Publication Date:
2015-09-20
Description:
The Cenozoic East African Rift System (EARS) extends from the Red Sea to Mozambique. Here we use seismic reflection and bathymetric data to investigate the tectonic evolution of the offshore branch of the EARS. The data indicate multiple and time-transgressive neotectonic deformations along ~800 km of the continental margin of northern Mozambique. We observe a transition from a mature rift basin in the north to a juvenile fault zone in the south. The respective timing of deformation is derived from detailed seismic stratigraphy. In the north, a ~30 km wide and more than 150 km long, N-S striking symmetric graben initiated as half-graben in the Late Miocene. Extension accelerated in the Pliocene, causing a continuous conjugate border fault and symmetric rift graben. Coevally the rift started to propagate southward, which resulted in a present-day ~30 km-wide half-graben, approximately 200 km further south. Since the Pleistocene, the rift has continued to propagate another ~300 km, where the incipient rift is reflected by sub-recent small-scale normal faulting. Estimates of the overall brittle extension of the matured rift range between 5 and 12 km, with an along-strike southward decrease of the extension rate. The offshore portion of the EARS evolves magma-poor, similar to the onshore western branch. The structural evolution of the offshore EARS is suggested to be related to and controlled by differing inherited lithospheric fabrics. Pre-existing fabrics may not only guide and focus extension but also control rift architecture.
Print ISSN:
0278-7407
Electronic ISSN:
1944-9194
Topics:
Geosciences
