The Franconian is the middle stage of the Upper or Late

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, equivalent to the Chinese Changshanian with a span of nearly 4.5 million years, from about 497 to 492.5 Ma. The name comes from the Franconia Formation, about 100 feet (30 m) of sandstone and green shale exposed near the town of

Franconia Franconia (german: Franken, ; Franconian dialect: ''Franggn'' ; bar, Frankn) is a region of Germany, characterised by its culture and Franconian dialect (German: ''Fränkisch''). The three administrative regions of Lower, Middle and Upper Fr ...

in eastern

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

, north of St Paul. The Franconian is preceded by the

Dresbachian The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 million years ago. It is part of the Upper Cambrian and is defined by four trilobite zones. It overlaps with the International Commission on Stratigraphy, IC ...

and followed by the

Trempealeauan The Trempealeauan is the upper or latest stage of the Upper or Late Cambrian in North America, spanning about 4 million years from about 492.5 to 488.3 m.y.a., equivalent to the Fengshanian of China. The name comes from the Trempealeau Formation, ...

, respectively the lower and upper stages of the North American Upper Cambrian or Croixan Series.

References

* Chen Jun-yuan & Teichert C, 1983; Cambrian Cephalopods, Geology Vol 11, pp647–650, Nov 1983 * Flower R.H.1964, The Nautiloid Order Ellesmerocerida (Cephalopoda) Menoir 12, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM *Harland, W. B. et al1 990. A Geologic Time Scale 1989. Cambridge University Press, Cambridge . Ref in Paleobiology Database on line. * Moore, Lalicker, and Fischer 1952; Invertebrate Fossils; McGraw- * Geowhen database

Cambrian geochronology Cambrian Minnesota Jiangshanian Paibian {{geochronology-stub