Tertiary Deposits Near Norseman, Western Australia. 
97 
with a light-coloured yellow-brown limestone above. A layer about five feet 
thick and made up almot^t entirely of fragments of Bryozoa overlies the 
pectinid bed. Dolomite two feet thick forms the toi) of tlie section and a 
superficial calcareous travertine rock, a product of arid weathering, over- 
lies the dolomite. The number of species in this deposit is small. 
The predominant })ectinids are Chlavuis murnujana (Tate) and Clilamys 
aldingensis (Tate). Other jxdecypods include ModiolarUi cf. arcacea (Tate). 
4. lake duxdas. 
Boloynite. — At the extreme north end of Lake Dundas, about five miles 
north-east of Norseman, there are scattered outcro])s of unfossiliferous 
dolomite on the edge of the lake and farther inland. A considerable 
thickness of superficial gravel and finer alluvial material forms low head- 
lands and terraces along the west side of the lake and in them dolomite 
crops out. Several short gullies, a mile or two long, which drain the hills 
of Pre-Cambrian gre(mstone enter the lake near its nortlnwn end and have 
exposed other patches (tf dolomite but nowhere is its contact with the 
Pre-Cambrian visible. Most of the smaller patches are shown on Camp- 
bell's nui}), but the largest which is farthest north-east, on the lake shore 
near an old ti’ack to Israelite Bay, is outside its limits. It is a eonspieuous 
■white hill over UK) yards long and rising steeply to about 4U feet above 
the lake, into wdiich it extends as a narrow headland for about 70 yards. 
The hill consists of dolomite which is a massive, erystalUne, almost mono- 
mineralic rock with oceasional angular (piart/. fragments and rounded 
limonitic ])ebhles as. in tin* rlolomites descriliial earlier in this paper. 
Weathering of this rock produces a rough, sculptured surface. Low out- 
crops extend sonth--west from the hill for 150 yards and the rock appears 
again in a promontory a})ont 250 yards south of the hill where it is 
overlain by gravel. 
Eiiealfipt Beds. — Campbell (1906, j). 22) re])ortcd the occurrence of 
.silicified spe<dmens of true cnealypt wood (determined by K. Etheridge 
Jun.) ‘^on the valley flat of the IMary Cater Oully and on the laterite 
flat on the north side of Israelite Bay Track near Lake Dundas. In the 
latter locality it occurs in a semi-chalcedonized matrix.’’ Camjihcll and 
Etheridge suggested that the wood-hearing strata may be pai’t of the 
Tertiary series. We were unable to visit the locality. 
r,. NORTH SHORE OF LAKE COWAX'. 
The .sponge spicule ln‘ds at the north end of Lake Cow’an svere not 
visited on this trip, (fiarke reported that they form ‘Mow' white cliffs 
•overlooking a small bay on the north shore of Lake Cowan south of the 
Paris Croup.” He mapped the approximate outline of the occurrence 
and submitted a speeimen to Simpson ((Marke, 1925, p. 13) who described 
it thus: — 
“The rock is moderately tough, very fine-grained and carries no car- 
bonates. Under the microscope it is seen to lie a fine-grained marine silt 
composed of kaolin and finely-divided quartz -with a few recognisable 
•sponge spicules in some bands, and in other bands innumerable siliceous 
spicules, both hexactinellid and lithistid. There is little doubt that this 
is an outlier of the Miocene Plantagenet Beds.” 
