Stream-scanning laser system, electric sensing counter and settling grain size analysis: a comparison using reference materials and marine sediments

Surface and deep-sea core sediments and two sets of standards were measured by three different techniques — Galai Cis-1 laser system, Coulter Counter TA II, and Micromeritics SediGraph 5000D — in order to compare the Galai results with the other two. The differences between the three types of measuring device turned out to be greater in sediments than in standards, and were attributed to the physical properties, shape, density and composition of the particles (complexity of the matrix). Comparison of moment statistics showed that the Galai determines coarser grain sizes than the Coulter and finer than the SediGraph, particularly as regards analysis of surface sediments. The relationships between Galai and SediGraph were estimated using analysis of variation/residuals within individual intervals. The analysis showed a higher variability of residuals for the coarser fractions (8–16 μm and 16–32 μm) with respect to the finer (2–4 μm and 4–8 μm) fractions. The <2 μm SediGraph fraction, with a cut-off at 0.49 μm, showed good correspondence with the <2.5 μm Galai analysis.     

Red micas from basal ignimbrites of Mt. Vulture (Italy): interlayer content appraisal by a multi-methodic approach

The crystal chemistry of red phlogopites from Mt. Vulture (Italy) ignimbrites has been studied by electron microprobe, secondary ion mass spectrometry (SIMS), single crystal structural investigation and Fourier transform infrared (FTIR) spectroscopy. The analysed phlogopite has Fe/(Fe + Mg) ∼ 0.35, TiO₂ (wt%): 2.8–5.0 and H₂O (wt%): 1.24–3.37. Infrared spectra revealed the presence of bands due to the NH₄⁺ and H₂O stretching and bending vibrations. The samples belong to the 1M polytype. The bimodal behaviour of several structural parameters allows red micas to be clustered into two distinct groups: K⁺ ↔ NH₄⁺, H₂O and M³⁺-vacancy substitutions dominate in the first group; M^3+,4+-oxy, in the second group. It has to be pointed out that quantitative analysis of hydrogen (via SIMS) together with the characterization of the local environment of the anionic site (via FTIR) are fundamental in assessing the correct structural formula and the substitution mechanisms in micas. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Impact of ocean acidification on the carbonate sediment budget of a temperate mixed beach

The production of sediments by carbonate-producing ecosystems is an important input for beach sediment budgets in coastal areas where no terrigenous input occurs. Calcifying organisms are a major source of bioclastic carbonate sediment for coastal systems. Increased levels of CO₂ in the atmosphere are leading to an increase in the partial pressure of CO₂ on ocean seawater, causing ocean acidification (OA), with direct consequences for the pH of ocean waters. Most studies of OA focus on its impact on marine ecosystems. The impact of OA on carbonate-producing ecosystems could be to reduce the amount of sediments supplied to temperate coastal systems. The aim of this study was to quantify the effect of the predicted OA on the long-term sediment budget of a temperate Mediterranean mixed carbonate beach and dune system. Based on projections of OA we estimated a fall of about 31% in the present bioclastic carbonate sediment deposition rate, with the biggest decreases seen in the dunes (? 46%). OA is also expected to affect the carbonate sediment reservoirs, increasing the dissolution of CaCO₃and causing net sediment loss from the system (~ 50,000 t century^?1). In the long-term, OA could also play a primary role in the response of these systems to sea-level rise. Indeed, the reduction in the quantity of carbonate sediments provided to the system may affect the speed with which the system is able to adapt to sea-level rise, by increasing wave run-up, and may promote erosion of dunes and subaerial beaches.     

Dramatic decrease of pelagic carbonate production by nannoplankton across the Early Toarcian anoxic event (T-OAE)

In this account we present estimates of nannofossil fluxes in four sections and one borehole all belonging to the Early Jurassic western Tethys. This study aims to map the distribution of pelagic carbonate production across the Early Toarcian anoxic event (T-OAE), and to understand which environmental parameters did control such production. Our results indicate important changes in carbonate production by nannoplankton occurring within the western Tethys and its variations through time. Nannofossil fluxes (specimens per m² per year) are extremely low during the T-OAE in all the studied settings. Higher fluxes are encountered in the westernmost part of the Tethys Ocean before the T-OAE, whilst pelagic carbonate production shifted towards the northern margin of the Tethys after the recovery from anoxic conditions. The dramatic decrease in nannoplankton production during the T-OAE has been interpreted in previous works as a biocalcification crisis related to high pCO₂ in the atmosphere/hydrosphere system. Although a high pCO₂ may have lowered the carbonate saturation state of Early Jurassic oceans and finally hampered biocalcification, we speculate that the most important effects of CO₂ increase were indirect, and affected pelagic producers via changes on climate and sea-level. Namely, it seems that precipitation/evaporation budgets and continental runoff that controlled nutrient levels and salinity in surface oceanic waters were important factors for pelagic biocalcifiers.     

Deriving Star Formation Histories: Evolutionary or Population Synthesis Codes versus Color-Magnitude Diagrams

The goal of this project is to analyze the integrated-light spectrum of a region in the LMC bar, for which HST images are already available yielding color-magnitude diagrams reaching the oldest main-sequence turnoff. Then, we can derive the star formation history in this field through evolutionary/population synthesis of the integrated light from 330 to 990 nm by a variety of independent methods and compare the results with the - in principle - more reliable results derived from the analysis of the color-magnitude diagram (CMD). This confrontation is the key ‘truth-test’ needed for the understanding of the abilities and the limitations of the evolutionary/population synthesis methods that must be applied of necessity to unresolved nearby and far-away galaxies. We report here on the observational part of the project. This revised version was published online in September 2006 with corrections to the Cover Date.     

First historical evidence of a significant Mt. Etna eruption in 1224

The 1224 Mt. Etna eruption is a significant event both in terms of the mass of erupted materials and because it involved the lower eastern slope of the volcano, reaching down to the sea. Nevertheless, it is unknown to current historical catalogues. According to the historical sources, only two other lava flows actually reached as far as the sea: in 396 BC, just north of the present-day inhabited area of Acireale, according to the geological data alone, and in 1669, when the lava covered the south-eastern flank of Mt. Etna and damaged Catania. We present and discuss the two medieval sources that attest to the eruption of 1224 and make available the original texts. Furthermore, through the close analysis of the historical and topographic context of the Etna area, taking account of the roads and ports in the early 13th century, we have tried to single out the possible area of the lava's outlet into the sea in 1224 on historical grounds. A repeat of an eruption similar to that of 1224 would have a serious impact today as the coast is densely populated.     

Inverse analysis of stochastic moment equations for transient flow in randomly heterogeneous media

We present a nonlinear stochastic inverse algorithm that allows conditioning estimates of transient hydraulic heads, fluxes and their associated uncertainty on information about hydraulic conductivity (K) and hydraulic head (h  ) data collected in a randomly heterogeneous confined aquifer. Our algorithm is based on Laplace-transformed recursive finite-element approximations of exact nonlocal first and second conditional stochastic moment equations of transient flow. It makes it possible to estimate jointly spatial variations in natural log-conductivity (Y=lnK)$(Y=\ln K)$, the parameters of its underlying variogram, and the variance–covariance of these estimates. Log-conductivity is parameterized geostatistically based on measured values at discrete locations and unknown values at discrete “pilot points”. Whereas prior values of Y at pilot point are obtained by generalized kriging, posterior estimates at pilot points are obtained through a maximum likelihood fit of computed and measured transient heads. These posterior estimates are then projected onto the computational grid by kriging. Optionally, the maximum likelihood function may include a regularization term reflecting prior information about Y. The relative weight assigned to this term is evaluated separately from other model parameters to avoid bias and instability. We illustrate and explore our algorithm by means of a synthetic example involving a pumping well. We find that whereas Y and h can be reproduced quite well with parameters estimated on the basis of zero-order mean flow equations, all model quality criteria identify the second-order results as being superior to zero-order results. Identifying the weight of the regularization term and variogram parameters can be done with much lesser ambiguity based on second- than on zero-order results. A second-order model is required to compute predictive error variances of hydraulic head (and flux) a posteriori. Conditioning the inversion jointly on conductivity and hydraulic head data results in lesser predictive uncertainty than conditioning on conductivity or head data alone.     

Prehistoric shepherds and caves in the Trieste Karst (Northeastern Italy)

One of the basic problems in the prehistoric studies of the Trieste Karst (northeastern Italy) is that of understanding the use of the numerous caves, which represent the only sites known from Palaeolithic to Middle Bronze Age. Recent sedimentological and soil micromorphological analyses add new data to the traditional archaeological ones. In our opinion, the data should be approached from other than an exclusively chronotypological point of view. The inferences of the data indicate that certain areas of four caves were used for stabling animals, and that this model of site use may be extended to most of the Karst cave sites for the period from the Neolithic to Early Bronze Age. © 2000 John Wiley & Sons, Inc.     

Geological evolution of Mount Etna volcano (Italy) from earliest products until the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data

We present an updated geological evolution of Mount Etna volcano based on new ⁴⁰Ar/³⁹Ar age determinations and stratigraphic data integrating the previous K/Ar ages. Volcanism began at about 500 ka ago through submarine eruptions on the Gela–Catania Foredeep basin. About 300 ka ago fissure-type eruptions occurred on the ancient alluvial plain of the Simeto River forming a lava plateau. From about 220 ka ago the eruptive activity was localised mainly along the Ionian coast where fissure-type eruptions built a shield volcano. Between 129 and 126 ka ago volcanism shifted westward toward the central portion of the present volcano (Val Calanna–Moscarello area). Furthermore, scattered effusive eruptions on the southern periphery of Etna edifice occurred until about 121 ka ago. The stabilization of the plumbing system on the Valle del Bove area is marked by the building of two small polygenic edifices, Tarderia and Rocche volcanoes. Their eruptive activity was rather coeval ending 106 and 102 ka ago, respectively. During the investigated time-span volcanism in Etna region was controlled by a main E–W extensional tectonic related to the reactivation of Malta Escarpment fault system in eastern Sicily. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users. An erratum to this article can be found at