Comments on the geochronology of the Carboniferous to Triassic times

Thanks to the relatively numerous and more or less reliable radiometric dates obtained from the Carboniferous to Triassic sequences it is possible to choose the best calibration points before trying to draw a picture of the corresponding numerical time-scale. In this context, the analysis of Forster & Warrington in the introduction to their chapter is a most welcome reminder of the criteria for data selection, sometimes neglected or forgotten by other authors. Taking this into account, one may be sure that the portion of the time-scale proposed is probably one of the most objectively founded in this book for: (1) The authors are fully aware of the various uncertainties arising in the exercise of assessing a calibration point. (2) They actually use their own recommendations, when possible, and try to discuss each of the different areas of uncertainty (i.e.) the stratigraphical and the geochemical as well as the analytical ones in order to weight the reliability of a given date. (3) They have found in the literature a large number of data from which they selected 45. These are supported by other results which, although only briefly mentioned and less significant, are useful to reinforce their arguments. The result of this considerable work is a time-scale which certainly is a very good reference. The minor remarks proposed here must be considered therefore as a modest complement of information to emphasize some of the limited differences between this work and the synthesis edited by the author in 1982 (Odin 1982).