Initiation of the western branch of the East African Rift coeval with the eastern branch
نویسندگان
چکیده
The East African Rift System transects the anomalously high-elevation Ethiopian and East African plateaux that together form part of the 6,000-km-long African superswell structure. Rifting putatively developed as a result of mantle plume activity that initiated under eastern Africa. The mantle activity has caused topographic uplift that has been connected to African Cenozoic climate change and faunal evolution. The rift is traditionally interpreted to be composed of two distinct segments: an older, volcanically active eastern branch and a younger, less volcanic western branch. Here, we show that initiation of rifting in the western branch began more than 14 million years earlier than previously thought, contemporaneously with the eastern branch. We use a combination of detrital zircon geochronology, tephroand magnetostratigraphy, along with analyses of past river flow recorded in sedimentary rocks from the Rukwa Rift Basin, Tanzania, to constrain the timing of rifting, magmatism and drainage development in this part of the western branch. We find that rift-related volcanism and lake development had begun by about 25 million years ago. These events were preceded by pediment development and a fluvial drainage reversal that we suggest records the onset of topographic uplift caused by the African superswell. We conclude that uplift of eastern Africa was more widespread and synchronous than previously recognized.
منابع مشابه
Regional geology of eastern Africa
Abstract Introduction Regional geology of eastern Africa Rukwa Rift Basin Rift stratigraphy, sedimentation and palaeontology Volcanism and geochronology Provenance, drainage patterns and uplift Methods References Acknowledgements Author information Supplementary informationIntroduction Regional geology of eastern Africa Rukwa Rift Basin Rift stratigraphy, sedimentation and palaeontology Volcani...
متن کاملReceiver Function Imaging of Mantle Transition Zone Discontinuities Beneath the Tanzania Craton and Adjacent Segments of the East African Rift System
The mantle transition zone (MTZ) discontinuities beneath the Tanzania Craton and the Eastern and Western Branches of the East African Rift System are imaged by stacking over 7,100 receiver functions. The mean thickness of the MTZ beneath the Western Branch and Tanzania Craton is about 252 km, which is comparable to the global average and is inconsistent with the existence of present-day thermal...
متن کاملGiant Seismites and Megablock Uplift in the East African Rift: Evidence for Late Pleistocene Large Magnitude Earthquakes
In lieu of comprehensive instrumental seismic monitoring, short historical records, and limited fault trench investigations for many seismically active areas, the sedimentary record provides important archives of seismicity in the form of preserved horizons of soft-sediment deformation features, termed seismites. Here we report on extensive seismites in the Late Quaternary-Recent (≤ ~ 28,000 ye...
متن کاملWhy do continents break-up parallel to ancient orogenic belts?
The frequently observed parallelism between rifts and the pre existing orogenic fabric of continents suggests that the inherited tectonic fabric of the lithosphere influences the rupture of continents. We propose that the existence of a pervasive fabric in the lithospheric mantle induces an anisotropie strength in the lithosphere, that guides the propagation of continental rifts. Subcrustal ma...
متن کاملEast African Rift System - an Overview
The main characteristics of the East African Rift System are outlined from selected references. The difference between the Eastern Rift with high volcanicity on two domal uplifts as against the Western Rift of restricted volcanism, but sediment and lake filled grabens is pointed out. This is also evident from the earthquake activity: Large earthquakes occur in the Western Rift, whereas earthqua...
متن کامل