428
ISSN 1028-334X, Doklady Earth Sciences, 2008, Vol. 419A, No. 3, pp. 428–431. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © V.A. Sankov, A.V. Parfeevets, A.I. Miroshnichenko, L.M. Byzov, M.A. Lebedeva, 2008, published in Doklady Akademii Nauk, 2008, Vol. 419, No. 6,
pp. 799–803.
The relationship between the Late Cenozoic tec-
tonic deformations at the Siberian Platform (SP) mar-
gin and the adjacent Baikal Rift System is considered.
This study was aimed at estimation of the stress state
and conditions of neotectonic reactivation of faults in
the sedimentary cover of the eastern Irkutsk Amphithe-
ater (the Angara–Lena Uplift and Fore-Baikal Trough
coupling zone). On the basis of geological, structural,
and geomorphic methods, the Late Cenozoic fault
assemblages were investigated and the related stress
field was reconstructed to provide evidence for interre-
lated deformation of the Baikal Rift and the SP margin.
The dynamic interaction of the SP block with the
surrounding fold systems at the neotectonic stage and
the evolution of the Late Cenozoic faulting remain
poorly studied. A.G. Zolotarev developed the concept
of fore-rift troughs [5 among others]. The brittle frac-
turing of the upper Pleistocene sediments was docu-
mented in the Fore-Sayan Foredeep [1, 8]. The exist-
ence of recent seismic activity of the platform has been
proven in [2]. Seminsky et al. [8 and others] attempted
to demonstrate the interrelation between the seismic
activity and deformations in the Baikal Rift. However,
these issues remain insufficiently studied because of
short-term instrumental measurements and the absence
of seismic station network on the platform.
The northeastern part of the Irkutsk Amphitheater of
the SP is characterized by medium-intensity neotec-
tonic uplifting with an amplitude of 800 m relative to
the initial surface [4]. Such values have been estimated
for the Angara–Lena Uplift. The Fore-Baikal Trough,
which extends on the eastern side along the SP margin,
ascended less intensely (amplitude of vertical move-
ments was not greater than 200 m). The difference in
the present-day hypsometric position of these struc-
tures suggests a rather high velocity gradient of neotec-
tonic vertical movements in their coupling zone, pro-
viding prerequisites for differential motions along fault
zones.
The schematic map of faults in the Fore-Baikal
Trough and Angara–Lena Uplift coupling zone (Fig. 1)
is based on the interpretation of satellite images and
aerial photographs, analysis of a digital 3D model of
topography, results of field geostructural and geomor-
phic observations, and compilation of the State Geolog-
ical Mapping data.
The faults in the study territory make up a rather
dense network in comparison with inner sectors of the
SP, probably owing to the closeness with the Sayan–
Baikal mobile region. Paleozoic folds and faults signif-
icantly controlled the development of local neotectonic
structures. The northern part of the territory is domi-
nated by submeridional faults that reflect the general
strike of older linear structures in the study region
(Kirenga fold zone [3]). The NE-trending faults inherit
structures of the Zhigalovo–Tulukmur fold zone. The
neotectonic reactivation stage is characterized by non-
uniform manifestation over the study area (Fig. 1).
Judging from the density of neotectonic faults, the
northern Fore-Baikal Trough and the zone of its cou-
pling with the Angara–Lena Uplift were most active.
The maximums of fault density are confined to the
Khanda (southern end), Baldakhin’ya, and Novoselovo
basins. The platformal sedimentary cover in the northern
Angara–Lena Uplift is marked by minimum faulting.
Faults active at the neotectonic stage are divided
into two nearly equal (submeridional and northeastern)
varieties (Fig. 2). The longest faults are submeridional
ones, e.g., faults framing the Khanda, Baldakhin’ya,
and Novoselovo basins and faults in the Khanda–
Kirenga interfluve. Typical NE-trending faults are rep-
resented by the North Zhigalovo, Tutura–Chikan, and
Karam faults that bound the Tutura–Chikan and Karam
basins, respectively. The basins are filled with the upper
Miocene–Pleistocene sediments. Normal faults are pre-
dominant, although thrust faults are also noted at the
immediate boundary with the platform [4].
Coupling of Late Cenozoic Faulting
of the Siberian Platform Margin and Baikal Rifting
V. A. Sankov, A. V. Parfeevets, A. I. Miroshnichenko, L. M. Byzov, and M. A. Lebedeva
Presented by Academician Yu.G. Leonov April 6, 2007
Received April 10, 2007
DOI:
10.1134/S1028334X08030161
Institute of the Earth’s Crust, Siberian Branch,
Russian Academy of Sciences, ul. Lermontova 128,
Irkutsk, 664033 Russia
GEOLOGY