toME CHAPTERS OF THE TERTIARY HISTORY OF ICELAND 1 



(1) A Deep-Lower Tertiary flora of warm character. 



(2) A mixed flora with warm and cool elements. 



(3) A Tertiary flora of Hoifell and Tjornes type, ranging perhaps from 

 Upper Miocene to Upper Pliocene. 



(4) An Upper Tertiary and Pleistocene type flora. 



(5) A Pleistocene type flora. 



This scheme represents in a very broad sense a chronological order. 

 But it has been revealed that rather early there were considerable fluctuations 

 between "warm" and "cool" floras, whether or not this is a reflection of 

 climatic alternations or of the repeated and rapid changes in the other external 

 conditions which 1 have mentioned earlier. 



In western Iceland the localities of Skardstrond and the Northwestern 

 Peninsula belong to Pflug's first type. Hredavatn and Stafholt in Borgar- 

 fjordur still belong to this group, but Sleggjulaekur, a little higher than 

 Hredavatn, pertains to the second type. In the topmost plateau group we then 

 have the horizon of Litlisandur (Hvalfjordur) with a leaf bed in loess above 

 varve-clay and a moraine on a clearly glacier-striated floor (Fig. 3). This is 

 the lowest known glacial horizon in western Iceland. Above it are certainly 

 three reverse magnetic periods and three normal ones, and more probably the 

 total number of magnetic periods above this horizon is closer to 10. Pollen has 

 not been found in this horizon nor have the leaves been analyzed by experts. 

 They seem to belong to willows, birch, and alder. 



Fig. 4. Drawing of the impression of a 

 plant on the lower face of a basalt lava. 

 The plant stem is about 25 cm long, and 

 the width of it and the branches is 3-5 

 mm From Grafardalur near Hvalfjor- 

 dur. The lower surface of the lava must 

 have consolidated before the plant was 

 burned. 



In eastern Iceland the lowest plant horizon is that of Gerpir. It is considered 

 as Lowest Tertiary or even Uppermost Cretaceous by Pflug (1959). 



On top of this we have a 4500 m thick pile of lavas that have been mapped 

 by Walker (1959). Near the top of the pile, in which Walker did not find any 

 unconformity, are the lignite seams of Holmatindur and Tungufell. The 

 former seems to belong to the Lower Tertiary on palynological grounds 

 (Schwarzbach, private communication) and this is in keeping with the lack 

 of an unconformity between it and Gerpir. But a widely divergent view has 

 been expressed concerning Tungufell to which I shall return soon. 



Farther inland we have still higher members of the plateau basalts. These 



