06 Jul 2023
 | 06 Jul 2023
Status: a revised version of this preprint is currently under review for the journal GChron.

Late Neogene terrestrial climate reconstruction of the Central Namib Desert derived by the combination of U-Pb silcrete and TCN exposure dating

Benedikt Ritter, Richard Albert, Aleksandr Rakipov, Frederik M. Van der Wateren, Tibor J. Dunai, and Axel Gerdes

Abstract. The chronology of the Cenozoic, so called ‘Namib Group’ of the Namib Desert is rather poor in terms of direct radiometric dating. Most of the chronological information is based on the ostrich shell biochronostratigraphy. The widespread occurrence of calcretes and silcretes in the Namib Desert makes it possible to date important phases of landscape stability and to retrieve critical paleoclimatic and -environmental information on desertification and its paleoclimatic variability. The application of the U-Pb laser ablation dating technique to Plio/Pleistocene sil- and calcretes provides critical insights into groundwater calcrete formation and climate variability in the Central Namib. Microscale silcrete formation due to pressure solution by expanding calcrete cementation provides the opportunity to date multiple phases (multiple generation of silcrete as growing layers or shells) of silcrete formation and to trace their paleoclimatic and -environmental fingerprints. Groundwater sil- and calcrete formation occurred during the Pliocene. TCN exposure ages from flat canyon rim surfaces indicate the cessation of groundwater calcrete formation due to incision during the Late Pliocene/Early Pleistocene and mark a large-scale landscape rejuvenation due to climate shifts towards the Pleistocene. This study demonstrates the application of U-Pb laser ablation to groundwater sil- and calcretes in desert environments and opens up the possibility of dating numerous sedimentary sequences containing sil- and calcretes in arid environments. In particular, the use of silcretes (as described above) reduces potential effects of detrital components and bulk-signal measurements by using massive calcretes. Our study redefines and improves the generally accepted Late Cenozoic chronostratigraphy of the Namib Desert (Miller, 2008).

Benedikt Ritter et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2023-19', Anonymous Referee #1, 13 Jul 2023
    • AC1: 'Reply on RC1', Benedikt Ritter, 14 Sep 2023
  • RC2: 'Comment on gchron-2023-19', Anonymous Referee #2, 11 Aug 2023
    • AC2: 'Reply on RC2', Benedikt Ritter, 14 Sep 2023

Benedikt Ritter et al.

Benedikt Ritter et al.


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Short summary
Chronological information on the evolution of the Namib Desert is scarce. We used U-Pb dating of silcretes formed by pressure-solution during calcrete formation to track paleoclimate variability since the Late Miocene. Calcrete formation took place during the Pliocene with an abrupt cessation at 2.9 Ma. The end took place due to deep canyon incision which we dated using TCN exposure dating. With our data we correct and contribute to the Neogene history of the Namib Desert and its evolution.