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University of California Publications in Geology [Vol. 13 



to four feet, but on the whole is remarkably continuous. A seam of 

 graphitic limestone, believed to be a portion of the same, was seen more 

 than two miles farther west. 



At the mouth of Grapevine Canon the limestone overlies the meta- 

 morphosed quartzite and dips 40° southwest while the quartzite is 

 nearly vertical. The contact could not be closely examined because 

 of the large amount of talus, but, in view of the conformable relation- 

 ship near Horsethief Flat, it is probably a fault. Both are intruded 

 by an acid granite and some of the limestone is silicified ; some is also 

 streaked with colors, brilliant red, orange, yellow, and slaty blue. This 

 may well be due to mineralization associated with the granite and 

 later modified by meteoric water. Similar silicified and colored lime- 

 stone is also found along the contact of the limestone with the granite 

 in Blackhawk Canon where gold was formerly mined. 



On the north side of the range from Grapevine Canon westward 

 beyond Crystal Creek, the limestone dips in all directions, generally 

 at angles of less than 45°, in some cases lying horizontal. Just within 

 the canon south of Cushenbury Springs the limestone is much broken 

 and altered, forming colored streaks similar to those in Blackhawk 

 Canon. A large proportion has been recrystallized to a coarse-grained 

 white marble. In Furnace and Wild Rose canons granite has intruded 

 the limestone with the development of contact minerals, tremolite, 

 garnet, epidote, wollastonite, pyrite, chalcopyrite, and gold. 



West of Crystal Creek the limestone is limited by a heterogeneous 

 mass of intrusive granites. A large body of limestone brandies off to 

 the southwest to Greenlead Camp, where contact deposits were once 

 extensively mined for gold. The main part of the formation crosses 

 Holeomb Valley to Bertha Peak and thence eastward to Van Dusen 

 Canon. On the southwest side of the valley the limestone is intimately 

 associated with an area of Saragossa quartzite, both dipping about 

 75° to the southwest. To the west and south they are cut by intrusive 

 granite. Several smaller masses cut the limestone along the south 

 flank of the ridge east from Bertha Peak and in Van Dusen Canon 

 later masses separate it from the Saragossa quartzite. 



The thickness of the limestone can only be roughly estimated. 

 Between Crystal Peak and Marble Canon there is a limestone scarp 

 3000 feet high. West of Furnace Canon the limestone has been warped 

 a great deal, but its general attitude is horizontal. The height of the 

 scarp therefore represents part of the thickness of the limestone unless 

 there has been step faulting. South of Smart's Ranch and west of 



