RESUME OF LITERATURE. 31 



Shinarump groups, but as the lowest beds of the Mesozoic are of very friable mate- 

 rial, the exact junction was rarely seen (page 150). At the same time, that an inter- 

 ruption in sedimentation did occur at the top of the upper Aubrey group is indicated 

 by the following passage, quoted fi'om page 6!*: 



"The plane of deniarciition between the Shinarump group and the summit of 

 the Carboniferous is always well marked. Soft, gypsiferous shales are found at the 

 base of the upper group, and either a pure limestone, a cherty limestone, or a homo- 

 geneous sandstone at the summit of the Carbonifei'ous. In places, however, a con- 

 glomerate is found at the base of the Shinarump group, its coarser fragments being- 

 composed of cherty limestone which contains Upper Carboniferous fossils. So in 

 some places, at least, the epoch of change was a period of erosion." 



Accompanying the report upon the geology is a paleontologic report by C. A. 

 White, which forms an important part of the volume under discussion. He gives 

 faunal lists from the different formations of the Plateau province from which collec- 

 tions were obtained, discusses the ages of the beds and describes many new forms. 

 Carboniferous faunas are cited from the Red Wall and the upper and lower Aubrey 

 groups. His conclusions in regard to the Carboniferous faunas are expressed in the 

 following words (page 79): 



"■A large proportion of all these fossils are specifically identical with well-known 

 forms in the strata of the Carboniferous or Coal-Measure period in the States of the 

 Upper Mississippi Valley; and all but two of them belong to such types as we might 

 naturally expect to find in the equivalents of those strata. These two belong to the 

 two genera, respectively, Archimedes and Amplexvs, the former of which especially 

 has been regarded as an exclusively Subcarboniferous genus; and yet they are found 

 in the lower Aubrey group, nearly 3,000 feet above the base of the Carboniferous 

 series, and also above and mingled with types that have not hitherto been found 

 in strata so low as the Subcarboniferous. 



"Few or none of the fossils of the collections are of such a character as to sug- 

 gest the Permian age of the strata from which they were obtained, not even those 

 of the upper Aubrey group. I have elsewhere shown" that the prevalence of cer- 

 tain types which have been relied upon to prove the Permian age of the strata con- 

 taining them may be due to peculiar physical conditions, and I therefore regard it 

 as not improbable that the time of the Permian period may be represented in the 

 Plateau Province by the upper Aubrey group, although the distinguishing types are 

 wanting there. In view also of the mixture which we find, of Carboniferous and 

 Subcarboniferous types in the same strata, it seems probable that the time of the 

 whole Carboniferous age, including its three periods, Subcarboniferous, Carbonifer- 

 ous, and Permian, is collectivel}' represented by the four groups in the Plateau 

 Province." 



No fossils are cited from either the Lodore or the Uinta formations. The latter, 

 however, is provisionally referred to the Devonian by Powell (pages 70, IM), while 

 the Lodore group, which overlies it unconformably, is included in the Carboniferous. 



aGeology of Iowa, 1870, vol. 1, p. 249. 



