Named as one of six members of Lake Valley formation for Pryor Nunn Ranch on Tierra Blanca Creek, Otero Co, NM where excellent exposures and unusually prolific crinoid faunas have been collected. Type section is on Apache Hill at the type section of Lake Valley formation, NE1/4 NW1/4 sec 21, T18S, R7W, Sierra Co, NM in Orogrande basin. Consists of soft, blue-gray marls and nodular, crinoidal limestone beds which lie above the massive Alamogordo member (revised) of Lake Valley and beneath the more massive, gray, cherty beds of the Tierra Blanca (new) member of Lake Valley. The famous Lake Valley crinoids occur in Nunn member. Although crinoids occur in other members, the prolific faunas are invariably in the Nunn. Thickness varies from 100 ft in Santa Rita area (Grant Co, Basin-and-Range province) to 1 ft in Sacramento Mountains area (Otero Co, Orogrande basin). Rapid lateral variation in thickness is common in Sacramento Mountains where biohermal structures occur. Is Osage (Mississippian) in age. Measured sections, cross sections, areal extent maps.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Is a member of Lake Valley Limestone in southwest NM. Columnar sections at Bear Mountain, Grant Co, and in North Cooks Range, Luna Co (both in southeastern Basin-and-Range province) and at Lake Valley, Sierra Co (western Orogrande basin). Overlies Alamogordo Member of Lake Valley; underlies Tierra Blanca Member of Lake Valley. Is not present in section at Bear Mountain, where Alamogordo underlies Tierra Blanca; absence apparently due to facies change. No microfossil zone data; stratigraphic position dating indicates equivalent to upper part zone 7 (Osagean, Lower Mississippian). Regional correlations on fig. 2; is correlated with middle part of Witch Member of Keating Formation in Escabrosa Group in Pedregosa basin. Kinderhookian-Osagean provincial series boundary questionably placed at lower contact of Nunn. Age is Osagean (Early Mississippian).

Source: GNU records (USGS DDS-6; Denver GNULEX).