526 GEOLOGY AXD PETBOGHAPHY OP CLARENCETOWX-PATERSOX DISTRICT, ii., 



system of fractures and then planated or reduced to a surface with a few very 

 broad valleys, and that on this peneplain basalts were extruded before the present 

 topography was developed. This would place the faults as pre-Mioeene or pre- 

 Pliocene in age. Further, since they almost undoubtedly belong to the same 

 series which have affected the Permo-Carboniferous and Carboniferous strata to 

 the south and south-west, a pre-Mesozoie age may be assigned to tbem, for Prof. 



■ David found evidence of the occurrence of faulting and erosion of the Permo- 

 Carboniferous beds to the extent of 5,000 feet before the Triassic sediments 

 w-ere laid down upon the eroded surface of the Palaeozoic rocks. 



The origin of the faulting is a matter of interest. As the dislocations are, 

 with one small exception, normal, one must see evidence of tensional forces at 

 the time of their development. Chamberlin and Salisbury (1905, p. 521), James 

 Geikie (1905, p. 109) and others, adhere to the general conception that block 

 (noi-mal) faulting is the outcome of tensional stress indicating a local extension 

 of the earth's crust, reversed faulting being due to compression ; alid Hobbs 



■ (1921, p. 48-49) has shown that a constant cumulative compressional stress exists 

 within the earth's shell, whose effects, though temporarily superseded by the dis- 

 placements during periods of sudden relief, are reasserted immediately after such 

 periods. The writer has shown (Osborne, 1921), from a study of the late Palaeo- 

 zoic folding in the area a little to the south — folding which produced the struc- 

 tures now under discussion — that heavy normal faulting occurred at the close of 

 the folding period. This is equivalent to saying that at the close of the period 

 of folding, the extent of the vertical displacements had reached the maximum, 

 but since folding implies compression, it seems reasonable to regard the extent 

 of faulting as now measured, as representing the integration of a large number 

 of small displacements which occui-red during short periods of tensional stress, 

 or periods of relief from the longer intervals of compression which obtained 

 during the folding. 



The folding itself is the outcome of thrusting in an east-west direction. It 

 is difficult to say exactly in which sense this force acted, but with the conception 

 of oceanic and continental segments in the earth's crust, and of crumpling along 

 their borders by segmental adjustments on the principle of isostasy, it is natural 

 to regard the sagging of the Pacific Ocean segment, which has been a subsidence 

 area for a long time {cf. Andrews, 1922, p. 14) as contributing to the folding 

 which compressed the rocks of the Hunter District. It is also possible that some 

 thrusting in an easterly direction may have originated by the sinking of the im- 

 portant synclinal segment which exists between southern New England and the 

 Bathurst area. 



Structural Eelations betiveen the Kuttung Series and the Permo-Carhoniferous 

 System. 

 Much has been said upon the question of the actual relationship between the 

 Kuttnng Series and the Permo-Carboniferous beds. C. A. Sussmilch is positive 

 in his view of conformity in the Paterson-Seaham District, while T. W. E. David 

 shows that there is distinct unconformity between the two at Pokolbin and 

 hesitates to make a definite conclusion about the series generally. There is much 

 work yet to be done, and the writer' has not been able to find, in the area he has 

 examined, any definite evidence either way. In almost every locality where a 

 passage might be expected, one of two sets of conditions occurs. Either alluvium 

 puts the determination of ' the relationship beyond possibility or no reliable dips 

 p-an be obtained sufficiently near the supposed junction line. It is interesting 



