president's address — SECTION c. 69 



a chain of volcanoes appears to have commenced to form 

 on a north-west and south-east line, following approximately 

 the trend of the coast of that period 



An interesting section lately exposed at the Seven Miles, 

 near Raymond Terrace, shows that these eruptions com- 

 menced just prior to the commencement of the formation of 

 the Greta Coal Measures. Showers of volcanic dust, which 

 accumulated in places to a depth of over one hundred feet, 

 fell on the surface of the low-lying land or swamp-flats where 

 the coal was commencing to accumulate. Hence, in this 

 district portion of the Greta seams were actually formed on 

 a bed of volcanic tuff. This seam at the Seven Mile has 

 thin layers of volcanic tuff interstratified with it, and is 

 capped by a thickness of about 300 feet of strata composed 

 partly of tuffs and partly of a mixture of subaqueous tuffs 

 and clay-shale very carbonaceous in places. 



Thick sheets of lava, which may provisionally be termed a 

 diabasic dolerite, then covered these tuff-beds, there being at 

 least two distinct lava flows separated from one another by 

 tuff-beds, and by thin layers of coal much intermixed with 

 tuftaceous material. The whole of this volcanic series, 

 including the tuffs, has a thickness of from 1000 to 2000 feet. 



One of the points of eruption of these volcanic rocks was 

 probably the hill called Paddy's Sugar-loaf, between Ray- 

 mond Terrace and Stroud. 



In the Illawarra Coal-field volcanic energy developed itself 

 a little later than at Raymond Terrace, and, in this case, the 

 horizon of the volcanic rocks lies over 2000 feet above the 

 Greta Coal Measures, at the top of the Permo-Carboniferous 

 Upper Marine series, and at the base of the Permo-Carboni- 

 ferous Bulli Coal Measures. 



The contemporaneity of these lavas and tuffs with the 

 Permo-Carboniferous system was first pointed out by the 

 late Government Geologist of New South Wales, Mr. C. S. 

 Wilkinson. 



This volcanic series is from 1000 feet to 1400 feet thick, 

 and is built up of at least three sheets of lava and one thick 

 bed of coarse red tuff. The eruptions commenced with 

 andesitic dolerites, and concluded with olivine basalts. The 

 former contain metallic copper in small quantities in minute 

 shrinkage cracks throughout their mass. The volcano which 

 poured out those lavas and tuffs near Kiama was probably 

 in its first stages submarine, and made its appearance in the 

 shallow Permo-Carboaiferous ocean within about thirty miles 



