Cenozoic magmatism on the northern Somali plate:

a re-evaluation

Daniel MEGEPlanetology and Geodynamics Lab, Nantes, France

Peter PURCELLP & R Geological Consultants, Scarborough, Australia

Fred JOURDANWestern Australia Argon Isotope Facility, Curtin University of Technology, Perth, Australia

What is the extent and form of Cenozoic volcanismon the Somali plate?

ETHIOPIANVOLCANICPROVINCE

YEMEN VOLCANICPROVINCE

?30-31 Ma

Geologic mapof Somalia, 1994

Geologic mapof Ethiopia, 1996

Cenozoic volcanic rock exposures

AFAR

Gulf of Aden

Indian ocean

100 km

Kenya

Gulf of Aden

Indian ocean

100 km

AFAR

Kenya

Cenozoic volcanic rock exposures

Geologic mapof Somalia, 1994

Geologic mapof Ethiopia, 1996

Field data (and radiochronology)

Oil and water wells

Aeromagnetic measurements

Satellite/aerial imagery

Data and data sources

Fafen

Shebele

Juba

Meandering basaltic flows

20 km

Fafen

Shebele

Juba

Meandering basaltic flows

5 km

Magnetic meanders of the Bur Acaba High

Quaternary

Oligo-MioceneCretaceous

Jurassic

B

A

BA

OLIGOCENEOR MIOCENE

(Esso, 1984)

(Pexco, 2008)

PaleoceneEocene

Oligocenevolcanics

Magnetic meanders of eastern Ogaden

buried volcanic meanders

GABBRO

BASALT

0 m

79 m

522 m

EOC

ENE

PALE

OC

.U

P. C

RET

.

EOCENEFLOW

122 m

671 m

Buriedbasaltic flows

Water wells in central Somaliawhich have penetrated basalts

Faillace, 1993

B

A

A BEOCENE FLOW?

magnetic anomaly(Esso, 1984)

Buriedbasaltic flows

Oil wells thatpenetratedbasalts in theOgaden andcentral Somalia

A

A

GABBRO

BASALT

0 m

79 m

522 m

EOC

ENE

PALE

OC

.U

P. C

RET

.

EOCENEFLOW

122 m

671 m

OLIGOCENEFLOW

B

B

Ogaden Dyke Swarm(Whitestone, 1976, Pexco, 2008)

DYKE

20 km

24.40±0.7 Ma24.85±0.5 Ma

25.4±0.7 Ma26.56±0.4 Ma

30±1.9 Ma

Ogaden Dyke Swarm400 km

Summary

buried tabular flowsOLIGOCENE

buried meanders andtabular flows EOCENE

dyke swarmOLIGOCENE

Jijiga volcanic plugs(MIOCENE K/Ar)

basalticconglomerate≥ OLIGOCENE

volcanic plugsOLIGOCENE

(Elf, 1978)

Dolo volcanic fieldOLIGOCENE

Synthesis and perspectives

█ … Too early for a synthesis!

█ Widespread Oligocene volcanism, evidence of Eocene flows

█ Long meandering basaltic flows from Afar (or beyond) in former fluviatile systems

█ Evidence of overflow from fluviatile systems : most of the Ogaden and Somalia might have been been flooded by basalts

█ A major dyke swarm (400+ km) has been identifed, it is aligned with, and is of age similar to the age of the Red Sea dyke swarm

█ Correlations with the volcanism and tectonics of other regions of the Ethio-yemenite LIP remain to be explored!