Grainstone

Thin-section of a grainstone with calcitic ooids; Carmel Formation, Middle Jurassic, of southern Utah, USA.

Grainstone (Brassfield Formation near Fairborn, Ohio, USA). Grains are crinoid fragments.

Under the Dunham classification, grainstones are grain-supported carbonate sedimentary rocks that contain no micrite. The spaces between grains are filled with sparry cement.

References

• Dunham, R.J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W.E., ed., Classification of carbonate rocks: American Association of Petroleum Geologists Memoir 1, p. 108-121.