Abstract:
According to the data on heat-flow parameters, the active phase of rifting in the Algiers-Provencal basin started in the Early-Middle Oligocene, 34+ or -3 Ma, and this correlates with other geological and geophysical data. The high background heat-flow values (81 mW/m (super 2) ) and thin (45 km) lithosphere indicate that the Algiers-Provencal basin was formed by the sea floor extension and spreading. Contemporaneous formation of back-arc basins in the western and eastern Mediterranean during the Oligocene (Algiers-Provencal, Aegean, Cilician, or Adana) is connected with the change in the kinematic conditions in Africa-Eurasia convergence zone. For the Tyrrhenian Sea, the rate of spreading was calculated from heat-flow data for the three axes of spreading (Magnaghi, Vavilov, and Marsili). The rates of spreading received: 1.4 cm/yr (Magnaghi), about 3 cm/yr (Vavilov), and 5.7 cm/yr (Marsili), are very close to the rate values calculated from deep sea drilling data. The southeastward shift of the axes of spreading with a simultaneous acceleration of spreading may indicate the acceleration of the rollback of the African plate (i.e., an increase in its dip angle in the Calabrian subduction zone), in the context of blocking the subduction by the thick sedimentary strata of the Ionian basin.