Astronomically controlled aridity in the Sahara since at least 11 million years ago
Astronomically controlled aridity in the Sahara since at least 11 million years ago
The Sahara is the largest hot desert on Earth. Yet the timing of its inception and its response to climatic forcing is debated, leading to uncertainty over the causes and consequences of regional aridity. Here we present detailed records of terrestrial inputs from Africa to North Atlantic deep-sea sediments, documenting a long and sustained history of astronomically paced oscillations between a humid and arid Sahara from over 11 million years ago. We show that intervals of strong dust emissions from the heart of the continent predate both the intensification of Northern Hemisphere glaciation and the oldest land-based evidence for a Saharan desert by millions of years. We find no simple long-term gradational transition towards an increasingly arid climate state in northern Africa, suggesting that aridity was not the primary driver of gradual Neogene expansion of African savannah C4 grasslands. Instead, insolation-driven wet–dry shifts in Saharan climate were common over the past 11 Myr, and we identify three distinct stages in the sensitivity of this relationship. Our data provide context for evolutionary outcomes on Africa; for example, we find that astronomically paced arid intervals predate the oldest fossil evidence of hominid bipedalism by at least 4 Myr.
671-676
Crocker, Anya
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Naafs, B. David A.
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Westerhold, Thomas
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James, Rachael
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Cooper, Matthew
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Röhl, Ursula
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Pancost, Richard D.
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Xuan, Chuang
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Osborne, Colin P.
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Beerling, David J.
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Wilson, Paul A.
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August 2022
Crocker, Anya
1215fbdd-ad43-408a-bd79-c54c6847e68c
Naafs, B. David A.
b4e4a3c0-ef86-476f-a439-3ce7e192337a
Westerhold, Thomas
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James, Rachael
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Cooper, Matthew
54f7bff0-1f8c-4835-8358-71eef8529e7a
Röhl, Ursula
e3029111-f8cc-4bf9-9433-829590c8645d
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Xuan, Chuang
3f3cad12-b17b-46ae-957a-b362def5b837
Osborne, Colin P.
89fb6ad9-892c-4120-9f89-cdd6a492beef
Beerling, David J.
2d3b3a81-4c04-4048-8f25-5438bb70fc1e
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Crocker, Anya, Naafs, B. David A., Westerhold, Thomas, James, Rachael, Cooper, Matthew, Röhl, Ursula, Pancost, Richard D., Xuan, Chuang, Osborne, Colin P., Beerling, David J. and Wilson, Paul A.
(2022)
Astronomically controlled aridity in the Sahara since at least 11 million years ago.
Nature Geoscience, 15 (8), .
(doi:10.1038/s41561-022-00990-7).
Abstract
The Sahara is the largest hot desert on Earth. Yet the timing of its inception and its response to climatic forcing is debated, leading to uncertainty over the causes and consequences of regional aridity. Here we present detailed records of terrestrial inputs from Africa to North Atlantic deep-sea sediments, documenting a long and sustained history of astronomically paced oscillations between a humid and arid Sahara from over 11 million years ago. We show that intervals of strong dust emissions from the heart of the continent predate both the intensification of Northern Hemisphere glaciation and the oldest land-based evidence for a Saharan desert by millions of years. We find no simple long-term gradational transition towards an increasingly arid climate state in northern Africa, suggesting that aridity was not the primary driver of gradual Neogene expansion of African savannah C4 grasslands. Instead, insolation-driven wet–dry shifts in Saharan climate were common over the past 11 Myr, and we identify three distinct stages in the sensitivity of this relationship. Our data provide context for evolutionary outcomes on Africa; for example, we find that astronomically paced arid intervals predate the oldest fossil evidence of hominid bipedalism by at least 4 Myr.
Text
Crocker_NatGeo_all_final
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More information
Accepted/In Press date: 14 June 2022
e-pub ahead of print date: 25 July 2022
Published date: August 2022
Additional Information:
Funding Information:
This research used samples provided by (I)ODP, which was sponsored by the US National Science Foundation and participating countries under management of Joint Oceanographic Institutions, Inc. We thank W. Hale, H. Kuhlman and A. Wülbers of the Bremen Core Repository and R. K. James, A. McCombie and C. Evans for laboratory assistance, A. Calder for discrete XRF analysis and V. Lukies for assistance with XRF core scanning. Biostratigraphic information was provided by J. Backman, and S. Mulitza supplied the geochemical endmember unmixing code. We thank D. McGee, J. Tierney, T. Ezard, C. Gamble, A. Pike, T. Herbert, K. Grant, S. Feakins, E. Rohling and S. Mulitza for discussions and feedback that helped to improve this manuscript.
Funding Information:
This research was funded through ERC advanced grant CDREG no. 322998 (D.J.B.) and the Royal Society Challenge Grant CHG\R1\170054 (P.A.W.) and Wolfson Merit Award WM140011 (P.A.W.). Additional funding came from University of Southampton’s GCRF strategic development fund grant 519016 (P.A.W. and A.J.C.), advanced ERC grant T-GRES ref. 340923 (B.D.A.N. and R.D.P.) and a Royal Society Tata University Research Fellowship (B.D.A.N.). We thank the Natural Environment Research Council for partial funding of the mass spectrometry facilities at the University of Bristol (contract no. R8/H10/63). Financial support was also received from the Deutsche Forschungsgemeinschaft (DFG) (U.R. and T.W.), including project 242225091 (T.W).
Publisher Copyright:
© 2022, The Author(s), under exclusive licence to Springer Nature Limited.
Identifiers
Local EPrints ID: 469180
URI: http://eprints.soton.ac.uk/id/eprint/469180
ISSN: 1752-0894
PURE UUID: fc9afe2d-96cd-4e08-b022-098264899910
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Date deposited: 08 Sep 2022 17:08
Last modified: 15 Oct 2024 04:01
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Contributors
Author:
B. David A. Naafs
Author:
Thomas Westerhold
Author:
Ursula Röhl
Author:
Richard D. Pancost
Author:
Colin P. Osborne
Author:
David J. Beerling
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