Seafloor spreading south of the Agulhas Fracture zone

Abstract

FRANCHETEAU and Le Pichon¹ have suggested that before the break-up of Africa and South America the continental² Falkland Plateau fitted against the southern and southeastern margin of South Africa from the southern tip of the Agulhas Bank to a position between East London and Durban. During break-up the Plateau acted as part of the South American plate and moved past Africa along a line of shear which was coincident with an initial marginal offset of approximately 610 miles. If the hypothesis is correct and normal spreading took place to the present, the original offset should be preserved in the present-day mid-Atlantic Ridge. In addition, a fracture zone should bound the southern margin of Africa and extend westwards to the mid-Atlantic Ridge, and the Cainozoic³ and Mesozoic⁴ magnetic lineaments that have been traced in the Cape Basin should be present in the Natal Valley, Transkei Basin and northern Agulhas Basin south of the fracture zone, trending perpendicular to it. New magnetic and bathymetric data presented here lend qualified support to the hypothesis and give an indication of the possible seafloor spreading history of the area.