HISTORICAL REVIEW OF THE LARAMIE PROBLEM. 



23 



coal resources of this area, and after describing 

 briefly the Pierre shale and Fox Hills sandstone, 

 he wrote as follows concerning the Laramie: 



Above the Fox Hills sandstone lie the coal-bearing rocks 

 of Laramie ftge. These may be divided into two mem- 

 bers — a lower including several massive sandstone beds 

 and three or more of the most important coal beds of the 

 field, and an upper composed of clay shale, sandy shale, 

 and some sandstone with poorly developed coal beds. 



The best exposure of the sandy, coal-bearing member is 

 in Popes Bluff, where the base of the formation is com- 

 posed of a massive sandstone from 40 to 100 feet thick but 

 not sharply defined from the underlying Fox Hill. The 

 upper part of the sandstone member of the Laramie gi\ es 

 way gradually, toward the east, to shale with thin beds of 

 calcareous and ferruginous sandstone about 250 feet thick. 

 In the western part of the field the sandy member is about 

 200 feet thick. 



Owing to the incompleteness of the paleon- 

 tologic evidence, mainly that of fossil plants, 

 Goldman did not make definite age determina- 

 tions for the rocks above the Laramie, which 

 were described under the terms "conglom- 

 erate," "andesitic material," and "arkose," in 

 ascending order. 



In some parts of the field the shaly part oi 

 the Laramie is overlain by a conglomerate, 

 which has a maximum known thickness of 

 about 30 feet. "The lithologic similarity of 

 this bed to some parts of the Arapahoe forma- 

 tion in the Denver Basin is apparent." 



At a number of localities the conglomerate it 

 overlain by beds of andesitic material, "which 

 in lithologic composition is similar to the Den- 

 ver formation." The average thickness of the 

 beds of andesitic material is about 125 feet. 



Beds of arkose lie unconformably upon the andesitic 

 material and overlap the coal-bearing sandstone in the 

 southeast corner of sec. 6, T. 13 S., R. 67 W. The arkose 

 has two phases — (1) coarse arkose near the mountains, 

 some sandstone, and clay containing coarse quartz grains; 

 (2) fine-grained, very micaceous sandstone. Both phases 

 are very irregularly bedded, and most of the lithologic 

 units are of small horizontal extent. 



The greatest thickness of arkose measured 

 was 300 to 400 feet in Corral Bluffs, but the 

 total thickness was believed to be still greater. 



A number of collections of fossil plants made 

 in the immediate Colorado Springs area by 

 A. C. Peale, M. I. Goldman, and others were 

 submitted to me for study at this time (1908). 

 This material was not well preserved, owing to 

 the friable nature of much of the matrix, and 

 it was studied with difficulty. With the ma- 

 terial available I was not then able to differen- 



tiate the three formational units — Laramie, 

 Arapahoe, and Denver — that were theoretically 

 inferred to be present; in fact, the Laramie 

 elements appeared to preponderate so greatly 

 that I was inclined to refer all the plant collec- 

 tions to the Laramie. On bringing together 

 in a single list all the forms enumerated in 

 these collections, as well as those reported 

 originally by Lesquereux from the Gehrung 

 mine and Franceville — both in the acknowl- 

 edged Laramie — it was found that a total of 

 49 forms were represented. Of these 22 were 

 not specifically determined, leaving 27 named 

 species, most of which were known outside the 

 Colorado Springs area. On analysis, it ap- 

 peared that 19 of these forms were found in 

 Laramie or older beds, but, as will be pointed 

 out later, nearly all of these are found in the 

 lots which belong to the Laramie and about 

 which there is no question. There was one 

 lot, however, collected high in the section of 

 the bluffs just west of Templeton Gap that as 

 then identified did much to influence my refer- 

 ence of these beds to the Laramie. As origi- 

 nally listed this lot contained the following 

 forms ; 



Sequoia brevifolia Heer. 



Sequoia longifolia Lesquereux. 



Dammara sp. cf. D. acicularis. 



SalixVsp., fragment. 



Ficus trinervis Knowlton, fragment. 



Rhamnus salicifolius Lesquereux. 



Cyperacites sp. 



Viburnum? sp. 



Carpites sp. (poor). 



At the time these identifications were made 

 the "Monument Creek group" was supposed 

 to be of Oligocene age, and it was deemed 

 absolutely impossible that these plant remains 

 could be of this age; in fact, if they were 

 correctly identified and stood alone, there 

 would ordinarily be no hesitation in referring 

 them to the Laramie, which I did. Since that 

 time, however, I have twice visited this region 

 and collected material from this locality, as 

 well as from neighboring localities of similar 

 stratigraphic position, and I have also collected 

 material and studied several collections made 

 some 20 miles or more to the east, out on the 

 plains, with the result that I have acquired a 

 better understanding of the forms represented 

 and their stratigraphic relations. 



A number of the species of plants from the 

 Pulpit Rock area are the same as those occur- 



