334 



G. K. GILBERT AND F. P. GULLIVER — TEPEE BUTTES. 



their argillaceous character so well in approaching the base of the moun- 

 tains as to warrant the belief that the shore of the sea which received 

 them lay still farther west. They are essentially an off-shore or open 

 sea deposit. The tepee cores are restricted to a zone four or five hun- 

 dred feet thick occurring about midway in the shale series. The shale 

 of this zone is pale to medium gray in color, is distinctly argillaceous in 



^x^:^ 



*>3!^«*^*^^,w 



Figure 1. — Group of Tepee Buttes. 

 Drawn from a photograph. 



type and is finely laminated. It contains also somewhat abundant cal- 

 careous concretions which are arranged in horizontal rows. 



DISTRIB UTION. 



Within the field of our study the tepee zone outcrops as a belt extend- 

 ing from the vicinity of the town of Fountain south-southeast to the 

 Nussbaum mesa, and thence curving to the east. It reaches the Arkan- 

 sas river near Baxter and follows it to Nepesta, but does not pass south 

 of it. Little Buttes station, on the Denver and Rio Grande railroad, is 

 named from a group of tepee buttes. It is probable that the belt ex- 

 tends farther eastward in the Arkansas valley, and Mr T. W. Stanton 

 reports a few occurrences near Florence and Canyon City where a syn- 

 clinal basin determines an outlier of the Pierre. As to the further ex- 

 tension of tepee buttes within the Pierre group we have no information. 



Within the zone the grouping of tepee cores is irregular, both hori- 

 zontally and vertically. In places they are so thickly set that hundreds 

 of the resulting buttes may be seen from one point ; elsewhere they are 

 solitary or in groups of two or three. W^here they abound it is easy to 

 find rows of five or six, but it is equally easy to find rows in other direc- 

 tions, and we were unable to discover any law of arrangement. The 

 distribution of the buttes is further complicated b}^ the fact that part of 



