in particular, the development of a facies mosaic that can be underestimated by a classical 1D or 2D field analysis, especially in limitedly exposed outcrops.

Paleoenvironmental reconstruction by means of palynofacies and lithofacies analyses: An example from the Upper Triassic subsurface succession of the Hyblean Plateau Petroleum System (SE Sicily, Italy)

A combined palynofacies and lithofacies analysis was carried out on two borehole successions (Streppenosa 1 and Bimmisca 1) from the Hyblean Plateau Petroleum System (SE Sicily, Italy). It was found that both the wells penetrated the most important source and seal rocks of the Sicilian region (Noto and Streppenosa formations), previously assigned to the Late Triassic-Early Jurassic, deposited within a carbonate platform-basin system. Based on new palynological data, the organic rich succession (Noto Formation and Upper Streppenosa Member) can now be entirely assigned to the Rhaetian, thus constraining its deposition to a time interval characterized by increasing global humidity and seasonality. The integrated palynofacies and lithofacies data enabled characterization of the timing of the drowning phases of the carbonate platform-basin system as being controlled by relative sea level changes mostly triggered by the Triassic extensional tectonic activity. During the first phase of the relative sea-level rise, clayey and organic-rich sediments were deposited only in the deepest portion of the basin. As the sea level continued to rise, the entire system drowned completely and suboxic-anoxic basinal sediments were deposited across the whole Hyblean region, onlapping the shallow-water facies. In the meantime increasing global humidity contributed to an increased freshwater input in the marine depositional system as documented by the presence of fern spores and clay. It caused water stratification and subsequent anoxia at marine basins, favoring the preservation of sedimentary organic matter. This atmospheric change could be related to the degassing of the Central Atlantic Magmatic Province.

Magma–serpentinite interaction as the origin of diatremes: a case study from the Hyblean Plateau (southeastern Sicily)

Some diatremes formed in the Hyblean Plateau in a time span from 6.5 to 9.4 Ma, producing volcaniclastic deposits, which host deep-seated xenoliths. The origin of the explosive activity that has brecciated the magma and the country rocks is controversial, two are the prevalent models: phreatomagmatic and magmatic brecciation. We propose an alternative explanation based on the thermal and mechanical interaction of a rising basaltic magma with serpentinized mantle rocks, representing the main lithologies in the Permo–Triassic Hyblean basement. We suggest that magma–serpentinite interaction could have remobilized fluids from serpentinites that reached the overpressure necessary for the brecciation of country rocks. The possible depth of this interaction has been estimated considering variations of porosity and permeability at different depths in the Hyblean lithosphere. These properties have been taken into account in the dimensionless parameter Ve (Jamtveit et al. in Physical geology of high-level magmatic systems, vol 234. Geological Society, London, Special Publications, London, pp 233–241, 2004), which reflects the relative rates of heat and fluid transport, since a high fluid flux is enhanced by a high boiling temperature of pore water raised by magma–rock heat exchange. Ve remains less than 1 up to a depth of 7 km, corresponding to the average thickness of the sedimentary-volcanic sequence, characterized by a high permeability (k = 10−12–10−14 m2) that inhibits fluid overpressure built up, in contrast to both phreatomagmatic and magmatic models. At deeper levels (k ~ 10−19 m2), from 8 km downward, the value of Ve is greater than 1. Therefore, we propose that the dehydration of serpentinites, upon heating by hot basaltic magma, would have liberated huge amounts of fluids whose accumulation at an average depth of 8 km beneath the impermeable serpentinized level induced supercritical fluid overpressure, strong enough to exceed the lithospheric pressure. Fluid overpressure caused the opening of fractures in the overlying permeable upper crust, triggering the energetic fluid expansion and hence the brecciation of country rocks. Finally, we suppose that aforementioned conditions for supercritical fluid overpressure could have been gained in other areas of the Hyblean region in coincidence with various Mesozoic volcanic events, even though older diatremes may have been obliterated by subsequent sedimentary cycles and volcanic events, as well as in serpentinite diatremes in the Navajo Volcanic Field (Colorado Plateau, SW USA).

Geological and geodetic constraints on the active deformation along the northern margin of the Hyblean Plateau (SE Sicily)

A geologic and geodetic integrated analysis of the northern margin of the Hyblean Plateau (SE Sicily) has been carried out in order to test the relationship between the active deformation, recorded by GPS data, and the long-term tectonic evolution, reconstructed by the interpretation of structural and morphological data. Our study revealed the active growth of a large antiform, as a consequence of the positive tectonic inversion of the previous flexure, bordering the Hyblean Foreland. The deformation of Middle–Late Pleistocene marine terraces and the evolution of the drainage system are consistent with a progressive regional tilting of the entire eastern sector of the Hyblean Plateau (Siracusa Domain), representing the southern limb of the active antiform. The geometry of the Late Quaternary marine strandlines, compared with the results of analogue models, is compatible with the effects of the NW-ward propagation of a detachment fault at depth. The active deformation of the Hyblean region, coherent with the Nubia–Eurasia plate convergence, suggests to candidate the inverted tectonics at the northern border of the Hyblean Plateau as potential seismogenic sources of the area.

Mitochondrial phylogeography of the killifish Aphanius fasciatus (Teleostei, Cyprinodontidae) reveals highly divergent Mediterranean populations

We studied the genetic structure of the Mediterranean killifish Aphanius fasciatus. Analysis of the sequence variation in a 372-bp portion of the mitochondrial control region in 623 fish from 27 sampling sites along the species’ distributional range (Tyrrhenian coast, Sardinia, Sicily, Adriatic coast, Malta, Tunisia, and Greece) yielded 120 distinct haplotypes. Most of the haplotypes are unique, and only 15 % are shared among different populations. The high F ST value (=0.80) suggests a strong population genetic structuring. The phylogenetic analysis based on Bayesian inference, maximum likelihood and maximum parsimony, and the median-joining network show a sharp separation of the Southeastern Sicilian populations (belonging to the Hyblean region) and of the fluvial Tunisian population of Rio Melah from the others. The Adriatic, the Eastern Sicilian, and the Greek populations are well differentiated, while the group of populations from the Central-Western Mediterranean does not show a clear pattern of differentiation. Our findings indicate that the current genetic structuring of A. fasciatus reflects historical geographical patterns occurring within the Mediterranean basin from the Late Miocene to the Pleistocene. The presence of divergent evolutionary entities in the Hyblean region and the Tunisian Rio Melah supports their inclusion as target areas for the conservation of A. fasciatus.

Kinematics and dynamics of the Late Quaternary rift-flank deformation in the Hyblean Plateau (SE Sicily)

The southernmost branch of the Siculo–Calabrian Rift Zone (SCRZ), in SE Sicily, is flanked by an actively uplifting, 31 km wide and 40 km-long, rectangular-shaped crustal block (Siracusa Domain; SD), whose Late Quaternary tectonic evolution has been controlled by the active NW-verging thrusting along its northwestern margin, accompanied by an extension on the opposite side. Within the mobile block, a local extensional stress-field has produced two N140 oriented Late Quaternary collapsed basins, which opened roughly perpendicular to the direction of stretching along the SCRZ. Some tectonic peculiarities of the SD, such as the occurrence of shortening in absence of a crustal back-stop, the coexistence of local extensional and contractional stress-field and the primary role played by fluids in the deformational processes, suggest a possible connection between the shallower crustal dynamics with a deep-seated Mantle intrusion, beneath the region, as it is commonly documented to occur along the rift-zones, where the rift-flank volcanism develops. Similar dynamics and kinematics have been, in fact, described in the adjacent areas of the western flank of SCRZ, which are affected by volcanism (e.g. Eolian Islands and Mt. Etna). The results of our study in the Hyblean region give, thus, the opportunity to detail on the mode and the mechanics of faulting, that can be significant to interpret the seismicity and active deformation in the adjacent volcanic areas of Sicily.

Active tectonics of the Adriatic region from GPS and earthquake slip vectors

To investigate the kinematics of the Adriatic region, we integrate continuous and episodic GPS measurements with Mw > 4.5 earthquake slip vectors selected from the Regional Centroid Moment Tensor catalogue. Coherent motion of GPS sites in the Po Valley, in Apulia, and in the Hyblean Plateau allows us to estimate geodetically constrained angular velocities for these regions. The predictions of the GPS‐inferred angular velocities are compared with the earthquake slip vectors, showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion. The remarkable consistency between geodetic, seismological, and geological evidence of active tectonics suggests that active deformation in the central Adriatic is controlled by the relative motion between the Adria and Apulia microplates. The microplates' angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses (1) that Apulia forms a single microplate with the Ionian Sea and possibly with the Hyblean region and (2) that Adria and Apulia rotate in such a way as to accommodate the Eurasia‐Nubia relative motion. We suggest that the present‐day microplate configuration follows a recent fragmentation of the Adriatic promontory that during the Neogene rigidly transferred the Africa motion to the orogenic belts that now surround the Adriatic region.

The migration of plate boundaries in SE Sicily: Influence on the large-scale kinematic model of the African promontory in southern Italy

A detailed field mapping, coupled with structural analyses and morphological investigation, has been carried out along the northern and western borders of the Hyblean Plateau (SE Sicily), in order to define the nature and the kinematics of a major Quaternary fault belt. This, here designed as the Scicli Line Fault Belt, is composed of two N50 oriented extensional basins that, linked by a regional N10 trending transfer zone, originated during the Early Pleistocene and experienced, since the Late Quaternary, a positive tectonic inversion. In both the two stages of deformation, the Scicli Line Fault Belt has been characterised by displacement-rate comparable with the relative velocities measured between the distinct plates composing the central Mediterranean region. In the period going from 1.5–1.2 to 0.85 Ma, the fault belt accommodated the entire divergence between Adria and Nubia. At present, the Scicli Line Fault Belt absorbs most of the Nubia–Eurasia convergence, while the western divergent margin of the Adria microplate has jumped to the eastern and the southern margins of the Hyblean Plateau, along the Late Quaternary Siculo–Calabrian Rift Zone. The off-shore prolongation of the two tectonic boundaries of the Hyblean Plateau has been recognised in the Sicily Channel, where they are both interrupted by a WNW-ESE oriented dextral fault. According to our reconstruction, the Hyblean Plateau represents an isolated lithospheric block, whose evolution can be related to the propagation of the western divergent margin of the Adria microplate, accompanied with the southward migration of the triple junction between Eurasia, Nubia and Adria. In this new large-scale kinematic picture, the GPS velocity measured in the Hyblean region, at the permanent site of NOTO, is actually representative of the local kinematics, rather than of the entire African promontory of southern Italy. This implies a correction of previous regional kinematic models based on combination of GPS vectors. In particular, our data constrain a new interpretation both for the kinematics along the E–W oriented Nubia–Eurasia margin, dominated by prevalent dextral deformation rather than reverse motions, and for the intraplate deformation in the Sicily Channel, within the Africa promontory, which would be dominated by a roughly N110° oriented extension. This conclusion has implication also on the mechanism and the origin of the Pantelleria–Linosa–Malta Rift that is here interpreted as a transtensive feature developed along a major transform fault, rather than the result of passive rifting induced by the Nubia–Eurasia collision, as it is currently interpreted.

Variability of Bacterial Biofilms of the “Tina” Wood Vats Used in the Ragusano Cheese-Making Process

Ragusano cheese is a "protected denomination of origin" cheese made in the Hyblean region of Sicily from raw milk using traditional wooden tools, without starter. To explore the Ragusano bacterial ecosystem, molecular fingerprinting was conducted at different times during the ripening and biofilms from the wooden vats called "tinas" were investigated. Raw milks collected at two farm sites, one on the mountain and one at sea level, were processed to produce Ragusano cheese. Raw milk, curd before and after cooking, curd at stretching time (cheese 0 time), and cheese samples (4 and 7 months) were analyzed by PCR-temporal temperature gel electrophoresis (PCR-TTGE) and by classical enumeration microbiology. With the use of universal primers, PCR-TTGE revealed many differences between the raw milk profiles, but also notable common bands identified as Streptococcus thermophilus, Lactobacillus lactis, Lactobacillus delbrueckii, and Enterococcus faecium. After the stretching, TTGE profiles revealed three to five dominant species only through the entire process of ripening. In the biofilms of the two tinas used, one to five species were detected, S. thermophilus being predominant in both. Biofilms from five other tinas were also analyzed by PCR-TTGE, PCR-denaturating gradient gel electrophoresis, specific PCR tests, and sequencing, confirming the predominance of lactic acid bacteria (S. thermophilus, L. lactis, and L. delbrueckii subsp. lactis) and the presence of a few high-GC-content species, like coryneform bacteria. The spontaneous acidification of raw milks before and after contact with the five tinas was followed in two independent experiments. The lag period before acidification can be up to 5 h, depending on the raw milk and the specific tina, highlighting the complexity of this natural inoculation system.

The Monte Carrubba Formation (Messinian, Sicily) and its correlatives: New light on basin-wide processes controlling sediment and biota distributions during the Palaeomediterranean–Mediterranean transition

A little known marine Miocene (Messinian) succession in the Hyblean region of south eastern Sicily preserves a carbonate ramp sequence which developed on the tectonically stable foreland margins of the African Plate (Pelagian Block). The ramp (Monte Carrubba Formation) was distally steepened and contained a shoalwater barrier and lagoonal inner ramp complex. The outer ramp is poorly preserved though distal deep water ramp facies (Tellaro Formation) in the south Hyblean region preserve a full Globorotalia mediterranea Subzone and major part of the Globigerina multiloba Subzone succession. This ramp sequence faithfully records the subtle interplay between the global eustatic curve and internal Palaeomediterranean base-level signatures for the Late Miocene. The earliest second order Palaeomediterranean lowstand occurred in the Late Tortonian at about 7.3 Ma and a second occurred at about 6.75 Ma within the Early Messinian G. mediterranea Subzone. Both were in the order of 40 m and global sea-level was probably restored to the Palaeomediterranean after the lowstands. Although the overriding control at the time was the global eustatic curve, harmonic discrepencies between it and the Palaeomediterranean curve resulted from constriction of the Atlantic connection during the latest Tortonian. From about 6.4 Ma until about 5.96 Ma increasingly restricted conditions developed across the Monte Carrubba inner ramp. These faithfully reflect many second order, constriction-driven Palaeomediterranean sea-level oscillations which were superimposed on to the falling global signal as the connecting Atlantic seaways became constricted. These oscillations resulted in major reductions in planktonic faunal diversity within the outer ramp, followed by total emergence of the inner ramp by about 6.05 Ma. Marine deposition continued until about 5.96 Ma in the southern part of the Hyblean region. However, between 6.05 Ma and about 5.6 Ma the amplitude of successive Palaeomediterranean sea-level oscillations increased to over 100 m, causing prolonged periods of total Palaeomediterranean isolation. The Hyblean carbonate suite also contains post-Messinian Salinity Crisis (post-MSC) ‘Lago Mare’ highstand deposits which are developed unconformably above the Monte Carrubba Formation. The widespread distribution of hyposaline to near-marine Congeria faunas within the Lago Mare episode argues for high post-MSC Mediterranean water levels in the Central Mediterranean Late Messinian. In this article we draw together disparate regional evidence from this stable foreland setting and assimilate it with published data from regions lying on the European Plate in order to demonstrate that the tectonically stable Monte Carrubba succession provides an unambiguous record of Central Palaeomediterranean base-level change during the Messinian. Furthermore, the post-MSC sequence demonstrates a prolonged Mediterranean base-level rise throughout the Late Messinian, leaving little readjustment necessary in order to restore Mediterranean base-level to global water levels in basal Pliocene times.

The seismic history of Catania

A detailed study of the most significant seismic effects that took place in the city of Catania has been performed in order to build up a site catalogue, to assess seismic hazard directly from it and to provide the picture of damage scenarios which happened in the past. In the last 1000 years Catania was destroyed twice (1169 and 1693) and more or less severely damaged twelve times (e.g., 1542, 1818, 1848, etc.). Destruction or severe damage are mainly related to earthquakes occurring in the coastal sector of the Hyblean foreland, while slighter, moderate effects are usually due to earthquakes taking place in the seismogenic sources of the Messina Straits and in the inner Hyblean region. The analysis of the historical reports allowed to delineate the damage scenarios of the most relevant events. In particular, for the 1693 case-history it has also been possible to map the damage distribution with reference to the existing urban settlement of the city. The site catalogue was used for assessing seismic hazard; the obtained estimates show that the probability of occurrence for intensity 7 and 10 exceeds 99.9% for 150 and 500 years, respectively. These values, associated with the high vulnerability caused by the city growth which occurred mainly before the introduction of the seismic code (1981) and without ad-hoc planning policies, implies that the urban system is exposed to high seismic risk.

Technology to Produce Ragusano Cheese: A Survey

A survey was carried out to characterize the composition of milk on 70 farms in the Hyblean region in the Province of Ragusa in Sicily, the processing methods used on the 20 of those farms producing the highest quality Ragusano cheese, and the average composition of the cheese at 4 to 6 mo of age. The milk used for cheese making is predominantly from the Modicana and Brown Swiss breeds, but some farms used Holstein cows. Characterization of the traditional Ragusano cheese manufacturing process (including times, temperatures, and pH) is needed. A flow chart of the average cheese-making conditions necessary for production of Ragusano cheese, has been created as an example of the first step that must be taken to document and preserve traditional cheese varieties that are part of the history and culture in various regions of the world. Ragusano is an aged pasta filata cheese. The process of Ragusano cheese making has some characteristics of cultured Mozzarella and some characteristics of Provolone manufacture. However, differences in the manufacturing and aging processes among the three cheeses produce different flavors and texture. The critical steps in the cheese-making process were identified, and recommendations were provided to cheese makers for practical approaches to improve the consistency of cheese quality. The results from the present study form the basis of future research designed to characterize cheese composition, chemical changes during aging, microbiology, yield, and flavor chemistry of Ragusano cheese.

Assessment of the Dairy Production Needs of Cattle Owners in Southeastern Sicily

This study was undertaken to investigate research and outreach priorities for Progetto Ibleo (Project Ibleo), a center created in 1990 with tripartite government funding to serve dairy producers in the Hyblean region of Sicily. Data comprised values for production and composition of milk from 1984 to 1989 from 35 herds of Modicana cows on a system based on pasture and that from 69 input-intensive herds of Holstein cows, associated lactation and reproduction measures, and yield and composition of forages from 4 of these farms in 1988. Season had a large effect on the neutral detergent fiber and crude protein composition of forages, production and composition of milk, and predicted yield of fresh Ragusano cheese manufactured from the milk of these cows. The poorest forage quality and the poorest cow performance were observed in summer and fall months (May to October). Lactation curves that were flat, without a discernible peak, or convex were observed for both systems, especially for cows calving in spring and in the dry summer seasons (March to July). These abnormalities, signifying substantial sacrifices in production potential, probably had a complex etiology that stemmed from low nutrient intake and high neutral detergent fiber and low crude protein composition of the grazed and preserved forages. Research and outreach priorities to support the Hyblean dairy industry should include chemical evaluation of forages and other feedstuffs, low moisture ensiling of high quality winter forages, better formulation of diets that are dense with nutrients, and the shifting of calving patterns to better exploit high quality winter forages.

Forage quality of native pastures in a Mediterranean area

Three field sites in the Hyblean region of Sicily were studied for their forage quality and botanical composition. A total of 70 plant species were analyzed. Another 36 were rare and of insufficient quantity for analysis. Forty-three bulk samples combining all existing species were also prepared and analyzed. The chemical analyses included were dry matter, ash, neutral-detergent fiber (NDF), acid-detergent fiber (ADF), lignin, total nitrogen, nonprotein nitrogen (NPN), soluble nitrogen and degradable protein. Quality varied over the growing season declining with forage maturity. The nutritional quality was high overall. Nongrass nonlegume species dominated. The most abundant species of high quality was a Compositae, Calendula arvensis, which represented approximately 22.8% of the available forage.

Sedimentary and tectonic evolution of the eastern Hyblean Plateau (southeastern Sicily) during late Cretaceous to Quaternary time

Two palaeogeographic domains have been distinguished in the Cretaceous-Quaternary sequences which crop out in the Hyblean region of southeastern Sicily. In the northeast shallow-water algal-bryozoan calcarenites of Oligocene-Miocene age overlie either Cretaceous rudist limestones or volcanics. Further to the northeast, the stratigraphic gap increases as the Miocene limestone thins, and in the A.G.I.P. well Catania 10, Plio-Pleistocene sediments and volcanics directly overlie Upper Jurassic rocks. In the southwestern part of the Hyblean Plateau pelagic sediments occupy the Cretaceous-Miocene interval. They were deposited in a shallow basin dipping gently towards the southwest. The transition between the two zones is marked by much evidence of synsedimentary tectonic activity, such as widespread slumping and the development of megabreccias composed of Cretaceous and Eocene blocks. The palaeogeographic picture is one of carbonate reefs and volcanic seamounts developing in the Upper Cretaceous. They formed platforms, fault bounded to the west and southwest, from which were derived the detrital sediments found in the basin, and occasional spectacular gravity slides. In present-day terms the structural high probably corresponds to the northeastern margin of the Hyblean Plateau and in part to the (Siracusa) Syracuse-Malta Escarpment. The pattern is little changed in the Upper Miocene with volcanoclastics of phreatomagmatic origin, intercalated with coral bioherms, overlying algal-bryozoan calcarenites. Upper Tortonian-Lower Messinian limestones with a restricted fauna indicate a shallow-water environment which grades up into continental conditions. In the eastern Hyblean Plateau, the Tertiary sequence is capped by Pliocene submarine to subaerial mafic lava flows. Lower Pleistocene sediments consist of biocalcarenites and clays which fill deep graben delimited by Plio-Pleistocene faults, the inshore continuation of the Malta-Syracuse Escarpment system of faults. From a tectonic standpoint the Hyblean region, a gently deformed segment of the African continental margin, acted as a foreland during Tertiary times. A Cretaceous-Eocene tectonic phase was responsible for the palaeogeographic pattern which existed during most of the Cenozoic. The present pattern is the result of three main tectonic phases following the regional Upper Miocene uplift, of Early-Middle Pliocene, Plio-Pleistocene and middle Pleistocene-Recent age which influenced the tectonic evolution of the present Ionian coast and the Malta-Syracuse Escarpment.

Late tortonian—lower messinian (miocene) palaeogeography of SE Sicily: information from two new formations of the sorting group

A thick volcanoclastic, biohermal and lagoonal sequence of strata succeeds the Siracusa Limestone Member (Monti Climiti Formation) of SE Sicily. This overlying sequence may be divided into two new formations on the basis of lithostratigraphy, petrology and palaeontology. The older formation, here named the Carlentini Formation, is predominantly a thick volcanoclastic sequence but with two intervening carbonate horizons. Faunas are rare within the volcanic strata but may be abundant and associated with corals and patch-reefs within the two carbonate levels. The younger formation, here named the Monte Carrubba Formation, is almost exclusively composed of oolitic grainstones and lagoonal wackestones. Peritidal carbonates are developed in the northeast of the area. Faunas are frequently of low diversity. Euryhaline mollusc associations are dominant, although Pecten vigolenesis occurs in the lower beds. Collectively the new formations span the late Tortonian—lower Messinian time interval and may be correlated with the Calcare di Base of the main sicilian basin to the west. The palaeoenvironmental reconstruction suggests that both formations were deposited around the SW margins to a low island or landmass lying to the north of the Hyblean region.

A class of distributions useful in life testing and reliability : Z. Govindarajula. IEEE Trans. Reliab.R-26, (1) 67 (April 1977)

A thick volcanoclastic, biohermal and lagoonal sequence of strata succeeds the Siracusa Limestone Member (Monti Climiti Formation) of SE Sicily. This overlying sequence may be divided into two new formations on the basis of lithostratigraphy, petrology and palaeontology. The older formation, here named the Carlentini Formation, is predominantly a thick volcanoclastic sequence but with two intervening carbonate horizons. Faunas are rare within the volcanic strata but may be abundant and associated with corals and patch-reefs within the two carbonate levels.The younger formation, here named the Monte Carrubba Formation, is almost exclusively composed of oolitic grainstones and lagoonal wackestones. Peritidal carbonates are developed in the northeast of the area. Faunas are frequently of low diversity. Euryhaline mollusc associations are dominant, although Pecten vigolenesis occurs in the lower beds.Collectively the new formations span the late Tortonian—lower Messinian time interval and may be correlated with the Calcare di Base of the main sicilian basin to the west.The palaeoenvironmental reconstruction suggests that both formations were deposited around the SW margins to a low island or landmass lying to the north of the Hyblean region.