Glacial-interglacial records of the reflectance of sediments from the Norwegian-Greenland-Iceland Sea (Nordic seas)

The reflectance of sediments (gray level) were measured on 11 sediment core s from the Norwegian-Greenland-Iceland Sea (Nordic seas). The analyzed time interval covers the past five glacial-interglacial cycles. Although the re sults demonstrate that the gray-level method has a potential for stratigrap hic purposes, it is indicated that gray-level changes in the Nordic seas ar e not necessarily driven by variations in the content of biogenic calcite. A detailed comparison of gray-level values with contents of total CaCO3, (c arbonate) and total organic carbon (TOC) reveals no overall causal link bet ween these proxies. However, specific glacial core sections with layers con taining organic-rich sediment clasts as a consequence of iceberg-rafting se em to col-relate well with law gray-level values. Of those cores which show relatively high and comparable carbonate values in the last three main int erglacial intervals (stages 11, 5.5, and 1), stage 11 is always marked by t he highest gray-level values. A close inspection of the surface structure o f the foraminiferal tests as well as the conduction of reflectance measurem ents on these tests leads to the conclusion that enhanced carbonate corrosi on occurred during stage 11. The test corrosion not only affected the refle ctance of the tests by making them appear whiter, it also seems responsible for the comparatively high gray-level values of the total sediment in stag e 11. In contrast, the relatively low gray-level values found in stages 5.5 , and 1 are not associated with enhanced test corrosion. This observation i mplies that variable degrees of carbonate corrosion call have a profound ef fect on total sediment reflectance.