ИСТИНА

The study site is located in the forest-steppe area of the Russian Plain in the historical part of the city of Tula within the fortified settlement (Kremlin). It is a flat surface of a high floodplain elevated 5- 6 m above the Upa river edge. The studied section includes a stratification of cultural layers (CL) and the soil buried in the 15th – 16th centuries (Fig). The buried soil formed in loess and is similar to the soils of the surrounding uplands (Chernic/Someric Phaeozems (Loamic, Aric)), indicating that the floodplain is a remnant of ancient basement covered with the loess mantle. The profile of the buried soil is well preserved showing signs of ancient cultivation (mixing and applying fertilizers). Cultural layers are characterized by a large number of anthropogenic materials introduced during construction (limestones and sand), as well as the maximum content of total phosphorus and sulfur, which is the result of the impact of ancient and modern human activity. The differences in the properties of the cultural layers may be related to the time of their formation, which falls on the Little Ice Age of the 14th – 19th centuries, which is characterized by unstable climatic conditions. According to the micromorphological analysis, CL1 contains highly transformed plant remains and bones; limestone fragments are dissolved, recrystallized, and included in the groundmass; there are many spots of iron oxides. Those features indicate that CL1 was under the influence of comparatively wet conditions. CL2 was formed in a slightly drier, but colder environment than CL1. In CL2, a large number of plant remains of varying degrees of preservation are observed, and special forms of secondary carbonates have been identified: phytomorphoses by the plant remains. Such carbonate pedofeatures are formed in contrast climate conditions with rapid freezing of soil solutions. Perhaps there were frosty winters. The anthropogenic impact is traced not only in the cultural layers of the section studied in the Tula Kremlin but also in the upper horizons of the buried soil – the entire profile is characterized by slightly alkaline pH values, which are not typical for the surrounding soils. Increased sulfur content is regularly detected in the upper parts of the Kremlin. The reason for this may be atmospheric pollution from enterprises or transport, as well as the use of deicing reagents on the territory of the Kremlin which is a museum nowadays. The study of the features of the paleosols and cultural layers of the Tula Kremlin made it possible to carry out paleoecological reconstruction for various stages of land use, as well as to characterize the early stages of human activity in this territory. Initially, on this territory Chernic Phaeozems under forest-steppe vegetation were developed, then plowing and burning of vegetation was carried out to create arable land. The functioning of the arable land was accompanied by periods of abandonment Fig.1. Buried soil and cultural layers of the Tula Kremlin site of the territory. Then the vegetation was burned to build the first wooden church in the 15th century. Then a stone church was built on this site, which lasted until the end of the 17th century. In the end, the Uspensky Cathedral was built on this territory, which still exists. In accordance with military and defensive purposes, Kremlins were usually built on a high watershed at the confluence of two rivers. The study of the buried soil formed in loess sediments with no signs of flooding and/or fluvial sedimentation made it possible to explain the location of a large cultural and economic center of the late Middle Ages, Tula Kremlin, at a low hypsometric level near the Upa River.