BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 23, pp. 267-276 JUNE 15, 1912 



THE MONUMENT CREEK GEOUP ' 



BY G. B. RICHARDSON 



(Read before the Society Decemher 27, 1911) 



CONTENTS 



Page 

 Introduction 207 



Previous work 267 



Present worlc 2(58 



The Castle Rock conglomerate 270 



The Dawson arkose ; 271 



Relations of the Dawson arkose to the Denver and Arapahoe formations. 274 



Correlation 275 



Introduction" 

 previous work 



The Monument Creek group is the name introduced l)y Hayden," in 

 1869, for the "series of variegated beds of sands and arenaceous clays 

 ... of various colors . . . and of various degrees of texture" which 

 occur on the Platte-Arkansas Divide along tlie base of the Front Range 

 in Colorado. Since their first description these rocks have been often 

 referred to, notably by Hayden,^ Cope/ Emmons,^ Eldridge,*^ Lee/ and 

 Darton.^ Hayden at first considered the Monument Creek group 

 "Modern Tertiary/' on the basis of its general appearance and uncon- 



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

 Manuscript received by the Secretary of the Society January 20. 1012. 



2 F. V. Hayden: I'reliminary Field Report of the U. S. Geological Survey of Colorado 

 and New Mexico, 1809, pp. .39-40. 



3 F. V. Hayden : Seventh Ann. Rept. IT. S. Geological and Geographical Survey, 1874, 

 pp. .S2 and .3.3; Eighth Ann. Rept. U. S. Geological and (ieographirai Survey. ISTfi. pp. 

 36 and 37. 



* E. D. Cope : Seventh Ann. Rept. U. S. Geological and Geographical Survey, 1874, 

 p. 430. 



" S. F. Emmons : Denver Monograph, T'. S. Geological Survey, no. xxvil, 1896, pp. 38 

 and 39. 



•^ G. H. Eldridge : Denver Monograph, U. S. Geological Survey, no. xxvii, 1896, pp. 252 

 and 254. 



'Willis T. Lee: American Geologist, February. 1902. pp. 101-103. 



* N. H. Darton : American Journal of Science, vol. 20, 1905, pp. 178-180. 



XIX— Bull. Geol. Soc. Am., Vol. 23, 1911 (267) 



