THE FLORA. 



103 



• Nelumbium tenuifolium. Sand Creek, Colorado (Prof. A. 

 Gardner). 

 Quercus viburnifolia. Sand Creek (A. R. Marvine). 



These species are similarly recorded in the 

 catalogue of fossil plants in the United States 

 National Museum, in Lesquereux 's own hand- 

 writing, so it may be presumed that the state- 

 ments are correct, at least so far as his informa- 

 tion went. The species obtained by Marvine 

 was doubtless collected on the occasion of his 

 visit there in 1873, but no data are available 

 as to the date on which the two species ac- 

 credited to Prof. Gardner were collected. 

 W. H. Holmes assisted Marvine , in his geo- 

 logic work in 1873, and the plants recorded 

 as having been collected by him were probably 

 obtained at that time, but on consultation 

 with Prof. Holmes I find that he has now no 

 recollection of having collected the plants, or, 

 indeed, of having visited any coal mines east 

 of Denver. This injects another element of 

 uncertainty into the already sufficiently com- 

 plicated matter, but we shall probably never 

 come any nearer to a complete explanation. 

 To sum up, it appears in its final analysis that 

 we do not know the precise locality for a single 

 one of these Sand Creek plants, though in all 

 reasonable probability fliey apparently! came 

 from the vicinity of the coal openings on Coal 

 or Sand Creek about 15 miles east of Denver; 

 but as the locality is in doubt, it naturally 

 follows that the horizon is also uncertain. 

 It was apparently assumed by Cross that they 

 came from the Arapahoe, for he stated that 

 along Sand Creek this formation rests on the 

 Laramie, but according to the map showing 

 the areal geology in the Denver Basin mono- 

 graph, the Laramie occurs on the north bank 

 of the creek, and the Denver on the south 

 bank, no Arapahoe being indicated. Cross, 13 

 in discussing the Sand Creek locality, said: 

 "The specimens preserved in the National 

 Museum do not satisfactorily indicate the 

 horizon from which they came. It seems 

 probable that a part of them came from the 

 Arapahoe beds and a part from the Laramie. " 



Up to this point, from the data available, it 

 appeared to me that if any. of the Sand Creek 

 plants came from the Laramie they probably 

 all did, and on this basis it was my original 

 intention to include them provisionally in the 



» Cross, Whitman, U. S. Geol. Survey Mon. 27, p. 225, 1896. 



present work. However, important observa- 

 tions made by W. T. Lee during the field season 

 of 1915 put an entirely different light on the 

 matter and have led me to exclude all the Sand 

 Creek species from both Arapahoe and Laramie, 

 and to refer them with little or no question to 

 the Denver. The evidence is as follows: Lee 

 examined the log of a deep well that has been 

 drilled about 2h miles northeast of Coal Creek 

 (or Sand Creek). This well starts at tbe sur- 

 face in sandy coal-bearing beds that are litho- 

 logically > and stratigraphically identical with 

 the beds in question along Sand Creek, and are 

 also the same as the coal-bearing beds at Scran- 

 ton, which from the presence of coal are sup- 

 posed to be in the upper part of the Laramie. 

 Lee's description of the well is as follows: 



Section of oil well east of Denver, Colo., in sec. M, T. 3 S., 

 R. 67 W. 



Denver: Feet. 



Clay, sand, and gravel 200 



Coal | . r 2 



Clay, sand, and arkose. r"*^* 011 ] 248 



Coal J I 4 



Sand, gravel, and clay 346 



Arapahoe: 



Conglomerate 50 



Laramie: 



Soft blue shale 175 



Sandstone and shale alternating. ... 275 



Shale, light colored 140 



Shale, dark colored 35 



Brown shale 65 



Coal 10 



Fox Hills: 



Massive sandstone containing ar- 



- tesian water 130 



Shale 10 



Sandstone 20 



Pierre: 



Shale and limestone (shells) . . 1,' 500-r 



The facts brought out by this well record are 

 of far-reaching significance. It shows that the 

 Scranton coal, heretofore thought to be in the 

 upner part of the Laramie, is about 350 feet 

 above what is believed to be the Arapahoe con- 

 glomerate. This conglomerate is about 50 feet 

 thick. It also appears that the Scranton coal 

 is more than 400 feet above beds that can with 

 reasonableness be referred to the Laramie, and 

 more than 1,000 feet above the main Laramie 

 coal. The thickness of beds between the 

 Scranton coal and the main Laramie coal is not 

 of particular significance in view of the fact 

 that the maximum thickness previously as- 



