116 PROCEEDINGS OF THE ACADEMY OP 



AVhite river. But the most remarkable feature of this basin is the wonderful 

 disturbance of the strata. So much are the beds disturbed and blended to- 

 gether by forces acting from beneath, that it seems almost hopeless to obtain 

 a section showing with perfect accuracy the order of superposition of the 

 different strata. 



The lignite beds throiighout this basin, though well marked, are of so earthy 

 a character as to have ignited spontaneously in but few places. Indeed the 

 impurity of the lignite forms the most essential lithological difference between 

 this deposit and the Great Lignite Basin below Fort Union. In some places 

 metamorphic rocks have been thrown up through the entire thickness of the 

 strata. Some remarks upon the age of this deposit will be found in a suc- 

 ceeding paper by F. B. Meek and the writer. 



Formation No. 1 ? of tee General Section, 

 As seen near the mouth of Judith river. 



Although the formation of which I am about to speak has already revealed 

 many important facts, the organic contents of its strata differ so materially 

 from those of any other with which I am acquainted in the North West, that 

 we are unable to fix with certainty its position in the geological scale. 

 From its lithological characters we may refer it to No. 1 of Vertical Section, no 

 difference being seen more than would be expected from their widely sepa- 

 rated geographical positions. These facts have already been published in the 

 Proceedings of the Philadelphia Academy of Natural Sciences, from which I 

 extract the following paragraph :* 



" In our section of the Nebraska formations, given in a paper published in 

 the 8th vol. of the Proceedings of the Academy, page 63, it will be remembered 

 we placed provisionally the beds of sandstone and clay composing formation 

 No. 1, seen at the Mouth of Big Sioux river and below there, along with the 

 Cretaceous strata, stating at the same time that they were not positively 

 known to belong to that system. We still think it barely possible these 

 beds may be older than Cretaceous, though if represented, as we think they 

 are, by similar beds seen holding about the same position near the mouth of 

 Judith river, far up towards the sources of the Missouri, we must either refer 

 them to the Cretaceous system, or admit the introduction of the genus Baculites 

 before that epoch, as we have fragments of a small species of that genus from 

 the Judith river beds. At the same time it should be borne in mind that 

 these strata at the last named locality are characterized by a group of fossils 

 remarkably distinct from those in the rocks above, and that one species be- 

 longs to the genus Ilettangia, a type of bivalves, not known to occur, in the 

 old world, in more modern formations than those of the age of the Lias. If not 

 older than Cretaceous, we think, from these facts, as well as from the strati- 

 graphical position of these beds, they probably represent some of the older- 

 members of that system." 



Although all our information as yet obtained respecting this sandstone 

 formation is obscure, we have indications that when thoroughly studied, it 

 will prove one of the most important and widely distributed in the far West. 

 From all the evidence I can obtain after a careful study and compai'ison of 

 these beds, with the minute descriptions of Sir John Richardson, and still later 

 those of Mr. Isbister, I am led to believe, with some confidence, that this forma- 

 tion is but a southern extension of the great lignite formations mentioned by 

 those gentlemen as stretching along the eastern slope of the Rocky Mountains, 

 far northward to the Arctic sea. Though, as suggested in a former paper by 

 Mr. Meek and me, some of these lignite deposits in the north western portions 

 of the British possessions may belong to the Tertiary epoch. 



* See a paper by F. B. Meek and F. V. Hayden, in Proc. Acad. Nat. Sci. November 

 1856 



[May, 



