Titre du document / Document title

Radiometric dating of young and old calcrete = Datations radiométriques de croûtes calcaires anciennes et récentes

Auteur(s) / Author(s)

GEYH M. A. ⁽¹⁾ ; EITEL B. ⁽²⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Niedersächsisches Landesamt für Bodenforschung, P.O. Box 51 0153, 30631 Hannover, ALLEMAGNE
⁽²⁾ Physische Geographie, Universität Passau, Schusterstr. 21, 94032 Passau, ALLEMAGNE

Résumé / Abstract

To obtain a better understanding of the relationship between calcrete genesis and the results of different absolute dating methods, thermoluminescence (TL), radiocarbon (14C) and uranium/thorium (U/Th) were applied to coeval samples taken from a very young calcrete profile in Namibia. The methodically different ages reflect the characteristics of the applied dating methods, the genetics of calcrete and different events of calcrete genesis. The conventional 14C ages and the TL dates cover the last 50 ka, while the corresponding U/Th dates of coeval samples are many times larger. Uranium-series dates are not related to the deposition of the host material or to its cementation if the ages are smaller than ca. 120 ka. The TL clock is set to zero during eolian transport and the corresponding radiometric ages of the quartz and feldspar grains date the time of their deposition. The 14C ages of the cement correspond, on the other hand, to a time shortly after the onset of the cementation and long before its termination. In the case of very old calcrete, the mixture of young and old cement results in ambiguous ages if they cannot be confirmed by an independent technique.

Revue / Journal Title

Radiocarbon   ISSN 0033-8222 

Source / Source

1998, vol. 40, n^o2, pp. 795-802 (17 ref.)

Langue / Language

Anglais

Editeur / Publisher

University of Arizona, Tucson, AZ, ETATS-UNIS  (1961) (Revue)

Mots-clés anglais / English Keywords

Geology and climatology ; Limestone ; Dating ; Method ; Chronology ; Thermoluminescence ; Radiocarbon ; Uranium-Thorium ; Comparison ; Africa ; Namibia ;

Mots-clés français / French Keywords

Géologie et climatologie ; Calcaire ; Datation ; Méthode ; Chronologie ; Thermoluminescence ; Radiocarbone ; Uranium-Thorium ; Comparaison ; Afrique ; Namibie ;

Localisation / Location

INIST-CNRS, Cote INIST : 502 B, 35400007025282.0240