Kinematics of the southern Red Sea–Afar Triple Junction and implications for plate dynamics

Abstract

GPS measurements adjacent to the southern Red Sea and Afar Triple Junction, indicate that the Red Sea Rift bifurcates south of 17° N latitude with one branch following a continuation of the main Red Sea Rift (∼150° Az.) and the other oriented more N‐S, traversing the Danakil Depression. These two rift branches account for the full Arabia–Nubia relative motion. The partitioning of extension between rift branches varies approximately linearly along strike; north of ∼16°N latitude, extension (∼15 mm/yr) is all on the main Red Sea Rift while at ∼13°N, extension (∼20 mm/yr) has transferred completely to the Danakil Depression. The Danakil Block separates the two rifts and rotates in a counterclockwise sense with respect to Nubia at a present‐day rate of 1.9 ± 0.1°/Myr around a pole located at 17.0 ± 0.2°N, 39.7 ± 0.2°E, accommodating extension along the rifts and developing the roughly triangular geometry of the Danakil Depression. Rotating the Danakil Block back in time to close the Danakil Depression, and assuming that the rotation rate with respect to Nubia has been roughly constant, the present width of the Danakil Depression is consistent with initiation of block rotation at 9.3 ± 4 Ma, approximately coincident with the initiation of ocean spreading in the Gulf of Aden, and a concomitant ∼70% increase in the rate of Nubia–Arabia relative motion.