456 THE FKESH-WATER LOCHS OF SCOTLAND 
certain localities. The precise date of this elevation cannot be 
definitely determined. As already indicated, no representatives of the 
Upper Oolite have been detected in the West Highlands, the highest 
Jurassic rocks being of Middle Oxfordian age. The continuity of the 
record in that region is further interrupted by the absence of equiva- 
lents of the Weald and of the Lower Greensand, for the lowest 
Cretaceous rpcks yet recorded belong to the Upper Greensand. These 
consist of glauconitic sands, becoming calcareous and passing into 
shelly limestones, belonging to the Pecten asper zone. According to 
Professor Judd, these strata are succeeded by estuarine sandstones 
followed by beds of white chalk with flints .containing Belemnitella 
mucronata^ while at the top of the series occur sandstones and marls 
with plant-remains and thin seams of lignite. From the character of 
the strata in this brief succession it is evident that they point to an 
alternation of estuarine and marine conditions similar to that which 
characterised the deposition of the Jurassic rocks. 
In the north-east of Scotland relics of Cretaceous strata have been 
found at various localities, but not in the position in which they were 
originally deposited. The evidence suggests that they have been 
more or less affected by glacial action since their formation. One of 
the best-known localities is at Moreseat in Aberdeenshire, where a fine- 
grained sandstone with colloid silica has yielded fossils characteristic 
of the Aptien stage of France or the Ix)wer Greensand of the Isle of 
Wia;ht. Lower Cretaceous fossils with a Neocomian facies have been 
recently recorded by the Geological Survey from a patch of concre- 
tionary sandstone in Caithness. Such evidence is of importance, as it 
points to the deposition of Lower Cretaceous strata either on or near 
the north-eastern seaboard of Scotland. In the drifts of the counties 
of Aberdeen, Banff, and Caithness numerous blocks of chalk and chalk 
flints with fragments of Inocemmus have been found. It is highly 
probable, therefore, that Upper Cretaceous rocks may occupy portions 
of the sea floor bordering these north-eastern counties. 
TERTIARY 
At the close of the great succession of mesozoic rocks there is a 
further blank in the geological history of Scotland. The records 
belonging to older Tertiary time point to extraordinary volcanic 
activity, when sheets of lava were piled on each other to a considerable 
depth, with occasional intercalations of beds of limestone and shale 
containing plant-remains, which were deposited during intervals of 
quiescence. These volcanic plateaux stretch over an extensive territory, 
reaching from Antrim by the Inner Hebrides to the Faroe Isles. In 
the West Highlands they are typically developed in Skye, Mull, 
Ardnamurchan, Morvern, Eigg, Muck, and Canna. The researches of 
