130 G. D. OSBORNE. 



showing that the accumulation of the Bolwarra con- 

 glomerate occurred at a general uniform level. These 

 considerations permit of the above choice being made with 

 confidence. 



To arrive at the present position of a datum plane, which 

 corresponds to the surface from which the strata rose, the 

 physiographic history of Eastern New South Wales in Post- 

 Permo-Oarboniferous time has been considered. The sur- 

 face which became wrinkled in post-Newcastle time stood, 

 (with the exception of the initial bulging referred to before), 

 essentially at sea-level. There have been no folding move- 

 ments impressed on the Hunter area since the close of the 

 Palaeozoic era, so that the only movements we have to 

 consider are of an epeirogenic nature. Although the con- 

 trasted low relief of the Lower Hunter valley, compared 

 with the bordering higher land, is due in a measure to 

 differential erosion on a grand scale, still it seems that the 

 Lower Hunter segment sagged behind in at least the last 

 upward movement which affected the Eastern portion of 

 New South Wales. This last statement is made mainly on 

 information kindly supplied by Mr. Sussmilch concerning 

 the tectonics of the southern margin of the Barrington 

 Tableland. On both stratigraphic and physiographic evid- 

 ence he has noted the very probable existence of heavy 

 step-faults flanking that tableland on the southern side, 

 (see < 13 )). 



Taking these facts into consideration and allowing for 

 the effect of comparatively recent movements along the 

 coast the writer has arrived at the figure of 1100 feet for 

 the post-folding uplift in the Hunter area. 



The section which is seventy-one miles in length was 

 divided up into seven portions, six of which being ten miles 

 long, and the seventh, which is the westernmost, being ten 

 and a half miles in length. The depth of the folded block 



