File:Quartzose breccia (Deadwood Sandstone, Upper Cambrian; Hayward West Hilltop Outcrop, east of Keystone, Black Hills, South Dakota, USA) 1.jpg

English: Quartzose breccia from the Cambrian of South Dakota, USA. (7.9 cm across at its widest)

Outcrops of the Upper Cambrian Deadwood Sandstone encircle the Black Hills Uplift in western South Dakota. The unit represents the initial Cambrian transgression onto what is now Black Hills Precambrian basement rocks. The basal Deadwood Sandstone is usually conglomeratic, as are most transgressive, coarse-grained siliciclastic successions. The above sample is from the basal Deadwood - the pebbles are angular to subangular, not rounded, so this is better called a breccia, not a conglomerate. The shiny grains are muscovite mica. The reddish brown coloration is due to iron oxide. A full lithologic term for this sample would be: ferruginous, muscovitic, quartzose breccia.

The Deadwood Sandstone was deposited in a shallow marine facies.

Stratigraphy: basal Deadwood Sandstone, Upper Cambrian

Locality: Hayward West Hilltop Outcrop - roadcut on the southern side of Rt. 40, ~1.35 miles west-northwest of the town of Hayward (measured along the road) & east of the town of Keystone, eastern Black Hills, western South Dakota, USA (43° 52' 37.01" North latitude, 103° 21' 23.64" West longitude)