Assessment of the ecological status of transitional waters in Sicily (Italy): First characterisation and classification according to a multiparametric approach

A 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari, Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance gave insights on microbial community efficiency in organic matter transformation and on allochthonous inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated.Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication gradient. The significant relationships among TRIX, trophic and microbial parameters suggested the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement the Water Framework Directive when assessing the ecological status of transitional water systems.     

OSL chronology of Quaternary terraced deposits outcropping between Mt. Etna volcano and the Catania Plain (Sicily,southern Italy)

In this paper we tested the applicability of the Optically Stimulated Luminescence (OSL) technique through Single-Aliquot Regenerative-dose (SAR) protocol, on single grain quartz extracted from alluvial–coastal sediments. Five samples were collected from deposits belonging to a flight of seven orders of coastal–alluvial terraces outcropping in the area between Mt. Etna volcano and the Catania Plain (Sicily, southern Italy), at the front of the Sicilian fold and thrust system. After various performance tests, we obtained OSL ages ranging between 240 ± 12 and 80 ± 4 ka, consistent with the normal evolutionary model of a terraced sequence, moving from the highest to the lowest elevation. Obtained data allowed us to determine a mean uplift rate of 1.2 mm/year during the last 240 ka, mostly related to regional uplift processes coupled with sea-level changes. Moreover, terraces belonging to the two highest orders are folded, forming a large anticline. According to our results, the frontal thrust of the Sicilian chain was active between 236 and 197 ka ago, even though seismological and geodetic data suggest current activity to the back.     

典型小陆块海相成钾机理——以西西里微陆块钾盐矿床为例

中国大陆是由多个小陆块经多期次离散碰撞拼合而成,而"小陆块是否能成大钾"一直是国内钾盐研究领域关注的科学问题。文章剖析了意大利西西里微陆块的典型海相钾盐矿床形成条件与机理,为中国小陆块成钾研究提供借鉴。在晚中新世墨西拿盐度危机(Messinian Salinity Crisis)最盛期(5.60~5.55 Ma),西西里岛的卡尔塔尼塞塔盆地聚集了高达2亿t的钾盐镁矾矿。通过对卡尔塔尼塞塔盆地钾盐矿的赋存地层格架、矿体特征、成矿模式和机理进行梳理和总结,指出该矿床呈层状赋存于地中海"再沉积下石膏组"的原生石盐岩中,形成于深水、分层的常年性盐湖环境;晚中新世中地中海碰撞挤压的构造活动导致卡尔塔尼塞塔盆地强烈挠曲下凹,形成多个次级成矿凹陷;次级凹陷接受海水的周期性补给;在墨西拿盐度危机最盛期,由于气候变冷变干、直布罗陀海峡关闭、海平面急剧下降,远离补给源的次级凹陷变得更加封闭,从而在5万年的极短时间内经强烈蒸发,聚集为大规模钾盐矿。西西里微陆块尽管陆块小、盆地小,但在满足封闭构造_干旱气候_充足物源三要素耦合的特定时期内,同样形成了大型钾盐矿床。因此,西西里微陆块的钾盐成矿实例证明海相小陆块同样具有形成大型钾矿床的潜力,这对中国海相小陆块汇聚区的找钾工作具有重要的借鉴意义。     

Active faulting and seismicity along the Siculo–Calabrian Rift Zone (Southern Italy)

Southern Italy is dominated by extensional tectonics that in the Calabrian arc and Eastern Sicily produced the development of the Siculo–Calabrian Rift Zone (SCRZ). This zone is represented by a ≈ 370 km-long fault belt consisting of 10 to 50 km long distinct fault segments which extend both offshore and on land being also responsible of the crustal seismicity of this region. The geological and morphological observations indicate that the active normal faults of the SCRZ are characterized by throw-rates ranging from 0.7 to 3.1 mm/a. They accommodate an almost uniform horizontal extension-rate of about 3.0 mm/a along a WNW–ESE regional extension direction. Based on our field observations and following empirical relationships between magnitude and surface rupture length connections between large crustal earthquakes and distinct fault segments of the SCRZ have been also tentatively tested. Our data indicate moreover that the magnitudes (M) of the historical and instrumental earthquakes are consistent with the estimated values and that the geometry and kinematics of the fault segments and the related different crustal features of the SCRZ control the different seismic behaviours of adjacent portions of the active rift zone.     

The evolution of the mantle source beneath Mt. Etna (Sicily,Italy): from the 600 ka tholeiites to the recent trachybasaltic magmas

ABSTRACT

The spatial/temporal proximity of Mt. Etna to the Hyblean Plateau and the Aeolian slab makes the discussion on the nature of its mantle source/s extremely controversial. In this study, a detailed geochemical overview of the entire Mt. Etna evolutionary sequence and a comparison with the magmatism of the Hyblean Plateau was proposed to: (i) simulate the composition of Mt. Etna tholeiitic to alkaline primitive magmas in equilibrium with a fertile mantle source; (ii) model the nature, composition and evolution of the mantle source from the tholeiitic stage (600 ka) to present magmatism. According to our simulations, two amphibole + phlogopite-bearing spinel lherzolite sources are able to explain the wide range of Etnean primary magmas. The enrichment in LILE, ⁸⁷Sr/⁸⁶Sr, Rb and H₂O of the magmas emitted after 1971 (but also discontinuously generated in both historic and prehistoric times) are caused by different melting proportions of amphibole and phlogopite in a modally and compositionally homogeneous mantle domain, with melting degrees analogous to those required to produce magmas erupted prior to 1971. The behaviour of the hydrous phases during melting could be ascribed to a variable H₂O/CO₂ activity in the mantle source, in turn related to the heat/fluxes supply from the asthenospheric upwelling beneath Mt. Etna. All these considerations, strengthened by numerical models, are then merged to review the complex Pliocene/Lower Pleistocene to present day’s geodynamic evolution of eastern Sicily.     

A rapid method to assess fire-related debris flow hazard in the Mediterranean region: An example from Sicily (southern Italy)

Increased atmospheric temperatures during the high-pressure which characterise the Mediterranean climate in the dry summer time, coupled with an increase in the intensity of storms in the following wet season over recent years, increase the risk of summer fires as well as debris flows and floods in the autumn and/or in the following years. In addition, the diffuse urbanization of Italy requires a rapid and reliable tool be available in order to obtain preliminary information, at the end of the summer season, that identifies newly fired areas that present a significant hazard to human populations. In such burned zones, soil instability may be more severe favouring debris flows which may impact on populated zones. Thus, in this paper we discuss a rapid methodology to: (i) identify burned areas using band ratio's using multitemporal LANDSAT ETM images; (ii) evaluate the potential of the burned areas as the source of debris flows based on morphometric parameters (slope and hill slope curvature); (iii) evaluate the structures, such as houses and roads, exposed to potential damage by debris flows. Hazardous areas were evaluated using a stochastical model coupled with an empirical relationship which accounts for the mobility of the debris flows. The methodology provides a classification of the most “dangerous” burned areas and the potentially maximum inundated downslope areas. This has been applied to Sicily for the period autumn 2001–autumn 2002. The total burned area was 76.37 km². According to the classification proposed 6.4% of the burned areas were consider of very high to high hazard potential, 54.4% of medium hazard and 43.2% of low hazard potential.     

Soil erosion prediction at the basin scale using the revised universal soil loss equation (RUSLE) in a catchment of Sicily (southern Italy)

Soil erosion by water is a serious problem in southern Italy, particularly in Sicily which is one of the Italian administrative regions prone to desertification. Soil erosion not only affects soil quality, in terms of agricultural productivity, but also reduces the availability of water in reservoirs. This study was conducted in the Comunelli catchment in south-central Sicily, to predict potential annual soil loss using the revised universal soil loss equation (RUSLE) and to test the reliability of this methodology to predict reservoirs siltation. The RUSLE factors were calculated for the catchment using survey data and rain gauge measurement data. The R-factor was calculated from daily, monthly and annual precipitation data. The K-factor was calculated from soil samples collected in May and November 2004. The LS topographic factor was calculated from a 20 m digital elevation model. The C- and P-factors, in absence of detailed data, were set to 1. The results were compared with those obtained from another soil loss estimation method based on ¹³⁷Cs and with the soil loss estimated from the sediment volume stored in the Comunelli reservoir between 1968 and 2004.     

Magnetic stratigraphy of Etan products. I-medieval lavas

Summary Mean magnetisation directions from 6 lava flows of questionable historical age have been determined. The results, which are based upon very stringent linearity criteria during demagnetisation, point out erroneous dating and the corresponding lavas can be ascribed to medieval activity of Mount Etna, as already suggested for some of the investigated flows, covering a time interval of some centuries around AD 1000. The site mean direction of AD 1536 historically dated lava flow agrees with a previous study (Tanguy et al., 1985), while the site mean directions of AD 1566 and AD 1169/812 differ significantly from those reported earlier. Neither AD 812 nor AD 1169 dating is consistent with the site mean direction of the related flow being compatible with an emplacement age possibly a few decades before AD 1000. The 3 lava flows historically dated AD 1595 exhibit different within site mean directions indicating that they cannot be referred to coeval activity of the volcano; the site mean direction of one of the flows is compatible with an emplacement occurring very close to AD 1000. The resulting SVC is significantly shifted eastwards with respect to that of previous study (Tanguy et al., 1985). However, its older part nearly overlaps the medieval Vesuvius SVC relocated to Etna. This indicates that the strict linearity analysis carried out during demagnetisation has allowed to clearly define the characteristic magnetisations of the investigated lava flows. The adopted procedure is appropriate for performing successful magnetic stratigraphy surveys in volcanic areas.