296 S. PAIGE ORIGIX OF THE HOMESTAKE ORE BODY 



followed. Such beds are the quartzites and the conglomeratic quartzites. 

 But, fortunately, the results obtained 1)}' following these traceable beds 

 are checked by the differences in lithologic character of certain other 

 beds or groups of beds — such, for example, as the garnetiferous. schists, 

 the limestones, and the slates, which maintain their structural relations 

 to the quartzites and quartzite conglomerates over considerable distances. 



In general, folding within any of the homogeneous units — the garnet- 

 iferous schists, the slates, or the limestones — can not be deciphered with 

 sufficient definiteness to be shown on a map, though abundant evidence 

 is presented in the field to indicate that such minor folds are present. 



By pursuing the method of tracing the quartzites and quartzite con- 

 glomerates, the following facts were established : In the western division 

 a group of at least five quartzites were traced more or less continuously 

 from the divide north of Sheeptail Gulch to a point east of Whitewood 

 Creek, north of Englewood. Many attempts were made to discover if 

 the quartzites of this series were duplicated by folding. All such at- 

 tempts ultimately failed to show a repetition of beds and apparent incon- 

 sistencies of outcrop, such as sudden termination of beds, and sudden 

 minor changes of strike were found to be due to either a change in the 

 resistance of the bed to forces of weathering or to minor changes of strati- 

 graphic succession, which are normal when sandy beds are involved. 



Less than half a mile east of this group of quartzites a second group 

 of similar beds were traced. Here, however, the results indicate a closely 

 compressed synclinal fold — synclinal because the general pitch of the 

 folding is southward and because this fold apexes to the north. As 

 nearly as could be determined, the outer quartzite of this series turns or 

 apexes on the south side of Sawpit Gulch about one-half mile west of 

 the town of Central. The turning points of the remaining quartzites 

 are naturally farther south, but were not determined. 3 



The outcrop of the quartzites forming the two limbs of this fold may 

 be traced. The eastern set are cut off at Kirk by the great fault. The 

 western set, at least the westernmost member, may be said to maintain its 

 integrity for three miles, though it is not exposed continuously through- 

 out this distance. 



If, now, the beds east of the fault-plane are examined in more detail, 

 the following relations are of importance : The series as a whole strikes 

 north-northeast and, except in one region to be described later, clips at a 

 high angle to the east. This series is structurally discordant with the 

 rocks on the west side of the fault, and as they differ lithologically from 

 those rocks no hypothesis of folding will explain their observed relations. 



3 Porphyry intrusions, overlying Cambrian strata and forest cover combine to conceal 

 outcrops of pre-Cambrian strata. 



