^l^Wd^i 



THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Art. XL1II. — Topographic Development of the Triassio For- 

 mation of the Connecticut Valley • by "WiLTfrAM Morris 

 Davis. 



[Published, as far as relates to work done for the. U. S. Geological Survey, with 

 the permission of the Director.] 



Coisttents : — Itinerary of Harvard Summer School of Geology — 

 Faults in the Mericlen region — Cross-section of the District — 

 Means of detecting the unfaulted sequence of Triassic beds — 

 Mechanism of monoclinal faulting — Topographic development 

 of the Triassic belt — Initial constructional stages represented 

 by the faulted blocks of Southern Idaho — Mountain ranges of 

 the Great Basin equivalent to a later Jurassic Stage — The 

 whole region base-leveled in late Cretaceous time — The present 

 valleys worn in the Cretaceous base-level plain after its eleva- 

 tion — Polygenetic topography — The origin of the Connecticut 

 river outlet via Middletown — The Connecticut river was orig- 

 inally consequent on the monoclinal faulting, and still persists 

 near the course then taken, but has entered a second cycle of 

 life as a result of the elevation of the lowland that was pro- 

 duced in its first cycle. 



Since presenting two years ago a suggestion to account for 

 the mechanical origin of the faulted Triassic monocline* I 

 have visited the region about Meriden with the Harvard 

 Summer School of Geology during its sessions of 1887 and 

 1888. An itinerary of the excursions made by the school in 



' * This Journal, xxxii, 1886, 342-352 ; Proc. Amer. Assoc, xxxv, 1 886, 224-227 ; 

 Seventh Ann. Report U. S. Geol. Survey, 1886, just issued. 



Am. Jodr. Sci.— Third Series, Vol. XXXVII, No. 222.— June, 1889. 

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