Diabasbrottet quarry

The Diabasbrottet quarry (58°21′32.2″N 12°30′08.6″E / 58.358944°N 12.502389°E / 58.358944; 12.502389), located on Mt. Hunneberg, Västergötland, Sweden, is the location of the Global Boundary Stratotype Section and Point (GSSP) which marks the boundary between the Floian and Tremadocian stages of the Early Ordovician. It was selected over "The Ledge" in western Newfoundland in 2000 and ratified as the GSSP by the International Union of Geological Sciences in 2002.

The first appearance of Tetragraptus approximatus, a graptolite, defines the boundary. The rock section, dominated by shale, is unusually fossiliferous, including fossilized remains of graptolites, conodonts, and trilobites. It is highly compressed, and the Ordovician section is only 12 m thick.

References

• "The Ordovician System" (DOC). http://www.quaternary.stratigraphy.org.uk/noticeboard/TheOrdovicianSystem.doc. Retrieved 2006-06-30. 
• Bergström, Stig M.; Anita Löfgren, Jörg Maletz (December 2004). "The GSSP of the Second (Upper) Stage of the Lower Ordovician Series: Diabasbrottet at Hunneberg, Province of Västergötland, Southwestern Sweden" (PDF). Episodes (274): 265–272. http://www.episodes.org/backissues/274/265-272%20Bergstrom.pdf. Retrieved 2006-06-30.