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The development of late-stage continental breakup: seismic reflection and borehole evidence from the Danakil Depression, Ethiopia

The development of late-stage continental breakup: seismic reflection and borehole evidence from the Danakil Depression, Ethiopia
The development of late-stage continental breakup: seismic reflection and borehole evidence from the Danakil Depression, Ethiopia
During continental breakup, the locus of strain shifts from a broad region of border faulting and ductile plate stretching to a narrow zone of magma intrusion in a young ocean basin. Recent studies of volcanic rifts and margins worldwide suggest this shift occurs sub‐aerially, before the onset of seafloor spreading. We test this hypothesis using recently‐acquired seismic reflection and borehole data from the Danakil Depression, Ethiopia, a unique region of transition between continental rifting and seafloor spreading. Our data, located near Dallol, ~30km northwest of the Erta'Ale Volcanic Segment (EAVS), reveal a remarkably‐thick (>1km) sequence of young (~100ka) evaporites in a basin bound by a major (≤400m throw), east‐dipping normal fault. To generate such a large amount of subsidence in such a relatively short time, we propose that upper‐crustal extension in Danakil is currently dominated by faulting, not magmatic intrusion. Given the region's markedly thinned crust (~15‐km‐thick), relative to elsewhere in Afar where magma‐assisted rifting dominates and maintains crustal thickness at ~25km, mechanical extension in Danakil is likely coupled with ductile extension of the lower‐crust and mantle lithosphere. Despite proximity to the voluminous lavas of the active EAVS, evidence for igneous material in the upper ~2km of the 6–10‐km‐wide basin is limited. Late‐stage stretching was likely aided by thermal/strain‐induced lithospheric weakening following protracted magma‐assisted rifting. Basin formation immediately prior to the onset of seafloor spreading may also explain the accumulation of thick marine‐seepage‐fed evaporite sequences akin to those observed, for example, along the South Atlantic rifted margins.
0278-7407
Bastow, Ian D.
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Booth, Adam D.
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Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Keir, Derek
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Magee, Craig
2938e26f-c14f-4701-b349-329098afceef
Jackson, Christopher A-L.
afc8bdab-bd66-41ce-a30c-da7427bdc5ae
Warren, John
11e02c7c-2d55-47fa-b61d-3896bf521e49
Wilkinson, Jason
de888221-a9a6-440f-ae03-e11bd1c8b32e
Lascialfari, Matteo
9a3f56fe-1e32-4c4d-87ab-811d7bd45dce
Bastow, Ian D.
6582ec72-87f5-471a-969d-5ace59397321
Booth, Adam D.
5788b24a-862c-4497-9bd8-bffcceba92c3
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Magee, Craig
2938e26f-c14f-4701-b349-329098afceef
Jackson, Christopher A-L.
afc8bdab-bd66-41ce-a30c-da7427bdc5ae
Warren, John
11e02c7c-2d55-47fa-b61d-3896bf521e49
Wilkinson, Jason
de888221-a9a6-440f-ae03-e11bd1c8b32e
Lascialfari, Matteo
9a3f56fe-1e32-4c4d-87ab-811d7bd45dce

Bastow, Ian D., Booth, Adam D., Corti, Giacomo, Keir, Derek, Magee, Craig, Jackson, Christopher A-L., Warren, John, Wilkinson, Jason and Lascialfari, Matteo (2018) The development of late-stage continental breakup: seismic reflection and borehole evidence from the Danakil Depression, Ethiopia. Tectonics. (doi:10.1029/2017TC004798).

Record type: Article

Abstract

During continental breakup, the locus of strain shifts from a broad region of border faulting and ductile plate stretching to a narrow zone of magma intrusion in a young ocean basin. Recent studies of volcanic rifts and margins worldwide suggest this shift occurs sub‐aerially, before the onset of seafloor spreading. We test this hypothesis using recently‐acquired seismic reflection and borehole data from the Danakil Depression, Ethiopia, a unique region of transition between continental rifting and seafloor spreading. Our data, located near Dallol, ~30km northwest of the Erta'Ale Volcanic Segment (EAVS), reveal a remarkably‐thick (>1km) sequence of young (~100ka) evaporites in a basin bound by a major (≤400m throw), east‐dipping normal fault. To generate such a large amount of subsidence in such a relatively short time, we propose that upper‐crustal extension in Danakil is currently dominated by faulting, not magmatic intrusion. Given the region's markedly thinned crust (~15‐km‐thick), relative to elsewhere in Afar where magma‐assisted rifting dominates and maintains crustal thickness at ~25km, mechanical extension in Danakil is likely coupled with ductile extension of the lower‐crust and mantle lithosphere. Despite proximity to the voluminous lavas of the active EAVS, evidence for igneous material in the upper ~2km of the 6–10‐km‐wide basin is limited. Late‐stage stretching was likely aided by thermal/strain‐induced lithospheric weakening following protracted magma‐assisted rifting. Basin formation immediately prior to the onset of seafloor spreading may also explain the accumulation of thick marine‐seepage‐fed evaporite sequences akin to those observed, for example, along the South Atlantic rifted margins.

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Accepted/In Press date: 19 July 2018
e-pub ahead of print date: 1 August 2018

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Local EPrints ID: 422872
URI: https://eprints.soton.ac.uk/id/eprint/422872
ISSN: 0278-7407
PURE UUID: 8dd1b51b-391d-414b-a09b-41154ded22b3
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 07 Aug 2018 16:30
Last modified: 14 Mar 2019 01:37

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Contributors

Author: Ian D. Bastow
Author: Adam D. Booth
Author: Giacomo Corti
Author: Derek Keir ORCID iD
Author: Craig Magee
Author: Christopher A-L. Jackson
Author: John Warren
Author: Jason Wilkinson
Author: Matteo Lascialfari

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