68 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1921. 



T'leuropliorus n. sp. 

 Plcurofomaria. 2 sp. 

 Naticopsis sp. 

 .\mmonite? 



Concerning these Moenkopi fossils Mr. Girty 

 says: 



Lists 6, 8, and 11 show what I regarcl as the normal 

 Moenkopi fauna. 



Besides these I recognize another group (list 7) wliich 

 presents a peculiar chert y lifhoIog>' and a fauna composed 

 chifley of small species of Bakeiivllia and Mi/ophorw . I 

 do not feel sure that this gi-oup does not represent a condi- 

 tion rather than a geologic horizon. 



List 5 may represent a distinct faunal facies, but I am 

 inclined to believe that it liolongs with list 7. 



T>ist 9 prol)ably belongs with lists fl, S, and 11, but it 

 may represent a distinct subfauna. 



List 10, \rith its innumerable .gastrojiods, is unique in 

 the collection, but the horizon is undoubtedly Moenkopi. 



Ri.>,garding the Triassic age of the Moenkopi, from which I 

 understand there has been obtained some verj- meager plant 

 evidence havdng a Permian cast, I will say the following: 



The age of these Moenkopi beds does not depend solely 

 upon the fossils immediately contained in them but is 

 bound up with the Lower Triassic fauna of 1 daho. There is 

 scarcely room for reasonable doubt that Walcott's "Per- 

 mian " of the Kanab Canyon section, which is Moenkopi, 

 is the same as the "Pemio-Carboniferous" of the Wasatch 

 Mountains, and that the "Permo-(."arboniferou,s " of the 

 Wasatcli Mountains is the same as the well-known Lower 

 Tiiassic of Idaho. This correlation is, I believe, in a 

 general way lieyond dispute. I am ]iersonally convinced 

 of it from my own studies. If the Moenkojn is Permian, 

 then, consequently, the Lower Triassic of Idaho is Per- 

 mian. Now, I have not investigated the question myself, 

 but there seems to be a general agreement as to the age 

 of the I)ed3 in Idaho. 



As regards the evidence fimiished liy the Moenkopi 

 beds themselves, I have identified Meekoceras, one of the 

 distinctive ammonites of the Idaho faunas, both in the 

 present collections and in Mr. Walcott's, and there are a 

 few other characteristic Triassic types, though less impor- 

 tant ones. I may also point out that there is an almost 

 complete faunal change from the Kaibab to the Moenkopi. 

 Both faunas are fairly extensive, but I know of no species 

 that they contain in common. I'^urthermore, all the 

 characteristic Paleozoic genera of brachiopods become 

 extinct with the Kailiab — Frodiictmt^ Chonetes, Derhya, 

 McehfUa, Spirifer, Composila, and a score of others — not 

 to mention the numerous biyozoan types — Fenestella, 

 Septoporn, Khomhopora, Stenopom, and many more. 

 These types appear neither in the typical Moenkopi nor 

 elsewhere in the Lower Triassic of this region. Further- 

 more, the Kaibab, wliich is corrtdated with part of the 

 Manzano group of New Mexico (the San Andres Ume- 

 Btone), is itself Permian, a reference suggested first by the 

 paleobotanic evidence from the untlerlj'ing Siipai foniia- 

 tion and then corroborated by tlie in\-ertelirates from the 

 Kailiab itself. In brief, I tliink that we have here an 

 almost perfect example of a boundary between two geologic 

 systems, the formations lieing sejiarated by a profound 

 erosional unconformity and by an almost complete change 

 of fauna, the upper formation containing many dia.guostic 



fossils of the later system and the lower formation con- 

 taining many diagnostic fossils of the earlier system. 



Tlie Shinarump conglomerate has been 

 accepted for many years as Triassic on the 

 basis of its flora and fauna and its stratigraphic 

 position and relations. The Chinle forma- 

 tion seems to be closely related to the Shina- 

 rimip by its fossils, and its assignment to the 

 Triassic is unquestioned. 



The massive sandstone overlying the Chinle 

 offers an opportunity for a wide difference of 

 opinion. Emery-"'' believed that the unit 

 which near the San Rafael vSwell almost cer- 

 tainly represents this sandstone was to be 

 correlated entirely with the Wingate sandstone 

 and that the marine Jurassic above it was 

 Gregory's Todilto formation and a still higher 

 formation the equivalent of the Navajo sand- 

 stone. Lee followed this view. Dake,''* how- 

 ever, believes that this sandstone is equivalent 

 to the whole La Plata group of Gregory and 

 that the marine Jurassic above it is to be cor- 

 related with some part of the McElmo forma- 

 tion. The problem is essentially one to be 

 solved by tracing in the field, though we be- 

 lieve that the character of the sandstone sug- 

 gests a correlation with the whole La Plata 

 group rather than with the Wingate alone, as 

 there is in our area nothing like the Navajo 

 sandstone above the marine beds. The ma- 

 rine series, however, contains peculiar greenish- 

 wliite beds which somewhat resemble the 

 greenish-white beds of the McElmo formation 

 farther east. As mentioned on page 63 Wal- 

 cott found in Kanab Valley in the top of the 

 Chinle formation or the base of this sandstone 

 fossils which have a Jurassic aspect. 



The variegated shale would seem to belong 

 to the same group as the marine Jurassic lime- 

 stone, in that there are thin limestones in its 

 upper part, though there may be an uncon- 

 formity between the two and a considerable 

 difference in age. 



The buff sandstones yielded no fossils but 

 suggest in position and lithology a correlation 

 with the Cretaceous beds farther north and 

 east, on Coal Creek, which have a thin coal- 

 bearing unit at the base overlain by sand- 

 stones containing marine Cretaceous fossils. 

 Still farther east, near Mount Carmel, appa- 



» Emery, W. B., The Orccn River Desert section. Utah: Am. Jour. 

 Sci., 4th ser., vol. 46, pp. .W-.iT'i, 1918. 



'« Dalce, C. L., Tlie horizon of the marine Jurassic of Utali: Jour. 

 GeoloK>', vol. 27, pp. fi:!4-r>ic.. una |ia20i. 



