TITLKS AM) ABSTRACTS OF PAPP:RS 127 



tht^ thin ovorthriist mass, or was it a lator and distinct opi^'xJ*' of fanltin« 

 uiitier «litYoivnt conditions? If the hitter, compressive stresses vvhicli j^ave rise 

 to the great overthrusts mnst have had relief and tension conditions set in. 



Dr. G. K. Mansfiki.u replied: The nt)rmal faulting is thoufj;lit to be asso- 

 cmted with extrusion of basalt, as indicated in one of the views shown, and 

 this was outpoured upon the ureatly eroded surface of the folded formations. 

 The normal faultini; is thus believed to l>e of incidentall.v hiter date than the 

 foldiMir and thrustini;. 



AUt: (U- TUK srXh'l' Ph'onrciSG FULTS of the off fat /M.S7V 



r.v (;kor(;k d. i.ori)KUHA( k 



{Ah.strtict ) 



The methtuls used in determining the age of tlie faults were outlined and 

 the relations of the scarps to the Tertiary sediments, lavas, and erosion sur- 

 fac*es discussed. A comparison was made of various scarps which have been 

 held i>y certain writers to be of different age, and also of different parts of 

 certain scarps that have been referred to different periods of activity. The 

 conclusion was reached that the present scarps originated in comparatively 

 re«vnt times, their l)eginnings i)robal)ly being not later than middle Pliocene 

 and possibly post-Pliocene. 



Presented without notes. 



FAl l.T SYSTEM AT THE SOUTH ER\ END OF THE SilERRA XAVADA. 



('AfJFORXIA 



HY JOHN P. HL'VVALUA^ 



(Abstract) 



The Sierra Nevada^ are prolonged in southern California by the Tehachapi 

 Mountains, which extend southwestward and join the Coast Ranges at Tejon 

 Tass. While the Sierras are probably a simple tilted block farther north, 

 their extreme southern end and the Tehachapi Mountains show acute defor- 

 mation along both tianks and <-onsi<lerablc faulting of Tertiary date within 

 the range. The fra<turcs api)ear to have occurred in at least two distinct 

 I>eriods. Thrust-faulting <-haracterized the earlier period. Roth the stresses 

 which uplifted tin* Sierra and those whi<*h folded the Coast Ranges seem to 

 liave participat<'d in drfornjing the southern Sierra region between Kern River 

 and Tejon Pass. 



Kead from manuscript, illustratcfl In lantcrii slides. 

 Discussed bv Messrs. A. M. Batenian, Klioi l^>la(kwclder, W. M. Davis 

 and J. E. Spurr, witli reply by the author. 



Former President W. ^I. Davis was called to the chair. 



' Introducpd by 11. K. JJrfKory. 



* Tilt" term ••Sierra Niivmla" Is [)n»|)»Tly i)|iiral. 



