In the geologic timescale, the Roadian is an age (geology), age or stage (stratigraphy), stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian Epoch (geology), Epoch or series (stratigraphy), Series. The Roadian lasted between and megaannum, million years ago (Ma). It was preceded by the Kungurian and followed by the Wordian.

Stratigraphy

In 1961, the regional timescale used for the southeastern US had the Wordian and Capitanian as subdivisions of the Guadalupian. Efforts to correlation, correlate the Permian stratigraphy of the southeastern US with that of Russia led to the conclusion that between the Wordian stage and the Russian Artinskian stage, another stage needed to be introduced. This stage, the Roadian Stage, was established in 1968 and took its name from the Road Canyon Formation in Brewster County, Texas, formerly considered the lower (oldest) part of the Word Formation. The stage was added to the internationally used IUGS timescale in 2001.; 1999: ''Proposal of Guadalupian and Component Roadian, Wordian and Capitanian Stages as International Standards for the Middle Permian Series'', Permophiles 34: pp 3–11. The base of the Roadian is defined as the place in the stratigraphic record where fossils of conodont species ''Jinogondolella nankingensis'' first appears. The global reference profile for the base (the GSSP) is located in Stratotype Canyon in the Guadalupe Mountains, Texas (). The top of the Roadian (the base of the Wordian Stage) is at the first appearance of fossils of conodont species ''Jinogondolella aserrata''.

Biodiversity

Olson’s Extinction, a worldwide loss of terrestrial vertebrate life occurred during the Permian#anchor 2, Early Guadalupian (Roadian, Wordian).

References

Literature

External links

GeoWhen Database - RoadianUpper Paleozoic stratigraphic chart
at the website of the subcommission for stratigraphic information of the ICS {{Geological history, p, p Roadian, Permian geochronology Permian North America, . Permian geology of Texas