INTERBEDDED QUARTZITES AND GRANITES. 423 



northern end of the range, there is a nearly continuous exposure of the 

 contact of granite and sedimentary pre-Mesozoic strata for at least seven 

 miles from the West branch of Feather river, near the middle of T. 24 

 X.. 15. 4 E., M. D. M., northeastward along the divide at the headwaters 

 of Kimshew creek. The sedimentary rocks approximate in character 

 the pre-Mesozoic rocks of * llaremoht ; they are imperfectly gneissoid and 

 chloritic in part. Their strike is nearly at right angles to the prevailing 

 strikes of the Sierra, namely, northeasterly, parallel to the contact just 

 mentioned: and they dip at comparatively low angles northwestward 

 away from the granite. They pass by the northern end of the western 

 area of granite exposure here at the northern end of the western division 

 of the range, as the Mesozoic rocks pass by the granite of the crest of the 

 eastern division between the Middle fork of the Feather and the North 

 fork of the Yuba. Across the area of outcrop of these strata on the 

 northwestern side of it. about 41 miles from the contact with the granite, 

 at the Chaparral house on the Oroville and Prattville stage road, in sec- 

 tion 10, T. 24 N., R. 4 E., are quartzites like those on the easterly face of 

 Spanish peak mountain, with the ordinary northwesterly strike and a 

 nearly vertical dip. The metamorphosed, imperfectly gneissoid and 

 chloritic strata outcrop here between the granites and quartzites, and are 

 probably lower than the latter. They may he contemporaneous with or 

 older than the granite, although 1 have seen no intrusions of the eruptive 

 rock in these strata. 



There are quartzites in the range contemporaneous with the granite 

 and imbedded with it, Such occur at and near the western edge of the 

 granite of the eastern division of the range, where the South Yuba Hows 

 oil' it. between live and six miles east of the village of Washington ; also 

 in granites outside of the Sierra proper, north of Sierra valley, at head- 

 waters of the Middle fork of the Feather. In both cases the quartzite is 

 probably a product of alteration of the granite itself. 



Pre-Mesozoic Rocks outside of i'i>i><r Feather River District. — The pre- 

 Mesozoic rocks of this district are not typical of the whole group in the 

 Sierra, inasmuch as they do not include limestones which occur in great 

 masses among the pre-Mesozoic rocks of the western Bank of the range 

 from the Mokelumne to near the Tuolumne river. These limestones 

 occur in a group consisting principally of micaceous schists and quartzites, 

 lying nexl to granite and in places surrounding isolated areas of tins 

 granite. Whitney describes the group in the " Geology of California " 

 and also in his ''Auriferous Gravels of the Sierra Nevada." On the 

 Mokelumne, at the mouth of the North fork. I found an exposure of this 

 limestone 100 feel thick in a series of mica slates which, becoming 

 gneissoid, join the granite aboul two miles easl of the lime-tone. Pre- 



