Abstract
A chirp sonar survey in the Ionian Sea investigated the Calabrian margin, the Calabrian accretionary wedge, the Taranto Trench and the Apulian foreland. Shallow tectonics structures have been related to deeper ones, recognised on CROP seismic profiles. The identified echo characters have been compared with those described in the modern literature and have been related to different kinds of sediments, on the basis of core samples. Based on echo character and morphology we have recognised: 1) A widespread presence of mounds, up to 50 m high, occurring on the Apulian plateau as isolated mounds in the deepest zones (1600-800 m) and in groups in the shallower ones (800-600 m); they have been interpreted as coral mounds, according to a recent discovery of living deep water coral colonies in this zone. 2) Some mud diapirs, isolated or in groups of two or three elements, widespread in the whole study area. In analogy of what has been observed on the Mediterranean Ridge, their presence suggests the activity of deep tectonic structures (thrusts and faults) and a reduced thickness (or absence) of Messinian evaporites in this part of the Ionian Sea.
Highlights
Introduction and geological settingIn March 2002 a cruise onboard the R/V Urania, collected about 1100 km of Chirp 2 sonar profiles in the Ionian Sea, from the inner parts of the Calabrian Arc accretionary prism to the Apulian foreland, crossing the Taranto Trench
The seismic section identified by means of chirp profiling can be referred to Plio-Pleistocene units on the Calabrian margin, the accretionary wedge and the Taranto Trench, whereas on the Apulian plateau Neogene – Pleistocene units outcrop, forming the Apulian swell; for stratigraphic and structural interpretation of CROP seismic line M5 we refer to Doglioni et al (1999) and Merlini et al (2000)
As for the Punta Stilo plateau, we suggest that the Taranto Trench is filled by coarse grained turbidites; reflectors identified on CROP
Summary
In March 2002 a cruise onboard the R/V Urania, collected about 1100 km of Chirp 2 sonar profiles in the Ionian Sea, from the inner parts of the Calabrian Arc accretionary prism to the Apulian foreland, crossing the Taranto Trench (fig. 1). The Apennine belt consists of thrust sheets of the sedimentary cover (Mostardini and Merlini, 1986; Sella et al, 1988; Patacca and Scandone, 2004), later cross-cut by deep normal faults, along which fluids migrate upwards (Doglioni et al, 1996). On the Calabrian margin this section crosses extensional faults, which inland are well known to form grabens (Val d’Agri, Vallo di Diano; Merlini et al, 2000) and are responsible for the high seismicity of the Southern Apennines (Amato and Selvaggi, 1993); on the eastern side the section crosses the Apulian swell which appears rather as a 100 km wide buckling anticline, deforming the entire lithosphere (Merlini et al, 2000). Objectives of our study are: 1) to identify the main shallow active tectonic structures; 2) to integrate these structures into the regional framework, defined by deeper seismics (CROP seismic line M5); 3) to eventually relate regional fluid flow with the presence of living coral colonies and with active tectonics
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