206 



southern side of the Maitland road, about a mile from 

 Ardrossan. The most northerly examples noted were patches 

 of large rounded stones in the paddocks on either side of the 

 private road going up to Mr. Dinham's farmstead in 

 Section 77. 



Lithologically, the beds give evidence of having been 

 laid down under alluvial conditions, the fragmental material 

 varying from fine sand to small quartz-gravel in grades up 

 to 1 inch in diameter. The sedimentation shows rapid 

 changes in short distances, both vertically and horizontally, 

 and is frequently current-bedded. An extensive silicification 

 has taken place over wide areas by the introduction of 

 secondary silica that has converted the open sediments into 

 a very compact, vitreous rock, with conchoidal fracture, and 

 by blending the original quartz material with the siliceous 

 cement makes a true quartzite. The cement is some- 

 times of a ferruginous character. The weathering of 



Fig. 2. 



Diagrammatic Section showing 3 patches of consolidated 

 ancient river alluvia (resting on Upper Cambrian Dolomite) at 

 successive altitudes; a, b, c, consolidated river deposits; r, r, 

 Recent mantle rock. Near district road, opposite Parara Head 

 Station. 



the rock varies according to the measure of siliceous 

 penetration. With a high proportion of introduced silica 

 the weathering is spheroidal (pi. xxiii.) in large blocks and 

 smooth surfaces, as Occurs at the southern end of the outcrops 

 near Parara. With less cement the clastic portions become 

 prominent and the stone takes on a gritty appearance. About 

 midway between Parara and Ardrossan a portion of these 

 beds are in a perfectly loose condition, not having passed 

 through the processes of consolidation, and are worked as 

 sand and gravel pits. In places a line of demarcation can be 

 seen with consolidated sands on the one side and loose sand 

 on the other. The breaks in the continuity of these beds 

 have undoubtedly arisen from the weathering and removal of 

 the looser portions of the sediments. On account of the 

 irregular action in the silicification of the beds the outcrops 

 sometimes weather into prominent and grotesque figures, and 



