STATEMENT OF RESULTS 575 



section than the hase of that formation farther north. The Punta de la 

 Mesa sandstone seems to be equivalent to a sandstone which in the vicin- 

 ity of Cabezon occurs in the Mancos shale 500 feet or more below the base 

 of the coal-bearing rocks — Mesaverde — of the San Juan Basin. 



(4) The fossil plants from tlie so-called "Laramie" of the San Juan 

 Basin indicate that this formation may be older than the Laramie of the 

 Denver Basin. 



(5) The flora of the coal-hearing rocks below, the unconformity in 

 the Raton field is similar to that of the Mesaverde, and tends to make 

 that formation the time-equivalent of tlie Mesaverde. It has a less 

 striking resemblance to the flora of the so-called "Laramie" of thv San 

 Juan Basin, which Doctor Knowlton regards as older tluin Laramie. 

 On the otlier hand, the fauna of the shale immediately below the coal- 

 l)earing rocks of the Eaton field is similar to that of the Lewis shale, and 

 tends to correlate the older coal -bearing rocks with the "Laramie" of the 

 San Juan Basin. 



(6) Unconformities, representing erosion that probably took place 

 after the close of the Cretaceous period, are found in all of the coal fields 

 described in this paper. So far as is now known, this erosion originated 

 in the post-Cretaceous uplift of the Eocky Mountains, but cut deeper in 

 some places than in others, and persisted in some places longer than in 

 others.^ 



Previous Investigation's 



In another section of this paper will ])e found a complete annotated 

 list of the principal publications consulted during its preparation. Where 

 practicable, the datar that may be found useful in gaining a proper under- 

 standing of the geologic relations here discussed are enumerated. Among 

 these publications there are many that give little new information, but 

 are devoted principally to discussion or to reviews of papers previously 

 published, and a few that have furnished practically all of the geologic 

 information hitherto known. An attempt is made below to give a brief 

 historic account of these investigations and place in chronologic order 

 the principal contributions made toward an understanding of the geo- 

 logic relations and age of the coals of central and western Xew Mexico 

 and the rock formations with wliich thev are associated. Most of those 



^ The results presented in this paper are so largely dependent on paleontology that 

 more than ordinary credit should he given to Dr. T. W. Stanton, who identified the 

 invertebrates and assisted the writer in other ways, and to Dr. F. H. Knowlton, who 

 identified the fossil plants and placed at the writer's disposal a large volume of infor- 

 mation not yet published, but which has a strong bearing on the problems of correlation. 



