Emery — Green River Desert Section, Utah. 565 



along the Reef the formation is white throughout its 

 entire thickness. Such inconstancy of color seems to 

 preclude its use as a diagnostic character, although it 

 was regarded as distinctive by Powell, Dutton, and Gil- 

 bert in their early reconnaissance work in Utah. The 

 extreme massiveness and cross-bedding of these sand- 

 stones, which features were of course recognized and 

 emphasized by these writers, seem indeed to be diagnostic 

 and to afford much safer ground for correlation pur- 

 poses than does color. 



There is generally a weaker zone between the massive 

 and resistant upper and lower portions of the Wingate 

 in both The Ledge and San Eafael Reef, but this zone 

 occurs at different stratigraphic positions in each section. 

 In the section at The Ledge it is 250 feet thick and starts 

 375 feet above the base of the formation, whereas in the 

 Temple Wash section it is only about 200 feet thick and 

 starts 150 feet above the base of the formation. The 

 beds in this zone are sandstones similar to those above 

 and below in all respects except that they are less mas- 

 sive, and so less resistant to erosion. There is no shale 

 or gypsum in this zone, but within a few feet of the top of 

 it in the Temple "Wash section are two beds of conglom- 

 erate each less than 4 feet thick containing angular lime- 

 stone and shale pebbles. These conglomerates lie about 

 550 feet below the top of the formation in this area. In 

 the section at The Ledge similar conglomerate was noted 

 about 100 feet below the top of the Wingate in the midst 

 of a thick series of very massive sandstones, but no such 

 conglomerate' is present here in the less massive middle 

 portion of the formation. Near the "Bowknot" loop of 

 the Green fragments of fossil wood are present in similar 

 conglomerate in the upper part of the Wingate. The con- 

 glomerate is apparently only locally developed and is 

 such as one would expect to form by the breaking up of 

 limestone and shale deposits laid down in little fresh 

 water lagoons. It marks no single definite horizon nor do 

 the less massive sandstone beds in the middle portion of 

 the Wingate represent a single period of widespread depo- 

 sition of this type. Rather they indicate that at different 

 times in different places conditions were right for the 

 deposition of more thinly bedded sandstone than were 

 laid down before or after. 



