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Geological evolution of the Boset-Bericha Volcanic Complex, Main Ethiopian Rift: 40Ar/39Ar evidence for episodic Pleistocene to Holocene volcanism

Geological evolution of the Boset-Bericha Volcanic Complex, Main Ethiopian Rift: 40Ar/39Ar evidence for episodic Pleistocene to Holocene volcanism
Geological evolution of the Boset-Bericha Volcanic Complex, Main Ethiopian Rift: 40Ar/39Ar evidence for episodic Pleistocene to Holocene volcanism
The Boset-Bericha Volcanic Complex (BBVC) is one of the largest stratovolcanoes of the northern Main Ethiopian Rift (MER). However, very little is known about its eruptive history, despite the fact that approximately 4 million people live within 100 km of the complex. Here, we combine field observations, morphometric analysis using high-resolution LiDAR data, geochemistry and 40Ar/39Ar geochronology to report the first detailed account of the geological evolution of the BBVC, with a focus on extensive young lava flows covering the two edifices, Gudda and Bericha. These lavas exhibit a bimodal composition ranging dominantly from basaltic rift floor lavas and scoria cones, to pantelleritic trachytes and rhyolite flows at Gudda, and comenditic rhyolites at Bericha. Further, several intermediate compositions are associated with fissure vents along the Boset-Kone segment that also appear to link the silicic centres. We divide the BBVC broadly into four main eruptive stages, comprising: (1) early rift floor emplacement, (2) formation of Gudda Volcano within two main cycles, separated by caldera formation, (3) formation of the Bericha Volcano, and (4) sporadic fissure eruptions. Our new 40Ar/39Ar geochronology, targeting a representative array of these flows, provides evidence for episodic activity at the BBVC from ~ 120 ka to the present-day. We find that low-volume mafic episodes are more frequent (~ 10 ka cyclicity) than felsic episodes (~ 100 ka cyclicity), but the latter are more voluminous. Over the last ~ 30 ka, mafic to intermediate fissure activity might have reinvigorated felsic activity (over the last ~ 16 ka), manifested as peralkaline lava flows and pyroclastic deposits at Gudda and Bericha. Felsic episodes have on average a higher eruption rate (2–5/1000 years) and productivity at Gudda compared to Bericha (1–2/1000 years). The young age of lavas and current fumarolic activity along the fault system, suggest that the BBVC is still potentially active. Coincident episodic activity within the BBVC and at several rift segments in the MER is observed, and facilitates continental rifting.
Episodic volcanism, Continental rifting, 40Ar/39Ar geochronology, Main Ethiopian Rift, Peralkaline
0377-0273
115-133
Siegburg, Melanie
b4801eca-cd00-401b-8cb0-a21da9754c42
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
Bull, Jonathan M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Barfod, Dan N.
443dd9b7-8319-47ef-8e18-f6f7e43a0a6b
Taylor, Rex N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Abebe, Bekele
e22be781-cbe3-4882-8bc9-724426b0168b
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Siegburg, Melanie
b4801eca-cd00-401b-8cb0-a21da9754c42
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
Bull, Jonathan M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Barfod, Dan N.
443dd9b7-8319-47ef-8e18-f6f7e43a0a6b
Taylor, Rex N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Abebe, Bekele
e22be781-cbe3-4882-8bc9-724426b0168b
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6

Siegburg, Melanie, Gernon, Thomas M., Bull, Jonathan M., Keir, Derek, Barfod, Dan N., Taylor, Rex N., Abebe, Bekele and Ayele, Atalay (2018) Geological evolution of the Boset-Bericha Volcanic Complex, Main Ethiopian Rift: 40Ar/39Ar evidence for episodic Pleistocene to Holocene volcanism. Journal of Volcanology and Geothermal Research, 351, 115-133. (doi:10.1016/j.jvolgeores.2017.12.014).

Record type: Article

Abstract

The Boset-Bericha Volcanic Complex (BBVC) is one of the largest stratovolcanoes of the northern Main Ethiopian Rift (MER). However, very little is known about its eruptive history, despite the fact that approximately 4 million people live within 100 km of the complex. Here, we combine field observations, morphometric analysis using high-resolution LiDAR data, geochemistry and 40Ar/39Ar geochronology to report the first detailed account of the geological evolution of the BBVC, with a focus on extensive young lava flows covering the two edifices, Gudda and Bericha. These lavas exhibit a bimodal composition ranging dominantly from basaltic rift floor lavas and scoria cones, to pantelleritic trachytes and rhyolite flows at Gudda, and comenditic rhyolites at Bericha. Further, several intermediate compositions are associated with fissure vents along the Boset-Kone segment that also appear to link the silicic centres. We divide the BBVC broadly into four main eruptive stages, comprising: (1) early rift floor emplacement, (2) formation of Gudda Volcano within two main cycles, separated by caldera formation, (3) formation of the Bericha Volcano, and (4) sporadic fissure eruptions. Our new 40Ar/39Ar geochronology, targeting a representative array of these flows, provides evidence for episodic activity at the BBVC from ~ 120 ka to the present-day. We find that low-volume mafic episodes are more frequent (~ 10 ka cyclicity) than felsic episodes (~ 100 ka cyclicity), but the latter are more voluminous. Over the last ~ 30 ka, mafic to intermediate fissure activity might have reinvigorated felsic activity (over the last ~ 16 ka), manifested as peralkaline lava flows and pyroclastic deposits at Gudda and Bericha. Felsic episodes have on average a higher eruption rate (2–5/1000 years) and productivity at Gudda compared to Bericha (1–2/1000 years). The young age of lavas and current fumarolic activity along the fault system, suggest that the BBVC is still potentially active. Coincident episodic activity within the BBVC and at several rift segments in the MER is observed, and facilitates continental rifting.

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Siegburgetal2017 - Accepted Manuscript
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Accepted/In Press date: 19 December 2017
Published date: 1 February 2018
Keywords: Episodic volcanism, Continental rifting, 40Ar/39Ar geochronology, Main Ethiopian Rift, Peralkaline

Identifiers

Local EPrints ID: 417228
URI: http://eprints.soton.ac.uk/id/eprint/417228
ISSN: 0377-0273
PURE UUID: e030f5cf-4a5d-4b0d-b9d9-212789fd268d
ORCID for Thomas M. Gernon: ORCID iD orcid.org/0000-0002-7717-2092
ORCID for Jonathan M. Bull: ORCID iD orcid.org/0000-0003-3373-5807
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446
ORCID for Rex N. Taylor: ORCID iD orcid.org/0000-0002-9367-0294

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Date deposited: 26 Jan 2018 17:30
Last modified: 27 Apr 2022 04:57

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Contributors

Author: Melanie Siegburg
Author: Derek Keir ORCID iD
Author: Dan N. Barfod
Author: Rex N. Taylor ORCID iD
Author: Bekele Abebe
Author: Atalay Ayele

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