18 
THE BOOK CLIFFS COAL FIELD. 
Three-fourths of a mile northwest of Cameo, about 100 feet above 
the upper coal, a narrow leaf, apparently Salix, Sequoia Reichen- 
bachil (Gein.) Heer, and fragments of dicotyledons were found. 
Fifty feet above Ballard's coal mine north of Thompsons Anemia 
elongate, (Newb.) Knowlton and Myrica Torreyi Lesq. were found. 
About 200 feet above the coal at Carbonera fragments of dicotyle- 
dons, including Myrica Torreyit Lesq., were found. 
About 8 miles north of Thompsons, 250 feet below the conglomer- 
ate which is regarded as marking the base of the Eocene, the follow- 
ing were obtained : 
Fossil leaves from a locality about 8 miles north of Thompsons. 
Sequoia Reichenbachi (Gein. 
Sabalites Grayanus? Lesq. 
Ficus planicostata Lesq. 
Cinnamomum affine? Lesq. 
Heer. 
Malapoenna new. 
Ficus sp., very large, apparently new. 
Dicotyledon, very large, with three ribs, 
prominent teeth, etc., probably new. 
The only fossil bones from this formation were obtained east of 
Green River, about 500 feet above the top of the Mancos shale. 
They were determined by J. W. Gidley, of the United States National 
Museum, to be the distal ends of femurs of a dinosaur. 
There has been much misapprehension concerning the age of the 
coal-bearing rocks of the Uinta Basin. In the Book Cliffs field, as 
already stated, Peale mapped the rocks here referred to the Mesa- 
verde as two formations and correlated them respectively with the 
"Fox Hills" and the "Laramie." Later writers have considered the 
entire formation to be Laramie, because it overlies marine Cretaceous 
beds and in turn is overlain by Wasatch strata, and the fauna and 
flora were believed to belong to the Laramie. 
Just what constitutes the Laramie has long been a problem with 
geologists, but recent studies of the Rocky Mountain coal fields by 
the United States Geological Survey have thrown new light on the 
subject. The reason for assigning the coal-bearing formation of the 
Book Cliffs to the Mesaverde is explained in the following extract 
from a letter of T. W. Stanton to the writer, reporting upon fossils 
collected from this field. 
In northwestern Colorado, southern Wyoming, and elsewhere, many of the coal- 
bearing rocks previously called Laramie are really older and are overlain by marine 
Cretaceous formations, thus corresponding with the Mesaverde formation first described 
in southwestern Colorado. The Mesaverde formation has been identified in the 
Yampa field, where the stratigraphic evidence is satisfactory that it underlies a thick 
marine Cretaceous formation, correlated with the Lewis shale, which in turn is over- 
lain by the Laramie and later formations. South of the Yampa field, in the Danforth 
Hills and the Grand Hogback, the Mesaverde is clearly recognizable, but here there 
is an erosional unconformity which cuts out the Lewis and the Laramie and brings the 
Mesaverde in contact with the Fort Union" and possibly later formations. 
«Gale, H. S., Coal fields of the Danforth Hills and Grand Hogback in northwestern Colorado: Bull. U. S. 
Geol. Survey, No. 316, 1907, pp. 264-301. 
