Nd and Sr Isotope Composition in the Tooth Enamel from Fe–Mn Nodules of the Cape Basin (Atlantic Ocean): Age and Sources
- 29 Downloads
Abstract—The Nd and Sr isotope compositions were determined for the first time in biogenic apatite sampled throughout the tooth section (from the base to tip) of predatory fish in the nucleus of Fe–Mn nodules from the Cape Basin. The results showed that diagenetic recrystallization of apatite does not affect the 87Sr/86Sr ratio in the tooth enamel, but leads to the decrease of Sr content. The age of tooth was determined using Sr isotope stratigraphy at 5.2 ± 0.2 Ma for sample 2188/4 and 6.6 ± 0.3 Ma for sample 2188/5. The calculated growth rate of Fe and Mn oxyhydroxide layers varies within 0.4–2.8 mm per 1 Ma. The 143Nd/144Nd ratio in the tooth enamel varies within single station and depends on the local Nd sources in pore water. The value of εNd varies from –5.2 to –6.9 in the enamel of tooth 2188/4 and remains constant at –8.7 ± 0.1 in sample 2188/5. A change of Nd isotope composition in sample 2188/4 likely reflects temporal variations of Nd fraction from bottom and pore waters that penetrated inside the enamel during REE diffusion. The value of εNd in the oxyhydroxide layers of Fe–Mn nodule 2188/4 (from –7.8 to –7.9) is homogenous for the external and internal parts of the tooth. In order to use εNd in apatite enamel and authigenic Fe and Mn oxyhydroxides in sediments for paleoreconstructions of thermohaline water circulation, it is necessary to develop additional criteria for selecting diagenetically unaltered matter.
Keyword:Sr isotope stratigraphy Nd isotope composition of fish tooth Fe–Mn nodules Cape Basin
This work was supported by the Russian Foundation for Basic Research (project no. 17-05-00339), while technique of purification of biogenic apatite was developed in the framework of the IO RAS State Assignment (theme no. 0149-2014-0037).
- 3.A. V. Dubinin, “Inductively coupled plasma mass-spectrometry. Determination of the rare-earth elements in standard samples of oceanic bottom sediments,” Geokhimiya, No. 11, 1605–1619 (1993).Google Scholar
- 5.T. Edvin and Y. Rundberg, “Post-Eocene strata of the southern Viking Graben, northern North Sea; Integrated biostratigraphic, strontium isotopic and lithostratigraphic study,” J. Norwegian Geology 87, 391–450 (2007).Google Scholar
- 8.J. D. Gleason, T. C. Moore, D. K. Rea, T. M. Johnson, R. M. Owen, J. D. Blum, S. A. Hovan, and C. E. Jones, “Ichthyolith strontium isotope stratigraphy of a Neogene red clay sequence: calibrating eolian dust accumulation rates in the central North Pacific,” Earth Planet Sci. Lett. 202, 625–636 (2002).CrossRefGoogle Scholar
- 10.E. A. Gusev, A. B. Kuznetsov, E. E. Taldenkova, S. D. Nikolaev, A. Yu. Stepanova, and E. S. Novikhina, “Past sedimentation rates and environments of the Mendeleev Rise inferred from Sr isotope and δ18O chemostratigraphy of its Late Cenozoic sediments,” Dokl. Earth Sci. 473 (3), 354–358 (2017).CrossRefGoogle Scholar
- 19.A. B. Kuznetsov, D. V. Zarkhidze, A. V. Krylov, and A. V. Maslov, “Strontium isotope stratigraphy of Late Cenozoic deposits in the Timan–Uralian region by mollusk shells: definition of the Eopleistocene age,” Dokl. Earth Sci. 458 (6), 687–691 (2014b).Google Scholar
- 24.J. M. McArthur, R. J. Howarth, and G. A. Shields, “Strontium isotope stratigraphy,” The Geologic Time Scale 2012, Ed. by F. M. Gradstein, J. G. Ogg, M. Schmitz, and G. Ogg, (Elsevier, Amsterdam, 2012), pp. 127–144.Google Scholar
- 25.S. M. McLennan, “Rare earth elements in sedimentary rocks: influence of provenance and sedimentary processes,” Rev. Mineral. 21, 169–200 (1989).Google Scholar
- 32.N. V. Zarubina, M. G. Blokhin, P. E. Mikhailik, and A. S. Segrenev, “Determination of element composition of standard samples of ferromanganese sediments by inductively coupled plasma mass spectrometry,” Standartnye obraztsy, No. 3, 33–44 (2014).Google Scholar