Petrography and stable isotope aspects of cold-vent activity imprinted on Miocene-age “calcari aLucina” from Tuscan and Romagna Apennines,Italy

Over 20 occurrences of discontinuous limestone blocks, locally called calcari aLucina, were mapped in the Tuscan—Romagna region of the northern Italian Apennines. The limestones, consisting of a variable mixture of authigenic carbonates (calcite, dolomite, and aragonite), sulfides (primarily pyrite), and allogenic silicates, occur in association with turbidite and hemipelagite units that were deposited in foredeep basins during early to late Miocene times. The limestone blocks are interpreted to represent relicts of carbonate buildups formed around methane-rich fluid vents on the basis of their (1) striking petrographic similarities to carbonates from cold vents in the modern oceans; (2) unique chemosynthetic-like fauna, and (3) anomalously negative ¹³C values ( ¹³C = – 16 to – 58 PDB). The contemporaneous tectonism of the Apennine orogeny is likely to be the primary cause for the expulsion of the methane-rich fluids to the seabed in a manner analogous to the fluid-flow processes occurring at modern accretionary prisms.     

The Crati Submarine Fan,Ionian Sea

The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length.     

The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007.
The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic     ) radio sources south of  δ=−15°  with      Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz.
In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming   S ∝ν^α  , decreases from  α^8.6_4.8= 0.11  between 4.8 and 8.6 GHz to  α²⁰_8.6=−0.16  between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has  α²⁰_8.6 > −0.5)  . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies.     

Observed and predicted earthquake damage scenarios: the case study of Pettino (L’Aquila) after the 6th April 2009 event

A damage scenario based on observational data collected in L’Aquila Municipality after the 6th April 2009 earthquake is compared with a predicted damage scenario derived from the application of a simplified analytical method for seismic vulnerability assessment of Reinforced Concrete (RC) buildings at large scale. The observational damage scenario is derived from a database of 131 RC buildings located in the Municipality of L’Aquila, which after the 2009 earthquake were subjected to post-earthquake usability assessment procedure. The simplified analytical approach adopted is based on the Capacity Spectrum Method to evaluate seismic capacity at different Damage States (DSs) based on the displacement capacity of structural and non-structural elements. DSs and the corresponding displacement capacity are defined through the interpretation of the observational-based DSs provided by the European Macroseismic Scale EMS-98. Data predicted by the adopted methodology are in good agreement with the observed damage distribution. The observed damage scenario is also compared with predicted scenarios derived from other methodologies from literature.     

New geological insights and structural control on fluid circulation in La Fossa cone (Vulcano,Aeolian Islands,Italy)

Electric resistivity tomography (ERT), self-potential (SP), soil CO₂ flux, and temperature are used to study the inner structure of La Fossa cone (Vulcano, Aeolian Islands). Nine profiles were performed across the cone with a measurement spacing of 20 m. The crater rims of La Fossa cone are underlined by sharp horizontal resistivity contrasts. SP, CO₂ flux, and temperature anomalies underline these boundaries which we interpret as structural limits associated to preferential circulation of fluids. The Pietre Cotte crater and Gran Cratere crater enclose the main hydrothermal system, identified at the centre of the edifice on the base of low electrical resistivity values (<20 Ω m) and strong CO₂ degassing, SP, and temperature anomalies. In the periphery, the hydrothermal activity is also visible along structural boundaries such as the Punte Nere, Forgia Vecchia, and Palizzi crater rims and at the base of the cone, on the southern side of the edifice, along a fault attributed to the NW main tectonic trend of the island. Inside the Punte Nere crater, the ERT sections show an electrical resistive body that we interpret as an intrusion or a dome. This magmatic body is reconstructed in 3D using the available ERT profiles. Its shape and position, with respect to the Pietre Cotte crater fault, allows replacing this structure in the chronology of the development of the volcano. It corresponds to a late phase of activity of the Punte Nere edifice. Considering the position of the SP, soil CO₂ flux, and temperature maxima and the repartition of conductive zones related to hydrothermal circulation with respect to the main structural features, La Fossa cone could be considered as a relevant example of the strong influence of pre-existing structures on hydrothermal fluid circulation at the scale of a volcanic edifice.     

Paving the way for conservation?

Limestone pavement is a unique part of Britain's physical landscape. Along with other forms of naturally weathered rock, it is under threat from exploitation for the horticultural market. Valued for its delicate and sculptured form, limestone pavement has been frequently used as decorative stone in rockeries and other landscaped ground. If this unique landscape is to be protected, its exploitation must stop. Yet it must be remembered that the use of rock in gardens and landscaped ground has an important role in raising the public profile of geology within urban areas. We have a simple message: the use of limestone pavement is wrong and must stop, but the use of other forms of stone in urban gardens is beneficial for the Earth sciences.     

Solar opacity, neutrino signals and helioseismology

In connection with the recent suggestion by Tsytovich et al. that opacity in the solar core could be overestimated, we consider the following questions: (i) What would a 10% opacity reduction imply for the solar neutrino puzzle? (ii) Is there any hope of solving the solar neutrino puzzle by changing opacity? (iii) Is a 10% opacity reduction testable with helioseismological data?     

The Australia telescope 20 GHz survey: hardware, observing strategy, and scanning survey catalog

The Australia Telescope 20 GHz (AT20G) survey is a large area (2?? sr), sensitive (40 mJy), high frequency (20 GHz) survey of the southern sky. The survey was conducted in two parts: an initial fast scanning survey, and a series of more accurate follow-up observations. The follow-up survey catalog has been presented by Murphy et al. (MNRAS 402:2403, 2010). In this paper we discuss the hardware setup and scanning survey strategy as well as the production of the scanning survey catalog.