The Franconian is the middle stage of the Upper or Late

Cambrian The Cambrian Period ( ; sometimes symbolized 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 years ago ...

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 th ...

, 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 The Franconia Formation is a geologic formation in the upper mid-western United States, with outcroppings found in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. It preserves fossils dating back to the Cambria ...

, 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 ...

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 t ...

, 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