UPPER CRETACEOUS. 697 



For an account of the Edmonton and Paskapoo series, see Chapter XVI 

 (pp. 781-782). 



In the easterp portion (M-N 13-14) of the area under consideration the classi- 

 fication of the Cretaceous differs from that given for the western portion (M-N 11-12) 

 in the recognition, by T3aTell,^^^^ of Dakota, Niobrara, and Benton. T5nTeU gives 

 the following systematic account in a report which contains also many local details : 



The Dakota sandstone formation, resting unconformably on the limestones of the Devonian, 

 is composed of white or reddish sandstones, either cemented by a calcareous matrix or often 

 quite incoherent, being then an even-grained white quartzose sand. It grades up into a light- 

 green and rather hard sandstone, commonly interstratified with thin bands of shale. 



Very few fossils have been found in this sandstone, and those that have been found are con- 

 fined to the greenish upper beds. 



Overlying the Dakota sandstones, the Benton formation occurs as a band of dark-gray, 

 almost black shale, holding a considerable quantity of carbonaceous material. This shale is 

 evenly bedded and breaks down readily into thin flakes, on which account it generally forms 

 sloping banks. With the dark shales are associated thin beds of white, soft, sweet-tasting 

 magnesian clay. 



It is generally quite destitute of fossils, but in a few places undeterminable fragments of 

 oysters and Inocerami have been collected from the shale. 



The Niobrara formation conformably overlies and is an upward extension of the Benton. 

 The rock, however, instead of beiag a soft fissile shale, with little or no admixture of calcareous 

 material, is a lighter-gray calcareous shale or marl, sometimes varying to a band of moderately 

 hard limestone. This is especially the case at the top of the terrane, where a band of grayish 

 chalky limestone is generally met with. This band is often highly charged with pyrite. 



A very characteristic feature of the formation is the presence of a large number of Forami- 

 nifera, among which Globigerina cretacea is often very conspicuous and in great abundance." 



The terrane varies considerably in thickness. In the Manitoba Oil Co.'s bore on Vermilion 

 River it appears to have a thickness of 130 feet. On North Pine Creek its total thickness is 

 less than 400 feet and probably is not more than 200 feet. On Bell River it is probably less 

 than 250 feet. In the Swan River valley, near Thunder Hdl, it would seem to have a thickness 

 of 540 feet, but it is quite possible that the upper beds represent a foraminiferous horizon in 

 the overlying Pierre formation. 



This terrane is known to extend southward through the western portion of the province of 

 Manitoba, having been recognized in the valleys of the Assiniboine and other streams near the 

 face of the Manitoba escarpment and in the borings from the deep weUs at Morden and Deloraine. 

 It is doubtless continuous with the Niobrara shales and limestones, originally described by Messrs. 

 Meek and Hayden, from the banks of the Missouri River in Nebraska. Northwest of the area 

 now described a fragment of typical Niobrara rock was collected from Carrot River, about 

 west longitude 103°, by Mr. A. L. Russell, beyond which it has not been traced, and its exact 

 correlation with the beds on Athabasca River is not yet known. 



sic** * * * *** 



Grading upward fiom the top of the Niobrara formation the Pierre shales occupy the 



summits of all the higher lands of the Riding, Duck, and Porcupine mountains. In the Riding 



Mountain and farther south this formation naturally separates itself into an upper and a lower 



subdivision, which the writer has elsewhere called the Millwood and the Odanah series.'' 

 ******** * 



Farther west the Pierre is highly fossUiferous, but in northwestern Manitoba fossils are 

 very scarce, and of those recorded in the following list " the Radiolaria are from a bed of shale on 



a For list see the work cited. — B. W. 



ft Tyrrell, J. B., The Cretaceous of Manitoba: Am. Jour. Sci., vol. 40, 3d ser., 1890, pp. 227-232. 



