Tectonic and sedimentary evolution of the Lower Pliocene Periadriatic foredeep in Central Italy

The Periadriatic foredeep (Italy) was generated by Neogene downbending of the Adria Plate under the Apennine Chain. The basin is filled with Plio-Pleistocene siliciclastic turbidites. Its substratum consists of the carbonate succession of the southwestern Adria Plate margin. The influence of the basin’s morphology on sedimentation and subsequent tectonic evolution is investigated in the Abruzzo sector of the foredeep (Cellino Basin). The substratum is composed of Messinian evaporites that dip towards the Apennines (W). A NNW component along the depocentral axis is divided into four blocks with different depths. The substratum was also affected by a Messinian extensional fault system, not involving the overlying Pliocene sequence. This morphology controlled the distribution of the turbidites in the lower part of the Cellino Basin. The Plio-Pleistocene compressional deformation of the foredeep produced an inner complex structure (Internal Structure), involving the foredeep substratum and an outer imbricate thrust system (Coastal Structure), detached over the faulted Messinian evaporites. This thrust system is parallel to the extensional faults, suggesting a strong influence of the substratum morphology on the development of the compressional structures. The overall structural setting was validated with a balanced cross-section. Out-of-sequence thrusting and non-coeval deformation within each thrust sheet characterize the local tectonic history.     

Anatomy of a late Pleistocene clinoformal sedimentary body (Le Castella,Calabria, southern Italy): A case of prograding spit system?

The Le Castella marine terrace is the smallest and youngest terrace of the Crotone area (southern Italy), and formed after a rapid marine ingression due to a glacio-eustatic rise outpacing the regional uplift of the area. The most prominent feature of the terrace deposits is a seaward-accreting clinoform about 10 m thick, inferred to be formed during forced regressive conditions. This prograding body is mostly composed of bioclastic material, and shows an internal complexity consisting of alternating oblique and sigmoid elementary units inferred to be produced mainly by changes of accommodation development. Foreset avalancing was due to sediment accumulation by gravity-flow processes, while topsets were characterized by the migration of medium- to large-scale dunes showing a unimodal palaeocurrent pattern, oblique with respect to the dip direction of the large-scale clinoform foresets. The Le Castella clinoform starts to develop from a topographic step on the basement due to tectonics, which also controlled the palaeoshoreline trend.The recognized stratigraphic and facies architectures, the palaeocurrent pattern, and the inferred palaeogeographic setting during deposition, all suggest that the Le Castella clinoform is an example of spit system attached to the mainland and accreted due to longshore transport. The present example contributes to establish criteria allowing the recognition of ancient spit systems, which still are poorly known and rarely documented in the pre-Quaternary geological record.     

Growth of myrmekite coronas by contact metamorphism of granitic mylonites in the aureole of Cima di Vila, Eastern Alps, Italy

In the contact aureole of the Oligocene granodiorite of Cima di Vila, granitic pegmatites of Variscan age were strongly deformed during eo‐Alpine regional metamorphism, with local development of ultramylonites. In the ultramylonite matrix, consisting of quartz, plagioclase, muscovite and biotite, microstructures show grain growth of quartz within quartz ribbons, and development of decussate arrangements of mica. These features indicate that dynamic recrystallization related to mylonite development was followed by extensive static growth during contact metamorphism. K‐feldspar porphyroclasts up to 1.5 cm are mantled by myrmekite that forms a continuous corona with thickness of about 1 mm. In both XZ and YZ sections, myrmekite tubules are undeformed, and symmetrically distributed in the corona, and oligoclase‐andesine hosts have random crystallographic orientation. Myrmekite development has been modelled from the P–T–t evolution of the ultramylonites, assuming that the development of the ultramylonites occurred during eo‐Alpine metamorphism at c. 450 °C, 7.5 kbar, followed by contact metamorphism at c. 530 °C, 2.75 kbar. Phase diagram pseudosections calculated from the measured bulk composition of granitic pegmatite protolith indicate that the equilibrium assemblage changes from Qtz–Phe–Ab ± Zo ± Cpx ± Kfs during the ultramylonite stage to Qtz–Pl(An_30–40)–Ms–Kfs–Bt(Ann₅₅) during the contact metamorphic stage. The thermodynamic prediction of increasing plagioclase mode and anorthite content, change of white mica composition and growth of biotite, occurring during the end of the heating path, are in agreement with the observed microstructures and analysed phase compositions of ultramylonites. Along with microstructural evidence, this supports the model that K‐feldspar replacement by myrmekite took place under static conditions, and was coeval with the static growth accompanying contact metamorphism. Myrmekite associated with muscovite can develop under prograde (up‐temperature) conditions in granites involved in polymetamorphism.     

Three Reflection Telescopes for Wide Field Space Astronomy. First Results from a 30 cm Prototype and Prospects

We present the basic concepts of the two-mirror, three-reflection optical system (2MTRT), and discuss the important benefits of such a system for space projects: wide ( 2^°) correctedand unvignetted FOV, without the use of refractive optics for thefield correction, planarity of the focal surface for an optimizedinstallation of wide area detectors, easy telescope adjustement, small volume and little mass.We also report the results of optical tests made with a 30 cm prototype,equipped with a 2k × 2k CCD camera, and give examples of scientific programmes which can be performed from space and in hostile terrestrial sites such as the Antarctic Plateau.     

GNSS software receiver for the MAGIA (Missione Altimetrica Geofisica GeochImica lunAre) mission

In recent years a number of missions have been conceived to acquire and track signals from GPS satellites at altitudes higher than the GPS constellation itself. The main purpose of SDR is to reduce the number of hardware components, projected for specific unmodifiable uses, and utilize general purpose units: on board CPU, DSP or FPGA. In this paper he study and design of a GNSS Software Receiver for space application, applied to a Lunar Mission, is presented with particular attention on Space Segment device and on Ground Facilities.     

Detection of HCO+ towards Cygnus OB2 No. 12

HCO⁺ has been detected for the first time towards the star Cygnus OB2 No. 12 through emission of the 1–0 rotational transition at 89 GHz. The CO( J =2−1) transition has also been observed. The observations are consistent with a model of dense regions embedded in a low-density clump gas. If actually present, the dense component would have an aggregate size L 1300 au, in agreement with estimates of small-scale density fluctuations observed along diffuse lines of sight.     

Evidence for Late Carboniferous subduction-type magmatism in mafic-ultramafic cumulates of the SW Tauern window (Eastern Alps)

Hectometric bodies of fresh mafic-ultramafic cumulates have been discovered within the Central Gneiss of the Zillertal massif, SW Tauern window (eastern Alps, Italy). The cumulates, intruded by the Central Gneiss granitoids, are amphibole-bearing harzburgites and norites made of cumulitic olivine (Fo_73-80), spinels, sulphides and plagioclase (An_79-87), included in orthopyroxene (En_76-83) and Ti-pargasite (Mg#=0.73-0.81). Major and trace element geochemistry indicates that these rocks represent olivine + spinel - plagioclase cumulates, in which interstitial melt crystallized as orthopyroxene + Ti-pargasite. The parental melt has trace element patterns typical of subduction zone magmas. The crystallization sequence, mineral compositions, and modes indicate that cumulates formed from a H₂O-rich basaltic andesite, which intruded at low-pressure (~2 kbar) and temperatures of 1,050-1,100 °C. SHRIMP U-Pb dating of zircons from ultramafic cumulates and adjacent metagranodiorite yielded ages of 309LJ and 295Dž Ma, respectively. In agreement with field relationships, these results show that the mafic-ultramafic cumulates represent a co-genetic, early product of the Late Carboniferous plutonic activity in the western Tauern window, which started in the Westphalian, earlier than previously thought. Our data on the most primitive rocks in the Zillertal massif permit, for the first time, insight into the parental magma and thus into the origin of this Late Carboniferous calc-alkaline magmatism, which was most likely related to slab break off during the Late Variscan convergence.     

Comet Machholz (C/2004 Q2): morphological structures in the inner coma and rotation parameters

Extensive observations of comet C/2004 Q2 (Machholz) were carried out between August 2004 and May 2005. The images obtained were used to investigate the comet’s inner coma features at resolutions between 350 and 1500 km/pixel.     

Seismic characterization of shallow bedrock sites with multimodal Monte Carlo inversion of surface wave data

Sites with a limited overburden over a stiff basement are of particular relevance for seismic site response. The characterization of such stratigraphies by means of surface wave methods poses some difficulties in interpretation. Indeed the presence of sharp seismic contrasts between the sediments and the shallow bedrock is likely to cause a relevance of higher modes in the surface wave apparent dispersion curve, which must be properly taken into account in order to provide reliable results. In this study a Monte Carlo algorithm based on a multimodal misfit function has been used for the inversion of experimental dispersion curves. Case histories related to the characterization of stations of the Italian accelerometric network are reported. Spectral ratios and amplification functions associated to each site are moreover evaluated to provide an independent benchmark test. The results show the robustness of the inversion method in such non-trivial conditions and the possibility of getting an estimate of uncertainty related to solution non-uniqueness.