The motion between Nubia and Somalia from magnetic anomaly and fracture zone crossings flanking the Southwest Indian Ridge
Lemaux, James Wilmer, II
Gordon, Richard G.
Master of Arts
Previous reconstructions for anomaly 5 and older anomalies flanking the Southwest Indian Ridge (SWIR) have indicated no statistically significant evidence for motion between the Nubian and Somalian plates. Recently, an analysis of current plate motion across the SWIR indicates significantly different Nubia-Antarctica and Somalia-Antarctica angular velocities. Herein the motion across the SWIR is examined since chron 5 (11 Ma) and chron 6 (20 Ma). I identify 238 Anomaly 5 crossings, 140 Anomaly 6 crossings, and many fracture zone crossings. The new results show that the Nubia-Antarctica and Somali a-Antarctica rotations differ significantly. The results have several implications. (1) Earlier motion differs significantly from that since 3.2 Ma, implying that Nubia-Somalia motion began before 3.2 Ma. (2) Poles of rotation for motion since chron 5 and since chron 6 poles differ significantly from those after 3.2 Ma suggesting a component of right-lateral shearing has occurred along the East African rift since 11 and 20 Ma. (3) Data suggest that the boundary between Nubia and Somalia is narrow where it intersects the SWIR near the Andrew Bain fracture zone complex.
Geodesy; Geophysics; Physical oceanography