Growth history of manganese nodules and crusts of the Peru Basin
| Autor: | U. Von Stackelberg |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
geography
geography.geographical_feature_category fungi Geochemistry chemistry.chemical_element Sediment Geology Ocean Engineering Manganese Structural basin engineering.material Sink (geography) Diagenesis Todorokite chemistry Mining engineering engineering Layering Carbonate compensation depth Water Science and Technology |
| Zdroj: | Geological Society, London, Special Publications. 119:153-176 |
| ISSN: | 2041-4927 0305-8719 |
| DOI: | 10.1144/gsl.sp.1997.119.01.11 |
| Popis: | In the nodule field of the Peru Basin, situated south of the zone of high bioproductivity, a relatively high flux of biogenic matter explains a distinct redox boundary at about 10 cm depth separating very soft oxic surface sediments from stiffer suboxic sediments. Maximum abundance (50 kg m −2 ) of diagenetic nodules is found near the calcite compensation depth (CCD), currently at 4250 m. There, the accretion rate of nodules is much higher (100 mm Ma −1 ) than on ridges (5 mm Ma −1 ). Highest accretion rates are found at the bottom of large nodules that repeatedly sink to a level immediately above the redox boundary. There, distinct diagenetic growth conditions prevail and layers of dense laminated Mn oxide of very pure todorokite are formed. The layering of nodules is mainly the result of organisms moving nodules within the oxic surface sediment from diagenetic to hydrogenetic environments. The frequency of such movements is much higher than that of climatic changes. Two types of nodule burial occur in the Peru Basin. Large nodules are less easily moved by organisms and become buried. Consequently, buried nodules generally are larger than surface nodules. This type of burial predominates in basins. At ridges where smaller nodules prevail, burial is mainly controlled by statistical selection where some nodules are not moved up by organisms. |
| Databáze: | OpenAIRE |
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