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Quaternary Volcanism And Faulting At O’A Caldera, Central Ethiopian Rift

P. Mohr, J. Mitchell, R. G. Raynolds
Published 1980 · Geology

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O’a is the largest of the Quaternary caldera volcanoes that punctuate the axis of the Ethiopian rift valley. The known volcanic history of O’a is brief: eruptions of restricted ash-flow tuffs and «tufolavas» were followed by extensive pumice deposition with intervening paleosols, lacustrine sediments, and flows of occasional welded tuffs and rare basalts. Ensuing caldera collapse at c. 0.24 m.y. ago was accompanied by emplacement of two massive ignimbrite flow units comprising a single cooling unit: the first was much more severely welded than the second which shows lahar characteristics. Post-caldera volcanism at O’a has been sparse compared with most other Ethiopian rift centres.O’a volcano exemplifies the common rift association of a caldera set tightly between two offset segments of the Wonji fault belt. The Wonji fault belt marks the youngest tectonism of the rift floor, and in the vicinity of O’a has been active in a major way since caldera subsidence. This faulting is clearly younger than the massive rift margin faulting, which to the northeast of O’a occurred during a tectonic climax dated at c. 1.0 m.y. ago.Radiometric analysis suggests a rather regular level of initial40Ar in O’a basalt lavas sampled near to their original vents. If this level also applies to near-vent basalts dated from other parts of the Ethiopian rift, a regional rift paroxysm of crustal extension and related silicic and basaltic volcanism is evident at c. 0.30–0.20 m.y. ago. Episodic dilatation and associated volcano-tectonism separated by long periods of quiescence appears to be a general feature of continental rift valleys.



This paper is referenced by
Tectonic stress regime of the Cascades region and tectonic classification of large calderas
C. Ferrall (1986)
10.1016/J.QUASCIREV.2008.09.010
Middle Stone Age (MSA) site distributions in eastern Africa and their relationship to Quaternary environmental change, refugia and the evolution of Homo sapiens
L. Basell (2008)
10.1007/978-94-017-8026-1_17
The Geomorphology of the Lake Region (Main Ethiopian Rift): The Record of Paleohydrological and Paleoclimatic Events in an Active Volcano-Tectonic Setting
Marco Benvenuti (2015)
10.1007/0-306-48201-0_1
A 300 Million Years History of Rift Lakes in Central and East Africa: An Updated Broad Review
J.-J. Tiercelin (2002)
10.1002/2016GC006395
Causes of unrest at silicic calderas in the East African Rift: New constraints from InSAR and soil‐gas chemistry at Aluto volcano, Ethiopia
William Hutchison (2016)
Gravity Survey of the Shalla Caldera and its Environs for the Exploration of Geothermal Energy
Harbie Hussen (2001)
10.1130/GES01119.1
Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex
William Hutchison (2015)
10.1029/96TC03935
Successive orthogonal and oblique extension episodes in a rift zone: Laboratory experiments with application to the Ethiopian Rift
Marco Bonini (1997)
Late Quaternary lacustrine ostracoda of the Ziwal | ' rmental indicatorsas Paleoenvlrot
B. Atnafu (2011)
10.1029/2018GC007686
Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift
Keri McNamara (2018)
10.1016/J.JVOLGEORES.2016.09.010
The eruptive history and magmatic evolution of Aluto volcano : new insights into silicic peralkaline volcanism in the Ethiopian rift
William J. Hutchison (2016)
10.1002/9781118782095.CH39
39. The Roots of Ash Flow Calderas in Western North America: Windows into the Tops of Granitic Batholiths
Collected Reprint Series (2014)
GIS Based Potential Volcanic Hazard Zonation in Ethiopia the Case of Aluto Volcano
Mesfin Mengistu Mekuria (2018)
10.1016/J.JAFREARSCI.2006.10.006
Temporal geochemical variation in Ethiopian Lakes Shala, Arenguade, Awasa, and Beseka: Possible environmental impacts from underwater and borehole detonations
S. Klemperer (2007)
10.1016/S0031-0182(98)00220-X
The Ziway–Shala lake basin system, Main Ethiopian Rift: Influence of volcanism, tectonics, and climatic forcing on basin formation and sedimentation
C. L. Turdu (1999)
10.1130/GES01615.1
Magmatically assisted off-rift extension—The case for broadly distributed strain accommodation
Brandon Chiasera (2018)
10.1017/CBO9780511978012
Eruptions that Shook the World: Contents
C. Oppenheimer (2011)
10.1016/J.QUAINT.2013.03.010
Chronological and behavioral contexts of the earliest Middle Stone Age in the Gademotta Formation, Main Ethiopian Rift
Y. Sahle (2014)
10.1016/J.EARSCIREV.2009.06.005
Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa
G. Corti (2009)
10.1016/S0040-1951(98)80063-2
Quaternary oblique extensional tectonics in the Ethiopian Rift (Horn of Africa)
M. Boccaletti (1998)
10.1016/S0377-0273(02)00342-6
Elliptic calderas in the Ethiopian Rift: control of pre-existing structures
V. Acocella (2003)
10.1130/0-8137-2345-0.83
Volcanism, tectonism, sedimentation, and the paleoanthropological record in the Ethiopian Rift System
G. Woldegabriel (2000)
10.1016/J.JVOLGEORES.2019.06.008
Local seismicity near the actively deforming Corbetti volcano in the Main Ethiopian Rift
Aude Lavayssière (2019)
10.1016/J.JVOLGEORES.2017.04.003
Seismicity associated with magmatism, faulting and hydrothermal circulation at Aluto Volcano, Main Ethiopian Rift
M. Wilks (2017)
10.1016/j.jhevol.2015.11.006
The pattern of emergence of a Middle Stone Age tradition at Gademotta and Kulkuletti (Ethiopia) through convergent tool and point technologies.
Katja Douze (2016)
10.1016/J.JVOLGEORES.2018.02.001
Contrasting styles of post-caldera volcanism along the Main Ethiopian Rift: Implications for contemporary volcanic hazards
K. Fontijn (2018)
10.1002/2017GC006975
Spatially Variable CO2 Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift-Related Emissions
J. Hunt (2017)
10.1038/ncomms13192
A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans
William J. Hutchison (2016)
10.1016/j.lithos.2019.105291
The Cenozoic magmatism of East Africa: Part II – Rifting of the mobile belt
T. Rooney (2020)
10.1016/J.JAFREARSCI.2003.10.007
Tensional fissures and crustal extension rates in the northern part of the Main Ethiopian Rift
F. M. Williams (2004)
10.1144/sjg22020225
K–Ar systematics in Tertiary dolerites from West Connacht, Ireland
J. Mitchell (1986)
10.5860/choice.49-3275
Eruptions That Shook The World
C. Oppenheimer (2004)
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