Vol. 57.] THE CRUSH-CONGLOMEKATES OF ARGYLLSHIRE. 313 



24. On the Crtjsh-Conglomerates of Argyllshire. By James 

 Bastian Hill, Esq., R.N. (Communicated by E. S. Heeries, 

 Esq., M.A., Sec.G.S.^ Eead May 22nd, 1901.) 



[Map on p. 316.] 



Contents. 



Page 



I. Introductory 313 



II. General Descinption of the Area 314 



III. Description of the Orush-Conglomerates 320 



IV. General Remarks 324 



V. Conclusions 325 



I. I:ntroductory. 



In a former communication to this Society ^ dealing with the 

 Dalradian schists of Argyllshire, I described a deposit known as the 

 Boulder-bed, which occurs in the Highland Series along a horizon 

 extending from Aberdeenshire to Islay. I pointed out that this 

 abnormal conglomerate owed its origin to aqueous deposition, and 

 supported that contention by showing that, in various localities 

 along its outcrop, it contains boulders of foreign material. 



At that time, with the exception of the Isle of Man, where the 

 phenomena of crush-conglomerates had been brought to light by 

 the researches of Mr. G. W. Lamplugh, the occurrence of pseudo- 

 conglomerates had not been recorded in Britain. M}^ subsequent 

 work, however, on the Geological Survey in Cornwall, revealed their 

 existence in that county on a large scale : this was described in 

 the Summary of Progress of the Geological Survey for 1899 (pp. 89 

 et seqq.), and in a paper read before the Geological Society of 

 Cornwall last November,^ On continuing my work in the High- 

 lands last summer I was able to show that these structures occur 

 in Scotland among the Dalradian Series, where they bear so marked 

 a resemblance to many portions of the Highland Boulder-bed that 

 they may readily be confounded together, especially as they are both 

 met with on the same horizon. 



In my above-mentioned communication to this Society, T sought 

 to demonstrate that the typical crystalline schists of the Central High- 

 lands, when followed into the Loch Awe Basin, pass laterally into 

 sediments which are comparatively unaltered. Having shown the 

 passage of the more important stratigraphical zones from the Loch 

 Awe region into the Central Highlands, I pressed the argument still 

 further by showing that the Highland Boulder-bed is met with in 

 both areas occupying the same stratigraphical position. Although 

 it was pointed out that from Aberdeenshire in the east to Islay in 

 the extreme west, foreign boulders (mainly of granite) had been 



^ Communicated by permission of the Director of H.M. Geological Survey. 

 • 2 Quart. Journ. Geol. Soc. vol. Iv (1899) pp. 470-92. 

 ^ Trans. Geol. Sec. Cornw. vol. xii, pt, vi (1901) p. 403. 



