Application of revised ray tracing migration to imagine lateral variations of seismic fabric corresponding to different tectonic styles in the northern Apennines

Migration of zero-offset seismic sections of deep crust can be done with methods based on ray tracing. We modify the classical ray tracing migration method (RTM), introducing a consistency check to control whether back-propagated rays satisfy the condition of strict normal incidence at the migrated reflector. A synthetic test shows the effectiveness of the method; in particular the control of normal incidence allows elimination of physically inconsistent reflectors from the migrated section. Then RTM is applied to a crustal seismic profile acquired in central Italy, using a velocity model obtained from wide-angle data that reproduces the gross structures of the Apenninic crust. The lateral variation of the seismic fabric shown from the migrated section reveals the presence of coexisting extensional and compressional tectonic regimes. Kinematic diffraction modelling gives additional information about both the distribution of seismic velocities and major active geodynamic processes in the upper lithosphere. The migrated section supports the subdivision of northern Apennines in two tectonic regions: a stretched upper plate (Tuscany and northern Thyrrenian), supported by a rise of the asthenosphere, and a downwarped lower plate (Adria), subducted below the mountain belt.     

Biogeochemical effects of disturbance in shallow water sediment by macroalgae harvesting boats

In the shallow water of Orbetello lagoon, macroalgae harvesting boats produce sediment disturbance. To evaluate the effect of this, during 2001-2002, a trial study was carried out in the lagoon in order to: verify seasonal and diurnal trends in nutrients and estimate the quantity of resuspended organic sediment. An unbalanced and balanced ANOVA (one and two way) analysis was applied. The disturbance did not produce strong and lasting eutrophication effects. In the seasonal survey, dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) showed significant decreases in disturbed areas at the end of the trial, while the control area showed a constant, significant increase. Dissolved organic nitrogen (DON) and phosphorus (DOP) significantly increased everywhere. In disturbed areas, sediment redox (Eh((NHE))) increased and porosity values decreased, contrary to the control area. Total organic carbon (TOC) remained unchanged in disturbed areas, but increased in the control area, where the C:P ration increased. The fall-out of sedimentary material resuspended by boat action for as far as 50 m from the boat route, was 189 g(dw)m(-2) made up mainly of organic matter. This disturbance could be the cause of change in vegetation in the lagoon.     

Effects of Soft Corals on Scleractinian Coral Recruitment. II: Allelopathy, Spat Survivorship and Reef Community Structure

Abstract. Two field experiments were performed on the Great Barrier Reef, Australia, at Orpheus Island and Lizard Island, respectively, to investigate the effects of allelopathic soft corals on survivorship and community structure of scleractinian coral spat. Ceramic tiles were placed around the allelopathic soft corals Sinularia flexibilis (Quoy & Gaimard 1833) and Sarcophyton glaucum (Quoy & Gaimard 1833), and controls. One control consisted of settlement plates surrounding a scleractinian coral (non‐allelopathic planktivore); another control had no adult soft or scleractinian coral present. The experimental soft corals affected the recruitment of various taxonomic groups of coral spat differentially, as evidenced by the diversity of coral spat settling in treatments and controls. At Orpheus Island (O.I., n = 1038 spat) and Lizard Island (L.I., n = 7032 spat), there were significant differences between recruitment success of the two dominant coral taxa, Pocilloporidae (O.I., 61.4 %; L.I., 20.5 %) and Acroporidae (O.I., 33.7 %; L.I., 53 %). Settlement plates exposed to Sinularia flexibilis at either site had the lowest proportion of acroporid recruits. Diversity indices (Shannon‐Wiener Indices) varied significantly between treatments at both Orpheus and Lizard Islands. This appears to be due to selective inhibition of acroporid spat by Sinularia flexibilis at both sites. Growth of coral spat was higher on settlement plates in the presence of Sarcophyton at Lizard Island. Settlement of most associated epibiota was generally inhibited under these conditions. Coral spat survivorship was highest in the presence of Sinularia at Orpheus ­Island; at Lizard Island, this was the case with the Sarcophyton treatment. Higher survivorship, and in some cases growth, of coral spat near soft corals was apparently due to reduced competition for space between spat and associated epibiota. This hypothesis is supported by the results of a sister experiment where a coating of Sinularia flexibilis extract on settlement tiles significantly decreased fouling by sessile epibiota. Soft corals have an allelopathic effect on recruitment and early development of scleractinian corals and, consequently, on early coral reef community succession.     

High-temperature behaviour of melilite: in situ X-ray diffraction study of gehlenite–åkermanite–Na melilite solid solution

High-temperature X-ray diffraction experiments have been performed on melilite solid solutions, on single crystal and powder samples. In åkermanite–gehlenite series, the volumetric thermal expansion increases from gehlenite, 26.5(2) E-06 K-1, to åkermanite, 31.2(1) E-06 K-1. The variation is related to the cation content in the tetrahedral T1 site of the structure, and the linear expansion along the a axis has the greatest variation as a function of composition. The expansion perpendicular to the tetrahedral layers does not present any significant variation as a function of composition. In the åkermanite–Na melilite series, the presence of Na in the [8]-coordinated site strongly increases the linear expansion along the c axis, while the volumetric expansion decreases from åkermanite to Na melilite, whose value can be extrapolated to 27.4 E-06 K-1     

Geological evolution of Mount Etna volcano (Italy) from earliest products until the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data

We present an updated geological evolution of Mount Etna volcano based on new ⁴⁰Ar/³⁹Ar age determinations and stratigraphic data integrating the previous K/Ar ages. Volcanism began at about 500 ka ago through submarine eruptions on the Gela–Catania Foredeep basin. About 300 ka ago fissure-type eruptions occurred on the ancient alluvial plain of the Simeto River forming a lava plateau. From about 220 ka ago the eruptive activity was localised mainly along the Ionian coast where fissure-type eruptions built a shield volcano. Between 129 and 126 ka ago volcanism shifted westward toward the central portion of the present volcano (Val Calanna–Moscarello area). Furthermore, scattered effusive eruptions on the southern periphery of Etna edifice occurred until about 121 ka ago. The stabilization of the plumbing system on the Valle del Bove area is marked by the building of two small polygenic edifices, Tarderia and Rocche volcanoes. Their eruptive activity was rather coeval ending 106 and 102 ka ago, respectively. During the investigated time-span volcanism in Etna region was controlled by a main E–W extensional tectonic related to the reactivation of Malta Escarpment fault system in eastern Sicily. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Characterization of sub‐daily thermal regime in alpine rivers: quantification of alterations induced by hydropeaking

The thermal regime of rivers is threatened by anthropogenic stresses at a large variety of timescales. We focus on sub‐daily thermal alterations induced by the release of hypolimnetic water for hydropower production (thermopeaking). We analyse the thermal signal focusing on the following characteristics that are potentially affected by hypolimnetic releases: (i) sub‐daily thermal rate of change and (ii) oscillation frequencies contained in the thermal signal. Through a proper scaling, we derive two dimensionless at‐a‐station indicators to compare alterations among stations with different locations and physiographic characteristics of the basins. Then we analyse the data from two different thermal datasets (Italy/Switzerland) for a total of 48 stations with 10 min time resolution of temperature data. The stations are grouped according to the absence of upstream hydropeaking releases (29 stations, reference group) and the existence of upstream hydropeaking, hence potentially impacted by thermopeaking (19 stations, altered group). Using a simple statistical approach, based on a non‐parametric definition of outliers, we identify the range of variability of the two indicators for the reference, unaltered group. This range measures the ‘natural’ sub‐daily thermal variability of the proposed indicators. Finally, we investigate the seasonality effects on the two proposed indicators and it results, that sub‐daily alterations mostly occur during summer. The two indicators represent a novel tool for the assessment of river thermal regime alterations and can be easily included in existing methodologies to assess river quality. Copyright © 2015 John Wiley & Sons, Ltd.     

Deriving vulnerability curves using Italian earthquake damage data

The concerted effort to collect earthquake damage data in Italy over the past 30 years has led to the development of an extensive database from which vulnerability predictions for the Italian building stock can be derived. A methodology to derive empirical vulnerability curves with the aforementioned data is presented herein and the resulting curves have been directly compared with mechanics-based vulnerability curves. However, it has been found that a valid comparison between the empirical and analytical vulnerability curves is not possible mainly due to a number of shortcomings in the database of surveyed buildings. A detailed discussion of the difficulties in deriving vulnerability curves from the current observed damage database is thus also presented.     

Users’ perception analysis for sustainable beach management in Italy

It is generally accepted that end-users’ perception is likely to play a pivotal role for planning and policy consideration. Beach user analysis is thus an important component defining beach management policies. In the framework of a wider project on beaches management, an investigation on residents and tourists was conducted. A survey conducted through questionnaires and interviews was carried out in six coastal municipalities. Results allowed obtaining a clear picture about user profile, perception of the beaches, awareness and attitude about themes related to beach management (i.e. Blue Flag award and beach nourishment practices). Their integration with the “expert knowledge” based analysis allowed to support the definition of beach management interventions.     

High-precision late Aptian Pb/U age for the Punta del Barco Formation (Baqueró Group), Santa Cruz Province,Argentina

The Baqueró Group holds a rich fossil flora including macrofloristic and palynological remains that characterize the Early Cretaceous vegetation of Argentina. The age of the upper part of the Group, known as Punta del Barco Formation, has been a topic of several discussions in the past. The type locality of this stratigraphic unit exposes fossiliferous tuffs together with muddy tuffs and tuffaceous sandstones beds. However, there have been no reliable age constraints for the fossil assemblages. ²⁰⁶Pb/²³⁸U analyses of zircon crystals yielded an age of 114.67 ± 0.18 Ma. This age control makes possible an improved analysis and comparison of the floras in the southern region.