Tectonostratigraphic evolution and significance of the Afar Depression

Abstract

The Afar Depression is a unique place on Earth where active rift processes can be directly observed. It is believed to be close to continental breakup. The Afar hotspot has a strong influence on the geology of the Depression. Despite the strong geological interest in the region, difficult field access slowed scientific discoveries. During the last two decades, new projects and studies resulted in a better characterization of the region. New field data and global advances in understanding rift processes call for an integrative and holistic review of the tectonostratigraphic evolution of the Afar Depression. This study compiles new geological maps and reviews the stratigraphy and the geological history of the Afar Depression and the Afro-Arabian Rift System. A new kinematic evolution model and integrative paleogeological maps are proposed. Results show that geological events are diachronous throughout the region. We consider the Afar Rift to be distinct from the Red Sea Rift, both being separated by the Arrata Microplate. The Afar Rift is propagating northwards and forms a relay structure with the Red Sea Rift, linked to the counter-clockwise rotation of the Danakil Block since the Mid- to Late Miocene. The Afar Depression can be segmented into two distinct domains, Central Afar and the Danakil Depression. Central Afar experienced significant extension, protracted and extensive magmatism and magma-compensated thinning. It is believed to be strongly influenced by the Afar hotspot. In comparison, the Danakil Depression is younger and went through less extension and less magmatic activity until Recent (∼0.6 Ma) times. The absence of magma-compensated thinning allowed the development of an evolved stage of continental breakup. The tectonostratigraphic evolution of the Afar Depression with distinct rifting styles shows the complexity of continental break-up.