NO. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. I/ 



of the Highlands becomes apparent. But it is not a level plateau ; 

 on the northern boundary line of Connecticut it attains an eleva- 

 tion of about 1700 feet above the sea in the west and descends to 

 an elevation of about 600 feet at the eastern limit of the State. 

 From this elevation on the north the plateau slopes southward, 

 and the place where it reaches sea level determines the Connect- 

 icut shore line of Long Island Sound. At the southern limit the 

 dissected Highlands therefore grade into an undissected lowland, 

 albeit one of rocky character. The result is that along the shore 

 Lowland and Highlands lose their distinction in elevation; and 

 the only railroad which runs across the State independently of 

 both rock structure and river valleys is the line of the New York, 

 New Haven and Hartford Railroad which runs along the shore 

 from the New York to the Rhode Island boundary. On the 

 Highlands the soil is in general thinner and more stony than on 

 the Lowland, and agriculture meets with less reward. 



The Highland surface, like that of the Lowland, truncates the 

 rock structure. It is, therefore, like the latter, the product of 

 erosion, but during an earlier geologic period, when this plateau 

 surface lay near the level of the sea, and erosion continued to sap 

 the slopes of all hills which rose above its surface, but could not 

 carve the rocks below. The hills gradually melted down until 

 they possessed but a remnant of their former height. The valleys 

 became broad and open. A peneplain extended far and wide, 

 interrupted by a few remaining mountain knots. Then after a 

 long interval a broad swelling uplift of the land created a lower 

 sea level a lower base-level toward which the rivers began to 

 etch their channels and the Highlands began to be destroyed. 



The plateau surface has commonly been considered as entirely 

 the product of one cycle of river erosion, but upwarped and tilted 

 in several stages until it reached its present altitude. The opinion 

 is held by many geologists that before the uplift the sea had 

 planed the surface as far north as Meriden and Middletown, 

 laying down a thin mantle of coastal plain deposits which since 

 the uplift have been eroded from the surface as far south as 

 Long Island. 



Studies by the writer have led him, however, to a somewhat 

 different view, 1 the detailed evidence for which has not as yet 



> Barrell, J., Piedmont Terraces of the Northern Appalachians and their Mode 

 of Origin: Post-Jurassic History of the Northern Appalachians. Bull. Geological 

 Soc. Am., vol. 24, pp. 688-691, 1913. 

 2 



