382 NOTES ON NATIVE FLORA OF NEW SOUTH WALES, IV., 



hundred feet above the sea Had this low-lying 



country along the coast then existed it must have been covered 

 by the Miocene sea. . . . But it is very probable that until 

 or during the Pliocene period it stood at a 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. . . . 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 contemporaneous with the 

 extensive volcanic eruption of the Upper Pliocene period during 

 which the southern portion of Victoria especially was the locale 

 of great volcanic activity. How far this old land extended to 

 the east it is difficult to indicate; but no doubt future observa- 

 tions upon the distribution of the marine and terrestrial fauna 

 and flora of the South Pacific region will throw much more light 

 upon the subject." 



Professor David"^ also gives evidence to show that the Coal- 

 measures upon which the Narrabeen Shales are superimposed 

 rise towards the eastward of Port Jackson, and it therefore 

 follows that these shales must also have risen (evidence of which 

 has already been given from the results of the Balmain shaft and 

 Cremorne bore), and may in part have formed the eastern margin 

 of the depression in which the Hawkesbury Sandstone was 

 deposited. Subsequently to Triassic time continuous erosion and 

 denudation would remove much of the Hawkesbury Sandstone 

 from the eastern edge, thus exposing the Narrabeen Beds; and 

 this formation, or the Permo-Carboniferous, or possibly the 

 upturned edges of both, would remain exposed until the final 

 subsidence, which is estimated to have occurred in late Pliocene 

 or Post-Tertiary time. The extension of that former land-surface 

 for some distance north and south, and possibly its eastern margin 

 also, would probably be composed of Permo-Carboniferous forma- 



* Journ. and Proc. Roy, Soc. N.S.Wales. Vol.xxx, pp.43, 48, 69. 



