New Insights Into Continental Transfer Zones: Evidence From the Tanganyika-Rukwa-Malawi System

Abstract

Transfer zones between major rift basins are critical locations in rift architecture as they often form long lived structural features that are pervasive during lithospheric extension from rifting through into post-rift passive margins. Here we undertake a regional structural analysis of the Tanganyika-Rukwa-Malawi (TRM) system, which is located on the Western Branch of the East African Rift System (EARS). The TRM fault zone is a 1000 km long and 200 km wide zone that follows the trend of the Ubendian Orogeny Precambrian lineament. Additionally, the region is within rifted Permo-Triassic (Karoo) and Cretaceous rifting. Much debate has centered about the role of the Rukwa basin within this part of the EARS, specifically whether it forms a transfer between the en echelon troughs of the Tanganyika and Malawi Rifts; and whether it has opened in oblique or pure extension. Recent studies have highlighted the possibility of more than one orientation of rifting both within the Rukwa Rift and surrounding rift basins, and there is much potential for the inheritance from and reactivation of existing earlier rift faults. Although a number of studies have considered the evolution of each of these basins, these have tended to consider basins in isolation. In this study we integrate existing seismic reflection data with new high resolution reflection, Full Tensor Gradient and Digital Elevation Modelling data to construct a unified structural model of the TRM system. The structural model allows us to investigate a number of key parameters, including the distribution of strain across the system, the role of pre-existing fabrics on fault geometry, the distribution of volcanics and the role of stress obliquity on fault evolution. These findings provide a new understanding of the evolution of this area but also insights into the processes involved at transfer zones in both mature rift basins and passive margin settings.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015