STRATIGRAPHIC SECTIONS IN UTAH AND ARIZONA. 



61 



forms a conspicuous member of the Moenkopi 

 formation, perhaps 75 feet thick, and may be 

 traced as a series of three marked benclies 

 near the base of the red cHffs of softer rock 

 which stand high above the Hurricane fault 

 scarp. West of this fault the Virgin limestone 

 is conspicuous in every exposure of the lower 

 part of ' the Moenkopi formation. In the 

 Washington dome it is 160 feet thick and 

 locally shows four limestone beds instead of 

 the usual three beds. In the Bloomington 

 dome it is 130 feet thick. Near Black Rock 

 Spring it is 100 feet thick. The Shnabkaib 

 shale member is a marked unit in the upper 

 part of the Moenkopi formation at least as 

 far east as a locality 8 or 10 miles east of 

 Fredonia, Ai'iz. The Virgin limestone member 

 was not observed here and may be entirely 

 absent. The calcareous unit of Ward's typical 

 section farther east may represent the exten- 

 sion of the Virgin limestone. 



The sandstones in the upper red beds are 

 not very conspicuous near Virgin City, but 

 they are present along the Virgin anticline and 

 northwest of St. George; along the Arrowhead 

 Trail to Los Angeles they make up a consider- 

 able part of the upper red-bed unit. Though 

 they nowhere stand up in massive cliffs they 

 suggest in their position the De Chelly sand- 

 stone of Gregory, wliich occurs in eastern 

 Arizona between the usual red beds of the 

 Moenkopi formation and the Shinarump con- 

 glomerate. 



The red sandstones of the Moenkopi are 

 spotted locally with green copper stains that 

 have caused much fruitless prospecting. The 

 upper limestone of the Virgin limestone mem- 

 ber at many places contains disseminated 

 lead, zinc, and copper sulphides in small 

 amount. 



Huntington and Goldthwait " give a section 

 of the Moenkopi formation near Toquerville, 

 about halfway between oiu* two complete sec- 

 tions, in which our units are recognizable but 

 the thicloiesses are very dift'erent. This section 

 shows, at the base, soft red shales, 170 feet; 

 gray and red shales with three limestone 

 benches, 115 feet; soft red shales, with some 

 harder gray layers, 250 feet; white and red 

 shales, 390 feet; chocolate-colored, gray, and 



" Huntington, Ellsworth, and Goldthwait, J. W., The Hurricane fault 

 in the Toquerville district, Utah: Harvard Coll. Mus.Comp.Zool. Bull,, 

 vol. 42, p. 203, 1904. 



32333°— 22 o 



lavender shale and sandstone, 380 feet; total, 

 1,205 feet. There is no apparent thinning 

 westward from Virgin City to Toquerville, but 

 rather the reverse, and we question the accu- 

 racy of this section. 



Near Cedar City, Utah, Lee '' measured sec- 

 tions which show a total thickness of 2,650 feet 

 for the beds here called the Moenkopi forma- 

 tion. They contain a fossiliferous limestone 

 member equivalent to the Virgin limestone 

 member. About 50 miles farther north Lee 

 found the Virgin limestone fauna to persist 

 through a thickness of 350 feet of shale and 

 limestone, overlain by unfossiliferous limestones 

 making a total of at least 600 feet of strata 

 with limestone beds above the fossiliferous 

 Kaibab limestone. 



Longwell '" found that in the Muddy Moun- 

 tains of Nevada the Moeiikopi formation con- 

 sists of tliin-bedded limestones, shale, and sand- 

 stone. The thickness ranges from 1,200 to 

 1,600 feet, of which the lower half is predomi- 

 nantly marine limestone and the upper half 

 continental deposits. 



Apparently the red beds of the typical 

 Moenkopi formation pass westward and north- 

 westward into marine limestones. The thin 

 limestone of the typical area is the edge of a 

 wedge which increases to the Virgin limestone 

 member and then to the thicker limestone 

 members found by Lee and Longwell. 



Walcott -" found in Kanab Valley a lime- 

 stone and shale unit like om- lower Moenkopi 

 beds, 198 feet thick, overlain by a shale and 

 sandstone unit 666 feet thick. These beds lie 

 between the "BeUerophon limestone" of the 

 Kaibab formation and the Shinarump conglom- 

 erate. The limestone m the lower division 

 carries Walcott's "Permian " fauna, now known 

 to be Lower Triassic. 



The Moenkopi formation is unconformable 

 on the Kaibab limestone. The basal con- 

 glomeratic member of the Moenkopi, the varia- 

 tion in the thiclviiess of the Harrisburg member 

 of the Kaibab limestone, and the presence of 

 a gash cut deep into the massive Kaibab and 

 filled with jMoenkopi materials near the heail of 

 Rock Canyon show an erosion interval. Evi- 

 dence of an erosional interval at this horizon 



" Lee, W. T., The Iron County coal Held, Utah: U. S. Geol. Survey 

 Bull. 316, p. 362, 1907. 



" Longwell, C. R., op. cit., p. 49. 



20 Walcott, C. D., The Permian and other Paleozoic groups of the 

 Kanab Valley, Arij.: Am. Jour. Sci., 3dser., vol. 20, pp. 221-225, 1S*0. 



