38 T. W, E. DAVID. 
' “The abrupt eastern margin of the Blue Mountains, up which 
the Great Western Railway Zig-zag ascends at Lapstone Hill, 
near Emu Plains, marks the line of a similar though not such an 
extensive fault, by which all the country between it and the coast 
was thrown down to its present level—the depression being so 
great that the ocean water flowed into the old river valleys, one 
of which forms the beautiful harbour of Port Jackson. * * 
We have evidence that these faultings probably took place towards 
the close of the Tertiary epoch ; for no marine Tertiary deposits 
are known along this portion of the coast of Australia, whereas 
in New Guinea on the north, and in Victoria on the south, the 
marine Miocene beds occur at elevations up to eight hundred feet 
above the sea. Had this low-lying country along the east coast 
of Australia then existed, it must have been covered by the 
Miocene sea, and doubtless some traces of the marine strata of 
that period would have escaped denudation and remained as those 
have which are seen in Victoria and elsewhere; but it is very 
probable that until or during the Pliocene period it stood ata 
much higher level, and extended some distance beyond the present 
coast line. Then, again, the Tertiary deposits throughout East 
Australia show that the valleys draining the Great Dividing 
Range have been chiefly eroded since the Miocene period, for we 
find deep valleys and ravines cutting through later Tertiary form- 
ations ; therefore the sinking of the land traversed by any of 
these valleys such as that of Port Jackson, evidently took place 
in comparatively recent geological times, and may have been con- 
temporaneous with the extensive volcanic eruptions of the Upper 
Pliocene Period, during which the southern portion of Victoria 
especially was the Jocale of great volcanic activity. How far this 
old land extended to the east it is difficult to indicate ; but no 
doubt future observations upon the distribution of the marine 
and terrestrial fauna and flora of the South Pacific region will 
throw much more light upon the subject.” 
In 1882, the Rev. J. E. Tenison-Woods contributed an impor- 
tant paper on the Hawkesbury Sandstone,! reference to which and 
1 Journ. Roy. Soc. N. 8. Wales, Vol. xv1., 1882, pp. 53-116. 
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