Triassic Fault of Southern Connecticut. 497 



The topography of Newark time was, of course, quite 

 different on the two sides of the fault. To the east there 

 were the hills or mountains whose erosion supplied 

 material for the strata near the fault. These mountains 

 were bounded on the west by a scarp, the height and 

 steepness of which varied from time to time. Bordering 

 the scarp on the west was a belt of alluvial fans, the slopes 

 of which were occasionally as high as several hundred 

 feet a mile. Farther west were the flat, featureless 

 plains, diversified only by occasional lakes or playas. 



Summary of Geologic History. 



Probably during the closing stages of the Appalachian 

 Revolution, almost certainly by the middle of Newark 

 time, movement began along the Great Fault. The crys- 

 tallines along the fault plane were first sheared and 

 crushed, and later they were partly replaced by a quartz 

 lode, and the fissure was temporarily healed up. During 

 this time the larger cross faults of the Triassic were 

 probably either faults or zones of weakness. During 

 Newark time the sediments accumulated in a depression 

 formed by intermittent movement along the Great Fault, 

 Alluvial fans were built into the plains to the west by 

 streams draining from the fault block range formed at 

 this time. Three or more lava flows were poured out, 

 one of which at least thinned out against the fans. Por- 

 tions of the flows that had spread over east of the Fault 

 Plane were raised up and their fragments washed into the 

 trough. After the deposition of the sediments, further 

 movement took place along the great fault, and the sedi- 

 ments were tilted, shattered, faulted, and, near the Great 

 Fault, warped into saucer-like folds. 



List of References. 



1. Joseph Barrell : Central Connecticut in the Geologic Past, Conn. State 



Geol. Survey, Bull. No. 23, 1915. 



2. William Davis: The Triassic Formation of Connecticut, U. S. G. S., 



18th Ann. Eeport, pt. II, p. 126, 1896-7. 



3. William Davis: The Eastern Boundary of the Connecticut Triassic, Geol. 



Soc. Am, Bull., Vol. 5, p. 526, 1894. 



4. G. F. Loughlin: The Gabbros and Associated Eocks at Preston, Con- 



necticut, U. S. G. S., Bull. 492, p. 143, 1912. 



5. William Davis: The Triassic Formation of Connecticut. U. S. G. S., 



18th Ann. Eeport, pt. II, p. 129, 1896-7. 



6. William Davis: The Eastern Boundary of the Connecticut Triassic, 



Geol. Soc. Am., Bull. vol. 5, p. 528, 1894. 



