The Cassinian is the latest age of the
Canadian Epoch {{Short description, Lower or Early Ordovician in North America
The Canadian is the Lower or Early Ordovician in North America. The term is common in the older literature and has been well understood for more than a century. However it has no offici ...
when thought of temporally and the uppermost stage of the Canadian Series when thought of stratigraphically. The Canadian, either as a series or as an Epoch is the name that has been given to the Lower, or Early, Ordovician in North America and has been applied worldwide.
[Flower, R. H. 1964. The Nautiloid Order Ellesmeroceratida (Cephalooda), Memoir 12, State Bureau of Mines and Mineral Resources, Socorro, New Mexico.][Moore, Lalicker, and Fischer 1952. Invertebrate Fossils, McGraw-Hill]
The Cassinian is named for the Fort Cassin Formation of Vermont. Rocks of Cassinian age are found in the Champlain Valley and among other places in North America in the Great Basin of Western Utah and Nevada, and in the uppermost El Paso Group in southern New Mexico and west Texas.
[
The Cassinian has been given a span of only 1.2 million years, with a range from 473 - 471.8 m.y.a.]
Geowhencephalopod
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
evolution [Teichert et al, 1964. Treatise on Invertebrate Paleontology Part K Mollusca 3, Teichert and Moore eds.]
In worldwide terms the Cassinian is upper, or late Arenigian which is exactly equivalent to the newly proposed Floian
The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The ...
, both spanning the same 6.8 million years.[ In the four part Canadian series, the Cassinian is late upper Canadian, preceded by the Jeffersonian, and is equivalent to the upper Blackhillsian stage of the ]Ibexian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. 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 Ordovici ...
which has been sought to replace the Canadian as the Lower Ordovician in North America. However the Ibexian, named for the Ibex region in western Utah, extends 2.7 .m.y. into the Cambrian taking up more than half of the Trempealeauan.[ The Cassinian is followed in North America by the ]Whiterockian
The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in ...
and by the newer ICS Dapingian
The Dapingian is the third stage of the Ordovician system and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The base of the Dapingian (and the top of the Floian) is defined as t ...
, given respective durations of 9.8 and 3.7 m.y. and in older chronologies [ by the 7.8 million year Llanvirnian.
]
''References''
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Paleozoic