Oxygen-isotope profiles for the Late-Glacial carbonate sediments from
Red Bog and adjacent Lough Gur in County Limerick in western Ireland a
re readily correlated with the classical biozones delineated on pollen
diagrams for the same cores. The estimated summer temperatures of the
Bolling/Allerod were as high as those in the early Holocene and are c
orrelated with increasing Milankovitch summer insolation. This warm ph
ase was abruptly terminated in the Younger Dryas cold episode by a dep
letion of 4 parts per thousand, in delta(18)O, suggesting a summer atm
ospheric temperature decrease of about 12 degrees C, comparable to tha
t inferred from fossil beetle data. The Younger Dryas phase is attribu
ted to a major cooling of the sea-surface temperature by a postulated
discharge of icebergs similar to that of the Heinrich events, for the
icebergs were much more effective than simple meltwater in cooling the
sea surface and thus the climate over Europe. Shorter-term cool phase
s (Older Dryas, Gerzensee, Preboreal oscillation) are also recognized.