No. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. 25 



older rock structures. These sediments thicken to the southeast, 

 and their nature and that of the floor which they rest upon give 

 the evidence on which the preceding statements have been based. 1 



But by the beginning of the Cretaceous period the inland up- 

 warping had slackened, while the seaward downwarping still pro- 

 gressed. The rivers were therefore no longer supplied with 

 sufficient sediment to maintain their delta plains above the surface 

 of the sea. Erosion continued to degrade, the mountains on the 

 northwest and the sea began to plane far inland from the 

 southeast. 



A sinking land, especially one in which sinking accompanies 

 a seaward tilting, permits the waves to roll inland with but little 

 diminished force and to erode vigorously at the shore. The 

 residual hills left by river erosion, projecting as headlands and 

 islands, are planed away, and the peneplain developed by sub- 

 aerial erosion becomes converted into a plain of marine 

 denudation. As the Cretaceous strand-line, owing to these 

 actions, advanced farther inland, submergence at the same time 

 brought deeper water over the more seaward portions and de- 

 position of marine sediments began. 



Davis was the first of geologists to point out the evidence, 

 shown by the river courses, that the sea probably advanced as far 

 as central Connecticut, or about to the line of the structure section 

 shown in this paper; but, as stated previously, the writer holds 

 that there is evidence of another kind that the Cretaceous sea at 

 its maximum extended even farther, spreading in fact to the foot 

 of the White and Green Mountains, and covering what are now 

 the high plateaus south and east of the mountains. During the 

 rest of the Cretaceous and perhaps well into the Tertiary Con- 

 necticut remained a coastal plain. Slight oscillatory vertical move- 

 ments of the sea or land caused wide movements of the strand- 

 line, and the portion north of Middletown emerged permanently 

 from the waters long before the southern portion of the State. 

 The nature of its surface then resembled the present surface of 

 southern New Jersey and the eastern shore of Maryland ; that is, 

 it consisted of low sandy plains shelving put into a shallow sea. 

 From the emerged portion the soft sediments were soon washed 



1 The writer has discussed this subject more fully on pages 405-414, Vol. 23, 

 Bull. Geological Society of America, 1912. 



