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New age data of buried peat deposits from the site "Fili Park" (Moscow, Russia) by the uraniumthorium dating and palynological analysis and its stratygraphic significance

Kuznetsov V. Yu., Arslanov K. A., Alekseev M. N., Pisareva V. V., Chernov S. B., Maksimov F. E., Baranova N. G.

Geochronometria

2002

Vol. 21

41-48

The chronostratygraphically important Quaternary buried peats from the site "Fili Park" (located on the territory of Moscow) on the Russian Plain were studied by the methods of uranium-thorium dating (UTD) and palynological analysis. The deposits under study were the subject of intense debate: some number of the palynologists assigned ones to the Mikulino (Eem) Interglacial, while the another investigators - to the Odintzovo Interglacial (Middle Pleistocene). Detailed palynological study gave the possibility to mark out the 3 palynozones (M2, M3 and M4) in section vertical profile and refer the deposits to the Mikulino (Eem) Interglacial. The uranium-thorium dating (by "leachate alone" method) was carried out in the middle layers, which would be expected to be a closed system in respect to uranium and thorium isotopes. The direct uranium-thorium dating of inner layers showed the first UTD ages from 78.9 to 105.0 ka for deposits from the site "Fili Park". The corrected uranium-thorium age of buried peat turned out to be younger than the currently adopted boundaries of the last Interglacial (116-128 ka) and comprised 89š11 ka. There was probably an additional post-deposition uranium uptake in the internal section layers that in general have led to an underestimated age value. Nevertheless, we refered these questionable in chronostratigraphic respect deposits to the Mikulino Interlacial. The geochronological data obtained were compared with the uranium-thorium dating results (113š11 ka) for the closed geochemical samples from the Mikulino (Eem) Interglacial peats of the stratotypical section "Mikulino" (Russian Plain). This comparison confirmed the reliability of our conclusions.

230Th/U and 14C dating of mollusc shells from the coasts of the Caspian, Barents, White and Black Seas

Arslanov K. A., Tertychny N. I., Kuznetsov V. Yu., Chernov S. B., Lokshin N. V., Gerasimova S. A, Maksimov F. E., Dodonov A. E

Geochronometria

2002

Vol. 21

49-56

We dated Holocene and Late Pleistocene mollusc shells collected from coastal sediments of the Caspian, Barents, White and Black Seas by means of both a modified 230Th/U method and the radiocarbon method. Essence of the modification is the removal of the surface (about 1/3 of the weight) of the mollusc shells by nitric acid as it may contain adsorbed detrital 232Th and 230Th. The 230Th/U dates of the inner part of the shells do not require detrital correction with the 232Th activity and well agree with the corresponding reservoir-corrected and calibrated 14C ages of mollusc shells with ages between 1300 and 13,500 BP. We tested the modified 230Th/U method on thick-walled and well-preserved mollusc shells from the transgression sediments of the Barentz, White and Black Seas derived during the Mikulino Interglacial (MIS 5e) and the Early Valday Glaciation (MIS 5c). The 230Th/U ages of the inner part of the shells from the Boreal (Eem) transgression sediments of the Barentz and White Seas ranged from 86 to 114 ka and those from the Karangat (Eem) transgression in the Black Sea (Maly Kut and Eltigen sections) from 95 to 115 ka. The new 230Th/U dates of the shells from the section Eltigen ranged from 100 to 125 ka.

Rozwój systemu jaskiniowego Szczeliny Chochołowskiej (Tatry Zachodnie) w świetle wyników datowania nacieków metodą uranowo-torową

Hercman H., Nowicki T., Lauritzen S. E.

Studia Geologica Polonica

1998

Vol. 113

85-103

Datowanie 31 próbek nacieków z jaskini Szczelina Chochołowska metodą uranowo-torową umożliwiło rekonstrukcję warunków klimatycznych w okresie ostatnich 350 tysięcy lat w rejonie Doliny Chochołowskiej oraz etapów rozwoju jaskini. Wydzielono 7 generacji nacieków, które wskazują na okresy ciepłego, wilgotnego klimatu, oddzielone okresami pogorszenia warunków klimatycznych. Wyniki datowania nacieków w powiązaniu z obserwacjami z jaskini umożliwiły stwierdzenie 2 etapów rozwoju Szczeliny Chochołowskiej. Pierwszy etap tworzenia jaskini zakończył się około 350 tysięcy lat temu, a ponowne uaktywnienie krążenia wód i przemodelowanie części jaskini autorzy wiążą z rozwojem lodowca w okresie młodszego plejstocenu.

31 speleothem samples collected in Szczelina Chochołowska Cave (Western Tatra Mts., Poland) were dated using (Figs 1 & 2) 230Th/234U method (Ivanovich & Harmon, 1992). Dates spanning from 2 ka to ca 350 ka (a-particle counting, Tab. 1, Fig. 3) have been identified. On the basis of these dating results it was possible to estimate the climatic changes in Tatra Mts over the last 350 ka. Seven periods of speleothem crystallisation were recognised from the data (Fig. 4). These record periods of warm, humid conditions separated by cold, dry ones marked by breaks in speleothem deposition. The development of the Szczelina Chochołowska Cave is show schematically in Fig. 5. Some 350 ka ago the valley floor was ca 35-45 m above its present level. The passages between cave entrances III and II were dry and speleothem crystallisation was able to start. The second stage of cave activity followed with water flow between III and I entrances and Rura passage development. The water flow through Rura was extorted by big rock fall in Ślepa Komora ca 115-95 ka ago. Later, glacier development in Chochołowska Valley probably created a hydrological barrier in the valley and the water used the older cave passages as a simpler way of circulation.