314 T. G. TAYLUR AND D. MAWSON. 
indicates that the drift was partially derived from lavas 
earlier than the basalt capping. The iron cement was 
either leached out from the later covering of basalt or, as 
at the time of deposition these gravels occupied the river 
beds, it may have been derived from contemporaneous 
chalybeate springs. 
3d. Triassic Deposits. 
(a) The Wianamatta shales extend over a considerable 
area of the district, and largely occupy trough faults and 
areas of depression, as in the Mittagong valley. The > 
thickest beds in our district occur at the north entrance 
of the Gib tunnel where they are 80 feet thick. Inspection 
showed they had been preserved by a capping of basalt, 
which has since been denuded away with the exception of 
loose boulders on Hynde’s Farm. ee 
(b) The Hawkesbury Sandstone occurs as beds 600 feet 
thick. Much has been turned into quartzite of varying 
degrees of hardness through alteration by “‘ the Gib”’ and 
other centres of eruption. To this latter cause also must 
be ascribed the occurrence, in a glassy quartzite in a cut- 
ting on the Joadja tram line near Currockbilly, of bright 
glistening particles of graphite about 1 cubic millimetre 
in size. 
4. Permo-Carboniferous Deposits. 
These have already been described very fully by W. 8S. 
Wilkinson, as noted previously. Three well defined areas 
occur at Mittagong: 
(a) Anthracite valley at head of the Nattai River. 
(b) At the end of Mittagong Coal Co’s tramway on 
Nattai River, four miles below (a). 
(c) Extensive series of shales near Powell’s Creek and 
Jellore Creek. 
With respect to the first outcrop Mr. J. B. Jaquet says: 
“These beds are exposed to the north of Mittagong, where 
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