THE HIGHLAND BORDER ROCKS OF THE ABERFOYLE DISTRICT. 
203 
the whole of the area occupied by the Lower Series. The relation of the beds of 
the two Series prior to the post-Margie folding is shown diagrammatically in fig. 2. 
The inclusion of fragments of the cherts, black shales, and spilites in the Margie 
breccias and grits is in itself good evidence of unconformity ; the overlapping 
of the Margie beds from the black shales on to the spilites, as revealed by the 
detailed mapping (see map, and figs. 3 to 7), gives even more convincing proof of 
that relationship. 
The Post-Margie Movements. — At a later period the rocks of both Series were 
involved in movements which produced intense folding, faulting, and crushing. The 
faults and crush lines are usually parallel to the general strike of the beds. The 
pressure came chiefly from the north-west, and has resulted at places in an intimate 
1 
j._ jJSHL 
fRi 
1 Sp ' 
o - 1". 
b#£cc/a 
mmm 
j_J r J r 
A4AAG/B BLACrf SB/L/TB 
SBB/BS SBALi r <£■ LAMS 
CBB/tT S£/t/£S 
SBBBB/V T//V£, 
GABBBO 
Fig. 2. — Diagrammatic section showing original relation of Upper to Lower Series. 
folding and faulting of the Margie Grits into the underlying cherts and shales. This 
is particularly well seen about 300 yards north of the spot at which the old 
Aqueduct crosses the valley north-west of the Drum of Clashmore. Occasionally 
the grits have snapped in the cores of nearly vertical folds, yielding phacoids or 
lenticles lying in crushed black and cherty shales, — as, for instance, along the northern 
margin of the belt half a mile north-east of Maol Ruadh, and again at the side of 
the Aqueduct road south-west of Clashbeg Wood, where the phacoids are sometimes 
over two feet in length. Sometimes lenticles of dark grit are seen in the cherty 
shales of Clashbeg Wood and also immediately south and west of the Bofrishlie Burn, 
where it makes a sharp bend to the north between the south-western ends of 
Arndrum and Dungarrow. The crush lines along which the phacoids , are seen 
usually occur within a few yards of the line or lines of dislocation separating the 
Highland Border Rocks and the Leny Grits. 
The Belt of Metamorphic Rocks. — Intense shearing along a definite narrow belt, 
