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Floian

From HandWiki - Reading time: 3 min

Short description: Second and last age of the Early Ordovician epoch
Floian
477.7 ± 1.4 – 470.0 ± 1.4 Ma
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of the Graptolite Tetragraptus approximatus
Lower boundary GSSPDiabasbrottet quarry, Västergötland, Sweden
[ ⚑ ] 58°21′32″N 12°30′09″E / 58.3589°N 12.5024°E / 58.3589; 12.5024
GSSP ratified2002[1]
Upper boundary definitionFAD of the Conodont Baltoniodus triangularis
Upper boundary GSSPHuanghuachang section, Huanghuachang, Yichang, China
[ ⚑ ] 30°51′38″N 111°22′26″E / 30.8605°N 111.3740°E / 30.8605; 111.3740
GSSP ratified2007[2]

The Floian is the second stage of the Ordovician 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 477.7 to 470 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.[3]

Naming and history

The Floian Stage is named after Flo, a village in Västergötland, southern Sweden. The name "Floan" was proposed in 2004, but the International Commission on Stratigraphy adapted Floian as the official name of the stage.[4]

GSSP

The GSSP of the Floian is the Diabasbrottet Quarry ( [ ⚑ ] 58°21′32″N 12°30′09″E / 58.3589°N 12.5024°E / 58.3589; 12.5024) 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.[4] Radiometric dating has set the Tremadocian-Floian boundary at 477.7 million years ago.[3]

References




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