GEOLOGICA CARPATHICA, 49, 1, BRATISLAVA, FEBRUARY 1998
THE DEVONIAN PALEOMAGNETIC POLE FOR THE SOUTHERN
PART OF THE RUSSIAN PLATFORM (DONETS BASIN)
AND ITS GEODYNAMIC IMPLICATION
Institute of Geophysics, Ukrainian Academy of Sciences, Palladin av. 32, 252680 Kiev-142, Ukraine
(Manuscript received March 18, 1997; accepted in revised form December 11, 1997)
Abstract: Detailed paleomagnetic studies of Middle-Upper Devonian sedimentary and volcanic rocks from the zone
of the junction of the Donbass with the Near-Azov block of the Ukrainian Shield have detected the following main
components of natural remanent magnetization: B-metachronic component (R-polarity) whose nature is secondary on
the basis of the data of statistical tests (before and after tectonic correction) and magnetic-mineralogical studies: A1
and A2-synchronous (N and R-polarity) is interpreted as having been acquired during deposition. The southern paleo-
magnetic pole calculated from mean directions the B-component (Lat. = 36
, Long. = 338
, dp = 6.6
, dm =3.4
agrees well with the paleomagnetic poles of Permian sediments of the Donets Basin. The paleopoles calculated from
A1 (Middle Devonian) and A2 (Upper Devonian) components have the following coordinates: A1 (Lat. = 13
, Long. =
, dp = 9.8
, dm = 4.9
) and A2 (Lat. = 3.7
, Long. = 359
, dp = 4.7
, dm = 2.3
). The significant deviation of
paleopoles A1 and A2 from the Eifel-Famenian segment of APWP for Baltica may reflect the effect of the local tectonic
rotation of the block enclosing the rocks studied.
Key words: Middle-Upper Devonian rocks, magnetization components, paleomagnetic poles.
In recent yearsnew confident data on the position of paleo-
magnetic poles in the Devonian have been obtained for the
East-European platform (EEP). EEP sediments in normal sec-
tions show clearly enough the pole positions in the Early De-
vonian (Smethurst & Khramov 1992; Orlova 1992; Mikhailo-
va et al. 1994). Less clear are the poles of Middle and
especially the Late Devonian since they are similar to Permi-
an ones. This is illustrated by synthetized curves of APWP
set up for the Baltic region (Torsvik et al. 1992; Lewandows-
ki 1993) which the autors consider to be a great part of the
East-European platform. According to these curves, the pale-
omagnetic pole was shifted in the Devonian from an equatori-
al latitude (Early Devonian) to the latitude of the Permian-
Carboniferous poles (Late Devonian).
The present paper aimes to elucidate the results of paleo-
magnetic studies of the clearly stratified Middle-Upper De-
vonian sediments from the Donbass-Near-Azov-block junc-
tion zone of the Ukrainian Shield, including studies of their
The Eufelian-Famenian sedimentary-volcanic rocks of the
Donets Basin are a continuous succession of four formations
(upwards): Nikolaevskaya (Middle Devonian), Antonovskaya
(Middle-Upper Devonian), Dolginskaya and Razdolnenskaya
(Upper Devonian) (Aizenverg & Lagutin 1974) with normal
stratigraphic boundaries and subhorizontal occurrence. Togeth-
er with overlaying Carboniferous sediments this mass forms
the so-called southern stepped monocline of the Donbass dip-
ping northward at an angle to 1020
(Fig. 1c,d). Lithological-
ly, the Middle and Upper Devonian sediments are gravelites,
differently composed and grained sandstones, argillites, volca-
nic tuffs (Fig. 1b). In the middle part a mass of differently com-
posed effusives occurs. Their age is estimated at 387360 Ma.
Methods of sampling and laboratory studies
Within the territory considered of sedimentary and volcanic
rocks one in the area of Nikolaevka village 10 partial
sections and another in the area of Razdolnoe village 2
partial sections (Fig. 1b,c) were studied. The tested thickness
of the former and the latter sections is 384 m and 232 m re-
spectively. The oriented samples were taken at 15 m inter-
vals along the section. The sedimentary and the majority of
the volcanic rocks were oriented in the bedding plane and for
the some effusives an arbitrary plane which was then referred
to a horizontal one. In general, the sampling was made by a
conventional method. Each section horizon is represented by
a thin sample from which at least eight 2
2 cm cubes
were then sawn up for further studies. The stratigraphic suc-
cession of the samples is shown on the lithologic columns of
the partial sections (Fig. 1c). Measuring of natural remanent
magnetization (NRM) and magnetic susceptibility were per-
formed with astalic magnetometers MA-21, LAM-2 and with
JR-3, KLY-1 devices.
The following laboratory tests were employed to deter-
mine the stability as well as the origin of the NRM: alternat-
ing field (AF) demagnetization with steps at 2.5, 7.5, 10,
16 mT up to 200 mT and thermal demagnetization (T) with
steps of 50100
C up to 700
C in field-free space; determi-
nation of partial thermo-remanent magnetization (PTRM),
Curie temperature (Tc), acid leaching HCl. Chemical leach-
ing of the secondary magnetic minerals was performed on
the cube samples with the special shaped cross-sections.
These cross-sections allowed enlargement of the surface of
the sample for more effective leaching by HCl acid. The du-
ration of the sample exposure in acid was different and it de-
pended on rock porosity and composition of ferrimagnetic
mineral (the minimal-exposure was 24 h and the maximal
one 220 h). After each leaching cycle the cubes were ex-
tracted from acid, washed with water, dried and measured.
The chemical leaching was continued till the separation of
magnetization component with stable orientation. This pro-
cedure was frequently combined with T-demagnetization. In
some cases the samples were first demagnetized by AF to 10
mT or exposed to acid during 24 h and then tested by thermal
method. The method for determination of original NRM
based on a comparison of the spectrum of isothermal rema-
nent magnetization (IRM) curves was devised by Cholpo
(1977, pers. com.). The NRM directions remaining after each
demagnetization step were analysed using the Zijderveld or-
tagonal vector projections. The magnetic minerals were iden-
tified by both the rock magnetic and microscopic methods.
Laboratory works were carried out by the instruments and ap-
paratus of the Institute of Geophysics of the UAS.
Fig. 1. The geological map of the paleomagnetic sampling area, showing the location of the sites of Middle-Upper Devonian sedimentary
and volcanic rocks in the Donets Basin with US joint zone. 1 Precambrian granites; 2 Upper-Middle Devonian sedimentary-volca-
nic rocks; 3 Middle Devonian volcanic; 4 Upper Devonian volcanics; 5 Carbonate sedimentary units; 6 faults; 7 Late Pale-
ozoic intrusions; 8 sampling sites (sections): 9 the points reflecting the stratigraphic order of sampling and the sample numbers (the
investigated thickness shown on the right side the partial sections); 10 sandstones; 11 volcanic tuffs; 12 argillites; 13 lime-
stones; 14 gravel; 15 map; 11, 22 cross sections lines. Numbers inside of a circle: 1, 2, 3, 10 Razdolnenskaya Formation
(D3 RS); 9,11 Antonovskaya Formation (D-2-3 AN); 48 Nikolaevskaya Formation (D2 N).
THE DEVONIAN PALEOMAGNETIC POLE FOR THE SOUTHERN PART OF THE RUSSIAN PLATFORM 47
The magnetic properties of the sedimentary and volcanic
rocks were described in a previous study (Orlova 1992;
Mikhailova et al. 1994).
Combined laboratory studies show inhomogeneity of the
NRM composition of the rocks studied. Together with the one-
component magnetization generally marked in effusives (Fig. 2,
samples 105, 59), the great majority of the rocks studied has
polycomponent NRM structure consisting of two or more com-
ponents of different orientation (Fig. 2, samples 40, 27).
The complicated NRM composition is shown by magnet-
ic-mineralogical analysis to be due to the concentration and
proportion of ferrimagnetic minerals of different generation
in rocks. These are firstly primary homogeneous magnetites,
titanomagnetite, synchronous in time with rock formation
which were presented as relicts of mostly greatly changed
grains in effusives and their detritus in sediment and second-
ary maghemite, titanomaghemite and hematite of oxides
which appeared both at the pre-lithification stage and during
diagenesis and finally, iron hydroxides formed in hypergenic
conditions. Together with multi-domain titanomagnetite and
fine-dispersed hematite they cause low-coercive including
The results of the component analysis have allowed sug-
gestion of the following interpretation:
1. Soft component oriented with present geomagnetic field.
It is generally destroyed by alternating magnetic field to
20 mT, heating to 100150
C and sometimes to 250
posure to concentrated HCl acid for 24 h. As this component
does not carry information on the ancient geomagnetic field it
has not been considered here.
2. B-component (R-polarity) that is hard in effusive rocks
(AF = 70 mT, T = 500600
C) and relatively soft in the
sediments (AF = 5200 mT, T = 20300
C) practically ex-
ists in all rocks of the studied sections. The tectonic correc-
tion for the tilt angle of the thickness (Fig. 4ac) showing
the change of the Fisher parameters k and
Fig. 2. Progressive T-demagnetization diagrams of A1, A2 andesite from the Antovskaya Formation sampled near village of Razdol-
noe, B basalt (v. Nikolaevka) from the Razdolnenskaya Formation. Open (closed) symbols represent projections of the end points of
NRM vectors on the vertical (horizontal) planes.
Fig. 3. The mean directions of characteristic magnetizations A1 and A2 with the circles of 95 % confidence: a the mean directions of
component A1 of the Nikolaevskaya and b Antonovskaya Formations (1, 2 from sections near village of Nikolaevka, 3, 4 sec-
tions near v. Razdolnoe), c the mean directions of component A2 of Razdolnenskaya Formation from sections near v. Nikolaevka, d
from sections near v. Razdolnoe.
cates the secondary post-fold nature of this component,
which agrees with the data of magneto-mineralogical studies
of rocks. The mean direction of the B-component of all sec-
tions studied D = 225
, I = 18
, coincides well with the di-
rection of synchronous magnetization of Permian sediments
of the Donets Basin (Chramov 1992 in Orlova 1992).
3. The hard component A1(R and N-polarity) exists in
NRM of some effusives and in sediments as a single compo-
nent, but in most cases together with the B-component. In the
sediments it is distinguished in the 20500
and in volcanites in 20450
C temperature range
(Fig. 3a,b). As seen from this figure the A1-component orien-
tation does not notably differ in the formations of the Ni-
kolaevskaya and Antonovskaya Formations (Middle Devo-
nian age). The mean direction of the A1 component is D =
, I = 4
for rocks of the Nikolaevskaya Formation in the
section near village of Nikolaevka. Similar A1-component di-
rections are seen for volcanites of the Antonovskaya Forma-
THE DEVONIAN PALEOMAGNETIC POLE FOR THE SOUTHERN PART OF THE RUSSIAN PLATFORM 49
Fig. 4. Tilt corrected characteristic mean directions of samples with the B-component show with the circles of 95 % confidens: a the
Nikolaevskaya Formation, b the Antonovskaya Formation, c the Razdolnenskaya Formation, d mean directions of the B-compo-
nents from the sections a, b, c corrected respecting the present day bed thicness; 1 mean direction, 2 the Nikolaevskaya Formation,
3 the Antonovskaya Formation, 4 the Razdolnenskaya Formation.
tion both in village of Nikolaevka section and near village of
Razdolnoye (Fig. 3a,b). Magneto-mineralogical data clearly
show the A1-component to be synchronous with the forma-
tion of rocks of Eufelian-Givetian age in the study region.
The mean directions calculated for rocks of all sections of
this age (Nikolaevskaya and Antonovskaya Formations) have
coordinates Dm = 292
, Im = 5
4. The hard component A2 (R and N-polarity) of Razdol-
nenskaya Formation (Upper Devonian age) oriented also with
a slight difference in directions both in near village of Ni-
kolaevka and near village of Razdolnoe sections, but notably
differs from A1-component in declination (Fig. 3c,d). The
mean direction of the A2-component Dm = 210
and Im = 3
roughly coincides with the Famenian geomagnetic field di-
rection for Baltica.
The A1 and A2 components are due to primary ferrimag-
netics of the first generation and are synchronous with the
rock formation moment, i.e. with the Devonian period. The
Age of the charac- D
The southern pole
teristic magneti- degree degree degree
Lat. Long. @
degree degree degree degree
5 9.81 10.7 19
12.7 289 9.84 4.94
3 4.66 25.1 36
37 359 4.66 2.33
(B-component) 225 18 6.34 12.9 38
36 338 6.58 3.42
Table 1: Mean paleomagnetic directions and pole position for
Middle-Devonian sedimentary and volcanic rocks determined in
this study, Donets Basin.
Fig. 5. Comparison of the paleopoles A1 and A2 with APWP for
Baltica (Lewandowski 1993). The poles rotated around the Euleri-
an pole located at the point 50N/39E. Such a rotation places the A1
and A2 poles at the Eifel-Vizean part (points 385 MA and 374
MA, respectively) of APWP.
B-component is a superimposed one and reflects the rock
maghemitization and hematization time.
From the statistically averaged orientations of the A1, A2
and B-components the paleomagnetic poles have been calcu-
lated (Table 1). Their comparison with a synthesized curve of
APWP in the Phanerozoic for the Baltic region (Fig. 5) shows
an agreement of the B-component pole with that of the curve
and the proximity of the A2 pole to it, though the curve seg-
ment age does not completely correspond with Famenian age
of the rocks studied. At the same time the result obtained,
gives reason to consider the high-latitude position of the Up-
per Devonian pole to be a feature of the Devonian geomag-
netic field, which agrees with the present viewpoint on this
problem (Torsvic et al. 1992; Lewandowski 1993) but it is not
the result of remagnetization of Devonian rocks by the Permi-
an field as was postulated earlier.
The significant north-westwards (A1-paleopole) and south-
eastwards (A2-poleopole) deviation from the Eifel-Famenian
segment of APWP for Baltica may be attributed to the clock-
wise rotation of the area in question by about 34
Middle Devonian and 17
in the anti-clockwise direction dur-
ing the Upper Devonian. This interpretation does not contra-
dict the geological insight into the Dnieper-Donets paleorift
formation, i.e. at the rifts formation moving apart of blocks
with rotation was of great importance as well as the earths
crust becoming less concentrated because of extension
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