THE GEOLOGY OF SOUTH-EASTERN KINCARDINESHIRE, 941 
olivine, and augite. These associated lavas also exhibit evidence of having undergone 
contemporaneous erosion. 
Between the porphyritic basalts and the ce of the Crawton group there intervenes 
a series of volcanic conglomerates, tufts, and ‘‘ Highland” conglomerates,* with one 
small intercalation of basic andesites or basalts near Whistleberry Castle. 
The tuffs and voleanic conglomerates attain their maximum development between 
Bervie Bay and Whistleberry. In that tract, indeed, the ‘“ Highland” conglomerates 
play quite a minor part. The tuffs are built up essentially of angular and subangular 
fragments of hornblende and biotite andesites and felsites, the andesites always pre- 
dominating. Locally they contain in abundance angular pieces of a green rock which 
resembles the spilitic lavas of the Upper Cambrian series. ‘They are frequently 
calcareous, and weather with characteristic honeycombed and furrowed surfaces. Like 
the tufts, the volcanic conglomerates consist mainly of the debris of hornblende and 
biotite andesites. A noteworthy feature is the large size of the well-rounded boulders 
of hornblende andesite—a section across one in a conglomerate near Shieldhill 
measured 9 feet x 10 feet. The relative proportion of boulders and matrix is variable, 
but the latter, which has much the same composition as the associated tufts, is always 
more abundant than in the “ Highland” conglomerates. The latter are characterised 
as usual by the almost bewildering variation in their composition as any one particular 
bed is traced from point to point. As a rule they contain a fair proportion of volcanic 
rocks belonging to Old Red Sandstone types. But the feature which, despite the 
extraordinary variety of the constituents, always arrests attention, and which serves to 
distinguish the ‘‘ Highland” conglomerates of this group from all the others, is the 
abundance of boulders derived from the Upper Cambrian series. The green spilitic 
lavas are often so numerous as to impart a general greenish hue to whole belts of the 
conglomerate. The occurrence of “ Haggis rock” boulders is also noteworthy. At 
many points, and particularly in the vicinity of Shieldhill, excellent examples of 
contemporaneous erosion can be seen where these conglomerates rest on an uneven 
surface of tuffs and volcanic conglomerates. 
To the north and south of the Bervie-Whistleberry tract there is a marked change 
in the character of the sediments between the Crawton basalts and the base of the 
group. The tuffs and volcanic conglomerates play a smaller and smaller part in the 
succession as they are traced in either direction from the above centre, and their place 
is taken by conglomerates in which ‘‘ Highland” rocks predominate and by brown 
tuffaceous sandstones. The lowest conglomerates in the neighbourhood of Todhead 
Point contain a big proportion of basic lavas, derived perhaps from the contemporaneous 
erosion of the underlying Tremuda Bay series of basalts. At a higher horizon, and 
separated from the above by a bed of acid tuff, a somewhat remarkable conglomerate 
* Throughout this paper the term “ Highland conglomerate” is used to designate a conglomerate in which the 
majority of the boulders belong to rock types occurring in the Highland area. Similarly, quartzite conglomerate 
and volcanic conglomerate denote conglomerates whose predominating pebbles are respectively quartzites- and 
volcanic rocks, 
