THE GEOLOGY OF SOUTH-EASTERN KINCARDINESHIRE. 935 
conditions. In Kincardineshire no evidence has been obtained so far which would 
point to marine sedimentation. No undoubtedly marine organism has been found, 
and the association of the eurypterids with plant remains, scorpion fragments, galley- 
worms, and a larval form of insect appears to show that the green and grey mudstones 
were laid down in close proximity to a land area, and, at the most, can imply only 
estuarine conditions; the interbedded ochreous sandstones with their characteristic 
false-bedding, and the development of sun-cracks in the red mudstones, point con- 
clusively to deposition in shallow water. The coarse volcanic conglomerate, like those 
of the Old Red Sandstone, is in all likelihood a torrential flood gravel. 
No contemporaneous voleanic rocks have been found in the Downtonian series of 
the Southern Uplands; the earliest lavas and tuffs invariably overlie the basement 
oreywacké conglomerate of the Lower Old Red Sandstone. Sir ARcHIBALD GEIKIE”* has 
correlated the initial outbreak of voleanic activity in “‘ Lake Caledonia” with the coming 
on of the conditions which gave rise to the lowest of the massive quartzite conglomerates 
at Stonehaven. That volcanoes were active in this region at a much earlier period is 
seen from the development of tuff and volcanic conglomerates in the Downtonian 
sequence. The lowest voleanic conglomerate is about 2500 feet below the above- 
mentioned quartzite conglomerate. As we have already seen, the lowest zone of 
volcanic conglomerates and tuffs can be traced inland until it is lost against the 
Highland fault. There is abundant evidence also to show that the materials of all 
the associated sediments were derived from the Highland area. One must conclude, 
therefore, that early in Downtonian times (or perhaps in pre-Downtonian, but sub- 
sequent to the movements which folded the eastern schists) voleanic activity had 
already begun in the schist country to the north of the Highland fault. 
In the Southern Uplands the Downtonian series passes down conformably into the 
Ludlow. The presence of quartzite conglomerates shows that the sediment, in part 
at least, was derived from the Highland area. At Stonehaven the Downtonian rests 
unconformably on rocks of a much lower horizon (probably Upper Cambrian), and 
there is in all probability a marked overlap as the Lower Old Red Sandstone formation 
is traced over the Highland area to the west. In Kincardineshire the Downtonian 
series passes up conformably into the Lower Old Red Sandstone ; in the Southern Uplands 
it has been found that the two series are separated by an unconformity in the Pentland 
Hills and Ayrshire ; while in Lanarkshire there is an “apparent conformability,” the 
basal conglomerate of the Lower Old Red Sandstone series being made up everywhere 
mainly of boulders of greywacké derived from the rocks of the Silurian tableland to 
the south. 
Consideration of the chief points in the above comparison leads to the following 
conclusions :— 
(1) During early Downtonian times there was continuous subsidence of the 
southern part of the central valley and the area now occupied by the Southern 
* Ancient Volcanoes of Great Britain, vol. i. p- 303. 
