GLACIATION OF AN ICELANDIC VALLEY 



129 



moraines is distinctly striated adjacent to the moraine, the scratches 

 often running under the moraine itself. 



On the southern side of the valley one of the higher moraines 

 is nearly horizontal, with the gently tilted basalt flows resting against 

 it, as if the moraine had originally been deposited on a sloping sur- 

 face and had been subsequently buried by overlapping lava flows. 

 Later tilting has given the 

 position shown in Fig. 9. 



There are certain points 

 of similarity in these differ- 

 ent Tertiary morainal beds 

 which are worth noting: 



The indurated moraines 

 are weaker members of the 

 cliffs than are the basalts, 

 and hence tend to form 

 shelves and have their lower 

 contacts, the critical points 

 of such beds, covered by 

 talus. Whenever the con- 

 tact is visible, as in the two 

 points mentioned above, and 

 in several other localities in 

 the vicinity of the Hvalfjord, 

 it is smoothed or striated. 



Fig. "].- — Sandstone above the second moraine. 



In nearly every case the moraine is overlain by bedded material, 

 as if from deposits laid down by glacial streams during a retreat 

 of the ice-sheet. No delta beds, so common in our glacio-fluva- 

 tile deposits, were seen, but perhaps these might be found if the 

 sedimentary beds of the basalt plateau were studied in greater 

 detail. 



The lower surfaces of the basalt flows lying above the sandstone 

 seem much more brecciated than those which rest on other basalt 

 flows. This brecciation may have been caused by explosions due 

 to the presence of standing water when the lava was fluid. 



The inconstant nature of the moraines and sandstones is very 

 noticeable; the beds change greatly in size in a very short distance. 



