STEATIGRAPHIC SECTIONS IN UTAH AND .\KIZONA. 



59 



beds locally contain an abundance of a species 

 of Bellerophon and arc tlie "BelleropJwn lime- 

 stone" of some of the earlier geologists. 



The Kaibab limestone of our area, as is shown 

 in the data here presented, differs from that of 

 the typical area in the absence of definite large 

 sandstone units. This difference is apparent 

 even in Hacks Canyon and Toroweap Valley. 

 The upper cherty limestone of the Shinumo sec- 

 tion (see p. 58) is comparable to our Harrisburg 

 gypsiferous member, the 200-foot limestone 

 to our upper cliff-forming member, the next 

 lower 155 feet to our upper slope-forming 

 member, the next lower 400 feet to our lower 

 cliff-forming member, and the thin lower sand- 

 stone to our lower slope-forming member. 



Longwell '" found in the Muddy Mountains 

 of Nevada that the Kaibab limestone contained 

 four divisions much like our four lowest mem- 

 bers described above. The Harrisburg gyp- 

 siferous member, if present, is placed in his 

 Moenkopi formation. The thickness ranges 

 from 400 to 700 feet. 



In tabular form the thickness of the several 

 units in our sections may be stated thus: 



Thickness of members of the Kaibab limestone, in feet. 



fl Numbers refer to detailed sections given on pp. 69-77, except No. 23, 

 which is the section in tile typical area in the Shinumo quadrangle, and 

 to localities shown on the map (fig. 10} . 



i*^ Longwell, 0. R., Geology of the Muddy Mountains, Nev., with a 

 section to the Grand Wash Cliffs in western Arizona: Am. Jour. Sci. 

 Sthser., vol. 1, p. 48, 1921. 



MOENKOPI FORMATION. 



The name Moenkopi formation was applied 

 by Ward " to the beds known in the older 

 literature as the lower division of the "Shina- 

 rump group, " boiuided below by Carboniferous 

 limestone and above by the Shinarump con- 

 glomerate. A generalized section compiled 

 by Gregory ^^ from Ward's descriptions gives 

 a thickness of about 700 feet, composed of 

 saliferous and gypsiferous chocolate-brown 

 shale and sandstone in the upper 500 feet, 

 imderlain by 100 feet of wliite calcareous 

 shales, underlain in tm'n by 100 feet of brown 

 shale. Ward mentions a discontinuous bed 

 of white impure limestone in the calcareous 

 unit. Gregorv gives also an accurate section 

 to serve as a type section, measured on Little 

 Colorado River 5 miles below Tanner's Crossuig 

 and showing a thickne.ss of 389 feet, mainly 

 red and brown gypsiferous shale and sand- 

 stone, with unconformities at the top and 

 bottom. Some conglomerate also is present. 

 In eastern Arizona Gregory found a massive 

 sandstone formation, the De Chelly sandstone, 

 appearing between the ordinary Moenkopi 

 red beds and the Shinarump conglomerate. 



Shimer '^ traced the Moenkopi formation 

 from the type locality to Hurricane, Utah, 

 and found it, though variable m composition, 

 to extend over the entu'e area as a series of 

 "thin-bedded red shales and sandstones, sep- 

 arated at usually rare mtervals b}^ limestone 

 lenses." 



In the area reconnoitered l)y us the beds 

 that lie between the Carboniferous limestone 

 and the Shinarump conglomerate and are 

 referred to the Moenkopi formation are much 

 thicker than at the typical locality. They 

 may be grouped into five persistent lithologic 

 imits, with another discontinuous one at the 

 base of the formation. The persistent units 

 are (1) lower red beds, consisting of red to 

 brown shale and sandstone with soft tan sand- 

 stone near the base and gypsum thi'oughout in 

 layers, streaks, and veinlets; (2) a limestone 

 member consisting normally of three layers of 

 yellow earthy limestone separated by yellow 

 and red calcareous shale and carrying abundant 



u Ward, L. F., Statu.s of the Mesozoic floras of the United States; 

 U. S. Geol. Survey Mon. 4S, pt. 1, pp. l.S-19, 1905. 



^ Gregory, H. E., Geology of the Navajo country: U. S. Geol. Survey 

 Prof. Paper 93, p. 23, 1917. 



13 Shimer. H. W., Perrao-Triassic of northwestern Arizona: Geol. Soc. 

 America Bull., vol. 30, pp. 493-494, 1919. 



