940 DR ROBERT CAMPBELL ON 
swing round the synelinal fold, and the characteristic Crawton basalts reappear on the 
coast section at the village of Crawton, where they attain their maximum thickness. 
From Crawton their outcrop may be followed in a north-north-westerly direction 
| parallel to the coast to Gallowton, when, interrupted by a fault, it bends abruptly 
round to the east, and the group comes back to the coast at Thornyhive Bay. On the 
northern limb of the syncline the Crawton basalts appear in the Glaslaw Burn, and 
may be traced towards the south-south-west in bare rocky knolls in the fields almost 
as far as Upper Criggie. 
On the shore section near the village of Crawton it can be seen that the Crawton 
type of basalt occurs in three successive flows, each with a slaggy upper and under 
surface, and a massive, columnar central portion. The parallel arrangement of the 
tabular felspars imparts to the rock a marked platy structure. The lowest flow shows 
a somewhat unusual type of weathering. On a gently sloping rock platform, which has 
been carved out in the massive portion of the flow between low- and high-water marks, 
the sea has worked out a regular series of pot-holes, each of which coincides in position 
with the centre of one of the hexagonal basalt columns. Apparently some agency 
acting along the joints has hardened the margins of the columns, while the centres have 
been left an easy prey to the eroding action of the sea. In many places the vesicular 
surfaces of the Crawton lavas show the characteristic sandstone-veinings. But perhaps 
the most striking feature of the group is the evidence which it everywhere gives of 
contemporaneous erosion. ‘This is particularly well seen at the top of the highest flow 
at Crawton. The overlying conglomerates are seen to rest on an irregular eroded 
surface of the lava (Plate I. fig. 4). Sometimes the slaggy top of the latter has been 
entirely removed, and the pockets of conglomerate rest directly on the massive central 
portion. The eroded hollows coincide in position with prominent joint fissures, which 
are seen to narrow as they are traced downwards, and to be occupied by successively 
finer and finer pebbly sandstones, until they end off in minute cracks filled with very 
fine silt. Obviously the lavas had cooled and consolidated before the advent of the 
currents which carried out the work of erosion. Although the overlying conglomerates 
contain occasional large slagey boulders of the Crawton basalt, still the proportion of 
such boulders is remarkably small, and certainly does not suggest that the conglomerates 
have been derived by wave action from an old shore cliff of Crawton lava. ‘To this 
point we shall return later. Meanwhile, it may be noted that the restriction of the 
Crawton basalts to one definite horizon, coupled with their occurrence as boulders in 
the overlying conglomerates, has been of great service in mapping the latter. 
Associated with the basalts of the Crawton type are other basalts which will be 
described in detail in another paper. The most widespread is a type, sparingly por- 
phyritic with olivine and augite, which overlies the normal group from Crowhillock, 
Kinneff, to Gallowton. Occasionally, too, there are small intercalations of coarsely 
crystalline non-porphyritic basalts—for example, at Bervie Brow and Whistleberry ; and 
in the Glaslaw Burn section the highest flow is a basalt with porphyritic plagioclase, 
