ISSN 01476874, Moscow University Soil Science Bulletin, 2013, Vol. 68, No. 1, pp. 10–19. © Allerton Press, Inc., 2013. Original Russian Text © V.E. Prikhod’ko, I.V. Ivanov, D.V. Manakhov, T.A. Sokolova, S.S. Chernyanskii, 2013, published in Vestnik Moskovskogo Universiteta. Pochvovedenie, 2013, No. 1, pp. 13–22.
SOIL GENESIS AND GEOGRAPHY
Physical, Chemical, and Mineralogical Characteristics of Steppe Paleosols of the Ural Region1 V. E. Prikhod’koa, I. V. Ivanova, D. V. Manakhovb, T. A. Sokolovab, and S. S. Chernyanskiic a
Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, Pushchino, 142290 Russia b Department of Soil Science, Moscow State University, Moscow, 119991 Russia c Institute of Ecological Planning and Research, Moscow, 119991 Russia email:
[email protected] Received April 17, 2012
Abstract—Investigation of paleosols with different ages of burial mounds and the unique fortified city of Arkhaim in the steppe zone of the Southern TransUrals (Chelyabinsk region) is carried out. They are located on the remnants of the Big Karaganka River valley. The time of construction of archaeological monuments dates back to the Early Iron Age (Sarmatian Culture, 2300–2200 years ago) and Middle Bronze Age (Sintashta culture, 3800–4100 years ago). The soils are of medium and light loamy granulometric composi tion. Morphological, chemical, and mineralogical investigations of paleosols and background soils indicate that, in the Sarmatian time, the climatic conditions in the region were drier than currently, while during the Sintashta cultural development, the climate of the region was similar to the present one. Keywords: steppe paleosols, properties, humus, clay minerals. DOI: 10.3103/S0147687413010067 1
Europe and North Khazakhstan were shown. The pos sibility of using various characteristics of humic acids isolated from paleosols for the reconstruction of the natural environment of natural and agrolandscapes of the past was revealed [8]. For the first time, a charac terization of paleosols of the Arkhaim settlement was given and they were compared with the submound soils of its necropolis. An analysis of the particularities of change in the soils of the Bronze and Early Iron Ages in various regions of Russia was performed, which is important for determining the rate and direc tion of their development with change in climatic parameters, for revealing climate variability, and for identifying the causes of colonization of the Ural region.
INTRODUCTION
Twentytwo fortified settlements and numerous archaeological monuments united in the Strana Gor odov complex have been found in the southern Trans Urals [10]. Many of them date back to the Middle Bronze Age and belong to the Sintashta archaeological culture (3700–4100 years ago), which goes back to the Ancient Yam historical community [10, 16, 17, 24]. It was named after the archaeological complex which is situated on the bank of the Sintashta River, Chelyab insk oblast. Paleosols of the great Sintashta mound were characterized [23, 25]. The first wellpreserved ancient settlement of the Bronze Age was found in 1987 and was given the name Arkhaim after Mount Arkhaim (398 m above sea level), which is the highest point of the area. To preserve this unique object, a nature reserve with the same name was founded in 1991. A deciphering of aerial photographs helped esti mate that archaeological monuments occupy around 1% of the territory of the Arkhaim valley [10]. The soils of various archaeological monuments of the Strana Gorodov were studied [12, 18, etc.]. Evolution of the TransUrals chernozems over the last 4000 years was characterized; the similarity and differences in their development compared with those of the Eastern
EXPERIMENTAL The objects of the study were paleosols buried under mound walls of the Arkhaim fortified settlement built at the turn of the third and second millennia BC and the mounds of its necropolis. The mounds were built 3900 and 2300 years ago in the valley of the Big Karaganka River near the village of Aleksandrovskii, which is situated 1.5 km from the Arkhaim Reserve. A detailed characterization of the paleosols of this necropolis is given in [12]. The monuments are located in the Bredinskii district of Chelyabinsk oblast (52° N, 58–60° E) and were studied by archaeologists
1 The
study was financially supported by the Russian Foundation for Basic Research (grant no. 090592106Yapha and reserve “Arkhaim”).
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PHYSICAL, CHEMICAL, AND MINERALOGICAL CHARACTERISTICS
under the direction of Professor G.B. Zdanovich. The basis of the fortification structures of the Arkhaim ancient settlement consisted of a ditch and inner and outer walls built of ground and wood. According to the calculations of archaeologists, the height of earthen rampart walls of the ancient settlement was 0.7 and 1.4 m; at present, it has decreased by approximately a factor of two. The archaeological monument is located on a residual gill of the proluvial–alluvial surface at the confluence of the Utyaganka River and Big Karaganka River (tributary of the Ural River) at an absolute height of 314.5 m above sea level and encompasses this surface almost completely. The size of the hill is 200 × 300 m2. It occupies a separate place since it is sur rounded by the floodplains of these rivers and a depression (former canal) from different sides. Mod ern background soils outside the hill occupy small areas. A field morphological method was used in studying the soils with a description and photographing. Reconstruction of the ecological conditions of past epochs was performed on the basis of comparing the properties of the buried paleosols and day background (modern) soils. Plots similar to the cultural–historical complex in absolute height above sea level were selected for the characteristic of background soils. Since the territories have varying granulometric com position of soilforming rocks and soils, 10 small trenches 50 cm in depth were dug out when choosing background soils for a comparison with paleosols. After their morphological analysis, the position of the main sections was chosen. The chemical properties of soils were determined using generally accepted meth ods [4, 5]. The silt fraction was isolated using the method of decantation according to Aidinyan [1] after the removal of carbonates. The mineralogical composi tion of silt was determined using the method of Xray diffractometry, and the quantitative content of distinct groups of silt minerals was estimated by the modified method of E.A. Kornblum [20]. The content of illites was determined by the gross content of K2O in the silt fraction on the basis of the supposition that illites con tain 7.5% potassium oxide. An analysis of the gross content of elements of the silt fraction of soils was per formed by P.I. Kalinin using a Spektroskan MAKC GV spectrometer at the Center of Collective Use of Scientific Equipment, Institute of Physicochemical and Biological Problems of Soil Science, Russian Academy of Sciences. The monuments were dated using the archaeologi cal method according to the periodization and chro nology of archaeological cultures and by the radiocar bon age of the humus of paleosols [10, 17]. Let us briefly describe the modern natural environ ment of the studied territory. The climate of the region is continental. The average annual temperature is +1 to +3°C, and the average temperatures in January and July are –17 to –18°C and +19 to +20°C, respectively. MOSCOW UNIVERSITY SOIL SCIENCE BULLETIN
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The sum of temperatures higher than 10°C is 1950– 2300°; the duration of the frostfree period is 111– 125 days. The amount of precipitation is 300–360 mm per year; of this amount, 45% falls in the summer as downpours and 10–12% falls in winter. The thickness of the snow cover does not exceed 0.25 m. The soils freeze to the depth of 0.8–2.0 m. The snow thaws on frozen soil, so the soil does not absorb the water. The annual evaporation amounts to 450–650 mm. The coefficient of humidification is 0.4–0.8. Hot, dry winds and deflation affect the soils and crops signifi cantly. Before the establishment of the reserve, the ter ritory around the butte was used as a pasture. The veg etative cover is represented by motley grass–fescue– feather grass association and shrubbery (spiraea and elm). RESULTS AND DISCUSSION Background (modern) soils of Arkhaim were studied in ten sections. The lithologic profile is as follows: the upper layer (80–100 cm) is represented by light loams and loamy sands with a large amount of particles of large and small sand (57–68%), as well as gravel and peb ble (6–17%). The lower underlying mass, 100–220 cm thick, consists of lamellar sand with alternating layers of grains with varying sizes. Therefore, no sections deeper than 1.8–2.2 m were dug. The granulometric composition of the upper horizons of the modern and ancient soils has no fundamental differences. A small weighting of it in the second halfmeter of background soils was observed, while a decrease in the content of physical clay was noted in the 50–100 cm layer of paleosols. The general properties of the soils are given in Table 1. The humus profile (A + AB horizons) of background soils is of small thickness (37 ± 4 cm; its range varies from 26 to 45 cm). The thickness of the A1 humus horizon is 22 ± 6 cm; it varies from 18 to 27 cm. The surface layer contains 3.04 ± 0.38% organic mat ter, which decreases abruptly down the profile: to 1.43 ± 0.18% in horizon AB and to 0.51 ± 0.14% in horizon Bca. An alternation of dark tongues with yel lowbrown wedges is registered in the upper part of the soil profile. The tongues are formed as a result of win ter frost penetration and summer dessication. Effervescence with 10% HCl in the material between humus tongues begins at a depth of 25–35 cm; uniform effervescence is observed in the 38–220 cm layer. At a depth of 37–53 cm, the content of carbonates amounts to 4.9 ± 3.7%. The maximum amount of car bonates is registered at a depth of 70–150 cm (9.3– 10.5%), while lower, in the subjacent mass, carbonates are not abundant. The weighted mean content of CaCO3 in the 0–10 cm layer is 7%. The carbonates are represented by rare spots, specks, and finedispersion form. Gypsum is observed from the depth of 50 cm. Beginning with the depth of 20–25 cm, easily soluble salts appear, and their content varies from 0.4 to 0.7%. The anion composition of easily soluble salts in the Vol. 68
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Table 1. Properties of background modern soils and paleosols buried under the walls of the Arkhaim settlement
Soil
Back ground, ordinary chernozem (section 6)
14 Å region. More precise diagnostics of these minerals is complicated owing to the low content and disorderliness of layer alternation. Within the limits of the entire mass, the mineralog ical composition of the clay fraction is somewhat dif ferentiated: compared with the horizons that lie lower, the humus horizon contains more illite and less kaolin in sum with chlorite owing to a decrease in the amount MOSCOW UNIVERSITY SOIL SCIENCE BULLETIN
Na2O
TiO2
3.16 2.84 2.50 2.24
0.75 1.14 1.07
0.76 0.83 1.10 0.70
0.79 0.36 0.49
2.02 1.77 1.35
1.41 1.54
0.64 0.69 0.60
0.63 0.51 0.42
2.39 2.27 1.66
1.11 1.17 1.23
1.04 0.97 0.65
of the latter. This pattern is confirmed by the decrease in the intensity of the 14 Å maximum after calcination at 550° and the decrease in the gross content of Fe2O3 in this horizon (Table 3). The increase in the number of illites in the composition of the clay fraction is char acteristic of chernozems and most other soils of the steppe zone and is explained by the processes of illiti zation [14, 15] and/or processes of physical fragmen tation of illite minerals that are part of larger fractions [2]. These processes flow the most intensely in the upper horizons. The decrease in the number of chlorites in the A1 horizon compared with the lower lying ones can be explained by its destruction or transformation changes as the least stable clay mineral [14, 15, 20]. Background (modern) soils of Aleksandrovskii vil lage by morphological and physicochemical proper ties are close to those of Arkhaim. Differences between them consist in a lesser amount of easily soluble salts and carbonates in modern soils near Aleksandrovskii village. Background soil is ordinary chernozem of small thickness, with low humus content, moderately and weakly calcareous, heavily solonetzic, and light loamy. Paleosols buried under the rampart walls of Arkhaim village. Seven soils were studied, in which the thick ness of the humus horizon (35 ± 4 cm) is close to back ground soils. The humus content of the profile of paleosols is slightly lower than that of modern soils. In the A1 horizon, the content of Corg constitutes 1.17%, the reconstructed Corg content is 2.93 ± 0.33, and that of background soils is 3.04 ± 0.38%. The reconstructed content of Corg is found from the calculation that, in the process of longterm burial of soils, it decreases by 60% as a result of diagenetic processes [11]. The morphology and location of humus tongues in the profile of buried and background soils are identi cal. In ancient soils of Arkhaim, the carbonate maxi mum is located at the same depth as in background Vol. 68
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14.7
3.6 3.4
10.8
7.3
20−35 cm
14.3
14.3
4.3
5.0 4.8
7.3
10.2 10.2
a
7.3
b
10.3
14.6 15
4.3
14.3
7.3 7.3
4.9
10.2 10.2
a
b
10.3
14.3
14.7
5.0
7.2
10.2
3.6 3.4
7.3
14.5
Section D371, paleosol, 3900 years ago 0−20 cm
c
c d d
3.6 3.4
10.2
7.3
3.4
14.5
25−40 cm
14.3
c
d
5.0 4.8 7.3
a b
7.2
10.3 10 10.2
7.3
14.3
b
14.7
3.2 3.9
4.3
6.4 5.9
7.3
5.0
3.6
7.3
12.6 10.3 10.3 10.3 10.3
a
14.3
14.3
19.2 14.5
14.8
Section D373, paleosol, 2200−2300 years ago 3−25 cm
c
d
Fig. 1. Xray diffractograms of the fraction
