Three North African dust source areas and their geochemical fingerprint
Three North African dust source areas and their geochemical fingerprint
North Africa produces more than half of the world's atmospheric dust load. Once entrained into the atmosphere, this dust poses a human health hazard locally. It also modifies the radiative budget regionally, and supplies nutrients that fuel primary productivity across the North Atlantic Ocean and as far afield as the Amazonian Basin. Dust accumulation in deep sea and lacustrine sediments also provides a means to study changes in palaeoclimate, particularly those associated with rainfall climate change. Systematic analysis of satellite imagery has greatly improved our understanding of the trajectories of long-range North African dust plumes, but our knowledge of the dust-producing source regions and our ability to fingerprint their contribution to these export routes is surprisingly limited. Here we report new radiogenic isotope (Sr and Nd) data for sediment samples from known dust-producing substrates (dried river and lake beds), integrate them with published isotope data and weight them for dust source activation. We define three isotopically distinct preferential dust source areas (PSAs): a Western, a Central and an Eastern North African PSA. More data are needed, particularly from the Western PSA, but our results show a change in PSA dust source composition to more radiogenic Nd- and less radiogenic Sr-isotope values from west to east, in line with the overall decreasing age of the underlying bedrock. Our data reveal extreme isotopic heterogeneity within the Chadian region of the Central PSA, including an extremely distinctive geochemical fingerprint feeding the Bodélé Depression, the most active dust source on Earth. Our new analysis significantly improves the reliability by which windblown dust deposits can be geochemically fingerprinted to their distant source regions.
87Sr/86Sr, Bodélé Depression, North Africa, dust source, radiogenic isotopes, εNd
Jewell, Amy Margaret
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Drake, Nick
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Crocker, Anya
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Bakker, Natalie
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Kunkelova, Terezia
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Bristow, Charlie
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Cooper, Matthew
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Milton, James
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Breeze, Paul
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Wilson, Paul A.
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15 January 2021
Jewell, Amy Margaret
3de1a5a3-b62c-4069-a06e-b2fedb6456e7
Drake, Nick
825cef91-08e8-4533-afd1-992c1738e828
Crocker, Anya
1215fbdd-ad43-408a-bd79-c54c6847e68c
Bakker, Natalie
401a7720-fe86-444f-9b69-144e36e5b5f6
Kunkelova, Terezia
32818c35-f763-4ba3-8640-b9334ad4ae6e
Bristow, Charlie
2ddde010-4d19-47e8-bbfe-98c01201b618
Cooper, Matthew
54f7bff0-1f8c-4835-8358-71eef8529e7a
Milton, James
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Breeze, Paul
a86faa04-cbf3-4fed-8034-96ea40d5de2e
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Jewell, Amy Margaret, Drake, Nick, Crocker, Anya, Bakker, Natalie, Kunkelova, Terezia, Bristow, Charlie, Cooper, Matthew, Milton, James, Breeze, Paul and Wilson, Paul A.
(2021)
Three North African dust source areas and their geochemical fingerprint.
Earth and Planetary Science Letters, 554, [116645].
(doi:10.1016/j.epsl.2020.116645).
Abstract
North Africa produces more than half of the world's atmospheric dust load. Once entrained into the atmosphere, this dust poses a human health hazard locally. It also modifies the radiative budget regionally, and supplies nutrients that fuel primary productivity across the North Atlantic Ocean and as far afield as the Amazonian Basin. Dust accumulation in deep sea and lacustrine sediments also provides a means to study changes in palaeoclimate, particularly those associated with rainfall climate change. Systematic analysis of satellite imagery has greatly improved our understanding of the trajectories of long-range North African dust plumes, but our knowledge of the dust-producing source regions and our ability to fingerprint their contribution to these export routes is surprisingly limited. Here we report new radiogenic isotope (Sr and Nd) data for sediment samples from known dust-producing substrates (dried river and lake beds), integrate them with published isotope data and weight them for dust source activation. We define three isotopically distinct preferential dust source areas (PSAs): a Western, a Central and an Eastern North African PSA. More data are needed, particularly from the Western PSA, but our results show a change in PSA dust source composition to more radiogenic Nd- and less radiogenic Sr-isotope values from west to east, in line with the overall decreasing age of the underlying bedrock. Our data reveal extreme isotopic heterogeneity within the Chadian region of the Central PSA, including an extremely distinctive geochemical fingerprint feeding the Bodélé Depression, the most active dust source on Earth. Our new analysis significantly improves the reliability by which windblown dust deposits can be geochemically fingerprinted to their distant source regions.
Text
Jewell_etal_2020_ACCEPTED
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More information
Accepted/In Press date: 17 October 2020
e-pub ahead of print date: 27 October 2020
Published date: 15 January 2021
Additional Information:
Funding Information:
This work was supported by the Natural Environment Research Council [grant number NE/L002531/1 to AMJ and NE/L002485/1 to NLB] and Royal Society Challenge Grant CH160073 and Royal Society Wolfson Merit Award to PAW. Research by PSB and ND utilised in this paper was funded by the Leverhulme Trust (grants RPG-2016-115 & ECF-2019-538 ). We thank Prof. Zongbo Shi and Clarissa Baldo from the University of Birmingham and Thomas Baird from University College London for their kind assistance. We are indebted to Dr. Moussa Abderamane from the University of N'Djamena and Dr Ahmed Adam from the University of Khartoum for their help arranging fieldwork and sample permits. We thank two anonymous referees for their constructive comments which helped improve the final manuscript.
Publisher Copyright:
© 2020 Elsevier B.V.
Keywords:
87Sr/86Sr, Bodélé Depression, North Africa, dust source, radiogenic isotopes, εNd
Identifiers
Local EPrints ID: 444841
URI: http://eprints.soton.ac.uk/id/eprint/444841
ISSN: 0012-821X
PURE UUID: cb92a83b-4a2b-4337-9ce4-402e3d89fbc2
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Date deposited: 06 Nov 2020 17:31
Last modified: 19 Apr 2024 01:54
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Author:
Nick Drake
Author:
Natalie Bakker
Author:
Charlie Bristow
Author:
Paul Breeze
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