A sediment core from the Wrangel abyssal plain (T3 69-12, lat. 80°21.9^primeN, long. 173°33^primeW, water depth: 2,867 m; core length: 374 cm) was analyzed for CaCo₃, Mn, P₂,O₅, Al, Fe, and trace elements; in total, 15 samples from the interval 0-350 cm were used for these analyses. Three carbonate layers were found (5-16% CaCO₃), interspaced by carbonate free strata (0-2% CaCO₃), resembling lithologic variations described by Herman in other Arctic cores.

The carbonate-free fractions of the carbonate layers show higher contents of Mn (0.4-0.9%) and P₂O₅ (0.215-0.237%) than the carbonate-poor layers in which the corresponding values range between 0.15-0.25% and 0.183-0.211%. The Al and Fe values show no major variations, ranging between 7.5-9.9 and 4.3-5.5%,

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respectively, suggesting that most abiogenic constituents are terrigenous.

The stratigraphy by Herman suggests that the CaCO₃-Mn-P₂O₅-rich layers were deposited during glacial periods. Similar climatically related variations are described from the Caribbean by Wangersky and Hutchins, and by the writer. Analyses of pelagic sediments from the Coral Sea, the Black Sea, and western Pacific show that similar variations also occur in other oceanic regions; future dating of these cores will illuminate this problem further. The origin of these sediments is very poorly understood. A possible but unlikely explanation (proposed earlier by the writer) is that chemical weathering was more intense during glacial periods. It is characteristic, however, that all sediments with CaCO₃-Mn-P₂O₅ covariations, with ut exception, are found in basins with restricted entrances, but nowhere in the major oceanic basins. During the glacial maxima, sea level was considerably lower than at present, enhancing the isolation of many of these basins. As a result, oxygen-poor bottom waters were more likely to develop, enhancing the migration of manganese upward as has been described from the East Pacific by Lynn and Bonatti. The Mn-rich layers in the sediments thus could be "fossil top sediments" enriched in manganese. This mechanism may not explain the enrichment in P₂O₅. However, in more poorly vented basins, labil layering and overturn of water masses are known to occur under certain circumstances. This could explain the covariation between CaCO₃, Mn, and P₂O_{5 /SUB> in many of these cores.}

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