704 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



denudation, underlie the valley all the way to the Ramparts, a distance of 90 miles. The fos- 

 sils obtained both from this area and from the one above Bear River consist of fragments of 

 ammonites and Inocerami, too imperfect for specific determination. 



A hundred and twenty miles below the Ramparts the Mackenzie enters a third Cretaceous 

 area, and the largest one on the river. Cretaceous beds appear in the banks a short distance 

 below old Fort Good Hope and extend down the Mackenzie to the head of its delta and westr 

 ward across the Rocky Mountains and down the Porcupine to about longitude 139° west. They 

 consist on the Mackenzie of coarse shales interstratified with some sandstones and fine-grained 

 conglomerates; in the mountains of several thousand feet of barren sandstones and quartzites 

 underlain by dark shales; and on the Porcupine of the same two series underlain by a great 

 thickness of alternating shales, sandstones, and conglomerates, holding Aucella mosquensis var. 

 concentrica. The intermediate dark shales are probably of Benton age, while the lower division, 

 so far as the fossil evidence goes, represents the Queen Charlotte Island formation and the Dakota. 



Cretaceous shales holding Aucella and passing upward into fine-grained conglomerates 

 occur on the Yukon for many miles above and below the mouth of the Tatonduc and were 

 traced by Ogilvie up the latter stream for some distance. They have been greatly disturbed 

 and are folded up in broad bands with the underlying Paleozoic limestones. 



These rocks are described in greater detail by Brooks and Kindle. ^"^ 

 The area of Cretaceous west of Great Bear Lake is briefly described by J. M. 

 Bell.''* The rocks are shales and sandstones which lie in nearly horizontal attitude. 

 On Bear River the strata dip very gently downstream and consist of dark ferrug- 

 inous and arenaceous shales overlain by thin-bedded and jointed sandstones. No 

 fossils were collected and the correlation as Cretaceous depends on stratigraphic 

 and lithologic comparison. 



The paleontology of this area is discussed by F. B. Meek.^*^ 



B 5. NORTHERN ALASKA, ARCTIC SLOPE. 



(See Chapter XIV, p. 636.) 



■ R 33. WEST COAST OF GREENLAND. 



The Nugsoak Peninsula and Disco Island, on the west coast of Greenland, 

 present sections of late Lower Cretaceous and of Upper Cretaceous littoral strata. 

 The coast of the Cretaceous sea was apparently not far from the present seacoast, 

 the more easterly exposures of the sediments carrying plant fossils without marine 

 remains and being coarse clastic rocks, whereas the strata farther west are marine 

 clays. The latest account of these strata is that given by White and Schuchert,^"^ 

 whose conclusions are in part as follows: 



The Cretaceous and Tertiary rocks in the region described lie everywhere unconformably 

 upon a hilly basement of old crystallines, chiefly gneiss and diorite (Ksersut, Pagtorfik, Ekorfat), 

 or upon early Cretaceous or pre-Cretaceous ( ?) basalts (Niakornat, Alinaitsunguak, Atanikerd 

 luk). The greatest altitude of the -sedimentary terranes is at Atanikerdluk, 3,400 feet above 

 sea leveL The old basalts are highly altered and usually occur as breccias (Niakornat, Alinait- 

 sunguak). 



The prevailing easterly dips of the Lower Cretaceous along the north side of Nugsoak 

 Peninsula, in which the strata should dip westerly, since it is in that direction that the higher 

 and younger beds appear, may be in part explained by fault compensation, as illustrated at 

 Ujarartorsuak. A certain degree of irregularity of dip, the variable and often strong coast- 

 ward dips as well as the low altitude of the Tertiary at its eastern border on the south side of 



