Named for exposures at Sage Junction (U.S. Hwys 30N and 89), NW1/4 SE1/4 and S1/2 NW1/4 sec 7, T21N, R119W, Lincoln Co, WY in the Greater Green River basin. Consists of light-gray and locally tan calcareous sandy siltstone; fine- to very fine but partly medium-grained sandstone and quartzite; light-gray, tan, and grayish-red mudstone and claystone; some thin beds of grit and conglomerate in upper part; numerous thin beds of white, gray, and green to pink porcelanite through all but uppermost several hundred ft; a few brown to gray fossiliferous limestone beds. A few thin coal beds are in the lower part. Is 2,270+ ft thick at type section where it overlies Cokeville Formation (new name). Is unconformably overlain by Tertiary and Quaternary strata. A section 4 mi north-northeast of type in sec 20, T22N, R119W that is 1,100 ft thicker than type is designated a reference section. Fossils (leaves, mollusks, gastropods) indicate an Early Cretaceous age. Correlates with Aspen Shale; the upper part of Sage Junction may be equivalent in age and lithologic character to parts of Frontier Formation to east. May be equivalent to Aspen Shale.

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