SEDIMENTARY ROCKS OF THE LOWER SHOALHAVEN RIVER. 325 
In one spot no less than four were found, one above the 
other. The lower two were each about one foot in thick- 
ness and ten feet apart, and the topmost two were only 
two or three inches thick and two feet six inches apart. 
Mr. E. C. Andrews’ mentions strata with plant remains 
from Yalwal goldfield, further to the south, but does not 
give many particulars of their occurrence. 
(b) The Conglomerates.—These are best studied about 
three miles west of Yalwal Oreek. The Devonian here 
reach a height of about 100 or 150 feet. Immediately above 
lies the conglomerate, occupying the same relative position 
in regard to the Devonian and the EKdmondia sandstone 
that the Freshwater Series do further to the east. The 
height of the hills on either side of the river rises as 
we go westward, and strange to say the conglomerate also 
thickens, though the height of the Devonian remains 
stationary and the sandstone cap still occurs above. At 
this spot there is a thickness of about 300 feet of con- 
glomerate. It is remarkably homogeneous in character, 
the pebbles being usually from two to six inches in diameter, 
set ina sandy and somewhat argillaceous groundmass. One 
huge waterworn boulder however was over three feet in 
diameter. 
The topmost beds of the conglomerate here form a 
prominent escarpment below the sandstone capping. Owing 
to the soft nature of the binding material the rock is easily 
disintegrated; consequently numerous deep rock shelters 
have been formed, some with very narrow openings. In 
these, deposits of alunogen are very common. In one place 
through this wearing or fretting on unexposed surfaces, a 
perfect natural arch has been formed. The peculiar 
appearance of the conglomerate, of which great masses 
* Report on Yalwal Goldfield, p.17, Geol. Surv. N.S. Wales, Mineral 
Resources, No. 9. 
