Nd-isotope evidence for the distal provenance of the historical (c. <3000BP) lateritic surface cover underlying the Equatorial forest in Gabon (Western Africa).

Thieblemont, D., Guerrot, C., Negrel, Ph., Braucher, R., Bourles, D. L. and Thieblemont, Remi (2014) Nd-isotope evidence for the distal provenance of the historical (c. <3000BP) lateritic surface cover underlying the Equatorial forest in Gabon (Western Africa). Aeolian Research, 15 . pp. 177-192. DOI 10.1016/j.aeolia.2014.06.002.

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Supplementary data:

Abstract

Highlights:
• The first Nd isotopic data on the lateritic surface cover (Cover Horizon) of western Equatorial Africa.
• Clearly different Nd isotopic signatures between the Cover Horizon and underlying basement.
• A consistent model attributing the Cover Horizon to the settling of aeolian particles derived from the Namib desert.

Abstract:
Surficial formations in Gabon, as well as in other places of western Central Africa include a ubiquitous, homogeneous and 1–3 m-thick clayey to sandy lateritic surface cover known as the ‘Cover Horizon’. From 14C radiometric dating it has been concluded that the emplacement of this unit was correlative with a major environmental crisis which affected Central Africa c. 3000–2000 years ago. 10Be and Nd-isotopic analyses have been performed to provide new constraints on the age and origin of this layer. Six samples from two depth profiles investigated for 10Be exhibit an almost constant concentration consistent with a very recent deposition age. Nd-isotopic analyses performed on the silt to clay fraction of eleven samples from widely spaced locations over Gabon attest for mildly radiogenic signatures (εNd = −23 to −17) in ten of them, and a slightly radiogenic signature (εNd = −9) in one sample. TDM model ages range from 1.6 to 2.6 Ga, and a perfect discrimination is observed between the Nd-isotopic signature of the Cover Horizon and that of the underlying Congo Craton. This makes an aeolian origin as the most probable for the Cover Horizon. The average εNd (c. −20) is however rather unusual for aeolian sediments or aerosols. A possible source of particles is therefore tested by considering the present-day atmospheric flux over Gabon and adjacent regions. Combined atmospheric modeling and Nd-isotopes leads to the conclusion that the fine fraction of the Cover Horizon could have originated from the northern part of the Namib desert.

Document Type: Article
Additional Information: WOS:000344423300014
Keywords: Gabon; Namib desert; Nd-isotopes; Upper Holocene; Aeolian sedimentation; Climatic crisis
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.aeolia.2014.06.002
ISSN: 1875-9637
Date Deposited: 21 Aug 2014 12:06
Last Modified: 21 Jan 2019 12:21
URI: http://oceanrep.geomar.de/id/eprint/25480

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