Showing papers by "Jürgen Mienert published in 1990"

Physical and Acoustic Properties of Arctic Ocean Deep-Sea Sediments: Paleoclimatic Implications

Abstract: Six sediment cores from the Eurasian Basin were studied to determine and understand climatically driven changes of Arctic Ocean basins. Detailed time control of sediments for the last 45 kyr is based on accelerator mass spectrometry (AMS) C14-dating of biogenic carbonate (N. pachyderma, left coiling). The most important results from our study are summarized as follows. From 45 to 13.5 ka low sedimentation rates prevailed (0.35 cm/kyr). They increased drastically at the transition from the last glacial to interglacial (Termination Ia, 13.5 ka) leading into high Holocene sedimentation rates (1.06 cm/kyr). Low carbonate concentrations (< 4%) prevailed from 13.5 to 9 ka at Termination I. Decreased salinities can be expected for Termination la (Zahn et al., 1985, Jones & Keigwin, 1988, Mienert et al., 1989) due to glacial meltwater influence possibly accompanied by sea ice melting. As a result of the freshwater influence, productivity of planktic foraminifers decreased and this, in turn, resulted in a drastic decrease in carbonate concentration during Termination Ia. Although carbonate concentration varies only between 0 and 9%, it distinctly changes both the compressional-wave velocity (from 1485 to 1510 m/s) and the wave attenuation (from 0.1 to 0.45 dB/m/kHz) in the sediment. Climatically driven changes in magnetic susceptibility have proved to be a valuable paleoclimatic tool for intercore correlations. Our results indicate that the same general conclusions are valid for pelagic environments of both Atlantic and Arctic Ocean basins.