This paper summarizes' certain results-obtained in recent field work in eastern Utah and adjacent parts of Arizona, New Mexico, and Colorado and revises the interpretations and correlations of the Jurassic formations of the area as they are affected by these results. The name "Glen Canyon group" is applied to the lower part of the sequence, including the Wingate sandstone, the Kayenta formation, and the Navajo sandstone. The name "Kayenta" is used for the beds heretofpre correlated doubtfully with the Todilto limestone of New Mexico. The Wingate sandstone and Kayenta formation form large lenses whose boundaries can be approximated, particularly on the northeast and southwest. The Navajo sandstone forms a great wedge with the thick part to the southwest in Nevada and the thin edge in western Colorado. It is not known to enter New Mexico. It is believed that the typical Nugget sandstone is equivalent to the Navajo sandstone. Questions as to the real relationship of the formations are raised by differences between the Navajo sandstone and the Wingate and Kayenta formations in distribution and lithologio character and by .the nature of the lower boundary of the Wingate, but for convenience they are kept together as a group. The name "San Rafael group" applies to the middle part of the sequence, including the Carmel formation, the Entrada sandstone, the Curtis formation, and the Summerville formation. All these formations continue northwestward beyond the area considered but are sharply limited on the south, scarcely entering Arizona and New Mexico. The Carmel and Summerville formations do not extend far eastward into Colorado. The Curtis formation is interpreted as represented in the area considered in this paper by several fairly well defined lobes extending southeastward, one of which enters northwestern Colorado and has been misidentified as Twin Creek formation in recent literature. The Entrada sandstone is interpreted as extending widely into Colorado, where it forms the lower part of the typical. fLa Plata sandstone V of Cross and the upper part of the so-called "Nugget" sandstone of northwestern Colorado. The Morrison formation is interpreted as including, besides the more usual variegated mudstones (fMcElmo formation of many authors), in New Mexico the Todilto limestone and beds heretofore called " Navajo" sandstone (fZuni sandstone of Button) and in Colorado beds formerly assigned to the middle and upper f La Plata sandstone by Cross and others. Ten series of columnar sections are presented and discussed to show in some detail the correlations offered in the paper, and a summary diagram assembling the sections into one picture is presented. Eight tables are shown to interpret the nomenclature of previous publications in terms of the nomenclature of this paper.

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Mapped, edited, and published by the Geological SurveyControl by USGS and USC&GS Topography from aerial photographs by multiplex methods Aerial photographs taKen 1946. Field check 1948 Polyconic projection. 1927 North Am_erican datum 10,000-foot Qrid based ori Utah coordinate system, central zone Unchecked elevations are shown in brown Dashed land lines indicate approximate location

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