PREVIOUS INVESTIGATIONS 577 



Tijeras and referred again to the occurrence of coal in the Ccrrillos and 

 Eio Puerco fields, and near Tierra Amarilla in the San Juan Basin. 



In 1869 Hayden (19), after a brief visit to the Cerrillos coal field, 

 referred the coal beds to the Tertiary, basing his conclusion on the fossil 

 plants which he found in abundance and which were later examined by 

 Lesquereux. In 1870 Eaymond (16) published a description of the coal 

 beds of the Cerrillos and other coal fields, treating them from an eco- 

 nomic standpoint. Tlie following year Newberry (17) published a brief 

 statement to the effect that the anthracite near Cerrillos is of Cretaceous 

 age, and in 1872 Lesquereux (18) followed with descriptions of the fossil 

 plants that had been collected from the Cerrillos coal measures and re- 

 ferred the beds containing them to the Tertiary, as Hayden had done 

 three years before. A year later, 1873, (21) he correlated the Cerrillos 

 coal beds with others which he regarded as Tertiary, notably with those 

 at Raton, New Mexico (which have recently been shown to consist of 

 two formations somewhat widely separated in time), and with the coal 

 measures near Canyon City, Colorado, the age of which is still debatable. 

 In the same article he refers to the coal measures in the Tijeras field, 

 and also to coal near San Felipe — doubtless at the northern end of the 

 Hagan field. 



During the controversy over the geologic age of the "lignitic group" of 

 Hayden, which raged in the early seventies, several more or less obscure 

 references were made to the coal beds of northern New Mexico, but too 

 little was known of them to bring them seriously into the controversy. 

 Many of these are noted in the list of publications on pages 659-686, 

 but need not be mentioned here, inasmuch as the character of the infor- 

 mation contained is indicated by the notes, accompanying the titles of the 

 papers. 



During the years 1871 to 1873, inclusive, certain explorations were 

 made in regions west of the 100th meridian, including the areas de- 

 scribed in this paper. Several geologists w^ere connected with these 

 explorations and published, in the Wheeler reports and elsewhere, many 

 facts of interest regarding the coal measures of New Mexico. Loew (30) 

 mentions the occurrence of "Cretaceous lignite beds" in the San Juan 

 Basin near Nacimiento, and Cope (26) also published in 1874 a descrip- 

 tion of the coal measures exposed farther north in the same basin along 

 the tributaries of the Chama River and elsewhere, in wiiich he shows that 

 marine rocks of Cretaceous age occur above the coal beds. These are 

 evidently the Mesaverde coals of northwestern New Mexico, and the 

 marine rocks above them constitute the Lewis shale of later writers. 



