68 Robert Campbell — South-Eastem Kincardineshire. 



predominating constituents in the conglomerates and tuffs are rhyolites 

 and hornblende-biotite andesites. It seems clear, then, that early 

 in Downtonian times (or perhaps in pre-Downtonian) rhyolites and 

 acid andesites flowed out in abundance over the schist and granite 

 country to the north of the Highland fault. Further evidence of the 

 existence of this series of volcanics is obtained from the character of 

 the sediments of the Lower Old Red Sandstone formation. 



The highest beds in the above table pass conformably up into the 

 massive quartzite conglomerate of Downie Point, which may be 

 considered as the base of the Lower Old Red Sandstone. 



Lower Old Red Sandstone. 



"While the palaaontological evidence here is so meagre that it affords 

 little assistance, lithological evidence, on the other hand, obtained 

 from conglomerates, lavas, and tuffs, has aided materially in 

 elucidating the structure of the area occupied by the Lower Old 

 Red Sandstone. 



The conglomerates fall into two well-marked classes: (1) those in 

 which quartzites or other ' Highland ' rocks predominate ; (2) those 

 which are made up almost entirely of volcanic rocks — volcanic 

 conglomerates. Detailed examination of the character and distribution 

 of these conglomerates is being carried out. Meanwhile mention may 

 be made of some points which are of especial interest. 



In the ' Highland ' conglomerates at different horizons occur 

 numerous pebbles of greywacke, including many of the ' Haggis 

 Rock ' type, showing just as little evidence of schistosity as the 

 greywackes of the southern uplands. The boulders of ' Haggis 

 Rock ' consist chiefly of angular and subangular fragments of jasper, 

 chert, and ' green rocks ' (probably spilitic lavas), the rock types 

 which predominate in the Cambrian (?) Series at Craigeven Bay. 

 In all probability these boulders have been derived from the Margie 

 Series described by Mr. Barrow. 1 All the ' Highland ' conglomerates 

 contain boulders of the jasj)er-green rock series. In many of the 

 conglomerates low down in the succession these rocks are almost the 

 only types represented ; it is only in the highest conglomerates that 

 the)- begin to play an insignificant part. The evidence given by 

 these conglomerates seems to point conclusively to a former wide 

 extension of Cambrian (?) and Margie rocks over the country now 

 occupied by the granites and Dalradian schists. 



Thick volcanic conglomerates, the pebbles of which are chiefly acid 

 andesites and rhyolites, occur at three different horizons, and, in one 

 case at least, the conglomerate has its maximum development at the 

 Highland fault. Further, the sandstones at every horizon contain 

 invariably a considerable amount of the debris of rhyolites and acid 

 andesites. Here again, as in the Downtonian succession, there is 

 evidence of long-continued denudation of a series of acid lavas, which 

 must have extended far to the north of the Highland fault. 



Only one limestone has been noted in the Lower Old Red Sandstone 

 succession. It occurs at several localities in the Howe of the Mearns, 



1 Q.J.G.S., vol. lvii, p. 331, 1901. 



