418 W. M. DAVIS AND S. W. LOPER — FOSSILIFEROUS TRIASSIC SHALE. 



good reasons can be shown for provisionally regarding it as of earlier date 

 than the tilting and faulting. of the formation, and hence of roughly syn- 

 chronous date with the overflows. Besides various miuor sheets and dikes 

 of undetermined relations, there is a great mass of dikes in Mount Carmel 

 which may be plausibly regarded as marking the vent through which the 

 lava of the sheets rose to the surface. All of this inferred original structure 

 is illustrated in figure 1. 



Deformation. — The time of deposition appears to have been terminated by 

 an upheaval, accompanied by tilting and faulting. The tilting is generally 

 to the eastward, or somewhat south of eastward. The faulting has not been 

 well made out except in the neighborhood of Meriden, where the lines of 

 fracture run northeastward or east-northeastward with much regularity. 

 As this direction corresponds with the strike of the underlying schists, where 

 they are seen beyond the limits of the Triassic beds toward the southwest 

 and toward the northeast, it may be supposed that the trend of the faults was 

 determined by the strike of the schists ; I. e., that the forces by which the 

 formation was disturbed reached deep below the foundation of the Triassic 

 beds and moved the schists as well, and the latter slipping and faulting 

 along or nearly along their planes of foliation, the overlying Triassic beds 

 broke in the same direction, the dislocations of the smaller superficial mass 

 being guided by those of the greater underlying mass, as has been suggested 

 for the origin of the Great Basin ranges by Gilbert.^ 



Be this as it may, it is clearly determined that the whole sequence of 

 aqueous and igneous beds has been tilted and strongly faulted, the entire 

 mass being thus divided into a number of long narrow blocks from an eighth 

 of a mile to a mile or more in width, and separated from one another by dis- 

 locations, varying from a few tens of feet up well toward two thousand feet. 

 In nearly all cases the heave or upthrow is on the southeastern side of the 

 fracture, and the amount of heave is in a rough way proportionate to the 

 width of the next block toward the southeast ; and this seems to be strongly 

 confirmatory of the theory above stated concerning the cause of the faulting. 



In the southeastern corner of the present Triassic area the strata were 

 gently folded, or dished, as well as faulted ; and here the ridges formed on 

 the harder trap sheets are consequently curved. 



If the deformation thus described went on with ordinary geological rapid- 

 ity, the constructional form of the country produced by it must have been 

 peculiar, to say the least. The nearest existing likeness to it that I have 

 found is in southern Oregon, in the region of the tilted and faulted blocks 

 of lava so well described by Kussell ; f but there the breaking of the orig- 

 inally even mass into blocks is not so orderly as it was in Connecticut, or at 

 least about Meriden. 



* Wheeler's Surveys West of the 100th Meridinn, vol. Ill, 1875, p, 62. 

 t Fourth Annual Report, U. S. Geol. Survey, 1884, p. 44a et seq. 



