THE LOMBARD OVERTHRUST AND RELATED FEATURES 279 



stone immediately below the brown Jefferson dolomitic limestone 

 contains Upper Cambrian fossils, the writer believes that at this 

 contact there is a disconformity involving a hiatus in the sedi- 

 mentary record of this region from the close of the Upper Cambrian 

 to Lower Devonian time. 



Further evidence in favor of this disconformity and strati- 

 graphic overlap is brought out by the presence in sections in neigh- 





-V-.* 



Fig. 6. — Cliff of Jefferson limestone north of Crane Station 



boring regions to the west and southwest of intervening strata of 

 different lithologic character between the Yogo limestone and the 

 Jefferson limestone, which in some cases contain fossils of Ordo- 

 vician and Silurian ages. One very complete section from the 

 Randolph quadrangle 1 in northeastern Utah, with 3,000 feet of 

 Ordovician and Silurian strata between the Upper Cambrian lime- 

 stone and the Jefferson limestone, shows very clearly the hiatus 

 in the sections in the Three Forks quadrangle and the neighboring 

 region to the north and northeast. 



1 G. B. Richardson, Amer. Jour. Sci., XXXVI (1913), 406-416. 



