71 



Evidences of Extinct Glacial Action in 

 Southern Yorke's Peninsula. 



By Walter Howchin, F.G.S. 



[Read June 5, 1900.] 



Glacial deposits have already been described in the Transac- 

 tions of this Society as occurring on the eastern and southern 

 shores of Gulf St. Vincent, and in most cases such deposits 

 extend seawards and pass from view below low-water mark. It 

 may, therefore, be inferred that the southern portion of the 

 present gulf occupies an eroded hollow or depression in what was 

 formerly an extended area of glacial till. On this assumption it 

 seemed highly probable that the southern portions of Yorke's 

 Peninsula would be included in the extinct glacial field. This 

 supposition has been amply confirmed by discoveries made during 

 Easter week of the present year. The southern portions of the 

 Peninsula have a lateral extension, shaped like a human foot ; 

 the northern and southern coasts of this area were visited, and 

 very instructive sections of the glacial beds were observed, whilst 

 many localities inland furnished confirmatory evidences of the 

 previous existence of ice on a large scale. 



Southern Coast. 



Troubridge Hill. — The first locality visited was Troubridge 

 Hill, about ten miles from Edithburg, in a south west direction^ 

 via Honiton. The sea-cliffs near the Hill are composed of cal- 

 ciferous sandstones capped by travertine limestone. The sea 

 breaks at the base of the cliffs, which are being rapidly under 

 mined. At a distance of about half a mile to the west from 

 Troubridge Hill the base of the Eocene beds is exposed, and the 

 latter are seen to rest on an eroded surface of glacial till. The 

 Eocene beds are here reduced in thickness to a layer of three 

 feet, consisting of loosely held comminuted fragments of polyzoa, 

 with countless numbers of the small echinoderm, Fibularia gregata. 

 The occurrence of this echinoid in the bed referred to fully justi- 

 fies its specific name, as it is mostly aggregated in clusters, 

 varying in size up to a foot in diameter. 



The following is a section of the cliffs as seen at this spot : — 



1. Recent —Travertine limestone ... ... ... 10 feet 



2. Eocene — Fossiliferous (Fibularia gregata) limestone 3 " 



3. Pre-Tertiary — Glacial till with erratics ; thickness 



unknown ; height exposed above sea level ... 8 " 



