264 T. W. STANTON DAKOTA SANDSTONE PROBLEMS 



onous flora which Lee 10 and Knowlton 11 have reported from "the type 

 section of the Morrison formation." The plants from Morrison, Colo- 

 rado, are obviously not only younger than the Morrison formation, but 

 also younger than the Lakota and Fuson. 



The Black Hills section above the Dakota, as compared with the eastern 

 Nebraska section, shows a thickening of all the marine Cretaceous forma- 

 tions with the possible exception of the Niobrara. The Niobrara and the 

 Greenhorn, with their characteristic faunas, serve as convenient key hori- 

 zons for the accurate correlation of the different parts of the section, and 

 between these formations the zone of Prionocydus wyomingensis and 

 Scaphites warreni is another key horizon with a characteristic fauna which 

 is very widely distributed in the Eocky Mountain region. Still another 

 key horizon beneath the Greenhorn limestone is the Mowry shale, which 

 is useful in some areas to the west where the Greenhorn is not recog- 

 nizable. 



Just beneath the Mowry member, and separated from it by a few feet 

 of dark shale, is a variable sandstone, ranging from to 30 or 40 feet in 

 thickness, which is worthy of more than passing mention. Darton treated 

 it as a member of the Graneros shale, lying about 200 feet above its base. 

 More recently Hancock named it the Newcastle sandstone member, say- 

 ing that it is the "muddy" sand of the drillers in that area. Darton re- 

 ported that a lenticular sandstone 15 feet thick in the same stratigraphic 

 position on the east side of the Black Hills, near Hermosa, South Dakota, 

 contains abundant fossil plants, and in July, 1921, I visited the locality 2 

 miles northwest of Hermosa and made a collection which has been exam- 

 ined by F. H. Knowlton, who reported on them as follows: 



"This material is very fragmentary, most of the leaves being without mar- 

 gins and few with complete nervation. The appearance of the matrix and the 

 general facies of the leaves suggest Dakota, and without information to the 

 contrary they would probably have been so determined. For instance, I note 

 what appears to be : 



Salioe protect folia Lesq. ? 

 Laurus antecedens Lesq.? 

 Andromeda parlatorii Heer? 



"All are Dakota species." 



Does this thin sandstone really belong to the Dakota? If so, should 

 the Dakota also include the upper sandstone of the main hogback as well 

 as the 200 feet of shale between these sandstones? These questions are 



Am. Jour. Sci., 4th ser., vol. 49, pp. 1S3-1S4. 

 Idem, pp. 189-194. 



