Folarin Kolawole , Max C. Firkins, Thuwaiba S. Al Wahaibi, Estella A. Atekwana, Michael J. Soreghan

Although much is known about the interaction of faulting and sedimentation within the basins of active segmented continental rift systems, little is known about these processes within the interaction zones of varying geometries that separate the young interacting segments. We address this problem in the humid, magma-poor juvenile western branch of the East African Rift System (WB-EARS). First, we present a broader classification of rift interaction zone (RIZ) geometries that accommodate both the plan-view geometries and border fault polarity patterns of the interacting rift segments. Within the framework of the RIZ geometries, we explore the large-scale cross-over relief profiles, and the relationships with the spatiotemporal development of rift-linking faults (breaching faults) and axial stream patterns. Our results show that: 1.) distinct long-wavelength 2-D cross-over topographic relief shapes, directionality of axial stream flow (sediment routing patterns), and breaching fault patterns characterize RIZs at the various stages of the linkage of interacting rift basins; 2.) these stages include unbreached, partially-breached, recently-breached, and breached RIZs; 3.) deforming RIZs exhibit different styles of directionality of breaching, including a unidirectional (distinct propagator and receiver segments), bi-directional propagation (both segments act as propagators and receivers), and nucleation and outward propagation of a narrow intra-RIZ subsidiary rift basin; 4.) RIZ breaching is facilitated by overlap rift-flank deformation, and/or rift tip propagation structures in the form of rift splaying, border fault rotation (rift-tip rotation), and fault cluster networks; 5.) the lateral propagation of breaching faults at the rift tips and flanks, facilitated by localized stress concentrations, is modulated by the extension direction and inherited basement structures. Our findings offer a broader insight into the geometries and structural evolution of rift interaction zones, and provide first-order predictions of large-scale sedimentation patterns of humid early-stage continental rift environments. Our models provide testable hypotheses for linking rift architecture and patterns of early-stage sedimentation applicable to ancient rift basins.