The upper-mantle low-velocity anomaly beneath Ethiopia, Kenya, and Tanzania: Constraints on the origin of the African superswell in eastern Africa and plate versus plume models of mantle dynamics

Special Paper of the Geological Society of America

Volumn 478, Issue , 2011, Pages 37-50

  Nyblade, Andrew A ^a  

^a PENNSYLVANIA STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

PLATES (STRUCTURAL COMPONENTS); SEISMOLOGY; SURFACE WAVES; TOMOGRAPHY; TOPOGRAPHY; VELOCITY;

410-KM DISCONTINUITY; BODY-WAVE TOMOGRAPHIES; LITHOSPHERIC MANTLE; LOW-VELOCITY ANOMALY; MANTLE TEMPERATURES; RECEIVER FUNCTIONS; SURFACE WAVE DISPERSION; THERMAL STRUCTURE;

STRUCTURAL GEOLOGY;

BODY WAVE; LITHOSPHERE; LOW VELOCITY ZONE; MANTLE PLUME; NUMERICAL MODEL; RIFTING; SEISMIC DATA; TEMPERATURE; THERMAL STRUCTURE; TOMOGRAPHY; UPPER MANTLE; WAVE DISPERSION;

ETHIOPIA; KENYA; TANZANIA;

EID: 80051871637     PISSN: 00721077     EISSN: None     Source Type: Book Series    
DOI: 10.1130/2011.2478(03)     Document Type: Article

References (106)

1. Achauer, U., and Masson, F., 2002, Seismic tomography of continental rifts revisited: From relative to absolute heterogeneities: Tectonophysics, v. 358, p. 17-37, doi:10.1016/S0040-1951(02)00415-8. (Pubitemid 35289011)
2. Achauer, U., Glahn, A., Ritter, J.R.R., Maguire, P.K.H., Meyer, R.P., Davis, P., Slack, P., and Green, W.V., 1994, New ideas on the Kenya Rift based on the inversion of the combined dataset of the 1985 and 1989/90 seismic tomography experiments: Tectonophysics, v. 236, p. 1-4, 305-329.
3. Ammon, C.J., Randall, G.E., and Zandt, G., 1990, On the nonuniqueness of receiver function inversions: Journal of Geophysical Research, v. 95, p. 15, 303-15, 318, doi:10.1029/JB095iB10p15303.
4. Anderson, D.L., 2005, Scoring hotspots: The plume and plate paradigms, in Foulger, G.R., Natland, J.H., Presnall, D.C., and Anderson, D. L., eds., Plates, Plumes, and Paradigms: Geological Society of America Special Paper 388, p. 31-54, doi:10.1130/0-8137-2388-4.31.
5. Ayalew, D., Barbey, P., Marty, B., Reisberg, L., Yirgu, G., and Pik, R., 2002, Source, genesis, and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts: Geochimica et Cosmochimica Acta, v. 66, no. 8, p. 1429-1448, doi:10.1016/S0016-7037(01)00834-1. (Pubitemid 34465997)
6. Baker, J., Snee, L., and Menzies, M., 1996, A brief Oligocene period of flood volcanism in Yemen: Earth and Planetary Science Letters, v. 138, p. 39-55, doi:10.1016/0012-821X(95)00229-6.
7. Bastow, I.D., Stuart, G.W., Kendall, J.-M., and Ebinger, C.J., 2005, Upper mantle seismic structure in a region of incipient continental breakup: Northern Ethiopian rift: Journal of Geophysical Research, v. 162, p. 479-493, doi:10.1111/j.1365-246X.2005.02666.x. (Pubitemid 41632718)
8. Bastow, I.D., Nyblade, A.A., Stuart, G.W., Rooney, T.O., and Benoit, M.H., 2008, Upper mantle seismic structure beneath the Ethiopian hot spot: Rifting at the edge of the African low-velocity anomaly: Geochemistry Geophysics Geosystems, v. 9, Q12022, doi:10.1029/2008GC002107.
9. Benoit, M.H., Nyblade, A.A., and VanDecar, J.C., 2006a, Upper mantle P wave speed variations beneath Ethiopia and the origin of the Afar hotspot: Geology, v. 34, p. 329-332, doi:10.1130/G22281.1.
10. Benoit, M.H., Nyblade, A.A., Owens, T.J., and Stuart, G., 2006b, Mantle transition zone structure and upper mantle S velocity variations beneath Ethiopia: Evidence for a broad, deep-seated thermal anomaly: Geochemistry Geophysics Geosystems, v. 7, Q11013, doi:10.1029/2006GC001398.
11. Berhe, S.M., and Desta, B., Nicoletti, M., and Teferra, M., 1987, Geology, geochronology and geodynamic implications of the Cenozoic magmatic province in W and SE Ethiopia: Journal of the Geological Society of London, v. 144, p. 213-226.
12. Bina, C.R., and Helffrich, G., 1994, Phase transition Clapeyron slopes and transition zone seismic discontinuity topography: Journal of Geophysical Research, v. 99, p. 15, 853-15, 860, doi:10.1029/94JB00462.
13. Buck, W.R., 1986, Small-scale convection induced by passive rifting: The cause for uplift of rift shoulders: Earth and Planetary Science Letters, v. 77, p. 362-372, doi:10.1016/0012-821X(86)90146-9.
14. Burke, K., 1996, The African plate: South African Journal of Geology, v. 99, no. 4, p. 341-409. (Pubitemid 126632323)
15. Burke, K., and Gunnell, Y., 2008, The African Erosion Surface: A Continental-Scale Synthesis of Geomorphology, Tectonics, and Environmental Change over the Past 180 Million Years: Geological Society of America Memoir 201, 66 p.
16. Burke, K., and Şeng̈r, A.M.C., 1986, Tectonic escape in the evolution of the continental crust, in Barazangi, M., and Brown, L., eds., Refl ection Seismology-The Continental Crust: American Geophysical Union Geodynamic Monograph 14, p. 41-53.
17. Burke, K., and Torsvik, T.H., 2004, Derivation of large igneous provinces of the past 200 m.y. from long-term heterogeneities in the deep mantle: Earth and Planetary Science Letters, v. 227, p. 531-538, doi: 10.1016/j. epsl.2004.09.015. (Pubitemid 39428200)
18. Burke, K., Macgregor, D., and Cameron, N., 2003, African petroleum systems: Four tectonic "aces" in the past 600 million years, in Arthur, T.J., Macgregor, D.S., and Cameron, N.R., eds., Petroleum Geology of Africa: New Themes and Developing Technologies: Geological Society of London Special Publication 207, p. 21-60. (Pubitemid 37142130)
19. Chernet, T., Hart, W.K., Aronson, J.L., and Walter, R.C., 1998, New age constraints on the timing of volcanism and tectonism in the northern Main Ethiopian Rift-southern Afar transition zone (Ethiopia): Journal of Volcanology and Geothermal Research, v. 80, no. 3-4, p. 267-280. (Pubitemid 28415877)
20. Coulié, E., Quidelleur, X., Gillet, P.Y., Courtillot, V., Lefèvre, J.C., and Chiesa, S., 2003, Comparative K-Ar and Ar/Ar dating of Ethiopian and Yemenite Oligocene volcanism: Implications for timing and duration of the Ethiopian Traps: Earth and Planetary Science Letters, v. 206, p. 477-492, doi:10.1016/S0012-821X(02)01089-0. (Pubitemid 36211295)
21. Courtillot, V.C.J., Manighetti, I., Tapponnier, P., and Besse, J., 1999, On casual links between flood basalts and continental breakup: Earth and Planetary Science Letters, v. 166, p. 177-195, doi:10.1016/S0012-821X(98)00282- 9. (Pubitemid 29427518)
22. Davis, P.M., and Slack, P.D., 2002, The uppermost mantle beneath the Kenya dome and relation to melting, rifting and uplift in East Africa: Geophysical Research Letters, v. 29, no. 7, 1117, doi:10.1029/2001GL013676.
23. Dawson, J.B., 1992, Neogene tectonics and volcanicity in the North Tanzania sector of the Gregory Rift Valley: Contrasts with the Kenya sector: Tectonophysics, v. 204, p. 81-92, doi:10.1016/0040-1951(92)90271-7.
24. Debayle, E., Levque, J.J., and Cara, M., 2001, Seismic evidence for a deeply rooted low-velocity anomaly in the upper mantle beneath the northeastern Afro/ Arabian continent: Earth and Planetary Science Letters, v. 193, p. 423-436. (Pubitemid 34054524)
25. Deuss, A., 2007, Seismic observations of transition zone discontinuities beneath hotspot locations, in Foulger, G., and Jurdy, D., eds., Plates, Plumes, and Planetary Processes: Geological Society of America Special Paper 430, p. 121-136, doi:10.1130/2007.2430(07).
26. Deuss, A., Redfern, S.A.T., Chambers, K., and Woodhouse, J.H., 2006, The nature of the 660-kilometer discontinuity in Earth's mantle from global seismic observations of PP precursors: Science, v. 311, no. 5758, p. 198-201, doi:10.1126/science.1120020. (Pubitemid 43108179)
27. Doucouré, C.M., and de Wit, M.J., 2002, Temporal variation in rigidity and mechanical behaviour of old thick continental lithosphere: South African Journal of Geology, v. 105, p. 39-50, doi:10.2113/1050039.
28. Dugda, M.T., Nyblade, A.A., Julià, J., Langston, C.A., Ammon, C.J., and Simiyu, S., 2005, Crustal structure in Ethiopia and Kenya from receiver function analysis: Implications for rift development in eastern Africa: Journal of Geophysical Research, v. 110, B01303, doi:10.1029/2004JB003065. (Pubitemid 40517758)
29. Dugda, M.T., Nyblade, A.A., and Julià, J., 2007, Thin lithosphere beneath Ethiopia and Djibouti revealed by a joint inversion of Rayleigh wave group velocities and receiver functions: Journal of Geophysical Research, v. 112, B08305, doi:10.1029/2006JB004918. (Pubitemid 47578265)
30. Dugda, M.T., Nyblade, A., and Julià, J., 2009, S-wave velocity structure of the crust and upper mantle beneath Kenya in comparison to Tanzania and Ethiopia: Implications for the formation of the East African and Ethiopian Plateaus: South African Journal of Earth Science, v. 112, p. 241-250.
31. Ebinger, C., and Sleep, N., 1998, Cenozoic magmatism throughout east Africa resulting from impact of one large plume: Nature, v. 395, p. 788-791, doi:10.1038/27417. (Pubitemid 28485443)
32. Ebinger, C.J., Bechtel, T.D., Forsyth, D.W., and Bowin, C.O., 1989, Effective elastic plate thickness beneath the East African and Afar Plateaus and dynamic compensation of the uplifts: Journal of Geophysical Research, v. 94, no. B3, p. 2883-2901, doi:10.1029/JB094iB03p02883.
33. Ebinger, C., Yemane, T., Harding, D.J., Tesfaye, S., Kelley, S., and Rex, D.C., 2000, Rift defl ection, migration, and propagation: Linkage of the Ethiopian and Eastern Rifts, Africa: Geological Society of America Bulletin, v. 112, p. 163-176, doi:10.1130/0016-7606(2000)1122.0.CO;2. (Pubitemid 32828193)
34. Foster, A., Ebinger, C., Mbede, E., and Rex, D., 1997, Tectonic development of the northern Tanzanian sector of the East African Rift system: Journal of the Geological Society of London, v. 154, no. 4, p. 689-700, doi:10.1144/gsjgs.154.4.0689.
35. Furman, T., Kaleta, K., Bryce, J., and Hanan, B., 2006, Tertiary mafic lavas of Turkana, Kenya: Constraints on East African plume structure and the occurrence of high-μ volcanism in Africa: Journal of Petrology, v. 47, no. 6, p. 1221-1244, doi:10.1093/petrology/egl009. (Pubitemid 43779086)
36. Gashawbeza, E.M., Klemperer, S.L., Nyblade, A.A., Walker, K.T., and Keranen, K.M., 2004, Shear-wave splitting in Ethiopia: Precambrian mantle anisotropy locally modified by Neogene rifting: Geophysical Research Letters, v. 31, L18602, doi:10.1029/2004GL020471. (Pubitemid 39660808)
37. George, R., Rogers, N., and Kelley, S., 1998, Earliest magmatism in Ethiopia: Evidence for two mantle plumes in one flood basalt province: Geology, v. 26, p. 923-926, doi:10.1130/0091-7613(1998)0262.3.CO;2. (Pubitemid 29139666)
38. Grand, S.P., 2002, Mantle shear wave tomography and the fate of subducted slabs: Philosophical Transactions of the Royal Society of London, ser. A, v. 360, p. 2475-2491, doi:10.1098/rsta.2002.1077.
39. Grand, S.P., van der Hilst, R.D., and Widiyantoro, S., 1997, Global seismic tomography: A snapshot of convection in the Earth: GSA Today, v. 7, no. 4, p. 1-7. (Pubitemid 27472170)
40. Green, W.V., Achauer, U., and Meyer, R.P., 1991, A three-dimensional seismic image of the crust and upper mantle beneath the Kenya Rift: Nature (London), v. 354, p. 199-203. (Pubitemid 21896811)
41. Gurnis, M., Mitrovica, J.X., Ritsema, J., and van-Heijst, H.-J., 2000, Constraining mantle density structure using geological evidence of surface uplift rates: The case of the African superplume: Geochemistry Geophysics Geosystems, v. 1, no. 7, 1020, doi:10.1029/1999GC000035.
42. Hendrie, D.B., Kusznir, N.J., Morley, C.K., and Ebinger, C.J., 1994, Cenozoic extension in northern Kenya; a quantitative model of rift basin development in the Turkana region: Tectonophysics, v. 236, no. 1-4, p. 409-438.
43. Hirose, K., 2002, Phase transitions in pyrolitic mantle around 670-km depth: Implications for upwelling of plumes from the lower mantle: Journal of Geophysical Research, Solid Earth, v. 107, no. B4, 2078, doi:10.1029/ 2001JB000597.
44. Hofmann, C., Courtillot, V., Feraud, G., Rochette, P., Yirgu, G., Ketefo, E., and Pik, R., 1997, Timing of the Ethiopian flood basalt event and implications for plume birth and global change: Nature, v. 389, p. 838-841, doi:10.1038/39853. (Pubitemid 27462975)
45. Holmes, A., 1944, Principles of Physical Geology: Edinburgh, Thomas Nelson and Sons Ltd., 532 p.
46. Huerta, A.D., Nyblade, A., and Reusch, A., 2009, Mantle transition zone structure beneath Kenya and Tanzania: More evidence for a deep-seated thermal upwelling in the mantle: Geophysical Journal International, v. 177, no. 3, p. 1249-1255, doi:10.1111/j.1365-246X.2009.04092.x.
47. Julià, J., Ammon, C.J., Herrmann, R.B., and Correig, A.M., 2000, Joint inversion of receiver functions and surface wave dispersion observations: Geophysical Journal International, v. 143, p. 99-112, doi:10.1046/j.1365-246x. 2000.00217.x.
48. Julià, J., Ammon, C.J., and Herrmann, R.B., 2003, Lithospheric structure of the Arabian Shield from the joint inversion of receiver functions and surfacewave group velocities: Tectonophysics, v. 371, p. 1-21. (Pubitemid 37050104)
49. Julià, J., Ammon, C.J., and Nyblade, A.A., 2005, Evidence for mafic lower crust in Tanzania, East Africa, from joint inversion of receiver functions and Rayleigh wave dispersion velocities: Geophysical Journal International, v. 162, no. 2, p. 555-569, doi:10.1111/j.1365-246X.2005.02685.x. (Pubitemid 41632724)
50. Kampunzu, A.B., Bonhomme, M.G., and Kanika, M., 1998, Geochronology of volcanic rocks and evolution of the Cenozoic western branch of the East African Rift system: Journal of African Earth Sciences, v. 26, p. 441-461, doi:10.1016/S0899-5362(98)00025-6. (Pubitemid 28415796)
51. Keir, D., Bastow, I.D., Whaler, K.A., Daly, E., Cornwell, D.G., and Hautot, S., 2009, Lower crustal earthquakes near the Ethiopian rift induced by magmatic processes, Geochemistry Geophysics Geosystems, v. 10, Q0AB02, doi:10.1029/2009GC002382.
52. Kendall, J.-M., Stuart, G.W., Ebinger, C.J., Bastow, I.D., and Keir, D., 2005, Magma-assisted rifting in Ethiopia: Nature, v. 433, p. 146-148, doi:10.1038/nature03161.
53. Keranen, K., Klemperer, S., Julià, J., Lawrence, J., and Nyblade, A., 2009, Low lower-crustal velocity across Ethiopia: Is the Main Ethiopian Rift a narrow rift in a hot craton?: Geochemistry Geophysics Geosystems, v. 10, Q0AB01, doi:10.1029/2008GC002293.
54. King, L.C., 1962, The Morphology of the Earth: Edinburgh, Oliver and Boyd, 699 p.
55. King, S.D., 2007, Hotspots and edge-driven convection: Geology, v. 35, p. 223-226, doi:10.1130/G23291A.1. (Pubitemid 46437826)
56. King, S.D., and Anderson, D.L., 1995, An alternative mechanism of flood basalt formation: Earth and Planetary Science Letters, v. 136, p. 269-279, doi:10.1016/0012-821X(95)00205-Q. (Pubitemid 26460966)
57. King, S.D., and Anderson, D.L., 1998, Edge-driven convection: Earth and Planetary Science Letters, v. 160, p. 289-296, doi:10.1016/S0012-821X(98)00089- 2. (Pubitemid 29105700)
58. King, S.D., and Ritsema, J., 2000, African hot spot volcanism: Small-scale convection in the upper mantle beneath cratons: Science, v. 290, no. 5494, p. 1137-1140, doi:10.1126/science.290.5494.1137.
59. Langston, C.A., 1979, Structure under Mount Rainier, Washington, inferred from teleseismic body waves: Journal of Geophysical Research, v. 84, no. B9, p. 4749-4762, doi:10.1029/JB084iB09p04749.
60. Larson, E.W.F., and Ekstrom, G., 2001, Global models of surface wave group velocity: Pure and Applied Geophysics, v. 158, no. 8, p. 1377-1399, doi:10.1007/PL00001226. (Pubitemid 32812356)
61. Ligorria, J., and Ammon, C.J., 1999, Iterative deconvolution of teleseismic seismograms and receiver functions estimation: Bulletin of the Seismological Society of America, v. 89, p. 1395-1400. (Pubitemid 30135069)
62. Lithgow-Bertelloni, C.A., and Silver, P.G., 1998, Dynamic topography, plate driving forces and the African superswell: Nature, v. 395, p. 269-272, doi:10.1038/26212. (Pubitemid 28447549)
63. MacDonald, R., Rogers, N.W., Fitton, J.G., Black, S., and Smith, M., 2001, Plume-lithosphere interactions in the generation of the basalts of the Kenya Rift, East Africa: Journal of Petrology, v. 42, no. 5, p. 877-900, doi:10.1093/petrology/42.5.877. (Pubitemid 32425016)
64. Marty, B., Pik, R., and Gezahagen, Y., 1996, Helium isotopic variations in the Ethiopia plume lavas; nature of magmatic sources and limit on lower mantle contribution: Earth and Planetary Science Letters, v. 144, p. 223-237, doi:10.1016/0012-821X(96)00158-6.
65. Mechie, J., Keller, G.R., Prodehl, C., Khan, M.A., and Gaciri, S.J., 1997, Structure and dynamic processes in the lithosphere of the Afro-Arabian Rift system: A model for the structure, composition and evolution of the Kenya Rift: Tectonophysics, v. 278, p. 95-119.
66. Mohr, P., 1983, Ethiopian flood basalt province: Nature, v. 303, p. 577-584, doi:10.1038/303577a0.
67. Mohr, P., and Zanettin, B., 1988, The Ethiopian flood basalt province, in Mac-Dougall, J.D., ed., Continental Flood Basalts: Dordrecht, the Netherlands, Kluwer Academic Publishers, p. 63-110.
68. Montagner, J.P., Marty, B., Stutzmann, E., Sicilia, D., Cara, M., Pik, R., Leveque, J.-J., Roult, G., Beucler, E., and Debayle, E., 2007, Mantle upwellings and convective instabilities revealed by seismic tomography and helium isotope geochemistry beneath eastern Africa: Geophysical Research Letters, v. 34, L21303, doi:10.1029/2007GL031098. (Pubitemid 351149067)
69. Morley, C.K., Wescott, W.A., Stone, D.M., Harper, R.M., Wigger, S.T., and Karanja, F.M., 1992, Tectonic evolution of the northern Kenyan Rift: Journal of the Geological Society of London, v. 149, p. 333-348, doi:10.1144/gsjgs.149.3. 0333.
70. Mutter, J.C., Buck, W.R., and Zehnder, C.M., 1988, Convective partial melting: 1. A model for the formation of thick basaltic sequences during the initiation of spreading: Journal of Geophysical Research, v. 93, p. 1031-1048, doi:10.1029/JB093iB02p01031.
71. Noble, W.P., Foster, D.A., and Gleadow, A.J.W., 1997, The post-Pan-African thermal and extensional history of crystalline basement rocks in eastern Tanzania: Tectonophysics, v. 275, no. 4, p. 331-350, doi:10.1016/S0040-1951(97)00026-7.
72. Nyblade, A.A., 2002, Crust and upper mantle structure in East Africa: Implications for the origin of Cenozoic rifting and volcanism and the formation of magmatic rifted margins, in Menzies, M.A., Klemperer, S.L., Ebinger, C.J., and Baker, J., eds., Volcanic Rifted Margins: Geological Society of America Special Paper 362, p. 15-26.
73. Nyblade, A.A., and Langston, C.A., 2002, Broadband seismic experiments probe the East African Rift: Eos (Transactions, American Geophysical Union), v. 83, p. 405-408, doi:10.1029/2002EO000296.
74. Nyblade, A.A., and Robinson, S.W., 1994, The African superswell: Geophysical Research Letters, v. 21, p. 765-768, doi:10.1029/94GL00631.
75. Nyblade, A.A., Vogfjord, K.S., and Langston, C.A., 1996, P wave velocity structure of Proterozoic upper mantle beneath central and southern Africa: Journal of Geophysical Research, Solid Earth, v. 101, no. B6, p. 13, 973, doi:10.1029/96JB01483.
76. Owens, T.J., Nyblade, A.A., Gurrola, H., and Langston, C.A., 2000, Mantle transition zone structure beneath Tanzania, East Africa: Geophysical Research Letters, v. 27, p. 827-830, doi:10.1029/1999GL005429.
77. Park, Y., and Nyblade, A.A., 2006, P-wave tomography reveals a westward dipping low velocity zone beneath the Kenya Rift: Geophysical Research Letters, v. 33, L07311, doi:10.1029/2005GL025605. (Pubitemid 43772875)
78. Pasteels, P., Villeneauve, M., De Paepe, P., and Klerkx, J., 1989, Timing of the volcanism of the southern Kivu Province: Implications for the evolution of the western branch of the East African rift system: Earth and Planetary Science Letters, v. 94, p. 353-363, doi:10.1016/0012-821X(89)90152-0.
79. Pasyanos, M.E., 2005, A variable resolution surface wave dispersion study of Eurasia, North Africa, and surrounding regions: Journal of Geophysical Research, v. 110, B12301, doi:10.1029/2005JB003749. (Pubitemid 43159828)
80. Pasyanos, M., and Nyblade, A., 2007, A top to bottom lithospheric study of Africa and Arabia: Tectonophysics, v. 444, p. 27-44, doi:10.1016/j.tecto. 2007.07.008. (Pubitemid 47541908)
81. Pik, R., Deniel, C., Coulon, C., Yirgu, G., and Marty, B., 1999, Isotopic and trace element signatures of Ethiopian flood basalts: Evidence for plumelithosphere interactions: Geochimica et Cosmochimica Acta, v. 63, no. 15, p. 2263-2279, doi:10.1016/S0016-7037(99)00141-6. (Pubitemid 30014920)
82. Pik, R., Marty, B., Carignan, J., and Lave, J., 2003, Stability of the upper Nile drainage network (Ethiopia) deduced from (U-Th)/He thermochronometry; implications for uplift and erosion of the Afar plume dome: Earth and Planetary Science Letters, v. 215, p. 73-88, doi:10.1016/S0012-821X(03)00457-6. (Pubitemid 37257171)
83. Pik, R., Marty, B., and Hilton, D., 2006, How many mantle plumes in Africa? The geochemical point of view: Chemical Geology, v. 226, no. 3-4, p. 100-114, doi:10.1016/j.chemgeo.2005.09.016. (Pubitemid 43240038)
84. Priestley, K., McKenzie, D., Debayle, E., and Pilidou, S., 2008, The African upper mantle and its relationship to tectonics and surface geology: Geophysical Journal International, v. 175, p. 1108-1126, doi:10.1111/j.1365- 246X.2008.03951.x.
85. Ritsema, J., Nyblade, A.A., Owens, T.J., Langston, C.L., and VanDecar, J.C., 1998, Upper mantle seismic velocity structure beneath Tanzania, East Africa: Implications for the stability of cratonic lithosphere: Journal of Geophysical Research, v. 103, p. 21, 201-21, 213, doi:10.1029/98JB01274. (Pubitemid 29126313)
86. Ritsema, J., van Heijst, H.J., and Woodhouse, J.H., 1999, Complex shear wave velocity structure beneath Africa and Iceland: Science, v. 286, p. 1925-1928, doi:10.1126/science.286.5446.1925. (Pubitemid 129515894)
87. Ritter, J.R.R., and Kaspar, T., 1997, A tomography study of the Chyulu Hills, Kenya, in Fuchs, K., Altherr, R., Müller, B., and Prodehl, C., eds., Structure and dynamic processes in the lithosphere of the Afro-Arabian Rift System: Tectonophysics, v. 278, p. 149-169.
88. Rondenay, S., Bostock, M.G., and Fischer, K.M., 2005, Multichannel inversion of scattered teleseismic body waves: Practical considerations and applicability, in Levander, A., and Nolet, G., eds., Seismic Earth: Array Analysis of Broadband Seismograms: Washington, D.C., American Geophysical Union Geophysical Monograph 157, p. 187-204.
89. Schilling, J.-G., Kingsley, R., Hanan, B., and McCully, B., 1992, Nd-Sr-Pb isotopic variations along the Gulf of Aden: Evidence for the Afar mantle plume-lithosphere interaction: Journal of Geophysical Research, v. 97, p. 10, 927-10, 966, doi:10.1029/92JB00415.
90. Sebai, A., Stutzmann, E., Montanger, J.-P., Sicilia, D., and Beucler, E., 2006, Anisotropic structure of the African upper mantle from Rayleigh and Love wave tomography: Physics of the Earth and Planetary Interiors, v. 155, p. 48-62, doi:10.1016/j.pepi.2005.09.009. (Pubitemid 43380610)
91. Shackleton, R.M., 1986, Precambrian collision tectonics in Africa, in Coward, M.P., and Reis, A.C., eds., Collision Tectonics: Geological Society of London Special Publication 19, p. 329-349.
92. Sicilia, D., Montagner, J.-P., Cara, M., Stutzmann, E., Debayle, E., Lépine, J.-C., Lévêque, J.-J., Beucler, E., Sebai, A., Roult, G., Ayele, A., and Sholan, J.M., 2008, Upper mantle structure of shear-wave velocities and stratifi cation of anisotropy in the Afar hotspot region: Tectonophysics, v. 462, p. 164-177, doi:10.1016/j.tecto.2008.02.016.
93. Simmons, N.A., and Gurrola, H., 2000, Multiple seismic discontinuities near the base of the transition zone in the Earth's mantle: Nature, v. 405, p. 559-562, doi:10.1038/35014589. (Pubitemid 30367725)
94. Simmons, N.A., Forte, A.M., and Grand, S.P., 2007, Thermochemical structure and dynamics of the African superplume: Geophysical Research Letters, v. 34, L02301, doi:10.1029/2006GL028009. (Pubitemid 47277650)
95. Slack, P.D., Davis, P.M., Dahlheim, H.A., Glahn, A., Ritter, J.R.R., Green, W.V., Maguire, P.K.H., and Meyer, R.P., 1994, Attenuation and velocity of P-waves in the mantle beneath the East African Rift, Kenya: Tectonophysics, v. 236, no. 1-4, p. 331-358.
96. Spiegel, C., Kohn, B., Belton, D., and Gleadow, A., 2007, Morphotectonic evolution of the central Kenya rift fl anks: Implications for late Cenozoic environmental change in East Africa: Geology, v. 35, p. 427-430, doi:10.1130/G23108A.1. (Pubitemid 46746404)
97. Trampert, J., Deschamps, F., Resovsky, J., and Yuen, D., 2004, Probabilistic tomography maps chemical heterogeneities throughout the lower mantle: Science, v. 306, p. 853-856, doi:10.1126/science.1101996. (Pubitemid 39446990)
98. Vacher, P., Mocquet, A., and Sotin, C., 1998, Computation of seismic profi les from mineral physics: The importance of the non-olivine components for explaining the 660 km depth discontinuity: Physics of the Earth and Planetary Interiors, v. 106, no. 3-4, p. 275-298, doi:10.1016/S0031-9201(98)00076-4. (Pubitemid 28441273)
99. VanDecar, J.C., 1991, Upper-Mantle Structure of the Cascadia Subduction Zone from Nonlinear Teleseismic Travel-Time Inversion [Ph.D. thesis]: Seattle, University of Washington, 168 p.
100. VanDecar, J.C., and Crosson, R.S., 1990, Determination of teleseismic relative phase arrival times using multi-channel cross-correlation and least squares: Bulletin of the Seismological Society of America, v. 80, p. 150-169.
101. Van der Beek, P., Mbede, E., Andriessen, P., and Delvaux, D., 1998, Denudation history of the Malawi and Rukwa Rift flanks (East Africa Rift system) from apatitefission track thermochronology: Journal of African Earth Sciences, v. 26, p. 363-385, doi:10.1016/S0899-5362(98)00021-9. (Pubitemid 28415792)
102. Van der Lee, S., Paulssen, H., and Nolet, G., 1994, Variability of P660s phases as a consequence of topography of the 660 km discontinuity: Physics of the Earth and Planetary Interiors, v. 86, p. 147-164, doi:10.1016/0031-9201(94) 05066-X.
103. Walker, K.T., Nyblade, A.A., Klemperer, S.L., Bokelmann, G.H.R., and Owens, T.J., 2004, On the relationship between extension and anisotropy: Constraints from shear wave splitting across the East African Plateau: Journal of Geophysical Research, v. 109, B08302, doi:10.1029/2003JB002866. (Pubitemid 39428436)
104. Weeraratne, D.S., Forsyth, D.W., Fischer, K.M., and Nyblade, A.A., 2003, Evidence for an upper mantle plume beneath the Tanzanian craton from Rayleigh wave tomography: Journal of Geophysical Research, Solid Earth, v. 108, no. B9, 2427, doi:10.1029/2002JB002273.
105. WoldeGabriel, G., Walter, R.C., Hart, W.K., Mertzman, S.A., and Aronson, J.L., 1999, Temporal relations and geochemical features of felsic volcanism in the central sector of the Main Ethiopian Rift: Acta Vulcanologica, v. 11, no. 1, p. 53-67.
106. Wolfenden, E., Ebinger, C., Yirgu, G., Deino, A., and Ayalew, D., 2004, Evolution of the northern Main Ethiopian Rift: Birth of a triple junction: Earth and Planetary Science Letters, v. 224, p. 213-228, doi:10.1016/j.epsl.2004.04. 022. (Pubitemid 38964595)