Dataset on the soils of medieval archaeological monuments in the forest-steppe zone of the East European plain

One of the natural archives that can save information about the environmental conditions of the past is soils buried under embankments of burial complexes. Due to isolation from external environmental factors soils retain information about the features of the natural environment at the time of its burial. In this work we present a dataset on soils buried under four mounds in the Middle Ages. The soils were buried under mounds in a short time interval – 25–50 years. For comparison, the data on the surface soil located near the barrows are also presented. Obtained dataset includes detailed morphological field description of the soils and their physico-chemical analysis, such as granulometry, elemental analysis, fractions of iron and selected chemical data. Obtained data can be used to identify the dynamics of forest-steppe landscapes in the XIth century. The Medieval Warm Period and the subsequent humidisation of the climate over a short time interval had a significant impact on natural conditions and the migration of the population of the steppes of Eurasia. A comparative analysis of the properties of soils buried under archaeological sites of different ages allows examining in details the changes in the natural environment and its components over time. Moreover, soils are capable of storing a whole range of additional features of non-pedogenic origin that can be used for a more detailed reconstruction of the natural environment. The data on spores, pollen and non-pollen palynomorphs of the soil profiles are also presented in this article.


a b s t r a c t
One of the natural archives that can save information about the environmental conditions of the past is soils buried under embankments of burial complexes. Due to isolation from external environmental factors soils retain information about the features of the natural environment at the time of its burial. In this work we present a dataset on soils buried under four mounds in the Middle Ages. The soils were buried under mounds in a short time interval -25-50 years. For comparison, the data on the surface soil located near the barrows are also presented. Obtained dataset includes detailed morphological field description of the soils and their physicochemical analysis, such as granulometry, elemental analysis, fractions of iron and selected chemical data. Obtained data can be used to identify the dynamics of forest-steppe landscapes in the XIth century. The Medieval Warm Period and the subsequent humidisation of the climate over a short time interval had a significant impact on natural conditions and the migration of the population of the steppes of Eurasia. A comparative analysis of the properties of soils buried under archaeological sites of different ages allows examining in details the changes in the natural environment and its components over time. Moreover, soils are capable of storing a whole range of additional features of non-pedogenic origin that can be used for a more detailed reconstruction of the natural environment. The data on spores, pollen and nonpollen palynomorphs of the soil profiles are also presented in this article.
© 2020 The Author(s  [1] , soil colour was determined in the field using the Munsell Soil Colour Charts [2] , field identification of soils was performed according to the WRB [3] . Laboratory analyses were performed on samples taken equidistantly (10 cm down to 1 m and 20 cm below 1 m). The elemental analysis was performed using the X-ray fluorescence spectrometry method after loss on ignition determination (10 0 0 C) using the Philips PW2400 Sequential WXRF Spectrometer (Malvern Panalytical, Almelo, The Netherlands). Two methods to determine the granulometric composition of soils were used: pipette method, in which soil is dispersed by treating with a solution of sodium pyrophosphate (Na 4 P 6 O 18 ) and laser granulometry method on the device "Analysette 22. Laser Klasse 1. Fritsch". The dithionite and oxalate extractable fractions of iron were acquired according to Mehra and Jackson [4] and analysed using a Cary 60 Spectrophotometer (Agilent Technologies, the USA); the total carbonate content was determined on the base of the destruction of CaCO 3 by acid and subsequent precipitation of the carbonate ion [5] ; рН in water suspension (soil: water ratio 1:2.5) were analysed using standard methods [6] .

Value of the data
• Data contained can be used for paleoclimatic reconstrutions of the second half of the Holocene in the forest-steppe zone. • Data may be useful for researches who studying soil genesis and evolution.
• Data provides wide range of analysis of the surface and certain buried soils in XI century AD. • Data could be useful for palynologists to supplement existing spore-pollen data for the Medieval time period. • Data on archaeological objects obtained by a combination of various natural-scientific methods can give the ideas about the migration of ancient ethnic groups. Fig. 1 shows location of the dataset area and soil images with boundaries and indexes of the horizons according to the FAO Guidelines for Soil Description [1] .

Dataset area and objects
Archaeologiacl excavations of the Gochevsky archaeological complex located on the right bank of the river Psel near settlement Gochevo, Belovsky district, Kursk region, were provided in 2019. The area is located within the Central Russian forest-steppe province of the East European Plain. Gochevsky burial ground contains funeral rites of the old Russian population of the southeast of Russia at the end of the X -XII centuries AD. All pits are located in a watershed surface under a forestland in Kursk region.
Soils buried under four mounds were examined. The soil profile can be considered as a data archive containing unique information about the features of past natural settings. All mounds were built in onetime interval but the difference between them is 25-50 years. The thickness of the mounds is 40-60 cm. The buried and surface soils were formed on the same topographical position, under the forestland and on the similar loess sediments. The distance between soils is ∼20 m. To compare the conditions of the past to the modern ones, the surface soil was also studied (1f-19). The soil 2b-19 was buried in the second half of XIth century, when the soils 3b-,4b-,5b-19 were buried in the second quarter/middle of XIth century. Samples for spore-pollen analysis from soil 2b-19 and 5b-19 were taken in two replicates due to fuzzy border of the buried soils. All soils were identified according to the WRB [3] as Greyzemic Luvic Phaeozem Cutanic .

Sampling and laboratory analysis
Samples from buried soils were collected below the burial embankment. Soil samples were taken from every 10 cm down to 1 m and 20 cm before 1 m but leaving the boundaries of the soil horizon intact. Samples for the spore-and-pollen analysis were collected from the upper 0-5 cm of buried and surface soils.
The soils were described according to the FAO Guidelines for Soil Description [1] . Soil colour was determined in the field using the Munsell Soil Colour Charts [2] .    The total carbonate content was determined on the base of the destruction of CaCO 3 by acid and subsequent precipitation of the carbonate ion [5] рН in water suspension (soil: water ratio 1:2.5) were analysed using standard methods [6] . Carbon and nitrogen content for C/N ratio were obtained using CHNS Elementar Analysensysteme. Dithionite and oxalate extractable fractions of iron were determined according to Mehra and Jackson [4] .
Two methods to determine the granulometric composition of soils were used: pipette method, in which soil is dispersed by treating with a solution of sodium pyrophosphate (Na 4 P 6 O 18 ) and laser granulometry method on the device "Analysette 22. Laser Klasse 1. Fritsch".
For elemental analysis, ∼1 g of sample was dried in the oven at 105 °C. Samples were powdered, and mixed with a lithium tetraborate flux and then melted to produce a glass disc. The concentrations of major and trace elements were analysed by XRF after the determination of the loss on ignition (10 0 0 °C).
The taxonomic identification of microfossils was carried out using published keys and atlases [7][8][9] , as well as electronic databases of photo pollen and non-pollen palynomorphs (NPP database, Paldat, European pollen database, etc.) with a use of a Motic-B1-microscope 220A at magnification × 400. Non-pollen palynomorphs were additionally examined ( Fig. 3 ): organic residues of aquatic microorganisms, spores of coprotrophic and parasitic fungi on decaying plants and roots of trees, and difficult and indefinable spores of fungi are combined into this group. In each sample, the number of coal microparticles, which are among the effective     eco-indicators, was also calculated. To calculate percentage ratios and build spore-pollen diagrams, the Tilia/TiliaGraph/TGView software package [ 10 , 11 ] was used. In the percentage calculation, the sum of the pollen of trees and shrubs (AR) and herbaceous plants (NAP) -AP + NAP is taken as 100%. The percentage of all taxa is calculated from this amount.