Mascall Formation

{{Short description|Geological formation in Oregon, United States}} {{Infobox rockunit | name = Mascall Formation | image = Mascall Formation near Picture Gorge.jpg | caption = Outcrop near Picture Gorge | type = [[Sedimentary]] | age = [[Hemingfordian]]-[[Barstovian]]<br>~{{fossil range|20.4|13.6}} | period = Langhian | prilithology = [[Sandstone]], [[conglomerate (geology)|conglomerate]] | otherlithology = | namedfor = Mascall Ranch (south of [[Dayville, Oregon|Dayville]]) | namedby = J. C. Merriam | year_ts = 1901<ref>Merriam, J. C., 1901. A contribution to the geology of the John Day Basin, Oregon: Univ. Calif., Dept. Geol. Sci. Bull., v. 2, p. 269-314.</ref> | region = | country = | coordinates = | unitof = | subunits = | underlies = [[Rattlesnake Formation]] | overlies = [[John Day Formation]] | thickness = {{convert|2000|ft|m}} | extent = eastern [[Oregon]] | area = John Day Valley, Fox Basin | map = | map_caption = }} [[File:NPS john-day-fossil-beds-geologic-map.jpg|thumb|right|250px|John Day Fossil Beds map]] The '''Mascall Formation''' is a [[Miocene]] [[geologic formation]] found along the [[John Day River|John Day River Valley]] of [[Oregon]], in the [[Western United States]].

==Description== The formation is described in ''Geologic Formations of Eastern Oregon'' (1972) 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 (geology)|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]]."<ref name=GFOEO>''Geologic Formations of Eastern Oregon'' (East of longitude 121°30'), 1972. John D. Beaulieu. [http://www.oregongeology.org/pubs/B/B-073.pdf Bulletin 73]. Oregon Department of Geology and Mineral Industries.</ref><ref>Davenport, R. E., 1970. ''Geology of the Rattlesnake and older ignimbrites in the Paulina Basin and adjacent area, central Oregon'': [[Oregon State University]] doctoral dissertation, 132 p., unpublished. </ref>

==Age== The ignimbrite was [[Radiometric dating|radiometrically dated]] at 13 million years.<ref name=GFOEO/> Parts of the Mascall are interfingered with the [[Columbia River Basalt Group]].

==Fossils== [[Barstovian]] [[vertebrate]]s have been recovered from the Mascall.

==References== {{Reflist}}

[[Category:Geologic formations of Oregon]] [[Category:Neogene geology of Oregon]] [[Category:Sandstone formations of the United States]] [[Category:Tuff formations of the United States]] [[Category:Conglomerate formations of the United States]]