The Geolofjij of the Loiver LeUjh Valley. 63 



The remaiuiiig eocene sections noted on the accompanying 

 map of the Leigh River are to the north of Dog Island, and in 

 the surveyed area. As pointed out by Mr. Wilkinson, they are 

 of a different character to the beds which have just been 

 described. On proceeding northwards from the amphitheatre, 

 the horizontal bands of limestone, which there stand out so 

 prominently on the face of the escarpment, soon disappeai', Ijeing 

 afterwards masked either by basalt or a covering of surface soil. 

 From the neighbourhood of Dog Island there is a lava flow at 

 the summit of the eastern as well as of the western bank, and by 

 the Survey these flows are considered to originate from separate 

 vents. At one spot, between Dog Island and the so-called Dog 

 Rocks, there is a bold bluff of basalt, and below it limestone, 

 apparently unfossiliferous, resting upon ordovician slates, which 

 now become a conspicuous feature in the river-bed, and also for 

 some distance up the banks on either side. A section in this 

 neighbourhood is quoted by the Survey as showing the following 

 succession of rocks : — 



Vesicular basalt. 

 Soft yellow coralline limestone. 

 Thin bedded silurian sandstone. 

 The section we examined (No. XI.) is at the Dog Rocks, close 

 to a deep pool of water, which bars further progress along the 

 base of the escarpment on the eastern bank. Its position is 

 approximately marked upon the map. The rocks there displayed 

 are : — 



Basalt ... ... ... ... 60 feet 



Polyzoal limestone .. . ... ... 55 ,, 



Almost vertical ordovician ... ... 125 ,, 



Total height of bank ... ... 240 feet 



Concerning the coralline limestone or, as it is more correctly 

 termed, " polyzoal limestone," near the mouth of Reid's Creek 

 and in a few other places, Mr. Wilkinson says : " These upper 

 beds consist of a soft yellow limestone, composed of an aggregate 

 of fragments of polyzoa, corals, spines of echinoderms, and a few 

 shells, chiefly terebratuia, osti'ea, pecten, etc. So broken are 

 these fossils that one is rarely found perfect. The limestone is 



