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Aeolian sedimentation in Pribaikalye (Late Pleistocene–Holocene)
Quaternary International 355 (2015) 52e56
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Aeolian sedimentation in Pribaikalye (Late PleistoceneeHolocene) T.G. Ryashchenko, V.V. Akulova*, M.N. Rubtsova Institute of the Earth's Crust, Siberian Branch, Russian Academy of Science, 664033 Irkutsk, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 22 September 2014
The processes of aeolian sedimentation in the Pribaikalye (Late PleistoceneeHolocene) are reviewed. They gave rise to loessial deposits represented by sandy loams and cohesive sands (vQ3-4) and modern aeolian sands (vQ4) related to the development of a particular landscape type. © 2014 Elsevier Ltd and INQUA. All rights reserved.
Keywords: Eolian Pribaikalye Late Pleistocene Holocene
1. Introduction The reconstruction of formation conditions for the Quaternary deposits in southern East Siberia involves the processes of loess lithogenesis and characteristics of models proposed for Priangarye (combined), Zabaikalye (proluvial), and Pribaikalye (aeolian) (Ryashchenko et al., 2008, 2011, 2012). Of particular importance is the study of processes of aeolian sedimentation. Pribaikalye exemplifies the late PleistoceneeHolocene aeolian activity that led to the formation of thin (thickness up to 3 m) sheet-like deposits of loess and dune microrelief in the areas, for deposition of ancient and recent aeolian sands, and contributions to sediment accumulation in Lake Baikal (Fig. 1). 2. Loessial deposits of the aeolian complex Loessial deposits of the aeolian unit include sandy loams and cohesive sands (vQ33 e vQ3-4). They are deposited in the Selenga River basin on the surface of a 10e25-m high alluvial terrace and in the Tunka basin where they unconformably overlie the gruss and sand-pebble deposits of the Anosov suite (upper Neogene), Triassic (?) pyroclastic rocks, and middle Pleistocene fluvio-glacial sand and gravel (Fig. 1). In contrast to Pribaikalye, up to 15e20 m thick loessial deposits occupying the second-fifth terraces of the Angara River and its tributaries in the Irkutsk amphitheater (Upper Priangarye) were formed by deluvial processes (dQ33). The aeolian sedimentation was discontinuous and periodic (Fig. 1) (Ryashchenko, 2010).
* Corresponding author. E-mail addresses: [email protected] (T.G. Ryashchenko), akulova@crust. irk.ru (V.V. Akulova). http://dx.doi.org/10.1016/j.quaint.2014.08.016 1040-6182/© 2014 Elsevier Ltd and INQUA. All rights reserved.
The study of loessial deposits of the aeolian unit involves 14C dating of buried soil horizons in some of the cross-sections. The analyses were made in the Laboratory of Quaternary Paleogeography and Geochronology of the Faculty of Geography and Geoecology at Saint-Petersburg State University. As shown on 1937 aerial photographs, loessial sandy loams are present in a gully head near the village of Elovka (Figs. 1 and 2a). These deposits, 1.5e2.0 m thick, overlie Neogene formations of the Anosov suite of proluvial origin. Before the aeolian deposition, the Neogene proluvial strata had undergone extensive erosion. The erosion recurred as the gully incision has reworked the aeolian deposits, and partly Neogene sediments, to the Elovka River. Based on a radiocarbon date of 1040 ± 40 BP (Table 1) from the Elovka River floodplain deposits, the aeolian activity ended by late Holocene. Table 1 Radiocarbon age determinations for the buried soil samples. Area
Sample number e sampling interval, m
Laboratory number
Radiocarbon age, BP
Calendar age, BPa
Flood plain of the Elovka River Talskaya Mount Volcano (old pit)
T4 e 1.63e1.86
LU-5570
1040 ± 40
985 ± 60
T10 e 1.66e1.80
LU-5573
30,400
a
Calendar age determined from CAL 25 software.
The volcanogenic sedimentary rocks (Tunka valley, Talskaya Mount Volcano) are overlain by sheet-like aeolian loess bodies up to 3 m
T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
53
Fig. 1. Location of the investigated areas of aeolian deposits in Pribaikalye: 1 e Selenga River basin; 2 e Tunka basin e area near the Village of Elovka; 3 e old pit near the Talskaya Mount Volcano; 4 e Urochishche (stow) Badary; 5 e Khoitogol valley, 6 e Turan cross-section; 7 e Upper Priangarye; 8 e “Novorazvodnaya” Quarry near the Town of Irkutsk; 9 e Akademichesky Ridge; 10 e areas of research of aaeolian deposits.
thick (Fig. 1). The cross-section of an old pit revealed a buried soil horizon separating the deposits of the aeolian unit into two cyclothems (Figs. 1 and 2b). This horizon was radiocarbon-dated at 30,400 BP (Table 1). The formation of the upper part of deposits
(to a depth of 1.6 m) with evidence for cryogenic processes was assigned a later period. It is therefore expected that the lower cyclotherm formed in the late Pleistocene, and the upper one in the early Holocene. Along the right bank of the Irkut River near Datsan (Figs. 1 and 2), aeolian deposits, 1.5e2.5 m thick and composed of cohesive sands, are exposed above Neogene fluvial gravels (Turan crosssection). The cohesive sands are aeolian formations (vQ3-4) that were ordinary sands (without evidence for coherence) at the period of sedimentogenesis. During the post-diagenetic stage, the processes of loess lithogenesis (periglacial and cold semiarid climate type) turned these sands into a non-standard variety with loessial features. Among these features are macro porosity, aggregationbased skeletal microstructure, fine sediment, high carbonate content, and subsidence. 3. Modern aeolian sands
Fig. 2. Aeolian sheet (cohesive sands) covering the Neogene gravel-cobble sediments (a), Turan cross-section (b).
Modern aeolian sands prevail in the Tunka valley crossing the East Sayan piedmont area (Fig. 1). On the highland (Khoitogol valley), these sands form elongated dunes covered by vegetation (Fig. 3). On the lowland (Urotchishche Badary), the sands constitute dome-shaped dunes 3 m high, 75 m in diameter, and >0.5 km spacing (Fig. 4) (Akulov and Rubtsova, 2011). More than half of the aeolian sands deposited in Urotchishche Badary are medium-to-fine-grained (0.25e0.10 mm in diameter) (Fig. 5a). These sands are composed mainly of quartz (52%) and plagioclase (36%). The heavy minerals in the sands are dominated by amphiboles, diopside, and garnets (Figs. 5b and c). Similar grain size and composition also mark the aeolian sands deposited in the Khoitogol valley. Ancient (Pleistocene) aeolian sand deposits in the Tunka valley have higher contents of silt and unstable minerals, especially mica, epidote, sphene, and apatite groups.
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T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
Fig. 3. Modern aeolian sands of the Tunka basin (piedmont East Sayan area, Khoitigol valley).
4. Aeolian processes and lacustrine sedimentation in Lake Baikal It has been shown that a significant portion of sediment deposited in Lake Baikal is of aeolian origin (Votintsev and Mesheryakova, 1961; Agafonov, 1990; Vologina and Potemkin, 2001). Vologina and Fedotov (2013) attributed the abnormally high chloritoid contents in the late Pleistocene sediments capping the subaqueous Akademichesky Ridge in Lake Baikal to the more intense aeolian processes at that time, which brought chloritoid materials from the schists of the Anaiskaya suite in the upper reaches of the Lena River. By using the content of amphiboles, which are believed to originate from the outwash plains of Prisayanye and the Neogene proluval-alluvial formations of Prisayan depressions, Ryashchenko and Akulova (1998) were able to correlate the terrestrial aeolian sequences (Upper Priangarye) to the lacustrine deposits in Lake Baikal (Fig. 1, Table 2).
Table 2 Content (%) of amphibole and garnet (Upper Priangarye). Interval, (m)
Zone
Amphibole
Garnet
0e11 11e7 17e21 21e25
III II I Eluvial zone in Jurassic rock formation
15e40 5e32 1e5 <1
6e13 11e16 14e34 to 62
There is another interesting fact about the concentration of some microelements, chromium in particular. The chromium content was thoroughly determined in the cross-section of the “NovoRazvodnaya” Quarry (Irkutsk suburbs) where 23 samples were taken every 20 cm from the 0.3e0.6 m depth interval and its depth distribution curve was drawn (Figs. 1 and 6). The curve clearly shows the peaks corresponding to an abrupt (in 8e12 times) decrease in chromium content: 0.7 m (sample 2); 1.1 m (4); 2.3 m (11); and 4.5 m (19).
Fig. 4. Aeolian sands in Urotchishche Badary: a e formation of a dome-shaped dune; b, c e aeolian ripples of a deflation basin (b) and of the downwind side of a dune (c).
Fig. 5. Distribution of particle size classes (a), the mineral composition of the light fraction (b) and heavy minerals (c) of aaeolian sands in the section of the pit (Urotchishche Badary).
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T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
corresponding to an abrupt (8e12 times) decrease in chromium content can clearly be seen. 5. Conclusion 1. The processes of late PleistoceneeHolocene aeolian sedimentation gave rise to the formation of loessial deposits and sands. 2. The modern aeolian sands, which form distinct dunes, are medium-to-fine-grained and composed mainly of quartz and plagioclase with minor heavy minerals dominated by amphiboles, diopside, and garnets. 3. Amphiboles, chlorotoids, and chromium were delivered by aeolian processes, and can be used to interpret the sources of the sediments in Lake Baikal. References
Fig. 6. Variation of chromium content in loessial deposits (“Novorazvodnaya” Quarry).
We therefore hypothesize that aeolian processes stopped at certain periods, in which case chromium-poor elementary layers formed due to deluvial drift. The curve shows some rhythmicity of the upper loessial cyclite in the strata. Chromium content beyond the peaks is rather constant (110e140 ppm) and, therefore, aeolian processes were dominant during that period. The peaks
Agafonov, B.P., 1990. Exolithodynamics of the Baikal rift zone. Nauka, Novosibirsk, 176 pp. (in Russian). Akulov, N.I., Rubtsova, M.N., 2011. Aeolian deposits of rift zones. Quaternary International 234, 190e201. Ryashchenko, T.G., 2010. Regional Soil Science (East Siberia). Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Science, Irkutsk, 287 pp. (in Russian). Ryashchenko, T.G., Akulova, V.V., 1998. Soils of Southern East Siberia and Mongolia. Siberian Branch, Russian Academy of Science, Novosibirsk, 156 pp. (in Russian). Ryashchenko, T.G., Akulova, V.V., Erbaev, M.A., 2008. Loessial soils of Priangaria, Transbaikalia, Mongolia, and northwestern China. Quaternary International 179, 90e95. Ryashchenko, T.G., Akulova, V.V., Erbaev, M.A., 2012. Formation of loess-like deposits in Transbaikalia (a case study on sample plots). Geography and Natural Resources 4, 117e125 (in Russian). Ryashchenko, T.G., Akulova, V.V., Ukhova, N.N., 2011. Processes and loessal lithogenesis during the PleistoceneeHolocene (southeastern Siberia). Quaternary International 240, 150e155. Vologina, E.G., Potemkin, V.L., 2001. Characteristics of aeolian transport in the region of the Akademichesky Ridge (Lake Baikal) in winter period. Geologiya i Geofizika (Russian Geology and Geophysics) 1e2, 254e257. Vologina, E.G., Fedotov, A.P., 2013. Chloritoid in the bottom sediments of the Akademichesky Ridge of Lake Baikal, an indicator of aeolian transportation. Russian Geology and Geophysics 54 (1), 55e63. Votintsev, K.K., Mesheryakova, A.I., 1961. Role of aeolian transportation in formation of bottom sediments and chemical composition of water in Lake Baikal. Doklady Akademie Nauk SSSR 141 (6), 1426e1428 (in Russian).
Contents lists available at ScienceDirect
Quaternary International journal homepage: www.elsevier.com/locate/quaint
Aeolian sedimentation in Pribaikalye (Late PleistoceneeHolocene) T.G. Ryashchenko, V.V. Akulova*, M.N. Rubtsova Institute of the Earth's Crust, Siberian Branch, Russian Academy of Science, 664033 Irkutsk, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 22 September 2014
The processes of aeolian sedimentation in the Pribaikalye (Late PleistoceneeHolocene) are reviewed. They gave rise to loessial deposits represented by sandy loams and cohesive sands (vQ3-4) and modern aeolian sands (vQ4) related to the development of a particular landscape type. © 2014 Elsevier Ltd and INQUA. All rights reserved.
Keywords: Eolian Pribaikalye Late Pleistocene Holocene
1. Introduction The reconstruction of formation conditions for the Quaternary deposits in southern East Siberia involves the processes of loess lithogenesis and characteristics of models proposed for Priangarye (combined), Zabaikalye (proluvial), and Pribaikalye (aeolian) (Ryashchenko et al., 2008, 2011, 2012). Of particular importance is the study of processes of aeolian sedimentation. Pribaikalye exemplifies the late PleistoceneeHolocene aeolian activity that led to the formation of thin (thickness up to 3 m) sheet-like deposits of loess and dune microrelief in the areas, for deposition of ancient and recent aeolian sands, and contributions to sediment accumulation in Lake Baikal (Fig. 1). 2. Loessial deposits of the aeolian complex Loessial deposits of the aeolian unit include sandy loams and cohesive sands (vQ33 e vQ3-4). They are deposited in the Selenga River basin on the surface of a 10e25-m high alluvial terrace and in the Tunka basin where they unconformably overlie the gruss and sand-pebble deposits of the Anosov suite (upper Neogene), Triassic (?) pyroclastic rocks, and middle Pleistocene fluvio-glacial sand and gravel (Fig. 1). In contrast to Pribaikalye, up to 15e20 m thick loessial deposits occupying the second-fifth terraces of the Angara River and its tributaries in the Irkutsk amphitheater (Upper Priangarye) were formed by deluvial processes (dQ33). The aeolian sedimentation was discontinuous and periodic (Fig. 1) (Ryashchenko, 2010).
* Corresponding author. E-mail addresses: [email protected] (T.G. Ryashchenko), akulova@crust. irk.ru (V.V. Akulova). http://dx.doi.org/10.1016/j.quaint.2014.08.016 1040-6182/© 2014 Elsevier Ltd and INQUA. All rights reserved.
The study of loessial deposits of the aeolian unit involves 14C dating of buried soil horizons in some of the cross-sections. The analyses were made in the Laboratory of Quaternary Paleogeography and Geochronology of the Faculty of Geography and Geoecology at Saint-Petersburg State University. As shown on 1937 aerial photographs, loessial sandy loams are present in a gully head near the village of Elovka (Figs. 1 and 2a). These deposits, 1.5e2.0 m thick, overlie Neogene formations of the Anosov suite of proluvial origin. Before the aeolian deposition, the Neogene proluvial strata had undergone extensive erosion. The erosion recurred as the gully incision has reworked the aeolian deposits, and partly Neogene sediments, to the Elovka River. Based on a radiocarbon date of 1040 ± 40 BP (Table 1) from the Elovka River floodplain deposits, the aeolian activity ended by late Holocene. Table 1 Radiocarbon age determinations for the buried soil samples. Area
Sample number e sampling interval, m
Laboratory number
Radiocarbon age, BP
Calendar age, BPa
Flood plain of the Elovka River Talskaya Mount Volcano (old pit)
T4 e 1.63e1.86
LU-5570
1040 ± 40
985 ± 60
T10 e 1.66e1.80
LU-5573
30,400
a
Calendar age determined from CAL 25 software.
The volcanogenic sedimentary rocks (Tunka valley, Talskaya Mount Volcano) are overlain by sheet-like aeolian loess bodies up to 3 m
T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
53
Fig. 1. Location of the investigated areas of aeolian deposits in Pribaikalye: 1 e Selenga River basin; 2 e Tunka basin e area near the Village of Elovka; 3 e old pit near the Talskaya Mount Volcano; 4 e Urochishche (stow) Badary; 5 e Khoitogol valley, 6 e Turan cross-section; 7 e Upper Priangarye; 8 e “Novorazvodnaya” Quarry near the Town of Irkutsk; 9 e Akademichesky Ridge; 10 e areas of research of aaeolian deposits.
thick (Fig. 1). The cross-section of an old pit revealed a buried soil horizon separating the deposits of the aeolian unit into two cyclothems (Figs. 1 and 2b). This horizon was radiocarbon-dated at 30,400 BP (Table 1). The formation of the upper part of deposits
(to a depth of 1.6 m) with evidence for cryogenic processes was assigned a later period. It is therefore expected that the lower cyclotherm formed in the late Pleistocene, and the upper one in the early Holocene. Along the right bank of the Irkut River near Datsan (Figs. 1 and 2), aeolian deposits, 1.5e2.5 m thick and composed of cohesive sands, are exposed above Neogene fluvial gravels (Turan crosssection). The cohesive sands are aeolian formations (vQ3-4) that were ordinary sands (without evidence for coherence) at the period of sedimentogenesis. During the post-diagenetic stage, the processes of loess lithogenesis (periglacial and cold semiarid climate type) turned these sands into a non-standard variety with loessial features. Among these features are macro porosity, aggregationbased skeletal microstructure, fine sediment, high carbonate content, and subsidence. 3. Modern aeolian sands
Fig. 2. Aeolian sheet (cohesive sands) covering the Neogene gravel-cobble sediments (a), Turan cross-section (b).
Modern aeolian sands prevail in the Tunka valley crossing the East Sayan piedmont area (Fig. 1). On the highland (Khoitogol valley), these sands form elongated dunes covered by vegetation (Fig. 3). On the lowland (Urotchishche Badary), the sands constitute dome-shaped dunes 3 m high, 75 m in diameter, and >0.5 km spacing (Fig. 4) (Akulov and Rubtsova, 2011). More than half of the aeolian sands deposited in Urotchishche Badary are medium-to-fine-grained (0.25e0.10 mm in diameter) (Fig. 5a). These sands are composed mainly of quartz (52%) and plagioclase (36%). The heavy minerals in the sands are dominated by amphiboles, diopside, and garnets (Figs. 5b and c). Similar grain size and composition also mark the aeolian sands deposited in the Khoitogol valley. Ancient (Pleistocene) aeolian sand deposits in the Tunka valley have higher contents of silt and unstable minerals, especially mica, epidote, sphene, and apatite groups.
54
T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
Fig. 3. Modern aeolian sands of the Tunka basin (piedmont East Sayan area, Khoitigol valley).
4. Aeolian processes and lacustrine sedimentation in Lake Baikal It has been shown that a significant portion of sediment deposited in Lake Baikal is of aeolian origin (Votintsev and Mesheryakova, 1961; Agafonov, 1990; Vologina and Potemkin, 2001). Vologina and Fedotov (2013) attributed the abnormally high chloritoid contents in the late Pleistocene sediments capping the subaqueous Akademichesky Ridge in Lake Baikal to the more intense aeolian processes at that time, which brought chloritoid materials from the schists of the Anaiskaya suite in the upper reaches of the Lena River. By using the content of amphiboles, which are believed to originate from the outwash plains of Prisayanye and the Neogene proluval-alluvial formations of Prisayan depressions, Ryashchenko and Akulova (1998) were able to correlate the terrestrial aeolian sequences (Upper Priangarye) to the lacustrine deposits in Lake Baikal (Fig. 1, Table 2).
Table 2 Content (%) of amphibole and garnet (Upper Priangarye). Interval, (m)
Zone
Amphibole
Garnet
0e11 11e7 17e21 21e25
III II I Eluvial zone in Jurassic rock formation
15e40 5e32 1e5 <1
6e13 11e16 14e34 to 62
There is another interesting fact about the concentration of some microelements, chromium in particular. The chromium content was thoroughly determined in the cross-section of the “NovoRazvodnaya” Quarry (Irkutsk suburbs) where 23 samples were taken every 20 cm from the 0.3e0.6 m depth interval and its depth distribution curve was drawn (Figs. 1 and 6). The curve clearly shows the peaks corresponding to an abrupt (in 8e12 times) decrease in chromium content: 0.7 m (sample 2); 1.1 m (4); 2.3 m (11); and 4.5 m (19).
Fig. 4. Aeolian sands in Urotchishche Badary: a e formation of a dome-shaped dune; b, c e aeolian ripples of a deflation basin (b) and of the downwind side of a dune (c).
Fig. 5. Distribution of particle size classes (a), the mineral composition of the light fraction (b) and heavy minerals (c) of aaeolian sands in the section of the pit (Urotchishche Badary).
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T.G. Ryashchenko et al. / Quaternary International 355 (2015) 52e56
corresponding to an abrupt (8e12 times) decrease in chromium content can clearly be seen. 5. Conclusion 1. The processes of late PleistoceneeHolocene aeolian sedimentation gave rise to the formation of loessial deposits and sands. 2. The modern aeolian sands, which form distinct dunes, are medium-to-fine-grained and composed mainly of quartz and plagioclase with minor heavy minerals dominated by amphiboles, diopside, and garnets. 3. Amphiboles, chlorotoids, and chromium were delivered by aeolian processes, and can be used to interpret the sources of the sediments in Lake Baikal. References
Fig. 6. Variation of chromium content in loessial deposits (“Novorazvodnaya” Quarry).
We therefore hypothesize that aeolian processes stopped at certain periods, in which case chromium-poor elementary layers formed due to deluvial drift. The curve shows some rhythmicity of the upper loessial cyclite in the strata. Chromium content beyond the peaks is rather constant (110e140 ppm) and, therefore, aeolian processes were dominant during that period. The peaks
Agafonov, B.P., 1990. Exolithodynamics of the Baikal rift zone. Nauka, Novosibirsk, 176 pp. (in Russian). Akulov, N.I., Rubtsova, M.N., 2011. Aeolian deposits of rift zones. Quaternary International 234, 190e201. Ryashchenko, T.G., 2010. Regional Soil Science (East Siberia). Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Science, Irkutsk, 287 pp. (in Russian). Ryashchenko, T.G., Akulova, V.V., 1998. Soils of Southern East Siberia and Mongolia. Siberian Branch, Russian Academy of Science, Novosibirsk, 156 pp. (in Russian). Ryashchenko, T.G., Akulova, V.V., Erbaev, M.A., 2008. Loessial soils of Priangaria, Transbaikalia, Mongolia, and northwestern China. Quaternary International 179, 90e95. Ryashchenko, T.G., Akulova, V.V., Erbaev, M.A., 2012. Formation of loess-like deposits in Transbaikalia (a case study on sample plots). Geography and Natural Resources 4, 117e125 (in Russian). Ryashchenko, T.G., Akulova, V.V., Ukhova, N.N., 2011. Processes and loessal lithogenesis during the PleistoceneeHolocene (southeastern Siberia). Quaternary International 240, 150e155. Vologina, E.G., Potemkin, V.L., 2001. Characteristics of aeolian transport in the region of the Akademichesky Ridge (Lake Baikal) in winter period. Geologiya i Geofizika (Russian Geology and Geophysics) 1e2, 254e257. Vologina, E.G., Fedotov, A.P., 2013. Chloritoid in the bottom sediments of the Akademichesky Ridge of Lake Baikal, an indicator of aeolian transportation. Russian Geology and Geophysics 54 (1), 55e63. Votintsev, K.K., Mesheryakova, A.I., 1961. Role of aeolian transportation in formation of bottom sediments and chemical composition of water in Lake Baikal. Doklady Akademie Nauk SSSR 141 (6), 1426e1428 (in Russian).