Sediments of Late-glacial origin from the Elan Valley in Cardiganshire have been subjected to close-interval pollen, spore and macrofossil analysis. From the results of this analysis an attempt has been made to reconstruct contemporary plant species assemblages and to follow the changes in these communities during the climatically unstable Late-glacial period. Conventional zonation required some modification for adequate representation of the dynamic state of both environment and vegetation at the time, hence a series of transitional zones has been constructed. Certain species are found to reach their greatest abundance in these transitional periods and are considered to be relatively thermophilous yet intolerant of competition.
Certain of the types found, e.g. Artemisia c.f. norvegica, Linnaea borealis, Tofieldia and Scleranthus perennis are of particular interest, both because of the infrequency with which they have been recorded in British quaternary deposits in the past, and because of their present day disjunct and sometimes anomalous distributions. Their presence in mid-Wales during Late-glacial times throws further light upon these distributions.