GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 47 



history, and on the chalk bluffs there are many of these hieroglyphics 

 in positions totally inaccessible to the Indian at the present time. ilTone 

 of them now living know anything about them, and it is supposed that 

 they must be very ancient, and that, since they were made, great changes 

 must have been wrought in these bluffs by the waters of the Missouri, 

 These markings are at least fifty feet above the water and fifty feet or 

 more below the summit of the bluff, so that they must have been made 

 before the lower portion of the bluff was washed away by the Missouri. 

 It seems strange that none of these hieroglyphical writings which occur 

 quite often on the chalk-rocks of the Niobrara group, higher up the 

 Missouri, are known to any Indians now living. Manuel's Creek is called 

 in Dakota language the creek where the dead have worked, on account 

 of the markings on the rocks. 



The accompanying illustration conveys an idea of the sandstones of the 

 Dakota group as they front the Missouri, and shows the wearing away 

 of the material of the rock underneath during high water. This erosion 

 is continued for a series of years until the superincumbent rocks fall 

 down and are washed away by the river. Near the mouth of Omaha 

 Creek are some very high vertical bluffs of sandstone, from which some 

 rock has been taken for building purposes. It is useful, since no better 

 can be found in the vicinity. For a considerable distance along the 

 hills opposite Sioux City, beds of the gray quartzite are found, which 

 are worked to considerable extent, and furnish a very good supply for 

 the inhabitants. A few impressions of plants and a few fossil shells 

 were found here. Near Sioux City, on the Iowa side of the Missouri, 

 is a high cut bluff extending to the mouth of the Big Sioux Eiver. 



Here was formerly a large exposure of the rocks of the Dakota group, 

 and these rocks exhibited well their variegated texture and composition. 

 The color seems to differ, depending upon the amount of ferruginous 

 matters in them. Only about twenty feet of the different layers are 

 exposed, and only about five feet hard enough for building purposes. 



This quarry has been wrought for twelve years or more, and at this 

 time seems to have given out, for very little suitable building-stone can 

 be found, mostly loose sandstone and clay. In former years I have ob- 

 tained impressions of dicotyledonous leaves, as willow, laurel, &c., with 

 some fossil shells of the genera Pharella, Axinea, and Cyprma^ which 

 are either estuary or marine in their character. 



Near the northern boundary of the Omaha reserve, traces of a whitish 

 chalky limestone, almost entirely made up of the shells of a species of 

 Inocerarmts, make their appearance on the high hills. This rock indi- 

 cates the first appearance of the Cretaceous division. 



Numbers, or the Niobrara. In passing northward, as we continue up the 

 Missouri, we find this formation becoming more and more conspicuous, 

 until opposite Sioux City it is from 50 to 100 feet in thickness. It is of 

 much importance to this region of the country on account of its value 

 as lime, and it supplies a large district with that valuable material. 

 Omaha is largely supplied with lime from the region of the Platte. Be- 

 tween Omaha and the northern boundary of the Indian reservation, a 

 distance of eighty miles or more, extending southward to the Platte, 

 near Columbus, there are five or six counties entirely destitute of lime- 

 stone. This limestone of the Niobrara group becomes very valuable 

 therefore, and it will be from this upper district that the counties under- 

 laid by sandstones of the Dakota group must obtain their supply of lime. 

 Number 2, or Fort Benton group, seems to be wanting until we reach a 

 point near the mouth of Iowa Creek. This is a thin bed, not over 40 feet 

 in thickness at any one point, and is characterized by black plastic clay 



