271 
having a dip of 60°, whilst the tertiary beds rest uncon- 
formably against the face of the older slates. The latter 
exhibit a series of anticlinal and synclinal folds, reaching а 
maximum dip of 65”. Near their western extremity a syn- 
clinal fold occurs, in the centre of which the beds are much 
broken and confused. 
The hill on which the Noarlunga Church stands, together 
with the eastern side of the “horseshoe,” and for more than a 
mile up the river, the purple slates show a gesat develop- 
ment, forming hills several hundreds of feet in height. In 
the cliff face under the church the beds dip south-south-west 
at 15^, and for a mile up stream they exhibit an undulating 
dip, which, for the most part, is at a comparatively low 
angle. 
In Section 63, near the mouth of a small tributary on the 
south side of the river, the beds increase in dip, with a roll 
from south-west to south-east and south-south-east, at 40°. 
Following up this gully an instructive section is obtained. 
The dip changes to west at 60^, and the beds develop marked 
cleavage, which has a north-and-south strike, with an easterly 
dip at 48^. Тһе appearance of this outerop from across the 
valley is misleading, as the chief weathering is shown on the 
cleavage planes, giving a wrong impression as to the lie of the 
beds. Higher up, the dip passes rapidly to west-north-west at 
73°, and at the junction of an eastern branch of the creck tha 
dip is temporarily changed to south-east at 20°, but in a few 
yards reverts to the west. Following the eastern branch, in 
a short distance the beds become vertical, changing again to 
east-south-east at 73^, as they abut against the great strike 
fault (C) (see map, Plate xliv.) which runs in a north-east and 
south-west direction, and crosses the Onkaparinga, near the 
Ford, between Sections 48 and 56. 
. The main body of the purple slates oa the Onkaparinga is 
circumscribed by two great faults. On the north the beds 
are cut off by an important dip fault, running east and 
west, through the northern parts of Sections 46, 47, 48; 
and by a strike fault, having a direction north-east and 
south-west, crossing the river at the Ford. In addition to 
this main outcrop there are other important areas occupied 
by these beds which will be referred to when dealing with 
& ye ing that has taken place on the eastern side of the 
eld. 
Lithologically, the purple slates of the Onkaparinga dis- 
trict very closely resemble those which occur in the Field 
Iver, Hallett's Cove, and Marino outerops. The stone is 
extensively jointed and cleaved, has a characteristic banded 
åppearance, caused by alternating darker and lighter bands 
