Pg. 9-11, 24-27. Calvert ash bed of Ash Hollow member of Ogallala formation. Name applied to volcanic ash bed. Thickness about 22 feet. Lies in lower half of Ash Hollow member and stratigraphically lower than Reager ash (new). Age is Pliocene.
Named from pit of Wyandotte Chemicals Corp., at Calvert, northeastern Norton Co., northwestern KS.

Source: US geologic names lexicon (USGS Bull. 1200, p. 587).

Pg. 244 (fig. 1), 251. Calvert ash bed of Valentine member of Ogallala formation. Reallocated to Valentine member. Present in northwestern Kansas. Age is Pliocene.

Source: US geologic names lexicon (USGS Bull. 1200, p. 587).

Calvert Mine Ash Bed of Ogallala Formation. A volcanic ash in Norton County, northeastern Kansas. Is Calvert Ash Bed of Carey and others (1952), Calvert Volcanic Ash Bed of Frye and others (1956). Previously included in the Valentine Member of Ogallala Formation; authors restrict the Valentine from Kansas. Geochemical studies suggest source of this ash bed is the Bruneau-Jarbridge volcanic field of Snake River Plain volcanic province, southern Idaho. Age is middle Miocene; Clarendonian NALMA, basal C5 chron zone (reversed magnetic polarity). S.L. Potter, 1991 (Fort Hays State Univ., MS thesis) reported a fission-track age of 11.5 +/-0.48 Ma. (Miocene boundaries and subdivisions based on Alroy, 2000, Gradstein and others 2004, Harland and others, 1990, Hilgen and others, 2005, International Commission on Stratigraphy, June 2009, Steinminger and others, 1997, and Van Couvering and others, 2000.)

Source: Publication.