154 PROCEEDINGS OP THE ACADEMY OF 



In making some general remarks in regard to the geology of the Bad Lands, 

 I propose to take Fort Pierre as the starting point, pass up the valley of the 

 Teton River to its source, and over the Plateau, skirting the northern side of 

 the Bad Lands, enter the basin at Bear Creek, cross White River near Ash 

 Grove Spring, and descend the valley of White River on the south side of the 

 Bad Lands, below its confluence with the Missouri to Bijou Hills. 



Leaving Fort Pierre, on our route to the Bad Lands, we take a course a little 

 south of west along the valley drained by the Teton River and its tributaries. 

 This region is underlaid by Formation* No. 4 of the Cretaceous system. The 

 surface is quite undulating, presenting the usual indications of sterility, with 

 verylittlf to break themonotony of the scenery until reaching Grindstone Hills, 

 about eighty miles from our starting point, where a new feature presents itself. 

 These hills strike the eye of the traveller on account of their peculiar form, 

 heighth and the immense ledges of rock that cap their summits. These rocks 

 present an exceedingly variable structure. Some are formed of an aggregation 

 of quartz fragments cemented with carbonate of lime ; others form a coarse- 

 grained sandstone, or a conglomerate of water-worn pebbles mixed with angular 

 grains of quartz. This bed is undoubtedly an outlier of the Tertiary formations 

 of the Bad Lands. Underneath is the yellow arenaceous bed No. 5 of the Creta- 

 ceous system, and underlying this is No. 4, with its peculiar concretions and 

 a few fossils. Scattered through the valley of the little stream that flows at 

 the base of the hills are slabs of Tertiary limestone containing fresh-water 

 shells of the genera Limnea, Pla7iorbis, &c. On ascending the hills, the lofty 

 spires of the Bad Lands first rise to view like a magnificent city imprinted on 

 the sky. At the head of Teton River the Cretaceous bed No. 5 becomes qiiite 

 conspicuous, attaining a thickness of about eighty feet. Very few fossils are 

 found in it at this locality. I succeeded in finding a single shell and the tooth 

 of a fish, and Mr. Meek discovered in 1853 tracks of Planarian worms. Here 

 the country changes fi'om dreary sterility, with poor water and grass, to a 

 cheerful aspect, fine springs, and a comparatively luxuriant vegetation. 



Ascending the high hills at this point, we pass over the broad Plateau along 

 side of the Bad Lands, their lofty pyramids rising high above the surrounding 

 prairie. Eight miles farther we come to Pinao's Spring, a noted camping place 

 for travellers. Near this place a ridge extends from the Bad Lands across the 

 prairie toward the head of opening creek, about thirty feet in height, its sides 

 gently sloping and covered with grass. Scattered over this ridge are numerous 

 thin slabs of whitish limestone with fresh water shells, which have been changed 

 into a semitransparent chalcedony. There are also concretionary masses of 

 argillaceous limestone fully charged with these fossils in a fine state of pre- 

 servation. These fossils were first discovered by Drs. Evans and Shumard in 

 1853, and have been indicated by them in the Proceedings of the Philadelphia 

 Academy. They consist of Planorbis, Limnea, Physa and a small crustacean. 

 Several undescribed species have since been obtained from this locality, also a 

 few teeth and jaws of Mammals, comminuted remains of fishes, and the seeds 

 of a small species of Chara. The discovery of these fossils afforded us positive 

 evidence of the lacustrine character of this deposit. 



This ridge forms bed D of the vertical section, and is composed mainly of 

 yellow and light yellow calcareous marl. 



Approaching Sage creek the country becomes exceedingly broken. The Cre- 

 taceous bed No. 5 forms numerous pyramidal hills, some of them with almost 

 vertical sides, their summits paved with well water- worn pebbles from the Drift. 

 In the channel of Sage creek the Cretaceous bed No. 4 makes its appearance, 

 and forms a remarkable locality for its peculiar fossils. Continuing our west- 

 erly course, we come to Bear creek, the usual camping place of visitors to the 



* See Vertical Section, in a paper by F. B. Meek and F. V. Hayden, in Proceedings of 



the Acauemy for May, 1857. 



[June, 



