PRESIDENTIAL ADDRESS. 33 



coal basin) running N.N.W. and S.S.E., inclining to a more 

 meridional direction southwards towards Kosciusko, and 

 newer trends running parallel or sub-parallel to the present 

 Pacific Coast, and that trends N. by E. to S. by W. 



The latter trends are well shown by Mr. Andrews. 1 The 

 tectonic feature which is most conspicuous in the geology 

 of New South Wales is the great syncline, in which lies the 

 Permo-Oarboniferous coal-basin, the main axis of which 

 extends from Sydney to Gunnedah and Narrabri. This 

 divides at once the Bathurst-Monaro highlands, or tableland, 

 from the New England tableland. In the former tableland 

 the older trend lines are well shown by the direction of 

 outcrop of the chief beds of limestone, of Silurian age, which 

 there run N. and S. Towards the northern edge of this 

 plateau these fold lines swing more to the W. of N., the 

 chief synclinal troughs in the upper Devonian series lying 

 along N.N.W. to N. 30° W. directions. There is a strongly 

 marked unconformity, recorded and figured by Dr. W. G. 

 Woolnough in the gorge of the Shoalhaven near Tallong, 

 between the Ordovician slates and the Silurian limestones. 

 The folding of the Ordovician rocks has also been much 

 more intense than those of the Silurian. In the Yass district 

 the general trend of the folds in the Silurian and Lower 

 Devonian rocks is about N. 15° W. and S. 15° E., as shown 

 by Mr. Harper 3 and myself. 4 The prevailing dip is to about 

 W. 15° S. At Yalwal Mr. Andrews has shown that the 

 Upper Devonian rocks, lying in a long and narrow basin, 

 trend nearly due N. 30° E. (true). If we examine the 

 direction of strike of elongated masses of intrusive granite 

 from Delegate on the S. to Bathurst on the N., we find 

 that there is a slight tendency to virgation, the great mass 



1 This Society's Journal, Vol. xliv, p. 347. 



2 Proc. Linn. Soc. N.S. Wales, 1909, Vol. xxxiv, pp. 783-5. 



3 Geol. Surv. N.S. Wales, 1909, Vol. ix, pt. 1, pp. 1 - 53. 



i Ann. Rep. Depart. Mines, 1882, p. 148, with maps and sections. 



C— May 3, 1911. 



