HIXTZIJ, GEOLOGY OF WASATCH MOUNTAINS, UTAH 



105 



Middle Cambrian. 



Lower Cambrian. 



C Linyulclla clla 

 Kutorpina pannula 

 Hyolithes Wllingsi 

 Leperditia argent a 

 Ptychoparia quadrans 

 Bathyuriscus producta 



(Olenellus gilherti 

 1 Cruziana sp. 



Dr. Walcott continues : "As in the Eureka and Highland Range sec- 

 tions, the Olenellus zone is confined to a very narrow belt just above the 

 quartzite. The silico-argillaceous shales (Alta) above occupy the position 

 of the 4650 feet of Prospect Mountain limestone and Secret Canyon shale 

 of the Eureka section. The Hamburg limestone and Hamburg (Dunder- 

 burg) shale of the latter are absent in the Big Cottonwood section, caus- 

 ing an unconformity by non-deposition. The section in the Oquirrh range 

 above Ophir City has a quartzite at the base with shales above it carrying 

 TAngulella ella. Olenellus gilherti and Bathyuriscus productus, as deter- 

 mined by the collections brought in by the Wheeler survey. It is prob- 

 able, however, that as in the case of the Big Cottonwood section, Olenellus 

 gilherti occurs at the base of the shale, and the other two species at a 

 higher horizon." 



From this, it appears that the Middle Cambrian is only represented by 

 the middle and upper part of the Alta shale, and the Upper Cambrian is 

 wanting altogether. There exists, therefore, within the shale a discon- 

 formity between the Lower and Middle Cambrian strata and at the top a 

 great hiatus representing the entire Upper Cambrian series. 



ORDOVICIAN^ STRATA 



Disconformably overlying the Alta shale is a limestone and shale series 

 of which the following section, measured at the south end of the Reade 

 and Benson ridge at the head of South Fork, is typical : 



Section in South Fori: 



Feet 

 13. Alternating blue shale and limestone conglomerate in beds 1-6 inches 



thick 10 



12. Alternating shale and limestone, passing into shale 20 



11. Thin fissile blue shale 6 



10. Dark blue thin-bedded limestones, partings exceedingly irregular 55 



9. Dark blue heavy bedded limestone with a wormy appearance, holes far 



apart 45 



8. White limestone, thin bedded 10 



