Pastore, Guido;
Garzanti, Eduardo;
Vermeesch, Pieter;
Bayon, Germain;
Resentini, Alberto;
Braquet, Nadine;
Overare, Brume;
(2023)
The Zircon Story of the Niger River: Time-Structure Maps of the West African Craton and Discontinuous Propagation of Provenance Signals Across a Disconnected Sediment-Routing System.
JGR: Earth Surface
, 128
(11)
, Article e2023JF007342. 10.1029/2023JF007342.
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Abstract
The Niger River drains a large part of the West African Craton, where rocks ranging in age from Paleoarchean to recent offer an unexcelled opportunity to map the diverse time structures of sediment sources and provide essential information for provenance diagnoses. In this study, U-Pb zircon dating is complemented with bulk-sand geochemical (Zr, Hf, REE) and Nd-Hf isotope data to pin-point parent rocks of zircon grains and draw inferences on sediment generation across sub-Saharan western Africa. In Upper Niger sand, zircon ages pass from exclusively Archean in Guinea headwaters to dominantly Paleoproterozoic in the Inner Delta in Mali, testifying to the progressive dilution by tributary sediment derived from the Birimian domain. Zircon ages abruptly change to dominantly Neoproterozoic downstream of the Inner Delta, becoming indistinguishable from those in Saharan eolian dunes across the Sahel. Most of the sediment generated in the headwaters is thus dumped in the marshlands and bedload is reconstituted downstream by recycling eolian sand. Zircon grains in the Lower Niger yielded virtually the same U-Pb ages as in Benue sediment, indicating an overwhelming supply from the Benue tributary. In the Niger Delta, however, Archean zircons reappear, and both εNd and εHf values become notably more negative, indicating extensive reworking of sand deposited along the coastal plain at earlier times of wetter climate, when artificial barriers to the sediment flux did not exist in the upper to middle Niger River catchment.
| Type: | Article |
|---|---|
| Title: | The Zircon Story of the Niger River: Time-Structure Maps of the West African Craton and Discontinuous Propagation of Provenance Signals Across a Disconnected Sediment-Routing System |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2023JF007342 |
| Publisher version: | https://doi.org/10.1029/2023JF007342 |
| Language: | English |
| Additional information: | Copyright © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
| Keywords: | Detrital-zircon geochronology; Zr/Hf ratio; Hf model ages; man shield; Nigeria basement complex; Niger and Benue rivers; sub-Saharan western Africa |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10183263 |
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