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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
Western Australia Argon Isotope Facility, Curtin University of Technology, Perth, Australia
What is the extent and form of Cenozoic volcanism
on the Somali plate?
YEMEN VOLCANIC
PROVINCE
ETHIOPIAN
VOLCANIC
PROVINCE
30-31 Ma
?
Cenozoic volcanic rock exposures
100 km
Gulf of Aden
AFAR
Indian ocean
Geologic map
of Somalia, 1994
Kenya
Geologic map
of Ethiopia, 1996
Cenozoic volcanic rock exposures
100 km
Gulf of Aden
AFAR
Indian ocean
Geologic map
of Somalia, 1994
Kenya
Geologic map
of Ethiopia, 1996
Data and data sources
 Field data (and radiochronology)
 Oil and water wells
 Aeromagnetic measurements
 Satellite/aerial imagery
Meandering basaltic flows
20 km
Meandering basaltic flows
5 km
Magnetic meanders ofAthe Bur Acaba High
OLIGOCENE
OR MIOCENE
Quaternary
Oligo-Miocene
Jurassic
Cretaceous
B
A
(Esso, 1984)
B
Magnetic meanders of eastern Ogaden
(Pexco, 2008)
buried volcanic meanders
Eocene
UP. CRET. PALEOC.
EOCENE
0m
Paleocene
79 m
BASALT
122 m
EOCENE
FLOW
522 m
GABBRO
671 m
Oligocene
volcanics
A
B
EOCENE FLOW?
magnetic anomaly
(Esso, 1984)
A
B
Water wells in central Somalia
which have penetrated basalts
Faillace, 1993
Buried
basaltic flows
A
Oil wells that
penetrated
basalts in the
Ogaden and
central Somalia
B
UP. CRET.
PALEOC.
EOCENE
0m
A
79 m
BASALT
122 m
EOCENE
FLOW
522 m
GABBRO
671 m
Buried
basaltic flows
OLIGOCENE
FLOW
B
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
Ogaden Dyke Swarm
400 km
Jijiga volcanic plugs
(MIOCENE K/Ar)
basaltic
conglomerate
≥ OLIGOCENE
Dolo volcanic field
OLIGOCENE
dyke swarm
OLIGOCENE
buried meanders and
tabular flows EOCENE
meanders
Upper OLIGOCENE
buried tabular flows
OLIGOCENE
buried or partly exposed
meanders OLIGOCENE
volcanic plugs
OLIGOCENE
(Elf, 1978)
Summary
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!