Three sites from Leg 151 were selected for a study of orbital- and millennial-scale
climate variability during the last 140,000 years. This interval, from marine isotope Stage (MIS) 6
to
the present, includes the last large climate cycle of the Quaternary. Sites 907, 909, and 910
constitute
a transect, roughly north-south, from the Iceland Plateau, through the Fram Strait, to the Yermak
Plateau. Sediment cores from these sites were analyzed for the abundance and diversity of
planktonic
foraminifers and the quantity and composition of ice-rafted debris (IRD).
Leg 151 drilling was successful in recovering young sediments. This is best
demonstrated in Hole 907A, which has a sedimentation rate of 1.7 cm/k.y., where an
11,000-year-old
volcanic ash is disseminated at a depth of 0.2 meters below seafloor (mbsf), indicating good
recovery
of the overlying Holocene section.
The last climate cycle in Hole 907A is well defined by faunal assemblages and
abundances, which indicate that mild conditions were limited to peak interglacials. Ice-rafted
debris
is abundant at all other times, although discrete peaks in the ratio of ice-rated grains to
foraminifers,
perhaps analogous to the Heinrich events of the North Atlantic, occur only during MIS 2-4 and 6.
Site 909 in the Fram Strait has a sedimentation rate of 3.4 cm/k.y., and is characterized by
variability
in the abundance of detrital coal mark MIS 6, and contrast with the last (MIS 2) glaciation. Site
910
on the Yermak Plateau has a sedimentation rate of 2.7 cm/k.y., and is dominated by detrital
sediments. The abundance of coarse sediment remains high with little variation throughout the
study
interval. Ice-rafted clastic rock fragments are relatively less important on the Yermak Plateau than
in the Fram Strait, implying different glacial source areas. The similarity between the last two
glacial
and interglacial pairs seen on the Iceland Plateau (as in the subpolar North Atlantic) is less evident
in our high latitude cores.
Date of initial receipt: 11 July 1995
Date of acceptance: 30 December 1995
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