Pg. 1840-1841, 1842-1843, 1845-1846. Ali Baba member of Moenkopi formation. Recognized in southwestern Colorado and southeastern Utah. Consists mainly of red-brown to purplish ledge-forming beds of conglomeratic arkosic sandstone separated by interbedded red- and chocolate-brown silty shale and thin layers of fine- and coarse-grained sandstone. Exhibits marked facies change from northeast to southwest near Uncompahgre Plateau, to northeast, ledge-forming beds of sandstone are highly arkosic, heavily conglomeratic, and constitute dominant part of member. To southwest, sandstones become progressively finer grained, better sorted, and less abundant. Southwest of Moab Valley becomes lithologically indistinguishable from overlying Sewemup member (new). Thickness 0 to 290 feet. Over most of salt anticline region, Ali Baba unconformably overlies Tenderfoot member (new), and locally in Sinbad Valley, Paradox Valley, and around Fisher Valley unconformity is sharply angular. In Sinbad Valley, rests locally on Paradox member of Hermosa formation. In Paradox Valley, rests in places on Cutler formation. In Fisher Valley, rests locally on the Cutler and on Paradox member. Cut out toward Uncompahgre Plateau in vicinity of Gateway, Colorado, by angular unconformity at base of Chinle. In Sinbad Valley, thins locally by internal angular uncomformities and is overlapped by Sewemup and Pariott (new) members toward axis of salt anticline. Age is Early Triassic.
Type section: east side of Sinbad Valley, in sec. 15, T. 49 N., R. 19 W., Mesa Co., southwestern CO. Named from Ali Baba Ridge in Sinbad Valley, hogback underlain by conglomeratic sandstone of member.

Source: US geologic names lexicon (USGS Bull. 1200, p. 51).