Mario Pistolato

Los ostràcodos actuales de la laguna de Venecia (NE de Italia)

In the Venice lagoon, ostracods from 99 recent samples were studied. The biocoenosis is more abundant in the inner margin, near some little channels. The microfaunal analysis delimited three estuarine associations, with numerous valves of Cyprideis torosa, and one marine association (Pontocythere turbida). Salinity, hydrodynamics, nutrients and substrate are the main factors which control the distribution of these microorganisms. This distribution is very similar in other recent lagoons of Italy.

Geochemical characteristics of Western Ross Sea (Antarctica) sediments

Abstract A geochemical study of bottom sediments from 50 stations in various Ross Sea sedimentary environments, ranging from the coastal strip to the external platform, situated off Southern Victoria Land between the David and Mariner glaciers has demonstrated the silicate nature of these sediments and significant variations in the major element concentrations. The presence and concentrations of the trace elements studied (Cr, Ni, Co, V, Cu, Pb, Zn and Cd) differ from one geographic area to another, and within a given basin. A statistical analysis of the geochemical variables using the cluster method shows that Si is independent of the other elements, which group into associations. A multivariate statistical analysis based on geochemical, granulometric and environmental parameters identifies five distinct sediment groups located in different areas of sedimentation and with peculiar geochemical characteristics. Group 1, on the external platform, which comprises very fine sediments, is characterised by the highest contents of Mg, LOI, Cr, Ni and V, and of Cu and Zn. Group 2, from the banks formed by pelitic sands, is distinguished on the basis of lower Cu and Zn and higher Cr and Si. Group 3, on the internal platform consisting of sandy sediments, comprises high values of Na, Al, Ca and Pb and low values of Zn and V. Group 4, in the coarse coastal sands, is enriched in Co and Ca, Na, K and Al. Group 5, formed by materials with different grain-size distribution located south of Coulman Island, is distinguished by a very high content of Zn, Fe, Ti and Na, with Cr, Co, Pb and Si being found at lower levels. The materials are glacial-detrital, are derived from the rocky hinterland formations, and are reworked by transport and deposition processes depending on the energy level of the marine sedimentary environments. Given the scarcity of comparison data from the hinterland rocks it is difficult to establish the parent rocks of these glaciomarine sediments on the basis of geochemical data alone. Only in the case of the sediments south of Coulman Island can one be certain of a contribution from the McMurdo volcanics. For the external platform sediments, the highest contents of Si and L.O.I. confirm the input of material from biogenic neoformation.

Grain size, mineralogy and geochemistry in Late Quaternary sediments from the Western Ross Sea outer slope as proxies for climate changes.

Textural, mineralogical and geochemical investigations of three sedimentary sequences from the Ross Sea continental slope allow to give some important indications on climatic and environmental changes occurred during the Late Quaternary. The cores show cyclical changes in several proxies (grain size, mineralogical and geochemical parameters) which are in phase with glacial/interglacial changes (MIS 1–8). Such fluctuations are supposed to be driven by changes in transport mechanisms, reworking and provenance of the material, as well as by changes in direction and strength of marine currents induced by variations in the ice coverage.

Stratigraphy and Geochemical Characterization of the Middle Triassic - Carnian Sequence of the Lumiei Valley (Carnia, Northeastern Italy)

Stratigraphy of carbonate and terrigenous beds of the Anisian, Ladinian and Carnian of the Lumiei Valley (Middle-Western sector of Carnia, NE Italy) is updated and referred to the new chronological scale of Triassic. Western Carnian Alps were emerged in Early Anisian time. The sea transgressed southward and the region was covered by a thick sequence of lagoonal, clastic, and pelagic sediments. The sequence is thicker in this area, where a system of synsedimentary faults increased the subsidence. Tectonic activity increased during Middle(?) Anisian; this area turned into a topographic and structural high, divided by synsedimentary faults from neighbouring open-marine areas that received large amounts of terrigenous sediments. The latest Anisian and the Ladinian are characterized by a general progradation of the platform facies. Basin areas with pelagic and volcanic sediments were mostly developed in this area and towards the Carnian-Julian Alps. In the Late Ladinian a local resuming of volcanism is present in the transgression marked by the Acquatona Formation. The topmost part of the Ladinian is characterized by the general and wide diffusion of the inner platform, mostly with peritidal facies. At the Ladinian-Carnian boundary, tensional tectonics caused the breaking up of the Schlern platform and increased the subsidence. In the Early-Middle Carnian, this area is dominated by a marine transgression with marly limestone, pelagic, and terrigenous sediments. Moreover, major, minor and trace elements were determined. Statistical multivariate analysis methods were applied to experimental geochemical data to study the stratigraphic sequence. The purpose of this paper was to verify the capacity of these methods to describe the different lithologies of the sequence through its geochemical analysis. A multivariate statistical analysis based on geochemical parameters identifies distinct groups of sediments corresponding to lithological intervals of the examined sequence. In this way a good correspondence between geochemical groups and the lithologies was established.