FLORA OF THE FEUITLAND AND KIETLAND FORMATIONS. 



329 



that is composed of red, gray, yellow, and white pebbles. 

 The position of these beds is below what may be called 

 the type of the Puerco or basal Eocene. * * * Below 

 the conglomerate there is a series of shales and sandstones, 

 evenly stratified and usually horizontal, in wliich there 

 is much less cross-bedding than commonly occurs in the 

 Laramie of the northern United States. 



The shales below the conglomerates that contain numer- 

 ous dinosaur and turtle remains I shall designate as the 

 Ojo Alamo beds. They are estimated to be about 200 

 feet tliick, but owing to lack of time I was unable to deter- 

 mine their relations to the underljing formations. 



Also in 1910 appeared a paper by Gardner ' 

 that involved incidentally the beds vinder dis- 

 cussion. He records the Puerco as resting 

 luiconformably on the underlying beds, as 

 Brown had reported, and he states that at 

 Ojo Alamo he "obtained dinosaurs from beds 

 unconformably above the ' Laramie ' and below 

 the Wasatch." Tlaesebeds are, of course, the 

 Ojo Alamo beds of Brown. 



From the preceding brief statements it 

 appears that for more than 40 years the upper 

 coal-bearLng rocks of the San Juan Basin have 

 been regarded more or less definitely as of 

 Laramie age, though during quite half of this 

 tune there has been growing an undercurrent of 

 opinion that the beds may be older than the 

 Laramie. The object of the present study is 

 to ascertain the bearing of the fossil plants on 

 this question, and it may be stated here that 

 the plants appear fully to sustain the opinion 

 that the beds are older than the Laramie. 



The fossil plants upon which the present 

 report is based were obtained by C. M. Bauer 

 during his geologic studies of the season of 

 1915 in that portion of the San Juan Basin, 

 embraced within San Juan County, N. Mex. 

 The stratigraphic results of his investigations 

 are set forth at length in the paper by Bauer,- 

 and in the present connection it is necessary 

 only to give them in brief outline. In that 

 portion of the coal-bearing and associated 

 rocks previously referred to as the "Laramie" 

 of that region Bauer has recognized two htho- 

 logic tmits. The lower of these units, called 

 the Fruitland formation, is about 300 feet thick 

 and includes the coal-bearing beds. Above it 

 is a series of shales, called tlie Kirtland shale, 

 with an intercalated sandstone, the Farmington 

 sandstone member, and the whole formation 

 has a maximmn thickness of nearlj^ 1,200 feet. 



1 Gardner, J. H., The Puerco and Torrejou formations of the Naci- 

 miento group: Jour. Geology, vol. 18, pp. 702-741, 1910. 



2 U. S. Geol. Survey Prof. Paper 98, pp. 274-275 ( Prof . Paper 98-P). 



Above the Kirtland shale, without observed 

 stratigraphic break, is the Ojo Alamo sandstone, 

 which Bauer thinks shotild be grouped with the 

 imderlying Kirtland and Fruitland formations. 

 A graphic presentation of the older and 

 newer views is given below: 



Older interpretat ion . 



Ojo Alamo. 

 Unconformity- 



■ Laramie. ' 



Pictured Cliffs. 



Newer interpretation. 



Ojo Alamo sandstone. 

 Conformity 



Farmington sand- 

 stone member. 



Shale. 



Fruitland formation. 



Pictured Cliffs sandstone. 



THE FLORA. 



The material on which the present report is 

 based comprises 20 collections, of which 15 are 

 from the Fruitland formation, 3 from the 

 Kirtland shale (2 from the extreme top and 1 

 from the base of the formation), and only 1 

 from the Ojo Alamo sandstone. The bulk of 

 the material comes from the lower or coal- 

 bearing portion of the section, and much of 

 this is preserved on a red baked shale, indi- 

 cating proxunity to coal. 



The material in the single collection from the 

 Ojo Alamo beds is so fragmentary that it can 

 not be identified witn satisfaction. It includes 

 portions of a large leaf of unknown affinity, a 

 small willow-hke leaf, and a large leaf that 

 appears to be an Araha of the type of Aralia 

 nofata Lesquereux, a species very abundant 

 and widely distributed in the Fort Union for- 

 mation. Nothing like this has been noted in 

 the underlymg beds, and to a certain extent 

 it argues for the Tertiary age of the Ojo Alamo 

 beds, though obviously the evidence is not 

 strong. For the present, therefore, the dictum 

 based on the evidence of the fossil vertebrates 

 that these beds can not be separated from tlie 



