366 T. W. E. DAVID. 



bending and shearing thus amounts to probably over 500 

 feet. It may be added that on December 14th, Mr. Pittman 

 and I found evidence of this fault being strongly developed 

 at a locality called the Mountain Lagoon about 5£ miles 

 N. 3° E. from the foot of the "Out Rock." (See plan, PL 16.) 



The Wianamatta Shales are strongly developed on the 

 downthrow side of the fault at the Mountain Lagoon, and 

 it is clear that the lagoon owes its origin to the fault. On 

 the upthrow side of the fault the Wianamatta Shales have 

 been completely denuded away, so that accurate measure- 

 ments of the throw could not be made by us there. It is 

 clear, however, that the throw is fully 400 feet, as deter- 

 mined by aneroid measurements. There appears to be less 

 bending of the strata as they approach the fault plane at 

 the Mountain Lagoon than at the Out Rock, for within 30 

 yards easterly of the fault plane at the former locality the 

 dip is north-easterly at a low angle, that is in a direction 

 aivay from the fault plane. It is evident from the con- 

 figuration of the country that the fault extends at least as 

 far north as the Colo River. The fault plane has not yet 

 been traced by me to the south of the Cut Rock, but it is 

 evident from the trend of the strong escarpment for many 

 miles to the south that the fault must extend at least as 

 far south as the Grose Valley, and probably as suggested 

 earlier in this paper, extends to the westerly flexure at 

 Glenbrook Railway Station. The total distance from 

 Glenbrook Railway Station to the Colo River is about 27 

 miles. If now the Kurrajong Heights structures be com- 

 pared with those of Lapstone Hill, it may be stated that 

 at Kurrajong Heights the easterly monocline displaces the 

 strata about 1,060 feet, measured vertically from the hori- 

 zontal, and lowers them about 860 feet below their original 

 position due to normal easterly dip, the figures for similar 

 displacements at the Lapstone Hill monocline being respec- 



