68 president's address — section c. 



of the eruptions was contiguous to the coast line of that 

 period. 



In Queensland, in the Bowen River Coal-field extensive 

 eruptions of a diabasic character took place some time probably 

 about the close of the Carboniferous period or at the com- 

 mencement of the Permo-Carboniferous period. These lavas, 

 termed " bedded porphyrites " by Mr. R. L, Jack, F.G.S., 

 Government Geologist of Queensland, immediately underlie 

 the lowest members of the Marine Permo-Carboniferous 

 group, being capped by a formation which can be directly 

 correlated with the Lower Marine series of New South 

 Wales. Lithologically these porphyrites closely resemble 

 the Permo-Carboniferous lavas of New South Wales, though 

 they must be geologically older. The occurrence of car- 

 bonate of copper in the steam-holes of the porphyrite, and 

 the presence of metallic copper in the lavas of Permo-Car- 

 boniferous age at Kiama, and at the Canobolas, near Orange, 

 in New South Wales, is somewhat remarkable, though 

 perhaps merely an accidental point of resemblance, and not 

 necessarily implying that these lavas were erupted syn- 

 chronously with the porphyrites. 



Although now far inland, the Bowen River porphyrites, if 

 lavas, must have been erupted from volcanoes fringing a shore- 

 line, and their eruption was followed by a considerable sub- 

 sidence, during which the Upper Marine series and over- 

 lying Coal Measures of Permo-Carboniferous age were formed, 

 the aggregate thickness of which Mr. Jack estimates at 

 about 2800 feet. 



In New South Wales during the Permo-Carboniferous 

 period volcanic energy manifested itself on a grand scale in 

 those areas which were contiguous to the margin of the 

 Permo-Carboniferous ocean, and which also bordered on 

 areas where heavy sedimentation was in progress. In the 

 neighbourhood of Raymond Terrace, near Maitland, marine 

 Permo-Carboniferous sediments, having a thickness of at 

 least 2000 feet, were deposited in a great basin forming an 

 arm of the sea, which perhaps completely severed the New 

 England table-land from the Alpine plateau in the southern 

 portion of New South Wales. While, however, the central 

 portions of this basin where the sedimentation was most 

 heavy were undergoing subsidence, the north-eastern shore- 

 line of this Permo-Carboniferous sea was probably either 

 stationary or rising. Contemporaneously with the formation 

 of the Greta Coal Measures in the Raymond Terrace District, 



