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Cenozoic magmatism on the northern Somali plate: a re-evaluation

Cenozoic magmatism on the northern Somali plate: a re-evaluation. Daniel MEGE Planetology and Geodynamics Lab, Nantes, France Peter PURCELL P & R Geological Consultants, Scarborough, Australia Fred JOURDAN

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Cenozoic magmatism on the northern Somali plate: a re-evaluation

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  1. Cenozoic magmatism on the northern Somali plate: a re-evaluation Daniel MEGE Planetology and Geodynamics Lab, Nantes, France Peter PURCELL P & R Geological Consultants, Scarborough, Australia Fred JOURDAN Western Australia Argon Isotope Facility, Curtin University of Technology, Perth, Australia

  2. What is the extent and form of Cenozoic volcanism on the Somali plate? YEMEN VOLCANIC PROVINCE ETHIOPIAN VOLCANIC PROVINCE ? 30-31 Ma

  3. Cenozoic volcanic rock exposures 100 km Gulf of Aden AFAR Indian ocean Geologic map of Somalia, 1994 Geologic map of Ethiopia, 1996 Kenya

  4. Cenozoic volcanic rock exposures 100 km Gulf of Aden AFAR Indian ocean Geologic map of Somalia, 1994 Geologic map of Ethiopia, 1996 Kenya

  5. Data and data sources • Field data (and radiochronology) • Oil and water wells • Aeromagnetic measurements • Satellite/aerial imagery

  6. Fafen Shebele Juba Meandering basaltic flows 20 km

  7. Fafen Shebele Juba Meandering basaltic flows 5 km

  8. B A OLIGOCENE OR MIOCENE Quaternary Jurassic Oligo-Miocene A Cretaceous B Magnetic meanders of the Bur Acaba High (Esso, 1984)

  9. Magnetic meanders of eastern Ogaden (Pexco, 2008) Eocene buried volcanic meanders Paleocene Oligocene volcanics 0 m 79 m EOCENE BASALT 122 m EOCENE FLOW PALEOC. 522 m UP. CRET. GABBRO 671 m

  10. A B magnetic anomaly (Esso, 1984) A B Water wells in central Somalia which have penetrated basalts Faillace, 1993 EOCENE FLOW? Buried basaltic flows

  11. A Oil wells that penetrated basalts in the Ogaden and central Somalia B B A OLIGOCENE FLOW GABBRO 0 m 79 m EOCENE BASALT 122 m EOCENE FLOW PALEOC. 522 m Buried basaltic flows UP. CRET. 671 m

  12. Ogaden Dyke Swarm (Whitestone, 1976, Pexco, 2008) 24.40±0.7 Ma 24.85±0.5 Ma 25.4±0.7 Ma 26.56±0.4 Ma 30±1.9 Ma 20 km DYKE

  13. Ogaden Dyke Swarm 400 km

  14. Jijiga volcanicplugs (MIOCENE K/Ar) Summary buriedmeanders and tabularflows EOCENE basaltic conglomerate ≥ OLIGOCENE dyke swarm OLIGOCENE Dolo volcanicfield OLIGOCENE meanders Upper OLIGOCENE buriedtabularflows OLIGOCENE buried or partlyexposed meanders OLIGOCENE volcanicplugs OLIGOCENE (Elf, 1978)

  15. Synthesis and perspectives • … Tooearly for a synthesis! • WidespreadOligocenevolcanism, evidence of Eoceneflows • Long meanderingbasalticflowsfrom Afar (or beyond) in • former fluviatile systems • Evidence of overflowfrom fluviatile systems : most of the • Ogaden and Somaliamight have been beenflooded by basalts • A major dyke swarm (400+ km) has been identifed, itisaligned • with, and is of agesimilar to the age of the RedSea dyke swarm • Correlationswith the volcanism and tectonics of otherregions • of the Ethio-yemenite LIP remain to beexplored!

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