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Late Quaternary inundation and desiccation of Megalake Chad traced in dust records from the Equatorial Atlantic Ocean

Late Quaternary inundation and desiccation of Megalake Chad traced in dust records from the Equatorial Atlantic Ocean
Late Quaternary inundation and desiccation of Megalake Chad traced in dust records from the Equatorial Atlantic Ocean
Modern Lake Chad has shrunk in area by around 90 % since the 1960s under the twin pressures of climate change and increasing water demand. During the early to mid Holocene, the Chad basin featured a megalake with an area approximately 100 times larger than its modern remnant. In the mid/late Holocene (approximately 5000 years ago), this megalake dried out leaving behind vast deposits of readily deflated fine-grained sediments that are suggested to contribute ∼25 % of the annual total global atmospheric mineral dust load. Erosion has obliterated much of the evidence of earlier North African humid periods within the Lake Chad basin, limiting our understanding of the relationship between global/regional climatology, local hydrology and dust export. Here, we present new records of thorium-normalized flux estimates of mineral dust and its radiogenic isotope composition deposited at Ocean Drilling Program Site 662, situated downwind of Megalake Chad underneath the North African winter dust plume, in the equatorial Atlantic Ocean. Our records show that sediments of the Megalake Chad basin have a distinct neodymium isotopic signature that can be traced thousands of kilometers downwind from their source when the megalake basin was dry and dust-active, whereas the fingerprint of its input was strongly suppressed at times of high lake levels. Our results show that marine sedimentary archives can preserve uninterrupted proxy records of climate-driven hydrological change on the continents, in this case, a bellwether region of Africa that features the world's most active dust source, the Bodélé Depression.
Africa, Atlantic Ocean, Chad, Dust, Holocene, Paleoclimatology, Quaternary, Radiogenic isotopes, Sahara, U-Th series
0277-3791
Crocker, Anya J.
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Kinsley, Christopher W.
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Jewell, Amy M.
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Breeze, Paul S.
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Drake, Nicholas A.
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McGee, David
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Bristow, Charles S.
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Manning, Katie
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Di Biagio, Claudia
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Formenti, Paola
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Burton, William R.C.
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Murray, Annie L.
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Barlow, James
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Cooper, Matthew J.
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Xuan, Chuang
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Wilson, Paul A.
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Crocker, Anya J.
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Kinsley, Christopher W.
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Jewell, Amy M.
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Breeze, Paul S.
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Drake, Nicholas A.
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McGee, David
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Bristow, Charles S.
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Manning, Katie
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Di Biagio, Claudia
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Formenti, Paola
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Burton, William R.C.
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Murray, Annie L.
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Barlow, James
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Cooper, Matthew J.
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Xuan, Chuang
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Wilson, Paul A.
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Crocker, Anya J., Kinsley, Christopher W., Jewell, Amy M., Breeze, Paul S., Drake, Nicholas A., McGee, David, Bristow, Charles S., Manning, Katie, Di Biagio, Claudia, Formenti, Paola, Burton, William R.C., Murray, Annie L., Barlow, James, Cooper, Matthew J., Xuan, Chuang and Wilson, Paul A. (2025) Late Quaternary inundation and desiccation of Megalake Chad traced in dust records from the Equatorial Atlantic Ocean. Quaternary Science Reviews, 366, [109503]. (doi:10.1016/j.quascirev.2025.109503).

Record type: Article

Abstract

Modern Lake Chad has shrunk in area by around 90 % since the 1960s under the twin pressures of climate change and increasing water demand. During the early to mid Holocene, the Chad basin featured a megalake with an area approximately 100 times larger than its modern remnant. In the mid/late Holocene (approximately 5000 years ago), this megalake dried out leaving behind vast deposits of readily deflated fine-grained sediments that are suggested to contribute ∼25 % of the annual total global atmospheric mineral dust load. Erosion has obliterated much of the evidence of earlier North African humid periods within the Lake Chad basin, limiting our understanding of the relationship between global/regional climatology, local hydrology and dust export. Here, we present new records of thorium-normalized flux estimates of mineral dust and its radiogenic isotope composition deposited at Ocean Drilling Program Site 662, situated downwind of Megalake Chad underneath the North African winter dust plume, in the equatorial Atlantic Ocean. Our records show that sediments of the Megalake Chad basin have a distinct neodymium isotopic signature that can be traced thousands of kilometers downwind from their source when the megalake basin was dry and dust-active, whereas the fingerprint of its input was strongly suppressed at times of high lake levels. Our results show that marine sedimentary archives can preserve uninterrupted proxy records of climate-driven hydrological change on the continents, in this case, a bellwether region of Africa that features the world's most active dust source, the Bodélé Depression.

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Submitted date: 12 March 2025
Accepted/In Press date: 23 June 2025
Published date: 8 July 2025
Keywords: Africa, Atlantic Ocean, Chad, Dust, Holocene, Paleoclimatology, Quaternary, Radiogenic isotopes, Sahara, U-Th series

Identifiers

Local EPrints ID: 504228
URI: http://eprints.soton.ac.uk/id/eprint/504228
ISSN: 0277-3791
PURE UUID: 10f8a9f4-6c36-458b-b1b2-d894c7d42751
ORCID for Anya J. Crocker: ORCID iD orcid.org/0000-0001-9561-5750
ORCID for Matthew J. Cooper: ORCID iD orcid.org/0000-0002-2130-2759
ORCID for Chuang Xuan: ORCID iD orcid.org/0000-0003-4043-3073
ORCID for Paul A. Wilson: ORCID iD orcid.org/0000-0001-6425-8906

Catalogue record

Date deposited: 01 Sep 2025 16:38
Last modified: 02 Sep 2025 01:55

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Contributors

Author: Anya J. Crocker ORCID iD
Author: Christopher W. Kinsley
Author: Amy M. Jewell
Author: Paul S. Breeze
Author: Nicholas A. Drake
Author: David McGee
Author: Charles S. Bristow
Author: Katie Manning
Author: Claudia Di Biagio
Author: Paola Formenti
Author: William R.C. Burton
Author: Annie L. Murray
Author: James Barlow
Author: Chuang Xuan ORCID iD
Author: Paul A. Wilson ORCID iD

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