GEOLOGICAL NOTES ON THE CENTRAL BRANCH U. P. R. R. 131 



2. loo feet probably all shales ; same chert on slopes.. 



3. Four feet Magnesian limestone in layers of four to twelve inches. 



4. Fifteen feet shales with small geodes. 



5. Four feet limestone in sixteen inch layers ; color, whitish drab with blue 

 chert between the layers. This limestone is much used in building at Blue Rap- 

 ids, and affords a handsome building rock. 



6. Thirty feet shales. 



7. One and one-half feet good bed of building stone, coarsely cellular; also 

 extensively used. 



8. Thirty feet shales, red in lower part. 



9. Four feet limestone. 



10. Four feet nodular shales. 



On river bluffs above, the red shales at several places carry lenticular forms 

 of gypsum, often snowy, and in quantity sufficient to utilize. There is a mill at 

 Blue Rapids constantly engaged in grinding it up for plaster. Some of these beds 

 are nine feet thick. A strange feature was observed in some of the lower beds 

 of these rocks. In five feet thickness observed four beds of rock of nearly uni- 

 form thickness, sixteen to twenty inches, each one with a layer of blue chert on 

 top. 



Fusulina cylindrica abounds, also found Atthyris subfilifa, Produdus semireticu- 

 laius, Chonetis granulifera, Eumicrotis haurii, Hemipronites crenistria. 



Borings at Blue Rapids reveal a thin coal seam, only a few inches. 



Five miles west, at Waterville, we find the rock corresponding to that on 

 hilltop at Blue Rapids, but here it lies not far above base of hill, and is the chief 

 rock used for building purposes. It also corresponds to the Mayville rock. 



At Palmer Station we find that we have left the Upper Carboniferous and 

 Permian and entered the Cretaceous. The red sandstone of the Dacotah stands 

 out prominently at Palmer. At Concordia this sandstone lies low in the hills, 

 and is used in the construction qf buildings, as is also the lower beds of the Ft. 

 Benton Cretaceous. At Beloit and Cawker they obtain a ten-inch bed of very 

 tough limestone, but at the same time soft enough to saw or cut easily. Half the 

 buildings of these towns are constructed of it. It is a yellowish brown color with 

 a dark brown or red band at the center, along which it can be split. 



Inoceramus problematicus was almost the only fossil seen. 



At Glen Elder there is exposed about thirty feet of shales, and thin Umestone 

 layers of the Ft. Benton group. Off from the railroad these beds contain Am- 

 monites. 



A wonderful thing is the Spirit Spring three miles east of Cawker. We here 

 find a knoll of thinly laminated rock about twenty-five feet high, 100 feet across 

 at summit and 300 feet at base. Between this knoll and adjacent bluff lies a 

 hollow twenty-five feet deep. The slope is gradual on all sides except the south, 

 where it is perpendicular. On top we find a spring sixty feet in diameter, and 

 having a margin of not over twenty feet outside of the water to connect with the 



