128 
BATHYMETRICAL SURVEY OF 
Notes on the Geology of the Tay Basin. 
By B. N. Peach, ll.d., f.r.s., and J. Horne, ll.d., f.r.s. With 
Geological Map (Plate XXXIV.). Published by permission of the 
Director of H.M. Geological Survey. 
The Tay basin may be divided geologically into two parts, the 
boundary between the two being defined by the great fault along the 
Highland border which runs from Glen Artney, by Crieff, Murthly, and 
Blairgowrie, towards Cortachy and Stonehaven. The area north-west 
of this line is mainly occupied by the metamorphic rocks of the Eastern 
Highlands, which are pierced by masses of granite, diorite, and other 
igneous intrusions, the latter being of special importance in connection 
with the history of the glaciation of the region. In the western part of 
the metamorphic area, on the lofty peaks of the Black Mount forest, 
there is a remnant of the contemporaneous volcanic rocks of Lower Old 
Red Sandstone Age, which are so prominently developed in the Lome 
plateau. The tract, south-east of the Highland fault, embraces the 
lower and smaller portion of the Tay basin. With the exception of a 
small patch of Carboniferous strata near Bridge of Earn, the whole of 
this tract is occupied by rocks of Old Red Sandstone age. 
In connection with the Lake Survey, the area north-west of the 
Highland fault is of special interest, as it includes most of the lochs 
which have been sounded by the staff. The metamorphic rocks which 
floor the greater part of this tract are bounded on their south-east 
margin, for a considerable distance, by the great dislocation along the 
Highland border. Indeed, the fault-line in places gives rise to a 
prominent feature, and the change, in the geological formations on 
either side, is indicated by a marked difference in the topography. The 
age of the metamorphic rocks of the Eastern Highlands has not 
been definitely fixed, and the original sequence of deposition is still 
uncertain, but they have been arranged in certain groups, which appear 
in a definite order as the observer proceeds northwards from the border 
fault. 
Apart from the crystalline schists termed the Moine Series ” by 
the Geological Survey, which occur in the northern part of the area, 
the groups of metamorphic strata met with in the Tay basin are given 
in the subjoined table ; — 
11. Quartzite and quartz-schist with pebbly conglomerate and 
boulder bed. 
10. Blair Atholl limestone. 
9. Black schist with thin limestone bands. 
8. Calc-sericite schists and phyllites. 
