^°^' ^^^^^'] Armitage, Country about West Essendon. 83 



NOTES ON THE COUNTRY ABOUT WEST ESSENDON. 



By R. W. Armitage. 

 {Read before the Field Naturalists' Club of Victoria, Sth August, 1910.) 



The following contribution is an expansion of, and addition to, 



the report of the Club's excursion recently held at Essendon (i). 



General Physiographic Features. 



The area under discussion has been mapped by the Geological 

 Survey of Victoria on Quarter Sheet No. i, N.W., Melbourne, 

 and mainly lies in section vii., allotments i, 2, and 3, and 

 section viii. of the parish of Doutta Galla, and in section xx., 

 allotment 2, of the parish of Cut-Paw-Paw. 



The fiat ridge along which part of the main railway line to 

 Sydney has been laid in this locality, and which divides the 

 valley of the Moonee Ponds Creek from that of the Saltwater 

 River, consists of Tertiary sands, grits, and clays, mainly (as 

 will be shown later) of Kalimnan age. These unconformably 

 overlie small areas of ferruginous deposits of Barwonian age. 

 Both sets of sediments rest on the eroded surface of the Older 

 Volcanic basalt which is met with at varying depths from the 

 surface. 



The greater portion of this ridge — viz., that part which ex- 

 tends from near the North Melbourne station to within a mile 

 north of the Essendon station — has never been covered by the 

 Newer Volcanic lava flows, as its surface was at a greater eleva- 

 tion than would allow of the lavas covering it. Since that time 

 denudation has steadily lowered the ridge, until now much of 

 the area covered by the Newer Volcanic lavas is higher than the 

 Tertiary sediments of the ridge. 



The Essendon ridge shows a rather mature character in its 

 stream development, and this is well illustrated immediately 

 to the west of the Essendon station by a shallow and small 

 tributary valley running in a southerly direction down towards 

 the Saltwater River, and debouching into the swampy area at 

 the west end of Holmes-road, Moonee Ponds. The Essendon 

 station stands at an elevation (2) of 148 feet above sea level, on 

 the eastern edge of this valley, the thalweg crossing Buckley- 

 street at Lincoln-road being 70 feet above sea level, while the 

 western edge is 127 feet in height. This valley, then, about 

 50 chains across, has a vertical depth of about 70 feet, with a 

 slope of I in 30 on the eastern flank, and a sharper grade of i in 

 18 on the west side, thus giving the contours in cross section of 

 a fairly mature, broadly open, concave valley. Such valleys are 

 characteristic of those portions of the country in and about 

 Melbourne which have never been covered by the Newer Volcanic 

 lava flows, and show a sharp contrast with the gorges carved out 

 in country covered by those lava flows. 



