Will Elder, NPS
Graywacke sandstone is the product of underwater landslides that carry sand, silt, rock fragments, and plant and animal debris off of the continental margin and rapidly deposit them in deep ocean environments. Graywacke is associated with subduction zones, where sediments are being shed off a continent at high rates. Little sorting of mineral types, rock types, or particle size occurs before deposition of these rocks; hence their other name, "dirty sandstone."
Did You Know?
The National Cemeteries Act was based on the principles articulated by President Lincoln in his Gettysburg Address--"that these dead shall not have died in vain." Passed by Congress in 1863, the law established thirteen cemeteries to inter veterans of the Armed Forces and their families.