Mascall Formation

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

Description

The formation is described in Geologic Formations of Eastern Oregon as follows: "The Mascall Formation consists of a maximum of 2,000 feet of fluvial sandstone, ash, light colored water-laid tuff, and well-rounded conglomerate. 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."

Age

The ignimbrite was radiometrically dated at 13 million years. Parts of the Mascall are interfingered with the Columbia River Basalt Group.

Fossils

s have been recovered from the Mascall.