- Accueil
- Volume 115 (1992)
- Fascicule 2 - Devonian-Carboniferous boundary
- The age of the Devonian-Carboniferous boundary
Visualisation(s): 435 (0 ULiège)
Téléchargement(s): 800 (0 ULiège)
The age of the Devonian-Carboniferous boundary
Abstract
The Devonian-Carboniferous boundary is now one of the most securely dated positions in the Phanerozoic column. Coincident with redefinition of the boundary, a thin volcanic layer has been identified 35 cm above the boundary in the Hasselbachtal section in Germany, now one of the auxiliary global stratotypes, and a tuff has been located at a similar biostratigraphic level in Australia. Ion microprobe zircon dating of the two horizons has yielded indistinguishable ages, and indicates 353.2 ± 4.0 Ma (2σ) as the age of the boundary.
Recent previous estimates of the age of this boundary have suggested dates with a spread of 25 Ma. A review of historical contraints shows that this uncertainty rested mainly upon biostratigraphic difficulty in correlating dated volcanics in terrestrial sediments with the type marine stratigraphy. Recognition of a dateable volcanic layer in the Hasselbachtal auxiliary stratotype eliminates this source of doubt. Future refinements of the age of the Devonian-Carboniferous boundary will depend on re-analysis of this uniquely placed volcanic, and this highlights the value of defining stratotypes in the vicinity of known dateable horizons.