512 Notices of Memoirs — British Association — 



3. About 60 feet below the Dlctyocaris horizon there is a thickness 

 of about 40 feet of volcanic conglomerates and tuffs, the presence of 

 which implies that the volcanic activity, which was so marked a feature, 

 in the history of this area during the Lower Eed Sandstone period, had 

 already been initiated in Downtonian times. 



Neither Bictyooaris nor Ceratiocaris has been found elsewhere in rocks 

 younger than Upper Silurian, and, apart from the occurrence of tuffs, 

 the lithological characters of the above succession recall at once the 

 typical Downtonian rocks of the south of Scotland. The highest 

 beds of the Downtonian pass conformably up into the micaceous sand- 

 stone and conglomerates of Stonehaven Harbour which may be considered 

 as the base of the Lower Old Red Sandstone. 



II. — Old Red Sandstone. 



(a) Lower. — ^The Lower Old Red Sandstone Series consists of a great 

 thickness of coarse conglomerates and sandstones with intercalated lavas 

 and tuffs. Palseontological evidence is everywhere meagre, but the 

 recognition of a number of well-marked volcanic zones has been of 

 value in elucidating the structure of the area. The lavas include dacite, 

 hornblende-biotite andesites, augite andesites, hypersthene andesites, 

 hypersthene basalts, and olivine basalts. The tuffs are all acid in 

 character. Minor intrusions of presumably Old Red Sandstone age occur 

 in the form of dykes and thin sills of quartz porphyry, biotite porphyry, 

 dolerite, and lamprophyre. The distribution of the lavas indicates 

 that the centres of eruption lay along two lines — one to the east of 

 the present coast-line, the other over the area of Dalradian Schists to 

 the north of the Highland boundary fault. 



The coarse conglomerates, which build up a great part of the suc- 

 cession, fall readily into two groups: (1) those in which boulders of 

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

 are made up almost exclusively of volcanic rocks — volcanic conglomerates. 

 Two points of particular interest may be noted in the former group — the 

 occurrence of boulders of the ' Haggis rook ' type of greywacke, and 

 the abundance of boulders of the ' newesr ' granites, which have been 

 collected even from the lowest conglomerates. The distribution of the 

 volcanic conglomerates points clearly to the denudation of a thick 

 series of rhyolites and acid andesites which must have extended far 

 to the north of the Highland fault. 



The chief structural feature of the Lower Old Red Sandstone area 

 is a continuation of the well-known synclinal fold of Strathmore. In 

 Kincardineshire, however, in the district to the west of Elfhill, there 

 intervenes between the syncline and the Highland fault a steep-limbed 

 anticline, pitching out to the south-west. The southern limb of the 

 syncline is traversed by numerous powerful dip faults. 



(6) Upper. — The Upper Old Red Sandstone occupies a small area on 

 the coast in the neighbourhood of St. Cyrus. Although no fossils have 

 been recorded, the lithological evidence — and particularly the occurrence 

 of characteristic cornstones — leaves no room for doubt that here we are 

 dealing with an outlier of the more extensive tract of Upper Old Red 

 Sandstone of Arbroath. In Kincardineshire the Upper Old Red Sand- 

 stone is everywhere faulted against the Lower. 



v.— On an Actinolite-beaeing Rock allied to Serpentine.' By 

 A. W. GiBB, M.A., D.Sc. 



THIS rock is associated with the intrusion of bade rocks in Belhelvie, 

 Aberdeenshire. Towards the northern end of this mass, which 

 consists of troctolites, serpentines, and allied types, a rock is occasionally 



^ Abstract of paper read before the British Association, Section C (Geology), 

 Dundee, September, 1912. 



