930 DR ROBERT CAMPBELL ON 
reddened spilites has also been found of great assistance in distinguishing these rocks 
from the overlying Downtonian. 
Detailed examination of an exposure between two of the small hitch faults—such, 
for example, as that shown in Plate I. fig. 2—shows clearly that the junction is not 
a fault plane but an unconformity. It can be seen, moreover, that the younger rocks 
rest on a highly irregular eroded surface of the older. 
An overthrust fault, which crosses Ruthery Head in north-easterly direction, shifts 
the outcrop of the lowest Downtonian breccias 160 yards to the south-west. From the 
fault the unconformity can be traced, although not so easily as in the section just 
described, along the foreshore in a westerly direction, until it is cut out again by the 
Highland fault near the mouth of the small stream which flows past St Mary’s Chapel. 
V. Upper Sinurian (DowntTontay). 
The rocks overlying the Upper Cambrian were formerly mapped as part of the 
Lower Old Red Sandstone formation. The paleontological evidence recently obtained, 
however, shows that the “ Stonehaven Beds” must now be regarded as of Downtonian 
age. No marked discordance has been detected anywhere in the upward succession 
from Downtonian to Old Red Sandstone in this area; and since, in their lithological 
characters the former is of the nature of a transition series, it is not easy to fix the 
boundary between the two formations. In the description of the coast section given in 
my preliminary note, I took the massive conglomerate of Downie Point as the base of 
the Old Red Sandstone, but further study of the inland sections has led me to include 
with the basement conglomerates the brown micaceous pebbly sandstones at Stonehaven 
harbour along with the intervening tuffs and volcanic conglomerate. The sandstones 
contain numerous pebbles of quartzite, and herald the oncoming of the coarse “ quartzite 
conglomerates” which form so characteristic a feature of the Lower Old Red Sandstone. 
_ The succession of the Downtonian beds as seen in the coast section from the mouth 
of the Cowie Water to Ruthery Head is as follows (in descending order) :— 
Feet. 
7. Tuffs and tuffaceous sandstones : f 800 
6. Grey sandstone and fossiliferous sandy aneileed and batashones 
(with fish band) . , : : ’ . »i600 
5. Red sandstones ; ; ; f ; 60 
4, Voleanic conglomerate and tafls : ; : 40 
3. Grey and brown sandstones with thin red easton ‘ 2) 1000 
2. Purple sandstones. : ‘ 60 
1. Basement breccias with aaiciaalsiea sintly siasbonnae « 9/200 
The basement beds include a succession of breccias interstratified with finely bedded 
sandstones and sandy mudstones. The breccias consist in large part of angular and 
