The reprocessing of MCS reflection lines and sampling data across the SW Tyrrhenian Basin, from the Sardinia-Tunisia Strait (STS) to the Orosei Canyon Line (OCL), show that the acoustic basement of the area is made by Variscan crystalline-metamorphic rocks covered by a thick sequence of sediments, including the Messinian interval. The pre-Messinian sequence can be subdivided into three seismic intervals or subunits, largely calibrated by sampling data. The oldest pre-Messinian subunit is strongly deformed by compressional and/or transpressional structures and the recovered samples are deep-water arkosic sediments, Aquitanian in age; however, the whole interval may encompass a wider time span, probably from Late Oligocene to Langhian. This subunit was laid down in a fore-arc basin located between a volcanic are (Sardinia) and an accretionary wedge (Calabrian-Peloritanian-Kabilide or CK units) prior to the collision of the latter elements with the continental margin of Africa in Sicily and Tunisia along the so-called Drepano Thrust Front (DTF). Coeval to collision, the generation of the Main Sardinia Thrust (MST) occurred, carrying the Sardinia basement rocks o ver the CK units, and deforming the fore-arc basin sediments. The intermediate pre-Messinian sedimentary subunit spans from part of Serravallian to part of Tortonian. It is post-tectonic with respect to the underlying subunit, but it represents a pre-rift succession, if related to the overlying one. It consists of terrigenous deposits prograding from Sardinia to the ENE into a basin some hundreds of meters deep, which was left in the area after collision. The youngest pre-evaporitic subunit (late Tortonian-early Messinian in age) displays wedge-shaped reflectors in the Sardinia Basin, and forms the lower portion of a syn-rift complex including the Messinian and part of the Pliocene sediments. This succession records the onset of extensional tectonics in the area, as also testified by the Tortonian age of exumation of the basement. While in the Tyrrhenian Basin, north of the OCL, intra-Tortonian to intra-Pliocene rifting was strong but discontin-uous and migrating with time to the east, in the SW Tyrrhenian Basin, in contrast, rifting was less severe but continuous during the same time interval. This emphasizes the role played by the OCL, a inherited Mesozoic discontinuity reactivated as a transfer zone during the Neogene. These new data allow correlation of the main Miocene deformational events observed in the study area to those of the adjacent emerged areas, namely the Peloritani and Maghrebian units in Sicily, prior to the Pliocene-Quaternary full development of the southern Tyrrhenian Sea.
Neogene evolution of the southwestern Tyrrhenian Sea (Sardinia Basin and western Bathyal plain)
Carrara G;Zitellini N
2001
Abstract
The reprocessing of MCS reflection lines and sampling data across the SW Tyrrhenian Basin, from the Sardinia-Tunisia Strait (STS) to the Orosei Canyon Line (OCL), show that the acoustic basement of the area is made by Variscan crystalline-metamorphic rocks covered by a thick sequence of sediments, including the Messinian interval. The pre-Messinian sequence can be subdivided into three seismic intervals or subunits, largely calibrated by sampling data. The oldest pre-Messinian subunit is strongly deformed by compressional and/or transpressional structures and the recovered samples are deep-water arkosic sediments, Aquitanian in age; however, the whole interval may encompass a wider time span, probably from Late Oligocene to Langhian. This subunit was laid down in a fore-arc basin located between a volcanic are (Sardinia) and an accretionary wedge (Calabrian-Peloritanian-Kabilide or CK units) prior to the collision of the latter elements with the continental margin of Africa in Sicily and Tunisia along the so-called Drepano Thrust Front (DTF). Coeval to collision, the generation of the Main Sardinia Thrust (MST) occurred, carrying the Sardinia basement rocks o ver the CK units, and deforming the fore-arc basin sediments. The intermediate pre-Messinian sedimentary subunit spans from part of Serravallian to part of Tortonian. It is post-tectonic with respect to the underlying subunit, but it represents a pre-rift succession, if related to the overlying one. It consists of terrigenous deposits prograding from Sardinia to the ENE into a basin some hundreds of meters deep, which was left in the area after collision. The youngest pre-evaporitic subunit (late Tortonian-early Messinian in age) displays wedge-shaped reflectors in the Sardinia Basin, and forms the lower portion of a syn-rift complex including the Messinian and part of the Pliocene sediments. This succession records the onset of extensional tectonics in the area, as also testified by the Tortonian age of exumation of the basement. While in the Tyrrhenian Basin, north of the OCL, intra-Tortonian to intra-Pliocene rifting was strong but discontin-uous and migrating with time to the east, in the SW Tyrrhenian Basin, in contrast, rifting was less severe but continuous during the same time interval. This emphasizes the role played by the OCL, a inherited Mesozoic discontinuity reactivated as a transfer zone during the Neogene. These new data allow correlation of the main Miocene deformational events observed in the study area to those of the adjacent emerged areas, namely the Peloritani and Maghrebian units in Sicily, prior to the Pliocene-Quaternary full development of the southern Tyrrhenian Sea.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
