Neogene sedimentary processes forming the NAMIB sand sea

Caracciolo L, Stollhofen H, Garzanti E, Vainer S, Limonta M, Hatzenbühler D, Liedel S, Vermeesch P, Joachimski M, Dor YB (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Pages Range: 105247

Article Number: 105247

DOI: 10.1016/j.earscirev.2025.105247

Abstract

Sand accumulation in the Namib Sand Sea (NSS) results from long-distance northward longshore transport from the Orange River delta, fuelled by swells generated at high southern latitudes. The build-up and position of the northern and southern hemisphere ice sheets regulate wind intensity and aridity in Namibia, and consequently the northward littoral transport, water discharge, and ultimately the Benguela Current. The latter extends beyond the NSS during periods of high wind intensity (increasing aridity), while it turns westward before reaching the Namibian coast during periods of less intense wind (decreasing aridity). Hence, the behaviour of the Benguela Current can be used as a diagnostic parameter to discriminate arid vs semi-arid climate during the Cenozoic. The interplay of such a powerful system controls long-distance northward sediment transfer with part of the sand being blown inland and stored in the erg. Literature data suggest that fluvial-aeolian interactions in the inner part of the NSS result in choking of river valleys and a composition of dune sand indistinguishable from the Orange River sand.

Previous studies support a model where sediment transport and climatic settings were constant since at least the Early Miocene and possibly the Eocene or even the Cretaceous. However, available data from offshore cores in front of Walvis Bay indicate that the Benguela Current (i) initiated between 10 and 12 Ma, (ii) deviated westward several times in the past without reaching as far north as today, (iii) hyperarid climate was not constant over the last 20 Ma, and (iv) climate became more stable since 5 Ma. Hence, water and sediment discharge of inland-sourced rivers flowing westward into the NSS and beyond were higher during humid stages of the past suggesting that fluvial-aeolian interactions may have notably changed through time. We test this hypothesis by analysing the sediment character and provenance features of the aeolian and fluvial sandstones of the Oligocene to Pliocene Langer Heinrich (LH), Tsondab (TS), Karpfenkliff/Kamberg (KK), and Oswater (OW) formations*, which* preserve an excellent record of fluvial/aeolian interactions in the eastern Namib desert. We compare the dynamics of modern ephemeral river*-*dune interactions in the areas of Sossusvlei and Tsondabvlei, where the Tsauchab and Tsondab rivers, respectively, are dammed and dormant within the dune belts to form playa-lakes (locally called vleis = pans). Integrating sand and sandstone detrital modes and heavy mineral assemblages of modern and ancient fluvial and aeolian deposits, detrital zircon geochronology of the dunes of the Tsondab Fm., together with stable isotopes on sandstone carbonate cements and calcrete sediments reveals that (i) the material of the Orange River did not reach the inner NSS as far eastwards as today (ii) that the Late Miocene (Tsondab) Sand Sea in this region was largely sourced by local rivers, and that, (iii) Unlike the Tsauchab River and the nearby dunes of the Sossusvlei area, the sand of Tsondabvlei and the dunes surrounding it is not derived from the Orange River, making it a desert within a desert. Based on cosmogenic-nuclide modeling, the last phase of aridification in the NSS, which caused extensive sand dispersion, occurred approximately 2 Myr ago. For marginal sand deposits, we estimate that sand at the northern margins of the erg had a residence time of approximately 1.5 Myr as it travelled northward.

Authors with CRIS profile

Involved external institutions

University of Milano-Bicocca / Università degli Studi di Milano-Bicocca, UNIMIB Italy (IT) University College London (UCL) United Kingdom (GB) Géosciences Environnement Toulouse (GET) France (FR) Geological Institute of Istrael Israel (IL)

How to cite

APA:

Caracciolo, L., Stollhofen, H., Garzanti, E., Vainer, S., Limonta, M., Hatzenbühler, D.,... Dor, Y.B. (2025). Neogene sedimentary processes forming the NAMIB sand sea. Earth-Science Reviews, 105247. https://doi.org/10.1016/j.earscirev.2025.105247

MLA:

Caracciolo, Luca, et al. "Neogene sedimentary processes forming the NAMIB sand sea." Earth-Science Reviews (2025): 105247.

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