Arabia/Africa/Eurasia kinematics and the Dynamics of Post-Oligocene Mediterranean Tectonics
Abstract
Geodetic and plate tectonic observations indicate that the rate of Africa (AF) - Eurasia (EU) convergence slowed by ~50% at 24 +/- 4 Ma when AF began to separate from Arabia (AR) initiating extension along the Red Sea and Gulf of Aden. A further ~50% slowing of AF-EU convergence occurred at 11+/- 2 Ma when extension in the Gulf of Aden evolved to full ocean spreading, completely severing this segment of the AR-AF plate boundary, thereby reducing the slab-pull from Zagros-Makran subduction on the AF plate. This change in torque balance also caused an increase in the N-S component of AR-AF motion resulting in kinematic changes in both the northern (Dead Sea Fault/Sinai/Gulf of Suez) and southern (Danakil/Afar) Red Sea. While AF-EU convergence slowed, AR-EU convergence remained approximately constant from >21 Ma to the present. Contemporaneous with the initial slowing of AF-EU convergence, extension initiated along the entire AF-EU boundary (Alboran, Central Mediterranean [Tyrrenian, Balearic], and Aegean basins). The timing of the initial slowing of AF-EU convergence (~25 Ma; Late Oligocene/Early Miocene) corresponds to the initiation of extensional tectonics in the Mediterranean Basin (Alboran, Central Mediterranean [Tyrrenian, Balearic], and Aegean basins), and the second phase of slowing to changes in the character of Mediterranean extension reported at ~ 11 Ma (Tortonian). Based on theoretical considerations indicating that buoyancy forces on the subducted lithosphere are proportional to the rate of subduction, we hypothesize that the slowing of AF-EU convergence caused an imbalance in the dynamic equilibrium of the subducting Neotethys oceanic lithosphere beneath the Mediterranean segment of the plate boundary, resulting in foundering of the subducted plate, and associated southward migration of the trench system. Southward trench migration resulted in contemporaneous ~N-S extension within the Mediterranean Basin. The detailed configuration of these extensional basins likely reflects the segmentation and geometry of the subducted lithosphere. These observations are consistent with the notion that pulling by the subducted ocean lithosphere is the dominant force driving plate convergence with EU, and provides a unifying, and conceptually simple, dynamic mechanism for post-Late Oligocene (~30 Ma) tectonic deformation in the Mediterranean/Middle East zone of plate interaction.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.T14D..01M
- Keywords:
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- 8107 TECTONOPHYSICS / Continental neotectonics;
- 8120 TECTONOPHYSICS / Dynamics of lithosphere and mantle: general