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Neogene oceanographic variations recorded in manganese nodules from the Somali Basin |
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| Authors: | VK Banakar RR Nair M Tarkian B Haake |
| Institution: | a National Institute of Oceanography, Geological Oceanography Division, Dona-Paula, Goa-403 004, India b Mineralogisch-Petrographisches Institut Universität Hamburg, Grindelallee 48, 2000, Hamburg 13, Germany c Institut für Biogeochemie und Meereschemie Universität Hamburg, Bundesstraβe 55, 2000, Hamburg 13, Germany |
| Abstract: | A detailed study of a nodule from the Somali Basin dated by 230Thexcess was correlated with the paleoceanographic events recorded in Site 236 (Leg 24) Deep Sea Drilling Project (DSDP) cores. Tentative indications are that the phase of nodule accretion starting with the development of pillar structure at a depth of 20 mm in the nodule around 13 Ma coincides with increased Antarctic Bottom Water (AABW) flow and an elevated calciumcarbonate compensation depth (CCD). The Late Miocene lowering of the CCD is represented by the mottled zones between 8 and 18 mm in the nodule is characterised by an abundant silicate component (>20%) of aeolian origin. The Miocene/Pliocene boundary (5 Ma) occurs at a depth of about 8 mm and is represented by the development of pillar structure and a minimum of aeolian dust (10.3%). The increased biological productivity of the Somali surface water since the Middle Miocene is demonstrated by the increasing Corg content of the nodule (from 0.11 to 0.19%) towards its surface. |
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