42 Harris and Crawford : 



Within the mapped area the Quarter Sheets show the follow- 

 ing rocks, Macedon igneous rocks excluded, 

 (i.) Alluvium, 

 (ii) Upper Volcanic, 

 (iii.) Newer and Older Pliocene, 

 (iv.) Oolitic, 

 (v.) Lower Silurian. 

 Of these the Lower Silurian would now be termed Ordovi- 

 cian. The so-called Oolitic is the Kerrie Conglomerate. 



(b) Proposed Revised Classification. 



We propose the following classification : — 

 (i.) Alluvium, 

 (ii.) Newer Volcanic, 

 (iii.) Pre-Newer Volcanic Gravels, 

 (iv.) Kerrie Conglomerate, 

 (v.) Ricldell Grits. 



(vi.) Upper Ordovician. Shales, slates and sandstones., 

 (vii.) Lower Ordovician. ,. „ „ „ 



This classification differs from the earlier one in its division 

 ot the Ordovician, in distinguishing the Riddell Grits as a dis- 

 tinct geological phase, and in specifically indicating the Kerrie 

 Conglomerate. 



V. — Physiographical Features. 



Physiographically -the. district may be divided into two areas,, 

 western and eastern. The division line is the Djerriwarrh fault 

 line running south from Gisborne to the Djerriwarrh Creek, the. 

 valley of which follows it for some distance. This fault de- 

 termines the boundary of Upper and Lower Ordovician. Lower 

 Ordovician rocks predominate in the western area, but are not. 

 found in the eastern, which is for the most part covered with 

 basalt of the Newer Volcanic flows. Throughout this eastern 

 area are more or less isolated exposures of palaeozoic sedimentary 

 rocks, of which the oldest are Upper Ordovician. Upper Or- 

 dovician rocks do not appear west of the fault line. (Fig. 3). 



The stream development of the western area has been pro- 

 foundly modified by the Djerriwarrh Fault, and the lava flows 

 from Mount Bullengarook and Hare's Hill. As showing the 

 pre-Newer Volcanic age of the Djerriwarrh Fault, it may be~ 

 noted that it in no place dislocates the basalt, and, secondly,, 

 that in parts all trace of it has been obliterated by the infilling:' 



