142 W. O. CROSBY ARCHEAN-CAMBRIAN CONTACT IN COLORARO 



ing the Williams Canyon section, he f<ays : "The Hedinientary beds fill 

 up in a remarkable manner the inequalities of the original surface of the 

 metamorphic rocks." Later* Hayden published an illustration of the 

 Williams Canyon contact which is reproduced here (figure 1). It cer- 



FiGURK 1. — Cambrian Sandstone in Williams Cam/on, Colorado (Hayden). 

 The sandstone rests iiuconformably on gneissoid granite. 



tainly tells a very different storj^ ; but having read the statement of 1873 

 before my first visit to Manitou, I concluded that the illustration had 

 been selected simply to show a clear unconformity, and was not to be con- 

 sidered representative as to details. I anticipated, therefore, a repetition 



of the phenomena of the Boston basin, where the basal Carboniferous 

 strata fill marked depressions and even crevices in the granite surface 

 (figure 2), which is full}' comparable in ruggedness with that which the 

 granite presents on the same coast today. I was thus wholly unprepared 



* .'\un. Rep. U. S. Geol. and Geog. Surv. of the Territories, 1874, pi. G, fig. li. 



