ISSN 0869-5938, Stratigraphy and Geological Correlation, 2017, Vol. 25, No. 4, pp. 419–444. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © G.N. Aleksandrova, T.V. Oreshkina, P.V. Smirnov, A.O. Konstantinov, O.B. Kuzmina, 2017, published in Stratigrafiya, Geologicheskaya Korrelyatsiya,
2017, Vol. 25, No. 4, pp. 62–88.
Age and Genesis of the Upper Cenozoic Deposits
of the Tyumen Oblast (Western Siberia) Enriched in Biogenic Silica
G. N. Aleksandrova
*, T. V. Oreshkina
, P. V. Smirnov
A. O. Konstantinov
, and O. B. Kuzmina
Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia
Tyumen State Oil and Gas University, ul. Respubliki 47, Tyumen, 625000 Russia
Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences,
pr. Akad. Koptyuga 3, Novosibirsk, 630090 Russia
Received March 21, 2016; in final form, May 25, 2016
Abstract⎯An integrated micropaleontological study of deposits enriched in biogenic silica was conducted on
material drilled in the Zyryanka and Uspenka fields of the southwestern Tyumen oblast (Western Siberia).
The data obtained on palynology and diatoms allowed the assignment of the Zyryanka Field to the Turtas
Formation (lower part of the Chattian Stage of the Oligocene) and the deposits of the Uspenka Field to be
dated as Pleistocene. The absence in the Zyryanka Field diatom assemblage of in situ marine taxa and the
mass occurrence of freshwater species, gemmuloscleres of freshwater sponges, and zygospores of Zygnema-
tales algae suggest that a nonmarine basin existed in the early Turtas time. A considerable proportion of rede-
posited diatoms and dinocysts in the Quaternary deposits of the Uspenka Field suggest strong erosional pro-
cesses during the time of deposition.
Keywords: Oligocene, Pleistocene, stratigraphy, diatoms, palynomorphs, Tyumen oblast, Western Siberia,
In the southwestern part of Tyumen oblast, deposits
enriched in biogenic silica are often differently dated
during geological mapping works (Kuznetsov, 1963;
Kamenskikh, 1976; Sokolkin, 2012; Chanbaeva, 2013;
Smirnov et al., 2015). In accordance with the State
Geological Map of the Russian Federation (Gosudarst-
vennaya…, 2011), the Lower Oligocene Kurtamysh
Formation recognized in this region is composed of
fine-grained sands with layers of silt and clay, with
inclusions of lignitized wood and overlain by lacustrine-
alluvial deposits of terraces III–IV above the floodplain
(limnoalluvial, deluvium, and Neopleistocene loess).
Other data (Sokolkin, 2012; Chanbaeva, 2013) suggest
the occurrence of Quaternary deposits in the studied
area, underlain by the Upper Oligocene Turtas Forma-
tion, the top of which is recorded at a depth of 12–16 m.
Thus the age of these rocks is not reliably determined;
the same situation is typical of the border regions
between the Transuralian and Central facies districts of
the West Siberian region.
The purpose of this study is to update and refine
the stratigraphic position of these deposits, which is
important in the context of a detailed study of the sed-
imentary sequence and major geomorphological ele-
ments of the southwestern regions of Western Siberia
and Transuralia, and to recognize the main features of
geological and geomorphological processes in this
region in the Cenozoic. In addition, this region has
been extensively explored for mineral resources: build-
ing sand and ceramsite clay, groundwater, and, from
2014, siliceous resources (Smirnov and Ivanov, 2014;
Smirnov et al., 2015). Thus, the study of the strati-
graphic position of the productive horizons is import-
ant to locate the regions prospective for various min-
MATERIALS AND METHODS
Material. This study is based on samples from sec-
tions of exploration boreholes drilled in the Zyryanka
and Uspenka fields (Figs. 1, 2), prospective for biosili-
ceous deposits of the Paleogene Turtas Formation
(Smirnov et al., 2015). For the core drilling, we used a
PBU-2 post drill mounted on a ZIL121/N1.
The explored boreholes were located in terraces III–
IV over the floodplain on the interfluve of the Tura–
Pyshma rivers. The area is a slightly inclined plain with
absolute heights of 65–110 m and is slightly erosional.