Jökull - 01.12.1982, Page 8

the lower-lying areas, has existed. Thoroddsen
(1906), who also referred to earlier investigators,
mentioned glacial till as well as striae from many
sites. Kjartansson (1955) in his important paper on
glacial striae in Iceland and on hisgeologicalmapof
Iceland (sheet 3, Museum oj Natural History 1960)
demonstrated a great number of striae and he also
indicated the presence of glacial drift at several
places. His observations are extended in the second
edition of the same map prepared by Saemundsson
and Einarsson (Museum of Natural Histoiy 1980). My
own observations, mainly of striae, were made on
several occasions, especially in 1970 and 1974. Evi-
dence that the ice-sheet covered the entire coastal
area can be deduced from the rather complicated
pattern ofglacial striae, as outlined below.
An understanding of the shifting direction of the
striae can only be gained if we consider that ice
recession in the lower areas took place with the ice
front standing in the sea; at the time of ice retreat
sea-level in this area stood aboutöO to 70 m higher
than now, relative to land (Th. Einarsson 1968, p.
287). As with Grímsey the ice front tends to align
itself parallel to the depth contours; furthermore ice
movement is directed at right angles to the ice front.
In consequence the direction of the youngest striae
in areas below the marine limit are more a result of
dcpth conditions at the ice front than of events in
the accumulation areas of the ice sheet. When the
ice front then during its retreat reaches land the
older recession pattern continues to exert a strong
influence at least for a certain time.
The Reykjanes Peninsula illustrates the princip-
les just given. In the westernmost extremities the
striae point to the west, but in more easterly localit-
ies they change direction - to the north in the north-
ern part and to the south in the southern part; i.e.
the striae are always oriented at approximately 90°
to the present shoreline. The last ice remnants were
localized in the central parts of the peninsula. How-
ever, it is most probable that also at the glacial
maximum the ice surface was higher over central
Reykjanes Peninsula than, for instance, in the Faxa-
flói area where the outflow of ice always must have
been strong. Keeping the same principles in mind it
is not diflicult to understand why the glacial striae
6 JÖKULL 32. ÁR