94 Armitage, Country about West Essendon. [^'*^Sep^^*^ 



Tate, Cyprcea suhsidua (?), Tate, and a Cidaroid spine. These 

 specimens are quite typical enough to fix the age of these beds, 

 which here he close above the eroded Older Basalt, as being 

 Barwonian (Eocene). These beds in this district occupy small 

 pockets in the eroded Older Volcanic, and are overlain un- 

 conformably by extensive deposits of Kalimnan age. It is quite 

 safe to assert that the grits and sands of the Sand Pits, as well as 

 the quartzite and greywacke, are of Kalimnan (Miocene) age. 

 The Older Volcanic is Barwonian (Eocene), and the Newer 

 Volcanic probably Werrikooian (Pliocene) in age. The above 

 new records, and those previously established (lo and 23), 

 together with the absence of records of the presence of Barwonian 

 fossils further inland, tend to indicate that, in the area north- 

 west of Melbourne, the shore-line of the Barwonian sea extended 

 through Royal Park, Moonee Ponds, West Essendon, and Keilor. 



Summary of the Geological History of the Locality. 



Through the Upper Palaeozoic and ]\Iesozoic periods erosion 

 of the Melbournian (Silurian) sandstones and shales proceeded, 

 laying bare the plutonic igneous rocks which had consolidated 

 beneath. The drainage system developed was obliterated by 

 an outpouring of lavas — the Older Volcanic basalts — of early 

 Tertiary (Barwonian) times. These basalts were deeply eroded, 

 and then the area was sunk beneath a shallow sea, in the prox- 

 imity of a shore-line. Barwonian sediments of a highly fossil- 

 iferous character were laid down. Uplift occurred with sub- 

 sequent denudation of the land. This was followed again by 

 a subsidence, which resulted, in the main, in shallow marine 

 conditions. Oscillatory movements of the area took place on 

 a minor scale while the Kalimnan sediments, which were derived 

 from an area mainly of granitic rocks, were being deposited. 

 The land was re-elevated and dissected, with the development 

 of a new river system, which was soon followed by the extrusion 

 of the Newer Volcanic basalts of the Keilor Plains. The latest 

 stages of vulcanicity in the locality were marked by sporadic 

 springs, which silicified patches of the Tertiary sediments. The 

 lava floods smothered out of existence the last-developed river 

 system, and on them was superimposed a new set of drainage 

 channels, one of which developed into the present Saltwater 

 River. Small oscillations of level of the land with relation to 

 sea level continued. These probably resulted in the formation 

 of river terraces. The latest movement has been one of sub- 

 sidence, causing a cessation in the active work of vertical 

 corrasion being carried on by the Saltwater River, and drowning 

 the stream for some miles up from its mouth, so that sea water 

 is found above the Horseshoe Bend. The valley of the river is 

 at present undergoing the process of being slowly widened out 



