Sequential variations in manganese (Mn) content and color of deepsea sediments retrieved from the Lomonosov Ridge (87°N) in the central Arctic Ocean apparently mimic low-latitude δ 18 O glacial-interglacial cyclicity, thereby providing stratigraphic information that together with biostratigraphic data permit the construction of a detailed chronological model. Correlation of this Mn and color chronology to established apparent Brunhes-age estimates of geomagnetic excursions reveals a remarkable fit between these two independently derived time scales. The Mn and color cycles probably provide paleoenvironmental information about material fluxes in the Arctic Ocean over the past 1 m.y. We suggest that the primary source for the observed manganese variations in our sediment core is northern Siberia, which has extensive peat bogs and boreal forests. These Siberian source areas could operate in an off and on mode tuned to Pleistocene glacial and interglacial periods. Contrasts in ventilation of Arctic Ocean waters during interglacial-glacial cycles probably could also enhance the observed Mn and color variability.

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Scanning electron microscope examinations have revealed fossilized cell-like structures randomly distributed in near-surface oxidized deposits of red and gray Fe-rich chert and Fe-Si oxyhydroxides of the Trans-Atlantic Geotraverse (TAG) hydrothermal mound, Mid-Atlantic Ridge at 26 ± 08 0 N. Chemically, these structures are carbon-based with the morphology of half-spheroids that are 2 to 3 ¹m in diameter and are mostly arranged in the form of clusters and long thread-like cellular masses that resemble single-celled microorganisms. The wide range of intracrystalline silica concentration, which seems to replace the original chemistry, suggests that the microorganisms were subjected to various degrees of silica mineralization, which was probably controlled by the thermal development of this hydrothermal site.