IV - On the plant-remains from the Downtonian of England and Wales

Abstract

The strata from which the plant-remains to be described in this paper are derived are those which are grouped as Downtonian in the extended sense of this term employed by Mr. W. Wickham King. They therefore include not only the Ludlow Bone-bed, the Downton Sandstone, and the Temeside Shales, i.e ., the Grey Downtonian, but a much greater thickness of red marls and sandstones that were formerly classed with the Lower Old Red Sandstone, but are now spoken of as the Red Downtonian. This way of regarding the rocks of this horizon has been fully discussed in the light of the history of opinions by O. T. Jones (1929, pp. 110- 121) and need not be considered further here. These strata have been included at different times in the Silurian or in the Old Red Sandstone. It is not necessary here to enter into the question as to the best limit between the Silurian and the Devonian. Reference may be made to Stamp (1923), O. T. Jones (1929), and to Wickham King’s recent paper (1934). It is sufficient for the purposes of this study of the plants to recognize that the Downtonian strata come above the more definitely marine Ludlovian rocks and below the more definitely continental beds of the Lower Old Red Sandstone. The transitional nature of the Grey Downtonian has long been accepted and can readily be extended to the succeeding beds included in the Downtonian by Wickham King.