NO. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. 27 



breaking of the crust into great blocks which slipped past each 

 other and rolled over so that all sloped to the east. The New 

 Jersey area of Triassic rocks is also faulted, but the blocks there 

 were rotated in the opposite direction and now slope fifteen to 

 twenty degrees to the west. These opposite slopes suggest the 

 sides of a wide mountain arch raised between the Connecticut 

 and the Hudson River, whose axis was continued southward 

 through the region of the New Jersey coastal plain and offshore 

 waters. But the raising of the arch was accompanied or followed 

 by the fracture and settling which show on its sides. Wherever 

 the Triassic sediments have been preservd in the Appalachians 

 they show this phenomenon of tilting and faulting, indicating a 

 general crustal movement. Each block lifted up would form a 

 ridge or mountain, each block let down would form a trough or 

 basin. Where the principal movement of the blocks was tilting, 

 rather than elevation or subsidence relative to adjacent blocks, 

 the upturned edge of each block would form a ridge with a steep 

 face along the fault plane and a gentle slope following the dip 

 of the strata. The lack of any known sediments deposited in 

 basins from the erosion of the fault blocks suggests that general 

 uplift prevailed over the whole Appalachian province and that 

 the differential movement between the blocks was one of different 

 degrees of uplift ; that there was nowhere real downsinking. The 

 greatest erosion was on the two sides of the basins facing each 

 other. From those sides the sediments have been completely 

 removed, which, along with the sloping away of the crust blocks 

 from the central axis, sKows that the uplift was between the Con- 

 necticut and Hudson valleys. Over this region the only remnant 

 of Triassic sediments preserved lies in the Pomperaug Valley. 

 The least uplift was on the western side of the New Jersey Trias- 

 sic area and the eastern side of the Connecticut area, for in those 

 marginal belts the greatest depths of Triassic sediments remain. 

 In Connecticut the regional eastward dip shows that the western 

 side of each block was elevated relatively to the eastern side and 

 the difference in the elevation varied with the width of the block. 

 In New Jersey the dip and therefore the relative movement was 

 in the opposite direction. 



Yet, in spite of this great crust movement, which could not 

 have been earlier than the beginning of the Jurassic, a peneplain 



