1913] 



Louderback : The Monterey Series 



217 



are much crushed and folded, it is not possible to say with cer- 

 tainty that there is at all places an unconformity between the 

 Vaqueros sandstone and the overlying strata." 



The fact that everywhere else the Monterey series exhibits 

 a conformable relation throughout and that even within this 

 area the sandstones . underlying the shale in some places are 

 distinctly conformable below them, and that where unconform- 

 able relations are suggested by different dips the contact areas 

 are not distinctly visible should make one doubt the correctness 

 of this determination which the authors themselves speak of in 

 a doubtful way. However, even if the suspected unconformity 

 does occur, it must be a very local and minor feature and can 

 hardly be accepted as marking a time boundary between two dis- 

 tinct formations, which as has been frequently pointed out, are 

 "determined" in general by quite different characteristics which 

 change at various horizons. 



The idea expressed (p. 10, col. 3) that "after the deposition 

 of the Vaqueros sandstone at least a portion of the region appears 

 to have been raised, and was probably folded and faulted; in 

 parts of the area considerable erosion appears to have taken 

 place," does not seem diastrophically probable. That within 

 part of that comparatively small area such activities as uplift, 

 folding, faulting, considerable erosion and then subsidence, 

 should take place, while over other parts of the area and in the 

 neighboring regions quiet deposition was going on is hardly to 

 be expected and should be backed up by very definite or strong 

 evidence before it can be accepted. 



Again the authors say "There are few localities where the 

 Vaqueros sandstone is fossiliferous, but at those places the rocks 

 yield an abundant fauna of unmistakable lower Miocene age. 

 As would be expected in a formation composed largely of con- 

 glomerates and coarse sandstones, the Vaqueros contains a shallow 

 water or littoral fauna" (p. 4, col. 3). 



In other words, all of the sandstones and conglomerates not 

 found above diatomaceous shale were placed in this "formation" 

 on a lithologic basis, while the fauna found in a few localities 

 was considered "characteristic" of the horizon supposedly repre- 

 sented by them all. 



