On the dynamics of the Juan de Fuca plate

We propose alternative kinematics for the Arabia¯India¯Somalia triple junction based on a reinterpretation of seismological and magnetic data. The new triple junction of the ridge¯ridge¯ridge type is located at the bend of the Sheba Ridge in the eastern gulf of Aden at 14.5°N and 56.4°E. The Owen fracture zone (Arabia¯India boundary) is connected to the Sheba Ridge by an ultra-slow divergent boundary trending N80°E±10° marked by diffuse seismicity. The location of the Arabia¯India rotation pole is constrained at 14.1°N and 71.2°E by fitting the active part of the Owen fracture zone with a small circle. The finite kinematics of the triple junction is inferred from the present-day kinematics. Since the inception of the accretion 15¯18 Ma ago, the Sheba Ridge has probably receded ~300 km at the expense of the Carlsberg Ridge which propagated northwestward in the gulf of Aden, while an ultra-slow divergent plate boundary developed between the Arabian and Indian plates. The overall geometry of the new triple junction is very similar to that of the Azores triple junction.