Tracing the boundaries of Cenozoic volcanic edifices from Sardinia (Italy): a geomorphometric contribution

Unequivocal delimitation of landforms is an important issue for different purposes, from sciencedriven morphometric analysis to legal issues related to land conservation. This study is aimed at giving a new contribution to the morphometric approach for the delineation of the boundaries of volcanic edifices, applied to 13 monogenetic volcanoes (scoria cones) related to the Pliocene–Pleistocene volcanic cycle in Sardinia (Italy). External boundary delimitation of the edifices is discussed based on an integrated methodology using automatic elaboration of digital elevation models together with geomorphological and geological observations. Different elaborations of surface slope and profile curvature have been proposed and discussed; among them, two algorithms based on simple mathematical functions combining slope and profile curvature well fit the requirements of this study. One of theses algorithms is a modification of a function introduced by Grosse et al. (2011), which better performs for recognizing and tracing the boundary between the volcanic scoria cone and its basement. Although the geological constraints still drive the final decision, the proposed method improves the existing tools for a semi-automatic tracing of the boundaries

Effect of probiotics on oral candidiasis: A systematic review and meta-analysis

Oral candidiasis (OC) is an increasing health problem due to the introduction of new drugs, population aging, and increasing prevalence of chronic illness. This study systematically reviews the effects of the oral intake of probiotics, prebiotics, and synbiotics on Candida spp. counts (colony-forming units (CFU)/mL) in oral and palatal samples. A literature search was conducted. Twelve studies, eight randomized clinical trials (RCTs), and four pre-post studies, resulted as eligible for the meta-analysis, which was performed through a Bayesian random-effects model. All studies analyzed probiotics, and none of them analyzed prebiotics or synbiotics. The treatments effects were measured in terms of odds ratio (OR) of OC (CFU/mL >102, 103, or 104). The meta-analytic OR was 0.71 (95% credibility interval (CrI): 0.37, 1.32), indicating a beneficial effect of treatment; the I2 index was 56.3%. Focusing only on RCTs, the OR was larger and more precise at 0.53 (95% CrI: 0.27, 0.93). The effect of treatment appeared to be larger on denture wearers. Our findings indicate that the intake of probiotics can have a beneficial effect on OC and that the effects could vary according to the patients’ characteristics. Due to the presence of medium–high-risk studies, the results should be interpreted with caution

I caratteri tessiturali delle ignimbriti saldate dell’Isola di San Pietro (Sardegna; Italia)

Welded ignimbrites show a large variability of welding intensity and of post-depositional crystallization. According to existing literature, a fine characterization of welded ignimbritic units involves: 1) a classificatiory scheme which includes 5 up to 6 categories of welding intensity, 2) the definition of the style of post depositional crystallization. This classification can result time-consuming and out of the standards required by a general description of ignimbrite units in the case of regional geological survey of volcanic terrains. In the new 1:50,000 geological mapping survey of the San Pietro Island (Sardinia, Italy) performed in the framework of the national CARG Project, a large number of samples of ignimbrite products has been collected. The geology of the area is characterized by Oligo-Miocene volcanic deposits, which testify to an intense explosive activity basically featured by the deposition of many variably welded ignimbritic units and, subordinately, by effusive activity, mainly characterized by lava coulees. All the products derive from the eruption of highly evolved magmas of both calc-alkaline and peralkaline affinity. We present here a simplified scheme for microscopic facies classification of ignimbrite deposits, based on the aspect ratio of the fiammae, the strength of glass shards alignment, and the style of crystallization of the matrix, that can be used for the lithological characterization of ignimbritic units in other mapping projects

A simplified scheme for the description of textural features in welded ignimbrites: the example of San Pietro Island (Sardinia; Italy)

Welded ignimbrites show a large variability of welding intensity and post-depositional crystallization. According to existing literature a complete characterization of welded ignimbritic units involves: l) a classification scheme which includes up to 5-6 categories of welding intensity; 2) the definition of the style of post depositional crystallization. This classification can be very time-consuming and well beyond the standards required for a general description of ignimbrite units for regional geological mapping purposes. During the geological survey of the San Pietro Island (Sardinia, Italy) in the framework of the new geological map of Italy on a scale l:50000 (CARG Proiect), a large number of samples from different ignimbritic units has been collected. The geology of the area is characterized bv Oligocene-Miocene volcanic deposits, which testify for the intense explosive activity with the deposition of many variably welded ignimbritic units and, subordinately, local effusive activity, mainly characterized by the emplacement of lava coulees. All rhe products derive from the eruption of highly evolved magmas of both calc-alkaline and peralkaline affinity. We present here a new simplified scheme for the facies classification of these ignimbritic deposits. The scheme is based on three main textural feaiures: the aspect ratio of the fiammae, the degree of shards alignment and the style of crystallization of the matrix. All these features can be used to describe the ignimbrite units for the scope of their lithological characterization in mapping projects. We suggest that the scheme can have a general interest for the geological mapping of areas dominated by the presence of welded ignimbritic units

Stratigraphy of a Slightly Peralkaline, Rheomorphic Welded Ignimbrite:The Monte Ulmus Unit (SW Sardinia).

Volcanic deposits of the south-western sector of Sardinia are referred to an eruptive activity owing to a magmatic arc active between 32.4 and 13.8 Ma [Lecca et al.1997] as results of subduction of oceanic lithosphere NNW direct [Cioni et al. 2005]. Magmatic activity is linked with the opening of Mediterranean sea and 60° counter-clock-wise rotation of the Sardinia-Corse microplate that ends 19 Ma ago [Savelli et al. 2002]. The oligo-miocene volcanic activity can be subdivided into two phases: an Older phase (28.4-17.7 Ma) and an Younger phase (17.6 – 13.8 Ma) during that sixteen calc-alkaline and peralkaline, dacitic to rhyolitic ash flow tuff were emplaced [Mundula et al. 2009]. Monte Ulmus unit has yielded a K-Ar date of 15,5 ± 0,5 Ma [Morra et al. 1994]. It is a rheomorphic high-grade, low-aspect-ratio rhyolite to comenditic ignimbrite with thickness comprise between 8 to 98 m, spread in an area of 300 km2. About 41 stratigraphic sections, site in San Pietro, Sant’Antioco and Sulcis-Iglesiente areas , were studied and described . The Monte Ulmus unit drapes the Upper Commenditic Units (Ventrischio unit) in all its outcroups even if in the northern sector of San Pietro island, rest on some comenditic lava flow units ( Nasca and Vinagra units). The Monte Ulmus is overlains by the late Miocene events, testify by the Paringianu and Serra di Paringianu ignimbrite units and by the last comenditic lava flow event (Monte Tortorisio unit). The Monte Ulmus unit is divided into four main eruptive phases: a fall-out deposit followed by three pyroclastic flow events (named A, B1 and B2), separate by a sharp contact and as viewable by the vertical bulk rock densities trends; erosion surface absence and a columnar jointing that cross cutting the ignimbrites point out that this phases were emplaced during the same eruption or in a shortly time. The eruptive centre is hardly to locate but flow lineation trend (NW-SE in Sulcis area and NE-SW in San Pietro island), isophacs of ground fall-out and proximal facies present in the northern sector of San Pietro island may be locate the eruptive centre in the northern sector. The coarse, massive, totally argillified ash fall deposit have thickness comprise between 20cm and 2 cm. Where physical alteration is lesser (San Pietro), the average grain-size is comprise between fine to medium lapilli. Upon the fall deposit there is a basal vitrophire, 30 cm thick, generally strongly argillified although in some section is more preserved. In Sant’Antioco areas the basal vitrophire, have oblate eutaxitic white fiamme (10%) with average size of 3 cm and aspect ratio 2:1-3:1. Quartz and alkali feldspar crystal (lower than 5%) have 2 mm maximum size and rare rounded lithics clast with pressure shadows have maximum size of 3 cm. The core of sub-unit “A” is a 2 to 32m thick, reddish, fine ash, locally rheomorphic high-grade ignimbrite that croup out principally in Sant’Antioco island and it shows character of deposition in sub-aerial and shallow water environment. It contain two kinds of fiamme : a blackish(10-15 %) , obsidian-like, parataxitic fiamme with aspect ratio variable from 15:1 to 30:1 and a whitish ones (6-7%), highly compacted , sub-rounded to oblate shapes(aspect ratio variable from 2:1 to 5:1). Quartz and alkali feldspar crystal (1-2%) have maximum size of 3 mm and lithics (1-2 %) are sub-angular shaped and they are an older ignimbrites units fragments. The sub-unit, in section thicker than 10 meters, shows a gradual changes in welding e rheomorphic facies. A lower massive densely welded zone is overlain by a flow-banded densely welded core with rotational structure and by a highly rheomorphic zone that increase magnitude upward. Folds smaller than 0.5 m , prolate vesicles, sheet-joint and breccias are localized at the ground of rheomorphic zone, while, at top of sub-unit, where the ignimbrite is lava-like, there are folds bigger than 1meter, diapiric structures and 10meters radius blisters. Sub-unit B is a 3 to 52 m thick, locally reomorphic, dm-size components rich, poor porfiritic (Qtz+Sd), high grade ignimbrite composed by two layers (B1 and B2) divided by a sharp contact that croup out principally in San Pietro island and Sulcis area. This sub-unit is characterize by an high-concentration of chemically different juvenile pyroclasts randomly oriented, that are deposed in physical different status. The sub-unit B1, 2 to 24m thick, is a reddish, massive, fine grained welded tuff matrix with three typologies of juvenile clasts: a blackish high porphiritic (Sd) no vesiculated fiamme, a reddish low porfiritic fine grained fiamme and a whitish vesiculated fiamme. The blackish fiamme, around lithics clast, are warp while the white fiamme, where undergo no-coaxial stress, bend the matrix. Lithics fragments are principally old ignimbrite fragments with square to partially rounded border. This sub-unit shows rheomorphic facies in Sant’Antioco where covered the thicker crop out of sub-unit A and in San Pietro island where is filled into a valley. Sub-unit B2, 5 to 28 thick, is light-gray locally rheomorphic moderately welded tuff with two typologies of juvenile clast (blackish and whitish) . Fragments decrease in size (from dm-size to mm-size) and percentage upwards. Furthermore at ground, juvenile clasts have size comprise between 5 to 60 cm and they are randomly oriented with a rough out parataxitic structure. Juvenile fragment are blackish,glassy, high porfiritic (Sd) eutaxitic, no-vesiculated, dm-size fiamme and whitish eutaxitic vesiculated dm-size fiamme. Lithics fragments are rounded reddish high porfiritic older welded tuff with maximum size of 70cm in San Pietro. Into San Pietro island paleovalley, the ground portion of sub-unit B2 is highly rheomorphic whitish densely welded with >1m folds while at top it pass, sideways gradually and vertically with a sharp contact, to a blackish, component poor, vitric

The Monte Ulmus Unit (SW Sardinia, Italy): stratigraphy of a rheomorphic welded ignimbrite.

Monte Ulmus Ignimbrite (MUI) is a high-grade, rhyolitic, welded, locally rheomorphic, low-aspect-ratio ignimbrite. Three main pyroclastic flow units (in the sense of Smith, 1960), preceded by a basal fall-out deposit (F) have been distinguished, named A, B1 and B2. Each flow unit is constituted by different lithofacies strongly related to the morphology at emplacement. Unit A is a 2 to 32 m thick, reddish to grey, fine grained, high-grade, welded ignimbrite that crops out mainly in Sant’Antioco Island. A basal vitrophyre, 30 cm thick, represents the base of unit A, overlain by a massive glassy lithofacies. These two lithofacies develop independently by paleotopography. In paletopographic lows, the main part of the ignimbrite is characterized by the presence of a rheomorphic facies with thinly spaced sheet joints and decimetric to decametric rheomorphic folds. This rheomorphic portion of unit A develops a secondary vesiculation and a granophyric crystallization style. Units B1 and B2, 5 to 52 m thick, crop out mainly in San Pietro Island and Sulcis area. They are represented by a poorly porphyritic, Quartz- and Sanidine-bearing, high grade deposit in which four different lithofacies have been described. These units are characterized by a high concentration of different, randomly oriented, juvenile pyroclasts and present rheomorphic deformation in correspondence of topographic lows. Vertical variation of textural features along MUI clearly reflect into the observed variation of bulk rock density. On topographic highs, discontinuities in the textural and physical features along the ignimbrite sequence clearly trace the transition between different flow units. On topographic lows and on gently dipping paleovalley slopes, the rheomorphic processes smoothed the discontinuities between the different flow units, locally inducing secondary vesiculation which disturbs the vertical density profile. The occurrence of coarse lithic boulders in the northern sector of San Pietro Island, and the inferred dispersal of the fall deposits at the base of the ignimbrite suggest that the source was possibly located north-northeast of the San Pietro Island

The explosive activity of the 1669 Monti Rossi eruption at Mt. Etna (Italy)

Preceded by 14 days of intense seismic activity, a new eruption started on the south flank of Mt Etna, Sicily (Italy) early in the morning of 11 March 1669 opening up a series of NS eruptive fissures. The eruption is one of the most destructive flank eruptions of Etna in historical times; it lasted until 11 July, and was characterized by simultaneous explosive and effusive activity during the first three months, while only lava flow output in the last month. The activity built up the large composite cone of the ``Monti Rossi{'' at the lower end of the eruptive fissures, and caused severe damage to the nearby inhabited areas. The prolonged effusive activity generated lava flows for >15 km, which destroyed several villages and the western part of the town of Catania before reaching the coastline and entering the sea. In this paper, we examine the tephro-stratigraphy of the products of the explosie activity. An in-depth analysis of historical accounts was used to define the chronology of the main eruptive phases (precursors, explosive activity and initial effusive phenomena). The geology of the cone and of the fallout deposits were defined through a field survey over a distance of 5 km from the Monti Rossi. Textural (grain-size, morphological, componentry), density and petrological analyses of tephra samples provided a sedimentological, physical and geochemical characterization of erupted products. Integrating ground and historical data enabled defining the evolution of the cone, identifying and correlating four main cone-forming units. By tracing the dispersal map of the main distal tephra beds (the finer ash being dispersed mainly to the NE as far as Calabria and to the south of Sicily and the 10-cm isopach of the total deposit covering an area up to 53 km(2)), we estimated a total tephra fallout volume, including the Monti Rossi cone, of about 6.6 x 10(7) m(3) (about 32 x 10(7) m(3) DRE). The 1669 event can be considered an archetype of the most hazardous expected eruption on the densely populated flanks of Etna. Reconstructing the eruptive chronology and styles of the 1669 eruption therefore, represents the basic data to assess volcanic hazard from eventual similar flank events in the future. (C) 2016 Elsevier B.V. All rights reserved.}Published115-1333V. Dinamiche e scenari eruttiviJCR Journalrestricte