Submission of Hartfell Score (south Scotland) as a GSSP for the base of the middle stage of the Upper Ordovician Series.
Reference:
Zalasiewicz,J. et al. (2004)
Submission of Hartfell Score (south Scotland) as a GSSP for the base of the middle stage of the Upper Ordovician Series. International Subcommission on Ordovician Stratigraphy, Report
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