| 释义 |
Downtonian, a. Geol.|daʊnˈtəʊnɪən|
[f. Downton, name of a locality in Herefordshire + -ian.]
Of, pertaining to, or designating a stratigraphic stage or series in Europe placed at the top of the Silurian system or the bottom of the Devonian, and the age or epoch during which it was deposited. Also absol.
1879C. Lapworth in Ann. & Mag. Nat. Hist. 5th Ser. III. Table facing 455 Silurian System: Upper Division (Downtonian). 1910Lake & Rastall Text-bk. Geol. xx. 334 The Downtonian series varies little. Wherever it occurs, whether on the Welsh borders, in the Lake District or in the south of Scotland, it is essentially an arenaceous deposit and was formed in shallow water. 1938A. K. Wells Outl. Hist. Geol. vii. 66 Both Downtonian and Dittonian represent successive stages in the transition from marine to continental conditions. Ibid. 67 The thickness of the Downtonian Stage diminishes. 1955G. G. Woodford tr. Gignoux's Stratigr. Geol. iv. 110 Similar sediments are seen on the edges of the Baltic Shield... This Baltic Downtonian is attached to the Silurian by Scandinavian geologists. 1967D. H. Rayner Stratigr. Brit. Isles v. 140 Molluscs..are often abundant in the lower Downtonian beds. 1971B. W. Sparks Rocks & Relief viii. 295 In this account the Downtonian will be included in the Devonian. |