Pg. 275, 300-306, 329-337, 345-349, figs. 1-5, 11-17. Olcott Formation of Hemingford Group. Fluviatile deposit. Consists of massive, well-sorted brown and gray quartz sand, silty sand, and gray sandy ash. Thickness up to about 78 feet. Is uppermost formation of Hemingford Group; formerly called "Lower Snake Creek" beds by Matthew (Amer. Mus. Nat. Hist. Bull., v. 50, art. 2, p. 71, 1924). Unconformably underlies Snake Creek Formation (restricted) of Ogallala Group; formations separated by an erosional hiatus representing medial to late Barstovian NALMA and all of Valentinian [approx. = latest Barstovian to earliest Clarendonian NALMA]. Unconformably overlies Harrison Formation of Arikaree Group, or, locally, Sheep Creek Formation (restricted) of Hemingford Group. Fossils (vertebrates). Includes Lower Snake Creek fauna. Age is middle Miocene (early Barstovian NALMA). Formation includes several quarries in its type area, in Matthew's (1924, p. 63, fig. 1) "Sinclair draws" and "Olcott Hill." Quarries in the "Sinclair draws" area are grouped into 3 depositional subcycles, which are separated by minor erosional hiatuses.
Type section: on northeast face of Matthew's (Amer. Mus. Nat. Hist. Bull., v. 50, art. 2, 1924, p. 63, fig. 1) "Olcott Hill," in NW/4 SE/4 SE/4 sec. 3, T. 25 N., R. 55 W., [University Lake NW 7.5-min quadrangle], Sioux Co., northwestern NE. [Recognized locally in type area.]

Source: Publication; US geologic names lexicon (USGS Bull. 1564, p. 121).

Pg. 211, 212 (fig. 4). Olcott Formation of Ogallala Group. Transferred to Ogallala Group, [†Hemingford Group abandoned]. Is older than Valentine Formation and younger than Sheep Creek Formation (both of Ogallala Group). Age is Miocene, [shown on fig. 4 from about 15 to 14 Ma +/-].

Source: Publication.