J. B. Tyrrell — Cretaceous of Manitoba. 227 



Art. XXIX. — The Cretaceous of Manitoba • by J. B. 

 Tyrrell, M. A., B.Sc, Geologist on the Geological Survey 

 of Canada. 



Stretching northward through the western portion of the 

 province of Manitoba, the escarpment of the Pembina, Riding, 

 Duck and Porcupine Mountains has long been known as the 

 approximate eastern outcrop in that province of the Cretaceous 

 terranes that underlie the whole country westward to the foot 

 of the Rocky Mountains. The terranes have also been known 

 to consists of shales of more or less varied character, and most 

 of these shales have been considered as representing the Fort 

 Pierre shales of Meek and Hayden, or the Pierre shales of 

 the Canadian geologists. 



During the summers of 1887 and 1889 the writer was en- 

 gaged in field work in northwestern Manitoba, and part of the 

 time was spent in studying the structure of this escarpment in 

 the few natural sections cut by the streams flowing eastward 

 into Lake Winnipegosis, and for a short distance in the banks 

 of the valleys of the Assiniboine and Bird-Tail Rivers. A few 

 sections in southern Manitoba were also hastily visited, and the 

 logs, with typical specimens, were obtained of the well bored 

 on the north side of the Riding Mountain by the Manitoba Oil 

 Co., and of the well that is now being drilled at Deloraine in 

 southwestern Manitoba. 



Most of the natural exposures are comparatively low and 

 disconnected, so that it is rarely possible to obtain the exact 

 thickness of the different terranes, but the following notes will 

 give a general idea of the relationships of the different beds, 

 and an approximate idea of their thickness. 



In northwestern Manitoba the Cretaceous rests unconform- 

 ably on a floor of Paleozoic limestones and dolomites, which, 

 wherever seen, were found to be of Middle or Upper Devon- 

 ian age. These limestones are well shown around the shores of 

 lakes Manitoba and Winnipegosis, and are always lying moder- 

 ately horizontal, but much broken by small faults. The pre- 

 Cretaceous surface of the limestone is everywhere uneven 

 having been very severely eroded between Devonian and 

 Middle Cretaceous times, and as is shown by these irregulari- 

 ties, the erosion was still in progress up to the time when the 

 country was immersed in the Cretaceous sea. Besides the 

 local irregularities the pre-Cretaceous floor is shown by borings 

 to have a general light slope toward the southwest or west. 



The Cretaceous of Manitoba falls very well into the groups 

 that were first marked out by Messrs. Meek and Hayden, the' 

 Fox Hills Group being the only terrane that has not yet been 



