The Holocene-Pleistocene boundary zone in the Lagoon of Venice (Italy)

The results of a detailed study on the sediments representative of the boundary area from the Late-Pleistocene and the Lower-Holocene sedimentations are reported. Mineralogical, granulometric and geochemical investigations have been carried out to characterize the clay-rich samples taken along the littoral bar and representative of the continental and marine sedimentations. Particular attention was devoted to the study of the overconsolidated clay layer considered to be the last continental deposit before the Holocene (Flandrian) transgression and interpreted as a paleosol

Studio dei sedimenti tardo-quaternari del litorale veneziano: contributo alle indagini paleoclimatiche ed ambientali

ABSTRACT The imprints of paleoevolutionary processes that affected the Venice lagoon and its littoral during the Late-Quaternary can be found in the sand and c/ay layers underlying the Venetian basin. Sedimentological characteristics of the Late-Pleistocene and Holocene sand and clay sedimentation during the past 25-30.000 years, before the human impact, in the lagoon of Venice, are reported. The multidisciplinary investigation of clay and sand sediments and the development and application of new analytical techniques and methodologies, allowed the detailed mineralogical, geochemical and textural characterization of the recent sediments. The new data obtained not only may contribute to better understand the paleoevolutionary events that took place in the Venetian basin and the impact of the paleoclimatic variations on the depositional environments, but also they may be used as a sediment natural reference base for a more accurate quantification of the pollution level in the bottom sediments of the lagoon of Venice. RIASSUNTO Gli strati di sabbia e di argilla sottostanti il bacino veneziano conservano le tracce dei processi paleoevolutivi che hanno influenzato la laguna di Venezia ed il suo litorale. Lo studio multidisciplinare dei sedimenti sabbiosi ed argillosi depositatisi durante gli ultimi 25-30.000 anni, prima dell'impatto antropico, e lo sviluppo ed utilizzo di nuove metodologie analitiche, hanno permesso una caratterizzazione mineralogica, geochimica e tessiturale dettagliata dei sedimenti recenti. I nuovi dati ottenuti possono non solo contribuire a meglio comprendere gli eventi paleoevolutivi succedutisi nel bacino veneziano e l'impatto delle variazioni paleoclimatiche sugli ambienti deposizionali, ma possono anche servire come base naturale di riferimento per una più accurata quantificazione dei livelli di inquinamento dei sedimenti di fondo soggetti ad antropizzazione della laguna di Venezia

Recent sand sediments grain-size determination by Image Analysis

Presented in this study is the application of the Image Analysis (I.A.) technique as alternative to the traditional mechanical sieving methods for grain size determination (Bonardi & Tosi, 1994a). The application of Image Analysis technique to study the grain size of recent sand sediments has produced analytical data that are comparable to those obtained by conventional methods. Furthermore, the use of the Image Analysis has provided additional morphological parameters such as grain elongation, shape and roundness that can be useful clues to depositional environment reconstruction

Studio sedimentologico di un livello di argilla sovraconsolidata sottostante il litorale veneziano

ABSTRACT The effect of global climatic changes that occurred since the last Würmian glaciation is recognizable in the stratigraphic sequences of the Pleistocene-Holocene boundary zone from several coastal areas in different locations around the world. This study gives the results of mineralogical, chemical, and textural investigations of about fifty samples of the hard clay layers and the clay layers above and below underlying the Venice littoral. This hard clay layer, locally known as caranto, from few centimeters to few meters thick, represents the Holocene/Pleistocene boundary and it carries the marks of climate changes that characterized the last phase of the Pleistocene and the early part of the Holocene. The very dry climate during a period of very limited sedimentation and a long subaerial exposition, desiccated, compacted and oxidized the clay previously deposited, to form the overconsolidated clay level (caranto). RIASSUNTO Gli effetti delle variazioni climatiche succedutesi, su scala globale, a partire dall'ultima glaciazione würmiana sono riconoscibili nelle sequenze stratigrafiche in varie località costiere sparse in tutto il mondo. In questo studio vengono riportati i risultati preliminari di una indagine sulle caratteristiche mineralogiche, geochimiche e tessiturali di circa cinquanta campioni di un livello di argilla sovraconsolidata e degli strati argillosi sopra e sottostanti, lungo il litorale veneziano. Questo strato di argilla sovraconsolidata, noto come "caranto", con spessore variante da pochi centimetri ad alcuni metri, rappresenta il limite Olocene/Pleistocene e conserva gli effetti dei cambiamenti climatici che hanno caratterizzato l'ultima fase del Pleistocene e quella iniziale dell'Olocene. Il clima freddo e molto arido, durante un periodo di sedimentazione molto limitata e la prolungata esposizione subaerea hanno determinato l'essiccamento, la compattazione e l'ossidazione dell'ultima sedimentazione continentale argillosa, sino a formare quel livello sovraconsolidato che e' noto col nome locale di caranto

Studio granulometrico mediante Image Analysis (I.A.) delle sabbie tardo quaternarie del cordone litoraneo della laguna di Venezia

Vengono riportate le analisi granulometnche, ottenute mediante l'analizzatore d'immagini (I.A.) , di 140 campioni di sabbia, prelevati da 18 sondaggi a carotaggio continuo terebrati lungo il cordone litorale veneziano. Queste analisi sono state eseguite per contribuire allo studio sedimentologico dei terreni incoerenti con lo scopo, unitamente ad altre indagini multidisciplinari, di ricostruire le varie fasi evolutive tardo pleistoceniche ed oloceniche dell 'area litorale veneziana. L'utilizzo dell 'I.A. e' nato dall 'esigenza di determinare le variazioni della granulometria di campioni rappresentati da livelli sabbiosi a volte molto sottili e spesso con quantita' minime di materiale a disposizione, sui quali successivamente o contemporaneamente dovevano essere eseguite altre indagini mineralogiche e geochimiche. L'I.A., oltre ad offrirei queste possibilita', ha anche permesso la determinazione di altri paramentri morfologici quali il grado di allungamento e di arrotondamento di ogni grano di sabbia, non ottenibile con il metodo di setacciatura tradizionale. L'analisi granulometrica delle sabbie eseguito con l 'LA. non solo ci fornisce dati paragonabili a quelli ottenibili con i metodi tradizionali, ma presenta anche il vantaggio di poter essere eseguito congiuntamente allo studio mineralogico e chimico effettuato mediante un microscopio elettronico a scansione (SEM) o una microsonda elettronica (EMP)

Investigation of Late-Quaternary sediments from the South Yellow Sea and the Yangtze River Delta (China)

The results of a study to determine the geochemical, mineralogical, magnetic and textural characteristics done on Late-Quaternary sediments from drill cores from the South Yellow Sea (core H106) and the Yangtze River Delta (core LA) (China) are reported. The Late-Pleistocene continental sedimentation is represented by clayey silt and hard clay layers, while the marine Holocene sediments consist mainly of clay (H106) and sand and clay layers (LA)

MORPHODYNAMICS PROCESSES IN THE LAGOON OF VENICE: THE SCANELLO SALT MARSH AREA

Geomorpholgical variations have been naturally occurring in the Lagoon of Venice since its formation. In recent times, however, complex morphodynamic changes, caused by natural processes and by the direct or indirect impact of man activities have been recognised. Moreover, there remains a lack of knowledge concerning sediment erosion, re-suspension, transport and sedimentation, sea-lagoon balance and the role played by the hydrodynamics. A detailed study of the Scanello salt marsh area, in the Northern part of the Venice Lagoon, was carried out, in order to better understand the erosion-transport-sedimentation processes and the hydrodynamics interaction. Understanding the role that the hydrodynamics plays in the erosion, transportation and deposition of sediments in this test area, is essential to the understanding the morphological variations, that are presently occurring in the Venice Lagoon and morphological and environmental restorations required. A 2D hydrodynamic finite element model was used to provide the circulation field of the entire Venice basin. Results obtained by different simulations allowed the investigation of the main hydrodynamic features of the Scanello area

Subsidence due to peatland oxidation in the Venice Lagoon catchment

Abstract. The Venice Lagoon is characterized by a fast morphodynamics appreciable not only over the geological scale but also in historical and modern times. The lagoon environment proves very sensitive to even minor modifications of the natural and anthropogenic controlling factors. An important human endeavor accomplished in the past century is the reclamation of the southernmost lagoon area that has been turned into a fertile farmland. The reclaimed soil is reach in organic matter (peat) that may oxidize with release of carbon dioxide to the atmosphere. The continuous loss of carbon is causing a pronounced settlement of the farmland that lies below the present sea/lagoon level. This enhances the flood hazard and impacts noticeably on the maintenance and operational costs of the drainage system. Total peatland subsidence is estimated at 1.5 m over the last 70 years with a current rate of 1.5-2 cm/year. The geochemical reaction is primarily controlled by soil water content and temperature, and is much influenced by agricultural practices, crop rotation, and depth to the water table. A small (24 km2) controlled catchment located in the area has been instrumented for accurately monitoring the basic parameters and recording the ground motion. The in situ measurements have been integrated with the combined use of remote sensing data to help cast light on the process and identify the mitigation strategies.Published81-906A. Monitoraggio ambientale, sicurezza e territorioope

Natural History and Outcome of Hepatic Vascular Malformations in a Large Cohort of Patients with Hereditary Hemorrhagic Teleangiectasia

BACKGROUND: Hereditary hemorrhagic telangiectasia is a genetic disease characterized by teleangiectasias involving virtually every organ. There are limited data in the literature regarding the natural history of liver vascular malformations in hemorrhagic telangiectasia and their associated morbidity and mortality. AIM: This prospective cohort study sought to assess the outcome of liver involvement in hereditary hemorrhagic telangiectasia patients. METHODS: We analyzed 16 years of surveillance data from a tertiary hereditary hemorrhagic telangiectasia referral center in Italy. We considered for inclusion in this study 502 consecutive Italian patients at risk of hereditary hemorrhagic telangiectasia who presented at the hereditary hemorrhagic telangiectasia referral center and underwent a multidisciplinary screening protocol for the diagnosis of hereditary hemorrhagic telangiectasia. Of the 502 individuals assessed in the center, 154 had hepatic vascular malformations and were the subject of the study; 198 patients with hereditary hemorrhagic telangiectasia and without hepatic vascular malformations were the controls. Additionally, we report the response to treatment of patients with complicated hepatic vascular malformations. RESULTS: The 154 patients were included and followed for a median period of 44 months (range 12-181); of these, eight (5.2%) died from VM-related complications and 39 (25.3%) experienced complications. The average incidence rates of death and complications were 1.1 and 3.6 per 100 person-years, respectively. The median overall survival and event-free survival after diagnosis were 175 and 90 months, respectively. The rate of complete response to therapy was 63%. CONCLUSIONS: This study shows that substantial morbidity and mortality are associated with liver vascular malformations in hereditary hemorrhagic telangiectasia patients