16 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



ters of the lower sandstone, as well in (he northern area of the Lignite as in 

 the southern, and has come to the same conclusion expressed here, that it 

 exposes a gradual change or transition, by (he slow upheaval of the land, 

 merely a passage from a marine Cretaceous formation to a Tertiary land 

 formation. 



In the report above quoted, sections are given of the distribution of the 

 Lignite at Canon City near Pueblo, Gehring's Coal near Colorado Springs, 

 Golden, etc., which represent the same general distribution of the strata, 

 with mere local modifications, which do not affect in any way the general 

 cliaracters of the group. I can give only a few of the most important sec- 

 lions, especially those which give a satisfactory representation of the capacity 

 of the measures for combustible mineral. 



At Golden, seventeen miles west of Denver, the Tertiary Measures, 

 thrown up by the upheaval of the mountains against a basaltic ridge parallel 

 to their base, have been forced up in a vertical position, and thus, from this 

 place to Coal Creek, the Lignitic beds are exposed and worked from their 

 edges, their thickness varying from four to fourteen feet. 



Further north, in the Boulder Valley, the measures come to their normal 

 position, dipping in various degrees from the mountains toward the plains, 

 and at Marshall a fine exposition of the Lignitic is presented, as seen in the 

 following section. It is copied from Dr. Hayden's Report, 1869, p. 129, and 

 is scarcely different from that published before, from the same locality, by 

 Dr. John L. Le Conte, and also from that which I received later from the 

 proprietor of the coal : — 



48. Drab clay, with iron ore along the top of the ridge. 

 47. Sandstone. 

 46. Drab clay and iron ore. 

 45. Coal (No. 11), no development. 

 44. Drab clay. 

 43. Sandstone 15 to 20 feet. 

 42. Drab clay and iron ore. 

 41. Coal (No 10), no development. 

 40. Yellowish-drab clay, 4 feet. 

 39. Sandstone, 20 feet. 



38. Drab clay, full of the finest quality of iron ore, 15 feet. 

 37. Thin layer of sandstone. 



