The Franconian is the middle stage of the Upper or Late

Cambrian 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 Ordov ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, 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 ( ; ; ) is a geographical region of Germany, characterised by its culture and East Franconian dialect (). Franconia is made up of the three (governmental districts) of Lower Franconia, Lower, Middle Franconia, Middle and Upper Franco ...

in eastern

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

, north of St Paul. The Franconian is preceded by the Dresbachian and followed by the Trempealeauan, 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