The influence of preexisting structure on the evolution of the Cenozoic Malawi rift (East African rift system)

This paper analyzes the importance of preexisting structure for the evolution of the Cenozoic Malawi rift, which constitutes the southernmost part of the western branch of the East African rift system. Kinematic analyses demonstrate that the regional extension direction rotated clockwise from ENE to SE during rifting. Cenozoic rift faults (of dip‐, oblique‐, and strike‐slip character) rejuvenated crustal structures whenever those were properly oriented with respect to the extension directions. Depending on these boundary conditions the rift attempts to find the easiest pathway in order to develop in a mechanically modest way. Proterozoic basement structures represent the basic anisotropy which already influenced pre‐Cenozoic rifts and also the Cenozoic Malawi rift. Amongst these basement structures, Pan‐African retrograde to cataclastic, strike‐slip shear zones have the strongest influence on later rift structures. Rift‐related transfer faults appear as differently striking passive structures, and their orientation seems to be controlled by a variety of steep basement structures (retrograde shear zones, foliation planes, and fracture arrays).