UTAH PENEPLAINS 
135 
sion of coal-yielding beds which, around the southern Rockies were 
so long denominated the Laramie Coal Series, were found after¬ 
wards to comprise rocks of very different geological ages. Often 
they were Cretacic in the lower part of the “Laramie” section, and 
Tertic in the upper portion. 
Identical vertical sequences obtain in the Raton Range of 
northeastern New Mexico as in the High Plateaux of Utah. In 
both of these widely separated districts a notable erosion-plane is 
found to divide an otherwise apparently unbroken sequence. In 
neither locality do true Laramie beds appear to be represented. 
South of the Wyoming line the epoch seems to have been a vast 
erosion interval, during which more than a mile of strata was 
removed. 
Recent introduction of a new nomenclature for the Cretacic 
formations on the west side of the Cordilleran belt notably com¬ 
plicates rather than affords solution to the vexed Laramie ques¬ 
tion. Because of their errors in correlation the early workers 
in the field. King, Hayden, Powell, and White, completely mis- 
interprete Utah diastrophics. They mistake the later named 
Mesa Verde lignites for the typical Laramie deposits; whereas 
there are two distinct lignite formations, separated elsewhere by 
more than 2000 feet of marine shales. Failure to recognize the 
diastrophic factor over the Cordilleran tract also acts in another 
curious way, especially as concerns some of the more recent in¬ 
vestigations in this field. As a direct result no exact adjustment 
of the Cretacic sections on the west and east sides of the Rockies is 
possible. 
Were this possible correlation made directly across the Cordil¬ 
leran uplift would be an easy matter. Western brackish, or 
fresh-water, or epirotic, deposits, separately or together, of the 
Mesa Verde and typical Laramie formations are merely extended 
into eastern marine sequence represented by the Coloradan and 
Montanan series. This relationship is readily traced around the 
southern end of the Rockies, in central and northern New Mexico. 
The Mesa Verde sandstones are thus regarded as a thick littoral 
terrane intercalated in the middle of the great section of Montanan 
shales of marine origin. Whether or not an equivalent of the 
formation is ever recognizable in the Montanan section of the 
