The International Subcomission on Ordovician Stratigraphy (ISOS) of the International Commission on Stratigraphy (ICS) recently defined the base of the global Upper Ordovician Series to be at the first appearance datum (FAD) of the graptolite species Nemagraptus gracilis in the Fågelsång GSSP in southern Sweden. This designation recognized the tremendous utility for global correlation of the first appearance of a cosmopolitan taxon that occurs within a consistent succession of other first appearance datums (e.g., Finney and Bergström, 1986; Bergström et al., 2000). Current efforts by the ISOS have focused on subdividing the Upper Ordovician into three stages and choosing appropriate levels and stratotypes for the bases of the middle and upper of these stages. The purpose of the present report is to describe the GSSP of the middle stage, for which the name Katian Stage was approved by the ISOS and ratified by the ICS in 2006 (Bergström et al., 2006). For a recent review of the long process of developing the new subdivisions of the Ordovician, see Finney (2005).
Copyright © 2007, Geological Society of India
Geological Society of India
Goldman, Daniel; Leslie, Stephen A.; Nõlvak, Jaak; Young, Seth; Bergström, Stig M.; and Huff, Warren D., "The Global Stratotype Section and Point (GSSP) for the base of the Katian Stage of the Upper Ordovician Series at Black Knob Ridge, Southeastern Oklahoma, USA" (2007). Geology Faculty Publications. 6.
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