1875.1 4:0 J Stevenson. 



ordinarily a not very compact sandstone, rusty yellow in color and con- 

 cretionary in structure. lu parts it is calcareous, and where it shows 

 such a composition, is very fossiliferous. Dr. Hayden notes the interest- 

 ing fact respecting the Fort Pierre and this group, that there are zones 

 or belts in which they are almost non-fossiliferous. This feature, ob- 

 served in the Upper Missouri Region,! found to be quite chai-acteristic of 

 the Upper Cretaceous in Colorado and New Mexico. The group is marked 

 by a rich fauna, largely of Cretaceous forms, but mingled with many 

 types of more recent character. 



Above the unquestioned Cretaceous, there comes the great lignite series, 

 termed by Dr. Hayden, the Fort Union Group. This is an immense mass 

 of sandstones, shales, and beds of lignite, having a maximum thick- 

 ness of not far from four thousand feet. Marine organic remains are com- 

 monly found in the lower portions, but over a part of the area, as one as- 

 cends in the series, he finds the traces of marine life disappearing, while 

 land and fresh-water shells occur associated with vast numbers of leaves 

 of dicotyledonous plants. The northern and southern portions of this 

 group have never been joined by direct tracing. At the north it under- 

 runs the White River Group near Fort Fetterman. From that point 

 southward it is concealed for about three hundred miles, re-appearing 

 from under the same group in Colorado, twenty miles south from Chey- 

 enne. A careful study of Dr. Hayden's reports leaves no room to doubt 

 the correctness of his conclusion that the formation near Fort Fetterman 

 and that south from Cheyenne are the same. 



The Lower Lignitic Group. 



For convenience in this connection I thus designate the Dakota Group, 

 Cretaceous No. 1. This yields lignites over an enormous area, reaching 

 from the Arctic Ocean into New Mexico, but for the most part the beds 

 are thin and the lignite itself is very impure. 



The only detailed reference to this group in British America, which I 

 have at hand is that of Dr. Hector.* Sir J. Richardson's "Journal of a 

 Boat Voyage through Prince Ru]Dert'sLand," is not within my reach, and 

 his statements in the Appendix to Franklin's Expedition are very unsat- 

 isfactory. Dr. Hector's observations were made upon the Saskatchewan 

 River and its tributaries. He found a well-defined series of coal-bearing 

 strata on the North Saskatchewan, or Red Deer River, and on Battle 

 River. On Red Deer River he obtained the following section, descend- 

 ing, 



1. Sandstones and dark clays. 



2. Banded marlites, clays, and limestones. 



3. Shell conglomerate. 



4. Clay. 



5. Banded clays with clay-iron stone. 



6. Coal, three feet thick. 



7. Clays. 



8. Silicified wood and brown coal. 



9. Sandy clays. 



Total thickness of section, 600 feet. 



* Journal of the G-eological Society, 1861. 



