BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



VOL. 20, PP. 357-368, PLS. 28-30 NOVEMBER 10, 1909 



U^ T 00KF0EMITY IN THE SO-CALLED LAEAMIE OF THE 

 EATON COAL FIELD, NEW MEXICO 1 



BY WILLIS T. LEE 



(Read before the Society December 29, 1908) 



CONTENTS. 



Page 



Preliminary statement of results 357 



Location and condition of the rocks described 358 



Rock formations 359 



Evidence of unconformity 361 



Conglomerate 363 



Measure of erosion 364 



Correlations 365 



Plant forms from the Raton coal field, New Mexico 367 



Preliminary Statement of Eesults 



The purpose of this paper is to describe an unconformity hitherto un- 

 known that is of more than ordinary interest because it divides rocks, 

 previously referred to the Laramie, into two distinct formations. The 

 investigation is not complete, but enough is known to warrant the state- 

 ment that during the time interval represented by the unconformity the 

 sedimentary rocks previously laid down within the Eaton field were sub- 

 jected to erosion for a considerable length of time and the Eocky moun- 

 tains west of this field were elevated and eroded to a depth of several 

 thousand feet. 



The positions in the geologic column of the two coal-bearing formations 

 are not yet fully determined. Until they are studied in detail and final 

 correlations made, the positions here assigned and the names used should 

 be regarded as serving only the temporary purpose of giving dehniteness 

 to the description. The upper formation has the stratigraphic position 

 of the Arapahoe of the Denver basin, but contains a flora apparently 

 more closely related to that of the Denver formation than it is to the 

 Laramie of the Denver basin. The lower one has the stratigraphic posi- 



1 Published by permission of the Director of the U. S. Geological Survey. 

 Manuscript received by the Secretary of the Society September 15, 1909. 



XXXI — Bull. Geol. Soc. Am., Vol. 20, 1908 (357) 



