peale-J RESUME CENOZOIC EOCKS— TERTIARY. ' 



The following is the section of the Tertiary formations : 



Tertiary section. 



635 



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14. Soft yellow sands and marls. 

 13. Gray sandstones. 

 12. White and light brown limestones. 

 11. With interlaiainated shales. 

 10. Pea-green sands and shales. 

 9. Coarse conglomerates. 



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8. Somber colored soft clays and sands, sometimes variegated near the base, 

 hut generally of a dull gray color. 



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7. White calcareous shales and sands, with intercalated limestones. 



6. Thin fissile white shales ; yellow sandstones. 



5. Greenish and whitish shales and sands and limestones ; yellow sandstones. 



15 = 



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4. Coarse limestone conglomerates with siliceous cement. 

 3. Coarse red, purple, and yellow sandstones. 

 2. Variegated clays and sands. 

 1. White sandstones. 



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Total 



2,500 

 +ft. 









In this section I have included only the undoubted Tertiary. At no 

 place was the Salt Lake Group seen resting on the Bridger Group, nor 

 was the latter well shown anywhere in the district. 



WAHSATCH GROUP. 



After the Post-Cretaceous uplift the region of the Green Eiver Basin 

 was occupied by a lake which extended westward in our district to the 

 Bear Eiver Range. It appears that in its early stages this lake was 

 much smaller than the area now covered by the deposits indicates, for 

 wherever the beds referable to the period were seen, they were found 

 resting on the upturned and much eroded edges of the older strata, which 

 include rocks from Silurian age to the Laramie Group, and the deposits 

 represent only the upper part of the group. 



The largest areas of the Wahsatch are in the northern portion of the 

 Green River Basin, where a large j>art of the surface is covered by its 

 deposits. The overlying Green Biver Group in this region is mostly 

 absent, having been eroded away. Isolated buttes, however, still remain, 

 proving its former existence and extension over the whole region. Along 

 the southwestern slopes .of the Wind Biver Mountains the Wahsatch 

 beds rest on the granitic rocks, and were evidently derived from the dis- 

 integration of the granitic rocks that farther to the eastward make up 

 the main range. They consist of yellow, gray, and pink sands and marls, 

 which dip from 5° to 10° from the mountains. West of Green Biver the 

 character of the beds is similar to those on the east. They are generally 

 brick-red in color and weather into picturesque bad-land forms. Along 

 the edge of the basin they are found to be composed mainly of conglom- 



