THE BUILDING OF THE COLORADO ROCKIES 



229 



the Long's Peak quadrangle, one had to be satisfied with the land 

 surveyor's map of Grand County and the Department of Agri- 

 culture's Forest Service map of the Holy Cross National Forest, 

 which together cover the remainder of the section. 



Throughout this section of 135 miles, the dips of the strata 

 were read wherever obtainable, and were plotted to scale as the 



Fig. 9. — State Bridge sheet (No. 9) on right and Castle Peak sheet (No. 10) on 

 left. Formations: (i) pre-Cambrian; (2) Sawatch; (4) Blue limestone; (5) Weber 

 and Maroon formations; (6) Red Beds; (7) Morrison; (8) Dakota; (9) and (10) Man- 

 cos; (11) Mesa Verde. 



Fig. 10. — Gj^sum sheet (No. 11) on the right and Dotsero sheet (No. 12) on the 

 left. The peneplain level appears high above the present surface because this section 

 is within the Grand River Valley. Conventions as before. 



basis for the reconstruction of the original folded structure. Com- 

 pared with the Pennsylvania Appalachians, the Colorado Rockies 

 present greater obstacles to an investigation of this sort, because 

 it is impossible to obtain equally complete data. In the Appala- 

 chians of Pennsylvania the sedimentary beds still persist throughout 

 the mountainous region to such an extent that from the remnants 

 the original outlines of the folds may be reconstructed with the 

 assurance of reasonable accuracy. But among the Colorado 



