Franconian (stage)

The Franconian is the middle stage of the Upper or Late Cambrian

Cambrian

The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

 in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, 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 in eastern Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

, north of St Paul.

The Franconian is preceded by the Dresbachian

Dresbachian

The Dresbachian is the lower stage of the Late or Upper Cambrian Period in North America, equivalent to the Chinese Guzhangian which spans about 4 million years, from...

 and followed by the Trempealeauan

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...

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