Structure and Dynamics of the Tyrrhenian Basin

I. M. Sborshchikov, E. V. Verjbitsky, A. A. Schreider

The Tyrrhenian Sea is a recently subsided oceanic basin. Young tholeiitic volcanoes are found in the central part of this sea as well as sea mount fragments of continental blocks formed by Alpine folding complexes.

Mesozoic ophiolites are found on Baronie and DeMarchi sea mounts and Site 651 (Leg 107). Soviet investigations show that Baronie serpentinites are covered by thick carbonate rocks of Late Jurassic age, and these deposits are comparable with ophicalcites of the Ligurian Alps. The ophiolites are traced across the basin indicating the connection to north Corsican and Calabrian structures. The fracture zone of 41°N is possibly the fault which controls microplate displacement.

Rifting occurred quickly and migrated toward the Eolian arc. There is no direct evidence of regular spreading (linear magnetic anomalies) in the Tyrrhenian Sea now, and opening rate calculations are difficult. Detailed heat-flow data, similar to data of typical spreading centers, allow us to estimate the gradient of the thinning lithosphere outside to axis volcanoes (Vavilov and Marsili). The calculated rifting rate on this basis is about 1-2 cm/year relative to each stretching center.

The Tyrrhenian Sea has developed as a back-arc basin within the collision zone of thick continental plates. Calabrian and Hellenic Benioff zones are configured as sharply curved arcs "ingressed" to the southeast and south. Such a configuration may be caused by pressure of local asthenospheric flow. In the case of the Calabrian arc, this flow consequently rotated the Iberian, Corsica-Sardinia, and Calabria blocks. In such a process the subducted plate can be broken, defining the phases of back-arc basin development.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.