THE SVINAFELL LAYERS 38 1 



How deep below the plain the Svinafell layers reach between Godagil and 

 Snidagil cannot be said with certainty; in the author's opinion it is hardly 

 more than ten meters or so. A normally magnetized basalt layer at their base 

 at Breidagil is doubtless a sill. Two normally magnetized dykes cut through 

 the layers and sills emerging from these dykes are intercalated between the 

 sedimentary beds. One intrusive sheet connected with the northernmost 

 dyke is only 5 cm thick and thoroughly conformable with the beds (PI. Ill, 2). 

 The maximum visible thickness of the sedimentary layers at Snidagil is about 

 140 m and, as their base a little farther north is at least 10 m lower and the 

 layers are practically horizontal, the total thickness there has been at least 

 150 m. Towards the south the sediments are limited by Snidabrekka, the 

 base of which consists of reversely magnetized basalt-globe breccia with 

 individually scattered lava nodules. 



On the west face of Svinafellsfjall as well as at Gapar on its east face, the 

 Svinafell layers are covered by a 200-300 m thick series of tillites, basalt 

 intrusions, and basalt-globe breccias with irregular layers of globular basalt. 

 This series is capped by beds of subaerial lava. For the most part the tillite 

 rests directly and uncomformably on the Svinafell layers. For a short distance, 

 however, a basalt sill is intercalated between the tillite and the layers. The 

 tillites at Svinafell have been described by Noe-Nygaard (1953, pp. 223-227; 

 Nielsen and Noe-Nygaard, 1936, Figs. 2 and 3). Of their true morainic nature 

 there is no doubt; they certainly contain beautifully striated boulders. In 

 the author's opinion the two tillite beds as well as all tuff breccias between the 

 Svinafell layers and the subaerial basalts 200-300 m higher up belong to the 

 same Glacial, whereas a lower tillite bed in the ravines above the Svinafell 

 farms may well belong — though this is not certain — to an older Glacial 

 (cf. Noe-Nygaard, 1953. p. 224). 



The subaerial lava beds capping the subglacially formed rock series could 

 possibly be interpreted as the top layers of a table mountain and in that case 

 could belong to the same Glacial as the underlying tuff breccias. More likely, 

 however, these layers belong to the following Interglacial. These basalts are 

 partly covered by a bed of grayish tuff breccia containing angular boulders. 

 The author, who has had only a hasty glance at this breccia, is inclined to 

 interpret it as subaerial eruptive breccia of the kind found around some 

 Post-glacial explosion craters such as Hverfjall, 



Over the subaerial layers is deposited a basalt-globe breccia forming the 

 uppermost part of Svinafellsfjall. 



DESCRIPTION OF THE SVINAFELL LAYERS 



The Svinafell layers are for a great part lacustrine. The lower part of the 

 formation shows a distinct macroscopic and partly graded bedding (rhytmites) 

 which is horizontal except for the upper part of the contact zone towards 



