88 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



nearer ithe source of sediment. One should expect to find in that 

 direction the same conditions as appear on the western border, where 

 important coals occur in the Benton. 



The Cerillos coal field, a few miles south from Santa Fe, New 

 Mexico, has been examined by several geologists whose conclusions 

 are not in agreement.^^ Stevenson thought that the coal-bearing 

 group belongs to the Laramie ; Johnson referred it to the Fox Hills ; 

 but Lee recognized the true relations and determined that it is 

 Mesaverde, the Middle Pierre in this field. The coal group is 

 about 1,200 feet thick and rests on Mancos shale, of which the top 

 150 feet carries Pierre fossils. The basal rock of the coal group 

 is a sandstone, 300 feet thick and without coal. It has an assem- 

 blage of fossils which suggests Fox Hills conditions. The coal 

 seams are numerous but variable. The sections of one bed at four 

 openings, as given by Stevenson, are 



Coal I ft. 2 in. Thin Streaks Absent 



Clay I ft. 3 in. 6 ft. o in. 12 ft. o in. 8-10 ft. 



Coal 2 ft. 3 in. 2 ft. 5 in. 4 ft. 7 in. 3 ft. lO in. 



Coaly shale .... 3 ft. 5 in. Absent Absent i ft. 



In one mine the coal has been replaced with sandstone in a space 

 75 feet wide and several hundred feet long, a case of contemporane- 

 ous erosion. Gardner^^ saw an apparently similar replacement in 

 the Omera field, east from Cerillos. At 500 feet from the outcrop 

 in a mine, the roof descended and cut out the coal. In 1879, 

 Stevenson noted a ripple-marked sandstone and an underclay with 

 roots. 



The only information available for present purposes, respecting 

 coal fields between Cerillos and the great San Juan Basin at the 

 west, is contained in Lee's publications. °-' The Hagan field directly 

 west from the Cerillos differs notably from the latter. The most 

 striking difference is due to increase of Mesaverde at expense of the 



■"^^J. J. Stevenson, U. S. Geog. Expl. W. of looth Men, Vol. III., Suppl., 

 pp. 147 ff. ; N. Y. Acad. Sci., Vol. XV., 1896, pp. 105 ff. ; D. W. Johnson, Sch. 

 Mines Quart., Vols. XXIV., XXV., 1903; W. T. Lee, Bull. Geol. Soc. Amer., 

 Vol. 23, pp. 642, 658; Bull. 531-^ 1913; Prof. Paper 95-C, 1915, p. 41. 



^3 J. H. Gardner. Bull. 381, 1910, p. 448. 



G^W. T. Lee, Bull. 389, 1909, pp. 5-40; Bull. Geol. Soc. Atner., Vol. 23, 

 pp. 622-642. 



