494 Russell— Relations of the Great 



Possible throw before the New- Unknown, 

 ark deposition 

 (Movement ES, Throw RS> 



If part of the Newark strata accumulated a warped or 

 folded depression, this would introduce a correction 

 which should be subtracted from the sum of the foregoing 

 values. However, as the quartz lode probably indicates 

 that there was faulting before the formation of the 

 Newark strata, and as the fangiomerates and the pebbles 

 of the quartz lode occurring in them show that faulting 

 had begun again at least by the time when the trap sheets 

 were extruded, and that the Triassic did not then extend 

 east of the outcrop of the fault plane, it seems unlikely 

 that any appreciable part of the depression was produced 

 by warping. 



Taking all the foregoing facts into consideration, the 

 minimum throw of the fault may be estimated at 16,000 

 feet. However, it may well have been 20,000 feet, and it 

 is possible that it was as much as 30,000 feet. 



The Problem of the Cross Faults. 



Where the three great northeast-southwest faults of 

 the Triassic intersect the Great Fault, the latter turns and 

 runs along the cross fault in a northeast direction. As 

 this happens three times it can hardly be a coincidence. 

 Davis explained this by assuming that the cross fault 

 brought down the sandstones which he thought existed 

 east of the Great Fault. 5 and 6 The relations as he imag- 

 ined them are shown in fig. 6. There is definite field 

 evidence for the faults AB, BC, CD and CF. (5 and 6) 

 Davis believed that fault KB continued to the north to 

 form BE, while CF continued to the south to form HC, 

 though no field evidence for the existence of these faults 

 is given. The cross faults, according to Davis, have a 

 throw of about half a mile, and this he believed to be 

 sufficient in each case to bring the base of the Triassic 

 below the surface of block EBCF. Assuming that the 

 base of the sandstones in this block was originally nearly 

 on a level with the present surface of the upland, Davis 

 estimates the depth of the lower sandstones on the 

 eastern side of block EBCF to be about 1,600 feet in the 

 case of the South Manchester Fault block, and 1,400 feet 

 in the case of the South Glastonbury block. It would be 



