i;U CAKUONIKKKol'S FOBMATIUNS AND FAUNAS OF CULOKADO. 



Iili)(i(l-n'(l sliali's. I'tilldwcil in most casets Uy iii;i.s.si\ o })rick-rcd sandstone. In I'nii- 

 \vo(>p Canyon the sundstonos are laminated, wiiile northward and westward tliey 

 seem to he eonsolidated into one niassi\e l)ed. The^' are f(jllowed, as we descend 

 in the sei'ies, hy sliak's and hlood-red sandstones, which, on the Dolores, change 

 gradually into gypsifcrous shales and sandstones." (P. S(i.) 



Tl)e beds last mentioned are probably those which form the upper division of 

 the Permian of his Salt Creek section. This description can not lie strictly titted to 

 the section of the Triassic series observed in Sinljads Valley, and other sections show 

 similar deviations in detail. The Jurassic consists of variegated shales and marls, 

 with thin bands of limestone near the base. 



This series can most appropriately be compared with those of the San Juan 

 district and of the Crested Butte quadrangle. The lowest bed seen can probably be 

 correlated with that widespread calcareous horizon, the Leadville or Ouray limestone. 



The shaly sandstone above, of which Peale cites a thickness of more than 3,500 

 feet, seems to correspond to the Hermosa formation of the San Juan region. The 

 Red Beds are the probable equivalents of the Dolores and La Plata formations, while 

 the Jurassic is almost certainly the McElmo foi-mation. 



The correlation of the Hermosa formation with Peale's Carboniferous beds has 

 much to recommend it, yet the latter have a thickness of over 3,500 feet, while the 

 Hermosa contains but 1,800 feet. However, the fauual break between the Hermosa 

 formation and the Rico is sufficiently important to suggest an unrepresented time 

 interval between tho-e formations, to which the upper lieds in Sinbads Vallej' may 

 correspond. The onlj'' fossils we have from Sinbads Valley come from near the top 

 of the supposed Hermosa. The fauna is quite distinct from the Rico fauna, and 

 yet presents a diti'erent f acies from the Hermosan fauna. So far the . paleontologic 

 evidence is favorable to this correlation and to the explanation suggested for the 

 difficulties which arise from it. 



Lithologically the 300 feet of yellowish and black shale which Peale includes with • 

 the Permian is unlike the Red Beds above and more similar to the Hermosa formation, 

 with which it seems to me more appropriate to unite it. This course is also justified 

 by the overlap of the Red Beds iwrtion of the "Permian" upon the granite, as 

 reported by Peale. The Rico fauna has not yet been found in the Sinbads Vallev 

 section, but it may occur there, as so little is known of the paleontology of that area. 

 If the Rico does occur, however, it must have undergone a lithologic change, as there 

 are no chocolate or dark maroon measures at the base of the Red Beds. The possi- 

 ble correlation of the Rico formation with the upper member of the Maroon has 

 alread}^ been suggested, and the total absence of the series in Sinbads Valley would 

 be quite in line with its great reduction in the San Juan region. Assuming that the 

 Rico is absent in this area, that the base of the Red Beds begins with the upper half 

 of Peale's Permian, and that the top ends with the base of his Jurassic, the interme- 



