Geological evolution of the Ischia volcanic complex (Naples Bay, Tyrrhenian sea) based on submarine seismic reflection profiles

Autor: Gemma Aiello Ennio Marsella
Jazyk: angličtina
Rok vydání: 2015
Předmět:
Zdroj: International Workshop on Volcanic Rocks and Soils, pp. 180–181, Ischia, September 2015
info:cnr-pdr/source/autori:Gemma Aiello Ennio Marsella/congresso_nome:International Workshop on Volcanic Rocks and Soils/congresso_luogo:Ischia/congresso_data:September 2015/anno:2015/pagina_da:180/pagina_a:181/intervallo_pagine:180–181
Popis: The geological evolution of the Ischia active volcanic complex (Naples Bay, Southern Tyrrhenian sea) has been reconstructed based on recently acquired submarine seismic reflection data. Implications on submarine slope stability both in the northern and western submerged flanks of the island, characterized by thick submarine slide deposits and southern flank of the island, characterized by active erosion of the coastal systems due to submarine canyons, will be discussed. A densely spaced grid of single-channel seismic profiles has been recently acquired and interpreted in the frame of research programs on marine cartography (CARG Project) financed by the Campania Region (Sector of Soil Defence, Geothermics and Geotechnics) during the mapping of the marine areas of the geological sheet n. 464 "Isola d'Ischia" at the scale 1:25.000 (Aiello et al., 2009b; 2012; Monti et al., 2012; Aiello and Marsella, 2014). The seismic grid was recorded using a Sparker Multitip seismic source (Biagio, 2007; Corradi et al., 2009; Giordano et al., 2013). Some of these profiles have been presented and discussed in the above mentioned papers. New geological data on the Ischia volcanic complex are here presented based on the integrated geological interpretation of Multibeam bathymetric and single channel seismic data to constrain the Ischia geologic evolution during Quaternary times. Marine geophysics around the Ischia island has shown a great improvement during the last ten years, due to the bathymetric surveys acquired by the GNV and CARG Projects. These bathymetric surveys resulted in a Multibeam coverage all around the Ischia island (Chiocci and de Alteriis, 2006; Aiello et al., 2009a). Swath bathymetry was acquired in a wide depth range, with various echosounders, each characterized by its own frequency (from 60 to 300 kHz) and spatial resolution (from 0.3 to 10 m the footprint). The merging of these surveys with the island subaerial topography has allowed the construction of a DTM in which the elementary cell size has been averaged to 20 m obtaining a good compromise among coverage depth and resolution in shallow waters. The sea floor structure has been determined through the analysis of the DTM. The study grid is composed of dip lines perpendicular to the shoreline and tie lines parallel to the shoreline, interpreted accordingly to criteria of seismic stratigraphy and volcanic geomorphology (Mitchum et al., 1977; Vail et al., 1977; Catuneanu et al., 2009; Thouret, 1999; Thouret and Nemeth, 2012). The classification of volcanic landforms has been recently improved taking into account the complexity in the generation of volcanic structures and their control factors, such as the magmatic systems, the styles of eruption and the erupted materials. The DEM datasets are often available, making possible the morphometric characterization of large composite volcanoes at a global scale. Main volcanic and tectonic lineaments on the Ischia shelf and slope have been represented (Fig. 1). New insights into seismo-stratigraphy and Ischia geologic evolution are here discussed. The Ischia offshore is characterized by alkali-potassic volcanic rocks (trachytes, latites, alkali-basalts) and pertains to a volcanic complex emplaced during the last 55 ky. Four main phases have been distinguished in the eruptive activity of the Ischia volcanic complex from 150 ky B.P. to 1302 A.D. (Chiesa et al., 1985; Poli et al., 1987).
Databáze: OpenAIRE
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