Are sedimentation rates of one cycle per year credible?
According to radioisotope dating, the Cretaceous period lasted 80 million years – a stretch of time that, accustomed though we are to such figures, is unimaginable. Is it also imaginary? Since the figure is based on data extraneous to the properties of the rocks themselves, those properties can provide a test of the timescale, and as we have seen, in the case of chalk sequences, they do not agree with ages of this magnitude. To put it another way, if we were to consider the primary evidence on its own merits, we would have no grounds for inferring the miniscule rates of sedimentation the radioisotope timescale imposes. A typical chalk-marl couplet has a thickness of around 50 cm, sometimes less. Before compaction the thickness might have been double that, around 100 cm. Averaged over 20,000 years, this gives a sedimentation rate of 0.05 mm, or half a hair’s breadth, per year. That too is difficult to imagine. By contrast, if the couplets were annual, the sedimentation rate would have a
