BY W. G. WOOLNOUGH. 785 



south, at Bungonia, fossils are more numerous, and Hellolites 

 and Stroniatopora are additional forms represented there. East- 

 wards, the Silurian rocks are interrupted by the Ordovician belt, 

 while their western limit has not been traced fully. It is partly 

 outlined by a belt of porphyritic rocks extending from the Glen- 

 rock grano-diorite. 



The limestones, where they are least altered, are dark blue 

 and compact, but almost everywhere more or less intense meta- 

 morphism has obliterated original features and rendered the 

 rock crystalline. To the east of Hogg's Lime-kilns the texture 

 is that of an extremely coarse-grained white marble. Other 

 forms of contact-metamorphism will be referred to later. 



The limestones and associated mechanical sediments have a 

 very constant direction; the dip is W. 10° N. at 53° and does not 

 vary much from tliese figures. 



There are two very persistent limestone-horizons of which the 

 lower is the thicker. The section of the Silurian rocks is shown 

 on Plate Ixvi. As there indicated, there is a very marked uncon- 

 formity between the Ordovician and Silurian sediments. The 

 Silurian rocks are tilted but are not noticeably folded, while the 

 Ordovician strata are crumpled into most extraordinary shapes. 

 This alone indicates a decided stratigraphical break between the 

 two formations, but, in addition, in the creek below the lime- 

 kilns, the unconformity is beautifully shown. The lower lime- 

 stone bed of the Silurian, dipping westwards, rests directly on the 

 Ordovician slates dipping easterly at high angles. 



Devonian, 



It is doubtful whether Devonian rocks occur anywhere in the 

 area dealt with in the present paper. Fossiliferous limestones of 

 Devonian age are known to occur at Windellama, about 22 miles 

 to the south. The geological map of New South Wales shows 

 Devonian right up to Bungonia Creek. A belt of limestone, 

 quite different in character from the Bungonia limestone, occurs 

 to the west of the latter. It is possible that this is the continu- 

 ation of the Windellama bed. Rocks of this type have not been 

 81 



