Narrabeen Shales. 
183 
Carboniferous, the intervening Narrabeen Shales 
being absent. In most of the gorges on the 
mountains, beyond Mount Victoria, the Narrabeen 
beds can be easily recognised cropping out in the 
cliffs, the reddish-brown colour of some of these 
shales contrasting strongly with lighter coloured 
sandstones. They can be seen to advantage, also, in 
the cuttings on the railway, above Eskbank. The 
Narrabeen beds are not more than 350ft. in thickness 
on the western flank of the mountains above Lithgow. 
These shales are, therefore, not unlike a great saucer, 
the centre and thickest portion of which is under the 
district around Sydney, and the thin edge of which 
sweeps round from Coal Cliff to Lithgow, and from 
there to the coast north of Narrabeen. 
Origin of the Narrabeen Shales. — Glancing 
at a collection of the fossils that occur so plentifully in 
the shales, we note an abundance of plant remains, 
many in a beautiful state of preservation. The only 
shells known to occur are decidedly not marine. 
There is, then, no evidence of the shales being a 
marine formation. They were certainly not depos- 
ited in the sea. But this much we do know, they 
were laid down as sediments in water. One of the 
most impressive of the silent witnesses to this fact is 
the “ ripple-marks ” still preserved on some of the 
slabs. The lapping of the water on the as yet un- 
hardened sands left lines of tiny ridges along the 
edges of a lake. Dry sand was then blown down, and 
in this way a mould was cast that has lasted to this 
