156 Proceedings of tlie Royal Society of Victoria. 



there is a wide stretch of country constituting the Powlett and 

 Tarwin Plains, covered in the main with pebbly drift, gravels 

 and sands, with a few isolated patches of laterite tuffs and plugs 

 of basalt. 



Division 4. — Between the Middle and Lower Powlett and the 

 coast there is a varying, though thin, capping of sediments, 

 chiefly clays, and sands of ajolian origin covering the Powlett 



Plains. 



The greater portion of the coast line itself is composed of 

 Jurassic strata forming bold cliffs. This series extends to the 

 hill country, underlying the thin covering of Cainozoic sediments 

 over the greater part of the area. Jurassic rocks are visible at the 

 .surface for some little distance inland from the coast between 

 Wreck Creek and Cape Paterson ; while between Cape Paterson 

 and West's Creek there are two inliers of Silurian strata, 

 discovered by Mr. W. H. Ferguson, during the progress of his 

 survey of the Cape Paterson Quarter-sheet. 



During the progress of my survey of the Jumbunna Quarter- 

 sheet, extending from the Powlett Valley to Korumburra, 

 numerous small and large volcanic plugs and stumps of old 

 volcanoes were found, as has already been mentioned. They 

 have been intruded into or thrust through the carbonaceous strata 

 of the Jurassic system. They comprise three general types of 

 rock : — 



{a) A coarsely crystalline rock, probably dolerite, comprising 

 the largest neck, and several smaller ones. 



(b) A dense olivine basalt with large included crystals of 

 hornblende, biotite and felspar scattered through it, besides 

 fragments and blocks of the invaded strata, and usually occurring 

 as small and medium plugs. 



{c) A dense or finely crystalline basalt as a rule, with or 

 without amygdules of calcite, and small patches of olivine. This 

 occurs as small plugs and dykes. 



An occurrence similar to these was, therefore, expected at 

 Townsend Bluff", but examination revealed a neck of different 

 character. Though containing a considerable amount of basalt 

 it consists for the greater part of clastic volcanic material such 

 as agglomerate, tuff", lapilli, and what appears to be volcanic mud 

 with included blocks and fragments of the adjacent Jurassic 



