This paper presents an overview of the physical properties and sedimentologic results
from six Ocean Drilling Program Leg 151 sites cored on the Iceland Plateau (Hole 907A), in the Fram
Strait region (Sites 908 and 909), and on the Yermak Plateau (Sites 910-912). The primary objective
of this paper is to determine to what extent wet bulk density measured using the gamma-ray
attenuation porosity evaluator (GRAPE) can be used to interpret textural and compositional changes
in sediment accumulation at the various sites around the Nordic Seas and Arctic Ocean. To
accomplish this objective, we have first established quantitative relationships between discrete
measurements of bulk density and GRAPE bulk density at nine holes and have evaluated the
frequency distribution of GRAPE bulk density data at the same holes to detect significant differences
between sites. We have also evaluated the frequency distribution of magnetic susceptibility data at
these holes because this rock magnetic parameter is most often used in combination with GRAPE
measurements for correlation purposes. These two parameters are also used for evaluating
compositional and textural changes in sedimentary inputs.
Composite depth profiles have been developed for three sites (Sites 908, 909, and 911)
using both GRAPE bulk density and magnetic susceptibility measurements made on cores from
multiple, adjacent holes at these sites. The composite depth profiles provide a more continuous record
of property variations in the upper 100 meters below seafloor at a given site than is provided by the
data collected at a single hole. The composites also provide the framework for more detailed
paleoceanographic and paleoclimatic analyses of the records from these sites (i.e., spectral analysis
of time series, astronomic tuning of records, etc.). These activities will be pursued in future
contributions related to these data.
Efforts have been made to identify the sources of variation in the GRAPE bulk density
records, and to a lesser extent the magnetic susceptibility records, using the available ground
truth" provided by sedimentologic analyses of discrete samples from selected holes. Textural and
mineralogic analyses are compared to GRAPE bulk density records to identify to what extent we are
able to explain the density fluctuations in terms of (1) changes in the accumulation of coarse-grained
material in various grain-size subfractions, which are primarily transported to the deep sea by sea ice
and icebergs during glacial intervals and are influenced by oceanic currents to varying extents, and
(2) by changes in the mineralogy and in the relative percentages of various sedimentary inputs, which
may provide information about changing source regions for these materials between glacial and
interglacial periods in the Nordic Seas and Arctic Ocean.
Date of initial receipt: 5 January 1996
Date of acceptance: 10 May 1996
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