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Mechanism, of inheritance of rift faulting in the western branch of the East African. Examples include Longonot-Hells Gate (Kenya), Mount Meru (Tanzania) and Nyiragongo (Democratic Republic of Congo). International Geological Congress, Section I 1, pp. Tectonophysics 213, 235–256. E. Woldegabriel, G., Aronson, J.L., Walter, R.C., 1990. It is clear, that large segments of the rift system developed far from, the locations of plume impacts, as is the case for all the, southern segment of the western branch. Wohlenberg, J., 1975b. (C) in Kenya, along shore west, activity. This may, Cut along road in Ruzizi valley of north Tanganyika plain, showing tilted blocks bounded by listric normal faults. The seismicity trends parallel to the rift system, with a shallow focal depth of 12–15 km (7.5–9.3 mi) beneath the rift axis. Reidel, Dordrecht. To the north, there is a Neogene White, Nile graben. Volcanology and Geothermal Research 132, 283–310. Location is shown (rectangle) in Fig. The volcanoes are rooted on open fractures such a, sion joints, tail-cracks or tensional releasing bends (, perhaps if the opening of large tension fractures happened, by reactivation of Precambrian zones of weakness, in some, places apart from the main line of the rift valley. The eastern crest line elevations vary between, The rift is segmented into graben basins, each one asym-, metric, the graben fill dipping east, and the major fault, lying along the eastern side. au rifting: le cas du bassin nord-Tanganyika, rift est-, sler, A. These essential works were focused on map-, lasting in the 1970s, with more regional scale studies of, some aspects of the geology, especially tectonics, volcanism. Tectonophysics 236, 465–, Kilembe, E.A., Rosendahl, B.R., 1992. In this interpre-, The other NW-striking zones are not all so typical, and, can be considered as partly diffuse transforms, in which. Hence, some of the deepest lakes of the world can be found in the area, most of them stretched in a north-south direction in the western branch of the Rift Valley (figure 19.1). << western scarp border of Kerio graben is lightly eroded. La bielette danakile: un mode, Simiyu, S.M., Keller, G.R., 1997. The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. It can be regarded as an intra-continental ridge system comprising an axial rift. Prior to rifting, enormous continental flood basalts erupted on the surface and uplift of the Ethiopian, Somali, and East African plateaus occurred. Le Rift est aussi le lieu de découvertes paléontologiques spectaculaires et l'un des plus grands conservatoires de fossiles du monde. Strecker, M.R., Blisniuk, P.M., Eisbacher, G.H., 1990. Complete Registration FREE TRIAL Form, File will be Downloaded Automatically. Rifting in the western branch remains controversial and is suggested to have initiated either during the middle Late Miocene, around 12 Ma, ... Rifting in the western branch remains controversial and is suggested to have initiated either during the middle Late Miocene, around 12 Ma (Chorowicz, 2005) or synchronously with the East branch around 25 Ma . Geophysics of the Usangu, flats, Tanzania. The northern end of the trough shows a obvious half-graben symmetry, with very well developed border scarps. This is responsible for eventual reversal in rift asymmetry from one basin to the next. /BitsPerComponent 8 Africa: the influence of reactivated steep basement shear zones. Geology of East Africa. Geology 18, 299–302. NW- to NNW-, extension direction in the Ethiopian Rift deduced from the orientation, of tension fractures and fault slip analysis. Reactivation of a lateral ramp or tear fault forms, ). Tiercelin, J.-J., Stoffers, P., Tschiband Kimun, Nzojibwami, E., 1992b. Line, Chorowicz, J., Sorlien, C., 1992. frequency domain using transform equations. Tiercelin, J.-J., Chorowicz, J., Bellon, H., Richert, J.P., Mwanbene, J.T., Walgenwitz, F., 1988. Reconnaissance potassium-argon geochronology of the Suregei-Asille. sion, but part of the drainage is deflected away from rift. spreading-transform system?. The, cumulate quantity of movement concerning the eastern, and western branches is badly known and variable from, Africa/Somalia Eulerian pole is badly constrained. /SMask /None>> /Height 499 Each half-graben is filled with late, basins were initiated west of lake Turkana during late Oli-, gocene-early Miocene times, then faulting gradually shifted, in the western and eastern plateaus of the MER is 51, The Kenyan (Gregory) rift region corresponds to the, (Kenya 5200 m, Elgon 4321 m, Kilimanjaro 5964) are situ-, The northern Kenyan rift is developed in the northern, part of the dome. Les relativement courtes longueurs moyennes (11.0-13.2Jim) et larges distributions (1.3-2.3Jim) des traces de fission suggerent un refroidissement prolonqe pour la region, allant du Permien (Karoo) ala periode recente. The rift can propagate outside the area influ-, enced by a plume. Singularités Plurielles est une ASBL qui a pour objectif de permettre le développement global de la personne, qu'il soit individuel, familial et/ou professionnel. Initially we focus on large-scale geological controls on productive geothermal reservoirs, such as the role crustal-scale structural discontinuities play in localizing highly productive geothermal reservoirs. Mohr, P.A., 1974. Journal of Geophysical Research 97 (B8), 11739–. Structural Settings. (oblique extension), and comprise major strike-slip faults. H., Varet, J., 1972. Hendrie, D.B., Kusznir, N.J., Morley, C.K., Ebinger, C.J., 1994. Journal of Volcanology and Geothermal Research 1, 55–, Mohr, P.A., Baker, B.H., Williams, L.A., 1972. L'évolution de son remplissage sédimentaire qui reflète un enregistrement des variations climatiques en région tropicale, se situe dans un cadre de riftogenèse actif depuis le Miocène. 2014;Ebinger 2005). Source mechanisms and focal depths of East. Tilted blocks and fault scarps on black and white Landsat TM image of southern Afar. New geochronological (KAr, 14C), isotopic (δ18O, δ13C) and magnetostratigraphical data allow the determination of the succession of palaeoclimatic and tectonic phases. In an attempt to make a point on the rift system evolution through time and space, it is clear that the role. The Rift System and the East African Swell. /Length 7 0 R The following stages of rift evolution can be defined, Mondeguer et al., 1989; Hayward and Ebinger, 1996, movements (along a given fault more ancient striations are, the focal mechanisms of earthquakes are distinctly strike-, energy seismicity, formation of en-echelon tension gashes, and dense distribution of small-throw strike-slip and obli-, que-slip faults, with a strike-slip stress-field (, izontal). Late Eocene-Recent volcanism and faulting in the southern. alignment. Shudofsky, G.N., 1985. Movements can, be deduced from focal mechanisms of earthquakes, bore-. Vertical lines are inferred dyke intrusions. Bosworth, W., Maurin, A., 1993. Geologic and geomorphologic constraints on the, evolution of the Red Sea Gulf of Aden and Afar Depression. Clifton, A.E., Schlische, R.W., Withjacj, M.O., Ackermann, R.V., 2000. Finally, the proposed technique is a passivity preserving model order reduction method, since it is proven that the reduced order model of G(F(s)) is still positive-real. /Filter /DCTDecode the African Rift System. Oblique extensional tectonics in the, Malawi Rift. by faulting and subsidence, forming elongate, narrow rifts, while the lithospheric mantle is subjected to sharpl, ductile thinning, inducing ascension of asthenospheric, The most characteristic features in the rift system are, then these narrow elongate zones of thinned lithosphere, related to deep intrusions of asthenosphere in the upper, mantle. In an overall E-W-extending system of partly overlapping arcuate rift branches 53,72-77 , our edgedriven microplate model intrinsically leads to local WNW-ESE extension directions. At the Tanzania divergence, the Eastern Branch separates into three strands that, in part, die out against the strong lithosphere of the Archean Tanzania craton, ... Based on present-day and inferred past regional extension directions and our model results, we can synthesize the three EARS opening models presented in Fig. Seismicity occurs throughout the depth range, these major normal and detachment faults, which generates, a general asymmetric roll-over structure. Faulting and bloc rotation in the Afar. After the discovery expeditions, detailed local geologica, studies span from the beginning of the 1930s to the end, of the 1960s. Rotation of. This situation essentially corresponds to the main, 9.2. less defined graben basins comprise Lake Kariba. This paper is about studying the frequency of the above-generated functions in time as well in the, In mammography units, mammograms are taken at the cathode (chest wall) side rather than at the center position of the effective X-ray field (image receptor support) in clinical usage. The EARS can then be taken as the beginning, Bosworth, 1994; Fantozzi and Sgavetti, 1998, , the late Quaternary Eulerian pole is in, ), the main boundary fault changes side across trans-, ). This paper aims at clarifying case marking forms in Indonesian and how the forms are translated into English. Geophysical Research Letters 22 (17), Bosworth, W., 1985. There is not. Vue générale des ‘champs’ Cénozoïques. De la Corne de l’Afrique aux Grands Lacs, de l’Éthiopie au Mozambique, le Rift est-africain s’étend en une succession de dépressions, de hauts plateaux, de lacs et de volcans, le long d’une fracture majeure du continent africain. /ColorSpace /DeviceRGB American Association of Petroleum Geologists Studies in Geology 44. Datations K–Ar de quelques laves du Rift-. Developments in the structural geology of rifts over. Over time, many theories have tried to clarify the evolution of the East African Rift. Bosworth, W., 1987. Tectonophysics 148, 241–252. The seismicity of the East African rift, Fairhead, J.D., Henderson, N.B., 1977. Oblique-slip, deformation in extensional terrains: a case study in the lakes. These diverging, half-graben valleys are outside the Kenyan dome, and, Pn wave velocities indicate that there are no broad, (>100 km wide) thermal anomalies in the uppermost man-, these half-graben basins affect only the crust and are not, underlain by asthenospheric ascent. Journal of Structural Geology 4, 105–115. It has suffered anti-, The Somalian plateau, lying to the south of the Afar, is, tion. Geocongress 86, 751–753. basaltic rocks. A detailed study of the deposits along the border of the rift and at the bottom of the basin allows nine lithostratigraphical units to be distinguished. Journal African Earth Sciences 26 (3), 441–, Katz, M.B., 1987. The East African rift system is a series of several thousand kilometers long aligned. endobj Harkin, P.A., 1960. Tectonophysics 212, 257–, Oxburgh, E.R., Turcotte, D.L., 1974. Tazieff, H., 1973. They are mostly parallel to the main trend of, the margin and may have been favored by tendency to. Le Fournier, J., Chorowicz, J., Thouin, C., Balzer, F., Chenet, Y. Henriet, J.-P., Masson, D., Mondeguer, A., Rosendahl, B., Spy-. Tel un grand livre ouvert, le Rift s'offre comme un vaste laboratoire naturel permettant de retracer l'histoire de notre planète, de comprendre l'évolution de l'écorce terrestre, la formation des océans et des volcans. der Borntraeger, Berlin, Stuttgart, 484 p. ographie Physique et de Geologie Dynamique 15 (2), 341–346. 1 0 obj ), Tectonics, Sedimentation and Volcanism in the East African Rift System. The. Identification of a fossil wood in the Red, Sandstone Group of Southwestern Tanzania: stratigraphic and. A. Seismic reflection profile of Lake Malawi (Specht and Rosendahl, 1989; Rosendahl et al., 1992). The result of this simulations are indicative of the correlation between step square waving and reductions in total harmonic distortion (THD) during DC to AC conversion. It is located apart from, the main region of half-grabens and can be considered as, an appended basin. ), Geosciences of Rift Systems-. Comptes Rendus Acade. Gibbs, A.D., 1990. Geodynamic evolution of the Afro-Arabic Rift System. Bulletin Centres de Recherches. In the younger layers, the number of faults decreases with, time. attesting to more recent formation than the eastern scarp. Geologische Rundschau 69 (1), 49–62. Nature of the crust beneath magmatically active. [27], Coordinates: 3°00′00″S 35°30′00″E / 3.0000°S 35.5000°E / -3.0000; 35.5000, An active continental rift zone in East Africa, GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre (June 8, 2020), "Continental break-up: The East African perspective", "One of Africa's Tectonic Plates Is Rotating in a Different Direction to All the Others", "Why the Victoria Plate in Africa rotates", "A catalogue of deep mantle plumes: New results from finite‐frequency tomography", "A common mantle plume source beneath the entire East African Rift System revealed by coupled helium-neon systematics", "Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography", "Upper mantle earth structure in Africa from full‐wave ambient noise tomography", "Contrasted continental rifting via plume-craton interaction: Applications to Central East African Rift", "Plume-induced continental rifting and break-up in ultra-slow extension context: Insights from 3D numerical modeling", "Geology and Nonfuel Mineral Deposits of Africa and Middle East", "Great Rift Valley Ecosystem – UNESCO World Heritage Centre", List of countries where Arabic is an official language, https://en.wikipedia.org/w/index.php?title=East_African_Rift&oldid=980479648, Wikipedia articles needing page number citations from March 2019, Short description is different from Wikidata, Wikipedia articles with WorldCat-VIAF identifiers, Creative Commons Attribution-ShareAlike License, This page was last edited on 26 September 2020, at 19:21. The rift system, can propagate outside the area influenced by plume. Nature 215, 578–, McConnel, R.B., 1972. First- and second-order patterns of stress in the, lithosphere: the World Stress Map project. main Ethiopian rift, located between these two nucleations, than early Miocene volcanic events in the Turkana region, In the western branch, the first lavas erupted in the, dle to late Miocene), the northern basin between 8 and 7, across transfer fault, with frequent reversal in asymmetry. /CA 1.0 Rift est-africain est également un terrain propice à l'exploration des relations entre l'homme et le milieu, à la reconstitution des temps anciens des sociétés humaines. Other uplifted areas in. Several lines of propagation, are defined, near Lake Mweru, at Lake Kariba, along the, Mozambique coast and more to the south along the, constrained, but should be at least at Limpopo valley or, The various rift segments are at different evolutionary, stages, depending on the age of rift initiation and distance, to the Eulerian pole. East African Rift. New age, constraints of the timing of volcanism and tectonism in the northern, main Ethiopian Rift–Southern Afar transition zone (Ethiopia). Fitch, F.J., Hooker, P.J., Miller, J.A., Mitchell, J.G., Watkins, R.T., 1985. The main phenomena are forma-, tion of domes related to plume effect, weakening the lith-, osphere and, long after, upper mantle failure inducing, asthenospheric intrusion and related thermal uplift of, shoulders. Petrological evidence regarding the evolution of the. on the development of the Kenya Rift, East Africa. The focal spot size and distribution of the X-ray intensity influencing spatial resolution are important factors in mammograms. Journal. The tilt direction of imbricate normal-fault blocks within large extensional allochthons is commonly away from the transport direction of these sheets, but in many cases tilts are in the same direction as transport, thus limiting the usefulness of the direction of tilting as a transport indicator. Geological Society of America 136, 67, Special. Eruptions of the Rungwe volcano occurred in relationships, with activity of NW-striking faults bounding the Rukwa, in a releasing bend relay (accommodation) zone, belonging, to the Tanganyika–Rukwa–Malawi dextral fault zone. fault, abruptly connected to lisric major border fault, accommodates horizontal extensional movement (4 in, focused (tens of kilometers wide) subsidence in the crust is, superimposed to wide rise of the lithosphere. Continental rifting parallel to ancient. The Tana basin, Ethiopia: intra-plateau uplift, rifting and, Chorowicz, J., Collet, B., Bonavia, F., Korme, T., 1999. The Geology of Ethiopia. the African, Arabian and Somalian plates. 1. This pattern of folds explains why some segment border areas of the Tanganyika rift form low plains instead of the usual high, faults paralleling the movement of divergence. (Eds. East African rift system. Nature 303 (5918), Mohr, P.A., 1992. Journal of Geophysical Research 98 (17), 821–. The majority of earthquakes occur near the Afar Depression, with the largest earthquakes typically occurring along or near major border faults. The original, distribution of the mid-Tertiary trap basalts and the Tana, dome, prior to opening of the Red Sea and Gulf of Aden, had an ovoid shape in plan view, with a longitudinal axis, passing much closer to Lake Tana than to the middle of, the Afar. Extension and subsidence adjacent to, a ‘‘weak’’ continental transform: an example of the Rukwa Rift, East. (1972), Mohr (1982). (1) divergence of continental, blocks; (2) strain focused along former weak suture zone induces local thinning, asthenospheric diapir; (3) induced heating of the lithosphere, responsible for wide (hundreds of kilometers) uplift of the area; (4) in the crust, a unique, major normal fault abruptly linked in depth to a low-angle detachment fault reactivates deep part of former frontal ramp of ancient belt, and. Off-axis volcanism in the Gregory rift, east Africa: implications for models of continental rifting. ties for a main regional stress field to suffer local deviations, e.g. C. Inferred lithospheric cross-section of the northern Kenyan rift. Normal and strike-slip, faults sometimes interact to form spoon faults (e.g., Living-, In the case of tension fractures, the horizontal transver-, sal throw component predominates. Transfer faults and pull-apart, model in the Rhinegraben from analysis of multisource data. Location in, Virunga, massif fissure volcanism started between 11 and, 9 Ma, and after a long period of quiescence (9–3 Ma), large, Pliocene-Pleistocene central volcanoes were formed, made. initiated even earlier. Although most of these mountains lie outside of the rift valley, the EAR created them. -from English summary, The recent lacustrine deposits of the Mpulungu basin were studied on the basis of sediment sampling and high-frequency seismic echograms (3.5 kHz). The graben valleys, and basins are organized over a major failure in the lithospheric mantle, and in the crust comprise a major border fault, linked in depth to, a low angle detachment fault, inducing asymmetric roll-over pattern, eventually accompanied by smaller normal faulting and tilted, blocks. The equipment manufactures specify their focal spots sizes at reference exis which corresponds to the center position of the effective X-ray field. They have to be considered, as essentially crustal structure, with no significant upper, This work started in Eastern Africa at end of the 1970s, with support from Centre National de la Recherche, for a scientist specialized in the Alps, it, have a better knowledge of the early basin and transform, fault history of belts. Tectonics and environ-, mental control on rodent diversity in the Plio-Pleistocene sediments of. The discussion of case marking in this paper include possessive marking, In this paper, positive-real systems under lossless positive-real transformations are investigated. forming longer basins, often occupied by a great lake. 1a) is the classic example of an active continental rift associated with a plume 6,7 . Chapman & Hall, London, pp. Structural evolution of Lake Malawi, Africa. Geophysikalische Aspekte der ostafrikanischen. the boundary fault is simply one of the many smaller faults. -from Authors, The structural observations, presented here, include reinterpretation of seismical profiles and of Landsat scenes. Along, the western branch, after arrival of the plume and related, panache, failure nucleated likely in Kivu-northern. [15] Seismic events in the past century are estimated to have reached a maximum moment magnitude of 7.0.

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