TJie Stony Creek Basiv, Daylesford. 369 



midway between them. ]»lark clays similar to those of the 

 basin are found also under the basalt at Sailor's Fall (the 

 same flow which passes the basin) and north of Daylesford 

 railway station, also under volcanic rocks. Here, at the 

 Exchequer Company's shaft, the upper parts were shaly. It is 

 pi-obable that the shaly parts are also uppermost at the basin. 



The probable secpience of events is as follows : — -The black 

 clays were deposited prior to the volcanic activity, or perhaps 

 durino' the first modifications of the drainasre system by volcanic 

 action. Subsequently, by subsisdence on the course of a well- 

 defined line of weakness, a portion of these black clays have 

 been depressed below the levels of the surrounding country. 

 The creeks of the period flowed west and north of the basin, 

 and may have flooded it. A branch from the lead seems to 

 enter the basin ; this would con-espond to a diversion of part 

 of the stream into the subsided area. (The lead on the north 

 side is probably a tributary ; there is also a small area of basalt 

 east of the Ballan road not shown on the map.) The lava streams 

 from Leonard's Hill have then buried these old valleys, and 

 perhaps part at least of the area of the basin. A part of the 

 waters then flowed down the western side of the basalt forming 

 the present Sailor's Creek. The eastern tributaries formed the 

 present Stony Creek. The course of this creek cutting across 

 the basalt at the outlet from the basin was only able to deepen 

 slowly at this place. While its level was thus maintained it 

 cut out a plain at the site of the basin in these easily-eroded 

 materials. A considerable area of basalt could have been re- 

 moved at the same time by the creek undercutting it if rested 

 on these clays. When the basaltic barrier at the outlet was 

 cut through, this flood plain was finally deserted, and the talus 

 from the weathering of the steep banks on the north and east 

 sides to some extent covered the plain. It would seem uncertain 

 how much of the disturbance of the east bank is due to the 

 original subsidences and how much to later landslips. It will 

 be noticed that this explanation regards the basin not as a filled- 

 in lake, but as a flood-plain of the creek, formed because of 

 the presence of the easily-eroded lacustrine deposits and the 

 maintenance of the creek level by the basaltic barrier ; but 



