508
ISSN 1069-3513, Izvestiya, Physics of the Solid Earth, 2009, Vol. 45, No. 6, pp. 508–519. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © O.V. Pilipenko, Z.V. Sharonova, V.M. Trubikhin, H. Abrahamsen, 2009, published in Fizika Zemli, 2009, No. 6, pp. 44–55.
INTRODUCTION
The continuity and completion of a paleomagnetic
record, which allow its correlation with other paleo-
magnetic records of the same age, are necessary for the
study of geomagnetic field evolution. These conditions
restrict the number of natural objects suitable for the
study. Continental loess–soil sections are interesting
and rich in information. A high sedimentation rate
makes it possible to use such sections for reconstruct-
ing the pattern of geomagnetic field changes in the past.
In our previous works, we repeatedly studied the struc-
ture and evolution of the geomagnetic field in the Late
Pleistocene, which is recorded in loess–soil deposits of
the south of Russia and Ukraine (Pekla, Tuzla, and
Roxolany sections) [Sharonova et al., 2004; Pilipenko
et al., 2005; 2006; 2007]. However, it is difficult to find
loess–soil sections, which would preserve a continuous
consecutive record over a prolonged time interval. As
some authors believe, the process of soil formation can
completely rework any sediment [Shantser, 1982].
Other authors think that the sedimentation rate in a soil
horizon can be slowed down by over three times [Moro-
zova, 1981], which makes the dating of loess–soil com-
plexes difficult. Marine deposits presented by marine
terraces contain more detailed records of the newest
stage of geological events, although the age sequence
of deposits has often been the subject for discussion.
The section of the Karadzha Range (λ = 47°Ö, ϕ =
40°N, Mingechaur water storage reservoir, Azerbaijan)
is a unique object in terms of its completeness for the
study of geomagnetic field evolution over the past mil-
lion years. This section contains a complete sequence
of deposits about 1000 m thick, which corresponds to
the time interval from the Early to the Late Pleistocene,
inclusively. The presence of the volcanic-ash interlayer,
whose age is determined by the fission-track method at
~600 ka [Ganzei, 1984], allows the dating of late-Bak-
inskian deposits’ bedding on the Neopleistocene base.
Nondislocated deposits of two marine terraces in the
uppermost part of the Karadzha section are enclosed
into heavily dislocated Pleistocene late-Khazarian
deposits [Trubikhin, 1987]. The age of late-Khazarian
deposits in the Caspian basin is determined on the basis
of the available radioisotope dating [Popov, 1983] and
the geological correlation of these deposits with the
well-dated Late-Pleistocene Karangatian deposits of
the Black Sea [Geochronology of the USSR, 1984;
Arslanov et al., 1985; Dodonov et al., 2000] and corre-
sponds to the age of OI stage 5. The maximums of
transgressions of the Caspian and Black Sea basins in
the Holocene (OI stage 1) are virtually synchronous
and lie in the interval 4–6 ka ago [Geochronology of the
Anomalous Directions and Paleointensity of the Geomagnetic
Field Based on Paleomagnetic Investigations of Rocks
from the Karadzha Range (Azerbaijan) of the Age 45–20 ka
O. V. Pilipenko
a
, Z. V. Sharonova
a
, V. M. Trubikhin
b
, and N. Abrahamsen
c
a
Schmidt Institute of Physics of the Earth (IPE), Russian Academy of Sciences,
Bol’shaya Gruzinskaya ul. 10, Moscow, 123995 Russia
b
Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia
c
University of Aarhus, Aarhus, Denmark
Received May 12, 2008; in final form, November 13, 2008
Abstract—Paleomagnetic investigations of marine and subaqueous deposits in the 12-meter marine terrace of
a section of the Karadzha Range (Azerbaijan) are performed. These deposits correspond to OI stage 3 and
encompass the time interval ~45–20 ka. Four anomalous deviations of the magnetization from the dipole field
at the sampling site are recorded in the upper and lower transgressive members of deposits. Investigations of
the influence of the anisotropy of the magnetic susceptibility (AMS) on directions of the natural remanent mag-
netization (NRM) showed that only three of the four identified intervals can actually reflect geomagnetic field
changes. The fourth interval of the anomalous NRM behavior is recorded in samples demonstrating the pres-
ence of the identified AMS direction pointing to a possible deformation of layers, which could turn the NRM
vector toward the direction of the acting factor. Based on the age of the terrace under investigation, three other
anomalous horizons could correspond to heavily reduced records of the Mono and Lashamp excursions of the
geomagnetic field.
PACS numbers: 91.25.Ng; 91.25.Ux
DOI: 10.1134/S1069351309060044