J.F. McManus, C.O. Major, B.P. Flower, and T. Fronval


  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

Return to Contents of Leg 151
Return to Contents of Scientific Results