526 DAVIS AND GRISWOLD — BOUNDARY OF CONNECTICUT TRIASSIC. 



of the saucers to perpendicular at the saucer rmis. These saucer-like 

 half-synclines have anticlinal separations which have been eroded ; the 

 rock series was originally continuous throughout, and now the edges of 

 this rock series, repeated in reverse order six times, abut against the old 

 crystallines.* This in itself is a conclusive argument for a fault contact 

 along this part of the line, and, furthermore, affords data for computing 

 the amount of dislocation. The throw must equal at least the thickness 

 of Triassic rocks between the lowest and highest beds found abutting 

 against the line ; but such a measurement do^s not include the lowest 

 beds of Trias which cannot be denied to exist on the eastern side of the 

 Triassic basin though not exposed at the surface, and surely these beds 

 as well as those measured have been eroded from the uplifted crystalline 

 foundation on the east side of the great fault-line. Reckoning these 

 lower sandstones at one-half the thickness on the eastern side that they 

 have on the western (the formation thinning on the eastern side because 

 nearer the conceived shoreline of the old Triassic basin), the minimum 

 throw of the fault in the central part of the Totoket saucer is 9,000 feet ; 

 thirteen miles further north, in the central part of the Middletown saucer, 

 the throw is 8,000 feet. Thus the amount of dislocation seems to decrease 

 on going northward, and other sections confirm this idea. 



In the above explanation it has been assumed that the folding pre- 

 ceded the faulting, though it might be urged that the semblance of fold- 

 ing was given as a result of differential movement on the fault-line. 

 This would necessitate a differential throw in the two southern saucers 

 of over 4,000 feet within a lateral distance of about 16,000 feet, and this 

 process twice reversed or four times repeated. This supposition seems, 

 therefore, less probable than the assumption that the folding and fault- 

 ing were successive. 



Fault number 3 has one important locality giving evidence of faulting. 

 At Highland Park paper mill, Triassic conglomerates were found not far 

 distant from the old crystallines, and a trench was dug to show the char- 

 acter of the contact. The conglomerates were found to be less compact 

 near the contact, becoming so loose that they were easily worked with a 

 pick. Sandy layers at the contact gave a dip of 45° to the west, show- 

 ing a strong drag movement. The small surface of the contact that was 

 uncovered had a dip of 55° to the west and a strike north and south. 

 The crystalline rocks at the contact were much shattered atid decom- 

 posed, so that they also were easily worked with a pick. Twenty to 

 thirty feet away, however, though much contorted, they have been so 

 consolidated by the vein-forming process that they rise in a bold bluff 



*0n the map the Pond mountain and Totoket mountain saucers are well outlined by the main 

 trap; the north side of the Middletown saucer is bordered by the posterior trap which is repx'e- 

 sented near the margin at South Glastonbury, but is not here shown. 



