36 
E. DE C. Clarke and C. Teichert 
but farther west it iiica*eases again until it reaches a maximum of 60-63 feet 
at Tooloiiga Hills. At Thirindiiie it is still 52 feet thick, but from there 
westward the thickness decreases somewhat irregularly. In the Butte sec- 
tion in Second Gully it is still 35 feet, but at Second Gully Point it has- 
dwindled to three feet and at Alinga has disappeared. At Meanarra this- 
shale is about 15 feet thick. 
5. Alinga Beds. 
Derivation of name. — Alinga, four-and-a-half miles N.W. of Murchison 
Homestead, is a prominent i.>oint in the chalk scarps, a little more than 
a mile north of Mullewa Point. 
Areal distribution and outcrojys.— The Alinga Beds could be follorved 
from Mullewa Point in the west to the eastern termination of our survey 
area, one-and-a-half miles east of the telegraph line. They form an easily 
recognizable zone of dark rock between the whitish Thirindine Shales 
below and the chalk above, but actual outcrops are poor, owing to the 
softness of the rock. Tliere is much slipping so that it is often difficult 
to get a correct picture of the lithology of the beds. Gully erosion and 
subsurface erosion are cutting strongly into this zone and removing large 
(|uantiti)‘s of it. About nine miles to the north-east of the area mapped 
the junior author found the Alinga Beds overlying the Thirindine Shales- 
at Weerinoogudda Dam where they form the top of the escarpment north 
of the dam. The Alinga Beds are also probably present at Meanarra 
Hill south of the Murchison hiver; no good outcrops have been seen 
but they most probably occur in a zone with no outcrops between the 
toj) of the Thirindine Shale and the base of the chalk. 
LithoJo(jif . — The Alinga Beds consist of dark green, always strongly 
glauconitic clays, shales, and sands. In general it seems that sandy 
components predominate to the noHh-east and that towards the south- 
west the beds become increasingly clayey and shaly. At Weerinoogudda 
Dam, nine miles north-east of our survey area and* 21 miles east of the 
coast, the Thirindine Shale is overlain by greensand Avhieh forms an 
escarpment immediately north of the dam. No higher strata are exposed 
in this \'icinity. Immediately west of the telegraph line, in the vicinity 
of the emergency latiding ground, the Alinga Beds are predominantly 
shaly, but farther west in the PillaraAva section they are sandy through- 
out the lower 15 fe(d, changing intn shales above which contain a number 
gypseous layers. Still farther west at Bracken’s Point the top of the 
Alinga Beds is formed by reddish Aveathering clay which changes down- 
ward into clayey greensand. In the Toolonga Hill section and to the 
west thereof the Alinga Beds change into almost pure glauconitic clay 
Avhich liere and there may contain beds or pockets of glauconitic sand 
such as are well exjioscd near the butte in Second Gully. At Alinga 
I oint (text fig. 12) the predominating sediment seems to be a very fino 
sandy clay or shale of very niiiform lithology. 
Fossds. The only fossils seen in these beds are belemnites, probably 
of the genus Dimdtohelus, which occur in great quantity at Alinga Point, but 
also at Thirindine Point and in the south-western part of the Toolonga 
