The research laboratory “Geomorphologic and paleogeographic studies of Polar regions and World Ocean” was completely granted by the Government - 11.G34.31.0025. Up to the end of the year 2012, the researchers conducted a wide range of field, marine, cartographic and other studies [1]. After the Grant expired, on-going activities have mainly concentrated on geochronological dating and research. Thus, the latter will be considered. Reconstruction of palaeogeographical and geological events, recovery of history of environmental changes such as landscape, climatic and vegetation variations, sea level changes, etc. during Middle and Late Pleistocene and Holocene is based on comprehensive environmental studies including radioisotope dating results obtained for natural materials. We provide radioisotope geochronological research of Quaternary oceanic and terrestrial sediments applying U-series dating methods jointly with radiocarbon method. The solution of the tasks connected with expediency of application of one or other radioisotope methods means carrying out comprehensive radiochemical, geochemical and micropalaeontological investigations of varying sediment types. The results of the critical analysis of the theoretical framework and the improvement of the geochronology methods based on U-series radioisotopes in dating Quaternary oceanic and terrestrial deposits are reported. Our studies support both the 230Th- and 231Pa-methods of determining the age of pelagic sediments (including foraminiferal and metalliferous deposits) as well as ferromanganese nodules and crusts [2]. The case studies of foraminiferal and metalliferous sedimentary cores by 230Th- and 231Pa-dating in combination with 14C, 18O/16O, geochemical and micropalaeontological analyses are also reported. Growth rates of ferromanganese nodules and crusts from the Pacific Ocean determined by both methods of 230Th- and alpha-radiographic (alpha-track) dating [2]. Our analytical studies of mollusk shells showed that reliable 230Th/U-age can be obtained if the requirements of sampling and of radiochemical analysis are fulfilled. According to these recommendations we dated Eemian (Tyrrhenian) mollusk shells from the Black and Mediterranean seas [3]. Possibilities and limitations of the 230Th/U-dating of seafloor massive sulfide (SMS) deposits at the Mid-Atlantic Ridge (MAR) were substantiated experimentally and the first geochronological results were obtained [2, 4]. In recent two decades, the uranium-thorium (230Th/U) radioisotope method is used for dating terrestrial Interglacial (Interstadial) organic-rich deposits with age up to 300-350 ka [2, 5]. Up to now a strict approach to practical application of this method has not been devised and the 230Th/U dating of these deposits has not become a widely applied method. We initiated comprehensive radiochemical, radiochronological and biostratigraphical studies of organic-rich sediments to substantiate the capabilities and limitations of the 230Th/U-method for their dating. Up to now we have obtained a number of age data for the Late and Middle Interglacial/Interstadial buried deposits from the East European Plain and Siberia [2, 6, 7]. Case study of paired 14C and 230Th/U methods in dating organic-rich sediments from the North-Western Russia supports the reliability of the ages obtained [8]. First ages and prospects of 230Th/U dating of travertine and fossil wood remnants are discussed in the report [9]. Unfortunately, accumulated knowledge and skills of the laboratory team are presently being realized mostly within this, rather narrow from the scientific point of view, sphere. Researchers hope that wider projects will also start in coming years, especially those that are related to nationally extremely important Arctic studies.
[1] Antarctic. Geomorphologic atlas.International issue / A.N. Lastochkin, A.I. Zhirov, Y.M. Artemyev, S.F. Boltramovich & oth.SPb.: SPbSU, JSC "Karta", 2013, 168 p. [2] Kuznetsov V.Yu., Maksimov F.E., 2012. Metody chetvertichnoy geokhronometrii v paleogeografii I morskoy geologii (Methods of Quaternary Geochronometry in Palaeogeography and Marine Geology).Saint-Petersburg, Nauka.191 p. (in Russian). [3] Dodonov A.E., Trifonov V.G., Ivanova T.P., Kuznetsov V.Yu., Maksimov F.E., Bachmanov D.M., Sadchikova T.A., Simakova A.N., Minini H., Al-Kafri A.-M. and Ali O. Late Quaternary marine terraces in the Mediterranean coastal area of Syria: Geochronology and neotectonics // Quaternary International. 2008. Vol. 190. Issue 1. P. 158-170. [4] Kuznetsov V., Maksimov F., Zheleznov A., Cherkashov G., Bel’tenev V., Lazareva L. 230Th/U chronology of ore formation within the Semyenov hydrothermal district (13031’ N) at the Mid-Atlantic Ridge // Geochronometria. 2011. Vol. 38. P. 72-76. [5] Geyh M.A., Miller H. Numerical 230Th/U dating and palynological review of the Holsteinian/Hoxnian Interglacial // Quaternary Science Reviews. 2005. Vol. 24. P. 1861-1872. [6] N.G. Razjigaeva, L.A. Ganzey, T.A. Grebennikova, N.I. Belyanina, V.Yu. Kuznetsov, F.E. Maksimov. Last interglacial climate changes and environments of the Lesser Kuril arc, north-western Pacific // Quaternary International. 2011. Vol. 241. P. 35-50. [7] Maksimov F.E., Laukhin S.A., Arslanov Kh.A., Kuznetsov V.Yu., Shilova G.N. First 230Th/U date of Middle Pleistocene peat bog in Siberia (key section Krivosheino, Western Siberia) // Geochronometria. 2012. Vol. 39. No. 4. P. 241-251. [8] F. E. Maksimov, V.Yu. Kuznetsov, N. E. Zaretskaya, D. A. Subetto, V. V. Shebotinov, I. E. Zherebtsov, S. B. Levchenko, D. D. Kuznetsov, E. Larsen, A. Lyso, and M. Jensen. The First Case Study of 230Th/U and 14C Dating of Mid Valdai Organic Deposits //Doklady Earth Sciences. 2011. Vol. 438. Part 1. P. 598–602. [9] Nikitin M.Yu., Medvedeva A.A., Maksimov F.E., Kuznetsov V.Yu., Zherebtsov I.E., Levchenko S.B., Baranova N.G. Genesis and geological age of travertine carbonates from the Pudost Massive // Society, Environment, Development. 2012. No. 4. P. 231-236 (InRussian).