On the Mesozoic Ionian Basin

Abstract

SUMMARY New seismic reflection profiles of the Italian deep crust project CROP provide new insights on the structure of the Ionian sea. In spite of the Apennines and Hellenides Neogene subduction zones, two conjugate passive continental margins are preserved at the margins of the Ionian sea, along the Malta escarpment to the southwest and the Apulian escarpment to the northeast. The Ionian sea is likely to be a remnant of the Mesozoic Tethys Ocean, confined by these two conjugate passive continental margins. The transition from continental to oceanic crust appears sharper to the northeast than to the southwest. The basin between southeast Sicily and southwest Puglia was about 330 km wide and suggests a low spreading rate. The inferred oceanic ridge should have been flattened by thermal cooling and buried by later sediments. Based on stratigraphic and structural constraints to the north in the Apennines belt, the ocean continued to the northwest. This palaeogeography is supported by the seismicity of the Apennines slab underneath the southern Tyrrhenian sea, which implies downgoing oceanic lithosphere. The adjacent absence or paucity of deep seismicity does not imply absence of subduction, but rather it can be interpreted as due to the more ductile behaviour of the subducted continental lithosphere. Surprisingly, we note that where the oceanic inherited basin is subducting underneath the Apennines, in the hangingwall of the subduction hinge there are outcropping slices of continental crystalline basement previously deformed by the Alpine orogen.

First report of live deep-water cnidarian assemblages from the Malta Escarpment

“…Triassic-Neogene shallow-water to basinal carbonate sequences outcrop along the escarpment (Scandone et al 1981;Casero et al 1984). The Malta Escarpment incorporates extensional block faulting and sinistral strike-slip deformation as a result of the different rates of underthrusting between the buoyant Malta Plateau and the Ionian crust (Grasso 1993;Adam et al 2000;Catalano et al 2000). The Malta Escarpment can be classified as a sediment-starved margin (at least since the Messinian), with an estimated post-Messinian sedimentation rate of~6 cm ka −1 (Max et al 1993;Osler & Algan 1999).…”

Décollement depth versus accretionary prism dimension in the Apennines and the Barbados

“…The downgoing plate is characterized by a composite lithosphere: in the north and the southwest it consists of thinned continental lithosphere, while in the Calabria-Ionian area it consists of oceanic lithosphere. This configuration corresponds to the continental passive margins of the Adriatic and Africa plates and to an intervening branch of the Tethys ocean which opened in the Jurassic [Bonardi et al, 2001, and references therein;Catalano et al, 2001, and references therein].…”

Shallow structures at the outer Calabrian accretionary wedge (NW Ionian Sea): new insights from recently migrated reflection data

“…The grid of the interpreted (CROP) multichannel seismic profiles (bold segments), together with the locations of seismic reflection lines, seismic refraction profiles and drilling that contribute to the seismic interpretations proposed in this paper, are shown. Main structural features based on present and previously published (Catalano et al, 2001;Chamot-Rooke et al, 2005) studies are displayed. Inset shows a schematic structural map of the study area and surrounding area.…”

“…Inferences from seismic data (Catalano et al, 2001;see fig. 8 therein) suggest that the substratum of the Messinian evaporites consists of a 4-km-thick unit, seismically interpreted as pelagic deposits from the Mesozoic to Early Messinian.…”

“…The SE-verging ECA is an active arcshaped accretionary wedge (Sartori, 1982), developing above the NWplunging Ionian oceanic basement and its Mesozoic to Tertiary (Catalano et al, 2001) sedimentary cover.…”