44 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [hull. 106. 



Laramie affinities to the Montana formation. If the true Laramie is 

 present it is represented by the strata above No. 10 of the section and 

 these have yielded no fossils. 



The beds beneath the Coalville section are not exposed in the imme- 

 diate neighborhood, but near Roekport, on the Weber river, 12 miles 

 above Coalville, the continuation of the section down to the Trias 

 may be seen. The strata are highly disturbed, dipping northward at 

 angles varying from 30° to 80°. There are at least two faults in the 

 series, and the great apparent thickness of the section suggests that 

 there may be others by which strata are repeated. 



The lowest fossiliferous zone of the Coalville section with the char- 

 acteristic species, such as Barbatia micronema, Mactra utahensis, Modiola 

 mult ilinig era, and others, is well developed. Beneath (south of) this 

 bed there are no good exposures for a distance of 2,200 feet. Then 

 come the following strata in descending order: 



Feet. 



1. Alternating beds of coarse sandstone and shale. The beds of sandstone 



vary in thickness from 10 feet to over 100 feet, and their aggregate thick- 

 ness is somewhat less than that of the shales. A few specimens of Ostrea 

 and casts of Cardium and other bivalves were found in the lower por- 

 tions. Total apparent thickness 2, 500 



2. Drab .shales with indurated bands in which numerous scales of fishes and 



an obscure impression of an Ammonite were collected 215 



3. Covered for a distance of 700 



4. Reddish and brownish shales alternating with thinner beds of coarse gray 



sandstone, changing to brown pebbly conglomerate in the lower 650 feet. 2, 400 



5. Reddish shales with thin beds of brown sandstone . 433 



6. Dark greenish gray sandstone, somewhat calcareous, especially toward the 



top. A specimen of Trigonia quadraiujulavis f and a few other obscure fos- 

 sils indicate that this bed is Jurassic 55 



7. Gray and reddish sandy shales, with bands of sandstone 1, 205 



8. Yellowish gray shales, becoming calcareous toward the base 935 



9. Blue thin bedded limestone and calcareous shales containing Pentaerinus 



asteriscas, Pleuromya siibcomjircssa, and other Jurassic fossils 422 



10. Reddish brown thin bedded Triassic ? sandstone, exposed 750 



The thicknesses given are from measurements made on the assump- 

 tion that there is no duplication of strata by faulting. The observed 

 faults that have been mentioned are not within the limits of the sec- 

 tion. If the beds down to and including No. 4 be regarded as Creta- 

 ceous, this gives an apparent thickness of over 0,000 feet of Cretaceous 

 strata beneath the Coalville section. On East Canyon creek below 

 Parley's park the thickness from the base of the conglomerates, like 

 those of No. 4, to the top of the fossiliferous sandstone there exposed 

 seemed to be a little over 5,000 feet, but that was only an estimate 

 based on observed dips and paced distances. 



The conglomerates of No. 4 were mapped as Dakota by Mr. Emmons, 

 and the two other a Dakota " areas that 1 have visited in this region — 

 one on East Canyon creek and the other on Chalk creek — show the 

 same beds. That they are Cretaceous is very probable, but that they 



