34 



cannot give an estimate of the average thickness, but I have 

 obtained fragments fully an inch in thickness. I have also 

 obtained portions of a similar travertine and about the same 

 thickness from the excavations recently carried out in deepen- 

 ing the Patawalonga at Grlenelg. 



If our theory be correct, the section at Glanville affords an 

 interesting record of the oscillations which have taken place 

 in the coast line within comparatively recent times. The cal- 

 careous sand and shell bed, which forms the bottom of the 

 excavation, is a true marine deposit, which was probably formed 

 in shallow water, but covered at all states of the tide. The 

 passage from this marinebed to the overlying clay is very abrupt, 

 and looks on the face of it as a case of non-continuity of deposit, 

 a view which the presence of the travertine at the line of 

 juncture strongly confirms. The fine silt or loam which over- 

 lies the travertine crust is most probably of fresh-water origin, 

 as the non-occurrence of fossils in it, whilst the beds above and 

 below are highly fossiliferous, is difiicult to explain on any 

 other hypothesis. It marks a period of elevation when the 

 marine bed on which it rests was raised above high-water mark 

 and received the wash of fluviatile matter over its surface. 

 Whether the deposit owed its origin to lacustrine conditions 

 or simply river sediment, cannot be shown at present. When 

 this clay was being deposited the drainage of the country may 

 have been locally intercepted in its seaward flow (much as it 

 is at present in the case of the Eiver Torrens), causing a deposit 

 of light clayey and sandy material over a wide area, and 

 which is represented by this clay bed of the Glanville section. 

 Then the vertical fissures which exist in the upper part of this 

 clay bed, with their derived fossil remains, point as forcibly to 

 dry land conditions as does the travertine crust which under- 

 lies it. The change in the character of the deposit at the upper 

 parting of this clay bed is also very marked, for the white sand 

 and shells of the littoral deposit which overlies it can be 

 brushed from its upper surface, revealing the dark blue ground 

 of the clay bed sharply defined in the parting. Before the 

 superimposed sixteen feet of beach deposit could be thrown 

 down in the position in which it occurs, we must suppose that 

 there followed once more a depression of the land so as to 

 bring this fresh-water clay below sea level. Such a supposi- 

 tion falls in with the view v/hich Prof. Tate has at various times 

 expressed with regard to the inner line of sand-hills which 

 follow a more or less regular trend from Glenelg to about Dry 

 Creek, that they represent the old coast sand-hills when these 

 recent marine beds were in course of formation. 



That there was a considerable interval of time separating the 

 upper and lower marine beds in the section is borne out by the 



