What level of resolution is attainable in a deep-sea core? Results of a spectrophotometer study

A Minolta CM-2022 spectrophotometer has been used to characterize downcore fluctuations in sediment lightness and color in core NEAP15K, a 7-m core collected from the northeast Atlantic Ocean. High-resolution data series, measured using a 4-mm-diameter measurement spot and a l-cm sampling interval, were generated along two independent tracks down the core to investigate the statistical significance of fluctuations across the 2-20-cm-depth range. This small-scale variability is characterized by abrupt changes in the lightness and color of the sediment that are several orders of magnitude greater than the instrumental precision. Our results establish that significant information is preserved at the l-cm scale in spite of bioturbation effects. These findings demonstrate that high-resolution studies using conventional paleoclimatic proxies have the potential to recover meaningful century-scale climate records in regions of the ocean where sedimentation rates exceed 10 cm per thousand years. The coherency of these downcore records also implies that the spectrophotometer is a powerful instrument for establishing precise centimeter-scale stratigraphic correlations between cores.