544 



N. H. DARTON FISH REMAINS IN ORDOVICIAN ROCKS 



Generalized Section in the Bighorn Mountains 



Formation. 



( De Smet tarma- 

 cs tion. 

 .2 I 



g ! Kingsbury cou- 

 rt J glomerate. 

 a I 

 ^ I Piney formation... 



I 



Parkman(Fox Hills?) 

 sandstone. 



Pierre shale 



Colorado formation. 



Cloverly formation. 



Morrison formation... 

 Sundance formation.. 



Chugwater formation 



Tensleep sandstone.., 

 Amsden formation.... 



Madison limestone... 

 Bighorn limestone.... 



Deadwood formatioi 



Character and age. 



Gray sandstone and carbonaceous 

 shales, with lignite deposits. 



Local conglomerate of central-eastern 

 district. 



Brown and gray sandstones and 

 shales. 



Soft, buff, massive sandstone with 

 harder darker concretions. 



Granite., 



Dark gray shale with concretions 



Gray shales, thin brown sandstones 

 below, hard fine gray sandstones 

 (Mowry beds) in middle part, con- 

 cretions with Prionocyclus, etcet- 

 era, at top. 



Buff, coarse massive sandstone below 

 with light-colored shales and some 

 sandstones above. 



Massive shales, greenish-gray, buff, 

 maroon, with thin sandstones. 



Soft sandstones overlain by greenish- 

 gray shale ; several hard fossilifer- 

 ous layers near top and bottom. 



Red shales and soft sandstone, thin 

 limestone layers near top and bot- 

 tom, and gypsum deposits. 



Massive buff to gray sandstone, cal- 

 careous near top. 



Red shales or sandstone at base, over- 

 lain by fine grained white lime- 

 stone, cherty near top. 



Light colored limestones, very mass- 

 ive near top. 



Mostly hard massive limestones with 

 streaks of silica, overlain by series 

 of softer purer limestones with 

 local shaly limestones, 0-30 feet of 

 white sandstone at base. 



Feet. 



Slabby limestones with flat- 

 pebble limestone conglom- 

 erates, sandy to southeast.. 200 



Green shale with sandstone 

 layers 300-600 



Brown massive sandstones.... 0-400 



Gray and red of various kinds, pene- 

 trated by diabase and other dikes. 



Average 

 thickness. 



Feet. 

 5,000 + 



0-2,000 



2,000-3,000 



300- 500 



1,200-3,500 

 1,250-1,500 



80- 200 



150- 300 

 250- 450 



700-1,300 



30- 150 

 200- 350 



700-1,100 

 250- 300 



900-1,150 



Age. 



Upper Cretaceous (and 

 Eocene ?). 



Upper Cretaceous (and 

 Eocene ?). 



Upper Cretaceous (and 

 Eocene?). 



Upper Cretaceous. 



Upper Cretaceous. 

 Upper Cretaceous. 



Upper and Lower Creta- 

 ceous (Dakota-Fuson 

 Lakota). 



Lower Cretaceous ? 



Jurassic. 



Triassic ? and Permian. 



Carboniferous (Penn- 

 sylvanian). 



Carboniferous (Penn- 

 sylvanian and Mis- 

 sissippian ?). 



Carboniferous (Missis- 

 sippian). 



Ordovician (lower 

 member Trenton), 

 upper member Rich- 

 mond). 



Middle Cambrian. 



Archean or Algonkian. 



Ordovician of the Bighorn Mountains 

 general relations 

 As indicated in the above table, the Ordovician representative in the 

 Bighorn mountains has been designated the Bighorn limestone,* and 



* Bull. Geol. Soc. Am., vol. 15, 1904, p. 395. 



