THE HAWKESBURY SANDSTONE. 87 
the Mesozoic period. The plants give us no great clue. They are 
those hich belong to the Upper Coal basin, such as Thinn/eldia 
We cannot fix any age for these beds. Similar deposits overlay 
marine beds with chalk fossils in Queensland. These cretaceous 
bury sandstone has been less disturbed than the formations of other 
parts of the continent. Here then we may suppose has survived 
the world’s natural history and perhaps a link which connects 
us with the present time. t 
been relates to the period of volcanic activity. This was shared 
US now, as far as the fossils will guide us. I may thus summarize 
the results of this essay :— 
_ 1. That the Hawkesbury sandstone is a wind-blown formation, 
interspersed with lagoons and morasses, with impure peat. 
2. That: there has been no upheaval, but rather a subsidence, 
Which probably extends from the base of the range to 
3. That the peculiar lamination of the beds is due to the angle 
at which dry sand slips and rests when blown by the wind. 
4 The beds of ironstone represent vegetable matter destroyed 
: oxidizing the iron, and this is why so few plant remains are 
5. The irregular layers of the sandstone formation probably 
“Present what was a tranquil portion of the surface for a time, 
. which there may have been a vegetable growth now represented 
¥ Ironstone bands, 
uc, The smaller gravel may be wind-blown ; the larger may have 
ta derived from creeks. ‘This is also the origin of the fragments 
ot shale. The creeks have undermined them and broken them up. 
ek Conglomerates may have been derived from stony deserts, 
.* 'as we have in the centre of Australia. They represent all 
1), Sones of a sandhill district from which the sand has been 
Oh a 
\ L away, 
