GSSP for Katian Stage
Definition:
The base of the Katian Stage is defined at the 4.0m-level above the base of the Bigfork Chert in the Black Knob Ridge Section, southeastern Oklahoma, U.S.A. The GSSP coincides with the first appearance datum of the graptolite Diplacanthograptus caudatus. The FAD of D. caudatus occurs very near the first occurrences of D. lanceolatus, Corynoides americanus, Orthograptus pageanus, Orthograptus quadrimucronatus, Dicranograptus hians, and Neurograptus margaritatus.
Location:
The GSSP Section is located on the western slope of Black Knob Ridge about 5km north of the town of Atoka, Atoka County, Oklahoma, U.S.A. (SW1/4, Section 31, T. 1S, R. 12E) at a latitude of 34°25'49.74"N and a longitude of 96° 4'28.38"W (GPS coordinates provided by Steve Leslie and Dan Goldman; and supersede values in the Episodes article).
The Black Knob Ridge Section is comprised of about 50m of black, graptolite-rich Womble Shale, overlain by 145m of Bigfork Chert, followed by the Polk Creek Shale. The Bigfork Chert is composed of nodular and bedded chert which is intercalated with black shale and siliceous limestone. The GSSP is located 4.0m above the base of the Bigfork Chert.
Primary Markers:
First appearance of graptolite Diplacanthograptus caudatus 4.0m above the base of the Bigfork Chert.
Secondary Markers:
Graptolites The first occurrences of D. lanceolatus, Corynoides americanus, Orthograptus pageanus, Orthograptus quadrimucronatus, Dicranograptus hians, and Neurograptus margaritatus occur very near the FAD of Diplacanthograptus caudatus. Conodonts The GSSP is located in the uppermost part of the Amorphognathus tvaerensis conodont zone.
Correlation Events:
Graptolite FAD Diplacanthograptus caudatus
Other Locations around the World:
The base of the Katian Stage at Black Knob Ridge can be easily correlated with sections in Australia, Scotland, China, Newfoundland, Eastern North America and Scandinavia with the help of the FAD of Diplacanthograptus caudatus and the FADs of D. lanceolatus, Corynoides americanus, Orthograptus pageanus, Orthograptus quadrimucronatus, Dicranograptus hians, and Neurograptus margaritatus