SOME STAGES OF APPALACHIAN EROSION. 525 



plain features which in the field can be traced past one another as parts of different 

 peneplains. In other cases a i^eneplain actually slopes, but its slope is with the 

 fall of the stream and in a direction contrary to that demanded by the extreme 

 theory of warpin<2i. In short, the slopes of the peneplains are so slight in the great 

 majority of cases as to distinguish warping as the exceptional form of uplift. Al- 

 though the process was a simple one, the succession of uplifts was long and quite 

 complex. A. full understanding of the different stages demands the expenditure 

 of much time and connected field work, and will be made the subject of future 

 publications. 



The following paper was read by title : 



THE CERRILLOS COAL FIELD OF NEW MEXICO 

 BY JOHN J. STEVENSON 



\_Abstract] 



During August, 1835, the writer had an opportunity to revisit the Placer coal field 

 of New Mexico, now known as the Cerrillos coal field. It is about 25 miles south 

 from Santa Fe and directly beyond the Galisteo river. The field is small, appar- 

 ently a detached portion of the Laramie area extending far southward within the 

 Rio Grande region. 



The district of especial interest is that lying south from Cerrillos and Waldo, 

 stations on the Santa Fe railroad. It is less than two miles wide, and reaches south- 

 ward to little more than five miles from the Galisteo, but it contains evidently all 

 of the workable coal beds, and exhibits the transition from bituminous to anthra- 

 cite in a very satisfactory manner. The mines are all on Coal canyon, which ex- 

 tends from the Placer or Ortiz mountains at the south to Waldo at the north, some- 

 what more than six miles. 



The Ortiz mountains are largely trachytic; from them there extend northward 

 two plates, each about 200 feet thick, which pass between l^aramie strata and follow^ 

 very closely the dip of the stratified beds. The upper plate covers the area east 

 from Coal canyon, and is now the surface rock, the overlying beds having been 

 removed. It extends northward to somewhat less than two miles south of Waldo, 

 terminating opposite the lower end of the village of Madrid, where are the offices 

 of the Cerrillos Coal Company. The lower plate, about 400 feet below the upper, 

 does not come to the surface on Coal canyon, but it was reached in a boring on the 

 mesa immediately west and comes out in an arroyo within a few rods west from 

 the boring. Several dikes extend upward from this plate, one evidently vei'y large 

 being shown west from Coal canyon, which mus:: have been connected with the 

 upper plate, as it rises very high above the mesa ; a second is seen in Coal canyon, 

 not more than 10 or 12 feet wide; it does not reach the upper plate ; a third, very 

 narrow, found in the same canyon at a mile and a half above Madrid, passes dis- 

 tinctly into the upper plate. Professor Kemp examined the specimens from several 

 exposures and recognizes the close resemblance in composition throughout. 



The only stratified rocks within the district examined belong to the Laramie, and 

 the exposed section is somewhat more than 1,000 feet thick. The rocks resemble 

 those of the same age in the Trinidad coal field, but shale is present in greater pro- 

 portion. Limestone is wholly absent, apparently, and the sandstones are unusually 

 non-fossiliferous. The coal beds are numerous, but most of them are very thin and 

 several are not persistent in all of the sections. 



LXIII— Bull, Geol. Soc. Am., Vol. 7, 1895, 



