68 STANTON: UPPER CRETACEOUS STRATIGRAPHY 



the Claggett formation and again recurring about 2000 feet 

 higher in the same section where there is no reason to question 

 the structure or stratigraphic position. At Cutbank the fossils 

 are about 300 feet above the Eagle or more than 1500 feet below 

 the Bearpaw. From this locality there are practically contin- 

 uous exposures down Cutbank Creek to its mouth where the base 

 of the Eagle is exposed. Thence westward up Two Medicine 

 Creek there are continuous exposures and simple structure up to 

 and thru the Bearpaw with its 500 feet of dark shale. Above 

 the Bearpaw is a sandstone which makes conspicuous cliffs 

 near the Holy Family Mission (Family P. O.) on Two Medicine 

 Creek. Here and at other exposures farther west on the creek 

 it yielded Tancredia americana, Cardium speciosum, Mactra, etc., 

 identical with those fo^nd at the much lower horizon, together 

 with a number of other forms not found there. This sandstone 

 is approximately in the position of the Fox Hills and is doubtless 

 the same sandstone which Dawson identified as Fox Hills in the 

 adjacent area on the north, tho from the evidence at hand it 

 would be rash to say that it is strictly identical with the Fox Hills 

 of South Dakota. At most localities where it has been examined 

 in the Blackfeet reservation it has proved unfossiliferous or 

 yielded only Ostrea suhtrigonalis and other brackish-water forms 

 which are found both in Dawson's St. Mary River formation 

 above it and in the beds beneath the Bearpaw, but here, on Two 

 Medicine Creek, there was an incursion of strictly marine water 

 with an abundant fauna of Fox Hills type. 



After this brief digression in pursuit of a recurrent fauna let 

 us return, for a few moments, to the main topic, which is contem- 

 porary variation in sedimentation and its bearing on strati- 

 graphy and geological history. The sedimentary records of the 

 Blackfeet country, aided by the paleontologic evidence, show 

 that during the long quiet deposition of the Colorado shale and 

 while the Eagle sandstone was being laid down by the stronger 

 currents of the shallowing sea the physical conditions there were 

 about the same as in a large area on the east and southeast. 

 Later, during Claggett time, while purely marine conditions still 

 prevailed a short distance to the east, near Judith, for example. 



