Obtaining a long-term history of this water mass is one of the primary scientific objectives of this site. In particular, Site 983 lies on the northwest margin of the Iceland Basin directly downstream of overflows from the Iceland-Faroe Ridge. MST data allowed the construction of a continuous composite section for this site and preliminary studies aboard ship indicate strong variance throughout the section in a number of parameters on both Milankovitch and sub-Milankovitch time scales. The sediments at Site 983 are predominantly composed of rapidly accumulated fine-grained terrigenous particles with minor amounts of biocarbonate and biosilica.
Authigenic iron sulfides, primarily in the form of disseminated pyrite, are also typically present.
The dominant lithologies include silty clay, clay, clayey nannofossil mixed sediment, and clay with variable amounts of nannofossils and silt. Nannofossil oozes with variable amounts of clay and sponge spicules also occur. Subtle but distinct boundaries that delimit three subunits occur at depths of 120 mbsf and 180 mbsf. The shallower boundary is recognized primarily in the spectral reflectance signal. The deeper boundary is recognized in visual examination of split cores and smear slides, and is characterized by a downcore absence of layers in which biocarbonate is predominant.