Geologic heroin at the Pallisades of John Day Fossil Beds Nat'l Monument, Clarno Unit, OR.
A volcanic complex to the south produced prodigious ash fall and tuffs. Over time these slid away in lahars or welded into ignimbrite. In this area this led to huge, well-stratified, windswept cliffs that include many fossils, mostly petrified wood and leaf impressions. This is the Pallisades Mudflow Member of the Clarno Formation (57-40 Ma or so)