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



as one of the districts to be visited by the Harvard Summer School of 

 Geology. The following papers have been published during the progress 

 of my study : 



" Brief Notice of Observations on the Triassic Trap Eocks of Massachusetts, Con- 

 necticut and New Jersey : " Amer. Journ. Sci., 3d ser., vol. XXIV, 1882, pp. 345- 

 349. 



"The Structural Value of the Trap Kidges of the Connecticut Valley:" Proc. 

 Bost. Soc. Nat. Hist., vol. XXII, 1882, pp. 116-124. 



"The Relations of the Triassic Traps and Sandstones of the Eastern United 

 States: " Bull. Mus. Comp. Zool. at Harv. Coll., geol. series i, 1883, pp. 249-309, 

 with three folded plates. 



" Mechanical Origin of the Triassic Monoclinal in the Connecticut Valley : " 

 Proc. Amer. Assoc, vol. XXXV, 1886, pp. 224-227. 



"The Structure of the Triassic Formation of the Connecticut Valley: " Amer. 

 Journ. Sci., 3d ser., vol. XXII, 1886, pp. 342-352. 



" The Structure of the Triassic Formation of the Connecticut Valley : " 7th An- 

 nual Rep. U. S. Geol. Surv., 1888, pp. 461-490, with one plate. 



"The Ash Bed at Meriden and its Structural Relations: " Proc. Meriden Scient. 

 Assoc, III, 1889, pp. 23-30. 



" Topographic Development of the Triassic Formation of the Connecticut Valley : " 

 Amer. Journ. Sci., 3d ser., vol. XXXVII, 1889, pp. 423-434. 



"The Faults in the Triassic Formation near Meriden, Connecticut; a week's work 

 in the Harvard Summer School of Geology : " Bull. Mus. Comp. Zool., geol. series ii, 

 1889, pp. 61-87, with five plates. 



" The Intrusive and Extrusive Triassic Trap Sheets of the Connecticut Valley ; " 

 By W. M. Davis and C. L. VS^hittle : Ihid., pp. 99-138, with five plates. 



Structure of the Triassic Formation about Meriden. 



Origin of the Deposits. — As at present understood, the structure of the 

 formation may be described as follows : The Triassic strata were deposited 

 in a body of water formed by the submergence of a peneplain of crystalline 

 schists and gneisses ; detritus was washed down from the unsubmerged por- 

 tions of the region on either side, east and west. The pre-Triassic surface is 

 spoken of as a peneplain because it is, in the first place, manifestly a surface 

 of deep erosion on strongly deformed schists ; and second, because the line 

 of contact of this deeply eroded surface with the Triassic beds along the 

 under or western margin of the formation is at present so nearly straight. 

 If the pre-Triassic surface had been very uneven, as it must have been for 

 much of the time during its deep erosion, the unevenness should now make 

 itself manifest in a very irregular boundary along the base of the formation ; 

 but, as stated above, this is not the case: the base of the formation appears 

 to rest on a relatively even foundation, an ancient peneplain. In a small way, 

 this is best shown in a ravine Avest of Southington, where a sandy basal con- 

 glomerate is seen lying directly on the evenly eroded surface of the tilted 

 crystallines. 



