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University of California . 



[Vol. 3. 



tion;* but it seems worthy of consideration as an alternative to 

 the at present more favorably received hypothesis, which 

 explains jointage as a result of tangential compression, entirely 

 independent of, and antecedent to, erosion. 



This hypothesis of jointage as entertained by the writer modi- 

 fies the views, which might otherwise be entertained, as to the 

 role which this structure has played in the general morphogeny 

 of the Upper Kern Basin. If the jointage were strictly an ante- 

 cedent structure, simply revealed by erosion, then we should 

 expect it to exercise an important influence upon the direction of 

 the maximum erosion lines; and this may be true of the vertical 

 jointage. But if the jointage be a function of erosion to any 

 extent, then the control exercised by jointage upon the course of 

 erosion is correspondingly diminished. Nevertheless, since joint- 

 age is developed in the rock mass in advance of the surface due 

 to erosion at any given time, it greatly facilitates erosion, 

 whether the latter be effected by atmospheric, stream, or glacial 

 agencies. The relation of the relief to the jointage of the region 

 would require a careful, detailed survey, and no more positive 

 statement can at present he made concerning it. 



Faults and Fissures. — No notable faults have been detected in 

 the Upper Kern Basin, but in view of the homogeniety of the 

 rocks this is not surprising, and they may easily exist. Faults 

 are usually made apparent by the discordance of the rocks on 

 either side of the plane or zone of dislocation; but in the ease of 

 massive granites such discordance is not in evidence and they 

 escape detection. The character of the eastern rim of the basin 

 is, it is scarcely necessary to say, due to the great fault which 

 limits the Sierra Nevada on the east. The east front of the 

 range is a fault scar]) which has been modified by degradation, 

 and in its upper part been accentuated in sheerness by cirque 

 erosion. As will appear in the part of the paper dealing 



*Mr. G. K. Gilbert kindly reviewed the MS. of this paper and has communi- 

 cated to the writer his opinion that only the curved jointage parallel t<> the surface 

 may be hypothetieally explained in the way here suggested. It must be confessed 

 that the statements which are made of the horizontal, oblique and curved jointage 

 cannot be urged with the same force with reference to the vertical jointage, par- 

 ticularly in the sheeted granite. The writer, therefore, does not here attempt to 

 apply the hypothesis to the vertical joints, although he believes that they also are 

 due to expansive stresses and not to compression as ordinarily held. 



