LATE PALiEOZOIO FOLDING IN THE HUNTER RIVER DISTRICT. 133 



IV. Preliminary Discussion of the Results. 

 From the results obtained above it is seen that the 

 diastrophism which affected the lower Hunter area in late 

 Permo-Oarboniferous time was of an intermediate inten- 

 sity, producing a crustal compression whereby 70*56 miles 

 of the earth were shortened by 7*46 miles. 



The shell involved in the folding appears to have been a 

 fairly thin one, and, at first sight of a peculiar shape. The 

 margins of the tract in question are underlain by the 

 deepest zones, and the central portion is the surface of a 

 comparatively thin block. 



Turning to the values for the depths of the earth blocks 

 for the individual section portions one is struck by the low 

 values obtained for sections No. IV and No. VI. The 

 numerical value of the thickness of the folded block is 

 obtained from a fraction whose value is dependent on the 

 measure of the crustal shortening and the average vertical 

 bulging per mile. In the case of Section No. VI the amount 

 of the height of the folded structure above the datum plane 

 is very small, since the Upper Coal Measures, (the topmost 

 strata of the section under consideration), are in places 

 below the line of the datum plane. 



This is undoubtedly due to the fact that after the folding, 

 or, at any rate, towards the close of the folding, heavy 

 faulting occurred letting some of the strata down to the 

 extent of 5000 feet. Thus to arrive at the depth of the 

 zone under the portion No. VI one must consider the 

 restored section in its pre-faulting position. A similar 

 procedure should be adopted for the whole section in order 

 to gain a truer conception of the nature of the deformed 

 zone. 



The original procedure of reconstructing the whole 

 section without allowing for faulting was quite justifiable 

 for the following reason. There was no conclusive evid- 



