598 ^V. T. LEE STRATIGRAPHY OF COAL FIELDS OF NEW MEXICO 



collected by the writer, T. W. Stanton makes the following statement, 

 covering both the Mancos and the Mesaverde fauna : 



"The distribution of the faunas agrees with the field determination that the 

 coal-bearing rocks of the Cerrillos, Hagan, Tijeras, and Rio Puerco fields 

 [also those of the Cabezon region] all belong to one formation. In the Tijeras 

 and Rio Puerco fields the marine fauna associated with the coal occurs in 

 rocks overlying part of the coal beds as well as immediately beneath them [as 

 described by Mr. Lee, who collected the fossils]. This fauna is closely related 

 to the Cretaceous faunas of the Gulf and Atlantic borders and is especially 

 related to the fauna which occurs a short distance beneath the coal at San 

 Carlos near the Rio Grande in western Texas. It apparently does not extend 

 far northward, the most northern point at which it has been found being in 

 the neighborhood of Cabezon. It is, of course, true that there are some similar 

 and perhaps a few identical species in the Montana group faunas of Colorado 

 and more northern areas, but the general association of forms and most of the 

 species are entirely different Its horizon is that of the lower part of the 

 Montana group not far above the horizon of the Austin and the Niobrara, and 

 hence apparently somewhat lower than the upper part of the Mancos as devel- 

 oped in southwestern Colorado. It is my judgment, therefore, that the base of 

 the coal-bearing rocks in the central New Mexican fields mentioned is lower, 

 perhaps by several hundred feet, than the base of the Mesaverde in the neigh- 

 borhood of Durango, Colorado. It is worthy of note that Mr. Lee's collections 

 show a good development of the Benton fauna in the beds underlying those 

 containing the fauna associated with the coal, and this Benton fauna is, with 

 some additions, essentially the same that occurs in the lower 400 feet of the 

 Mancos shale in its tyi>e area, and also in the Benton east of the mountains in 

 Colorado." 



MESAVERDE FORMATION 



The Mesaverde consists principally of sandstone, shale, and coal. It is 

 423 feet thick near Dnrango, Colorado, and about the same at Monero, 

 New Mexico, but is very much thicker farther south. Most of the sand- 

 stone is yellow and occurs in beds, some of which are massive and thick, 

 alternating with shale. In some places the sandstone is more or less 

 lenticular and contains irregular masses of impure limestone with great 

 numbers of marine invertebrates. Some of the shale also contains marine 

 fossils. These rocks of marine origin alternate with those containing 

 beds of coal and fossil plants. 



Fossils were collected from the Mesaverde at many localities. Those 

 collected where the sections were measured are denoted by the lot 

 numbers, which identify them in the collections of the United States 

 Geological Survey, and the same numbers are placed in the generalized 

 sections, figure 2, to mark the horizons from which they came. The 

 localities where they were collected are also indicated by the same num- 

 bers on the accompanying map. Those collected at a distance from the 



