PALEOZOIC STRATIGRAPHY OF ROCKY MOUNTAINS 115 



Because of the well-known scarcity of fossils in the strata which 

 were to form the subject of his investigation, the writer set out with 

 intent to make the greatest possible use of correlation by means 

 of lithologic characters. To this end he made accurate measure- 

 ments and described in detail, in every section, each member of 

 the sequence which could be distinguished from other members by 

 its lithological characters. Collections of fossils, although made 

 secondary to the work of lithological description and measurement, 

 and in no case exhaustive, were made wherever opportunity pre- 

 sented itself, and in each case served to corroborate the correlation 

 which otherwise would have been made on the basis of lithology 

 alone. For instance, the presence of the Ordovician Bighorn 

 dolomite as the thick basal member of the so-called "Jefferson 

 limestone" in the areas of the Absaroka, Wyoming (No. 52), and 

 Livingston, Montana (No. 1), folios was established beyond doubt 

 by both lines of evidence, though it would have been well established 

 by either one alone. 



In these correlations it was realized that the coincidence of the 

 lithological characters of a single member at one locality with those 

 of one member in the same stratigraphic position in another locality 

 is much more inconclusive (although significant) than the corre- 

 spondence of several successive members in one section to the same 

 number of members occurring in the same order and in the same 

 stratigraphic position in another. In nearly every case where a 

 single bed in one section was found to correspond accurately in 

 character to one bed in another section, not less than two other 

 contiguous members were found to correspond in like manner. 

 Where several members of one section appeared to be missing from 

 another section, a hiatus was inferred in the latter; and such 

 inference was substantiated in several cases by more direct evidence 

 at the suspected horizon. 



LOCATIONS OF SECTIONS MEASURED, 19 15 



(See map, Fig. 1) 



I. (Partial.) In the northwest wall of the canyon of Big Goose Creek, 

 about 20 miles southwest of Sheridan, Wyoming. 



II. Goose Creek Ridge. — On the crest of the "limestone front ridge" on 

 the northeast flank of the Bighorn Range, between Big and Little Goose 

 creeks, about 20 miles southwest of Sheridan, Wyoming. 



