canyons ranges from a few hundred metres to
more than 1 km. Their depth ranges from 250 m
at the shelf edge to some 1300 m at the junction
with the bathyal plain, the dip of their walls
attains some 35° in the steepest sectors.
The Dohrn Canyon starts on two major
curved branches. The northern branch merges
into the shelf through a 1.5 km wide and a 20-40
m deep channel ("Ammontatura") characterised
by a flat bottom and asymmetrical levees and by
curved shape in plain view (Figs. 2 and 3). The
origin of the CCAmmontatura" shallow channel
can tentatively be correlated to the hydrodynamic regime driven by the northern axis of Dohrn
canyon. Its emplacement seems to post-date the
latest stages of erosion and transport in the
canyon and to pre-date the formation of the most
recent volcanic edifices in the bay of Pozzuoli. as
suggested by its abrupt termination towards the
Nisida submarine volcanic edifice.
The southern branch is laterally fed by several tributary channels, whose pattern seems
partly fault controlled. The location of this
branch and several lines of evidence based on
seismic stratigraphy suggest a genetic link
between the activity of the Dohrn canyon and
the Sarno paleo-drainage system during sea
level lowstands. A seismic sequence, 30-40 m
thick, overlying older undisturbed reflectors
and including overbank deposits with channellevee complexes (Fig. 7), has been located on
both sides of the Dohrn southern branch. These
deposits do not seem to be related to the main
branches, which result deeply incised. but to the
presence of tributary channels, controlling the
overflowing of sediment fluxes in the surrounding areas.
The erosion and the transport of the volcanodastic input in the western sector of the bay
(offshore of Ischia and Procida islands) has acted
along the axis of the Magnaghi Canyon which
appears unrelated to present or past fluvial
drainage system on land. Its head is typically
trilobate with three main tributary channels
joining basinwards into the main axis.
Multibeam survey shows the occurrence of erosional phases presently acting on the continental
slope located south-east of Procida Island and of
debris "outrunner" blocks (Prior et at 1984) a
few km south-east of the Banco di Ischia volcanic
edifice (Figs. 2 and 3).
A relative abundance of U -shaped morphologies with respect to the V-shaped, typically
Morphobathymetry in the Bay of Naples
7
erosional, profiles has been observed, suggesting
recent phases of canyon filling. Nevertheless several submarine slides and scars are still evident
on the canyon's walls especially along the western flanks and on the continental slope as well.
They involve large volumes of sediments (sometimes up to 10 6 m 3 ), in the bathymetric range
from -250 m to -800/900 m. Factors known to
control submarine slides include loading and
underconsolidation of sediments due to rapid
sedimentation, oversteepening of slopes consequent to phases of deep linear erosion, earthquakes and sea-level changes (Suov and
Nieuwenhuis 1982; 0' Leary and Dobson 1992).
This appears to be one of the most significant
problems to be investigated further, due to the
risk of anomalous waves over the coastal zones,
originated by large submarine instability.
Acknowledgements. The authors thank the scientific party. the
officers and the crew of cruises GMS97-1 and GMS98-1. The
paper has been supported by the National Research Council
grants developed to Geomare sud Institute and by the
National Geological Survey of Italy (CARG project). The
authors wish to thank two anonymous reviewers for improving the comprehension of the text.
References
Aiello G, Budillon F. de Alteriis G, Di Razza O. De Lauro M,
Marsella E. Pelosi N, Pepe F, Sacchi M, Tonielli R (1997a)
Seismic exploration of the perityrrhenian basim in the
Latium-Campania offshore. Abstr Int Congr "ILP Task
Force: Origin of Sedimentary Basins", Torre Normanna
(Palermo Italy) June 1997
Aiello G, Budillon F, de Alteriis G, Ferranti L, Marsella E, Pappone
G, Sacchi M (1997b) Late Neogene tectonics and basin evolution of the Southern Italy Tyrrhenian margin. Abstr Int
Congr"ILP Task Force: Origin of Sedimentary Basins", Torre
Normanoa (Palermo Italy) June 1997
Budillon F, Cristofalo GC, Tonielli R (in press.) Segnalazione di
terrazzi deposizionali sommersi in Penisola Sorrentina:
Atlante dei terrazzi deposizionali sommersi lango Ie coste
italiane. Mem descrittive della carta geo! d'Italia, vol 54
Capotondi L. Asiali A, Borsetti AM (1994) Ecozonazione a
Foraminiferi plantonici e paleoceanografia dell'ultima
deglaciazione nel Mediterraneo centrale. Atti 10° Conge
AIOL Alassio 4-6 Nov 1992: 107-115
Catalano R, Bartolini C, Fabbri A. Lembo P, Marani M, Marsella E,
Roveri M, Ulzega A (1996) Linee guida al. rilevamento geologico nelle aree marine da sottaporre al Servizio Geologico
Nazionale. Commissione di studio del CNR per la cartografta geol marina. Rapporto finale
Chioeci FL, Aiello G, Barsza ], De Lauro M, Ercilla G, Estrada P,
Tonielli R, Farran M, Martorelli E. Senatore MR, Tommasi P,
Bosman A, Cristofalo G, Ortolani U. Sarli R (1998) Ischia
debris avalanche: first evidence of a lateral collapse of the
Ischia southern flank from TOBI images. Presented at
Conference on Hard Soils and Soft Rocks, Napoli. october
1998
more than 1 km. Their depth ranges from 250 m
at the shelf edge to some 1300 m at the junction
with the bathyal plain, the dip of their walls
attains some 35° in the steepest sectors.
The Dohrn Canyon starts on two major
curved branches. The northern branch merges
into the shelf through a 1.5 km wide and a 20-40
m deep channel ("Ammontatura") characterised
by a flat bottom and asymmetrical levees and by
curved shape in plain view (Figs. 2 and 3). The
origin of the CCAmmontatura" shallow channel
can tentatively be correlated to the hydrodynamic regime driven by the northern axis of Dohrn
canyon. Its emplacement seems to post-date the
latest stages of erosion and transport in the
canyon and to pre-date the formation of the most
recent volcanic edifices in the bay of Pozzuoli. as
suggested by its abrupt termination towards the
Nisida submarine volcanic edifice.
The southern branch is laterally fed by several tributary channels, whose pattern seems
partly fault controlled. The location of this
branch and several lines of evidence based on
seismic stratigraphy suggest a genetic link
between the activity of the Dohrn canyon and
the Sarno paleo-drainage system during sea
level lowstands. A seismic sequence, 30-40 m
thick, overlying older undisturbed reflectors
and including overbank deposits with channellevee complexes (Fig. 7), has been located on
both sides of the Dohrn southern branch. These
deposits do not seem to be related to the main
branches, which result deeply incised. but to the
presence of tributary channels, controlling the
overflowing of sediment fluxes in the surrounding areas.
The erosion and the transport of the volcanodastic input in the western sector of the bay
(offshore of Ischia and Procida islands) has acted
along the axis of the Magnaghi Canyon which
appears unrelated to present or past fluvial
drainage system on land. Its head is typically
trilobate with three main tributary channels
joining basinwards into the main axis.
Multibeam survey shows the occurrence of erosional phases presently acting on the continental
slope located south-east of Procida Island and of
debris "outrunner" blocks (Prior et at 1984) a
few km south-east of the Banco di Ischia volcanic
edifice (Figs. 2 and 3).
A relative abundance of U -shaped morphologies with respect to the V-shaped, typically
Morphobathymetry in the Bay of Naples
7
erosional, profiles has been observed, suggesting
recent phases of canyon filling. Nevertheless several submarine slides and scars are still evident
on the canyon's walls especially along the western flanks and on the continental slope as well.
They involve large volumes of sediments (sometimes up to 10 6 m 3 ), in the bathymetric range
from -250 m to -800/900 m. Factors known to
control submarine slides include loading and
underconsolidation of sediments due to rapid
sedimentation, oversteepening of slopes consequent to phases of deep linear erosion, earthquakes and sea-level changes (Suov and
Nieuwenhuis 1982; 0' Leary and Dobson 1992).
This appears to be one of the most significant
problems to be investigated further, due to the
risk of anomalous waves over the coastal zones,
originated by large submarine instability.
Acknowledgements. The authors thank the scientific party. the
officers and the crew of cruises GMS97-1 and GMS98-1. The
paper has been supported by the National Research Council
grants developed to Geomare sud Institute and by the
National Geological Survey of Italy (CARG project). The
authors wish to thank two anonymous reviewers for improving the comprehension of the text.
References
Aiello G, Budillon F. de Alteriis G, Di Razza O. De Lauro M,
Marsella E. Pelosi N, Pepe F, Sacchi M, Tonielli R (1997a)
Seismic exploration of the perityrrhenian basim in the
Latium-Campania offshore. Abstr Int Congr "ILP Task
Force: Origin of Sedimentary Basins", Torre Normanna
(Palermo Italy) June 1997
Aiello G, Budillon F, de Alteriis G, Ferranti L, Marsella E, Pappone
G, Sacchi M (1997b) Late Neogene tectonics and basin evolution of the Southern Italy Tyrrhenian margin. Abstr Int
Congr"ILP Task Force: Origin of Sedimentary Basins", Torre
Normanoa (Palermo Italy) June 1997
Budillon F, Cristofalo GC, Tonielli R (in press.) Segnalazione di
terrazzi deposizionali sommersi in Penisola Sorrentina:
Atlante dei terrazzi deposizionali sommersi lango Ie coste
italiane. Mem descrittive della carta geo! d'Italia, vol 54
Capotondi L. Asiali A, Borsetti AM (1994) Ecozonazione a
Foraminiferi plantonici e paleoceanografia dell'ultima
deglaciazione nel Mediterraneo centrale. Atti 10° Conge
AIOL Alassio 4-6 Nov 1992: 107-115
Catalano R, Bartolini C, Fabbri A. Lembo P, Marani M, Marsella E,
Roveri M, Ulzega A (1996) Linee guida al. rilevamento geologico nelle aree marine da sottaporre al Servizio Geologico
Nazionale. Commissione di studio del CNR per la cartografta geol marina. Rapporto finale
Chioeci FL, Aiello G, Barsza ], De Lauro M, Ercilla G, Estrada P,
Tonielli R, Farran M, Martorelli E. Senatore MR, Tommasi P,
Bosman A, Cristofalo G, Ortolani U. Sarli R (1998) Ischia
debris avalanche: first evidence of a lateral collapse of the
Ischia southern flank from TOBI images. Presented at
Conference on Hard Soils and Soft Rocks, Napoli. october
1998