330 



THE LAKE GEORGE SENKUNGSFELD, 



dug in the vicinity seem to show that this material is in many 

 cases superficial, and lies over the silt and clay which occupies 

 the lake bed (see Section, fig. 1). 



Govef-nor's 



Fig. 1. —Section AB (see Plate vii.) showing the Senkungsfeld and Fault 

 Plane, also the High-level Gravels of the old outlet. 



Assuming a strike fmdt as being the cause of Lake George, let 

 us endeavour to reconstruct the topography of the country before 

 the faulting. If the Lake George Basin were raised some 300 

 feet, the four creeks (Murray, Taylor, Deep and Turallo) would 

 evidently unite into one river, which would flow towards the west 

 and ultimatel}' reach the Yass River above Gundaroo. Some 

 trace of this old river (which we ma}'- conveniently call Lake 

 George River) should remain in the form of an old valley, which, 

 owing to later erosion on a different system of drainage, should 

 appear much like a ivater-gap. In addition, it is nob too much 

 to expect tiiat some of the old river boulders shall have remained, 

 no longer necessarily in the lowest portions of the area of eleva- 

 tion (since the latter has been since modified by later stream- 

 action). If, as is often the case, the fault has diminished in 

 extent towards its extremities, we may expect that some (ante- 

 cedent) river-systems have been able to keep their old path in 

 spite of tectonic obstructions. 



All these phenomena are abundantly shown in the Lake George 

 area. Ascending the steep hill face, 300 yards north .of Grove 

 Creek, and \h miles south of the jjresent lowest point of the 

 CuUarin Range, a deposit of elevated river-gravels is reached. 



