STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 91 



Gardner"* afterwards examined this line more in detail. Here 

 he regarded the upper and middle groups of Schrader as Mesaverde 

 (here evidently in part Lower Pierre), to which he assigns a thick- 

 ness of about i,ooo feet east from Gallup. The coal seams are 

 numerous but variable ; " within a few miles, thin beds undoubtedly 

 thicken to valuable properties and thicker beds thin to mere traces." 



Farther north between San Mateo and Cuba, the Mesaverde, 

 1,200 feet thick, is coal-bearing throughout. Near the top is the 

 first appearance of the Lewis shale, which contains much sandstone 

 and sandy shale. There, one is little more than 40 miles north- 

 west from the Rio Puerco locality, where Lee found marine fossils 

 at top of the Mesaverde and thought that the deposits might be the 

 equivalent of Lewis shale. No trace of that shale is reported from 

 any locality farther south in the San Juan Basin. Along this por- 

 tion of the outcrop, the Mesaverde coal seams are in two groups, 

 separated by 300 feet of barren measures ; the seams are all lenticu- 

 lar and in several instances have bony coal at top or bottom or both. 

 Gardner's observations north and west from Cuba are important. 

 At a little north from Gallina, 14 miles north from Cuba, the Lewis 

 is 2,000 feet while westward it becomes only 250 near Raton Spring. 

 Gardner thinks this westward change due to replacement with sand- 

 stone, which has been regarded as Mesaverde. The condition south- 

 east from Cuba confirms the suggestion, for there the Mesaverde is 

 but 719 feet, with no coal in the basal 300 feet and only coaly shale 

 or thin coals at widely separated horizons in the upper part. The 

 thinning is more notable beyond Gallina, where the Mesaverde is 

 but 214 feet and contains 14 coal seams, of which only one is of 

 workable thickness. The coal is subbituminous, occasionally resin- 

 ous and the seams are variable to the last degree. The Mesaverde 

 is limited, top and bottom, by massive sandstones which persist 

 although the section is decreased. Lee''^ states that Gardner's col- 

 lections from Lewis shale and from Mesaverde south and southeast 

 from Cuba, are marine. He saw great numbers of petrified stumps 

 and logs in the lower part of the Mesaverde near Cabezon, where 

 the upper part of the Mancos has Pierre fossils. 



64 J. H. Gardner, Bull. 341, 1909, pp. 339, 343, 345, 366, 372, y]T, Bull. 381, 

 1910, pp. 463, 470. 



*^s W. T. Lee, Bull. Gcol. Soc. Anicr.. Vol. 23, pp. 619-621. 



