Paléomagnétisme en zone d'accrétion : le cas de l'Afar

A paleomagnetic investigation has been undertaken to study the Asal rift zone and the border zone between Asal and Yoboki. In both zones sampling has been carried out along the vertical surfaces of the sections exposed by the rift faults and the Edayle canyon, on the south side of Ghoubbet. The results of the rift zone indicate a magnetization of normal polarity for all the sites. Moreover, the corrections for the tilt of the strata show that in the "small rift" the observable tectonism is older than the emplacement of the lava flows. Outside the rift, 18 flows with normal and reversed polarity belong to the stratoid series (1-4 m.y.). They yield a mean direction of D = 10°E and 1 = + 13°, which can be explained either by a non dipolar or non CO-axial geomagnetic field for this interval in the Afar region, or by an important regional tectonic displacement. Structural measurements would be necessary to choose between these alternatives to explain the observed directions. [NOT CONTROLLED OCR]