60 



SHORTER CONTRIBrTIOXS TO GENERAL GEOLOGY. 1021. 



marine fossils, chiefly peleeypods; {'■]) middle 

 red beds, much Hke the lowest unit but purer 

 red in color; (4) gray to white sandy shale and 

 soft sandstone, with some pink layers and much 

 gypsum, presenting a marked banded unit in 

 clift' faces; (5) upper red beds, consisting of 

 brick-red to deep-red and brown shale and 

 sandstone, color in upper part very dark, lo- 

 cally containing massive beds of yellow me- 

 dium-grained sandstone. The writers propose 

 the name Virgin limestone member for the 

 second unit above the basal conglomerate mem- 

 ber of the formation, from Virgin City, where 

 the unit is splendi<lly exposed. For the white 

 banded sandy shale unit the name vSlmal)kaib 

 shale member is proposed, from the striking 

 isolated mesa which lies 2 miles southwest of 

 the town of Washington, on the northwest 

 flank of the Wasliington dome, and which is 

 still knowTi by its old Indian name." (See PI. 

 X.) vSection 13 (p. 73), measured near Virgin 

 City, and section 14 (p. 73), measured 2 miles 

 east of vShnabkaib, show the thickness and re- 

 lation of these units to the whole formation. 



The basal discontijiuous unit is an exceed- 

 ingly variable assemblage of shale, luueston«\ 

 gypsum, conglomerate, and a minor amount 

 of sandstone. To this unit we have given the 

 name Rock Canyon conglomeratic mtunber, 

 irom Rock Canyon, .■> miles north of Anteloj)e 

 Sprmg, .\j-iz. A detailed section at this locality 

 is given on page 70 (section 6). The limestone 

 is gi'ay to pmk, is usually coaise, and contains 

 chert fragments. The shale may be gray, 

 yellow, or red. The congknnerate is made up 

 of limestone and chert boulders, locally as 

 much as 3 feet in diameter but usally less than a 

 foot, in a limestone cement and occurs in very 

 iiTegular beds, which may lie at any strati- 

 graphic level in the basal unit. Locally the 

 included limestone fragments are angular and 

 the material is really a bi'eccia, though at most 

 points observed they are roimded or only sub- 

 angular. Locally this basal member is absent, 

 as the sections show, and the lower red beds 

 rest directly on Imiestones containing Kaibab 

 fossils. At the head of Rock Canyon a great 

 gash 700 feet wide and 250 feet deep has been 

 cut into the Kaibab and filled with a confused 

 mass of limestone, shale, gypsum, and conglom- 



1* Sluiabkaibissaidby Dr.. I. P. HLirriityt on, of the Bureau of American 

 Ethnology, to be most probably a forruptiou of shoua'agaiv, from 

 Shoua'a, coyote, and gaiv or taib, rocky hili, or moimtain. 



erate. This mass contains thin veins of 

 asphaltite and zones impregnated with as- 

 phaltic material. 



Lee " found near Cedtir City conglomeratic 

 beds 175 feet thick restmg unconformably on 

 hard cherty Kaibab limestone and overlain by 

 red shales. About 50 miles farther north, in 

 Beaver Canyon, lunestones and shales contain- 

 ing the Virgin limestone fauna rest on a thin 

 conglomerii^te, and this in tiu'n rests on cherty 

 fossiliferous Kaibab limestone. Long;well '" 

 found in the Muddy Mountains of Nevada 

 depressions in the top of the Kaibab limestone 

 filled with chert and limestone fragments. 

 These fragmental deposits are the base of the 

 Moenkopi formation. 



Two complete sections were measured 

 tlu'ough the Moenkopi formation. Section 13 

 (p. 73), measured near Vngin City, shows a 

 total thickness of 1,775 feet, of which 170 feet 

 is the Rock Canyon conglomeratic member, 

 360 feet the lower red beds, SO feet the Virgin 

 lunestone member, 400 f(H^t the middle red 1ieds, 

 3()0 feet the Shnabkaib shale member, and 405 

 feet the upper red beds. The other complete 

 section (No. 14, p. 73) was measured on the 

 south side of the Harrisburg dome, S miles west 

 of Virgin City. Here the total thickness is 

 2,035 ftH^t, of which 335 feet is assigned to the 

 lower n^l beds, 1(30 feet to the Virgin limestone 

 member, 435 feet to the middle red beds, 630 

 feet to the Shnabkaib shtile member, and 475 

 feet to the upper red beds. The Rock Canyon 

 conglomeratic member seems to be lackmg at 

 the Harrisburg dome. 



Sections of parts of the formation were 

 measured at several localities. In the Wash- 

 ington dome, just west of the Harrisburg dome 

 (section 15, p. 74), the Rock Canyon conglom- 

 eratic miit is 288 feet thick, and the lower 

 red beds are 320 feet thick. In the Bloom- 

 ington dome (section 16, p. 74), south of St. 

 George, the lower red beds are about 320 feet 

 thick. Near Black Rock Spring (section 18, 

 p. 75) the lower red beds are ISO feet thick. 

 Near BuUrush, 12^ miles southwest of Free- 

 donia, Ariz, (section 3, p. 70), the Virgin lime- 

 stone member seems to be represented by a 

 calcareous unit 11 feet thick. Farther west, 

 in the neighborhood of Antelope Spring, it 



i> Lee, W. T., The Iron County coal field, Utah: U. S. Geol. Survey 

 Bull. 316, J). 31)2. Iy07. 

 18 LongwcU, C. R., op. cit., p. 4'.*. 



