Heavy metal and arsenic distributions in sediments of the Elba-Argentario basin, southern Tuscany, Italy

 Arsenic, chromium, cobalt, copper, lead, nickel, vanadium and zinc distributions in surficial and core sediments of the Elba-Argentario marine basin (southern Tuscany, central-western Italy) are reported. Analysis of such distributions compared with grain size and mineralogical data allowed the identification of areas showing trace element enrichments with respect to natural background. These enrichments are moderate and essentially restricted to Pb and Zn; only As shows a widespread, though not high, positive anomaly. This general pattern is in good agreement with the minor industrialization affecting the basin's watershed. An unexpected anomaly, concerning Co, Pb, and As, as well as Fe and Ti, has been pointed out close to Montecristo Island. This has been ascribed to illegal local dumping of chemical waste. Received: 12 January 1996 / Accepted: 9 September 1996     

Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin

The onset of continent-wide glaciation in Antarctica is still poorly understood, despite being one of the most important palaeoclimatic events in the Cenozoic. The Eocene/Oligocene boundary interval has recently been recognized as a critical time for Antarctic climatic evolution, and it may mark the preglacial–glacial transition. Magnetic susceptibility, intensity of natural and artificial remanences, hysteresis parameters and magnetic anisotropy of the lower half (late Eocene/early Oligocene) of the CIROS-1 core (from McMurdo Sound, Antarctica) reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core. Pseudo-single-domain magnetite is the main magnetic mineral throughout the sequence, and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the Eocene/Oligocene boundary. The detrital magnetite originated from weathering of the Ferrar Group (which comprises basic extrusive and intrusive igneous rocks). Weathering processes and input of magnetite to the Victoria Land Basin were intense during periods when the Antarctic climate was warmer than today, but during intervals when the climate was relatively cool, chemical weathering of the Ferrar Group was suppressed and input of detrital magnetite to the Victoria Land Basin decreased. Our results also indicate that a cold and dry climate was not established in Antarctica until the Eocene/Oligocene boundary, with major ice sheet growth occurring at the early/late Oligocene boundary. Some earlier cold intervals are identified, which indicate that climate had begun to deteriorate by the middle/late Eocene boundary.     

Applicability of landslide susceptibility and hazard zoning at different scales

Landslide susceptibility and hazard zoning can notably improve land-use planning, and thus can be considered an efficient way to reduce future damage and loss of lives caused by landslides. However, the lack of standard procedures restricts the use of susceptibility and hazard-zoning maps, notwithstanding their extensive development over the last decades.JTC-1, the Joint Technical Committee on Landslides and Engineered Slopes, fills this void by proposing International Guidelines for Landslide Susceptibility, Hazard and Risk Zoning for land-use planning, which provide definitions, terminology and international standards for methods, levels, scales and types of zoning. The Guidelines also promote the use of quantitative risk-management principles, essential to compare risk from landslides with risks related to other hazards and with loss of life tolerance criteria.This paper focuses on the applicability of landslide susceptibility and hazard zoning at different scales. Several zoning examples, referring to active, dormant and occasionally reactivated slides, provide insights into and highlight the relationships among different methods, levels and types of zoning. The examples also stress the importance of a correct characterization of the processes leading to landsliding to produce reliable susceptibility and hazard-zoning maps.     

Genetic evolution of Permo-Triassic volcaniclastic sequences at Uspallata, Mendoza Precordillera, Argentina

Permo-Triassic volcanic rocks of the Choiyoi Group crop out at Quebrada de Santa Elena and del Telégrafo, Mendoza Precordillera, Argentina. In this area, six volcanic events were generated through three volcanic stages that include collapse of voluminous Plinian columns associated to caldera pressurization and depressurization, emplacement of sub-volcanic bodies and dikes connected to depressurization of the magmatic chamber and establishment of resurgent domes and lava associated to caldera collapse events.

Petrologic and geochemical data indicate increasing acidification toward younger events varying from dacitic to rhyodacitic and rhyolitic rocks. The lithofacial organization allows correlating with the Lower to Upper Permian Horcajo Formation described in the Valle del Río de los Patos, San Juan province. Geochemical data suggests subduction-related arc magmatism in an extensional condition during Lower to Upper Permian.     

Contrasting tectonic settings in Northern Chon Aike Igneous Province of Patagonia: subduction and mantle plume-related volcanism in the Marifil formation

ABSTRACT

The northern zone of the Chon Aike Igneous Province, located in the North Patagonian Massif, exhibits extensive outcrops of Jurassic volcanic rocks of the Marifil Formation. In the Arroyo Verde area, the initial volcanic stage of the Marifil Formation, that we denominate V0 (192.6 ± 2.5 Ma), includes coulées, megabreccias and lapilli tuffs assigned to plinian-type volcanism. This magmatism was generated by cold-wet-oxidized magmas that resemble those produced in active continental margins and volcanic arcs. The second stage, located unconformably over the first, includes welded lava-like ignimbrites, massive lapilli tuff and rhyolitic lava flow that resemble the Snake River-type volcanism. The magma that produces this volcanic stage exhibit the characteristics of hot-dry-reduced magmas emplaced in intraplate continental environments associated with continental rifting. This stage coincides with the V1 volcanic episode early recorded in the Marifil Formation.     

Spatial Overlap and Coexistence in a Mussel-Associated Polychaete Assemblage on a South American Rocky Shore

Abstract. Mussel beds in the intertidal of subtropical South America are known to harbour a large number of invertebrates, particularly polychaetes. This paper presents a quantitative analysis of the patterns of spatial overlap and coexistence in an assemblage of polychaetes associated with mussel beds in a rocky intertidal habitat on the Pacific coast of Peru. Mussel beds are made up of two zones in the intertidal: the lower, more extensive zone formed by Semimytilus algosus and the upper zone formed by Perumytilus purpuratus . Null models were employed to assess the magnitude of spatial overlap between pairs of taxa encompassing a total of seven taxonomic groups. Two taxa belonging to the same functional group tended to be spatially segregated in the Semimytilus bed: Pseudonereis vs. Halosydna (large free-ranging predators) and Scoloplos vs. Mediomastus (deposit feeders), with further segregating tendencies between Pseudonereis and Mediomastus , and between Halosydna and Scoloplos . Small-sized, free-ranging ' Typosyllis ' and the bottom-dwelling scavenging predator Lumbrineris were also spatially associated. Thus, this polychaete assemblage appears to be loosely organised around groupings of taxa which are somewhat different in ecological traits and form mosaic patterns of distribution with reduced overlap within the Semimytilus bed. These relationships were weak to non-existent in the upper, drier Perumytilus habitat where polychaete density was low.     

Decomposition algorithms for system reliability estimation with applications to interdependent lifeline networks

Reliability and risk assessment of lifeline systems call for efficient methods that integrate hazard and interdependencies. Such methods are computationally challenged when the probabilistic response of systems is tied to multiple events, as performance quantification requires a large catalog of ground motions. Available methods to address this issue use catalog reductions and importance sampling. However, besides comparisons against baseline Monte Carlo trials in select cases, there is no guarantee that such methods will perform or scale well in practice. This paper proposes a new efficient method for reliability assessment of interdependent lifeline systems, termed RAILS, that considers systemic performance and is particularly effective when dealing with large catalogs of events. RAILS uses the state‐space partition method to estimate systemic reliability with theoretical bounds and, for the first time, supports cyclic interdependencies among lifeline systems. Recycling computations across an entire seismic catalog with RAILS considerably reduces the number of system performance evaluations in seismic performance studies. Also, when performance estimate bounds are not tight, we adopt an importance and stratified sampling method that in our computational experiments is various orders of magnitude more efficient than crude Monte Carlo. We assess the efficiency of RAILS using synthetic networks and illustrate its application to quantify the seismic risk of realistic yet streamlined systems hypothetically located in the San Francisco Bay Region.     

Inter-annual changes in fish communities of a tropical bay in southeastern Brazil: What can be inferred from anthropogenic activities?

We assessed inter-annual changes in fish assemblages of a tropical bay which experienced a heavily industrialized process in the last decades. A highly significant difference in community structure among the bay zones, and a decrease in fish richness and abundance over time were found. Changes in fish richness and abundance between the two first (1987–1988 and 1993–1995) and the two latter time periods (1998–2001 and 2012–2013) were sharpest in the inner bay zone, the most impacted bay area, and in the middle zone, whereas the outer zone remained comparatively stable over time. These changes coincided with increased metal pollution (mainly, Zn and Cd) in the bay and with the enlargement of the Sepetiba Port. Spatial changes in the fish community structure among the bay zones were related to differences in salinity, transparency and depth with this latter variable acting as a buffer stabilizing temporal community changes.