The high-amplitude variability in the MST data at both Site 984 (Bjorn Drift) and Site 981 (Feni Drift) reflects real changes in sediment properties at those sites. Site 981 appears to be a two-component system, with glacial-interglacial changes in the relative proportion of felsic terrigenous material and biogenic carbonates best represented by NG. The mineralogy of the terrigenous fraction here is relatively constant.
The sedimentology at Site 984 is more complicated than at Site 981. In addition to periodic input of felsic material characterized by high clay mineral abundances and high NG, a major sedimentary component is basaltic material with a low NG but high MS signature transported from Iceland. NG and MS do not appear to vary in concert with each other at Site 984, and we do not observe the relatively simple two-component system seen at Site 981. Instead, there are probably four important independently varying sedimentary components: biogenic carbonate, felsic IRD, mafic terrigenous material derived from Iceland, and a fine amorphous component that may be biogenic silica. Unlike at Site 981, carbonate content and foraminiferal abundance are low at Site 984 and do not correlate tightly with other sedimentary components.
GRAPE wet bulk density does not correlate particularly well with any sedimentological properties measured at either site, although it clearly increases during glacial intervals at Site 981. One possible unconstrained source of the variance in GRAPE data could be changing biogenic silica content in the sediments. The MST records, in particular MS and NG, appear to be a valuable resource for constructing long, high-resolution records of the concentration of different sedimentary components at Sites 981 and 984.