23 
and the general succession indicates a condition such as 
is often found in proceeding from a shore-line to deeper areas 
of deposition. The limestones are clearly of marine origin, and 
as the siliceous beds are found to alternate with them, it may be 
inferred that they were also laid down in the sea. of which the 
southern margin is defined by the beds of Mount Yahagong, in 
lat. 27 deg. South, to which reference has already been made. The 
Nullagine Sea. therefore, extended over about fourteen degrees of 
latitude, north of Mt. Yahagong, near Gabanintha, 
Lying conformably above the Caravvine Dolomite Series is a 
considerable thickness of arenaceous sediments, quartzites, ferru- 
ginous sandstones, grits with subordinate sandy shales. At Mount 
Margaret in the llamersley Range, these arc represented by very 
fine-grained ferruginous Haggy sandstones with some very siliceous 
l)ands. and also some banded ironstones, the beds liciug practically 
horizontal. The ferruginous beds contain magnetite and hematite, 
the percentage of iron being as much as from 28 to oT per cent. 
These ferruginous quartzites, jaspers or cherts, are sometimes 
somewhat calcareous. 'Fhese iDanded ores bear a verv remarkable 
resemblance to those hande<l ores, jaspilites, etc., which make such 
conspicuous features in most of the southern goldfields, and sug- 
gest a common origin for the two. An excellent cxam])le of these 
l)anded jaspers is to he seen in the Coongan River at Marble Bar, 
which perhaj)s may be regarded as typical. (Rig. 24). 
Fig. 24. 
Jaspilites, The Marble Bar, Coongan River, Tilbara Goldfield. 
Here the laminae forming the “Bar” dips at an 
angle of fiOdeg. to the west. The thickness of 
the bed is about 220 feet from wall to wall. The rock 
