518 DAVIS AND GRISWOLD — BOUNDARY OF CONNECTICUT TRIASBIC. 



the new shoreline. Thus introduced into a new cycle of erosion, the 

 region has agam been seriously denuded. Whatever cover of Cretaceous 

 strata there was has been stripijed ofif from New England, the edges of the 

 retreating strata appearing now in a tame escarpment, cloaked with glacial 

 moraines, on Long Island, while Long Island sound is the valley, now sub- 

 merged, that usually occurs between such an inland-facing escarpment 

 and the land over which the strata of the escarpment formerly extended. 



During the Tertiary cycle of erosion the harder crystalline rocks east 

 and west of the Triassic belt have been dissected by narrow valleys, of 

 which the upper Farmington is the type in the western crystalline plateau 

 of Connecticut, and of which the beautiful gorge of the Connecticut river, 

 from Middletown to the Sound, is the type in the eastern plateau. These 

 plateaus may therefore be said to have reached an adolescent stage of de- 

 nudation. But in the intermediate belt of weaker Triassic rocks the sur- 

 face is as a rule well reduced toward the present baselevel, and an exten- 

 sive lowland separates the two cr3^stalline plateaus. It is true that here 

 and there the trap sheets and the harder sandstones and conglomerates 

 have not yet been much consumed beneath the surface of the peneplain 

 to which they were worn down in Cretaceous time ; but as a whole the 

 Triassic belt has acquired a distinctly past-mature, almost an old, expres- 

 sion. This expression was essentially reached before the earliest ice- 

 sheet of the glacial period entered the region, and although a consider- 

 able amount of glacial erosion was then accomplished ; although certain- 

 significant oscillations of level took place, and although broad sheets of 

 stratified drift were laid down in the valleys, still all these changes are of 

 minor importance compared to those by which the adolescent stage of the 

 crystalline plateaus and oldish stage of the Triassic belt were reached. 



The recognition of these successive chapters in the history of the region 

 has required a general understanding of its structure, and the more 

 minute! interpretation of the trap ridges by which the Triassic lowland 

 is interrupted has required a close study of the monoclinal faulting 

 which introduced the post-Triassic cycle. But all this has not required 

 any close knowledge of the relation of the former and present bounda- 

 ries of the Triassic strata. This particular question is here discussed. 



Faults. 



faults in general. 



A few paragraphs may be allowed on the subject of faults in general, 

 for the reason that some geologists have expressed a feeling that faults 

 were an easy recourse for the explanation of perplexing difficulties, and 

 that their existence was sometimes too lightl}^ entertained. In order 

 to avoid the just aj)plication of such a criticism to our work, we first 



