The base of the Sandbian Stage is defined 1.4m below a phosphorite marker bed in the E14b outcrop along the south bank of the Sularp Brook at Fågelsång, 8km east of the center of the city of Lund, Scane, southern Sweden. This level coincides with the first appearance datum of the graptolite Nemagraptus gracilis.
The GSSP Section is located along the south bank of the Sularp Brook at Fågelsång, 8km east of the center of the city of Lund, Scane, southern Sweden at a latitude of 55°42'49.3"N and a longitude of 13°19'31.8"E (according to Google Earth).
The Fågelsång Section is condensed, but remarkably complete. It consists mainly of dark-gray shale and mudstone. About 1.4m above the base of the Nemagraptus gracilis Biozone is a 0.15m thick, partly conglomeratic and pyritic bed of phosphorite. A few centimeters below this phosphorite bed is a 2 - 3cm thick layer of partly conglomeratic, fine-grained limestone.
The first appearance of graptolite Nemagraptus gracilis is 1.4m below a phosphorite marker bed.
Graptolite FAD Nemagraptus gracilis
The base of the Nemagraptus gracilis graptolite biozone can be recognized at Calera, Northeast U.S.A. and in a section in the Dawangou Gorge, Tarim, Zinjiang Autonomous Regioan, westernmost China.
Bergström, S. M., Finney, S. C., Chen Xu, Påsson, C., Wang Zhi-hao, and Grahn, Y., 2000. A proposed global boundary stratotype for the base of the Upper Series of the Ordovician System: The Fågelsång section, Scania, southern Sweden. Episodes 23/3, p. 102 - 109.