84 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



trunks along with worm borings and impression-like Halymenites. 

 The extreme instability of conditions on the sandy flats, where coal 

 accumulated, is shown by variations in the Trinidad coal bed, mined 

 at Engle and Starkville. Stevenson's measurements are given in 

 the preceding table. 



These measurements are all within 3 miles from the first and the 

 position to the Trinidad sandstone precludes all probability of error 

 in correlation. The Trinidad sandstone is practically without coal.^^ 



Fox Hills conditions are distinct farther north on the Arkansas 

 River in the Canyon City coal field. Stevenson visited this field in 

 1873, but the movements of the party, to which he was attached, 

 were so rapid as to give opportunity only for errors. He visited it 

 again in 1881 and W'ashburne examined it in detail during 1908. 

 These observers recognized the Trinidad sandstone, from which 

 Stevenson, in both visits, obtained Halymenites. The Vermejo for- 

 mation is about 500 feet thick, including the basal sandstone and 

 its uppermost member is a massive sandstone, 145 feet, containing 

 abundant Halymenites. According to Washburne, this member, 

 nearer the mountains, loses its marine fossils, is less massive, is 

 cross-bedded and has all the characteristics of a fluviatile deposit. 



The coal seams are numerous and some are important. One, 

 resting on the Trinidad sandstone, is 3 ft. 4 inches thick with at 

 times shale, at others, sandstone as the roof, the less thickness be- 

 ing under the sandstone. The shale is o to 7 feet thick, showing 

 that the erosion followed deposition of the shale. Sandstone 

 " rolls " were seen by Washburne in a bed about 275 feet above the 

 Trinidad sandstone. These extend for long distances and the sand- 

 stone passes through the roof clay, often through the coal to the 

 floor. These " rolls " have rounded bottom, curved sides and the 

 trend is toward northeast throughout the mine. The current bed- 

 ding in the " rolls " indicates a northeast flow for the streams. 

 Resin occurs in the lowest coal seam. 



Fox Hills has been recognized in the Denver Basin by Eldridge 



^1 J. J. Stevenson, U. S. Geog. Expl. W. of looth Aler., Vol. III., sppl, 

 1881, pp. 102 ff. ; G. B. Richardson, Bull. 381, 1910, pp. 385, 386, 395, 411 ; W. T. 

 Lee, Bull. Geol. Soc. Amer., Vol. 23, 1912, p. 611. It is unfortunate that Lee's 

 elaborate report on the Raton coalfield is still unpublished. 



