128 
Parwan. It is 3 miles south, of the Parwan Railway Station. The hollow 
is beautifully regular, and the rocks around it are basalt, scoria, and 
some tuff, which includes fragments of what are apparently Ordovician 
rocks, also waterworn quartz pebbles. One small piece of included 
rock was of great interest, as it contained' one valve of a bivalve shell, 
with the hinge line teeth well preserved. This shell appears to be 
of marine origin, and may be of Tertiary age, and, if this is the case, 
it indicates that there were beds of Tertiary marine strata underlying 
the volcanic rocks. This is not surprising, for at Mt. Mary, 5 miles 
to the south-east, blocks of white and yellow argillaceous sandstone 
containing Miocene Tertiary fossils are embedded in the scoriaceous 
lava of Mt. Mary,’^ according to the note on the geological map. 
(Quarter sheet, 8 S.W.) 
Hone of the basaltic flows were traced to their point of origin. 
Some may have issued from Mt. Mary, or there may have been a series 
of fissure vents along a line from Mt. Mary to the small crater just 
described; or, as the land is higher in that direction, some may have 
come from the north-west. 
Sands, Gravels, and Clay Inter-stratified with the Basalt. 
The Tertiary rocks inter-stratified with the lava flows exposed in 
the cliffs along the Werribee River consist of sands, gravels, earthy 
grits, clays, and some sandy ferruginous rocks. Some of the sands are 
fine grained, but not pure white in colour. A band of sandy clay is 
lignitiferous, and there is a layer of black clay in part earthy, and in 
part unctuous. Some of the sandy clays are very saline and effloresce, 
the mineral tasting like common salt. The layers of basalt and Tertiary 
sediments are arranged more or less horizontally, and in places the sur¬ 
face of the ground slopes very gradually to the river. If a layer of sand 
or gravel occurs at the top of the river cliff, it may extend back over 
half-a-mile before it gives place to a—presumably overlying—layer of 
basalt. This occurrence is illustrated in section (Pig. 46). 
""^dMs'.c/ai/s 
’ od!>d/L 3/}af grams 
Sands.c/agsandgrave/s 
Basd/t 
■■ Basa/t 
'lave/ of tferribee R/yer 
Fia. 46.—iSection in cliff along Werribee River. Not to scale. 
