REPORT OF TEE GRIEF ASTRONOMER 85 



SESSIONAL PAPER No. 25a 



thin beds of limestone and ferruginous sandstone. Weller's collections from 

 outcrops north of lower Sherburne lake in Swift Current valley, and from 

 southern slopes of Chief mountain, were submitted to Mr. Stanton, who 

 identifies Inoceramus labiatus Schlotheim, Prionotropis sp., Ostrea con- 

 gesta Conrad (?), Camptonectes sp., Scaphites ventricosus Meek and Hay- 

 den, Anomia sp., Tellina sp. Among these the Inoceramus, Prionotropis, 

 and Scaphites are classed as characteristic Benton forms. 



' The topographic relations of the Dakota outcrop on Kennedy creek 

 and the highest Benton outcrops under Chief mountain are such that if 

 the beds were strictly horizontal the thickness of Cretaceous rocks would 

 be 2,700 feet. As there is a slight dip from the former beneath the latter, 

 this may be increased to 3,500 feet or more. It is, however, possible that 

 the over thrusts which traverse the Algonkian are paralleled by others in 

 the apparently undisturbed Cretaceous beds, and, if so, no estimate of thick- 

 ness can be based on the meagre data now available. 



' Just northeast of the northern end of Lower Saint Mary lake Weller 

 collected from a gray sandstone and according to Stanton's determination 

 obtained Inoceramus sp., possibly young of /. libiatus, Mactra emmonsi 

 Meek (?), Tellina modesta Meek, Donax cuneata Stanton, Corbula sp., 

 Turritella sp., and Lunatia sp. Of these Stanton says : " Although the 

 evidence of these fossils is not absolutely conclusive as to the horizon, it 

 is probable that they are from the Benton or at least from some horizon 

 within the Colorado group." 



' Laramie. — Ten miles east of Lower Saint Mary lake, on the middle 

 fork of Milk river, occur outcrops of thin-bedded and cross-bedded gray 

 sandstone and arenaceous shale. Some of the layers contain scattered and 

 fragmentary plant remains. Others are barren of fossils. Certain ones 

 are composed of oyster shells. In a section measuring 70 feet Weller 

 found five oyster beds, from which he collected Ostrea glabra Meek and 

 Hayden, Corbicula occidentalis Meek and Hayden, and small specimens of 

 an undetermined Melania, which may be the young of M. wyomingensis 

 Meek. The Ostrea of the highest stratum is said by Stanton to approach 

 more nearly to 0. subtrigonalis Evans and Shumard. These are all classed 

 as belonging to the Laramie fauna.' 



In his summary of the geology of the Bocky Mountain region in Canada, 

 Dawson writes: — 



' The aggregate thickness of the Upper Cretaceous in the southern 

 part of the Laramide range — Front range — (including the lower portion of 

 the Laramie, which may be regarded as Cretaceous) is found to be about 

 10,000 feet. It is unnecessary, however, to do more than allude to this 

 section here, as it is more properly to be regarded as the western margin 

 of the Cretaceous of the plains than as characteristic of the Cordilleran 

 region.'" 



* G. M. Dawson, Bull. Geol. Soc. America, Vol. 12, 1901, page 78. 



