Fróðskaparrit - 01.01.1975, Qupperneq 106

114
Glacial Erratics
The high relative abundance o£ erratics o£ tuff carbonate
sediments at station 5 and the likely occurrence of two tuff
carbonate concretions without signs of glacial transport on
Sandoy Bank suggest that these sediments have been derived
locally from the outer shelf. They are much softer than the
basalts and they are therefore probably more widespread be-
low the Quaternaty deposits than their number suggests. The
tuffaceous beds on the Faeroe Islands lack carbonate and are
usually red coloured; we have not found any sediments like
these in the dredge hauls.
The ashes in the tuff carbonate sediments must have been
erupted from the vicinity because some of the ash layers are
several centimeters thich and coarsely sandy. The strong altera-
tion points to a raher old age for the ashes. The sediments
therefore very probably have been deposited in connection
with the building up of the Faeroese basalt plateau, i. e. they
are of Lower Tertiary age.
The other sediments and the metamorphic and plutonic rocks
almost certainly originate from outside the Faeroe shelf. They
are very scarce on the shelf itself, and on the slope, where they
are abundant, there is a wide range of rock types. A palyno-
logicai investigation of some of the sediments by Finn Bertel-
sen at the Geological Survey of Denmark shows a range of
ages from Middle Devonian to Cretaceous. Most of the arkoses
and many of the other sandstones have probably been derived
from the Old Red Sandstone belt between Scotland and the
Shetland Islands and most of the gneisses probably originated
from the Caledonian metamorphic terrains in Scotland, the
Shetland Islands and Norway.
Glaciological implications
We consider that the sudden decrease in the proportion of
foreign erratics towards the top of the continental slope south-
east of the Faeroe Islands is caused by the front of the Faeroese
ice sheet standing along the edge or uppermost part of the