Mr P. Evans, congratulated the authors on a very interesting and useful piece of work. There had been so much difference of opinion about the age of high-level erosion surfaces that it was important to have this definite evidence of a Pliocene surface.
The low relief of the 450 m Brassington surface suggested that it had been eroded to a base-level only a little below this. Sissons's Holme Moss surface was about 100 m higher, and Mr. Evans agreed that it would have supplied sediment: base-level might well have been the Bradfield level of about 400 m which is traceable at intervals as far as the south of France.
Old high sea-levels back to about 200 m at something over a million years ago could be plotted to give the rate of fall of sea-level for that spell of time, but to continue back to earlier periods was guesswork. His independent guess put the Brassington Beds at 4 million years, and the authors had guessed 7. In the present state of ignorance about Pliocene dates, the difference between guesses of 4 and 7 million years was not worth arguing about.
The Authors thanked Mr. Percy Evans for his kind remarks, but would naturally prefer to have their 7 million year dating for the sub-Brassington Formation surface accepted as a carefully-reasoned deduction, after many years of palaeobotanical research rather than a 'guess'. Having ascertained that the Kenslow flora was approximately of Mio-Pliocene boundary age, the 7 million year figure was derived