Deadwood Formation

It is of Late Cambrian to Early Ordovician age and was named for exposures in Whitewood Creek near Deadwood, South Dakota.

[3] In Saskatchewan the Deadwood consists of fine to very coarse, commonly glauconitic, micaceous, feldspathic, slightly argillaceous and calcareous quartzose sandstones, with minor shales and conglomerates.

They typically consist of Precambrian rock fragments set in finer-grained sediments, and are normally poorly sorted and unstratified.

[6] In most areas the sediments of the Deadwood Formation were deposited in near shore, shallow water environments as an ancient sea advanced across the exposed and weathered landscape of Precambrian rocks.

It thickens westward throughout Saskatchewan and Montana to the Saskatchewan-Alberta border, where it exceeds 300 metres (980 ft).

The angular unconformity between the Deadwood Formation and the underlying Precambrian metamorphic rocks near Rapid City, South Dakota .
A piece of stone about the size of a typical flag stone, held up for the camera by someone. The rock has ridges and burrows throughout, and is pinkish-red.
A slab of the pinkish-red Cambrian Deadwood Sandstone float shows clear evidence of bioturbation and worm burrows. Exposed from an outcrop off SD 44, west of Rapid City.
A poorly-sorted, clast-supported, pebble-to-cobble, quartzic conglomerate sits on a bed of pine needles, with a rock hammer propped in front for scale. Section shows the typical Deadwood Fm coloring of pinkish-red.
A typical exposure of the basal conglomerate in the Deadwood Formation, near Nemo, SD. Note the lack of sorting and stratification in the clasts, as well as their mainly quartzic provenance. Rock hammer for scale.