The Floian is the second stage of the

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The lower boundary is defined as the first appearance of the graptolite species '' Tetragraptus approximatus''.

Naming and history

The Floian Stage is named after

Flo ''Flo'' is an American sitcom television series and a spin-off of ''Alice'' that aired on CBS from March 24, 1980, to June 30, 1981. The series starred Polly Holliday reprising her role as sassy and street-smart waitress Florence Jean "Flo" Castl ...

, a village in

Västergötland Västergötland (), also known as West Gothland or the Latinized version Westrogothia in older literature, is one of the 25 traditional non-administrative provinces of Sweden (''landskap'' in Swedish), situated in the southwest of Sweden. Vä ...

, southern Sweden. The name "Floan" was proposed in 2004, but the

International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigr ...

adapted Floian as the official name of the stage.

GSSP

The

GSSP A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted ...

of the Floian is the Diabasbrottet Quarry () which is an outcrop of a shale-dominated stratigraphic succession. The lower boundary of the Floian is defined as the first appearance of '' Tetragraptus approximatus'' which is above the base of the Tøyen Shale. Radiometric dating has set the Tremadocian-Floian boundary at million years ago.

References

{{Geological history, p, p, state=collapsed . Ordovician geochronology