NO. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. 3! 



The layers of clay left by the flood waters subsiding from the 

 basin floor were dried, cracked, and the edges curled up in dry- 

 ing. The lighter fragments were blown away by wind, but 

 the wind buried other portions of the cracked and curled clay 

 layers beneath drifting sand, and so preserved them in the same 

 curled form in which they dried. While yet soft and unburied, 

 the clay surfaces were often spattered with rain, or received the 

 enigmatical impressions of the varied insect and reptilian life. 



Davis in his report on the Triassic rocks of the Connecticut 

 Valley gives estimates of the thickness of each portion of the 

 formation. The sum of his minimum figures is 10,500 feet, the 

 sum of his maximum figures gives 13,100; neither estimate in- 

 cludes the intrusive rocks 500 or 600 feet in thickness. In these 

 estimates, the shales, sandstones, and conglomerates above the 

 uppermost lava flow and constituting the highest part of the 

 formation are estimated as 3,500 feet in thickness, but Davis 

 states that they are possibly much thicker. Following the regional 

 dip and the location of faults as shown by Davis gives, however, 

 on this structure section, a thickness to these upper rocks of be- 

 tween 6,000 and 7,000 feet, but undetected flattenings in the dip 

 or the presence of unmapped faults may reduce this thickness. 

 This section as shown in Figure I gives as much as 14,000 feet 

 of strata remaining, and implies possibly as much as 18,000 feet 

 deposited in the region of Middletown. In New Jersey careful 

 measurements by Kummel gave a total thickness of 20,300 feet, 

 notwithstanding the seeking for evidence which would reduce 

 this large figure. This is even greater than the greatest thickness 

 shown in Connecticut on the present structure section. It is clear 

 then that at least three miles of sediment was deposited in the 

 tracts of greatest subsidence. The basin floors in those places 

 subsided at least three miles during the progress of the period, 

 yet the sediment was sufficiently abundant to keep the basins con- 

 tinuously full of sediment. Slow movements intermittent in 

 nature went forward therefore for a vast period of time, during 

 which erosion planed ever deeper into the folded and metamor- 

 phosed rocks of the rising tracts of the Appalachian system, the 

 rock waste being swept into the sinking intermontane basins. 

 Miles of erosion and miles of deposition took place without there 



