Aleksandra A. Golyeva^1,*, Vladimir Yu. Koval^2,**

¹Institute of Geography RAS, Moscow, Russia
²Institute of Archaeology RAS, Moscow, Russia

*E-mail: golyevaaa@yandex.ru
**E-mail: kovaloka@mail.ru

Keywords: occupational layer, gross phosphorus, phytoliths, biogenic streak, the Golden Horde period.

The article discusses the genesis of the so-called “sand” layer, a characteristic feature of the occupational layer in the central part of Bolgar. In previous studies, this layer was associated with the consequences of the Bolgar defeat by the Mongol army in 1236, since a coal (fire) streak had always been found under it. Based on a complex of physicochemical and microbiomorphic methods the study shows that in all cases this layer is distinguished from the rest in terms of the content of gross phosphorus, amorphous and biogenic silica. The “sand” proper constitute only a small proportion of it, moreover, traces of thermal effects were not observed. Therefore, the genesis of this layer is not mineral, but mainly biogenic in nature. The authors propose several hypotheses about the origin of this layer as accumulations of manure of herbivores or remains of adobe structures transformed by natural processes.

DOI: 10.31857/S086960630013721-2