Growth response of a deep-water ferromanganese crust to evolution of the Neogene Indian Ocean

摘要: Abstract A deep-water ferromanganese crust from a Central Indian Ocean seamount dated previously by 10 Be and 230 Th excess was studied for compositional textural variations that occurred throughout its growth history. The / 9 interval (upper 32 mm) yields an uniform rate of 2.8±0.1 mm/Ma [Frank, M., O'Nions, R.K., 1998. Sources Pb crusts: record Himalayan erosion. Earth Planet. Sci. Lett., 158, pp. 121–130.] which gives extrapolated age ∼26 Ma the base at 72 mm is comparable to maximum derived Co-model based estimates. This study shows Fe–Mn oxyhydroxide precipitation did not occur time emplacement during Eocene (∼53 Ma) until late Oligocene (∼26 Ma). paucity probably result nearly overlapping palaeo-CCD palaeo-depth formation, increased early productivity, instability reworking surface rocks on flanks seamount, lack oxic in nascent Ocean. Crust accretion began (older zone) with formation isolated cusps oxide high detritus influx, due early-Miocene intense erosion associated exhumation Himalayas (op. cit.). cuspate textured zone extends 42 representing period. Intense polar cooling mixing deep intermediate waters close might have led oxygenation bottom-water basin. considerable expansion vertical distance between seafloor depth CCD Miocene addition influx oxygenated likely initiated formation. Pillar structure characterises younger zone, 40 crust, i.e., ∼15 Present. characterised >25% higher content oxide-bound elements than older possibly corresponding further bottom-waters, stability slope, gradually reduced input continental Himalayas. Middle Antarctic glaciation, peaked ∼12–13 ago, basin resulting low detritus. Therefore, started accrete response shift circulation towards contemporary pattern, produced pillar up present.