134 C. W. TOMLINSON 



base of the Fish Haven dolomite in the Randolph quadrangle, Utah; but 

 this may perhaps be at the base of the Trenton.) 



b) In the Crandall Creek, Dead Indian Creek, and Teton River sections 

 there is at the base of the Upper Bighorn (or Leigh) a breccia or conglomerate 

 of dolomite pebbles in dolomitic or shaly matrix, up to several feet thick; and 

 similar conglomerate occurs at the base of the Upper Fish Haven in the Black- 

 smith Fork section. 



c) Thin lenticular bands of deeply stained shale appear in and above the 

 conglomerate in the Dead Indian Creek section, and the matrix of the con- 

 glomerate is deeply iron-stained both there and in the Teton River section. 



d) Member 5 is not known south or southwest of Cody, Wyoming. 



e) A hiatus between Trenton and Richmond was inferred by Darton 1 in 

 the Bighorn Range from paleontological evidence. 



1. At the base of the Middle Ordovician series (Lower Bighorn, 

 Lower Fish Haven) : 



a) Throughout Wyoming, Montana, and South Dakota, wherever the 

 Bighorn formation (or a formation correlated with it) exists it rests upon strata 

 which are classed as Cambrian, and which certainly in no case are younger than 

 Beekmantown. 



b) The basal member of the Bighorn at several localities in Wyoming is 

 a sandstone, of variable thickness, suggesting deposition on an uneven surface. 2 



c) In the Dead Indian Creek section the base of the Bighorn is a slightly 

 irregular surface. 



d) In the Randolph quadrangle the Fish Haven dolomite (all of Richmond 

 age[ ?]) rests disconformably on the Swan Peak quartzite. 



e) The Swan Peak quartzite is entirely missing from the Blacksmith Fork 

 section, although it is several hundred feet thick a few miles northeast and a 

 few miles southwest of that locality. 



/) In eastern Nevada the contact between the Lone Mountain limestone 

 and the Eureka quartzite is clearly an erosion surface. . 



1 N. H. Darton, "Description of the Bald Mountain and Dayton Quadrangles," 

 Geol. Atlas U.S. (Folio 141, 1906), p. 4. 



2 Cf. N. H. Darton, "A Resume of the Ordovician Geology of the Northwest," 

 Bull. Geol. Soc. Amer., XVII (1905), 547. 



[To be continued] 



