HISTORICAX, REVIEA\' OF THE LAEAMIE PROBLEM. 



of the invertebrates of the upper Missouri River 

 region, but before beginning the technical part 

 of the paper they again went over the geologj' 

 of the region, reafhi-ming their conclusion that 

 the lignite-bearing beds are of Miocene age. 



The next paper of importance dealing with 

 the geology of this region was anotlier by 

 Meek and Hayden " published in 1S61. In a 

 "general section of the Cretaceous rocks of 

 Nebraska" (p. 419) the stratigraphic units 

 previously known only by number first re- 

 ceived the names by which they are now so 

 widely recognized. These are as follows: 



No. 5= Fox Hills. 

 No. 4=Fort Pierre. 

 No. 3=Niobrara. 

 No. 2= Fort Benton. 

 No. l=Dakota. 



Meek and Hayden also presented in this 

 paper (p. 433) the first complete section of 

 Tertiary rocks of the upper Missouri River 

 region, given in the following sequence: 



Loup River beds. 



White River group. 



Wind River deposits. 



Fort Union or Great Lignite group. 



As we are concerned in the present connec- 

 tion only with the lower of these divisions, the 

 others may be passed over. Their description 

 of the Fort Union is as follows : 



Beds of clay and sand, with ferruginous concretions and 

 numerous beds, seams, and local deposits of lignite; great 

 numbers of dicotyledonous leaves, stems, etc., of the 

 genera Platanus, Acer. Ulinws, Populns, etc., with very 

 large leaves of fan palms; also Helix, Melania, Vivipara, 

 Corbicula, Unio, Ostrea, Pholadomomya, and scales of 

 Lepidotus, with bones of Trionyx, Emys, Compsemys. 

 Croeodilus, etc., occupy the whole country around Fort 

 Union, extending north into the British possessions to 

 unknown distances, also southward to Fort Clark. Seen 

 underneath the ^\'hite F.i\er group on North Platte River. 

 Also on west side of Wind River Mountains. 



Their conclusion as to the age of the Fort 

 Union was not very definite, owing largely to 

 the difficulty of interpreting the somewhat 

 conflicting plant and invertebrate evidence, 

 but the facts that it had been observed beneath 

 the White River deposits (regarded by them as 

 of Miocene age but now assigned to the Oligo- 

 cene) and that it contains certain vertebrate 

 remains not known in Europe above the Eo- 



** Meek, F. B., and Hayden, F. V., Description of new Lower Silurian, 

 Jurassic, Cretaceous, and Tertiary fossils, collected in Nebraska, * * * 

 with some remarks on the rocks from which they were obtamed: Acad. 

 Nat. Sci, Philadelphia Proc, vol. 13, p. 415, 1861. 



cene "strengthen the impression that this Fort 

 Union lignite group probably represents the 

 Eocene of Europe." 



For a number of j^ears succeeding the publi- 

 cation of the last-mentioned paper, or during 

 the years covered by the Civil War, there was 

 little scientific activity in the vast and then 

 almost unknown Western Temtories, but in 

 the spring of 1867 Hayden secured an appro- 

 priation from Congress for the geologic inves- 

 tigation of Nebraska. His report on this 

 area '^ was submitted from the field on Julj- 1, 

 1867. In tins he quoted without change the 

 general sections of the Cretaceous and Tertiary 

 rocks of Nebraska, from the paper of 1861, 

 above mentioned. The area supposed to be 

 covered by the "Fort Union or Great Lignite 

 group" was greatly extended, occupj-ing not 

 only all the country along the Missouri from 

 Heart River to the Musselshell, most of the 

 valley of the Yellowstone, and northward into 

 the British possessions, but southward as far 

 as the North Platte and "coming to the surface 

 again at Pikes Peak, Colorado, and extending 

 to Raton Pass, in New Mexico." The coal near 

 Denver and Golden, in the Denver Basin, as well 

 as what is now known as the Canon City field 

 and thence southward to the Raton Pass dis- 

 trict, was considered to be of Tertiary age, and 

 this view was affirmed the following year.'* 

 In Hayden's third annual report," which em- 

 braced Colorado and New Mexico, the area 

 over which the coal-bearing rocks are dis- 

 tributed was greatly extended. "I regard all 

 the coal beds of the West as lower Tertiary" (p. 

 189) is his final word at this time. 



At this point a brief review may be given 

 of the reasons which up to this time had led 

 Hayden and others to regard the "Great 

 Lignite deposits" of the West as of Tertiary 

 age. These beds had been first studied in 

 the upper Missouri River region, where their 

 position above the marine CretaceouS section 

 was plainly marked. Although they were not 

 known to be separated from the marine Cre- 

 taceous by a discordance of any kind, they 

 were obviously above it. The paleontologic 

 evidence, at least so far as concerned the 



15 Hayden, F. V., U. S. Geol. Survey Terr. First Ann. Kept., pp. 

 1-64, 1867; reprint, 1S73. 



IS Hayden, F. V,, Notes on the lignite deposits of the West: Am. Jour, 

 Sci., 2d ser., vol. 45, p, 198, 1868; U. S. Geol. Survey Terr. Second .\nn. 

 Kept., 1868: reprint, 1873. 



" V. S. Geol. Survey Terr. Third Ann. Rept., 1869; reprint, 1873. 



