44 Harris and Crawford : 



by basalt of valleys cut back from its scarp. Such infilled valleys 

 occur north-west of Gisborne, near Slocombe's Corner, and at 

 the Glendoon Spur. (QSs. 6 SW. and 7 NW.) 



There is evidence that the Macedon platform was a definite 

 geological feature at the time of the faulting, the throw seeming 

 to diminish as it approaches Mount Macedon, while north of the 

 Mount no dislocation is shown by the palaeozoic rocks, Lower 

 Ordovician (Darriwil) graptolites being found at Woodend, east 

 of Carlsruhe, and at Newham. N 



While the evidence for the re-construction of obliterated 

 physiography must of necessity be more or less inconclusive, it 

 is probable that the history of the western area is as under: — 



(a) Previous to the Djerriwarrh Fault a stream — the 

 " ancient Bullengarook " of Messrs. Officer and Hogg 

 — rose north of Gisborne, and flowed south-west to- 

 wards Bacchus Marsh. 



(b) The Djerriwarrh Fault reversed the direction of the 

 portion of this stream west of Gisborne, so that a 

 new local watershed was formed near the present 

 Mount Bullengarook. 



(c) On this Divide volcanic activity built up Mount 

 Bullengarook and Hare's Hill, which sent lava flows 

 down the valleys to the north-east and south-west, 

 forming the ridge now followed by the Gisborne- 

 Bacchus Marsh Road, and also the outliers along 

 upper Jackson's Creek. 



(d) Erosion in post-Newer Volcanic times developed the 

 present stream system. 



Further details will be given when treating of the eastern 

 area. It may be noted that the northern and north-eastern slopes 

 of the Bullengarook area are gradual, and are covered by wide- 

 spread gravel deposits. The southern slopes, the Py'rete Ranges, 

 consist of steep' hills often 1600 feet above sea level, sloping 

 steeply to valleys 200 or 300 feet below. Gravels are absent. 

 The highest bed rock in the area is around Mount Bullengarook. 

 Sediments outcropping on the Bacchus Marsh road on the north- 

 western slope of the mountain are 1900 feet above sea level. 



The development of the drainage system of the eastern area 

 is typically what may be expected on an extensive lava flow which 

 has covered and obliterated the earlier river valleys. The higher 

 portions of the watersheds project as hills, or have been exposed 

 "by vertical erosion. The position of these inliers indicates that 



