RECENT STUDIES IN THE GEOLOGY OF THE FAEROES 33 



SE. and on Vagar 3° ESE., this sequence goes below sea level in the northern 

 part of Suduroy, and in the western part of Vagar. An excellent view of this 

 sequence is to be had in the naked, steep, sometimes quite vertical, rocky 

 wall to the west. The thickness of the individual basalt beds generally ranges 

 from IC to 30 m, although thinner beds do occur; the greatest measured 

 thickness of a basalt bed in this sequence is about 70 m. Petrographically the 

 flows ar-? very uniform. They consist of homogeneous, hard, dark, fine 

 grained, only exceptionally porphyritic basalts often with a well-developed 

 columnar structure. The surface of the individual flows is slaggy, porous, red, 

 due to either the oxidation or to the heating effect of the overlying flow. 



Intrabasahic sediments are of rather subordinate significance. Besides the 

 prevailing tuff" layers, 1 to 4 m in thickness, intrabasaltic, fluvial, conglomer- 

 ates and shales of almost the same thickness as the tuff layers occur, sometimes 

 containing sporadic coal in very tliin layers or lenses. 



All the known part of the Lower Basalt sequence (about a 1000 m thick) is 

 of subaerial, volcanic origin. However, since its substratum and consequently 

 the absolute thickness of the whole sequence is unknown, as mentioned above, 

 nothing can be stated regarding a possible earher submarine volcanic phase. 



THE COAL-BEARING SERIES 



Subsequent to the formation of the Lower Basalt sequence there occurred 

 a quiet period in the volcanic activity, an interval of a rather long duration, 

 represented by a Coal-bearing series (Fig. 1). This rests immediately on the 

 surface of the Lower Basalt sequence and occurs thus in the northern part of 

 Suduroy and in the westernmost part of Vagar. On Suduroy (Fig. 2) the 

 Coal-bearing series has its highest position in the southwest at about 425 m, 

 and on Vagar in the northwest at about 250 m above sea level. The surface of 

 the Lower Basalt sequence has undergone a rather high degree of subaerial 

 weathering, and the Coal-bearing series, therefore, rests on a strongly 

 undulating surface. The coals in the Coal-bearing series are the only ones in the 

 Faeroes of any economical interest. They are allochtonous, deposited in a 

 basin or a lake, and cover an area of about 23 km^. In Fig. 3 is drawn a 

 characteristic profile section through the Coal-bearing series, the thickness of 

 which usually reaches 10-15 m. The sequence is as follows: 



1. Light grayish-yellow or gray bottom clay (Faeroic: Banki). 



2. Lower coal band (Faeroic: Stabbi). 



3. Dark shale (Faeroic: Rann). Some coals often occur in this shale, 

 especially in the southern area. 



4. Upper coal band (Faeroic: Kolband). 



5. Roof clay (Faeroic: Tak). 



The roof clay is of rather variable nature, and sometimes fluvial conglomer- 

 ates entirely of basaltic origin occur. They occur mainly towards the outer 



