Tremadocian
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The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from 486.85 to 477.1 million years ago. The base of
Rock from the Skiddaw Group, of Ordovician (Tremadocian) age, at Scawgill Bridge quarry in Cumbria, England, UK
Silurian
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The Silurian is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at 443.1 Ma to the beginning of the Devonian Period, 419.62 Ma. The Silurian is the thir
Tremadocian
…Tremadocian Chronology −485 — – −480 — – −475 — – −470 — – −465 — – −460 — – −455 — – −450 — – −445 — – Paleozoic Ordovician S Early Middle Late L Tremadocian Floian Dapingian Darriwilian Sandbian Katian Hirnantian Rhuddanian Ꞓ F Stage 10 ← First land plant spores ← Ordovician…
Ordovician-Silurian boundary on Hovedøya, Norway: the brownish late Ordovician mudstone and later dark deep-water Silurian shale layers have been overturned by the Caledonian orogeny.
Fossils of the late Silurian sea bed, England
Diorama of a Silurian seafloor
Cooksonia, the earliest vascular plant, middle Silurian