All dropstones, which are never common, occur above this deeper horizon. There is no evidence of significant sediment disturbance, winnowing, or erosion at Site 983, although bioturbation is ubiquitous throughout the cores. Calcareous nannofossils are the dominant fossil group at this site and are generally abundant and well-preserved. All the standard Quaternary nannofossil zones were recognized. Planktonic foraminifers are generally common to abundant and well-preserved throughout the uppermost Pliocene to Holocene sequence, although rare barren intervals are observed.
Benthic foraminifers are present at most of the levels examined and preservation is good throughout.
Diatoms at Site 983 were common to abundant and exhibit moderate to good preservation. Pore-water profiles from Site 983 are typical of sediments in which sulfate reduction and methanogenesis are occurring. Sulfate concentrations decrease from seawater values at the top of the core to zero at about 100 mbsf. The boundary between sulfate reduction and methanogenesis is very sharp at 120 mbsf, presumably because utilization of methane by sulfate-reducing bacteria prevents significant diffusive penetration of methane into the sulfate reduction zone above.