Geology of the Raditladi quadrangle, Mercury (H04)

In this work, we present a 1:3,000,000-scale geologic map of the Raditladi quadrangle (H04) of Mercury. The area covers nearly 7% of the entire planet and encompasses several features of interest such as the Caloris basin, the Raditladi basin, hollow clusters and volcanic features. The mapping took advantage of the data produced during MESSENGER's orbital phase. The mapped deposits include impact-related units observed at several scales from the Caloris basin to the secondary crater chains. The Smooth Plains unit covers the majority of the area, mantling the older Intercrater Plains and Bright Intercrater Plains units. Results show that the emplacement of all the main units and the Caloris impact event, representing the main geologic events in the quadrangle, were concentrated between 3.96 and 3.72 Ga. After this intense phase, the geologic framework was modified only by local events such as impact craters and hollow formation. This map is among the first products for the detailed geologic characterization of Mercury at such a scale. It will contribute as a constraint and a support for both further local investigation and mapping, and targeting of the forthcoming BepiColombo ESA/JAXA joint exploration mission to Mercury

Urban Geology for the Enhancement of the Hypogean Geosites: the Perugia Underground (Central Italy)

AbstractUrban geology analyses natural risks and promotes geoheritage in urban areas. In the cities, characterized by a high cultural value, the hypogean artificial cavities, often present in the downtown, offer a unique opportunity to show the geological substratum. Moreover, these places could be a point of interest in urban trekking with the abiotic component of the landscape as a topic (geotourism). To investigate these areas, rigorous bibliographic research and a geomorphological assessment are the first steps, but, besides, non-invasive methods are new techniques increasingly in demand. In this paper, we present a multidisciplinary study on the Etruscan Well (third century B.C.), one of the most important Etruscan artefacts in Perugia (Umbria region, Central Italy). The characteristics of the sedimentary deposits outcropping along the perimeter walls have been collected. Moreover, to show the underground geoheritage, we provide a 3D model of the well and the surrounding area integrating a georeferenced laser scanner survey with ground-penetrating radar prospecting. We aim to obtain a tridimensional mapping of accessible internal rooms to depict the geological characteristics of the Etruscan Well, also revealing a surrounding network of buried galleries. The results are not only a meaningful advancement in the archaeological, geological and historical knowledge of the downtown of Perugia but are a hint for the geoheritage promotion and dissemination, providing images and 3D reconstruction of underground areas

Retrieving magma composition from TIR spectra: implications for terrestrial planets investigations

Emissivity and reflectance spectra have been investigated on two series of silicate glasses, having compositions belonging to alkaline and subalkaline series, covering the most common terrestrial igneous rocks. Glasses were synthesized starting from natural end-members outcropping at Vulcano Island (Aeolian Islands, Italy) and on Snake River Plain (USA). Results show that the shift of the spectra, by taking Christiansen feature (CF) as a reference point, is correlated with SiO2 content, the ScfM factor and/or the degree of polymerization state via the nBo/t and temperature. the more evolved is the composition, the more polymerized the structure, the shorter the wavelength at which CF is observable. CF shift is also dependent on temperature. The shape of the spectra discriminates alkaline character, and it is related to the evolution of Qn structural units. Vulcano alkaline series show larger amount of Q4 and Q3 species even for mafic samples compared to the subalkaline Snake River Plain series. Our results provide new and robust insights for the geochemical characterization of volcanic rocks by remote sensing, with the outlook to infer origin of magmas both on Earth as well as on terrestrial planets or rocky bodies, from emissivity and reflectance spectra

Tectonic evolution of the Lachlan Fold Belt, southeastern Australia: constraints from coupled numerical models of crustal deformation and surface erosion driven by subduction of the underlying mantle

We have used a coupled thermo-mechanical finite-element (FE) model of crustal deformation driven by mantle/oceanic subduction to demonstrate that the tectonic evolution of the Lachlan Fold Belt (LFB) during the Mid-Palaeozoic (Late Ordovician to Early Carboniferous) can be linked to continuous subduction along a single subduction zone. This contrasts with most models proposed to date which assume that separate subduction zones were active beneath the western, central and eastern sections of the Lachlan Orogen. We demonstrate how the existing data on the structural, volcanic and erosional evolution of the Lachlan Fold Belt can be accounted for by our model. We focus particularly on the timing of fault movement in the various sectors of the orogen. We demonstrate that the presence of the weak basal decollement on which most of the Lachlan Fold Belt is constructed effectively decouples crustal structures from those in the underlying mantle. The patterns of faulting in the upper crust appears therefore to be controlled by lateral strength contrasts inherited from previous orogenic events rather than the location of one or several subduction zones. The model also predicts that the uplift and deep exhumation of the Wagga-Omeo Metamorphic Belt (WOMB) is associated with the advection of this terrane above the subduction point and is the only tectonic event that gives us direct constraints on the location of the subduction zone. We also discuss the implications of our model for the nature of the basement underlying the present-day orogen

Effects of lateral variations of crustal rheology on the occurrence of post-orogenic normal faults: The Alto Tiberina Fault (Northern Apennines, Central Italy)

The Northern Apennines (NA) are characterized by formerly compressive structures partly overprinted by subsequent extensional structures. The area of extensional tectonics migrated eastward since the Miocene. The youngest and easternmost major expression of extension is the Alto Tiberina Fault (ATF). We estimate 2D rheological profiles across the NA, and conclude that lateral rheological crustal variations have played an important role in the formation of the ATF and similar previously active faults to the west. Lithospheric delamination and mantle degassing resulted in an easterly-migrating extension-compression boundary, coinciding at present with the ATF, where (i) the thickness of the upper crust brittle layer reaches a maximum; (ii) the critical stress difference required to initiate faulting at the base of the brittle layer is at a minimum; and (iii) the total strengths of both the brittle layer and the whole lithosphere are at a minimum. Although the location of the fault is correlated with lithospheric rheological properties, the rheology by itself does not account for the low dip (~ 20°) of the ATF. Two hypotheses are considered: (a) the low dip of the ATF is related to a rotation of the stress tensor at the time of initiation of the fault, caused by a basal shear stress (~ 100 MPa) possibly related to corner flow associated with delamination; or (b) the low dip is associated to low values of the friction coefficient (≤ 0.5) coupled with high pore pressures related to mantle degassing. Our results establishing the correlation between crustal rheology and the location of the ATF are relatively robust, as we have examined various possible compositions and rheological parameters. They also provide possible general indications on the mechanisms of localized extension in post-orogenic extensional setting. The hypotheses to account for the low dip of the ATF, on the other hand, are intended simply to suggest possible solutions worthy of further study

GPR Detection of Fossil Structures in Conductive Media Supported by FDTD Modelling and Attributes Analysis: An Example from Early Pleistocene Marine Clay at Bargiano Site (Central Italy)

The application of Ground Penetrating Radar (GPR) prospecting to the search of fossil structures, particularly using advanced techniques like Finite-difference time-domain (FDTD) modelling and GPR attribute analysis, is currently poorly exploited in paleontology. Here, we promote the use of such a GPR workflow at Bargiano (Umbria, central Italy), a unique paleontological site known for the discovery of cetacean skeletons, dolomitized sperm-whale cololites (Ambergrisichnu salleronae), and layered fossil assemblages. The study site is characterized by a very uneven topography shaping highly conductive clayey deposits, representing not exactly ideal conditions for GPR surveying. After generating models encompassing a real topography and variable electrical properties of media, we simulated buried fossil structures at variable depth with different size and geometry, using different operative frequencies. After obtaining information on the characteristics of reflections, investigation depth, and detectability, we provide a comparison with experimental data, also used to compute instantaneous amplitude and phase attributes. Upon depicting a peculiar GPR signature for our targets, we discuss the results in light of ground-truthing performed through trenching. Our workflow allowed us to restrict the excavation areas, extending the surface information in depth in a non-invasive way, and optimizing the field operations, necessary for the preservation of the study site

The geodynamical evolution of the Northern Apennines chain (Central Italy): an exploring numerical model

In this paper, 2D thermo-mechanical models with crustal deformation, driven by subduction, are performed to test the geodynamical scenario of a slab-retreat for the Northern Apennines chain (Central Italy). In the models, the lithosphere is regarded as

\u201cGeophysical paleoseismology\u201d through high resolution GPR data: A case of shallow faulting imaging in Central Italy

In this work we report a GPR study across a tectonic discontinuity in Central Italy. The surveyed area is located in the Castelluccio depression, a tectonic basin in the Central Apennines, close to thewestern border of theMt. Vettore. Its West flank is characterised by a set ofW-dipping normal faults, considered active and capable of generating strong earthquakes (Mw=6.5, Galli et al., 2008). A secondary fault strand, already studied with paleo-seismological analysis (Galadini and Galli, 2003), has been observed in the Quaternary deposits of the Prate Pala alluvial fan. We first defined the survey site using the data available in literature and referring to topographic and geological maps, evaluating also additional methodologies, such as orthophoto interpretation, geomorphologic analysis and integrating all the information in a GIS environment. In addition, we made extensive use of GPR modelling, reproducing the geometric characteristics of the inferred fault area and interpreting the synthetic profiles to recognise local geophysical indications of faulting on the radargrams. Finally, we performed a GPR survey employing antennas with different frequencies, to record both 2D Common Offset profiles and Common Mid Point (CMP) gathers for a more accurate velocity estimation of the investigated deposits. In this paper we focus on the evaluation of the most appropriated processing techniques and on data interpretation. Moreover we compare real and synthetic data, which allow us to better highlight some characteristic geophysical signatures of a shallow fault zone