io8 



ELIOT BLACKW ELDER 



Along the flanks of the Owl Creek and Wind River mountain 

 ranges the basal part of the Tertiary strata contains wedge-shaped 

 beds of coarse conglomerate interleaved with the finer sediments 

 and pinching out away from the mountains. The pebbles are ill 

 rounded and consist wholly of rocks which outcrop near by. The 

 lithologic varieties are many and not well assorted. These facts 

 suggest the local deposition of alluvial fans by mountain creeks along 

 the border of a lowland. Similar conditions exist today in the 

 California valley. 



Fig. 6 



Again, some small parts of the sequence have evidently been 

 deposited in lakes, since from the valley of the north fork of the 

 Gros Ventre River, Mr. Perry^ of the Hayden Survey reports five 

 successive beds of freshwater limestone containing recognizable 

 lacustrine shells. There is equally good evidence that some of 

 the material was laid down in marshes, for thin lignitic seams 

 have been found in many localities, and especially in the section 

 last mentioned. There Perry found in a single exposure no less 

 than forty-seven beds of lignite, most of them very thin. Similar 

 beds occur in the Bighorn and Wind River basins. 



• Hayden Survey report for 1878, Part 2, pp. 223-24. 



