Study area located near the village Filippovka in Orenburg Region, Cis-Ural, Russia
It is an accumulative limnetic-alluvial plain formed in the Neogene-Quaternary. The parent material is laminated, and can be characterized by light and middle loamy texture. In past the parent rocks contained many easily soluble salts. The modern climate is continental. Within the Chernozem-steppe belt of the Orenburg region, the climate is the warmest and driest in the study area: the mean temperature in January is –15°C, and that of +22°C in July. The mean annual precipitation is around 350 mm; evaporation exceeds the annual precipitation by 1.5 times. About 60% of the precipitation falls during the vegetation season. As a rule, the summer precipitation is represented as downpours which fall under high air temperature and vapor very quickly. High temperature periodicity on the soil surface is one of the unfavorable climatic phenomenon. In extreme cases, in June-July, the temperature reaches 65°C and even in September the soil surface may heat up to 50°C. Stable snow cover appears from the end of November; the average snowcover reaches 30-40 cm (110 cm at is maximum) and the average depth of the frozen soil layer is around 100-120 cm and reaches it’s maximum at the end of February. The Southern Chernozems (Aridic Mollisols) commonly develop on loamy sand parent material, and are predominant in the soil cover of the territory. These soil types are practically ploughed all over the examined area. The characteristic sign of the soils in the Cis-Ural steppe is taken to be a tongue-like lower boundary of the humus horizons. This phenomenon can be connected with the cracking of the soil mass. Very high soil surface temperatures in summer and the downward filtration of humus material in the cracks are responsible for these typical lower boundaries. Vegetation of rare non-arable sites is represented by steppe associations with the predominance of feather grass and Festuca species (Klevtsova et al., 2007).
Based on archaeological data the functioning period of the Filippovka 1 cemetery can be placed between the middle of the 5th century B.C. and the middle or end of the 4th century B.C.
Studying the morphological properties of paleosols and modern soil analogues has shown that paleosols can be divided into two groups. For paleosols buried under kurgans 1, 4, 15, 16, 26, 27 the more expressed "arid" signs were characteristic: the tongue-like lower boundary of humus horizon and organic accumulative horizons gentle painted by humus, weak digging up by burrowers in the uppermost 1 meter within the profile and distinct carbonate white soft spots in the Bk horizon. These paleosols showed reaction with HCl in the deeper sections as well. Paleosols buried under kurgans 11, 13, 23, 25, 28 showed more expressed "humid" signs: undulating lower boundary of humus horizon and its darker color, strong digging up by burrowers in the uppermost 1 meter within the profile and indistinct carbonate white soft spots more similar to impregnation in the Bk horizon.
The morphological signs in the modern background soils vary. The tongue-like lower boundary of humus horizon was clear expressed in profiles 115, 127. The humus horizon had homogeneous dark grey and grey color till the transition into the Bk horizon in profiles 111, 128. Transitional profiles in which the tongues in the humus horizon were only weakly expressed, occurred as well in the examined area. Variation in the depth of HCl effervescence in the profile of modern soils was high. For instance, in some soils, where the upper horizons were ploughed, the reaction with HCl coul be observed already from the surface, whereas in profile 128 this reaction only occurred from the depth of 80 cm. The simple hypothesis that a modern analogue soil for each paleosol is situated within the surroundings of its kurgans, appeared incorrect in most cases. Only for two pairs «modern analogue – paleosol» (profile Nr. 101 and 1, profile Nr. 115 and 15) this hypothesis was right, other pairs showed significant differences. As a result, field observations have already shown the absence of only one modern analogue for all the paleosols studied.
Comparison of the groups obtained by two means allow us to be sure to refer kurgans 1, 4, 15 and 27 to the earliest in the kurgan cemetery studied and kurgans 11, 13, 23 and 25 – to the latest. The paleosol buried under kurgan 28 for which the “humus” date did not turn out, has to refer to the latest group based on its set of morphological and analytical properties. The high degree of bioturbation also testifies to attribution of this paleosol to the humid paleosol group. The paleosol under the kurgan 16, based on its practically absolute resemblance with that under kurgan 15 has been referred to the earliest arid group (kurgans 1, 4, 27, 15). The kurgan 26 has been referred to the earliest arid group based on the absolute similarity of the set of morphological properties with the paleosols of the closest kurgan 27.
The conclusion about the heightened climatic continentality at that time has been earlier made based on the study of paleosols buried at the second part of the 5th century B.C. in the Pokrovka 10 (Malashev & Yablonskiy, 2008) and Shumaevo 2 (Morgunova et al., 2003) kurgan cemeteries in Orenburg region. Hence, the study of the paleosols in the Filippovka 1 kurgan cemetery confirmed that conclusion. In addition, the conclusion on intensification of humidity and softening of climatic continentality degree at the functioning period of the cemetery was done.
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