The Katian is the second stage of the Upper Ordovician. It is preceded by the

Sandbian The Sandbian is the first stage of the Upper Ordovician. It follows the Darriwilian and is succeeded by the Katian. Its lower boundary is defined as the first appearance datum of the graptolite species '' Nemagraptus gracilis'' around million yea ...

and succeeded by the

Hirnantian The Hirnantian is the final internationally recognized stage of the Ordovician Period of the Paleozoic Era. It was of short duration, lasting about 1.4 million years, from to Ma (million years ago). The early part of the Hirnantian was charac ...

Stage. The Katian began million years ago and lasted for about 7.8 million years until the beginning of the

million years ago. During the Katian the climate cooled which started the

Late Ordovician glaciation The Andean-Saharan glaciation, also known as the Early Palaeozoic Icehouse, the Early Palaeozoic Ice Age, the Late Ordovician glaciation, the end-Ordovician glaciation, or the Hirnantian glaciation, occurred during the Paleozoic from approximatel ...

Naming

The name Katian is derived from Katy Lake (

Atoka County Atoka County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 14,007. Its county seat is Atoka. The county was formed before statehood from Choctaw Lands, and its name honors a Choctaw Chief named ...

Oklahoma Oklahoma (; Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a state in the South Central region of the United States, bordered by Texas on the south and west, Kansas on the north, Missouri on the northeast, Arkansas on the east, New ...

, United States).

GSSP

The GSSP of the Katian Stage is the Black Knob Ridge Section in southeastern

(United States). It is an outcrop of the Womble Shale and the Bigfork Chert, the latter containing the lower boundary of the Katian. The lower boundary is defined as the

first appearance datum First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a particu ...

of the

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian ( Miaolingian, Wuliuan) through t ...

species '' Diplacanthograptus caudatus''. This horizon is 4.0 m above the base of the Bigfork Chert.

References

. Ordovician geochronology {{Geology-stub