1,721,003 research outputs found
Holocene opening directions along the axes of Red Sea (Afar) and Main Ethiopian rifts: an overview
No full textThe role of pre-existing structures in the origin, propagation and architecture of faults in the Main Ethiopian rift
No full textRates of Late Quaternary deformation along the Wonji fault belt in the Lakes Region, Main Ethiopian Rift.
No full textPlio-Quaternary volcano-tectonic activity in the northern sector of the Main Ethiopian Rift (MER): relationships with oblique rifting
No full textQuaternary faulting and volcanism in the main Ethiopian Rift
No full textThe Main Ethiopian Rift (MER) is associated with bimodal Quaternary magmatism. Field, remote sensing, and geochronology data are used to examine the relationships between axial acidic volcanoes and basaltic eruptions. Two main Quaternary magmatic episodes are recognizeable in MER: a) basaltic flows followed by ignimbrites and silicic centers in the rift floor (2-1 Ma) and b) axial silicic volcanoes and basalts since ~650 Ka. The first episode consists mainly of basaltic flows related to the Afar Stratoid and outcrops in the central and northern MER. Scattered silicic centers developed subsequently along the rift floor. In the second episode, spatial and temporal correlation between rift localization and silicic centers becomes more evident. The silicic centers are located at the intersection of the WFB with earlier structures, especially E-W faults. With ageing, these centers become faulted and allow basalts to erupt right through the volcanic edifice, suggesting a decrease in the amount of differentiation in the magma chambers, possibly due to their cooling. This style of evolution appears to be characteristic of continental rifts prior to the onset of drifting
Cartografia geomorfologica di dettaglio e analisi statistica in ambiente GIS dei processi di versante nel bacino di Dessie (Wollo, Etiopia)
No full textStructure of Tendaho Graben and Manda Hararo Rift: implications for the evolution of the Red Sea propagator in Central Afar
No full textThe Red Sea and Aden rifts (or propagators) meet in Afar. Here we use remote sensing and field analyses to define the geology and structure of the southern part of the Red Sea propagator, in Central Afar. This consists of the NW-SE trending Tendaho Graben (TG) and the younger and active NW-SE trending Manda Hararo Rift (MHR), partly within TG. Tectonic and volcanic activity within TG developed mostly between ~1.8 to ~0.6 Ma, with a stretching factor ~1.1, an extension rate ~3.6 mm/yr and the fissural eruption of part (~7000 km3/Ma) of the Afar Stratoid sequence (mainly basaltic lava flows and ignimbrites). MHR, before terminating southward, has a ~1.04 and extension rate ~1.2 mm/yr, and is associated with the emission of ~600 km3/Ma of basalts in the last ~0.2 Ma. These data suggest that, after the exceptional amount of magma erupted between ~1.8 to ~0.6 Ma, magmatic and tectonic activity significantly decreased along the southern part of the Red Sea propagator in the last ~0.2 Ma. This decrease coincides with the on-land development and migration of the more active (inferred extension rate in the order of ~10 mm/yr, as proposed in previous studies) Aden propagator, suggesting that spreading in Central Afar mainly occurred along one active propagator at any one time
Stile deformativo e reticolo idrografico lungo la scarpata del Plateau Somalo al margine meridionale dell'Afar
No full textStyle of faulting and drainage pattern along the Somalian plateau escarpment at the southern Afar margin (Ethiopia) [Stile deformativo e reticolo idrografico lungo la scarpata del Plateau Somalo al margine meridionale dell’Afar (Etiopia)]
No full textAn integrated structural and geomorphologic study along the Somalian Plateau escarpment at the southern Afar margin (Dire Dawa area, Ethiopia), provides insights into the rift geometry, timing and evolution of this sector of the East Africa Rift system. Late Triassic-Jurassic sandstones and carbonate sequences lie in nonconformity over the pre-Cambrian metamorphic basement and are in turn disconformably covered by Early Cretaceous continental and transitional sandstones and conglomerates. After another disconformity a thick sequence of Flood Basalt was deposited during the Oligocene and today crop out close to the margin of the Rift at an elevation of about 3500 m in the Somalian Plateau. Rift architecture in the study area is characterized by faulted blocks tilting away from the Afar Depression «domino-style faulting», as already described by MORTON & BLACK (1975). Major faults are ca. E-W oriented and show high-angle geometry. Kinematic indicators measured along the fault planes commonly show a slight left lateral component providing a ca. NNWSSE direction of extension. Faulted monoclines composed of footwall anticline-hanging-wall syncline pairs are observed adjacent to many of the block-bounding and intra-block faults. We interpret this structural style to have formed in response to fault-propagation folding in extensional regime. The drainage pattern in the study area is strongly influenced by the main E-W trending faults and by the NNW-SSE system of fractures and doleritic dikes emplaced during the Oligocene volcanic event. Two main stages of fault activation can be recognised in the area. In fact, the faulted blocks, although usually quite dissected, sometimes have a flat top ridge preserving the remain of a former planation surface, most probably a huge pediment that connected the main escarpment to the Afar. This pediment erase some of the faults and in the distal area is covered by Early-Middle Pleistocene Afar flood basalts. After the modelling of the pediment that also cancelled the previous drainage network, a new phase of fault activity is documented. An even older drainage has been recognised in the Plateau area, where broad paleovalleys cut for over 1400 m below the original plateau in the area which separated the Afar depression from the Somalian lowlands. Originally, they were alimented from the «Afar sector» (i.e., from the north) most probably as a consequence of the upwarping that followed the emplacement of the Trap, and evolved as superimposed rivers. The northward drainage is therefore the result of river reversion as a consequence of the down-faulting associated to the rift activation and evolution. These evidence suggest that the emplacement of the Trap occurred at low elevation and was followed by upwarping and much later by rifting processes and down-faulting
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