The Mascall Formation is a Miocene geologic formation found along the John Day River Valley of Oregon, in the Western United States.

Within the Mascall Formation is a widespread ignimbrite unit which consists of 97 to 99 percent glass shards and minor amounts of anorthoclase, quartz, magnetite, zircon, and clinopyroxene.

"[2][3] The ignimbrite was radiometrically dated at 13 million years.

[2] Parts of the Mascall are interfingered with the Columbia River Basalt Group.

This article about a specific stratigraphic formation in the United States is a stub.