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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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slide1

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

slide2

What is the extent and form of Cenozoic volcanism

on the Somali plate?

YEMEN VOLCANIC

PROVINCE

ETHIOPIAN

VOLCANIC

PROVINCE

?

30-31 Ma

slide3

Cenozoic volcanic rock exposures

100 km

Gulf of Aden

AFAR

Indian ocean

Geologic map

of Somalia, 1994

Geologic map

of Ethiopia, 1996

Kenya

slide4

Cenozoic volcanic rock exposures

100 km

Gulf of Aden

AFAR

Indian ocean

Geologic map

of Somalia, 1994

Geologic map

of Ethiopia, 1996

Kenya

slide5

Data and data sources

  • Field data (and radiochronology)
  • Oil and water wells
  • Aeromagnetic measurements
  • Satellite/aerial imagery
slide6

Fafen

Shebele

Juba

Meandering basaltic flows

20 km

slide7

Fafen

Shebele

Juba

Meandering basaltic flows

5 km

slide8

B

A

OLIGOCENE

OR MIOCENE

Quaternary

Jurassic

Oligo-Miocene

A

Cretaceous

B

Magnetic meanders of the Bur Acaba High

(Esso, 1984)

slide9

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

slide10

A

B

magnetic anomaly

(Esso, 1984)

A

B

Water wells in central Somalia

which have penetrated basalts

Faillace, 1993

EOCENE FLOW?

Buried

basaltic flows

slide11

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

slide12

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

slide14

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)

slide15

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!