Tremadocn.
/trɪˈmadək/ Geology.
Used attributively to designate a series of Tremadocian rocks (see Tremadocian adj.) about 300 metres thick that form the top of the Harlech Dome and comprise mudstones, shales, and slates; also, more widely, = Tremadocian adj.
ΘΚΠ
the world > the earth > structure of the earth > age or period > stratigraphic units > [adjective] > primary or Palaeozoic > Ordovician > specific
Caradoc1835
Tremadoc1847
Arenig1854
Skiddaw1897
Cincinnatian1899
Skiddavian1905
Caradocian1910
Tremadocian1910
1847 A. Sedgwick in Q. Jrnl. Geol. Soc. 3 145 The anomalous position of the Tremadoc rocks,..and the dislocation of the beds above noticed along the Merioneth coast, were probably all produced by the same set of disturbing forces.
1847 A. Sedgwick in Q. Jrnl. Geol. Soc. 3 157 The Festiniog or the Tremadoc group.
1882 A. Geikie Text-bk. Geol. 655 12 species of lamellibranchs from the Tremadoc beds of Ramsay Island and St. David's.
1885 C. Lyell Student's Elem. Geol. (ed. 4) xxviii. 448 Mr. Callaway has shown that the Shineton shale of Shropshire is of Lower Tremadoc age.
1885 C. Lyell Student's Elem. Geol. (ed. 4) xxviii. 448 Orthoceras sericeum and Cyrtoceras præcox are of the Upper Tremadocs.
1938 A. K. Wells Outl. Hist. Geol. iii. 20 The graptolites..had made their first appearance in Tremadoc (Upper Cambrian) times.
1970 R. M. Black Elements Palaeontol. xiv. 222 Primitive pterobranchs are found in rocks of Tremadoc age.
1974 Encycl. Brit. Micropædia X. 108/3 Important Tremadoc sequences are..known from Australia.
This entry has not yet been fully updated (first published 1986; most recently modified version published online December 2019).
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