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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.
The ancestors of coleoids (including most modern cephalopods) and the ancestors of the modern nautilus, had diverged by the Floian Age of the Early Ordovician Period, over 470 million years ago. We know this because the orthocerids were the first known representatives of the neocephalopoda, [ 40 ] were ultimately the ancestors of ammonoids and ...
In common practice (e.g. MLK 1952, Weller 1960) the Canadian has been viewed as the Early, or Lower Ordovician. Flower however (1957, 1964) separated the Canadian from the rest of the Ordovician and defined it as a four-part system, divided in ascending order into the Gasconadian, Demingian, Jeffersonian, and Cassinian which stands today.
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.
Early Ordovician life (5 C, 1 P) F. Floian (14 P) L. Lower Ordovician Series (7 P) T. Tremadocian (19 P) Pages in category "Early Ordovician" The following 5 pages ...
This allows to judge the level of development of reef ecosystems of the Early Ordovician. [16] Conodonts Serratognathus, Prioniodus and Oepikodus were distributed in Kazakhstan, Korea, China, Indochina and Australasia during the Floian age. Two species of Paroistodus are known from the Floian deposits of Baltoscandia and South China. [17]
The Hirnantian glaciation, also known as the Andean-Saharan glaciation, Early Paleozoic Ice Age (EPIA), [1] the Early Paleozoic Icehouse, [2] the Late Ordovician glaciation, or the end-Ordovician glaciation, occurred during the Paleozoic from approximately 460 Ma to around 420 Ma, during the Late Ordovician and the Silurian period.