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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 Period in Britain was traditionally broken into Early (Tremadocian and Arenig), Middle (Llanvirn (subdivided into Abereiddian and Llandeilian) and Llandeilo) and Late (Caradoc and Ashgill) epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, or Upper part of the column.
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 Great Ordovician Biodiversification Event (GOBE) was an evolutionary radiation of animal life throughout [1] the Ordovician period, 40 million years after the Cambrian explosion, [2] whereby the distinctive Cambrian fauna fizzled out to be replaced with a Paleozoic fauna rich in suspension feeder and pelagic animals.
The Cambrian (/ ˈ k æ m b r i. ə n, ˈ k eɪ m-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. [5] The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma.
The Ordovician mass extinction did not leave the trilobites unscathed; some distinctive and previously successful forms such as the Telephinidae and Agnostida became extinct. The Ordovician marks the last great diversification period amongst the trilobites: very few entirely new patterns of organisation arose post-Ordovician.
Recent estimates (ICS and Cosuna) place the beginning of Gasconadian, and Ordovician, anywhere from about 488 to 500 million years ago, with a duration ranging from 9.7 to 10 million years respectively putting the end about 464 m.y.a. Both give estimates of over half the Early Ordovician. 60 percent according to the ICS, 2/3 according to Cosuna.
The Caledonian Wilson cycle commenced with the continental break-up of Rodinia [17] and the opening of the Iapetus ocean about 616–583 Ma ago. [18] [19] [20] The Iapetus was at its widest in the Late Cambrian–Early Ordovician [21] [1] before it began to close by subduction of Iapetus oceanic crust along the Gondawanan and Laurentian margins starting between 500 and 488 Ma ago.