3 4 The Badland Formations of the Black Hills Region 



fullers' earth. East of the Hills the White River group is usually 

 divisable into two formations — the Titanotherium beds or 

 Chadron formation below, and the Oreodon beds or Brule clay 

 above. The Chadron formation consists of fullers' earth, light- 

 gray, drab, pale-green or pinkish tints, traversed by channels 

 filled with gray sandstone. At the base there is usually a bed 

 of coarse gravel composed of rocks derived from the Black 

 Hills. The Brule clay is a thickly laminated sandy clay of pale 

 flesh and drab colors. * * * The following bones determined 

 by Prof. F. A. Lucas, were obtained in beds high up on the 

 flanks of the Black Hills west of Fairburn : Oreodon culbertsoni, 

 Poebrotherium wilsoni, Stylemus neb rase en sis, and Hyracodon 

 uebrascensis.''* 



Beyond the Cheyenne river, southeast, south and south- 

 west of the main uplift, the deposits are thicker and more repre- 

 sentative than elsewhere. They have there been more carefully 

 studied paleontologically and the various beds have been denned 

 with a considerable degree of completeness. It is possible to 

 distinguish for this part of the region the several individual 

 formations. The following sections and plate will serve as a 

 good introduction to the more detailed description of the various 

 subdivisions : The first section, page 35, from Wortman's strat- 

 igraphic table of the formations in the Big Badlands ;f Figure 

 6, Darton's section, near Adelia, Nebraska, at the base of Pine 

 Ridge ;* Plate 4, Osborn's Idealized Bird's Eye View of the 

 Big Badlands looking from near the Black Hills toward Por- 

 cupine Butte. § This latter is a combination, slightly modified, 

 cf the stratigraphic table by Wortman, and the Columnar sec- 

 tion from Osborn reproduced in Figure 8. 



*Darton, N. H. Preliminary Description of the Geology and 

 Water Resources of 'the .Southern Half of the Black Hills and Ad- 

 joining Regions 'in South Dakota and Wyoming, U. S. Geol. Surv., 

 Twenty-first Ann. Rent., Part IV, 1901, pp. 5 42-543. 



tWortman, J. L. On the Divisions of the White River or Lower 

 Miocene of Dakota. Am. Mus. Nat. Hist., Bull. Vol. 5, 1893, pp. 95- 

 105. 



t'Darton, N. H. Preliminary Report on the Geology and Water 

 Resources of Nebraska West of the One Hundred and Third Meridian. 

 U. S. Geol. Sm.rv., Nineteenth Ann. Rept., pt. IV, 18 9 9, p. 757, and 

 with slight modification, U. S. Geol. Surv., Prof. Paper No. 17, 1903. 



§ Osborn, H. F. Cenozoic Mammal Horizons of Western North 

 America, U. S. Geol. Surv., Bull. No. 3 61, 1909. 



