The geophysical and geological setting of northern Ischia island (Naples Bay, Southern Tyrrhenian sea, Italy) based on high resolution seismic reflection profiles

Aiello, Gemma (2017) The geophysical and geological setting of northern Ischia island (Naples Bay, Southern Tyrrhenian sea, Italy) based on high resolution seismic reflection profiles. In: Horizons in World Physics. Nova Science Publishers, Hauppage USA, pp. 53-86. ISBN 978-1-53612-307-4

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Abstract

Significant geophysical studies on Ischia Island have been recently produced based on the geological interpretation of Sparker data within marine geological projects. High resolution seismic reflection profiles (Sparker Multitip) have been presented. In this framework, new geological data are herein provided concealing the slide deposits and the canyon systems in the Ischia offshore through seismo-stratigraphic interpretation aimed at improving the knowledge on the Ischia geologic evolution during Quaternary times. In this chapter, a stratigraphic and structural interpretation of the seismic profiles recorded in the northern Ischia Island is presented aimed at improving the knowledge of the northern Ischia coastal belt and its relationships with the emplacement of the slide deposits in the offshore surrounding the Ischia island, which has been controlled by the complex and different volcano-tectonic events. The Casamicciola town is located in the northern Ischia sector and is characterized by an active seismicity and by the occurrence of the reworked deposits pertaining to the Ischia activity and suggesting a cyclical slope instability. The marine counter-part of this instability is represented by the wide submarine landslides which, in the Casamicciola offshore, correspond to the wide hummocky topographies observed on the Multibeam, Sidescan Sonar and seismic data. The relationships among the seismicity and the structural elements in the Ischia Island have been studied through the macro-seismic data analysis and the structural geology. The structural analysis of the faults occurring in the volcanic deposits of the Casamicciola outcrops has evidenced a main tectonic extension, N-NNE trending in the oldest pyroclastic rocks, whose age exceeds 35 ky B.P. A secondary tectonic extension occurs along a NNW direction and seems to affect also the younger formations. The two extensional tectonic episodes have been recognized in correspondence with the E-W and WNW-ESE trending geological structures. The hummocky area offshore the Northern Ischia Island in correspondence with the Casamicciola town has been singled out and mapped based on the Multibeam bathymetry. The hummocky deposits occupy a tongue extending from Lacco Ameno to Punta La Scrofa (northern Ischia Island) towards the Tyrrhenian sea, culminating in correspondence with the Punta Cornacchia submarine canyon’s head. The hummocky topographies, located at water depths ranging between 20 m and 180 m, show the large blocks, cropping out at the sea bottom and partly buried by the Holocene sediments. These deposits form a wide field cropping out at the sea bottom, whose shape is sub-circular. This field is bounded by the morphologic reliefs represented by the depositional levees of turbiditic slope systems, triggered by the strong erosion and by the canyon development. In fact, the portion of the sea bottom occupied by the hummocky topographies is involved by a network of erosional gullies, shown by the Multibeam bathymetric data. The hummocky deposits (H1 and H2) are distinguished from two different bodies, which have been identified on the seismic profiles. They are characterized by an acoustically-transparent seismic facies. The H1 body is overlain by the forced regression system tract deposits (FST), deposited on the continental shelf offshore the Casamicciola town. The occurrence of the two different wedges, which have been detected based on the seismic data interpretation, suggests that two distinct volcano-tectonic events have probably controlled the emplacement of the Casamicciola slide deposits. Moreover, the seismo-stratigraphic data collected from other authors have suggested that the incised fan-shaped valley, which develops offshore the Lacco Ameno town, should be related with the emplacement of a recent landslide event.

Item Type:	Book Section
Uncontrolled Keywords:	Ischia, Casamicciola, submarine landslides, seismic interpretation
Subjects:	500 Scienze naturali e Matematica > 550 Scienze della Terra > 554 Scienze della terra – Europa (Classificare qui la Geologia, i rilevamenti geologici, la stratigrafia dell’Europa)
Depositing User:	Dr Gemma Aiello
Date Deposited:	06 Sep 2017 09:23
Last Modified:	06 Sep 2017 09:23
URI:	http://eprints.bice.rm.cnr.it/id/eprint/16556

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