GEOLOGY OF THE JENOLAN CAVES DISTRICT. 



341 



The Cave limestone is about 550 feet thick, strikes 

 N. 20° W. and extends north with an unbroken outcrop for 

 three miles and southwards for upwards of two miles. It 

 is bluish-grey to blue-black in colour and is very massive 

 in character and almost devoid of bedding planes; near the 

 top of the bed however, some interstratification with shales 

 takes place and the bedding planes thus become marked. 



Fig. 1. — Sketch Section of Strata, Jenolan District, on line W Z on map. (Plate LV). 

 Vertical Scale 1 inch = 2500 feet. Horizontal Scale 1 inch = 2000 feet. 



A Radiolarian cherts (? Ordovician), B Silurian slates; C Rhyolite porphyry (? Lava 

 Flow); D Gave limestone; E Eastern limestone belt; F Qaartzttes; (x Intrusive andesite; 

 H Quartz-porphyrite (pink variety); I Quartz-porphyrite (green variety); K Probable 

 overthrust fault; S Grand Arch. 



Tins may be seen on the Tarana road, at the place marked 

 B on the map, just above the Cave House; the dip here is 

 to the west at about 60°. Jointing is, however, strongly 

 developed, there being in general two main sets, approxi- 

 mately at right angles to one another ; these are well shown 

 in the Devil's Ooach House and at the eastern entrance to 

 the Grand Arch. In the Lucas Cave large masses of lime- 

 stone have broken away from the roof of the cave and here 

 the joints are particularly well shown. 



Visible fossils are not frequent except in a few localities 

 the best being the road-cutting on the Tarana Road about 

 a quarter of a mile from the Cave House, just at the sharp 

 bend behind the Engineer's cottage at the place marked C 

 on the map. The following is a list of those fossils so far 

 identified from this district: — 



Hydrozoa ...Stromatopora 



Actinozoa ...Favosites gothlandica,Heliolites porosa 



Crinoidea ...Stems and ossicles 



