358 MR. HELGI PJETURSSON ON A SHELLY [Aug. I903, 



often being amygdaloidal and decomposed, from the sheets of basalt 

 which are interbanded with the ' breccia-formation.' 



The moraines (b) and (/)are of a bluish-grey colour, and contain 

 numerous distinctly-striated stones of various sizes. 



The volcanic breccias of different kinds and colours, from nearly 

 black to yellowish-brown, attain — on both sides of the section 

 exposed — a thickness of probably not less than 300 feet, and their 

 maximal thickness is even much greater, for in places the breccias 

 of the plateau rise into hills several hundred feet high. These 

 breccias are not post-Glacial, for erratics and loose glacial 

 rubbish are commonly found strewn over their surface. 



Some little distance from the farm of Mavahlid, the sheet of 

 columnar basalt (e), with the overlying moraine and the underlying 

 conglomerate (d), is well seen ; while the lower moraine can hardly 

 be distinguished from the conglomerates, and the fundamental basalt 

 only appears in the corrie towards the left. On the right, volcanic 

 breccia, which thickens southward, is seen overlapping the upper 

 moraine. 



Nevertheless, interesting as are the sections briefly described 

 above, showing as they do that Glacial conditions existed here at 

 a time when the contour and relief of the region differed very greatly 

 from what is now the peninsula of Snsefellsnes, they are surpassed 

 in interest by a section near Bulandshofdi, on the northern face of 

 the escarpment, where is clearly exposed a shelly Boulder-Clay, 

 reaching a height of more than 600 feet above the sea and buried 

 under hundreds of feet of conglomerate, lava, and volcanic breccias 

 (' palagonitic breccias '), which show a glaciated surface (erratics 

 and loose glacial rubble). 



The succession of the beds is shown in fig. 2 (p. 359). 



The top of the shelly Boulder-Clay (b) reaches a height of rather 

 more than 600 feet above the sea, 1 and its total thickness is 70 to 80 

 feet. The clay is indurated, shows no stratification, and through it 

 are scattered numerous blocks of basalt of various sizes, hardly 

 exceeding, however, 8 inches in diameter. Some of the boulders are 

 angular, others rounded ; many, especially of the bigger blocks, are 

 so well polished and striated that they could serve as beautiful 

 types of glacier-stones. 



This Boulder-Clay is more interesting than others of the moraines 

 of the ' paiagonite-formation ' by reason of the shells, which occur 

 in very great numbers throughout the whole thickness of the 

 bed (6), with the exception of some 10 feet of laminated sandy clay 

 (/3) towards its base. 



The shells are, as a rule, highly triturated, unbroken specimens 



1 This, even though the shells are of derivative origin, must probably be 

 taken as evidence of a much greater submergence of the country than was 

 previously suspected. The highest level at which a marine fossil had been 

 found was about 200 feet above the sea. This was a Balanus, obtained in 1899 

 in a bank of the Thjorsa, in marine clay probably corresponding in age to the 

 later Yoldia-beds of Scandinavia. 



