High resolution reconstructions of the Southwest Indian Ridge, 52 Ma to present: implications for the breakup and absolute motion of the Africa plate

SUMMARY We reconstruct the post-52 Ma seafloor spreading history of Southwest Indian Ridge at 44 distinct times from inversions ≈20 000 magnetic reversal, fracture zone and transform fault crossings, spanning major regional tectonic events such as Arabia–Eurasia continental collision, Arabia Peninsula’s detachment Africa, arrival Afar mantle plume below eastern Africa initiation rifting in Africa. Best-fitting noise-reduced rotation sequences for Nubia–Antarctic, Lwandle–Antarctic Somalia–Antarctic Plate pairs indicate that rates everywhere along ridge declined gradually by ≈50 per cent ≈31 to 19–18 Ma. A concurrent similar-magnitude slowdown component Plate’s absolute motion parallel suggests both were caused a 31–18 change forces drove resisted Africa’s motion. Possible causes this include effects on or Somalia Plate, which culminated 20–18 with onset Gulf Aden. At earlier times, an apparently robust but previously unknown ≈6-Myr-long period rapid kinematic occurred 43 37 Ma, consisting rate 40 followed full recovery 30–40° clockwise plate slip direction Although these changes coincided reconfiguration palaeoridge geometry, their underlying cause is unknown. abyssal hill azimuths are consistent directions estimated our newly derived angular velocities, adding confidence reliability. Lwandle–Antarctica has closely tracked since 50 slow-to-no between Lwandle plates much time. In contrast, Nubia–Somalia rotations new 189 ± 34 km WNW–ESE divergence Nubia northern including 70–80 17–16 slow no 26 17 109 38 ≈26 absent any deformation within Antarctica before