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South of the Brigantes, the geographer Ptolemy reported three tribes whose territories stretched from the Irish Sea to the North Sea. The Ordovices occupied the westward lands and had two noteworthy cities, Branogenium which was located 195 Roman miles from London, most likely at Leintwardine, and Mediolanum which was located 200 Roman miles from London.
The Early Ordovician is the first epoch of the Ordovician period, corresponding to the Lower Ordovician series of the Ordovician system. It began after the Age 10 of the Furongian epoch of the Cambrian and lasted from 486.85 to 471.3 million years ago, until the Dapingian age of the Middle Ordovician .
The Ordovician–Silurian extinction events may have been caused by an ice age that occurred at the end of the Ordovician Period, due to the expansion of the first terrestrial plants, [54] as the end of the Late Ordovician was one of the coldest times in the last 600 million years of Earth's history.
The Darriwilian is the upper stage of the Middle Ordovician.It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species Undulograptus austrodentatus around 469.4 million years ago.
In the geological timescale, the Llandovery Epoch (from 443.8 ± 1.5 million years ago to 433.4 ± 0.8 million years ago) occurred at the beginning of the Silurian Period. . The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosyste
The Late Ordovician is the third and final epoch of the Ordovician period, lasting 15.1 million years and spanning from around 458.2 to 443.1 million years ago. [ 4 ] [ 5 ] The rocks associated with this epoch are referred to as the Upper Ordovician Series.
Panorama of part of the Snowdon Massif including Snowdon (centre right) taken from Mynydd Mawr.The Glyderau are visible in the distance.. The bedrock geology of Snowdonia is largely formed from a sequence of sedimentary and igneous rocks originating during the early Palaeozoic (the Cambrian, Ordovician and Silurian periods, lasting between 539 and 419 million years ago).
The Ordovician Period of the Paleozoic Era, in the Phanerozoic Eon.. This category contains events which happened in the Ordovician, a division of the geologic time scale.See geologic time scale for information about its divisions and how they relate to each other.