CARBOXATE HILL. 253 



the upper portion of the Lower Quartzite adjoining the fault. A shaft still 

 lower down, opposite the sampling works on the edge of the creek bed, is 

 sunk several hundred feet in White Porphyry. 



Carbonate Hill. — The area east of Carbonate fault, included in the Car- 

 bonate Hill map, will be treated in detail in Part II, Chapter III, and only the 

 general features need here be mentioned. The strike of the Blue Lime- 

 stone is nearly north and south, bending somewhat to the eastward toward 

 the northern end of the hill. Its dip may be taken at an average of 21°, 

 but is found locally to vary very considerably on account of a series of 

 longitudinal waves or folds in the formation. The sheet of Gray or Mottled 

 Porphyry within the Blue Limestone is very persistent, and is evidently a 

 later intrusion. From data obtained from the few points at which it has 

 been proved by underground workings, it is evident that it is not confined 

 to any particular horizon, but locally cuts across the beds, sometimes at a 

 considerable angle. It is best shown in the Evening Star mine, where it 

 seems to be at the base of the Blue Limestone. What is apparently an 

 offshoot from it is found at the contact in the Morning Star mine and extend- 

 ing up into the overlying White Porphyry, while west of the line of the 

 fault in the Forsaken and Henriett mines the main sheet is found cutting 

 across the Blue Limestone, and the principal mineralization has taken place 

 between it and the portion of the Blue Limestone which underlies it. 



Of the country underlying Sti-ay Horse gulch. Stray Horse Ridge, and 

 Little Stray Horse gulch the structural data obtained from explorations are 

 somewhat unsatisfactory; but on Fryer Hill the continuation of Cai'bonate 

 fault is found to be a gentle anticlinal fold whose axis runs in a northeast- 

 erly direction through the Dunkin ground. 



Little Stray Horse synciine. — Betwccu Yankee Hill and the crest of Fryer 

 Hill, through which also runs a general anticlinal fold, is included a basin 

 or synclinal fold in the formation, whose deepest portion underlies Little 

 Stray Horse Park. The surface rock in the center of this basin is the main 

 sheet of Gray Porphyry, which is separated from the underlying Blue Lime- 

 stone by a comparatively thin sheet of White Porphyr3^ The angle of dip 

 of the beds follows the general rule which prevails in the folds in this region 

 and is steeper on the east side of this synciine than on the west. 



