Paleomagnetism of samples from the axial zone of the Afar depression

Abstract

A series of oriented lava flows has been collected for paleomagnetic work from an axial graben situated in the Afar depression. This graben has many geophysical and structural features which suggest a similarity with the median valleys found in many mid-oceanic ridges. The results of the paleomagnetic work show that all the samples collected from the graben have normal magnetizations. This, coupled with the fact that they are obviously very young, suggests that they were emplaced during the Brunhes normal epoch of the earth's magnetic field. A series of four older lavas was sampled. These lavas gave directions just below the horizontal, but with easterly declinations. These directions could have been caused by a deviation of the earth's field from its normal axial dipole direction, or they could be caused by large-scale rotation about a vertical axis. This rotation could be connected to the distortion necessary to close up the continental portions of crust around the Gulf of Tadjoura.