Geology of Cobvuvg Area. 



'This outcrop is much shattered and fractured, and it is difficult to 

 •determine bhe strike and dip of the beds. A bard hand of breccia 

 striking North and South forms a miniature waterfall. This breccia 

 is composed of angular and rounded Silurian fragments set in -,\ 

 finer paste of the same material, and the whole is iron-stained and 

 cemented with limonitic material. Siliea solutions also seem to 

 have played a part in the cementation, for some of the breccia has 

 the nature of a quartzite. The breccia is probably due to a North 

 .and South fault. The hade is obscured, hut what evidence there is 

 points to a Westerly one. A similar breccia occurs in an inlier of 

 Silurian to the North-West of this last outcrop. The direction of 

 the fault is obscure, there being only the one outcrop in the walls of a 

 road section running North and South. The fault, however, 

 appears to he an East ami West one. hading to the South. This 

 would suggest that pressures along both North and South, and 

 East and West lines have occurred, and have produced both folding 

 and faulting along these directions. This conclusion is further 

 borne out by a road section cutting through the Silurian inlier. 

 The latter is seen to he the axis of an E. and W. syncline. to which 

 fact it probably owes its preservation. To the N.E. of this inlier 



Sechon along Murray 



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ilcnc, ABC 



•again, in a river section near the waterfall on Falls Creek, the 

 same E. ami W. folds are again seen, this time in an anticlinal 

 axis. These East and West folds show very low dips, and un- 

 doubtedly the dominant fold movements are those in a North and 

 South direction. 



A liver section just N.E. of the northern end of Sydney 

 Road, and just North of Pentridge Stockade, shows the basalt rent- 

 ing upon the tilted and eroded surface of the Silurian sediments. 

 The Silurian mudstones dip in a Westerly direction at 25 to 30 

 deg. The joint planes and bedding planes just beneath the basalt 



