In the recent decades many studies have been carried out on rift formation, in order to understand causes and modes of whole lithospheric extension. Extensional basins have been studied and classified using 2D geological sections and thus also modelled prevalently in 2D. However, the complete process of continental break-up can be understood only through detailed 3D studies of rift evolution at varying stretching factors (Reston and Pe?rez-Gussinie?, 2007).The Tyrrhenian Sea, the youngest backarc basin of the Western Mediterranean (e.g., Dewey et al., 1989), is characterized by crustal thinning and opening of sedimentary basins (including the Vavilov basin). Within this geological framework, the Vavilov basin represents a perfectly preserved fossil triangular basin, where the extensional processes reached the mantle exhumation stage during the Pliocene (Mascle and Rehault, 1990; Milia et al., 2013) and moved eastwards in the Quaternary (Milia and Torrente, 2015; Milia et al, in press).In this study, we interpret seismic reflection profiles and wells data, in order to reconstruct the architecture and timing of rifting of the Vavilov basin. Our results show rift and supradetachment basins in the Vavilov rift zone and, for the first time, the kinematics of the entire triangular basin (from apex to distal zones). Furthermore, we compare the development of the Vavilov basin with two evolutionary models of triangular basins: a) the plate tectonic rift model, featuring a synchronous opening across the whole basin, from apex to the distal part around a rotation pole; b) the propagating rift model, characterized by an extension migration from the distal to the apex of the basin. On the base of this comparison and the crustal structure of the Vavilov basin (Tesauro et al. 2008), we propose a model of tectonic evolution of the study region. We observe that the apex basin corresponds to a sediment-balanced basin, with a sedimentary infill recording the episodes of basin evolution. In contrast, the distal basin corresponds to an underfilled basin, characterized by localized volcanic activity and a thin sedimentary succession that covers the exhumed mantle. We find that the rifting of the Vavilov triangular basin was synchronous from the apex to distal regions around a single Euler pole located in Latium. The kinematic evolution of the Vavilov basin occurred in two stages: initial pure shear mode produced high-angle normal faults and syn-sedimentary wedges, followed by simple shear mode that caused supradetachement. This interpretation implies also that the continental crust in the bathyal region has been locally thinned and extended more significantly than previously estimated. Based on constraints on the present-day crustal structure of the Vavilov basin, we obtain a stretching value (b =3.5) and extension rates (3 cm/yr) in the bathyal zone analogous to those reported for magma-poor rifted margins.
The evolution of a triangular backarc basin (Vavilov basin, Tyrrhenian Sea)
Alfonsa Milia;
2016
Abstract
In the recent decades many studies have been carried out on rift formation, in order to understand causes and modes of whole lithospheric extension. Extensional basins have been studied and classified using 2D geological sections and thus also modelled prevalently in 2D. However, the complete process of continental break-up can be understood only through detailed 3D studies of rift evolution at varying stretching factors (Reston and Pe?rez-Gussinie?, 2007).The Tyrrhenian Sea, the youngest backarc basin of the Western Mediterranean (e.g., Dewey et al., 1989), is characterized by crustal thinning and opening of sedimentary basins (including the Vavilov basin). Within this geological framework, the Vavilov basin represents a perfectly preserved fossil triangular basin, where the extensional processes reached the mantle exhumation stage during the Pliocene (Mascle and Rehault, 1990; Milia et al., 2013) and moved eastwards in the Quaternary (Milia and Torrente, 2015; Milia et al, in press).In this study, we interpret seismic reflection profiles and wells data, in order to reconstruct the architecture and timing of rifting of the Vavilov basin. Our results show rift and supradetachment basins in the Vavilov rift zone and, for the first time, the kinematics of the entire triangular basin (from apex to distal zones). Furthermore, we compare the development of the Vavilov basin with two evolutionary models of triangular basins: a) the plate tectonic rift model, featuring a synchronous opening across the whole basin, from apex to the distal part around a rotation pole; b) the propagating rift model, characterized by an extension migration from the distal to the apex of the basin. On the base of this comparison and the crustal structure of the Vavilov basin (Tesauro et al. 2008), we propose a model of tectonic evolution of the study region. We observe that the apex basin corresponds to a sediment-balanced basin, with a sedimentary infill recording the episodes of basin evolution. In contrast, the distal basin corresponds to an underfilled basin, characterized by localized volcanic activity and a thin sedimentary succession that covers the exhumed mantle. We find that the rifting of the Vavilov triangular basin was synchronous from the apex to distal regions around a single Euler pole located in Latium. The kinematic evolution of the Vavilov basin occurred in two stages: initial pure shear mode produced high-angle normal faults and syn-sedimentary wedges, followed by simple shear mode that caused supradetachement. This interpretation implies also that the continental crust in the bathyal region has been locally thinned and extended more significantly than previously estimated. Based on constraints on the present-day crustal structure of the Vavilov basin, we obtain a stretching value (b =3.5) and extension rates (3 cm/yr) in the bathyal zone analogous to those reported for magma-poor rifted margins.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
