18 



and Leda, while fragmentary Polyzoa make up the greater 

 part of the finer material of the limestone. 



To what extent these marine Cainozoic beds occur in the 

 district is unknown, as the country is uniformably covered 

 with alluvium of considerable thickness. There is reason to 

 believe, however, that the small outcrop at the Red Banks 

 forms part of an extended sheet of these beds existing in the 

 neighbourhood, but hid from sight by the newer deposits. 

 The extensive development of travertine limestone in the 

 district favours this view. A few miles out from Wasleys 

 railway station, on the road to the River Light, the ground 

 becomes distinctly calcareous and nodules of travertine are 

 thickly strewn over the cultivated land and are gathered up 

 and used for road metal. In several places this surface lime- 

 stone is sufficiently thick to be quarried. All the stone 

 buildings of Mallala and neighbourhood are constructed of 

 travertine limestone, the stone being obtained from local 

 quarries. Whilst it is not maintained that the marine lime- 

 stones are concurrent with this surface-travertine limestone 

 throughout the district, the very considerable development of 

 the latter, locally, can be best explained by assuming that 

 the extensive leaching of the older limestone has yielded the 

 greater part of the travertine, which is always a secondary 

 product. 



This small outlier of Lower Cainozoic rocks in the Light is 

 of considerable interest as bearing on the ancient topography 

 of the country, especially when studied in relation to other out- 

 liers of similar beds in adjacent districts. The nearest locality 

 for rocks of the same age is at Gawler, situated about 15 miles 

 in a direction south-easterly from the Red Banks. The two 

 outcrops are, however, of distinctly different lithological 

 types. In the case of the Gawler beds, the fossils occur in a 

 coarse grit, while the beds at Red Banks, on the Light, are 

 true limestones. Such strong contrasts must be referred to 

 different conditions of deposition. The Gawler beds give evi- 

 dence of strong currents, probably a shore-line, while the 

 Red Banks deposits were laid down at some distance from the 

 shore and in a position that was protected from land wash. 

 The material obtained from the Kent Town and Croydon 

 bores was fine-grained and strongly calcareous with a greater 

 likeness to the Red Banks outcrop than to the Gawler. 



The most interesting feature, however, is the remarkable 

 discordance which these several outliers, although relatively 

 adjacent, exhibit in relation to their respective elevations. 

 In the Kent Town bore the Lower Cainozoic beds were proved, 

 in their upper limits, at a depth from the surface of 127 ft., 



